SU420565A1 - METHOD OF OBTAINING EASILY FILTERED FLUORITE CALCIUM - Google Patents

Description

one

This invention relates to the production of fluoride salts, in particular, to the field of calcium fluoride.

A known method for producing easily filtered calcium fluoride from hydrofluoric acid solutions. According to this method, milk of lime is added to an aqueous solution of hydrofluoric acid (in the amount of 120-150% of stoichiometrically necessary, the pH of the medium is up to 10. To the formed calcium fluoride suspension, an aqueous solution of soda ash is added.

This method, however, has a greater efficiency in the process of settling the precipitate, since the size of its individual particles does not exceed 0.02 microns. The sedimentation rate of the suspension we exceeds 0.1–0.3 m / h, and the filtration rate 20–50 kg / h m. In addition, the product is contaminated with calcium carbonate and silica.

In the proposed method, instead of the known milk, a suspension of potassium carbonate (chalk pulp) is used. Pr, and this 1 aqueous solution of hydrofluoric acid will enter the chalky slurry, setting the reaction mixture at the level of 2-3.

As a result, the precipitated calcium fluoride precipitate settles and flutters much faster than it is observed, in

known method. In particular, the retraction rate does not reach 1 M / h, and the filtration rate is 500 g / h m. In addition, the resulting product is not contaminated with impurities.

Hydrofluoric acid is taken in an amount of PO-120% of the required amount. As aqueous solutions of hydrofluoric acid, predominantly used are aqueous solutions obtained by

absorption of waste fluorine-containing gases of phosphate processing. The hydrofluoric acid content in this solution is about 2%. In addition, the solution contains 0.12-0.72% fluorosilicic acid.

The ratio of t: g in the chalky zero should be 1: 3-1; 10. The reaction is carried out at 40-80 ° C. Example. To 1200 kg of chalky pulp

With stirring at 70 ° C, 5,700 kg of an aqueous solution containing 114 kg of hydrofluoric acid and 20.7 kg of hydrofluoric acid are added with stirring. As a result of the interaction of reagents

222.3 kg of calcium fluoride containing 2.2 kg of silica introduced with iron and 0.465 kg of a solution containing 26.5 1 kg of calcium fluorofluoride are obtained.

Sediment settling rate 0.82 m / h;

The rate of fnltratsni in terms of dry 3 sediment weight is 288 kg / hour m. The precipitate contains 96.2% calcium fluoride and 0.93% silicon dioxide. The subject of the invention. About obtaining an easily filtered fluoride-calcium by reacting (a hydrofluoric solution of hydrofluoric acid with a calcium-containing suspension, which, in order to accelerate the process of settling and improve the quality of the product, calcium calcium Entering an aqueous solution of hydrofluoric acid in its suspension until the pH of the reaction mixture reaches 2-3.