Insight into synergistic effect of co-pyrolysis of low-rank coal and waste polyethylene with or without additives using rapid infrared heating

Abstract

A newly infrared-heated reactor with a high heating rate (20 °C/s) was applied to explore the co-pyrolysis interactions between low-rank coal and waste polyethylene (PE), and further observe the effect of organic plastic additives (OPAs) in PE on co-pyrolysis interactions. PEs pyrolysis results revealed that white PE hose without additives (WPE) and black PE threading pipe with additives (BPE) exhibit significantly different product distribution. Co-pyrolysis results indicated that the addition of WPE in coal is conducive to forming tar, with a maximum tar yield increment of 6.23 wt% observed at coal/WPE (7:3). However, adding BPE in coal has a slight impact on the tar yield but significantly enhances the light fractions in tar, with a maximum light tar content increment of 6.00% at coal/BPE (9:1), revealing the interactions between OPAs volatiles and coal volatiles. The volatile-volatile interactions promote the cracking of waste PE to form short-chain aliphatic hydrocarbons and inhibit coal pyrolysis to generate aromatics and phenols. Furthermore, the chars from co-pyrolysis have a lower H/C ratio and higher C-centered radical concentration than coal char, further demonstrating that hydrogen has been transferred to the liquid products, which can provide an effective complement for understanding the co-pyrolysis interactions.