Extraction of lead from secondary lead through a low-temperature alkaline and sulfur-fixing smelting process

In view of serious shortcomings existing in a traditional secondary lead pyrometallurgical process such as high smelting temperature,large energy consumption and low concentration of SO₂ fume together with lead vapor pollution,a low-temperature alkaline and sulfur-fixing smelting process of secondary lead was proposed in this work based on a thermodynamic analysis of the NaOHC-PbSO₄-ZnO low-temperature alkaline system. The effects of NaOH amount,smelting temperature,coke amount and ZnO addition on the alkaline and sulfur-fixing smelting of spent lead-acid battery colloid sludge(hereinafter referred to as colloid sludge) which was used as the test material were investigated by single factor experiments. The optimum conditions were determined as follows:m(NaO H)/m(colloid sludge)=60%,temperature 860℃,m(coke)/m(colloid sludge)=10%,and m(ZnO)=m(theoretic). Under these above-mentioned optimum conditions,the average direct recovery ratio of lead was 99.09%,the average grade of crude lead was 98.86%,and the average sulfur-fixing rate for ZnO was 93.37%. XRD spectra indicated that sulfur contained in the material was mainly fixed in the solid residue in the form of zinc sulfide,most of NaO H was converted into Na₂CO₃,and no SO₂ emission existed in the smelting process.