No.6 無極性溶剤および水を用いた新規脱水・改質法による低品位炭の自然発火性抑制の試み(研究発表)

抄録

Efficient utilization methods of low rank coals must realize not only dewatering and upgrading but suppressing self-ignition tendency of low rank coals. The authors have recently proposed a novel method to dewater and to upgrade low rank coals. The method treats coals in non-polar solvent, such as 1-methylnaphthalene (1-MN), at temperatures below 350℃. In this study, the possibility of this solvent treatment was examined as a method to suppress self-ignition tendency of low rank coals as well as to dewater and to upgrade them. It was found that the samples obtained from an Australian brown coal by the treatment in either 1-MN or subcritical water were almost free from water, and their heating values were higher than the heating value of the original coal. The values ware as high as 30 MJ/kg on the treated coal basis which corresponded to the heating values of subbituminous or bituminous coals. The self-ignition tendencies of the solvent treated coal and the water treated coal were slightly higher or almost same as the self-ignition tendency of the raw coal. These treated coals were separated into the extracted fraction and the residue at the treatment temperature to investigate the change induced by the solvent treatment in more detail. It was found that the self-ignition tendencies of the extracted fractions were significantly suppressed, whereas the self-ignition tendencies of the residues were higher than that of the original coals. This self-ignition suppression of the extracted fraction was mainly realized by their thermoplastic property, which reduces their pore surface area and minimizes gaseous oxygen access. This result suggests that these extracted fractions can be used as an additive to suppress self-ignition tendency.