Characteristics of Air Gasification of 10 Different Types of Plastic in a Two-Stage Gasification Process

In this study, air gasification of 10 different types of plastic was conducted using a two-stage gasifier consisting of a fluidized bed gasifier and a tar-cracking reactor filled with activated carbon as a tar removal additive. The study aimed to show characteristics of the producer gases obtained from the two-stage gasification of individual plastics. Ten individual plastics were grouped into four according to their chemical compositional characteristics. In the experiment, product gases having tar contents in the range from 132 mg/Nm3 (ABS) to 0 mg/Nm3 (polyethylene and polyamide) were obtained. In the gasification of plastics having aromatic rings, the productions of char and tar in gas were higher than those of aliphatic plastics. The gasification of aliphatic plastics without heteroatoms, such as polyethylene and polypropylene, favored H2 production and had a maximum value of 26 vol %. Activated carbon played a significant role in lowering the tar content in gas and enhancing H2 production. Plastics having oxygen in their structures (PMMA, PA, PET, PU, and PC) enhanced the CO production. However, gasification of plastics having aromatic rings (PC, PET, and ABS) with sand as the bed material caused bed agglomeration and a severe coke buildup on an activated carbon bed. Dolomite as the fluidized bed material was found to be very effective in solving these operational problems.