Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
  • C25C7/06—Operating or servicing
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
  • C25C1/12—Electrolytic production, recovery or refining of metals by electrolysis of solutions of copper
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
  • C25C7/02—Electrodes; Connections thereof

Definitions

• the present invention relates to a process for the electrochemical winning or refining of copper by electrodepositing copper from an electrolyte solution containing the metal in ionogenic form, in which the electrolyte is passed through an electrolysis plant comprising at least one electrolytic cell, which in an electrolyte tank for receiving the electrolyte has at least two electrodes serving as anode and cathode, which are alternately ar- ranged at a distance from each other, and to a corresponding plant.
• pyrometallurgi- cal and hydrometallurgical processes For producing copper, a multitude of processes are known, in particular pyrometallurgi- cal and hydrometallurgical processes.
• pyrometallurgical processes enriched chal- copyrite is molten in a suspension furnace or bath-type melting furnace by adding oxygen to obtain a copper matrix, in converters is then converted to crude copper in two blowing steps, and is purified further in a final electrolytic refining step. This electrolysis is also referred to as refining electrolysis.
• hydrometallurgical processes on the other hand, in particular low-copper oxidic ores with a copper content of about 0.5 to 1 wt-% are used as starting materials.
• the starting ore poor in copper which due to its mineralogical composition cannot always be processed economically with other processes such as flotation, is leached e.g. with dilute sulfuric acid, and in an extraction plant the resulting solution rich in copper is treated with an organic extractant which selectively extracts copper ions from the solution.
• the copper-containing extractant is stripped with foul electrolyte with a copper content of about 30 to 40 g/l, which originates from the succeeding electrolysis plant, the copper from the extractant phase passing over into the electrolyte, which upon further purification for removing extractant residues and solids typically is recirculated to the electrolysis plant with a copper content of 40 to 50 g/l.
• Such electrolysis is also referred to as extraction electrolysis.
• the copper-coated cathodes are withdrawn from the electrolytic cell manually or by means of cranes and transferred to a stripping plant, in which the copper coatings are peeled (stripped) off the cathodes, before the cathode starting sheets are returned to the electrolytic cells after a corresponding aftertreatment.
• the copper peeled off is finally processed in melting furnaces.
• the current density on the cathode side is limited by the quality of the copper deposited, as due to the increased overvoltage on the cath- odes more impurities are deposited with increasing current density.
• the lead alloy used as electrode material for the extraction electrolysis becomes more unstable, and the copper anode used for the refining electrolysis becomes passivated with increasing current density.
• present-day electrolyses operate with a maximum current density of about 370 A/m 2 electrode surface.
• a higher current density can only be achieved by using expensive anode materials with a lower quality of the electrodeposited copper.
• electrodes with an electrolyte immersion surface of more than 1x1 m, and in particular electrodes with an electrolyte immersion depth of more than 1 m are not suitable for winning copper due to the non-uniform streamline distribution necessarily obtained at the electrodes - an electrolyte immer- sion depth of the electrodes of more than 1.2 m leads to a sufficiently uniform deposition of copper on the cathodes in processes for electrodepositing copper from an electrolyte solution containing the metal in ionogenic form also with the cathode materials commonly employed in the refining and extraction electrolyses and with the usually adjusted current densities.
• the immersion depth of the electrodes into the electrolyte preferably is an integral multiple of the commonly used immersion depth of about 1 m and particularly preferably about 2 m with a cathode width of about 1 m each.
• the advantage is that the melting furnaces, which because of the active cathode surface, i.e. the cathode surface immersed into the electrolyte, normally were designed for a size of 1x1 m in the known processes, can be used unchanged, in that the stripped copper sheets to be obtained with the process in accordance with the invention are reduced to the corresponding size of 1x1 m subsequent to the stripping operation and before being supplied to the melting furnace.
• the at least one electrolytic cell has more than 60 cathodes, particularly preferably more than 100 cathodes, and quite particularly preferably 114 cathodes.
• the efficiency of the process of the invention is further increased, as the size of the electrolytic cells caused by this measure provides for an inexpensive transport while at the same time reducing the number of cells per production capacity. This leads to a smaller tank- house, shorter cathode delivery paths and less stray currents.
• the cathodes can be made of all materials known to the skilled person for this purpose, stainless steel cathodes being preferred.
• the specific current intensity is 740 A per electrode with a current density of 370 A/m 2
• the specific current intensity is doubled in accordance with the invention to 1 ,480 A per electrode when using electrodes with an active surface of 1x2 m.
• the electrodes can in principle be positioned in the electrolytic cells, be fixed and supplied with current in any way known to those skilled in the art.
• electrodes with a horizontal hanger bar known per se which has a first end and a second end and preferably is made of the same material as the cathode surface, in particular steel, turned out to be advantageous.
• one end of the hanger bar of the cathodes each rests on a first contact bar connected to a power source, whereas one end each of the hanger bar of the anodes each is in con- tact with a second contact bar connected to the power source.
• the two contact bars are arranged on one contact bar each, which are provided at the edge of the electrolyte tank.
• the respectively second ends of the hanger bars of the electrodes can rest on a supporting surface of insulating material, which for instance is likewise arranged on the contact bars.
• the electrodes have the first end of their hanger bar each resting on one of the two contact bars via a two-line contact.
• a contact bar with an at least substantially trapezoidal indentation is used particularly preferably, onto which the first end of the hanger bar is applied with a contact surface having an at least substantially rectangular cross-section.
• the two-line contact can of course also be effected in any other way known to the skilled person for this purpose.
• the process of the invention preferably employs cathodes whose e.g. steel-sheathed hanger bar has a copper core. Due to the high electric conductivity of copper, the current thus transmitted from the contact bar to the hanger bar is transmitted to the active electrode surface with only minimal losses, whereas the steel sheath surface of the hanger bar provides the hanger bar in particular with a high mechanical strength and high corrosion resistance.
• the copper core preferably has the same geometry as the hanger bar.
• a hanger bar made of steel, which for instance is substantially square in cross-section likewise includes a substantially square copper core.
• the cathodes in this way have two electric contacts, namely on the one hand with a contact bar and on the other hand with an equalizer bar, whereby the distribution of current between the electrodes is rendered more uniform. This is expedient in particular with high specific current intensities, in order to minimize the transfer resistances and electric losses.
• the contact bars and/or possibly the equalizer bar or, particularly preferably, the intermediate contact bars, on which the contact bars and possibly the equalizer bars are arranged are cooled during the electrolysis, in order to avoid a power loss, which results from the higher specific current intensity and the related higher current load, and a heating of the corresponding conductor bars.
• a water cooling of the conductor bars turned out to be particularly expedient, which is realized for instance by passing cooling water through a cooling water channel provided in the bus bars. Good results are achieved in particular with cooling water channels having a diameter of about 15 to 20 mm.
• Extruded bus bars with embedded cooling channel are preferably used for this purpose, although good results are also achieved with bus bars with milled slots, which are subsequently covered and welded, or with soldered copper tubes.
• tubes of PVC or hoses of vinyl material turned out to be particularly useful.
• the cooling water supply can also be effected by two coolant circuits divided into a primary circuit, which at least partly extends through the intermediate bus bars to be cooled, and a secondary circuit, which preferably extends completely outside the bus bars to be cooled.
• the connection of the two circuits can be effected in any way known to the skilled person.
• shell-and-tube heat exchangers as well as plate-type heat exchangers turned out to be useful.
• the primary circuit exclusively extends through the bus bars to be cooled and is operated with high-purity cooling water, for instance water purified by a reverse osmosis plant, whereas the secondary circuit is fed with crude water and is recooled for instance by an atmospheric cooling tower.
• the same prefera- bly includes a water expansion tank.
• a fluid distributor in the at least one electrolytic cell, through which during operation of the extraction electrolysis a liquid, a gas, a gas mixture or a mixture of gas and liquid is introduced, particularly preferably from below, into the electrolytic cell. Due to the convection flow generated by such introduction of fluid a better intermixing of the electrolyte is achieved, which is why the copper is deposited on the cathodes more uniformly. Furthermore, the convection flow effects a reduction in thickness of the boundary layers at the electrodes, which results in a better and faster mass transfer of the copper ions to the electrode surface.
• An introduction of fluid from below into the electrolytic cell is particularly preferred, because in the upper region of the cell a certain convection flow is obtained automatically due to the gas bubbles released at the anode during the extraction electrolysis, and therefore in particular in the lower region of the electrolytic cell an additional convection flow is important.
• electrolyte solution or a mixture of electrolyte solution and gas bubbles is introduced into the electrolytic cell through the fluid distributor. Since electrolyte continuously refreshed with copper sulfate from the leaching plant must in any case be supplied to the electrolytic cell during operation of the electrolysis, the fluid supply system requires no increase in the investment and operating costs in the first case and only an insignificant increase thereof in the second case. To increase the convection, other liquids, gases or gas mixtures can also be supplied to the electrolytic cell instead of electrolyte solution or a mixture of electrolyte solution and gas bubbles, or other systems such as mechanical mixing devices or the application of ultrasound can be used.
• the fluid distributor as it is of simple construction and efficient in terms of operating costs, consists of two tubes arranged substantially parallel to the longitudinal sides of the electrolytic cells, which at their surfaces each have one or more fluid outlet holes.
• the tubes are disposed at a small distance from the side wall. The distance is defined by the fastening mechanism of the tube at the cell wall and provides for the deposition of electrolyte sludge at the cell bottom. Typically, the distance is 10-50 mm.
• the distance of the two tubes from the cell bottom should be chosen such that electrolyte sludge can be collected below the fluid distributor at the cell bottom. Typically, the distance from the cell bottom is 100-200 mm.
• a tube arranged in the middle of the end face of the electrolytic cell which with respect. to the electrolytic cell extends vertically from the top to the bottom and at its lower end branches into two tubes extending horizontally and parallel to the end face of the electrolytic cell, one of which tubes is each connected with one end of the tubes of the fluid distributor, which extend substantially parallel to the longitudinal sides of the electrolytic cells.
• the fluid distributor should have a high enough number of fluid outlet holes.
• the relative number of the fluid outlet holes with respect to the total number of electrode pairs per electrolytic cell is decisive.
• the fluid distributor has 1-5, particularly preferably about 1-2 fluid outlet holes per electrode pair and cell side provided in the electrolytic cell.
• the shape of the fluid outlet holes is less decisive in terms of the convection flow. However, it turned out to be advantageous to provide substantially circular fluid outlet holes.
• the cross-sectional area of the fluid outlet holes In the case of circular fluid outlet holes, the diameter thereof preferably is 1 to 10 mm, particularly preferably 5 to 7 mm, and in particular about 6 mm.
• the cathodes used have an indentation of V-shaped cross-section at their lower longitudinal edge.
• a densification of streamlines necessarily occurring at straight edges which leads to an - undesired - increased deposition of copper at the edges, can be reduced and optimally even be prevented completely.
• the indentation further- more effects a separation of the front and rear sides deposited on the cathode into two cathode sheets.
• Fig. 1 shows the basic structure of an electrolysis plant for winning or refining copper
• Fig. 2 shows a section along line A-A in Fig. 1;
• Fig. 3 schematically shows a section through an electrolytic cell with a cathode held by a hanger bar
• Fig. 4 schematically shows a section through an electrolytic cell with an anode held by a hanger bar
• Fig. 5 schematically shows two-line contacts between the hanger bar and a contact bar
• Fig. 6 schematically shows one-line contacts between the hanger bar and a contact bar with equalizer bar
• Fig. 7 schematically shows the structure of a pilot plant for performing the process of the invention.
• electrolytic cells 1 (dimensions L x W x H e.g. about 12.5 x 2 x 2.7 m) each with a plurality of e.g. 115 anodes 2 and 114 cathodes 3, which are each arranged alternately and are held at the edges of the electrolytic cells 1 via hanger bars 4, are provided in numerous cell rows.
• the hanger bar 4 with the electrodes suspended thereon can be transported between a maintenance area 6 for the anodes 2, the cells 1 as well as a stripping machine 7, in which the copper deposited at the cathodes 3 is stripped in a manner known per se.
• Fig. 3 schematically shows a cathode 3 resting on the edges of the electrolytic cell via the hanger bar 4.
• Fig. 4 shows an anode 2 which is likewise held by a hanger bar 4.
• the anode 2 additionally has holes 8 for spacers, which ensure the required uniform distance between anodes and cathodes of e.g. 50 mm each.
• the one end of the hanger bars 4 rests on a contact bar 10 arranged at the edge of the electrolyte cell(cf. Fig. 5), which is connected with a non- illustrated power source via a bus bar.
• the other end of the hanger bar 4 rests on an equalizer bar 1 1. In general, this is effected via a one-line contact (cf. Fig. 6).
• the effort involved in the cathode movements is halved by a factor of 2, so that, based on the same amount of copper produced, correspondingly smaller or less crane systems are required, for instance one instead of two cranes for handling the electrodes, a smaller number of stripping machines and thus less production area and personnel.
• the ground area required for mounting the electrolytic cells in the tankhouse is also drastically reduced.
• different contact bars and possibly equalizer bars are required due to the higher specific current intensity, and for the subsequent processing of the loaded cathodes crane systems with a higher load-bearing capacity are required due to the higher weight of these cathodes.
• the height of the tankhouse between upper cell edge and crane path must be adjusted for processing the extended cathodes, and the same is true for mounting the electrolytic cells with increased overall height. Due to the greater cathode surface, differently sized stripping machines as well as folding or comminution machines for folding the larger copper sheets before supplying the same to a melting furnace designed for conventional plants are required. As both investment and operating costs for the last-mentioned measures are smaller than the corresponding savings achieved due to the smaller number of cathode movements, a significant decrease of the production costs is achieved on the whole.
• two electrolytic cells 1a, 1b connected in parallel with respect to the electrolyte supply and a common electrolyte preparation and circulation system are provided. Both electrolytic cells are electrically connected in series (not shown).
• the electrolytic cell 1a is equipped with two lead anodes (A, width of 0.5 m and height of 2 m, immersed surface) and a centrally arranged cathode K.
• the electrolytic cell 1b has 3 anodes (A, width of 0.5 m and height of 1 m, immersed surface) and two cathodes K of equal size.
• the used number and size of the electrodes leads to the fact that in the case of a series connection equal current densities are achieved in both electrolytic cells.
• Both electrolytic cells are charged with the same amount of fresh electrolyte (20a and 20b).
• the inflow of electrolyte is adjusted such that during a stationary operation of both electrolytic cells a copper depletion of about 1.5 g/l is obtained.
• the depleted solution 21a and 21b, respectively, is supplied to the electrolyte circuit. It comprises a stirred leaching tank 22, in which the depleted amount of copper is compensated by adding copper oxide 23.
• the overflow of the leaching tank 22 (enriched electrolyte 25) is introduced into a pump recipient tank 24.
• the pump recipient tank 24 is electrically heated by the heater 26 and stirred by partial recirculation of the enriched electrolyte 25'.
• the pump 27 is used for circulating the electrolyte.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrolytic Production Of Metals (AREA)

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• 2004
  • 2004-02-20 DE DE102004008813A patent/DE102004008813B3/de not_active Expired - Fee Related
• 2005
  • 2005-02-04 CA CA2553926A patent/CA2553926C/en not_active Expired - Fee Related
  • 2005-02-04 WO PCT/EP2005/001127 patent/WO2005080640A2/en not_active Ceased
  • 2005-02-04 US US10/589,592 patent/US20080035473A1/en not_active Abandoned
  • 2005-02-04 AU AU2005214817A patent/AU2005214817B2/en not_active Ceased
  • 2005-02-14 PE PE2005000173A patent/PE20060033A1/es active IP Right Grant

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