高铅渣直接还原过程的PbO-FeO_x-CaO-SiO_2-ZnO多元系相平衡

Phase Equilibria of PbO-FeO_x-CaO-SiO_2-ZnO High-lead Slag System for Direct Reduction Process

高铅渣直接还原炼铅工艺的基本渣系为PbO-FeOx-CaO-SiO2-ZnO多元系。实际熔炼过程中熔渣组分特别是PbO,ZnO含量是不断变化的,其挥发迁移对炉渣成分、物理化学性能以及对还原过程顺行都起关键作用。本研究以直接还原炼铅工艺过程中的PbO-FeOx-CaO-SiO2-ZnO渣为研究对象,采用FACTSage软件计算了特定温度下高铅渣的相平衡,并结合熔融实验及X射线衍射仪（XRD）等分析手段对其进行了验证。相平衡分析显示,对不同铅含量的高铅渣,在700~1100℃温度范围内,均为固液两相共存区,主要的析出固相为长石系、橄榄石系、尖晶石类及单一氧化物。XRD分析结果表明,当炉渣w（CaO）/w（SiO2）为0.40,w（FeO）/w（SiO2）为1.54时,在900~1100℃范围内体系析出的主要复杂相为尖晶石类、橄榄石型、硅钙石、Fe2O3、Fe3O4以及长石（Pb,Ca）2（Fe,Zn）Si2O7。

PbO-FeOx-CaO-SiO2-ZnO multi-slag system was considered as the main slag composition for high-lead slag direct reduc- tion process. It was observed that the composition of the slag, especially PbO and ZnO content, varied constantly in the actual process of smelting. Volatilization of PbO and ZnO played a critical role in slag composition and physieo-chemical property variation, and sub- sequently ensured anterograde of reduction process. Phase equilibria of high-lead PbO-FeOx-CaO-SiO2-ZnO slag system for direct re- duction process at particular temperature were calculated using FACTSage software and verified by slag melting experiment combining with X-ray diffraction （XRD） analysis. Phase equilibria analysis showed that there were all solid-liquid two-phase coexistence region existing in different lead contents of PbO-FeOx-CaO-SiO2-ZnO slag in the temperature range of 700 -1100℃. The main precipitated phases were melitite, olivine, spinel and monoxides. When w （ CaO）/w （ SiO2 ） ratio was set as O. 40, w （ FeO）/w （ SiO2 ） ratio as 1.54, the main precipitated crystals were spinel, olivine, calcium silicates, Fe2O3, Fe3O4 and feldspar （Pb,Ca）2 （Fe,Zn） Si2O7 within the temperature range of 900 - 1100 ℃ showed by XRD analysis results.