RU1810319C - Method of calcium hydrophosphate production - Google Patents

Abstract

The phosphate feed is decomposed with nitric acid, the suspension is ammoniated, the precipitate of impurities is separated by filtration, dissolved in 50-60% nitric acid, taken in an amount of 100-130% of stoichiometry on the CaO precipitate; the resulting suspension is filtered and the resulting filtrate is heated to 100-120 ° C. The finished product, calcium hydrogen phosphate, is separated by filtration, and the filtrate formed is sent to the decomposition of the phosphate feed. The yield of PrO3 in the product is increased while maintaining its quality. 1 tab.

Description

The present invention relates to techniques for the preparation of pure phosphoric salts in the nitric acid processing of natural phosphates used in agriculture and in the ceramic industry.

The aim of the invention is to increase the yield of PaOs in a product while maintaining its quality.

This goal is achieved by a known method of producing pure calcium hydrogen phosphate by nitric acid decomposition of phosphate feedstock, followed by ammonization of the suspension and separation of the precipitate of impurities and the target product by filtration, in which the precipitate is dissolved in 50-60% nitric acid, taken in

100-130% per CaO precipitate, the precipitate of impurities is separated by filtration, the filtrate is heated to a temperature of 100-120 ° C and the resulting product is separated by filtration, and the solution is sent to the decomposition step.

Significant differences of the proposed method consist in processing the precipitate containing all the phosphorus extracted into the nitric phosphate solution with 50-60% nitric acid at a temperature of 50-60 ° C, taken in an amount of 100-130% of the stoichiometry on the CaO precipitate. The resulting suspension was filtered and the precipitate of impurities was separated. The filtrate is heated to tempera - rounds of 100-120 ° C, and the resulting solid phase

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(product) was separated by filtration. The solution (filtrate) is sent to the phosphate feed decomposition step.

These differences make it possible to completely transfer PzOs to the target product by separating the precipitate of impurities at a different process design (91-93%). This is due to the fact that from the nitrogen-phosphoric acid extract, all PaOs in the process of its ammonization is converted to a precipitate, which, along with calcium phosphates, contains impurities. This precipitate then dissolves in nitric acid. Components such as PaOs and CaO are transferred to the liquid phase, and most of the impurities remain in the sediment. The solution containing calcium ions and phosphate ions is heated, and pure calcium hydrogen phosphate is released into the solid phase, the solubility of which decreases with increasing temperature, while the impurities remain in the liquid phase. The precipitate of the desired product is separated by filtration, and the filtrate is used to decompose the phosphate feed. The yield of P20b in the finished product is 91-93%.

Example 1. 100 g of phosphorite (24.7% P205, 38.5% CaO, 4.8% MdO, 3.5% P2.0z, 2.2% F, 15.7% insoluble residue) are treated with 85.6 g of nitric acid solution 87.6 g of 50% nitric acid and 100 g of washings; After the insoluble residue (58.2 g) was separated by filtration, the solution (416 g) was neutralized with 4 kg of ammonia gas to a pH of 2.5. The mass (420 g) is filtered. The filtrate (368 g) can be used as a liquid fertilizer. The precipitate (52 g) was treated with 87.6 g of 50% nitric acid (100% of stoichiometry on the CaO precipitate). The suspension is filtered and 8.6 g of a precipitate of impurities are separated. The filtrate (131 g) was heated to. temperatures of 100 ° C and the precipitated solid phase is separated by filtration. The precipitate is washed with water and, together with the filtrate, is fed to the decomposition step of the phosphate feed. The product (45.4 g) contains 51% P2Os, 40.3% CaO and 0.1-0.04% F. The yield of P20b into the finished product is 91%.

EXAMPLE 2.100 g of phosphorite are treated with 91.7 g of nitric acid solution, 65.8 g of 55% nitric acid and 100 g of washings. After separation of the insoluble residue (58.5 g) by filtration, the solution (394 g) was neutralized with 4 g of ammonia gas to a pH of 2.5. The mass (398 g) is filtered. The precipitate (51.3 g) was treated with 91.7 g of 55% nitric acid (norm 115% of stoichiometry on CaO precipitate). The suspension (143 g) was filtered and 6.3 g of a precipitate of impurities were separated. The filtrate (136.7 g) is heated to a temperature of 110 ° and

solid phytogenous precipitate (product) was separated by filtration. The precipitate is washed with water and, together with the filtrate, is fed to the decomposition step of the phosphate feed. The product of the same composition as in example 1. The yield of P20s in the finished product 93%.

Example 3. SOH phosphorite is treated with 94.8 g of nitric acid solution, 49.5 g of 60% nitric acid and 100 g of wash water. The resulting mass was filtered and after separation of 58.3 g of insoluble residue, a solution (391 g) was neutralized with 4 g of ammonia gas to a pH of 2.5. The mass (385 g) is filtered. The precipitate (51.3 g) is treated with 94.9 g of 60% nitric acid (norm 130% of stoichiometry on CaO precipitate). A suspension of 145.8 g was filtered and 6.5 g was separated. sediment impurities. The filtrate (139.3 g) was heated to a temperature of 120 ° and the precipitated

the product was separated by filtration. The precipitate is washed with water and, together with the filtrate, is fed to the decomposition step of the phosphate feed. The product (44.5 g) of the same composition as in example 1. The output of P20s in the finished product

92%.

The table shows examples of the process within the stated limits of the parameters (Example 1-3) and their lower and upper levels.

A decrease in the concentration of nitric acid (Example 4) leads to a decrease in product yield due to dilution of the solutions. An increase in the concentration of nitric acid (Example 5) and a decrease in its rate of decomposition of the precipitate (Example 6) decreases the process indicators due to the increase in the viscosity of the solutions and incomplete dissolution of the initial precipitate of calcium hydrogen phosphate.

Decreasing the rate of nitric acid (Example 7) worsens the performance of the process due to an increase in the concentration of acid e of the final suspension and, as a result, a decrease in the degree of precipitation of calcium hydrogen phosphate.

A decrease in temperature at the crystallization stage (Example 8) leads to a decrease in the yield of P2O3 in the finished product due to its incomplete isolation into the solid phase.

An increase in temperature (Example 9) is impractical due to a sharp increase in the release of nitric acid vapors and nitrogen oxides into the gas phase.

Thus, carrying out the process within the specified limits of the parameters makes it possible to increase the yield of PaOs into the target product by 11–13%.

Claims (1)

The claims A method for producing calcium hydrogen phosphate by nitric acid decomposition of a phosphate feed, followed by ammonization of the suspension and separation of the precipitate of impurities and the target product by filtration, characterized in that, in order to increase the yield of PzOs in the product while maintaining its quality, the precipitate of impurities is dissolved in 50-60% nitric acid, taken in an amount of 100-130% of stoichiometry on CaO precipitate, the resulting suspension is filtered and the resulting filtrate is heated to 100-120 ° C and the finished product is separated by filtration, and the resulting filtrate is Aulus added for decomposition of the phosphate raw material.