Method for producing electronic grade nickel sulfate from nickel powder, crystallization apparatus, and method for controlling the crystallization apparatus

Abstract

Method for producing electronic grade nickel sulfate from nickel powder, crystallization apparatus, and control thereof The present invention provides a method for producing nickel sulfate, and nickel sulfate produced thereby. The process includes acid leaching, copper removal, acid adjustment, concentration, cooling crystallization, drying and sieving, and secondary leaching. Oxidation In the calcination furnace, the temperature is 400 to 700°C, and 1 kg of compressed air is used for each kilogram of nickel powder. ~5m 3 The reaction time is 1.0 to 2.5 hours, and the temperature during acid immersion is controlled to 45 to 70°C. Then, add dilute sulfuric acid to control the pH to 0.5-1.5 and react for 1-3 hours. The copper removal is to replace the copper with nickel powder, and the acid conditioning is to use nickel hydroxide or The pH is adjusted to 2.5-4.5 using nickel carbonate, and the filtrate is concentrated by The cooling crystallization method is to obtain nickel sulfate crystals and return the mother liquor to the concentrate. Drying and sieving is to add the undersieved material to the crystallizer as seed crystals, and secondary leaching is to Dilute sulfuric acid is added to the leaching slag, and it is reacted with nickel sulfate or hydrogen peroxide until nickel is less than 0.1%. If the first stage is full, the second leaching is continued. The crystallizer is a crystallizer that is connected in series with a second-stage crystallizer and a third-stage crystallizer. A crystallization frame, an oscillator provided under the crystallization frame, and an oscillator provided at the exit end of the crystallization frame. The crystallization frame is a rectangular parallelepiped. The bottom of the ribs are evenly spaced, with a cross section of a circular arc. The distance between two adjacent ribs is S is 1 / 25 to 1 / 15 of the width of the crystallization frame, and either the width b or the height h of the rib The width of the crystallization frame is 1 / 100 to 1 / 150 of the width of the crystallization frame. It does not add any new impurity ions, and does not add any oxidizing agent. The nickel sulfate crystal particles produced are uniform and are free of the static generation. This avoids caking of very large particles, irregularly shaped particles and crystals.

Description

[Technical Field]

[0001] The present invention relates to the technical field of non-ferrous metal hydrometallurgy, in particular to the production of nickel powder into electronic grade sulfuric acid. The present invention relates to nickel production technology, equipment, and control methods. [Background technology]

[0002] With the development of new energy electric vehicles, power batteries, which are an important component, are also developing rapidly. With the change of the market, the consumption of batteries is increasing, and the battery is one of the most important components. Currently, the cathodes used are mainly two types of silicon: lithium iron phosphate and nickel-cobalt-manganese ternary. Among them, nickel-cobalt-manganese ternary elements are used to improve the driving range of electric vehicles. As a result, the nickel content is increasing. At the time, nickel sulfate was the only source of nickel. The production capacity of manufacturing enterprises cannot meet the production demand of nickel, cobalt and manganese Many companies are already processing metallic nickel into the desired sulfur dioxide by dissolving it in acid. However, a large amount of hydrogen gas was generated during the dissolution of metallic nickel in the acid. The requirements for equipment, environment and operation are very high, and there are certain safety risks. In addition, a large amount of oxidizing agent must be added during the reaction process to increase production efficiency. This increases production costs and introduces new impurities. Therefore, a method is needed to prevent metallic nickel from generating hydrogen gas during the production process. , reduce the requirements for the environment and operation, and avoid safety risks in the production process. The addition of auxiliary materials during the process is reduced to avoid introducing impurities. Summary of the Invention [Problem to be solved by the invention]

[0003] The object of the present invention is to overcome the drawbacks and deficiencies described in the background art above and to provide a method for producing hydrogen gas during production. Electronic grade nickel sulfate that does not generate or introduce other impurity ions. A method for producing and controlling a crystallization apparatus and a crystallization apparatus are disclosed. [Means for solving the problem]

[0004] One of the technical solutions of the present invention is as follows: oxidation, cooling, acid leaching, copper removal, acid From nickel powder, including the steps of preparation, concentration, cooling crystallization, drying, sieving, and secondary leaching 1. A method for producing electronic grade nickel sulfate, comprising the steps of: The temperature of the nickel powder is controlled at 400 to 700°C, and compressed air is added to each kilogram of nickel powder. 1 to 5 m 3 and react for 1.0 to 2.5 hours to oxidize the nickel powder in the furnace. It is characterized by producing +2valent nickel oxide.

[0005] After the oxidation of the nickel powder is completed in the cooling step, the nickel powder is heated under the protection of nitrogen gas or inert gas. Cool to room temperature.

[0006] In the acid leaching, the temperature of the cooled nickel oxide is controlled to 45 to 70°C in the reactor. Dilute sulfuric acid is added to adjust the pH value to 0.5 to 1.5, and the reaction is carried out for 1 to 3 hours.

[0007] In the copper removal, after filtering the nickel sulfate solution, the reaction temperature in the reactor is set to 45 to 80 The temperature is controlled at ℃, nickel powder is added in an amount of 0.8 to 2.0 times the mass ratio of the copper content, and the pH value is controlled at 1.0 to 3.0. The mixture is then cooled and allowed to react for 0.5 to 2.5 hours.

[0008] In the acid adjustment, the nickel sulfate solution after copper removal is filtered, and the reaction temperature in the reactor is adjusted. The temperature is controlled at 55 to 90°C, and the pH is adjusted to 2.5 to 4.5 using nickel carbonate or nickel hydroxide. .

[0009] In the concentration step, the nickel sulfate solution after the acid adjustment is filtered, and the filtrate is concentrated.

[0010] In the cooling crystallization, the concentrated nickel sulfate solution is placed in a crystallization device, cooled, and then the nickel sulfate is added. The acid nickel is precipitated from the solution to form crystals, and after separating the crystals, the mother liquor is returned to the concentrate.

[0011] The nickel sulfate crystals separated in the drying and sieving process are dried in a vibrating fluidized bed to remove free water. The fine particles are then removed and sieved in a vibrating sieve. The remaining material is used as the nickel sulfate product. The bottom particles are used as seed crystals for crystallization.

[0012] In the secondary leaching, the leaching sludge containing a predetermined amount of nickel is placed in a reactor and diluted sulfuric acid is added. In addition, the pH value is controlled to 0.5 to 1.5, and the reaction temperature is controlled to 45 to 70°C. Use 15% to 35% of the content of nickel sulfide or hydrogen peroxide as a reducing agent and react for 1 to 3 hours. The nickel content was found to be less than 0.1%. The residue of 0.1% is used as waste, and the residue of 0.1% or more is returned to the secondary leaching, and the leachate is used as the base solution for acid leaching. The nickel content of the leachate is then reduced by 100%. Ensure recovery rates.

[0013] Furthermore, in the oxidation, the temperature of the nickel powder in the calciner is set to 450 to 600°C, preferably 50 The temperature was controlled at 0°C, and compressed air was applied at 3 to 4 m per kilogram of nickel powder. 3 Infuse for 1.0 to 1.5 hours Make it react.

[0014] Furthermore, in the acid leaching, the cooled nickel oxide is heated to a temperature of 50 to 60°C in the reactor. °C, add dilute sulfuric acid to adjust the pH value to 1, and react for 2 hours.

[0015] Furthermore, in the copper removal, after filtering the nickel sulfate solution, the reaction temperature in the reactor is The temperature is controlled to 45 to 70°C, preferably 55 to 70°C, and the copper content is 1.3 to 1.5 times that of the nickel powder in terms of mass ratio. Add the powder, adjust the pH to 2.0-2.5, and react for 1-2 hours.

[0016] Furthermore, in the acid adjustment, the nickel sulfate solution after copper removal is filtered, and the reaction The temperature is controlled at 60 to 80°C, and the pH value is adjusted to 3.0 to 4.0 using nickel carbonate or nickel hydroxide. Adjust.

[0017] Furthermore, in the acid adjustment, the nickel sulfate solution after copper removal is filtered, and the reaction The temperature is controlled at 70-75°C, and the pH is adjusted to 3.5 using nickel carbonate or nickel hydroxide. do.

[0018] Furthermore, in the secondary leaching, a leach sludge containing a predetermined amount of nickel is placed in a reactor, Dilute sulfuric acid is added to control the pH value at 1.0, and the reaction temperature is controlled at 50-65°C. Nickel sulfide is used as a reducing agent in an amount of 20% to 30% of the nickel content, and the reaction is carried out for 2 hours.

[0019] Another technical solution of the present invention is as follows: the first-stage crystallizer, the second-stage crystallizer, the third-stage crystallizer The crystallizer is a crystallizer connected in series, and the crystallizer comprises a crystallization frame and a crystallization frame It consists of an oscillator installed below and a drain port with a control valve installed at the exit end of the crystallization frame. The crystallization frame is a rectangular parallelepiped. A crystallization apparatus for producing a crystallizer, The crystallization frame has evenly spaced ribs with arc-shaped cross sections at the bottom, and two adjacent The distance S between the ribs is 1 / 25 to 1 / 15 of the width of the crystallization frame, and either the width b or the height h of the rib The width of the crystallization frame is also 1 / 100 to 1 / 150 of the width of the crystallization frame.

[0020] Furthermore, the distance S between two adjacent ribs is 1 / 20 of the width of the crystallization frame; The width b and height h of the rib are both 1 / 110 to 1 / 130 of the width of the crystallization frame, preferably The ratio is usually 1 / 120.

[0021] Another technical solution of the present invention is as follows: A method for controlling a crystallizer for producing nickel disulfate using the following steps:

[0022] a. Start the first-stage crystallizer, that is, put the concentrated nickel sulfate solution into the first-stage crystallizer. Then, the oscillator is turned on and the frequency of the oscillator is adjusted so that the cobalt sulfate solution does not spill out of the crystallization frame. When the temperature of the nickel sulfate solution reaches 45°C, the nickel sulfate solution is discharged through a control valve. The liquid flows into the second stage crystallizer from the liquid inlet, and the crystals in the crystallization frame are collected and combined. The process then begins.

[0023] b. Start the second-stage crystallizer, that is, after putting the nickel sulfate solution into the second-stage crystallizer, The remaining operations were the same as in the first step except for adding the fine particles of nickel sulfate crystals that were under the sieve in the sieving process. As with the stage crystallizer, when the temperature of the nickel sulfate solution reaches 35°C, the nickel sulfate solution is controlled. The liquid flows from the valve-equipped drain port to the third-stage crystallizer, where the crystals in the crystallization frame of the second-stage crystallizer are collected. The ingredients are then mixed together and the next step begins.

[0024] c. After starting the third-stage crystallizer, i.e., putting the nickel sulfate solution into the third-stage crystallizer, The remaining operations were the same as in the first step except for adding the fine particles of nickel sulfate crystals that were under the sieve in the sieving process. In the same manner as in the stage crystallizer 1, when the temperature of the nickel sulfate solution reaches room temperature, the nickel sulfate solution The liquid flows from the drain port with a control valve of the third-stage crystallizer to the storage tank, and then The crystals are concentrated and combined for further processing. [Effects of the Invention]

[0025] By adopting the above technical solutions, the present invention has the following advantages: (1) By adopting the above oxidation pretreatment and controlling the amount of oxygen gas added and the temperature at a constant level, Nickel is oxidized to divalent nickel oxide, which releases hydrogen gas when dissolved in acid. Furthermore, no large amounts of oxidizing agent are added.

[0026] (2) The copper removal method of replacing copper with nickel powder increases the number of new impurity ions. Increases nickel ion concentration without

[0027] (3) Since the acidity is adjusted using nickel hydroxide or nickel carbonate, impurities are not added. It also reduces the acidity of the solution and suppresses the free acid of nickel sulfate crystals.

[0028] (4) The crystallization is dynamic because a crystallization device is used, and the characteristics of the nickel sulfate crystals are Due to its special structure, there is no caking or formation of large irregular particles during crystallization.

[0029] (5) Sieve the mixture, and return the fine particles that fall under the sieve to the crystallizer as seed crystals. This results in more uniform nickel sulfate crystal particles.

[0030] (6) The use of a control method specific to the crystallization apparatus provides the following advantages: The crystallization process is carried out under controllable dynamic conditions, allowing for control of the crystal grain size.

[0031] b. Caking of large particles, irregularly shaped particles and crystals that occurs under static conditions is avoided.

[0032] c. By using three-stage cooling, the thickness of the crystal layer increases continuously during cooling crystallization. This avoids adversely affecting heat dissipation.

[0033] d) fine undersize nickel sulfate crystals in the second and third crystallization frames; By adding seed crystals, the proportion of nickel oxide oversized is ensured. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a flow chart of the process of the present invention.

[0035] [Figure 2] 1 is a schematic front view of an embodiment of a crystallization apparatus according to the present invention;

[0036] [Figure 3] 1 is a schematic top view of an embodiment of a crystallization apparatus according to the present invention;

[0037] [Figure 4] 1 is a schematic side cross-sectional view of a crystallization frame of an embodiment of the crystallization apparatus of the present invention;

[0038] [Figure 5] 1 is an enlarged schematic side cross-sectional view of a crystallization frame of an embodiment of the crystallization apparatus of the present invention.

[0039] 1-1st stage crystallizer, 2-2nd stage crystallizer, 3-3rd stage crystallizer, 4-crystallization frame, 5-exhaust Liquid outlet, 6-oscillator, 7-rib BEST MODE FOR CARRYING OUT THE INVENTION

[0040] The process for producing electronic grade nickel sulfate from nickel powder involves oxidation, cooling, acid leaching, copper The process involves the steps of stripping, acid adjustment, concentration, cooling crystallization, drying and sieving, and secondary leaching.

[0041] Preferably, in the oxidation, the temperature of the nickel powder is controlled at 650°C in the calciner. For every kilogram of powder, 3 m of compressed air is used. 3 The mixture was then reacted for 1.5 hours, and nickel powder was added. The powder is oxidized in a furnace to produce +2-valent nickel oxide.

[0042] Preferably, after the oxidation of the nickel powder is completed in the cooling step, nitrogen gas or an inert gas is used. Cool to room temperature under the protection of

[0043] Preferably, for cooled nickel oxide in the acid leaching, the temperature in the reactor is 55°C. The pH value is adjusted to 1.0 by adding dilute sulfuric acid, and the reaction is carried out for 2 hours.

[0044] Preferably, in the copper removal step, after filtering the nickel sulfate solution, the reaction temperature is The temperature was controlled at 75°C, and nickel powder was added in an amount 0.95 times the mass ratio of copper content, and the pH value was adjusted to 2. The temperature was controlled to 0 and the reaction was carried out for 1 hour.

[0045] Preferably, in the acid adjustment, the nickel sulfate solution after copper removal is filtered and reacted in a reactor. The temperature is controlled at 75°C, and the pH value is adjusted to 3.0 using nickel carbonate or nickel hydroxide. Adjust.

[0046] Preferably, in the concentration step, the nickel sulfate solution after the acid adjustment is filtered and the filtrate is concentrated.

[0047] Preferably, in the cooling crystallization, the concentrated nickel sulfate solution is placed in a crystallization apparatus and cooled. As the temperature drops, nickel sulfate precipitates from the solution and forms crystals. Afterwards, the mother liquor is returned to the concentrate.

[0048] Preferably, the nickel sulfate crystals separated in the drying and sieving step are dried in a vibrating fluidized bed; The free water is removed, and then the mixture is sieved in a vibrating sieve. The remaining material is the nickel sulfate product. Fine undersize particles are used as seed crystals for crystallization.

[0049] Preferably, in the secondary leaching, a leach tail containing a predetermined amount of nickel is placed in a reactor, Dilute sulfuric acid is added to control the pH value at 1.0, and the reaction temperature is controlled at 65°C. Using nickel sulfide or hydrogen peroxide at a concentration of 25% of the nickel content as a reducing agent, the reaction was carried out for 2 hours. The nickel content was detected by collecting the slag and found to be less than 0.1%. Anything above 0.1% is used as waste dregs, anything above 0.1% is returned to secondary leaching, and the leachate is used as the base solution. The nickel is then used for acid leaching or is combined with the first leaching solution for the next step. Ensure the recovery rate of the phosphate content.

[0050] The crystallization equipment for producing electronic grade nickel sulfate from nickel powder consists of three sets of identical structures. The crystallizers are connected in series, i.e., the first stage crystallizer 1, the second stage crystallizer 2, the third stage crystallizer The crystallizer is a crystallizer having a crystallization frame 4 and a crystallization frame 3 connected in series. An oscillator 6 is provided under the crystallization frame 4, and a drain with a control valve is provided at the outlet end of the crystallization frame 4. The crystallization frame 4 is a rectangular parallelepiped, and the bottom of the crystallization frame 4 is , the ribs 7 having a circular arc-shaped cross section are evenly arranged, and the distance S between two adjacent ribs 7 is is 1 / 20 of the width of the crystallization frame 4, and both the width b and the height h of the rib 7 are The width is 1 / 120 of the width of the frame 4.

[0051] The control method of the crystallization device for producing electronic grade nickel sulfate from nickel powder is as follows: Step a. Start the first crystallizer, i.e., concentrate the nickel sulfate solution The first stage crystallizer is placed in the crystallizer, the oscillator is turned on, and the frequency of the oscillator is adjusted to the frequency at which the cobalt sulfate solution crystallizes. When the temperature of the nickel sulfate solution reaches 45°C, the nickel sulfate The solution flows into the second stage crystallizer through a drain with a control valve, and the crystals are collected in the crystallization frame. The ingredients are then mixed together and the next step begins.

[0052] b. Start the second-stage crystallizer, that is, after putting the nickel sulfate solution into the second-stage crystallizer, The remaining operations were the same as in the first step except for adding the fine particles of nickel sulfate crystals that were under the sieve in the sieving process. As with the stage crystallizer, when the temperature of the nickel sulfate solution reaches 35°C, the nickel sulfate solution The liquid flows from the drain port with a control valve of the second-stage crystallizer to the third-stage crystallizer, and then passes through the crystallization frame of the second-stage crystallizer. The crystals inside are concentrated and combined for the next step.

[0053] c. After starting the third-stage crystallizer, i.e., putting the nickel sulfate solution into the third-stage crystallizer, The remaining operations were the same as in the first step except for adding the fine particles of nickel sulfate crystals that were under the sieve in the sieving process. In the same manner as in the stage crystallizer 1, when the temperature of the nickel sulfate solution reaches room temperature, the nickel sulfate solution The liquid flows from the drain port with a control valve of the third-stage crystallizer to the storage tank, and then The crystals are concentrated and combined for further processing. Embodiments of the present invention

[0054] In order to clearly understand the present invention, the following description will be given by way of specific embodiments with reference to FIGS. The present invention will now be further described.

[0055] Embodiment 1 As shown in Figure 1, the method for producing electronic grade nickel sulfate from nickel powder is as follows: The process involves cooling, acid leaching, copper removal, acid adjustment, concentration, cooling crystallization, drying and sieving, and secondary leaching. In the oxidation step, the temperature of the nickel powder is controlled to 400 to 700°C in the calcination furnace. Compressed air was blown at a rate of 1 to 5 m per kilogram of nickel powder. 3 Inject for 1.0 to 2.5 hours. The method is characterized in that the reaction is carried out for a period of time.

[0056] Furthermore, in the oxidation, the temperature of the nickel powder in the calciner is set to 450 to 600°C, preferably The temperature is controlled to about 500°C, and compressed air is blown at 3 to 4 m per kilogram of nickel powder. 3 Inject The mixture is reacted for 1.0 to 1.5 hours.

[0057] In some embodiments, the temperature of the nickel powder in the calciner is increased to 400°C, 450°C, 500°C, , and controlled at 550°C.

[0058] In some examples, 1 m of compressed air is used for 1 kg of nickel powder. 3 , 2m 3 , 3m 3 , 4m 3 , 5m 3 Inject.

[0059] Nickel powder is oxidized in a furnace to produce nickel oxide. Nickel is divalent, and the divalent When valent nickel is dissolved in sulfuric acid, it can be completely dissolved without adding a reducing agent.

[0060] In this step, nickel powder and air in a certain ratio undergo an oxidation reaction at high temperature to produce nickel. The nickel in the nickel powder is oxidized from 0 to +2. The experimental data are shown in Tables 1, 2, and 3. vinegar.

[0061] Table 1: Degree of oxidation at various compressed air volumes when reacted for 1 hour at 450°C

[0062] TIFF0007797761000001.tif69162

[0063] Table 2: Degree of oxidation at each reaction time under conditions of 450°C and compressed air of 4

[0064] TIFF0007797761000002.tif57152

[0065] Table 3: Degree of oxidation at each reaction temperature when compressed air is 4 and reaction time is 1 hour

[0066] TIFF0007797761000003.tif59156

[0067] The oxidation rate is calculated based on the nickel content of the nickel oxide being 78.58%. If the nickel content is below this level, a small amount of nickel will oxidize to trivalent nickel oxide. The nickel content of the nickel oxide was 70.98%.

[0068] After the oxidation of the nickel powder is completed in the cooling step, the nickel powder is heated under the protection of nitrogen gas or inert gas. The nitrogen or inert gas protection is necessary to prevent the hot nickel powder from being absorbed by the air during cooling. This is to prevent the nickel oxide from coming into contact with the oxygen in the The nickel in the nickel alloy is +3 valent, and +3 valent nickel is dissolved in acid. To get it to go into solution, a reducing agent must be added to reduce the +3 to +2 valence.

[0069] In the acid leaching, the cooled nickel oxide is heated to a temperature of 45 to 70°C in a reactor. Dilute sulfuric acid is added to adjust the pH value to 0.5 to 1.5, and the reaction is carried out for 1 to 3 hours.

[0070] Furthermore, in the acid leaching, the cooled nickel oxide is heated to a temperature of 50 to 100°C in the reactor. The temperature is controlled at 60°C, diluted sulfuric acid is added to control the pH value to 1, and the reaction is carried out for 2 hours.

[0071] After dissolving nickel oxide in sulfuric acid to produce nickel sulfate solution, the leaching slag still contains a predetermined amount of nickel. Nickel content is contained, which is mainly due to the presence of a certain amount of nickel oxide produced during oxidation. This is because the molten metal is not extracted and requires a secondary leach to be reduced.

[0072] In the copper removal, after filtering the nickel sulfate solution, the reaction temperature in the reactor is increased to 45 Control the temperature at 80℃, add nickel powder in an amount 0.8 to 2.0 times the mass ratio of copper content, and adjust the pH value The temperature is controlled to 1.0 to 3.0 and the reaction is carried out for 0.5 to 2.5 hours.

[0073] Furthermore, in the copper removal, after filtering the nickel sulfate solution, the reaction temperature in the reactor is The temperature is controlled to 45 to 70°C, preferably 55 to 70°C, and the mass ratio of the copper content is 1.3 to 1.5. Add 2 times the amount of nickel powder, adjust the pH value to 2.0-2.5, and react for 1-2 hours. In this step, nickel and copper ions in the solution undergo a substitution reaction using the activity of the metal. This produces sponge copper, which is then removed from the nickel sulfate solution. The figures shown in Tables 4, 5, 6 and 7.

[0074] Table 4: Effect of various nickel powder addition ratios at 50°C, pH 1.5, and 1 hour of reaction Table showing the results

[0075] TIFF0007797761000004.tif73137

[0076] Table 5: Efficiency at each reaction time in the case of 50°C, pH 1.5, and 1.5 times the amount of nickel powder Table showing the results

[0077] TIFF0007797761000005.tif77133

[0078] Table 6: Effects at various pH values ​​when reacting at 50°C, 1.5 times the amount of nickel powder, and for 1 hour. Table showing

[0079] TIFF0007797761000006.tif74143

[0080] Table 7: pH value 1.5, 1.5 times the amount of nickel powder, reaction time 1 hour, at each reaction temperature Table showing the effect of

[0081] TIFF0007797761000007.tif66142

[0082] In the acid adjustment, the nickel sulfate solution after copper removal is filtered, and the reaction temperature in the reactor is adjusted. The temperature is controlled at 55-90°C, and the pH is kept at 2.5-4 using nickel carbonate or nickel hydroxide. Adjust to 5.

[0083] Furthermore, in the acid adjustment, the nickel sulfate solution after copper removal is filtered, and the reaction The temperature is controlled at 60-80°C, and the pH is adjusted to 3. Adjust from 0 to 4.0.

[0084] Furthermore, in the acid adjustment, the nickel sulfate solution after copper removal is filtered and The reaction temperature is controlled at 70-75°C, and the pH value is adjusted using nickel carbonate or nickel hydroxide. Adjust to 3.5.

[0085] The pH adjustment is mainly to reduce the free acid in the nickel sulfate crystals and to increase the depth of the nickel ions. In order to improve the acidity and precipitate the impurity ions of iron during acid adjustment and separate it from the nickel sulfate solution, This is the case.

[0086] In the concentration step, the nickel sulfate solution after acid adjustment is filtered, and the filtrate is evaporated to concentrate it. By evaporating the water, the concentration of nickel ions is further increased, and nickel sulfate Promotes crystallization of

[0087] In the cooling crystallization, the concentrated nickel sulfate solution is placed in a crystallization apparatus and cooled. As the concentration decreases, nickel sulfate precipitates from the solution and forms crystals. After separating the crystals, The mother liquor is returned to concentration.

[0088] The nickel sulfate crystals separated in the drying and sieving process are dried in a drying facility to remove free water. The fine particles are then sieved into a vibrating sieve. The bottom particles are used as seed crystals for crystallization.

[0089] In the secondary leaching, the filtered leach residue after acid leaching also contains a predetermined amount of nickel. Therefore, the leaching sludge is placed in a reactor, and diluted sulfuric acid is added to control the pH value to 0.5 to 1.5. The reaction temperature is controlled at 45 to 70°C, and the amount of nickel added is 15 to 35% of the nickel content in the acid leaching sludge. A small amount of nickel sulfide or hydrogen peroxide is used as a reducing agent and the reaction is carried out for 1 to 3 hours. As a result of detecting the nickel content, the waste slag was found to contain less than 0.1% nickel. Anything above 0.1% is returned to the secondary leach. The leachate is used as the base solution for acid leaching, and This is then combined with the first leaching solution and sent to the next step, thereby ensuring the recovery rate of the nickel content. Protect.

[0090] Furthermore, in the secondary leaching, a leach sludge containing a predetermined amount of nickel is placed in a reactor, Add dilute sulfuric acid to control the pH value to 1.0, and control the reaction temperature to 50-65°C. Nickel sulfide was used as a reducing agent in an amount of 20% to 30% of the nickel content in the slag, and the mixture was reacted for 2 hours. To respond.

[0091] Embodiment 2 As shown in Figures 2 to 5, a crystallization apparatus for producing electronic grade nickel sulfate from nickel powder is used. The device is a series connection of three crystallizers with the same structure, namely, the first stage crystallizer 1, the second stage crystallizer 2, the third stage crystallizer 3, the fourth stage crystallizer 4, the fifth stage crystallizer 5, the sixth stage crystallizer 6, the sixth stage crystallizer 7, the sixth stage crystallizer 8, the sixth stage crystallizer 9, the sixth stage crystallizer 10, the sixth stage crystallizer 11, the sixth stage crystallizer A second-stage crystallizer 2 and a third-stage crystallizer 3 are connected in series, and the crystallizer is a crystallization frame. The crystallization frame 4 is provided with an oscillator 6 below it, and the crystallization frame 4 is provided with an oscillator 6 at the end of the crystallization frame 4. The crystallization frame 4 is a rectangular parallelepiped, and the crystallization frame 4 is a crystallization frame. The bottom of the frame 4 is provided with ribs 7 having a circular arc cross section, which are evenly arranged. The distance S between the ribs 7 is 1 / 25 to 1 / 15 of the width of the crystallization frame 4, and the ribs 7 Both the width b and height h are 1 / 100 to 1 / 150 of the width of the crystallization frame 4. It is characterized by:

[0092] Furthermore, the distance S between two adjacent ribs is 1 / 20 of the width of the crystallization frame; Both the width b and height h of the rib are preferably 1 / 110 to 1 / 130 of the width of the crystallization frame. Or 1 / 120.

[0093] The ribs are mainly formed by nickel sulfate crystal particles generated by the action of the oscillator during crystallization. By rolling in front of the rib, caking is prevented and the contact area is increased. This enhances the cooling effect.

[0094] The ratio of the distance S between two adjacent ribs 7 to the width of the crystallization frame 4 affects the oscillation effect of the crystal. The impact is shown in Table 8.

[0095] TIFF0007797761000008.tif61150

[0096] The above table shows the data of the raw liquid and the ratio of the width b and height h of the rib 7 to the width of the crystallization frame 4. If the case is the same, the detection data when cooled to 30°C is listed.

[0097] The influence of the ratio of the width b and height h of the rib 7 to the width of the crystallization frame 4 on the oscillation effect of the crystal is Shown in Table 9.

[0098] TIFF0007797761000009.tif68151

[0099] The above table shows the data of the raw solution and the ratio of the distance S between the ribs 7 to the width of the crystallization frame 4. If the temperature is the same, the detection data when cooled to 30°C is listed.

[0100] The control method of the crystallization device for producing electronic grade nickel sulfate from nickel powder is as follows: a. The first crystallizer 1 is started, that is, the concentrated nickel sulfate solution is The solution is put into the first-stage crystallizer 1, the oscillator 6 is turned on, and the frequency of the oscillator is adjusted to When the temperature of the nickel sulfate solution reaches 45°C, add the sulfuric acid The nickel solution flows from the drain port 5 into the second-stage crystallizer 2, and the crystals in the crystallization frame 4 are collected. The mixture is then sieved and sent to the next process.

[0101] b. The second-stage crystallizer 2 was started, that is, the nickel sulfate solution was poured into the second-stage crystallizer 2. After that, the remaining operations were carried out except for adding the fine particles of nickel sulfate crystals that were left over from the sieving process. In the same way as in the first stage crystallizer, when the temperature of the nickel sulfate solution reaches 35°C, The liquid flows from the drain port 5 to the third stage crystallizer 3, and the crystals in the crystallization frame 4 are collected and sieved. and proceed to the next step.

[0102] c. The third-stage crystallizer 3 was started, that is, the nickel sulfate solution was poured into the third-stage crystallizer 3. After that, the remaining operations were carried out except for adding the fine particles of nickel sulfate crystals that were left over from the sieving process. In the same manner as in the first-stage crystallizer 1, when the temperature of the nickel sulfate solution reaches room temperature, The liquid flows from the drain port 5 into the storage tank, and the crystals in the crystallization frame 4 are concentrated and combined. Proceed to the next step.

[0103] The advantages of this control method are: the crystallization process is carried out under controllable dynamic conditions; The grain size of the crystals can be controlled. The case of super large particles, irregularly shaped particles and crystals that occur under static conditions can be eliminated. By using three-stage cooling, the thickness of the crystal layer is reduced during cooling crystallization. The thickness of the second crystallization frame and the second crystallization frame are continuously increasing, which can adversely affect heat dissipation. By adding fine undersize nickel sulfate crystals as seed crystals to the third-stage crystallization frame, This ensures the proportion of nickel oxide sieve.

[0104] Example 1: The steps of the method for producing electronic grade nickel sulfate from nickel powder are as follows: a) The temperature of 5 kg of nickel powder was controlled at 500°C in a calcination furnace. For every kilogram of powder, 3 m of compressed air is used. 3 The mixture was then injected and allowed to react for 1.5 hours.

[0105] b. After the oxidation of the nickel powder was completed, it was cooled to room temperature under the protection of nitrogen gas. The weight of the nickel oxide was 6.5 kg and the nickel content was 76.85%.

[0106] c. The cooled nickel oxide was placed in a reactor, the temperature of which was controlled at 50°C, and diluted sulfuric acid was added. The pH was controlled at 1.5 using a filtration method, and the reaction was carried out for 2 hours. After filtration, the solution was subjected to the next step. The nickel sulfate solution was obtained in an amount of 42,900 mL, and the nickel content was 11 The nickel leaching rate was 97.49%. The leaching residue was 180.5g. and the nickel content of the slag was 69.53%.

[0107] d. The above leaching sludge is placed in a reactor, and diluted sulfuric acid is added to control the pH value at 0.5. The reaction temperature is The temperature was controlled at 62°C, and hydrogen peroxide was used in an amount that was 25% of the nickel content in the acid leaching slag. The mixture was allowed to react for 2 hours. After filtration, 1190 mL of nickel sulfate solution was obtained. The nickel content was 105.34g / L, and 17.5g of leaching residue was obtained. The amount was 0.083%. The leaching solution and the first leaching solution were combined and used in the next step. Combined with the leaching rate, the nickel leaching rate was 99.99%.

[0108] e. The nickel sulfate solution was detected and found to contain 0.009 g / L of copper. The reaction temperature was controlled at 70°C in the reactor, and nickel powder was added in an amount 1.5 times the mass ratio of copper content. The pH value was controlled at 2.3 and the reaction was carried out for 1 hour. After filtration, the copper content was found to be 0. It was 0.0005g / L.

[0109] f. After copper removal, the nickel sulfate solution was heated to 80°C in the reactor. The pH was adjusted to 3.5 with nickel oxide and filtered.

[0110] g. The nickel sulfate solution after acid adjustment was concentrated.

[0111] h) The concentrated nickel sulfate solution was placed in a crystallizer and cooled to 30°C, and the room temperature was then set to 23°C. After separating the crystals, the mother liquor was returned to the concentrate.

[0112] i. The separated nickel sulfate crystals were dried in a circulating drying cabinet to remove free water, and then placed on a vibrating sieve. The over-sieved material was used as the nickel sulfate product, and the under-sieved particles, which were finer, were used as seed crystals. The nickel sulfate crystals were analyzed and the detected data are shown below. Ni: 22.41%, Co:0.007%, Fe:0.0005%, Cu:0.0001%, N a:0.001%, Zn:0.0001%, Ca:0.0021%, Mg:0.0017 %,Mn:0.0002%, Cd:0.0001%, Hg:0.0001%, Cr:0. 0002%, Pb:0.0002%.

[0113] Example 2: The steps of the method for producing electronic grade nickel sulfate from nickel powder are as follows: a. The temperature of 5 kg of nickel powder was controlled at 520°C in a calcination furnace. 3.5 m of compressed air per kilogram of powder 3 The mixture was then injected and allowed to react for 1.5 hours.

[0114] b. After the oxidation of the nickel powder was completed, it was cooled to room temperature under the protection of nitrogen gas. The weight of the nickel oxide was 6.7 kg and the nickel content was 74.63%.

[0115] c. The cooled nickel oxide was placed in a reactor at a controlled temperature of 70°C and diluted sulfuric acid was added. The pH was controlled at 1.5 using a filtration method, and the reaction was carried out for 2 hours. After filtration, the solution was subjected to the next step. The nickel sulfate solution was obtained in an amount of 41,980 mL, and the nickel content was 11 The nickel leaching rate was 93.51%. The leaching residue was 462.4g. The nickel content of the slag was 70.13%.

[0116] d. The above leaching sludge is placed in a reactor, and diluted sulfuric acid is added to control the pH value at 0.5. The reaction temperature is The temperature was controlled at 57°C, and hydrogen peroxide was used in an amount equivalent to 18% of the nickel content in the acid leaching slag. After filtration, 2780 mL of nickel sulfate solution was obtained. The nickel content was 115.77g / L, and 23.3g of leach dregs was obtained. The leaching solution and the first leaching solution were combined and used in the next step, and the leaching residue was further The nickel leaching rate was 99.94% after two leaching steps. .

[0117] e. The nickel sulfate solution was detected and found to contain 0.016 g / L of copper. The reaction temperature was controlled at 50°C in the reactor, and nickel powder was added in an amount 1.5 times the mass ratio of copper content. The pH was adjusted to 2.7 and the reaction was continued for 1 hour. After filtration, the copper content was The concentration was 0.0005g / L.

[0118] f. After copper removal, the nickel sulfate solution was heated to 75°C in the reactor. The pH was adjusted to 3.2 with nickel oxide and filtered.

[0119] g. The nickel sulfate solution after acid adjustment was concentrated.

[0120] h) The concentrated nickel sulfate solution was placed in a crystallizer and cooled to 30°C, and the room temperature was then set to 22°C. After separating the crystals, the mother liquor was returned to the concentrate.

[0121] i. The separated nickel sulfate crystals were dried in a circulating drying cabinet to remove free water, and then placed on a vibrating sieve. The over-sieved material was used as the nickel sulfate product, and the under-sieved particles, which were finer, were used as seed crystals. The nickel sulfate crystals were analyzed and the detected data are shown below. Ni: 22.28%, Co:0.005%, Fe:0.0005%, Cu:0.0001%, N a:0.0031%, Zn:0.0001%, Ca:0.0058%, Mg:0.004 7%, Mn:0.0002%, Cd:0.0001%, Hg:0.0001%, Cr:0 .0002%, Pb:0.0002%.

[0122] Example 3: The steps of the method for producing electronic grade nickel sulfate from nickel powder are as follows: a. The temperature of 5 kg of nickel powder was controlled at 450°C in a calcination furnace. 2.5 m of compressed air per kilogram of powder 3 The mixture was then injected and allowed to react for 1.5 hours.

[0123] b. After the oxidation of the nickel powder was completed, it was cooled to room temperature under the protection of nitrogen gas. The weight of the nickel oxide was 6.43 kg and the nickel content was 77.76%.

[0124] c. The cooled nickel oxide was placed in a reactor, the temperature of which was controlled at 65°C, and diluted sulfuric acid was added. The pH was controlled at 1.5 using a filtration method, and the reaction was carried out for 2 hours. After filtration, the solution was subjected to the next step. The nickel sulfate solution was obtained in an amount of 40450 mL, and the nickel content was 12 The nickel leaching rate was 99.94%. The leaching residue was 4.2g. The nickel content of the slag was 66.79%. The pulp was used in the leaching process without extraction.

[0125] d) The nickel sulfate solution was detected and found to contain 0.041 g / L of copper. The reaction temperature was controlled at 50°C in the reactor, and nickel powder was added in an amount 1.5 times the mass ratio of copper content. The pH was adjusted to 2.0 and the reaction was allowed to proceed for 1 hour. After filtration, the copper content was found to be 0. 0003g / L.

[0126] e. After copper removal, the nickel sulfate solution was heated to 65°C in the reactor. The pH was adjusted to 3.8 with nickel oxide and filtered.

[0127] f) The nickel sulfate solution after acid adjustment was concentrated.

[0128] The concentrated nickel sulfate solution was placed in a crystallizer and cooled to 30°C. The room temperature was then adjusted to 22°C. After separating the crystals, the mother liquor was returned to the concentrate.

[0129] h. The separated nickel sulfate crystals were dried in a circulating drying cabinet to remove free water, and then placed on a vibrating sieve. The over-sieved material was used as the nickel sulfate product, and the under-sieved particles, which were finer, were used as seed crystals. The nickel sulfate crystals were analyzed and the detected data are shown below. Ni: 22.30%, Co:0.001%, Fe:0.0003%, Cu:0.0001%, N a:0.0011%, Zn:0.0001%, Ca:0.0052%, Mg:0.005 2%, Mn:0.0002%, Cd:0.0001%, Hg:0.0001%, Cr:0 .0002%, Pb:0.0002%.

[0130] Example 4: The crystallization apparatus for producing electronic grade nickel sulfate from nickel powder is shown in Figures 2- As shown in Figure 5, three crystallizers with the same structure are connected in series. The crystallizer is a series connection of a first stage crystallizer, a second stage crystallizer, and a third stage crystallizer. A crystallization frame 4, an oscillator 6 provided under the crystallization frame 4, and a The oscillator 6 is manufactured by Shanghai Dam Industrial Co., Ltd. The crystallization frame 4 was a rectangular parallelepiped. The crystallization frame 4 has ribs 7, each having an arc-shaped cross section, evenly arranged at the bottom. The distance S between the two ribs 7 is 1 / 20 of the width of the crystallization frame 4, and the width b of the rib 7 is Both the width and height h are 1 / 100 of the width of the crystallization frame 4 .

[0131] The technical effects of this embodiment are as follows: The crystallization process of nickel sulfate is made into a dynamic process. In addition, by performing the process under controllable dynamic conditions, the grain size of the crystals can be controlled. Caking of super-large particles, irregularly shaped particles and crystals that occurs under static conditions is avoided, and cooling This avoids the crystal layer thickness constantly increasing during crystallization, which adversely affects heat dissipation.

[0132] Example 5: Control method of a crystallizer for producing electronic grade nickel sulfate from nickel powder used the following steps:

[0133] a. The first-stage crystallizer 1 is started, that is, the concentrated nickel sulfate solution is poured into the first-stage crystallizer 1. The cobalt sulfate solution is crystallized in the frame. 4. When the temperature of the nickel sulfate solution reaches 45℃, The liquid flows from the drain port 5 with a control valve into the second-stage crystallizer 2, and the crystals in the crystallization frame 4 are collected. The ingredients are then mixed together and the next step begins.

[0134] b. The second-stage crystallizer 2 was started, that is, the nickel sulfate solution was poured into the second-stage crystallizer 2. After that, the remaining operations were carried out except for adding the fine particles of nickel sulfate crystals that were left over from the sieving process. In the same manner as in the first-stage crystallizer 1, when the temperature of the nickel sulfate solution reaches 35°C, The solution flows from the drain port 5 with a control valve of the second-stage crystallizer 2 to the third-stage crystallizer 3, and The crystals in the crystallization frame 4 are collected and combined for the next step.

[0135] c. The third-stage crystallizer 3 was started, that is, the nickel sulfate solution was poured into the third-stage crystallizer 3. After that, the remaining operations were carried out except for adding the fine particles of nickel sulfate crystals that were left over from the sieving process. In the same manner as in the first-stage crystallizer 1, when the temperature of the nickel sulfate solution reaches room temperature, The liquid flows from the drain port 5 with a control valve of the third-stage crystallizer 3 to the liquid storage tank, and the crystallization flow of the third-stage crystallizer 3 The crystals in frame 4 are collected and combined for the next process. The crystallization process is carried out under controllable dynamic conditions, allowing for control of the crystal grain size. This avoids the caking of very large particles, irregularly shaped particles and crystals that occurs under static conditions. By using three-stage cooling, the thickness of the crystal layer increases continuously during cooling crystallization, Avoiding adverse effects on heat dissipation. Second and third crystallization frames By adding fine undersized nickel sulfate crystals as seed crystals to the The proportion of

[0136] The above is merely a preferred embodiment of the present invention, and is not intended to limit the present invention. Various modifications and variations can be made to the present invention without departing from the spirit and principles of the present invention. All modifications, equivalent replacements, improvements, etc. made without departing from the scope of the present invention are included in the patent scope of the present invention. [Industrial Applicability]

[0137] This invention has already been applied to industrial production, and the produced nickel sulfate will eventually be used in electronic grade It meets the standard for nickel sulfate.

Claims

1. A method for producing nickel sulfate from nickel powder, comprising the steps of oxidation, cooling, acid leaching, copper removal, acid adjustment, concentration, cooling crystallization, drying and sieving, and secondary leaching, In the oxidation, the temperature of the nickel powder is controlled to 400 to 700°C in a calcination furnace, and 1 to 5 m3 of compressed air is injected per kilogram of nickel powder. The reaction is carried out for 1.0 to 2.0 hours, thereby oxidizing the nickel powder in the furnace and producing +2-valent nickel oxide; In the cooling step, after the oxidation of the nickel powder is completed, the nickel powder is cooled to room temperature under the protection of nitrogen gas or inert gas; In the acid leaching, the cooled nickel oxide is reacted for 1 to 3 hours while controlling the temperature in a reactor to 45 to 70°C and adjusting the pH value to 0.5 to 1.5 by adding dilute sulfuric acid. In the copper removal step, after filtering the nickel sulfate solution, the reaction temperature is controlled to 45 to 80°C in a reactor, nickel powder is added in an amount of 0.8 to 2.0 times the mass ratio of the copper content, and the pH value is controlled to 1.0 to 3.0, and the reaction is carried out for 0.5 to 2.5 hours. In the acid adjustment, the nickel sulfate solution after copper removal is filtered, and the reaction temperature in the reactor is controlled to 55 to 90°C, and the pH value is adjusted to 2.5 to 4.5 using nickel carbonate or nickel hydroxide; In the concentration step, the nickel sulfate solution after the acid adjustment is filtered, and the filtrate is concentrated. In the cooling crystallization, the concentrated nickel sulfate solution is placed in a crystallization apparatus and cooled. As the temperature decreases, nickel sulfate is precipitated from the solution to form crystals. After the crystals are separated, the mother liquor is returned to the concentration stage. In the drying and sieving step, the separated nickel sulfate crystals are dried in a vibrating fluidized bed to remove free water, and then sieved through a vibrating sieve, with the over-sieved particles being the nickel sulfate product and the fine under-sieved particles being used as seed crystals for crystallization; In the secondary leaching, leach slag containing a predetermined amount of nickel is placed in a reactor, dilute sulfuric acid is added to adjust the pH value to 0.5 to 1.5, the reaction temperature is controlled to 45 to 70°C, and nickel sulfide or hydrogen peroxide is used as a reducing agent in an amount that is 15% to 35% of the nickel content in the acid leaching slag is used for reaction for 1 to 3 hours, the slag is collected and the nickel content is detected, and slag having a nickel content of less than 0.1% is used as waste slag, and slag having a nickel content of more than 0.1% is returned to the secondary leaching, and the leachate is used as a base solution for acid leaching or is subjected to the next step together with the first leachate, thereby ensuring the recovery rate of the nickel content.

2. 2. The method for producing nickel sulfate from nickel powder according to claim 1, wherein the oxidation involves controlling the temperature of the nickel powder in a calciner to 450 to 600°C, injecting 3 to 4 m3 of compressed air per kilogram of nickel powder, and carrying out the reaction for 1.0 to 1.5 hours.

3. 2. The method for producing nickel sulfate from nickel powder according to claim 1, wherein in the acid leaching, the temperature of the cooled nickel oxide in the reactor is controlled to 50 to 60°C, dilute sulfuric acid is added to control the pH value to 1, and the reaction is carried out for 2 hours.

4. 2. The method for producing nickel sulfate from nickel powder according to claim 1, wherein, in the copper removal, after filtering the nickel sulfate solution, the reaction temperature in the reactor is controlled to 45 to 70°C, nickel powder is added in an amount 1.3 to 1.5 times the mass ratio of the copper content, and the pH value is controlled to 2.0 to 2.5, and the reaction is carried out for 1 to 2 hours.

5. 2. The method for producing nickel sulfate from nickel powder according to claim 1, wherein in the acid adjustment, the nickel sulfate solution after copper removal is filtered, and the reaction temperature in the reactor is controlled to 60 to 80°C, and the pH value is adjusted to 3.0 to 4.0 using nickel carbonate or nickel hydroxide.

6. 6. The method for producing nickel sulfate from nickel powder according to claim 5, wherein in the acid adjustment, the nickel sulfate solution after copper removal is filtered, and the reaction temperature in the reactor is controlled to 70 to 75°C, and the pH value is adjusted to 3.5 using nickel carbonate or nickel hydroxide.

7. 2. The method for producing nickel sulfate from nickel powder according to claim 1, wherein, in the secondary leaching, leach sludge containing a predetermined amount of nickel is placed in a reactor, dilute sulfuric acid is added to control the pH value to 1.0, the reaction temperature is controlled to 50 to 65°C, and nickel sulfide is used as a reducing agent in an amount that is 20% to 30% of the nickel content in the acid leaching sludge, and the reaction is carried out for 2 hours.

8. A crystallization apparatus for crystallizing a nickel sulfate solution, comprising: The crystallizer comprises a first-stage crystallizer, a second-stage crystallizer, and a third-stage crystallizer connected in series, each of which comprises a crystallization frame, an oscillator provided below the crystallization frame, and a drain port with a control valve provided at the outlet end of the crystallization frame; a crystallization frame having a rectangular parallelepiped shape, ribs having arc-shaped cross sections uniformly arranged on a bottom of the crystallization frame, a distance S between two adjacent ribs being 1 / 25 to 1 / 15 of the width of the crystallization frame, and a width b and a height h of the ribs being 1 / 100 to 1 / 150 of the width of the crystallization frame.

9. 9. The crystallization apparatus for crystallizing a nickel sulfate solution according to claim 8, wherein the distance S between two adjacent ribs is 1 / 20 of the width of the crystallization frame, and the width b and height h of the rib are both 1 / 110 to 1 / 140 of the width of the crystallization frame.

10. A method for controlling a crystallization apparatus for crystallizing a nickel sulfate solution, comprising: step a) starting a first-stage crystallizer; i.e., pouring concentrated nickel sulfate solution into the first-stage crystallizer; turning on an oscillator; adjusting the oscillator frequency so that the nickel sulfate solution does not spill out of the crystallization frame; and when the temperature of the nickel sulfate solution reaches 45°C, the nickel sulfate solution flows into the second-stage crystallizer through a drain port 5; and the crystals in the crystallization frame are concentrated and sieved, followed by entering the next process; Step b: start the second-stage crystallizer, i.e., after the nickel sulfate solution is poured into the second-stage crystallizer, the fine nickel sulfate crystals that are the under-sieve material from the sieving step are added, and the remaining operations are the same as those of the first-stage crystallizer. When the temperature of the nickel sulfate solution reaches 35°C, the nickel sulfate solution flows from the drain port 5 into the third-stage crystallizer, and the crystals in the crystallization frame are collected and sieved before entering the next step. and step c) of starting the third-stage crystallizer, i.e., after charging the nickel sulfate solution into the third-stage crystallizer, adding the fine nickel sulfate crystals that were undersized in the sieving step, while carrying out the same operations as in the first-stage crystallizer 1, and when the temperature of the nickel sulfate solution reaches room temperature, the nickel sulfate solution flows from the drain port into the storage tank, and the crystals in the crystallization frame are concentrated and combined, and then the nickel sulfate solution is sent to the next step.

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