Hydrogen-LNG Co-firing Test Study in a 20 kW Domestic Boiler

Carbon emissions are inevitable from fossil fuel-based technologies such as LNG and heavy oil. In this context, we present hydrogen combustion technology as a fundamental thermal solution for achieving carbon neutrality. The feasibility of hydrogen combustion was confirmed through a simple nozzle hole combustion test. Following this initial test, a 20 kW domestic boiler was modified to evaluate H₂-LNG combustion, conduct pure LNG combustion experiments, and carry out H₂-LNG co-firing and pure hydrogen combustion tests. During the pure LNG combustion test, boiler thermal efficiencies and NOx emissions were compared across various boiler thermal loads and combustion air ratios. The results indicated that a lower O₂ concentration in the exhaust gas corresponded to relatively higher boiler efficiency. The H₂-LNG co-firing tests were conducted at co-firing rates ranging from 21% to 71%. The thermal efficiency during co-firing was found to be reduced by approximately 1-2% compared to the pure LNG combustion test. In the pure hydrogen combustion experiments, NOx emissions were found to be about 4 to 5 times higher than those of LNG combustion.