Radiative characteristics of premixed Coke Oven Gas-Ammonia swirling flames

Coke Oven Gas (COG) is a by-product gas generated during coal carbonisation in coke ovens, containing H₂, CH₄, CO, CO₂, and N₂. Since COG is currently used as a heat source in steel works, co-firing COG with green ammonia is considered a promising decarbonisation method for steel works. However, experimental studies investigating the radiation characteristics of ammonia blended flames are limited, not only for COG-NH₃ blends. In this study, combustion experiments with premixed COG-NH₃ swirling flames are conducted at various COG-NH₃ blends (0 ≤ X_NH3 ≤ 0.9) and equivalence ratios (0.6 ≤ Φ ≤ 1.4), and their radiation characteristics are investigated. Specifically, an infrared spectrometer is used to investigate the typical wavelengths (2220, 2600 and 2700 nm) of NH₃, H₂O, and CO₂ in the post flame zone, and a theoretical analysis of the internal radiation of the combustor is conducted based on the exhaust gas temperature and concentrations measurements. The results revealed that radiation primarily from H₂O and CO₂ peak at stoichiometric conditions, and interestingly, the change in radiation is more gradual on the rich side than on the lean side. It is also found that as the NH₃ fraction in the fuel increase, H₂O derived radiation increase while CO₂ derived radiation decrease. Furthermore, the results suggest that while H₂O radiation is dominant over CO₂, differences in radiation due to blending are primarily caused by CO₂. The findings from this study significantly contribute to the development of ammonia blended combustion systems that take radiation characteristics into account.