- 48. Co-pyrolysis of hydrothermally upgraded brown coal and waste plastics
The authors have recently presented a new hydrothermal extraction method that not only removes water from brown coal but also separates the coal into upgraded coal and extract of low molecular mass compounds. The upgraded coal obtained contained much less oxygen than the raw coal and its elemental composition was close to higher rank coals. In this study co-pyrolysis of the upgraded coals and waxes formed from waste plastics was investigated as one of the methods of their effective utilization. Waxes were prepared through pyrolysis of high density polyethylene, polypropylene, and polyethylene terephtalate. Upgraded coals were then impregnated with the waxes by treatment in an autoclave at 200℃ under pressure. The mixtures of coal and wax were rapidly heated up to 1040℃ at about 3000℃/s using a Curie point pyrolyzer in an inert atmosphere. It was found that the char yield was greatly enhanced by a factor of 1.1 to 1.3 compared to the char yield obtained when the upgraded coals and waxes were pyrolyzed independently. Even at a slower heating rate (0.17℃/s) the char yields increased by a factor of 1.2 for all waxes. Since no such effect was found when using raw brown coal instead of the upgraded coal, it was suggested that the modification of the structure of brown coal by the hydrothermal extraction could enhance interactions between the coal and the wax when co-pyrolyzed.
石炭科学会議発表論文集 43 (0), 97-98, 2006