A process for co-production of ammonium magnesium phosphate hexahydrate and calcium hydrogen phosphate dihydrate by using potassium phosphate solution and dolomite powder

Abstract

The present application relates to potassium dihydrogen phosphate mother liquor recovery technical field, especially to a kind of process method for co-production of ammonium magnesium phosphate six water and calcium hydrogen phosphate two water by phosphorus potassium liquid and dolomite powder, comprising the following contents: with potassium dihydrogen phosphate crystallization mother liquor and dolomite powder as raw material, after heating and stirring solution, obtained mixed solution is added with ammonia water, then adjust pH, after stirring, standing, filtration, filter cake and filtrate are collected respectively, wherein filter cake is added with phosphoric acid and is treated with pulp, and solid phase and liquid phase are collected respectively;The collected solid phase is eluted and dried to obtain magnesium ammonium phosphate six water product, and the collected liquid phase is added with lime milk to adjust pH, concentrated, cooled and crystallized, filtered, and the collected solid is dried to obtain calcium hydrogen phosphate two water product.The above-mentioned process design is reasonable, and high yield, high purity and high yield of magnesium ammonium phosphate six water and calcium hydrogen phosphate two water products can be obtained.

Description

Technical Field

[0001] This invention relates to the field of potassium dihydrogen phosphate mother liquor recovery technology, and in particular to a process method for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium dihydrogen phosphate solution and dolomite powder. Background Technology

[0002] Corn soaking water is a major byproduct of corn starch production via wet milling. Currently, the comprehensive utilization of corn soaking water is mainly for the extraction of inositol and potassium dihydrogen phosphate. However, the mother liquor remaining after potassium dihydrogen phosphate extraction currently suffers from low resource utilization and low added value.

[0003] Magnesium ammonium phosphate (MAP, MgNH4+) ４ PO ４ ·6H ２ O), a high-quality slow-release fertilizer, provides multiple nutrients including nitrogen, phosphorus, and magnesium, effectively improving soil fertility in agricultural production. Existing technologies disclose processes for preparing magnesium ammonium phosphate and potassium chloride using potassium dihydrogen phosphate crystallization mother liquor, and also disclose the preparation of magnesium ammonium phosphate hexahydrate and potassium magnesium phosphate hexahydrate compound products using potassium dihydrogen phosphate crystallization mother liquor; dicalcium phosphate is the most mainstream high-efficiency calcium and phosphorus supplement in feed; however, there are currently no reports on processes for preparing magnesium ammonium phosphate hexahydrate and dicalcium phosphate using potassium dihydrogen phosphate crystallization mother liquor as raw material. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a process for the co-production of magnesium ammonium phosphate hexahydrate and calcium phosphate dihydrate using potassium phosphate solution and dolomite powder, which can simultaneously produce high-purity magnesium ammonium phosphate hexahydrate and calcium phosphate dihydrate products.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder, the process comprising the following steps:

[0007] (1) Take the mother liquor of potassium dihydrogen phosphate crystallization, add dolomite powder at a temperature not lower than 35°C, stir to dissolve, and use the resulting mixed liquid for later use;

[0008] (2) Take ammonia water, add it dropwise to the mixture in step (1) and stir. Adjust the pH to not less than 8.5 with potassium hydroxide solution, continue stirring, let stand, filter, and collect the filter cake for later use.

[0009] (3) Take the filter cake from step (2), add phosphoric acid and slurry it, filter it and collect the liquid phase and solid phase separately for later use;

[0010] (4) Take the solid phase described in step (3), rinse and dry it to obtain magnesium ammonium phosphate hexahydrate product;

[0011] (5) Take the liquid phase described in step (3), add lime milk to adjust the pH to not less than 5, and then concentrate, cool and crystallize and filter. The collected solid is dried to obtain the product of dicalcium phosphate dihydrate.

[0012] As an improved technical solution, the content of inorganic phosphorus in the potassium dihydrogen phosphate crystallization mother liquor in step (1) is 20% (calculated as phosphorus pentoxide); the content of magnesium oxide in the dolomite powder is 20% and the content of calcium oxide is 30%; wherein the amount of dolomite powder added in every 100g of potassium dihydrogen phosphate crystallization mother liquor is 13.5g-21g.

[0013] As an improved technical solution, dolomite powder is added in step (1) at a temperature of 35-45℃.

[0014] As an improved technical solution, the concentration of ammonia in step (2) is 23-28 wt%, wherein the amount of ammonia added to each 100g potassium dihydrogen phosphate crystallization mother liquor is 2.5-3.5g.

[0015] As an improved technical solution, in step (2), the concentration of potassium hydroxide solution is 30wt%, the pH is adjusted to 8.5-9, stirring is continued for 1.5-2.5h, then standing for 1.0-1.5h, and then filtered under the condition of 32-38℃.

[0016] As an improved technical solution, in step (3), phosphoric acid with a pH of 3-4 and 2-5 wt% is added and then pulped, wherein the filter cake and phosphoric acid are added in a mass-volume ratio of 1:3-4.

[0017] As an improved technical solution, in step (4), deionized water is used for rinsing, and hot air drying at 40-45℃ is used for 12-16 hours under normal pressure.

[0018] As an improved technical solution, the concentration of lime slurry in step (5) is 15-20 wt%, and the pH is adjusted to 5-7.

[0019] As an improved technical solution, in step (5), the concentration is carried out at -0.06 to -0.08 MPa and 80-85℃ until the endpoint is measured by a Baumé meter at 36-40℃, and then the temperature is lowered to 20-25℃ for crystallization treatment. The collected solid is dried at 60-70℃ for 3-4 hours.

[0020] After adopting the above technical solution, the beneficial effects of the present invention are:

[0021] This invention uses potassium dihydrogen phosphate crystallization mother liquor and dolomite powder as raw materials. The solution is heated and stirred, and ammonia is added to the resulting mixture. The pH is then adjusted, and after stirring, settling, and filtration, the filter cake and filtrate are collected separately. The filter cake is then treated with phosphoric acid to form a slurry, and the solid and liquid phases are collected separately. The collected solid phase is washed and dried to obtain magnesium ammonium phosphate hexahydrate. The collected liquid phase is mixed with lime milk to adjust the pH, and after concentration, cooling crystallization, and filtration, the collected solid is dried to obtain calcium phosphate dihydrate. This process design is reasonable and can produce high-yield, high-purity, and high-quality magnesium ammonium phosphate hexahydrate and calcium phosphate dihydrate, increasing economic benefits for enterprises. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] Example 1

[0024] A process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder includes the following steps:

[0025] (1) Take 1000g of potassium dihydrogen phosphate crystallization mother liquor (the content of inorganic phosphorus is 20% based on phosphorus pentoxide), add 13.5g of dolomite powder (the content of magnesium oxide is 20% and the content of calcium oxide is 30%) to every 100g of potassium dihydrogen phosphate crystallization mother liquor at 35℃, stir and dissolve, and then use the resulting 1135g of mixed liquid for later use.

[0026] (2) Add 23wt% ammonia water dropwise to the mixture in step (1) according to the dosage of 2.5g per 100g potassium dihydrogen phosphate crystallization mother liquor, stir, then add 16ml of 30wt% potassium hydroxide solution to adjust the pH to 8.5, continue stirring for 1.5h, let stand for 1h, then filter under the condition of 32℃, and collect 310g filter cake for later use.

[0027] (3) Take all the filter cake from step (2), i.e. 310g, add 930mL of phosphate with pH 3 and 2wt% according to the mass-volume (g:ml) ratio of 1:3, then pulverize, filter, and collect 1020mL of liquid phase and 230g of solid phase for later use.

[0028] (4) Take all the solid phase from step (3), i.e., 230g, and rinse it with deionized water to obtain 210g of wet filter cake (moisture content 34.5%). Dry it with hot air at 40℃ for 16h under normal pressure to obtain 137.5g of magnesium ammonium phosphate hexahydrate product. The purity of the product was determined by chemical titration to be 97.2%, and the yield was 86.8% based on the effective magnesium component of the system.

[0029] (5) Take 1020 mL of the liquid phase from step (3), add 15 wt% lime milk to adjust the pH to 5, the amount added is 42 g, concentrate under -0.06 MPa and 80 ℃ to obtain 500 mL of concentrated solution with a Baume degree of 36, then cool to 20 ℃ for crystallization and filtration, collect a total of 173 g of wet filter cake (33% moisture), dry at 60 ℃ for 4 h to obtain 115 g of dicalcium phosphate dihydrate product, the purity of the product is 96.6% by chemical titration, and the yield is 84.3% calculated based on the available phosphorus components in the liquid phase of step three.

[0030] Example 2

[0031] A process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder includes the following steps:

[0032] (1) Take 1000g of potassium dihydrogen phosphate crystallization mother liquor (the content of inorganic phosphorus is 20% based on phosphorus pentoxide), add 17.5g of dolomite powder (the content of magnesium oxide is 20% and the content of calcium oxide is 30%) to every 100g of potassium dihydrogen phosphate crystallization mother liquor at 40℃, stir and dissolve, and then use the resulting 1175g of mixed liquid for later use.

[0033] (2) Add 25wt% ammonia water dropwise to the mixture in step (1) according to the dosage of 3g per 100g potassium dihydrogen phosphate crystallization mother liquor and stir. Then add 22ml of 30wt% potassium hydroxide solution to adjust the pH to 8.8. Continue stirring for 2h and let stand for 1.2h. Then keep warm and filter at 35℃ and collect 400g filter cake for later use.

[0034] (3) Take all the filter cake from step (2), i.e. 400g, add 1400mL of phosphoric acid with pH 3.5 and 3.5wt% at a mass-volume (g:ml) ratio of 1:3.5, then slurry, filter, and collect 1490mL of liquid phase and 296g of solid phase for later use.

[0035] (4) Take all the solid phase from step (3), i.e., 296g, and wash it with deionized water to obtain 238g of wet filter cake (moisture content 37.7%). Dry it with hot air at 42℃ for 14h under normal pressure to obtain 148.2g of magnesium ammonium phosphate hexahydrate product. The purity of the product was determined by chemical titration to be 98.7%, and the yield was 93.6% based on the effective magnesium component of the system.

[0036] (5) Take 1490 mL of the liquid phase from step (3), add 18 wt% lime milk to adjust the pH to 6, the amount added is 48 g, concentrate under -0.07 MPa and 83 ℃ to obtain 720 mL of concentrated solution with a Baume degree of 38, then cool to 23 ℃ for crystallization and filtration, collect a total of 186 g of wet filter cake (moisture 32.5%), dry at 65 ℃ for 3.5 h to obtain 125.5 g of dicalcium phosphate dihydrate product, the purity of the product is 98.4% by chemical titration, and the yield is 92.8% calculated based on the available phosphorus component of the liquid phase in step three.

[0037] Example 3

[0038] A process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder includes the following steps:

[0039] (1) Take 1000g of potassium dihydrogen phosphate crystallization mother liquor (the content of inorganic phosphorus is 20% based on phosphorus pentoxide), add 21g of dolomite powder (the content of magnesium oxide is 20% and the content of calcium oxide is 30%) to every 100g of potassium dihydrogen phosphate crystallization mother liquor at 45℃, stir and dissolve, and then use the resulting 1210g of mixed liquid for later use.

[0040] (2) Add 28wt% ammonia water dropwise to the mixture in step (1) according to the dosage of 3.5g per 100g potassium dihydrogen phosphate crystallization mother liquor and stir. Then add 28ml of 30wt% potassium hydroxide solution to adjust the pH to 9. Continue stirring for 2.5h and let stand for 1.5h. Then filter under the condition of 38℃ and collect 470g filter cake for later use.

[0041] (3) Take all the filter cake from step (2), i.e. 470g, add 1880ml of phosphoric acid with pH 4 and 5wt% according to the mass-volume (g:ml) ratio of 1:4, then pulp, filter, and collect 1990mL of liquid phase and 358g of solid phase for later use.

[0042] (4) Take all the solid phase from step (3), i.e., 358g, and wash it with deionized water to obtain 212g of wet filter cake (moisture content 33.2%). Dry it with hot air at 45℃ for 12h under normal pressure to obtain 141.6g of magnesium ammonium phosphate hexahydrate product. The purity of the product was determined by chemical titration to be 97.8%, and the yield was 89.4% based on the effective magnesium component of the system.

[0043] (5) Take 1990 mL of the liquid phase from step (3), add 52 g of 20 wt% lime milk to adjust the pH to 7, concentrate at -0.08 MPa and 85 ℃ to obtain 920 mL of liquid with a Baume degree of 40, then cool to 25 ℃ for crystallization and filtration, collect a total of 179.4 g of wet filter cake (33.5% moisture) and dry at 70 ℃ for 3.0 h to obtain 119.3 g of dicalcium phosphate dihydrate product. The purity of the product was determined by chemical titration to be 97.5%, and the yield was 87.2% calculated based on the available phosphorus components in the liquid phase of step three.

[0044] To better demonstrate that the process method of the present invention has good technical effects, the following comparative examples are given with reference to Example 2, and the specific experimental data are detailed in Table 1.

[0045] Comparative Example 1

[0046] Unlike Example 2, in step (1), 10.5g of dolomite powder was added to every 100g of potassium dihydrogen phosphate crystallization mother liquor, and the rest of the operation was the same.

[0047] Comparative Example 2

[0048] Unlike Example 2, in step (1), 23g of dolomite powder was added to every 100g of potassium dihydrogen phosphate crystallization mother liquor, and the rest of the operation was the same.

[0049] Comparative Example 3

[0050] Unlike Example 2, in step (2), 2g of ammonia water was added to every 100g of potassium dihydrogen phosphate crystallization mother liquor, and the rest of the operation was the same.

[0051] Comparative Example 4

[0052] Unlike Example 2, in step (2), 4g of ammonia water was added to every 100g of potassium dihydrogen phosphate crystallization mother liquor, and the rest of the operation was the same.

[0053] Comparative Example 5

[0054] Unlike Example 2, in step (2), potassium hydroxide solution was used to adjust the pH to 8, while the rest of the operation was the same.

[0055] Comparative Example 6

[0056] Unlike Example 2, in step (2), potassium hydroxide solution was used to adjust the pH to 9.5, while the rest of the operation was the same.

[0057] Comparative Example 7

[0058] Unlike Example 2, in step (2), stirring was continued for 1 hour, and the rest of the operation was the same.

[0059] Comparative Example 8

[0060] Unlike Example 2, in step (2), stirring was continued for 3 hours, while the rest of the operation was the same.

[0061] Comparative Example 9

[0062] Unlike Example 2, in step (2), the sample was left to stand for 0.8 hours, while the rest of the operation was the same.

[0063] Comparative Example 10

[0064] Unlike Example 2, in step (2), the sample was left to stand for 1.8 hours, while the rest of the operation was the same.

[0065] Comparative Example 11

[0066] Unlike Example 2, step (2) involves heat preservation and filtration at 30°C, while the rest of the operations are the same.

[0067] Comparative Example 12

[0068] Unlike Example 2, step (2) involves heat preservation and filtration at 40°C, while the rest of the operations are the same.

[0069] Comparative Example 13

[0070] Unlike Example 2, in step (5), lime milk was added to adjust the pH to 4, and the rest of the operation was the same.

[0071] Comparative Example 14

[0072] Unlike Example 2, in step (5), lime milk was added to adjust the pH to 8, and the rest of the operation was the same.

[0073] Comparative Example 15

[0074] Unlike Example 2, in step (5), the temperature was lowered to 18°C ​​for crystallization, while the rest of the operation was the same.

[0075] Comparative Example 16

[0076] Unlike Example 2, in step (5), the temperature was lowered to 28°C for crystallization, while the rest of the operation was the same.

[0077] Comparative Example 17

[0078] Unlike Example 2, step (5) involves drying at 75°C, while the rest of the operation is the same.

[0079]

[0080] As can be seen from Table 1, the magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate products obtained in Example 2 using the process method of the present invention are superior to other examples and comparative examples in terms of yield, efficiency, and purity.

[0081] It should be noted that the products in Examples 1-3 were verified by thermal recrystallization, as detailed below:

[0082] Thermogravimetric analysis was performed on the dried products prepared in this process. The test temperature range was 25-220℃, and the heating rate was 10℃ / min.

[0083] Magnesium ammonium phosphate hexahydrate

[0084] The sample exhibited a continuous weight loss step in the 25-220℃ range, with a measured total weight loss rate of 43.8%, which is basically consistent with the theoretical weight loss rate (44.06%) of magnesium ammonium phosphate hexahydrate removing all 6 water molecules of crystallization. There was no high-temperature decomposition weight loss, which is consistent with the characteristics of water molecule removal, proving that the product stably binds 6 water molecules of crystallization.

[0085] dicalcium phosphate dihydrate

[0086] The sample exhibited a single, continuous weight loss step in the 25-220℃ range, with a measured total weight loss rate of 20.8%, which is basically consistent with the theoretical weight loss rate (20.94%) of calcium phosphate dihydrate removing all two water molecules of crystallization. This is consistent with the characteristics of water molecule removal, proving that the product stably binds two water molecules of crystallization.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder, characterized in that, The process includes the following steps: (1) Take the mother liquor of potassium dihydrogen phosphate crystallization, add dolomite powder at a temperature not lower than 35°C, stir to dissolve, and use the resulting mixed liquid for later use. (2) Take ammonia water, add it dropwise to the mixture in step (1) and stir. Adjust the pH to not less than 8.5 with potassium hydroxide solution, continue stirring, let stand, filter, and collect the filter cake for later use. (3) Take the filter cake from step (2), add phosphoric acid and slurry it, filter it and collect the liquid phase and solid phase separately for later use; (4) Take the solid phase described in step (3), rinse and dry it to obtain magnesium ammonium phosphate hexahydrate product; (5) Take the liquid phase described in step (3), add lime milk to adjust the pH to not less than 5, and then concentrate, cool and crystallize and filter. The collected solid is dried to obtain the product of dicalcium phosphate dihydrate.

2. The process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder according to claim 1, characterized in that, The content of inorganic phosphorus in the potassium dihydrogen phosphate crystallization mother liquor in step (1) is 20% (calculated as phosphorus pentoxide); the content of magnesium oxide in the dolomite powder is 20% and the content of calcium oxide is 30%; and the amount of dolomite powder added in every 100g of potassium dihydrogen phosphate crystallization mother liquor is 13.5g-21g.

3. The process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder according to claim 1, characterized in that... Dolomite powder is added at 35-45℃ in step (1).

4. The process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder according to claim 1, characterized in that... In step (2), the concentration of ammonia water is 23-28 wt%, and the amount of ammonia water added to each 100g potassium dihydrogen phosphate crystallization mother liquor is 2.5-3.5g.

5. The process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder according to claim 1, characterized in that... In step (2), the concentration of potassium hydroxide solution is 30wt%, the pH is adjusted to 8.5-9, stirring is continued for 1.5-2.5h, then it is allowed to stand for 1.0-1.5h, and then filtered under the condition of 32-38℃.

6. The process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder according to claim 1, characterized in that... In step (3), phosphoric acid with a pH of 3-4 and 2-5 wt% is added and then pulped. The filter cake and phosphoric acid are added in a mass-volume ratio of 1:3-4.

7. The process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder according to claim 1, characterized in that... In step (4), deionized water is used for rinsing, and hot air drying at 40-45℃ is used for 12-16 hours under normal pressure.

8. The process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder according to claim 1, characterized in that, In step (5), the concentration of lime slurry is 15-20 wt%, and the pH is adjusted to 5-7.

9. The process for co-producing magnesium ammonium phosphate hexahydrate and calcium hydrogen phosphate dihydrate using potassium phosphate solution and dolomite powder according to claim 1, characterized in that, In step (5), the solution is concentrated to the endpoint at -0.06 to -0.08 MPa and 80-85°C. The solution is measured at 36-40°C by a Baumé meter. Then, the solution is cooled to 20-25°C for crystallization. The collected solid is dried at 60-70°C for 3-4 hours.

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