On the Distillation Separation of Aluminum–Tellurium System Melts under Equilibrium Condition

The problem to purify secondary aluminum raw materials from tellurium can be solved by the distillation method based on phase diagrams with liquid and vapor coexistence fields. Similar diagrams can be generated based on the vapor pressure values of the components. In this regard, the vapor pressure values of tellurium and aluminum telluride were determined by the boiling point method. The aluminum vapor pressure values are found by integration of the Gibbs-Duhem equation. The boundaries of the system vapor-liquid equilibrium fields for the Al-Te system at 101.32 kPa and 6.67 kPa were calculated based on the vapor pressure values of the components. The following conclusion can be made from the consideration of the position of the liquid and vapor coexistence field boundaries under atmospheric pressure and in a vacuum. Aluminum can be quite completely purified from Al2Te3 and Te by distillation in a vacuum in one operation at temperatures above 1273 K. Tellurium will be in a complete vapor state under these conditions—above the boiling line in the Al2Te3-Te system

On the Distillation Separation of Aluminum–Tellurium System Melts under Equilibrium Condition

The problem to purify secondary aluminum raw materials from tellurium can be solved by the distillation method based on phase diagrams with liquid and vapor coexistence fields. Similar diagrams can be generated based on the vapor pressure values of the components. In this regard, the vapor pressure values of tellurium and aluminum telluride were determined by the boiling point method. The aluminum vapor pressure values are found by integration of the Gibbs-Duhem equation. The boundaries of the system vapor-liquid equilibrium fields for the Al-Te system at 101.32 kPa and 6.67 kPa were calculated based on the vapor pressure values of the components. The following conclusion can be made from the consideration of the position of the liquid and vapor coexistence field boundaries under atmospheric pressure and in a vacuum. Aluminum can be quite completely purified from Al2Te3 and Te by distillation in a vacuum in one operation at temperatures above 1273 K. Tellurium will be in a complete vapor state under these conditions—above the boiling line in the Al2Te3-Te system

On the Problem of the Distillation Separation of Secondary Alloys of Magnesium with Zinc and Magnesium with Cadmium

An alternative to the existing method of processing secondary magnesium raw materials by remelting in a salt furnace can be distillation separation into volatile metals (Mg, Zn and Cd), low-volatile metals (Al, Mn and Zr) and rare earth elements. The separation of metals may be tracked based on phase diagrams where the field boundaries of the vapor–liquid equilibrium are plotted. Due to the fact that Mg, Zn and Cd have comparable saturated vapor pressures, the possibility of the distillation separation of Mg–Zn and Mg–Cd systems using full state diagrams including the melt–vapor phase transition boundaries were determined in this work. The boundaries of these systems were calculated based on the partial values of saturated vapor, determined by the boiling point method, and presented in the form of temperature–concentration dependencies with the indicated boundaries. The field boundaries were calculated (L + V) at atmospheric pressure (101.33 kPa) and in vacuum (1.33 kPa and 0.7 kPa,) supposing the implementation of the process. The possibility of the separate extraction of zinc and cadmium from magnesium was considered using complete phase diagrams including the boundaries of the melt–steam phase transition. When considering the boundaries of the vapor–liquid equilibrium in the binary systems Mg–Zn and Mg–Cd, it was established that it is impossible to separate metals in one “evaporation–condensation” cycle in a vacuum of 1.33 and 0.7 kPa. The problem is caused by the small size of the fields (L + V) at the temperature, which suggests processes of the re-evaporation of the condensate from the previous distillation stage. The separation of zinc and cadmium from liquid alloys with magnesium under equilibrium conditions requires several repetitions of the condensate distillation process. In non-equilibrium conditions, the real processes will require a larger number of conversions. This implies the expediency of the joint evaporation of magnesium with zinc and cadmium and the use of condensate for additional charging to liquid magnesium, and the remainder of the distillation, where volatile metals such as Al, Mn, Zr and rare earth elements will be concentrated, should be directed to the preparation of ligatures for special magnesium-based alloys

Phase Transformations and Tellurium Recovery from Technical Copper Telluride by Oxidative-Distillate Roasting at 0.67 kPa

This paper presents the results of a study of phase transformations occurring in copper-telluride by-products during its processing of oxidation-distillate roasting at low pressure. The results show that copper telluride is oxidized through intermediate compounds to the most stable tellurate (Cu3TeO6) at low temperatures. The increase in the roasting temperature above 900 °C and the presence of an oxidizer favor the copper orthotellurate decomposition. Thus, the tellurium extraction rate is 90–93% at a temperature of 1000 °C, the oxidant flow rate is 2.2 × 10−2 m3/m2·s, and the roasting time is 60–90 min. One of the decomposition products is copper oxide alloy, which is the basis of the residue. The second product is tellurium in oxide form, which evaporates and then condenses in the cold zone of the condenser in crystalline form. The main constituent phase of the condensate is tellurium oxide (TeO2), which can be further processed during one operation to elemental chalcogen by thermal reduction or electrolytic method

Dearsenation of Gold-Bearing Composite Concentrates without Forced Displacement in a Sublimator

The primary devices for extracting volatile components from dispersed materials in a vacuum are devices with the movement of raw materials by directed vibrations. During the analysis of the operation of such installations, some shortcomings were identified, due to the supply of heat flow to the processed raw material and the requirements for the choice of structural materials. In this article, the authors tested a heating method and a design of a sublimator with the supply of heat flow to the dispersed material by radiation from the heater. The sublimation zone is made in the form of a shaft formed by simple-shaped plates, the design and material of which involve the use of refractory and ceramic materials that are inert with respect to an aggressive vaporous sulfide medium. The movement of bulk material through the volume of the sublimator occurs due to rheological properties: sliding along inclined plates. Technological tests on the sublimation of arsenic sulfides from gravity and flotation composite concentrates of the Bakyrchik deposit (Kazakhstan) have shown the possibility of a high degree of sublimation of arsenic (more than 96–99%) while preserving precious metal composites in the sublimation residue and stable operation of equipment. Sublimation residues containing 0.14–0.30% As can be processed by known methods. The possibility of sufficiently complete removal of arsenic and its compounds from composite concentrates at a reduced pressure with the removal of the latter in the most environmentally friendly sulfide form has been established