Study on nitrogen oxides reduction by advanced biomass reburning process

Advanced reburning (AR) tests were conducted in a vertical-tube experimental system using herbaceous biomass of cotton-haulm, corn-stalk, wheat-stalk and woody biomass of phoenix tree as reburning fuels. The results show that the R_ff of 20% and residence time of 0.7s are better for the reburning process. When the excess air ratio ranges from 0.7 to 0.9, and NH₃/NO mol ratio (NSR) is about 1.5, the maximum efficiency of nitrogen oxides (NO_{x) reduction at 1273K by cotton-haulm, corn-stalk, wheat-stalk and phoenix reburning reaches 89.11%, 88.34%, 90.33% and 88.28%, respectively, which is 25%~30% higher than that by general reburning. It indicates that the biomass reburning plays a great role for the NOx reduction in AR and the ammonia-ejection plays a role for optimizing the course. In a broad range of 1173K~1473K, the AR of all tested biomass could gain NOx reduction beyond 80%. The NOx reduction can be further meliorated by adding alkali metals and alkaline earth promoters with 100×10^-6 vol concentration, and the promoting effect differs from each other. The sodium carbonate and potassium carbonate can enhance the efficiency by 3%~6%; and the calcium acetate can enhance the efficiency by 4.0%~5.0% at 1273K~1473K but by nothing at 1073K~1273K.}