Trace Elements Behavior in Coal Gasification Based on Thermodynamics Equilibrium Calculation

Abstract

To understand behavior of trace elements in high temperature coal gasification accompanied with molten ash, the chemical compounds were estimated by thermodynamic equilibrium calculation. The calculation results were compared with the test results of a high temperature and pressurized coal gasification pilot plant with partial combustion. As for distribution of trace elements in slag discharged from pre-combustor, in the char separated by char collector and the product gas containing the fly ash, the estimated results for almost of non-volatile and some of volatile elements were corresponding to the test results well and those for semi-volatile elements as Mn, Cr, Pb, As and volatile elements as Hg and F were not well. The equilibrium calculation results of chemical compounds related to the semi-volatile elements suggested that the slagliquid phase exists together with solid phase in the char and the fly ash while the compounds in the molten slag discharged from the high-temperature gasifier over 1600°C were all slag-liquid phases. Furthermore, study on influence of operating condition on the chemical compounds suggested that increasing temperature of pre-combustor decreased the semi-volatile elements such as Pb in slag and increased it in char. Pressure increased it in slag and decreased it in other discharged. Gas cooling temperature strongly influenced the behavior, increased the semi-volatile elements in product gas and decreased it in slag and char.