Effect of H2O on the combustion characteristics and interactions of blended coals in O2/H2O/CO2 atmosphere

Abstract Blending coal combustion technology is commonly used in coal-fired power stations, and the combustion interactions (i.e., the ignition promotion and burnout inhibition) during blended coal combustion affect their combustion characteristics. The combustion interactions under conventional air-fuel condition have been well studied. Oxy-fuel firing considerably differs from air-fuel combustion and the combustion interactions of blended coals in O2/CO2 atmospheres have been investigated in our previous research. However, the H2O concentration in actual oxy-fuel condition is relatively high, which may influence the combustion interactions. This study further investigates the effect of H2O on the combustion characteristics and interactions of blended coals in O2/H2O/CO2 atmospheres. The results show that adding H2O into the oxy-fuel atmosphere remarkably affects the combustion characteristics with the more notable ignition delay, faster burnout and better comprehensive combustion characteristics (CCI). In addition, the presence of H2O strengthens the ignition promotion, the burnout inhibition and the comprehensive interactions, resulting in the more obvious non-additive behaviors of CCI. In O2/H2O/CO2 mixtures, enhancing the H2O/CO2 ratio slightly strengthens the ignition promotion, the burnout inhibition, and the comprehensive interactions, which increases the non-additive behaviors of CCI. Furthermore, both of increasing O2/H2O or O2/CO2 ratios significantly weaken the ignition promotion, strengthen the burnout inhibition and the comprehensive interactions, which increases the non-additive behaviors of CCI. The findings shed light on the interaction effects observed during blended coal combustion in O2/H2O/CO2 mixtures, which can provide useful information to improve the combustion characteristics of the blended coals in the real oxy-fuel atmospheres.