Analysis of co-pyrolysis characteristics of high-sulphur coking coal and polyethylene

Abstract

The co-pyrolysis of high-sulphur coking coal and plastics can not only recover the hydrocarbon resources in waste plastics to realise the effective utilisation of high-sulphur coking coal, but also realise the harmless treatment of waste plastics. In this article, high-sulphur prime coking coal, high-sulphur fat coal and plastic polyethylene were selected as the research objects. The co-pyrolysis of high-sulphur coking coal and plastic was carried out by means of thermogravimetric device and glial layer device. The thermogravimetric analysis revealed that the weight loss rate peaks for prime coking coal, fat coal and polyethylene occur within overlapping temperature ranges. This overlap facilitates hydrogen transfer from polyethylene to both prime coking coal and fat coal. Additionally, the addition of polyethylene reduces the temperature range for volatile release stage (II). Furthermore, the activation energy required for the pyrolysis of the mixture during the volatile release stage (II) increases with a higher proportion of polyethylene. In contrast, the activation energy needed for pyrolysis in the slow pyrolysis stage of semi-coke (III) decreases. Co-pyrolysis experiments indicated that the co-pyrolysis products exhibited a decrease in semi-coke yield with the addition of polyethylene. Moreover, the de-sulphurisation of semi-coke followed a non-linear trend, initially increasing and then decreasing. Additionally, the introduction of polyethylene resulted in a decrease in the bonding properties and content of anisotropic texture.