Separate two-step and continuous two-stage pyrolysis of a waste plastic mixture to produce a chlorine-depleted oil

• Published in: Energy (Oxford) 2022-04, Vol.244, p.122583, Article 122583
• Main Authors: Park, Ki-Bum, Choi, Min-Jun, Chae, Da-Yeong, Jung, Jaeheum, Kim, Joo-Sik
• Format: Article
• Language: English
• Subjects: Augers; Chlorine; Fluidized bed reactors; Fluidized beds; Mixtures; Oil; Petrochemicals; Petrochemicals industry; Plastic debris; Polyvinyl chloride; Polyvinylchloride; Pretreatment; Pyrolysis; Reactors; Two-stage; Waste plastic
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2021.122583

In this study, a separate two-step pyrolysis (using auger and fixed-bed reactors) and a continuous two-stage pyrolysis (using auger and fluidized bed reactors) were conducted. This two-step pyrolysis was conducted to understand the effect of a 300 °C thermal pretreatment with the auger reactor before main pyrolysis on the chlorine removal. The fixed-bed pyrolysis of a solid product obtained after the pretreatment produced an oil with 464 ppm chlorine. An oil with only 14 ppm of organic chlorine could be obtained when a solid containing CaO was pyrolyzed in the fixed-bed reactor. Thermal pretreatment also caused changes in the yield and product composition; pretreatment led to an increase in gas yield and aromatic content of the oil. In the continuous two-stage pyrolysis of a waste plastic mixture having 3 wt% polyvinyl chloride at 730 °C, chlorinated gases were removed in parallel from the outlet of the auger reactor line and through a CaO hot filter; this produced an oil with 6.3 ppm organic chlorine. In the two-stage pyrolysis, an aromatic-rich oil (80 wt%) was obtained. The two-stage pyrolysis successfully converted the waste plastic mixture into an oil which could be acceptable as a feedstock for petrochemical industries. •Separate two-step and continuous two-stage pyrolysis were conducted.•Thermal pretreatment affected yield and chlorine content and composition of product.•TG-FTIR proved that chlorine in PVC could be separated by temperature control.•Simultaneous use of two methods in the two-stage process was effective in Cl removal.•Oil with 6.3 ppm of organic chlorine could be obtained in the two-stage process.