The extraction of cadmium from zinc-containing materials and ores by the Waelz process using oil sludge

Abstract

Methods of extraction of cadmium from ores and zinc-containing materials are considered in the article. The Waelz process of Achisai ores (0.1–0.2 % of Cd) is carried out in the presence of 45–55 % of coke from the mass of ore charge in furnaces. Up to 92–95 % of cadmium is extracted into the sublimates. The yield of sublimates is 16–18 % of the mass of the ore charge. Sublimates of the Waelz process contain from 0.05 to 1.2 % of Cd. The efficiency of the processing cadmium-containing ores and semi-products by the Waelz process largely depends on the degree of replacement of coke breeze with less expensive materials. Research results are presented, which justify the possibility of using oil sludge while the Waelz processing cadmiumcontaining materials, by calculating ΔGT 0, determined thermodynamic probability of cadmium recovery from cadmium-containing compounds in the presence of carbon, oil sludge and its constituent hydrocarbons in different temperature zones of the Waelz furnace. Due to thermodynamic modeling with the use of the software complex «Astra» there were established the equilibrium recovery degree and transition of cadmium to the gas phase, the composition of the gas phase in the temperature range of 300–1500 K and pressures of 0.05–0.5 MPa. It is established that the initial reactivity of the reductant with respect to CdO varies in a series, and with respect to CdS this series has the form: H2>CnHm>>CdSO4 >H2O>C. At high temperatures, the form of the reductant does not affect the distillation of Cd (it is > 99 % at T > 1300 K). The interaction in the system CdO-CdS-oil sludge is observed at temperature > 400 K by the reduction of Cd from CdO. Subsequently, Cd is reduced from CdS at T > 1100 K reaching maximum at T ≥ 1300 K.