Abstract

When impurities are removed from crude lead by metallic zinc, a silver foam (SF) containing lead, zinc, and silver forms on the melt surface along. Vacuum distillation can be used to separate the SF components, since it is one of the most environmentally friendly and highly efficient technologies in pyrometallurgy. Phase diagrams are used to choose the system temperature and pressure and to estimate the efficiency of the separation of the components during vacuum distillation. The aim of this work is to calculate VLE (vapor–liquid equilibrium) states, including the temperature dependence of the phase composition (T–x), at a given pressure for binary Zn–Ag alloys during vacuum distillation using MIVM (molecular interaction volume model) and SMIVM (simple molecular interaction volume model), which contains a smaller number of variable system parameters, in particular, for fixed values of coordination numbers Z_i and molecular volume V_mi of the alloy components. As a result, the adequacy of SMIVM used in the calculation is confirmed. Information on the influence of the temperature and the residual pressure in the system on the sublimation and separation of the metals from Zn–Ag alloys of variable composition is obtained. The saturated vapor pressures (Pa) for zinc (\(p_{{{\text{Zn}}}}^{*}\) = 5.79 × 10²–3.104 × 10⁴) and silver (\(p_{{{\text{Ag}}}}^{*}\) = 5.25 × 10^–9–5.1 × 10^–5) at T = 823–1073 K are determined. The large differences between \(p_{{{\text{Zn}}}}^{*}\) and \(p_{{{\text{Ag}}}}^{*}\) cause high values of separation coefficient log β_Zn = 8.32–12.18 and imply the possibility of separation of zinc by sublimation into the gas phase (β_Zn > 1) and the concentration of silver in the liquid phase. An increase in the mole fraction of silver in the alloy composition from 0.1 to 0.9 and or in the system temperature from 823 to 1073 K leads to an increase in the mole fraction of silver in the gas phase from 1 × 10^–15 to 8.5 × 10^–7. The following thermodynamic functions are calculated for the equilibrium state of the liquid and gas phases of the Zn–Ag system: \(G_{{\text{m}}}^{E}\) = 0.08–1.36 kJ/mol, –\(H_{{\text{m}}}^{E}\) = 1.52–5.73 kJ/mol, and \(S_{{\text{m}}}^{E}\) = (1.57–5.38) × 10^–3 J/(mol K). The equilibrium VLE diagrams of a Zn–Ag alloy can be used at the preliminary stages of designing pilot equipment for vacuum distillation and to choose the temperature and pressure ranges in the system in order to manufacture Zn- and Ag-containing products of a given composition.

中文翻译：

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真空蒸馏过程中锌银合金的相平衡

摘要

当金属锌从粗铅中去除杂质时，会在熔体表面形成含有铅、锌和银的银泡沫 (SF)。真空蒸馏可用于分离 SF 组分，因为它是火法冶金中最环保、最高效的技术之一。相图用于选择系统温度和压力，并估计真空蒸馏过程中组分的分离效率。这项工作的目的是计算 VLE（汽液平衡）状态，包括相组成的温度依赖性 ( T – x)，在给定压力下使用 MIVM（分子相互作用体积模型）和 SMIVM（简单分子相互作用体积模型）真空蒸馏二元 Zn-Ag 合金，其中包含较少数量的可变系统参数，特别是对于固定值合金组分的配位数Z _i和分子体积V _{m i}。结果，证实了计算中使用的 SMIVM 的充分性。获得了系统中温度和残余压力对金属从不同成分的 Zn-Ag 合金升华和分离的影响的信息。锌的饱和蒸气压 (Pa) ( \(p_{{{\text{Zn}}}}^{*}\) = 5.79 × 10 ²–3.104 × 10 ⁴ ) 和银 ( \(p_{{{\text{Ag}}}}^{*}\) = 5.25 × 10 ^–9 –5.1 × 10 ^–5 ) 在T = 823–1073 K 是决定。\(p_{{{\text{Zn}}}}^{*}\)和\(p_{{{\text{Ag}}}}^{*}\)之间的巨大差异导致高分离值系数 log β _Zn = 8.32–12.18，这意味着通过升华到气相（β _Zn> 1) 和液相中银的浓度。合金成分中银的摩尔分数从 0.1 增加到 0.9 和/或系统温度从 823 增加到 1073 K 导致气相中银的摩尔分数从 1 × 10 ^–15增加到 8.5 × 10 ^{– 7}。为 Zn-Ag 系统的液相和气相的平衡状态计算以下热力学函数：\(G_{{\text{m}}}^{E}\) = 0.08–1.36 kJ/mol，- \(H_{{\text{m}}}^{E}\) = 1.52–5.73 kJ/mol，而\(S_{{\text{m}}}^{E}\) = (1.57–5.38 ) × 10 ^–3J/(mol K)。锌银合金的平衡 VLE 图可用于设计真空蒸馏试验设备的初步阶段，并选择系统中的温度和压力范围，以制造给定成分的含锌和银的产品.