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Number of lead-based alloy vacuum distillation separation and purification

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Tutor: DaiYongNian YangBin
School: Kunming University of Science and Technology
Course: Non-ferrous metallurgy
Keywords: Lead Based Alloy,Vacuum Distillation,Molecular Interaction Volume Model (MIVM),M
CLC: TF812
Type: PhD thesis
Year:  2010
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With the decrease of the non-ferrous minerals and the increase of the wasted non-ferrous resources, it is exigent to reclaim and reuse the wasted resources. Lead free of solder and electron device greately deepened the deleading degree of lead based alloys. Owing to small space occupied, simple operation and friendly with the environment, vacuum distillation always has distinct characteristics and powerful vitality in non-ferrous metallurgy area. In this paper, certain lead based alloys, (Pb-Sn binary alloy, Pb-Sn-Sb ternary alloy and lead based multi-component alloy) familiar in non-ferrous field, were just separated with vacuum distillation method.Thermodynamic properties of an alloy play a key role in calculating separation degree with vacuum distillation, but due to the complexity of high temperature experiment, there is no enough available experimental data of thermodynamic properties to use, this can not meet the requirement of the researchers. Molecular dynamics (MD) method is an atomic level computer simulation, and is mostly used in materials and quantum chemistry science but less in metallurgy engineering. Monographes about thermodynamic properties have not been presented yet. Combined feature of vacuum distillation and advantage of MD method, thermodynamic properties of some Pb-X alloys, such as enthalpy of formation, free energy of formation and excess free energy etc., were simulated with molecular dynamics method. Exploratory research of vacuum distillation progress with MD method was carried out in this paper.Activtiy coefficients of some binary alloys, included in the lead based alloy, were calculated with¦molar interaction volume model(MIVM) and compared with available experimental ones,activity coefficients of Pb-Sn, Sb-Sn and Pb-Sb alloys, at 800-1300¡æwere predicted to calculate the feasibility and separation degree of vacuum distillation. Thermodynamic and kinetic analyses, such as saturated vapor pressure, separation coefficient and diagram of vapor-liquid phase equilibrium, of lead based alloys with vacuum distillation were performed.Based on systemic laboratory experiments of total components Pb-Sn alloy, industrialized experiments were carried out successfully. For the high lead material (Sn 22%-Pb 78%), the distillation temperature was controlled at 950¡æ, vacuum degree was 0.5Pa, and treatment capacity was 10t/a. The product was the cured lead with the purity over 99.5%and the cured tin in which lead content was about 8%. The high tin material (Sn 86%-Pb 12%) need to be treated two times at 1100¡æand 1200¡æ, and the lead content in the tin was decreased below¡¯0.01%, treatment capacity was 8t/a. With the improvement of condenser inside of the equipment, the industrial vacuum distillation experiment of Pb-Sn alloy was implemented successfully and energy consumption has been decreased about 20%. Modification of the outlet system lengthened service life of the components and parts of the equipment. Treatment scope was extended to total components Pb-Sn alloy and treatment capacity of the equipment was enlarged to 10t/d. The lead in the tin was successfully removed to less 0.01%. Treatment progress of total compoents Pb-Sn alloy with vacuum distillation has been proposed and applied to ECS Refining Texas, LLC, USA, Quexin Aifa Metal (Shenzhen) Co., Ltd, China, Yunnan Tin Group (Holding) Co., Ltd, China etc., and certain economic benefit has been achieved.According to the features of two, ternary Pb-Sn-Sb alloys, different forms of equipments were designed and the two alloys were separated in industrialized vacuum distillation experiments.The corrosion from high-temperature; antimony liquid to stainless steel tube was effectively slowed. For the Sn26%-Pb66%-Sb6% ternary alloy,.continuous distillation equipment was designed, and the experimental parameter was:.distillation temperature was 1150¡æ, distillation time was 50min, vacuum degree was 0.5Pa and daily capacity was 10 tons.For the Sn81%-Pb10%-Sb6% alloy, semi-continuous equipment was designed, the experimental parameter was 1200¡æ,40min,0.5Pa,and daily capacity was 5tons.The antimony content in both obtained crud tin was less than 1%, and the crude tin can meet the requirement of de-antimony with aluminum refining progress.Small scale, enlarged scale and repeatable experiments of lead based multi-component alloy-(Au259g/t-Ag3.11%-Cul.69%-Pb47.48%-Bi5.84%-Sb27%-Sn8.35%-As2.8%) were carried. out and the.noble metals, gold.and silver, were enriched .5-6 times, removing rate of lead and bismuth was more than 99%.. It was proved that separating the multi-component alloy with vacuum distillation can decrease the loss of noble metal, decrease the recovery cost, and increase the recovery efficiency of late treatment progress.
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