SU570547A1 - Method of preparing phosphoric acid - Google Patents

Description

(54) METHOD FOR OBTAINING PHOSPHORIC ACID

one

The invention relates to the field of extraction of phosphoric acid, used for the production of mineral fertilizers.

A known method of producing extraction phosphoric acid by sulfuric acid decomposition of phosphate raw materials in the presence of circulating pulp and phosphoric acid in the dihydrate mode with crystallization of calcium sulfate dihydrate and separation of the latter from phosphoric acid on vacuum filters 1.

Due to the uneven distribution of sulfuric acid in the volume of the reaction pulp, poorly filtered calcium sulfate dihydrate crystals are formed.

A known method of producing extraction phosphoric acid by pre-mixing sulfuric and circulating phosphoric acids, decomposing the resulting mixture of phosphate raw materials, for example, in the hemihydrate mode, cooling the resulting pulp in vacuum evaporators and filtering calcium sulfate hemihydrate precipitate. Filtration capacity for dry draft is 900 2.

There is also known a method for producing extraction phosphoric acid by preliminarily mixing sulfuric and circulating phosphoric acids, decomposing the resulting mixture of phosphate raw materials, for example, in the dihydrate mode, cooling the resulting slurry with air, and filtering the resulting precipitate of calcium sulfate dihydrate. The acid feed rate to the mixing stage is 3 m / s. 80-100 thousand of air and its subsequent purification from fluoride compounds is needed to cool the pulp. Filtration capacity for dry sediment is 650-700 3.

The disadvantage of this method is the low productivity of the filtration stage, which does not allow to intensify the process as a whole.

In order to increase the filtration rate of the proposed method, circulating phosphoric acid is fed to the mixture at a speed of 5-10 m / s, preferably 7 m / s, sulfuric acid at a speed of 7-25 m / s,

preferably 15 m / s, and the mixture of acids is cooled with air, which is supplied in the amount of 5-15 thousand MV4, and before decomposition the phosphate raw material is mixed with water at a water supply rate of 5-15 m / s, preferably

12 m / s

These differences make it possible to increase the filtration capacity from 650–700 to 760–800 for the dihydrate process and from 900 to 1000 for the hemihydrate process and simplify the flow chart.

process by reducing the working volumes of the absorption system.

Example 1. In the mixer of the film type, mounted on the lid of the extractor, 19.5 t / h of 93% sulfuric acid are fed at a speed of 15 m / s and 56.5 t / h of circulating phosphoric acid at a speed of 7 m / s. The film of the mixture of acids is cooled with air supplied in (Amount 12 thousand. In another mixer, also installed on the lid of the extractor, 20 t / h of apatite and 8 t / h of water are fed at a speed of 12 m / s. The reaction temperature in the extractor is 75 ° C, the concentration of PcB and C30 in the liquid phase of the pulp is 30 and 2.5%, respectively.The resulting pulp, containing phosphoric acid and calcium sulfate dihydrate, is cooled in a vacuum evaporator and fed to a filter for separation. em 800.

Example 2. In the film-type mixer mounted on the lid of the extractor, 19.5 t / h of 93% sulfuric acid are fed at a speed of 15 m / s and 44.5 t / h of circulating phosphoric acid at a speed of 10 m / s. The acid mixture film is cooled with air supplied in the amount of 10 thousand. In another mixer, also installed on the lid of the extractor, 20 t / h of apatite and 8 t / h of water are fed at a speed of 12 m / s. The reaction temperature in the extractor is 98 ° C, the concentration of PcB and C30 in the liquid phase of the pulp is 40 and 1%, respectively. The resulting slurry is cooled in a vacuum evaporator and fed to a filter for separation. Filtration capacity is 1000.

Example 3. In the cyclone-type mixer mounted on the lid of the extractor, serves 19.5 t / h 93% acid at a rate of

18 m / s and 56.5 t / h of circulating phosphoric acid at a speed of 10 m / s. Yield sh.yu on a cyclone mixture of acids is cooled with air supplied in the amount of 15 thousand. 20 t / h of apatite and 8 t / h of water at a speed of 15 m / s are fed to another cyclone type mixer, also installed on the lid of the extractor.

Next, the process is conducted as indicated in example 1.

Filtration performance is 780.

Claims (3)

1. A method of producing phosphoric acid by mixing sulfuric and circulating phosphoric acids, decomposing the phosphate raw material with this mixture and separating the product from the precipitate by filtration is distinguished by the fact that, in order to increase the filtration rate, recycled phosphoric acid is fed into the mixture at a rate of 5-10 m / s, preferably 7 m / s, sulfuric acid at a speed of 7-25 m / s, preferably 15 m / s, and the mixture of acids is cooled with air, which is served in an amount of 5-15 thousand, and the phosphate raw material is mixed with water at a water flow rate s 5-15 m / s, preferably 12 m / s. P1 sources of information taken into account in the examination 1.Volfkovich S.I. et al. Proceedings of the PFSP, vol. 153, 1940, p. 12. 2.Dahlgren S.E., R. Hakansson. Acta Polytechn. Scand ch. 52 (1966). 3. Kopylev B. A. Technologists of extraction phosphoric acid. L., “Himi 1972, p. 173-175.