Zinc smelting with coal as the principal heat source and reducing agent

Recent progress in fluidized bed coal combustion and gasification suggests possibilities for the substitution of coal for coke in metallurgical smelting processes. One such possibility was ex-plored in a laboratory study of zinc smelting with coal. A two-stage reactor was constructed, which gasified coal in the lower stage to produce a reducing gas mixture. In the upper stage, the reducing gas was passed through a fixed bed containing a mixture of ZnO and either coal or coke. The extent of reduction of the ZnO was measured as a function of reaction time, temperature, and gas composition. Temperature was found to be the most important variable. At temperatures of 1000 °C or higher in the fixed bed, more than 97 pct of the ZnO was reduced in a few hours. No difference was found between the uses of coal and coke in the fixed bed. An important remaining step in proving process feasibility is condensation of metallic Zn from the product gas.