Morwell brown coal was swollen in a pressurized vapor of methanol, ethanol, propanols, and butanols at 260 and 280 degrees C. The pressure was then explosively released, and the coal was rapidly quenched. FT-IR spectra and elemental analyses of treated coals revealed that alcohols were chemically incorporated into the coal mainly in the form of aryl alkyl ethers and that a part of hydrogen bonds of the coal were irreversibly disrupted. The effect of explosion on thermal degradability of the coal was examined from the distribution of pyrolysates obtained by flash pyrolysis at 764 degrees C. Explosion with methanol and a-propanol increased the tar yield to 31 and 33 kg per 100 kg of original coal, respectively, from 17 kg of the original coal. The tar yields were equivalent to those from coals modified by base-catalyzed O-methylation and O-isopropylation. Swelling in alcohol vapor, instantaneous pressure release, and rapid quenching were essential for the enhancement.