SU929141A1 - Method of crystallizing salts out of solutions - Google Patents

Description

I

The invention relates to methods for obtaining a large-crystalline product from salt solutions and can be used in the chemical, food and metallurgical industries.

A known method for the crystallization of salts from solutions by evaporating the solvent from the circulating suspension involves mixing the initial solution with the circulating suspension, heating the mixture and boiling to form secondary vapor. This method is widely used in evaporating and self-evaporating crystallizers with natural and forced circulation of the suspension Ll The disadvantage of this method is the impossibility of obtaining a crystalline product.

The closest to the proposed by the technical nature of the method is the crystallization of salts from pacTi thieves by evaporation of the solvent,

involving mixing the circulating suspension with superheat by a mixture of the initial and clarified mother liquors and boiling the resulting mixture 2,

The disadvantage of this method is due to the fact that when the superheated mixture of the initial solution and the clarified mother liquor is mixed with the circulating suspension and the newly obtained mixture is transported to the boiling zone, the growing crystals come into contact with the unsaturated solution. This leads

15 to partially dissolve the crystals and increase the supersaturation of the solution in the boiling zone, as a result of which the efficiency of the crystallization process decreases and the bulk of the final product decreases, and consequently its quality deteriorates.

The purpose of the invention is to improve the quality of the crystalline product 3 and the efficiency of the crystallization process. The goal is achieved by the method of salt crystallization from solutions, which includes mixing the circulating suspension with a superheated mixture of the original and clarified mother liquor and boiling the newly obtained mixture, mixing the circulating suspension with the superheated mixture in the boiling zone. Entering the suspension directly into the supersaturation creation zone eliminates the contact of the production crystal with the superheated, unsaturated mixture, which ensures continuous growth of crystals throughout the entire volume of the circulating suspension. The process technology is as follows. The original solution is mixed with the clarified mother liquor, and the superheated mixture is fed to evaporation under vacuum. A circulating suspension is also introduced into the boiling zone, where it is mixed with the boiling mixture. The result is

Size of crystals, mm

More than 1.6

More than 1.0 More than 0.63 More than 0, More than 0.25 Content by a known method, wt.%

0,

, 0

The content of the proposed method, May.

0.8

22.3 The granulometric composition of the product obtained by the proposed method fully complies with the requirements of GOST 9097-7 for the highest grade crystalline ammonium sulfate in which the content of the fraction less than 0.25 mm is allowed to be no more than 5%; The granulometric composition of the product obtained in a known manner meets the requirements of this GOST for ammonium sulfate of the first type. At present, coking plants currently produce ammonium sulphate, 60 of which, in terms of their grain size distribution, corresponds to the highest grade and AO to first grade. According to the proposed method

83.9

91.8

WOULD

80.0

98.5

Claims (2)

96.3 4 crystals, which are withdrawn in the form of the finished product, the mother liquor and condensate solvent. PRI me R. 1 m of the initial saturated ammonium sulphate solution with a temperature, density of kg / m and a content of 48.3 masad of ammonium sulphate is fed to the crystallization. The initial solution is pre-mixed with 12 m of a clarified mother liquor having a temperature of iiSc and a concentration of 45.3 wt.% Ammonium sulfate, and then the mixture is fed into the boiling zone under vacuum at 5 ° C. 86 m of the circulating suspension is also fed to the boiling zone of the mixture and bulk solids content. The result is 102 kg of ammonium sulfate crystals, 43 kg of condensate and 1100 kg of mother liquor. The resulting ammonium sulfate crystals are withdrawn as a finished product. The test results for the proposed and known method are presented in the table. Sob the whole product corresponds to the highest grade. Save from using the proposed method will be 2 rubles. in the production of 1 ton of ammonium sulfate. Claims. The method of crystallization of salts from solutions, which includes mixing the circulating suspension with the superheated mixture of the initial and clarified mother liquor and boiling the resulting mixture, characterized in that, in order to increase the efficiency of the process and improve the quality of the crystalline product, the mixture of the circulating suspension with the superheated mixture is carried out in the boiling zone. 59291 1 Sources of information. M., 1968, p. 210-220; taken into account in the examination. . 2. USSR author's certificate 1. Matusevich L.N. Crystallization N 239224, cl. At 01 D 9/00, 1967 from solutions in the chemical industry, 5 (prototype).