Exhaust Gas Recirculation at Elevated Pressure Using a FLOX^® Combustor

To reduce CO₂ emissions from the combustion of fossil and alternative fuels, carbon capture technologies present a promising approach. But the efficiency of the capture process depends on the CO₂ concentration in the exhaust gas which is relatively low for gas turbine power plants. Exhaust gas recirculation (EGR) is a promising approach to increase the CO₂ concentration in the exhaust gas stream and thus reduce the energy losses. In this study a FLOX^® combustor was used to investigate the influence of EGR on the combustion process of natural gas at elevated pressure. The combustor stabilizes the flame without use of swirl, by creating a strong recirculation through high momentum injection of the fresh gas into the combustion chamber. This enables the establishment of a distributed combustion zone, which promises advantages for the use of gas mixtures with low reactivity like those occurring in EGR processes. At a pressure of 5 bar it was possible to increase the CO₂ concentration in the exhaust gas up to 7 vol%, which is already enough to realize an efficient CO₂ capture process. At 10 bar the CO₂ concentration could be increased to 9 vol%. The changes in flame stabilization due to pressure increase and different EGR rates are investigated by OH*-chemiluminescence imaging and discussed. The contribution of auto-ignition and flame propagation to flame stabilization is estimated by a kinetic model calculation.