Enhanced NOx reduction through reburning of potassium chloride doped biomass at intermediate temperature in oxy-biomass combustion

Abstract

The challenge of achieving low nitrogen oxide (NOx) emissions in carbon-negative oxy-biomass combustion remains significant. This study focuses on enhancing NOx reduction by doping washed biomass with varying ratios of potassium chloride (KCl) to determine the optimal quantity for maximum NOx reduction. Unlike the traditional high-temperature reburning method used in PC furnaces (above 1000 °C), this study explores reburning at intermediate temperatures (550–850 °C) to assess its feasibility in fluidized bed or grate fired furnaces. Flue gas analysis is performed using an FTIR gas analyzer (Gasmet DX-4000, Finland), while solid residue analysis utilizes SEM-EDS, XRD, XRF, and TGA techniques. Results demonstrate that the highest NO reduction efficiency, up to 80 %, is achieved at a stoichiometric ratio of 0.6, a temperature of 700 °C, and 1.5 % KCl doping in an oxygen-rich environment. These findings highlight the effectiveness of a small amount of KCl doping (1.5 %) in catalyzing heterogeneous NO reduction reactions for enhanced NO reduction. Furthermore, this same KCl doping quantity (1.5 %) effectively suppresses the formation of harmful substances such as HCN and N2O, thus improving the conversion of NO to N2. Overall, this study provides valuable insights for the development of NOx control methods in intermediate temperature oxy-biomass combustion systems.