Combustion Characteristics of a Multiple-Injection Combustor for Dry Low-NOx Combustion of Hydrogen-Rich Fuels Under Medium Pressure

An oxygen-blown integrated coal gasification combined cycle (IGCC) plant with pre-combustion carbon dioxide capture and storage (CCS) is one of the most promising means of zero-emission generation of power from coal. In an IGCC plant with CCS, hydrogen-rich syngas with a wide variation of hydrogen contents is supplied to a gas turbine. Such hydrogen-rich syngas poses a great challenge to a low NOx combustor based on premixed combustion technology, because its high flame speed, low ignition energy, and broad flammability limits can cause flashback and / or auto-ignition. On the other hand, a diffusion combustor suffers from the high flame temperature of syngas and the resulting high NOx emission. The authors applied a “multi-injection burner” (cluster burner) concept to a preliminary burner for hydrogen-rich syngas simulating that from IGCC with CCS. In a preliminary experiment under atmospheric pressure, the multi-injection burner worked without any flashback or any blowout. A prototype multi-cluster combustor based on the results of that preliminary study was made to be a dry low NOx combustor for hydrogen-rich syngas of IGCC with CCS. It was tested in experiments, which were carried out under medium pressure (0.6MPa) using test fuels simulating syngas from IGCC with a 0% carbon capture rate, a 30% carbon capture rate and a 50% carbon capture rate. The test fuels contained hydrogen, methane and nitrogen, and had hydrogen content ranging from 40% to 65%. The following conclusions were drawn from the test results: (1) The tested combustor allows stable combustion of fuels simulating 0%, 30%, and 50% CCS. (2) A convex perforated plate swirler is effective to suppress combustion oscillation, which allows NOx emissions to be less than 10ppm through the variation of fuel simulating 0%, 30% and 50% CCS.