SU632673A1 - Method of obtaining complex fertilizer - Google Patents

Description

I

This invention relates to a process for producing a complex fertilizer based on the nitric acid decomposition of a phosphate raw material.

A method of producing a complex fertilizer is known by decomposing the phosphate stock with nitric acid, followed by freezing the calcium nitrate formed. The resulting solution is subjected to step ammonization first to a pH of 2-2.5, and then to pH 6. The residue of calcium nitrate is removed by treating the solution with ammonium sulfate and separating the phosphogypsum ij

There is also known a method for producing a complex fertilizer by decomposing phosphate raw materials with nitric acid, followed by freezing the resulting calcium nitrate, ammonizing the resulting solution to a pH of 2-2.5 and treating the neutralized solution with sulfuric acid or its salts, followed by separating the phosphogypsum 2. A disadvantage of the known methods is loss

a significant amount of phosphorus pentoxide with phosphogypsum.

The aim of the invention is to reduce the loss of phosphorus pentoxide with phosphogypsum.

The goal is achieved by the fact that, in the CSE method of producing complex fertilizer, which includes decomposition of natural kaly1iy phosphate with nitric acid, separation of part calcium from liquid decomposition products in the form of calcium nitrate crystalline hydrate, precipitating phosphates of rare-earth elements from the nitrogen-phosphate by neutralizing calcium to neutralization of phosphates of rare-earth elements from an acidic solution by neutralizing calcium to hydrate of calcium nitrate by neutralizing phosphate of rare-earth elements from a nitrogenous solution of calcium nitrate by hydration of calcium nitrate in the form of crystalline hydrate. 5, processing the neutralized solution with sulfuric acid and / or its salts, separating the phosphogypsum precipitate from the mother liquor and processing the latter into the target product using known techniques , for treatment with sulfuric acid and / or its contacts, the SO-8O% of the waste stream of the neutralized solution is taken, and the resulting suspension is treated with the remaining amount of the solution.

The positive effect is explained by the fact that during the deposition of phosphogypsum by the proposed method, the probability of coprecipitation of dicalcium phosphate with phosphogypsum, apparently, is significantly reduced.

Example. The sample was taken from a sample of a neutralized to pH 1.39 raRTOR obtained on an experimental pilot plant as a result of the replenishment of apatite with nitric acid, the removal of strontium-containing sludge, the crystallization of calcium nitrate by 90% and the precipitation of rare earth elements phosphate with ammonia, containing% by mass:

Phosphorus thioxide 23,3

Calcium2,2

Fluoro 0.27

REE, O7

From 780 g of this solution, a part of it (390 g) is mixed in a reactor at 60 ° C with 101 g of 389fe-Horo ammonium sulfate solution and 15 g of 9% sulfuric acid. The consumption of sulfation and is 102 mass. % of stoichiometry based on total experience

solution. The resulting suspension is mixed with the remaining amount of the nonralized solution (390 g) at 6 ° C. After stirring for 15 minutes, the suspension is filtered on a vacuum filtrate, the precipitate of phosphogypsum on the filter is washed with water, taken in an amount of 2OO g. The weight of the washed precipitate is 82 g, the content of phosphorus pentoxide in it is 1.1 mass. % (loss of phosphorus pentoxide with phosphogypsum is 0.5 wt.%, taken from. with a neutralized solution).

The filtrate and the washings are combined. The weight of the resulting solution 101O g, the content of phosphorus pentoxide in it is 17.9 masses. % The resulting solution is processed into a nitroammofosk by known methods (neutralization to pH fc 5, addition of ammonium nitrate, evaporation, addition of potassium chloride and drying of the melt) to obtain 107 O g of the desired product. The content of phosphorus pentoxide is 16.9 wt.

The results of this and other experiments on the proposed method are shown in the table.

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Claims (2)

This is the table showing the results of the experiment performed under the conditions of iipoTirrHna, i.e. without treatment of ammonium sulfate and sulfuric acid part of the neutralized solution (experiment No. 8). As can be seen from the data presented in the table, the proposed method makes it possible to reduce the loss of phosphorus pentoxide with phosphogypsum compared with the prototype by an average of 1.6 times. The invention of the method of obtaining complex distillation by decomposing the phosphate raw material with zothic acid, separating the calcium nitrate formed by freezing, ammonizing the resulting solution to a pH of 2-2.5 and treating the neutralized solution with sulfuric acid or its salts, followed by separating the formed phos phypsum and dissolving the solvent. the fact that, in order to reduce the loss of phosphorus pentoxide with phosphogypsum, the treatment with sulfuric acid or its salts is carried out in 3080% of the neutralized solution of the total flow, and ohm suspension treated remainder of the solution. Sources of information taken into account in the examination: i- Romanian patent number 52446, cl. With OBB. 24.04.71. т. 76, № 3. 2. Baseline data and basic technical solutions for the design drawings for fertilizer production buildings 501-502, 1976 Inv. № 562, p. 4-20.