ELECTROCHEMICAL COGENERATION OF IRON AND COMMODITY CHEMICALS

Abstract

An electrochemical reactor comprising a source of a magnetic field positioned in proximity to a cathode and configured to generate a magnetic field; and an electrochemical cell comprising an anode and the cathode, and further comprising a catholyte channel configured to direct a catholyte stream comprising an iron-containing feedstock to the cathode; an anolyte channel configured to direct an anolyte stream comprising a metal chloride to the anode, wherein the catholyte channel and the anolyte channel are disposed between the cathode and the anode; and a separator disposed between the catholyte channel and the anolyte channel, wherein the electrochemical reactor is configured to electrochemically oxidize chloride anions to chlorine gas at a surface of the anode, and wherein the electrochemical reactor is further configured to electrochemically reduce the iron-containing feedstock to an iron particle comprising iron metal at the surface of the cathode and in the magnetic field.

Description

BACKGROUND

Aspects provide a departure from conventional aqueous metal electrolysis to achieve a net-negative CO₂ ironmaking process at a cost competitive with pig iron. Aspects provide: (i) production of valuable co-products Cl₂ and NaOH that help offset production cost of electrolytic iron and sequester CO₂ using product NaOH; (ii) powder-to-powder continuous production of iron metal from low-grade ores; and (iii) low cost pretreatment and solution purification methods to enable the use of low grade commercial iron ores and ore concentrates. The aspects may provide steel production at a levelized cost of 520 $/tonne-HRC (hot rolled coil steel) while eliminating ˜80 megatons of carbon dioxide per year (Mt—CO₂/y), or greater than 1.5% of total U.S. CO₂ emissions.

The above and other aspects and features are described and exemplified by the following figures and detailed description.

BRIEF DESCRIPTION

Provided is an electrochemical reactor comprising a source of a magnetic field positioned in proximity to a cathode and configured to generate a magnetic field at a surface of the cathode; and an electrochemical cell comprising an anode and the cathode, wherein the electrochemical cell further comprises: a catholyte channel configured to direct a catholyte stream comprising an iron-containing feedstock to the cathode; an anolyte channel configured to direct an anolyte stream comprising a metal chloride to the anode, wherein the catholyte channel and the anolyte channel are disposed between the cathode and the anode; and a separator disposed between the catholyte channel and the anolyte channel, wherein the electrochemical reactor is configured to electrochemically oxidize chloride anions to chlorine gas at a surface of the anode, and wherein the electrochemical reactor is further configured to electrochemically reduce the iron-containing feedstock to an iron particle comprising iron metal at the surface of the cathode and in the magnetic field.

Also provided is a method of operating the electrochemical reactor comprising flowing the catholyte stream through the catholyte channel; flowing the anolyte stream through the anolyte channel; applying the magnetic field at the surface of the cathode; applying a voltage between the cathode and the anode to: (i) electrochemically reduce the at least a portion of the iron-containing feedstock to produce the iron particle at the surface of the cathode while the magnetic field is applied at the cathode; and (ii) electrochemically oxidize at least a portion of the chloride anions to produce the chlorine gas at the surface of the anode; and contacting a cation of the metal chloride and a hydroxide anion to form a metal hydroxide in the catholyte stream to operate the electrochemical reactor.

The above and other aspects and features are described and exemplified by the following figures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are exemplary embodiments:

FIG. 1. shows a comparison of reactions and products for the chlor-alkali process and the chlor-iron process that occur in electrochemical cells, where the anode and cathode are separated by a separator (dashed line), the cathode is in contact with a catholyte (30 wt % of NaOH/H₂O), and the anode is in contact with an anolyte (NaCl/H₂O, pH of 2).

FIG. 2A is a schematic diagram of an embodiment of an electrochemical reactor system.

FIG. 2B is a graph of voltage, magnetic field, and iron ore or iron concentration, each versus time and each having arbitrary units, and corresponding schematic diagrams of an electrochemical reactor before, during, and after reduction, illustrating an embodiment of a method of producing iron metal from an iron-containing feedstock.

FIG. 3 shows output from cost and lifecycle emissions analysis for three steelmaking pathways: blast furnace-basic oxygen furnace (BF—BOF), chlor-iron plus electric arc furnace (EAF), and conventional alkaline iron electrolysis (alkaline Fe—O₂ electrolysis) with oxygen as the only coproduct plus EAF.

FIG. 4 is a Pourbaix diagram for the iron-water system according to one or more embodiments.

FIG. 5 shows the confluence of innovations to provide a practical and commercially viable chlor-iron technology according to one or more embodiments.

FIG. 6 shows the results of direct iron powder production from alkaline iron oxide slurry using a batch reactor according to one or more embodiments.

FIG. 7 shows the results of using a magnet or no magnet during the electrolysis of both hematite and magnetite slurries.

FIG. 8 shows the results of (a) Radial Helmholtz Coil FEMM simulation, (b) Single Radial EM FEMM simulation, and (c) Cast Alnico 5 Permanent Magnet FEMM simulation.

FIG. 9 shows a lab scale batch cell test vehicle for studying the impact of magnetic fields on ferromagnetic oxide particle reduction.

FIG. 10 are a sensors and controls schema for a chlor-iron electrolyzer.

FIG. 11 is a magnetorheology fixture for mounting on a torsional shear rheometer (from Ocalan & McKinley, 2013). All dimensions are shown in mm. The electromagnet windings generate a solenoidal field that is highly uniform and axially aligned and focused to pass through the sample (in black) and then through the rotating plate geometry (in blue). Space is provided below the sample holder for a non-magnetic spacer to be inserted and directly measure the magnetic field uniformity.

FIG. 12 shows Brownian dynamics simulations of dense suspensions containing attractive particles at high volume fraction show the appearance of a yield stress (finite intercept in the material flow curve) and highly anisotropic flow-aligned microstructures that vary with shear rate (or magnetic Mason number). The dashed red line shows a simple predictive analytical model (Bingham plastic) that can be extracted from fitting the experiments (blue circles) or model predictions (red triangles). Unpublished work, presented by More & McKinley, Proc. XIXth Int Cong. Rheol. (Athens), 2023.

FIG. 13 shows components of overpotential for typical diaphragm and membrane chlor-alkali cells compared against targeted overpotential for chlor-iron electrolyzers operating at 250 mA/cm².

FIG. 14 shows the microstructural differences of iron produced from magnetite feedstocks with different starting particle sizes.

FIG. 15 shows a process flow diagram for a chlor-iron process according to one or more embodiments.

FIG. 16 shows the synergistic pairing of electrolytic iron production through the chlor-iron process and the various applications for the resulting commodity coproducts of iron, chlorine, and caustic.

DETAILED DESCRIPTION

Aspects provide a low temperature (˜100° C.) approach to electrolytic iron production that has a path to supplant incumbent blast furnace-basic oxygen furnace (BF—BOF) steelmaking, without a green premium, while rendering the ironmaking process a net CO₂ sink rather than a prolific emitter. Towards overcoming these limitations, the term “chlor-iron” process is provided below in Equation 1 (net process) and is described herein. Also provided are the reactions occurring at the positive electrode (Equation 2) and the negative electrode (Equation 3).

Fe₂O₃+6NaCl+3H₂O→2Fe+6NaOH+3Cl₂  [1]

6NaCl→3Cl₂+6Na⁺+6e⁻  [2]

Fe₂O₃+3H₂O+6e⁻→2Fe+6OH⁻  [3]

The chemistry and operating conditions of the chlor-iron process align closely with the chlor-alkali process, as shown in FIG. 1, although the reaction chemistry differs. Both reactions operate at a similar temperature, a similar NaCl brine concentration and pH, a similar NaOH concentration, and a similar cell voltage. The two processes differ in the reduction reaction at the negative electrode. Hydrogen evolution occurs in the chlor-alkali process, whereas the reduction of iron oxide to iron metal occurs in the chlor-iron process.

The chlor-alkali industry defines an electrochemical unit (ECU) based on reaction stoichiometry that is typically indexed to chlorine generation. The ECU for chlor-alkali is 1.13 tonne of NaOH and 0.03 tonne of H₂ per tonne Cl₂. The low quantity of H₂ per ECU is why traditionally H₂ generated from the chlor-alkali process is either burned for process heat or simply vented. In contrast, the chlor-iron process has an ECU of 1.13 tonne of NaOH (identical to chlor-alkali process) and 0.5 tonne of Fe per tonne of Cl₂. The close alignment in product masses for the chlor-iron ECU makes it possible to offset a substantial fraction of the iron production cost through sale of the other commodity chemicals. In addition to their sale as commodity chemicals, both Cl₂ and NaOH may be recycled to pretreat low grade iron ore feedstocks, and NaOH may be used for CO₂ removal from air or ocean water, opening the possibility for net-negative emissions ironmaking (approx. 0.9 tonne of CO₂ captured per tonne of NaOH for ocean alkalinity enhancement. With approximately 16 Mt/y of chlorine generation capacity in the U.S., the chlor-iron process could provide 8 Mt/y of negative-emissions domestic iron production if all chlor-alkali facilities were converted to the chlor-iron process. In addition, at ˜80 Mt/y, global chlorine demand would support ˜40 Mt/y of iron production from the chlor-iron process.

In parallel to demonstrating the working principles of the chlor-iron process, the inventors have also developed a method to generate iron powder directly from iron oxide slurries, thereby eliminating reliance on conventional costly and time-intensive harvesting and stripping of iron plates. This may be accomplished by performing iron electrolysis in the presence of a magnetic field near the negative electrode (i.e., the cathode), while also manipulating other parameters such as the current density and the flow rate of the iron slurry in the cell. FIG. 2B illustrates the working principle according to various aspects wherein the applied voltage or current, the magnetic field, and the ore slurry flow rate may be modulated in concert to achieve a continuous iron powder production process. Briefly, as the ferromagnetic ore is introduced into the cell it is drawn toward the negative current collector by the magnetic field. After a period of reduction, the magnetic field may be modified to facilitate release of the reduced iron and the unreacted ore, which are entrained in the catholyte flow and separated downstream for product harvesting. An unanticipated consequence of reduction in the presence of a magnetic field is the marked reduction in substrate adhesion compared to non-magnetic cells, such that the reduced iron product may be fully released by modulating the magnetic field after a finite period of reduction.

According to an aspect, provided is an electrochemical reactor including a source of a magnetic field positioned in proximity to a cathode and configured to generate a magnetic field at a surface of the cathode, and an electrochemical cell including an anode and the cathode. The electrochemical cell further includes a catholyte channel that is configured to direct a catholyte stream to the cathode, wherein the catholyte stream includes an iron-containing feedstock. The electrochemical cell also includes an anolyte channel that is configured to direct an anolyte stream to the anode. The anolyte stream includes a metal chloride. In the electrochemical cell, the catholyte channel and the anolyte channel are disposed between the cathode and the anode. The electrochemical cell also includes a separator that is disposed between the catholyte channel and the anolyte channel.

The electrochemical reactor is configured to electrochemically oxidize chloride anions (Cl⁻)⁻ to chlorine gas (Cl₂ (g)) at a surface of the anode. For example, the electrochemical reactor may be configured to electrochemically oxidize at least a portion of the chloride anions to chlorine gas at the surface of the anode.

As used herein, “anode reaction zone” or “counter electrode reaction zone” refers to a region where oxidation occurs during electrolysis. For the chlor-iron process, the anode reaction zone is the region of chlorine generation from NaCl brine.

The electrochemical reactor is also configured to electrochemically reduce the iron-containing feedstock to an iron particle at the surface of the cathode and in the magnetic field, wherein the iron particle includes iron metal (Fe(0)). For example, the electrochemical reactor may be configured to electrochemically reduce at least a portion of the iron-containing feedstock to an iron particle at the surface of the cathode and in the magnetic field, wherein the iron particle includes iron metal (Fe(0)). In some embodiments, and as further provided below, the iron particle may be iron metal.

As used herein, “cathode reaction zone” or “working electrode reaction zone” refers to a region where a reduction reaction occurs during electrolysis. In the case of iron ore electrolysis, the cathode reaction zone is the region where reduction of iron oxide to iron metal occurs and where magnetic field properties are beneficial.

The iron-containing feedstock is typically not electrochemically reduced before the magnetic field is applied at the surface of the cathode. For example, the voltage is applied between the anode and the cathode while applying the magnetic field at the cathode to electrochemically reduce the iron-containing feedstock to produce the iron particle and to oxidize the chloride anions to produce the chlorine gas. In particular, the electrochemical reduction of the iron-containing feedstock occurs at the surface of the cathode and in the magnetic field, rather than the iron-containing feedstock being electrochemically reduced in the electrochemical cell and then subsequently having a magnetic field applied to collect the resulting iron particles.

In some embodiments, the electrochemical reactor may be configured to electrochemically reduce the iron-containing feedstock to the iron particle at a current efficiency ratio of at least 0.75, wherein the current efficiency ratio is a ratio of charge used for the reduction of the iron-containing feedstock to a total charge provided to the cathode. For example, at least a portion of the iron-containing feedstock may be electrochemically reduced to the iron particle at a current efficiency ratio of at least 0.75.

The electrochemical reactor includes an anode. The anode includes a suitable anode current collector. The anode current collector may be a metal, metal alloy, or a combination thereof. In some embodiments, the anode current collector may include lead, nickel, platinum, iridium, ruthenium, tantalum, titanium, an alloy thereof, or a combination thereof. In some embodiments, the anode current collector may be coated with mixed metal oxides of iridium, ruthenium, tantalum, or the like, or a combination thereof.

The anode current collector may have a thickness in the range from 0.05 to 0.5 centimeters (cm), such as from 0.1 to 0.3 cm. In some embodiments, the anode current collector may be at least partially porous.

The anode may be prepared from any suitable material that is capable of electrochemically oxidizing chloride anions to chlorine gas. In some embodiments, the anode may include carbon, titanium, lead, nickel, iron, platinum, iridium, ruthenium, tantalum, niobium, zirconium, vanadium, hafnium, aluminum, tin, cobalt, antimony, tungsten, copper, an alloy thereof, an oxide thereof, or a combination thereof.

In some embodiments, the anode may include a catalyst. Exemplary catalysts include a metal oxide catalyst, such as manganese oxide (e.g., MnO₂, Mn₂O₃, Mn₃O₄, or Mn_xO_y (where x=1 to 3 and y=1 to 8), or a combination thereof), nickel-doped manganese oxide (Ni—Mn_xO_y), nickel oxide (NiO_x), nickel oxyhydroxide (NiO_x(OH)_y), iron oxide (FeO_x), iron oxyhydroxide (FeO_x(OH)_y (where x=0 to 2 and y=0 to 3)), cobalt oxide (Co₃O₄, Co_xO_y (where x=1 to 3 and y=1 to 8)), manganese cobalt oxide (MnCo₂O₄, Mn_1+xCo_2−xO₄ (where x=0 to 2)), cobalt manganese oxide (CoMn₂O₄), nickel manganese oxide (NiMnO_x (where x=2 to 4)), manganese iron oxide (MnFe₂O₄, Mn_1+xFe_2−xO₄ (where x=0 to 1)), nickel-doped manganese oxide (Ni Mn_xO_y (where x=1 to 3 and y=1 to 8)), manganese cobalt iron oxide (Mn_xCo_yFe_zO₄ (where x=0 to 4 and y=0 to 4 and z=0 to 4)), zinc cobalt manganese oxide (ZnCoMnO₄, Zn_xCo_yMn_zO₄ (where x=0 to 4 and y=0 to 4 and z=0 to 4)), cobalt nickel oxide (CoNiO_x (where x=0 to 4)), calcium manganese oxide (CaMnO_x (where x=0 to 4)), lanthanum manganese oxide (LaMnO₃), lanthanum cobalt oxide (LaCo₂O₄, La_1+xCo_2−xO₄ (where x=0 to 2), lanthanum nickel oxide (LaNiO₃), lanthanum calcium aluminum manganese oxide (La_xCa_yAl_zMn_vO₃ (where x=0 to 3 and y=0 to 3 and z=0 to 2 and v=0 to 3)), nickel iron oxide (Ni_zFe_1−zO_x (where z=0 to 1 and x=0.5 to 2.5)), manganese ferrite (MnFe₂O₄), zinc ferrite (ZnFe₂O₄), nickel cobaltite (NiCo₂O₄), lanthanum strontium manganate (La_0.8Sr_0.2MnO₃), or the like, other transition metal oxides or nitrides (such as Fe₃N, FeCN, ZrN, Mn₄N, or a combination thereof), or a combination thereof. A combination comprising at least one of the foregoing oxides may be used. The particles of the catalyst may be coated by electrodeposition, electroless plating, or other chemical deposition process(es); for example, atomic layer deposition (ALD), thermal evaporation, sputtering, spray pyrolysis, solution-based deposition, hot dip coating, inkjet printing, or a combination thereof.

The electrochemical reactor also includes a cathode. The cathode includes a suitable cathode current collector. Preferably, the current collector of the cathode is selected to minimize or prevent adhesion of the iron-containing feedstock and/or the iron metal thereto. Exemplary materials that are suitable for use in the cathode include, but are not limited to, aluminum, carbon, molybdenum, copper, nickel, titanium, chromium, iron, an alloy thereof, or a combination thereof. For example, the cathode may include a stainless steel alloy such as 316, 316L, 304, or the like. In some embodiments, the cathode current collector may include steel, graphite, copper, nickel, iron, a nickel-iron alloy, or a combination thereof. In some embodiments, the cathode may further include an inert conductive matrix including carbon black, graphite powder, charcoal powder, coal powder, nickel-coated carbon steel mesh, nickel-coated stainless-steel mesh, nickel-coated steel wool, or the like, or a combination thereof.

The cathode current collector may have a thickness in the range from 0.05 to 0.5 cm, such as from 0.1 to 0.3 cm. In some embodiments, the cathode current collector may be at least partially porous.

In some embodiments, the cathode may further include one or more additive(s) to enhance the electronic and/or physical properties of the cathode. In some embodiments, the additive in the cathode may include one or more of bismuth (III) oxide (Bi₂O₃), bismuth (III) sulfide (Bi₂S₃), barium oxide (BaO), barium sulfate (BaSO₄), barium hydroxide (Ba(OH)₂), calcium oxide (CaO), calcium sulfate (CaSO₄), calcium hydroxide (Ca(OH)₂), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)₂), carbon nanotubes, carbon nanofibers, graphene, or a combination thereof.

In some embodiments, the cathode may further include one or more binder compound(s). In some embodiments, the binder compound may include polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVdF), polypropylene (PP), polyethylene (PE), polyacrylonitrile, styrene butadiene rubber, sodium carboxymethyl cellulose (Na-CMC), or the like, or a combination thereof.

The cathode may be prepared from any suitable material that is capable of electrochemically reducing the iron-containing feedstock to an iron particle comprising iron metal. In some embodiments, the cathode may include aluminum, carbon, molybdenum, copper, nickel, titanium, iron, an alloy thereof, or a combination thereof. For example, the cathode may include carbon, nickel, iron, an alloy thereof, or a combination thereof.

The cathodic material may be positively charged or negatively charged. The cathodic material may be charged by a direct current (“DC”) source, by an alternating current (“AC”) source, and/or by a pulsed current.

The catholyte stream generally includes an electrolyte. In some embodiments, the catholyte stream includes an aqueous solution of a metal hydroxide. The catholyte stream may be a solution including water as a solvent and one or more dissolved hydroxides. For example, the catholyte stream may include an aqueous solution of NaOH, KOH, LiOH, CsOH, or a combination thereof. Mentioned is an aspect wherein the catholyte stream includes an aqueous solution of NaOH.

The metal hydroxide may be present in the aqueous solution of the catholyte stream in an amount from 20 to 50 weight percent (wt %), based on a total weight of the catholyte stream. For example, the metal hydroxide may be present in the aqueous solution of the catholyte stream in an amount from 25 to 45 wt %, preferably 30 to 40 wt %, each based on a total weight of the catholyte stream.

As described herein, the catholyte stream may include from 0.1 to 30 wt % of the iron-containing feedstock, based on a total weight of the catholyte stream. Preferably, the catholyte stream includes 0.1 to 15 wt % of the iron-containing feedstock, more preferably 0.1 to 5 wt % of the iron-containing feedstock, each based on a total weight of the catholyte stream.

The catholyte stream may further include an aqueous solution that includes a metal hydroxide. The metal hydroxide includes an alkali metal hydroxide, an alkaline earth metal hydroxide, or a combination thereof.

In some embodiments, the metal hydroxide of the catholyte stream may be derived from the metal of the metal chloride of the anolyte stream. In some embodiments, at least a portion of the metal of the metal hydroxide is derived from the metal of the metal chloride of the anolyte stream, such that there initially metal hydroxide in the catholyte stream and the concentration of the metal hydroxide in the catholyte stream increases as the electrochemical reactor is operated, the iron-containing feedstock is reduced, and the chloride anions are oxidized.

The catholyte stream may optionally contain additives to promote or inhibit certain desired or undesirable reactions. Any suitable amount of additive(s) may be included in the catholyte stream. For example, the catholyte stream may further include a hydrogen evolution reaction suppressor (HER suppressor), an iron activator (e.g., a sulfide salt, such as bismuth sulfide (Bi₂S₃) or sodium sulfide (Na₂S)), or the like, or a combination thereof. In some embodiments, the catholyte stream may further include an alkali metal sulfide or a polysulfide including one or more of lithium sulfide (Li₂S) or lithium polysulfide (Li₂S_x, x=2 to 6), sodium sulfide (Na₂S) or sodium polysulfide (Na₂S_x, x=2 to 6), potassium sulfide (K₂S) or potassium polysulfide (K₂S_x, x=2 to 6), cesium sulfide (Cs₂S) or cesium polysulfide (Cs₂S_x, x=2 to 6), or the like, or a combination thereof. Non-limiting examples of additives include sodium sulfide (Na₂S), potassium sulfide (K₂S), lithium sulfide (Li₂S), iron sulfides (FeS_x, where x=1-2), bismuth sulfide (Bi₂S₃), lead sulfide (PbS), zinc sulfide (ZnS), antimony sulfide (Sb₂S₃), selenium sulfide (SeS₂), tin sulfides (SnS, SnS₂, Sn₂S₃), nickel sulfide (NiS), molybdenum sulfide (MoS₂), mercury sulfide (HgS), bismuth oxide (Bi₂O₃), or the like, or a combination thereof. In addition, the catholyte stream may include other additives, including those as described herein and those known in the art.

In some embodiments, the HER suppressor may include one or more of sodium thiosulfate, sodium thiocyanate, polyethylene glycol (PEG) 1000, trimethylsulfoxonium iodide, zincate (by dissolving ZnO in NaOH), hexanethiol, decanethiol, sodium chloride, sodium permanganate, lead (IV) oxide, lead (II) oxide, magnesium oxide, sodium chlorate, sodium nitrate, sodium acetate, iron phosphate, phosphoric acid, sodium phosphate, ammonium sulfate, ammonium thiosulfate, lithopone, magnesium sulfate, iron(III) acetylacetonate, hydroquinone monomethyl ether, sodium metavanadate, sodium chromate, glutaric acid, dimethyl phthalate, methyl methacrylate, methylpentynol, adipic acid, allyl urea, citric acid, thiomalic acid, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, propylene glycol, trimethoxysilyl propyl diethylene, aminopropyl trimethoxysilane, dimethyl acetylenedicarboxylate (DMAD), 1,3-diethylthiourea, N,N′-diethylthiourea, aminomethyl propanol, methyl butynol, amino modified organosilane, succinic acid, isopropanolamine, phenoxyethanol, dipropylene glycol, benzoic acid, N-(2-aminoethyl)-3-aminopropyl, behenamide, 2-phosphonobutane tricarboxylic, mipa borate 3-methacryloxypropyltrimethoxysilane, 2-ethylhexoic acid, isobutyl alcohol, t-butylaminoethyl methacrylate, diisopropanolamine, propylene glycol n-propyl ether, sodium benzotriazolate, pentasodium aminotrimethylene phosphonate, sodium cocoyl sarcosinate, laurylpyridinium chloride, steartrimonium chloride, stearalkonium chloride, calcium montanate, quaternium-18 chloride, sodium hexametaphosphate, dicyclohexylamine nitrite, lead stearate, calcium dinonylnaphthalene sulfonate, iron(II) sulfide, sodium bisulfide, pyrite, sodium nitrite, complex alkyl phosphate ester (e.g. RHODAFAC® RA 600 Emulsifier), 4-mercaptobenzoic acid, ethylenediaminetetraacetic acid, ethylenediaminetetraacetate (EDTA), 1,3-propylenediaminetetraacetate (PDTA), nitrilotriacetate (NTA), ethylenediaminedisuccinate (EDDS), diethylenetriaminepentaacetate (DTPA), and other aminopolycarboxylates (APCs), diethylenetriaminepentaacetic acid, 2-methylbenzenethiol, 1-octanethiol, bismuth sulfide, bismuth oxide, antimony(III) sulfide, antimony(III) oxide, antimony(V) oxide, bismuth selenide, antimony selenide, selenium sulfide, selenium(IV) oxide, propargyl alcohol, 5-hexyn-1-ol, 1-hexyn-3-ol, N-allylthiourea, thiourea, 4-methylcatechol, trans-cinnamaldehyde, iron(III) sulfide, calcium nitrate, hydroxylamines, benzotriazole, furfurylamine, quinoline, tin(II) chloride, ascorbic acid, tetraethylammonium hydroxide, calcium carbonate, magnesium carbonate, antimony dialkylphosphorodithioate, potassium stannate, sodium stannate, tannic acid, gelatin, saponin, agar, 8-hydroxyquinoline, bismuth stannate, potassium gluconate, lithium molybdenum oxide, potassium molybdenum oxide, hydrotreated light petroleum oil, heavy naphthenic petroleum oil (e.g., sold as Rustlick® 631), antimony sulfate, antimony acetate, bismuth acetate, hydrogen-treated heavy naphtha (e.g., sold as WD-40), tetramethylammonium hydroxide, NaSb tartrate, urea, D-glucose, C₆Na₂O₆, antimony potassium tartrate, hydrazinesulphate, silica gel, triethylamine, potassium antimonate trihydrate, sodium hydroxide, 1,3-di-o-tolyl-2-thiourea, 1,2-diethyl-2-thiourea, 1,2-diisopropyl-2-thiourea, N-phenylthiourea, N,N′-diphenylthiourea, sodium antimony L-tartrate, rhodizonic acid disodium salt, sodium selenide, or the like, or a combination thereof.

In some embodiments, the catholyte stream may further include a solid conductive additive. In an embodiment, the catholyte stream may further include carbon in an amount from 0.01 to 10 wt %, based on a total weight of the catholyte stream.

The anolyte stream includes a metal chloride. In some embodiments, the anolyte stream may include an aqueous solution that includes the metal chloride, and the metal chloride may be an alkali metal chloride, an alkaline earth metal chloride, or a combination thereof. Representative anolyte streams include aqueous solutions of strong acids having a pKa of 3 or less. For example, the anolyte stream may include a strong acid, such as HCl, and may comprise a supporting electrolyte compound to provide improved conductivity, preferably the supporting electrolyte compound is MClO₄, MNO₃, M₂SO₄, MF, MCl, MBr, or MI, where M=Li, Na, or K, or tetra-n-butylammonium X, where X is F, Cl, Br, I, or hexafluorophosphate; and water, and optionally further including a nonaqueous solvent, such as acetonitrile, dimethylsulfoxide, dimethylformamide, methanol, ethanol, 1-propanol, isopropanol, ether, diglyme, tetrahydrofuran, glycerol, or the like, or a combination thereof. In some embodiments, the anolyte may include one or more strong acids, optionally one or more supporting electrolyte compounds, and water. For example, the anolyte stream may include an aqueous solution of a strong acid, preferably HCl, and optionally a supporting electrolyte compound, preferably one or more of M₂SO₄, MCl, MBr, MI, or a combination thereof, where M is Li, Na, or K.

In some embodiments, the metal chloride may be present in the aqueous solution in an amount from 10 to 50 wt, based on a total weight of the anolyte stream. For example, the metal chloride may be present in the aqueous solution in an amount from 1 to 60 wt %, or 5 to 50 wt %, or 10 to 50 wt %, or 20 to 50 wt %, or 30 to 50 wt %, each based on a total weight of the anolyte stream.

In some embodiments, the anolyte stream may have a pH of less than 7. For example, the anolyte stream may have a pH from 0 to 7, or from 0 to 5, or from 0 to 3.

In some embodiments, the anolyte stream may further include a strong acid. For example, the anolyte stream may further include an acid having a pKa of 2 or less.

The electrochemical cell includes a separator that is disposed between the catholyte channel and the anolyte channel. Any suitable separator may be used.

The separator may be a passive separator, such as diaphragm separator, or may be an active separator, such as ion exchange membrane. In some embodiments, the separator may be chosen based on an ability to allow selective transfer of desired molecules or materials while substantially limiting or preventing transfer of undesired molecules or materials. For example, the separator may be an ion-selective membrane configured to allow the transfer of negative (or positive) ions while substantially preventing transfer of positive (or negative) ions. In other examples, the separator may be a material selected to allow or prevent the cross-over of gas bubbles from one side (e.g., associated with the working electrode) to the opposite side (e.g., associated with the counter-electrode).

In some embodiments, the separator may be formed of a dielectric material, or a porous material, which is permeable to positive ions, such as Li⁺, K⁺, Na⁺, Cs⁺, and/or NH₄⁺ ions, or the like, or a combination thereof, or negative ions, such as hydroxide ions, or the like. The separator may be impermeable or effectively impermeable to an active material of the catholyte or anolyte. In some embodiments, the separator may be a membrane, such as a membrane formed from a polymer with a tetrafluoroethylene backbone and side chains of perfluorovinyl ether groups terminated with sulfonate groups (e.g., a sulfonated tetrafluoroethylene membrane, a membrane made of polymers sold under the Nafion brand name, etc.), or the like.

In some embodiments, the separator may include an anion exchange membrane (AEM), a cation exchange membrane (CEM), a zwitterionic membrane, a porous membrane having an average pore diameter of less than 10 nanometers, a polybenzimidazole-containing membrane, a polysulfone-containing membrane, polycarboxylic-containing membrane, a polyetherketone-containing membrane, a membrane including polymer(s) of intrinsic microporosity (PIM), or the like, or a combination thereof. Preferably, the separator includes an anion exchange membrane (AEM) or a cation exchange membrane (CEM). In some embodiments, the separator may include a composite membrane including an inorganic material and an organic material. In some embodiments, the inorganic material may include a metal oxide or a ceramic material. In some embodiments, the organic material may include a polyether ether ketone (PEEK), a polysulfone, a polystyrene, a polypropylene, a polyethylene, or the like, or a combination thereof.

In some embodiments, a separator may be used that provides a physical barrier between the anolyte and the catholyte. For example, the separator may include a porous polyolefin film, a glass fiber mat, a glass frit, a cotton fabric, a rayon fabric, cellulose acetate, paper, or the like, or a combination thereof.

In some embodiments, the separator may include an anion exchange membrane, a cation exchange membrane, an anion selective membrane, a cation selective membrane, a zwitterionic membrane, a nanoporous membrane (e.g., having an average pore diameter of 10 nm or less), a polybenzimidazole-containing membrane, a polysulfone-containing membrane, a polycarboxylic-containing membrane, a polyetherketone-containing membrane, a membrane comprising a polymer of intrinsic microporosity, or a combination thereof. For example, the separator may include a cation selective membrane. In some embodiments, the separator may include a cation-selective membrane that is permeable to an alkali metal cation, an alkaline earth metal cation, or a combination thereof.

In some embodiments, the catholyte channel and the anolyte channel may be arranged vertically. For example, the catholyte channel and the anolyte channel may be arranged vertically with the separator disposed therebetween in a vertical configuration. For example, the catholyte channel and the anolyte channel may be arranged to provide vertical flow channels relative to the ground.

The interelectrode gap may also be varied, with a well-known impact on the ohmic drop. In some embodiments, the interelectrode gap may be 1 millimeter (mm) to 100 mm. For example, the interelectrode gap may be 2 mm to 50 mm, or 3 mm to 30 mm, or 4 mm to 20 mm.

In some embodiments, the electrochemical cell may have a zero-gap configuration. As used herein, a “zero-gap cell” refers to an electrochemical cell in which at least one electrode is in contact with the separator (in contrast to a cell in which each electrode has a non-zero gap between the electrode surface and the separator). The anode may be in contact with the separator or situated at an offset from the separator. The electrodes in zero-gap electrochemical cells are preferably porous to enable ion transport between the catholyte stream, the anolyte stream, and the separator. In some embodiments, at least one of the anode or the cathode is directly on the separator, preferably wherein the at least one of the anode or the cathode contacts the separator.

In other embodiments, the anode and the cathode each may be separated from the separator by any suitable distance. In some embodiments, a distance between a surface of the anode and the separator may be 0.001 cm to 2 cm. The cathode may be separated from the separator by any suitable distance. In some embodiments, a distance between a surface of the cathode and the separator may be 0.001 cm to 2 cm.

The iron-containing feedstock may include any suitable iron compound, and may include an oxide of iron. The iron-containing feedstock refers to an iron-containing material that is capable of undergoing reduction during operation of the electrochemical reactor. As used herein, the terms “iron ore” and “iron-containing feedstock” may be used synonymously to refer to iron-containing materials that may be used as the feedstock into the various systems and methods described herein. “Iron ores” and “iron-containing feedstocks” may include iron in any form, and can be an iron oxide, hydroxide, oxyhydroxide, carbonate, or combination thereof. Also mentioned are other iron-containing compounds, ores, rocks, or minerals, including any mixtures thereof, in naturally occurring states or purified states. The iron-containing feedstock may include materials recognized, known, or referred to in the art as iron ore, rock, natural rock, sediment, natural sediment, mineral, and/or natural mineral, whether in naturally-occurring states or in otherwise purified or modified states. A combination comprising at least one of the foregoing iron-containing feedstocks may be used. Some embodiments of processes and systems described herein may be particularly useful for iron-containing feedstocks including hematite, maghemite, goethite, magnetite, limonite, pyrite, red mud, siderite, ankerite, turgite, bauxite, or a combination thereof. In some embodiments, the iron-containing feedstock may include hematite, maghemite, magnetite, goethite, limonite, pyrite, red mud, or a combination thereof. Preferably, the iron-containing feedstock includes magnetite.

Specifically, the iron-containing feedstock may include metallic iron (Fe) and/or one or more iron hydroxides (e.g., Fe(OH)₂, Fe(OH)₃, or the like, or a combination thereof), anhydrous and/or hydrated iron oxyhydroxides (e.g., FeOOH; e.g., FeO(OH)·nH₂O where n is a number of water molecules in the hydrated iron hydroxide molecule, or the like), iron oxides, sub-oxides, mixed oxides, including FeO (wustite), FeO₂ (iron dioxide), a-Fe₂O₃ (hematite), g-Fe₂O₃ (maghemite), Fe₃O₄ (magnetite), Fe₄O₅, Fe₅O₆, Fe₅O₇, Fe₂₅O₃₂, Fe₁₃O₁₉, other iron-containing compounds, a polymorph(s) of these, or a combination of these. For example, in some embodiments, the iron-containing feedstock may include hematite (a-Fe₂O₃), maghemite (g-Fe₂O₃), magnetite (Fe₃O₄), goethite (a-FeOOH), limonite (FeOOH-nH₂O), or a combination thereof. In particular embodiments, the iron-containing feedstock may include magnetite (Fe₃O₄). In particular embodiments, the iron-containing feedstock may include maghemite, magnetite, or a combination thereof. The iron-containing feedstock may be a product of one or more of several sources. In some embodiments, the iron-containing feedstock may include raw material in the form of hematite, maghemite, magnetite, limonite, siderite, bog-iron ore, clay minerals, ores with concentrations of less than about 30% iron by weight, scrap metals, magnets, slag, fly ash, red mud, a combination thereof, or other materials that have iron as is known by those of ordinary skill in the art.

The iron-containing feedstock may include one or more impurities or minor components. Examples of impurities or minor components may include oxides and/or complexes of aluminum, magnesium, calcium, carbon, cobalt, chromium, silicon, titanium, phosphorus, sulfur, or a combination thereof. The total content of the one or more impurities may be 60 wt % or less, or less than 30 wt %, or less than 10 wt %, or less than 5 wt %, or less than 1 wt %, or less than 0.1 wt %, or less than 0.01 wt %, based on a total weight of the iron-containing feedstock. In an aspect, a total content of the one or more impurities is 0.001 to 10 wt %, or 0.01 to 4 wt %, or 0.01 to 1 wt %, based on a total weight of the iron-containing feedstock.

In some embodiments, the iron-containing feedstock has a total impurity content between 0.1 wt % and 3 wt %, wherein the iron-containing feedstock includes a silica content of less than 2 wt %. In some embodiments, the iron-containing feedstock has a total impurity content between 3 wt % and 10 wt %, wherein the iron-containing feedstock includes a silica content of greater than 2 wt %. In some embodiments, the iron-containing feedstock has a total impurity content of 10 wt % to 60 wt %, wherein the iron-containing feedstock has a silica content of greater than 5 wt %.

In some embodiments, the iron particle may have a total impurity content of less than 3 wt %, based on total weight of the iron particle. For example, the iron particle may have a total impurity content of less than 3 wt %, wherein the iron particle includes a silica content of less than 2 wt %, based on total weight of the iron particle. The one or more impurities may exist as phases that are not an iron oxide phase or a metallic iron phase.

The iron-containing feedstock in the catholyte stream may be a slurry or a suspension of iron-containing feedstock particles in the catholyte stream material. In some embodiments, the catholyte stream may include 0.1 to 80 wt %, or 0.1 to 30 wt %, or 0.1 to 15 wt %, or 0.1 to 5 wt %, or preferably 0.2 to 10 wt %, more preferably 0.2 to 2 wt % of the iron-containing feedstock, based on a total weight of the catholyte stream. The amount of the iron-containing feedstock in the catholyte stream may vary based on the type of iron-containing feedstock being used. In some embodiments, the iron-containing feedstock may include hematite, wherein the catholyte stream may include 1 to 30 wt %, preferably 2 to 15 wt %, more preferably 2 to 5 wt % of the iron-containing feedstock, based on a total weight of the catholyte stream. In some embodiments, the iron-containing feedstock may include magnetite, wherein the catholyte stream may include 0.1 to 30 wt %, or 0.1 to 10 wt %, preferably 0.1 to 5 wt %, more preferably 0.2 to 2 wt % of the iron-containing feedstock, based on a total weight of the catholyte stream. In some embodiments, the iron-containing feedstock may be present in the catholyte stream in an amount of at least 5 wt %, and preferably greater than 10 wt %, for example, 10 to 80 wt %, based on a total weight of the catholyte stream.

The iron containing feedstock may have any suitable particle size or shape. In some embodiments, the iron containing feedstock may have an average particle size (e.g., D50 particle size) of less than 20 micrometers (μm), or the iron containing feedstock may have an average particle size (D50) of 20 μm or greater. For example, the iron containing feedstock may have an average particle size (D50) of 0.1 to 20 μm, preferably 1 to 10 μm; or the iron containing feedstock may have an average particle size (D50) of 20 to 2000 μm, or 20 to 1000 μm, or 20 to 250 μm, or 20 to 100 μm, preferably 20 to 50 μm. When the particle has a circular cross-section, the average particle diameter refers to the average diameter (D50) of the particle. When the particle has a non-circular cross-section, the average particle diameter refers to the length of the major axis of the particle.

In some embodiments, the iron containing feedstock may have an average maximum dimension of between 5 and 1,000 μm, preferably 10 to 300 μm or 10 to 50 μm. In some embodiments, the iron containing feedstock may have an aspect ratio of 1 to 100, preferably 1 to 20.

In some embodiments, the iron containing feedstock may have a morphology of a spheroid, a flake, a sheet, a platelet, or a combination thereof. Preferably, the iron containing feedstock is in the form of a flowable powder or slurry.

The electrochemical reactor is configured to electrochemically reduce at least a portion of the iron-containing feedstock to an iron particle including iron metal at the surface of the cathode and in the magnetic field of the source of a magnetic field. In some embodiments, the iron particle may include an iron metal powder. In still other embodiments, the iron particle may be an iron metal powder.

The iron particle may have any suitable particle size or shape. In some embodiments, the iron particle may have an average particle size (D50) of 0.1 to 1000 micrometers (μm), preferably 0.1 to 500 μm, more preferably 0.1 to 200 μm. In some embodiments, the iron particle may have an average particle size (D50) of 50 to 1000 μm, or preferably 50 to 200 μm. In other embodiments, the iron particle may have an average particle size (D50) of 0.1 to 20 μm, or preferably 0.1 to 10 μm.

In some embodiments, the iron particle may have an average maximum dimension of between 0.1 and 1,000 μm, preferably 0.1 to 500 μm or 0.1 to 200 μm. In some embodiments, the iron particle may have an aspect ratio of 1 to 100, preferably 1 to 20.

In some embodiments, the iron-containing feedstock has an average particle size of less than 20 μm, preferably 1 to 10 μm, and the iron particle has an average particle size of 50 to 1000 μm, preferably 50 to 200 μm. In some embodiments, the iron-containing feedstock has an average particle size of 20 μm or greater, preferably 20 to 50 μm, and the iron particle has an average particle size of 50 to 1000 μm, preferably 50 to 200 μm.

In some embodiments, the iron particle may have a morphology of a spheroid, a flake, a sheet, a platelet, a needle, or a combination thereof. Preferably, the iron particle is in the form of a flowable powder or slurry.

In some embodiments, the iron particle may have one or more of the following properties: a specific total embedded emissions of less than 0.8 tons of CO₂ per ton of the iron metal, when determined according to the European Union simplified bubble approach method for determining specific embedded emissions under the Carbon Border Adjustment Mechanism; a carbon emission intensity of less than 1100 kilograms of CO₂ per ton of the iron metal, when determined according to ISO 14404; a carbon emission intensity of less than 900 kilograms of CO₂ per ton of the iron metal, when determined according to the Intergovernmental Panel on Climate Change Methodology 2006 Guidelines for National Greenhouse Gas Inventories; a carbon emission intensity of less than 1500 kilograms of CO₂ per ton of the iron metal, when determined according to the 2017 World Steel Life Cycle Inventory Methodology; a carbon emission intensity of less than 1300 kilograms of CO₂ per ton of the iron metal, when determined according to the 2008 World Resource Institute Iron and Steel Greenhouse Gas Protocol; a carbon emission intensity of less than 800 kilograms of CO₂ per ton of the iron metal, when determined according to the Commission Implementing Regulation (EU) 2018/2066; the iron particle has a specific total embedded emissions of less than 0 tons of CO₂ per ton of the iron metal, when determined according to the European Union simplified bubble approach method for determining specific embedded emissions under the Carbon Border Adjustment Mechanism; or a combination thereof.

The electrochemical reactor may operate with a suitable fluid flow, which may be varied based on operating conditions. The fluid flow may be a laminar flow, a turbulent flow, or a combination thereof. The fluid flow may be present as a flow rate. Any suitable flow rate may be used. The flow rate may include, but is not limited to, at least 0.01 liters per minute per square meter of cathode area (L/min/m²), for example, 0.05 to 5 L/min/m², or 0.1 to 2.5 L/min/m².

The electrochemical cell of the electrochemical reactor may be a recirculating cell, where the anolyte stream is recirculating through the cell and the catholyte stream is recirculated through the cell. In some embodiments, the electrochemical reactor may be configured to provide a continuous flow of the catholyte stream, the anolyte stream, or a combination thereof through the electrochemical cell.

In some embodiments, the electrochemical reactor may be configured to electrochemically reduce at least 10 wt % of the iron-containing feedstock with each recirculation pass of the catholyte stream through the catholyte channel, based on a total amount of the iron-containing feedstock in the catholyte stream. For example, the electrochemical reactor may be configured to electrochemically reduce at least 15 wt %, preferably at least 30 wt % of the iron-containing feedstock with each recirculation pass of the catholyte stream through the catholyte channel, based on the total amount of the iron-containing feedstock in the catholyte stream.

In some embodiments, the electrochemical reactor may further include an anolyte stream reservoir and an anolyte pump for recirculating the anolyte stream through the electrochemical cell. When the electrochemical reactor includes a plurality of electrochemical cells as described below, the anolyte stream reservoir and the anolyte pump may be configured to recirculate the anolyte stream through any number of the electrochemical cells. The electrochemical reactor may include more than one anolyte pump.

In some embodiments, the electrochemical reactor may further include a catholyte stream reservoir and a catholyte pump for recirculating the catholyte stream through the electrochemical cell. When the electrochemical reactor includes a plurality of electrochemical cells as described below, the catholyte stream reservoir and the catholyte pump may be configured to recirculate the catholyte stream through any number of the electrochemical cells. The electrochemical reactor may include more than one catholyte pump.

In some embodiments, the electrochemical reactor may be configured to flow the catholyte stream through the catholyte channel in a unidirectional flow from a region of the catholyte channel that is upstream of the cathode to a region of the catholyte channel that is downstream of the cathode. For example, the electrochemical reactor may be configured to flow the catholyte stream through the catholyte channel in a unidirectional flow from a region of the catholyte channel that is upstream of the cathode to a region of the catholyte channel that is downstream of the cathode during reduction of the iron containing feedstock to the iron particle.

In some embodiments, the electrochemical reactor may be configured to flow the anolyte stream through the anolyte channel in a unidirectional flow from a region of the anolyte channel that is upstream of the anode to a region of the anolyte channel that is downstream of the anode. For example, he electrochemical reactor may be configured to flow the anolyte stream through the anolyte channel in a unidirectional flow from a region of the anolyte channel that is upstream of the anode to a region of the anolyte channel that is downstream of the anode during oxidation of the chloride anions to the chlorine gas.

In some embodiments, the electrochemical reactor may further include a gas separation unit that is in fluid communication with the anolyte channel. The gas separation unit may be configured to separate at least a portion of the chlorine gas from the anolyte stream.

In some embodiments, the electrochemical reactor may further include an iron metal separation unit that is in fluid communication with the catholyte channel. The iron metal separation unit may be configured to separate the iron particle from the catholyte stream. For example, the iron metal separation unit may be configured to separate at least a portion of the iron particle from the catholyte stream.

The electrochemical reactor may be operated at a temperature of 50° C. to 140° C., preferably 70° C. to 110° C., more preferably 85° C. to 110° C. For example, the catholyte stream and/or the anolyte stream may be at a temperature of 50° C. to 140° C., preferably 70° C. to 110° C., more preferably 85° C. to 110° C. before the catholyte stream and/or the anolyte stream is introduced to the electrochemical reactor, such that the temperature of the catholyte stream and/or the anolyte stream in the electrochemical reactor may be 50° C. to 140° C., preferably 70° C. to 110° C., more preferably 85° C. to 110° C. The operating temperature of the electrochemical reactor may refer to the temperature during which the magnetic field is applied to the electrochemical reactor.

The operating temperature of the catholyte stream and/or the anolyte stream in the electrochemical reactor may be controlled through any one or more of a variety of means, including, for example, heat exchange, an immersion heating element, an in-line heating device (e.g., a heat exchanger), or the like, preferably coupled with one or more feedback temperature control means for efficient process control. The operating temperature of the catholyte stream and/or the anolyte stream in the electrochemical reactor may be achieved through self-heating of the electrochemical reactor due to heat generation associated with operating at less than 100% energy efficiency. In the case of self-heating, a cooling system may be implemented to prevent the electrochemical cell from reaching temperatures greater than the optimal operating range.

In some embodiments, the electrochemical reactor may further include a voltage source that is electrically connected to the anode and the cathode. The voltage source may be configured to apply a voltage to the electrochemical cell to provide the chlorine gas and the iron particle.

In some embodiments, the voltage of the electrochemical cell may be from 1.5 to 5.0 Volts (V), preferably from 1.6 to 2.9 V, and more preferably from 1.7 to 2.8 V. In still other embodiments, the voltage of the electrochemical cell may be from 2.6 to 5.0 V, or from 2.8 to 4.0 V. The mechanism for selecting the cell voltage within the electrochemical cell will vary in accordance with various exemplary aspects and embodiments as described herein. Moreover, the overall cell voltage achievable is dependent upon a number of other interrelated factors, including reaction chemistry, electrode spacing, the configuration and materials of construction of the electrodes, the configuration and materials of construction of the separators, the catholyte stream and the anolyte stream concentrations and iron concentration in the catholyte stream, current density, the catholyte stream and the anolyte stream temperatures, and, to a smaller extent, the nature and amount of any additives to the electrochemical process (such as, for example, flocculants, surfactants, or the like).

In some embodiments, a current density at the cathode for the reduction of the iron-containing feedstock may be 40 to 5,000 milliamperes per square centimeter (mA/cm²), preferably 150 to 1,000 mA/cm². In some embodiments, the current density at the cathode may be selected to promote the formation of iron dendrites at the surface of the cathode. The current density may be periodically pulsed, modulated, or a combination of pulsing and modulation used to control the iron metal dendrite growth or to limit the competing HER at the cathode.

In the electrochemical reactor, the source of the magnetic field (which is also referred to herein as the “magnetic field source”) is positioned in proximity to the cathode of the electrochemical cell. The source of the magnetic field is configured to generate a magnetic field at the surface(s) of the cathode that is in contact with the catholyte stream. When the magnetic field is applied at the surface(s) of the cathode, the iron-containing feedstock is electrochemically reduced to an iron particle at the surface(s) of the cathode. In some embodiments, the source of the magnetic field may be positioned in proximity to the cathode and configured to provide a magnetic field at the surface of the cathode that is at least 0.025 Tesla, preferably 0.05 to 10 Tesla, more preferably 0.05 to 1 Tesla.

Any suitable source of a magnetic field may be used to generate the magnetic field at the surface of the cathode. In some embodiments, the source of a magnetic field includes a permanent magnet, an electromagnet, an electropermanent magnet, or a combination thereof.

Preferably, the source of a magnetic field includes an electromagnet. For example, the source of the magnetic field may include an electromagnet, and the electromagnet may be positioned adjacent to the cathode and opposite to the catholyte stream.

In some embodiments, the source of the magnetic field may be configured to provide a modulated magnetic field.

In some embodiments, the magnetic field source may be positioned external to the catholyte channel, such that the source of a magnetic field does not contact the catholyte stream. In other embodiments, at least a portion of the magnetic field source may be positioned within the catholyte channel, such that at least a portion of the magnetic field source may be in physical contact with the catholyte stream. For example, at least a portion of the magnetic field source that is in contact with the catholyte stream may be enclosed within a protective sheath to prevent corrosion from the catholyte stream. In some embodiments, a portion of the magnetic field source may be positioned within the catholyte channel including the catholyte stream, and the source may be enclosed within a protective sheath. Exemplary materials that may be used to provide the protective sheath to the magnet device include, for example, a polymeric material such as a polycarbonate or a polyethylene film, a metal-containing material (e.g., such as those having a similar composition to the cathode current collector), or a combination thereof.

In some embodiments, the electrochemical reactor may further include an additional source of a magnetic field (e.g., an additional magnetic field source or a second magnetic field source) that is positioned in proximity to (e.g., adjacent to) the anode. The electrochemical cell may be disposed between the source of a magnetic field and the additional source of a magnetic field. The electrochemical reactor may be configured to electrochemically reduce the iron-containing feedstock to the iron particle at the surface of the cathode in a magnetic field provided by the source and the additional source. For example, the source and the additional source may be configured to provide a magnetic field at the surface of the cathode that is at least 0.025 Tesla, preferably 0.05 to 10 Tesla, more preferably 0.05 to 1 Tesla. In some embodiments, the source and the additional source may be configured to provide a magnetic field at the surface of the cathode that is at least 0.025 Tesla, preferably 0.05 to 10 Tesla, more preferably 0.05 to 1 Tesla.

The additional magnetic field source may be a field generating device or a field propagating device. For example, the additional magnetic field source may be a field generating device, wherein the additional magnetic field source includes a permanent magnet, an electromagnet, an electropermanent magnet, or a combination thereof. In other embodiments, the additional magnetic field source may be a field propagating device. The magnetic field sources are described in further detail hereinbelow.

As used herein, a “field generating device” refers to a magnetic field source that produces a magnetic field, which can be achieved using a permanent magnet, an electromagnet, or an electropermanent magnet. As used herein, a “field propagating device” refers to a magnetic field source with a high magnetic susceptibility and a low magnetic coercivity (e.g., iron).

Aspects provided herein relate to generating precision magnetic fields for electrochemical cells. The magnetic field may be provided by the magnetic field source. Some aspects provide magnetic fields to keep the magnetic products under cathodic protection until being intentionally released.

According to various aspects, the magnetic fields (i.e., as provided by the magnetic field source and any additional magnet device(s)) may be used to keep magnetic products at or near the current collector surface and thereby keep the magnetic products under cathodic protection until intentionally released. The magnetic field strength, gradient, homogeneity, and/or orientation with respect to the area of interest are properties that can influence the properties of the iron product or production efficiency. Additional aspects provide magnetic field-generating devices in combination with scaled electrolyzer cell stackups, each with flexibility in terms of material selection, surface area, volume, power, spacing, orientation, target area, coupling phenomena, design, and/or dimensions to vary the generation and control of magnetic fields.

The magnet device and the corresponding magnetic field may be positioned to modify the kinetics of iron-containing feedstock transport to or assembly at the cathode (e.g., the cathode current collector), such as to enhance deposition kinetics. This may be done over an entire surface of the cathode or may be done in selected regions. In some embodiments, the magnet device may enhance deposition over substantially the entire surface of the cathode, such as by providing magnet device(s) to provide a magnetic field that is effective over the entire surface of the cathode. In some embodiments, one or more magnet devices may be positioned at particular locations of the cathode to preferentially pull materials susceptible to magnetization to those locations. Additional magnet devices may be used in conjunction with the magnetic field source.

When the additional magnetic field source is a field generating device, the magnetic field source the additional magnetic field source may be arranged in a Helmholtz configuration or an anti-Helmholtz configuration. For example, the magnetic field source and the additional magnetic field source may be arranged in a Helmholtz configuration.

In some embodiments, the source of the magnetic field may be considered a first source of a magnetic field and the additional source may be a second source of a magnetic field. In some embodiments, the electrochemical reactor may further include additional sources of a magnetic field. For example, the electrochemical reactor may include a first source and a second source, and may further include a third source of a magnetic field that is positioned adjacent the first source, and a fourth source of a magnetic field that is positioned adjacent the second source. In such a configuration, the first source and the second source may be arranged in a Helmholtz configuration, and the third source and the fourth source may be arranged in an anti-Helmholtz configuration.

In some embodiments, the source is distinct from a current collector of the cathode, such that the reduction of the iron-containing feedstock does not occur on a surface of the source. The strength of the source, and the one or more optional additional sources may be selected based on the amount of iron-containing feedstock in the catholyte stream, for example to limit the thickness of any layers formed from unreduced magnetite on the cathode current collector. In some embodiments, the orientation of the magnetic field with respect to the electrical field may be chosen to minimize the adhesion of the reduced iron metal to the cathode current collector. In some embodiments, the orientation of the magnetic field may be varied over time, for example by using a rotating magnetic field or an alternating magnetic field.

In some embodiments, the first source, the second source, and/or the one or more additional sources may be configured to be coupled sources of a magnetic field(s). As used herein, “coupled sources of a magnetic field(s)” refers to the enhancement or extension of a magnetic field through the use of two field generating devices or a single field generating device with one or more field propagating devices.

In some embodiments, the first source, the second source, and/or the one or more additional sources may be non-coupled magnetic devices. As used herein, “non-coupled magnetic field device” refers to an isolated magnetic field generating device with no other field generating devices or field propagating devices nearby, e.g., in proximity, resulting in an unamplified magnetic field.

Magnetic fields can be generated from permanent magnets, electromagnets, electropermanent magnets, or a combination thereof. In some embodiments, the first source, the second source, and optionally one or more additional sources are each independently a permanent magnet, an electromagnet, or an electropermanent magnet. Any suitable magnet may be used.

Permanent magnets are composed of paramagnetic materials that remain magnetized (have a persistent net magnetic dipole moment) at steady-state to generate a magnetic field. As used herein, a “permanent magnet” refers to an object made from a material that is magnetized and creates its own persistent magnetic field. A permanent magnet as used herein may also refer to a plurality of smaller permanent magnets that are arranged in a configuration that generates specific magnetic field gradients. Suitable permanent magnets may include, for example, neodymium iron boron (NdFeB or NIB) magnets, samarium cobalt (SmCo) magnets, alnico magnets, ceramic magnets, ferrite magnets, or a combination thereof. Some aspects provide a permanent magnetic array. Permanent magnet arrays, such as quadrupoles, include multiple permanent magnets arranged in a specific configuration to generate magnetic gradients. Quadrupoles, in particular, can provide a highly stable and adjustable magnetic field, enabling precise control over particle trajectories within the electrochemical cell(s). This arrangement has applications in various fields, including water purification, particle separation, and biochemical processes, where a controlled and uniform magnetic field is critical for efficiency and precision. Some aspects provide interpole magnets using a combination of materials with varying magnetic properties to generate high gradient magnetic fields and additionally limit the interaction of magnetic fields to only be orthogonal to the surfaces of interest.

Electromagnets generate a magnetic field by the motion of electrons within a conducting circuit, as can be described by Faraday's law of induction. As used herein, an “electromagnet” refers to a magnet wherein the magnetic field is produced by an electric current. The electromagnets can be coupled in a Helmholtz, a Maxwell, or a Helmholtz/Maxwell combination.

In some embodiments, Helmholtz coils are used to generate a homogeneous magnetic field where the coils run current in the same direction. Magnetic fields orthogonal to the working electrode enable colloidal dipole-dipole interactions which are conducive to powder production but also change the rheology of slurries. Coupling Helmholtz coils create a high degree of uniformity in the axial and transverse directions. Additionally, the strength of the magnetic field is also significant as the coil's magnetic vector fields are summative. Helmholtz coils create minimal gradients in the axial direction based on radius and separation. Although minimal, this gradient can contribute to attracting slurry particles to the working electrode. This concept can be applied to hollow coils or electromagnets. Generally, a series connection is preferential. For example, the first magnet device and the second magnet device may be arranged as a Helmholtz coil configuration, where the current in the first magnet device and the current in the second magnet device flow in the same direction.

In some aspects, Maxwell coils may be used. Maxwell coils apply similar principles as the Helmholtz coil, however, the coils run current in opposing directions. When the fields oppose each other, energy may be lost, and the arrangement can create a homogenous linear gradient. The Maxwell coil can be incorporated into an electrolyzer stack. For example, the first magnet device and the second magnet device may be arranged as a Maxwell coil configuration, where the current in the first magnet device and the current in the second magnet device flow in opposite directions.

In some embodiments, Helmholtz and Maxwell coils may be used together to create a strong gradient. Summing the fields creates a strong gradient in a homogenous manner. The strong gradient can be incorporated into an electrolyzer stack. For example, the first magnet device and the second magnet device may be arranged in a Helmholtz coil configuration and a Maxwell coil configuration. For example, the first magnet device may include two magnet subdevices, and the second magnet device may include two magnet subdevices, wherein a first magnet subdevice of the first magnet device and a first magnet subdevice of the second magnet are arranged in a Helmholtz coil configuration, and a second magnet subdevice of the first magnet device and a second magnet subdevice of the second magnet device are arranged in a Maxwell coil configuration.

In some aspects, due to wire resistance, electromagnets dissipate electrical energy as heat. This heat can be repurposed for various applications, such as heating cells or heating the catholyte stream and/or the anolyte stream or extracting work. Electrolysis reactions are often temperature-sensitive, and precise temperature control may be used to provide improved performance.

Electropermanent magnets regulate their external magnetic field by an electrical pulse and retain their magnetic state with zero power. As used herein, an “electropermanent magnet” refers to a permanent magnet wherein the external magnetic field can be switched on or off by a pulse of electric current in a wire winding around part of the magnet. For example, an electropermanent magnet may include two magnetic materials, one magnetically hard (e.g., Nd—Fe—B) and one semi-hard, (e.g., Alnico), capped at both ends with a magnetically soft material (e.g., iron) and wrapped with a coil. A current pulse of one polarity magnetizes the materials together, increasing the external flow of magnetic flux. A current pulse of the opposite polarity reverses the magnetization of the semi-hard material, while leaving the hard material unchanged. This diverts some or all of the flux to circulate inside the device, reducing the external magnetic flux. The instantaneous power draw during the switching pulse for an electropermanent magnet is an order of magnitude greater than that of an equivalent electromagnet. However, the switching time is short, often only 100 picoseconds (ps).

Also provided is an electrochemical reactor that includes a plurality of electrochemical cells, for example a plurality of electrochemical cells that are disposed between a source of a magnetic field and an additional source of a magnetic field. In some embodiments, the electrochemical cell may be a plurality of electrochemical cells. For example, the electrochemical cell may include 2 to 500 electrochemical cells, more preferably 5 to 200 electrochemical cells, or 50 to 170 electrochemical cells.

The plurality of electrochemical cells may be arranged in a bipolar configuration or a monopolar configuration.

As used herein, “bipolar” refers to a configuration wherein pairs of cathodes and anodes electrodes are electrically mated together, such that the cathode of one electrochemical cell is electrically connected to the anode of the next electrochemical cell. Current collection generally occurs over an area equivalent to the geometric area of the electrochemical cell, thereby reducing ohmic losses resulting from current collection relative to when current collection occurs in a direction perpendicular to the active area of the cell, e.g., where current is carried in a perpendicular direction and through a small cross sectional area of current collecting material. In some embodiments, the plurality of electrochemical cells may be connected in series.

As used herein, “monopolar” refers to distinct anodes and cathodes, where the cathode of one electrochemical cell is adjacent to the cathode of a next electrochemical cell, and the anode of one electrochemical cell is adjacent to the anode of a next electrochemical cell. When in a monopolar configuration, a group of electrodes may be connected in parallel. Multiple electrochemical cells may be connected in parallel.

In some embodiments, the plurality of electrochemical cells may include adjacent electrochemical cells that are arranged in a bipolar configuration. For example, when the plurality of electrochemical cells is arranged in a bipolar configuration, the electrochemical reactor may further include one or more bipolar plates that are arranged between the adjacent electrochemical cells. In some embodiments, the electrochemical reactor may include (n−1) bipolar plates, wherein n is the number of electrochemical cells in the plurality of electrochemical cells, and n is 2 to 1000, preferably 4 to 500. For example, the electrochemical reactor may include a bipolar plate between a pair of adjacent electrochemical cells, or, for example, the electrochemical reactor may include a bipolar plate between each pair of adjacent electrochemical cells.

The bipolar plates typically include an anode side that is in electrical contact with the anode of a first electrochemical cell and a cathode side that is in electrical contact with the cathode of a second electrochemical cell, wherein the first electrochemical cell and the second electrochemical cell are adjacent. In other embodiments, the bipolar plates may each include a cathode side that is in electrical contact with the cathode of a first electrochemical cell, and an anode side that is in electrical contact with the anode of a second (adjacent) electrochemical cell.

When the electrochemical reactor includes (n−1) bipolar plates, the plurality of electrochemical cells may be connected in series and configured to have a reactor potential applied between a cathode of an initial electrochemical cell and an anode of a final electrochemical cell, wherein the reactor potential is a cell potential multiplied by n, wherein n is the number of electrochemical cells in the plurality of electrochemical cells.

In some embodiments, one or more of the bipolar plates may further include an additional magnet device that is disposed between adjacent anode and cathode sides, wherein the electrochemical reactor is configured to electrochemically reduce at least a portion of the iron-containing feedstock to iron metal at the cathode of each of the electrochemical cells and in a magnetic field provided by the first magnet device, the second magnet device, the additional magnet device, or a combination thereof. For example, the electrochemical reactor may include (n/m−1) additional magnet devices, wherein m is a number of the electrochemical cells that are influenced by the magnetic field provided by a single pair of magnet devices, preferably wherein m is an integer from 1 to 10, and wherein n is a number of electrochemical cells in the plurality of electrochemical cells. When a bipolar plate further includes an additional magnetic device disposed therein, it may further include an insulator to prevent the conduction of current through the embedded magnetic device.

When the electrochemical cells are arranged in a bipolar configuration, each additional magnet device independently may be a field generating device or a field propagating device. For example, each additional magnet device independently may include a permanent magnet, an electromagnet, or an electropermanent magnet. In some embodiments, the one or more additional magnet devices may be arranged as a Helmholtz coil configuration or a Maxwell coil configuration, where such configurations may further incorporate or include the first magnet device and/or the second magnet device.

In some embodiments, the plurality of electrochemical cells may include adjacent electrochemical cells that are arranged in a monopolar configuration, such that the anodes of adjacent cells are adjacent, and the cathodes of adjacent cells are adjacent. In such an arrangement, the plurality of electrochemical cells may be connected in parallel and configured to have a same cell potential applied between the cathode and the anode of each electrochemical cell.

The plurality of electrochemical cells may be arranged in series or parallel. In some embodiments, the plurality of electrochemical cells may be connected in series and may be configured to have a reactor potential that is applied between a cathode of an initial electrochemical cell and an anode of a final electrochemical cell, wherein the reactor potential is defined as a cell potential multiplied by n, wherein n is a number of electrochemical cells in the plurality of electrochemical cells (wherein n is 2 to 1000, preferably 4 to 500). In some embodiments, the plurality of electrochemical cells may be connected in parallel and may be configured to have a same cell potential that is applied between the cathode and the anode of each electrochemical cell in the plurality of cells.

As described above, when the electrochemical cell includes a plurality of electrochemical cells, it may further include one or more internal sources of magnetic fields that are arranged between adjacent electrochemical cells, wherein the electrochemical reactor may be configured to electrochemically reduce the iron-containing feedstock to iron metal at the cathode of each of the electrochemical cells and in a magnetic field provided by the first source, the additional (second) source, the one or more internal sources, or a combination thereof. For example, the electrochemical reactor may include (n/m−1) internal sources of magnetic fields, wherein n is a number of electrochemical cells in the plurality of electrochemical cells; and m is a number of the electrochemical cells that are influenced by the magnetic field provided by a single pair of source of a magnetic fields, preferably wherein m is an integer from 1 to 10 and n is an integer from 2 to 1000, preferably 4 to 500.

When the electrochemical reactor includes a plurality of internal sources of magnetic fields, each internal source of may be independently a field generating device or a field propagating device. In some embodiments, each internal source may independently include a permanent magnet, an electromagnet, or an electropermanent magnet.

In another aspect, a method of processing an iron-containing feedstock to produce iron metal is provided. The method includes flowing the catholyte stream including the iron-containing feedstock through the electrochemical cell of the electrochemical reactor as described herein, applying a magnetic field at the cathode of the electrochemical cell, electrochemically reducing the iron-containing feedstock to produce the iron particle comprising iron metal at the cathode while the magnetic field is applied at the cathode, and collecting the iron particle from the cathode using the catholyte stream.

In some embodiments, the step of collecting may further include stopping the electrochemical reduction of the iron-containing feedstock, releasing or partially releasing the magnetic field from the cathode, and flushing the iron metal from the surface of the cathode using the catholyte stream. For example, the step of stopping the electrochemical reduction may include substantially reducing the applied voltage to the cathode. In some embodiments, the step of stopping the electrochemical reduction may include stopping the applied voltage to the cathode. In some embodiments, the step of stopping the electrochemical reduction may include reducing the voltage applied to the cathode to stop the electrochemical reduction of the iron-containing feedstock.

A continuous flow of the catholyte stream and/or the anolyte stream may be maintained through the electrochemical cell during the step of electrochemically reducing the iron-containing feedstock to the iron metal, which may maintain a substantially constant concentration of iron-containing feedstock species during the reduction step. The remaining non-reduced iron oxide and/or iron hydroxide species in the iron-containing feedstock of the catholyte stream may be separated from the iron metal collecting on the cathode current collector during the collecting step. The non-reduced iron-containing feedstock in the catholyte stream may be returned to an input catholyte stream that feeds the electrochemical cell.

In some embodiments, the method may further include treating the iron-containing feedstock prior to entering the catholyte stream to decrease a particle size of the iron-containing feedstock, to decrease an impurity amount of the iron-containing feedstock, or a combination thereof. For example, the treating may include physical grinding, selective separation by particle size or density, flotation, leaching with caustic solution, leaching with acidic solution, or a combination thereof.

Shown in FIG. 2A is a schematic diagram of an embodiment of the electrochemical reactor system. The electrochemical reactor system 1000 includes an electrochemical reactor 100, an iron-containing feedstock handling system 200, an iron product handling system 300, and a chlorine gas product handling system 400. The electrochemical reactor 100 includes a cathode 120, e.g., a working electrode, and an anode 110, e.g., a counter electrode, which are spaced apart from each other and separated by a separator 118. The cathode 120 is disposed in contact with a catholyte channel 125. The anode 110 is disposed in contact with an anolyte channel 115. The catholyte channel 125 includes a catholyte stream 160, and the anolyte channel 115 includes an anolyte stream 150. The iron-containing feedstock 135 is susceptible to magnetization. In proximity to the cathode is a source of a magnetic field 140. The magnetic field source 140 may include an electromagnet or other source of a magnetic field as provided herein. In operation, the iron-containing feedstock 135 is reduced to provide iron particles comprising iron metal 145 at the surface of the cathode 120.

The catholyte stream 160 is provided to the catholyte channel 125 of the electrochemical reactor 100 by the iron-containing feedstock handling system 200. The iron-containing feedstock handling system 200 optionally includes a mixing tank 210 for mixing a concentrated ore slurry from a concentrated ore unit 220 with a catholyte slurry from a catholyte unit 230. Optionally provided is a catholyte stream purification unit 240 providing catholyte purification. The catholyte stream purification unit 240 may optionally include a filter, may optionally control a pH or a temperature of the catholyte stream, and/or may optionally provide an additive to the catholyte stream. Any suitable catholyte additive may be used, including combinations of two or more additives. When the purification unit 240 includes a filter, the filter may be used to remove unwanted solids from the catholyte stream to provide purified the purified catholyte stream. The purified catholyte stream may be charged downstream of the catholyte stream purification unit 240 to the catholyte stream unit 230.

The anolyte stream 150 is provided to the anolyte channel 115 of the electrochemical reactor 100 by the anolyte stream handling system 400. Optionally provided is an anolyte stream purification unit 440 providing anolyte purification. The anolyte stream purification unit 440 may optionally include a filter, may optionally control a pH or a temperature of the anolyte stream, and/or may optionally provide an additive to the anolyte stream. Any suitable anolyte additive may be used, including combinations of two or more additives. The purified anolyte stream may be charged downstream of the anolyte stream purification unit 440 to the anolyte channel 115.

From the electrochemical reactor 100 a catholyte product stream 310 including the catholyte stream, and optionally the iron particle product or unreacted iron-containing feedstock, to the catholyte stream product handling system 300. The catholyte stream product handling system 300 may optionally include a separation unit 320. The separation unit 320 may be configured to separate the iron particle product from unreacted iron-containing feedstock material, and may include a magnetic separator or a physical separator. The catholyte stream product handling system 300 may optionally include a post processing unit 330. The post processing unit 330 may wash, dry, and/or densify the product. The post processing unit 330 may be fluidly connected to the separation unit 320 via product post-processing stream 280. The catholyte stream product handling system 300 may also optionally include residuals separation unit 340 configured to separate residual iron-containing feedstock from the catholyte stream. The separation unit 320 may be fluidly connected upstream to the residuals separation unit 340 via residuals separation stream 270. The residual iron-containing feedstock may be provided by the concentrated ore slurry to the concentrated ore unit 220 via ore stream 260 and the catholyte stream provided to the catholyte unit 230 via the catholyte stream 250. Additional iron-containing feedstock may be added from a feedstock source via a stream (not shown) that is connected to the ore stream 260 to make up for iron-containing feedstock converted to iron metal in the electrochemical reactor. In some embodiments, the catholyte stream may be transported to the separation unit 320, where at least a portion of the iron particles may be separated from the catholyte stream and other processing may occur as described herein, and the catholyte stream may be recirculated back to an upstream region of the catholyte channel, such as into the mixing tank 210.

On the anolyte channel side, an anolyte product stream 410 including the anolyte stream, and optionally the chlorine gas product or unreacted metal chloride, to the anolyte stream product handling system 400. The anolyte stream product handling system 400 may optionally include a separation unit 420. The separation unit 420 may be configured to separate the chlorine gas product from unreacted metal chloride, and may include liquid-gas separation system. The anolyte stream product handling system 400 may optionally include a post processing unit 430.

The post processing unit 430 may further purify the chlorine gas product. The post processing unit 430 may be fluidly connected to the separation unit 420 via product post-processing stream 380. In some embodiments, the anolyte stream may be transported to the separation unit 420, where at least a portion of the chlorine gas may be separated from the anolyte stream and other processing may occur as described herein, and the anolyte stream may be recirculated back to an upstream region of the anolyte channel 115. Additional metal chloride may be added from a metal chloride source via a stream (not shown) that is connected to the conduit 450 connecting the anolyte stream purification unit 440 to the anolyte channel 115, and to a region upstream of the anolyte channel 115 to make up for metal chloride converted to chlorine gas and metal cation in the electrochemical reactor.

Shown in FIG. 2B are graphs of voltage (arbitrary units), magnetic field (arbitrary units), ore concentration (arbitrary units), and iron concentration (arbitrary units), each versus time (arbitrary units) with corresponding schematic diagrams of the electrochemical reactor to illustrate an embodiment of the disclosed process. In a first step 2A, with the source of the magnetic field off, the catholyte stream and the iron-containing feedstock (labeled with arrow 2000) may be added to the electrochemical reactor. As shown in FIG. 2B, the iron-containing feedstock concentration increases upon addition. The source is then turned on to attract iron-containing feedstock particles to the cathode. Increasing the voltage results in reduction of the iron-containing feedstock to iron metal, indicated by the increasing content (e.g., concentration) of iron in the electrochemical reactor as shown in step 2B. Also, while illustrated to have the magnetic field on before the voltage is increased, also disclosed is an aspect in which the voltage is increased before the magnetic field is increased. In an aspect, the iron-containing feedstock may be continuously provided to the electrochemical reactor, thus the concentration of ore in the electrical corrector is constant. In an aspect, the catholyte stream and unreacted ore may exit the electrochemical reactor as shown with arrows 2010 and be recycled to the electrochemical reactor.

Harvesting the iron product may be facilitated by reducing the voltage and reducing the magnetic field, as shown in step 2C. When the magnetic field is reduced or the source is turned off, the iron metal product may release from the cathode, facilitating recovery of the product. As shown in step 2C with arrow 2020, the catholyte stream, unreacted ore, and the product may exit the electrochemical reactor for separation of the product and recycling of the unreacted ore and the catholyte stream to the electrochemical reactor. Also, the voltage may be modulated, or turned off, to select the particle characteristics of the product or to facilitate harvesting of the product. In step 2C, while illustrated to have the magnetic field decreased after the voltage is decreased, also disclosed is an aspect in which the voltage is decreased after the magnetic field is decreased or removed. Alternatively, in step 2C, the magnetic field may be stopped entirely during the harvesting step.

Also provided is a method of operating the electrochemical reactor comprising flowing the catholyte stream through the catholyte channel; flowing the anolyte stream through the anolyte channel; applying the magnetic field at the surface of the cathode; applying a voltage between the cathode and the anode to: electrochemically reduce the at least a portion of the iron-containing feedstock to produce the iron particle at the surface of the cathode while the magnetic field is applied at the cathode; and electrochemically oxidize at least a portion of the chloride anions to produce the chlorine gas at the surface of the anode; and contacting a cation of the metal chloride and a hydroxide anion to form a metal hydroxide in the catholyte stream to operate the electrochemical reactor.

The method may further include contacting the surface of the cathode with the catholyte stream to remove the iron particle from the cathode.

In some embodiments, the method may include directing the catholyte stream to an iron separation unit fluidly connected to a downstream side of the catholyte channel; separating at least a portion of the iron particle from the catholyte stream to provide a separated catholyte stream; and returning the separated catholyte stream to an upstream side of the catholyte channel.

In some embodiments, the method may include reducing the voltage to stop the electrochemical reduction of the iron-containing feedstock, decreasing the magnetic field at the cathode, and contacting the surface of the cathode with the catholyte stream to flush the iron particle from the cathode.

Still another aspect provides a method of processing an iron-containing feedstock to produce iron metal that includes continuously flowing a catholyte stream including the iron-containing feedstock through a catholyte channel of an electrochemical cell as provided herein, wherein the electrochemical cell includes an anode and a cathode. A magnetic field is applied at the cathode of the electrochemical cell, the iron-containing feedstock is electrochemically reduced to produce the iron metal on a surface of the cathode while the magnetic field is applied at the cathode, and the iron particle is collected from the surface of the cathode using the catholyte stream.

The iron particles (for example, the iron powder) that are formed in the electrochemical cell may be harvested or collected from the surface of the cathode, for example, by releasing or partially releasing the magnetic field from the surface of the cathode. Any suitable method may be used to harvest the iron product from the cathode in accordance with various aspects. The optimal harvesting mechanism will depend largely on a number of interrelated factors, primarily current density, iron concentration in the catholyte stream, the catholyte stream flow rate, and the catholyte stream temperature. Other contributing factors include the level of mixing within the electrochemical reactor, the frequency and duration of the harvesting method, and/or the presence and amount of any process additives (such as, for example, flocculant, surfactants, or the like).

In situ harvesting configurations, either by self-harvesting (described below) or by other in situ devices, may be desirable to minimize or avoid the need to remove and handle cathodes to facilitate the removal of iron metal from the electrochemical cell. Moreover, in situ harvesting configurations may advantageously permit the use of fixed electrode cell designs. As such, any number of mechanisms and configurations may be used.

Exemplary harvesting mechanisms include vibration (e.g., one or more vibration and/or impact devices affixed to one or more cathodes to displace iron metal from the cathode surface at predetermined time intervals), a pulse flow system (e.g., catholyte flow rate increased dramatically for a short time to displace iron metal from the cathode surface), use of a pulsed power supply to the cell, use of ultrasonic waves, and/or use of other mechanical displacement means to remove iron metal from the cathode surface, such as intermittent or continuous air bubbles. Alternatively, under some conditions, “self-harvest” or “dynamic harvest” may be achievable, when the catholyte flow rate is sufficient to displace iron metal from the cathode surface as it is formed, or shortly after reduction occurs.

In accordance with an aspect of an exemplary embodiment, the catholyte stream that includes an iron metal slurry from the catholyte channel may be subjected to an apparatus for separating at least a portion of the catholyte stream from the iron metal, such as, for example, a clarifier, a spiral classifier, other screw-type devices, a countercurrent decantation (CCD) circuit, a thickener, a filter, a conveyor-type device, a gravity separation device, a magnet, or other suitable apparatus.

Aspects provided herein couple the coproduct advantages of the chlor-iron process with the ability to continuously process iron oxide slurries into iron powder products. These two methods may be enhanced by suitable ore pretreatment and alkaline catholyte stream purification methods to achieve a highly differentiated and commercially viable zero-carbon ironmaking process.

Aspects also relate to achieving zero direct emissions from ironmaking while achieving cost parity with today's highly mature and exceptionally low cost carbothermic blast furnaces. Emerging electrochemical technologies are positioned to address the 7% of global CO₂ emissions stemming from iron and steelmaking, providing a long-term pathway to virtually eliminate both scope 1 and 2 emissions from this critical sector of the global economy. Low-temperature iron ore electrolysis in particular has the potential to integrate favorably with variable renewable generators by operating flexibly in response to changing electricity markets, thereby addressing scope 2 emissions. However, electrifying ironmaking without incurring a significant “green premium” remains a substantial barrier. The cost challenge is not unique to electrochemical methods. Using carbon capture and storage (CCS) to reduce BF—BOF emissions to desirable levels (<0.7 tonne CO₂ per tonne HRC steel) has been estimated to add ˜150 $/t to the production cost of hot melt Fe.

According to some aspects, the chlor-iron process, through production of valuable coproducts and low capital costs enabled by high current density and continuous powder-to-powder iron production, may reduce or eliminate the green premium for zero-carbon ironmaking. Aspects provided herein include a process to produce an iron product with zero direct non-biogenic emissions. The iron powder produced by this process has applications in steelmaking and potentially as an active material in iron-air batteries for long duration energy storage.

FIG. 3 shows output from cost and lifecycle emissions analysis for three steelmaking pathways: BF—BOF, chlor-iron+EAF, and alkaline Fe—O₂ electrolysis+EAF. The Fe—O₂ electrolysis data is included to highlight the cost and emissions advantages of the chlor-iron process over a related emerging low temperature iron electrolysis technology. The baseline cost assumptions were from ARPA-E for ore feedstock and beneficiation and EAF steelmaking, where the inlet and outlet concentrations of reactants are those typical for membrane chlor-alkali operations. To estimate capital costs for electrolytic ironmaking, a phenomenological model may be used (Stinn and Allanore [10.1149/2.F06202IF]). In this model, capital cost are the sum of three components: front end processing, electrolysis and product handling, and rectifier costs. All three components scale linearly with temperature, and electrolysis and product handling scale with the inverse of current density to the power 0.9. As such, the capital cost of alkaline iron electrolysis, with its low temperature and relatively high current density, is on the order of $1000 to $1300 per tonne annual iron production capacity. Capital costs therefore align closely with those in chlor-alkali rather than other metal electrolysis processes like high temperature Hall-Heroult (>$5000/t-Al/y) or low current density (<1000 A/m²) Cu electrowinning (˜$4000/t-Cu/y) and acid iron electrolysis. The low capital cost may lower the barrier to commercial deployment by making plant financing easier to attain.

The operating expenses for the two electrolysis processes described are dominated by electricity. For alkaline Fe-O₂+EAF processes, capex and electricity costs are nearly equivalent to the total production cost of HRC by BF—BOF. Considering the remaining cost elements, Fe—O₂+EAF process has an estimated production cost >800 $/tonne-HRC. Electricity and feedstock costs for the chlor-iron process may be higher than Fe—O₂ electrolysis. The chlor-iron cell voltage is about 1 Volts (V) greater because of the pH gradient and because the chlorine evolution reaction is 247 millivolts (mV) more positive than oxygen evolution at a pH of 2 ([10.1021/acscatal.9b01159]). Feedstock costs include NaCl brine at 40 $/t-NaCl (the typical range is 15 to 50 $/tonne-NaCl), brine treatment chemicals, and steam for evaporating water to generate the 50 wt % of NaOH product from 32 wt % generated by electrolysis ([EuroChlor, The Electrolysis process and the real costs of production]). The value of the coproducts differentiates the chlor-iron process from the alkaline Fe—O₂ process and other emerging electrolysis technologies. The calculations are based on a selling price of 150 $/tonne-Cl₂ with industry conversations suggesting delivered prices as high as 800 $/tonne today) and 325 $/tonne-NaOH (domestic prices are >500 $/tonne dry basis, down from >1000 $/tonne in the past year). An additional facet of the cost and LCA model is the utilization of NaOH for carbon dioxide removal (CDR) applications. The baseline assumption is that 65% of the caustic generated in the chlor-iron process may be used for carbon dioxide removal in applications such as ocean alkalinity enhancement, where 1 tonne of NaOH can remove ˜0.9 tonne of CO₂, and assuming a value of 30 $/tonne-CO₂. As alternative embodiments to the embodiments presented in FIG. 3, which modifies the tradeoff of NaOH used in conventional and CDR applications, achieving emissions parity with Fe-O₂+EAF steelmaking (0.6 tonne-CO₂/t-HRC) while maintaining cost parity with BF—BOF steelmaking may be achieved by utilizing 10% of produced NaOH for CDR applications while selling NaOH at 225 $/tonne and Cl₂ at 100 $/tonne for conventional use cases. Aspects demonstrate the robustness of the chlor-iron process to fluctuations in market prices of NaOH and Cl₂. Table 1 shows a comparison of the three steelmaking pathways considered above across key parameters.

TABLE 1
Parameter	BF-BOF	Alk. Fe—O2 + EAF	Chlor-Iron + EAF
Ironmaking emissions	1-2 t-CO2/t-Fe	0 t-CO2/t-Fe	0 t-CO2/t-Fe
GHG emissions*	1.4-3 t-CO2/t-HRC	0.6 t-CO2/t-HRC	−0.3 t-CO2/t-HRC
Process and product	≥15 Mt—Fe/y, 2040	No limit with O2	40 Mt—Fe/y based on current
scalability potential	(program req.)	generation	global Cl2 demand
Production cost	520 $/t-HRC	>800 $/t-HRC	519 $/t-HRC
Product	Pig iron	Iron plate (semi-	Iron powder (continuous), Cl2,
		continuous)	NaOH
t: tonne

According to some aspects, provided is the ability to offset emissions with a commodity coproduct, where the chlor-iron process does not have to rely exclusively on hydropower or expensive firmed variable renewable electricity to achieve zero or possibly net negative emissions, which may help speed transition to low carbon iron and steelmaking. The high surface area of the iron powder produced by the electrochemical process, coupled with the ability to dissolve gangue content in the caustic electrolyte, could provide a viable high purity active material for long duration iron-air batteries with minimal processing. For steelmaking applications, the targeted 95 wt % of metallic iron and 1 wt % of SiO₂ may provide advantages in the EAF process by reducing energy and flux requirements. According to some aspects, a 2.5% reduction in energy and 19% reduction in flux (assuming 50% of the charge is electrolytic iron) may be achieved by the methods described herein, resulting in a 13 $/tonne-HRC cost reduction.

Three electrolytic ironmaking technologies, all with distinct electrolytes, have reached the demonstration stage: (1) molten oxide electrolysis (MOE, >1500° C.), (2) acidic electrowinning from ferric and ferrous ionic solutions (40-80° C.), and (3) alkaline electrolysis (80-110° C.). The demonstrations of molten salt systems (500-835° C.) are limited to academia ([10.1179/174328108X293444,10.1016/j.jelechem.2012.11.027, 10.1016/j.electacta.2013.06.013]). The chlor-iron process is the only electrolytic ironmaking process that yields >1 mole of commodity products for every mole of electrons (6 moles of electrons yields 11 moles of product).

In theory, limiting current density increases with temperature because reaction kinetics and species diffusivity are both enhanced. MOE attempts to access these higher production rates to counter high capital costs [(Stinn Allanore DOI 10.1149/2.F06202IF]). One commercial venture claims a current density range from 0.3 to 10 A/cm² when paired with inert anodes and 0.4 to 50 A/cm² when paired with graphite anodes ([Australian Patent Publication No. 2022200687A1],) which would produce CO and CO₂ in a reaction similar to the Hall-Heroult process. Realization of durable, cost-effective inert anodes remains a longstanding challenge for the Al industry. The higher operation temperature of iron MOE suggests the problem will be even more stubborn, with experimental demonstrations realizing faradaic efficiencies of 25-36% at current densities on the order of 0.1-1 A/cm² ([DOI: 10.1038/nature12134, DOI 10.1007/s10800-017-1143-5, 10.1149/1.3560477, 10.1149/1.3623446]). Halogenated electrolytes may reduce operating temperature, but may also impose strict safety and maintenance requirements, along with low oxide solubility.

In comparing the relative merits of aqueous alkaline and acidic electrolysis, attention may be drawn to a Pourbaix diagram for the iron-water system at a typical iron electrowinning temperature of 80° C., as provided in FIG. 4. The potential difference between the oxygen evolution reaction and the Fe²⁺→Fe⁰ reaction is lower at pH 14. This minimizes the theoretical energy consumption of the electrolysis reaction, which could be further reduced by careful selection of anode reaction. The potential difference between the hydrogen evolution reaction and the iron reduction reaction dictates HER overpotential under operating conditions. This delta is less at pH 14 than at pH 2, implying higher achievable efficiencies at a given current density in the alkaline regime. In the acidic regime, free Fe²⁺ species may be oxidized to Fe³⁺ in air or through crossover to the counter electrode, which may then precipitate as Fe(OH)₃ sludge ([Schlesinger & Paunovich Modern Electroplating]). These phenomena may be managed by introducing an additional flow-battery-like stage to reduce Fe³⁺ to Fe²⁺ immediately before electroplating. In contrast, iron is sparingly soluble in the alkaline regime as Fe(OH)₃⁻ and Fe(OH)₄⁻, impeding oxidation state cycling ([DOI 10.1149/1.2952547, Lavelaine XIDERWIN project: electrification of primary steel production for direct CO2 emission avoidance]).

The low solubility of iron in caustic may be seen to limit accessible current densities; in practice, electrolysis of high purity Fe₂O₃ powders in 30-50 wt % NaOH can yield Faradaic efficiencies over 85% at rates up to 1.8 A/cm² ([10.1149/1.3039998s]). Rates on the order of 1 A/cm² are competitive with those observed in MOE cells, and an order of magnitude greater than the rates obtained in acidic systems (<0.1 A/cm⁻²) ([Nature, 2013, 497, 353-356; 10.1016/j.hydromet.2007.07.014]). Without wishing to be bound to theory, the anomalously high rates achieved for iron reduction in alkaline electrolytes may be attributed to a series of galvanic coupling reactions that dramatically increase solubility at the reaction front ([Allanore thesis, DOI 10.1149/1.2790285, DOI 10.1016/j.electacta.2010.02.040]). For this reason, mass transport of solid oxide particles to the interface may be critical, and faradaic efficiency may be enhanced by establishing electrical contact via forces normal to the electrode surface ([Lavelaine IERO, DOI 10.1051/metal/2009079, DOI 10.1016/j.colsurfa.2012.09.002, DOI 10.1149/1.2790285, 10.1149/1.3039998s]). According to some aspects, a method and system are provided to achieve electrical contact using magnetic attraction during the electrochemical reaction, which simultaneously improves energy efficiency and enables continuous processing of the metallic iron powder.

According to some aspects, a magnetic field gradient may be used to exert a force on the magnetic feedstock particles in the electrochemical cell, establishing electrical contact and improving faradaic efficiency. Unlike other methods that use gravity to achieve contact ([10.1051/metal/2009079, Lavelaine IERO, Siderwin final report]), magnetic attraction is compatible with traditional chlor-alkali stacks in the vertical electrode configuration, and may provide maximal buoyancy force for bubble evacuation; and magnetic attraction may reduce the oxide loading in the slurry, simplifying slurry handling sub-processes, improving catholyte conductivity, and reducing abrasion on membranes; and the iron powder product may be dynamically released from the cell without stopping or opening it, avoiding the cell degradation associated with shutdowns in the chlor-alkali industry ([Hine Handbook vol 1 and vol 4, 10.1016/j.compchemeng.2018.08.030, 10.1016/j.electacta.2014.09.024]). The powder-to-powder production process further enables other aspects of this disclosure.

According to some aspects, the chlor-iron process leverages commonalities in the alkaline iron electrolysis and the chlor-alkali process to produce high-quality iron with zero direct carbon emissions at costs competitive with BF—BOF. An advantage of the coproducts enabled in the chlor-iron process, particularly Cl₂, is that perfect faradaic efficiency for iron reduction is not required to achieve economic viability. Based on a technoeconomic model, iron production cost may be minimized when running at 85-87% Fe because of a shift in the chlor-iron ECU toward a greater relative mass fraction of coproducts. In some aspects, the chlor-iron process may be run at higher current densities relative to traditional Fe—O₂ alkaline electrolysis (and well beyond acidic electrowinning), further pushing the space-time yield and reducing capex per unit of iron in chlor-iron process. In addition, the NaOH and Cl₂ co-products can be sold as commodity chemicals, or recycled into hydrometallurgical processes for the pretreatment of commercial iron ore feedstocks, and may further enable other aspects of this disclosure.

FIG. 5 shows the interrelationship between three areas of development: valuable coproduct generation, continuous processing, and entitlement of scalable commercial feedstocks. Without being limited to theory, these may form the foundation for the chlor-iron paradigm: a practical path to zero-carbon steelmaking.

In some embodiments, the chlor-iron process may be able to achieve one or more parameters according to Table 2.

TABLE 2
Parameter	Example A	Example B	Example C
Feedstock	Ore	Ore	High purity
			iron oxide
Powder wt %	99	98	95
(g-Fe0 powder/total g-Fe0)
Powder metallization	95	92	92
(wt %, g-Fe0/g-total powder)
Silica content in Fe0 product	1	2	2
(wt % SiO2)
Current density	400	250	250
(mA/cm2)
Faradaic efficiency	87	85	83
(%)

In some embodiments, the chlor-iron process may eliminate the green premium on zero-carbon ironmaking by generating valuable coproducts. Compatibility with the coproducts of interest, NaOH and Cl₂, may be facilitated by introducing magnetic fields to increase efficiency (fore example, in the vertical configuration, but not limited thereto), and to encourage powder production for continuous processing. In some embodiments, the hydrometallurgical treatment of ores and caustic electrolytes enables the use of scalable feedstocks.

Current interruptions resulting in depolarization may lead to reverse currents in the chlor-iron process, which contaminate the caustic product, reduce chlorine yield, and corrode cathode chamber components ([Hine Handbook vol 1 and vol 4, 10.1016/j.compchemeng.2018.08.030, 10.1016/j.electacta.2014.09.024]). This may complicate integration with traditional alkaline iron electrowinning strategies, which would necessitate depolarization to extract iron plates. To overcome this obstacle, some aspects rely on continuous powder-to-powder processing methods. In some aspects, the application of magnetic field gradients during electrowinning may both improve faradaic efficiency and yield powdery deposits. FIG. 6 shows the results from a lab scale cell in which magnetite ore was converted to iron metal with an 83% current efficiency at 1000 A/m², The iron metal was collected as free powder without the need for physical stripping from the current collector. FIG. 7 compares results for both Fe₂O₃ and Fe₃O₄ reduction with and without magnetic field enhancement. In both cases, the reduction in a magnetic field dramatically increased faradaic efficiency and powder fraction, even at iron oxide concentrations of only 0.25 wt %. Without wishing to be bound to any particular theory, this advantage may be derived from the force of magnetic attraction. A small, magnetic particle with magnetic moment, m, experiences a force: F=∇m·B. The magnetic moment is related to the intrinsic material property, susceptibility (χ). Common iron-bearing phases of iron ore including magnetite (χ=2.85×10⁻⁴−1.23×10⁻³ m³ kg⁻¹), maghemite (χ=2.83-8.45×10⁻⁴ m³ kg⁻¹), and hematite (χ=0.013-3.83×10⁻⁶ m³ kg⁻¹) ([Faivre 2016]), possess actionable magnetic susceptibilities. While powdery deposits can also be produced in purely mass-transport limited conditions ([10.1149/1.3039998]), they would likely detach from the current collector and quickly self discharge (see FIG. 4). Magnetic fields keep magnetic products at the current collector surface and thereby keep them under cathodic protection until intentionally released.

In some aspects, the magnetic field strength, gradient, homogeneity, and/or orientation with respect to the area of interest may be optimized to produce iron electrochemically. Some aspects provide a finite element analysis software as shown in FIG. 8 to model a range of magnetic field-generating devices, to understand how material selection, surface area, volume, power, spacing, orientation, target area, coupling phenomena, design, and dimensions impact the generation and control of magnetic fields.

Some aspects provide custom batch cell test vehicles to study the impact of various parameters such as current density, iron oxide phase, slurry solids content, and caustic concentration and other electrolyte parameters on the morphology and Faradaic efficiency of iron oxide and iron ore reduction. Embodiments also used these test vehicles to investigate the role of magnetic fields in the reduction of hematite and magnetite feedstocks. FIG. 9 shows a photograph of a batch cell and a rendering of an improved batch test vehicle to enable application of a more uniform magnetic field across the active area. Embodiments may leverage the simplicity and robustness of batch cells to systematically study high purity iron oxide reduction to develop a comprehensive understanding of the main effects that drive powder formation with high efficiency, as well as quantify interactions between key variables.

In some embodiments, iron reduction efficiency may be determined using gravimetric analysis in combination with titration using a potentiometric method derived from ISO 16878 to determine the metallic fraction of retrieved deposits, which may be mixed with residual iron oxides and gangue minerals. Aspects may use analytical characterization techniques such as ICP-OES to determine the degree of additive incorporation in the final iron product. Additionally, other alkali hydroxides such as KOH may be included in the catholyte stream. Not only might this impact the iron reduction reaction, but it may also impact the precipitation of insoluble aluminosilicates that may inhibit iron reduction and cause membrane fouling. For example, thermodynamic simulations suggest that insoluble aluminosilicate formation occurs much less readily in KOH solutions compared to NaOH solutions. In some embodiments, the interaction of iron oxide suspensions with magnetic fields to isolate field effects from fluid dynamics in flow cells may be provided. Some embodiments provide tunable magnetic fields via current magnitude and direction to control strength, gradient, and orientation, which optionally may be coupled.

In some embodiments, the catholyte slurry may be fed into the cell in a single pass configuration. This may simplify harvesting of product iron powder and may enable quantification of the conversion rate for different feedstocks as a function of component design and operating conditions. This information may be used to inform recirculation circuits for catholyte slurry in larger prototypes.

Another aspects provides a sensors and controls scheme, as shown in FIG. 10. Some aspects provide for interlock operation and hazard mitigation due small size, confirming full system shutdown in response to controlled deviations in key signals while working with controllable volumes of hazardous materials. Some embodiments may use electrochemical methods, including chronopotentiometry and chronoamperometry, in combination with hydrogen gas sensing and metallic iron quantification to track parameters as provided in Table 2. Iron products derived from these analyses may be characterized using gravimetric analysis, metallic iron titration, SEM for morphology, and/or ICP-OES for impurity analysis. EIS and CV may be used to offer additional insight into electrochemical processes within the flow cell. A thermocouple in the cell may be used to monitor the consistency of cell temperature over time. Pressure and flow sensor measurements can be used for monitoring clogs or leaks in the system and motivate design changes to mitigate them.

Natural iron ores are typically associated with gangue minerals. These include but are not limited to quartz, SiO₂; kaolinite, Al₄(Si₄O₁₀)(OH)₈; gibbsite, Al(OH)₃; minnesotaite, (Mg,Fe)₃Si₄O₁₀(OH)₂; orthoclase, KAlSi₃O₈; stilpnomelane, (K,Na,Ca)_0.6(Mg,Fe²⁺, Fe³⁺)₆Si₈Al(O,OH)₂₄·2H₂O; albite, NaAlSi₃O₈; and pyrolusite, MnO₂ ([Lu, L. (Ed.) (2022). Iron ore: Mineralogy, processing and environmental sustainability. Woodhead Publishing. https://doi.org/10.1016/C2013-0-16476-8]). Some of these impurities are removed using beneficiation techniques like gravity concentration, magnetic separation and flotation. Even after beneficiation, the chemical composition of the iron ore feedstock is very variable and is dependent on the source. This is a challenge to the chlor-iron process since the composition of the iron ore feedstock has a direct impact on the purity and composition of the produced NaOH and metallic iron in the catholyte. This is especially true for impurities like kaolinite, gibbsite, quartz, etc. that dissolve in concentrated NaOH solutions. Additionally, some of these impurities when dissolved may react to form insoluble compounds (sodium aluminosilicates) that may passivate the electrodes and hence impact the current efficiency of the iron reduction reaction.

In order to reduce the iron ore source variable and achieve the chlor-iron feedstock specification, some embodiments provide for pretreatment and removal these impurities before iron ore is sent to the chlor-iron cell for reduction.

Any suitable iron ore feedstock may be used. In some embodiments, the iron ore feedstock may include at least two of each of magnetite, hematite, and goethite iron phases. The magnetite iron ore may come from Minnesota taconite. The hematite iron ore may be from either Canada or Brazil and the goethite iron ore may be from Australia. The iron ore feedstocks may range from low SiO₂ and Al₂O₃ to high SiO₂ and high Al₂O₃.

Iron ore feedstocks may be fully characterized for their physical and mineralogical properties. A combination of wavelength dispersive X-ray spectroscopy (WDXRF), titration, inductively coupled plasma optical emission spectroscopy (ICP-OES), and/or carbon-sulfur analyzer may be used to determine the elemental chemical composition of the different iron ore samples. X-ray diffraction (XRD) may be used to determine the phase composition and mineralogical association of the different iron ores. Optical microscopy and scanning electron microscopy with integrated energy dispersive X-ray spectroscopy (SEM-EDS) may be used to examine the micro-morphological examinations of different iron ore samples. Finally, thermal gravimetric analysis with differential scanning calorimetry (TG-DSC), particle size analysis (PSA), and Brunauer-Emmett-Teller (BET) may assist in physical characterization of the iron ores.

Simulation of the acidic and alkaline leaching of impurities contained in iron ore may be performed using OLI Studio 11.5 thermodynamic database. The simulations may be carried out in pure iron oxide and natural iron ore systems. The simulation results may be used to screen potential solvents and equilibrium conditions for impurity removal from the iron ores.

Some aspects will provide an understanding of the kinetics of the alkaline leaching of the different impurities (especially SiO₂, Al₂O₃, CaO, MgO, TiO₂, Mn, V, S, and P) from iron ore feedstocks. The conditions to be examined may include particle size of the feedstock, BET surface area, concentration(s) of alkaline lixiviants (solvents), liquid-to-solid ratio (pulp density), temperature, time, and/or mixing rate.

Some embodiments provide different acidic solvents and conditions for the removal of the different impurities from iron ore feedstocks. The conditions to be examined may include particle size of the feedstock, concentration(s) of acidic lixiviants, liquid-to-solid ratio, temperature, time, and/or mixing rate.

Some embodiments provide a fusion-water-mild acid leach for the removal of the different impurities from iron ore feedstocks. The conditions to be examined may include particle size of the feedstock, fusion temperature, time, and/or concentration of mild acid or mild alkaline solutions to be used as solvents after the fusion.

Some aspects provide a pretreatment process having an ability to modify iron ore into a desired iron ore feedstock spec.

Pretreatment processes may be compared based on a number of factors: 1) ability to modify iron ore into a desired iron ore feedstock spec. 2) performance of the pretreated iron ore in the chlor-iron process (highest efficiency), 3) cost for pretreatment, and 4) compatibility of pretreatment to the chlor-iron process.

In some embodiments, optimal slurry flow conditions may provide (1) homogeneous coverage of the current collector by iron ore particles at high flow rates to enable high conversion efficiency at high current density, (2) effective flushing of converted iron powder from the cathode chamber to enable continuous product harvesting, (3) mitigation of clogging, sedimentation in unwanted regions of the cathode chamber, and excessive agglomeration/accumulation of iron or iron ore that could lead to cell shorting.

Some aspects may include computational models to inform iron electrowinning cell design and operational parameters by developing an understanding of the rheology of the high volume fraction particulate iron systems from both an experimental and theoretical framework.

Some embodiments provide characterization hardware and experimental characterization of iron oxide and iron ore slurry rheology in the presence of magnetic fields. In previous work, the NNF lab at MIT developed a magnetorheological fixture for mounting on a research grade Controlled Stress Rheometer (FIG. 11) (Ocalan & McKinley, 2013). The design uses a Helmholtz coil to generate a uniform magnetic field (0≤B≤0.7T) that is orthogonal to the direction of shear. Some embodiments of the electrolyte cell described herein may use this same geometric configuration. The apparatus may be used for systematic measurements of the effective viscosity of the particulate slurries as functions of composition (volume fraction of iron oxide/ore powder, size of particulates, iron oxide phase), field strength, and wall shear rate. The measured rheological properties may be used as inputs to subsequent computational models.

Some embodiments provide for the characterization of ferromagnetic particle dynamics (agglomeration, surface accumulation, etc.) in the presence and absence of magnetic fields to inform the process parameters needed for continuous iron product harvesting and mitigate the risk of clogs. A continuous iron electrowinning flow cell ideally should provide the complete harvesting of iron from the cathode via fluid flushing after reduction is completed. In high volume fraction suspensions there is a strong propensity for local wall slip and/or local penetration/adsorption of sub-micron components (“fines”) into the microtexture. Some aspects may relate to the effects of wall roughness and texturing (designed to match the surface roughness and textural attributes of the electrode surfaces used in the electrolytic flow cells at Form Energy) on particle dynamics. Measurements of shear forces needed to dislodge iron particles attached to the current collector will be used to inform the fluid shear stresses and velocity profiles required for effective iron harvesting. The effect of reversing the polarity of the magnetic field to actively repel iron powder from the electrode, rather than only relying on flow shear stress, may also be described.

Some embodiments provide rheology measurements to develop computational models of iron oxide slurries to inform the design of electrowinning flow cells. These designs build on existing Brownian dynamics codes to model the thixotropic (i.e., time-dependent) and composition-dependent rheology of particulate suspensions at high volume fractions. These tools have previously been used to explore the roles of particle shape and local friction in waxy crude oil suspensions (Jamali et al., 2019; 2020) and the ability to use shear flow strength and history to target assembly of local colloidal microstructures (Helal et al., 2016). Simulation tools widely available at present do not incorporate magnetic susceptibility or polarization of the particles, nor interactions of polarized particles with an external field/field gradient. The relative magnitudes of magnetic field effects (which can be controlled by the strength of the applied field) and viscous shear stresses (which are controlled by particle size/shape and by the effective mean-field rheology of the suspension) may be parameterized by a dimensionless parameter known as the Mason number (Ocalan & McKinley, 2013; Olsen et al., 2016). Identical effects may also be observed in electrorheological suspensions (Helal et al., 2016), with electric field strengths and polarizabilities playing a similar role to magnetic polarization effects.

Some embodiments provide a code (e.g., based on COMSOL Multiphysics, but embodiments are not limited thereto) to understand the lateral migration of individual magnetically-susceptible microparticles undergoing shearing between two electrodes with an orthogonally-imposed magnetic field. The effects of nonlinear interactions between particles at higher volume fractions may be explored using in-house bespoke codes developed by MIT (FIG. 12), but the high computational costs associated with resolving many-body interactions and particle jamming preclude its use as a rapid design tool. In some aspects, exploratory calculations may be used to understand the magnitude of the yield stress σ_y(B, ϕ) that develops in the magnetized suspension at high fields (B) and large volume fractions (ϕ) and guide the scaling of key constitutive model parameters. These computations may then be used to develop a closed-form constitutive model (e.g., the Bingham or Herschel-Bulkley model) for the nonlinear shear rheology of the resulting “pasty” material as a function of composition and Mason number. Quantifying this thixotropic yield stress response is essential for designing optimal flow cell geometries, as shown previously in designing and optimizing flow battery cell designs (Chen et al., 2016; Narayanan et al., 2021). Overall, the model may calculate the trajectory and cross-stream migration of ferromagnetic particles based on the balance of forces at each time step—drag force, imposed pressure gradient, gravity, magnetic polarization force, and/or friction forces.

Some aspects provide for experimentally validating computational models by observing slurry flows in several configurations of slurry composition, flow velocity, and/or magnetic field strength. The slurry composition may be selected based on favorable electrochemical results in batch cell experiments. The experiments may use PIV to quantify the velocity fields in the slurry or video recordings to observe the motion and settling locations of magnetic particles in the cathode chamber.

In some embodiments, the cell may be optimized based on one or more optimal ranges of channel aspect ratios, particle residence times, slurry flow velocities, and/or magnetic field strengths and orientations—for electrowinning cells at different size scales.

Component specifications for flow through electrolyzer prototypes may be guided by overpotential requirements to meet energy targets. The overall cell voltage is defined by Equation 4:

$\begin{array}{cc}{E}_{\mathrm{cell}}=E_{0,a}-E_{0,c}+{\eta }_a-{\eta }_c+{\mathrm{iR}}_{\mathrm{sol},a}+{\mathrm{iR}}_{\mathrm{sol},c}+{\mathrm{iR}}_{\mathrm{sep}}+{\mathrm{iR}}_{\mathrm{hw}}& \left[4\right]\end{array}$

where E_cell is the operating voltage of the cell, E₀ is the reversible electrode potentials at the operating conditions of the cell, q is the overpotential for reaction, i is the current density, and R is the area specific resistance of the solution (sol), separator/membrane (sep), and hardware (hw). Subscripts a and c denote anodic and cathodic contributions, respectively. Under typical membrane chlor-alkali conditions, E_0,a is 1.232 V. [Hine vol. 1] Taking the reversible cathodic potential for the chlor-iron process to be 100 mV more negative than the hydrogen evolution reaction, E_0,c is −1.094 V [10.5281/zenodo.4327314], yielding a reversible chlor-iron cell potential of 2.327 V. Based on a simplified Tafel relationship, η=k log(i/i₀), and measured kinetic parameters on RuO₂/TiO₂ anodes, η_a is 69.6 mV at 250 mA/cm². [Hine vol. 1]

This analysis may allow establishing a budget for component overpotentials and resistances (FIG. 13), which may guide selection of current collector material, magnetic field properties, cell design, auxiliary system design, and/or operating conditions. Some aspects provide electrolyte treatments to include in electrolyte circulation loops to minimize membrane degradation, maintaining a low R_sep. Some aspects provide a reduced R_sep, η_c, and/or R_sol,c by preventing abrasion-related membrane damage, ensuring intimate, homogeneous contact of feedstock particles to the cathode, and minimizing solids loading in the catholyte slurry. R_sol,c may be further reduced through effective removal of dissolved gangue compounds.

In some embodiments, each chlor-iron electrolysis cell may be operated to include periodic short rests to calculate area specific resistance (ASR) and to detect pinholes in the bilayer membrane. Additional diagnostic tests, like EIS, may be conducted as needed. Faradaic efficiency may be measured for both the anode and cathode reactions using a combination of mass measurement and gas sensing. Chlorine production may be measured via an in-line chlorine sensor preceding the quench reactor, indicating anode efficiency. Since hydrogen evolution competes with iron reduction on the cathode side, instantaneous cathodic faradaic efficiency may be estimated via in-line hydrogen gas detection. Iron titration using a potentiometric method derived from ISO 16878 may be used to determine the metallic fraction of retrieved deposits, which may be mixed with residual iron oxides and gangue minerals. Total faradaic efficiency is derived from the mass of zero-valent iron. Product iron materials may be additionally characterized by ICP-OES to calculate silica content.

Aspects also provide supporting subsystems for the chlor-iron process concerned with handling and upgrading of reagents and products, namely commercially scalable ores, spent electrolyte, product iron, and product NaOH. The major inputs to the chlor-iron process include a catholyte, comprising iron ore and NaOH solution, and an anolyte, comprising acidified brine. Some aspects provide for catholyte transporting of both solid reagents and products. Separating solid reagents from products to upgrade metallized iron fraction may be accomplished through a combination of physical separation techniques, leveraging the distinct physical properties of the original ore particles and reduced iron powder. The presence of these solids and gradual leaching of gangue minerals has potential to influence properties of the product NaOH.

Some aspects provide for the safe and effective handling of product iron powders that meet particular specifications to evaluate performance in iron-air batteries. This may include the separation of product iron from iron oxide feedstocks, removal and reclamation of NaOH, establishment of safe drying procedures, and potential form factor modifications to prepare for shipping.

In some embodiments, the product iron metal may be continuously extracted from the catholyte stream as it is generated. Swift removal and washing reduces the risk of spontaneous re-oxidation in the caustic environment, which may occur in a matter of minutes after removal of cathodic protection. Separation of product iron from feedstocks may be accomplished through suitable physical or magnetic methods. In the context of electrolysis, separators could be introduced either before or after a solid/liquid separation step, where solids are diverted from the caustic NaOH steam to allow for catholyte stream purification.

Magnetic separation is widely used in iron ore beneficiation. It is enabled by the generation of strong gradients in a magnetic field, B. A small, magnetic particle with magnetic moment, m, experiences a force: F=∇m·B. Accordingly, particles can be classified based on differences in m for a given field, B. The magnetic moment is related to the intrinsic material property, susceptibility (z). Materials with high susceptibility, like iron, magnetite, and maghemite, are more strongly attracted by the magnetic force than materials with low susceptibility, like hematite, quartz, and other gangue minerals. While hematite is antiferromagnetic, possessing a non-negligible initial susceptibility of 0.013-3.83×10⁻⁶ m³ kg⁻¹ [Faivre 2016], it is easily distinguished from ferromagnetic iron (χ=25,500 m³ kg⁻¹) [DOI 10.1118/1.597854] and ferrimagnetic magnetite (χ=2.85×10⁻⁴−1.23×10⁻³ m³ kg⁻¹) [Faivre 2016]. The efficiency of magnetic separation of iron from hematite and iron from magnetite will be determined experimentally using lab-scale magnetic separation strategies with varying field gradients.

Some aspects provide for the separation of metallic iron from magnetite- and/or maghemite-based ores. For example, iron powders produced through alkaline electrolysis have distinct physical properties compared to the starting oxide, which may allow a combination of physical and magnetic separation to harvest Fe powder from solution while enabling recirculation of unreacted ore. FIG. 14 highlights microstructural observations of iron powder formed from magnetite feedstocks of differing particle size. When using feedstocks with very small particle size, on the order of 1 micron, iron crystallites grown in a magnetic field form long needles, much larger than the feedstock particle in at least one dimension. In the presence of larger feedstock particles with diameter on the order of 10 microns, iron crystallites grow as smaller polyhedra which are easily dispersed. Some aspects use these distinctions to separate iron from magnetic feedstocks, which would otherwise prohibit magnetic separation. Exemplary physical separation methods may include sieving, hydrocyclone, and/or centrifugation. These may be characterized for separation efficiency based on metallic iron fraction of the processed powder.

After separation, the isolated iron powders may be contaminated with caustic catholyte electrolytes and are washed to prevent corrosion, improve purity, and reclaim NaOH. Hydrometallurgical techniques may be used for washing of product powders. ICP and/or pH testing may be used to assess the success of washing experiments. The product may then be dried. Given the fine particle sizes of some samples (1-100 microns), the product may be expected to have properties similar to carbonyl iron powder, which is considered a combustible dust known to self-heat through exothermic oxidation when exposed to air and is handled with extreme caution.

FIG. 15 shows an exemplary flow diagram for a chlor-iron process according to one or more aspects, but embodiments are not limited thereto.

Some embodiments provide for catholyte stream and/or anolyte stream purification. For example, the NaOH used to prepare the catholyte stream may have the properties shown in Table 3, but embodiments are not limited thereto.

	TABLE 3
	NaOH	49-51%
	Na2O	38-39.5%
	NaCl	<100	ppm
	Fe	<5	ppm
	Na2CO3	<0.1%
	Na2SO4	<100	ppm
	NaClO3	<65	ppm

Some embodiments provide for purification of NaOH through the use of sodalite or similar desilication products to sequester impurities through incorporation in its zeolite-like high surface area structure.

In accordance with some aspects, retrofitting all chlor-alkali plants in the U.S. with the proposed chlor-iron process could provide 8 million metric tonnes of iron production per year, or nearly 30% of domestic iron demand. [USGS ref from ROSIE FA]

FIG. 16 shows material flows and markets for the chlor-iron process in accordance with some aspects. Electrolytic Fe has no sulfur contamination, enabling production of higher-grade steel products. Some aspects provide electrolytic iron from low-grade ores with low cost, no carbon content, and low gangue, all of which are important characteristics for a battery active material. Some embodiments may provide a high surface area powder product that can support high specific discharge capacity in battery applications. Using iron from the chlor-iron process to support long duration energy storage applications provides a synergistic opportunity to combine electrochemical ironmaking with decarbonization of the electricity sector. Variable renewable generation using long duration iron-air batteries can provide a reliable, low-carbon electricity for chlor-iron ironmaking and EAF steelmaking with high capacity factor.

This disclosure further encompasses the following aspects.

Aspect 1. An electrochemical reactor comprising a source of a magnetic field positioned in proximity to a cathode and configured to generate a magnetic field at a surface of the cathode; and an electrochemical cell comprising an anode and the cathode, wherein the electrochemical cell further comprises: a catholyte channel configured to direct a catholyte stream comprising an iron-containing feedstock to the cathode; an anolyte channel configured to direct an anolyte stream comprising a metal chloride to the anode, wherein the catholyte channel and the anolyte channel are disposed between the cathode and the anode; and a separator disposed between the catholyte channel and the anolyte channel, wherein the electrochemical reactor is configured to electrochemically oxidize chloride anions to chlorine gas at a surface of the anode, and wherein the electrochemical reactor is further configured to electrochemically reduce the iron-containing feedstock to an iron particle comprising iron metal at the surface of the cathode and in the magnetic field.

Aspect 2. The electrochemical reactor of aspect 1, wherein the electrochemical reactor is configured to electrochemically reduce the iron-containing feedstock to the iron particle at a current efficiency ratio of at least 0.75, wherein the current efficiency ratio is a ratio of charge used for the reduction of the iron-containing feedstock to a total charge provided to the cathode.

Aspect 3. The electrochemical reactor of aspect 1 or 2, wherein the iron particle comprises an iron metal powder.

Aspect 4. The electrochemical reactor of any of aspects 1 to 3, wherein the iron-containing feedstock comprises hematite, maghemite, magnetite, goethite, limonite, pyrite, red mud, or a combination thereof; preferably magnetite or hematite.

Aspect 5. The electrochemical reactor of any of aspects 1 to 4, wherein the catholyte stream comprises from 0.1 to 30 weight percent of the iron-containing feedstock, preferably 0.1 to 15 weight percent of the iron-containing feedstock, more preferably 0.1 to 5 weight percent of the iron-containing feedstock, each based on a total weight of the catholyte stream.

Aspect 6. The electrochemical reactor of any of aspects 1 to 5, wherein the catholyte stream further comprises an aqueous solution comprising a metal hydroxide, wherein the metal hydroxide comprises an alkali metal hydroxide, an alkaline earth metal hydroxide, or a combination thereof.

Aspect 7. The electrochemical reactor of aspect 6, wherein the metal of the metal hydroxide is derived from the metal of the metal chloride of the anolyte stream.

Aspect 8. The electrochemical reactor of aspect 6 or 7, wherein the metal hydroxide is present in the aqueous solution in an amount from 20 to 50 weight percent, preferably from 25 to 45 weight percent, based on a total weight of the catholyte stream.

Aspect 9. The electrochemical reactor of any of aspects 1 to 8, wherein the anolyte stream comprises an aqueous solution comprising the metal chloride, and wherein the metal chloride comprises an alkali metal chloride, an alkaline earth metal chloride, or a combination thereof.

Aspect 10. The electrochemical reactor of aspect 8, wherein the anolyte stream has a pH of less than 7, preferably from 0 to 5.

Aspect 11. The electrochemical reactor of aspect 9 or 10, wherein the metal chloride is present in the aqueous solution in an amount from 1 to 60 weight percent, preferably 5 to 50 weight percent, more preferably 10 to 40 weight percent, based on a total weight of the anolyte stream.

Aspect 12. The electrochemical reactor of any of aspects 1 to 11, wherein the anolyte stream further comprises an acid having a pKa of 2 or less.

Aspect 13. The electrochemical reactor of any of aspects 1 to 12, wherein the separator comprises an anion exchange membrane, a cation exchange membrane, an anion selective membrane, a cation selective membrane, a zwitterionic membrane, a nanoporous membrane, a polybenzimidazole-containing membrane, a polysulfone-containing membrane, a polycarboxylic-containing membrane, a polyetherketone-containing membrane, a membrane comprising a polymer of intrinsic microporosity, or a combination thereof, preferably wherein the separator is a cation selective membrane.

Aspect 14. The electrochemical reactor of any of aspects 1 to 13, wherein the separator comprises a cation-selective membrane that is permeable to an alkali metal cation, an alkaline earth metal cation, or a combination thereof.

Aspect 15. The electrochemical reactor of any of aspects 1 to 14, wherein the cathode comprises aluminum, carbon, molybdenum, copper, nickel, titanium, iron, an alloy thereof, or a combination thereof, preferably carbon, nickel, iron, an alloy thereof, or a combination thereof.

Aspect 16. The electrochemical reactor of any of aspects 1 to 15, wherein the anode comprises carbon, titanium, lead, nickel, iron, platinum, iridium, ruthenium, tantalum, niobium, zirconium, vanadium, hafnium, aluminum, tin, cobalt, antimony, tungsten, copper, an alloy thereof, an oxide thereof, or a combination thereof.

Aspect 17. The electrochemical reactor of any of aspects 1 to 16, further comprising a gas separation unit in fluid communication with the anolyte channel, wherein the gas separation unit is configured to separate at least a portion of the chlorine gas from the anolyte stream.

Aspect 18. The electrochemical reactor of any of aspects 1 to 17, further comprising an iron metal separation unit in fluid communication with the catholyte channel, wherein the iron metal separation unit is configured to separate the iron particle from the catholyte stream.

Aspect 19. The electrochemical reactor of any of aspects 1 to 18, wherein the electrochemical reactor is configured to operate at a temperature of 50° C. to 140° C., preferably 70° C. to 110° C., more preferably 85° C. to 110° C.

Aspect 20. The electrochemical reactor of any of aspects 1 to 19, further comprising a voltage source electrically connected to the anode and the cathode, wherein the voltage source is configured to apply a voltage to the electrochemical cell to provide the chlorine gas and the iron particle.

Aspect 21. The electrochemical reactor of any of aspects 1 to 20, wherein the source of the magnetic field comprises a permanent magnet, an electromagnet, an electropermanent magnet, or a combination thereof.

Aspect 22. The electrochemical reactor of any of aspects 1 to 21, wherein the source of the magnetic field is positioned in proximity to the cathode and configured to provide a magnetic field at the surface of the cathode that is at least 0.025 Tesla, preferably 0.05 to 10 Tesla, more preferably 0.05 to 1 Tesla.

Aspect 23. The electrochemical reactor of any of aspects 1 to 22, wherein the source of the magnetic field is configured to provide a modulated magnetic field.

Aspect 24. The electrochemical reactor of any of aspects 1 to 23, wherein the source of the magnetic field comprises an electromagnet, and the electromagnet is positioned adjacent to the cathode and opposite to the catholyte stream.

Aspect 25. The electrochemical reactor of any of aspects 1 to 24, further comprising an additional source of a magnetic field positioned in proximity to the anode, wherein the electrochemical cell is disposed between the source and the additional source, and wherein the electrochemical reactor is configured to electrochemically reduce at least a portion of the iron-containing feedstock to the iron particle at the surface of the cathode in a magnetic field provided by the source and the additional source.

Aspect 26. The electrochemical reactor of aspect 25, wherein the additional source is a field generating device or a field propagating device.

Aspect 27. The electrochemical reactor of aspect 25 or 26, wherein the additional source comprises a permanent magnet, an electromagnet, an electropermanent magnet, or a combination thereof.

Aspect 28. The electrochemical reactor of any of aspects 25 to 27, wherein the source of a magnetic field and the additional source of a magnetic field are arranged in a Helmholtz configuration or an anti-Helmholtz configuration.

Aspect 29. The electrochemical reactor of any of aspects 1 to 28, wherein the electrochemical cell is a plurality of electrochemical cells, preferably comprising 2 to 500 electrochemical cells, more preferably 5 to 200 electrochemical cells, or 50 to 170 electrochemical cells.

Aspect 30. The electrochemical reactor of any of aspects 1 to 29, wherein the electrochemical cell is a plurality of electrochemical cells between the source and an additional source of a magnetic field.

Aspect 31. The electrochemical reactor of any of aspects 1 to 30, wherein: the iron-containing feedstock has an average particle size of less than 20 micrometers, preferably 1 to 10 micrometers, and the iron particle has an average particle size of 50 to 1000 micrometers, preferably 50 to 200 micrometers; the iron-containing feedstock has an average particle size of 20 micrometers or greater, preferably 20 to 50 micrometers, and the iron particle has an average particle size of 50 to 1000 micrometers, preferably 50 to 200 micrometers; the iron particle has a morphology of a spheroid, a flake, a sheet, a platelet, a needle, or a combination thereof, preferably wherein the iron particle is in the form of a flowable powder or slurry; the iron-containing feedstock has a morphology of spheroid, a flake, a sheet, a platelet, or a combination thereof, preferably wherein the iron containing feedstock is in the form of a flowable powder or slurry; the iron particle has an average maximum dimension of between 0.1 and 1,000 micrometers, or has an aspect ratio of 1 to 100, preferably 1 to 20; the iron-containing feedstock has an average maximum dimension between 5 and 500 micrometers, preferably 10 to 50 micrometers, or has an aspect ratio of 1 to 100, preferably 1 to 20; the iron particle has a specific total embedded emissions of less than 0.8 tons of CO₂ per ton of the iron metal, when determined according to the European Union simplified bubble approach method for determining specific embedded emissions under the Carbon Border Adjustment Mechanism; the iron particle has a carbon emission intensity of less than 1100 kilograms of CO₂ per ton of the iron metal, when determined according to ISO 14404; the iron particle has a carbon emission intensity of less than 900 kilograms of CO₂ per ton of the iron metal, when determined according to the Intergovernmental Panel on Climate Change Methodology 2006 Guidelines for National Greenhouse Gas Inventories; the iron particle has a carbon emission intensity of less than 1500 kilograms of CO₂ per ton of the iron metal, when determined according to the 2017 World Steel Life Cycle Inventory Methodology; the iron particle has a carbon emission intensity of less than 1300 kilograms of CO₂ per ton of the iron metal, when determined according to the 2008 World Resource Institute Iron and Steel Greenhouse Gas Protocol; the iron particle has a carbon emission intensity of less than 800 kilograms of CO₂ per ton of the iron metal, when determined according to the Commission Implementing Regulation (EU) 2018/2066; the iron particle has a specific total embedded emissions of less than 0 tons of CO₂ per ton of the iron metal, when determined according to the European Union simplified bubble approach method for determining specific embedded emissions under the Carbon Border Adjustment Mechanism; or a combination thereof.

Aspect 31a. The electrochemical reactor of any of aspects 1 to 30, wherein: the iron-containing feedstock has an average particle size of less than 20 micrometers, preferably 1 to 10 micrometers, and the iron particle has an average particle size of 50 to 1000 micrometers, preferably 50 to 200 micrometers; the iron-containing feedstock has an average particle size of 20 micrometers or greater, preferably 20 to 50 micrometers, and the iron particle has an average particle size of 50 to 1000 micrometers, preferably 50 to 200 micrometers; the iron particle has a morphology of a spheroid, a flake, a sheet, a platelet, a needle, or a combination thereof, preferably wherein the iron particle is in the form of a flowable powder or slurry; the iron-containing feedstock has a morphology of spheroid, a flake, a sheet, a platelet, or a combination thereof, preferably wherein the iron containing feedstock is in the form of a flowable powder or slurry; the iron particle has an average maximum dimension of between 0.1 and 1,000 micrometers, or has an aspect ratio of 1 to 100, preferably 1 to 20; the iron-containing feedstock has an average maximum dimension between 5 and 500 micrometers, preferably 10 to 50 micrometers, or has an aspect ratio of 1 to 100, preferably 1 to 20; the iron particle has a specific total embedded emissions of less than 0.8 tons of CO₂ per ton of the iron metal, when determined according to the European Union simplified bubble approach method for determining specific embedded emissions under the Carbon Border Adjustment Mechanism; the iron particle has a carbon emission intensity of less than 1100 kilograms of CO₂ per ton of the iron metal, when determined according to ISO 14404; the iron particle has a carbon emission intensity of less than 900 kilograms of CO₂ per ton of the iron metal, when determined according to the Intergovernmental Panel on Climate Change Methodology 2006 Guidelines for National Greenhouse Gas Inventories; the iron particle has a carbon emission intensity of less than 1500 kilograms of CO₂ per ton of the iron metal, when determined according to the 2017 World Steel Life Cycle Inventory Methodology; the iron particle has a carbon emission intensity of less than 1300 kilograms of CO₂ per ton of the iron metal, when determined according to the 2008 World Resource Institute Iron and Steel Greenhouse Gas Protocol; the iron particle has a carbon emission intensity of less than 800 kilograms of CO₂ per ton of the iron metal, when determined according to the Commission Implementing Regulation (EU) 2018/2066; or a combination thereof. When the specific total embedded emissions or the carbon emission intensity is less than zero tons of CO₂ per ton of the iron metal, the process provides a net negative emission of carbon dioxide during the processing of the iron-containing feedstock to produce the iron metal. For example, under reaction conditions to produce a caustic product such as NaOH, the produced NaOH may be used for CO₂ removal from air or ocean water, enabling the possibility for net-negative emissions ironmaking.

Aspect 32. A method of operating the electrochemical reactor of any of aspects 1 to 31, the method comprising flowing the catholyte stream through the catholyte channel; flowing the anolyte stream through the anolyte channel; applying the magnetic field at the surface of the cathode; applying a voltage between the cathode and the anode to: (i) electrochemically reduce the at least a portion of the iron-containing feedstock to produce the iron particle at the surface of the cathode while the magnetic field is applied at the cathode; and (ii) electrochemically oxidize at least a portion of the chloride anions to produce the chlorine gas at the surface of the anode; and contacting a cation of the metal chloride and a hydroxide anion to form a metal hydroxide in the catholyte stream to operate the electrochemical reactor.

Aspect 33. The method of aspect 32, further comprising contacting the surface of the cathode with the catholyte stream to remove the iron particle from the cathode.

Aspect 34. The method of aspect 32 or 33, further comprising: directing the catholyte stream to an iron separation unit fluidly connected to a downstream side of the catholyte channel; separating at least a portion of the iron particle from the catholyte stream to provide a separated catholyte stream; and returning the separated catholyte stream to an upstream side of the catholyte channel.

Aspect 35. The method of any of aspects 32 to 34, further comprising: directing the anolyte stream to a liquid/gas separation unit fluidly connected to a downstream side of the anolyte channel; separating the chlorine gas from the anolyte stream to form a separated anolyte stream; and returning the separated anolyte stream to an upstream side of the anolyte channel.

Aspect 36. The method of any of aspects 32 to 35, further comprising reducing the voltage to stop the electrochemical reduction of the iron-containing feedstock, decreasing or removing the magnetic field at the cathode, and contacting the surface of the cathode with the catholyte stream to flush the iron particle from the cathode.

Aspect 37. The method of any of aspects 33 to 36, further comprising treating the iron-containing feedstock prior to entering the catholyte stream to decrease a particle size of the iron-containing feedstock, to decrease an impurity amount of the iron-containing feedstock, or a combination thereof, preferably wherein the treating comprises physical grinding, selective separation by particle size or density, flotation, leaching with caustic solution, leaching with acidic solution, or a combination thereof.

Aspect 38. The method of aspect 37, wherein the treating comprises physical grinding, selective separation by particle size or density, flotation, leaching with caustic solution, leaching with acidic solution, or a combination thereof.

Aspect 39. The method of any of aspects 32 to 36, further comprising purification of the catholyte through selective precipitation or removal of dissolved impurities liberated from the iron-containing feedstock.

The compositions, methods, and articles can alternatively comprise, consist of, or consist essentially of, any appropriate materials, steps, or components herein disclosed. The compositions, methods, and articles can additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any materials (or species), steps, or components, which are otherwise not necessary to the achievement of the function or objectives of the compositions, methods, and articles.

All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of “up to 25 wt %, or, more specifically, 5 wt % to 20 wt %”, is inclusive of the endpoints and all intermediate values of the ranges of “5 wt % to 25 wt %,” etc.). “Combinations” is inclusive of blends, mixtures, alloys, reaction products, and the like. The terms “first,” “second,” and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” and “the” do not denote a limitation of quantity and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. “Or” means “and/or” unless clearly stated otherwise. Reference throughout the specification to “some embodiments,” “an embodiment,” “an aspect,” and so forth, means that a particular element described in connection with the embodiment and/or aspect is included in at least one embodiment and/or aspect described herein, and may or may not be present in other embodiments and/or aspects. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments and/or aspects. A “combination thereof” is open and includes any combination comprising at least one of the listed components or properties optionally together with a like or equivalent component or property not listed.

Unless specified to the contrary herein, all test standards are the most recent standard in effect as of the filing date of this application, or, if priority is claimed, the filing date of the earliest priority application in which the test standard appears.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this application belongs. All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference.

While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art.

Claims

1. An electrochemical reactor, comprising: a source of a magnetic field positioned in proximity to a cathode and configured to generate a magnetic field at a surface of the cathode; andan electrochemical cell comprising an anode and the cathode,wherein the electrochemical cell further comprises: a catholyte channel configured to direct a catholyte stream comprising an iron-containing feedstock to the cathode;an anolyte channel configured to direct an anolyte stream comprising a metal chloride to the anode, wherein the catholyte channel and the anolyte channel are disposed between the cathode and the anode; anda separator disposed between the catholyte channel and the anolyte channel,wherein the electrochemical reactor is configured to electrochemically oxidize chloride anions to chlorine gas at a surface of the anode, andwherein the electrochemical reactor is further configured to electrochemically reduce the iron-containing feedstock to an iron particle comprising iron metal at the surface of the cathode and in the magnetic field.

2. The electrochemical reactor of claim 1, wherein the electrochemical reactor is configured to electrochemically reduce the iron-containing feedstock to the iron particle at a current efficiency ratio of at least 0.75, wherein the current efficiency ratio is a ratio of charge used for the reduction of the iron-containing feedstock to a total charge provided to the cathode.

3. The electrochemical reactor of claim 1, wherein the iron particle comprises an iron metal powder.

4. The electrochemical reactor of claim 1, wherein the iron-containing feedstock comprises hematite, maghemite, magnetite, goethite, limonite, pyrite, red mud, or a combination thereof; preferably magnetite or hematite.

5. The electrochemical reactor of claim 1, wherein the catholyte stream comprises from 0.1 to 30 weight percent of the iron-containing feedstock, preferably 0.1 to 15 weight percent of the iron-containing feedstock, more preferably 0.1 to 5 weight percent of the iron-containing feedstock, each based on a total weight of the catholyte stream.

6. The electrochemical reactor of claim 1, wherein the catholyte stream further comprises an aqueous solution comprising a metal hydroxide, wherein the metal hydroxide comprises an alkali metal hydroxide, an alkaline earth metal hydroxide, or a combination thereof.

7. The electrochemical reactor of claim 6, wherein the metal of the metal hydroxide is derived from the metal of the metal chloride of the anolyte stream.

8. The electrochemical reactor of claim 6, wherein the metal hydroxide is present in the aqueous solution in an amount from 20 to 50 weight percent, preferably from 25 to 45 weight percent, based on a total weight of the catholyte stream.

9. The electrochemical reactor of claim 1, wherein the anolyte stream comprises an aqueous solution comprising the metal chloride, andwherein the metal chloride comprises an alkali metal chloride, an alkaline earth metal chloride, or a combination thereof.

10. The electrochemical reactor of claim 8, wherein the anolyte stream has a pH of less than 7, preferably from 0 to 5.

11. The electrochemical reactor of claim 9, wherein the metal chloride is present in the aqueous solution in an amount from 1 to 60 weight percent, preferably 5 to 50 weight percent, more preferably 10 to 40 weight percent, based on a total weight of the anolyte stream.

12. The electrochemical reactor of claim 1, wherein the anolyte stream further comprises an acid having a pKa of 2 or less.

13. The electrochemical reactor of claim 1, wherein the separator comprises an anion exchange membrane, a cation exchange membrane, an anion selective membrane, a cation selective membrane, a zwitterionic membrane, a nanoporous membrane, a polybenzimidazole-containing membrane, a polysulfone-containing membrane, a polycarboxylic-containing membrane, a polyetherketone-containing membrane, a membrane comprising a polymer of intrinsic microporosity, or a combination thereof, preferably wherein the separator is a cation selective membrane.

14. The electrochemical reactor of claim 1, wherein the separator comprises a cation-selective membrane that is permeable to an alkali metal cation, an alkaline earth metal cation, or a combination thereof.

15. The electrochemical reactor of claim 1, wherein the cathode comprises aluminum, carbon, molybdenum, copper, nickel, titanium, iron, chromium, an alloy thereof, or a combination thereof, preferably carbon, nickel, iron, chromium, an alloy thereof, or a combination thereof.

16. The electrochemical reactor of claim 1, wherein the anode comprises carbon, titanium, lead, nickel, iron, platinum, iridium, ruthenium, tantalum, niobium, zirconium, vanadium, hafnium, aluminum, tin, cobalt, antimony, tungsten, copper, an alloy thereof, an oxide thereof, or a combination thereof.

17. The electrochemical reactor of claim 1, further comprising a gas separation unit in fluid communication with the anolyte channel, wherein the gas separation unit is configured to separate at least a portion of the chlorine gas from the anolyte stream.

18. The electrochemical reactor of any of claim 1, further comprising an iron metal separation unit in fluid communication with the catholyte channel, wherein the iron metal separation unit is configured to separate the iron particle from the catholyte stream.

19. The electrochemical reactor of claim 1, wherein the electrochemical reactor is configured to operate at a temperature of 50° C. to 140° C., preferably 70° C. to 110° C., more preferably 85° C. to 110° C.

20. The electrochemical reactor of claim 1, further comprising a voltage source electrically connected to the anode and the cathode, wherein the voltage source is configured to apply a voltage to the electrochemical cell to provide the chlorine gas and the iron particle.

21. The electrochemical reactor of claim 1, wherein the source of the magnetic field comprises a permanent magnet, an electromagnet, an electropermanent magnet, or a combination thereof.

22. The electrochemical reactor of claim 1, wherein the source of the magnetic field is positioned in proximity to the cathode and configured to provide a magnetic field at the surface of the cathode that is at least 0.025 Tesla, preferably 0.05 to 10 Tesla, more preferably 0.05 to 1 Tesla.

23. The electrochemical reactor of claim 1, wherein the source of the magnetic field is configured to provide a modulated magnetic field.

24. The electrochemical reactor of claim 1, wherein the source of the magnetic field comprises an electromagnet, andthe electromagnet is positioned adjacent to the cathode and opposite to the catholyte stream.

25. The electrochemical reactor of claim 1, further comprising an additional source of a magnetic field positioned in proximity to the anode, wherein the electrochemical cell is disposed between the source and the additional source, and wherein the electrochemical reactor is configured to electrochemically reduce at least a portion of the iron-containing feedstock to the iron particle at the surface of the cathode in a magnetic field provided by the source and the additional source.

26. The electrochemical reactor of claim 25, wherein the additional source is a field generating device or a field propagating device.

27. The electrochemical reactor of claim 25, wherein the additional source comprises a permanent magnet, an electromagnet, an electropermanent magnet, or a combination thereof.

28. The electrochemical reactor of claim 1, wherein the source of a magnetic field and the additional source of a magnetic field are arranged in a Helmholtz configuration or an anti-Helmholtz configuration.

29. The electrochemical reactor of claim 1, wherein the electrochemical cell is a plurality of electrochemical cells, preferably comprising 2 to 500 electrochemical cells, more preferably 5 to 200 electrochemical cells, or 50 to 170 electrochemical cells.

30. The electrochemical reactor of any of claim 1, wherein the electrochemical cell is a plurality of electrochemical cells between the source and an additional source of a magnetic field.

31. The electrochemical reactor of claim 1, wherein: the iron-containing feedstock has an average particle size of less than 20 micrometers, preferably 1 to 10 micrometers, and the iron particle has an average particle size of 50 to 1000 micrometers, preferably 50 to 200 micrometers;the iron-containing feedstock has an average particle size of 20 micrometers or greater, preferably 20 to 50 micrometers, and the iron particle has an average particle size of 50 to 1000 micrometers, preferably 50 to 200 micrometers;the iron particle has a morphology of a spheroid, a flake, a sheet, a platelet, a needle, or a combination thereof, preferably wherein the iron particle is in the form of a flowable powder or slurry;the iron-containing feedstock has a morphology of spheroid, a flake, a sheet, a platelet, or a combination thereof, preferably wherein the iron containing feedstock is in the form of a flowable powder or slurry;the iron particle has an average maximum dimension of between 0.1 and 1,000 micrometers, or has an aspect ratio of 1 to 100, preferably 1 to 20;the iron-containing feedstock has an average maximum dimension between 5 and 500 micrometers, preferably 10 to 50 micrometers, or has an aspect ratio of 1 to 100, preferably 1 to 20;the iron particle has a specific total embedded emissions of less than 0.8 tons of CO2 per ton of the iron metal, when determined according to the European Union simplified bubble approach method for determining specific embedded emissions under the Carbon Border Adjustment Mechanism;the iron particle has a carbon emission intensity of less than 1100 kilograms of CO2 per ton of the iron metal, when determined according to ISO 14404;the iron particle has a carbon emission intensity of less than 900 kilograms of CO2 per ton of the iron metal, when determined according to the Intergovernmental Panel on Climate Change Methodology 2006 Guidelines for National Greenhouse Gas Inventories;the iron particle has a carbon emission intensity of less than 1500 kilograms of CO2 per ton of the iron metal, when determined according to the 2017 World Steel Life Cycle Inventory Methodology;the iron particle has a carbon emission intensity of less than 1300 kilograms of CO2 per ton of the iron metal, when determined according to the 2008 World Resource Institute Iron and Steel Greenhouse Gas Protocol;the iron particle has a carbon emission intensity of less than 800 kilograms of CO2 per ton of the iron metal, when determined according to the Commission Implementing Regulation (EU) 2018/2066;the iron particle has a specific total embedded emissions of less than 0 tons of CO2 per ton of the iron metal, when determined according to the European Union simplified bubble approach method for determining specific embedded emissions under the Carbon Border Adjustment Mechanism; ora combination thereof.

32. A method of operating the electrochemical reactor of claim 1, the method comprising: flowing the catholyte stream through the catholyte channel;flowing the anolyte stream through the anolyte channel;applying the magnetic field at the surface of the cathode;applying a voltage between the cathode and the anode to: (i) electrochemically reduce the at least a portion of the iron-containing feedstock to produce the iron particle at the surface of the cathode while the magnetic field is applied at the cathode; and(ii) electrochemically oxidize at least a portion of the chloride anions to produce the chlorine gas at the surface of the anode; andcontacting a cation of the metal chloride and a hydroxide anion to form a metal hydroxide in the catholyte stream to operate the electrochemical reactor.

33. The method of claim 32, further comprising contacting the surface of the cathode with the catholyte stream to remove the iron particle from the cathode.

34. The method of claim 32, further comprising: directing the catholyte stream to an iron separation unit fluidly connected to a downstream side of the catholyte channel;separating at least a portion of the iron particle from the catholyte stream to provide a separated catholyte stream; andreturning the separated catholyte stream to an upstream side of the catholyte channel.

35. The method of claim 32, further comprising: directing the anolyte stream to a liquid/gas separation unit fluidly connected to a downstream side of the anolyte channel;separating the chlorine gas from the anolyte stream to form a separated anolyte stream; andreturning the separated anolyte stream to an upstream side of the anolyte channel.

36. The method of claim 32, further comprising reducing the voltage to stop the electrochemical reduction of the iron-containing feedstock,decreasing or removing the magnetic field at the cathode, andcontacting the surface of the cathode with the catholyte stream to flush the iron particle from the cathode.

37. The method of claim 32, further comprising treating the iron-containing feedstock prior to entering the catholyte stream to decrease a particle size of the iron-containing feedstock, to decrease an impurity amount of the iron-containing feedstock, or a combination thereof, preferably wherein the treating comprises physical grinding, selective separation by particle size or density, flotation, leaching with caustic solution, leaching with acidic solution, or a combination thereof.

38. The method of claim 37, wherein the treating comprises physical grinding, selective separation by particle size or density, flotation, leaching with caustic solution, leaching with acidic solution, or a combination thereof.

39. The method of claim 32, further comprising purification of the catholyte through selective precipitation or removal of dissolved impurities liberated from the iron-containing feedstock.