Slagging Characteristics and Kinetic Analysis of Direct Reduction Smelting for Treating Lead-Silver Leaching Residues Mixed with Lead Concentrates
It has become a general developing trend to resource recycling lead-containing solid waste,such as lead-silver leaching residues by lead smelting.However,due to the obvious difference of raw material structure,the conventional direct reduction control theory of high-lead slag is not suitable for that of the mixed lead-silver leaching residues and lead concentrates.To investigate the slag formation characteristics and reaction kinetics of the direct reduction process for recycling lead-silver slag leaching residues,on the basis of the occurrence state analysis of raw materials and thermodynamic calculation,combined subsequent reduction experiments.The results show that both the early and late stages of reduction(＞30 min)are controlled by interfacial reactions,and the 20-30 min of reduction is controlled by external diffusion.Therefore,the reduction reaction efficiency can be enhanced by increasing the reaction interface and reducing the viscosity of slag.As the reduction process proceeds,the lead-containing phase in the slag is vanished off,the zinc melilite and iron-zinc spinel phases is gradually increased,the silicate structure of slag is changed from simple SiO44-to Si2O74-,and the melting temperature and viscosity of the slag increase accordingly.The direct smelting process for treating lead-silver leaching residues mixed with lead concentrates can meet the requirements of reduction smelting production though controlling reduction smelting slag with FeO/SiO2=1.6,CaO/SiO2=0.6,and ZnO≤20 wt.％.
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