Thermal Plasma Treatment and Co-processing of Sludge for Utilization of Energy and Material

Thermal plasma treatment of sludge has a significant benefit in converting hazardous waste into renewable combustible gas and inert solid product, which is a workable solution for energy and material recovery. The advantages of this approach also lie in its flexibility, smaller installation, greater compactness, fewer contaminant emissions, and minimization of mass and volume. The present review focuses on various thermal plasma processes for sludge treatment and co-processing. The review starts with fundamental aspects of plasma and mechanisms of thermal plasma sludge treatment and then four basic thermal plasma systems used in previous studies. Five main thermal plasma conversion processes of sludge are classified and discussed, namely, plasma combustion, plasma pyrolysis and vitrification, plasma gasification and vitrification, plasma co-processing, and pre-processing combined with thermal plasma unit. Specifically, key parameters influencing thermal plasma treatment of sludge are distinguished and discussed as well as energy and material recovery. On these bases, the challenges and future research perspectives are addressed.