Strategic combustion technology with exhaust tube vortex flame: Combined effect of biomass co-firing and air-staged combustion on combustion characteristics and ash deposition

A 16-kWth coal-fired furnace with a dual swirl burner was constructed to investigate the combustion characteristics with/without an exhaust tube vortex (ETV) flame, the combined effect of ETV flame and air staging on pollutant emissions, and the carbon burnout performance. The without ETV flame was more favorable than those of with ETV flames in terms of NO emission. However, its CO emission was primarily higher than those of with ETV flames. Through the correlation between pollutant emissions and carbon burnout, it was confirmed that the case with ETV flame exhibited higher stability than that without ETV flame. Consequently, the ETV flames have a positive effect on carbon burnout performance at every air staging level. In addition, the effects of woody biomass co-firing ratios with ETV flame were evaluated according to pollutant emissions and combustion characteristics, as well as ash deposition using scanning electron microscopy-energy dispersive spectroscopy. The increase in woody biomass co-firing ratio exhibited a positive effect on the NO and unburned carbon reduction. The air-staged combustion was more favorable than the unstaged combustion in terms of NO reduction and ash deposition. Air-staged combustion technology should be applied to reduce ash deposition at the co-firing ratio of 20% or more. •Behaviors of the burner aerodynamics and exhaust tube vortex flames are investigated.•Combustion stability and carbon burnout are improved with exhaust tube vortex flames.•Woody biomass co-firing with coal is evaluated during air-staged combustion.•Effect of the co-firing ratio with air staging on fly ash deposition is investigated.•The 20% co-firing ratio has a stable combustion environment compared to other ratios.