Sodium Cyanide Generation by Coal Gasification

Abstract

This study investigates the technological feasibility of producing sodium cyanide through coal gasification, focusing on the influence of key process parameters—temperature, reaction duration, and coal type—on the concentration of sodium cyanide in the resulting solutions. Experiments were conducted on a laboratory-scale setup featuring a tubular corundum furnace. Lignite and charcoal, pre-crushed to increase specific surface area, were used as carbon sources. Sodium cyanide was obtained by capturing hydrocyanic acid (a syngas component) through sorption in a sodium carbonate solution. Absorption was enhanced by using a NaOH solution (pH = 10) maintained in an ice bath. Sodium cyanide concentration in the solution was determined using a titrimetric method, while thermodynamic simulations were performed using HSC Chemistry 5.1.

Gasification of charcoal within the 600–800 °C range yielded sodium cyanide concentrations between 0.03–0.08 wt%. However, raising the temperature to 900 °C under identical experimental conditions resulted in a fourfold decrease in NaCN concentration. A regression equation was derived to describe the dependence of NaCN concentration on gasification temperature and process duration. The findings confirm that sodium cyanide concentrations achieved under laboratory conditions are comparable to those required for gold cyanidation in gold recovery plants. Implementing on-site sodium cyanide generation at mining facilities could significantly reduce production costs by eliminating the need for external procurement, transportation, and storage of reagents.