Chloridizing Roasting of Complex Material Containing Low Tin and High Iron at High Temperature

摘要

The compositions of the equilibrated gas phases of the chloridizing reactions of Sn, Pb, Zn, Cu, In, Cd, Bi and As oxides with CaCl2 and MgCl2 as chlorinating agent, the thermal decomposition reaction of FeAsO4 and the reduction reaction of the iron phase were calculated, and log PCO2/PCO - log PMeC12 - T diagrams were drawn. Bench-scale chloridizing roasting tests were carried out under various conditions of atmosphere, temperature, type and amount of chlorinants and burden composition. The starting sticking temperatures of more than 100 burdens were measured. The data obtained were processed by mathematical statistics, diagrams of the degree of iso-volatilization and volatilizing speed of various elements being drawn, and empirical formulae and nomograms for calculating the sticking temperature of the burdens were summarized. On the basis of these results the proper conditions for chloridizing roasting were determined. Scale-up and pilot-plant tests (1/day) were carried out under the defined process conditions. In these tests the degree of volatilization of metals was Sn>97%, Pb>99%, Zn 70-80%, As 90-97% and In, Bi and Cd>85%. The grades of tin and lead concentrates were better than 50%, and the recoveries of Sn and Pb were 85-88% and >90%, respectively. The contents of impurities in the roasted pellets containing 48-54% Fe could basically meet the blast-furnace requirements. Therefore, it is concluded that recoveries from the beneficiation and smelting of tin and comprehensive extraction of valuable elements can be improved by use of this process for the treatment of complex material containing low tin and high iron.