INTENSIFICATION OF A BRINE PURIFICATION PROCESS IN THE OF SODA ASH PRODUCTION BY THE INTRODUCTION OF FLOCCULANTS

Abstract

This article considers the results of studying the purification of the sodium chloride brine used for manufacturing soda ash by the ammonia method. The purpose of the study was to develop a purification method involving coagulation and flocculation processes using polyacrylamide flocculants in the presence of surface-active substances as crystallization modifiers. A complex technology for purification of the brine from magnesium and calcium compounds and sulfate ions is proposed, which includes three stages for sodium chloride solutions with a high Mg²⁺ content and two stages for the brines with a low Mg²⁺content. The article contains the results of experiments to investigate the effect of the concentration of anionic polyacrylamide flocculants on the height of the clarified layer when removal of calcium and magnesium ions. The best result was achieved at using an anionic polyacrylamide flocculant Flopam AN 934 PWG at its concentration of 0.004% wt. The introduction of sodium tripolyphosphate improves the flocculating effect of the anionic polyacrylamide flocculant and increases the suspension clarification rate. The best indicators were obtained at 0.05% wt of sodium tripolyphosphate. With the simultaneous use of a cationic polyacrylamide additive Superfloc C-498 (4·10^–4% wt.) and sodium tripolyphosphate (0.05% wt.), the concentration of sulfate ions in the purified brine was 0.016 g/l; this corresponds to the purification efficiency of 99.75%. It has also been established that the use of surface-active substances in combination with polyacryamide flocculants makes it possible not only to increase the suspension clarification rate, but also to obtain the cleaner brine.