Method for controlling ion concentration and volume balance in electrolyte by using nickel hydroxide

Abstract

The invention discloses a method for controlling ion concentration and volume balance in an electrolyte by using nickel hydroxide. The method comprises the following steps: preparing a reaction base solution containing a first complexing agent and a first alkali; the first anolyte, a second complexing agent solution and a second alkali solution are simultaneously added to the bottom of the reaction base solution for stirring reaction, solid-liquid separation is performed after nickel hydroxide reaches the target particle size, and filtrate and a filter cake are obtained; washing the filter cake, and slurrying the filter cake by using a second anolyte to obtain a nickel hydroxide slurrying material; and adjusting the sodium ion concentration, pH and nickel ion concentration of the third anolyte by adopting a sodium hydroxide solution, a nickel hydroxide slurrying material and a nickel sulfate solution to obtain the catholyte. According to the invention, a feeding mode of feeding at the bottom is adopted, and a complexing agent is matched, so that crystals can stably grow and are convenient to filter; in the preparation process, aging and too high pH conditions are not needed, operation is simpler, labor intensity is small, the reaction rate is higher, and continuous treatment of the anolyte can be achieved.

Description

Technical Field

[0001] The present application relates to the technical field of nickel electrolysis, and in particular to a method for controlling ion concentration and volume balance in an electrolyte by using nickel hydroxide. Background Art

[0002] Nickel electrolysis is a process in which nickel ions are reduced to metallic nickel on the cathode under the action of current by supplying power to the electrolytic cell through an external power source. In the nickel electrolysis process, the electrolyte circulation is a closed-loop system, that is, the cathode electrolyte (i.e., cathode liquid) percolates out of the diaphragm to the anode chamber, and the anode electrolyte (i.e., anode liquid) returns to the cathode chamber after purification. In order to maintain long-term normal production, the total volume of electrolyte circulating in the entire system must remain roughly unchanged. However, the volume of the electrolyte often changes during the production process. Among them, the reasons for the reduction of the electrolyte volume include: electrolyte evaporation takes away some water, the produced slag takes away some water, and some electrolyte is extracted during the preparation of nickel carbonate; the reasons for the expansion of the electrolyte volume include: water brought in by the supplementary nickel sulfate solution, water brought in by the reagent added during purification, and backwash water in the pipeline. In actual production, the chance of electrolyte volume expansion is much greater than the chance of volume reduction, especially the water brought in by the supplementary nickel sulfate solution. If the operation is not properly controlled, the electrolyte volume will expand rapidly. Therefore, the volume of water introduced and the volume of part of the electrolyte extracted during the preparation of nickel carbonate must be strictly controlled during the production process to adjust the total volume of the electrolyte. During nickel electrolysis, a certain concentration of sodium ions can improve the conductivity of the electrolyte, reduce the resistance of the solution, and reduce power consumption. However, if the sodium ion concentration is too high, it will not only increase the internal stress of the cathode nickel, causing the nickel plate to crack and bend, but may also make the electrode polarization phenomenon more serious. In addition, if the sodium ion concentration is too high, it will also increase the viscosity of the solution and the resistance of the diaphragm bag, affect the filtration performance, produce crystals, block pipes and valves, and affect normal production. However, since sodium carbonate solution is needed to adjust the pH value of the electrolyte during electrolyte purification, the sodium ion concentration in the electrolyte will gradually increase. In order to keep the sodium ion concentration in the electrolyte within a certain range, a certain amount of sodium salt must be regularly removed in the production system. At present, the more common method of removing sodium salt is to extract a part of the anolyte from the closed-loop circulation system of the electrolyte, use the nickel sulfate in the anolyte to react with sodium carbonate to generate nickel carbonate and sodium sulfate, and then return the nickel carbonate as a neutralizer to the electrolyte circulation system. The solution after the precipitation of nickel carbonate contains a large amount of sulfate ions, sodium ions and water, which are discarded to achieve the purpose of sulfur balance, sodium balance and volume balance of the production system. In this process, the chemical reaction equations involved include: NiSO 4 +Na 2 CO 3 =NiCO 3 ↓+Na 2 SO 4 NiCO 3 +2H + =Ni 2+ +H 2 O+CO 2 ↑ However, in the existing method of controlling ion concentration and volume balance using nickel carbonate, due to the large solubility product of nickel carbonate, the precipitation reaction is incomplete, the nickel content in the waste liquid filtered after precipitation is high, and wastewater treatment is more difficult. In order to make the reaction more sufficient, an aging process is often required, which will lead to complicated processes and high labor intensity. At the same time, in the process of putting into sodium carbonate, the liquid inlet mode of adding raw material liquid and alkali solution from the tank entrance in parallel is adopted, the reactant concentration is too large, the precipitation reaction is carried out in an instant, and a large number of crystal nuclei are generated. The crystal nucleus formation rate is very fast and the crystal growth rate is very slow, and it is easy to generate colloidal solids and basic carbonates that are difficult to filter, causing the quality fluctuation of electrolytic nickel products. In addition, the existing nickel carbonate production process is carried out under high temperature conditions of 85°C, which is not suitable for the long-term operation of instruments and meters.

[0003] Therefore, there is an urgent need to provide a new method for controlling the ion concentration and volume balance in the electrolyte to solve the above problems. Summary of the invention

[0004] The purpose of this application is to overcome the above-mentioned technical deficiencies and propose a method for controlling the ion concentration and volume balance in the electrolyte using nickel hydroxide, so as to solve the technical problems of the prior art method for controlling the ion concentration and volume balance using nickel carbonate, which has complex process, high labor intensity and difficulty in filtering nickel carbonate slurry.

[0005] The present application provides a method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide, comprising the following steps: S1, preparing a reaction base solution containing a first complexing agent and a first base; S2, adding the first anolyte, the second complexing agent solution and the second alkali solution to the bottom of the reaction bottom solution at the same time for stirring reaction, and performing solid-liquid separation after the nickel hydroxide reaches the target particle size to obtain a filtrate and a filter cake; S3, washing the filter cake and slurrying it with a second anode liquid to obtain a nickel hydroxide slurry; S4. Using sodium hydroxide solution, nickel hydroxide slurry and nickel sulfate solution, the sodium ion concentration, pH and nickel ion concentration of the third anode liquid are adjusted to obtain a cathode liquid.

[0006] Compared with the prior art, the beneficial effects of this application include: The present application adopts a bottom-feeding feeding method and is combined with a complexing agent to allow the crystals to grow stably and be easy to filter; the preparation process of the present application does not require aging and excessively high pH conditions, the operation is simpler, the labor intensity is low, the reaction rate is higher, and the continuous preparation of nickel hydroxide and the continuous disposal of the anode liquid can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 The present invention provides a process flow chart of a method for controlling ion concentration and volume balance in an electrolyte by using nickel hydroxide according to an embodiment of the present invention. DETAILED DESCRIPTION

[0008] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0009] See also Figure 1 The present application provides a method for controlling the ion concentration and volume balance in an electrolyte using nickel hydroxide, comprising the following steps: S1, preparing a reaction base solution containing a first complexing agent and a first base; S2, adding the first anolyte, the second complexing agent solution and the second alkali solution to the bottom of the reaction bottom solution at the same time for stirring reaction, and performing solid-liquid separation after the nickel hydroxide reaches the target particle size to obtain a filtrate and a filter cake; S3, washing the filter cake and then slurrying it with the second anode liquid to obtain a nickel hydroxide slurry; in this step, by washing the filter cake, impurities such as sodium ions and complexing agents entrained in the filter cake can be washed; S4. Using sodium hydroxide solution, nickel hydroxide slurry and nickel sulfate solution, the sodium ion concentration, pH and nickel ion concentration of the third anode liquid are adjusted to obtain a cathode liquid.

[0010] The present application uses nickel hydroxide to control the ion concentration and volume balance in the electrolyte. Specifically, in terms of ion concentration balance, the nickel ions consumed in the nickel electrolysis process are supplemented by nickel hydroxide slurry and high-concentration nickel sulfate solution, thereby achieving a balance in nickel ion concentration; however, due to the supplementation of high-concentration nickel sulfate solution and sodium hydroxide solution and the electrolysis of water during the electrolysis process, the concentrations of sodium ions, hydrogen ions, and sulfate ions in the anode liquid continue to increase, and the hydrogen ions are neutralized by the nickel hydroxide acid and base. The excess sodium sulfate is discharged during the preparation of nickel hydroxide along with high-concentration sodium sulfate wastewater (filtrate after solid-liquid separation), thereby achieving a balance in sulfate ion and sodium ion concentrations. In terms of volume balance, the supplemented high-concentration nickel sulfate solution will introduce a large amount of water, and the excess water will also be discharged during the preparation of nickel hydroxide along with high-concentration sodium sulfate wastewater, thereby achieving volume balance. During the electrolysis process, the reactions occurring at the cathode and anode are as follows: cathode:

[0011] anode:

[0012] The present application can assist the rapid growth of nickel hydroxide particles by adding a complexing agent. If a complexing agent is not added, the reaction rate is slow, a rapid reaction cannot be achieved, and the particle size that meets the target range is rare. Specifically, the formation of spherical nickel hydroxide undergoes three processes: nucleation, crystal growth, and aggregation. Among them, the two processes of nucleation and crystal growth determine the size of nickel hydroxide crystallites. If the nucleus formation rate is very fast and the crystal growth rate is very slow, a colloidal solid will be formed, otherwise large crystals will be formed. Compared with the ordinary nickel hydroxide production process, in the method of the present application, by adding a complexing agent, the Ni 2+ The complex is formed with the complexing agent, and then the complex is precipitated with the hydroxide ions in the solution. In this process, the formation of the complex greatly reduces the free Ni 2+ The concentration of Ni in the material is 2+ Rapid dilution. Both of these factors make the reaction ion Ni 2+ The supersaturation decreases. Since the nucleation rate v is proportional to the supersaturation S of the reaction material that generates the crystal, this controls the nucleation rate so that it is not too fast and avoids the formation of colloidal precipitates. At the same time, strong stirring causes the microcrystals to collide and agglomerate into spherical aggregates as soon as possible, and its shear force also prevents the agglomerated particles from being too large, and finally obtains a nickel hydroxide product with a moderate particle size distribution and easy solid-liquid separation. Among them, taking ammonia water as a complexing agent as an example, the relevant reaction formula in the preparation process of nickel hydroxide is: Ni 2+ +xNH 3 ·H 2 O=[Ni(NH 3 ) x ]2+ +xH 2 O [Ni(NH 3 ) x ] 2+ +2OH - =Ni(OH) 2 +xNH 3 Compared with the existing method of using nickel carbonate to control ion concentration and volume balance, the solubility product of nickel hydroxide is smaller, the reaction is more thorough, the wastewater contains less nickel, and the wastewater treatment pressure is small; the present application adopts a bottom feeding method and is combined with a complexing agent, so that the initial reaction concentration is not too high, and the crystals can grow stably and are easy to filter.

[0013] Compared with the existing method of using nickel carbonate to control ion concentration and volume balance, the present invention uses nickel hydroxide to adjust the pH of the anolyte, and no CO is generated during the reaction. 2 Gas, no need to install special CO in the reactor 2 The collection device also avoids the large amount of CO 2 Risk of leakage due to gas generation.

[0014] Compared with other existing methods for controlling ion concentration and volume balance, after the reaction is stable, the method of the present application can ensure that each kettle (reactor volume 36m 3 ) Anode liquid feed at 6m 3 / h, which has obvious speed advantage and can consume the anode liquid faster and relieve the pressure of volume expansion.

[0015] Compared with other existing methods for preparing nickel hydroxide, the preparation process of the present application does not require aging and excessively high pH conditions, the operation is simpler, the reaction rate is higher, and the continuous preparation of nickel hydroxide can be achieved.

[0016] In this embodiment, in the first anolyte, the second anolyte and the third anolyte, the nickel sulfate content is 50-90g / L, including but not limited to 50g / L, 60g / L, 70g / L, 80g / L, 90g / L, etc.; the pH is 0.5-2, including but not limited to 0.5, 1, 1.5, 2, etc.; the sodium sulfate content is 20-40g / L, including but not limited to 20g / L, 25g / L, 30g / L, 35g / L, 40g / L, etc.; the boric acid content is 2-8g / L, including but not limited to 2g / L, 3g / L, 4g / L, 5 / L, 6g / L, 7g / L, 8g / L, etc.; and other components are trace impurities.

[0017] In this embodiment, in step S1, the first complexing agent is ammonia water.

[0018] In this embodiment, in step S1, the first alkali is sodium hydroxide.

[0019] In this embodiment, in step S1, the concentration of the first complexing agent in the reaction base solution is 3-6 g / L, including but not limited to 3 g / L, 4 g / L, 5 / L, 6 g / L, etc.

[0020] In this embodiment, in step S1, the pH of the reaction base solution is 10-11, including but not limited to 10, 10.2, 10.4, 10.6, 10.8, 11, etc.

[0021] In this embodiment, in step S1, the preparation process of the reaction base liquid includes: uniformly mixing the first complexing agent, the first base and water to obtain the reaction base liquid.

[0022] Preferably, the first complexing agent is added in the form of a solution, and the mass fraction of the first complexing agent solution is 15%-18%, including but not limited to 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, etc.

[0023] Preferably, the first alkali is added in the form of a solution, and the mass fraction of the first alkali solution is 30%-33%, including but not limited to 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, etc.

[0024] Preferably, the first complexing agent, the first base and the water are uniformly mixed by stirring, and the stirring speed is 10-20 Hz, including but not limited to 10 Hz, 12 Hz, 14 Hz, 16 Hz, 18 Hz, 20 Hz and the like.

[0025] In this embodiment, in step S2, the second complexing agent is aqueous ammonia.

[0026] In this embodiment, in step S2, the mass fraction of the second complexing agent solution is 15%-18%, including but not limited to 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, etc.

[0027] In this embodiment, in step S2, the second alkali is sodium hydroxide.

[0028] In this embodiment, in step S2, the mass fraction of the second alkaline solution is 30%-33%, including but not limited to 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, etc.

[0029] In this embodiment, in step S2, the amount of the reaction base liquid is 22%-25% of the volume of the reactor, including but not limited to 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, etc.

[0030] In this embodiment, in step S2, the feed rate ratio of the first anolyte, the second alkaline solution, and the second complexing agent solution is 1m / s. 3 / h: (0.25-0.35) m 3 / h: (40-50) L / h, further 1m 3 / h: 0.3m 3 / h:45L / h.

[0031] In some specific embodiments of the present application, in step S2, the volume of the reactor is 35-40m 3 , the feed rate of the first anolyte is 5-7m 3 / h, including but not limited to 5m 3 / h、5.5m 3 / h、6m 3 / h、6.5m 3 / h、7m 3 / h, etc.; the feed rate of the second complexing agent solution is 250-300L / h, including but not limited to 250L / h, 260L / h, 270L / h, 280L / h, 290L / h, 300L / h, etc.; the feed rate of the second alkali solution is 1-2.5m 3 / h, including but not limited to 1m 3 / h、1.2m 3 / h、1.5m 3 / h、1.8m 3 / h、2m 3 / h、2.2m 3 / h、2.5m 3 / h, etc.

[0032] In the present embodiment, in step S2, during the stirring reaction, the pH of the upper liquid level of the reactor is controlled to be 10-11, including but not limited to 10, 10.2, 10.4, 10.6, 10.8, 11, etc. The present application controls the pH of the reaction system to be 10-11, so that the nickel ions are basically precipitated completely and the particle size of the nickel hydroxide meets the requirements. If the pH of the reaction system is too low, not only will the particle size of the nickel hydroxide be too small, but also a large amount of nickel ions will remain in the solution, and the filtrate needs to be further processed to recover the precious metal nickel, which brings great pressure to the wastewater treatment; if the pH of the reaction system is too high, the particle size of the reaction product will also be too small, and alkali will be wasted.

[0033] In this embodiment, in step S2, during the stirring reaction, the total concentration of the first complexing agent and the second complexing agent on the upper liquid level of the reactor is controlled to be 2-4 g / L, including but not limited to 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, etc. In the reaction system, the concentration of the second complexing agent is closely related to the particle size of the nickel hydroxide. In the present invention, the nickel hydroxide obtained by controlling the concentration of the second complexing agent in the reaction system within the above range is more conducive to filtration.

[0034] In this embodiment, in step S2, during the stirring reaction, the reaction temperature is 50-60° C. By controlling the reaction temperature at 50-60° C., the present application can not only make the nickel ions basically precipitate completely, but also reduce the damage of equipment (such as automatic control equipment, etc.) at high temperature. At the same time, the lower temperature consumes less steam, which can save costs.

[0035] In this embodiment, in step S2, during the stirring reaction, the stirring speed is 15-25 Hz, including but not limited to 15 Hz, 17 Hz, 19 Hz, 21 Hz, 23 Hz, 25 Hz, etc. In this application, by controlling the stirring speed within the above range and coordinating with other reaction conditions (such as pH, ammonia concentration, etc.), when the reaction is stable, when the solid-liquid mixture gradually reaches the overflow port, the crystal particle size D50 also grows to 15-25 um, at which time it just flows out of the reactor and enters the filter press for filtration, and no difficult-to-filter basic carbonate is produced.

[0036] In this embodiment, in step S2, the target particle size D50 is 15-25 μm. By controlling the target particle size D50 in the range of 15-25 μm, the present application is not only beneficial to the solid-liquid separation of the nickel hydroxide solution, but also to the pH adjustment. If the target particle size is too small, it is easy for the nickel hydroxide to pass through the filter cloth during filtration, and it is difficult for the nickel hydroxide to form a filter cake, and it is difficult to remove the residue; if the target particle size is too large, the large particles of nickel hydroxide cannot be quickly dissolved when the pH value is adjusted, which easily leads to the adjustment exceeding the required pH range.

[0037] In this implementation, step S2 specifically includes: S21, adding reaction bottom liquid into the reactor; S22, adding the first anolyte, the second complexing agent solution and the second alkali solution to the reaction bottom solution from the bottom of the reactor simultaneously and continuously, and stirring the reaction; S23, after the nickel hydroxide reaches the target particle size, the nickel hydroxide rises to the upper layer of the reactor under the action of stirring, and enters the filter press through overflow for filtration to obtain a filtrate and a filter cake. In the present application, if the target particle size is too large, the nickel hydroxide will easily sink to the bottom, and it will be difficult to make the nickel hydroxide slurry overflow out of the reactor by stirring.

[0038] The present application uses stirring to make the material flow upward. When the reaction is stable, when the solid-liquid mixture gradually reaches the overflow port, the crystal particle size D50 also grows to 15-25um, at which time it just flows out of the reactor and enters the filter press for filtration, and no difficult-to-filter basic carbonate is produced.

[0039] In the present application, it should be noted that in the initial stage of the reaction, due to the limitation of the volume of the reactor, when the solid-liquid mixture gradually reaches the overflow port, the crystal particle size D50 may not reach 15-25um. At this time, the overflowed nickel hydroxide that has not reached the target particle size can be treated separately; when the particle size D50 reaches 15-25um, the reaction is stable, and the overflowed nickel hydroxide that has reached the target particle size is subjected to subsequent solid-liquid separation to achieve continuous production.

[0040] More specifically, the first anolyte, the second complexing agent solution and the second alkali solution can be added to the bottom of the reaction bottom solution at the same time by extending the feeding tube into the bottom of the reaction kettle.

[0041] In this embodiment, in step S2, the process of solid-liquid separation after the nickel hydroxide reaches the target particle size also includes: continuously introducing the first anode liquid, the second alkaline solution, and the second complexing agent into the bottom of the reactor to maintain the reaction temperature to achieve continuous preparation of nickel hydroxide.

[0042] In this embodiment, in step S3, the present invention does not limit the solid-liquid ratio used in the slurrying process, and those skilled in the art can make a choice according to actual conditions, and can use the second anode liquid to slurry the filter cake to facilitate pipeline transportation and subsequent addition to the reactor.

[0043] In some embodiments of the present invention, in step S3, the nickel content in the nickel hydroxide slurry is 230-300 g / L.

[0044] In this embodiment, in step S4, the mass fraction of the sodium hydroxide solution is 20%-40%, including but not limited to 20%, 25%, 30%, 35%, 40%, etc.

[0045] In this embodiment, in step S4, the concentration of the nickel sulfate solution is 140-150 g / L, including but not limited to 140 g / L, 142 g / L, 145 g / L, 147 g / L, 150 g / L, etc.

[0046] In this embodiment, in the cathode liquid, the sodium ion concentration is 25-35 g / L, the nickel ion concentration is 90-100 g / L, and the pH is 3-3.5.

[0047] In this embodiment, step S4 specifically includes: adjusting the sodium ion concentration, pH and nickel ion concentration of the third anode liquid by using sodium hydroxide solution, nickel hydroxide slurry and nickel sulfate solution in sequence to obtain a cathode liquid.

[0048] In the present application, Na ions can be supplemented by adding sodium hydroxide solution to the third anode liquid to achieve Na ion balance; after supplementing Na ions, continuing to add nickel hydroxide slurry can adjust the pH to 3-3.5 to meet the pH requirements of the cathode liquid; finally, by supplementing nickel sulfate solution, the nickel ion content reaches 90-100 g / L to achieve nickel ion concentration balance.

[0049] Example 1 This embodiment provides a method for controlling the ion concentration and volume balance in an electrolyte using nickel hydroxide, wherein the raw materials include: 32% by mass of liquid alkali, 16% by mass of ammonia water; the composition of the anolyte is: 70 g / L of nickel sulfate, pH 1.25, 30 g / L of sodium sulfate, 5 g / L of boric acid, and other components are trace impurities. The specific steps are as follows: (1) 8m of pure water 3 , 200L ammonia water and 20L liquid caustic soda are added to a volume of 36m 3 In the reactor, pure water, ammonia water and liquid alkali were appropriately added for fine adjustment to control the pH value to 10.5, the ammonia concentration to 4.5 g / L, and the stirring speed to 15 Hz to obtain the reaction bottom liquid; (2) The anolyte is heated to 6 m 3 / h rate, liquid alkali at 1.8m 3 / h rate, ammonia water is continuously added to the bottom of the reactor at a rate of 270L / h as a benchmark. During the reaction process, the pH value at the upper liquid surface of the reactor is controlled at 10-11, the ammonia concentration is controlled at 2-4g / L, the stirring speed is 20Hz, the temperature is controlled at 50-60℃, and sampling is performed every half hour; after 3.5h of reaction, the particle size D50 of nickel hydroxide at the upper liquid surface of the reactor is detected to be in the range of 15-25μm, and the nickel hydroxide in the reactor rises to the upper layer of the reactor under the action of stirring, enters the filter press through overflow for filtration, and the filtrate obtained after filtration (nickel ion concentration is 30-40mg / L) is discharged as wastewater, and the front side of the filter cake residue is washed for 30 minutes; (3) The filter cake is removed from the slurry and placed in a slurry barrel, where it is mixed with the anode liquid at a solid-liquid ratio of 1:4 to obtain a nickel hydroxide slurry having a nickel content of 230-300 g / L; (4) Use liquid alkali to convert the anolyte (actual volume of the anolyte is 15m 3 , reactor volume 25m 3 ) was adjusted to a sodium ion concentration of 25-35 g / L, and then 1 m 3The pH of the anode liquid is adjusted to 3-3.5 by nickel hydroxide slurry, and finally the nickel ion concentration of the anode liquid is adjusted to 90-100 g / L by a nickel sulfate solution with a concentration of 145 g / L to obtain a cathode liquid.

[0050] Comparative Example 1 Compared with Example 1, the only difference is that the pH value of the upper liquid level of the reactor in step (2) is controlled at 8.5-9.5. In this comparative example, after reacting for 3.5 hours, the particle size D50 of nickel hydroxide is detected to be 5-20 μm; and the nickel ion concentration in the filtrate obtained after filtration is 100-200 mg / L.

[0051] Comparative Example 2 Compared with Example 1, the only difference is that the pH value of the upper liquid level of the reactor in step (2) is controlled at 11-12. In this comparative example, after reacting for 3.5 hours, the particle size D50 of nickel hydroxide is detected to be 7-15 μm.

[0052] By comparing Example 1 with Comparative Examples 1-2, it can be seen that in the system of the present application, the pH of the reaction system needs to be strictly controlled. Too high or too low pH of the reaction system is not conducive to complete precipitation of nickel ions and obtaining nickel hydroxide that meets the target particle size range.

[0053] Comparative Example 3 Compared with Example 1, the only difference is that in step (2), the stirring speed is adjusted to 35 Hz. In this comparative example, after reacting for 3.5 hours, the particle size D50 of nickel hydroxide is detected to be 10-20 μm.

[0054] By comparing Example 1 with Comparative Example 3, it can be seen that in the system of the present application, the stirring rate needs to be strictly controlled. If the stirring rate is too high, the particle size will reach the overflow port before reaching the target range, and nickel hydroxide that meets the target particle size requirements cannot be obtained.

[0055] Comparative Example 4 Compared with Example 1, the only difference is that no ammonia water is added during the preparation of the reaction base solution and the reaction process. In this comparative example, after reacting for 3.5 hours, the particle size D50 of nickel hydroxide is detected to be 3-8 μm.

[0056] By comparing Example 1 with Comparative Example 4, it can be seen that in the system of the present application, if ammonia water is not added, the particle size of nickel hydroxide will be significantly reduced, which is not conducive to the subsequent solid-liquid separation process and cannot meet the requirements of rapid and continuous reaction.

[0057] Performance Testing Nickel hydroxide was produced according to the reaction conditions of Example 1. The test results of the particle size of nickel hydroxide during continuous production for different time periods after the reaction stabilized are shown in Table 1.

[0058] Table 1 The particle size of nickel hydroxide measured at different time periods under stable conditions by continuous reaction

[0059] Please refer to Table 1. It can be seen from Table 1 that during the preparation of nickel hydroxide, when the reaction is stabilized and the production is continued for different time periods, the particle size D50 of nickel hydroxide is controlled at 15-25 μm. It can be seen that the method of the present application can be used to prepare nickel hydroxide, and the particle size D50 of nickel hydroxide can be controlled at 15-25 μm, with stable quality, and is also convenient for subsequent filtration and pH adjustment.

[0060] The specific implementation methods of the present application described above do not constitute a limitation on the protection scope of the present application. Any other corresponding changes and modifications made according to the technical concept of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide, characterized in that: The following steps are involved: S1, preparing a reaction base solution containing a first complexing agent and a first base; S2, adding the first anolyte, the second complexing agent solution and the second alkaline solution to the bottom of the reaction bottom solution at the same time for stirring and reacting, and performing solid-liquid separation after the nickel hydroxide reaches the target particle size to obtain a filtrate and a filter cake; S3, washing the filter cake and slurrying it with a second anode liquid to obtain a nickel hydroxide slurry; S4. Using sodium hydroxide solution, the nickel hydroxide slurry and nickel sulfate solution, the sodium ion concentration, pH and nickel ion concentration of the third anode liquid are adjusted to obtain a cathode liquid.

2. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that: In the first anolyte, the second anolyte and the third anolyte, the nickel sulfate content is 50-90 g / L, the sodium sulfate content is 20-40 g / L, the boric acid content is 2-8 g / L, and the other components are trace impurities.

3. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that: In the reaction base liquid, the first complexing agent is ammonia water, the first alkali is sodium hydroxide, the concentration of the first complexing agent is 3-6 g / L, and the pH is 10-11.

4. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that: The second complexing agent is ammonia water, and the mass fraction of the second complexing agent solution is 15%-18%; the second alkali is sodium hydroxide, and the mass fraction of the second alkali solution is 30%-33%.

5. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that: The feed rate ratio of the first anolyte, the second alkaline solution and the second complexing agent solution is 1 m / s. 3 / h: (0.25-0.35) m 3 / h: (40-50) L / h.

6. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that: During the stirring reaction, the volume of the reactor is 35-40m 3 The amount of the reaction bottom liquid is 22%-25% of the volume of the reactor; the feeding speed of the first anolyte is 5-7m 3 / h, the feed rate of the second complexing agent solution is 250-300L / h, and the feed rate of the second alkali solution is 1-2.5m / h. 3 / h.

7. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that: During the stirring reaction, the pH of the upper liquid level of the reactor is controlled to be 10-11, the total concentration of the first complexing agent and the second complexing agent is controlled to be 2-4 g / L, the reaction temperature is controlled to be 50-60° C., and the stirring speed is controlled to be 15-25 Hz.

8. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that: The target particle size D50 is 15-25 μm.

9. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that: Step S2 specifically includes: Adding reaction bottom liquid into the reactor; Adding the first anolyte, the second complexing agent solution and the second alkaline solution into the reaction bottom solution from the bottom of the reactor simultaneously and continuously, and performing stirring reaction; After the nickel hydroxide reaches the target particle size, the nickel hydroxide rises to the upper layer of the reactor under the action of stirring, and enters the filter press through overflow for filtration to obtain a filtrate and a filter cake.

10. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that: Step S4 specifically includes: The sodium ion concentration, pH and nickel ion concentration of the third anode liquid are adjusted in sequence using a sodium hydroxide solution, the nickel hydroxide slurry and a nickel sulfate solution to obtain a cathode liquid; wherein, In the cathode liquid, the sodium ion concentration is 25-35 g / L, the nickel ion concentration is 90-100 g / L, and the pH is 3-3.5.

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