SU1414775A1 - Method of defluorinating wet-process phosphoric acid - Google Patents

Abstract

The invention relates to a process for the Purification of an extraction phosphoric acid (EPA) from impurities of fluorine compounds during its evaporation and can be used in the production of fertilizers and feed phosphates. The aim of the invention is to intensify and simplify the process while maintaining a high degree of defluorization. The defluorination of EPA is carried out by the introduction into it of hydroxyethylidene diphosphonic acid in an amount of 0.5-1.0 mol per 1 mol of aluminum, which is in acid, followed by evaporation and trapping of off-gases. The degree of evaporation reaches 93%. The amount of silica gel reduced in the absorption apparatus decreases, the quality of the acid increases due to a decrease in the content of insoluble impurities. 1 tab. (/)

Description

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The invention relates to a method for the purification of extraction phosphoric acid (EPA) from impurities of fluoride compounds during its evaporation and may be - SO. used in production of fertilizers; and feed phosphates. : The aim of the invention is; process simplification and increasing the degree of | defluorization .tO

: EXAMPLE 1 Weigh of EPA obtained from apatite concentrate and containing I,%: Pjp5 24.4; 0.23; I SOj 1.58; CaO 0.22; F 1.2, evaporated in portions of not more than 100 g at 100-105 C in a column of fluoroplast: Blowing acidic heated air through the first layer of acid to a concentration of 58%. The process is carried out in three ways: in the absence of defluorizing additives, in the presence of -. 20 VII 1.5 kg of SiO-2 per 1 kg of fluorine (white carbon) and when dissolved in EPA, hydroxyethylidene diphosphonic acid (HEDP) in an amount of 1 mol per 1 mol of aluminum (9.3 g of HEDP per 1 kg of solution), 25 which is administered before evaporation. The mass fraction of fluorine in the evaporated acid samples is 0.29, 0.24 and 0.21%, respectively. The degree of defluorization is 90.92, 30% and 93%, respectively. A tube with a diameter of 5 mm, through which sucking of fluorine-containing gases, is carried out, is filled with silica gel during evaporation without additives after 8 cycles, in

P-jOf concentration of 50% phosphoric acid derived from phosphate, containing,%: V-iOg 27.1;

, 3 2.2; MgO 1.76; AljOj 1.3; F 1.45. The residual fluorine content in the acid after evaporation without additives of refluxing reagents is 1.10%, with additives as in Examples 1-2, 0.80% F (in the process according to a known method) and 0.62% F (process according to the proposed method). The degree of defluorization is respectively 59, 70 and 77%.

Example Under the conditions described in example 1, model phosphoric acid solutions containing 45% P-iOf, 0.5% F (as HF) and different amounts of aluminum, and HEDP OR white carbon black are evaporated to

Pl05

58%.

The results of the experiments are given in the table.

From the data of the table, it follows that in the absence of aluminum, the degree of defluorization during refilling is high (84), in the presence of aluminum and with the addition of silicon dioxide, the degree of defluorization decreases (/ 69%). With the introduction of HEDP, the degree of defluorination increases,. At a molar ratio of HEDP: A1 less than 0.5, the degree of defluorination during heat treatment of EPA becomes low. When the amount of HEDP is more than 1 mole per

the presence of silica gel in EPA (35 ° process — degree of defluorization of cy-according to a known method) —through 5 cycles; in the presence of HEDPH — after 10 cycles. Reduced driving in comparison with process in the absence of Additives

Does not increase significantly.

The invention allows to reduce the amount of silica gel deposited in the ducts and absorbers, and to reduce

due to the increase in relative 49 fluorine in one stripped off acid

fractions of HP and mixtures of HF and SiF4 as a result of the binding of aluminum into strong complexes with HEDP and the destruction of fluoroaluminium compounds in the solution of EPA.

by 12-40%. In addition, one stripped off acid does not contain a suspension of silicon compounds. Products based on EPC contain less harmful impurities.

According to the known method of extraction, ds, HEDP additive improves consumer

Any phosphoric acid (29%, 2% F) is evaporated to a concentration of P 05-45%, the fluorine content is 0.8%. Then silica is introduced in the amount of 051-2.0% of the mass of the starting acid and evaporated to 50% PQ05, fluorine content 0.07%. Silicon dioxide consumption 0.79 kg per 1 kg of fluorine in the acid intermediate concentration. The degree of defluorination is 98%. Silica, which is introduced in excess, contaminates the production acid.

Example 2. Under the conditions described in example 1, evaporated to con 50

55

properties of feed means and fertilizers.

Claims (1)

Invention Formula A method of defluorinating phosphoric acid extraction, including evaporation of the acid in the presence of a defluorising additive, followed by trapping of waste gases, characterized in that, in order to simplify the process and increase the degree of defluorization, oxyethylidene di-SO is used as an additive. tO 15 . 20 25 30 47752 P-jOf concentration of 50% phosphoric acid derived from phosphate, containing,%: V-iOg 27.1; , 3 2.2; MgO 1.76; AljOj 1.3; F 1.45. The residual fluorine content in the acid after evaporation without additives of refluxing reagents is 1.10%, with additives as in Examples 1-2, 0.80% F (in the process according to a known method) and 0.62% F (process according to the proposed method). The degree of defluorization is respectively 59, 70 and 77%. Example Under the conditions described in example 1, model phosphoric acid solutions containing 45% P-iOf, 0.5% F (as HF) and different amounts of aluminum, and HEDP OR white carbon black are evaporated to concentration Pl05 58%. The results of the experiments are given in the table. From the data of the table, it follows that in the absence of aluminum, the degree of defluorization during refilling is high (84), in the presence of aluminum and with the addition of silicon dioxide, the degree of defluorization decreases (/ 69%). With the introduction of HEDP, the degree of defluorination increases,. At a molar ratio of HEDP: A1 less than 0.5, the degree of defluorination during heat treatment of EPA becomes low. When the amount of HEDP is more than 1 mole per  ° —the degree of defluorization is not substantially increased. The invention allows to reduce the amount of silica gel deposited in the ducts and absorbers, and to reduce  fluorine in one stripped off acid by 12-40%. In addition, one stripped off acid does not contain a suspension of silicon compounds. Products based on EPC contain less harmful impurities. additive eddc improves consumer properties of feed means and fertilizers. Invention Formula A method of defluorinating phosphoric acid extraction, including evaporation of the acid in the presence of a defluorising additive, followed by trapping of waste gases, characterized in that, to simplify the process and increase the degree of defluorization, hydroxyethylidene diene is used as an additive, 31414775 phosphonic acid in the amount of 0.5% in acid, and addition of 1.0 mol per 1 mol of aluminum, containing before evaporation.