Electric arc furnace dust is generated as a result of the remelting of automobile scrap in an electric arc furnace (EAF). Typically, the major metal values in the dust are zinc and iron, but numerous other metals can be present, some of which are hazardous. Recycling of the dust for metal recovery has a number of advantages and in this paper, the differential speciation of the metals via chlorosulphation was investigated. The process was simulated using a thermodynamic model, which was developed using the Equilibrium module of HSC Chemistry® 7.1. The effects of operating parameters, on the equilibrium compositions of the reaction products were determined and the optimum conditions were established. At a temperature of 800 °C, 95% of the zinc oxide was converted to gaseous zinc chloride, containing less than 1% iron. About 90% of the calcium oxide was converted to calcium sulphate and 98% of the iron could be retained as iron oxide. These thermodynamic results provide a framework for future experimental test work.