| With the rapid development of iron&steel industry of China, it is of significance to intensify utilization of domestic complex iron ore resources. The complex iron ores containing tin,zinc and arsenic are typical intractable ones, great reserves of which are found in China. In tin,zinc and arsenic-containing iron ores, taken from Huanggang in Inner Mongolia Autonomous Region, magnetite is the main mineral and cassiterite,sphalerite and arsenopyrite is the chief mineral of tin,zinc and arsenic. Cassiterite,sphalerite and arsenopyrite in iron ores in the forms of irregular fine monomer and fine grains embedded in magnetite, and can not be efficiently separated from the tin,zinc and arsenic-containing iron concentrate. In this research, tin,zinc and arsenic-containing iron concentrate, taken from Huanggang in Inner Mongolia Autonomous Region, was used to investigate CO reduction behavior of tin, zinc, arsenic and wustite, and provide the theoretical basis of the new technology of multipurpose utilization of tin,zinc and arsenic-containing complex iron ores.The volatile rate of tin of non-preoxidated pellets is higher than that of preoxidated pellets by weak reduction roasting. The optimized conditions of selective separation of tin,zinc,and arsenic from tin,zinc and arsenic-containing iron ores preoxidated pellets, preoxidated temperature and time of which is725℃and10min, is1000℃(roasting temperature),100min(roasting time) and50%(the content of CO of the reducing atmosphere). Under the optimized conditions, the volatile rate of tin,zinc and arsenic was75.88%,71.68%and84.43%, the residual content of tin,zinc and arsenic in the pellets was0.068%,0.0325%and0.046%, which met the requirement of the blast furnace production.With selective separation of tin, zinc and arsenic, the iron oxides of tin,zinc and arsenic-containing iron ores is reduced to the wustite. However, as the reducing atmosphere is getting strong, the wustite is gradually reduced to MFe, which shows that the wustite can be reduced under the strong reducing atmosphere. Under the strong reducing atmosphere of1050℃(roasting temperature),60min(roasting time) and100%(the content of CO of the reducing atmosphere), tin,zinc and arsenic-containing iron ores preoxidated pellets complete the reduction of wustite, and the content of MFe and TFe was81.45%and86.36%. The metallization rate of pellets reached94.31%. With20min of temperature rising(from1000℃to1050℃),2.5℃/min of the speed of temperature rising,100%(the content of CO of the reducing atmosphere),1050℃(roasting temperature),40min(roasting time), the metallization rate of pellets reached94.32%, which is similar with the results of the former.An analysis of the pellets after weak and strong reduction roasting was performed by optical microscopy, XRD, SEM and EDS. The experimental results show that, high temperature and strong reducing atmosphere led to the products of Fe-Sn alloys and metallic tin, which is the main reason of volatile rate of tin geting down. The investigations disclosed that the weak reduction roasted pellet was mainly bonded by the recrystallization of wustite at high temperature, and the wustite particles were connected with each other, which made pellets becoming denser. So the pellets couldn’t be reduced further, and the metallization rate became lower.The isothermal and non-isothermal reduction kinetics of FeO→Fe was investigated using CO as a reduction agent. The results indicated that the controlling mechanism of isothermal reduction reaction was similar to that of the non-isothermal reaction.In this research,through the research of CO reduction behavior of tin,zinc and arsenic-containing iron concentrate ores, a kind of new technology of multipurpose utilization of tin,zinc and arsenic-containing complex iron ores was recommended. The cores of the new technology were selective separation of tin, zinc and arsenic by weak reduction roasting, and preparation of metallic pellets (DRI) by strong reduction roasting. |
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