Removal of HCl produced by PVC pyrolysis using CaO

Abstract

Polyvinyl chloride (PVC) is a polymer made by free radical polymerization and is a common plastic raw material in our life. Currently, one of the ways to recycle PVC is to burn and pyrolysis it, and the HCl produced by pyrolysis has adverse effects on the environment and the human body. The objective of this research was to the pyrolysis of PVC during slow pyrolysis in a tubular heating furnace. Moreover, to evaluate the effect of different temperatures with different calcium oxide (CaO) addition ratios on the removal of HCl generated by PVC pyrolysis. In addition, the tar and gas produced by pyrolysis were also analyzed. Firstly, the solid-phase products resulting from the co-pyrolysis of PVC with CaO addition were observed using scanning electron microscopy (SEM) and X-ray energy spectrometry (EDS). Next, the crystalline content of the solid phase products was analyzed using X-ray diffractometry (XRD). FTIR analysis of the liquid-phase products of PVC pyrolysis under CaO addition was performed. The gas phase products were analyzed by GC for common gas compositions. The results showed that more reactive sites were provided at a Ca/Cl addition ratio of 2:1. The peak value of alkaline calcium chloride was highest at 500°C, which indicates that the removal of HCl is best at 500°C. It was observed that the HCl removal efficiency reached 93.4% at a Ca/Cl ratio of 2:1 at a temperature of 550°C. This study provides a new theoretical basis for the pyrolytic removal of HCl from PVC.