Method for purifying phosphoric acid raffinate and recovering magnesium ammonium phosphate hexahydrate

Abstract

The invention relates to a method for purifying phosphoric acid raffinate and recovering magnesium ammonium phosphate hexahydrate. According to the technical scheme, the method for purifying the phosphoric acid raffinate and recovering the magnesium ammonium phosphate hexahydrate comprises the steps that, water is added to the phosphoric acid raffinate according to the mass ratio of the phosphoricacid raffinate to water of 1 to (0.1-0.3), the mixture is stirred at room temperature for 0.5-1h, and the diluted phosphoric acid raffinate is obtained; and urea is added to the diluted phosphoric acid raffinate according to the mass ratio of the urea to the diluted phosphoric acid raffinate of (0.5-2) to1, the mixture is stirred at a temperature of 70-100 DEG C until a pH value is 5-6, the mixture is cooled, subjected to solid-liquid separation and washed to obtain iron-removing aluminum liquid and an iron-containing aluminum residue; and then the iron-removing aluminum liquid is stirred at70-100 DEG C until a pH value is 6-7, the iron-removing aluminum liquid is cooled, subjected to solid-liquid separation and washed to obtain a phosphoric acid raffinate purifying solution and the magnesium ammonium phosphate hexahydrate. The method for purifying the phosphoric acid raffinate and recovering the magnesium ammonium phosphate hexahydrate has the characteristics of short process flow,small phosphorus loss and easy recycling of metal ions.

Description

technical field [0001] The invention belongs to the technical field of phosphoric acid raffinate. Specifically relates to a method for purifying phosphoric acid raffinate and recovering magnesium ammonium phosphate hexahydrate. Background technique [0002] Phosphoric acid is an important intermediate product in the phosphorus chemical industry and is widely used in fertilizers, food, medicine and other chemical fields. The production of phosphoric acid is mainly divided into thermal method and wet method. The energy consumption of phosphoric acid produced by thermal method is high, and it is mainly used to produce high-purity and high value-added products; while the energy consumption of phosphoric acid produced by wet method is relatively low, but a large amount of impurities such as Fe, Al, Mg, etc. enter the leachate with phosphorus during the production process. , resulting in difficulty in the subsequent separation of phosphorus and impurity ions. Although the wet p...

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Problems solved by technology

The energy consumption of phosphoric acid produced by thermal method is high, and it is mainly used to produce high-purity and high value-added products; while the energy consumption of phosphoric acid produced by wet method is relatively low, but a large amount of impurities such as Fe, Al, Mg, etc. enter the leachate with phosphorus during the production process. , resulting in difficulty in the subsequent separation of phosphorus and impurity ions

Although the wet phosphoric acid solvent extraction process has significant economic benefits, there are two main problems: one is that the phosphorus is extracted during the extraction process, impurity ions are enriched, the raffinate acid has a very high viscosity, and a large amount of colloidal precipitates appear. Filtration is very difficult. Plate and frame filter presses are often used in industry, but the efficiency is low; second, raffinate still contains a certain concentration of phosphorus, which is often used to produce agricultural monoammonium phosphate or diammonium phosphate, but Fe, Al, Mg The content of impurity ions is very high, resulting in the substandard purity of subsequent phosphorus products, which brings certain difficulties to the recovery of phosphorus in raffinate

This process uses conventional neutralizer-ammonia gas to treat raffinate phosphoric acid. Although the impurity removal effect is good, there are still three problems: one is that a large amount of colloidal precipitates are generated during the impurity removal process, and the loss of phosphorus is large, generally reaching 25 ~30%; the second is that the purity of the two neutralization precipitation residues is not high, and it is difficult to comprehensively utilize the magnesium ions in the raffinate phosphoric acid; the third is to use ammonia to remove impurities, and it is difficult to prevent ammonia from escaping from the reactor during the operation process , The operating environment of the laboratory and industrial field is poor

However, the existing solvent extraction and ion exchange processes can only treat certain ions in phosphoric acid raffinate. Although it is feasible to process different impurities in stages, the process flow is long, and the phosphorus-containing intermediate products produced are relatively more, reducing the total recovery of phosphorus

[0006] In summary, the existing phosphoric acid raffinate purification technology mainly has disadvantages such as long process flow, large loss of phosphorus, and difficult recovery of metal ions.

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