Effects of N2, CO2 Dilution on Emission Characteristics of Partially Premixed Syngas Flame

Abstract

Coal thermal power generation had advantage in plenty reserves and low cost, but it had pollution problem. Integrated coal-gasification combined-cycle power system (IGCC) is improved power generation technology which reduce sulfur oxides, nitrogen oxide, and carbon oxide largely. IGCC has been being developed and constructed globally, also domestically Taean IGCC plant is now being constructed. Gasified fuel called syngas contains H2, so to prevent flash-back combustion should be non-premixed. In this study, dilution is investigated to control NOx formed in non-premixed combustion. We conducted combustion test in model gas turbine combustor equipped with copied GE7EA nozzle varying diluent and dilution placement to understand which factor affects emission characteristics in dilution condition. Concentration of emission was measured in exhaust pipe, cross section of flame was attained by Abel transformed photograph of OH chemiluminescence. Result of diluent comparison test showed that there was other factor which affected emission characteristics in addition to temperature decrease caused by diluent, through flame structure analysis the factor was identified as degree of mixing determined by fuel-air jet momentum ratio. Comparing dilution placement, fuel-side dilution reduced more NOx because proportion of diluent that passed through flame front was bigger in fuel-side dilution than that in air-side dilution. CO was emitted below 10 ppm over almost the whole operation region, but CO emission increased sharply at low equivalence ratio dilution condition in which CO incompletely combusted.