Patent Application
20210054515
The conduction of electrolytic processes for electrowinning nonferrous metals with lead anodes cells from sulfurous solutions in electrolytic, since the beginning of its scientific dissemination by Michael Faraday (1833), the main operational limitations of the process of electrowinning metals, have been, and still continue to be:
Inhomogeneous transfer of ionic mass, from the electrolyte to the surfaces of cathodic plates in the interelectrode spaces; and smooth, uniform compaction of deposits when operating the electrodeposition process of non-ferrous metals above its so called “limit current density”; in this condition, the process variables begin to lose the equilibriums with which acceptable deposit results are uniformly achieved, and objectionable defects and physical quality impairments of the metal plates begin to become aleatory generalized with as degraded chemical composition due to the presence of electrolyte impurities electrodeposited together with the metal.
Generation of acid mist due to the inevitable generation of anodic oxygen electrochemical decomposition of water in the electrolyte aqueous solution, according to the intensity of the direct current that passes through “insoluble” anode plates.
In prior art of the copper electrowinning processes, over time several solution strategies for each of these limitations have been proposed separately, since they represent—in each “electrolytic cell”—two different problems caused by the current intensity in the same electrochemical process; such as, on the one hand, the control and mitigation of the acid mist generated effluent, and on the other, improving at high current densities—sustained and consistently over time—the transfer of ionic mass from the electrolyte to the cathodes plate, simultaneously with homogeneous compact adhesion of the metal, from the beginning to the end of each electrodeposition cycle.
Until the present invention, both electrochemical limitations of the process have not been fully and definitively resolved simultaneously and sustainably, “as and where” these limitations originate, that is, in such a way as to enable the industrial operation of the electrowinning process at high current intensities, in permanent and stable, predictable, sustainable and “environmentally friendly manner”, with substantial decrease in acid mist generation, and taking advantage of favorable synergies existing in the actual environment of the process, which until now, have not been exploited either; on the one hand, to increase both productivity and quality simultaneously with chemical and physical electrodeposition of metal cathode plates; and on the other, to recover/recycling electrolyte aerosols, water vapor, acid; but above all, to be able to reduce, substantially and simultaneously, the consumption of energy (thermal and electrical) and water, to minimum levels compared to the consumption of current art.
In this invention, we understand by “electrolytic cell”, the electrochemical arrangement of each pair of vertical and parallel surfaces of “anodes-cathodes”, arranged facing each other at a fixed distance—which we call “unit cells”—; the “unit cells”, therefore, although they share a common electrolyte volume with a plurality of successive unit cells installed in the same electrodeposition container, in practice they DO NOT operate at the same current density despite the fact that each container—named “electrolytic cell” in current art—is powered by a stable current intensity. The above condition depends, among others, on the quality of the electrical contacts of each unit cell with the current bar of the container, and other physical conditions, which generate operational problems outside the scope of this invention.
The solutions proposed in this invention provide within a single electrolytic container different synergic sets of equipment and additional means to the unit cells in their container, designed ad-hoc to overcome each limiting problem with their respective coordinated online operation, so that both limitations are simultaneously overcome together with the operation of the process in the electrochemical reactor.
In the first place, the first limiting indicated, is a direct function of the intensity of current operated, and is determined according to the First Law of Faraday. Theoretical amount of electroplated metallic copper per reactor is calculated with Equation 1 below:
Where: m is the mass of electrodeposited copper in g, M is the molar mass of copper in g/mol, i is the current density in A/m2, A is the area of cathodic electrodeposition in m2 per reactor, t is the operating time in s, z is the valence of the ions involved in the electrochemical reaction and F is the Faraday constant in A/mol.
From this equation, it follows that, if it is desired to increase the amount of electroplated copper with a given reactor size, the increase in production can be achieved, among others, by increasing the current intensity, and also, by correcting other factors, such as example, the verticality of electrodes, decreasing the content of Fe+3 ion in electrolyte, among others.
According to U.S. Pat. No. 8,454,818 B2, the current art industrial electrolytic cell performance uses only about 30 to 40% of the theoretical limit current intensity iLimit.
This intensity iLimit (in Equation 2) is a function of the concentration of copper ions in the electrolyte (C0) and the thickness of the diffusion layer δN at the cathodes. Note that, N, is the number of ions involved in the process, F, the Faraday constant and D, the diffusion coefficient, which are all constant.
The calculation of performance at the theoretical limit current density, according to the same above patent, gives values of approximately 1000 A/m2 as a theoretical maximum; with equipment configurations and other limiting industrial practices of current art, industrial current densities only reach about maximum 300-350 A/m2.
However, sustained industrial operation at current intensities at substantially higher than those of the current art, brings with it inevitable unique occurrences of dendritic formations in the electrodeposit, whose accelerated preferential growth ends up generating severe electrical short circuits, which represent significant risks of operational and safety incidents, which also reduce both electrical efficiency and electrodeposited cathodic quality.
The industrial challenge of increasing the productivity of the electrowinning process without compromising quality and excessive electrical consumption, essentially translates into reducing the thickness of the Nernst diffusion layer in the vicinity of the cathodes; which in turn requires the implementation of a strategy with hydrodynamic means to increase in a sustained and controlled manner the relative movements between the electrolyte and the electrodes as in the present application.
In this invention, it is proposed to achieve the aforementioned by incorporating an Electrolyte Soft Agitation System “AGSEL”(1) based on the directed and controlled diffusion of rows of air bubbles of uniform characteristics, in each unit cell, in precise diameter, flow and pressure ranges to provide ad-hoc soft agitation with bubbling patterns of bubble sizes and sequences and other characteristics so that, by superimposing the diffusion of ad-hoc flows of controlled bubbles of external air to the “random natural agitation” of the electrolyte with O2 bubbles generated in the surface of the energized anodes, as a whole, generate the effective relative movements—between the electrolyte and the cathodes—to optimize the homogeneity of ion mass transfer in each unit cell, managing to sustain a higher speed of electrodeposition with optimal quality and electrical efficiency at operation with the high current intensities desired industrially.
At the same time, this invention further provides synergic sets of CAR(2) and SIRENA(3) Systems with means functionally concatenated to the overall flow rate of air bubbles that diffuse into the electrolyte for substantial decrease of inline acid mist at the current intensities to be operated. To overcome the second limitation, CAR+SIRENA use the natural O2 bubbling flow of the anodes, suitably modified by the flow rates of the complementary controlled aeration provided by AGSEL, which is directed towards the intercathode spaces of the unit cells to enhance the transfer promotion ionic mass to operated current density.
In short, with the simultaneous operation of the CAR and SIRENA with their operational variables duly adjusted to complement the anode O2 flow rate resulting from the actual current density operated, and with additional ad hoc bubbles of external electrolyte agitation air, it has been proven possible to sustain continuously balanced over time up to seven simultaneous operations on each of the unit cells of the container operated at high current densities; and also with a simultaneous substantial decrease in the resulting acid mist: the first four on-line operations are completed with the CAR System inside the container: “contain”, “confine”, “coalesce” and “recycle”, representing the abatement of a substantial portion of the acid mist flow at the same time that it is generated; and the remaining three operations in line refer to the flow of the gaseous fluid effluent outside of the electrolytic container with the SIRENA System, installed on one of the front walls of the container to “capture”, “condense” and “dilute” the level of contaminants in the gaseous fluid effluent from the container; as required by applicable environmental sustainability standards. In this invention, it is optional to continue the depuration of the effluent gaseous fluid until achieving a required safety level is achieved before being discharged to open atmosphere; but always the depuration includes capture, and recovery of electrolyte aerosols and water vapor and acid contained in the effluent gaseous fluid flow extracted from the reactor before discharging in open atmosphere.
The controlled operation of Copper electrowinning process gained by incorporating the systems of the present invention, in fact, converts the so-called “electrolytic cell” of current art, properly speaking, into the “electrochemical reactor” proposed in this invention; that is, a suitable container of current art supplied to take advantage of the unique synergistic contribution provided by thermal conservation provided by the same installation of the CAR roofing system to “contain”, “confine” and “coalesce” and “recycle” the acid mist; in fact, CAR together with retaining the electrolyte inside the container of each electrochemical reactor, also avoids the evaporation of water and loss of acid into the atmosphere of the electrolyte fed at temperatures of 45-50° C., because the removable anode covers provide insulation thermal to the contents inside the container of the coldest external environment. In particular, the thermal temperature gradient of the electrolyte is decreased in its passage from the infeed end of the container to the overflow end, maintaining the most uniform temperature on the immersed surfaces of the cathodes in operation in each unit cell, singularly favoring homogeneity of transfer of ionic mass in the intercathode spaces of the electrochemical reactor.
Summing up, the proposed invention overcomes the two historical limitations of the current art electrodeposition process, simultaneously, jointly and sustained over time in each unit cell together with its operation; and with this, “each container that install a plurality of unit cells” begins to function as an “electrochemical reactor”; and the plurality of “reactors” operated simultaneously with common process variables, constitute the “cell banks” that form an industrial plant of current art.
The concept of “unit cell” approach—which we call cell by cell—should be understood as “unit cell” to “unit cell”, which is simultaneous and synergistic in time for each limiter, and is embodied in the present invention as: “each electrochemical reactor at high current densities has incorporated the equipment and ad hoc means necessary to simultaneously and sustainably perform 2 additional functions to electrode position: substantially decrease the flow rates of its own acid mist at the same time that it is generated, and recover the condensates of the acid mist recycling them to the EW process that originated them”.
From the revision of the U.S. Pat. No. 1,032,623 granted in 1912 to C. J. Reed, where he proposes an alternative conduction of the electrodeposition process with extraction of the usable anodic gas by means of a first electrode provided with a mini O2 sensor chamber, originally, the “cell by cell” concept of solution to the problem of acid mist arose. Reed's goal—removal of the anode gas—is accomplished “anode by anode” in the process operation itself. Reed's “simultaneity” triggered—100 years later—the “unitary” solution approach at the same point of generation to substantially decrease the limiting “acid mist” proposed in this invention; This has required the development, materialization and validation of “ad hoc unit media” arranged, in up to seven successive simultaneous online operations, until the acid mist and its contamination are substantially reduced to levels with the operation of the electrochemical process itself.
Indeed, the anodic bell “ad hoc” of C. J. Reed has pioneered the concept “incorporation of a non-invasive anode-to-anode cover”—as a device or unit medium—to achieve—in a first stage—the specific purpose of substantially reducing acid mist in the same container—in simultaneously and jointly—with the normal operation of the electrolytic process: the mist is lowered at the same time that it is generated.
The acid mist effluent gaseous fluid generated by the continuous operation of the electrochemical reactor is immediately depurated, subsequently decreasing it substantially in a second in-line stage, at the container outlet, with the simultaneous operation of the Acid Mist Recycling System (SIRENA)—described in U.S. Pat. No. 9,498,745 (2016), and INAPI CL 55.012-2017 (patent application CL 2013-1789)—on the same exterior front wall of the container through which the effluent gaseous fluid is extracted.
On the other hand, it should be noted that the successful materialization and validation of the “cell by cell” solution methodology applied to the acid mist of the present invention was carried out in parallel during the 10 years of introduction of the Electrolyte Soft Aeration System to improve the transfer of copper ionic mass to the cathodic plates of the electrowinning process of the current art; In these circumstances, the technological development of the substantial decrease in acid mist from the electrowinning process was enriched by having in view the operational experience and results of the other innovation, with its many “lessons learned”, necessary to successfully materialize its continuous stable industrial operation.
The general electrolysis equation indicates what happens chemically in the electrowinning of copper: CuSO4+H2O→Cuo+½O2+H2SO4 and the following is deduced:
1 mole of Sulfate (CuSO4) generates 1 mole of O, or ½ mole of O2 or, 1 mole of electroplated Cu generates 1 mole of O, or ½ mole of O2.
This is equivalent to:
63.54 gr of Cu deposited generate 16 gr of O2, which means that the generation of →Oxygen is 0.2518 gr of O2 for each gr of Cu deposited.
According to Faraday Equation 1, the copper deposit is proportional to the circulating current intensity (Amperes). To operate a standard 60-cathode cell of the current art at 300 A/m2, a current intensity of 36,000 A is required. To operate at current intensities raised above 400-450 A/m2, 48,000 A to 54,000 A is required, with which It generates between 25% and 50% more acid mist flow rate than at 300 A/m2.
The homogeneity in the transfer of ionic mass achieving its adhesion to the cathode plates depends, substantially, on having a sufficient concentration of mass of metal ions available in the electrolyte solution, and on its temperature, a variable that is critical in the boundary layer of the cathodes; so that by maintaining an abundant stock of ionic mass ready available for electrodeposition, it is possible to effectively deposit metal ions on the cathode plate according to the intensity of the current operated. To achieve and sustain said stable conditions over time, the hydrodynamic condition of the flow rate of infeed and distribution of the electrolyte inside the container is very important; in particular, the location of the discharge points in the container and the resulting hydrodynamics of the electrolyte with respect to the electrodes. For example, to improve the mass transfer of metal ions in copper electrodeposition cells of the current art, the industry has adopted the use of forced feeding of the electrolyte through a “tuning fork” type system. The “tuning fork” configures the supply of the electrolyte inside the container, by means of an inlet pipe attached vertically on the inside to one of the front walls of the container, which extends from the edge to the bottom of the container; from there, by means of a “T”, the vertical pipe is connected with two orthogonal pipes directed towards the side walls; which by means of 90° curved elbows, both infeed pipes extend parallel lengthwise, a short distance from the container floor, for the entire length of both side walls. The electrolyte infeed of the “tuning fork” is made up of both horizontal sections close to the floor, provided with rows of ad hoc spaced holes and of appropriate diameters to discharge the electrolyte in continuous trickles from each hole, on both surfaces at the top of the “tuning fork”, pointing towards the center of the interelectrode spaces, at an angle of 45° with respect to the vertical.
For more than a decade, industrial practice in copper electrodeposition has recognized that, in order to increase the productivity of the process with higher current intensities without reducing the quality of the electrodeposition, it is necessary to improve, in parallel, the conditions for the transfer of ionic mass to cathode plates. The feeding of the electrolyte under hydraulic pressure to the container is limited by the unfavorable turbulences generated by the discharge of electrolyte jets at excessive pressures into the interelectrode spaces of the unit cells, and with this, the transfer is hindered to achieve the necessary homogeneity and adhesion with good flatness of metal compaction in all copper electrodeposits in all cathode plates.
The insufficiencies in the transfer of ionic mass to the cathode plate and non-uniformities of deposit at current intensities of the current art—which the same inventor disclosed in patent applications CL 2009-893 and CL 2011-2661—are incorporated as precedents in the present invention patent application—and are now resolved by introducing radical configuration and capability improvements to extend and improve the benefits for continuous operation at substantially high current intensities which have not been developed in this technical field to date.
A functional improvement validated in the state of the art was the installation of a system for external, orthogonal and horizontal air diffusion—over the “tuning fork”- and below the electrodes; The stable flow at controlled pressure of the system dosages air flows in the form of rows of small rising bubbles in the electrolyte, from its diffusing isobaric ring near the bottom of the container to provide “soft agitation” throughout the bulk of the container electrolyte. In the interelectrode spaces of the unit cells, the upward flow of agitation air bubbles is mixed and added to that of the “natural” O2 bubbles of the process that emerge randomly from the anodes; when mixed together they rise by their own buoyancy, and both are driven by the flow of the electrolyte feed flow forced by hydraulic pressure from the tuning fork; the rising gas volume, increased by both bubbles, sweep the cathodic and anode surfaces in each unit cell. Indeed, hydrodynamics in the intercathode spaces is enhanced, first, by the force-feeding effectiveness of the bulk of the rich electrolyte mass directed from the holes of the “tuning fork” towards the centers of the interelectrode spaces; and then, adding the contribution additional soft turbulence provided by the mixing air bubble flow rates mixed with the natural O2 bubbles in their sweep of the cathodic electrodeposition surfaces; These two correctly combined effects homogenize the movement of copper ion mass transfer and shorten the distance from the boundary layer to the cathodic surfaces. At the current intensities of current art, the result is a matching and compaction of the thickness of the metal deposit on the plates, significantly reducing nodulations. The improvement in the effectiveness and efficiency in the transfer of ionic mass must be sustained simultaneously in each intercathode space to substantially increase productivity in all the “unit cells”, improving the overall electrical efficiency of the process. The stable achievement of this key effect allows the current density supplied to each anode of the “anode—cathode” pair to be maintained at 280-300 A/m2 in the current art. The flatness characteristics, thickness uniformity of the metal plates, surface smoothness with minimal nodulation in the respective electrodeposits, in turn, visibly improve—and therefore—also the chemical purity of copper in each “unit cell”. (See CODELCO Publication—Gabriela Mistral Division, Minera Gaby, by Francisco Sanchez Pino in Copper 2013, attached)
Note: The disclosed experience was achieved, with the current intensity available at the Minera Gaby EW Plant, simply by removing a number of cathode plates from the experience cells, which operated at higher current density with the same current intensity at the Plant.
The electrolyte aeration systems described correspond to the devices and configurations disclosed in patent applications CL 2009-893 and CL 2011-2661 by the same inventor. The Electrolyte Soft Aeration Systems of the indicated technology were not intended—nor were they designed—to overcome the limitation of ion mass transfer above 280-300 A/m2.
Therefore, the indicated systems of soft aeration of the electrolyte of the current art suffer from insurmountable limitations of capacity—flow and pressure—and cannot be overcome by the diffusion of air fed by means of an isobaric diffuser ring or other means (isobaric diffuser ring also generator other functional and operational problems), and above all, due to the longitudinal arrangement of the diffusers parallel to the central axis of the container, which were designed to discharge bubbles into the bulk of the electrolyte, and specifically, do not deliver the rows of directed bubbles in the intercathode spaces where they are essential. These limitations do not guarantee benefits if the industrial EW process is to be operated continuously at currents above 330-350 A/m2 upwards.
Self-supporting isobaric structure formed by a hollow structural frame made of three materials over a hollow thermoplastic core covered with layers of resin saturated glass fiber blankets, which are covered with a thermoset polymeric composite material, forming a monolithic resistant structural compound.
Method of operation of gas bubble diffuser system comprising range of: a) gas flow referred to each cathode between 0.2-1.7 lpm per cathode and/or, b) gasification rate referred to electrolyte volume, c) gauge pressure of the gas flow, d) range of gas pressure drop, e) gas flow rate; and diffuser system.
The AGSEL System in the present application has been embodied with a transverse arrangement of the smooth agitation diffuser tubes—parallel to the anodes and cathodes of each unit cell—specifically addressed to bubble in the interelectrode space of each unit cell of the electrochemical reactor. In the current art, the diffuser tubes are arranged longitudinally and coupled to the diffuser ring, whose maximum flow rate is limited by the practical maximum 14-15 diffuser tubes parallel to the longitudinal axis of the electrochemical reactor in the typical widths of the industrial containers of the current art.
To accompany the increases in acid mist flow generated with the high currents intensities at which it is intended to operate, it is required to increase the aeration flow of the current art electrolyte agitation systems from 25 to 50%, and accordingly, the total footage of smooth agitation diffuser tubes; this range of flow increase is impossible to achieve with a longitudinal arrangement of diffuser tubes in their isobaric diffuser ring.
Regarding the second limitation—substantial decrease in acid mist —, the volumes of oxygen (O2) generated in current industrial electrowinning processes for copper and other non-ferrous metals are directly proportional to the current intensities applied to the anodes, and consequently, to the environmental contamination associated with the operation of the electrowinning cells of the current art. As noted, O2 gas is given off randomly in the form of individual bubbles of undetermined size from the surfaces of the flat faces of the anode plates; bubbles rise to the surface of the electrolyte; and together with emerging into the atmosphere, they explode by pressure differential, with which their interfaces are divided into liquid micro particles forming aerosols of electrolyte (sulfuric acid) that are incorporated into the gaseous fluid of O2 emerging from the anodes, together with vapor of water (and if the electrowinning process already has soft agitation of the electrolyte, also air) in the electrolyte; all these constituents form a toxic and corrosive gaseous phase on the container, called “acid mist”; The environmental regulations require due protection for the health of the operators, according to Occupational Health and Hygiene legislation, as it is a polluted gaseous fluid highly harmful to human health, as well as highly corrosive to all equipment, structural and civil elements of the Plant industrial and stainless steel of cathode plates, and particularly of the welds between the electrode plates and their hanging bars of the electrical connection bars.
The acid mist health and hygiene problem apparently did not affect the industry until half a century after the U.S. Pat. No. 1,032,623 (probably due to the low current intensities operated at that time), but 54 years later, in 1976, MITSUI in GB 1,513,524, it proposes an insoluble anode covered with a fabric woven with parallel inert fiber and spaced from the anode, which extends over the electrolyte level to avoid the generation of acid mist to the environment, and to recover the generated effluent; the portion of the anode on the electrolyte is covered with an impermeable film on a mesh of the same material to form a sealed chamber that is provided with an outlet.
Similarly, in 1978, International Nickel Corporation INCO in U.S. Pat. No. 4,087,339, proposed separating each cathode from its adjacent anode with a pair of diaphragms; and in 1980, in U.S. Pat. No. 4,201,653, it also suggests bagging the anode.
In 1984, Smith in U.S. Pat. No. 4,584,082, proposed a method and apparatus for acid mist reduction based on a masking device to promote coalescence of acid mist bubbles. The masking device reduces the free surface of the electrolyte between the electrodes, which forces the bubbles to approach and their coalescence, and consequently, their increase in size, which results in a reduction in the volume of aerosols in the generated acid mist.
The same inventor, in 1987, proposed in U.S. Pat. No. 4,668,353, another improved coalescer device, attached to each anode.
In 1995, Minnesota Mining & Manufacturing, 3M, in patent application CL 1999-580, proposed to reduce the formation of acid mist by adding aliphatic fluoride surfactants that inhibit acid formation, with low foam formation.
Bechtel, in 1997, in U.S. Pat. No. 5,609,738, proposes a multi-element covering system installed below the electrical connections of the electrodes and on the surface of the electrolyte; is covered, it is evacuated in the interstices, in the confinement space, under it and over the electrolyte with a flow that exceeds the stoichiometric ratios that can cause the confined volume to escape, with the aim of avoiding the emission of acid mist on the cell.
CODELCO, in 1999, in patent application CL 1999-2684, proposed a procedure to inhibit the formation of acid mist in aerosols by adding an antifoam formulation composed of a glycol ester, an ethoxylate of alkyl phenol in a solvent paraffinic oil.
SAME, in 1999, in patent application CL 1999-247, proposed a high-energy hood for suction and capture of acid mist, connected to a centralized exhaust ventilation system, remote to the cells.
Also in 1999, Electro Copper Products in U.S. Pat. No. 5,855,749, proposed a system of transverse forced ventilation over the electrolyte.
Always in 1999, Hatch Africa in U.S. Pat. No. 6,120,658, proposed a method to capture, confinement and extraction of acid mist by a continuous enveloping anode cover, which is open at its lower end and closed at its upper end, adhered to the anode surface. The shell is formed of hydrophilic fibers that absorb liquid aerosols, returning them to the electrolyte, and simultaneously with porosity that allows the effluent gaseous fluid to escape.
TECMIN SA, in 2001, in patent application CL 2001-527, proposes an electrolytic cell for “zero emission of acid mist over the cell”, through capture, and forced extraction of acid mist to be remotely depurated, using thermal covers with irrigation of the electrical contacts, placed on the front walls higher than the side walls; said cell, which substantially decreases the acid mist in the operators working atmosphere, but does not depurated it to innocuous levels, works in conjunction with an electrolyte agitation system to simultaneously improve the transfer of ionic mass between the electrodes, in fact it is the precursor to the “triad” of the present invention.
CODELCO, in 2002, in patent application CL 1994-1965, proposes the inhibition or elimination of acid mist by adding to the electrolyte a soluble surfactant derived from the Quillaja Saponaria Molina tree.
NEW TECH COPPER, in 2004 and 2005, in patent applications CL 2004-2875 and CL 2005-570, proposes devices to control the acid mist produced, which includes insufflation of an air curtain on the free surface of the electrolyte with compressed air coming of distribution ducts and air injection nozzles located inside on both sides of the electrolytic container, inhibiting the release or formation of acid mist through heat exchange.
Ignacio Munoz Quintana, in 2005, in patent application CL 2005-2518, proposes plastic floating elements with elements adhered to the external surface of the float, which traps the polluting aerosols of the mist, preventing their release to the environment.
In 2006, BASF, in patent application CL 2006-328, proposed a process to reduce acid mist with at least one nonionic surfactant in the electrolytic solution.
COGNIS IP, in patent application CL 2007-2892, discloses alkoxylated compounds or sulfodetaines as anti-acid mist agents, with sulfate or sulfonate ends added in the electrolytic solution.
In 2007, TECNOCOMPOSITES SA, patent application CL 2007-2451, disclosed a system for the capture and removal of acid mist from the electrolytic cell, which has a plurality of flexible ceilings between anode and cathode, with a longitudinally concave shape in all its contact extension with removable lateral channels drilled above the electrolyte level and under the flexible ceilings.
In 2010 and 2011, NEW TECH COPPER, in patent applications CL 2010-1216 and CL 2011-1978, respectively proposed a system to confine the space on the electrolyte in a cell, and a mini-depurator device to reduce the leakage of sprays into the environment.
In 2013, Victor Vidaurre H., in U.S. Pat. No. 9,498,795 and INAPI CL 55,012-2017 (patent application CL 2013-1789) proposed a system for recovery and recycling of 99% of the acid mist generated in cells for electrowinning of copper, with discharge of the gaseous effluent with innocuous contents to the atmosphere.
The simultaneity of the development and introduction to the market of solutions for both limiting problems of current art, stimulated the technical feasibility research to expand synergic possibilities between both solutions “cell by cell”, and led to the functional development of the joint operation as a triad for the holistic objective of this invention, which includes and takes advantage of a new thermal synergy that is incorporated into the concept of “electrochemical reactor”, specifically, an electrochemical reactor with the ability to simultaneously resolve the two limitations of the electrodeposition process in the electrowinning of copper.
From what has been said above, the present invention specifically refers to an innovative electrochemical reactor consisting of a container of the current art specially configured to house and operate in line a triad of synergic systems developed and implemented “cell by cell”, adjusting to the needs of existing plants with electrowinning processes for copper and other non-ferrous metals, conducted in specific plants. The triad consists of the following online devices:
With all the above, the objectives of this invention are:
1.—To provide an electrochemical reactor, including: a container suitable for integrating one-method devices and a complex system of in-line functional means to produce favorable holistic effects that allow the stable conduction of copper electrodeposition process to be continuously sustained over time—and other non-ferrous metals—in a plurality of electrowinning reactors operating simultaneously at high current intensities.
2.—A Soft Electrolyte Agitation System (AGSEL) installed in the container to radically improve ionic mass capacity restrictions and air flow control of bubbling aeration directed to the intercathode spaces on the electrolyte, in determined flow rates, in ranges of continuous and pulsating pressure to provide soft air bubbling agitation directed into the intercathode spaces of the unit cells, in such a manner that it effectively usefully enhances the natural random bubbling of O2 generated at the anodes of the cells of the current art in the cited Patents, and thereby making it technically feasible simultaneously to increase the productivity of the copper electrowinning process by continuously operating the electrolytic cells at high current intensities above 50% of current art standards (typically 280-300 A/m2); the containers can be the existing ones, suitably adapted to receive the “triad”, or new ones built to incorporate it. Increasing the current density at each cathode achieving ion mass transfer effectively applied compactly on their surfaces, as stated, simultaneously improves the physical and chemical quality of the copper electrodeposit, and therefore requires coupling online of a suitable system of substantial decrease of the acid mist resulting in the electrodeposition process, immediately installing in the container, said coupled system and in line with the agitation system, but with means for the substantial decrease of the global acid mist, that unlike patent application CL 2001-527, this invention proposes the means for global abatement with recovery of substances for recycling of acid mist, ensuring the environmental sustainability of the global electrodeposition process.
3.—A system for the substantial reduction of process acid mist at the same time that it is generated in electrochemical reactors, recovering it substantially suitable for immediate recycling to the process, which includes two in-line subsystems:
4.—Ensure that the process management has global sustainability, not only complying with environmental sustainability with the substantial reduction of the harmful acid mist, but also improving the operational problems of current art, by simultaneously minimizing both energy consumption (thermal and electrical), as well as losses of water vapor, electrolyte and acid sprays, to the ambient atmosphere when conducting the process.
5.—Substantially decrease the operational risks of the current art due to the action of harmful anions that attack the integrity of the electrodes in the areas highly exposed to the path of escape of the acid mist inside the electrochemical reactor, particularly in the welds of the electrodes with their hanging bars. This risk particularly affects the copper electrowinning industry in Chile, due to the presence of anions in the electrolytes from the leaching of oxidized minerals contained in the copper oxide deposits, especially in northern Chile.
The accompanying drawings are included to provide a better understanding of the principles of functional concatenation to achieve the seven simultaneous in-line operations on the container operated at high current densities in this invention, illustrated, in a preferred embodiment for continuous operation. of the electrochemical reactor, with manual controls by trained operators; which is not restrictive, since it constitutes the simplest way, of several possible alternatives, for the continuous operation of the electrochemical reactor with more sophisticated semi-automatic and automatic control controls in versions that have already been validated; and that, moreover, they are not limiting for the development of electrochemical reactor improvements for which industrial protection is requested.
The arrangement and material specifications of flexible seals are designed to allow controlled atmospheric air flow rates (210) to enter with the minimum suction necessary to prevent confined acid mist (3) from leaking into the atmosphere, and at the same time, said suction manages to “aerate” the mini perimeter ventilated chambers (209), sharing the volume with the acid mist inside. However, the atmospheric ventilation incoming air, due to its lower temperature compared to the acid mist temperature under the CAR System (200), initiates the coalescence of the electrolyte liquid droplets suspended as aerosols in the acid mist, at the same time, that the cold air flow rates of ventilation promote the increase of the already coalesced electrolyte droplets (5).
The objectives of the invention are implemented for a set of electrochemical deposition reactors (1) for copper—and other non-ferrous metals—operating with aqueous sulfuric solutions and anodic plates (10) of insoluble lead that generate O2 bubbles (7), specifically configured to install and allow continuous operation of the triad of systems and equipment to accommodate specific “cell by cell” copper (and other non-ferrous metal) electrowinning processes conducted in various industrial plants currently operating at densities current of 250-320 A/m2; the installation and concatenation of the triad in the containers (2) enables them to operate sustainably with current intensities above 400 A/m2; the innovations presented serve as well for the design and construction of new electrowinning Plants for operation at high current densities from 350 A/m2 and upwards, incorporating the same triad systems (
(4) “CAP”—abbreviation for “Programmable Automation Controller” in Spanish AGSEL System (100) Soft Agitation of Electrolyte serves to increase and improve homogeneity in the transfer of ionic mass from the electrolyte (5) to the cathodes (11) (
CAR System (200) serves to contain, confine, coalesce and recycle acid mist as it is generated in each electrochemical reactor (1) by means of Removable Anodic Covers (201) (
SIRENA Acid Mist Recycler System (300) serves to recycle aerosols and condense polluting vapors (
The continuous operation of the triad of systems, in the plurality of existing containers (2), in the tankhouse or electrowinning plant, can be operated and maintained concatenated, either manually or automatically, with the incorporation of a suitable Programmable Automation Controller (CAP) (400), which includes access to monitoring and instant registration of process variables.
The description below includes sufficient details to improve the understanding of the global concatenation of the triad of systems that make up the present invention and their sustained operation over time; therefore, they are incorporated and constitute part of the description with one of the preferred embodiments of the invention, which explain the application of the novel principles of the “cell by cell” solution and make viable its adoption on an industrial scale in existing industrial containers of the current art.
The Soft Electrolyte Agitation System (AGSEL) (100) installed in each container (2) of the electrochemical reactor (1), parallel and at a short distance from the bottom of the container (2), shown in
The sustainability over time of the aeration ranges at the appropriate flow rates and pressures is maintained with a programmable solenoid valve that controls the flow of air supplied by pulses with a determined pressure and frequency that ensures that the holes of the diffuser flexible tubes are maintained free of obstructions.
In the AGSEL System (100) the minimum separation between adjacent rows of bubbles in the thermo-perforated flexible diffuser tubes (107) directed to each intercathode space can be reduced to 15 mm, a dimension that is 4 times less than the current art minimum of 70 mm.
The greatest generation of acid mist expected with the operation of the electrochemical reactor (1) at high current intensities is managed in coordination with the online installation of the pair made up of the CAR (200) and SIRENA (300) Systems, to configure with the AGSEL System (100) the triad of the present invention.
The Soft Electrolyte Agitation System (AGSEL) (100) is installed at a short distance on the bottom of the container (2) of the electrochemical reactor (1), in
The sustained operation of the electrochemical reactor (1) at high current intensity levels will test, sooner rather than later, the level of manual skill requirement of trained operators to keep the concatenation of the equipment consistently stable over time. Therefore, in order to project the indicated levels of raised current density, both the development and the validation of semi-automatic and automatic process control systems have already been advanced, and even the “firmware” required for eventual autonomous optimized operation of the complete electrowinning process if desired.
The air supply to the AGSEL System (100) requires pneumatic feeding devices to deliver a continuous flow range of 0 to 400 liters per minute at a pressure of 0 to 3 atmospheres, with means to generate pulses of controlled duration and spacing, including a rotameter and pressure switch (110); a pipe connects it (optionally) to pneumatic anti-siphon (111) and anti-return (112) devices, after connecting to the air inlet point (103) in the self-supporting monolithic structural frame (101), which is a PVC tube, typically at least 10 inches in diameter, externally reinforced by a continuous filament fiberglass and resin blanket. The air flow moves through the tube through the self-supporting monolithic structural frame (101), which supplies the air at the supply connection points (105) to each rectangular module that supports the air diffuser tubes (102), through the power connection point (105), which in turn feeds the manifold (108) of the rectangular module that supports air diffusers (102) and finally, to the thermo-perforated flexible diffuser tubes (107).
Each flexible diffuser tube with thermo-drilled holes (107) is attached to the manifold (108) with a feeder connector (106), from which air is diffused in rows of bubbles to the electrolyte (5); the ends of each flexible diffuser tube are blocked with a blind connector (114), where it is attached to the blind counter manifold (109); This, in turn, is fixed to the self-supporting monolithic structural frame (101) by means of bolts (113).
The distributor manifold (108) is molded of a monolithic polymeric compound and the blind counter manifold (109) houses the blind connectors (114) to remove the thermo-perforated flexible diffuser tubes (107). The manifold (108) is bolted to the self-supporting monolithic structural frame (101) through bolts (113) and likewise, the blind counter manifold (109) is fixed to the homologous member of the self-supporting monolithic structural frame (101) with bolts (113).
The number of rectangular air diffuser carrying modules (102) in the self-supporting monolithic structural frame (101) depends on the length of the container (2) of the electrochemical reactor (1), on the diameter of the thermo-perforated flexible diffuser tubes (107), and the separation distance between axles; and also of the hole-hole patterns in the surface of the thermo-perforated flexible diffuser tubes (107) and of the diameter of the holes and perforation patterns; all of which determines the air flow capacity required by the AGSEL System (100), which is calculated once the current intensity range at which the electrochemical reactor (1) is to be operated with its complete supply of electrodes is determined.
The AGSEL System (100) has height adjustable support supports (116) on the floor of the container (2), to be adjustable, as required, to maintain the horizontality of the self-supporting monolithic structural frame (101) with respect to the lower edges of the anode plates (10) and cathode plates (11) of the electrochemical reactor (1); and they can compensate for inclinations of the bottom or floor that the container (2) may have to facilitate its overflow.
Notwithstanding the foregoing, the AGSEL System (100) can also be supplied prepared to add thermo-perforated flexible diffuser tubes (107) in the total or partial perimeter of the self-supporting monolithic structural frame (101) in order to diffuse additional aeration to obtain effects hydrodynamic that may be necessary to support stable operation at high current intensities, to enhance additional diffusion favorable to the primary objective of directed external air bubbling in intercathode spaces.
A longitudinal section elevation of an electrochemical reactor (1) shown in
The CAR System (200), container, confiner, coalescer and also recycler of acid mist, in each electrochemical reactor (1), confines the aerosols of the acid mist (6) in the perimeter mini-ventilated chambers (209) where the micro drops of electrolyte in suspension forming drops of greater size and weight; as the micro drops gain weight, they first adhere to the available surfaces pushed by the ventilation generated by the entrance of atmospheric air to the container (2) through the plurality of multiple parallel flexible longitudinal seals (207) of the CAR system (200); As the droplets weight continues to grow, eventually they detach themselves cells from the surfaces to which they adhered, precipitating by gravity to the electrolyte (5) of the electrochemical reactor (1), in fact self-recycling.
After installing a removable anode cover (201) on each anode plate (10), with two vertical guide horns (204) provided, connected together by a horizontal seating plate (205) (for optional installation of wireless differential pressure sensor (605) (not shown) as required under the CAR System (200)); the vertical guide horns (204) are monolithic with the structural body (206) of dielectric polymeric mortar compound, highly corrosion resistant. The structural body (206) on both outer lateral sides, lodges multiple parallel flexible longitudinal seals (207) that protrude horizontally to contact the adjacent cathodic plates (11); while towards the inside of the lateral sides of the structural body there are two rows of flexible clamping tongues (212) to affix each anodic removable cover (201) onto each anodic plate (10). On the front ends, there are affixed two separate front seals (208) that cover the electrolyte (5) over the lateral channels (211) of the container (2). The multiple parallel flexible longitudinal seals (207) form at least two superimposed mini perimeter ventilated chambers (209), to: a.-) Promote the coalescence of the acid mist confined inside; coalescence is enhanced by ventilation with the entry of controlled flow rates of atmospheric air (210) that keep the mist confined under the multiple parallel flexible longitudinal seals (207). Coalescence takes place in the perimeter mini-ventilated chambers (209), since the controlled atmospheric air flow rates (210) are at a lower temperature than typical 50° C. of the electrolyte (5) in the copper electrowinning process, favoring the initiation of coalescence of the acid mist (6) with growth in size of the aerosols until reaching such a size that, due to their own weight, they fall back into the hot electrolyte (5) in the container (2) of the electrochemical reactor (1) that originated them. Recycling occurs simultaneously with the generation of acid mist in the operation of the electrochemical reactor (1), b.-) The multiple parallel flexible longitudinal seals (207) designed for the entry of atmospheric ventilation with the suction by the SIRENA system (300) in each mini ventilated perimeter chamber (209) of each removable anode cover (201) also serve to sweep cathodic and anode surfaces and keep them clear of vapors and aerosols, thereby providing anti-corrosive protection for body/hanger bar welds cathodic (11) and anodic (10) plates due to the possible presence of anions, (which are generally present in the electrolyte (5) and come from the ore leaching stage, as entrained contaminants). Removable Anodic Covers (201) substantially prevent the formation of copper sulfate in the socket contacts of the electric bars/electrode hanger bars, thus avoiding process current leaks.
To implement anion protection with the multiple parallel flexible longitudinal seals (207) of the CAR System (200) it is necessary to establish the average level of the electrolyte (5) in the industrial container (2) of the current art—or in the electrochemical reactor (1)—of a given Plant or tankhouse, to fix the distance of the multiple parallel flexible longitudinal seal (207) with respect to the position of the structural body of monolithic polymeric compound (206) of the removable anode cover (201) already seated on the anodic plate (10) such that the line of contact of the multiple parallel flexible longitudinal seal (207) of the mini perimeter ventilated chamber (209) closest to the level of the electrolyte (5) with the cathodic plate (11) is just above said level, so that the volume of gaseous fluid confined by the CAR System (200) in the electrochemical reactor (1) is entrained and extracted from it together with the acid mist.
With reference to the drawings,
The SIRENA System (300), linked in line with the CAR System (200), recovers and substantially reduces acidic vapors, recycling the acid mist aerosols (6) remaining in the flow of the gaseous effluent fluid extracted “cell by cell” (303) of the electrochemical reactor (1), to be immediately depurated, outside the container (2) of the electrochemical reactor (1), in the first instance, by means of a gaseous fluid bubbler (305) that operates under a liquid column (306) of adjustable height in the DEVA “V4” acid effluent vapor depurator (302) installed on the outer front wall (4) of each container (2). Each bubbler (305) of the DEVA “V4” (302) recovers substantially, of the order of 95˜98% of the uncoalesced micro aerosols in the container (2) and which are dragged to the DEVA “V4” (302) and recovered in the form of liquid condensate; at the same time, on the liquid column (306) of the bubbler (305), always inside the DEVA “V4” (302), with the bubble, bubble explosions take place when emerging from the level of liquid condensate. To minimize water vapor and new aerosols generated in DEVA “V4” (302), forced condensation is introduced by means of a heat exchanger (307), to substantially recover the new aerosols and vapors in the effluent gaseous fluid extracted from the DEVA “V4” (302). The suction of the extraction flow of the extracted effluent gaseous fluid “cell by cell” (303), is provided, in the preferred embodiment, by means of a pneumatic air amplifying device (500), which operates with dry and compressed atmospheric air (801), preferably provided by a screw compressor (800), or alternatively, with a mini turbine (309) provided with its frequency variator (310) to control the extraction flow, installed in each container (2) of the electrochemical reactor (1).
The continuous operation over time of a plurality of electrochemical reactors (1) requires setting the overall flow rate of extraction of individual effluent gaseous fluid from each electrochemical reactor (1), in such a way that said suction maintains a depression over time of at least 2 mbar under the removable anode covers (201) of the CAR System (200) of each container (2) of the electrochemical reactor (1). This condition is essential to guarantee zero emission of acid mist from the electrochemical reactor (1) to the working environment.
The triad of the present invention—as stated—can be operated and maintain the indicated essential condition manually, automatically or autonomously.
In case of using a Programmable Automation Controller (CAP) (400); with or without autonomic capacity, the mini extraction turbines (309) or preferably, the air amplifiers (500) and Vortex tubes (501), in each electrochemical reactor (1), are in charge of moving the extracted effluent gaseous fluids “cell by cell” (303) of each electrochemical reactor (1) discharging them directly to their DEVA “V4” acid effluent steam depurator (302), which when cooled prior to their global discharge into the atmosphere (311), by heat exchanger (307) with atmospheric air cooled preferably by pneumatic device Vortex Tube (501), or alternatively by a Chiller (308) that cools conventional refrigerant fluid, such as Glycol, cooled in a range of 1 to 4° C.
The SIRENA System (300) is designed to safely discharge the global gaseous effluent from each electrochemical reactor (1) directly into the atmosphere. Alternatively, or as required, the SIRENA (300) is also designed to be able to incorporate online, prior to discharge to the atmosphere, a second DECOMUVA multi-stage depurator/condenser (312) and to couple a pneumatic air supply system atmospheric pressure of the triad to maximize the safety of the effluent gaseous fluid.
| Number | Date | Country | Kind |
|---|---|---|---|
| 757-2018 | Mar 2018 | CL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CL2019/050018 | 3/21/2019 | WO | 00 |
