Equilibrium Speciation of As, Cd, Cr, Hg, Ni, Pb, and Se in Oxidative ThermalConversion of Coal. A Comparison of Thermodynamic Packages

摘要

The paper predicts the equilibrium speciation of the trace elements As, Cd, Cr,Hg, Ni, Pb, and Se in a model system, assuming ideal gas and pure condensed phases and taking into account the presence of a sorbent material for sulfur capture. The model system is based on a demonstration-scale pressurized fluidized-bed combustor, firing a Pittsburgh No. 8 bituminous coal, using dolomite as sorbent for sulfur capture and a ceramic filter for particulate removal. Results from four different thermodynamic packages (MINGYSYS, NASA-CET89, FACT, and SOLGASMIX) are compared over the temperature range 700-2000 K, at pressures of 1 and 20 atm. For As, Hg, and Se, almost identical equilibrium distributions were predicted by the four packages were observed. These differences may be due to different solution techniques, convergence criteria, and/or thermodynamic packages.