Passage of trace metal contaminants through hot gas paths of gas turbines burning biomass and waste-fuels

Abstract

Integrated gasification combined-cycles (IGCC) are the basis for high efficiency power generation units. IGCC systems lend themselves to gasification of biomass and waste-fuels in place of, or when co-fired with, fossil fuels to contribute to low greenhouse gas emissions. However, the use of biomass and waste-fuels to produce fuel gases for gas turbines introduces the concern that trace elements they contain may form molten surface deposits on high temperature blades and vanes along the gas path and thereby initiate hot corrosion. In this study, example fuel analyses (from the ECN PHYLLIS fuels database) have been used in a series of thermodynamic assessments using the MTDATA software package. The volatile trace species produced by gasification have been identified. Further assessments were then made to identify which of these trace elements would be removed by hot gas cleaning prior to transportation in the gasifier derived fuel gases for combustion in the gas turbine. The third stage of thermodynamic assessments, again carried out using MTDATA, identified which of the trace elements remaining in the cleaned fuel gases would, when combusted in the gas turbine, pass through the gas turbine gas path in a volatile form and which have the potential for producing condensed surface deposits on hot components, and could thus initiate hot corrosion. These assessments identified trace species containing cadmium, lead and antimony, in addition to alkali metals, as having the potential for initiating hot corrosion in gas turbines burning biomass and waste-fuels.