Coal bed methane potential and biogasification of soma lignite

Official URL: http://192.168.1.20/record=b1416927 (Table of Contents)

Coal bed methane (CBM) can arise from both thermogenic and biogenic activity on the coal beds and adsorb on the porous matrix of the coal. Therefore, investigation of pore structure and gas capacity of the coal is essential for accurate estimations of coal bed gas potential. Coal samples of lignite to sub-bituminous rank were obtained from different depths of Soma basin and were characterized by low pressure CO2 adsorption isotherms at 273 K. Micropore surface areas of the samples were calculated by using D-R model, changed from 224.909 m2/g to 287.097 m2/g. Micropore volume and capacity were determined by Dubinin-Radushkevich equation to vary between 0.070 and 0.093 cm3/g and between 39.06 m3/ton and 48.44m3/ton, respectively. Pore widths of all samples were below 1 nm; suggesting that micropore ratios of the samples are very high. On the other hand, high pressure (up to 17 MPa) adsorption isotherms suggest that methane adsorption capacity of the as receive Soma Lignites vary from 12.99 m3/ton to 18.13 m3/ton. Effects of outgas temperature, organic carbon content on gas adsorption capacity of the samples were determined. Results showed that microporosity and methane adsorption capacity of the samples increases with increasing micropore ratio. Carbon isotope analyses of the coal gas desorbed from coal core samples of the Soma lignite basin in Turkey suggests bacterial origin. In order to have a better understanding of secondary biogenic gas potential of the samples, biogasification experiments have been conducted. Results have shown that methane production by using just methanogens is very limited. When, free hydrogen gas was given the system, methane production has gradually increased. This proved that hydrogen was the limited reagent for microbial methane formation. After 20 days of incubation 1 m3/ton methane production was measured.