diffusion, grain size, mesopores, micropores, nitrogen sorption, subbituminous coal.

This contribution aims to examination of possible changes in kinetics during the adsorption and desorption (N2 at 77 K) in micro- and mesopores on three grain-sized fractions (< 60 ?m, 60 - 150 ?m and 150 - 540 ?m) of natural subbituminous coal. Horvath - Kawazoe and modified Kelvin relations were respectively used to identify sorption isotherm data related to filling/emptying of micro- and mesopores. Kinetic data were fitted by a Crank?s intraparticle diffusion model to obtain effective diffusivities. It was revealed that transport kinetics significantly changes during adsorption and desorption in pores between 1 and 20 nm in size. Moreover, different grain sizes of the same subbituminous coal affect both their textural characteristics and the transport rates especially during the adsorption in different-sized pores. Diffusions into different-sized pores for individual fractions are discussed in the contribution...