Study on pyrolysis behavior of the coal fractions based on macro maceral separation

Abstract In this paper, a sub-bituminous coal was separated into several maceral-rich fractions by float-sink method and the low temperature pyrolysis behavior of the separated fractions were further evaluated. The results showed that, the raw coal could be successfully separated into vitrinite-rich, inertinite-rich and mineral-rich fractions. Compared with the raw coal, the vitrinite was enriched from 50.8% to 65.2% in the vitrinite-rich fraction, the inertinite was enriched from 37.2% to respectively 47.3% and 51.6% in the two inertinite-rich fractions, and the minerals content increased from 11.20% to 38.40% in the mineral-rich fraction. The enriched aliphatic long-chain structures and alkyl side chains on aromatic rings caused the highest tar yield (dry basis) of 16.21% in the vitrinite-rich fraction, almost 4.16% higher than that of the raw coal (12.05%). Moreover, the tar also had the highest aliphatic hydrocarbons content which is beneficial for further upgrading. The inertinite-rich fractions were enriched in regular aromatic and hydroaromatic structures, so that a higher polycyclic and naphthol content in the tar was obatained. The mineral-rich fraction had the highest stacking height for the carbon crystallites and was enriched in small aromatic clusters, resulting in a larger amount of benzenes and naphthalene in the tar. It is believed that this work provides a good guidance that the prior separation is beneficial to the further staged utilization of sub-bituminous coal.