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

Abstract

To reveal the effects of CO2 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 CO2 or N2 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 CO2 atmosphere, the NO conversion ratio was nearly zero during the NO–CO reduction process, and for NO–char reduction, the NO conversion ratio in CO2 was lower than that in N2. 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 N2, 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 CO2 atmosphere.