Efficient and energy-saving copper electrolyte purification method and nickel sulfate crystal

Abstract

The invention discloses an efficient and energy-saving purification method for a copper electrolyte. The purification method comprises the following steps: performing MVR (Mechanical Vapor Recompression) concentration; cooling and crystallizing; filtering and separating; electrodeposition copper and impurity removal by a circulation method; freezing and crystallizing; performing centrifugal separation; according to the method, in the MVR concentration process, a high-energy-efficiency steam compressor is used for compressing secondary steam generated by evaporation of the copper electrolyte, the enthalpy of the secondary steam is improved, and the secondary steam with improved heat energy is pumped into a plate heat exchanger to exchange heat with the copper electrolyte, so that the existing heat energy of the secondary steam is recycled; therefore, the consumption of external steam can be reduced to realize evaporation and concentration of the copper electrolyte to produce crude copper sulfate; in the circulation method electrodeposition copper removal and impurity removal process, the crystallization mother liquor is supplemented into the impurity removal circulation liquid, so that copper ions can be kept in an efficient impurity removal concentration range, and the removal efficiency of impurities such as arsenic is improved; a refrigerator is adopted to cool the electrolyte after electrodeposition copper removal and impurity removal, and then a centrifugal machine is adopted to realize solid-liquid separation of nickel sulfate crystals.

Description

Technical Field

[0001] The invention relates to the technical field of copper electrolyte impurity removal, and in particular to a high-efficiency and energy-saving copper electrolyte purification method and nickel sulfate crystals. Background Art

[0002] During the copper electrolytic refining process, the copper ion concentration in the electrolyte will continue to rise, the acid concentration will decrease, and at the same time, impurities such as Ni, As, Sb, and Bi in the anode copper will continue to accumulate in the electrolyte. Since the standard potential of As, Sb, and Bi is similar to that of copper, they may be discharged and precipitated at the cathode, which will affect the quality of the cathode copper. Therefore, in order to maintain the impurities such as Cu, Ni, As, Sb, and Bi in the electrolyte at a certain level, part of the electrolyte needs to be regularly extracted for purification.

[0003] In the existing copper electrolyte purification process, the main method for removing copper is conventional vacuum evaporation, where steam and electrolyte are introduced into the heat exchange plate to evaporate the water under vacuum conditions. The removal of impurities such as As, Sb, and Bi is widely carried out by induction electrolytic removal. The removal of Ni is mainly done by electroevaporation. The above methods have obvious defects, which are mainly manifested in:

[0004] (1) During the copper removal process, the steam consumption is large, and a lot of acidic wastewater is produced after steam condensation. The energy consumption of wastewater treatment in the later stage is large and the cost is high; the evaporation effect is poor and the evaporation specific gravity is not high, which seriously affects the efficiency of the back-end impurity removal;

[0005] (2) During the induction electrowinning process of removing impurities such as As, Sb, and Bi, the concentration of copper ions is difficult to control, and toxic arsenic gas may be produced, which is harmful to people's health;

[0006] (3) During the electroevaporation removal of Ni, there is a lot of acid mist on site, the working environment is poor, the energy consumption is extremely high, and the concentrated acid is highly corrosive. Summary of the invention

[0007] The purpose of the present invention is to provide an efficient and energy-saving copper electrolyte purification method and nickel sulfate crystals. The efficient and energy-saving copper electrolyte purification method has low steam and energy consumption, high impurity removal efficiency of impurities such as copper, arsenic, antimony, bismuth and nickel, is not easy to produce toxic gases such as arsenic, has good environmental protection, can continuously and uninterruptedly purify the copper electrolyte, does not need to stop the normal production activities of the copper electrolysis production system, and can effectively ensure the production capacity of the copper electrolysis production system.

[0008] To achieve the above object, the present invention adopts the following technical scheme: a method for purifying a highly efficient and energy-saving copper electrolyte, the purification method specifically comprising the following steps:

[0009] S1) MVR concentration: After preheating the copper electrolyte containing impurities, send it to the high-efficiency evaporation kettle, use a compressor to increase the temperature and pressure of the secondary steam produced by the copper electrolyte to maintain the evaporation state of the copper electrolyte itself, and after the copper electrolyte is concentrated to more than 1 times, keep continuous liquid inflow and continuous liquid outflow to obtain concentrated copper electrolyte;

[0010] S2) cooling crystallization: the concentrated copper electrolyte obtained in S1) is poured into a crystallization tank with a water cooling circulation system, and the temperature is cooled to 25-35° C. at a stirring speed of 60-100 r / min for crystallization to obtain a crystalline copper electrolyte;

[0011] S3) filtration separation: the crystalline copper electrolyte obtained in S2) is filtered through a centrifugal diaphragm pump to a belt filter to obtain crude copper sulfate and a crystallization mother liquor;

[0012] S4) Circulation method for electrowinning copper removal and impurity removal: introducing the crystallization mother liquor obtained in S3) into the electrowinning impurity removal tank and mixing it with the circulating impurity removal liquid to obtain a mixed liquor, and applying an electric field to cause the copper, arsenic, antimony, and bismuth impurity ions in the mixed liquor to undergo oxidation-reduction reactions on the electrodes, thereby achieving separation and removal of copper, arsenic, antimony, and bismuth impurities;

[0013] S5) freezing crystallization: firstly, precooling the electrolyte obtained by electrowinning and de-coppering and de-impurifying in S4) through a heat exchanger using water as a heat exchange medium, and then pumping it into a freezing crystallization tank, and circulating heat exchange between brine and electrolyte to cool the electrolyte and reduce the solubility of nickel sulfate therein, so that nickel is precipitated in the form of nickel sulfate crystals;

[0014] S6) Centrifugal separation: The frozen electrolyte is pumped into a scraper centrifuge to obtain nickel sulfate crystals through solid-liquid separation.

[0015] Furthermore, the copper ion concentration of the impure copper electrolyte in S1) is 40-60 g / l, and the acidity is 170-210 g / l; the copper ion concentration of the concentrated copper electrolyte is 80-120 g / l, and the acidity is 340-420 g / l.

[0016] Furthermore, the specific process of preheating the copper electrolyte in S1) is as follows: the condensed water after the secondary steam condensation is stored in a condensed water tank, the first-stage preheating uses condensed water to preheat the copper electrolyte to 50-60°C, the second-stage preheating uses the residual steam in the upper part of the condensed water tank to preheat the copper electrolyte to 60-75°C, and the third-stage preheating introduces external steam to preheat the copper electrolyte to 75-90°C.

[0017] Furthermore, the circulation method for electrowinning of copper and impurities in S4) is to use insoluble titanium-based lead dioxide anode electrowinning, pass direct current, and introduce the electrolyte into the electrowinning de-impurity tank as a mixture of the impurity-removed liquid and the crystallization mother liquor to maintain the copper ion concentration in the electrowinning liquid at 2-10 g / l.

[0018] Furthermore, the current of the direct current is 10000A-15000A, and the power-on time is 5-8 days.

[0019] Furthermore, the freezing crystallization tank described in S5) is a jacketed type, the tank body is wrapped with a jacket filled with brine, and the jacket is wrapped with insulation material. A motor is attached above the freezing crystallization tank for stirring, and the brine circulation pipeline is connected in series with multiple freezing crystallization tanks, and brine enters from top to bottom in each freezing crystallization tank.

[0020] Furthermore, the brine is composed of calcium chloride, sodium dichromate, sodium hydroxide and water, wherein the concentration of calcium chloride is 1.15-1.30 g / L, the concentration of sodium dichromate is 1.55-1.80 g / L, the concentration of sodium hydroxide is 0.44 g / L, and the density of the brine is 1.28-1.30 g / cm 3 , the pH value of brine is 7.5-8.5.

[0021] Furthermore, the freezing crystallization time of the electrolyte in each freezing crystallization tank is 10 hours, the stirring speed is 40r / min, and the terminal temperature of freezing crystallization is -15°C to -12°C.

[0022] Furthermore, the cooling crystallization in S2 specifically adopts jacketed water-cooled crystallization, the jacket is divided into an inner jacket and an outer jacket, and the jacket is a water-cooled circulation system.

[0023] A nickel sulfate crystal is prepared by adopting the purification method.

[0024] After adopting the above technical scheme, the present invention has the following beneficial effects: in the MVR concentration process, the present invention adopts MVR high-efficiency evaporation, which uses a high-efficiency steam compressor to compress the secondary steam generated by the evaporation of the copper electrolyte itself, converts electrical energy into thermal energy, and increases the enthalpy of the secondary steam. The secondary steam with increased thermal energy is pumped into a plate heat exchanger for heat exchange with the copper electrolyte to achieve the recycling of the existing thermal energy of the secondary steam, thereby reducing the amount of external steam to achieve the evaporation and concentration of the copper electrolyte to produce crude copper sulfate; in the cyclic electrolytic decoppering and de-impurity process, the mother liquor of crystallization separated by filtration in the previous stage is supplemented into the de-impurity circulating liquid (i.e., the de-impurity liquid), so that the copper ions can be maintained within the high-efficiency de-impurity concentration range. , thereby improving the removal efficiency of impurities such as arsenic; frozen crystallization uses a refrigerator to cool the electrolyte after electrolytic decoppering and impurity removal, and can increase the precipitation speed and precipitation rate of nickel sulfate through a brine composed of calcium chloride, sodium dichromate, sodium hydroxide and water, and quickly precipitate nickel sulfate from the electrolyte in an efficient and energy-saving manner, and then use a centrifuge to achieve solid-liquid separation of nickel sulfate crystals; therefore, the steam and energy consumption of the efficient and energy-saving copper electrolyte purification method are small, the impurity removal efficiency of impurities such as copper, arsenic, antimony, bismuth and nickel is high, it is not easy to produce toxic gases such as hydrogen arsine, it has good environmental protection, and can continuously and uninterruptedly purify the copper electrolyte without stopping the normal production activities of the copper electrolysis production system, which can effectively ensure the production capacity of the copper electrolysis production system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flowchart of a highly efficient and energy-saving copper electrolyte purification method. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] The present invention provides a high-efficiency and energy-saving copper electrolyte purification method, comprising the following steps:

[0028] S1, MVR concentration: After preheating the copper electrolyte containing impurities, send it to the high-efficiency evaporation kettle, use a compressor to increase the temperature and pressure of the secondary steam produced by the copper electrolyte to maintain the evaporation state of the copper electrolyte itself, and after the copper electrolyte is concentrated to more than 1 times, keep continuous liquid inflow and continuous liquid out to obtain concentrated copper electrolyte;

[0029] S2, cooling crystallization: the concentrated copper electrolyte is poured into a crystallization tank with a water cooling circulation system, and the temperature is cooled to 25-35° C. at a stirring speed of 60-100 r / min for crystallization to obtain a crystalline copper electrolyte;

[0030] S3, filtration separation: the crystallized copper electrolyte is filtered through a centrifugal diaphragm pump to a belt filter to obtain crude copper sulfate and a crystallization mother liquor, the crude copper sulfate is returned to the copper electrolysis production system or used as a refined copper sulfate raw material, and the crystallization mother liquor enters a circulation method electrowinning copper removal and impurity removal system;

[0031] S4, circulation method for electrowinning copper removal and impurity removal: introducing the crystallization mother liquor into the electrowinning impurity removal tank and mixing it with the circulating impurity removal liquid to obtain a mixed liquor, and applying an electric field to make the copper, arsenic, antimony, and bismuth impurity ions in the mixed liquor undergo oxidation-reduction reaction on the electrode to achieve separation and removal of copper, arsenic, antimony, and bismuth impurities;

[0032] S5, freezing crystallization: firstly, precooling the electrolyte after the electrowinning copper removal and impurity removal through a heat exchanger with water as the heat exchange medium, and then pumping it into a freezing crystallization tank, and circulating heat exchange between brine and electrolyte to cool the electrolyte and reduce the solubility of nickel sulfate therein, so that nickel is precipitated in the form of nickel sulfate crystals;

[0033] S6. Centrifugal separation: The frozen electrolyte is pumped into a scraper centrifuge to obtain nickel sulfate crystals through solid-liquid separation. The centrifuged electrolyte is then transported back to the copper electrolysis production system for use.

[0034] Preferably, the freezing crystallization tank in step S5 is a jacketed type, the tank body is wrapped with a jacket filled with brine, and the jacket is wrapped with insulation material. A motor is attached above the freezing crystallization tank for stirring, and the brine circulation pipeline is connected in series with multiple freezing crystallization tanks, and brine enters from the bottom and exits from the top in each freezing crystallization tank.

[0035] Preferably, the brine in step S5 is composed of calcium chloride, sodium dichromate, sodium hydroxide and water, wherein the concentration of calcium chloride is 1.15-1.30 g / L, the concentration of sodium dichromate is 1.55-1.80 g / L, the concentration of sodium hydroxide is 0.44 g / L, and the density of the brine is 1.28-1.30 g / cm 3 , the pH value of brine is 7.5-8.5.

[0036] Preferably, in step S5, the freezing crystallization time of the electrolyte in each freezing crystallization tank is 10 hours, the stirring speed is 40 r / min, and the terminal temperature of the freezing crystallization is -15°C to -12°C.

[0037] Preferably, before MVR concentration in step S1, the copper ion concentration of the copper electrolyte is 40-60 g / l and the acidity is 170-210 g / l. After MVR concentration, the copper ion concentration of the concentrated copper electrolyte is 80-120 g / l and the acidity is 340-420 g / l.

[0038] Preferably, the specific process of preheating the copper electrolyte in step S1 is as follows: the condensed water after the secondary steam condensation is stored in a condensed water tank, the first-stage preheating uses condensed water to preheat the copper electrolyte to 50-60°C, the second-stage preheating uses the residual steam in the upper part of the condensed water tank to preheat the copper electrolyte to 60-75°C, and the third-stage preheating introduces external steam to preheat the copper electrolyte to 75-90°C.

[0039] Preferably, the cooling crystallization in step S2 specifically adopts jacketed water-cooled crystallization, the jacket is divided into an inner jacket and an outer jacket, and the jacket is a water-cooled circulation system.

[0040] Preferably, the belt filter for filtration and separation in step S3 washes the separated crude copper sulfate with water and controls the water content of the crude copper sulfate.

[0041] Preferably, the parameters of the electric field in step S4 are: the alternating current is converted into direct current through a thyristor rectifier transformer, the current of the direct current is 10000A-15000A, and the power-on time is 5-8 days.

[0042] Preferably, the cyclic electrowinning method for copper removal and impurity removal in step S4 adopts insoluble titanium-based lead dioxide anode electrowinning, direct current is passed, and the electrolyte introduced into the electrowinning impurity removal tank is a mixture of the impurity removal liquid and the crystallization mother liquor, so as to maintain the copper ion concentration in the electrowinning liquid at 2-10 g / l, so as to precipitate impurities in large quantities without producing arsine.

[0043] Example

[0044] like Figure 1 As shown, a highly efficient and energy-saving copper electrolyte purification method comprises the following steps:

[0045] S1, MVR concentration: After preheating the copper electrolyte containing impurities, send it to the high-efficiency evaporation kettle, use a compressor to increase the temperature and pressure of the secondary steam produced by the copper electrolyte to maintain the evaporation state of the copper electrolyte itself, and after the copper electrolyte is concentrated to more than 1 times, keep continuous liquid inflow and continuous liquid out to obtain concentrated copper electrolyte;

[0046] Before MVR concentration in step S1, the copper electrolyte had a copper ion concentration of 50.63 g / l and an acidity of 190 g / l. After MVR concentration, the copper ion concentration of the concentrated copper electrolyte was 102.51 g / l and an acidity of 396.3 g / l.

[0047] The specific process of preheating the copper electrolyte in step S1 is as follows: the condensed water after the secondary steam condensation is stored in a condensed water tank, the first-stage preheating uses the condensed water to preheat the copper electrolyte to 55°C, the second-stage preheating uses the residual steam in the upper part of the condensed water tank to preheat the copper electrolyte to 70°C, and the third-stage preheating introduces external steam to preheat the copper electrolyte to 85°C;

[0048] S2, cooling crystallization: the concentrated copper electrolyte is poured into a crystallization tank with a water cooling circulation system, and the temperature is cooled to 30° C. at a stirring speed of 80 r / min for crystallization to obtain a crystalline copper electrolyte;

[0049] The cooling crystallization in step S2 specifically adopts jacketed water-cooling crystallization, the jacket is divided into an inner jacket and an outer jacket, and the jacket is a water-cooling circulation system;

[0050] S3, filtration separation: the crystallized copper electrolyte is filtered through a centrifugal diaphragm pump to a belt filter to obtain crude copper sulfate and a crystallization mother liquor, the crude copper sulfate is returned to the copper electrolysis production system or used as a refined copper sulfate raw material, and the crystallization mother liquor enters a circulation method electrowinning copper removal and impurity removal system;

[0051] The belt filter used for filtering and separating in step S3 washes the separated crude copper sulfate with water and controls the water content of the crude copper sulfate;

[0052] S4, circulation method for electrowinning copper removal and impurity removal: introducing the crystallization mother liquor into the electrowinning impurity removal tank and mixing it with the circulating impurity removal liquid to obtain a mixed liquor, and applying an electric field to make the copper, arsenic, antimony, and bismuth impurity ions in the mixed liquor undergo oxidation-reduction reaction on the electrode to achieve separation and removal of copper, arsenic, antimony, and bismuth impurities;

[0053] The parameters of the electric field in step S4 are: the alternating current is converted into direct current through a thyristor rectifier transformer, the current of the direct current is 13000A, and the power-on time is 6 days;

[0054] The cyclic electrowinning method for copper and impurity removal in step S4 uses an insoluble titanium-based lead dioxide anode for electrowinning, passes direct current, and introduces an electrolyte into the electrowinning impurity removal tank as a mixture of a de-impurity solution and a crystallization mother solution to maintain a copper ion concentration of 4 g / l in the electrowinning solution, so as to precipitate a large amount of impurities without producing arsine.

[0055] S5, freezing crystallization: firstly, precooling the electrolyte after the electrowinning copper removal and impurity removal through a heat exchanger with water as the heat exchange medium, and then pumping it into a freezing crystallization tank, and circulating heat exchange between brine and electrolyte to cool the electrolyte and reduce the solubility of nickel sulfate therein, so that nickel is precipitated in the form of nickel sulfate crystals;

[0056] The freezing crystallization tank in step S5 is a jacketed type, the tank body is wrapped with a jacket filled with brine, and the jacket is wrapped with a heat-insulating material. A motor is attached to the top of the freezing crystallization tank for stirring, and the brine circulation pipeline is connected in series with six freezing crystallization tanks, and brine enters from the top and exits from the bottom in each freezing crystallization tank;

[0057] The brine in step S5 is composed of calcium chloride, sodium dichromate, sodium hydroxide and water, wherein the concentration of calcium chloride is 1.25 g / L, the concentration of sodium dichromate is 1.65 g / L, the concentration of sodium hydroxide is 0.44 g / L, and the density of the brine is 1.30 g / cm 3 , the pH value of the salt water is 8;

[0058] In step S5, the freezing crystallization time of the electrolyte in each freezing crystallization tank is 10 hours, the stirring speed is 40r / min, and the terminal temperature of freezing crystallization is -13°C;

[0059] S6. Centrifugal separation: The frozen electrolyte is pumped into a scraper centrifuge to obtain nickel sulfate crystals through solid-liquid separation. The centrifuged electrolyte is then transported back to the copper electrolysis production system for use.

[0060] The impurity content of the impurity-containing copper electrolyte before preheating in step S1 (i.e., the impurity content that has not been removed) is shown in Table 1, and the impurity content of the electrolyte after centrifugation in step S6 (i.e., the impurity content that has been removed) is shown in Table 2.

[0061] Comparative Example 1

[0062] A method for purifying copper electrolyte comprises the following steps:

[0063] S1, MVR concentration: After preheating the copper electrolyte containing impurities, send it to the high-efficiency evaporation kettle, use a compressor to increase the temperature and pressure of the secondary steam produced by the copper electrolyte to maintain the evaporation state of the copper electrolyte itself, and after the copper electrolyte is concentrated to more than 1 times, keep continuous liquid inflow and continuous liquid out to obtain concentrated copper electrolyte;

[0064] Before MVR concentration in step S1, the copper electrolyte had a copper ion concentration of 50.63 g / l and an acidity of 190 g / l. After MVR concentration, the copper ion concentration of the concentrated copper electrolyte was 102.51 g / l and an acidity of 396.3 g / l.

[0065] The specific process of preheating the copper electrolyte in step S1 is as follows: the condensed water after the secondary steam condensation is stored in a condensed water tank, the first-stage preheating uses the condensed water to preheat the copper electrolyte to 55°C, the second-stage preheating uses the residual steam in the upper part of the condensed water tank to preheat the copper electrolyte to 70°C, and the third-stage preheating introduces external steam to preheat the copper electrolyte to 85°C;

[0066] S2, cooling crystallization: the concentrated copper electrolyte is poured into a crystallization tank with a water cooling circulation system, and the temperature is cooled to 30° C. at a stirring speed of 80 r / min for crystallization to obtain a crystalline copper electrolyte;

[0067] The cooling crystallization in step S2 specifically adopts jacketed water-cooling crystallization, the jacket is divided into an inner jacket and an outer jacket, and the jacket is a water-cooling circulation system;

[0068] S3, filtration separation: the crystallized copper electrolyte is filtered through a centrifugal diaphragm pump to a belt filter to obtain crude copper sulfate and a crystallization mother liquor, the crude copper sulfate is returned to the copper electrolysis production system or used as a refined copper sulfate raw material, and the crystallization mother liquor enters a circulation method electrowinning copper removal and impurity removal system;

[0069] The belt filter used for filtering and separating in step S3 washes the separated crude copper sulfate with water and controls the water content of the crude copper sulfate;

[0070] S4, circulation method for electrowinning copper removal and impurity removal: introducing the crystallization mother liquor into the electrowinning impurity removal tank and mixing it with the circulating impurity removal liquid to obtain a mixed liquor, and applying an electric field to make the copper, arsenic, antimony, and bismuth impurity ions in the mixed liquor undergo oxidation-reduction reaction on the electrode to achieve separation and removal of copper, arsenic, antimony, and bismuth impurities;

[0071] The parameters of the electric field in step S4 are: the alternating current is converted into direct current through a thyristor rectifier transformer, the current of the direct current is 13000A, and the power-on time is 6 days;

[0072] The cyclic electrowinning method for copper and impurity removal in step S4 uses an insoluble titanium-based lead dioxide anode for electrowinning, passes direct current, and introduces an electrolyte into the electrowinning impurity removal tank as a mixture of a de-impurity solution and a crystallization mother solution to maintain a copper ion concentration of 4 g / l in the electrowinning solution, so as to precipitate a large amount of impurities without producing arsine.

[0073] S5, freezing crystallization: firstly, precool the electrolyte after electrowinning copper removal and impurity removal through a heat exchanger with water as the heat exchange medium, then pump it into a freezing pool with a temperature of 0°C, freeze crystallize for 10 hours, and precipitate nickel in the form of nickel sulfate crystals;

[0074] S6. Centrifugal separation: The frozen electrolyte is pumped into a scraper centrifuge to obtain nickel sulfate crystals through solid-liquid separation. The centrifuged electrolyte is then transported back to the copper electrolysis production system for use.

[0075] Comparative Example 2

[0076] A method for purifying copper electrolyte comprises the following steps:

[0077] S1, MVR concentration: After preheating the copper electrolyte containing impurities, send it to the high-efficiency evaporation kettle, use a compressor to increase the temperature and pressure of the secondary steam produced by the copper electrolyte to maintain the evaporation state of the copper electrolyte itself, and after the copper electrolyte is concentrated to more than 1 times, keep continuous liquid inflow and continuous liquid out to obtain concentrated copper electrolyte;

[0078] Before MVR concentration in step S1, the copper electrolyte had a copper ion concentration of 50.63 g / l and an acidity of 190 g / l. After MVR concentration, the copper ion concentration of the concentrated copper electrolyte was 102.51 g / l and an acidity of 396.3 g / l.

[0079] The specific process of preheating the copper electrolyte in step S1 is as follows: the condensed water after the secondary steam condensation is stored in a condensed water tank, the first-stage preheating uses the condensed water to preheat the copper electrolyte to 55°C, the second-stage preheating uses the residual steam in the upper part of the condensed water tank to preheat the copper electrolyte to 70°C, and the third-stage preheating introduces external steam to preheat the copper electrolyte to 85°C;

[0080] S2, cooling crystallization: the concentrated copper electrolyte is poured into a crystallization tank with a water cooling circulation system, and the temperature is cooled to 30° C. at a stirring speed of 80 r / min for crystallization to obtain a crystalline copper electrolyte;

[0081] The cooling crystallization in step S2 specifically adopts jacketed water-cooling crystallization, the jacket is divided into an inner jacket and an outer jacket, and the jacket is a water-cooling circulation system;

[0082] S3, filtration separation: the crystallized copper electrolyte is filtered through a centrifugal diaphragm pump to a belt filter to obtain crude copper sulfate and a crystallization mother liquor, the crude copper sulfate is returned to the copper electrolysis production system or used as a refined copper sulfate raw material, and the crystallization mother liquor enters a circulation method electrowinning copper removal and impurity removal system;

[0083] The belt filter used for filtering and separating in step S3 washes the separated crude copper sulfate with water and controls the water content of the crude copper sulfate;

[0084] S4, circulation method for electrowinning copper removal and impurity removal: introducing the crystallization mother liquor into the electrowinning impurity removal tank and mixing it with the circulating impurity removal liquid to obtain a mixed liquor, and applying an electric field to make the copper, arsenic, antimony, and bismuth impurity ions in the mixed liquor undergo oxidation-reduction reaction on the electrode to achieve separation and removal of copper, arsenic, antimony, and bismuth impurities;

[0085] The parameters of the electric field in step S4 are: the alternating current is converted into direct current through a thyristor rectifier transformer, the current of the direct current is 13000A, and the power-on time is 6 days;

[0086] The cyclic electrowinning method for copper and impurity removal in step S4 uses an insoluble titanium-based lead dioxide anode for electrowinning, passes direct current, and introduces an electrolyte into the electrowinning impurity removal tank as a mixture of a de-impurity solution and a crystallization mother solution to maintain a copper ion concentration of 4 g / l in the electrowinning solution, so as to precipitate a large amount of impurities without producing arsine.

[0087] S5, freezing crystallization: firstly, precool the electrolyte after electrowinning copper removal and impurity removal through a heat exchanger with water as the heat exchange medium, then pump it into a freezing pool at a temperature of -30°C, freeze crystallize for 10 hours, and precipitate nickel in the form of nickel sulfate crystals;

[0088] S6. Centrifugal separation: The frozen electrolyte is pumped into a scraper centrifuge to obtain nickel sulfate crystals through solid-liquid separation. The centrifuged electrolyte is then transported back to the copper electrolysis production system for use.

[0089] The impurity content of the impurity-containing copper electrolyte before preheating in the embodiment, comparative example 1 and comparative example 2 (i.e., the impurity content that has not been de-impurified) is shown in Table 1; the impurity content of the electrolyte after centrifugation in step S6 of the embodiment (i.e., the impurity content that has been de-impurified by the frozen crystallization of the present application) is shown in Table 2; the impurity content of the electrolyte after centrifugation in step S6 of comparative example 1 (i.e., the impurity content that has been de-impurified by the frozen crystallization of comparative example 1) is shown in Table 3; the impurity content of the electrolyte after centrifugation in step S6 of comparative example 2 (i.e., the impurity content that has been de-impurified by the frozen crystallization of comparative example 2) is shown in Table 4.

[0090] Table 1 Impurity content of the copper electrolyte without dedoping in Example, Comparative Example 1 and Comparative Example 2

[0091] Cu(g / l) As(g / l) Sb(g / l) Bi(g / l) Ni(g / l) Not demixed 50.63 12.31 0.38 0.32 11.33

[0092] Table 2 Impurity content of the copper electrolyte using the frozen crystallization and impurity removal of the present application

[0093] Cu(g / l) As(g / l) Sb(g / l) Bi(g / l) Ni(g / l) Decontaminated 0.79 2.29 0.07 0.02 1.14

[0094] Table 3 Impurity content of the copper electrolyte using the frozen crystallization and impurity removal of Comparative Example 1

[0095] Cu(g / l) As(g / l) Sb(g / l) Bi(g / l) Ni(g / l) Decontaminated 0.79 2.29 0.07 0.02 5.56

[0096] Table 4 Impurity content of the copper electrolyte using the frozen crystallization and impurity removal of Comparative Example 2

[0097] Cu(g / l) As(g / l) Sb(g / l) Bi(g / l) Ni(g / l) Decontaminated 0.79 2.29 0.07 0.02 6.07

[0098] It can be seen from Tables 1 to 4 that the high-efficiency and energy-saving copper electrolyte purification method of the present invention has high impurity removal efficiency for impurities such as copper, arsenic, antimony, bismuth and nickel, is not easy to produce toxic gases such as hydrogen arsine, has good environmental protection, can continuously and uninterruptedly purify the copper electrolyte, does not need to stop the normal production activities of the copper electrolysis production system, and can effectively ensure the production capacity of the copper electrolysis production system; and it can be seen from Tables 2 to 4 that the impurity removal efficiency of nickel is obviously not as good as the freezing crystallization method of the present application by using the freezing crystallization method of Comparative Examples 1 and Comparative Examples 2. The present application can improve the precipitation speed and precipitation rate of nickel sulfate by using a brine composed of calcium chloride, sodium dichromate, sodium hydroxide and water, and quickly precipitate nickel sulfate from the electrolyte in an efficient and energy-saving manner, and then use a centrifuge to achieve solid-liquid separation of nickel sulfate crystals.

[0099] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for purifying an efficient and energy-saving copper electrolyte, characterized in that: The purification method specifically comprises the following steps: S1) MVR concentration: After preheating the copper electrolyte containing impurities, send it to the high-efficiency evaporation kettle, use a compressor to increase the temperature and pressure of the secondary steam produced by the copper electrolyte to maintain the evaporation state of the copper electrolyte itself, and after the copper electrolyte is concentrated to more than 1 times, keep continuous liquid inflow and continuous liquid outflow to obtain concentrated copper electrolyte; S2) cooling crystallization: the concentrated copper electrolyte obtained in S1) is poured into a crystallization tank with a water cooling circulation system, and the temperature is cooled to 25-35° C. at a stirring speed of 60-100 r / min for crystallization to obtain a crystalline copper electrolyte; S3) filtration separation: the crystalline copper electrolyte obtained in S2) is filtered through a centrifugal diaphragm pump to a belt filter to obtain crude copper sulfate and a crystallization mother liquor; S4) Circulation method for electrowinning copper removal and impurity removal: introducing the crystallization mother liquor obtained in S3) into the electrowinning impurity removal tank and mixing it with the circulating impurity removal liquid to obtain a mixed liquor, and applying an electric field to cause the copper, arsenic, antimony, and bismuth impurity ions in the mixed liquor to undergo oxidation-reduction reactions on the electrodes, thereby achieving separation and removal of copper, arsenic, antimony, and bismuth impurities; S5) freezing crystallization: firstly, precooling the electrolyte obtained by electrowinning and de-coppering and de-impurifying in S4) through a heat exchanger using water as a heat exchange medium, and then pumping it into a freezing crystallization tank, and circulating heat exchange between brine and electrolyte to cool the electrolyte and reduce the solubility of nickel sulfate therein, so that nickel is precipitated in the form of nickel sulfate crystals; S6) Centrifugal separation: The frozen electrolyte is pumped into a scraper centrifuge to obtain nickel sulfate crystals through solid-liquid separation.

2. The purification method according to claim 1, characterized in that: The copper ion concentration of the impure copper electrolyte in S1) is 40-60 g / l and the acidity is 170-210 g / l; the copper ion concentration of the concentrated copper electrolyte is 80-120 g / l and the acidity is 340-420 g / l.

3. The purification method according to claim 1, characterized in that: The specific process of preheating the copper electrolyte in S1) is as follows: the condensed water after the secondary steam condensation is stored in a condensed water tank, the first-stage preheating uses the condensed water to preheat the copper electrolyte to 50-60°C, the second-stage preheating uses the residual steam in the upper part of the condensed water tank to preheat the copper electrolyte to 60-75°C, and the third-stage preheating introduces external steam to preheat the copper electrolyte to 75-90°C.

4. The purification method according to claim 1, characterized in that: The circulation method for electrowinning of copper and impurities in S4) is to use insoluble titanium-based lead dioxide anode electrowinning, pass direct current, and introduce the electrolyte into the electrowinning impurity removal tank as a mixture of the impurity-removed liquid and the crystallization mother liquor to maintain the copper ion concentration in the electrowinning liquid at 2-10 g / l.

5. The purification method according to claim 4, characterized in that: The current of the direct current is 10000A-15000A, and the power-on time is 5-8 days.

6. The purification method according to claim 1, characterized in that: The freezing crystallization tank described in S5) is a jacketed type, the tank body is wrapped with a jacket filled with brine, and the jacket is wrapped with insulation material. A motor is attached above the freezing crystallization tank for stirring, and the brine circulation pipeline is connected in series with multiple freezing crystallization tanks, and brine enters from top to bottom in each freezing crystallization tank.

7. The purification method according to claim 6, characterized in that: The brine is composed of calcium chloride, sodium dichromate, sodium hydroxide and water, wherein the concentration of calcium chloride is 1.15-1.30 g / L, the concentration of sodium dichromate is 1.55-1.80 g / L, the concentration of sodium hydroxide is 0.44 g / L, and the density of the brine is 1.28-1.30 g / cm 3 , the pH value of brine is 7.5-8.

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8. The purification method according to claim 6, characterized in that: The freezing crystallization time of the electrolyte in each freezing crystallization tank is 10 hours, the stirring speed is 40r / min, and the terminal temperature of the freezing crystallization is -15°C to -12°C.

9. The purification method according to claim 6, characterized in that: The cooling crystallization in S2 specifically adopts jacketed water-cooling crystallization, the jacket is divided into an inner jacket and an outer jacket, and the jacket is a water-cooling circulation system.

10. A nickel sulfate crystal, characterized in that: The nickel sulfate crystals are prepared by the purification method according to any one of claims 1 to 9.

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