Investigation of NO reduction mechanism of nitrogen-impregnated biomass across wide temperature range

Abstract

Traditional denitrification methods for coal-fired power boilers face challenges like reduced flue gas temperature at low loads, decreased efficiency of existing denitrification devices, and increased ammonia consumption. Biomass, a renewable energy source, has proven effective for denitrification in medium to high-temperature ranges. To improve denitrification efficiency at low loads, this study focuses on optimizing re-burning denitrification of biomass by nitrogen-impregnated of corncob at room temperature. Investigating the effects of nitrogen impregnation and washing on biomass re-burning denitrification reactivity within 550–950 °C, the study finds that denitrification efficiency improvement is not caused only by surface-covered urea or washing. Nitrogen impregnation enhances biomass pyrolysis, releasing more CO, HCN, and NH3 products, thereby enhancing NO reduction during denitrification. Additionally, nitrogen impregnation boosts nitrogen-containing functional groups such N-6 on biomass char surfaces during the re-burning process, improving denitrification efficiency. The maximum denitrification efficiency of the nitrogen impregnated sample reached 97.52 % at 950 °C, while it reached 76.51 % at 650 °C when the coated urea was washed. Furthermore, chlorine and alkali metal contents in biomass notably decrease after nitrogen-impregnation and washing, optimizing biomass combustion conditions for furnace protection. This study offers theoretical insights for promoting and applying biomass denitrification techniques.

Keywords

• Biomass
• Low load denitrification
• Nitrogen impregnation
• Re-burning