Sn separation from Sn-bearing iron concentrates by roasting with waste tire rubber in N2 + CO + CO2 mixed gases.

Abstract

The waste tire rubber releases CO, H2S, SO2 and COS during pyrolysis process in N2+CO+CO2 mixed gases, which can reduce and sulfurize SnO2 to SnS thermodynamically. Correspondingly, a new process to separate Sn from Sn-bearing iron concentrates through roasting with waste tire rubbers at a relative low temperature (1273 K) is put forward in the present paper. The formation of Fe-Sn alloy restricts Sn volatilization obviously during the roasting process, and its formation mechanism differs related to roasting temperature and CO content in the mixed gases. The Fe-Sn alloy formation could be weakened and the Sn residual content is decreased to 0.020 wt % at a roasting temperature of 1273 K and waste tire rubber amount of 10 wt %. Meanwhile, the Fe content in the roasted residue increases to 72.25 wt % through a reduction of Fe3O4 to FeO under a mixed gas of 58%N2+21%CO+21%CO2, realizing the tin removal and iron resource utilization from Sn-bearing concentrates. Besides, the zinc which originated from waste tire rubber in the roasted residue is low to 0.015 wt %, implying that it is concentrated in the dust and could be recovered using a dust collection process.