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

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.