A production process of ammonium dihydrogen phosphate for battery

Abstract

The present application relates to the technical field of battery preparation, and specifically discloses a production process of ammonium dihydrogen phosphate for batteries, which comprises eleven process steps of dearsenicating, decolorizing, aerating, filtering, decolorizing after preheating, defluorinating, neutralizing, circulating, crystallizing, separating, drying and packaging wet-process phosphoric acid to produce battery-grade ammonium dihydrogen phosphate. In the dearsenicating, decolorizing and defluorinating processes, only one filtration using a membrane filter is required after decolorizing, and there is no need to add a filter in each step, so the process flow is not shortened, the production efficiency of battery-grade ammonium dihydrogen phosphate is improved, and the reduction of filtering equipment reduces the production input cost.

Description

Technical Field

[0001] The invention relates to the technical field of battery preparation, and in particular to a production process of ammonium dihydrogen phosphate for batteries. Background Art

[0002] With the rapid development of the new energy storage industry, the demand for lithium iron phosphate battery materials, anode materials, has soared, and the market for its raw material, battery-grade ammonium dihydrogen phosphate, has experienced explosive growth. Ammonium dihydrogen phosphate (also known as monoammonium phosphate) is one of the phosphorus sources for synthesizing lithium iron phosphate cathode materials.

[0003] At present, most of the domestic production of ammonium dihydrogen phosphate is done by wet phosphoric acid. The impurities in wet phosphoric acid are divided into anion and cationic impurities. Taking the dihydrate process as an example, the main components and impurities are as follows:

[0004] <![CDATA[P2O5%]]> <![CDATA[SO4%]]> F％ As% <![CDATA[Fe2O3%]]> ≥47 3.0-4.2 1.5 0.3 ＜0.88

[0005] The main components and impurities after extraction and purification are as follows:

[0006] <![CDATA[P2O5%]]> Fe% As% F％ Chroma ≥54 0.003～0.005 0.007 0.03 600～1000

[0007] The requirements for purified phosphoric acid for the production of battery-grade ammonium dihydrogen are as follows:

[0008] <![CDATA[P2O5%]]> Fe% As% F％ Chroma ≥54 0.002 0.0005 0.01 20

[0009] After wet phosphoric acid is purified, most of the anionic and cationic impurities such as sulfur, fluorine, and arsenic can be removed. However, if it is directly used to produce ammonium dihydrogen phosphate, there are fluorine, arsenic, and iron impurities exceeding the standard, and the color of the crystals is not up to standard. The produced ammonium dihydrogen phosphate can only be industrial grade, with a high impurity content. The use of industrial-grade ammonium dihydrogen phosphate to produce lithium iron phosphate will affect its product quality and make it difficult to meet the requirements of preparing battery grade, especially the cationic impurities have a greater impact on the performance of subsequent lithium iron phosphate. In order to improve its purity, most phosphorus chemical companies add industrial ammonium purification to the battery-grade monoammonium process route based on the original industrial monoammonium phosphate device, but due to the high content of arsenic, fluorine, sulfate, and iron, it is necessary to carry out dearsenicization, desulfurization, defluorination and other treatment processes. For example, the Chinese invention patent with the publication number of "CN116425132A" discloses a method for preparing high-quality industrial-grade monoammonium phosphate. This method uses wet phosphoric acid as a raw material, undergoes desulfurization, defluorination, and chelating agent chelation for impurity removal. Since each step requires filtration, it not only prolongs the process flow, resulting in reduced production efficiency, but also requires the installation of multiple filter presses or filtration devices, resulting in increased equipment investment costs. Summary of the invention

[0010] The object of the present invention is to provide a production process of diammonium phosphate for battery, so as to solve the problem that the existing use of wet-process phosphoric acid to prepare diammonium phosphate leads to prolonged production time and increased production cost.

[0011] In order to solve the above problems, the technical solutions provided are as follows:

[0012] A production process of ammonium dihydrogen phosphate for batteries, comprising the following steps:

[0013] S1: Arsenic removal: The extracted and purified wet phosphoric acid is cooled to below 35°C, P2S5 is added to the extracted and purified wet phosphoric acid to generate H2S, and H2S reacts with arsenic ions to generate arsenic sulfide precipitation for arsenic removal.

[0014] S2: Decolorization: Activated carbon decolorizer is added to the arsenic removal reaction liquid for adsorption and decolorization, and arsenic sulfide impurities are adsorbed at the same time;

[0015] S3: Aeration: Blow air into the reaction solution with excess H2S gas to aerate it, so that the excess H2S gas can be removed;

[0016] S4: Filtration: The aerated phosphoric acid containing arsenic sulfide precipitate is filtered through a membrane to remove arsenic sulfide precipitate and activated carbon;

[0017] S5: Decolorization after preheating: the dearsenicized phosphoric acid and the purified finished product 75% phosphoric acid are preheated and then enter hydrogen peroxide for decolorization;

[0018] S6: Defluorination: After decolorization, the phosphoric acid enters the steam defluorination tower for stripping and defluorination;

[0019] S7: Neutralization reaction: After defluorination, the finished acid is cooled to 80 degrees through heat recovery in steps S5 and S1, and then enters MAP ammonia (neutralization reactor and ammonia gas) for neutralization reaction to generate diammonium phosphate after iron removal.

[0020] S8: Circulation reaction: diammonium phosphate is extracted after the reverse circulation system pump and enters the crystallization system;

[0021] S9: Crystallization: Saturated diammonium phosphate enters the circulation guide tube in the crystallizer for vacuum crystallization;

[0022] S10: Separation: The slurry produced by the crystallizer is concentrated by a thickener and then enters a centrifuge for separation;

[0023] S11: Drying: The separated ammonium dihydrogen phosphate solid crystals are firstly deironed by an iron remover and then enter a fluidized bed dryer to remove surface moisture;

[0024] S12: Packaging: The diammonium phosphate crystals dried in the fluidized bed dryer and cooled to meet the standards are then packaged in the clean area.

[0025] The beneficial effects of the above technical solution are:

[0026] 1. This process uses activated carbon to adsorb inorganic colored matter and hydrogen peroxide to oxidize colored organic matter for decolorization. This process innovatively uses activated carbon decolorization followed by membrane filtration after arsenic removal. Activated carbon not only adsorbs inorganic matter for decolorization, but also adsorbs As2S3 for filtration, solving the problem of difficulty in filtering due to small amount of As2S3 precipitate. This process reduces the filtration process, reduces equipment investment, and improves the filtration effect of As2S3 precipitate.

[0027] 2. Arsenic is the main control index of battery-grade ammonium dihydrogen, and its content is required to be ≤5PPM. This process adopts the process of extracting acid and then removing arsenic. The arsenic removal agent does not bring in other impurities. Therefore, P2S5 solid is selected to pre-mix with the purified finished phosphoric acid to generate H2S, and then H2S and As + The reaction generates As2S3 precipitate. Since H2S is highly toxic and As + The reaction with H2S requires 10 times excess H2S. Direct addition of H2S in a high temperature environment will cause a violent reaction, which not only poses a safety hazard, but also makes it easy for excess H2S to overflow the reaction system, making it difficult to ensure the safety of As. + Precipitation effect: This process uses low-temperature premixing below 35°C to produce phosphoric acid containing excess H2S, which is then added to the arsenic removal reactor at the reaction temperature to react and precipitate As2S3. This not only solves the problem of safe P2S5 feeding and H2S generation and overflow, but also improves the reaction efficiency of arsenic removal.

[0028] Preferred solution 1: As a further optimization of the basic solution, the H2S gas removed in step S3 is subjected to alkali washing and then discharged. The H2S gas will not cause pollution to the environment after being subjected to alkali washing and then discharged.

[0029] Preferred solution 2: As a further optimization of preferred solution 1, after the crystallization in step S9, decrystallization is required: decrystallization is to collect large-particle diammonium phosphate crystals with good crystallinity by settling them to the bottom of the crystallizer through a bottom circulation agitator, and collect fine crystals with poor crystallinity on the top through the upper side collection to the fine crystal eliminator for decrystallization circulation. The saturated slurry after neutralization enters the crystallizer. This process can produce diammonium phosphate crystal products by using a crystallizer combined with an external decrystallization system. By adding side collection to the decrystallizer in the fine crystal zone circulating in the crystallizer, unqualified fine crystals are circulated to the neutralizer and then recrystallized to the crystallizer through thermal dissolution, thereby solving the problem of poor quality of large-particle crystalline products caused by the accumulation of fine crystal nuclei. The code difference caused by the particle size of the crystallization product is used to collect the unqualified MAP product with a smaller code from the side line to the decrystallizer for reheating and dissolution, and then circulate to the reaction system as a mother liquor to improve the qualified rate of the product.

[0030] Preferred solution three: As a further optimization of preferred solution two, low-pressure steam of 0.5 MPa is introduced during the crystallization elimination process.

[0031] Preferred solution four: As a further optimization of preferred solution three, the mother liquor separated from the thickener and the centrifuge in step S10 is stored in a centrifugal mother liquor tank, and desalted water is added to the centrifugal mother liquor tank to form a saturated mother liquor of dihydrogen ammonium. The saturated mother liquor of dihydrogen ammonium is returned to the neutralization reactor of step S7 after iron removal to participate in the neutralization reaction. The above purified 75% phosphoric acid is used to enter the neutralization reactor, and the neutralization degree of the neutralization reaction can be adjusted by the flow rate of the circulating unsaturated mother liquor and the amount of desalted water added to the mother liquor, so as to meet the requirements of crystallization of the dihydrogen ammonium neutralization reaction, and avoid the risk of blockage of the circulating mother liquor due to saturated crystallization. In addition, the medium that inevitably contacts the iron material in the upstream of the process enters the system and produces excessive iron. This process adds a liquid-phase electromagnetic iron remover to the circulating mother liquor and a solid-phase electromagnetic iron remover to the product, respectively, to solve the problem of excessive iron particles in the product.

[0032] Preferred solution five: As a further optimization of preferred solution four, the wet-process phosphoric acid extracted and purified in step S1 is first preheated in a preheater, and the low-pressure steam flowing out of the fine crystal eliminator in step S9 and the fluidized bed dryer in step S10 is passed into the preheater and used as a heat source.

[0033] Preferred solution six: As a further optimization of preferred solution five, the fluidized bed dryer in step S11 is connected to a product cooler, and circulating water flows in the product cooler. The diammonium dihydrogen product is very easy to absorb moisture and agglomerate. Compared with the traditional single-stage fluidized bed using ambient air, it is difficult to ensure that the product is cooled to a temperature that does not agglomerate due to environmental changes. This solution uses a fluidized bed plus a circulating water solid cooler to solve the problem of high product temperature and easy agglomeration. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the arrangement of process equipment according to an embodiment of the present invention;

[0035] Figure 2 for Figure 1 The middle A part is split and enlarged;

[0036] Figure 3 for Figure 1 The enlarged schematic diagram of the split of the middle B part;

[0037] Figure 4 for Figure 1 Schematic diagram of the enlarged split of the middle C part.

[0038] The figure marks in the drawings of the specification include: premixer 1, preheater 2, deweighting reactor 3, decolorization reaction tank 4, aeration reaction tank 5, membrane filter 6, decolorization preheater 7, decolorization tower 8, defluorination tower 9, neutralization reactor 10, circulating heat exchanger 11, DBT vacuum crystallizer 12, crystallization elimination buffer tank 13, crystallization elimination heater 14, thickener 15, centrifuge 16, centrifugal mother liquor tank 17, first liquid phase electromagnetic iron remover 18, second liquid phase electromagnetic iron remover 19, fluidized bed dryer 20, air heater 21, product cooler 22. DETAILED DESCRIPTION

[0039] The following is further described in detail through specific implementation methods:

[0040] The process equipment used in the embodiment is arranged basically as shown in the attached Figure 1-4 As shown:

[0041] The specific implementation process is as follows:

[0042] A production process of ammonium dihydrogen phosphate for batteries, comprising the following steps:

[0043] S1: Arsenic removal: first add wet-process phosphoric acid cooled to below 35°C for extraction and purification into the premixer 1, then add P2S5 solid material to prepare a premixed liquid, preheat 75% of the extracted phosphoric acid from the upstream extraction and concentration section to 80°C in the preheater 2, and simultaneously inject the premixed liquid and the heated extracted phosphoric acid into the de-weighting reactor 3 for de-weighting reaction;

[0044] The equation for the de-weighting reaction is as follows:

[0045] P2S5+8H2O=2H3PO4+5H2S↑

[0046] 2H3AsO3+3H2S=As2S3↓+6H2O

[0047] S2: Decolorization: After the arsenic removal reaction, the material is pumped to the decolorization reaction tank 4, and activated carbon decolorization is added to the decolorization reaction tank 4 for agglomeration, precipitation and decolorization;

[0048] S3: Aeration: The reaction liquid with excess H2S gas overflows to the aeration reaction tank 5 for aeration, and air is blown into the aeration reaction tank 5 to remove excess H2S gas;

[0049] S4: Filtration: The reaction liquid after the aeration reaction in the aeration reaction tank 5 is pumped into the membrane filter 6 for filtration;

[0050] S5: Decolorization after preheating: After filtration, the clear acid is heated to 120°C in the decolorization preheater 7 through the finished phosphoric acid and enters the decolorization tower 8 for decolorization. Hydrogen peroxide and phosphoric acid are added to the decolorization tower 8 for mixed decolorization under the action of fillers. The filter residue falls into the residue slurry tank and the phosphoric acid is recovered;

[0051] S6: Defluorination: The decolorized phosphoric acid is heated to 135-140°C by a steam heater and sent to a defluorination tower 9. The defluorination tower 9 uses low-pressure superheated steam for stripping and defluorination. The fluorine-containing steam discharged from the top of the defluorination tower 9 is used as a heat source for extracting wet-process phosphoric acid.

[0052] S7: Neutralization reaction: The finished phosphoric acid after defluorination is heat exchanged with the decolorization preheater 7 and cooled to 80-90°C before being sent to the neutralization reactor 10;

[0053] S8: Circulation reaction: After the liquid ammonia is gasified, it is passed into the circulation heat exchanger 11, and after the flow rate is adjusted, it enters the reactor with the purified phosphoric acid and the purified acid is metered into the reactor for rapid amination reaction. A forced circulation pump is used to make the reaction more complete, and the slurry neutralization degree is controlled to be conducive to the formation of a saturated monoammonium phosphate solution and precipitation after the metal ion amination. At the same time, the crystallization mother liquor is added and fully mixed, and the pH value and neutralization degree of the reaction slurry are adjusted to 0.8-0.86, and the specific gravity of the neutralized slurry reaches 1.25-1.3, and then it is pumped to the crystallization system; the equation of the neutralization reaction is as follows:

[0054] H3PO4+NH3=NH4H2PO4

[0055] S9: Crystallization: The reaction slurry and the solution of the crystal cultivation (fine crystal elimination) stage enter the bottom of the single-stage DBT vacuum crystallizer 12 and mix with the circulating crystal slurry. The large-particle diammonium phosphate crystals with good crystallinity in the bottom circulating agitator settle at the bottom of the DBT vacuum crystallizer 12 and are extracted;

[0056] S10: Decrystallization: Fine crystals with poor crystallinity on the upper part of the vacuum crystallizer 12 are collected from the upper side to the crystallization elimination buffer tank 13 for decrystallization circulation. The crystallization elimination buffer tank 13 is connected to the crystallization elimination heater 14 for heating the fine crystals with poor crystallinity; the code difference generated by the particle size of the crystallized product is used to collect the unqualified MAP product with a smaller code from the side line to the decrystallizer for reheating and dissolution, and then circulated to the reaction system as a mother liquor to improve the qualified rate of the product;

[0057] S11: Separation: The crystallization discharge pump transports the slurry (solid content of about 25%) from the DBT vacuum crystallizer 12 to the thickener 15, where the slurry is settled and thickened to a solid content of about 50-60%. The slurry with a higher solid-liquid ratio at the bottom of the thickener 15 enters the centrifuge 16 for centrifugal separation, and the overflow liquid at the top of the thickener 15 overflows into the centrifugal mother liquor tank 17. At the same time, desalted water is added to the centrifugal mother liquor tank 17. The centrifuge 16 centrifuges to separate the wet crystal product, and the separated centrifugal mother liquor also enters the centrifugal mother liquor tank 17. The mother liquor in the centrifugal mother liquor tank 17 is treated by the first liquid phase electromagnetic iron remover 18 and then returned to the neutralization reactor 10 for diluting the neutralization reaction slurry;

[0058] S12: Drying: After centrifugal separation, the wet crystal (water content ≤ 5%) product passes through the second liquid phase electromagnetic iron remover 19 and enters the fluidized bed dryer 20. Under the action of vibration force, the material is thrown forward along the horizontal fluidized bed and moves continuously. The hot air passes through the fluidized bed upward and exchanges heat with the material, and is discharged from the exhaust port. The dry material is discharged from the discharge port with a temperature of ≤ 45°C. The air sent by the hot air blower enters the front area of ​​the fluidized bed after heat exchange with the steam in the air heater 21, and exchanges heat with the wet material in the fluidized bed to remove moisture from the product, so that the moisture content of the dried product is less than 0.2%. Natural wind is blown into the rear area of ​​the fluidized bed to cool the heated material. The fluidized bed dryer 20 is connected to a product cooler 22, and circulating water flows in the product cooler 22.

[0059] S13: Packaging: The dried material is connected to the belt conveyor from the fluidized bed outlet, cooled by circulating water to a temperature of ≤35°C, and then weighed and packaged. Unqualified products are sent to the dissolving tank for dissolution and then returned to the reaction system.

[0060] This process adds deep arsenic removal, decolorization and defluorination processes on the basis of traditional extraction and purification of phosphoric acid. The above process steps will be tested. For the requirements for the production of battery-grade diammonium hydride, the colorless crystalline diammonium hydride products with a particle diameter less than 3MM and uniform particle size are qualified products, otherwise they are unqualified products.

[0061] The method uses low-temperature premixing to produce phosphoric acid containing excess H2S, which is then added to a de-weighting reactor at the reaction temperature to react and precipitate AsS. This not only solves the problem of safe P2S5 feeding and H2S generation and overflow, but also ensures safety while improving the efficiency of the arsenic removal reaction.

[0062] The production of battery-grade ammonium dihydrogen phosphate requires strict control of the chromaticity of phosphoric acid. The color of phosphoric acid comes from the presence of trace organic and inorganic impurities. Therefore, in steps S2 and S5, activated carbon is used to adsorb inorganic colored matter and hydrogen peroxide is used to oxidize colored organic matter for decolorization to ensure the decolorization effect. In step S2, activated carbon decolorization is performed after arsenic removal, and then membrane filtration is performed. There is no need to filter after arsenic removal, which reduces the filtration process and equipment investment, and at the same time improves the filtration effect of AsS precipitates.

[0063] Battery-grade ammonium dihydrogen phosphate requires the fluorine content in phosphoric acid to be less than 100 PPM. The fluorine content of phosphoric acid after extraction, concentration and purification is usually 300 PPM. Therefore, step S6 uses steam stripping to defluorinate the phosphoric acid to reduce the fluorine content in the phosphoric acid to an average of less than 20 PPM. At the same time, the defluorination steam is returned to the upstream extraction and concentration section for reuse, which can effectively save energy and reduce consumption.

[0064] In step S7, purified 75% phosphoric acid is introduced into the neutralization reactor. In step S10, the degree of neutralization of the neutralization reaction can be adjusted by the flow rate of the circulating unsaturated mother liquor and the amount of desalted water added to the mother liquor, so as to meet the crystallization requirement of the dihydrogen ammonium neutralization reaction, thereby avoiding the risk of blockage of the circulating mother liquor due to saturated crystallization.

[0065] In step S9, a single-stage DBT crystallizer is used in combination with an external crystallization system to produce diammonium dihydrogen crystalline products. By adding side sampling to the crystallization device in the fine crystal area circulating in the DBT, unqualified fine crystals are thermally dissolved and then circulated to the crystallizer in the neutralizer for recrystallization, thereby solving the problem of poor quality of large-particle crystal products caused by accumulation of fine crystal nuclei.

[0066] Since free iron particles are an important control indicator of battery-grade ammonium dihydrogen phosphate, phosphoric acid is highly corrosive, and the medium that inevitably contacts the iron material in the upstream process enters the system and is likely to cause excessive iron. Therefore, steps S10 and S11 respectively add liquid-phase electromagnetic iron removers at the centrifugal mother liquid tank and the centrifuge to solve the problem of excessive iron particles in the product.

[0067] Since the diammonium hydrogen product is very easy to absorb moisture and agglomerate, the single-stage fluidized bed uses ambient air, which is difficult to guarantee the product to be cooled to the temperature required without agglomeration due to environmental changes. Therefore, step S11 adds a circulating water solid cooler to the fluidized bed to solve the problem of the product temperature being too high and easy to agglomerate;

[0068] The reaction temperature of arsenic removal in the above process steps is 80 degrees, the temperature of the purified acid from extraction and concentration is usually 70-80 degrees, the reaction temperature of hydrogen peroxide decolorization is about 120 degrees, and the operating temperature of steam stripping defluorination is about 135 degrees. The small temperature difference heat exchange network is reasonably used to control the temperature rise of phosphoric acid step by step to meet the temperature requirements of the above reaction operations. At the same time, a high-temperature and corrosion-resistant graphite heat exchanger is used to preheat the feed material through heat exchange of the inlet and outlet materials, and the waste heat of the finished phosphoric acid discharge is recovered.

[0069] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A production process of diammonium phosphate for battery, characterized in that: The following steps are involved: S1: Arsenic removal: The extracted and purified wet-process phosphoric acid is cooled to below 35°C, P2S5 is added to the extracted and purified wet-process phosphoric acid to generate H2S, and H2S reacts with arsenic ions to generate arsenic sulfide precipitation for arsenic removal; S2: Decolorization: Activated carbon decolorizer is added to the arsenic removal reaction solution for adsorption and decolorization, and arsenic sulfide impurities are adsorbed at the same time; S3: Aeration: Blow air into the reaction solution with excess H2S gas to aerate it, so that the excess H2S gas can be removed; S4: Filtration: The aerated phosphoric acid containing arsenic sulfide precipitate is filtered through a membrane to remove arsenic sulfide precipitate and activated carbon; S5: Decolorization after preheating: the dearsenicized phosphoric acid and the purified finished product 75% phosphoric acid are preheated and then enter hydrogen peroxide for decolorization; S6: Defluorination: After decolorization, the phosphoric acid enters the steam defluorination tower for stripping and defluorination; S7: Neutralization reaction: After defluorination, the finished acid is cooled to 80 degrees through heat recovery in steps S5 and S1, and then enters MAP ammonia for neutralization reaction to generate diammonium phosphate after iron removal; S8: Circulation reaction: diammonium phosphate is extracted after the reverse circulation system pump and enters the crystallization system; S9: Crystallization: Saturated diammonium phosphate enters the circulation guide tube in the crystallizer for vacuum crystallization; S10： Separation: The slurry produced by the crystallizer is concentrated by a thickener and then enters a centrifuge for separation; S11: Drying: The separated ammonium dihydrogen phosphate solid crystals are firstly deironed by an iron remover and then enter a fluidized bed dryer to remove surface moisture; S12： Packaging: After being dried in a fluidized bed dryer, the diammonium phosphate crystals are firstly removed by an iron remover and cooled to reach the qualified product before entering the clean area for packaging.

2. The production process of diammonium phosphate for battery according to claim 1, characterized in that: The H2S gas removed in step S3 is then washed with alkali and then discharged.

3. The production process of diammonium phosphate for battery according to claim 2, characterized in that: After the crystallization in step S9, decrystallization needs to be performed: decrystallization is performed by using a bottom circulating agitator to allow large-particle diammonium phosphate crystals with good crystallinity to settle at the bottom of the crystallizer and be collected, and fine crystals with poor crystallinity at the top are collected from the upper side to a fine crystal eliminator for decrystallization circulation.

4. The production process of diammonium phosphate for battery according to claim 3, characterized in that: During the crystallization elimination process, low-pressure steam of 0.5 MPa is introduced.

5. The production process of diammonium phosphate for battery according to claim 4, characterized in that: The mother liquor separated from the thickener and the centrifuge in step S10 is stored in a centrifugal mother liquor tank, and desalted water is added to the centrifugal mother liquor tank to form a saturated mother liquor of dihydrogen ammonium. The saturated mother liquor of dihydrogen ammonium is returned to the neutralization reactor in step S7 to participate in the neutralization reaction after iron removal.

6. The production process of diammonium phosphate for battery according to claim 5, characterized in that: The wet-process phosphoric acid purified by extraction used in step S1 is first preheated in a preheater, and the low-pressure steam flowing out of the fine crystal eliminator in step S9 and the fluidized bed dryer in step S10 is introduced into the preheater for use as a heat source.

7. The production process of diammonium phosphate for battery according to claim 6, characterized in that: The fluidized bed dryer in step S11 is connected to a product cooler, and circulating water flows through the product cooler.

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