Reduction behavior of SnO2 in the tin-bearing iron concentrates under CO–CO2 atmosphere. Part I: Effect of magnetite

•Effect of magnetite on phase transformation of SnO2 roasted in CO–CO2 atmosphere was studied.•Reasons for the low tin volatilization ratio at higher reduction temperature were revealed.•The formation of Fe–Sn spinel was characterized by XRD, SEM–EDS, etc.•The negative effect of generated Fe–Sn spinel on reduction volatilization of SnO2 was explained.

A selective reduction volatilization (SRV) process developed by the authors could remove excessive tin from the complex tin-bearing iron concentrates. But it was especially noteworthy that the volatilization ratio of Sn and the residual tin content were obviously influenced by the variation of roasting parameters during the SRV process. Hence, the existence form of residual tin in the roasted products and the possible reactions between SnO2 and Fe3O4 need to be further determined. In the present study, the effect of roasting parameters on the reduction of SnO2 in the tin-bearing iron concentrates was first investigated. Then, samples with diverse cassiterite/magnetite (C/M) mass ratios were used to determine the effect of magnetite on phase transformation of SnO2 by using XRD, SEM–EDS, etc. The results indicated that magnetite markedly affected the tin volatilization and phase transformation of SnO2 under CO–CO2 atmospheres. Fe–Sn spinel was easily formed during the reduction process, and higher roasting temperatures promoted the formation of Fe–Sn spinel, which had an adverse effect on the Sn volatilization ratio.

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