鼓风炉渣碳基还原回收铅、锌、铁及尾渣环境特征

Recovery of Lead,Zinc and Iron from Blast Furnace Slag by Carbothermic Reduction and Environmental Characteristics of Tailings

针对云南省个旧市历史遗留鼓风炉渣的安全处置,采用碳热还原-磁选方法回收铅、锌和铁,并高温固化获得稳定化尾渣.研究了温度、时间、还原剂用量对铅、锌和铁的回收影响,碳基还原过程铅、锌、铁的还原行为和磁选尾渣的环境风险.结果表明,在温度1300℃、还原时间60 min、还原剂用量4%的条件下,铅、锌的挥发率分别达91.97%和96.96%,铁的金属化率96.94%;在磁场强度为250 MT的磁选条件下,铁的回收率78.93%,铁精矿中铁品位为90.94%.SEM-EDS和XRD分析结果表明:鼓风炉渣经高温碳热还原后,渣中铅以硫化物和铅铁矾的形式镶嵌于硅酸盐晶体中,渣中其他重金属则均匀分布在硅酸盐晶体中.磁选尾渣中铅、锌、砷、镉浸出值未超过国标GB 5085.3-2007规定限值;Tessier重金属形态分析结果显示尾渣中铅、锌、砷、镉残渣态比例相比于鼓风炉渣增大,表明鼓风炉渣碳热还原后环境风险降低,实现了鼓风炉渣的资源化及无害化.

For the safe disposal of historical blast furnace slag in Gejiu City,Yunnan Province,the carbon thermal reduction-magnetic separation method is used to recover lead,zinc,and iron,and high-temperature solidifica-tion is employed to obtain stabilized tailings.The effects of temperature,time,and reductant dosage on the recovery of lead,zinc,and iron are studied,as well as the reduction behavior of lead,zinc,and iron in the carbon-based reduction process and the environmental risk of magnetic separation tailings.The results show that at a tem-perature of 1300℃,reduction time of 60 minutes,and reductant dosage of 4%,the volatilization rates of lead and zinc reach 91.97%and 96.96%,respectively,and the metallization rate of iron is 96.94%.Under magnetic separation conditions with a magnetic field strength of 250 MT,the recovery rate of iron is 78.93%and the iron grade in the iron concentrate is 90.94%.SEM-EDS and XRD analyses show that after high-temperature carbon thermal reduction of the blast furnace slag,lead ip the slag is embedded in the silicate crystals in the form ofsulfides and lead iron sulfate,while other heavy metals in the slag are uniformly distributed in the silicate crystals.The leaching values of lead,zinc,arsenic,and cadmium in the magnetic separation tailings do not exceed the limit values specifed by the national standard GB 5085.3-2007.Tessier heavy metal speciation analysis results indicate that the residual proportions of lead,zinc,arsenic,and cadmium in the tailings inerease compared to those in the blast furnace slag,suggesting that the environmental risk of the blast furnace slag is reduced after car bon thermal reduction,and the slag is both resourceful and harmless.