Method for reducing the content of water-insoluble substances in monoammonium phosphate produced by the wet-process phosphoric acid slurry method

Abstract

The present application relates to a fertilizer, in particular to a method for reducing the content of water insoluble substance in monoammonium phosphate produced by wet-process phosphoric acid slurry method. The method is carried out according to the following steps: S1, adding substance A into the phosphoric acid solution, wherein the substance A is H2O2; S2, adding ammonia into the phosphoric acid solution for primary neutralization; S3, adding a chelating agent into the primary clarified solution after the reaction of step S2; S4, adding ammonia into the solution in step S3 for secondary neutralization; S5, performing pressure filtration on the secondary clarified solution generated in step S4; S6, crystallizing monoammonium phosphate at 45-50 DEG C from the solution obtained in step S5 and a saturated monoammonium phosphate solution under the temperature condition; S7, performing solid-liquid separation on the product in a centrifugal separator, and dehydrating and drying the separated solid in a drying device to obtain an industrial-grade monoammonium phosphate product. 3 The present application makes the content of insoluble substance in the high-quality product qualified and up to the standard, and the aqueous solution of the product becomes clear.

Description

TECHNICAL FIELD

[0001] The present application relates to a fertilizer, in particular to a method for reducing the content of water insoluble substance in monoammonium phosphate produced by wet-process phosphoric acid slurry method. BACKGROUND

[0002] Currently, the production of monoammonium phosphate by wet-process phosphoric acid slurry method mainly adopts one-time and two-time ammonia neutralization to control the neutralization degree, so that the non-water-soluble substances in the slurry are naturally settled and separated by filtration. In order to reduce the content of water insoluble substance, the following measures are usually taken: adjusting the MER value of phosphate concentrate to improve the quality of phosphoric acid; controlling the one-time and two-time neutralization degree; diluting phosphoric acid to improve the settling effect of the slurry; optimizing the wall cleaning scheme of the crystallization kettle. These measures have many control points, and the factors affecting the product quality cannot be accurately judged, resulting in large changes in the volume of pressurized filtrate during the working cycle, changes in the chemical composition of the pressurized filtrate, and increased instability of the product quality. The chemical composition changes, the concentration of non-water-soluble substances in the pressurized filtrate increases, and the percentage content of insoluble substances in the product exceeds the standard.

[0003] Chinese patent application No. 202011583241.5 discloses a production method of water-soluble fertilizer monoammonium phosphate. The content of water insoluble substance in the application is in the range of 0.09-0.48%, which has a large fluctuation range and is unstable. SUMMARY

[0004] The present application aims to solve the above technical problems, and provides a method for reducing the content of water insoluble substance in monoammonium phosphate produced by wet-process phosphoric acid slurry method, which reduces the concentration of non-water-soluble substances in the pressurized filtrate and improves the yield of industrial-grade monoammonium phosphate superior product.

[0005] The technical solution adopted by the present application to solve the technical problems is as follows:

[0006] A method for reducing the content of water insoluble substance in monoammonium phosphate produced by wet-process phosphoric acid slurry method, comprising the following steps:

[0007] S1, adding substance A to the phosphoric acid solution, the mass fraction of substance A to phosphoric acid is 1:200-250, and substance A is H2O2;

[0008] S2, adding ammonia to the phosphoric acid solution for one-time neutralization, the PH value is below 3.7, and the settling time is 5-10h;

[0009] S3, adding a chelating agent to the one-time clarified liquid after step S2;

[0010] S4, adding ammonia to the solution in step S3 for two-time neutralization, the PH value is 4.2-4.5;

[0011] S5, performing pressure filtration on the two-time clarified liquid generated in step S4, and the pressurized filtrate is subjected to a concentration process;

[0012] S6、reach specific gravity 1.33~1.36g / cm 3 and the temperature condition of the saturated solution of monammonium phosphate, into the crystallization process, crystallization at 45~50℃ monammonium phosphate precipitate;

[0013] S7, the product into the centrifugal separator for solid-liquid separation, after separation of the solid into drying equipment for dewatering drying to get industrial grade monammonium phosphate product, the non-water-soluble phosphate cations in the filtrate and the chelating agent added to form a chelate because of not to reach the saturation state continues to retain in the centrifugal mother liquor, so that the percentage of insoluble in the good industrial grade monammonium phosphate content qualified.

[0014] The beneficial effects of the application compared with the prior art are:

[0015] The substance added in the phosphoric acid makes the unstable low valence ions in the phosphoric acid into stable high valence ions, the chelating agent and the high valence cations in the non-water-soluble phosphate which are not separated in the clear solution occur complexation reaction to form a series of stable chelates existing in the clear solution, and the chelates continue to remain in the centrifugal mother liquor because of not reaching the saturation state during centrifugal separation, so that the non-water-soluble substances and the product are well separated, and the percentage of insoluble in the good product is qualified.

[0016] Further, the optimization scheme of the application is:

[0017] In the step S1, the mass concentration of the phosphoric acid solution is 19%~23%.

[0018] In the step S1, the reaction time is 20~60min.

[0019] In the step S2, the mass fraction ratio of ammonia to phosphoric acid is 1:20~30, and the reaction temperature is 80~100℃.

[0020] In the step S3, the mass fraction ratio of chelating agent to phosphoric acid is 1:500~800, and the reaction temperature is 70~90℃.

[0021] In the step S3, the chelating agent is EDTA.

[0022] In the step S4, the mass fraction ratio of ammonia to phosphoric acid is 1:150~250, and the reaction temperature is 80~100℃. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The flow chart of the embodiment of the application. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Example 1

[0025] A method for reducing the water-insoluble content in the production of monoammonium phosphate using the wet-process phosphoric acid slurry method comprises the following steps:

[0026] S1. Add substance A, H2O2, to a 19% phosphoric acid solution. The mass ratio of H2O2 to phosphoric acid is 1:200. The reaction equation is:

[0027] 2Fe 2+ + X +2H + ---2Fe 3+ +2H₂O, Fe 3+ +H3PO4----FePO4·2H2O+3H+, reaction time is 20 min.

[0028] S2. Add ammonia to the phosphoric acid solution for neutralization. The mass fraction ratio of ammonia to phosphoric acid is 1:20, the pH value is below 3.7, the reaction temperature is 80℃, and the sedimentation time is 5h.

[0029] S3. Add a chelating agent, EDTA, to the clarified solution after step S2. The mass ratio of the chelating agent to phosphoric acid is 1:500. The reaction temperature is 70℃. The reaction equation is:

[0030] Fe 3+ +HY 3 - --FeY - +H + Fe 2+ +2OH - --Fe(OH)₂ white solid, Fe 3+ +3OH - ---Fe(OH)3 colloid.

[0031] S4. Add ammonia to the solution in step S3 for secondary neutralization. The mass fraction ratio of ammonia to phosphoric acid is 1:250. The reaction temperature is 80℃ and the pH value is 4.2.

[0032] S5. The secondary clarified liquid generated in step S4 is subjected to pressure filtration, and the filtrate is then concentrated.

[0033] S6. Once a monoammonium phosphate saturated solution with a specific gravity of 1.33 and at this temperature is obtained, it enters the crystallization process, where monoammonium phosphate crystallizes out at a temperature of 45°C.

[0034] S7, the product enters into a centrifugal separator for solid-liquid separation, the separated solid enters into a drying device for dehydration and drying to obtain an industrial-grade monoammonium phosphate product, the chelate formed by the cations in the non-water-soluble phosphate in the filter liquor and the added chelating agent is continuously retained in the centrifugal mother liquor because it does not reach a saturated state, so that the insoluble content (solid phase content) of the excellent industrial-grade monoammonium phosphate is 0.09%, and the standard requirement is <0.1%, and the product is qualified.

[0035] The test results of the reaction process of the embodiment are shown in the following table

[0036]

[0037] The obtained monoammonium phosphate of the embodiment reaches an excellent product, and the test results are as follows:

[0038] Example 2

[0039] A method for reducing the water-insoluble content of monoammonium phosphate produced by a wet-process phosphoric acid slurry method is performed according to the following steps:

[0040] S1, a substance A is added to a phosphoric acid solution with a mass concentration of 21%, the substance A is H2O2, the mass ratio of H2O2 to phosphoric acid is 1:225, and the reaction equation is as follows:

[0041] 2Fe 2+ + X +2H + --2Fe 3+ +2H2O, Fe 3+ +H3PO4--FePO4·2H2O+3H+, and the reaction time is 40 min.

[0042] S2, ammonia is added to the phosphoric acid solution for primary neutralization, the mass ratio of ammonia to phosphoric acid is 1:25, the PH value is below 3.7, the reaction temperature is 90°C, and the settling time is 7.5 h.

[0043] S3, a chelating agent is added to the primary clarified liquid after the reaction in step S2, the chelating agent is EDTA, the mass ratio of the chelating agent to phosphoric acid is 1:650, the reaction temperature is 80°C, and the reaction equation is as follows:

[0044] Fe 3+ + HY 3- --FeY - +H + , Fe 2+ +2OH - --Fe(OH)2 white solid, Fe 3+ +3OH - ---Fe(OH)3 colloid.

[0045] S4, adding ammonia to the solution in step S3 for double neutralization, the mass fraction ratio of ammonia to phosphoric acid is 1:250, the reaction temperature is 90℃, and the PH value is 4.3.

[0046] S5, the secondary clarified solution generated in step S4 is subjected to pressure filtration, and the pressure filtrate is subjected to a concentration process.

[0047] S6, the specific gravity of the product is adjusted to 1.34 g / cm 3 and the saturated solution of monammonium phosphate under this temperature condition, enters a crystallization process, and monammonium phosphate is crystallized and precipitated at a temperature of 47.5℃.

[0048] S7, the product enters a centrifugal separator for solid-liquid separation, the separated solid enters a drying device for dehydration and drying to obtain an industrial-grade monammonium phosphate product, the chelate formed by the cations in the non-water-soluble phosphate in the pressure filtrate and the added chelating agent continues to remain in the centrifugal mother liquor because it does not reach a saturated state, so that the insoluble content (solid phase content) of the premium industrial-grade monammonium phosphate is 0.06%, which meets the standard requirement of <0.1%.

[0049] The test results of the reaction process of this embodiment are shown in the following table

[0050]

[0051] The monammonium phosphate obtained in this embodiment reaches a premium grade, and the test results are as follows:

[0052] Example 3

[0053] A method for reducing the water-insoluble content of monammonium phosphate produced by a wet-process phosphoric acid slurry method, is carried out according to the following steps:

[0054] S1, adding substance A to a phosphoric acid solution with a mass concentration of 22%, the substance A being H2O2, the mass fraction ratio of H2O2 to phosphoric acid being 1:250, and the reaction equation being:

[0055] 2Fe 2+ + X +2H + ---2Fe 3+ +2H2O, Fe 3+ +H3PO4----FePO4·2H2O+3H+, the reaction time being 60 min.

[0056] S2, adding ammonia to the solution in step S3 for double neutralization, the mass fraction ratio of ammonia to phosphoric acid being 1:30, the PH value being 4.2, the reaction temperature being 100℃, and the settling time being 9h.

[0057] S3. Add a chelating agent, EDTA, to the clarified solution after step S2. The mass ratio of the chelating agent to phosphoric acid is 1:800. The reaction temperature is 90℃. The reaction equation is:

[0058] Fe 3+ + HY 3- --FeY - +H + Fe 2+ +2OH - --Fe(OH)₂ white solid, Fe 3+ +3OH - ---Fe(OH)3 colloid.

[0059] S4. Add ammonia to the solution in step S3 for secondary neutralization. The mass ratio of ammonia to phosphoric acid is 1:200. The reaction temperature is 100℃ and the pH value is 4.4.

[0060] S5. The secondary clarified liquid generated in step S4 is subjected to pressure filtration, and the filtrate is then concentrated.

[0061] S6, achieving a specific gravity of 1.35 g / cm³ 3 The saturated solution of monoammonium phosphate under these temperature conditions is then introduced into the crystallization process, where monoammonium phosphate crystallizes out at a temperature of 50°C.

[0062] S7. The product enters a centrifuge for solid-liquid separation. The separated solids enter a drying equipment for dehydration and drying to obtain industrial-grade monoammonium phosphate. The cations in the non-water-soluble phosphate present in the filter press and the chelate formed by the added chelating agent continue to remain in the centrifugal mother liquor because they have not reached saturation. As a result, the percentage of insoluble matter (solid phase) in the superior grade industrial-grade monoammonium phosphate is 0.04%, which meets the standard requirement of <0.1% and is qualified.

[0063] The test results of the reaction process in this embodiment are shown in the table below.

[0064]

[0065] The monoammonium phosphate obtained in this embodiment reached the superior grade, and the test results are as follows:

[0066] Example 4

[0067] A method for reducing the water-insoluble content in the production of monoammonium phosphate using the wet-process phosphoric acid slurry method comprises the following steps:

[0068] S1, adding substance A into a 23% mass concentration phosphoric acid solution, the substance A is H2O2, the mass ratio of H2O2 to phosphoric acid is 1:250, the reaction equation is:

[0069] 2Fe 2+ + X +2H + ---2Fe 3+ +2H2O, Fe 3+ +H3PO4----FePO4·2H2O+3H+, the reaction time is 60 min.

[0070] S2, adding ammonia into the solution in step S3 for secondary neutralization, the mass ratio of ammonia to phosphoric acid is 1:30, the PH value is 4.2, the reaction temperature is 100℃, and the sedimentation time is 10h.

[0071] S3, adding a chelating agent into the once clarified solution after the reaction in step S2, the chelating agent is EDTA, the mass ratio of the chelating agent to phosphoric acid is 1:800, the reaction temperature is 90℃, and the reaction equation is:

[0072] Fe 3+ + HY 3- --FeY - +H + , Fe 2+ +2OH - --Fe(OH)2 white solid, Fe 3+ +3OH - ---Fe(OH)3 colloid.

[0073] S4, adding ammonia into the solution in step S3 for secondary neutralization, the mass ratio of ammonia to phosphoric acid is 1:150, the reaction temperature is 100℃, and the PH value is 4.5.

[0074] S5, performing pressure filtration on the secondary clarified solution generated in step S4, and the pressure filtrate is subjected to a concentration process;

[0075] S6, reaching a specific gravity of 1.36 g / cm 3 and a saturated ammonium phosphate solution under the temperature condition, and entering a crystallization process, and crystallizing ammonium phosphate at a temperature of 50℃.

[0076] S7, the product enters a centrifugal separator for solid-liquid separation, the separated solid enters a drying device for dehydration and drying to obtain an industrial-grade ammonium phosphate product, and the chelate composed of the cations in the non-water-soluble phosphate in the pressure filtrate and the added chelating agent is continuously retained in the centrifugal mother liquor because it does not reach a saturated state, so that the insoluble content (solid phase content) of the superior industrial-grade ammonium phosphate is 0.08%, which meets the standard requirement of <0.1%.

[0077] The test results of the reaction process of this example are shown in the following table

[0078]

[0079] The monoammonium phosphate obtained in this example reaches the superior product, and the test results are as follows:

[0080]

[0081] The indicators of the superior product of industrial-grade monoammonium phosphate are as follows: phosphorus pentoxide (calculated as P2O5) ≥ 60%, nitrogen (calculated as N) ≥ 11.8%, moisture ≤ 0.5, water-insoluble substance ≤ 0.1%, heavy metal 0, arsenic 0, and fluoride 0.

[0082] Comparative Example 1

[0083] a. Take 1000 g of phosphoric acid with a phosphorus pentoxide content of 35.69%, and the temperature is 78℃.

[0084] b. The acid solution obtained in step a is neutralized with ammonia gas, and the neutralization degree is 1.08.

[0085] c. The slurry obtained in step b is atomized and dried to obtain water-soluble fertilizer monoammonium phosphate. The inlet air temperature of the atomization tower is 150-180℃, and the outlet air temperature is 80-110℃; the oven temperature is 50-80℃, and the drying time is 30-80 min.

[0086] The water-insoluble substance (G4) in the water-soluble fertilizer monoammonium phosphate produced according to the method described in Comparative Example 1 is 8.42%.

[0087] Comparative Example 2

[0088] a. Take 1000 g of phosphoric acid with a phosphorus pentoxide content of 25.71%, and the temperature is 69℃. After adding 2.3 g of chelating agent diethylene triamine pentaacetic acid and polyamino polyether methylene phosphonic acid under stirring, continue stirring for 20 min.

[0089] b. The acid solution obtained in step a is neutralized with ammonia gas, and the final neutralization degree of the monoammonium phosphate slurry is 0.92.

[0090] c. The slurry obtained in step b is atomized and dried to obtain water-soluble fertilizer monoammonium phosphate. The inlet air temperature of the atomization tower is 150-180℃, and the outlet air temperature is 80-110℃; the oven temperature is 50-80℃, and the drying time is 30-80 min.

[0091] The water-insoluble substance (G4) in the water-soluble fertilizer monoammonium phosphate produced according to the method described in Comparative Example 2 is 4.87%.

[0092] Comparative Example 3

[0093] a. Take 1000g of phosphoric acid with 30.11% of P2O5 content, and the temperature is 87℃.

[0094] b. The acid solution obtained in step a is neutralized by ammonia gas, and the neutralization degree is 0.36. At this time, the ammonium phosphate slurry is 992g, and 2.0g of ATMPA is added, and the reaction is continued for 20min.

[0095] c. The slurry obtained in step b is continuously neutralized by ammonia gas, and the final neutralization degree of the ammonium phosphate slurry is 0.97. The water-soluble fertilizer ammonium phosphate is obtained by atomization and drying. The inlet air temperature of the atomization tower is 150-180℃, and the outlet air temperature is 80-110℃. The oven temperature is 50-80℃, and the drying time is 30-80min.

[0096] The water-insoluble substance (G4) in the water-soluble fertilizer ammonium phosphate produced according to the method described in Comparative Example 3 is 6.42%.

[0097] The above description is only the preferred embodiments of the present application, and does not limit the scope of the present application. Any equivalent structural changes made according to the content of the present application and the drawings are included in the scope of the present application.

Claims

1. A method for reducing the content of water-insoluble substances in monoammonium phosphate produced by a wet-process phosphoric acid slurry method, comprising the following steps: S1. Adding a substance A to a phosphoric acid solution, the mass ratio of the substance A to the phosphoric acid being 1:200-250, and the substance A being H2O2; S2. Adding ammonia to the phosphoric acid solution to perform a first neutralization, the PH value being below 3.7, and the settling time being 5-10 hours; S3. Adding a chelating agent to the first clarified solution after the step S2; S4. Adding ammonia to the solution in the step S3 to perform a second neutralization, the PH value being 4.2-4.5; S5. Performing pressure filtration on the second clarified solution produced in the step S4, and the pressure filtrate being subjected to a concentration process; S6, the specific gravity is 1.33~1.36g / cm 3 and in 45 ℃~50 ℃ under the monopotassium phosphate saturated solution, into the crystallization process, in 45~50 ℃ crystallization precipitation monopotassium phosphate; S7. The product being subjected to solid-liquid separation in a centrifugal separator, the separated solid being subjected to dehydration and drying in a drying device to obtain an industrial-grade monoammonium phosphate product, and the chelate formed by the cations in the non-water-soluble phosphate in the pressure filtrate and the added chelating agent being continuously retained in the centrifugal mother liquor due to not reaching a saturation state, so that the percentage content of insoluble substances in the high-quality industrial-grade monoammonium phosphate is qualified and up to standard.

2. The process of reducing the water insolubles content of monoammonium phosphate produced by the wet-process phosphoric acid feed method according to claim 1, characterized by: In the step S1, the mass concentration of the phosphoric acid solution is 19%-23%.

3. The process of reducing the water insolubles content of monoammonium phosphate produced by the wet-process phosphoric acid feed method of claim 1, characterized by: In the step S1, the reaction time is 20-60 minutes.

4. The process of reducing the water insolubles content of monoammonium phosphate produced by the wet-process phosphoric acid feed method of claim 1, characterized by: In the step S2, the mass ratio of the ammonia to the phosphoric acid is 1:20-30, and the reaction temperature is 80-100℃.

5. The process of reducing the water insolubles content of monoammonium phosphate produced by the wet-process phosphoric acid feed method of claim 1, characterized by: In the step S3, the mass ratio of the chelating agent to the phosphoric acid is 1:500-800, and the reaction temperature is 70-90℃.

6. The process of reducing the water insolubles content of monoammonium phosphate produced by the wet-process phosphoric acid feed method of claim 1, characterized by: In the step S3, the chelating agent is EDTA.

7. The process of reducing the water insolubles content of monoammonium phosphate produced by the wet-process phosphoric acid feed method of claim 1, characterized by: In the step S4, the mass ratio of the ammonia to the phosphoric acid is 1:150-250, and the reaction temperature is 80-100℃.

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