Expansion of stable operational range in MILD hydrogen combustion based on catalytic techniques

Abstract

While hydrogen is a promising clean fuel for gas turbines, reconciling its physical and chemical characteristics with the requirements of low NOx emissions is challenging. Consequently, hydrogen combustion often results in high NOx emissions and susceptibility to flashbacks, limiting its widespread application in the gas turbine industry. While moderate or intense low-oxygen dilution (MILD) combustion technology offers the potential to address these problems, its performance degrades significantly under partial-load conditions, making it unsuitable for the wide range of load requirements of gas turbines. This study explores a novel method for expanding the stable operating range of MILD combustion using catalytic combustion to promote the development of a carbon-free energy society and address the severe performance degradation of MILD combustion. Increasing the heat energy of the gas to compensate for the lack of kinetic energy in the air reduced the dependence of MILD combustion on the recirculation ratio, resulting in high combustion efficiency and low NOx emissions. The performance of a simplified combustor model was studied through numerical simulations using a decoupling catalytic and MILD combustion strategy. Under two typical operating conditions, the numerical results showed combustion efficiencies of 99.99% with NOx emissions of 23 ppm and 3 ppm, thus demonstrating that the proposed scheme can achieve MILD combustion with high efficiency and low NOx emissions under different load conditions, thereby realising stable operation. Moreover, this approach can provide a feasible combustion path for future decarbonisation of gas turbines.