SU1063798A1 - Process for producing phosphorus fertilizers - Google Patents

Abstract

1. A method of producing phosphorus fertilizers, including the decomposition of phosphoric raw materials with phosphoric acid, granulation, drying of the product and the subsequent purification of waste gases from dust and fluorine, characterized in that in order to increase the yield of the product product and reduce the release of fluorine in the gas phase, phosphoric the acid is pre-mixed with monocalcium phosphate, taken in an amount of 0.9-14 wt.% by weight of phosphoric acid, and mixing is carried out for 2-15 minutes.

Description

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The invention relates to a method for producing mineral fertilizers.

A known method of producing fertilizer by decomposing phosphate phosphate with phosphoric acid at a concentration of 50% PjOj, granulating, drying the product, and purifying waste gases from fluorine and dust.

The disadvantage of this method is the need to preliminarily evaporate phosphoric acid, and then, when granulating, to introduce water or steam. As a result, during granulation and drying, a product containing PjOjAe 43% is obtained, and the yield of the product fraction does not exceed 65%. -.

The closest in technical essence and the achieved result to the proposed is a method of obtaining phosphate fertilizers, including the decomposition of phosphate raw materials with phosphoric acid, granulation, drying of the product and the subsequent purification of waste gases from dust and fluorine. According to this method, the decomposition is carried out with phosphoric acid of a concentration of 27-30%, and the purification of gases - with water and hydrofluoric acid with a subsequent neutralization of wastewater 2.

The resulting product contains 4,345%. The disadvantage of the method is that the yield of the product product fraction (particle size 1-3 mm) does not exceed 65%. In addition, up to 50% of the fluorine introduced into the gas phase is released into the gas phase which entails the need to use large volumes of absorption equipment.

The purpose of the invention is to increase the yield of product fractions and

reduction of fluoride release into the gas phase.

This goal is achieved by the fact that according to the method of obtaining phosphoric; fertilizers, including decomposition of phosphate raw materials with phosphoric acid, granulation, drying of the product and subsequent purification of waste gases from dust and fluorine, phosphoric acid is pre-mixed with monocalcium phosphate, taken in an amount of 0.9-14 wt.% by weight of phosphoric acid, and mixing lead for 2-15 minutes

At the same time, a suspension of phosphoric acid with moncalcium phosphate can be prepared by washing the waste gases with phosphoric acid.

The essence of the method is that when preparing a suspension of monocalcium phosphate in phosphoric acid, the reaction of Ca proceeds (using fluorine contained in phosphoric acid to form fluoride and calcium hexafluorosilicate, which drastically reduces the elasticity of the K2SiF vapor over the phosphoric acid solution. pure phosphoric acid, a significant amount of fluoride in the feedstock, as a result of the strong heating of the mass, is released into the gas phase before the formation of monocalcium phosphate. Laga decomposition method vedets feed at a constant presence of calcium phosphate, which leads to the binding of fluorine and reduce its release into the gas phase.

The mixing time of the reagents was chosen based on the completeness of the reactions indicated.

The table shows the dependence of the amount of fluorine emitted into the gas phase in time of mixing the reactants

The amount of fluorine in the gas phase,% of that introduced with the feedstock

The amount of monocalcium phosphate in all the experiments listed in the table is 7% by weight of phosphoric acid. As can be seen from the table, a decrease in mixing time of less than 2 minutes is not beneficial, since a decrease in the degree of fluoride release in the gas phase is insignificant compared with the control experiment. An increase in the mixing time of more than 15 minutes in the future does not affect the decrease in the release of fluorine compounds.

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In the READY product there are products of the reaction of monocaly, iphosphate with fluorine, which favorably affects the output of the product fraction (particles 1-3 mm in size).

The dependence of the yield of commodity FoCation on the time of the mixing of monocalcium phosphate with phosphoric acid, the amount of the added monocalcium phosphate 3%, the mixing time the yield of the commodity components, min fraction,%

170

275

5 7

80 85 85 85 85

10 15 17

The dependence of the yield of the commodity fraction on the amount of mono-calcium phosphate taken:

Amount of input Output of commodity monocalcium phosphate,% fraction,%

0.775

0.980

85 85 85 85 85 75 70

Example 1. 1000 kg of phosphate are decomposed with a mixture of phosphoric acid and monocalcium phosphate (double superphosphate) containing 2166 kg,. containing 27% PjOj, 1.8% fluorine and 300 kg of monocalcium phosphate. The pulp is granulated, dried, classified and 2300 kg of finished product are obtained with a content of 44.5%.

the yield of marketable fraction of 75%.

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A suspension of phosphoric acid and monocalcium phosphate is prepared by flushing the phosphoric acid fluoride gases. Mix time 9 min. The gases obtained after decomposition, granulation and drying contain 11.5 kg of fluorine (17% of that introduced with the feedstock). In the absorption system, 120 kg of hydrofluoric acid are captured.

0

Example 2. 2500 kg of phosphoric acid composition according to example 1 is mixed for 15 minutes with 220 kg of monocalcium phosphate and decomposed with this mixture of 1000 kg of phosphate. The pulu pu is granulated, sushat and klascifi- cate. Get 2300 kg of finished product with a content of 46% PjOyijcjj. The output of the commodity fraction of 85%. Gases obtained after decomposition, drying and granulation are sent to the system.

0 absorption. They contain 11 kg of fluorine (15% of the feed with feedstock). Upon absorption, 138 kg of 10% hydrofluoric acid hydrogen fluoride are obtained.

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Using the proposed method will reduce the release of fluorine in the gas phase from 50 to 15%, which ultimately will lead to a decrease in the volume of absorption equipment

0 to 30-50%. In addition, the use of monocalcium phosphate exhaust gases for the preparation of a suspension will not only increase the utilization rate of the raw material, but also significantly

5 to improve sanitary conditions by reducing the content of dust in gases.

Claims (1)

1. METHOD FOR PRODUCING PHOSPHORUS FERTILIZERS, including decomposition of phosphorus raw materials with phosphoric acid, granulation, drying of the product and subsequent purification of exhaust gases from dust and fluorine, characterized in that, in order to increase the yield of the product fraction of the product and reduce the release of fluorine into the gas phase, phosphoric acid pre-mixed with monocalcium phosphate, taken in an amount of 0.9-14 wt.% by weight of phosphoric acid, and mixing is carried out for