RU2133304C1 - Electrolyzer for deposition of metal - Google Patents

Abstract

FIELD: recovery of metals from solutions by electrolysis; may be used in nonferrous metallurgy for electric extraction of metals and in treatment and regeneration of sewage waters of metal electroplating processes. SUBSTANCE: electrolyzer has body, cover, fixed anodes arranged in two rows and disk cathodes rotating between anodes, and current leads. Electrolyzer body is multisectional with inlet and outlet pipes and intersection partitions with overflowing pipes located in them at different heights reducing in direction of outlet pipe. Force fans are located in the upper part of body. Cover is provided with branch pipes connected with receiver for discharge of steam-air mixture and hatches for loading of matrixes for metal deposition and removal of matrices with deposited metal. Hatches are made in each section. Cathodes are assembled of sectors forming disk. Sectors of assembled cathodes are trapezoidal in shape with put-on handle from dielectric material. Disk sectors are placed in radial guides accommodating in their internal sides, in special grooves, current lead busses interconnected through bushing, shaft and current leads with power supply source. Installed on guides facing opening is fixing device. EFFECT: higher productivity of electrolyzer. 2 cl, 5 dwg

Description

 The invention relates to the extraction of metals from solutions by electrolysis and can be used in the purification and regeneration of wastewater from galvanic plants, in non-ferrous metallurgy for electroextraction of metals.

Такие электролизеры обеспечивают возможность регулирования кислотности раствора без применения диафрагм. Однако использовать такие электролизеры при извлечении металлов из разбавленных растворов, какими являются сточные воды, нецелесообразно, так при этом будет велико падение напряжения в электролите ΔV_R. Падение напряжения в электролите определяется следующим уравнением (В. Н. Флеров. Сборник задач по прикладной электрохимии. М.: Высшая школа, 1976 г.)

где æ_э - удельная электропроводность;
l_э - расстояние между электродами;
j_пр - проходная плотность тока.Known electrolyzer for the treatment of aqueous solutions (A. S. USSR N 1597344 class. C 02 F 1/46 publ. 30.12.86), containing a housing with coaxial cylindrical electrodes placed in it, made so that the ratio of the external areas (S _external ) and internal (S _int ) electrodes satisfies the condition

Such electrolyzers provide the ability to control the acidity of the solution without the use of diaphragms. However, it is not practical to use such electrolyzers when extracting metals from dilute solutions, such as wastewater, since the voltage drop in the electrolyte ΔV _R will be large. The voltage drop in the electrolyte is determined by the following equation (V. N. Flerov. Collection of tasks in applied electrochemistry. M: Higher school, 1976)

where æ _e - electrical conductivity;
l _e - the distance between the electrodes;
j _CR - the passage current density.

где j_к и j_а - катодная и анодная плотности тока, соответственно и равные отношению тока в электролизере к площади соответствующего электрода.Feedthrough current density is determined by the expression

where j _k and j _a are the cathodic and anodic current densities, respectively, and equal to the ratio of the current in the cell to the area of the corresponding electrode.

 In relation to the considered system of coaxial electrodes, this leads to an increase in voltage drop in the electrolyte from 30 to 300 times and an increased consumption of electricity for electrolysis.

 A known apparatus for the electrochemical extraction of metals (German patent N 2652934, class C 02 C 5/12), which has a housing, a rotating cylindrical cathode and anodes located outside and inside the cathode. The processed solution circulates in the electrolyzer-pump-capacity-electrolyzer system, and the extracted metal settles on the cathode, falls to the bottom and then is removed through a special outlet. The rotation of the cathode reduces the diffusion limitations of the process of metal extraction from wastewater and allows to achieve a high degree of purification.

 The disadvantage of this apparatus is the difficulty in removing the cathode metal, if it is obtained in the form of a dense compact precipitate, therefore, the process of metal separation is carried out at current densities significantly higher than the diffusion limit when the metal is deposited in the form of powder. Under these conditions, other side reactions occur at the cathode (as a rule, hydrogen evolution), as a result of which the current efficiency decreases, and the energy consumption increases.

 Another disadvantage of this electrolyzer is that the unloading of metal that has fallen to the bottom presents certain technical difficulties and requires additional devices, for example, hydrocylones. Partial loss of crumbled metal due to its reaction with the working solution is also possible.

 In addition, during electroextraction, the metal content in the circulating solution decreases and the current efficiency decreases, and the unproductive power consumption increases.

 Of the known technical solutions, the closest to the claimed is an electrolyzer for the separation of metals from aqueous solutions, described in A.S. USSR N 1675539, class C 25 C 7/00, C 25 C 1/18, publ. 04/15/88. This electrolyzer consists of a housing, fixed anodes and disk cathodes rotating between them on a common shaft, current leads, power collectors, a spent electrolyte collector trough and knives for cutting the cathode deposit fixed on the electrolyzer cover.

 Such an electrolyzer allows you to conduct the process of metal extraction with high current efficiency, to obtain uniform compact metal precipitation. However, they can be used only in the case of soft metals, such as, for example, lead, which is easily removed with a knife.

 The use of this method of removing the precipitate for harder metals, especially such as nickel, chromium is almost impossible.

 Another disadvantage of electrolyzers of this type is their inapplicability for the deposition of metal on a base (matrix) of the same metal as the precipitated one, since removal of the precipitate requires disassembling almost the entire electrolyzer.

 The disadvantages include the fact that in the case of the use of such electrolytic cells in wastewater treatment, the current efficiency for the recoverable metal will decrease as the metal concentration in the solution decreases and, accordingly, lead to increased energy consumption and reduced productivity.

 The problem solved by the proposed device is the improvement of the electrolyzer for the separation of metals from solutions, the improvement of working conditions, the ability to extract metals from both dilute and concentrated solutions. The technical result from the use of the invention is to increase the productivity of the electrolyzer by simplifying and shortening the time when removing the cathode metal, increasing the current efficiency, improving the quality of the cathode metal, and the possibility of using any conductive materials as the cathode matrix, including bases of the same metal as deposited, from carbon fiber and volume-porous materials, etc., reducing costs in the manufacture and operation of electrolyzers. This result is achieved by the fact that in the electrolyzer containing a housing, a cover, fixed anodes arranged in two rows, disk cathodes rotating between them, current leads, the electrolyzer case is made multi-section with inlet and outlet nozzles, with intersection partitions containing overflow nozzles located at different heights, decreasing in the direction of the outlet pipe, pressure fans are located in the upper part of the body, the electrolyser cover is equipped with connected to the collector nozzles from each section for exit steam mixture and hatches for loading dies for metal deposition and recess matrices deposited metal executed in each section, and the cathodes formed teams consisting of sectors forming the drive assembly.

 The sectors of the prefabricated disk cathode are made in a trapezoidal shape with an overlaid handle made of dielectric material, the sectors of the disks are placed in radial guides, on the inside of which there are contact rails in special grooves connected through the sleeve, shaft and current leads to the power source, and on the guides facing the solution , a device for fixing sectors of the disk.

 In FIG. 1 shows a front view of the proposed electrolyzer, in FIG. 2 is a section AA in FIG. 1, in FIG. 3 is a partial cathode, side view, in FIG. 4 is a front view of FIG. 3, in FIG. 5 is a sectional view of an explosive in FIG. 3. The cell contains a housing 1, with intersectional partitions 2, with overflow pipes 8 located at different heights for the flow of the treated solution, with pressure fans 4 located in the upper part of the housing, with an inlet pipe 5 and an outlet pipe 6, a cover 7, with nozzles 3 for the exit of the vapor-air mixture connected to the manifold 9, with hatches 10 for loading and excavating the matrices with deposited metal. In the case in two rows there are fixed anodes 11 having independent current leads 12. Between the anodes there are combined disk cathodes 14 rotating on a common shaft 13, current to which is fed through current leads 15. The shaft with disk cathodes is rotated from the electric motor 16 through any speed variator 17 of a known type, for example, frictional (Designer Handbook, edited by Yavlinsky K.N., L .: Mechanical Engineering, 1989, pp. 406-408).

 To ensure ease and speed of removal of the deposited metal from the electrolyzer, the collection cathode 14 consists of a metal sleeve 18 having the shape of a half-coil, which is attached to the shaft 13 by any known method, for example, using fixing screws. To the end part of the sleeve having a larger diameter on both sides in a known manner, for example, radial guides 19 made of dielectric material are fastened with screws, in which sectors of the collecting cathode 20 are placed. On the inner side of the guides in a special groove in the grooves are the tonopod tires 21, connected to the sleeve 18 and through which the current from the power source through the current leads 15 and the shaft 13 is supplied to the sector 20 of the collecting cathode.

 At the end of the guides, which are facing the solution, a fixing device of a known type is placed, for example, made in the form of a bracket 22 of non-corrosive material. On the one hand, the bracket is attached to the axis 23 located in the groove 24, and on the other hand it enters the same groove on the parallel guide. Thanks to the locking device 22, the sectors do not fall out during the rotation of the disk and good contact between the current-carrying bus 21 and the sector 20 is ensured.

 The sectors from which the prefabricated disk cathode is formed have a trapezoid shape, which almost completely eliminates the generation of waste when they are cut and made from rectangular sheets, while in the manufacture of round solid disks, the waste is 25-30%. The number of sectors, based on obtaining the maximum coverage area, must be at least four, the maximum number is not limited.

 For ease of removal and installation, the end parts of the sectors facing the solution have a handle in the form of restrictive plates 25 fixed to the sectors, made of dielectric materials and having the shape of segments with an opening 26 for ease of grip. In addition, the segments protect the end parts of the sectors from dendritic formation during metal deposition due to the edge effect.

 The device operates as follows.

 First, through the hatches 10, the sectors of prefabricated disk cathodes 14 are mounted in all sections of the electrolyzer body 1, for which the sectors 20 are inserted all the way between the guides 19 and then fixed with a bracket 22.

 Through pipe 5 and overflow pipes 3 fill all sections of the cell with the treated solution. The liquid level in each section is determined by the height of the overflow pipes 3, decreasing in the direction of the outlet pipe 6. Next, fans 4 are used, which create an air stream blowing the sectors of the cathode 14 not immersed in the solution, an electric motor 16 for rotating the shaft 13, and current is supplied through current leads 12 and 15 to anodes 11 and prefabricated disc cathodes 14. Prefabricated disc cathodes are partially immersed in the treated solution. The rotation of the disk cathodes makes it possible to create intensive mixing of the solution, due to which the delivery of discharging metal ions to the cathode surface is facilitated, the diffusion limitations of the process are removed, the cathodic polarization is reduced and, therefore, the voltage across the electrolyzer, and the electric power consumption is reduced. In this case, the process goes into the kinetic region, i.e., it is controlled by non-diffusion stages and the conditions for the formation of powdery deposits on the cathode are excluded. Dense compact precipitates are of higher quality due to the absence of the inclusion of metal hydroxides in the precipitate, which occurs when powdered precipitates are obtained at the cathode.

 During rotation, the disk cathode carries out on the surface in the space between the solution mirror and the lid 7 of the electrolyzer a processed solution forming a film on the surface of the disk cathodes. The air flow from the pressure fans 4 contributes to the intensive evaporation of water from the treated solution, due to which the concentration of discharging metal ions in the treated solution increases, which increases the allowable current to the electrolyzer, reduces the size of the equipment and, therefore, its performance, creates conditions for increasing the yield current. After evaporation of 10-15% of the solution volume in the first section, a continuous flow of the solution to be treated is included in an amount corresponding to the design capacity. From the outlet pipe 6, a solution flows, the metal content of which corresponds to the required technology. In the case of wastewater treatment, the solution treated in this way can be drained into the sewer, and during electroextraction of metals in non-ferrous metallurgy, it can be leached into the technological cycle.

 To remove the cathode metal, the flow of solution into the electrolyzer 1 is turned off, the current to the electrolyzer is turned off, the electric motor 16 is turned off, the fan 4 is turned off, the hatch 10 is opened, the fixing bracket 22 is removed from the grooves 24 from the sectors opposite the hatch, and using a hole 26 for convenience of the restrictive plate 25, sectors 20 with the metal deposited on them are removed one after the other from all disk cathodes in all sections, inserting new matrices in their place.

 After replacing all sectors, the electrolyzer is turned on as described above. The proposed technical solution allows the cathode to be replaced quickly, to minimize downtime of the electrolyzer and thereby increase the productivity of the equipment.

 The vapor-air mixture fans 4 through the nozzles 8 and the manifold 9 are sent either to the atmosphere or to condensate water in any known manner, for example, using mixing capacitors (Planovsky A.N., Nikolaev P.I. Processes and devices of chemical and petrochemical technology. M .: Chemistry, 1987, p. 162-167).

 It is also possible the operation of the proposed device in pre-accumulation mode, when only the rotation of the shaft 13 with the precast disk cathodes 14 and fans 4 is turned on, and the current to the electrolysis is not turned on. In this case, evaporation of water and an increase in the concentration of discharging metal ions occur. This mode is advisable to use when treating diluted wastewater.

 When processing highly concentrated solutions, you can use the mode when the rotation of the shaft 13 with prefabricated disk cathodes 14 and the current to electrolysis are turned on, and pressure fans 4 are turned off.

 The use of electrolyzers of the proposed type makes it possible to increase the productivity of the equipment by increasing the concentration of metal ions during water evaporation, reducing the dimensions of the equipment, reducing the time to replace cathodes, increasing the current efficiency, improving the quality of the deposited metal by removing diffusion limitations of the process, using any materials as matrices including volume-porous, made of the same metal as the deposited metal, reduce the cost of manufacturing cathodes by using trapezoidal sectors, reduce the cost of operation of the electrolyzer.

Claims (2)

 1. The electrolyzer for the separation of metals from solutions, containing a housing, a cover, fixed anodes located in two rows, and disk cathodes rotating between them on a common shaft, current leads, characterized in that the electrolyzer body is multi-sectioned with input and output nozzles with intersection partitions with overflow nozzles located in them, located at different heights, decreasing in the direction of the outlet nozzle, with pressure fans located in the upper part of the housing, the cover is equipped with a connection connected to the collector nozzles for the exit of the vapor-air mixture and hatches for loading the matrices for the deposition of metal and excavation of the matrices with deposited metal, made in each section, the cathodes are prefabricated, consisting of sectors that make up the disk assembly.  2. The electrolyzer according to claim 1, characterized in that the sectors of the prefabricated disk cathode are made in a trapezoidal shape with an overlay handle made of dielectric material, and the sectors of the disks are placed in radial guides, on the inside of which there are current-carrying buses connected through a sleeve, a shaft in special grooves and current leads with a power source, and at the ends of the rails facing the solution, a fixing device is installed.

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