Determination of adsoption and desorption properties of lignites

Gas adsorption on coals, as well as identifying coal gas content of coal seams, have a vital role in terms of prediction and prevention either gas outbursts or explosions in coal mines. That is why coal samples with their own properties should be characterized in terms of their adsorption capacities. Coals depending on their structural and compositional characteristics, they have different potentials of adsorption of various gases with changing pressures. Likewise, coal desorption characteristics changes with coal properties and the environment conditions. In order to understand the adsorption and desorption behavior of coals better, pore distribution inside the coal matrix should be further investigated. Coal seams can enclose gases especially methane in its body either in the pores with free status or the gas molecules are adsorbed on the surface of cleats, micro fractures or pores. In any mining operation of these abovementioned coal seams, depending on the operation conditions, pressure and temperature profiles and more or less depending on the mechanization and fragmentation of coals, desorption of these gases are readily to be occured. Especially methange gas, as being with its stabilized condition in its adsorbed form in the body of coal matrix, can be desorbed and result in either outbursts or explosions with the abovementioned parameters effects. With this thesis study additionally there would be available data as regards to gas deposition capacities on local coal seams and fields. In the context of this study, nitrogen, carbondioxide and methane gases adsorpstion on various types of coals were investigated, and adsorption isoterms were plotted as regards to coal types and pressure changes. In the scope of this study, some Turkish lignites were studied. Petrographical observations were carried out and the effect of coal petrographical composition on adsorption behavior of coals was investigated.