Pyrolysis kinetics of refuse plastic fuel (RPF)

Pyrolysis has been gradually rising in demand over the past few years due to its ability to lessen the harmful gaseous by-products. This study aims to identify kinetic parameters such as activation energy and reaction rate constant for the pyrolysis of polypropylene (PP), high density polyethylene (HDPE) and polyethylene terepthalate (PET), as well as binary and ternary mixtures of the aforementioned plastics through an inert environment of nitrogen gas. The pyrolysis of the pure samples and the mixtures was done at varying heating rates, namely 20, 40, 60 and 80 oC/min. It was observed from differential thermogravimetric (DTG) plots among pure samples that PET had the highest starting decomposition temperature while HDPE had the lowest. It was also generally observed that the maximum pyrolysis rate increased with heating rate. All models yielded coefficients of determination near unity, and are considered to be adequate in characterizing the kinetics of the pyrolysis of pure, binary and ternary samples. For pure samples, PET had the highest activation energy while HDPE had the lowest. The activation energy of binary samples between PP and PET increases with PET content. For ternary samples, the PET-rich sample yielded the highest activation energy. Using the kinetic parameters obtained from the OFW model and the mean temperature at which a particular degree of conversion was attained, it was found that the minimum value for the rate constants varies from 0.3 to 0.4 min-1, and the maximum values range from 1.5 to 2.0 min-1, thus showing that kinetic compensation effect is not only observed with variations in heating rate, but also in variations in composition of the plastic sample in question