Numerical simulation of the effects of hydrogen and carbon monoxide ratios on the combustion and emissions for syngas fuels in a radiant burner

In this study, the performance of a gas-fired radiant-tube which was fuelled with syngas and air mixtures was investigated numerically using ANSYS Fluent version 17.2. The burner was operated in a non-premixed mode with swirled air. The exhaust emissions of nitrogen oxides (NOx) and carbon monoxide (CO) as well as the temperature distributions along the radiant tube were analysed for three different syngas fuels which were composed of hydrogen (H2) and CO, with ratios (by vol.) of 75:25, 50:50, and 25:75. The simulations were conducted at equivalence ratio values of 0.82, 0.7 and 0.5, while the air flow Reynolds numbers were set to 5400, 6320 and 8850. Based on the simulation results under all the tested conditions, it was found that the 75H2:25CO syngas fuel performed better, where the non-uniformity parameter calculated for this fuel was 35% lower than that of the 25H2:75CO. In terms of CO emissions, 75H2:25CO had the lowest value among the tested fuels, where the maximum difference as compared to that of the 25H2:75CO was up to 93%. Meanwhile, the NOx emissions predicted for 75H2:25CO were approximately 67% lower than those of the 25H2:75CO.