576 / 2018-10-25 14:35:09

Effects of CO2 and CO on the reduction of NO in CFB oxy-fuel combustion

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To reveal the effects of CO2 and CO on the reduction of NO in oxy-fuel combustion, NO-CO reduction catalyzed by calcined limestone or char and NO-char reduction experiments were carried out in a suspension-bed reactor under CO2 atmosphere. Results shows that calcined limestone is an effective catalyst for NO-CO reaction, as temperature increases, the reaction active energy decreases, which is owing to the different reaction mechanisms between high and low temperature. Because of the recarbonation of calcined limestone and the competition of surface absorption sites between CO2 and NO, the NO-CO reduction over CaO is seriously suppressed under CO2 atmosphere. Besides, the NO-char reduction is inhibited by CO2 as well, and the inhibiting effect will be enhanced with the increase of the intensity of char-CO2 gasification. CO can promote the NO reduction by char, however, as temperature increases, the promotion effect becomes weaker and it will nearly disappear above 900 oC. Furthermore, NO reduction by CO over char is also inhibited by CO2.