Experiment Study on NOx Reduction Through Biomass Reburning in an Entrained Flow Reactor

Abstract

The reburning experiments with six kinds of biomass (including rice straw, wheat straw, maize stalk, cotton stalk, rice husk and bagasse,) and one biochar (wheat straw char) was carried out in an entrained flow reactor. The effects of biomass type, stoichiometric ratio in the reburning-zone (SR2), reaction temperature in the reburning-zone (t ₂), particle sizes of biomass (d _p), and reburning fuel fraction (R _ff) on NO reduction efficiency analysed. The NO heterogeneous reduction contribute of biochar was also analyzed. The results indicate that NO reduction efficiency behaves a trend of first increase and then decrease with decreasing of SR2 or increasing of R _ff. The higher NO reduction efficiency (more than 50%) can be achieved at the range of SR2 = 0.7–0.8 or R _ff = 20–26% during reburning with six tested biomass. Cotton stalk with higher volatiles and the highest contents of K, Na alkali metals behaves the best performance of NO reduction. In the range of t ₂ = 900–1,100°C NO reduction efficiency increases with increasing of reburning-zone reaction temperature at the same SR2. NO reduction efficiency increases insignificantly with decreasing of particle size of biomass while d _p < 425μm. The contribution of NO heterogeneous reduction by wheat straw char to the total NO reduction is in the higher range of 59–68% while R _ff = 10–26%.