Pyrolysis of Polypropylene in a Nitrogen Plasma Reactor

Plasma pyrolysis of polypropylene is studied for the purpose of converting waste plastics into gaseous fuel and useful chemicals. The plasma reactor has a dc arc nitrogen plasma generator with a maximum electric power input of 62.5 kV(.)A and a reaction chamber of 50 mm inner diameter and 1000 mm height. The results of a series of experiments show that, under our optimum experimental conditions of a power input of 35.2 kV(.)A and a feed rate of 60 g/min, the concentration of hydrogen in the gaseous product can reach up to 18% and that of acetylene up to 5%. Steam injection is introduced for improving the product quality and extending the application range; by water steam injection, the sum of hydrogen and carbon monoxide can reach up to 40% in the gaseous product, while the decrease of the acetylene concentration is slight. A solid conversion of 96% and a gas productivity of 2160 mL/g are achieved. The results indicate that plasma-assisted thermal decomposition of polypropylene may be a useful way for recovering energy and useful chemicals of waste plastics.