SU1018904A1 - Process for producing superphosphoric acid - Google Patents

Abstract

METHOD FOR OBTAINING SUPERFOS. HFORNIC ACID, including evaporation of phosphoric acid at elevated temperatures; in the presence of an additive, characterized in that, in order to reduce energy consumption and to obtain a product with a concentration of 63-66% and a polymerization degree of 15-40%, directly used in the manufacture of liquid complex fertilizers, evaporation is carried out at 160210 ° C, and as an additive take the mineral salts of ammonium or ammonium 6-amount of 2-10% by weight of acid in terms of apoto.

Description

The invention relates to a method for producing superphosphoric acid containing ortho and polyphosphoric acids and used in the manufacture of liquid complex fertilizers. Superphosphoric acid is obtained by concentrating one stripped extractive orthophosphoric acid containing 50–54%. A known method for producing superphosphoric acid t is by evaporation of extraphosphoric acid (25–55% P at a temperature of more than 120 ° C and a pressure less than or equal to 1 AT. An acid is obtained containing 69 -79% PjOs, with 2-30% P, 0 being in the form of polyphosphoric acids. The product also contains 1-10% impurities that are not precipitated due to the presence of polyphosphoric acids. To reduce the freezing temperature, 0.5- 3% with It is ammonium. For the preparation of liquid complex fertilizers (LCU), the acid is preliminarily diluted with water 1. The disadvantage of this method is increased energy consumption due to the high evaporation temperature - 260 s, as well as the insufficiently high content of polyphosphoric acids and the need to dilute the acid before producing fertilizer. a close technical solution - and the achieved result of the invention is a method for producing superphosphoric acid by evaporation by thermal or extraction thermal Coy phosphoric acid content up to 75% at iZ J. in the presence of potassium permanganate, taken in an amount of 0.510%. Superphosphoric acid is obtained, containing 77.5-79.5% of which 68-89.5% is in polyform 2. The disadvantages of this method are the use of expensive thermal or extraction-thermal phosphoric acid, increased energy costs (1500-1800 kcal / kg evaporated water), due to the increased evaporation temperature, as well as the impossibility of obtaining superphosphoric acid with the required degree of polymerization (not less than 15%) when sticking extraction phosphoric acid. The purpose of the invention is to reduce energy consumption and to obtain a product with a P2 content of 5-63-66% and a polymerization degree of 15-40%, which is directly used in the production of liquid coxtlex. fertilizer. The goal is achieved by the fact that according to the method, which involves evaporation of phosphoric acid at elevated temperature in the presence of an additive, evaporation is carried out at 160210 ° C, and mineral salts of ammonium or ammonia are taken in the amount of 2-10% by weight of acid in terms of nitrogen . The differences of the invention are the temperature regime, the additive and its consumption. These differences also allow to reduce energy consumption to 900-1100 kcal / kg of evaporated water, fuel (natural gas) consumption from 115130 to 30-60. The minimum concentration of superphosphoric acid, ammonium phosphate (10-34-0 LCU) is 63 -64% RLow when the degree of polymerization is not less than 15%. The introduction of ammonium and ammonia salts accelerates the polymerization of phosphoric acid. The effect of evaporation temperature, ammonia and ammonia consumption on the preparation and the properties of the product — superphosphoric acid, are presented in Table 1. From the data given in Table. 1, it follows that when ammonium or ammonia salts are consumed less than 2%, the degree of polymerization of phosphoric acid is low and the product is unsuitable for the production of liquid fertilizers. Consumption of more than 10% leads to the formation of a precipitate. When the process temperature is less than 160 ° C, the total concentration of P is not necessary to obtain liquid fertilizers. At a temperature above 210 ° C, the energy consumption increases without improving the quality of the product. As ammonium mineral salts, ammonium sulfates and nitrates are used. Example 1. In a bubbling airlift type concentrator with a capacity of 30,000 kg a day is fed with 1.3 evaporated orthophosphoric acid with a concentration of 52%, previously saturated with gaseous ammonia, calculated to 5 kg of ammonia nitrogen per 100 kg of acid. The same concentrator serves flue gases with a temperature of 900s and a speed of 35 m / s at a fuel consumption of 35 kcal / 1t with which the acid heats up to 170 ° C. At this temperature, the residence time of the acid in the concentrator is 40 s. The result is 1.1 MV superphosphoric acid containing 63.7% PjOy, while 15.9% P2 Oj is in the form of a polyform. The degree of polymerization is 25%. The specific heat consumption in this case is 1060 kcal / kg of evaporated water. Example 2. Ammonium sulfate is introduced into one stripped off ortho-phosphoric acid concentration of 51-52% PjOg in a bubbly-type fire park with a capacity of 950 kg. at the same time, 2500 flue gases are consumed (800-9 oO C) at a speed of 35-40 m / s. The results of evaporation to obtain superphosphoric acid are presented in table. 2.,.

From the resulting 63–64% superphosphate acid mixtures, liquid complex fertilizers with nitrogen content are obtained with a conversion degree of Pj Oj equal to 45-48%,

The invention will reduce the cost of producing 1 ton of superphosphoric acid by 18.3 rubles.

Table 1.

1.5

170

52

1010

63.7

Not suitable for utilities

Claims (1)

) METHOD FOR PRODUCING SUPERPHOSPHORIC ACID, including evaporation of phosphoric acid at elevated temperature in the presence of an additive, characterized in that, in order to reduce energy consumption and obtain a product with a concentration of P * Og of 63-66% and a degree of polymerization of 15-40% directly used in production liquid complex fertilizers, evaporation is carried out at 160210 ° C, and as an additive they take mineral salts of ammonium or ammonia · 2 · 10% of the weight of the acid in terms of nitrogen.