Combustion behavior of hydrogen-enriched natural gas in a self-regenerative furnace: Numerical and experimental analysis (Part I)

• Hydrogen addition enhances the combustibility of natural gas in the furnace. • Up to 40% vol.-H 2 reduces CO emissions to below detectable levels. • Hydrogen addition has a minimal impact on the furnace's temperature profile. • NOx emissions increase by 30 ppm with 40% vol.-H 2 at high excess air levels. As greenhouse gas emissions, such as CO₂, continue to rise, replacing conventional fuels with low-carbon alternatives is fundamental to advancing modern thermal systems. Hydrogen presents a promising option for reducing emissions while preserving operational stability. This study analyzes the performance of a self-regenerative crucible furnace operating at steady-state with natural gas-hydrogen blends at 20% and 40% vol.-H₂, using both experimental and numerical methods. The findings indicate that adding hydrogen reduces CO emissions from 615 ppm to 0 ppm, with an increase in NOx emissions up to 30 ppm at a high air-to-fuel equivalence ratio (approximately 2). Despite a decrease in total system power from 90.36 kW to 79.02 kW at higher hydrogen levels—caused by maintaining a constant discharge pressure and the resulting change in the Wobbe index—the normalized data enable direct comparison across hydrogen substitution scenarios. The results indicate that hydrogen enrichment shortens the reaction zone and concentrates heat near the lower furnace, enhancing overall combustion efficiency. At 20% vol.-H₂, an optimal balance is achieved with increased convective heat transfer due to higher gas flow velocity, complementing the radiative contribution from natural gas and improving crucible heating. Importantly, the burner design allows flexible adaptation to varying fuel compositions without significant operational disruption, supporting the feasibility of natural gas-hydrogen blending in industrial contexts. This paper constitutes Part I of a two-phase study, focusing on steady-state operation during the latent heat phase of material melting. Part II will investigate the transient phase and the regenerative heat cycle.