CFD SIMULATIONS OF AN ADDITIONAL H2 COMBUSTOR FOR IMPROVING EFFICIENCY IN CHEMICAL LOOPING COMBUSTION POWER PLANTS

Chemical looping combustion (CLC) is a promising technology for hydrocarbon fuel combustion with integrated CO2 capture. The CLC process imposes almost no direct energy penalty for separating CO2, but a large indirect energy penalty is encountered when CLC reactors are integrated into a combined cycle power plant due to the maximum reactor operating temperature that is far below the inlet temperature of modern gas turbines. Previous works have shown that additional fuel combustion after the CLC reactors can almost eliminate this energy penalty, although more expensive hydrogen fuel must be used to avoid CO2 emissions. This study conducts CFD simulations of an added combustor fired with hydrogen, focusing mainly on mechanisms to reduce NOx formation. Three mechanisms are explored: 1) a greater number of fuel injectors, 2) increased turbulence, 3) and lower O2 content of the air stream due to flue gas recirculation. Option 2 proved the most effective at reducing NOx, followed by Option 3. When combined, these mechanisms could result in NOx emissions below 50 ppm using a very compact combustor. In conclusion, low-NOx operation of the added combustor appears to be feasible and it is recommended for inclusion in future studies of CLC combined cycle power plants