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

Highlights: • A method to separate Sn from iron concentrates using waste tire rubbers is proposed. • The Fe-Sn alloy formation mechanism differs related to temperature and CO content. • The Sn content decreases to 0.020 wt % at 1273 K and waste tire rubber of 10 wt %. • The S content in the residue decreases to 0.022 wt % by the CO₂ oxidation to SO₂. • The zinc originated from waste tire rubber could be recovered from the dust. -- 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.