Stability and Emissions of a Lean Pre-Mixed Combustor with Rich Catalytic/Lean-burn Pilot

Abstract

Abstract In this work, a reactor network model was developed to study homogeneous gas-phase methane combustion taking place under typical operating conditions of lean pre-mixed combustors piloted by rich catalytic/lean-burn (RCL) systems. In particular, the thermo-kinetic interaction between the pilot stream (i.e. the stream exiting the RCL stage) and the main feeding stream to the homogeneous reactor was investigated in terms of combustion stability and emissions. The homogeneous combustor was modeled as a perfectly stirred reactor (PSR). The pilot stream was mixed with the main feeding stream prior to entering the PSR. Numerical results have shown that the opportunity to stabilize combustion is strongly linked to the presence of hydrogen in the pilot stream. Combustion stability is highly sensitive to variations in fuel split between catalytic pilot and homogeneous reactor. The increase in pilot fuel split (and, thus, in the inlet hydrogen concentration to the PSR) enlarges the operating window of stable combustion (in terms of higher heat losses, lower preheat temperatures and lower residence times), while still achieving NOx and CO emissions lower than 9 ppm (at 15% O2). These results highlight the potential of the RCL technology as a valuable alternative to conventional diffusion flame-based pilots.