Research On High-temperature Desulfurization And Carbon-thermal Reduction Of Lead-zinc Metallurgical Slags For Metals Recovery By Bath Smelting

A great number of metallurgical slags are generated in lead-zinc metallurgical industry, which lead to environmental pollution and waste of resources. Clean technologies for recycling metals from metallurgical slags are essential for sustainable development of metallurgical industries. Thermodynamic calculation and experiments were conducted to investigate high-temperature desulfurization and carbon-thermal reduction of bath smelting process adopted for disposal of lead-zinc metallurgical slags, which can provide theoretical insights for reclamation of metals from iron sinking slag and zinc leaching slag.Thermodynamic calculation demonstrates that the decomposition temperatures of CaSO4, In2(SO4)3, Fe2(SO4)3, ZnSO4, PbSO4is1316.1,1194.2,1103.7,1148.2and1500.0K, respectively. The sulfate decomposition was investigated through thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis, which confirmed the results of thermodynamic calculation. The ability of decomposition can be ordered as follows (from easy to difficult):In2(SO4)3, Fe2(SO4)3, ZnSO4, PbSO4, CaSO4. The phase transition and decomposition temperatures from thermodynamic calculation are consistent with TG-DSC results.Experiments of simulating high-temperature desulfurization in bath smelting process using chemical compounds demonstrate desulfurization ratio was up to99.55%and iron content was upgraded to37.92%under the conditions of temperature1573K, oxygen atmosphere and water-quenching. In the case of high-temperature desulfurization of iron sinking slag with lead smelting slag serving as flux, experimental results demonstrate that desulfurization ratio was up to99.40%and iron content was upgraded to27.94%under the conditions of temperature1673K, iron sinking slag and lead smelting slag ratio7:3, oxygen atmosphere and water-quenching.Experiments of simulating carbon-thermal reduction in bath smelting process using chemical compounds demonstrate uniformity metal melt was obtained under the conditions of coke used as reductant, temperature1723K and premixing feeding, and iron content of the melt was up to98.38%. TG-DSC analysis demonstrates that zinc ferrite in desulfurization product showed high stability. Reductant was necessary for decomposition and reduction of zinc ferrite.