A novel decoupled triple-fluidized bed reaction system for polyvinyl chloride (PVC) disposal: (I) Thermodynamic simulation and experimental investigation

ABSTRACT

In this work, a novel decoupled triple-fluidized bed reaction system was proposed to dispose of polyvinyl chloride (PVC). Thermodynamic simulation and thermogravimetric experiments were conducted to examine the dechlorination feasibility and analyze the effects of CaO and CaCl₂ on PVC pyrolysis. Besides, the quantitative removal efficiency of HCl was investigated in a lab-scale bubbling fluidized bed. Results indicated that HCl hardly interacted with the silica−alumina catalyst and Fe₂O₃ adsorbent, while for Na₂O and CaO adsorbents, HCl could convert into corresponding stable chlorides, demonstrating the theoretical feasibility of the system. Next, PVC pyrolysis was a multi-stage process, and CaO spontaneously reacted with the released HCl but simultaneously inhibited its alkylation reaction; moreover, CaCl₂ could act as a catalyst to facilitate its HCl release and alkylation reaction. Finally, as the temperature rose, the dechlorination efficiency first increased and then decreased, reaching a peak value of 87.6% at 700°C in the N₂ atmosphere. In addition, the dechlorination efficiency in the CO₂ atmosphere was higher at 400–900°C.

Highlights

• A novel decoupled triple-fluidized bed reaction system was proposed to dispose of PVC.

• The thermodynamic simulation results demonstrated the theoretical feasibility of the system.

• CaCl₂ facilitated the HCl release and alkylation reaction of PVC.

• The dechlorination efficiency first increased and then decreased with rising temperature.

KEYWORDS:

• Polyvinyl chloride (PVC)
• pyrolysis
• dechlorination
• thermogravimetric simulation
• bubbling fluidized bed

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the China Postdoctoral Science Foundation [2022M710544]; the Chongqing Municipal Education Commission Foundation [KJQN202301538]; the Chongqing Postdoctoral Science Foundation [No. 2022CQBSHTB3046]; the National Natural Science Foundation of China [52100138]; the Natural Science Foundation Project of Chongqing, Chongqing Science and Technology Commission [CSTB2022NSCQ-MSX0607].

Notes on contributors

Yu Yang

Yu Yang is an associate professor and master supervisor of Chongqing University of Science & Technology. His main research interests are the thermal treatment of organic solid wastes.

Hao Yu

Hao Yu is a master’s candidate at Chongqing University of Science & Technology. Her research interests are dechlorination and fast pyrolysis of PVC.

Lin Mei

Lin Mei received his Ph.D. in power engineering and engineering thermophysics from Chongqing University. His research areas are mainly focused on fluidized bed reactor.

Daiyang Long

Daiyang Long is a master’s candidate at Chongqing University of Science & Technology. His research interests are hydrogen rich syngas production from PVC gasification.

Shengji Zhang

Shengji Zhang is a master’s candidate at Chongqing University of Science & Technology. His research interests are hydrogen rich syngas and carbon nanotubes production from pyrolysis catalysis of waste plastics.