SU1027140A1 - Method of producing cryolite - Google Patents

Abstract

METHOD FOR OBTAINING CRYOLITE by treating a solution of alumium fluoride with a sodium reagent, followed by separating the precipitate of cryolite from the mother liquor by filtration, working out cryolite with soda and calcining it, so that, in order to obtain a product of uniform composition and to simplify the process technology, the cryolite is treated with 25% -30% soda solution at 70-100 s at the filtration stage.

Description

The invention relates to the production of cryolite (in particular, to the production of cryolite from hydrofluoric acid or hydrofluoric acid. A method is known for producing cryolite by reacting aluminum fluoride solution with soda, separating and calcining the precipitate. A solution of fluoride aluminum is obtained by neutralizing hydrofluoric acid hydrochloric acid with alkmini hydroxide and separating silica gel. Soda is used both in crystalline formj and in the form of mother liquors from the production of aluminum fluoride, containing 2-3% AtF. The disadvantage of this method is low, the modulus of the product obtained. Practically, a product with a modulus of 1.5 is not obtained due to a sharp deterioration in the filterability of the sediment and the quality of cryolite. The closest to the technical essence of the invention and the achieved result is a method for obtaining cryolite, in which to increase the cryolite module of the product, the solution of aluminum fluoride is worked up with sodium reagent, the precipitate of cryolite is separated from the mother liquor by filtration, the resulting cryolite is dried with soda in crystalline form, homo The resulting mixture is gendered and calcined at 300-600 ° C 2. A disadvantage of this method is the complexity of the process of homogenizing the wet sludge with dry soda. Cryolite sediment usually has a high moisture content (up to 45%), it sticks to the walls, freezes, as a result of which it is difficult to dose it into the mixer. Therefore, the cryolite-soda mixture and, ultimately, the finished product are heterogeneous in composition even in one batch. The purpose of the invention is to obtain a homogeneous product and simplify the process technology. The goal is achieved by the method of obtaining cryolite by treating a solution of aluminum fluoride with a sodium reagent, followed by separating the precipitate of cryolite from the mother liquor by filtration, processing cryolite with soda and calcining it, processing cryolite with 25-30% soda solution at TO-OO C at the stage of filtration. To prepare the soda solution, use the filtrate after separating the cryolite precipitate. The indicated lower limits of the change in the concentration and temperature of soda before feeding it to the mixing are due to the degree of completion of the reaction. The interaction of soda with cryolite precipitate: the lower the specified parameters, the lower the degree of completion of the process. Increasing the upper limits is not feasible for technological reasons: the process design is complicated. Example 1. Cryolite is obtained by a known method. 100 kg / h of cryolite precipitate with a humidity of 40% and 9 kg / h of soda with a content of 98% of the basic substance are fed into the mixer. Cryolite has the following composition (in dry matter), wt.%: F 53.8, Na 22.1, RS 17.3; cryolite module 1.5. The resulting mixture is fed to an oven, where it is calcined at 48 ° -5OO C. Sampling is carried out after 30 minutes. V. table.1 shows the composition of the selected samples of the finished product. As can be seen from the above data, the composition of the product is heterogeneous at the exit from the furnace: the cryolite modulus ranges from 1.81 to 2.57. EXAMPLE 2 Cryolite is obtained by the proposed method. 400 kg / hr of suspension of cryolite with T: W 1: 3, obtained by the interaction of a solution of fluorine alcumini with soda, are fed to the filtration. Cryolite has traceability composition (in dry matter), wt.%: F 53.6, Na 19.8, AC 20.1; module 1.32. Simultaneously with the cryolite suspension, 68 kg of a 25% soda solution are fed to the filtration, the solution temperature is 70 ° C. The precipitate is separated from the mother liquor and sent to calcination. The mother liquor is used to prepare soda solution. Oven samples were taken after 30 minutes. In tab. 2 shows the composition of the selected samples of the finished product. The proposed method allows to increase the technological process by eliminating the stages of mixing the reagents and homogenizing the cryolitho-soda suspension in solid form and obtaining a rhyolite with an increased modulus of uniform composition. The economic effect of the introduction-. and a method at an enterprise with a capacity of one installation of 2500 tons of rhyolite per year will be about 75 thousand. Ub.

Table 1

52.2 47.1 52.4 50.7 48.2

48.6 48.5 48.7 48.6 48.6

1.81

16.9 2.57 14.9 1.86 16.2

2.15 16.1 2.49 15.6

table 2

2.16

18.2 2.12 18.1 2.14 18.3 2.17 18.0 2.13 18.2

Claims (1)

METHOD FOR PRODUCING CRYOLITE by treating a solution of aluminum fluoride with a sodium-containing reagent, followed by separating the cryolite precipitate from the mother liquor by filtration, working out the cryolite with soda and calcining it, so that in order to obtain a product with a uniform composition and simplifying the process technology, cryolite is treated with a 25-30% soda solution at 70-100 ° C at the filtration stage.