Exergy analysis of hydrogen as an alternative fuel in corn drying: a comparative study with natural gas and propane

This study provides one of the first systematic exergy-based comparisons of hydrogen, natural gas, and propane in a commercial continuous-flow grain dryer, combining operational and fuel-based performance perspectives. A BROCK BCT-2500 dryer was modelled to dry corn grains from 25% to 15% moisture content under steady state and adiabatic conditions, evaluated at stoichiometric and lean combustion ratios. Exhaust gas properties for each fuel were determined from equilibrium calculations using NASA CEA software at both stoichiometric and lean combustion, which is then diluted in the mixing chamber with excess air to attain the required temperature and flow rate to dry these grains. The exergy balances were established across each component of the system while maintaining identical grain inlet and outlet conditions, corresponding to a fixed drying load basis. In addition, a complementary analysis was performed on a fixed fuel mass basis, varying exhaust gas and diluted exhaust gas temperatures to evaluate the intrinsic performance of each fuel per unit mass. Results indicate that combustion is the primary source of exergy destruction among all fuels. Hydrogen shows approximately 1.3% and 7% higher exergy destruction from natural gas and propane, respectively, under stoichiometric combustion and identical drying conditions, primarily due to higher exhaust gas temperatures; however, lean combustion substantially improves the exergy performance of hydrogen, making it a more viable option for low-carbon drying processes. Hydrogen exhibits the highest drying capacity of 3.3–5.6 kg of corn per gram of hydrogen, while propane maintains the highest exergy efficiency of up to 61% under current operating scenarios. Evaluating drying performance on a per-unit-mass-of-fuel basis provides a direct measure of the intrinsic fuel capability, independent of system-scale operating conditions. These findings reveal a critical trade-off between the thermodynamic efficiency and the drying capacity of fuels, offering quantitative insight into the feasibility of hydrogen in grain-drying systems. Furthermore, the evaluation of a 5% hydrogen blend with NG demonstrated that low-level hydrogen integration can be implemented within existing drying systems with limited infrastructure modifications.