Investigation on pore structures of a medium volatile bituminous coal with solvent extraction tests

This paper presents an experimental investigation on the changes of pore structures, pore morphology of a medium volatile bituminous coal through solvent extraction under ultrasonic irradiation. The solvent extraction experiments, carried out using four non- or weak-polarity solvents with the twice- and thorough-extraction methods, provided a series of extract residues for comparison study on the coal pore structure with reference to the coal sample. Scanning electronic microscopy (SEM) and mercury injection porosimetry (MIP) were used to study the morphological and structural changes of pores both the coal samples and the residues. The results show that most solvable organic components can be extracted from coal through twice-extraction method with the solvents used in this study; under the ultrasonic irradiation, the solvent extraction makes the surfaces of coal particles grow loose and thus come to pieces forming many intergranular pores. And the numbers of intergranular pores have a tendency to increase as the extraction degree increases; the solvent extraction produced the "pore expansion" effect and increased opening pores, and hence can improve the connectivity among pores and make the pore distribution more uniform