Reaction device and method for continuously preparing iron phosphate slurry

Abstract

The invention discloses a reaction device and method for continuously preparing iron phosphate slurry, and relates to the technical field of continuous production of iron phosphate. The reaction device comprises eight reaction tanks and five aging tanks, and steam inlet pipes are arranged at the bottoms of the reaction tanks and the bottoms of the aging tanks; the R1-R8 are reaction tanks, the R9-R13 are aging tanks, and the bottoms of the R1-R2, the R4 to R5, the R6 to R7, the R9 to R10 and the R11 to R12 are communicated; the tops of R2 to R3, R3 to R4, R5 to R6, R7 to R8, R8 to R9, R10 to R11 and R12 to R13 are communicated through overflow, a ferrous sulfate solution and a mixed solution of monoammonium phosphate and hydrogen peroxide are added into R1, a mixed solution of monoammonium phosphate and hydrogen peroxide is added into R3, phosphoric acid is added into R8, and iron phosphate dihydrate slurry overflows from the top of R13. The iron phosphate slurry is prepared in a multi-groove self-flowing / overflowing mode, continuous preparation and production are achieved, the back-mixing situation in the reaction process is remarkably reduced, the product consistency is good, and the production efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of continuous production of ferric phosphate, and in particular to a reaction device and a method for continuously preparing ferric phosphate slurry. Background Art

[0002] As an important inorganic material, iron phosphate has shown wide application value in many fields. Especially in the battery industry, iron phosphate is the raw material of lithium-ion battery positive electrode material, and its performance directly affects the overall performance of the battery. Therefore, efficient, continuous and stable preparation technology of iron phosphate dihydrate slurry is particularly important.

[0003] Traditional methods for preparing iron phosphate mostly use intermittent operation, that is, after each preparation, the reaction device needs to be shut down to clean up before the next preparation. This method has the following limitations:

[0004] Low production efficiency: intermittent operation leads to low equipment utilization and long preparation cycle, which makes it difficult to meet the needs of large-scale production.

[0005] Unstable product quality: Since there may be differences in the raw material ratio, reaction conditions, etc. during each preparation, the product quality fluctuates greatly, affecting the consistency of the product.

[0006] Serious environmental pollution: intermittent operation easily produces waste gas, waste water and other pollutants, causing certain pollution to the environment.

[0007] In order to overcome the limitations of traditional intermittent preparation technology, a reaction device and method for continuously preparing iron phosphate slurry are needed. Summary of the invention

[0008] The object of the present invention is to provide a reaction device and a method for continuously preparing ferric phosphate slurry, so as to solve the problems of low production efficiency and unstable quality caused by the existing intermittent process.

[0009] The scheme of the present invention is:

[0010] A reaction device for continuously preparing ferric phosphate slurry, characterized in that: it comprises 8 reaction tanks and 5 aging tanks, and the bottoms of the reaction tanks and the aging tanks are all provided with steam inlet pipes; R1-R8 are reaction tanks, and R9-R13 are aging tanks, wherein R1 to R2, R4 to R5, R6 to R7, R9 to R10, and R11 to R12 are connected at the bottom; R2 to R3, R3 to R4, R5 to R6, R7 to R8, R8 to R9, R10 to R11, and R12 to R13 are connected at the top through overflow, ferrous sulfate solution and a mixed solution of monoammonium phosphate and hydrogen peroxide are added to R1, a mixed solution of monoammonium phosphate and hydrogen peroxide is added to R3, phosphoric acid is added to R8, and the overflow from the top of R13 is ferrous phosphate dihydrate slurry.

[0011] A further technical solution is that baffles are provided at the connections between R1 and R2, R4 and R5, R6 and R7, R9 and R10, and R11 and R12, and the baffles are 2 to 5 cm away from the bottom of the groove.

[0012] A further technical solution is that overflow plates are provided at the connections of R2 to R3, R3 to R4, R5 to R6, R7 to R8, R8 to R9, R10 to R11, and R12 to R13, the bottom of the overflow plate is connected to the bottom of the trough, and the height of the top of the overflow plate decreases by 2 to 5 cm successively.

[0013] A further technical solution is that the preparation method of the reaction device comprises the following steps:

[0014] 1) removing impurities from ferrous sulfate solution;

[0015] 2) The ferrous sulfate solution after impurity removal and the prepared mixed solution of monoammonium phosphate and hydrogen peroxide are pumped into R1 of the reaction device, and the first stage of oxidation is carried out in R1 and R2;

[0016] 3) Add a mixed solution of monoammonium phosphate and hydrogen peroxide into R3, and perform the second stage of oxidation in R3, R4, and R5;

[0017] 4) After the second stage of oxidation, the product is kept warm in R6 and R7, phosphoric acid is added to R8 to adjust the pH value, and then the product enters R9 to R13 tanks for aging;

[0018] 5) When the liquid level in the R13 tank reaches the upper overflow port, the material is taken out to obtain ferrous phosphate dihydrate slurry.

[0019] A further technical solution is that the steps of removing impurities from the ferrous sulfate solution are:

[0020] S1. Dissolve the ferrous sulfate raw material in pure water to a concentration of 65 to 70 g / L to obtain a ferrous sulfate solution;

[0021] S2. Adding aqueous ammonia to the ferrous sulfate solution, stirring and filtering, and filtering the resulting product to obtain an aged ferrous sulfate solution, wherein the concentration of the aqueous ammonia is 20% to 27%;

[0022] S3. The Fe concentration of the ferrous sulfate solution is measured, and the aged ferrous sulfate solution is diluted with water according to the measurement result to adjust the Fe concentration of the ferrous sulfate to 50-55 g / L to obtain a finished ferrous sulfate solution to be reacted.

[0023] A further technical solution is that the concentration of monoammonium phosphate in the mixed solution of monoammonium phosphate and hydrogen peroxide is 17% to 23%, and the concentration of hydrogen peroxide is 26% to 30%; the molar ratio of ferrous sulfate to monoammonium phosphate and hydrogen peroxide is 1:0.88 to 0.99:0.6 to 0.7, and the addition ratio of the mixed solution of monoammonium phosphate and hydrogen peroxide in R1 and R3 is 6:4.

[0024] A further technical solution is that the reaction time of the first oxidation and the second oxidation is 10 to 30 minutes, and the reaction temperature is 45 to 60°C.

[0025] A further technical solution is that the insulation temperature is 50-65° C. and the insulation time is 20-40 minutes.

[0026] A further technical solution is that the phosphoric acid concentration is 83% to 87%, and the adjusted pH value is 1.5 to 2.0.

[0027] A further technical solution is that the aging temperature is 90-95° C. and the aging time is 80-90 minutes.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention uses the steam airflow at the bottom of each tank of the reaction device to mix, exchange heat and transport the materials. Compared with the traditional multi-tank series connection, it saves the cost of stirring each tank, heat exchange of the jacket and metering pump for transferring materials, and the temperature of each reaction tank can be adjusted at any time by controlling the airflow temperature, which is easy to operate;

[0030] 2. The "ammonium method" one-step ferric phosphate process adopted by the present invention first dissolves ferrous sulfate, and then adds an ammonia solution to remove impurities to ensure that the impurity content in the solution is qualified. The slurry does not need to be filtered or washed in the intermediate process, and the process flow is simple and easy to operate;

[0031] 3. In industrial large-scale production, a multi-trough gravity / overflow continuous preparation process is adopted. Except for shutdown, the intermediate reaction process continues to operate. In the process of industrial production of ferric phosphate dihydrate slurry, compared with the batch production method of kettle type, the multi-trough gravity / overflow reaction tank flow realizes continuous production, which is conducive to the stable control of the final ferric phosphate product indicators;

[0032] 5. The present invention adopts a multi-tank gravity / overflow process in a reaction device, and a baffle connected at the bottom or an overflow plate overflowing at the top is set at the connection of each tank. The residence time in each tank is relatively short, and the raw material feeding points are dispersed, which greatly reduces the back mixing of materials in each reaction tank;

[0033] 5. In the present invention, phosphoric acid is used to adjust the pH value instead of alkali solution. By calculating and controlling the amount of monoammonium phosphate added at the front end, after phosphoric acid is added at the back end, the phosphorus-iron molar ratio in the reaction system just reaches a suitable range. There is no need to use alkali solutions such as ammonia water or sodium hydroxide to adjust the pH value, thereby avoiding the introduction of new impurities into the reaction system.

[0034] 6. In the present invention, there is no need to wait for the completion of the batch reaction and the slurry to be pumped out, and then repeatedly heat and cool the reaction device, which reduces energy consumption, avoids waiting time and material transfer time during the reaction, and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of a reaction device for preparing iron phosphate slurry according to the present invention. DETAILED DESCRIPTION

[0036] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0037] Example 1

[0038] Figure 1 A reaction device for continuously preparing iron phosphate slurry is shown, including 8 reaction tanks and 5 aging tanks, which can be arranged in a multi-tank overall manner, as shown in FIG. Figure 1 As shown in the figure, the size of the 13 tanks is set according to the material processing volume, back mixing and residence time requirements. It is a self-flowing / overflowing integrated equipment that integrates reaction and aging. In order to facilitate the control of the temperature in the tank, steam inlet pipes are set at the bottom of the reaction tank and the aging tank. According to the temperature requirements in the tank, low-pressure steam is mixed with air to obtain hot air of corresponding temperature to flow into the tank, and the air intake volume is controlled separately.

[0039] Among them, R1-R8 are reaction tanks, R9-R13 are aging tanks, wherein R1 to R2, R4 to R5, R6 to R7, R9 to R10, R11 to R12 are connected at the bottom, and baffles are provided at the connection of R1 to R2, R4 to R5, R6 to R7, R9 to R10, R11 to R12, and the baffles are 2 to 5 cm away from the bottom of the tank, and the optimal distance is 2 cm. R2 to R3, R3 to R4, R5 to R6, R7 to R8, R8 to R9, R10 to R11, R12 to R13 are connected at the top through overflow, and overflow plates are provided at the connection of 2 to R3, R3 to R4, R5 to R6, R7 to R8, R8 to R9, R10 to R11, R12 to R13, and the bottom of the overflow plate is sealed and connected to the bottom of the tank, and the height of the top of the overflow plate decreases by 2 to 5 cm, and the optimal height is 2 cm. Ferrous sulfate solution and a mixed solution of monoammonium phosphate and hydrogen peroxide are added to R1, a mixed solution of monoammonium phosphate and hydrogen peroxide is added to R3, phosphoric acid is added to R8, and the overflow from the top of R13 is ferrous phosphate dihydrate slurry.

[0040] Example 2

[0041] The reaction of continuously preparing the ferric phosphate slurry using the reaction apparatus described in Example 1 is as follows:

[0042] 1) removing impurities from ferrous sulfate solution: dissolving ferrous sulfate raw material in pure water to a concentration of 69.56 g / L to obtain a ferrous sulfate solution; adding ammonia water to the ferrous sulfate solution, stirring and filtering, filtering the obtained product to obtain a ferrous sulfate aging solution, wherein the ammonia water concentration is 24.47%; determining that the Fe concentration of the ferrous sulfate solution is 60.32 g / L, supplementing and diluting the ferrous sulfate impurity removal solution with water, adjusting the Fe concentration of the ferrous sulfate to 53.33 g / L, and obtaining a ferrous sulfate impurity removal solution to be reacted.

[0043] 2) Steam is introduced into the bottom of the tank, and the ferrous sulfate solution, monoammonium phosphate and hydrogen peroxide mixed solution after impurity removal are pumped into R1 from the top, and after heating and mixing, they enter R2 from the bottom of the baffle. The liquid level of R2 gradually rises and overflows into R3. At the same time, the monoammonium phosphate and hydrogen peroxide mixed solution is pumped into R3, and the liquid level of R3 rises and overflows into R4. The R4 material enters R5 through the bottom of the baffle. The molar ratio of ferrous sulfate, monoammonium phosphate and hydrogen peroxide in R1-R5 is controlled to be 1:0.95:0.3; the monoammonium phosphate concentration in the monoammonium phosphate and hydrogen peroxide mixed solution is 20.82%, and the hydrogen peroxide concentration is 27.61%; the addition ratio of the monoammonium phosphate and hydrogen peroxide mixed solution in R1 and R3 is 6:4, the temperature in R1-R5 is controlled at 52-53°C, and the residence time of the reaction slurry in R1-R5 is 5min, 5min, 1.8min, 4.3min, and 4.3min, respectively.

[0044] 3) When the liquid level in R5 tank reaches the upper overflow port, it will overflow to R6 tank, so that the material in R6 tank flows into R7 tank through the bottom of the baffle. The temperature in R6 and R7 tanks is controlled by the steam hot air intake to keep the temperature of the material in R6 and R7 tanks at 52-54°C. The residence time of the slurry in R6-R7 is 15.2min and 15.1min respectively.

[0045] 4) pH adjustment: When the liquid level in the R7 tank reaches the upper overflow port, it will overflow to the R8 tank. At the same time, a phosphoric acid solution with a concentration of 84.87% is pumped into the R8 tank to adjust the pH value, and the pH of the material in the R8 tank is controlled to be 1.5-2.0. The reaction slurry stays in R8 for 7.3 minutes.

[0046] 5) High temperature aging: When the liquid level of the material in the R8 tank that has completed pH adjustment and temperature rise reaches the upper overflow port, it will overflow to the R9 tank and flow into the R10 tank through the bottom of the middle baffle. When the liquid level in the R10 tank reaches the upper overflow port, it will overflow to the R11 tank and flow into the R12 tank through the bottom of the middle baffle. When the liquid level in the R12 tank reaches the upper overflow port, it will overflow to the R13 tank. The material is aged in the R9 to R13 tanks, and the aging temperature is 92-93°C. The residence time of the slurry in R9-R12 is 21.5 minutes, and the residence time in R13 is 4.3 minutes. When the liquid level in the R13 tank reaches the upper overflow port, the material is taken out to obtain dihydrate iron phosphate slurry, with a yield of 94.7%, a particle size of 4.88 μm, and an iron content of 0.07% in the filtrate after filtration and separation.

[0047] Example 3

[0048] The reaction of continuously preparing the ferric phosphate slurry using the reaction apparatus described in Example 1 is as follows:

[0049] 1) removing impurities from ferrous sulfate solution: dissolving ferrous sulfate raw material in pure water to a concentration of 68.79 g / L to obtain a ferrous sulfate solution; adding ammonia water to the ferrous sulfate solution, stirring and filtering, filtering the obtained product to obtain a ferrous sulfate aging solution, wherein the ammonia water concentration is 22.58%; determining the Fe concentration of the ferrous sulfate solution to be 59.91 g / L, supplementing and diluting the ferrous sulfate impurity removal solution with water, adjusting the Fe concentration of the ferrous sulfate to 54.01 g / L, and obtaining a ferrous sulfate impurity removal solution to be reacted.

[0050] 2) Steam is introduced into the bottom of the tank, and the ferrous sulfate solution after impurity removal, the mixed solution of monoammonium phosphate and hydrogen peroxide are pumped into R1 from the top, and after heating and mixing, they enter R2 from the bottom of the baffle, the liquid level of R2 gradually rises and overflows into R3, and the mixed solution of monoammonium phosphate and hydrogen peroxide is pumped into R3 at the same time, the liquid level of R3 rises and overflows into R4, and the R4 material enters R5 through the bottom of the baffle, and the molar ratio of ferrous sulfate, monoammonium phosphate and hydrogen peroxide in R1-R5 is controlled to be 1:0.92:0.66; the concentration of monoammonium phosphate in the mixed solution of monoammonium phosphate and hydrogen peroxide is 21.14%, and the concentration of hydrogen peroxide is 27.83%; the addition ratio of the mixed solution of monoammonium phosphate and hydrogen peroxide in R1 and R3 is 6:4, the temperature in R1-R5 is controlled at 49-51° C., and the residence time of the reaction slurry in R1-R5 is 5 min, 4.8 min, 1.6 min, 4.4 min, and 4.3 min, respectively.

[0051] 3) When the liquid level in R5 tank reaches the upper overflow port, it will overflow to R6 tank, so that the material in R6 tank flows into R7 tank through the bottom of the baffle. The temperature in R6 and R7 tanks is controlled by the steam hot air flow intake, so that the temperature of the material in R6 and R7 tanks is maintained at 51-52°C. The residence time of the slurry in R6-R7 is 15min and 14.8min respectively.

[0052] 4) Adjusting pH: When the liquid level in the R7 tank reaches the upper overflow port, it will overflow to the R8 tank. At the same time, a phosphoric acid solution with a concentration of 84.79% is pumped into the R8 tank to adjust the pH value, and the pH value of the material in the R8 tank is controlled to be 1.89; the reaction slurry stays in R8 for 7.5 minutes.

[0053] 5) High temperature aging: When the liquid level of the material in the R8 tank that has completed pH adjustment and temperature rise reaches the upper overflow port, it will overflow to the R9 tank and flow into the R10 tank through the bottom of the middle baffle. When the liquid level in the R10 tank reaches the upper overflow port, it will overflow to the R11 tank and flow into the R12 tank through the bottom of the middle baffle. When the liquid level in the R12 tank reaches the upper overflow port, it will overflow to the R13 tank. The material is aged in the R9 to R13 tanks, and the aging temperature is 93-94°C. The slurry in R9-R13 has a residence time of 21.5 minutes in R9-R12 and a residence time of 4.4 minutes in R13. When the liquid level in the R13 tank reaches the upper overflow port, the material is taken out to obtain dihydrate iron phosphate slurry, with a yield of 92.4%, a particle size of 5.46 μm, and an iron content of 0.08% in the filtrate after filtration and separation.

[0054] Example 4

[0055] The reaction of continuously preparing the ferric phosphate slurry using the reaction apparatus described in Example 1 is as follows:

[0056] 1) removing impurities from ferrous sulfate solution: dissolving ferrous sulfate raw material in pure water to a concentration of 68.90 g / L to obtain a ferrous sulfate solution; adding ammonia water to the ferrous sulfate solution, stirring and filtering, filtering the obtained product to obtain a ferrous sulfate aging solution, wherein the ammonia water concentration is 25.58%; determining the Fe concentration of the ferrous sulfate solution to be 60.86 g / L, supplementing and diluting the ferrous sulfate impurity removal solution with water, adjusting the Fe concentration of the ferrous sulfate to 52.63 g / L, and obtaining a ferrous sulfate impurity removal solution to be reacted.

[0057] 2) Steam is introduced into the bottom of the tank, and the ferrous sulfate solution after impurity removal, the mixed solution of monoammonium phosphate and hydrogen peroxide are pumped into R1 from the top, and after heating and mixing, they enter R2 from the bottom of the baffle, the liquid level of R2 gradually rises and overflows into R3, and the mixed solution of monoammonium phosphate and hydrogen peroxide is pumped into R3 at the same time, the liquid level of R3 rises and overflows into R4, and the R4 material enters R5 through the bottom of the baffle, and the molar ratio of ferrous sulfate, monoammonium phosphate and hydrogen peroxide in R1-R5 is controlled to be 1:0.96:0.68; the concentration of monoammonium phosphate in the mixed solution of monoammonium phosphate and hydrogen peroxide is 19.98%, and the concentration of hydrogen peroxide is 27.14%; the addition ratio of the mixed solution of monoammonium phosphate and hydrogen peroxide in R1 and R3 is 6:4, the temperature in R1-R5 is controlled at 47-48°C, and the residence time of the reaction slurry in R1-R5 is 5.2min, 5min, 1.8min, 4.3min, and 4.2min, respectively.

[0058] 3) When the liquid level in R5 tank reaches the upper overflow port, it will overflow to R6 tank, so that the material in R6 tank flows into R7 tank through the bottom of the baffle. The temperature in R6 and R7 tanks is controlled by the steam hot air flow intake to keep the temperature of the material in R6 and R7 tanks at 47-50°C. The residence time of the slurry in R6-R7 is 15.1min and 15.1min respectively.

[0059] 4) Adjusting pH: When the liquid level in the R7 tank reaches the upper overflow port, it will overflow to the R8 tank. At the same time, a phosphoric acid solution with a concentration of 84.79% is pumped into the R8 tank to adjust the pH value, and the pH value of the material in the R8 tank is controlled to be 1.68; the reaction slurry stays in R8 for 7.7 minutes.

[0060] 5) High temperature aging: When the liquid level of the material in the R8 tank that has completed pH adjustment and temperature rise reaches the upper overflow port, it will overflow to the R9 tank and flow into the R10 tank through the bottom of the middle baffle. When the liquid level in the R10 tank reaches the upper overflow port, it will overflow to the R11 tank and flow into the R12 tank through the bottom of the middle baffle. When the liquid level in the R12 tank reaches the upper overflow port, it will overflow to the R13 tank. The material is aged in the R9 to R13 tanks, and the aging temperature is 92-94°C. The residence time of the slurry in R9-R12 is 21.4 minutes, and the residence time in R13 is 4.1 minutes. When the liquid level in the R13 tank reaches the upper overflow port, the material is taken out to obtain dihydrate iron phosphate slurry, with a yield of 91.1%, a particle size of 5.44 μm, and an iron content of 0.03% in the filtrate after filtration and separation.

[0061] Comparative Example 1:

[0062] A reaction device and method for continuously preparing ferric phosphate slurry are basically the same as Example 2, except that no ammonia water is added to the ferrous sulfate solution for impurity removal; the yield is 70.8%.

[0063] Comparative Example 2:

[0064] A reaction device and method for continuously preparing iron phosphate slurry are basically the same as Example 2, except that the mixed solution of monoammonium phosphate and hydrogen peroxide is not added in two times; the yield is 61.8%.

[0065] Comparative Example 3:

[0066] The ferric phosphate slurry was prepared according to the method of Example 2, except that no baffle was provided in the middle of the reaction device, the back mixing was obvious and large particles were easily generated; the yield was 75.2%.

[0067] Comparative Example 4:

[0068] The ferric phosphate slurry was prepared according to the method of Example 2, except that during the pH adjustment step, the pH in the R8 tank was adjusted to 2.27; the yield was 69.5%.

[0069] Comparative Example 5:

[0070] The ferric phosphate slurry was prepared according to the method of Example 2, except that during the high-temperature aging process, the aging temperature was adjusted to 88-90° C.; the yield was 81.3%.

[0071] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A reaction device for continuously preparing ferric phosphate slurry, characterized in that: It includes 8 reaction tanks and 5 aging tanks, and steam inlet pipes are arranged at the bottom of the reaction tanks and the aging tanks; R1-R8 are reaction tanks, and R9-R13 are aging tanks, wherein R1 to R2, R4 to R5, R6 to R7, R9 to R10, and R11 to R12 are connected at the bottom; R2 to R3, R3 to R4, R5 to R6, R7 to R8, R8 to R9, R10 to R11, and R12 to R13 are connected at the top through overflow, ferrous sulfate solution and a mixed solution of monoammonium phosphate and hydrogen peroxide are added to R1, a mixed solution of monoammonium phosphate and hydrogen peroxide is added to R3, phosphoric acid is added to R8, and the overflow from the top of R13 is ferrous phosphate dihydrate slurry.

2. A reaction device for continuously preparing iron phosphate slurry according to claim 1, characterized in that: Baffles are arranged at the connection points of R1 to R2, R4 to R5, R6 to R7, R9 to R10, and R11 to R12, and the distance between the baffles and the bottom of the groove is 2 to 5 cm.

3. A reaction device for continuously preparing iron phosphate slurry according to claim 1, characterized in that: Overflow plates are provided at the connections between R2 and R3, R3 and R4, R5 and R6, R7 and R8, R8 and R9, R10 and R11, and R12 and R13. The bottom of the overflow plate is connected to the bottom of the trough, and the height of the top of the overflow plate decreases by 2 to 5 cm.

4. A reaction device for continuously preparing iron phosphate slurry according to any one of claims 1 to 3, characterized in that: The preparation method of the reaction device comprises the following steps: 1) removing impurities from ferrous sulfate solution; 2) The ferrous sulfate solution after impurity removal and the prepared mixed solution of monoammonium phosphate and hydrogen peroxide are pumped into R1 of the reaction device, and the first stage of oxidation is carried out in R1 and R2; 3) Adding a mixed solution of monoammonium phosphate and hydrogen peroxide into R3, and performing the second stage of oxidation in R3, R4, and R5; 4) After the second stage of oxidation, the product is kept warm in R6 and R7, phosphoric acid is added to R8 to adjust the pH value, and then the product enters R9 to R13 tanks for aging; 5) When the liquid level in the R13 tank reaches the upper overflow port, the material is taken out to obtain ferrous phosphate dihydrate slurry.

5. A reaction device for continuously preparing iron phosphate slurry as claimed in claim 4, characterized in that: The steps of removing impurities from the ferrous sulfate solution are: S1. Dissolve the ferrous sulfate raw material in pure water to a concentration of 65 to 70 g / L to obtain a ferrous sulfate solution; S2. Adding aqueous ammonia to the ferrous sulfate solution, stirring and filtering, and filtering the resulting product to obtain an aged ferrous sulfate solution, wherein the concentration of the aqueous ammonia is 20% to 27%; S3. The Fe concentration of the ferrous sulfate solution is measured, and the aged ferrous sulfate solution is diluted with water according to the measurement result to adjust the Fe concentration of the ferrous sulfate to 50-55 g / L to obtain a finished ferrous sulfate solution to be reacted.

6. A reaction device for continuously preparing iron phosphate slurry as claimed in claim 4, characterized in that: The monoammonium phosphate concentration in the mixed solution of monoammonium phosphate and hydrogen peroxide is 17% to 23%, and the hydrogen peroxide concentration is 26% to 30%; the molar ratio of ferrous sulfate to monoammonium phosphate and hydrogen peroxide is 1:0.88 to 0.99:0.6 to 0.7, and the addition ratio of the mixed solution of monoammonium phosphate and hydrogen peroxide in R1 and R3 is 6:

4.

7. A reaction device for continuously preparing ferric phosphate slurry according to claim 4, characterized in that: The first stage oxidation and the second stage oxidation reaction time are 10 to 30 minutes, and the reaction temperature is 45 to 60°C.

8. A reaction device and method for continuously preparing ferric phosphate slurry as claimed in claim 4, characterized in that: The insulation temperature is 50-65° C., and the insulation time is 20-40 minutes.

9. A reaction device for continuously preparing ferric phosphate slurry as claimed in claim 4, characterized in that: The phosphoric acid concentration is 83% to 87%, and the adjusted pH value is 1.5 to 2.

0.

10. A reaction device for continuously preparing iron phosphate slurry according to claim 4, characterized in that: The aging temperature is 90-95° C., and the aging time is 80-90 minutes.

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