Dechlorination characteristics of PVC during mixed plastic pyrolysis

• Main Author: Tay, Joo Heng
• Other Authors: Wang Jing-Yuan
• Format: Final Year Project
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Environmental engineering::Waste management
• Online Access: http://hdl.handle.net/10356/63751
• Institution: Nanyang Technological University

Having a relative low plastics recycling rate of 9% in Singapore, it is necessary to work towards efficiently removing chlorine from municipal waste plastics (MWP). In this project, thermal degradation technology is carried out for both pure PVC and mixed plastics to investigate the dechlorination characteristics. Firstly, the thermogravimetric analysis of plastics samples which consisted of pure PVC, Polystyrene (PS), Polypropylene (PP), Polyethylene (PE), Polyethylene terephthalate (PET) and mixed plastics. Thermogravimetric analysis is an essential process necessary for the preliminary study of the degradation characteristics of each plastics sample. Thereby, allowing the temperature range for the pyrolysis of pure PVC to be quantified. To ensure consistent results, the pyrolysis of pure PVC was carried out twice at temperatures of 280ºC to 320ºC and 500ºC respectively. The dechlorination characteristic was then studied to determine the temperature at which dechlorination efficiency was the highest. The results revealed that the highest dechlorination efficiency of 92.1% took place at 500ºC. This temperature range used in the pyrolysis process of pure PVC was then used as a guide for the subsequent pyrolysis process of mixed plastics. A comparison was carried out between the dechlorination efficiency of pure PVC and mixed plastics. The key findings confirmed that mixed plastics which contained 23% of PVC produced only a maximum of 84.12% dechlorination efficiency. This was much lower as compared to the maximum dechlorination efficiency of 92.1%. These results suggest that the overall dechlorination efficiency of mixed plastics decreases with the reduction of PVC content in the feedstock and generally increases with the increase in temperature. Conversely, the chlorine content in the residues of mixed plastics and PVC decrease with an increase of the temperature. Thus, this paper aims to determine the optimum operating condition that would give the highest dechlorination efficiency of PVC during mixed plastics pyrolysis.