KINETICS STUDY OF A STAGED COMBUSTOR CONCEPT FOR OXY-FUEL COMBUSTION GAS TURBINE CYCLES

摘要

Oxy-fuel combustion has been identified as a promising technology for CO_2 capture and NO_x reduction. It has great potential to be applied in gas turbine cycles. Previous studies, however, reveal that simple oxy-fuel combustors suffer from issues like flame blowoff and CO emissions especially at part load, due to the high CO_2 content in the combustion atmosphere. In this paper, a staged combustor concept is proposed to mitigate flame blowoff and CO emissions issues for load operations. The conceptual combustor consists of three zones axially: primary zone, CO burnout zone, and dilution zone. All fuel is fed to the primary zone, while O_2 is distributed to the primary zone and CO burnout zone. CO_2 is distributed to the primary zone and dilution zone. By adjusting the distribution of the O_2 and CO_2, the primary zone operates at a relatively higher flame temperature at part load, which helps improve the flame blowoff performance. A chemical reactor network model is developed to study the effects of key design/operating parameters on flame blowoff and CO emissions. Results show that the distribution ratios of O_2, CO_2 and residence time between different zones are the key factors that influence flame blowoff and CO emissions. To mitigate flame blowoff and CO emissions at part load, the distribution of O_2 needs to be carefully chosen so that the primary zone operates under near-stoichiometric or slightly lean condition, while the distribution of CO_2 to the primary zone also needs to be reduced. The residence time split has stronger influence on CO emissions than CO_2 and O_2 distribution.