Combustion characteristics of hydrous ethanol as a sustainable diesel replacement in industrial boilers

Decarbonizing industrial thermal systems is often hindered by the prohibitive costs of hardware retrofitting and energy-intensive fuel processing. This study addresses a critical research gap concerning the industrial scalability of hydrous ethanol (95% vol.) as a direct, drop-in replacement for diesel in an unmodified 100-kW pressure-spray burner. While previous literature has primarily focused on costly anhydrous grades or small-scale laboratory burners, this work provides a high-resolution performance map of hydrous ethanol at industrial capacities. Experimental evaluations were conducted across varying firing rates and fuel equivalence ratios (ϕ) to benchmark axial temperature profiles, emissions (CO and NOx​), and combustion efficiency against standard diesel. The results demonstrate that while the lower heating value (LHV) of hydrous ethanol reduces the firing rate compared to diesel using identical injectors, it offers superior environmental benefits, including a 30–45% reduction in NOx​. Notably, ethanol exhibited higher peak temperatures in the near-nozzle region, reflecting rapid kinetic oxidation despite its 5% water content. A key innovation of this work is a novel, unified exponential CO trend for hydrous ethanol, establishing a new predictive framework for air-induced quenching in industrial burners. Despite physical differences in atomization, both fuels achieved high combustion efficiencies (99%) at equivalence ratios above 0.58. These findings establish the technical feasibility and operational limits for hydrous ethanol, providing an immediate cost-effective drop-in strategy for decarbonizing the industrial thermal power sector.