Characterization of pore structure of Turkish coals

Pore structure of coal has a great influence on its behavior during mining, preparation, and utilization; Characterization of the pore structure of tw elve Turkish coals from different geographic locations and with carbon cont ents varying between 61 and 84% (on dry ash-free basis) was carried out usi ng different techniques. The volume and area of macropores were determined by mercury intrusion porosimetry. Mesopore volumes and areas were determine d by N-2 gas adsorption at 77 K using the Barrett-Joyner-Halenda (BJH) meth od. Brunauer-Emmet-Teller (BET) areas were calculated using the same data. Micropore volumes and areas were determined by the application of the Dubin in-Radushkevich (DR) equation to the CO2 adsorption data at 298 K. True and apparent densities of coals were measured by helium-and mercury displaceme nt. 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 m(2)/g, was found for Tuncbilek coal which has a significant mesoporous volume; while t he corresponding values for the rest of the coals were less than 7 m(2)/g. DR surface areas which varied in the range 19-115 m(2)/g were larger than B ET areas indicating molecular sieve character of coals. SAXS areas were lar ger 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 poros ities, SAXS areas were found to be smaller; than DR areas which is attribut ed-to the inability of the method to distinguish ultramicropores of molecul ar dimensions which are probably accessible to CO2 molecules. SAXS surface area of Illinois No. 6 coal and a synthetic char (Spherocarb) were also mea sured and the values found agreed well with the ones given in the literatur e.