Co-pyrolysis of low-rank coal and waste truck-tire: A comprehensive study on product distributions, product properties, and synergistic effects

Abstract

Co-pyrolysis of low-rank coal and waste polymer materials is thought to be a promising way for solid waste disposal and recovering value-added chemicals. In our study, the co-pyrolysis of waste truck-tire (WTT) and Hongliulin low-rank coal (HLL) was carried out in a bench scale fixed-bed reactor to further investigate the synergistic effects during the co-pyrolysis process. The results showed that WTT volatiles inhibited the crosslinking and polycondensation reactions of HLL volatiles to a degree, showing an increase in tar yields. Volatiles-volatiles interactions improved the quality of tar products by enhancing the conversion of heavy components into more light tar, effectively lowering the average molecular weight of tars. The co-pyrolysis produced more chain hydrocarbons and aromatics while producing fewer terpenoids compared with individual pyrolysis, which was attributed mostly to the catalytic effects of char. Volatiles-char interactions increased the graphitization degree and ordered structure of the co-pyrolysis chars, and the pore structure of the co-pyrolysis chars became more developed. The large number of hydrogen-rich radicals produced by WTT pyrolysis consumed the reactive functional groups on the surface of HLL char, resulting in a decrease in the volatiles and cross-linking degree of co-pyrolysis chars. Finally, the potential synergistic mechanism for co-pyrolysis of WTT and HLL was summarized and depicted based on the analysis results.