Tin recovery from a low-grade tin middling with high Si content and low Fe content by reduction—sulfurization roasting with anthracite coal

Abstract

A new method for separating and recovering tin from a low-grade tin middling with high Si content and low Fe content by roasting with anthracite coal was researched by studying the reaction mechanism and performing an industrial test, in which the Sn was sulfurized into SnS(g) and then collected using a dust collector. The Fe-Sn alloy may be formed at roasting temperatures above 950°C, and like the roasting temperature increases, the Sn content and Sn activity in this Fe-Sn alloy decrease. Also, more FeS can be formed at higher temperatures and then the formation of FeO-FeS with a low melting point is promoted, which results in more serious sintering of this low-grade tin middling. And from the thermodynamics and kinetics points of view, the volatilization of the Sn decreases at extremely high roasting temperatures. The results of the industrial test carried out in a coal-fired rotary kiln show that the Sn volatilization rate reaches 89.7% and the Sn is concentrated in the collected dust at a high level, indicating that the Sn can be effectively extracted and recovered from the low-grade tin middling with a high Si content and low Fe content through a reduction—sulfurization roasting process.