Method for purifying low-grade natural gypsum or gypsum tailings by recrystallization

Abstract

The invention relates to the field of preparation of high purity gypsum and particularly relates to a method for purifying low-grade natural gypsum or gypsum tailings by recrystallization. The method provided by the invention mainly comprises the following six steps: crushing; screening; dissolving; crystallizing; washing; and drying. The method specifically comprises the following steps: crushing and screening the low-grade natural gypsum or gypsum tailings; then, adding the low-grade natural gypsum or gypsum tailings into an acid at special solubility; heating to a certain temperature till the low-grade natural gypsum or gypsum tailings is / are fully dissolved; carrying out solid-liquid separation to remove undissolved solid phase impurities while the solution is hot; cooling, recrystallizing a liquid phase at a relatively low temperature and carrying out solid-liquid separation; and washing and drying a filter cake to obtain the high purity gypsum. The liquid phase in the dissolving and crystallizing processes can be repeatedly used. According to the method provided by the invention, proper raw material granularity, solid liquid ratio, temperature and acid concentration are selected and the raw materials are dissolved and crystallized for a certain time to prepare gypsum with relatively high purity, so that the grade or performance of the gypsum is remarkably improved.

Description

technical field

[0001] The invention relates to the field of high-purity gypsum preparation, in particular to a method for recrystallizing and purifying low-grade natural gypsum or gypsum tailings. Background technique

[0002] Natural gypsum is one of the advantageous minerals in China. The proven reserves are 100 billion tons, ranking first in the world. With the rapid development of my country's construction industry and building materials industry, the demand for gypsum is increasing. The purity requirements are also getting higher and higher. At the same time, high-grade gypsum resources are gradually decreasing, so the full development and utilization of low-grade gypsum or gypsum tailings resources has been paid more and more attention. However, the low-grade natural gypsum or gypsum tailings have complex impurity components, poor gradation, and low purity, which creates obstacles for the resource utilization of low-grade natural gypsum or gypsum tailings. If the gyp...