Enshu coal was treated in methanol, methanol/water (1:1), or diluted acid solutions at room temperature for improvements of its grindability and extractability with LCO (light cycle oil) at 360℃. The impregnation in methanol or methanol/water (1:1) for 48h enhanced the coal grindability and increased the extraction yield compared to the non-treated coal. The solvent impregnation treatment under ultrasonic wave irradiation for 1h was more effective than the simple impregnation for long times. Such solvent treatments also removed some amounts of alkali and alkali-earth metals from the coal, indicating its another advantage for the production of ash-free coal (hyper-coal).
