Three-stage thermochemical conversion of waste polyvinyl chloride

This paper proposes a new-type three-stage thermochemical conversion process with an auger reactor (AR), fluidized bed gasifier (FBG), and tar-cracking reactor (TCR) to recover HCl and a clean and H2-rich syngas from waste PVC. In the AR heated to approximately 300 and 400 °C, pyrolysis produces HCl through dehydrochlorination. On the other hand, the FBG and TCR produce syngas from the pyrolysis residue. This study examined the effects of the reaction temperatures of the three reactors on the mass balance and HCl recovery. When the AR was unheated, the experiment was stopped due to hot filter clogging in the gasification part. When the AR was heated to 300 and 400 °C, approximately 70 wt% of the product was generated in the gasification part, and liquids collected in the AR part contained most of the chlorine present in waste PVC. The chlorine content in syngas and total tar yield decreased significantly when the AR was heated. The optimal FBG temperature appeared to be approximately 700 °C. The syngas and hydrogen yield and water conversion increased at a TCR temperature of 850 °C. The chlorine content in syngas was minimized to 10 ppm.