Topping Combustor Status for Second-Generation Pressurized Fluidized Bed Cycle Application

Second-generation Pressurized Fluidized Bed (PFB) combined cycles employ topping combustion to raise the turbine inlet temperature for enhanced cycle efficiency. This concept creates special combustion system requirements that are very different from requirements of conventional gas turbine systems. The topping combustor provides the means for achieving state-of-the-art turbine inlet temperatures and is the main contributor to enhanced plant performance. The objective of this program is to develop a topping combustor that provides low emissions, and is a durable, efficient device exhibiting stable combustion and manageable wall temperatures. The combustor will be required to burn a low-Btu Syngas under normal “coal-fired” conditions. However, for start-up and/or carbonizer outage, it may be necessary to fire a clean fuel, such as oil or natural gas. Prior testing has shown the Westinghouse Multi-Annular Swirl Burner (MASB) to have excellent potential for this application. Metal wall temperatures can be maintained at acceptable levels, even though most “cooling” is done by 1600°F vitiated air. Good pattern factors and combustion efficiencies have been obtained. Additionally, low conversion rates of fuel bound nitrogen to NO_x have been demonstrated. This paper presents an update of the status of an ongoing topping combustor development and test program for application to “Second-Generation Pressurized Fluidized Bed Combined Cycles (PFBCC).” The program is sponsored by the Department of Energy’s Morgantown Energy Technology Center (DOE/METC) and will first be applied commercially into the Clean Coal Technology Round V Four Rivers Energy Modernization Project. Phase 1 of the program involved a conceptual and economic study (Robertson et al., 1988); Phase 2 addresses design and subscale testing of components; and Phase 3 will cover pilot plant testing of components integrated into one system.