Ignition, combustion and pollutant emissions characteristics of excavated waste in low oxygen concentration and O2/CO2 atmosphere

Excavated waste (EW) combustion has garnered increasing attention due to landfill pollution and the growing shortage of land. However, improper combustion methods can lead to substantial pollutant emissions into the atmosphere. Low oxygen combustion is a promising technique for reducing pollutant emissions from EW. Despite this potential, the ignition, combustion, and pollutant emissions characteristics of EW under low oxygen conditions remain insufficiently studied. Additionally, EW combustion generates significant amounts of CO₂, making the investigation of low oxygen combustion in O₂/CO₂ atmospheres beneficial for carbon capture. In this study, the ignition, combustion and pollutant emissions of EW were investigated in O₂/N₂ and O₂/CO₂ atmospheres under various oxygen concentration (5%, 10% and 21%) using TG-MS and a tube furnace. The results indicate that the NO, CO and HCl emissions are lowest under 10% O₂/90% CO₂ conditions, which are 68%, 59% and 56% lower than conventional combustion (21% O₂/79% N₂), respectively. At the same oxygen concentration, the NO and CO emissions in O₂/CO₂ atmosphere are on average reduced by 40.95% and 16.45% respectively compared with those in O₂/N₂ atmosphere. In O₂/N₂ atmosphere, ignition indexes and comprehensive combustion characteristic indexes increased significantly as the oxygen concentration increased. Overall, low oxygen concentrations effectively reduce pollutant emissions, with the lowest emissions observed at moderate oxygen concentrations. The O₂/CO₂ atmosphere not only significantly reduces pollutant emissions but also enhances ignition and combustion performance. This study demonstrates the potential of MILD (moderate or intense low oxygen dilution) and oxy-fuel combustion for EW.