Method for regulating and controlling quality of iron phosphate finished product based on iron phosphate production line process material

Abstract

The invention discloses a method for regulating and controlling the quality of an iron phosphate finished product based on iron phosphate production line process materials, which comprises the following steps of: adding the iron phosphate production line process materials such as cold kiln leaked materials, demagnetized materials, dedusted materials, vibrating screen falling materials, packaging falling materials, hot kiln wall sticking materials and the like into the preparation process of the iron phosphate finished product in stages; according to the method, on one hand, waste is recycled, and resource waste is reduced; on the other hand, by means of the process materials and a regulation and control mode of step-by-step addition, the quality of the finished product of iron phosphate can be effectively and benign improved, and various indexes and morphological structures of the finished product of iron phosphate are optimized, so that the obtained dihydrate and anhydrous iron phosphate particles are more regular, and the core requirements of dispersity of the dihydrate iron phosphate and fluidity of the anhydrous iron phosphate are met respectively; the crystal form regulation and the reaction efficiency are both improved.

Description

Technical Field

[0001] This invention belongs to the field of ferric phosphate preparation, and particularly relates to a method for controlling the quality of finished ferric phosphate products based on process materials from a ferric phosphate production line. Background Technology

[0002] Against the backdrop of surging global demand for clean energy, lithium-ion batteries, with their advantages of high energy density, long cycle life, and low self-discharge rate, are widely used in electric vehicles, energy storage systems, and other fields. As the core precursor of lithium iron phosphate (LFP), the cathode material of lithium-ion batteries, the quality and performance of LFP directly determine the electrochemical performance of the LFP cathode material, thus affecting the overall performance and application prospects of lithium-ion batteries, and occupying a crucial position in modern industry.

[0003] However, current ferric phosphate production processes face numerous bottlenecks. The one-step ammonium method for synthesizing ferric phosphate, in particular, suffers from problems such as uneven particle size distribution, difficulty in controlling specific surface area, and poor tap density, all of which negatively impact the quality of the finished product.

[0004] Furthermore, in the one-step ammonium phosphate synthesis process line, key production steps such as cooling, impurity removal, dust removal, screening, roasting, and packaging generate process materials including cold kiln leakage material, demagnetized material, dust removal material, vibrating screen spillage material, hot kiln wall-sticking material, and packaging spillage material. These process materials have complex characteristics, and their inventory continuously increases with production. During storage, these process materials are prone to clumping, reducing space utilization; the simple and crude handling methods not only fail to fully exploit their potential value, causing economic losses, but also may pose safety and environmental risks due to long-term accumulation.

[0005] Based on this, we are now studying a novel method for controlling the quality of iron phosphate products in order to effectively improve product quality. Summary of the Invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to provide a process for controlling the quality of iron phosphate products.

[0007] Technical Solution: The method for controlling the quality of finished ferric phosphate product described in this invention is based on the distribution and addition of process materials during the ferric phosphate preparation process to achieve control, specifically including the following steps:

[0008] (1) Collect process materials by category and perform impurity removal and screening. The process materials include cold kiln leakage material, demagnetized material, dust removal material, vibrating screen fallen material, packaging fallen material, and hot kiln wall-adhering material.

[0009] (2) Mix the ferrous raw material and phosphate raw material according to the calculated amount of ferric phosphate to form a mixed solution; add the dust removal material and stir evenly to form solution A;

[0010] (3) Heat solution A to 60-70℃, then add hydrogen peroxide and demagnetizing material to solution A, and obtain solution B after oxidation reaction;

[0011] (4) Wash and filter solution B to obtain ferric phosphate dihydrate precursor filter cake; mix ferric phosphate dihydrate precursor filter cake, 60-70℃ hot water and phosphoric acid to make pulp, then add the material dropped by the vibrating screen, heat to 85-90℃ and keep warm and age until the ferric phosphate particles have grown.

[0012] (5) Add cold kiln feed to the slurry from step (4), keep it warm for 2-3 hours, then filter, wash, and press to obtain ferric phosphate filter cake dihydrate.

[0013] (6) The ferric phosphate dihydrate filter cake is flash-dried to obtain ferric phosphate dihydrate granules; the ferric phosphate dihydrate granules are calcined, and when the calcination temperature rises to 400-450℃, hot kiln wall-adhesive material is added. After the material is added, the temperature is further raised to 650-700℃ for heat preservation, and packaged waste material is added. The reaction is maintained until the tapped density is >0.6g / cm³. 3 At that time, stop the heat preservation to obtain the iron phosphate product.

[0014] Furthermore, in step (2) of the control method, the amount of dust removal material added is 3-5% of the total mass of ferrous raw material and phosphate raw material.

[0015] Furthermore, in step (3) of the control method, the amount of demagnetizing material added is 5-8% of the total mass of ferrous raw material and phosphate raw material.

[0016] Furthermore, in step (4) of the control method, the amount of material added to the vibrating screen is 4-6% of the mass of the iron phosphate dihydrate precursor filter cake.

[0017] Furthermore, in step (4) of this control method, the amount of phosphoric acid added is 10-15% of the total amount of iron in the system.

[0018] Furthermore, in step (5) of the control method, the amount of material added to the cold kiln is 2-3% of the mass of the iron phosphate dihydrate precursor filter cake.

[0019] Furthermore, in step (6) of the control method, the amount of hot kiln wall-adhesive added is 3-4% of the mass of ferric phosphate dihydrate particles.

[0020] Furthermore, in step (6) of the control method, the amount of the packaging material added is 1-2% of the mass of the iron phosphate dihydrate particles.

[0021] Beneficial effects: Compared with the prior art, the significant advantages of this invention are: This method is based on the process of ferric phosphate preparation, and by combining the process material of the ferric phosphate production line, and by adding the process material in stages, the quality of the prepared ferric phosphate product can be controlled, the quality of the finished ferric phosphate product can be improved, and the various indicators and morphological structure of the finished ferric phosphate product can be optimized, so that the dihydrate and anhydrous ferric phosphate particles are more regular, which respectively meet the core requirements of the dispersibility of dihydrate ferric phosphate and the flowability of anhydrous ferric phosphate, and achieve a dual improvement in crystal form control and reaction efficiency.

[0022] In addition, this method makes full use of various process materials that are about to be scrapped during the online recycling process, which greatly reduces resource waste, realizes the reuse of waste, and reduces economic losses. Attached Figure Description

[0023] Figure 1 The images are SEM images of ferric phosphate dihydrate, where ae corresponds to the SEM images of ferric phosphate dihydrate prepared in Examples 1-5, and f is the SEM image of ferric phosphate dihydrate prepared in Comparative Example 1.

[0024] Figure 2 Here are SEM images of ferric phosphate, where ae corresponds to the SEM images of ferric phosphate prepared in Examples 1-5, and f is the SEM image of ferric phosphate prepared in Comparative Example 1.

[0025] Figure 3 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0027] It should be noted that the specific components and some physicochemical properties of the process materials described in this invention are shown in Table 1:

[0028] Table 1. Physicochemical properties of the process materials used in this invention

[0029]

[0030] The process materials may vary in terms of trace magnetic impurities, sulfur content, and moisture content, but trace impurities will not have a significant impact on the overall performance. In this scheme, the phase properties (e.g., particle size and specific surface area) of the process materials have a significant impact on the results.

[0031] In addition, in the following examples and comparative examples, the ferrous raw material is ferrous sulfate heptahydrate, and its aqueous solution is prepared by adding sulfuric acid to the clear liquid after ferrous sulfate heptahydrate has been filtered to remove impurities with phosphoric acid and then mixing it to control the pH, with a pH of 1.6±0.15; the phosphate raw material is monoammonium phosphate, and its aqueous solution is prepared by mixing and dissolving monoammonium phosphate and phosphoric acid and then filtering the clear liquid, with a pH of 2.7±0.2.

[0032] In the following examples, in steps (2), (3), and (5), and in comparative examples 1-3, the pH value in the system needs to be controlled at 1.8 ± 0.2 in steps (2) and (4).

[0033] Example 1

[0034] This implementation outlines methods for controlling the quality of finished products during the production of ferric phosphate, such as... Figure 3 As shown, the process includes the following steps, and the amount of material added in each process is shown in Table 4:

[0035] (1) Collect process materials containing iron phosphate, such as cold kiln leakage material, demagnetized material, dust removal material, vibrating screen fallen material, packaging fallen material and hot kiln wall-adhering material, and remove metal impurities by magnetic separation and sieve to remove particles ≥50μm.

[0036] (2) Weigh the phosphate and ferrous raw materials according to the calculated amount of ferric phosphate to prepare aqueous solutions. Accurately add the measured amount of monoammonium phosphate and ferrous sulfate aqueous solution through the weighing device of the reactor, and record the amount added, with an error of ≤ ±0.2 kg. Start the stirring device of the reactor and set the speed to 500 r / min. Accurately add the dust removal material through the feeding device. The amount of dust removal material added is 3% of the mass of monoammonium phosphate and ferrous sulfate raw materials. The feeding time is 5 min, and the material is added at a uniform rate to avoid excessive local concentration caused by one-time addition. After the feeding is completed, continue to maintain the speed of 500 r / min to form solution A. At the same time, turn on the heating system and raise the temperature to 60°C at 8°C / min. Monitor the temperature in real time through the temperature sensor. When the temperature approaches 60°C, appropriately reduce the heating rate to avoid exceeding 70°C.

[0037] (3) Add 7.8% hydrogen peroxide dropwise to solution A. While adding hydrogen peroxide, add demagnetizing material at a uniform speed through a feeding device. The amount of demagnetizing material added is 5% of the mass of monoammonium phosphate and ferrous sulfate raw materials. The feeding time is 10 min, and the material is added at a uniform speed. The feeding process is maintained at a rotation speed of 500 r / min. During the feeding process, the solid content of the reaction system needs to be detected. The solid content is kept stable at 15%-20% by using a solid content detection instrument. If the solid content is lower than 15%, the feeding speed of the demagnetizing material is increased appropriately. If it is higher than 20%, the feeding speed is reduced until all the demagnetizing material is added. Continue stirring for 30 min to allow the reaction to proceed fully. After the hydrogen peroxide is added, the oxidation endpoint is determined by the indicator of potassium ferricyanide + phosphoric acid. The oxidation is complete when the solution turns yellow, which is solution B. The system temperature of solution B is controlled at 60℃, and the pH range is controlled at 1.8±0.2. Finally, a precipitated slurry is obtained.

[0038] (4) Start the plate and frame filter press, feed the precipitated slurry into the filter press, the feed pressure is 0.8MPa, and the feed speed is 1m.3 / h, by observing the liquid state at the outlet, when the liquid output decreases significantly and the liquid becomes clear, it is determined that filtration is complete, and the feed valve is closed; the pressing system is turned on, the pressing pressure is set to 1.5MPa, and the pressing time is 15min. After pressing is completed, the filter is opened, the ferric phosphate dihydrate precursor filter cake is taken out, and the moisture content of the filter cake is checked to be 45-50%. If the moisture content is higher than 35%, it needs to be pressed again. If the moisture content is too low, check whether the filtration process is normal and adjust the subsequent filtration parameters.

[0039] (5) Add hot water at 60℃ and phosphoric acid with a concentration of 85% to the pulping tank. The amount of phosphoric acid added is 10% of the total iron content. The overall solid content of the pulp is controlled at 10%. Transfer the ferric phosphate dihydrate precursor filter cake into the pulping tank. Using the weighing device of the pulping tank, accurately add 4% of the mass of the ferric phosphate dihydrate precursor filter cake to the vibrating screen. Record the addition amount error as ≤±0.1kg. Start the stirring device of the pulping tank and set the speed to 800r / min for pulping and dispersion. Set the dispersion time to 30min. During the dispersion process, take a sample every 10min to observe the particle dispersion and ensure that the dispersion is uniform and there is no obvious particle agglomeration. After the ferric phosphate dihydrate precursor filter cake is slurried and dispersed evenly, it is put into the aging kettle and heated to 85°C for heat preservation. After the material turns from yellow to pinkish-white, cold kiln material is added through the feeding device. The mass of the added material is 2% of the mass of the ferric phosphate dihydrate precursor filter cake. The feeding time is 5 min. During the feeding period, the rotation speed is maintained at 800 r / min and stirring is continued for 20 min to fully mix the cold kiln material with the ferric phosphate particles and guide the ferric phosphate particles to grow towards the target crystal form. The entire heat preservation time is 3 h. Then, the pinkish-white slurry is pressure filtered and washed according to the pressure filtration method in step (4) to obtain ferric phosphate dihydrate filter cake with a water content of 45-50%.

[0040] (6) Start the flash dryer preheating system and raise the inlet air temperature to 300℃ (the inlet air temperature is adjusted according to the moisture content of the wet material; when the moisture content is 40-45%, use 300-350℃; when the moisture content is 45-50%, use 350-400℃). After the inlet air temperature stabilizes, turn on the stirring and crushing system and set the speed to 800r / min; feed the wet iron phosphate material into the drying chamber through the screw feeder at a feeding speed of 0.5m. 3 The feed rate is adjusted according to the outlet air temperature (100℃) at a rate of / h. Higher outlet air temperatures result in higher feed rates, while lower temperatures result in slower feed rates. The dried powder is inspected, and ferric phosphate dihydrate granules are removed once they pass inspection. Parameter analysis of the ferric phosphate dihydrate granules is performed, and the results are shown in Table 2. Electron micrographs are shown below. Figure 1 As shown in Figure a.

[0041] (7) The ferric phosphate dihydrate granules are fed into a rotary kiln for calcination. The rotary kiln is started, and the kiln rotation speed is 1 r / min during calcination. The heating rate of the heating system is 10℃ / min. When the temperature inside the kiln reaches 400℃, hot kiln wall-adhering material is added through the kiln tail feed inlet. The amount of hot kiln wall-adhering material added is 3% of the mass of the ferric phosphate dihydrate granules, and the feeding speed is 0.5 kg / min. During the feeding process, the temperature is kept stable by the heating system, and the temperature fluctuation does not exceed ±5℃. After the hot kiln wall-adhering material is added, the temperature is continued to rise to 650℃, and then kept at that temperature for 1.5 h. 30 min after the start of the heat preservation, the packaging material is added. The mass of the packaging material added is 1% of the mass of the ferric phosphate dihydrate granules, and the feeding time is 5 min, added at a uniform rate. During the heat preservation process, the kiln temperature and particle density are checked every 20 min to ensure that the temperature is stable at 650℃±3℃ and the tapped density needs to be >0.6 g / cm³. 3 If the tapped density is too low, adjust the kiln speed and extend the holding time appropriately until the tapped density meets the requirements. Allow the material to enter the cooling kiln system for cooling. After cooling to below 100℃, it enters the vibrating screen and disc mill system through the conveying pipe, subsequently obtaining anhydrous ferric phosphate. Parameter testing of the ferric phosphate is shown in Table 3, and the electron micrographs are shown below. Figure 2 As shown in Figure a.

[0042] Example 2

[0043] The method for controlling the quality of finished product during the production of iron phosphate in this embodiment differs from that in Example 1 in that the following steps are different, and the amount of materials added in each process is shown in Table 4:

[0044] (2) Weigh the phosphate and ferrous raw materials according to the calculated amount of ferric phosphate to prepare aqueous solutions. Accurately add the original aqueous solutions of monoammonium phosphate and ferrous sulfate using the weighing device of the reactor and record the amount added, with an error of ≤ ±0.2 kg. Start the stirring device of the reactor and set the speed to 600 r / min. Accurately add the dust removal material through the feeding device. The amount of dust removal material added is 5% of the mass of monoammonium phosphate and ferrous sulfate raw materials. The feeding time is 10 min, and the material is added at a uniform speed to avoid excessive local concentration caused by one-time addition. After the feeding is completed, continue to maintain the speed of 600 r / min to form solution A. At the same time, turn on the heating system and raise the temperature to 70℃ at 8℃ / min.

[0045] (3) Add 7.8% hydrogen peroxide dropwise to solution A. While adding hydrogen peroxide, add demagnetizing material at a constant speed through a feeding device. The amount of demagnetizing material added is 8% of the mass of monoammonium phosphate and ferrous sulfate raw materials. The feeding time is 15 min, and the material is added at a constant speed. The feeding process is maintained at a speed of 600 r / min. During the feeding process, the solid content of the reaction system needs to be detected. The solid content is kept stable at 15%-20% by using a solid content detection instrument. If the solid content is lower than 15%, the feeding speed of the demagnetizing material is increased appropriately. If it is higher than 20%, the feeding speed is reduced until all the demagnetizing material is added. Continue stirring for 30 min to allow the reaction to proceed fully. After the hydrogen peroxide is added, the oxidation endpoint is determined by the indicator of potassium ferricyanide + phosphoric acid. The oxidation is complete when the solution turns yellow, which is solution B. The system temperature of solution B is controlled at 70℃, and the pH range is controlled at 1.8±0.2. Finally, a precipitated slurry is obtained.

[0046] (5) Add hot water at 70℃ and phosphoric acid with a concentration of 85% to the pulping tank. The amount of phosphoric acid added is 10% of the total iron content. The overall solid content of the pulp is controlled at 10%. Transfer the ferric phosphate dihydrate precursor filter cake into the pulping tank. Using the weighing device of the pulping tank, accurately add 6% of the mass of the ferric phosphate dihydrate precursor filter cake to the vibrating screen. Record the addition amount error as ≤±0.1kg. Start the stirring device of the pulping tank and set the speed to 1000r / min for pulping and dispersion. Set the dispersion time to 30min. During the dispersion process, take a sample every 10min to observe the particle dispersion and ensure that the dispersion is uniform and there is no obvious particle agglomeration. After the ferric phosphate dihydrate precursor filter cake is slurried and dispersed evenly, it is put into the aging kettle and heated to 85°C for heat preservation. After the material turns from yellow to pinkish-white, cold kiln material is added through the feeding device. The mass of the added material is 3% of the mass of the ferric phosphate dihydrate precursor filter cake and the feeding time is 8 minutes. During the feeding period, the rotation speed is maintained at 1000 r / min and stirring is continued for 20 minutes to fully mix the cold kiln material with the ferric phosphate particles and guide the ferric phosphate particles to grow towards the target crystal form. The heat preservation time is 2 hours. Then, the pinkish-white slurry is pressure filtered and washed according to the pressure filtration method in step (4) to obtain ferric phosphate dihydrate filter cake with a water content of 45-50%.

[0047] (6) Start the flash dryer preheating system and raise the inlet air temperature to 300℃ (the inlet air temperature is adjusted according to the moisture content of the wet material; 300-350℃ is used when the moisture content is 40-45%, and 350-400℃ is used when the moisture content is 45-50%). After the inlet air temperature stabilizes, turn on the stirring and crushing system and set the speed to 1000r / min; feed the wet iron phosphate material into the drying chamber through the screw feeder at a feeding speed of 1.3m. 3The feed rate is adjusted according to the outlet air temperature (100℃) at a rate of / h. Higher outlet air temperatures result in higher feed rates, while lower temperatures result in slower feed rates. The dried powder is inspected, and ferric phosphate dihydrate granules are removed once they pass inspection. Parameter analysis of the ferric phosphate dihydrate granules is performed, and the results are shown in Table 2. Electron micrographs are shown below. Figure 1 As shown in b.

[0048] (7) The ferric phosphate dihydrate granules are fed into a rotary kiln for calcination. The rotary kiln is started, and the kiln rotation speed is 1 r / min during calcination. The heating rate of the heating system is 15℃ / min. When the temperature inside the kiln reaches 450℃, hot kiln wall-adhering material is added through the kiln tail feed inlet. The amount of hot kiln wall-adhering material added is 4% of the mass of the ferric phosphate dihydrate granules, and the feeding speed is 1 kg / min. During the feeding process, the temperature is kept stable by the heating system, and the temperature fluctuation does not exceed ±5℃. After the hot kiln wall-adhering material is added, the temperature is continued to rise to 650℃, and then kept at that temperature for 1.5 hours. 30 minutes after the start of the heat preservation, the packaging material is added. The mass of the packaging material added is 2% of the mass of the ferric phosphate dihydrate granules, and the feeding time is 10 minutes, added at a uniform rate. During the heat preservation process, the kiln temperature and particle density are checked every 20 minutes to ensure that the temperature is stable at 650℃±3℃ and the tapped density needs to be >0.6 g / cm³. 3 If the tapped density is too low, adjust the kiln speed and extend the holding time appropriately until the tapped density meets the requirements. Allow the material to enter the cooling kiln system for cooling. After cooling to below 100℃, it enters the vibrating screen and disc mill system through the conveying pipe, subsequently obtaining anhydrous ferric phosphate. Parameter testing of the ferric phosphate is shown in Table 3, and the electron micrographs are shown below. Figure 2 As shown in b.

[0049] Example 3

[0050] The method for controlling the quality of finished product in the production of iron phosphate in this embodiment differs from that in Example 1 in that the following steps are different, and the amount of materials added in each process is shown in Table 4:

[0051] (2) The phosphate raw materials and ferrous raw materials are weighed according to the calculated amount of ferric phosphate to be generated, and aqueous solutions are prepared separately. The monoammonium phosphate and ferrous sulfate aqueous solutions are accurately added through the weighing device of the reactor, and the amount added is recorded with an error of ≤ ±0.2 kg. The stirring device of the reactor is started and the speed is set to 550 r / min. The dust removal material is accurately added through the feeding device. The amount of dust removal material added is 4% of the mass of monoammonium phosphate and ferrous sulfate raw materials. The feeding time is 8 min, and the material is added at a uniform rate to avoid excessive local concentration caused by one-time addition. After the feeding is completed, the speed is maintained at 550 r / min to form solution A. At the same time, the heating system is turned on and the temperature is raised to 65℃ at 7℃ / min. The temperature is monitored in real time through the temperature sensor. When the temperature approaches 60℃, the heating rate is appropriately reduced to avoid exceeding 70℃.

[0052] (3) Add 7.8% hydrogen peroxide dropwise to solution A. While adding hydrogen peroxide, add demagnetizing material at a constant speed through a feeding device. The amount of demagnetizing material added is 7% of the mass of monoammonium phosphate and ferrous sulfate raw materials. The feeding time is 15 min, and the material is added at a constant speed. The feeding process is maintained at a rotation speed of 550 r / min. During the feeding process, the solid content of the reaction system needs to be detected. The solid content is kept stable at 15%-20% by using a solid content detection instrument. If the solid content is lower than 15%, the feeding speed of the demagnetizing material is increased appropriately. If it is higher than 20%, the feeding speed is reduced until all the demagnetizing material is added. Continue stirring for 30 min to allow the reaction to proceed fully. After the hydrogen peroxide is added, the oxidation endpoint is determined by the indicator of potassium ferricyanide + phosphoric acid. The oxidation is complete when the solution turns yellow, which is solution B. The system temperature of solution B is controlled at 65℃, and the pH range is controlled at 1.8±0.2. Finally, a precipitated slurry is obtained.

[0053] (5) Add hot water at 65℃ and phosphoric acid with a concentration of 85% to the pulping tank. The amount of phosphoric acid added is 10% of the total iron content. The overall solid content of the pulp is controlled at 10%. Transfer the ferric phosphate dihydrate precursor filter cake into the pulping tank. Using the weighing device of the pulping tank, accurately add 5% of the mass of the ferric phosphate dihydrate precursor filter cake to the vibrating screen. Record the addition amount error as ≤±0.1kg. Start the stirring device of the pulping tank and set the speed to 900r / min for pulping and dispersion. Set the dispersion time to 30min. During the dispersion process, take a sample every 10min to observe the particle dispersion and ensure that the dispersion is uniform and there is no obvious particle agglomeration. After the ferric phosphate dihydrate precursor filter cake is evenly dispersed by slurrying, it is fed into an aging kettle and heated to 85°C. Once the material changes from yellow to pinkish-white, it is added to a cold kiln through a feeding device at a mass of 2.5% of the ferric phosphate dihydrate precursor filter cake mass. The feeding time is 7 minutes, and the rotation speed is maintained at 900 r / min during the feeding process. Stirring continues for 20 minutes to ensure thorough mixing between the cold kiln feed and the ferric phosphate particles, guiding the ferric phosphate particles towards the target crystal form. The holding time is 2.5 hours. Then, following the pressure filtration method in step (4), the pinkish-white slurry is pressure filtered and washed to obtain a ferric phosphate dihydrate filter cake with a moisture content of 45-50%.

[0054] (6) Start the flash dryer preheating system and raise the inlet air temperature to 300℃ (the inlet air temperature is adjusted according to the moisture content of the wet material; when the moisture content is 40-45%, use 300-350℃, and when the moisture content is 45-50%, use 350-400℃). After the inlet air temperature stabilizes, turn on the stirring and crushing system and set the speed to 900r / min; feed the wet iron phosphate material into the drying chamber through the screw feeder at a feeding speed of 1m. 3The feed rate is adjusted according to the outlet air temperature (100℃) at a rate of / h. Higher outlet air temperatures result in higher feed rates, while lower temperatures result in slower feed rates. The dried powder is inspected, and ferric phosphate dihydrate granules are removed once they pass inspection. Parameter analysis of the ferric phosphate dihydrate granules is performed, and the results are shown in Table 2. Electron micrographs are shown below. Figure 1 As shown in c.

[0055] (7) The ferric phosphate dihydrate granules were fed into a rotary kiln for calcination. The rotary kiln was started, and the kiln rotation speed was 1 r / min during calcination. The heating rate of the heating system was 14℃ / min. When the kiln temperature reached 450℃, hot kiln wall-adhering material was added through the kiln tail inlet. The amount of hot kiln wall-adhering material added was 3.5% of the mass of the ferric phosphate dihydrate granules, and the feeding speed was 0.8 kg / min. During the feeding process, the temperature was stabilized by the heating system, and the temperature fluctuation did not exceed ±5℃. After the hot kiln wall-adhering material was added, the temperature was continued to rise to 650℃, and then kept at that temperature for 1.5 h. 30 min after the start of the heat preservation, the packaging material was added. The mass of the packaging material added was 1.5% of the mass of the ferric phosphate dihydrate granules, and the feeding time was 8 min, added at a uniform rate. During the heat preservation process, the kiln temperature and particle density were checked every 20 min to ensure that the temperature was stable at 650℃±3℃ and the tapped density was >0.6 g / cm³. 3 If the tapped density is too low, adjust the kiln speed and extend the holding time appropriately until the tapped density meets the requirements. Allow the material to enter the cooling kiln system for cooling. After cooling to below 100℃, it enters the vibrating screen and disc mill system through the conveying pipe, subsequently obtaining anhydrous ferric phosphate. Parameter testing of the ferric phosphate is shown in Table 3, and the electron micrographs are shown below. Figure 2 As shown in c.

[0056] Example 4

[0057] The method for controlling the quality of finished product in the production of iron phosphate in this embodiment differs from that in Example 1 in that the following steps are different, and the amount of materials added in each process is shown in Table 4:

[0058] (2) The phosphate raw materials and ferrous raw materials are weighed according to the calculated amount of ferric phosphate to be generated, and then prepared into aqueous solutions. The original aqueous solutions of monoammonium phosphate and ferrous sulfate are accurately added through the weighing device of the reactor, and the amount added is recorded with an error of ≤ ±0.2 kg. The stirring device of the reactor is started and the speed is set to 550 r / min. The dust removal material is accurately added through the feeding device. The amount of dust removal material added is 3.5% of the mass of monoammonium phosphate and ferrous sulfate raw materials. The feeding time is 6 min, and the material is added at a uniform rate to avoid excessive local concentration caused by one-time addition. After the material is added, the speed is maintained at 550 r / min to form solution A. At the same time, the heating system is turned on and the temperature is raised to 65°C at 8°C / min. The temperature is monitored in real time through the temperature sensor. When the temperature approaches 60°C, the heating rate is appropriately reduced to avoid exceeding 70°C.

[0059] (3) Then, add 7.8% hydrogen peroxide dropwise to solution A. While adding hydrogen peroxide, add demagnetizing material at a uniform speed through a feeding device. The amount of demagnetizing material added is 6% of the mass of monoammonium phosphate and ferrous sulfate raw materials. The feeding time is 15 min, and the material is added at a uniform speed. The feeding process is maintained at a rotation speed of 550 r / min. During the feeding process, the solid content of the reaction system needs to be detected. The solid content is kept stable at 15%-20% by using a solid content detection instrument. If the solid content is lower than 15%, the feeding speed of the demagnetizing material is increased appropriately. If it is higher than 20%, the feeding speed is reduced until all the demagnetizing material is added. Continue stirring for 30 min to allow the reaction to proceed fully. After the hydrogen peroxide is added, the oxidation endpoint is determined by the indicator of potassium ferricyanide + phosphoric acid. The oxidation is complete when the solution turns yellow, which is solution B. The system temperature of solution B is controlled at 65℃, and the pH range is controlled at 1.8±0.2. Finally, the precipitated slurry is obtained.

[0060] (5) Add hot water at 65℃ and phosphoric acid with a concentration of 85% to the pulping tank. The amount of phosphoric acid added is 10% of the total iron content. The overall solid content of the pulp is controlled at 10%. Transfer the ferric phosphate dihydrate precursor filter cake into the pulping tank. Using the weighing device of the pulping tank, accurately add 4.5% of the mass of the ferric phosphate dihydrate precursor filter cake to the vibrating screen. Record the addition amount error as ≤±0.1kg. Start the stirring device of the pulping tank and set the speed to 900r / min for pulping and dispersion. Set the dispersion time to 30min. During the dispersion process, take a sample every 10min to observe the particle dispersion and ensure that the dispersion is uniform and there is no obvious particle agglomeration. After the ferric phosphate dihydrate precursor filter cake is evenly dispersed by slurrying, it is fed into an aging kettle and heated to 85°C. Once the material changes from yellow to pinkish-white, it is added to a cold kiln through a feeding device at a mass of 2.5% of the ferric phosphate dihydrate precursor filter cake mass. The feeding time is 7 minutes, and the rotation speed is maintained at 900 r / min during the feeding process. Stirring continues for 20 minutes to ensure thorough mixing between the cold kiln feed and the ferric phosphate particles, guiding the ferric phosphate particles towards the target crystal form. The holding time is 2 hours. Then, following the pressure filtration method in step (4), the pinkish-white slurry is pressure filtered and washed to obtain a ferric phosphate dihydrate filter cake with a moisture content of 45-50%.

[0061] (6) Start the flash dryer preheating system and raise the inlet air temperature to 300℃ (the inlet air temperature is adjusted according to the moisture content of the wet material; when the moisture content is 40-45%, use 300-350℃, and when the moisture content is 45-50%, use 350-400℃). After the inlet air temperature stabilizes, turn on the stirring and crushing system and set the speed to 900r / min; feed the wet iron phosphate material into the drying chamber through the screw feeder at a feeding speed of 1m. 3The feed rate is adjusted according to the outlet air temperature, with a feed rate of 110℃ per hour. Higher outlet air temperatures result in higher feed rates, while lower temperatures result in lower feed rates. The dried powder is inspected, and ferric phosphate dihydrate granules are removed after passing inspection. Parameter analysis of the ferric phosphate dihydrate granules is performed, and the results are shown in Table 2. Electron micrographs are shown below. Figure 1 As shown in d.

[0062] (7) The ferric phosphate dihydrate granules were fed into a rotary kiln for calcination. The rotary kiln was started, and the kiln rotation speed was 1 r / min during calcination. The heating rate of the heating system was 14℃ / min. When the temperature inside the kiln reached 450℃, hot kiln wall-adhering material was added through the kiln tail feed inlet. The amount of hot kiln wall-adhering material added was 3.5% of the mass of the ferric phosphate dihydrate granules, and the feeding speed was 0.8 kg / min. During the feeding process, the temperature was stabilized by the heating system, and the temperature fluctuation did not exceed ±5℃. After the hot kiln wall-adhering material was added, the temperature was continued to rise to 650℃, and then kept at that temperature for 1.5 h. 30 min after the start of the heat preservation, the packaging material was added. The mass of the packaging material added was 1.5% of the mass of the ferric phosphate dihydrate granules, and the feeding time was 8 min, added at a uniform rate. During the heat preservation process, the kiln temperature and particle density were checked every 20 min to ensure that the temperature was stable at 650℃±3℃ and the tapped density was >0.6 g / cm³. 3 If the tapped density is too low, adjust the kiln speed and extend the holding time appropriately until the tapped density meets the requirements. Allow the material to enter the cooling kiln system for cooling. After cooling to below 100℃, it enters the vibrating screen and disc mill system through the conveying pipe, subsequently obtaining anhydrous ferric phosphate. Parameter testing of the ferric phosphate is shown in Table 3, and the electron micrographs are shown below. Figure 2 As shown in d.

[0063] Example 5

[0064] The method for controlling the quality of finished product in the production of iron phosphate in this embodiment differs from that in Example 1 in that the following steps are different, and the amount of materials added in each process is shown in Table 4:

[0065] (2) The phosphate raw materials and ferrous raw materials are weighed according to the calculated amount of ferric phosphate to be generated, and then prepared into aqueous solutions. The original aqueous solutions of monoammonium phosphate and ferrous sulfate are accurately added through the weighing device of the reactor, and the amount added is recorded with an error of ≤ ±0.2 kg. The stirring device of the reactor is started and the speed is set to 550 r / min. The dust removal material is accurately added through the feeding device. The amount of dust removal material added is 4.5% of the mass of monoammonium phosphate and ferrous sulfate raw materials. The feeding time is 6 min, and the material is added at a uniform speed to avoid excessive local concentration caused by one-time addition. After the material is added, the speed is maintained at 550 r / min to form solution A. At the same time, the heating system is turned on and the temperature is raised to 65℃ at 8℃ / min. The temperature is monitored in real time through the temperature sensor. When the temperature approaches 60℃, the heating rate is appropriately reduced to avoid exceeding 70℃.

[0066] (3) Add 7.8% hydrogen peroxide dropwise to solution A. While adding hydrogen peroxide, add demagnetizing material at a constant speed through a feeding device. The amount of demagnetizing material added is 5.5% of the mass of monoammonium phosphate and ferrous sulfate raw materials. The feeding time is 15 min, and the material is added at a constant speed. The feeding process is maintained at a rotation speed of 550 r / min. During the feeding process, the solid content of the reaction system needs to be detected. The solid content is kept stable at 15%-20% by using a solid content detection instrument. If the solid content is lower than 15%, the feeding speed of the demagnetizing material is increased appropriately. If it is higher than 20%, the feeding speed is reduced until all the demagnetizing material is added. Continue stirring for 30 min to allow the reaction to proceed fully. After the hydrogen peroxide is added, the oxidation endpoint is determined by the indicator of potassium ferricyanide + phosphoric acid. The oxidation is complete when the solution turns yellow, which is solution B. The system temperature of solution B is controlled at 65℃, and the pH range is controlled at 1.8±0.2. Finally, a precipitated slurry is obtained.

[0067] (5) Add hot water at 65℃ and phosphoric acid with a concentration of 85% to the pulping tank. The amount of phosphoric acid added is 10% of the total iron content. The overall solid content of the pulp is controlled at 10%. Transfer the ferric phosphate dihydrate precursor filter cake into the pulping tank. Using the weighing device of the pulping tank, accurately add 5.5% of the mass of the ferric phosphate dihydrate precursor filter cake to the vibrating screen. Record the addition amount error as ≤±0.1kg. Start the stirring device of the pulping tank and set the speed to 900r / min for pulping and dispersion. Set the dispersion time to 30min. During the dispersion process, take a sample every 10min to observe the particle dispersion and ensure that the dispersion is uniform and there is no obvious particle agglomeration. After the ferric phosphate dihydrate precursor filter cake is evenly dispersed by slurrying, it is put into the aging kettle and heated to 85°C for heat preservation. After the material turns from yellow to pinkish-white, cold kiln material is added through the feeding device. The mass of the added material is 2.5% of the mass of the ferric phosphate dihydrate precursor filter cake. The feeding time is 7 min. During the feeding period, the rotation speed is maintained at 900 r / min. Stirring is continued for 20 min to make the cold kiln material and ferric phosphate particles fully mixed and guide the ferric phosphate particles to grow towards the target crystal form. The heat preservation time is 3 h. Then, the pinkish-white slurry is pressure filtered and washed according to the pressure filtration method in step (4) to obtain ferric phosphate dihydrate filter cake with a water content of 45-50%.

[0068] (6) Start the flash dryer preheating system and raise the inlet air temperature to 260℃. After the inlet air temperature stabilizes (the inlet air temperature is adjusted according to the moisture content of the wet material; when the moisture content is 40-45%, use 300-350℃; when the moisture content is 45-50%, use 350-400℃), turn on the stirring and crushing system and set the speed to 900r / min; feed the wet iron phosphate material into the drying chamber through the screw feeder at a feeding speed of 1m. 3The feed rate is adjusted according to the outlet air temperature (90℃) at a rate of / h. Higher outlet air temperatures result in higher feed rates, while lower temperatures result in lower feed rates. The dried powder is tested, and ferric phosphate dihydrate granules are removed after passing the tests. Parameter analysis of the ferric phosphate dihydrate granules is performed, and the results are shown in Table 2. Electron micrographs are shown below. Figure 1 As shown in e.

[0069] (7) The ferric phosphate dihydrate granules were fed into a rotary kiln for calcination. The rotary kiln was started, and the kiln rotation speed was 1 r / min during calcination. The heating rate of the heating system was 14℃ / min. When the temperature inside the kiln reached 450℃, hot kiln wall-adhering material was added through the kiln tail feed inlet. The amount of hot kiln wall-adhering material added was 3.5% of the mass of the ferric phosphate dihydrate granules, and the feeding speed was 0.8 kg / min. During the feeding process, the temperature was stabilized by the heating system, and the temperature fluctuation did not exceed ±5℃. After the hot kiln wall-adhering material was added, the temperature was continued to rise to 650℃, and then kept at that temperature for 1.5 h. 30 min after the start of the heat preservation, the packaging material was added. The mass of the packaging material added was 1.5% of the mass of the ferric phosphate dihydrate granules, and the feeding time was 8 min, added at a uniform rate. During the heat preservation process, the kiln temperature and particle density were checked every 20 min to ensure that the temperature was stable at 650℃±3℃ and the tapped density was >0.6 g / cm³. 3 If the tapped density is too low, adjust the kiln speed and extend the holding time appropriately until the tapped density meets the requirements. Allow the material to enter the cooling kiln system for cooling. After cooling to below 100℃, it enters the vibrating screen and disc mill system through the conveying pipe, subsequently obtaining anhydrous ferric phosphate. Parameter testing of the ferric phosphate is shown in Table 3, and the electron micrographs are shown below. Figure 2 As shown in e.

[0070] Comparative Example 1

[0071] This comparative example uses the existing ammonium method for synthesizing iron phosphate without adding process materials. The specific preparation method is as follows:

[0072] (1) Weigh out monoammonium phosphate and ferrous sulfate raw materials according to the calculated amount of ferric phosphate to be produced; accurately add the metered monoammonium phosphate and ferrous sulfate aqueous solution through the weighing device of the reactor, record the amount added, and the error is ≤ ±0.2 kg. Start the stirring device of the reactor, set the speed to 500 r / min, and at the same time turn on the heating system to raise the temperature to 60℃ at 8℃ / min.

[0073] (2) When the temperature in the reactor is stable at 60℃, the mass of hydrogen peroxide is measured according to the mass of ferrous sulfate. Then, hydrogen peroxide with a concentration of 7.8% is accurately added through the feeding device. It is added dropwise at a uniform speed for 45 minutes. After the feeding is completed, the stirring speed is maintained at 500 r / min for another 30 minutes. The oxidation endpoint is determined by a mixture of potassium ferricyanide and phosphoric acid. The reaction is complete when the solution turns yellow after the indicator solution is added. The next step is then carried out.

[0074] (3) Start the plate and frame filter press, feed the precipitated slurry into the filter press, the feed pressure is 0.8MPa, and the feed speed is 1m. 3 / h, by observing the liquid state at the outlet, when the liquid output decreases significantly and the liquid becomes clear, it is determined that filtration is complete, and the feed valve is closed; the pressing system is turned on, the pressing pressure is set to 1.5MPa, and the pressing time is 15min. After pressing is completed, the filter is opened, the ferric phosphate filter cake is taken out, and the moisture content of the filter cake is checked to be 30%. If the moisture content is higher than 35%, it needs to be pressed again. If the moisture content is too low, check whether the filtration process is normal and adjust the subsequent filtration parameters.

[0075] (4) Add hot water and 85% phosphoric acid to the pulping tank. The amount of phosphoric acid added is 10% of the total iron content. The overall solid content of the pulp is controlled at 10%. After thorough stirring and dispersion, transfer to the aging kettle, heat to 85°C, and continue aging for 4 hours to finally obtain a powdery white precipitated slurry.

[0076] (5) Wash and filter the powdery white precipitate slurry according to the method in step (3) to obtain ferric phosphate dihydrate filter cake.

[0077] (6) Start the flash dryer preheating system to raise the inlet air temperature to 300℃. After the inlet air temperature stabilizes, turn on the stirring and crushing system and set the speed to 800r / min. Feed the wet iron phosphate material into the drying chamber through the screw feeder at a feeding speed of 0.5m. 3 The air outlet temperature was 100℃, and the dried powder was tested at a constant temperature. Once the powder passed the test, the ferric phosphate dihydrate granules were removed. Parameter analysis of the ferric phosphate dihydrate granules was performed, and the results are shown in Table 2. Electron micrographs are shown below. Figure 1 As shown in f.

[0078] (7) Ferric phosphate dihydrate particles were fed into a rotary kiln for calcination. The rotary kiln was started, and the kiln rotation speed was 1 r / min during calcination. The heating rate of the heating system was 10℃ / min, and the temperature was raised to 650℃, and then held for 4 hours. During the holding process, the kiln temperature and particle tap density were checked every 20 minutes to ensure that the temperature was stable at 650℃±3℃ until the particle tap density met the requirements. After the holding was completed, the heating system was turned off, and the material was allowed to enter the cold kiln system for cooling. After the temperature dropped below 100℃, it was sent through the conveying pipe to the vibrating screen and disc mill system, and then packaged to obtain anhydrous ferric phosphate. The parameters of the ferric phosphate were tested, and the results are shown in Table 3. The electron microscope images are shown in Table 3. Figure 2 As shown in f.

[0079] Comparative Example 2

[0080] This comparative example uses the existing ammonium method for synthesizing iron phosphate without adding process materials. The specific preparation method is as follows:

[0081] (1) Weigh out monoammonium phosphate and ferrous sulfate raw materials according to the calculated amount of iron phosphate to be generated; accurately add the metered monoammonium phosphate solution and ferrous sulfate aqueous solution through the weighing device of the reactor, record the amount added, and the error is ≤ ±0.2kg; then start the stirring device of the reactor, set the speed to 500r / min, and at the same time turn on the heating system to raise the temperature to 50℃ at 8℃ / min.

[0082] (2) When the temperature in the reactor is stable at 50°C, the mass of hydrogen peroxide is measured according to the mass of ferrous sulfate. Then, hydrogen peroxide with a concentration of 7.8% is accurately added through the feeding device. The hydrogen peroxide is added at a uniform rate for 45 minutes. After the addition is completed, the stirring is continued at a speed of 500 r / min for 30 minutes. The oxidation endpoint is determined by a mixture of potassium ferricyanide and phosphoric acid. The reaction is complete when the solution turns yellow after the indicator solution is added. The next step is then carried out.

[0083] (3) Start the plate and frame filter press, feed the precipitated slurry into the filter press, the feed pressure is 0.8MPa, and the feed speed is 1m. 3 / h, by observing the liquid state at the outlet, when the liquid output decreases significantly and the liquid becomes clear, it is determined that filtration is complete, and the feed valve is closed; the pressing system is turned on, the pressing pressure is set to 1.5MPa, and the pressing time is 15min. After pressing is completed, the filter is opened, the ferric phosphate filter cake is taken out, and the moisture content of the filter cake is checked to be 30%. If the moisture content is higher than 35%, it needs to be pressed again. If the moisture content is too low, check whether the filtration process is normal and adjust the subsequent filtration parameters.

[0084] (4) Add hot water and 85% phosphoric acid to the pulping tank. The amount of phosphoric acid added is 10% of the total iron content. The overall solid content of the pulp is controlled at 10%. After thorough stirring and dispersion, transfer to the aging kettle, heat to 70°C, and continue aging for 4 hours to finally obtain a powdery white precipitated slurry.

[0085] (5) Wash and filter the powdery white precipitate slurry according to the method in step (3) to obtain ferric phosphate dihydrate filter cake.

[0086] (6) Start the flash dryer preheating system to raise the inlet air temperature to 350℃. After the inlet air temperature stabilizes, turn on the stirring and crushing system and set the speed to 800 r / min. Feed the wet iron phosphate material into the drying chamber through the screw feeder at a feeding speed of 0.5 m / min. 3 The air outlet temperature was 100℃, and the dried powder was tested at a rate of / h. Once the powder passed the test, the ferric phosphate dihydrate granules were removed. Parameter tests were performed on the ferric phosphate dihydrate granules, and the results are shown in Table 2.

[0087] (7) Ferric phosphate dihydrate particles were fed into a rotary kiln for calcination. The rotary kiln was started, and the kiln rotation speed was 1 r / min during calcination. The heating rate of the heating system was 10℃ / min, and the temperature was raised to 550℃, and then held for 4 hours. During the holding process, the kiln temperature and particle tap density were checked every 20 minutes to ensure that the temperature was stable at 550℃±3℃ until the particle tap density met the requirements. After the holding was completed, the heating system was turned off, and the rotary kiln was allowed to cool down naturally. The material was then fed into the cold kiln system for cooling. After the temperature dropped below 100℃, it was sent through the conveying pipe to the vibrating screen and disc mill system, and then packaged to obtain anhydrous ferric phosphate. The parameters of the ferric phosphate were tested, and the results are shown in Table 3.

[0088] Comparative Example 3

[0089] This comparative example uses the existing ammonium method for synthesizing iron phosphate without adding process materials. The specific preparation method is as follows:

[0090] (1) Weigh out monoammonium phosphate and ferrous sulfate raw materials according to the calculated amount of iron phosphate to be generated; accurately add the measured amount of monoammonium phosphate and ferrous sulfate raw materials through the weighing device of the reactor, record the amount added, and the error is ≤ ±0.2kg; then start the stirring device of the reactor, set the speed to 500r / min, and at the same time turn on the heating system to raise the temperature to 55℃ at 8℃ / min.

[0091] (2) When the temperature in the reactor is stable at 55℃, the mass of hydrogen peroxide is measured according to the mass of ferrous sulfate. Then, hydrogen peroxide with a concentration of 7.8% is accurately added through the feeding device. It is added dropwise at a uniform speed for 45 minutes. After the feeding is completed, the stirring speed is maintained at 500 r / min for another 30 minutes. The oxidation endpoint is determined by a mixture of potassium ferricyanide and phosphoric acid. The reaction is complete when the solution turns yellow after the indicator solution is added. The next step is then carried out.

[0092] (3) Start the plate and frame filter press, feed the precipitated slurry into the filter press, the feed pressure is 0.8MPa, and the feed speed is 1m. 3 / h, by observing the liquid state at the outlet, when the liquid output decreases significantly and the liquid becomes clear, it is determined that filtration is complete, and the feed valve is closed; the pressing system is turned on, the pressing pressure is set to 1.5MPa, and the pressing time is 15min. After pressing is completed, the filter is opened, the ferric phosphate filter cake is taken out, and the moisture content of the filter cake is checked to be 30%. If the moisture content is higher than 35%, it needs to be pressed again. If the moisture content is too low, check whether the filtration process is normal and adjust the subsequent filtration parameters.

[0093] (4) Add hot water and 85% phosphoric acid to the pulping tank. The amount of phosphoric acid added is 10% of the total iron content. The overall solid content of the pulp is controlled at 10%. After thorough stirring and dispersion, transfer to the aging kettle, heat to 95±2℃, and continue aging for 4 hours to finally obtain a powdery white precipitated slurry.

[0094] (5) Wash and filter the powdery white precipitate slurry according to the method in step (3) to obtain ferric phosphate dihydrate filter cake.

[0095] (6) Start the flash dryer preheating system to raise the inlet air temperature to 350℃. After the inlet air temperature stabilizes, turn on the stirring and crushing system and set the speed to 800 r / min. Feed the wet iron phosphate material into the drying chamber through the screw feeder at a feeding speed of 0.5 m / min. 3 The air outlet temperature was 100℃, and the dried powder was tested at a rate of / h. Once the powder passed the test, the ferric phosphate dihydrate granules were removed. Parameter tests were performed on the ferric phosphate dihydrate granules, and the results are shown in Table 2.

[0096] (7) Ferric phosphate dihydrate particles were fed into a rotary kiln for calcination. The rotary kiln was started, and the kiln rotation speed was 1 r / min during calcination. The heating rate of the heating system was 10℃ / min, and the temperature was raised to 700℃, then held for 4 hours. During the holding process, the kiln temperature and particle compaction density were checked every 20 minutes until the particle compaction density met the requirements. After the holding period ended, the heating system was turned off, and the material was allowed to enter the cold kiln system for cooling. After the temperature dropped below 100℃, it was sent through the conveying pipe to the vibrating screen and disc mill system, and then packaged to obtain anhydrous ferric phosphate. The parameters of the ferric phosphate were tested, and the results are shown in Table 3.

[0097] Table 2 Performance parameters of ferric phosphate dihydrate

[0098]

[0099] Table 3. Parameters of Anhydrous Ferric Phosphate

[0100]

[0101] Table 4. Mass percentage of materials added in each process step in the examples.

[0102]

[0103] Based on the performance data in the table above and the electron microscope images, it can be seen that after processing according to the present invention, the various indicators of the dried ferric phosphate dihydrate are improved compared to the product from the production line (i.e., ferric phosphate prepared by the existing ammonia method), especially the ferric phosphate dihydrate specific gravity is significantly improved, and the iron-phosphorus ratio is also improved and reduced to some extent. As shown in Table 2, the sulfur content of ferric phosphate dihydrate in Comparative Examples 1-3 is relatively high and concentrated in the range of 2320-2609 ppm. Although the iron-phosphorus ratio is close to the theoretical value, it fluctuates greatly, posing a risk of compositional deviation due to uneven impurities in the raw materials. After adding the process feed, as shown in Examples 1-5, the sulfur content is significantly reduced to 1546-2030 ppm, a reduction of 20%-40% compared to Comparative Examples 1-3, and the iron-phosphorus ratio is slightly lower than that of Comparative Examples 1-3, with smaller fluctuations and greater stability. In Examples 1-5, because the process feed has a uniform composition, it can dilute raw material impurities, calibrate the elemental ratio, and make the overall composition purity more stable.

[0104] Table 2 shows that for ferric phosphate dihydrate, the D50 of Comparative Examples 1-3 is relatively fine and fluctuates greatly, while the D100 is concentrated in the range of 12.31-13.1 μm, indicating a relatively high upper limit for coarse particles. After adding the process material, the D50 of Examples 1-5 stabilizes at 2.89-3.19 μm, which is more suitable for the optimal reaction range of 2.5-3.0 μm. The D100 decreases to 11.2-12.7 μm, with reduced fluctuations. For example, the D50 of Example 4 is 3.08 μm, compared to the D50 value of 1.95 μm in Comparative Example 2. This avoids the problem of excessively fine particles that occurs in existing production processes, resulting in a more uniform particle size distribution.

[0105] Table 3 shows that the performance differences between the examples and the comparative examples can be attributed to the control effect of the specific surface area of ​​the process feed: The examples, through optimization of the specific surface area of ​​the process feed, increased the D50 from 2.31-2.36 μm in the comparative example to 3.39-4.6 μm, resulting in a particle size distribution that better meets the application scenario's particle size requirements. Simultaneously, the D100 remained within a reasonable range of 30.9-40 μm, without excessive agglomeration leading to abnormally large particles. Regarding sulfur content, the examples (368-435 ppm) were 44%-56% lower than the comparative example (734-828 ppm). This was mainly due to the optimized specific surface area control of the process feed, which improved the reaction interface and impurity removal efficiency, effectively reducing sulfur residue. In terms of specific surface area, the examples (5.045-6.721 m² / g) were significantly higher than the comparative example (4.026-4.882 m² / g), and this positive correlation with the specific surface area of ​​the process feed verified the effectiveness of the process feed in controlling the specific surface area of ​​the product. Regarding tap density, the examples (0.69-0.87 g / cm³) showed a 6%-43% increase compared to the comparative examples (0.61-0.65 g / cm³), reflecting that the process feed optimized the particle packing morphology and improved material density. Notably, the anhydrous iron phosphate iron-to-phosphorus ratio in the examples exhibited minimal fluctuation, ranging from 96.75 to 97.13, indicating that the addition of the process feed did not disrupt the stability of the iron-phosphorus element stoichiometric ratio, ensuring the consistency of the product's core components. Overall data shows that by adjusting the specific surface area of ​​the iron phosphate process feed, key performance indicators such as particle size, sulfur content, specific surface area, and tap density can be simultaneously optimized without affecting the core element ratio, achieving a synergistic improvement in multiple dimensions.

[0106] like Figure 1 As shown, for example (ae) of ferric phosphate dihydrate: it forms loose small clusters with low interparticle binding and good dispersibility. Comparative example (f): it agglomerates into dense large clumps with blurred particle interfaces and poor dispersibility. Figure 2As shown, in Comparative Example 1(f), the anhydrous ferric phosphate particles are mainly irregularly shaped blocks and flakes, with disordered crystal stacking and only a small number of rudimentary spherical structures in local areas (uneven morphology). In Examples 1-5, the particles are mainly spherical agglomerates and flower-like / floccular stacked structures. For example, a and c exhibit "porous agglomerates" composed of numerous fine crystals interwoven into spherical clumps; b and d are "layered flower-like structures," with crystals stacked in layers, and the overall morphology tends to be spherical; e is a "dense spherical agglomerate," composed of even finer crystals agglomerated into clearly defined spherical blocks. The overall morphology has strong regularity and design, conforming to the morphological characteristics of anhydrous ferric phosphate under specific processes. The examples exist in the form of "loose small agglomerates," with low bonding between crystals within the agglomerates, and the outlines of individual crystals (or small crystal clusters) are still clearly distinguishable, indicating good dispersion. This loose agglomeration facilitates dispersion and performance enhancement in subsequent processing (such as the preparation of lithium-ion battery cathode materials). The change in its morphology is the main reason for the reduced sulfur content in the examples; stronger dispersibility significantly reduces the adsorption effect on sulfur-containing compounds, making them easier to precipitate. It is evident that the dihydrate and anhydrous ferric phosphate particles prepared by the present invention are more regular, respectively meeting the core requirements of dispersibility for dihydrate ferric phosphate and flowability for anhydrous ferric phosphate.

[0107] Based on the above efficacy data, further mechanistic analysis reveals that in the ferric phosphate precipitation reactor, dust removal material (similar to ultrafine active seed crystals) is first added. Utilizing its large specific surface area (20-30 m² / g) and high reactivity, it rapidly adsorbs Fe from the solution. 2+ With PO4 3- As a "crystal nucleus," it accelerates the precipitation reaction and avoids the generation of amorphous impurities. After the reaction starts (the solution becomes initially turbid), the demagnetizing material (solid content regulator) is slowly added. Its low magnetic impurity (≤0.003%) characteristics reduce the subsequent magnetic separation pressure, while the solid content of the reaction system is stably controlled at 15%-20%, ensuring the uniform growth of precipitated particles. Next, the vibrating screen discharge material (particle size distribution 1.2-5.0μm) added to the pulping tank fills the particle size gaps in the filter cake particles through its wide particle size range, making the overall particle distribution more in line with the requirements of subsequent screening. After uniform dispersion, cold kiln discharge material is added on this basis. Its high crystallinity and uniform particle size serve as a "directional template" to guide the filter cake particles to grow towards the target crystal form, reducing the energy consumption of crystal form conversion during the calcination stage. The wet iron phosphate material is flash-dried to obtain iron phosphate dihydrate, which is then sent to a rotary kiln for calcination. In the early stage of calcination, hot kiln wall-adhesive material is added. Its high-temperature stability can serve as a "high-temperature seed crystal" to accelerate the crystal form development of the dry powder and shorten the calcination holding time. In the later stage of calcination, packaged discharge material is added. Its high purity characteristics replenish the trace impurities lost by the dry powder during calcination, while also assisting in particle densification (increasing the tap density to above 0.70).

[0108] That is, through the layered arrangement of materials and the connection of reaction processes in this invention, the technical effect of optimizing the quality of iron phosphate products can be achieved.

[0109] In addition to the above embodiments, it should be noted that the technical effects claimed by the present invention can be achieved by using the preparation process and the limited parameter range of the present invention, and therefore no further examples will be provided to support these claims.

Claims

1. A method for controlling the quality of finished iron phosphate product based on process feed from an iron phosphate production line, characterized in that, Includes the following steps: (1) Collect process materials by category and perform impurity removal and screening. The process materials include cold kiln leakage material, demagnetized material, dust removal material, vibrating screen fallen material, packaging fallen material, and hot kiln wall-adhering material. (2) Mix the ferrous raw material and phosphate raw material according to the calculated amount of ferric phosphate to form a mixed solution; add the dust removal material and stir evenly to form solution A; (3) Heat solution A to 60-70℃, then add hydrogen peroxide and demagnetizing material to solution A, and obtain slurry after oxidation reaction; (4) Wash and filter the slurry to obtain the iron phosphate dihydrate precursor filter cake; mix the iron phosphate dihydrate precursor filter cake, 60-70℃ hot water and phosphoric acid to make a slurry, then add the material that fell on the vibrating screen, heat to 85-90℃ and keep warm and age until the iron phosphate particles have grown. (5) Add cold kiln feed to the slurry from step (4), keep it warm for 2-3 hours, then filter, wash, and press to obtain ferric phosphate filter cake dihydrate. (6) The ferric phosphate dihydrate filter cake is flash-dried to obtain ferric phosphate dihydrate granules; the ferric phosphate dihydrate granules are calcined, and when the calcination temperature rises to 400-450℃, hot kiln wall-adhesive material is added. After the material is added, the temperature is further raised to 650-700℃ for heat preservation, and packaged waste material is added. The reaction is maintained until the tapped density is >0.6g / cm³. 3 At that time, stop the heat preservation to obtain the iron phosphate product.

2. The method for controlling the quality of finished iron phosphate product based on process feed from an iron phosphate production line according to claim 1, characterized in that, In step (2), the amount of dust removal material added is 3-5% of the total mass of ferrous raw material and phosphate raw material.

3. The method for controlling the quality of finished iron phosphate product based on process feed from an iron phosphate production line according to claim 1, characterized in that, In step (3), the amount of demagnetizing material added is 5-8% of the total mass of ferrous raw material and phosphate raw material.

4. The method for controlling the quality of finished iron phosphate product based on process feed from an iron phosphate production line according to claim 1, characterized in that, In step (4), the amount of material added to the vibrating screen is 4-6% of the mass of the iron phosphate dihydrate precursor filter cake.

5. The method for controlling the quality of finished iron phosphate product based on process feed from an iron phosphate production line according to claim 1, characterized in that, In step (4), the amount of phosphoric acid added is 10-15% of the total amount of iron in the system.

6. The method for controlling the quality of finished iron phosphate product based on process feed from an iron phosphate production line according to claim 1, characterized in that, In step (5), the amount of material added to the cold kiln is 2-3% of the mass of the iron phosphate dihydrate precursor filter cake.

7. The method for controlling the quality of finished iron phosphate product based on process feed from an iron phosphate production line according to claim 1, characterized in that, In step (6), the amount of hot kiln wall-adhesive added is 3-4% of the mass of ferric phosphate dihydrate particles.

8. The method for controlling the quality of finished iron phosphate product based on process feed from an iron phosphate production line according to claim 1, characterized in that, In step (6), the amount of the packaged waste material added is 1-2% of the mass of the iron phosphate dihydrate particles.

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