Patent Application
20250223666
The present invention relates to a method and apparatus for continuous dissolution of a substance in a solvent.
There is present an increasing focus on mitigating climate change and reducing emissions of greenhouse gases. A vital part to achieve these goals is the electrifying of sectors presently applying fossil fuels as energy source. Many sectors involve mobility such that successful electrification of these sectors relies on access to high capacity and high energy density batteries enabling them to carry along their need for electric energy.
A secondary battery converts chemical energy stored in its electrochemical cell(s) to electric energy when being discharged, and stores imposed electrical energy as chemical energy in its electrochemical cell(s) when being charged. The cyclability, power delivering capacity, charging capacity, and especially the energy density both by mass and volume, are essential factors determining the applicability and usefulness of a secondary battery. Presently, secondary lithium ion batteries (LIB) deliver the best compromise on these parameters and are subject to an intense interest from the market. The cathode of secondary lithium ion batteries often applies mixed oxides containing nickel and/or cobalt, such as e.g. LiCoO2, LiNixMnyCozO2, LiNiCoAlO2, as the electrode active material.
According the S&P Global Market Intelligence, the global production of LIB is expected to more than triple from the present (2020) annual level of 455 GWh to nearly 1500 GWh in 2025. China and Europe is expected to be the largest contributors to this growth. The expected growth in the production of LIB will thus induce a comparable growth in the battery manufactures demand for high purity nickel and/or cobalt sulphate.
Nickel and cobalt metal may be made from a solution of the metal by electroplating to produce a plate, typically a few mm up to a few centimetres thick, of high purity nickel or cobalt as a deposit on the cathode. Nickel and cobalt made by electroplating, often denoted as electrolytic nickel or electrolytic cobalt, have in general very high purity making them suitable for use as raw material for LIB manufacturing without need for refining/purification.
However, the battery manufacturers utilise high purity aqueous solutions of Ni or Co sulphates in their manufacturing process such that the electrolytic nickel or electrolytic cobalt need to be dissolved in sulphuric acid to be applicable for the lithium ion battery industry. The dissolution of solid nickel or cobalt in sulphuric acid is however a rather slow process making it relatively costly to scale up the dissolution capacity to large scale industrial production volumes.
WO 2020/129396 discloses a production method and a production device which increase the processing amount per device of nickel sulfate. A first dissolving step I and a second dissolving step II are performed in order, the first dissolving step I comprising placing nickel briquettes, sulfuric acid, and water in a leaching tank and dissolving the nickel briquettes to obtain a primary nickel sulfate solution, and the second dissolving step II comprising placing the primary nickel sulfate solution and additional nickel briquettes in a leaching adjusting tank and dissolving the additional nickel briquettes with free sulfuric acid in the primary nickel sulfate solution to obtain a nickel sulfate solution. Continuous dissolution can be achieved without increasing retention time and without unnecessarily enlarging the device by making the leaching adjusting tank serve as a concentration adjusting tank in which nickel concentration is increased and free sulfuric acid concentration is reduced and by supplying sulfuric acid and water in addition to the nickel briquettes to the leaching tank.
There is a need for a relatively rapid dissolution process for dissolving metals such as e.g. Co, Fe, Mn, or Ni in a mineral acid to make electroplated high purity metals an asset for the battery industry.
The main objective of the invention is to provide an apparatus and method for producing a rich solvent containing an intended level of solute.
A further objective of the invention is to provide an apparatus and method for producing a rich solvent containing an intended level of a dissolved metal.
It is further an objective of the invention to provide a dissolution reactor for dissolving a metal having a self-drainage of hydrogen gas which may develop.
The objectives of the invention may be obtained by serially enriching successive volumes of solvent with solute by circulating one volume of solvent between a dissolution reactor containing the solid substance to be dissolved and a storage container until said volume of solvent is made rich by reaching its intended solute concentration, and then switch to enriching a new volume of (lean) solvent supplied from another storage container by circulating the new volume of solvent between the dissolution reactor and said another storage container. The process of enriching one volume of solvent in this manner is herein referred to as one dissolution cycle. By serially performing successive dissolution cycles, it becomes possible to obtain a semi-continuous production of rich solvent by alternately switching between at least two storage containers, one being engaged in enriching its solvent content and the other being prepared for a coming dissolution cycle by being emptied of rich solvent and re-filled with lean solvent and vice-versa. This arrangement makes the dissolution process in the dissolution reactor run practically continuously and uninterrupted, while the production of rich solvent becomes a batch-resembling process since each successive volume of solvent under enrichment is not emptied from the storage container before reaching its intended concentration level of solute.
Thus, in a first aspect, the invention relates to a method for producing a rich solvent containing a dissolved compound at an intended concentration level, wherein the method comprises:
The method according to the invention may be made fully continuous in the sense that also the production of rich solvent may made continuous by applying at least three storage containers for each dissolution reactor.
Thus, in a second aspect, the invention relates to a method for producing a rich solvent containing a dissolved compound at an intended concentration level, characterised in that the method comprises:
In one example embodiment, the steps i) to iii) in the method according to the second aspect of the invention may advantageously be executed simultaneously such that one storage container is engaged in enriching its content of solvent by solute, one storage container is being emptied of rich solvent (enriched in the previous dissolution cycle, and one storage container is being filled with lean solvent to be enriched in the next dissolution cycle. In a further example embodiment, the production of rich solvent may become practically continuous and uninterrupted by adapting the flow rate of rich solvent exiting the no. 2 labelled storage container such that it takes equally long time to empty the no. 2 labelled storage container for its rich solvent as it takes to arrive at the predetermined level of solute in the no. 1 labelled storage container. The adaption of the flow rate to make the emptying of the no. 2 labelled storage container to take equally long time as the enrichment of the solvent circulating between the dissolution reactor and the no. 1 labelled storage container may be obtained by simple trial and error attempts or by estimates/calculations of the reaction kinetics between the compound to be dissolved and the solvent. Both are within the ordinary skills of a person skilled in the art.
The term “intended concentration level” as used herein refers to a concentration level of dissolved compound in the rich solvent at which the enrichment is to be terminated. The intended concentration level may be specified by a customer, it May be determined from process considerations of a downstream handling of the solvent and its solute, or any other consideration which may affect how concentrated the solute is wanted to be in the rich solvent produced by the method. The term “dissolved compound” and “solute” are used interchangeably herein.
The method according to the first and second aspect of the invention is not tied to dissolution of any specific chemical compound but may be applied to dissolve any (solid) chemical compound in any liquid solvent. One advantage of the method of the first or second aspect of the invention is that it is versatile in the sense that it may easily produce solvent solution containing any level of solute from zero to a saturated solution by simply varying the cut-off threshold value (i.e. the intended concentration level) which terminates the enrichment of a volume of solvent being and initiates a new cycle of solvent enrichment. This makes the present method suited to serve several customers having different desires for solute level.
The term “compound to be dissolved” as used herein encompasses any chemical compound being soluble in a suitable solvent. In one example embodiment, the compound to be dissolved may be a metal, such as e.g. cobalt, copper, iron, manganese, nickel, zinc, or alloys thereof. An especially preferred compound to be dissolved is electrolytic nickel or electrolytic cobalt. In one example embodiment, the compound to be dissolved may advantageously be in the form of solid particulates/pieces, or alternatively briquettes of pressed particulates of the compound. The solid particulates/pieces, or alternatively briquettes, may have characteristic dimensions of a thickness from 1 to 20 mm, preferably from 3 to 15 mm, more preferably from 4 to 10 mm, and most preferably from 5 to 7 mm, a length in the range of from 1 to 10 cm, and a width in the range of from 1 to 10 cm. In one especially preferred embodiment, the compound to be dissolved is cathode deposited electrolytic nickel or electrolytic cobalt of 1-10 mm thickness cut into pieces of a width & length of 1×1″ (2.5×2.5 cm2), preferably of 2×2″ (5.1×5.1 cm2), and most preferably of 4×4″ (10.2×10.2 cm2). However, the invention is not tied to any specific shape or dimensions of the solid compound to be dissolved. It is also envisioned dissolving plates and/or larger pieces.
The term “solvent” as used herein encompasses any liquid capable of dissolving a compound. In one example embodiment, the solvent may be an acid solvent, e.g. a mineral acid such as e.g. hydrochloric acid (HCl), nitric acid (HNO3), or sulphuric acid (H2SO4), or a mixture thereof. The solvent may in one embodiment contain additives such as e.g. hydrogen peroxide (H2O2). An especially preferred solvent is a mixture of sulphuric acid, water and hydrogen peroxide. The peroxide enhances the dissolution rate of the metallic compounds and suppresses the formation of hydrogen gas. Even though the present invention is described herein by way of an example of a dissolution process and apparatus/plant for dissolving a metal in a mineral acid, the method and apparatus/plant according to the invention may be applied for dissolving practically any solid material in any solvent.
In one example embodiment applying a mineral acid as the solvent, the strength of the lean acid solvent may advantageously be adapted such that most or nearly all mineral acid is consumed when the intended concentration level of metal is obtained. This embodiment has the advantage of forming a product, rich solvent, containing relatively little of the highly corrosive mineral acid alleviating down-stream handling of the rich acid solvent and its solute. In one especially preferred embodiment, the lean solvent is sulphuric acid diluted with water to an acid concentration corresponding to having less than 50 g/l (0.51 molar), preferably less than 25 g/l (0.25 molar), more preferably less than 10 g/l (0.11 molar), preferably less than 7.5 g/l (0.08 molar), more preferably less than 5 g/l (0.05 molar), and most preferably less than 2.5 g/l (0.03 molar) of sulphuric acid per litre solvent remaining after finishing a dissolution cycle. The adaption of the acid strength of the lean acid solvent to reach an intended maximum level of remaining acid in the rich acid solvent is a matter of basic stoichiometric considerations/calculations within the common general knowledge of a person skilled in the art. For example, since the mole weight of Ni is 58.7 g and the mole weight of H2SO4 is 98.1 g, and the molar ratio nickel: sulphuric acid in the dissolution reaction is 1:1, dissolution of 1.0 g Ni-metal in an aqueous sulphuric acid solution consumes close to 1.7 g sulphuric acid. Thus, as an example, when the intended rich solvent shall contain 100 g Ni2+ ions per litre rich solvent and about 10 g/l remaining sulphuric acid, the amount of sulphuric acid in the lean (no dissolved Ni) solvent should be approx. 180 g/l (1.8 molar). The loss of water by evaporation and added volume of eventual additives such as e.g. H2O2 may also be taken into consideration.
In one embodiment, in the case of dissolving Ni or Co in an aqueous sulphuric acid solution, the intended concentration level of solute in the enriched solvent may preferably be from 10 to 200 g/l, more preferably from 50 to 150 g/l, and most preferably from 80 to 120 g/l.
In one embodiment, the method according to the invention may further comprise tempering the solvent to an intended temperature which may be in the range of from 20 to 105° C., preferably from 70 to 100°, more preferably from 60 to 85° C., and most preferably from 70 to 80° C. The tempering may in one embodiment be obtained by passing the circulating solvent through a heat exchanger. In the case of employing a mineral acid, and especially sulphuric acid, the heating may be obtained by e.g. diluting the acid with water to the intended acid concentration such as e.g. specified above.
In one example embodiment, the method according to the first and second aspects of the invention may further comprise applying a vertically oriented counter-current dissolution reactor where compound to be dissolved is entering the dissolution reactor at the top and the solvent is entering at the bottom of the dissolution reactor and wherein the circulating solvent exits the dissolution reactor via an outlet at the upper part of the dissolution reactor.
In a third aspect, the invention relates to a process plant, comprising:
The process plant according to the third aspect is suited for executing the method of the first or the second aspect of the invention. An example embodiment of a process plant is shown schematically in
As mentioned above, it may be advantageous to apply at least three storage containers to make the production of rich solvent fully continuous. Thus in one example embodiment, shown schematically in
It may be advantageous for large scale production that the dissolution reactor comprises a plurality of dissolution chambers to increase the volume rates of produced rich solvent. This may be envisioned both for serially connected dissolution reactors or parallel connected dissolution chambers, or a combination thereof. An example embodiment comprising two serially connected dissolution chambers is schematically shown in
Thus, in one embodiment, the process plant according to the third aspect of the invention, the dissolution reactor 1 may further comprise:
In a further embodiment, the process plant according to the third aspect of the invention may further comprise:
In one embodiment, the process plant according to the third aspect of the invention may further comprise a series of four, five, six, seven or eight dissolution chamber, each having a lower inlet for a solvent, an upper inlet for solid compound, and an outlet for solvent located below the inlet and above the inlet as described above, and which is serially interconnected by having the outlet of each dissolution chamber except the last of the series fluidly connected to the inlet of the next dissolution chamber, and where the inlet of the first dissolution chamber of the series is fluidly connected to the first liquid conduit and the outlet of the last dissolution chamber of the series is fluidly connected to the second liquid conduit.
An example embodiment of a process plant according to the third aspect of the invention applying two serially connected dissolution chambers 60-1, 60-2 is shown schematically in
Without being bound by theory, it is believed that the dissolution of a solid compound in a solvent is a surface reaction being rate controlled by diffusive mass transfer of solute across the solid-liquid boundary layer, which according to Fick's first law of diffusion, is proportional to the concentration difference of solute over the boundary layer. This concentration difference is sometimes denoted as the driving force of the mass diffusion. Solvent present at the surface of the solid compound will constantly be saturated by solute since the chemical dissolution reaction rate is more than adequate to keep up with the mass diffusion controlled removal of solute. The flux of solute through the solid-liquid boundary will therefore be controlled by the concentration level of solute in the bulk solvent. Thus, the mass flux of solute passing through the solid-liquid boundary layer into the bulk solvent is highest at the initial phase of a dissolution cycle when there is no or only little solute in the bulk solvent and then slows down gradually as the solute concentration builds up in the bulk solvent. Consequently, the dissolution rate is considerably slower towards the end of a dissolution cycle as compared to the initial phase. However, the total surface area of the particles/pieces of solid compound to be dissolved may also influence the dissolution rate since the total mass transfer of solute from the solid phase into the bulk solvent equals the mass flux across the boundary layer times the total surface area of the particles/pieces of solid compound. Thus, the dissolution rate is expected, and observed to be increased by increasing the surface to volume ratio of the particles/pieces of solid compound, i.e. decreasing the particle sizes.
Furthermore, for exothermic dissolution processes, it may be advantageous to apply relatively large particulates/pieces of solid compound in the initial phase of a dissolution cycle when the driving force of the mass diffusion is relatively large to avoid excessive heat development, and then switch to smaller particulates/pieces of solid at a later stage of the dissolution cycle to maintain a relatively high dissolution rate when the driving force becomes lower. In the example embodiment with two or more serially connected dissolution reactors, this effect may simply be obtained by loading at least the first dissolution reactor with the relatively largest particulates/pieces of solid compound to be dissolved and then loading at least the last dissolution reactor of the plurality with the relatively finest particulates/pieces of solid compound to be dissolved.
Thus, in one embodiment, the process plant according to the third aspect of the invention, the dissolution reactor 1 may further comprise:
In a further embodiment, the process plant according to the third aspect of the invention may further comprise:
In one embodiment, the process plant according to the third aspect of the invention may further comprise a second solvent pump 24 located in the second 20 liquid conduit for pumping solvent between the dissolution reactor 1 and one of the first 5, second 6, or if present, the third 7 storage container.
In one example embodiment, the process plant according to the third aspect of the invention may further comprise a solvent strength monitoring unit 52 located in either the first 10 or in the second 20 liquid conduit and being adapted to measure the acid strength and/or the solute concentration level in the solvent. The invention is not tied to any specific method to measure the concentration of a solvent, but may apply any method known to be suited by the person skilled in the art. In the case of applying an acid solvent, the monitoring of the acid strength may be obtained by e.g. measuring the pH, by titration, by spectrophotometry, etc.
In one embodiment, the process plant according to the third aspect of the invention may further comprise an inlet 51 located either in the first 10, second 20 or the fourth 40 liquid conduit, or in the first 5, second 6, or the third 7 storage container, or in the first 60-1, second 60-2 or the third 60-3 dissolution chamber for adding additives to the solvent, such as e.g. hydrogen peroxide.
In one example embodiment, the process plant according to the third aspect of the invention may further comprise a heat exchanger 50 located either in the first 10 or the second 20 liquid conduit for tempering the solvent being enriched. Depending on the compound to be dissolved and solvent being applied, the solvent may advantageously be heated or cooled by the heat exchanger. For example, exothermic dissolution of metals may require cooling the solvent passing through the heat exchanger.
In one embodiment, the process plant according to third aspect of the invention, each of the first to the twelfth valves may advantageously be actuator controlled valves regulated by a logical controller unit 53 loaded with logic commands which, when executed, controls and regulates the actuators of the first to the twelfth valves such that the process plant is made to execute the method according to the first or the second aspect of the invention.
In one embodiment, the first 12, second 13, third 21, fourth 22, fifth 31, sixth 32, seventh 41 and the eighth 42, and if present, the ninth 14, tenth 23, eleventh 33, twelfth 43, thirteenth 15, fourteenth 16, and the fifteenth 17 valves are actuator controlled valves, and the first 11, and if present, the second 24 solvent pumps are actuator controlled pumps. The term “actuator controlled valve” as used herein encompasses any known and conceivable valve comprising an actuator enabling automatically shutting-off and opening a conduit from zero to full through-flow of fluid in the conduit. The valve may advantageously e.g. be a throttle valve. The actuator may advantageously be electrically driven. The term “actuator controlled pump” as used herein encompasses any known and conceivable pump able to pump a liquid in a liquid conduit.
In one embodiment, the process according to the third aspect of the invention may further comprise a logic controller unit 53 comprising a processor loaded with a logic commands which when executed regulates the actuators of the first 12, second 13, third 21, fourth 22, fifth 31, sixth 32, seventh 41 and the eighth 42, and if present, the ninth 14, tenth 23, eleventh 33, twelfth 43, thirteenth 15, fourteenth 16, and the fifteenth 17 valves and the first 11, and if present, the second 24 solvent pumps such as to executing the method according to the first or the second aspect of the invention. The term “logic control unit” as applied herein, encompasses any known and conceivable control unit able to engage the above described actuators. Examples of suited logic control unit includes but is not limited to; a PID-controller, a feed-forward (open loop) controller, a fuzzy logic controller, a process-model based controller, or combinations thereof.
In a fourth aspect, the invention relates to a dissolution reactor, wherein the dissolution reactor comprises:
In one embodiment, the container 100 is made of a metal, preferably a stainless steel alloy. However, any material having the mechanical strength to carry and hold the solid to be dissolved and the solvent may be applied. In one embodiment, the inner wall of the container 100 may be lined with a corrosion resistant lining, such as e.g. a rubber, a polyethylene, a polytetrafluoroethylene, or a vinyl ester. In one embodiment, the abrasive and corrosion resistant basket 103 and the perforated bottom plate 104 is made of a polyethylene, a polyvinyl, a vinyl ester, or a polypropylene.
In one embodiment, the lid 110 and/or the upper part 111 of the container 100 may comprise one or more openings allowing false air to enter inside the lid and dilute eventual gases developed inside the dissolution reactor.
I one embodiment, the plant according to the third aspect of the invention or the method according to the first or second aspect of the invention may apply the reactor according to the fourth aspect of the invention.
The invention will be described in more detail by way of an example embodiment of a process plant according to the third aspect of the invention intended for dissolving cuttings of electrolytic nickel in sulphuric acid.
The example embodiment is illustrated schematically in
A funnel 107 having 10 mm thick wall of polyester polymer with an inner diameter of 60 cm at its upper end and an inner diameter of 40 cm at its lower end, is suspended coaxially from the top end 111 of the container 101 and protrudes downward a distance of 55 cm into the inner space of the cylindrical container 101. This makes the lower end 109 of the funnel to downwardly protrude approx. 5 cm into the upper part 108 of the basket 103. This has the advantage that metal cuttings fed through the funnel will enter and fall into the basket 103 without being in mechanical contact with the steel container.
The dissolution reactor will typically be made ready for a series of dissolution cycles by filling the entire inner space of the basket and funnel with metal cuttings. The metal cuttings may e.g. be 1 about cm thick and a few cm of length and width and will fill the inner section of the cylindrical container from bottom to top. A fluid outlet 106 is located at a height of 160 cm (from the bottom plate 102) and will make acid solvent flowing up through the container 101 to exit the dissolution reactor at about the upper end 108 of the basket 103. Thus, metal cuttings being inside the funnel being above the upper end of the basket being dry. They will only be exposed to the acid solvent when sinking below the fluid level of the solvent.
The dissolution of nickel in an aqueous sulphuric acid solution produces hydrogen. This is potentially hazardous. Hydrogen gas is highly explosive at certain stoichiometric ratios with oxygen gas (in the air). The dissolution reactor is therefore equipped with a pivotally hinged lid 110 which covers the upper end of the cylindrical container 101 and is in fluid connection with a fan operated gas evacuation 112. The lid 100 may be opened to allow filling of metal cuttings.
If the plant is to produce solved nickel at a solute level of 100 g Ni per litre solvent, the lean acid solution (no dissolved nickel) may advantageously have a sulphuric acid concentration of 170-175 g per litre. This corresponds to a 1.75-1.80 molar sulphuric acid solution. When the solvent is enriched to its intended solute level of 100 g/l, the rest concentration of the sulphuric acid will be approx. 0.1 molar.
The operation of the process plant may be as follows: At start up, the dissolution chamber 113 is filled with nickel cuttings and both storage containers 5, 6 and the dissolution chamber 113 may be empty of solvent. In this case, the dissolution process may be initiated by the logical controller opening e.g. the seventh valve 41 to fill the first storage container 5 with lean acid solvent (sulphuric acid) from the acid supply 8, and then closing the seventh valve 41 and opening the first 12 and the third valves 21 and engage pump 11 to circulate the acid solvent through the nickel cuttings filled space of the dissolution reactor. The acid solvent is circulated through the dissolution chamber 113 until the solvent strength monitoring unit 52 reports that the acid solvent has reached its intended solute level of 100 g nickel per litre solvent. Then the first dissolution cycle is terminated by the logical controller unit 53 shutting valves 12 and 21 to disengage the first storage container.
In the meantime, the logical controller unit 53 has prepared the second storage container by opening valve 42 to fill the storage container with lean acid solvent and then close valve 42. The second storage container is therefore ready to start the second dissolution cycle the moment the first dissolution cycle terminates by simultaneously opening valves 13 and 22 when valves 12 and 21 are being closed. In this manner, the flow of acid solvent through the dissolution reactor is made continuous.
While the second storage container 6 is occupied with executing the second dissolution cycle, the first storage container 5 is made ready for the third dissolution cycle by the logical controller unit 53 opening valve 31 to empty the first storage container for rich solvent which is passed to a downstream product handling facility 9, and then closing valve 31 and opening valve 41 to refill the first storage container with lean acid solvent and then closing valve 41.
In this manner the dissolution process is made continuous by interchanging between applying the first and second storage container to enrich the acids solvent.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20220405 | Apr 2022 | NO | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/058389 | 3/30/2023 | WO |
