Heng Xiong

Thermodynamics of removing impurities from crude lead by vacuum distillation refining

Abstract A novel technique was developed to remove impurities from crude lead by vacuum distillation. The thermodynamics on vacuum distillation refining process of crude lead was studied by means of saturated vapor pressure of main components of crude lead, separation coefficients and vapor-liquid equilibrium composition of Pb-i (i stands for an impurity) system at different temperatures. The behaviors of impurities in the vacuum distillation refining process were investigated. The results show that the vacuum distillation should be taken to obtain lead from crude lead, in which Zn, As and partial Sb are volatilized at lower temperature of 923-1023 K. Lead is distilled from the residue containing Cu, Sn, Ag and Bi at higher temperature of 1323-1423 K, but the impurity Bi is also volatilized along with lead and cannot be separated from lead.

Behavior of Intermediate CaTiO3 in Reduction Process of TiO2 by Calcium Vapor

Preparing titanium powders by calcium vapor reduction of titanium oxide directly is a new way with short flow sheet and CaTiO3 is the very important intermediate compound in this process. In this paper, the behavior of intermediate CaTiO3 in the reduction process of TiO2 was investigated. The thermodynamic calculation indicated that the Gibbs free energy change of the reaction to produce CaTiO3 by CaO and TiO2 was always negative below 1000 °C; The reaction Gibbs free energy change of the calciothermic reduction of CaTiO3 was lower than that of TiO, which would be the most predominant step from TiO2 to Ti. The experimental results showed that CaTiO3 phase derived from the reaction between TiO2 and the reduction by-product CaO, and the reaction between TiO2 and the decomposition product CaO from the additive of CaCl2 with crystal water as well in the calcium vapor reduction process of titanium oxide. But CaTiO3 could be reduced to Ti much easier than that of TiO2 by calcium vapor.

Removal of Sulfur from Copper Dross Generated by Refining Lead

Typical copper dross, the byproduct of lead bullion pyrometallurgical refining for copper removal, mainly contains Pb, Cu, S, As, Sb and Sn etc. In traditional treatment process, copper dross is transformed to be copper matte by smelting with iron scarp and iron pyrite. Here, a new treatment process of converting-vacuum distillation (CVD) was proposed and investigated. Based on this concept, the converting process was tentatively investigated in this paper. The results of element distribution of converting samples showed the sample has three layers. The upper layer is mainly sulfides of lead and copper, the middle layer is mainly copper arsenide, and the lower layer is lead arsenide and crude lead. On the condition of oxygen flow rate 400 ml/min, the converting temperature 1000 °C, the holding time 1 h, the converting time 10 min, the lead copper alloy containing 0.17% S was obtained.

Study on the Volatilization of Sb 2 S 3 in Vacuum

The thermogravimetric method was selected for investigating the evaporation of Sb2S3 in the pressure range of 50–300 Pa and in the temperature range of 823–1123 K, the gas phase diffusion was the rate-determining step for Sb2S3. The volatilization rate was related to the temperature and pressure, that the logarithm of volatilization rate yielded a line with the reciprocal of temperature and pressure. The volatilization rate for Sb2S3 was between 0–0.023 g·cm−2·s. The apparent activation energy was between 65.8 and 60.6 kJ/mol.

Purification of Indium by Vacuum Distillation

The average content of impurity elements of crude indium has been reduced, by employing the two-step vacuum distillation method. The two-step vacuum distillation were carried out to study the influence of distillation temperature, distillation time on the impurities. At the first step the content of impurities which has low boiling point namely Cd、; Zn、; Tl、; Pb in crude indium could be reduce to the standard of 5N about 950☐, 60min and 5Pa. At the second step the content of impurities which has high boiling point such as Cu、; Fe、; Sn、; Ni in crude indium could be reduce to the standard of 5N about 1075☐, 60min and 5Pa. The average content of impurity elements of crude indium(99.7%) has been reduced, by employing the two-step vacuum distillation method, to achieve 5N(99.9993) indium under the best conditions. The impurity analysis carried out using ELEMENT GD.