Hot gas cleaning - materials and performance

Hot gas cleaning systems for the removal of contaminants from combustion and gasification gas streams are critical components in the next generation of advanced coal/biomass/waste-fired combined cycle plants. The contaminants of concern are those environmental pollutants which would otherwise exceed emissions legislation and those which would directly impact on the life or operability of the gas turbine used in the cycle. It is essential that these 'solid fuel' plants can provide gases suitable for the advanced, high inlet temperature gas turbines being developed currently for natural gas combined cycle plants. Regardless of the gas turbine, the application of hot gas cleaning in solid fuel combined cycle plants leads to increased cycle efficiencies over those achievable with conventional wet scrubbing techniques and greatly reduces any waste water disposal problems. The introduction of systems for particulate removal, alkali reduction, H2S/SOx reduction, NH3/NOx reduction, HCl removal etc. into the advanced solid fuel processes leads to problems of integration as well as those of the materials and performance issues associated with the individual components. This paper reviews the major hot gas cleaning systems under development, identifies the materials challenges that these present and discusses possible consequences of their integration into solid fuel combined cycle processes.