METHOD FOR OBTAINING PURIFIED MONOAMMONIUM PHOSPHATE FROM ONE STRIPPED OFF EXTRACTION PHOSPHORIC ACID Russian patent published in 2021 - IPC C01B25/28 C05B7/00 

FIELD: chemical technology.

SUBSTANCE: invention relates to chemical technology and technology for producing mineral fertilizers, specifically to a method for producing purified monoammonium phosphate from one stripped off extraction phosphoric acid. The method includes dilution of the extraction phosphoric acid with water, sequential ammonization of this acid in several stages, filtration of the ammonized pulp with separation of impurity precipitate, evaporation of the filtered ammonium phosphate solution, crystallization of monoammonium phosphate by cooling the solution and separation of monoammonium phosphate crystals from the mother liquor by centrifugation followed by mother liquor together with impurity sludge for the production of complex fertilizers. The method is characterized in that the ammonization of the diluted extraction phosphoric acid is carried out sequentially in three stages in three successively installed ammonizers 5, 9 and 15, and at in the second and third stages in ammonizers 9 and 15, ammonization is carried out with gaseous ammonia 10 and 16 to pH 2.5-3.0 and 5.0-5.5, respectively, at a temperature of 60-90°С. At the second and third stages of ammonization, the initial streams 8 and 14 are mixed with the streams 11 and 17 circulating in the ammonizers 9 and 15 in a mass ratio of 1: (30-60) with a mass content of the solid phase in the circulating stream of 5-25% and a residence time 1-1.5 hours at each stage, followed by holding for 1-2 hours in tanks 12 and 18. After the third stage of ammonization, the ammonized slurry 20 is fed to the filtration stage 21, at which the impurity precipitate 22 is separated, and the filtered solution of ammonium phosphates 25 is evaporated into evaporator 26 to a mass concentration of monoammonium phosphate 45-55% at a temperature of 90-105°С. One stripped off solution 29 is fed for crystallization into crystallizer 30, cooled to 30-40°С and crystals of monoammonium phosphate 35 are separated by centrifugation. The mother liquor 36 is divided into two parts in the tank 39, the first part 6, which is 60-85% solution by weight, is fed to the first ammonization stage in the ammonizer 5, and the second part 23, together with the impurity precipitate 22, is fed to the production of complex fertilizers.

EFFECT: proposed method allows increasing the degree of use of raw materials, improve the quality of the finished product and reduce costs.

3 cl, 1 dwg, 1 ex