Direct reduction of lead sulfide with carbon and lime; Effect of catalysts:Part i. experimental
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I.
INTRODUCTION
M E T H O D S for recovering metals such as copper, lead, nickel, and zinc from corresponding sulfides without entailing SO2 emissions have received considerable attention in recent years. In these methods, sulfide minerals are reduced with either gaseous reactants (like hydrogen, carbon monoxide, and methane) or solid reductants such as carbon in the presence of sulfur-fixing agents such as lime, limestone, sodium carbonate, or potassium carbonate. A brief review of the pertinent previous work is given here. Od6en et al. ~ reacted a mixture of sulfide minerals PbS, CoS, FeS, NiS, Ag2S, CuS, and ZnS with carbon and lime (or NazCO3) under a flow of CO gas at high temperatures. Calcium fluoride (CaF2) or calcium carbide (CaC~) was used as a flux to ensure a fluid slag. Zinc vapors were collected at the top and Co, Fe, and Ni were tapped from the bottom of the furnace. A molten Pb-Ag layer separated below an iron layer but Cu remained in the slag as Cu2S. Pendar 2 extracted lead directly from lead sulfide by mixing it with 10 pct Na2CO3, 4 pct NaCI, 21.6 pct pyrite cinders, and 5 to 6 pct coal and smelting it at 900 ~ the product analyzed 97.6 pct Pb. Matsukawa and Tokumoto 3 smelted a mixture of PbS concentrate, pyrite cinders, coke, and lime at 1100 to 1200 ~ The solid lime reactant acted as a powerful desulfurizing agent for PbS yielding a 77 pct Pb product. Sushkov 4 investigated the smelting of sulfide concentrates with calcined soda. Elenkov 5 studied the reduction of PbS concentrates with calcined soda, sodium chloride, sodium sulfate, and anthracite at 1000 ~ the product contained 96 pct Pb. Okage and Oda 6 heated a mixture consisting of 61 pct galena, 13.6 pct iron, 24.5 pct Na2CO3, and 0.91 pct carbon black at 900 ~ to 1000 ~ and obtained a lead product. Sushkov 7 employed the "Soda Electrosmelting" technique to recover Pb and secondary metals like Ag, Bi, Cd, Mo, Se, and Te from a complex Y. K. RAO is Professor, Department of Matenals Science and Engineering, 323 Roberts Hall. FB-10. University of Washington. Seattle, WA 98195. S. K EL-RAHAIBY is Postdoctoral Research Associate. School of Materials Engmeenng, Purdue University, West Lafayette, IN 47907 Manuscript submttted August 29, 1983 METALLURGICALTRANSACTIONS B
concentrate. Chesti and Sircar s also used a soda ash flux and a carbon reductant to recover lead from sulfide ores. Sushkov and Sheinesson 9 used K : C 0 3 as the sulfur scavenging agent in the reduction of PbS both with and without carbon at 700 to 1000 ~ the presence of carbon was found to alter the mechanism of reduction. A number of researchers used hydrogen as the reductant and lime as the sulfur scavenging medium for sulfides. Oughton 1~developed a process for the recovery of Zn from ZnS using H2 gas and lime in the range 925 to 1200 ~ Baker Jl reduced pyrite samples in the range 800 to 1300 ~ to get iron and calcium sulfide. Cech and Tiemann ~2studied the reduction of Cu2S, Ni3S2, Co~$8, and FeS in the molten state. Habashi and co-workers ~ ~ investigated the reduction
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