Characterization of Pore Structure of Turkish Coals

• Published in: Energy & fuels 2001-03, Vol.15 (2), p.331-338
• Main Authors: Şenel, İ. Gökhan, Gürüz, A. Güniz, Yücel, Hayrettin, Kandas, Angelo W., Sarofim, Adel F.
• Format: Article
• Language: English
• Subjects: Applied sciences; Brown coal; Coal and derived products; Description; Energy; Exact sciences and technology; Fuels; Structure, chemical and physical properties; Wood. Peat. Brown coal
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef000081k

Pore structure of coal has a great influence on its behavior during mining, preparation, and utilization. Characterization of the pore structure of twelve Turkish coals from different geographic locations and with carbon contents varying between 61 and 84% (on dry ash-free basis) was carried out using different techniques. The volume and area of macropores were determined by mercury intrusion porosimetry. Mesopore volumes and areas were determined by N2 gas adsorption at 77 K using the Barrett−Joyner−Halenda (BJH) method. Brunauer−Emmet−Teller (BET) areas were calculated using the same data. Micropore volumes and areas were determined by the application of the Dubinin−Radushkevich (DR) equation to the CO2 adsorption data at 298 K. True and apparent densities of coals were measured by helium and mercury displacement. Pore size distributions were evaluated using data thus obtained. Small-angle X-ray scattering (SAXS) technique was also employed to determine the surface area of some samples. The highest BET surface area, 34 m2/g, was found for Tunçbilek coal which has a significant mesoporous volume; while the corresponding values for the rest of the coals were less than 7 m2/g. DR surface areas which varied in the range 19−115 m2/g were larger than BET areas indicating molecular sieve character of coals. SAXS areas were larger than DR areas for some coals which can be explained by the presence of closed pores in these samples. For some coals having relatively small porosities, SAXS areas were found to be smaller than DR areas which is attributed to the inability of the method to distinguish ultramicropores of molecular dimensions which are probably accessible to CO2 molecules. SAXS surface area of Illinois No. 6 coal and a synthetic char (Spherocarb) were also measured and the values found agreed well with the ones given in the literature.