Phase equilibria and thermodynamic modelling of the lead-sulfur-oxygen system and applications to direct lead smelting

Bullion-slag-SO{dollar}sb2{dollar}(or O{dollar}sb2{dollar})/N{dollar}sb2{dollar} reaction systems in the Pb-S-O system were investigated using the submerged injection technique at different temperatures. A thermochemical model was established for the Pb-S-O system with experimental results and other thermodynamic data. The model was developed with the aid of a computer program called STEPSOL, which can simulate either a steady-state or stepwise bath-smelting reactor. The thermochemical model comprises {dollar}Delta{dollar}G{dollar}spcircsb{lcub}rm f{rcub}{dollar} for all species present in the reaction system, a bullion model: (UNFORMATTED TABLE OR EQUATION FOLLOWS){dollar}{dollar}eqalign{lcub}&rm Ingamma S = -11000/T + 6.020 + (420/T - 1.452) XS +cr &qquadrm (117/T - 3.207)(XS)sp2cr &rm Ingamma Pb = ({lcub}-{rcub}1173/T + 0.618)(XS)sp2cr{rcub}{dollar}{dollar}(TABLE/EQUATION ENDS)and a slag model: (UNFORMATTED TABLE OR EQUATION FOLLOWS){dollar}{dollar}eqalign{lcub}&rm gamma PbSOsb4 = -4900/T + (10207/T) XPbSOsb4 - (8403/T)(XPbSOsb4)sp2cr &rm Ingamma PbO = ({lcub}-{rcub}4822/T)(XPbSOsb4)sp2cr{rcub}{dollar}{dollar}(TABLE/EQUATION ENDS); It was found that pure PbS could be converted to very low sulfur bullion without oxidizing metallic lead into slag, using a unique controlled-oxidation process. This finding led to the proposition of a novel degangue-matte oxidation process for the production of metallic lead from a clean Missouri concentrate. The process is based on new process chemistry and has the potential of producing very low sulfur bullion and discard slag. Several process routes were discussed. Processing could be a batch or continuous process.