Effects of CO 2 and CO on the reduction of NO over calcined limestone or char in oxy‐fuel fluidised bed combustion

To reveal the effects of CO 2 and CO on the reduction of NO in oxy‐fuel fluidised bed combustion, NO–CO reduction catalysed by calcined limestone and NO–char reduction were studied in a suspension‐bed reactor under CO 2 or N 2 atmosphere with the CO concentration varied from 0.28 to 1.88%. Results showed that the calcined limestone is an effective catalyst for NO–CO reduction. The activation energy of NO–CO reduction over calcined limestone was 157–164 kJ/mol at low temperature (600–800°C) and decreased to 58.7–102.1 kJ/mol at high temperature (800–100°C). In CO 2 atmosphere, the NO conversion ratio was nearly zero during the NO–CO reduction process, and for NO–char reduction, the NO conversion ratio in CO 2 was lower than that in N 2 . However, CO showed promotion effect on NO reduction. In NO–CO reduction process, as the CO concentration increased from 0.28% to 1.88%, the NO reduction ratio increased from 0.40 to 0.75. For NO–char reduction in N 2 , the NO conversion ratio was obviously higher when 1% CO was introduced, and the promotion effect of CO became weaker as the temperature increased. Moreover, the promoting effect of CO was inhibited in CO 2 atmosphere.