Pyrolysis of PVC medical plastic wastes by microwave dielectric heating

• Main Author: Nguyen, Phuong Ngoc Diem
• Format: text
• Language: English
• Published: Animo Repository 2006
• Subjects: Pyrolysis; Medical waste; Microwave heating; Plastic scrap; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/3547; https://animorepository.dlsu.edu.ph/cgi/viewcontent.cgi?article=10385&context=etd_masteral
• Institution: De La Salle University

Accumulation of enormous amounts of plastic waste produced all over the world has negative implications on the environment. Pyrolysis of these plastic wastes not only reduces the volume of these wastes but it could also have an important role in converting these wastes into economically valuable hydrocarbons. This can be used either as fuels or as feedstock in the petrochemical industry. Using microwave energy to pyrolyze plastic is a new technology. It combines the advantages of the pyrolysis technology with the fast heating capacity of microwave heating technology. In this present study, the decomposition of poly vinylchloride (PVC) and PVC blood bag through pyrolysis was investigated in microwave dielectric heating. The decomposition of PVC resin was determined using TGA-50 instrument. A microwave pyrolyzer system was fabricated using a Whirlpool domestic microwave oven with a capacity of 1000 watts and can produce a 2,450 MHz. The particle size of PVC was less than 2 mm while the charcoal powder was 0.01 mm. The charcoal powder acts as microwave absorber. Pyrolysis temperature was set at around 520oC. The parameters used in this study are residence time (5, 10, 20, and 30 mins) and weight ratio of PVC over charcoal (1/1, 1/1.5, 1/2). The pyrolytic oil was condensed at a temperature range of 810oC using Graham condensed system. The relationships between the percentages of decomposition, pyrolytic oil product, residual with the residence time and different weight ratio were investigated. Biological test was performed to determine the population of microorganisms on the PVC blood bag before pyrolyzing. It was found that PVC has two decomposition temperature zones. The first zone is at the range between 280400oC in which the dehydrochlorination of PVC occurred while the second zone is between 450560oC in which the hydrocarbon of PVC was released. The result for PVC resin and PVC blood bag using the microwave pyrolyzer show that the decomposition percentage and the pyrolytic oil percentage in all cases v were dependent on both weight ratio and residence time. The highest percentage of pyrolytic oil for PVC resin pyrolysis was 9.61 % at the weight ratio 1/2, while it was 6.64 % at 1/1.5 weight ratio for PVC blood bag. It was also noted that PVC could not decompose any more even the residence time was increased to 30 min. The results in analyzing PVC resin and PVC blood bag showed that the traced hydrocarbons were almost the same and it was not dependent on either the residence time or weight ratio of PVC and charcoal. It can be observed that the content of pyrolytic oil were benzene, toluene, heptane, heptene and some benzene derivatives. The results of the biological test show that there are around 1.3x106 colonies in one gram of simulated PVC blood bag. It shows that pyrolysis technology not only solve the problems on waste disposal but also turn these plastic wastes into a source of renewable energy. Pyrolysis is a suitable technology for treatment of hazardous wastes.