Investigation of hydrogen-LPG mixtures in industrial boilers: impacts on flame characteristics, emissions, and heat transfers

Decarbonizing industrial combustion in boilers by substituting LPG with hydrogen gas as fuel is poised to play a pivotal role in reducing CO2 emissions. Nevertheless, the adoption of hydrogen in existing LPG boilers is anticipated to introduce alterations coming from disparities in combustion properties between the two fuels. The present study investigated the combustion dynamics of H2-LPG fuel mixtures under both air and oxyfuel conditions. Utilizing a computational fluid dynamics (CFD) modeling approach, this work considered temperature and flame profiles, adiabatic flame temperature, as well as NOx emissions as core performance indicators across the investigated scenarios. The modeling results revealed that a 25% H2 mole fraction content had negligible impact on flame characteristics and emissions. However, higher H2 mixing ratios (50%, 75%, 100%) would result in a notable reduction in flame length and volume, accompanied by elevated maximum flame temperature. Oxyfuel combustion of H2 coupled with flue gas recirculation demonstrated a decline in temperature and NOx emissions, coupled with enhanced heat transfer.