Investigation of a Duct Burner Design Using CFD in Comparison With Full-Scale Experiments

Most new duct burners are supplied to heat recovery steam generator (HRSG) manufacturers for use in cogeneration systems. Key components of a simple cycle cogeneration plant include a turbine, generator, turbine exhaust gas duct, duct burner (optional), HRSG and downstream flue gas cleaning equipment. New developments in gas turbine technology are changing the boundary conditions for supplemental firing. In response, John Zink has an ongoing research project for the development of new duct burners achieving ultra low NOx emissions maintaining a good flame quality. The scope of this research work includes computational fluid dynamic modeling (CFD) and experimental testing of current design duct burner to obtain baseline data comparable with CFD results, and various experimental configurations through a full range of expected operating conditions. Experimental testing is performed in a test furnace at John Zink Company, Tulsa. Turbine exhaust gas (TEG) is simulated using John Zink Duct burners, which are supplied with air from a combustion air fan. Different O2 levels can be achieved by a combined water/steam injection. The temperature level of the TEG to the test burner can be adjusted with an air-cooled heat exchanger. Temperature and concentration measurements can be made at the test burner location and in the stack. Flame length, as well as NOx and CO emissions were measured for each data point. CFD modeling focused on the performance effects of turbine exhaust gas flow mal-distribution and the investigation on how reliable CFD models are, regarding flame stability calculations and NOx production. The results of this comprehensive testing and results from the CFD calculations will be compared and presented.