| Pb-Sb complex sulfide ores, mainly distributed in Guangxi Zhuang antonomous region, are important resources of lead and antimony in China. Presently these complex ores are treated by pyrometallurgical process. Although it has some advantages, its major disadvantages are inferior Pb-Sb separation result, low direct recoveries of Pb and Sb, and meaningless recycle of Pb and Sb in the smelting process. The existing pyrometallurgical flowsheet usually produces low-quality antimony or even lead-antimony alloy. So the Pb-Sb separation is a key problem in treating this kind of Pb-Sb complex ores. An innovative lead-antimony separation technology for Pb-Sb complex sulfide ores by oxidation and volatilization roasting with steam-air mixtures has been developed in this paper. Experimental results show that the complex ores are successfully separated into lead and antimony concentrates, respectively. The precious metals are concentrated in the roast. The technology developed has advantages over the existing process in: more satisfying comprehensive recoveries of metals, more simple separation process and less quantity of flux.Laboratory and kilogram-scale tests of roasting process of Pb-Sb complex sulfide ores with steam-air mixtures have been carried out systematacially. The optimum parameters for Pb-Sb separation have been determined. The mechanisms of reaction between the systems (PbS-Sb2S3, PbS-Sb2S3-FeS, PbS-Sb2S3-ZnS and PbS-Sb2S3-FeS-ZnS) and steam have been investigated thermodynamically and kinetically using SEM, EDAX, XRD, DTA-TG and chemical analysis. The sulfur-oxygen potential diagrams for Me-S-O-H systems have been plotted by employing Fact Sage 5.0 database. The behavior of the sulfides and oxides of interest has been investigated. The equilibrium constituents of the Pb-S-O-H and the Sb-S-O-H systems in vapor phase have been calculated by Constrained Chemical Potential Method (CCPM). The computational results are plotted in Gibbs triangles.1. The lead-antimony separation technology for Pb-Sb complex sulfide ores by oxidation and volatilization roasting with steam-air mixtures is proved to be highly effective. The optimum parameters for laboratory test are determined as: temperature 973-1023K, steam flow rate 1800~2500ml/min, sample size 2~3mm and roasting time 120-15Omin. Under optimum conditions, the roast contains 36-40% Pb and <2% Sb, and the dust 50-75 Sb and <3% Pb. The direct recoveries of Pb and Sb are >94% and >93%, respectively. The content of sulfur in the roast is 3-6% and the desulfurization efficiency is greater than 85%.The optimum experimental conditions for kilogram-scale test are obtained as follows: roasting temperature 973-1023K, steam flow rate 35L/min, air flow rate 6L/min, roasting time 180min, sample size 3~5mm, bed thickness 13.33mm. With the above parameters, the roast contains 32.68-39.78% Pb and <3.22% Sb. The dust contains 69.65-75.07% Sb and <1.5% Pb. The direct recovery of Pb is greater than 95% and that of Sb is up to 85%.2. The mechanisms of the novel technology for treating Pb-Sb complex sulfide ores have been investigated. In steam atmosphere, the results indicate that the reaction of Pb-Sb complex sulfide ores with steam can promote the Pb-Sb separation. The reason is that steam can decompose the jamesonite (FePb4Sb6Si4) and the complex intermediate products into simple sulfides of lead, antimony and iron. At the same temperature, the saturated vapor pressure of the Sb2S3 is higher than that of PbS and separation coefficient is much greater than 1. So, Sb2S3 will be preferentially volatized into vapor phase and PbS enriched in the roast. Besides Sb2S3 in the vapor phase can be selectively oxidized by steam into Sb2O3. As a result, the partial pressure of Sb2S3 in the vapor phase will be reduced and the volatilization of Sb2S3 will be promoted. In contrast, in inert atmosphere, the jamesonite (FePb4Sb6S14) can beVIdecomposed into single sulfides to some extent only. The remaining jamesonite brings the hindrance to volatilization of Sb...
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