110th Anniversary: MILD Combustion of Liquid Hydrocarbon-Alcohol Blends

Among the various low NOx combustion technologies, MILD combustion combines low pollutant emissions, combustion stability and efficiency, fuel flexibility, and noise reduction through a high preheating of the combustion chamber coupled with a massive exhaust gas recirculation at high turbulence level. In this work, the sustainability of MILD combustion for liquid hydrocarbon-alcohol blends (as possible constituents of surrogate fuels representing the behavior of blends of fossil fuels and biofuels) has been investigated experimentally using a dual-nozzle laboratory-scale burner. Several hydrocarbon-alcohol blends have been investigated to identify the regions (in the furnace temperature vs dilution ratio space) where MILD combustion can be sustained with low NOx and CO emissions. It has been found that the MILD combustion conditions of the various liquid fuel blends investigated differ slightly one to each other and are quite similar to that of the hydrocarbons without any oxygenated species. This means that a MILD combustion burner shows a large flexibility in terms of fuel properties, therefore creating a suitable environment for NOx and CO depression also for fossil fuels-biofuels blends.