Processing a Sn–Pb Alloy to Produce Tin

The aim of the work is to develop an optimal method for processing Sn–Pb alloy to obtain a marketable product-branded O1‒O3 tin (Sn ≥ 98.5%). The refining of Sn–Pb alloy composition, %, 53–60 Sn, 18–29 Pb, was carried out, first by vacuum distillation ( T = 1085‒1300°C, P = 15‒100 Рa; τ = 3‒36 h) for As, Sb, and Pb distillation and then by the reagent deposition of elemental sulfur and aluminum as part of the Al–Sn ligature in the presence of NH 4 Cl (twofold excess of sulfur in the presence of coke from the stoichiometricnecessary amount for admixtures in the Sn rough; ratio Sn : Al : NH 4 Cl = 45 : 4 : 1) for the separation of Cu, Fe, and Sb. Laboratory tests were performed at a temperature of ~1280°C, P = 20‒40 Pа, τ = 6 h; the Sn-containing residue (yield ~60%) of the composition was obtained, %: 92.39 Sn; 0.46 Pb. During the reagent refining of the Sn-containing residue, O3 grade tin was produced (metal yield ~68%), composition, %, 99.5 Sn, 0.009 Pb. To obtain a finished product of the O1 brand with a direct extraction of ≥90%, it is required to carry out refining from a decopperized Sn–Pb alloy. A schematic diagram is developed and recommendations are formulated for technological regulations for processing Sn–Pb alloy to produce technical tin and recovery of the resulting industrial products and waste. A furnace with the separate production of As, Sb, and Pb condensates of the composition 94.2‒98.3 As, 5.1‒14.5 Sb, and 78.9‒86.4 Pb, wt %, respectively, was chosen as the unit for vacuum distillation. The economic effect of processing ~480 t/year of Sn–Pb alloy (~50.8% Sn) with the production of ~235 t/year of O1‒O3 branded tin is ~39 million rubles/year.