Insight into combustion characteristics of municipal sludge under oxy-fuel conditions

Abstract This study investigates the combustion characteristics of municipal sludge under oxy-fuel conditions using a vertical tube furnace and high-speed imaging. Results reveal that temperature (600–1000°C) and oxygen concentration (10–100%) critically govern ignition mechanisms: heterogeneous char ignition dominates at low temperatures (600°C) and low oxygen (10%), while simultaneous homogeneous volatile ignition and heterogeneous char combustion occur at 600–700°C with 100% oxygen. At elevated temperatures (800–1000°C), homogeneous ignition prevails due to accelerated volatile release and flame propagation. Thermogravimetric analysis (TGA) identifies two combustion stages: volatile oxidation (293°C) and char oxidation (505°C), with volatiles enhancing combustion efficiency. These findings provide theoretical insights for optimizing oxy-fuel sludge combustion processes to improve energy efficiency and reduce pollutant emissions.