SYSTEM AND APPARATUS FOR ENHANCING CONVECTION IN ELECTROLYTES TO ACHIEVE IMPROVED ELECTRODEPOSITION OF COPPER AND OTHER NON FERROUS METALS IN INDUSTRIAL ELECTROLYTIC CELLS
A system and apparatus for enhancing convection in electrolytes for improved electrodeposition of copper and other non ferrous metals in industrial electrolytic cells at given a current density providing exact geometric locations of the electrolyte jet infeed supply system used to impart forced convection in the electrolyte, the gas bubbling system for low pressure/low volume convection enhancement, and the electrode bottom and lateral distancing system, and range of operational parameters, for correct electrolyte flow and air bubbling flow improving cell productivity, quality of metal plates with increased electrical efficiency for its industrial application. The system and apparatus can also be used in industrial cells with same optimal results but at increased current densities, provided sufficient suitable electrolyte and additional electric power is available.
This application is a non-provisional application of U.S. Provisional Patent Application No. 61/096,394 filed on Sep. 12, 2008, the entirety of which is hereby incorporated by reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
This invention was not federally sponsored.BACKGROUND OF THE INVENTION Field of the Invention
This invention relates to the general field of aqueous electrolytic electrodeposition, and more specifically toward a system and apparatus for enhancing convection in electrolytes to achieve improved electrodeposition of copper and other non ferrous metals in industrial electrolytic cells at industrial scale operations. The system and apparatus are useful in both electrowinning and electrorefining versions of electrodeposition.
Industrial electrodeposition of metals as practiced today is one of the most complex unit operations known due to the unusually large number of critical elementary related phenomena or process steps which control—and indeed determine—the success of the overall process. The nature of these complex phenomena ranges from physico-chemical through electrochemical to the purely electrical, and they interact simultaneously at distances from the electrode surfaces that range from an atomic radius to an electrode spacing in the cells.
Electrowinning is also the oldest industrial electrolytic process. Reportedly first demonstrated experimentally by von Leuchtenberg in 1747, the process was used by H. Davy to produce metallic potassium and sodium in a lab in 1807. The first commercial process for silver plating was developed by Siemens and patented by Elkington in 1865, and the first copper electrolytic refinery was built in New Jersey in 1883 to support the booming growth of telegraph and telephone wires. Large scale industrial electrowinning from leached copper oxides, as we know it today, was first developed in 1915 at Chuquicamata, Chile.
Substantial evolution has taken place in electrodeposition industrial plants in the last 100 years resulting from the constant efforts to substitute manual labor by mechanization, automation and process controls with technology. More recently, efficiency improvements in materials handling automation and safety in plant and equipment operation have been introduced, driven by the substantially improved performance and durability achieved by new anti-corrosive structural polymer composite materials.
By and large, however, the productivity and energy efficiency of the industrial process still remains poor mainly due to inefficient electrodes and inadequate functional arrangements of equipment inside electrolytic cells, which explains the moderate current densities used and overall insufficient process control that keep plant sizes large and metal inventory excessive. Notwithstanding, advances in hydrometallurgical recovery rates of metal ions by solvent extraction from leached low grade ores are more environmentally friendly, and economic electrolytes in recent years have boosted cost effectiveness and acceptance of the process in new mega size mining projects and entrepreneurial size mining ventures alike. Similar technology electrolytic cells are used at present in projects of all sizes, so the benefits of the system and apparatus of the present invention are especially adaptable to the needs of any existing industrial electrolytic cell regardless of plant capacity, whether new or already in operation. Increased productivity and quality with improved energy efficiency processes are highly desirable for a number of reasons and mandatory from a business sustainability perspective in the XXI Century.
The foregoing descriptions of shortcomings of the present art of electrodeposition refer to the copper electrowinning process, but are equally applicable to copper electrorefining process, and generically, to all electrorefining processes of non ferrous metals.
In the present art copper electrowinning industrial practice, current densities (typically in an average range of 250 to 350 amperes/m2) are applied to the electrodes in electrolytic cells to deposit high quality plates of copper (substantially complying with LME standards such as BS6017, ASTM B115, etc.) on the cathodes from given flows of varying composition electrolytes containing copper ions in acid solutions obtained by respective solvent extractions from suitably leached copper ores. In connection with the foregoing, the term “current density” is the ratio of direct electric current, expressed in amperes, to the surface area of cathodes in the electrolytic cells, expressed in square meters. In a more recent established copper electrowinning practice, the electrolytes are pressure jet fed from strategic locations into the interleaved anode-cathode spaces in the electrolytic cell from horizontal feed pipes generally pointing towards the interelectrode spaces, installed on the lower vertices of the side walls of the cell near the bottom, to create a suitable “forced” convection of the electrolyte relative to the surfaces of the energized electrodes, that can be adjusted to sustain other process variables in equilibrium to consistently deposit satisfactory physical, chemical and metallographic quality metal with acceptable productivity and current efficiency in time. A fundamental fact in this present practice of the art is that electrodeposition productivity is directly proportional to the current density, and accordingly, the long-sought ultimate goal is to run the process at maximum current density for maximum metal yield. However, a well established dictum supported by long-held practical experience holds that the maximum sustained current density to operate a given industrial plant in time—given its specific process technology, equipment, electrolyte chemical composition, additives, power and operational experience available—is that which allows it to successfully maintain process electrochemical and physico-chemical and the vital electrical variables substantially in stable equilibrium, thus enabling to steadily yield the desired quality of metal electrodeposition over time. One of the main obstacles preventing those skilled in the art from increasing the present art current density levels from presently achieved equilibriums is the lack of an electrolyte convection enhancing system tailored for the specific constraints of present art industrial electrolytic cells, that when implemented will provide a stable and reliable process, thus enabling operators to sustain the new successfully adjusted process variables in time at their new stable equilibriums to meet the quality of metal deposit objectives with the new increased current density.
The system and apparatus of the present invention are directed towards specifically enhancing the effects of convection in the electrolyte imparted by a pressure feed system in a state-of-the-art industrial copper electrowinning cell operating at a given current density, which is designed to provide a given “specific flow ratio” of electrolyte of a given composition to the total energized cathode surface area in the cell, expressed in cubic meters of electrolyte flow per hour per square meter of energized cathode surface. Said enhancement of convection is properly implemented, as proposed in this invention, by means of a low pressure, low volume gas diffusion system with suitable adjustments of the gas flow relative to the specific flow and should directly result in a first level of stable improvement in the quality of electrodeposit and in the electrical efficiency of the cell when the gas enhancement system is connected and correctly adjusted. Further, such enhancement of convection, generally maintaining the initial given specific flow, usually suffices to also allow increasing the initial current density in the industrial cell to a certain incremental level without detriment to the quality of electrodeposition while at the same time minimizing the incremental consumption of electric power. Essentially, in order to accomplish the above goals, the system and apparatus provided will need to first fix precisely the relative positions of both the existing electrolyte infeed system operating with its predetermined flow and discharge paths of the electrolyte relative to the electrode surfaces in the existing cell and the convection enhancement system specially tailored relative to the electrodes and the cell with its predetermined gas diffusers for given favorable bubbling sizes and discharge patterns. Then, the system and apparatus will need to incorporate the contributions of a low pressure, low volume gas diffusion in favorable size and patterns of bubbles from the convection enhancement system operating and positioned in a horizontal plane below and across the vertical faces of the electrodes with predetermined volume and pressure of gas for establishing such favorable bubbling sizes and discharge patterns. The enhancement effect occurs in the bottom-to-surface direction on the overall electrolyte convection in the interelectrode spaces, and is most generally effective if preferably guided laterally with strategic vertical convection baffles installed on the anodes of an electrode distancing system, to positively enhance and guide upward convection constricted in the interelectrode spaces that gently and uniformly sweeps across the entire electrode surfaces. This is preferably accomplished while positively maintaining the cathodes at their predetermined spacing from the anodes and also while maintaining them simultaneously insulated from each other at all times. A major benefit to be derived from the application of the complete system and apparatus of this invention is a significant reduction or elimination of electrical short circuits due to contacts between energized anodes and cathodes. This preventive feature not only reduces the need of dedicated amounts of tedious “systems work” in industrial practice to locate and correct electrical malfunctions and short circuits, but also increases productivity, deposit quality, and current efficiency as well as “wear and tear” of costly electrodes and electrical bus bars. In fact, taking care of “systems work” is an everyday problem in large electrowinning plants, some of which have 66,000 cathodes or more under current at any given time. For reference, if only half of one percent of the cathodes are in or near short circuit, it means 330 cathodes scattered through the huge electrowinning plant need urgent attention, representing a major yet inevitable problem to the uniform success of the massive electrowinning process. Improvements in current efficiency have become an imperative with increasing electrical power costs and growing scarcity of competent specialized labor.
A novelty of the present invention is in teaching exactly how the concatenation of the correctly designed and specified three subsystems operate interlinked as one holistic effective system to improve electrodeposition that can be implemented with present day practices in existing as well as in new industrial electrolytic cells, and further successfully coordinated for overall synergies adding up their individual contributions to increased quality and productivity. Some good ideas from past art have been salvaged, practically modified to eliminate short comings, and then placed in an effective holistic context, which is the novel strategy in which this invention helps to stably achieve the most favorable results or outcomes at industrial scale from the electrodeposition process at today's practical current densities, considering, of course, mandatory constraints in labor, environment and competitiveness of present (2008) industrial electrowinning plant operating practices. These primary goals or benefits are: increased productivity, better quality deposits—smooth and virtually free of porosity throughout all stages of growth from start until harvest—and higher current efficiency. Further, once these primary goals are achieved or substantially improved using the invention, since the benefits of the enhanced convection levels provided herein include substantially diminishing the present limiting diffusion layers of the electrolyte at the electrodes, the electrodeposition process using the same existing equipment, labor and operational practices can also be continuously run at higher current densities (providing sufficient volumes of satisfactory electrolytes and direct electric current can be made available efficiently) and doing so will, in turn, yield yet additional increased productivity and current efficiency, while retaining the characteristic high quality metal deposits.
To begin, U.S. Pat. No. 684,049 discloses, as early as 1901, an electrode distancing system with a toggle mechanism inside the cell manually operated from the outside, (Note: labor intensive system) for positive distancing of energized anodes and cathodes at their predetermined spacing inside electrolytic cells of a copper refinery in order to prevent ever present short circuits; and similarly, U.S. Pat. No. 1,397,735, of 1921, shows another electrode spacing concept using horizontal runners vertically slotted at the electrode spacing attached on the inner upper longitudinal edges of the lateral cell walls for positive permanent placement and vertically straight positioning of the electrodes in an electrolytic cell for coal recovery by a separation process.
Further, U.S. Pat. No. 1,260,830, of 1918, discloses an electrolytic process for ionic deposition of copper from acid solutions providing continuous agitation of the electrolyte, particularly across the face of the anodes, with a mixture of sulfur dioxide gas and steam sparged from nozzles in lead tubes—forming a transverse network of pipes permanently mounted at the bottom of the cell—(Note: cluttering the cell bottom with piping makes it difficult to clean anode slime periodically) to strategically impinge at favorable angles on the faces of anodes to maximize agitation across the respective face surfaces.
Another example is U.S. Pat. No. 3,928,152, of 1975, describing a method for improved electrolyte convection in copper electrowinning based primarily—and only—on air sparging, using bubbler tubes placed parallel to each cathode face at their lower edge, while the cathode-anode interspaces are diminished but positively distanced, and also conveniently enshrouded laterally with baffles to restrict the ascending flow of air bubbles within the space defined between the electrodes as a means to further enhance the beneficial effects air sparging by substantially directing the gas bubbling to the surfaces of the cathodes (Note: air bubbling as a stand alone means of convection enhancement in copper electrowinning is impractical because it requires very substantial volumes of sparging air resulting in significant turbulent flow of the electrolyte at the cathode surfaces compromising the purpose of uniform deposition quality; moreover, such increased air volumes adding to the normal volume of emission of acid mist, and utilizing complex structures made of non durable thermoplastic that clutter cell bottoms, make cells difficult to clean; air feeding to and control in cell are not disclosed).
Similarly, U.S. Pat. No. 4,263,120, of 1981, proposes transverse individual air bubbling devices attached to the lower edges of the anodes discharging curtains of air bubbles whose ascent is restricted within the interelectrode spaces formed by very closely spaced cathodes confined laterally by vertical insulator/spacer baffles mounted on both lateral edges of the anodes. (Note: relative volumes of electrolyte feed with sparging air feed to the cell are not resolved).
Similarly, U.S. Pat. No. 3,959,112, of 1976, describes the use of tubular air sparging elements cooperatively associated with each cathode on both opposing faces placed at their lower edges with air emerging as a uniform curtain of fine bubbles sweeping the plating surfaces of the cathode to substantially inhibiting the formation of rough surface deposits (Note: air feed and control to the sparging system not disclosed, correct positioning, attachment to the cell and connection to the air source not disclosed, cell bottom cleaning with air sparging system installed not disclosed).
More recently, U.S. Pat. No. 6,849,172 B2 of 2005, describes introduction of fresh electrolyte under pressure through jets mixed with sparging gas through a mixing nozzle from a combined feed system discharging in predetermined directions into the cell (Note: the pressurized jet infeed of electrolyte upon mixing with air preempts any discrete contributions of air bubbling by itself to the electrolyte) and PCT—WO2005/019502 A1 of March 2005, proposes a gas sparging system using predetermined volumes of low pressure air saturated with water vapor (Note: bringing air saturated with water into the sparging system inside the industrial cell eventually makes the water vapor in the air condense in the system, clogging it for air and the system turns into a water sparger into the cell, and/or adding substantial amounts of water into the electrolyte which is objectionable). The water saturated air is delivered from a manifold installed inside the cell (Note: manifold description is not disclosed in detail but description does mention the construction material is PVC pipe to which the hoses are attached, which is absolutely unsuitable structurally for the application because they will not hold the desired position) and the manifold is connected to microporous hoses “which can be easily replaced” (Note: how this is accomplished is not disclosed).
Finally, U.S. Pat. No. 3,483,568 of 1969, and U.S. Pat. No. 4,098,668 of 1978, disclose the merits of forced feeding of electrolyte directed to discharge from the bottom of the cell into the interspaces of individual anode-cathode pairs—while U.S. Pat. No. 5,492,608 of 1996, proposes similar forced discharge directed from the side walls—and all coinciding with the resulting positive effectiveness of forced feeding to control plated metal quality and purity even from electrolytes containing high concentrations of undesirable ions, which reportedly, thanks to the forced convection, do not deposit as impurities on the copper plate.SUMMARY OF THE INVENTION
The current invention provides just such a solution by having a system and apparatus for enhancing convection in electrolytes to achieve improved electrodeposition of copper and other non ferrous metals in industrial electrolytic cells at a given current density providing exact geometric locations of the electrolyte infeed system, especially where pressure infeed systems are deemed necessary to impart forced convection in the electrolyte, and the gas diffusion system for low pressure/low volume convection enhancement with adequate given favorable bubbling sizes and discharge patterns and the electrode bottom and lateral distancing system, and range of operational effective parameters, for correct electrolyte flow and air diffusion flow improving cell productivity, quality of metal plates with increased electrical efficiency for its industrial application. The system and apparatus can also be used in industrial cells with same optimal results at incrementally increased current densities, provided sufficient suitable electrolyte and additional electric power are available.
It can be concluded by the foregoing patent analysis that the technological solutions proposed in the various patents did not succeed in making their way into industry as innovations, principally because one or more necessary aspects or details deemed necessary to suit conditions for sustained success of the complex electrodeposition process in industrial scale electrolytic cells were simply omitted, were technically vague, uncertain and/or weak, simply incorrect, results reported deemed exaggerated, experimental, or not demonstrated validly at industrial scale, etc. Whatever the reasons, the fact remains that poor reception of enhanced electrolyte convection as an innovation by the industry have rendered the various partial solutions claimed either impractical or outright not viable for large scale operations. Unlike the prior art, the current invention provides a complex system correctly designed to efficiently and effectively enhance convection in electrolytes for improved electrodeposition of copper and other non ferrous metals in industrial electrolytic cells.
The present invention recognizes the present shortcomings of industrial practice and provides a global system for enhancing convection of electrolyte in industrial cells, specially aimed to industrial electrolytic cells used for copper electrowinning—and with suitable adaptations, also in cells for electrorefining of copper—focusing primarily on the strategy of effective characterization, monitoring and process control of final quality of metal plates harvested, and also their deposition growth in the cathodes, with simultaneous high current efficiency. The system proposed as one unit is formed by three subsystems wherein the first subsystem is an electrolyte infeed supply system for a given specific flow and composition, balanced for a given current density, which is provided in the case of copper electrowinning described herein preferably through dual manifold tubes installed horizontal and longitudinally along the lower vertices of the lateral walls near the cell bottom, with oriented perforations of given diameters in the piping for controlled pressure jetting electrolyte—in opposite predetermined paths—towards the interelectrode spaces providing a basic forced convection in the industrial cell. The first subsystem can be operated simultaneously interlinked with any one of the other two subsystems or preferably both (low pressure, low volume gas bubbling and positive spacing of electrodes and protection of gas bubbling system inside the cell). The specific object in copper electrowinning disclosed herein is enhancing the basic forced convection of the electrolyte generally provided by an electrolyte jet infeed subsystem, preferably located at each lower corner of the flat surfaces of the cathodes in an effective manner to achieve improved electric efficiency and quality electrodeposition of copper in industrial cells. Optimal results in productivity, quality of copper plates, and process current efficiency are obtained while operating simultaneously with all three subsystems linked together (concatenated), geometrically precisely installed relative to each other and exactly positioned with respect to the electrolytic cell in which they operate so they can be effectively and efficiently interlinked to produce the results sought.
The improvement of the art provided by this invention is multiple. First, the construction and installation of the equipment described is practical, validated for industrial scale operations and achieved by using only well-proven, durable and stable polymer composite materials specified for the ultra heavy duty of full immersion service in acid electrolytes. Second, providing the exact geometrical positioning of the three subsystems inside any existing—or new—industrial electrolytic cell that will allow effective adjustment of current density with predetermined volume flows of the fluids involved in favorable discharge paths to achieve the precise enhancement of the basic convection of electrolyte infeed uniformly sustained at the plating surfaces, while also promoting uniform distribution of metal ion concentration in the bulk electrolyte for a given set current density. Third, based on the evaluation of electrodeposition results of harvested metal plates showing stability and merits for attempting to increase also the productivity of the process, increase current density in incremental steps by functional fine tuning adjustments of the predetermined jetting of electrolyte infeed at favorable locations and paths under the electrodes with the corresponding correct low pressure, low volume flow of gas forming the required patterns of uniform and stable diffused gas bubbles sweeping the plating surfaces at the predetermined spacing of cathodic mother plates or permanent cathode blanks, until attaining the results expected, thereby the process variables functionally adjusted to maintain a stable process from the beginning of metal deposition through the end of each production cycle in the electrolytic cell. Fourth, for practical industrial operation, all three subsystems provided are readily displaced out of the way from their concatenated respective working positions when the industrial cell is periodically emptied for inspection, removal of anode slimes and cleaning its bottom. This is an important practical problem for the operation of industrial electrolytic cells that has remained as an unresolved practical obstacle until this invention.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. The features listed herein and other features, aspects and advantages of the present invention will become better understood with reference to the following description—exemplified by but not restricted to industrial electrowinning of copper—and appended claims. The accompanying drawings, which are incorporated in and constitute part of this specification, illustrate embodiments of the invention in industrial electrowinning of copper and, together with the description, serve to explain the generic principles of the invention in industrial electrowinning and electrorefining of copper, and electrodeposition processes of non ferrous metals.
The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of this invention.
Many aspects of the invention can be better understood with the references made to the drawings below. The components in the drawings are not necessarily drawn to scale. Instead, emphasis is placed upon clearly illustrating the components of the present invention. Moreover, like reference numerals designate corresponding parts through the several views in the drawings.
In the description that follows, all specialty polymer composite materials used are formulated according to U.S. Pat. No. 6,143,219 of the same inventor, and use only thermosetting polymer resins and consequently, the polymer composite materials made according to that patent are also substantially gas occlusion-free and highly compacted materials of suitable structural, dielectric, and corrosion resistance to withstand permanent 100% immersion in electrolyte that is required in the described applications. Most ordinary thermoplastic polymers are not suitable for this type heavy-duty service and simply cannot maintain their structural strengths and properties at operational temperatures.
A series of bases (4 are shown for the cell length shown, but it is envisioned that there could be more or less depending on the desired size of the cell in operation) support structures (2) molded of dielectric structural polymer composite materials withstanding corrosion from permanent immersion in electrolyte, assembled with transverse structural members (2B) and longitudinal structural members (2A) of similar polymer composite materials forming a perfectly horizontal, flat and reticulated, rectangular structure, and are placed one after the other at a given design clearance height from the bottom of generic industrial electrolytic cell (1), shown disposed for electrowinning copper sheets (over stainless steel cathode blanks or otherwise mother or base copper sheets) from an electrolyte (100) containing ionized copper in acid solution, such base support structure (2) having vertical height adjustment screws (3), for perfect horizontal leveling at the correct given design height clearance from the cell bottom to hold anodic slimes, and also horizontal lateral adjustment screws (4) for centering the reticulated rectangular structure holding the gas bubbling diffusers for electrolyte enhancement with respect to the center line of the cell and electrodes. The four base support structures (2) thus correctly installed constitute the basic or core system, which is designed ready to correctly support, position, and allow coordinated functioning of the three subsystems, namely, the electrolyte pressure jetting feed system with the convection enhancing system, and both positioned correctly relative to the cell electrodes for optimal results by means of the electrode distancing system to maximize the electrolytic cell electrodeposition results through enhanced convection.
A subsystem for electrolyte pressure infeed into the industrial cell by means of twin manifolds with perforated parallel PVC (polyvinyl chloride) or CPVC (chlorinated polyvinyl chloride) pipes (5) or (50) disposed at the lower portion of the lateral walls of generic electrowinning or electrorefining electrolytic cell (1) installed in correct positions, either shown as (5) or shown as (50), supported horizontally on the basic support structure (2) near the bottom and at a given appropriate distance from the electrodes and the lateral walls in alternate positions (2C) in structure (2). The electrolyte feed pipes (5) or (50), are connected with the external electrolyte source through down corner feed pipe (5A) attached to the front wall of the cell (1). Orifices (5B) on longitudinal pipes (5) or (50) are each strategically distanced to jet electrolyte streams at given angles into each inter electrode space, and preferably, jet orifices are sized proportional to distance away from down corner so as to maintain substantially uniform jet flows emerging throughout the entire length of cell (1).
A subsystem for enhancing convection of the electrolyte is provided alternatively formed with a monolithic self-supporting, reticulated structure (6) preferably internally reinforced with fiber reinforced plastic rebars (6A) molded with dielectric polymer material withstanding permanent immersion in electrolyte, of rectangular shape and mounted horizontally on the base support structure (2) previously installed at the correct level in lower perimeter of the lateral and frontal walls of generic cell (1). In fact, thermosetting polymers are mandatory for this type of service as ordinary PVC and other thermoplastics simply do not have the requisite durability for withstanding sustained immersion in hot (up to 65° C.) electrolyte. The reticulated structure (6) along its entire outside perimeter encapsulates hollow structural shapes of high strength, fiber reinforced structural polymer composite materials (7) hermetically assembled together forming a continuous hermetic isobaric rectangular loop (7) able to receive external gases at low pressure within the hollow interior of the shapes in the reticulated structure (6). The isobaric loop (7) feeds a closely monitored, predetermined volume flow of external gas—preferably air—to a plurality of parallel rows of elastomeric diffuser cylindrical elements, such as porous tubes shown as (9)—or preferably, each perforated in their lengths with appropriate orifices of given diameters at given distances from each other in appropriate patterns. The preferred execution, however, is the reticulated, self-supporting structure hermetically assembled with hollow structural shapes (6) shown on
It was discovered that using reticulated structure (6) with isobaric loop, the longitudinal disposition of gas diffuser means (as in PCT—WO2005/019502 A1 of March, 2005) parallel to the industrial electrolytic cell length dimension are much slower to react and stabilize with a given gas volume and pressure, and therefore they produce uneven or unsteady results in quality of electrodeposition, especially in cases when there are frequent interruptions to the constant gas supply. The transverse disposition of diffuser means relative to the cell length (preferred orientation in the art per some U.S. Patents reviewed) is very responsive instead, easier to adjust the pattern desired and evidences more stable favorable electrodeposition results. It is further discovered that it takes time (transverse diffusers orientation is faster and hollow isobaric structure (60) even faster) for the two systems working interlinked to achieve effective and stable patterns of flow. Essentially, the curtains, clouds, or scatter of diffused gas micro bubbles as they emerge into the electrolyte mingle with the electrolyte, which is already generally in ascending movements by virtue of its pressurized and directed jet infeed of electrolyte, and the apparent resulting local density reduction in the electrolyte by virtue of the gas microbubbles that provide air lift and spin in a favorable ascending, mild turbulent wiping movement very close to the cathode faces—just kissing or touching the electrode surfaces. Favorable convection enhancing wiping movement, as used previously and hereinafter, is shown by arrows 100A that convey a generally upward movement across the surface of the electrode, similar to the upward movement of an automobile windshield wiper. It is this latter subtler action achieved with sufficiently abundant microbubbles at low pressure which intensifies the convection in the bulk electrolyte in the interelectrode spaces, adding buoyancy to first imparted convection by the emerging jets under pressure from the electrolyte infeed subsystem (5) below, that imparts critical effectiveness. This subtler action is enhanced with more abundant, finer microbubbles—substantially all under 2 mm in diameter—easily obtained and sustained using the hollow structure (60). It was discovered unexpectedly that, contrary to prior art, substantially lower volumes of sparged gas and at very low pressures suffice to enhance original convection by imparting the very desirable gentle kissing turbulence at the cathode surfaces at a given current density. It was also verified through measurements in an industrial electrowinning environment that using lower volumes of gas and at minimum pressures for convection in the electrolytic cells positively do not contribute to generation of acid mist; quite the contrary, diffused air microbubbles appeared to diminish misting perhaps by dissolving some of the oxygen bubbles generated in the anode surfaces that are the cause and principal source of acid mist in electrowinning. The abatement of acid mist seems to be more effective with abundant cloud patterns of very fine microbubbles produced using hollow structure (60). In order to achieve the localized gentle kissing turbulence at the plating surfaces, not only does the diffusion of the emerging gas require even distribution throughout the electrolyte in the cell, but also meticulously adjusted to the pressurized infeed volume rate of electrolyte containing the plating ion species, so that the combined effect of gas and electrolyte infeed throughout the entire horizontal plane foot print of electrodes in the cell is stable enough in time to evenly distribute and homogenize the available concentration of the ion metal species, starting at a correct predetermined distance under the vertically hanging electrodes, so they are abundantly available for plating on the full cathodes surfaces up above. It is the proper combination of contributions from both the electrolyte jet infeed system plus the electrolyte enhancement system—particularly executed with hollow reticulated structure—in this invention that are the keys to achieve consistent, repeatable overall optimum electrolyte convection, resulting in uniform an sustained optimum quality electrodeposition. Generally, electrolyte volume flows in electrolytic cells are determined by chemical and mass transfer considerations and total available plating surface for a given current density, as discussed earlier and is generally referred as specific flow of the industrial cell. Appropriate low pressure gas volume flows are essentially established relative to the selected electrolyte specific volume flow into the industrial cell, choosing the lowest possible pressure drop diffuser elements so that the pressure in the system will be the lowest necessary to overcome the electrolyte hydraulic column and the pressure drop across the diffusers themselves and still produce stable microbubbles—all preferably under 4 mm in diameter—in uniform patterns. The harmonious, combined result inside the industrial cell—of pressure electrolyte feed combined with the steady low pressure/low volume gas bubbling enhancement of this invention—effectively diminishes the thickness of the diffusion layer at the electrode surfaces, and quite importantly also, enhances uniform distribution of the given current density throughout the cathode surfaces and uniform mass transfer of the plating ions species, both essential conditions for controlled, uniform growth of the cathode copper metal plates without pores and with uniform thickness throughout. It was discovered after repeated monitored trials that it is the superposition of these combined convection effects that principally promotes more homogeneous and steady copper ion mass transfer to the entire surfaces of the cathodes, ultimately resulting in substantially uniform, non porous, substantially free from deposited impurities, high density copper electrodeposition, flat and smooth metal plating throughout the cathode surfaces which is also faster and therefore proceeds with higher current efficiency. All prior art gas bubbling systems reviewed claim the use of at least twice the pressure and more than twice the gas volume flow than the amounts for good quality results disclosed in present invention. By using the correct combination of gas pressure under 1000 Nmbar and gas volume under 120 Nl/min in an industrial electrolytic cell of specific flow between approximately 0.10 and 0.20 cubic meter/hour/square meter of cathodic plating surface, the overall bulk electrolyte enhanced convection movement (100a) starting from below the foot prints of interelectrode spaces in the cell—as shown in
A subsystem for positively distancing the electrodes (10) that holds the anodes and cathodes from their bottom edges at all times is formed by two horizontal parallel solid channel structural shapes mounted upright on the cell bottom near the lateral walls of the cell (1), molded using high impact strength, dielectric polymer and/or elastomeric polymer composite materials withstanding corrosion of permanent immersion in electrolyte. The solid horizontal channels (10) are molded of one piece each and run perfectly parallel the full length of the cell (1), mounted—as shown in FIGS. 1 and 4—on top of their respective base support structures (2) duly centered longitudinally and transversely with respect to the cell (1) at the correct position with dovetails (10A). Channel structural shapes (10) hold distancing pyramids (12) which are molded with high impact polymer elastomeric materials withstanding corrosion of permanent immersion in electrolyte, designed to hold vertically in place near their lateral vertices the anodes and cathodes, their correct locations and given spacing of anodes and cathodes intercalated at their lower edges. In order to maintain the proper horizontal spacing distance and maintain the intercalated electrodes at all times positively insulated from each other, the vertical edges of the anodes are fitted with two parallel distancing insulator channels (13a) which prevent contact—and electric short circuits—with the cathodes in the cell when the electrodes are installed, and particularly when the cathodes are harvested and removed from the cell with the anodes remaining in the cell fully energized. Another complementary function of distancing insulator channels (13a) is providing an electric shield along the vertical edges of permanent cathodes so when they are energized and immersed in the electrolyte; they remain free of localized copper deposit along both vertical edges. This is very significant because upon harvesting from the cell, having the cathode blank edges free of copper deposit facilitates the stripping of the full copper plates deposited from both opposite surfaces of the permanent cathode blanks. Distancing pyramids shown (12) are fitted into the channel support structures (10) by sliding each into correct position under the vertical hanging intercalated cathodes/anodes and fixed in correct locations from the ends of each channel support structure (10) with set screws (not shown). Another important function of the pyramids (12) and baffles (11) in this subsystem is that they serve as sacrificial impact deflectors/protectors from eventual catastrophic impacts on the convection intensifying subsystem by the accidental fall of full cathodes, particularly from mother plates or soluble anodes in electrorefining industrial cells.
It should be understood that while the preferred embodiments of the invention are described in some detail herein are pertinent to the operation of an industrial copper electrowinning cell, the present disclosure is made by way of example only and that suitable variations and changes thereto are introduced for use in copper electrorefining and for use in electrodeposition processes of non ferrous metals without departing from the subject matter coming within the scope of the following claims, and a reasonable equivalency thereof, which claims I regard as my invention.
All of the material in this patent document is subject to copyright protection under the copyright laws of the United States and other countries. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in official governmental records but, otherwise, all other copyright rights whatsoever are reserved.
1. A system for electrodeposition of non ferrous metals comprising
- an operating electrolytic industrial cell with appropriate cathodes and anodes, and a given flow of an electrolyte composition and current density;
- a leveled and aligned horizontal support structure or individual supports correctly installed inside the cell in favorable position relative to the electrodes;
- a means of electrolyte infeed, where the means of electrolyte infeed allows discharge of the electrolyte relative to the electrodes and is aligned and leveled from the leveled and aligned horizontal support structure or individual supports;
- a means of enhancing convection, where the means of enhancing convection is supported from the leveled and aligned horizontal support structure or individual supports; and
- a means of positively distancing electrodes, where the means positively distancing electrodes is supported from the leveled and aligned horizontal support structure or individual supports.
2. The system of claim 1, wherein leveled and aligned horizontal support structure or individual supports comprises dielectric structural polymer composite materials.
3. The system of claim 1, wherein the leveled and aligned horizontal support structure or individual supports comprise a means of vertical height adjustment.
4. The system of claim 1, wherein the leveled and aligned horizontal support structure or individual supports comprises a means of horizontal lateral adjustment.
5. The system of claim 1, wherein the means of electrolyte infeed comprises electrolyte feed pipes.
6. The system of claim 5, wherein the electrolyte feed pipes are twin manifolds with perforated parallel PVC or CPVC pipes.
7. The system of claim 5, wherein the electrolyte feed pipes comprise a plurality of orifices to jet electrolyte streams at given angles into each interelectrode space.
8. The system of claim 1, wherein the means of enhancing convection is a continuous hermetic isobaric structurally self supporting loop, where the continuous hermetic isobaric loop comprises gas diffuser elements and gas hermetic connectors.
9. The system of claim 1, wherein the means of positively distancing electrodes horizontally comprises structural shapes under the electrodes.
10. The system of claim 9, wherein the means of positively distancing electrodes at their given distances horizontally further comprises distancing pyramids, where the distance pyramids are held at precise positions by the solid channel structural shapes.
11. A method of electrodeposition of non ferrous metals comprising the steps of
- obtaining an industrial electrolytic cell with vertically intercalated planar electrodes and appropriate infeed of electrolyte of given composition operated at a given current density
- locating individual supports or a support structure precisely inside the cell, a means of electrolyte infeed, a means of enhancing convention, and a means of positively distancing electrodes horizontally and/or vertically,
- supporting the means of electrolyte infeed, the means of enhancing convention, and the means of positively distancing electrodes at correct locations relative to each other by individual supports or a support structure,
- using at least the means of electrolyte infeed and the means of enhancing convention, and also the means of positively distancing electrodes, all concatenated to achieve desired quality deposit of non ferrous metals on cathode plate electrodes.
12. The method of claim 11, wherein the quality deposit of non ferrous metals is an electrowinning process.
13. The method of claim 11, wherein the quality deposit of non ferrous metals is an electrorefining process.
14. The method of claim 11, wherein the means of enhancing convection is comprised of a continuous gas hermetic isobaric loop, where the continuous hermetic isobaric loop comprises gas hermetic connectors and diffuser elements.
15. The method of claim 14, wherein the continuous hermetic isobaric structure receives external gases at low pressure and distributes the gases uniformly to chosen diffusers to generate bubbles of appropriate size, density and appropriate diffusion patterns that enhance convection and improve the quality of deposition of non ferrous metals and improve process productivity.
16. The method of claim 15, wherein the external gases are at a pressure of under 1000 Nmbar.
17. The method of claim 15, where the cathode plate electrodes have a plating surface, wherein the specific flow of electrolyte is between approximately 0.10 and 0.20 cubic meter/hour/square meter of cathodic plating surface in each electrolytic cell.
18. The method of claim 15, wherein the bubbles are less than 4 mm in diameter generated by diffusers able to diffuse up to 120 It/min/cell of air flow at maximum 1000 Nmbar pressure.
19. An apparatus for electrodeposition of non ferrous metals comprising
- an industrial electrolytic cell with vertically intercalated electrodes, given flow of appropriate electrolyte of given composition operated at a given current density,
- a support structure, electrolyte feed pipes, a reticulated gas diffusing structure, and solid horizontal channels;
- where the electrolyte feed pipes are twin manifolds with perforated parallel PVC or CPVC pipes, where the reticulated structure is hermetically assembled to form a continuous hermetic isobaric rectangular loop, where the solid horizontal channels support anodes and cathodes, and where the support structure supports the electrolyte feed pipes, the reticulated structure, and the solid horizontal channels.
20. The apparatus of claim 19, wherein the continuous hermetic isobaric rectangular loop comprises gas hermetic connectors and diffuser elements.
Filed: Sep 11, 2009
Publication Date: Mar 18, 2010
Inventor: Victor Vidaurre Heiremans (Santiago)
Application Number: 12/557,991
International Classification: C25D 21/10 (20060101); C25D 17/00 (20060101); C25B 15/00 (20060101);