Smouldering organic waste removal technology with smoke emissions cleaned by self-sustained flame

Smouldering is slow, low-temperature and flameless, and has been potentially regarded as an alternative for organic waste removal technology. However, as an incomplete combustion process, toxic smoke and pollution from the smouldering are significant concerns that limit its popularization. This work applies a newly developed smouldering-based waste removal technology to investigate the removal of coffee waste, wood waste, and organic soil (simulated sludge) via using a flame to clean smouldering emissions at different airflow velocities (3–24 mm/s). Once ignited from the top, the smouldering front first propagates downwards where a stable flame situated above could be piloted and sustained to purify the smouldering emissions until the smouldering front reached the bottom of the fuel bed. The efficiency of pollution mitigation was demonstrated by significantly lower CO and VOCs emission after purification by self-sustained flame. The equivalent critical mass flux of flammable gases required for igniting the smouldering emissions is 0.5 g/m²∙s, regardless of the fuel type. The smouldering temperature, propagation rate and burning flux all increase with the airflow velocity but are also slightly sensitive to the type of waste. This work enriches strategies for the clean treatment of smouldering emissions and promotes an energy efficient and environmentally friendly method for organic waste removal.