SU432113A1 - METHOD OF OBTAINING AMMOPHOS - Google Patents

Description

I

This invention relates to a process for the production of ammophos, used as a nitrogen-phosphate fertilizer.

Known process for the preparation of ammonium phosphate by decomposition of phosphate rock in an excess of ammonium fluoride is dissolved with filtering the resulting slurry to a mixture of fluoride and ammonium phosphate, followed by separating the resulting mixture into marketable product- ammonium phosphate, ammonium fluoride and calcium fluoride, which is processed on a calcium compound and fluoro returned to the stage of decomposition of apatite.

The proposed method differs from the well-known fact that calcium fluoride is treated with ammonium sulfate solution at 370-410 ° C, with an ammonium sulfate rate of 1.5-2, followed by separation of ammonia and hydrogen fluoride, which are sent for absorption by ammonium fluoride solution obtained by separating mixtures of phosphates and ammonium fluorides.

This difference contributes to an increase in the yield of a marketable product and a more complete use of the feedstock, since it makes it possible to conduct the process in a closed cycle.

Example. The decomposition of apatite concentrate in an excess of ammonium fluoride and the separation of a mixture of dissolved fluoride and ammonium phosphates was carried out in accordance with the description in the author. St. N ° 214550. The ammonium fluoride solution obtained from the separation of ammonium salts is directed to absorb ammonium fluoride, which is formed by treating calcium fluoride with ammonium sulfate, and then to washing calcium fluoride. The washing solution is fed to the decomposition of apatite.

Calcium fluoride, washed with a solution containing 45% NH4F, is mixed with circulating ammonium sulfate. The resulting mixture is subjected to heat treatment when

370 ° C for 1.5-3 hours at a rate of ammonium sulfate 1.5-2, followed by separation of ammonia, hydrogen fluoride and solid acidic sulphate residue. The mixture of gases is passed through a solution of ammonium fluoride,

obtained by separating dissolved NH4F and H2O without at the same time absorbing NHa (solution temperature 80-90 ° C). After absorption of NH4F, gas is mixed with gas from the decomposition reactor of apatite and fresh ammonia.

(introduced from the outside to the formation of pro.t, ukta - ammophos) and transferred to the ammonia carbonate conversion of the sulphate residue into calcium carbonate and ammonium sulphate.

Carbonate-sulphate conversion of acidic

the sulphate residue in the aqueous solution is carried out by sparging carbon dioxide and ammonia. The removal of ammonium sulfate solution must be carried out until the content of the crystal suspension-saturated solution {NH4) 2SO4 in the system is more than 34% water: this water content is due to the resulting concentration of ammonium fluoride solution (at least 45% NH4F).

Calcium carbonate, after washing the residues of ammonium sulfate, can be removed from the process or subjected to heat treatment to produce lime (CaO) as a product and return to the C02 cycle. In the latter case, the product withdrawn from the process contains (in kg per 1000 kg of the initial apatite concentrate):

CaO512

SaR (PO4) s20

SaRa30

CaSO412

574 kg

Subject invention

The method of obtaining ammophos by decomposing apatite in an excess of dissolved ammonium fluoride with filtration of the obtained suspension into a mixture of fluoride and ammonium phosphate with the following separation of the obtained mixture is a marketable product — ammonium phosphate, ammonium fluoride and calcium fluoride, which is recycled ammonia; apatite, characterized in that, in order to increase the yield of the commercial product and more fully utilize the original

Calcium fluoride feedstock is treated with ammonium sulfate solution at 370-410 ° C with an ammonium sulfate rate of 1.5-2, followed by separation of ammonia and hydrogen fluoride, which are sent for absorption by the ammonium fluoride solution obtained by separating a mixture of phosphates and ammonium fluorides.