A method for continuously preparing ferric phosphate using nickel-iron

Abstract

The invention discloses a method for continuously preparing ferric phosphate using nickel iron. The method comprises the following steps: 1) using water gas as a heat source to calcine nickel iron at high temperature. 2) using nickel iron to react with acid solution to obtain a leachate. 3) mixing the leachate with a phosphorus source and entering a reactor with an oxidant at the same time, wherein there is a mixed slurry of an inducer and pure water in the reactor. Then overflowing to an aging reactor. 4) after aging, solid-liquid separation is performed, and after collecting the filter cake for washing and drying, anhydrous ferric phosphate is obtained through flash evaporation and transformation, and the filtrate can be recycled for multiple times after acid supplementation. The nickel iron pretreatment used in the present invention only needs to be calcined at high temperature before use, and does not need to be crushed and screened, thereby reducing equipment investment, having good reaction activity, and being able to react at normal temperature and pressure. The leachate is first mixed with phosphoric acid to avoid the generation of ferric hydroxide in the subsequent reaction, and to prevent the agglomeration of ferric phosphate. The agglomeration of ferric phosphate is serious, which is not conducive to the subsequent grinding of lithium iron phosphate.

Description

Technical Field

[0001] The invention belongs to the technical field of new energy material preparation, and specifically discloses a method for continuously preparing battery-grade iron phosphate by utilizing nickel iron. Background Art

[0002] Lithium iron phosphate battery is a new type of lithium-ion battery. It has attracted much attention for its high safety, long cycle life and stability, and is widely used in electric vehicles, energy storage systems and other fields. As the core material of lithium iron phosphate, iron phosphate determines the performance of lithium iron phosphate batteries. The industry mainly uses the intermittent method to produce iron phosphate, which has low production efficiency, product stability and uniformity cannot be guaranteed, and has high energy consumption. In addition, the current mainstream process requires the use of liquid alkali or ammonia water to adjust the solution pH, which increases production costs, and there is a risk of excessive iron phosphate impurities.

[0003] Chinese patent CN116534824A discloses "a method for preparing iron phosphate by continuous oxidation process". The invention generates dihydrogen ferrous phosphate by reacting phosphoric acid and pure iron, then adds dilute phosphoric acid to adjust the ratio of iron and phosphorus in the solution, sends the ferrous solution into a multi-grid oxidation tank, then opens the hydrogen peroxide pump of the corresponding oxidation tank to add hydrogen peroxide, and the slurry of the last oxidation tank overflows into the aging kettle. After aging, the solid-liquid separation obtains dihydrated iron phosphate. However, the tap density of the iron phosphate produced is too low, which affects the performance of the subsequent lithium iron phosphate battery, the process is complicated, and the equipment investment cost is high. Summary of the invention

[0004] The purpose of the present invention is to provide a method for continuously preparing battery-grade iron phosphate using nickel iron, so as to solve the problems proposed in the above background technology that the tap density of the produced iron phosphate is too low, affecting the performance of subsequent lithium iron phosphate batteries, the process is complicated, and the equipment investment cost is high.

[0005] The present invention discloses a method for continuously preparing ferric phosphate by using nickel iron. The advantages thereof are:

[0006] 1. Nickel iron only needs high temperature calcination, no need for crushing, grinding or screening, thus reducing equipment investment.

[0007] 2. Continuous preparation of iron phosphate reduces batch differences caused by human operation, and the stability of iron phosphate is high.

[0008] 3. The production process does not require the use of liquid alkali / ammonia water to adjust the solution pH, reducing production costs.

[0009] 4. The filtrate of iron precipitation can be recycled many times to reduce the amount of wastewater treatment.

[0010] 5. Mixing the leaching solution with phosphoric acid first can avoid the formation of iron hydroxide in the subsequent reaction and prevent the iron phosphate from agglomerating.

[0011] 6. The lithium iron phosphate produced by it has higher compaction density, first efficiency and discharge specific capacity.

[0012] To achieve the above object, the technical solution of the present invention is as follows: a method for continuously preparing ferric phosphate using nickel iron, specifically comprising the following steps:

[0013] 1) Pre-treatment

[0014] Using water gas as a heat source, calcining the nickel iron at a high temperature of 400-1000°C for 2-8 hours, and collecting the nickel iron after it is cooled for later use;

[0015] 2) Acid leaching

[0016] The calcined nickel iron is acid-leached at normal pressure, and the leaching solution is obtained after filtration. The acid leaching time is 0.5 to 4.0 hours, and the acid leaching solid-liquid ratio is 1:4 to 8;

[0017] 3) Iron

[0018] The reactor is filled with a mixed slurry of water and an inducer until the stirring rod is just covered. The leaching solution and phosphoric acid are mixed and then enter the reactor together with the oxidant, and then overflow into the aging reactor. After the aging is completed, solid-liquid separation is performed to obtain iron phosphate dihydrate and nickel-containing filtrate;

[0019] 4) Post-processing

[0020] The obtained ferric phosphate dihydrate is washed, dried, transformed and packaged to obtain battery-grade anhydrous ferric phosphate. The nickel-containing filtrate obtained after iron precipitation is added with acid and returned to step 2) for use as a base liquid. After 3-6 cycles, a neutralizing agent is added and filtered to obtain a nickel sulfate solution.

[0021] Preferably, in step 2), the acid solution used for acid leaching is one or more of sulfuric acid, hydrochloric acid, and nitric acid, preferably sulfuric acid, with a sulfuric acid concentration of 0.5 to 5M.

[0022] Preferably, in step 2), the acid leaching temperature is 50-100° C., and the endpoint pH is 1.0-4.5.

[0023] Preferably, in step 3), the phosphoric acid concentration is 50-85%, and the molar ratio of the added phosphoric acid to the iron ions in the leaching solution is 1:1-2.

[0024] Preferably, in step 3), the molar ratio of the theoretical amount of the oxidant added to the divalent iron ions in the leachate is 1:0.2-0.8; preferably, the oxidant is one or more of hydrogen peroxide, potassium permanganate, sodium hypochlorite, sodium chlorate, preferably hydrogen peroxide.

[0025] Preferably, in step 3), the inducer is one or more of anhydrous ferric phosphate and dihydrate ferric phosphate, and the mass ratio of the inducer to the iron ions in the solution is 1:0.1-0.3.

[0026] Preferably, in step 3), the addition time of the leaching solution and the oxidant is controlled within 0.5 to 2 hours.

[0027] Preferably, in step 3), the feed temperature is 30-70°C, the aging temperature is 80-95°C, and the aging time is 2-8h.

[0028] Preferably, the neutralizing agent in step 4) is one or more of carbonates and hydroxides, preferably one or more of sodium bicarbonate, calcium carbonate, nickel carbonate, calcium hydroxide, and nickel hydroxide.

[0029] The present invention uses nickel iron as a raw material and water gas as a heat source. After high-temperature calcination, the generated carbon dioxide reacts with the carbon in the nickel iron to generate carbon monoxide gas. The surface structure of the nickel iron changes from being compact to being loose, thereby increasing the reaction area of ​​the nickel iron with the acid solution during the acid leaching process and accelerating the reaction rate.

[0030] Phosphoric acid is added to the obtained leachate to acidify the leachate, which can avoid the generation of iron hydroxide when reacting with hydrogen peroxide. Iron hydroxide will cause serious agglomeration of the generated iron phosphate, wrapping the remaining metal ions of the solution in the crystal nucleus, and the generated iron phosphate impurities exceed the standard and the particle size is too large. After the leachate phosphoric acid is mixed with hydrogen peroxide, it enters the inducer slurry at a uniform speed. As the feed liquid continues to enter the reactor, the concentrations of phosphoric acid and iron in the solution continue to increase, the solubility of iron phosphate in the solution decreases, and the iron phosphate adheres to the inducer and precipitates continuously. The generated iron phosphate particle size distribution is regular, and the iron phosphate slurry overflows to the aging kettle. The temperature in the aging kettle is high, which can increase the specific surface area of ​​the iron phosphate. The high specific surface area of ​​dihydrate iron phosphate is conducive to the subsequent washing of the iron phosphate and reduces the washing water.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The nickel iron used in the present invention only needs to be pre-treated by high-temperature calcination before use, and does not need to be crushed or screened, thus reducing equipment investment. The reaction activity is good and the reaction can be carried out at room temperature and pressure.

[0033] 2. The leaching solution is first mixed with phosphoric acid to avoid the formation of iron hydroxide in the subsequent reaction and prevent the agglomeration of iron phosphate. Severe agglomeration of iron phosphate is not conducive to the subsequent grinding of lithium iron phosphate.

[0034] 3. Continuous feeding and discharging, continuous production of iron phosphate with uniform particle size, reducing batch differences between products caused by human operation, and avoiding the impact of the bottom material left in the reactor on the iron phosphate.

[0035] 4. During the reaction process, there is no need to add liquid alkali to adjust the pH of the solution to avoid the introduction of new impurity ions.

[0036] 5. The filtrate of iron precipitation can be recycled many times to reduce the amount of wastewater treatment.

[0037] 6. The lithium iron phosphate produced by it has a higher compaction density, first efficiency and discharge specific capacity. The specific surface area of ​​anhydrous iron phosphate is ≥8m 2 / g, the compaction density of lithium iron phosphate prepared therefrom is >2.6g / cc, the 0.1C discharge specific capacitance is 160-165mAh / g, the 0.5C discharge specific capacitance is 154-160mAh / g, the 1.0C discharge specific capacitance is 147-151mAh / g, and the 0.1C first efficiency is >97%. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the SEM image of the nickel iron prepared in Example 1.

[0039] Figure 2 This is the SEM image of nickel iron of Comparative Example 1.

[0040] Figure 3 This is a SEM image of the anhydrous ferric phosphate prepared in Example 1 of the present invention.

[0041] Figure 4 This is a SEM image of the anhydrous ferric phosphate prepared in Example 2 of the present invention.

[0042] Figure 5 This is a SEM image of the anhydrous ferric phosphate prepared in Example 3 of the present invention.

[0043] Figure 6 This is a SEM image of the anhydrous ferric phosphate prepared in Example 4 of the present invention.

[0044] Figure 7 This is the SEM image of the anhydrous ferric phosphate prepared in Comparative Example 1.

[0045] Figure 8 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0046] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0047] An embodiment provided by the present invention:

[0048] A method for continuously preparing ferric phosphate by using nickel iron, comprising:

[0049] Example 1

[0050] 1) Pre-treatment

[0051] Nickel iron is calcined at 500°C for 8 hours, and then collected for later use after cooling;

[0052] 2) Acid leaching

[0053] Prepare 2L 4.5M sulfuric acid solution, add 332.5g nickel iron according to the solid-liquid ratio of 1:6, and react at 75°C for 4 hours. The end point pH is 1.3. After filtering, the leaching solution and leaching residue are obtained respectively. The nickel iron content in the leaching solution and the leaching residue is shown in Table 1;

[0054] 3) Iron

[0055] Take 0.5L of leaching solution and add 50% phosphoric acid to the leaching solution. The amount of phosphoric acid added is equal to the amount of Fe in the leaching solution. 3+ The mass ratio of water and anhydrous ferric phosphate was 1:1.05. The mixed slurry of water and anhydrous ferric phosphate was added to the reactor until it just touched the stirring paddle. The amount of anhydrous ferric phosphate added was proportional to the amount of Fe in the leaching solution. 3+ The molar ratio is 1:0.1, the reactor temperature is 40℃, the iron-phosphorus solution and hydrogen peroxide are added into the reactor at the same time, and the theoretical amount of hydrogen peroxide added is the same as the amount of Fe in the leaching solution. 2+ The molar ratio of the substances is 1:0.6; the temperature of the aging kettle is 95°C, the slurry in the reactor overflows into the aging kettle, and then aged for 2 hours, and then filtered to obtain ferric phosphate dihydrate and nickel-containing filtrate;

[0056] 4) Post-processing

[0057] The obtained dihydrate iron phosphate is washed, dried, transformed, crushed and packaged to obtain battery-grade anhydrous iron phosphate;

[0058] After iron precipitation, the filtrate is supplemented with acid and returned to step 2) as the leaching bottom solution. After three cycles, sodium bicarbonate is added to adjust the pH of the solution to 3.5, and the nickel sulfate solution is obtained by filtration.

[0059] Figure 3 The SEM photo of anhydrous ferric phosphate obtained in Example 1 of the present invention is as follows: Figure 3 It can be seen that the obtained anhydrous ferric phosphate particles are uniform and the product quality can meet the process requirements.

[0060] Example 2

[0061] 1) Pre-treatment

[0062] Nickel iron is calcined at 600°C for 6 hours and then collected for later use after cooling;

[0063] 2) Acid leaching

[0064] Prepare 2L 3.5M sulfuric acid solution, add 501.2g nickel iron according to the solid-liquid ratio of 1:4, and react at 85°C for 3 hours. The end point pH is 2.2. After filtering, the leaching solution and leaching residue are obtained respectively. The nickel iron content in the leaching solution and the leaching residue is shown in Table 1;

[0065] 3) Iron

[0066] Take 0.5L of leaching solution and add 60% phosphoric acid to the leaching solution. The amount of phosphoric acid added is equal to the amount of Fe in the leaching solution. 3+ The mass ratio of water and anhydrous ferric phosphate was 1:1.1. 0.2L of water and anhydrous ferric phosphate were added to the reactor until the mixture just touched the stirring paddle. The amount of anhydrous ferric phosphate added was proportional to the amount of Fe in the leaching solution. 3+ The molar ratio is 1:0.2. The reactor temperature is 50°C. The iron-phosphorus solution and hydrogen peroxide are added into the reactor at the same time. The theoretical amount of hydrogen peroxide added is proportional to the amount of Fe in the leaching solution. 2+ The molar ratio of the substances is 1:0.8; the temperature of the aging kettle is 90°C, the slurry in the reaction kettle overflows into the aging kettle, and then aged for 4 hours, and filtered to obtain ferric phosphate dihydrate and nickel-containing filtrate;

[0067] 4) Post-processing

[0068] The obtained dihydrate iron phosphate is washed, dried, transformed, crushed and packaged to obtain battery-grade anhydrous iron phosphate;

[0069] 1) After iron precipitation, the filtrate is supplemented with acid and returned to step 2) as the leaching bottom solution. After 4 cycles, calcium carbonate is added, the pH of the solution is adjusted to 4.1, and the nickel sulfate solution is obtained by filtration.

[0070] Figure 4 The SEM photo of anhydrous ferric phosphate obtained in Example 2 of the present invention is as follows: Figure 4 It can be seen that the obtained anhydrous ferric phosphate particles are uniform and the product quality can meet the process requirements.

[0071] Example 3

[0072] 1) Pre-treatment

[0073] Nickel iron is calcined at 700°C for 4 hours and collected for later use after cooling;

[0074] 2) Acid leaching

[0075] Prepare 2L 2.5M sulfuric acid solution, add 400.3g nickel iron according to the solid-liquid ratio of 1:5, and react at 90°C for 2 hours. The end point pH is 2.7. After filtering, the leaching solution and leaching residue are obtained respectively. The nickel iron content in the leaching solution and the leaching residue is shown in Table 1;

[0076] 3) Iron

[0077] Take 0.5L of leaching solution and add 75% phosphoric acid to the leaching solution. The amount of phosphoric acid added is equal to the amount of Fe in the leaching solution. 3+ The mass ratio of anhydrous ferric phosphate was 1:1.15. 0.2L of water and a mixed slurry of dihydrated ferric phosphate was added to the reactor until it just touched the stirring paddle. The amount of anhydrous ferric phosphate added was proportional to the amount of Fe in the leaching solution. 3+ The molar ratio is 1:0.3. The temperature of the reactor is 55°C. The iron-phosphorus solution and potassium permanganate solution enter the reactor at the same time. The theoretical amount of potassium permanganate added is proportional to the amount of Fe in the leaching solution. 2+ The molar ratio of the substances is 1:0.2; the temperature of the aging kettle is 85°C, the slurry in the reaction kettle overflows into the aging kettle, and then aged for 6 hours, and filtered to obtain ferric phosphate dihydrate and nickel-containing filtrate;

[0078] 4) Post-processing

[0079] The obtained dihydrate iron phosphate is washed, dried, transformed, crushed and packaged to obtain battery-grade anhydrous iron phosphate;

[0080] 2) After iron precipitation, the filtrate is supplemented with acid and returned to step 2) as the leaching bottom solution. After 5 cycles, nickel carbonate is added, the pH of the solution is adjusted to 4.3, and the nickel sulfate solution is obtained by filtration.

[0081] Figure 5 The SEM photo of anhydrous ferric phosphate was obtained for Example 3 of the present invention. Figure 5 It can be seen that the prepared anhydrous ferric phosphate particles are uniform and the product quality can meet the process requirements.

[0082] Example 4

[0083] 1) Pre-treatment

[0084] Nickel iron is calcined at 800°C for 2 hours and then collected for later use after cooling;

[0085] 2) Acid leaching

[0086] Prepare 2L 1.5M sulfuric acid solution, add 400.5g nickel iron according to the solid-liquid ratio of 1:5, and react at 95°C for 2 hours. The end point pH is 3.7. After filtering, the leaching solution and leaching residue are obtained respectively. The nickel iron content in the leaching solution and the leaching residue is shown in Table 1;

[0087] 3) Iron

[0088] Take 0.5L of leaching solution and add 85% phosphoric acid to the leaching solution. The amount of phosphoric acid added is equal to the amount of Fe in the leaching solution. 3+ The mass ratio of water and ferric phosphate dihydrate was 1:1.2. The mixed slurry of water and ferric phosphate dihydrate was added to the reactor until it just touched the stirring paddle. The amount of anhydrous ferric phosphate added was proportional to the amount of Fe in the leaching solution. 3+The molar ratio is 1:0.4. The temperature of the reactor is 60°C. The iron-phosphorus solution and potassium permanganate solution enter the reactor at the same time. The theoretical amount of potassium permanganate added is proportional to the amount of Fe in the leaching solution. 2+ The molar ratio of the substances is 1:0.4; the temperature of the aging kettle is 80°C, the slurry in the reaction kettle overflows into the aging kettle, and then aged for 6 hours, and then filtered to obtain ferric phosphate dihydrate and nickel-containing filtrate;

[0089] 4) Post-processing

[0090] The obtained dihydrate iron phosphate is washed, dried, transformed, crushed and packaged to obtain battery-grade anhydrous iron phosphate;

[0091] 3) After iron precipitation, the filtrate is supplemented with acid and returned to step 2) as the leaching bottom solution. After 6 cycles, calcium hydroxide is added to adjust the solution pH to 4.2, and the nickel sulfate solution is obtained by filtration.

[0092] Figure 6 The SEM photo of anhydrous ferric phosphate obtained for Example 4 of the present invention is as follows: Figure 6 The anhydrous ferric phosphate particles that can be prepared are uniform, and the product quality can meet the process requirements.

[0093] Comparative Example 1

[0094] 1) Pre-treatment

[0095] Nickel iron is not treated;

[0096] 2) Acid leaching

[0097] Use a beaker to prepare 2L 2M sulfuric acid solution, add 501g nickel iron according to the solid-liquid ratio of 1:4, put it in a 95℃ water bath to react at constant temperature for 8h, the end point pH is 0.6, and filter to obtain the leachate and leach residue respectively; the nickel iron content in the leachate and leach residue is shown in Table 1;

[0098] 3) Iron

[0099] Take 0.5L of leaching solution and add 85% phosphoric acid to the leaching solution. The amount of phosphoric acid added is equal to the amount of Fe in the leaching solution. 3+ The mass ratio of water and ferric phosphate dihydrate was 1:1.1. The mixed slurry of water and ferric phosphate dihydrate was added to the reactor until it just touched the stirring paddle. The amount of anhydrous ferric phosphate added was proportional to the amount of Fe in the leaching solution. 3+ The molar ratio is 1:0.4, the reactor temperature is 70℃, the iron-phosphorus solution and hydrogen peroxide are added into the reactor at the same time, and the theoretical amount of hydrogen peroxide added is proportional to the amount of Fe in the leaching solution. 2+ The molar ratio of the substances is 1:1; after the feeding is completed, the temperature of the reactor is raised to 95°C, aged for 6 hours, and filtered to obtain ferric phosphate dihydrate and nickel-containing filtrate;

[0100] 4) Post-processing

[0101] The obtained dihydrate iron phosphate is washed, dried, transformed, crushed and packaged to obtain battery-grade anhydrous iron phosphate;

[0102] Figure 7 The SEM photo of anhydrous ferric phosphate was obtained for Comparative Example 1 of the present invention. Figure 7 It can be seen that the anhydrous ferric phosphate primary particles prepared using an intermittent reactor are larger and irregular, which affects the quality of the ferric phosphate.

[0103] Figure 1 and Figure 2 The nickel-iron SEM images obtained in Example 1 and Comparative Example 1 are respectively Figure 1 and Figure 2 It can be seen that the nickel-iron particles prepared according to the method of the present invention are loose, which increases the contact area during the leaching reaction and can effectively improve the leaching efficiency.

[0104] The nickel-iron acid leaching results obtained in the examples of the present invention and the comparative examples are shown in Table 1.

[0105] The test data of the anhydrous ferric phosphate products produced in the embodiments of the present invention and the comparative examples are shown in Table 2.

[0106] The electrochemical and physicochemical data of the corresponding lithium iron phosphate prepared from the anhydrous iron phosphate produced in the embodiments of the present invention and the comparative examples are shown in Table 3.

[0107] As can be seen from Table 1, the leaching rate of the nickel-iron element obtained by the present invention is above 94%, and the leaching rate of the nickel element is above 90%. Compared with the comparative example, the leaching rate of the nickel-iron is higher, and the amount of residual slag is less. The leaching efficiency is higher, and the time used for acid leaching is significantly shorter than that of the comparative example. Leaching rate = (the total amount of a certain element in the nickel-iron - the total amount of the element in the leached slag) / the total amount of the element in the nickel-iron.

[0108] It can be seen from Table 2 that, compared with the comparative example, the anhydrous ferric phosphate obtained by the present invention has lower contents of key indicators S, Cr and Ni of ferric phosphate, more uniform particle size, lower water content, low impurities in the generated ferric phosphate, reduced entrainment of metal ions, and stable quality.

[0109] It can be seen from Table 3 that the lithium iron phosphate obtained by using the anhydrous iron phosphate of the present invention has a significantly improved discharge specific capacitance, first efficiency and compaction density compared with the control example, which proves that the lithium iron phosphate prepared by the anhydrous iron phosphate obtained by the method of the present invention has better performance.

[0110] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0111]

[0112] Table 1

[0113] Anhydrous Ferric Phosphate Data Example 1 Example 2 Example 3 Example 4 Comparative Example 1 iron,% 36.29 36.33 36.23 36.4 37.26 phosphorus,% 20.61 20.57 20.57 20.58 20.7 Iron / Phosphorus 0.976 0.979 0.9767 0.981 0.998 Moisture,% 0.23 0.26 0.25 0.22 0.49 pH 2.42 2.37 2.32 2.41 2.21 Particle size D50, μm 7.56 6.87 7.35 7.74 35.87 <![CDATA[BET,m 2 / g]]> 8.2 8.7 9.3 8.56 10.5 Chromium, mg / L 13.21 20.51 16.74 14.25 345.8 Calcium, mg / L 2.8 3.6 1.2 1.4 15.8 Aluminum, mg / L 11.5 10.7 12.4 11.8 26.7 Copper, mg / L 0.12 0.24 0.17 0.35 5.72 Potassium + sodium, mg / L 10.45 13.46 20.41 25.67 10.37 Magnesium, mg / L 2.16 2.20 2.29 2.8 2.7 Nickel, mg / L 24.8 22.7 23.4 25.7 246.7 Zinc, mg / L 5.19 5.25 5.3 4.7 8.9 Manganese, mg / L 0.24 0.17 15.36 25.47 3.23 Cobalt, mg / L 8.06 7.96 8.22 8.45 12.78 Magnetic foreign matter, mg / L 0.02 0.04 0.01 0.01 0.95 Sulfur, mg / L 52.7 30.6 42.8 36.9 3265.4 <![CDATA[TD,g / cm 3 ]]> 1.24 1.25 1.17 1.23 1.26

[0114] Table 2

[0115]

[0116] Table 3

Claims

1. A method for continuously preparing ferric phosphate using nickel iron, characterized in that: The specific steps include: 1) Pre-treatment Using water gas as a heat source, calcining nickel iron at a high temperature of 400-1000°C for 0.5-10 hours, and collecting the nickel iron after it is cooled for later use; 2) Acid leaching The calcined nickel iron is acid-leached at normal pressure, and the leaching solution is obtained after filtration. The acid leaching time is 0.5 to 4.0 hours, and the acid leaching solid-liquid ratio is 1:4 to 8; 3) Iron The reactor is filled with a mixed slurry of water and an inducer until the stirring rod is just covered. The leaching solution and phosphoric acid are mixed and then enter the reactor together with the oxidant, and then overflow into the aging reactor. After the aging is completed, solid-liquid separation is performed to obtain iron phosphate dihydrate and nickel-containing filtrate; 4) Post-processing The obtained ferric phosphate dihydrate is washed, dried, transformed and packaged to obtain battery-grade anhydrous ferric phosphate. The nickel-containing filtrate obtained after iron precipitation is added with acid and returned to step 2) for use as a base liquid. After 3-6 cycles, a neutralizing agent is added and filtered to obtain a nickel sulfate solution.

2. The method for continuously preparing ferric phosphate by using nickel iron according to claim 1, characterized in that: In step 2), the acid solution used for acid leaching is one or more of sulfuric acid, hydrochloric acid, and nitric acid, preferably sulfuric acid, and the concentration of sulfuric acid is 0.5-5M.

3. The method for continuously preparing ferric phosphate by using nickel iron according to claim 1, characterized in that: In step 2), the acid leaching temperature is 50-100° C., and the endpoint pH is 1.0-4.

5.

4. The method for continuously preparing ferric phosphate by using nickel iron according to claim 1, characterized in that: In step 3), the concentration of phosphoric acid is 50-85%, and the molar ratio of the added amount of phosphoric acid to the amount of iron ions in the leaching solution is 1:1-2.

5. The method for continuously preparing ferric phosphate by using nickel iron according to claim 1, characterized in that: In step 3), the molar ratio of the theoretical amount of the oxidant added to the divalent iron ions in the leachate is 1:0.2-0.8; preferably, the oxidant is one or more of hydrogen peroxide, potassium permanganate, sodium hypochlorite, sodium chlorate, preferably hydrogen peroxide.

6. The method for continuously preparing ferric phosphate by using nickel iron according to claim 1, characterized in that: In step 3), the inducer is one or more of anhydrous ferric phosphate and dihydrate ferric phosphate, and the mass ratio of the inducer to the iron ions in the solution is 1:0.1-0.

3.

7. The method for continuously preparing ferric phosphate by using nickel iron according to claim 1, characterized in that: In step 3), the addition time of the leaching solution and the oxidant is controlled within 0.5 to 2 hours.

8. The method for continuously preparing ferric phosphate using nickel iron according to claim 1, characterized in that: In step 3), the feed temperature is 30-70°C, the aging temperature is 80-95°C, and the aging time is 2-8h.

9. The method for continuously preparing ferric phosphate using nickel iron according to claim 1, characterized in that: Step 4) The neutralizing agent is one or more of carbonates and hydroxides, preferably one or more of sodium bicarbonate, calcium carbonate, nickel carbonate, calcium hydroxide, and nickel hydroxide.

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