Design and Evaluation of a Single-Can Full Scale Catalytic Combustion System for Ultra-Low Emissions Industrial Gas Turbines

The goal of the Advanced Turbine Systems (ATS) program is the design and development of high thermal efficiency gas turbines with pollutant emissions at single digit levels, through the development of advanced recuperated gas turbines. Following successful subscale catalytic reactor testing, a full scale catalytic combustion system was designed to be representative of a single can in a multi-can gas turbine combustor configuration. The full scale catalytic combustion system is modular in design and includes a fuel/air premixer upstream of the catalytic reactor and a post catalyst homogeneous combustion zone downstream of the catalyst bed to complete the homogeneous gas-phase reactions. System start-up is accomplished using a lean-premixed (LP) low emissions fuel injector. The system transitions to catalyst operation using a variable geometry valve that diverts air flow into the catalyst at loads greater than 50% of full load. The variable geometry valve is used to operate the catalyst within the narrow operating window due to limited fuel/air turndown allowed by the catalyst. A catalyst design with preferential catalyst coating on a corrugated metal substrate to limit catalyst substrate temperatures was selected for the system. Mean fuel concentration measurements at the inlet to the catalyst bed using an instrumented catalyst module showed the fuel/air premixing to be within catalyst specifications. Preliminary combustion tests on the system were completed. The catalytic combustion system was tested over the 50-to-100% load range. Using variable geometry control, emissions goals (< 5 ppmv NOx, < 10 ppmv CO and UHC corrected to 15% O₂) were achieved for catalyst operation between 50-and-100% load conditions. The system was started and operated under part-load conditions using the LP injector. Efforts are under way to accomplish successful transition from LP mode of operation to catalytic mode of operation using the variable geometry system.