Studies on the kinetics of slurry chlorination of a sphalerite concentrate by chlorine gas

Abstract

Studies on the chlorination of a sphalerite concentrate in aqueous slurry by gaseous chlorine have been carried out. The effect of time, flow rate of Cl₂, partial pressure of Cl₂ in N₂ (p_Cl2) particle size and pulp density of the sulphide concentrate and the temperature of chlorination, on the fraction of the zinc dissolved, has been investigated. At the optimum flow rate of Cl₂ (350 ml min^-1), the percent of Zn dissolved is found to be increasing with decrease in particle size and pulp density, proportional to p_Cl2 (0.2 to 1.0 atm) and increases with increase in temperature in the range of 10 to 28° C, studied. The activation energy of the chlorination process has been calculated to be 49.6 kJ mol^-1. In all the cases, the fraction of the Zn dissolved (a) in time (t) is found to follow a diffusion reaction control model: 1-2/3a-(1-a)^2/3=kt, where k is the rate constant. At 28° C, with 12 wt.% concentrate in the slurry and using pure Cl₂ gas with a flow rate of 350 ml min^-1, nearly 90% of Zn extraction has been achieved in about 17 min.