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

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 longchain 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.

Automated summary

This paper separated sub-bituminous coal into maceral-rich fractions using float-sink method and evaluated the low temperature pyrolysis behavior of the fractions. The study found that the enriched fractions had different characteristics with varying proportions of vitrinite, inertinite, and minerals. The tar yields and compositions of the enriched fractions also showed distinct differences, indicating the potential for staged utilization of sub-bituminous coal.