An experimental study of NO reduction by real biogas reburning at high temperature under oxy-fuel complex atmosphere

Abstract

• The effect of real biogas on NO reduction was studied in pyrolysis-reduction two-stage fixed bed reactor on oxy-fuel atmosphere. • The effect mechanism of real biogas on NO reduction under complex oxy-fuel atmosphere was studied. • The NO reduction characteristics by real biogas at high reduction temperature were studied on oxy-fuel atmosphere. • The reaction path of NO reduction by real biogas on oxy-fuel atmosphere was established. In order to systematically obtain the denitrification capacity of biogas in advanced oxy-fuel reburning system, the NO reduction by real biogas was studied in pyrolysis-reduction two-stage fixed bed reactor. The mechanism of NO reduction by real biogas at CO 2 atmosphere, such as reduction temperature (900 ∼ 1500 °C), complex atmosphere (O 2 /CO/H 2 O/NH 3 ) and pyrolysis temperature (600 °C, 750 °C, 900 °C) was revealed. The experimental results show that the NO reduction rate of different kinds of biogas increases first and then decreases with the reduction temperature increasing. The free radical pool in CO 2 atmosphere is mainly composed of OH radicals. The effect of O 2 on NO reduction shows an opposite trend in different temperature ranges. CO can promote the NO reduction at high temperature. Water vapor can promote the formation of OH radical and inhibit the NO reduction. C 4 H 8 in biogas plays a decisive role in NO reduction. In the absence of oxygen, the combination of biogas and NH 3 has a high reduction rate (>50 %) at 1100 ∼ 1400 °C, and the optimal reduction temperature shifts to the low temperature in the presence of oxygen. The combination of biogas and NH 3 ensures a high reduction rate (>50 %) at 900 ∼ 1300 °C under complex atmosphere. Finally, the reaction paths of NO reduction by biogas at CO 2 atmosphere are summarized.