Method for preparing feed-grade calcium hydrophosphate from raffinate acid

Abstract

The invention discloses a method for preparing feed-grade calcium hydrophosphate from raffinate acid, which comprises the following steps of: mixing alkali liquor D and raffinate acid, reacting, filtering after the reaction to obtain filtrate A and a filter cake E, and using the filter cake E for producing compound fertilizer, ammonium phosphate, superphosphate or rich calcium, and reacting the filtrate A with the calcium slurry, filtering after the reaction is finished to obtain a filtrate B and a filter cake C, returning the filtrate B to prepare an alkali liquor D, and finally drying and packaging the filter cake C to obtain the feed-grade calcium hydrogen phosphate. The method is simple in process, the value of the raffinate acid is increased, and the method is very convenient for actual production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical production, and particularly relates to a method for preparing feed-grade calcium hydrogen phosphate (DCP) from raffinate acid. BACKGROUND

[0002] The purification technology of wet-process phosphoric acid includes extraction, crystallization, electrodialysis, ion exchange and adsorption, etc., wherein the extraction is the most mature and the only industrialized purification method. A large amount of raffinate acid can be obtained after the solvent extraction of wet-process phosphoric acid, and the raffinate acid has high impurity content, large viscosity and low utilization rate, but the w(P2O5) can reach 45% or even higher. How to improve the utilization rate of the raffinate acid is a problem to be solved at present.

[0003] At present, the treatment of the raffinate acid at home and abroad mostly adopts the method of producing fertilizer ammonium phosphate, and the products mainly include fertilizer-grade and industrial-grade ammonium dihydrogen phosphate (MAP) and fertilizer-grade diammonium hydrogen phosphate (DAP). For the enterprises that have already owned the ammonium phosphate production equipment, this treatment method has high economy, but still has losses. Therefore, how to effectively improve the utilization value of the raffinate acid has become a technical problem to be solved in the phosphorus chemical industry.

[0004] Based on this, the present application is developed. SUMMARY

[0005] The application aims to overcome the defects of the prior art and provide a method for preparing DCP from raffinate acid. The method removes the metal ions in the raffinate acid by using alkali liquor or circulating alkali liquor, and then reacts with calcium slurry to prepare feed-grade calcium hydrogen phosphate.

[0006] To achieve the above-mentioned purpose, the application adopts the following technical scheme: A method for preparing DCP from raffinate acid, which mixes alkali liquor D with raffinate acid and then reacts, filters after the reaction is completed to obtain filtrate A and filter cake E, the filter cake E is used for producing compound fertilizer, ammonium phosphate, common calcium or calcium-rich; the filtrate A is reacted with calcium slurry, filters after the reaction is completed to obtain filtrate B and filter cake C, the filtrate B is returned to be used for preparing alkali liquor D, and finally the filter cake C is dried and packaged to obtain feed-grade calcium hydrogen phosphate. Specifically, all the reactions can be carried out at 40-80 DEG C for 0.5-3 hours.

[0007] Further, the alkali liquor can be at least one of ammonia water, potassium hydroxide and sodium hydroxide solution. The filter residue can be sent to diammonium and compound fertilizer devices or dried and sold separately.

[0008] Further, the pH value of the system in which the alkali liquor D is added and mixed with the raffinate acid for reaction is 2.0-4.0.

[0009] Specifically, the raw material of the calcium slurry can be at least one of calcium oxide, calcium hydroxide, and calcium carbonate, that is, the calcium slurry raw material is mixed with water to obtain the calcium slurry.

[0010] Further, the mass fraction of the calcium slurry can be 5%-30%. The calcium slurry is added to a system with a pH value of 5.0-7.5, where the system refers to a mixed system of the filtrate A and the calcium slurry.

[0011] Further, the filtrate B is all recycled into the lye D and mixed with the raffinate acid for reaction. The lye D can not contain the filtrate B in the first reaction.

[0012] Further preferably, the raffinate acid is a raffinate phase phosphoric acid byproduct of a wet-process phosphoric acid solvent extraction process, with a P2O5 content of 30%-50% and a MER value of 0.13-0.18. The MER value is the ratio of the sum of the contents of the oxides of aluminum, magnesium, and iron (MgO, Fe2O3, and Al2O3) in the raffinate acid to the content of the phosphorus pentoxide in the raffinate acid.

[0013] Further preferably, the P2O5 content in the slurry after the lye D is mixed with the raffinate acid for reaction is controlled to be 5%-15%. The MER value of the filtrate A is 0.06-0.10. The MER value is the ratio of the sum of the contents of the oxides of aluminum, magnesium, and iron (MgO, Fe2O3, and Al2O3) in the filtrate A to the content of the phosphorus pentoxide in the filtrate A.

[0014] The method for preparing DCP from raffinate acid of the application neutralizes and removes impurities in the raffinate acid to prepare feed-grade dicalcium phosphate.

[0015] Compared with the prior art, the method has the following advantages: 1) The lye used in the application can effectively separate the impurity metal ions in the raffinate acid; 2) The lye and the calcium slurry used in the application have a small addition amount and low cost, and are easy to add and suitable for industrial application; 3) The method of the application can use the raffinate acid to prepare DCP, which is simple in process and low in cost, and is very convenient for actual production. BRIEF DESCRIPTION OF DRAWINGS Figure 1 The process flowchart of the method of the application is shown in the figure. DETAILED DESCRIPTION

[0016] The technical solutions of the application are further described in detail below in combination with examples, but the protection scope of the application is not limited thereto.

[0017] Unless otherwise specified, the percentages used in the application are mass percentages.

[0018] In the following examples, the raw materials used are all ordinary commercially available products that can be purchased directly unless otherwise specified. For example, the used raffinate acid comes from a certain phosphorus chemical enterprise.

[0019] Example 1 A method for preparing DCP from raffinate acid is as follows: 48% P2O5raffinate acid (MER value is 0.17) 100g, add 200g water and stir evenly, add 38g lye (25% ammonia water) dropwise until pH reaches 3.1, react at 50°C for 1 hour, wash with 90g washing water and filter, obtain filtrate A and filter cake E, filter cake E is used to produce compound fertilizer, ammonium phosphate, general calcium or calcium-rich; add calcium slurry (26% CaO) to filtrate A (MER value is 0.09) until pH is 7, react at 50°C for 2 hours, filter, obtain filtrate B and filter cake C, filtrate B is returned to prepare lye, and filter cake C (80g, yield 81.56%) after drying meets the detection standard of feed-grade dicalcium phosphate (DCP).

[0020] The DCP product meets the national standard GB 22549-2017 Feed Additives Dicalcium Phosphate, the total phosphorus content is 17.51%, the water-soluble phosphorus content is 10.01%, the calcium content is 22.48%, the fluorine content is 1610mg / kg, the arsenic content is 0.41mg / kg, the lead content is 2.12mg / kg, the cadmium content is 0.67mg / kg, and the chromium content is 28.3mg / kg. It meets the requirements of type I feed-grade dicalcium phosphate in the standard.

[0021] Example 2 A method for preparing DCP from raffinate acid is as follows: 39% P2O5raffinate acid (MER value is 0.15) 100g, add 160g water and stir evenly, add 36g lye (25% ammonia water) dropwise until pH reaches 2.9, mix and react at 70°C for 1.5 hours, wash with 90g washing water and filter, obtain filtrate A and filter cake E, filter cake E is used to produce compound fertilizer, ammonium phosphate, general calcium or calcium-rich; add calcium slurry (27% CaO) to filtrate A (MER value is 0.10) until pH is 7.3, react at 70°C for 2 hours, filter, obtain filtrate B and filter cake C, filtrate B is returned to prepare lye, and filter cake C (80.49g, yield 86.27%) after drying meets the detection standard of feed-grade dicalcium phosphate (DCP).

[0022] The DCP product meets the GB 22549-2017 national standard for feed additives dicalcium phosphate, with a total phosphorus content of 16.60%, a water-soluble phosphorus content of 9.67%, a calcium content of 20.55%, a fluorine content of 1700 mg / kg, an arsenic content of 0.36 mg / kg, a lead content of 1.17 mg / kg, a cadmium content of 0.10 mg / kg, and a chromium content of 21.4 mg / kg. It meets the I-type feed-grade dicalcium phosphate index requirements in the standard.

[0023] Example 3 A method for preparing DCP from residual acid is as follows: 42% P2O5 residual acid (MER value of 0.14) 100g, add 160g water and stir evenly, add 50.5g alkali (20% calcium hydroxide) dropwise until pH reaches 3.8, mix at 60°C for 3 hours, wash with 90g washing water and filter to obtain filtrate A and filter cake E, filter cake E is used to produce compound fertilizer, ammonium phosphate, general calcium or calcium-rich; add calcium slurry (30% calcium carbonate) to filtrate A (MER value of 0.06) until pH is 5.9, react at 60°C for 2 hours, filter to obtain filtrate B and filter cake C, filtrate B is returned to prepare alkali, and filter cake C (79.56g, yield 80.41%) after drying meets the detection standard of feed-grade dicalcium phosphate (DCP).

[0024] The DCP product meets the GB 22549-2017 national standard for feed additives dicalcium phosphate, with a total phosphorus content of 16.60%, a water-soluble phosphorus content of 9.67%, a calcium content of 20.55%, a fluorine content of 1700 mg / kg, an arsenic content of 0.36 mg / kg, a lead content of 1.17 mg / kg, a cadmium content of 0.10 mg / kg, and a chromium content of 21.4 mg / kg. It meets the I-type feed-grade dicalcium phosphate index requirements in the standard.

[0025] Example 4 A method for preparing DCP from residual acid is as follows: 35% P2O5 residual acid (MER value of 0.16) 100g, add 160g water and stir evenly, add 45g alkali (30% calcium hydroxide) dropwise until pH is 3.6, mix at 80°C for 2.5 hours, wash with 90g washing water and filter to obtain filtrate A and filter cake E, filter cake E is used to produce compound fertilizer, ammonium phosphate, general calcium or calcium-rich; add calcium slurry (20% calcium carbonate) to filtrate A (MER value of 0.07) until pH is 6.5, react at 80°C for 2 hours, filter to obtain filtrate B and filter cake C, filtrate B is returned to prepare alkali, and filter cake C (80.89g, yield 83.39%) after drying meets the detection standard of feed-grade dicalcium phosphate (DCP).

[0026] The DCP product meets the GB 22549-2017 national standard for feed additives, calcium hydrogen phosphate, with a total phosphorus content of 18.01%, a water-soluble phosphorus content of 10.13%, a calcium content of 23.60%, a fluorine content of 1550 mg / kg, an arsenic content of 0.49 mg / kg, a lead content of 1.78 mg / kg, a cadmium content of 0.45 mg / kg, and a chromium content of 25.6 mg / kg. It meets the standard for type I feed-grade calcium hydrogen phosphate.

Claims

1. A process for the preparation of feed grade dibasic calcium phosphate from raffinate acid, characterized by, The filtrate A and filter cake E are obtained after mixing the lye D with the raffinate acid and carrying out the reaction, and filtering after the reaction is completed, the filter cake E is used for producing compound fertilizer, ammonium phosphate, common calcium or calcium-rich; the filtrate A is reacted with calcium slurry, the filtrate B and filter cake C are obtained after filtering after the reaction is completed, the filtrate B is returned for preparing the lye D, and finally the filter cake C is dried and packaged to obtain the feed-grade calcium hydrogen phosphate.

2. The process for preparing feed grade dibasic calcium phosphate from the raffinate acid as claimed in claim 1, wherein, All the reactions are carried out at 40-80℃ for 0.5-3 hours.

3. The process for preparing feed grade dibasic calcium phosphate from the raffinate acid as claimed in claim 1, wherein, The lye contains at least one of ammonia water, potassium hydroxide and sodium hydroxide solution.

4. The method for preparing feed-grade dicalcium phosphate from residual raffinate as described in claim 1, characterized in that, The pH value of the system in which the lye D is added and mixed with the raffinate acid for reaction is 2.0-4.

0.

5. The method for preparing feed-grade dicalcium phosphate from residual raffinate as described in claim 1, characterized in that, The raw material of the calcium slurry is at least one of calcium oxide, calcium hydroxide and calcium carbonate.

6. The method for preparing feed-grade dicalcium phosphate from residual raffinate as described in claim 1, characterized in that, The mass fraction of the calcium slurry is 5%-30%. The calcium slurry is added to the system with a pH value of 5.0-7.

5.

7. The method for preparing feed-grade dicalcium phosphate from residual raffinate as described in claim 1, characterized in that, The filtrate B is recycled into the lye D and mixed with the raffinate acid for reaction, and the lye D can not contain the filtrate B in the first reaction.

8. The process of claim 1, wherein the feed grade dibasic calcium phosphate is prepared from the raffinate acid. The raffinate acid is the raffinate phase phosphoric acid produced in the process of solvent extraction of wet-process phosphoric acid, the P2O5 content is 30%-50%, and the MER value is 0.13-0.18, the MER value is the ratio of the sum of the contents of the oxides (MgO, Fe2O3 and Al2O3) of aluminum, magnesium and iron in the raffinate acid to the content of P2O5 in the raffinate acid.

9. The method for preparing feed-grade dicalcium phosphate from residual raffinate as described in claim 1, characterized in that, The P2O5 content in the slurry in which the lye D is mixed with the raffinate acid for reaction is controlled to be 5%-15%.

10. The process of claim 1, wherein the feed grade dibasic calcium phosphate is prepared from the raffinate acid. The MER value of the filtrate A is 0.06-0.10, and the MER value is the ratio of the sum of the contents of the oxides (MgO, Fe2O3 and Al2O3) of aluminum, magnesium and iron in the filtrate A to the content of P2O5 in the filtrate A.

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