Experimental evaluation on NOx formation and burnout characteristics of oxy-fuel co-combustion of ultra-low volatile carbon-based solid fuels and bituminous coal

Abstract

Pyrolyzed semi-coke (SC) powder and gasification residual carbon are usually regarded as solid wastes, which feature high NOx formation amount and inferior burnout performance during burning process. Oxy-fuel co-firing of these ultra-low volatile carbon-based solid fuels (LVFs) with bituminous coal (BC) could reduce the NOx generation and realize the carbon capture to a large extent. However, the NOx formation and burnout features of oxy-fuel co-combustion of BC and LVFs are still unclear. Here, a two-staged drop-tube co-firing experimental system was employed to probe the oxy-fuel co-combustion characteristics of various blends. The experimental results show that the low ash melting temperature of coal-water-slurry gasification residual carbon yields an increase in Cfh with the temperature of burnout zone. The Cfh of BC/SC blend is decreased by 64.3% with the oxygen flow rate of primary air raised from 0.25 to 0.45 L min−1, which is the largest among all blends. The rise of difference between tube lengths in furnace of BC and LVF generates a decrease in NOx formation and an increase in Cfh. The present research could offer guidance for clean and efficient utilization of carbon-based solid wastes using oxy-fuel co-combustion technique, together with the encouraged development of carbon capture technology.