危险废物焚烧灰渣熔融过程中重金属元素热力学平衡计算

熔融固化是目前危废焚烧灰渣处置的有效方法之一。为了能够有效地控制熔融过程中重金属元素的迁移，采用HSC Chemistry软件模拟研究了重金属元素As、Pb、Zn、Cu、Ni、Cr等在熔融过程中的物质变化历程，考察了不同气氛、温度、氯化物种类的影响。结果表明：在还原性气氛下，As、Pb几乎100%以AsS(g)和PbS(g)的形式挥发进入气相；Zn主要以气态金属挥发，1 500 ℃时90.8%的Zn进入气相；Cu、Ni、Cr与灰渣中的Fe2O3、Al2O3等形成不易挥发的化合物，几乎完全被熔渣固化。氧化性气氛有利于各重金属元素的固化，除46.47%的Pb 以PbCl2(g)、PbCl(g)、PbO(g)的形式挥发外，其余重金属元素均能被固溶在渣中。与灰渣中NaCl相比，CaCl2不影响As、Cr的平衡形态分布，但能促进Pb、Zn、Cu、Ni以气态氯化物的形式挥发进入气相，不利于重金属元素的固化。

Thermodynamic equilibrium calculation of heavy metals during melting process of waste incineration ash

Vitrification is an effective way to dispose ash from hazardous waste incineration. In order to optimize heavy metals solidification, the migration characteristics of heavy metals in the vitrification process were studied by thermodynamic analysis. In this paper, the migration of heavy metals, such as As, Pb, Zn, Cu, Ni and Cr, were calculated under different atmospheres, temperatures and chloride species with HSC Chemistry software. The results showed that in reducing atmosphere, almost 100%of As and Pb were prone to volatilization in the form of AsS (g) and PbS (g), and 90.8% of Zn was in the form of metal Zn at 1 500 ℃. Cu, Ni and Cr were almost completely solidified due to the existence of Fe2O3 and Al2O3, which could help to solidify heavy metals. In oxidizing atmosphere, all the heavy metals were prone to solidification except that, 46.47% of Pb was prone to volatilization in the form of PbCl2 (g), PbCl (g) and PbO (g). Compared with NaCl in the ash, the addition of CaCl2 did not affect the migration of As and Cr, but on the other hand, it can help Pb, Zn, Cu and Ni to volatilize into gas phase in the form of chlorides. Therefore, the existence of CaCl2 was harmful for the solidification of heavy metals.