Fluidity of coal residues after extraction with mixed solvents

Abstract

The Gieseler fluidity of coal residues after their extraction with mixed solvents was investigated for four bituminous coals to elucidate the effect of low molecular weight extractable substances on the plasticity of coals. The maximum fluidity was found to decrease with an increase in extraction yield. At a low extraction yield, bulk softening was predominantly affected by the softening behaviour of low molecular weight substances originally present in coal, while the softening of pyrolytic products became dominant at a higher extraction yield. The resolidification temperature and the plastic range also decreased as the extraction yield increased. For a coal containing a higher concentration of extracts, the plastic range tends to increase. Three petroleum pitches were used as model compounds of the extracts. By addition of pitches to the residues of one coal, the maximum fluidity was shown to increase and the maximum fluidity temperature was found to be related to the pitch aromaticity. The role of the extracts in coal fluidity is discussed.