Heat Transfer in Vacuum Pyrolysis of Decomposing Hazardous Plastic Wastes

Vacuum pyrolysis has been widely used to decompose plastic wastes for obtaining purity chemicals or remove hazardous organic pollutants. The pyrolysis temperature determined the variety of pyrolysis products. The final (highest) temperature was the most investigated factor. However, temperatures used in vacuum pyrolysis were not equally distributed. The lowest temperature also determined the variety of the products. Regrettably, this vital factor has not been researched and reported. In this paper, the heat transfer process of vacuum pyrolysis was fully analyzed. The models for computing the lowest temperature were constructed. The models were certified by the vacuum pyrolysis of novolac epoxy particles collected from crushed waste printed circuit boards. According to the models, we found the heat transfer coefficient of the crucible and the inner diameters of the crucible and alundum tube were the key factors for controlling the lowest temperature. The models can help us to modify and adjust the lowest and highest (final) temperatures in vacuum pyrolysis. This contributed to recovering pure chemicals or removing pollutants from plastic wastes by vacuum pyrolysis.