SU1675203A1 - Method of producing monoammonium phosphate - Google Patents

Abstract

This invention relates to a process for the preparation of pure phosphate salts from extraction phosphoric acid, suitable for use in the microbiological industry and agriculture. The aim of the invention is to increase the P2U5 content in the product and reduce impurities. Monoammonium phosphate is obtained by introducing calcium-containing reagent into the acid in an amount of 50–80% of the total, treating with ammonia to pH 4–5, introducing the remaining calcium-containing reagent, keeping the mixture for 20–60 minutes, separating the precipitate of impurities by filtration, evaporating the filtrate, followed by drying the suspension. These differences make it possible to obtain monoammonium phosphate with a P20s content of 57.6 - 58% and a water-insoluble residue of 0.8 - 1.05% of 1 tab.

Description

This invention relates to a process for the preparation of pure phosphoric salts from extraction phosphoric acid, suitable for use in the microbiological industry and in agriculture.

The aim of the invention is to reduce the impurity content and increase the P2Os content in the product.

Example 1. B100 kg of extraction phosphoric acid, pre-defluorinated soda (22% P20s, 0.7% CaO 0.2% F), injected 1.0 kg of CaHPCm (50% of the total mass) and treated with 5.4 kg of gaseous ammonia at 100 ° C to pH 4, then another 1 kg of dicalcium phosphate (DCF) is added and the resulting mass is kept for 20 minutes. After separating the impurities, 82.5 kg of the purified solution (20% P20s, 0.25% CaO and 0.06% F) are obtained, the purified solution is evaporated to remove 45.0 kg of water and is served

for drying. 28.6 kg of monoammonium phosphate are obtained, containing 57.6% P20s and 1% insoluble precipitate.

According to a known method, monoammonium phosphate is obtained from a defluorinated extraction phosphoric acid by introducing into a dilute acid (16-18% P20b) a calcium-containing additive (slaked lime) at a rate of 35-40 kg CaO / m3. h, the subsequent introduction of a sulfate-containing additive (sulfuric acid) at a rate of 24–30 kg 503 / m h, keeping the mixture under stirring for 20–30 min, treatment with ammonia to a pH of 5.1-5.5 at a feed rate of 130 kg Batch / m h. The pulp is filtered, the filtrate is evaporated and dried. Monoammonium phosphate contains less than 56% P20s and more than 2% impurities (water-insoluble residue).

ate with

The table shows data on the effect of process parameters on its performance.

It can be seen from the table that a decrease in the supply of calcium-containing reagent at the 1st stage to 40% leads to an increased content of the insoluble residue due to the formation of a fine-grained sediment of impurities. In addition, the degree of defluorization of the extraction phosphoric acid is reduced.

Increasing the amount of calcium-containing reagent to 90% of the total mass reduces the quality of the product due to an increase in the content of insoluble sludge due to the lack of calcium ions in the 2nd purification stage to form a large sludge.

Reducing the pH of the ammoniated slurry to 3.5 increases the insoluble residue content due to incomplete precipitation of calcium phosphate with a precipitate of impurities.

Increasing the pH of the ammoniated suspension to 5.5 is impractical because the content of PaOs in the target product is reduced due to the partial formation of diammonium phosphate in the target product.

A decrease in the exposure time of the ammoniated suspension before filtration to 10 minutes degrades the quality of the product due to the lack of time for the coprecipitation of impurities, which increases their leakage into the purified solution.

An increase in the exposure time of the ammoniated suspension prior to filtration impairs the quality of the product due to the non-destruction of the structured precipitate due to the recrystallization of calcium-containing salts, which leads to an increase in water-insoluble compounds in the target product.

A two-stage supply of calcium-containing reagent allows, in the first stage of purification of extraction phosphoric acid, to remove the oversaturation of calcium ions in the liquid phase. This technique leads to the formation of a rather large structured sediment of calcium phosphates and fluorides, which serves as an auxiliary filtering material, reducing the formation of fine sediment at the 2nd purification stage and its breakthrough during separation

sediment impurities by filtration, which ultimately reduces the amount of calcium salts in the purified solution.

Example 2. 100 kg of phosphoric acid extraction composition, as in example

1, 1.6 kg of CaHPCM (80% of the bulk) was added, treated with 6.1 kg of gaseous ammonia at 100 ° C to pH 5. Then the remaining 0.4 kg of CaHPCM was introduced and held for 60 minutes. After separation of the sediment impurities

82.6 kg of the purified solution are obtained (20% P20s, 0.3% CaO and 0.05% F). The solution is evaporated to remove 45 kg of water and served for drying. 28.7 kg of monoammonium phosphate containing 57.6% of P205 are obtained.11%

insoluble residue.

Claims (1)

Claim method for producing monoammonium phosphate from phosphoric acid extraction, including processing it with ammonia in the presence of a calcium-containing reagent to form a precipitate of impurities, separating the precipitate of impurities by filtration, removing the filtrate and subsequent drying the suspension with the formation of a product, characterized in that, in order to reduce the content of impurities and increase the phosphorus pentoxide content in the product, 50–80% of the calcium-containing reagent of the total mass is introduced into the acid before treatment with ammonia, treatment with ammonia is carried out to a pH of 4-5, then input t the remaining amount of calcium-containing reagent and the mixture is kept for 20 - 60 minutes. Table continuation