A.A. Korolev, K.L. Timofeev, G.I. Maltsev.
ABSTRACT
Object of research: when refining rough lead from metallic zinc impurities, a silver foam (SF) containing lead, zinc and silver is formed on the surface of the liquid melt. To separate the components of the joint venture it is possible to apply vacuum distillation – environmentally friendly and high-performance technologies in pyrometallurgy. A preliminary analysis of the behavior of the polymetallic alloy in the process of distillation, in particular, the composition of the products of sublimation and the degree of separation of the alloy components at specified temperature and pressure is carried out using calculated equilibrium phase diagrams VLE (vapor liquid equilibrium), for example, the temperature–composition “T–x,” pressure–composition “P–x“. Objective: the calculation of the equilibrium “gas–liquid” for binary Zn–Ag alloy. Methods and approaches: when constructing the VLE, the activity coefficients of the Zn–Ag alloy components are calculated according to the volumetric model of molecular interaction molecular interaction volume model (MIVM). Novelty: the original information about the influence of temperature and residual pressure in the system on the degree of distillation and separation of metals from Zn–Ag alloys of variable composition is obtained. Main results: saturated steam pressures for Zn (5.79.102–3.104.104) and Ag (5.30.10–9–5.05.10–5) were calculated in the temperature range 823–1073 K. High values of p*Zn / p*Ag = 1.09.1011–6.14.108 ratio and separation coefficient logßZn = 8.318–12.180 create theoretical prerequisites for separation, when zinc suggest the possibility of separate extraction by sublimation of the zinc in gas phase (βZn> 1) and the concentration of silver in the liquid phase. The increase in the content of molar fractions of silver in the alloy from 0.1 to 0.9 and the system temperature from 823 to 1073 K leads to an increase in the molar fraction of silver in the gas phase from 1.10–15 to 8.5.10–7. The values of thermodynamic functions are calculated for the equilibrium state of the liquid and gas phases of the Zn–Ag system: = 0.08–1.36 kJ/mol; = 1.52-5.73 kJ/mol; = 1.57–5.38 J/mol.К are determined for the interface of liquid–gas Zn–Ag alloy. Practical relevance: equilibrium phase diagrams VLE Zn–Ag alloy is used in the preliminary stages of designing of experimental-industrial equipment for vacuum distillation technology, and to select ranges of temperature and pressure in the system with the purpose of obtaining a Zn- and Ag-containing products of a given composition.
KEY WORDS:
zinc, silver, equilibrium phase diagram, vacuum distillation, conventional (MIVM) and simplified (SMIVM) interaction models.
DOI: 10.31857/S0235010621020043