Combustion Interactions of Blended Chars under Oxidation and Gasification Competition in Oxy–Fuel Condition

Abstract

The combustion interactions during blended coal combustion affect their combustion characteristics, and the combustion interactions under air–fuel conditions have been well studied. However, oxy–fuel combustion considerably differs from air–fuel firing. Significantly, the char–CO2 gasification reaction under oxy–fuel and high-temperature conditions substantially affects the combustion behaviors, which may influence the combustion interactions. This paper is to study the effect of the char oxidation and gasification reaction competition on comprehensive interactions in O2/CO2 mixture. The results show that under high-temperature and low-oxygen (O2<4%) conditions, an intense gasification reaction is observed. The competition between the char–CO2 gasification and char–O2 oxidation reactions influences the comprehensive interactions during blended chars combustion. As the char–O2 oxidation reaction is strengthened and the char–CO2 gasification reaction is weakened, the comprehensive interactions during blended chars combustion gradually decrease. Moreover, under the competition between the char–CO2 gasification and char–O2 oxidation reactions, only enhancing the char–CO2 gasification reaction or enhancing the char–O2 oxidation reaction weakens the comprehensive interactions. The weaker comprehensive interactions result in the smaller nonadditive behavior of the comprehensive combustion index. The findings shed light on the interaction effects observed during blended chars combustion, which can provide useful information to improve the combustion behaviors of the blended coals in oxy–fuel conditions.