Method for producing battery grade monoammonium phosphate by purifying phosphoric acid

Abstract

The invention discloses a method for producing battery-grade monoammonium phosphate from purified phosphoric acid, which comprises the following steps: mixing an acid solution obtained by mixing purified phosphoric acid and desalted water with liquid ammonia through acid preparation, carrying out neutralization reaction, cooling and crystallizing the obtained neutralized solution, separating to obtain a solid, and drying the solid to obtain monoammonium phosphate. According to the production method of the purified phosphoric acid, the raw acid does not contain substances needing impurity removal, the utilization rate of the mother liquor is high, and phosphorus pentoxide can be completely utilized, so that the process flow is reduced, only the steps of neutralization, crystallization and drying are needed, the energy consumption is saved, and the production profit is effectively improved. The method does not need impurity removal equipment, so that the production cost can be reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of phosphorus chemical process, and particularly relates to a method for producing battery-grade monoammonium phosphate from purified phosphoric acid. BACKGROUND

[0002] There are two kinds of raw materials for producing industrial-grade ammonium dihydrogen phosphate, i.e. hot-process phosphoric acid and wet-process phosphoric acid. The production method using hot-process phosphoric acid as raw material is called hot-process ammonium dihydrogen phosphate, and the production method using wet-process phosphoric acid as raw material is called wet-process ammonium dihydrogen phosphate.

[0003] The process of hot-process ammonium dihydrogen phosphate is that yellow phosphorus is combusted and hydrated to generate high-concentration phosphoric acid, the phosphoric acid is ammoniated, centrifuged, concentrated, cooled, crystallized, dried, and industrial-grade ammonium dihydrogen phosphate is obtained. The process flow of hot-process ammonium dihydrogen phosphate is characterized by short process flow and high production cost.

[0004] The process of wet-process ammonium dihydrogen phosphate is that sulfuric acid is used to decompose ore slurry to prepare extracted wet-process phosphoric acid, the wet-process phosphoric acid is purified to obtain PPA purified acid, a pure ammonium dihydrogen phosphate solution is prepared, and then battery-grade ammonium dihydrogen phosphate is obtained through concentration, crystallization and drying.

[0005] The traditional method for producing battery-grade monoammonium phosphate from wet-process phosphoric acid brings a large amount of metal impurities in the production process, and the impurities need to be removed by a horizontal centrifuge and a surface filter after neutralization, which is complicated and requires a large amount of system cleaning, and the purity of the finished product is not high.

[0006] The patent application file with the publication number CN100558633A discloses a method for preparing industrial-grade phosphoric acid, food-grade phosphoric acid and industrial monoammonium phosphate from wet-process phosphoric acid. The wet-process phosphoric acid is purified through a series of chemical precipitation + organic solvent extraction + concentration + recrystallization to prepare industrial-grade phosphoric acid and food-grade phosphoric acid, respectively. Meanwhile, the invention uses part of the purified dilute phosphoric acid to prepare industrial monoammonium phosphate.

[0007] The patent application file with the publication number CN117361461A discloses a method for producing monoammonium phosphate from wet-process phosphoric acid, which can recover fluorine in the wet-process phosphoric acid to form sodium fluorosilicate product, thereby recycling fluorine resources and avoiding fluorine pollution caused by phosphorus fertilizer to the environment.

[0008] The patent application file with the publication number CN117776129A discloses a method for producing high-purity battery-grade ammonium dihydrogen phosphate from by-product residual acid of purified phosphoric acid, which comprises the following steps: diluting the by-product residual acid of purified phosphoric acid after desorption in a concentration tower with desalted water, neutralizing and reacting the diluted by-product residual acid with liquid ammonia in an ammoniation reactor to obtain a neutralization slurry, filtering the neutralization slurry to obtain a neutralization clear liquid, and then standing, aging, concentrating, cooling and crystallizing the neutralization clear liquid, and finally washing with salt, recrystallizing, and drying in a fluidized bed to obtain high-purity battery-grade ammonium dihydrogen phosphate.

[0009] However, the above patent application file fails to solve the technical problems of simplifying the process, reducing the cost and improving the purity of the finished product. SUMMARY

[0010] To solve the above technical problems, the present application provides a method for purifying phosphoric acid to produce battery-grade monoammonium phosphate.

[0011] The present application is achieved by the following technical solutions.

[0012] The method for purifying phosphoric acid to produce battery-grade monoammonium phosphate provided by the present application comprises the process of mixing the acid solution obtained by mixing the purified phosphoric acid with desalted water through acid preparation with liquid ammonia for neutralization reaction, cooling and crystallizing the obtained neutralization solution, and then separating the solid material to obtain the monoammonium phosphate after drying.

[0013] Preferably, in the acid preparation step, the purified phosphoric acid is prepared into a P2O5 solution with a concentration of 20-30% by mixing the purified phosphoric acid with a concentration of P2O5 of 55-65%, and the ammonia content of the liquid ammonia is ≥99%.

[0014] Preferably, in the neutralization reaction, the pH value is controlled between 4.3-4.7, the reaction temperature is 91-99℃, and the residence time of the mixed solution obtained by mixing the acid solution with liquid ammonia in the neutralization equipment is 20-40 minutes.

[0015] Preferably, in the neutralization reaction, the ammonia acid neutralization degree is controlled to be 0.8-1.2, and the ammonia acid reaction ratio is 1:1.

[0016] Preferably, the cooling and crystallization step comprises: pumping the neutralization solution into a crystallizer, adding steam for concentration, and then sending the obtained concentrated solution with a specific gravity of 1.4-1.6 into the crystallizer for cooling.

[0017] Preferably, in the cooling and crystallization step, the steam pressure is 0.2-0.3Mpa, the steam temperature is 120-130℃, and the steam flow is 3-6t / h.

[0018] Preferably, in the cooling step, the concentrated solution is cooled to 60-70℃.

[0019] Preferably, in the separation step, the solid material is obtained by centrifugal separation, and the centrifuge speed is 1300-1600r / min; the pushing frequency is 65-80 times per minute.

[0020] Preferably, in the drying step, the solid material drying temperature is 100-110℃, the residence time of the solid material in the drying equipment is 25-40 minutes, and the solid material is dried to a water content of 0.1-0.4%.

[0021] Preferably, the drying is performed under a negative pressure condition of -4 KPa to -2 KPa.

[0022] The present application has the following advantages: The purified phosphoric acid production method of the present application has a high utilization rate of mother liquor, and the phosphorus pentoxide can be fully utilized. The method reduces the process flow, only needs neutralization, crystallization and drying steps, saves energy consumption, and effectively improves production profit. Since the method does not need impurity removal equipment, the production cost can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a process flow chart of the present application; Figure 2 is a process flow chart of the prior art. DETAILED DESCRIPTION

[0024] The technical solutions of the present application are further described below, but the scope of protection is not limited to the description.

[0025] Monoammonium phosphate is obtained by neutralizing phosphoric acid with ammonia, and the main reaction equation is NH3+H3PO4=NH4H2PO4+126KJ The side reaction is that a small amount of impurities contained in wet-process phosphoric acid, such as Mg 2+ , Ca 2+ , Fe 3+ , Al 3+ , SO4 2- and F - , etc., generate various compounds in the neutralization process with ammonia. Some of these compounds are water-soluble, and some are insoluble. These insoluble compounds reduce the water-soluble phosphorus pentoxide and effective phosphorus pentoxide in the product. Therefore, the metal impurities should be removed by organic solvent extraction at the raw material end. The metal impurities are removed by the raffinate acid in the extraction process, so as to obtain phosphorus pentoxide with high purity in the organic solvent. Then, by adding carbonic acid, the remaining sulfate is removed, and then by back extraction, 25% phosphoric acid (phosphorus pentoxide content) is extracted, and then by evaporation, fluorine ions are removed to obtain purified phosphoric acid.

[0026] Example 1: As shown in Figure 1 , a method for producing battery-grade monoammonium phosphate from purified phosphoric acid, comprising the process of mixing the acid solution obtained by mixing purified phosphoric acid with desalted water through acid preparation with liquid ammonia for neutralization reaction, cooling and crystallizing the obtained neutralization solution, and then separating to obtain solid material, and then drying the solid material to obtain battery-grade monoammonium phosphate.

[0027] In the acid preparation step, the purified phosphoric acid and demineralized water are mixed by preparing the purified phosphoric acid from a 55% concentration of P2O5 to a 20-30% concentration of P2O5 solution. The liquid ammonia has an ammonia content of ≥99% and a residue of ≤1%.

[0028] The pH value is controlled at 4.3 and the reaction temperature is 91°C during the neutralization reaction. The mixed solution obtained by mixing the acid solution and liquid ammonia stays in the neutralization device for 20 minutes.

[0029] In the neutralization reaction, the degree of amino acid neutralization is controlled at 0.8, the amino acid reaction ratio is 1:1, and a slight negative pressure is maintained in the neutralization tank to avoid excessive heat of reaction causing vibration inside the tank.

[0030] The cooling crystallization step includes: pumping the neutralized solution into the Oslo crystallizer in the concentration flash chamber via a slurry feed pump, adding steam for concentration, and flushing and agitating the lower part of the Oslo crystallizer by a downcomer. The solid fine crystals in the crystallizer are repeatedly flushed, rise and expand, gradually grow, and then settle. The resulting concentrated solution with a specific gravity of 1.4 is then pumped into a new crystallizer for cooling by a crystal slurry pump.

[0031] In the cooling and crystallization step, the steam pressure is 0.2 MPa, the steam temperature is 120°C, and the steam flow rate is 3 t / h.

[0032] In the cooling step, the concentrated solution is cooled to 60°C.

[0033] The separation step involves obtaining a solid by centrifugation. The centrifuge operates at a speed of 1300 r / min and pushes the material 65 times per minute. By controlling the speed and the number of pushes, the crystal form can be preserved, maximizing the yield of the finished product with the most effective crystal form.

[0034] In the drying step, the solid material is dried at a temperature of 100°C, the solid material is stored in the drying equipment for 25 minutes, and the drying is carried out until the moisture content of the solid material reaches 0.1%. The drying is carried out under a negative pressure of -4 kPa.

[0035] Example 2: like Figure 1 As shown, a method for producing battery-grade monoammonium phosphate by purifying phosphoric acid includes mixing purified phosphoric acid and demineralized water into an acid solution and then mixing it with liquid ammonia to carry out a neutralization reaction. The resulting neutralized solution is cooled and crystallized, then separated to obtain a solid, which is then dried to obtain battery-grade monoammonium phosphate.

[0036] In the acid preparation step, the purified phosphoric acid and demineralized water are mixed by preparing the purified phosphoric acid from a 65% concentration P2O5 solution to a 30% concentration P2O5 solution. The liquid ammonia has an ammonia content of ≥99% and a residue of ≤1%.

[0037] The pH value in the neutralization reaction is controlled to be 4.7, the reaction temperature is 99℃, and the residence time of the mixed solution obtained by mixing the acid solution and liquid ammonia in the neutralization equipment is 40 minutes.

[0038] The neutralization degree of the ammonia acid in the neutralization reaction is controlled to be 1.2, the ammonia acid reaction ratio is 1:1, and a micro-negative pressure state is maintained in the neutralization tank to avoid excessive heat causing tank vibration.

[0039] The cooling crystallization step includes: pumping the neutralization solution into the concentration flash chamber Oslo crystallizer through the slurry pump, adding steam for concentration, and descending and flushing the lower material of the Oslo crystallizer through the downcomer to stir the lower material. The fine crystals in the crystallizer are repeatedly flushed, rise, expand, and gradually grow and then settle. Then, the concentrated solution with a specific gravity of 1.6 is pumped into the newly added crystallizer for cooling by the crystal slurry pump.

[0040] In the cooling crystallization step, the steam pressure is 0.3Mpa, the steam temperature is 130℃, and the steam flow is 6t / h.

[0041] In the cooling step, the concentrated solution is cooled to 70℃.

[0042] The separation step is to obtain solid material by centrifugal separation, the centrifugal speed is 1600r / min, and the pushing frequency is 80 times / min. Controlling the speed and pushing frequency can not damage the crystal form and maximize the effective crystal form of the finished product.

[0043] In the drying step, the solid material drying temperature is 110℃, the residence time of the solid material in the drying equipment is 40 minutes, and the moisture content of the solid material is dried to 0.4%. The drying is carried out under a negative pressure of -2KPa.

[0044] Example 3: As shown in Figure 1 A method for purifying phosphoric acid to produce battery-grade monoammonium phosphate, which includes the process of mixing purified phosphoric acid with desalted water by acid preparation, mixing the acid solution with liquid ammonia for neutralization reaction, cooling and crystallizing the obtained neutralization solution to obtain solid material, and drying the solid material to obtain battery-grade monoammonium phosphate.

[0045] In the acid preparation step, the purified phosphoric acid is mixed with desalted water to prepare a 25% P2O5 solution from a 61.7% P2O5 solution. The ammonia content of the liquid ammonia is ≥99%, and the residue is ≤1.

[0046] In the neutralization reaction, the pH value is controlled to be 4.5, the reaction temperature is 95℃, and the residence time of the mixed solution obtained by mixing the acid solution and liquid ammonia in the neutralization equipment is 30 minutes.

[0047] The neutralization degree of the ammonia acid is controlled to be 1.03, the ammonia acid reaction ratio is 1:1, a micro-negative pressure state is maintained in the neutralization tank to avoid excessive heat from causing tank vibration.

[0048] The cooling crystallization step includes: pumping the neutralization solution into the Oslo crystallizer of the concentration flash chamber through a slurry pump, adding steam for concentration, and descending and flushing the lower material of the Oslo crystallizer through a downcomer to stir the lower material, the fine crystals in the crystallizer are repeatedly flushed upward and expanded to gradually grow and then settle, and then the obtained concentrated solution with a specific gravity of 1.52 is pumped into a new crystallizer for cooling by a crystal slurry pump.

[0049] In the cooling crystallization step, the steam pressure is 0.26 Mpa, the steam temperature is 124℃, and the steam flow is 4t / h.

[0050] In the cooling step, the concentrated solution is cooled to 65℃.

[0051] The separation step is to obtain solid material by centrifugal separation, the centrifuge speed is 1475r / min, and the pushing frequency is 70 times / min, and the control of the speed and the pushing frequency can not damage the crystal form and maximize the effective crystal form of the finished product.

[0052] In the drying step, the solid material drying temperature is 107℃, the residence time of the solid material in the drying equipment is 30 minutes, and the solid material is dried to a water content of 0.2%; the drying is carried out under a negative pressure of-2.5KPa.

[0053] In Examples 1-3, after the neutralization reaction, the slurry is filtered to remove possible trace impurities in the system, a 500 mesh filter cloth is used to avoid impurities entering the subsequent process. After the neutralization reaction, the slurry is treated by removing magnetic particles to remove magnetic particles generated by friction between the slurry and the equipment, ensuring that the magnetic particles in each kilogram of battery-grade ammonium phosphate are below 200.

[0054] Comparative Example 1: As Figure 2As shown, a method for producing battery-grade monoammonium phosphate, the steps are: after the wet-process phosphoric acid is configured with industrial water (the phosphoric acid concentration is configured from 48% P2O5 to 25% P2O5) and liquid ammonia from the ammonia station (ammonia content ≥ 99%, residue ≤ 1), a neutralization reaction is carried out, the reaction PH value is controlled between 4.3-4.7, the ammonia acid neutralization degree is taken as the control index, the ammonia acid reaction ratio is taken as 1:1 reaction, the temperature is 95°C, a micro-negative pressure state is maintained in the neutralization tank to avoid excessive heat in the tank causing vibration. The prepared slurry is separated by a horizontal screw machine, the solid slurry is transferred into the finished product system to produce ammonium phosphate, the liquid phase part is further separated by a surface filter, the impurity part and the slurry part are transferred into the finished product system together, and the clear liquid enters the concentration evaporation system for concentration. After concentration, the slurry is transported to the Oslo crystallizer in the flash chamber, and the slurry cooled to 65°C by circulating cooling water in the coil and shell, enters the centrifuge from the bottom of the crystallizer, the centrifuge speed is 1475 r / min; the pushing frequency is 70 times / min; strictly controlling the speed and pushing frequency can not destroy the crystal form, and the effective crystal form of the finished product is obtained to the maximum extent. The mother liquor separated by the centrifuge is used in the acid preparation tank; the centrifugal solid phase crystals are automatically unloaded to the drying machine for drying, the drying temperature is controlled at 100-110°C, the negative pressure in the drying machine is -2.5 KPa, the residence time is 30 minutes, the water content is 0.2%, and the production of monoammonium phosphate is completed.

[0055] Comparative Example 2: The method of Example 1 in the method for directly producing battery-grade monoammonium phosphate from wet-process phosphoric acid with publication number CN115285956B is used.

[0056] Battery-grade monoammonium phosphate is produced using the methods of Examples 1-3 and Comparative Examples 1-2, respectively, wherein the amount of 85% phosphoric acid (63% P2O5) is 1 ton, and the results of the battery-grade monoammonium phosphate obtained are shown in the following table.

[0057] As shown in the above table, Example 3 can produce 1 ton of battery-grade monoammonium phosphate using 1 ton of 85% phosphoric acid (63% P2O5), and the phosphorus pentoxide can be fully utilized, while the highest yield of wet-process phosphoric acid in the comparative examples can only be 55%.

[0058] Quality analysis data of the monoammonium phosphate products produced in Examples 1-3 and Comparative Examples 1 and 2 are shown in the following table.

[0059] Comparison table of purified phosphoric acid and wet-process phosphoric acid product analysis results

[0060] From the above data, the main content of the product produced by purified phosphoric acid can reach more than 99.5%, and the nutrient is stable at more than 73.72%, the salt impurities in the product except ammonium dihydrogen phosphate are very low, almost no impurities except water, high-purity battery ammonium has the conditions to produce battery raw materials. Wet-process phosphoric acid production even has a multi-step impurity removal process, but the total nutrient can only be above 72%, and the main content can only reach more than 98%, and a small amount of metal elements will still exist in the product in the form of ammonium salt. Under the current situation that battery-grade ammonium product is the main raw material for new energy, high-nutrient, low-impurity battery ammonium product has a large market demand, stable nutrient, as a battery-grade raw material product has market competitiveness, and ordinary industrial ammonium product can only be used as fertilizer, with low market value.

[0061] In the production of battery-grade ammonium phosphate by wet-process phosphoric acid, one person is needed to maintain the centrifugal impurity removal post, and the labor cost is about 100,000 yuan per year, and the equipment maintenance cost is about 50,000 yuan per year. One person is needed to maintain the filter impurity removal, and the outsourcing maintenance surface filter costs about 100,000 yuan per year, and the equipment maintenance cost is about 100,000 yuan per year. The production of purified phosphoric acid in the present application can save these costs.

Claims

1. A process for purifying phosphoric acid to produce battery grade monoammonium phosphate, characterized by: The process comprises mixing the purified phosphoric acid with desalted water by acid matching, mixing the acid solution with liquid ammonia to carry out neutralization reaction, cooling and crystallizing the obtained neutralization solution to separate solid material, and drying the solid material to obtain monoammonium phosphate.

2. A process for purification of phosphoric acid for production of battery grade monoammonium phosphate as claimed in claim 1 wherein: In the acid matching step, the purified phosphoric acid is matched to a P2O5 concentration of 20-30% from a P2O5 concentration of 55-65%, and the ammonia content of the liquid ammonia is ≥99%.

3. A process for purification of phosphoric acid for production of battery grade monoammonium phosphate as claimed in claim 1 wherein: In the neutralization reaction, the pH value is controlled between 4.3-4.7, the reaction temperature is 91-99℃, and the residence time of the mixed solution obtained by mixing the acid solution with liquid ammonia in the neutralization equipment is 20-40 minutes.

4. A process for purification of phosphoric acid for production of battery grade monoammonium phosphate as claimed in claim 1 wherein: In the neutralization reaction, the ammonia acid neutralization degree is controlled to be 0.8-1.2, and the ammonia acid reaction ratio is 1:

1.

5. A process for purification of phosphoric acid for production of battery grade monoammonium phosphate as claimed in claim 1 wherein: The cooling and crystallizing step comprises pumping the neutralization solution into a crystallizer, adding steam to concentrate, and then sending the obtained concentrated solution with a specific gravity of 1.4-1.6 into the crystallizer for cooling.

6. A process for purification of phosphoric acid for production of battery grade monoammonium phosphate as claimed in claim 5 wherein: In the cooling and crystallizing step, the steam pressure is 0.2-0.3Mpa, the steam temperature is 120-130℃, and the steam flow is 3-6t / h.

7. A process for purification of phosphoric acid for production of battery grade monoammonium phosphate as claimed in claim 5 wherein: In the cooling step, the concentrated solution is cooled to 60-70℃.

8. A process for purification of phosphoric acid for production of battery grade monoammonium phosphate as claimed in claim 1 wherein: In the separation step, the solid material is obtained by centrifugal separation, the centrifuge speed is 1300-1600r / min, and the pushing frequency is 65-80 times / min.

9. A process for purification of phosphoric acid for production of battery grade monoammonium phosphate as claimed in claim 1 wherein: In the drying step, the solid material drying temperature is 100-110℃, the residence time of the solid material in the drying equipment is 25-40 minutes, and the solid material is dried to a water content of 0.1-0.4%.

10. A process for purification of phosphoric acid for production of battery grade monoammonium phosphate as claimed in claim 9 wherein: The drying is carried out under negative pressure of-4KPa to-2KPa.

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