In order to examine the effect of solvent-extraction and preheating-treatment upon the dilatation of coal, the following samples were prepared for four Japanese coals (Oyubari 85.9% C, Oshima 84.9% C, Hashima 86.4% C and Eri 86.2% C): (1) coals extracted with pyridine at 10, 30 and 50°C, (2) coals extracted with benzene at 150°C, (3) coals preheated at 300, 350 and 400°C, (4) preheating coals extracted with chloroform.
There is a statistical linear relation between the dilatation of parent coals and their pretreating coals and their volatile matter. And the better linear relation exists between the dilatation of them and the weight loss heating them up to 400°C under 3mmHg (except for Eri coal, because of their small dilatation).
There is nearly linear relation between the dilatation of sample (1) and the extraction yield, the more extracted, the smaller swelling becomes. But the relation between the benzene extraction yield and the dilatation of the residue does not agree with the relation in the case of the pyridine extraction.
When preheating temperature is higher, the dilatation of preheated coal becomes lower. For the same coal sample the relation between the swelling of the sample (3) and chloroform-extraction yield is linear (except for Eri coal). These results may be explained by the extract flowing out of the interior of coal particle to the surface by preheating.
It seems that the condensable gas (tar) produced at the softening temperature range is reponsible to the dilatation of coal, but the non-condensable gas has little affect on the dilatation.
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