SU1647000A1 - Process for preparing monoammonium phosphate - Google Patents

Description

one

(21) 4289070/26

(22) 07.24.87

(46) 07.05.91. Bul №17

(71) Leningrad Institute of Technology. Lensoveta

(72) R.Y. Zinyuk, B.D. Guller, D.G. Nagolov, A.I. Alekseev, M.A. Shapkin, L.P. Buslakova. V.A. Konkin A.M. Nazarov and Yu.D. Perevalov

(53) 631.58 (0888)

(56) USSR Author's Certificate No. 350709, cl. From 05 to 1/06. 1972.

(54) METHOD OF OBTAINING AMMOPHOS

(57) The invention relates to a technology for the production of complex nitrogen-phosphate fertilizers on osmor of phosphoric acid extraction. The purpose of the invention is to increase the degree of decomposition of natural phosphate and reduce the release of fluoride compounds in the gas phase. The method of producing ammophos is carried out by decomposing natural phosphate with phosphoric acid, previously mixed with the obtained suspension of calcium sulfate in phosphoric acid 1-6% solution of calcium dihydrogen phosphate, taken in an amount of 0.5-15.0 parts per 1 part of acid, with 60-80 ° C. with the release into the gas phase of fluorine compounds, neutralization of the resulting suspension of calcium sulfate in a phosphoric acid solution of dihydrophosphate with calcium ammonia, drying the mass in the presence of retur. tab.

This invention relates to a process for the production of complex nitrogen-phosphate fertilizers from phosphoric acid extraction.

The aim of the invention is to increase the degree of decomposition of natural phosphate and reduce the release of fluorine into the gas phase.

Example. In a stirred reactor, 40 t / h of extraction phosphoric acid (51.4% P2Os, 2.5% 503 and 0.8% F) are preferably treated at 60-80 ° C with 20-600 t / h (0.5-15 h. per 1 part of acid) calcium sulphate suspension in 1-6% phosphoric acid solution of calcium dihydrophosphate. When this occurs, the calcium dihydrogen phosphate reacts with sulfuric acid contained in one stripped off phosphoric acid, and sulphate and calcium fluoride, 60-640 tons / h, of the resulting mixture are transferred to the next reactor, where 1.5-2 are simultaneously introduced, 5 t / h of apatite concentrate (39.4% PaOs and 3% fluorine). As a result of dissolution of the latter at 70 ° C (decomposition degree 97.7- 99%), 8–16 kg / h of fluorine are released into the gas phase (0.02–0.04 parts per 100 parts of acid) and a sulfate suspension is formed. Calcium in a 1–6% phosphoric acid solution of calcium dihydrogen phosphate, part of which (20–600 t / h) is returned to phosphoric acid treatment, and the remaining amount (41.5–42.5 t / h) is fed to neutralization with ammonia. The latter is carried out in two stages: in the first stage, the pH of the mass is maintained at 2.5-2.8, then it is mixed with the retur and further neutralized in an ammoniation granulator, and then dried. The result is 40-40.9 t / h ammopho

containing 52.5–53% of assimilable P20s and 11.8–12% nitrogen.

Indicators of the stage of decomposition of natural phosphate in the dependence on the conditions of pretreatment of phosphoric acid with a suspension of calcium sulfate in a phosphoric acid solution of calcium dihydrophosphate are given in the table.

The essence of the invention is the preliminary (prior to the introduction of phosphate raw material) mixing of extraction phosphoric acid with a suspension of calcium sulfate in a 1-6% phosphoric acid solution of calcium dihydrogenphosphate, taken in an amount of 0.5-15 hours for 1 hour, acid, the mixing was carried out are at 60-80 ° C.

The following transformations proceed during the pre-mixing process.

Reaction of sulfuric acid, contained in a solution of extraction phosphoric acid, with calcium dihydrogen phosphate:

H2S04 + Ca (H2RSm) 2 + H20 -

 CaS04 -pNzO + 2NzRSm (solution).

Reaction of fluoride components contained in one stripped off extraction phosphoric acid with calcium dihydrogen phosphate.

2HF + Ca (H2P04) 2

- CaF2 + 2НзР04 (solution).

The removal of supersaturation in SaZSm-pNgO and CeP2 with the precipitation of CaS04-nH20, CaP2 and products of mixed composition tCa5CM pCaP2.

These processes take place in the absence of grains of natural phosphate, the introduction of which is carried out in the next stage, thereby preventing the slurry of the grains of the phosphate raw material and increasing its decomposition.

At the same time, as a result of pre-mixing, the precipitation of calcium fluoride and the solid phases of the mCaS04 pCaF2 composition is achieved, thus reducing the release of fluoride compounds into the gas phase without introducing any additional precipitating reagents (sodium, barium, potassium salts).

As can be seen from the data presented in the table, with preliminary mixing of phosphoric acid with 0.5-1.5 parts per 1 part of acid and calcium sulfate suspension in 1-6% phosphoric acid solution of calcium dihydrogenphosphate, the highest are achieved (97.7%). -99%) of the degree of decomposition of apatite, corresponding to those in the production of extraction phosphoric acid, and, consequently, not

an increase in the total consumption of PgOb per 1 t of P20s in ammophos.

When the content of Ca (H2PCm) 2 in the liquid phase of the suspension is less than 1%, the degree of deposition of apatite, despite its small consumption (1.4 t / h), is 95-95.5%, which is similar to that achieved by a known method (95.5% ) at the same dosage of natural phosphate. Release of fluoride to gas

0 while large (0.06 hours per 100 hours of acid). This is due to the incompleteness of CaSCM pNgO, CaPa and mCaS04-pCaF2 precipitation at the stage of mixing and crystallization of a significant part of these salts at the stage

5 decomposition of phosphate, accompanied by slimeing of the grains of the latter.

If the content of Ca (H2P04) 2 exceeds 6%, the degree of phosphate decomposition is reduced to 93.7-94.2%, which is undesirable.

0 due to an increase in the total consumption of P20b in the production of ammophos, and the release of fluorine into gas increases to 0.09 parts per 100 parts of acid. The decrease in the degree of dissection is due to a decrease in the rate of decomposition due to an increase in the content of calcium dihydrogen phosphate in the mixture entering the interaction with phosphate: an increase release of fluorine into gas is associated with the introduction of large quantities into the process.

0 phosphate raw materials.

With a low flow rate of circulating pulp (less than 0.5 h), the degree of decomposition does not exceed this indicator of the known method, while the release of fluorine in

5, the gas increases due to incomplete precipitation of salts at the mixing stage. An increase in circulation of more than 15 parts per 1 part of acid is also undesirable because of the removal of unreacted phosphate grains to ammonization.

0 Reducing the temperature below 50 ° C

This is advantageous from the point of view of a small amount of fluorine in the gas phase (less than 0.02 parts per 100 parts of acid), however, it is associated with the organization of a cooling unit for the reaction mass. An increase in temperature above 80 ° C leads to an increase in the release of fluorine, as well as to the need for heat supply from the outside. Considering the above, a temperature range of 60-80 ° C was chosen as preferred.

When carrying out the process by a known method while maintaining similar ratios between the flows of phosphoric acid and apatite, the degree of its decomposition

5 is 88.1-95.5%, and 20-40 kg / h of fluorine are released into the gas phase (0.05-0.10 parts per 100 parts of acid).

The proposed method achieves a significant increase (up to 97.7-99%) in the decomposition of natural phosphate.

(an increase of 2-11% compared with the known) and a decrease of 1.25-5 times the degree of fluoride in the gas phase.

Claims (1)

DETAILED DESCRIPTION OF THE INVENTION A method for producing ammophos, which includes decomposing natural phosphate with extractive phosphoric acid, liberating fluorine compounds in the gas phase, and neutralizing the resulting suspension of calcium sulfate in a phosphoric acid solution of calathe apatite dihydrogenphosphate (g / h) chi ammonia, drying the mass in the presence of retour, characterized in that, in order to increase the degree of decomposition of the natural phosphate and reduce the excretion fluorine compounds in the gas phase, the extraction phosphoric acid is preliminarily mixed with the resulting suspension of calcium sulfate in a phosphoric acid 1-6% solution of calcium dihydrogen phosphate until it is neutralized, taken in an amount of 0.5-15 hours for 1 hour. acid, at 60-80 ° C.