Three-stage air gasification of waste polyethylene: In-situ regeneration of active carbon used as a tar removal additive

Abstract

Air gasification of waste polyethylene (PE) was conducted using active carbon as a tar removal agent in a new type of three-stage gasifier. The main focus was on the in-situ regeneration of active carbon, which was conducted simply with air treatment, which was mainly performed with variations of treatment time and air flow rate. In the experiments, active carbon was found to be very effective in hydrogen production and tar removal. The maximum hydrogen content of the producer gas obtained with active carbon was approximately 27 vol%, while the producer gas was free of tar. Active carbon, treated with air for 10 min, while stopping feeding, had a surface area of 937 m2/g (83% recovery rate). A 4 h of gasification performed with a dolomite guard bed and a mesh type distributor produced a gas having H2 and heavier tar than toluene contents of 28 and 0 vol%, respectively. The regeneration study suggested that a severe coke formation could be diminished, when methods such as frequent air regeneration with short treatment time, the use of other regeneration agents, such as CO2 or H2O and/or the selection of a proper distributor would be applied.