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.