Computational fluid dynamic-assisted interchangeability study of natural gas and syngas co-firing in bluff-body burner

Abstract

Co-firing syngas and natural gas in applications where natural gas is the primary fuel could be a viable strategy for incorporating alternative fuels into combustion processes. The proportion of syngas depends on its energy content, which is linked to its composition. Likewise, the properties of natural gas also constrain the syngas percentage. Gas interchangeability methods provide insights into the maximum syngas share to prevent combustion device malfunction. However, these methods do not assess the impact of syngas on burner operation and performance. This study uses validated computational fluid dynamics simulations to examine the influence of syngas-natural mixtures on the operation and performance of a combustion device. The syngas composition corresponds to that obtained in experimental tests for the co-gasification of coal and biomass in a top-lit updraft gasifier using air. The maximum syngas share was 15 vol%, as determined by gas interchangeability theory. The simulations allow for the investigation of syngas effects on flue gas composition, gas velocity, temperature, and OH and NO concentrations. The study includes simulation results for two different burners that validate the model. The results show that adding 15 vol% of syngas led to quicker production and consumption of H₂ and CO. The main differences were observed for OH and NO concentrations, which were 7.2 % higher and 14.1 % lower, respectively, when the burner operated with syngas-natural gas mixtures. The evaluated scenarios demonstrate the combustion potential of syngas-natural gas mixtures and highlight critical areas for further investigation. Additionally, the simulation results supplement results from the gas interchangeability theory.