The Velenje lignite is more gas-bearing than mostly normal for lignites. It can contain 10 to 25 m3 of gas per tonne of lignite. High gas-prone (CH4 rich) coals are mostly bituminous coals in which thermogenic gas was formed during physicochemical stage of the coalification process. Interestingly, thermogenic gas occurs also in the Velenje lignite but is of endogenic origin as interpreted on the basis of C isotopic analyses. The isotopic analyses also revealed some other origins of the gas components, (microbial fermentation, CO2 reduction). CO2 and CH4 occur in very different ratios from CO2:(CO2+CH4) 1:2,5 to almost 100 % CO2 composition. CO2 is more dangerous because it is heavier and less mobile (more insidious) than CH4, and can cause more violent explosions of gas and coal. As measured in boreholes ahead of the working face, CO2 versus CH4 ratio considerably changes during advancement of the coal excavation front toward the measured sites. In first some weeks (depending on the rate of the advancement, and the mass of coal between the measured sites and coal excavation front), CH4 increasingly desorbs from coal. Approximately when methane concentration starts to decrease, concentration of CO2 starts to increase. Dynamics of the gas concentration shanges is crucial for understanding how to plan the dynamics of mine workings in regard to enable as safe as possible mining conditions. Especialy dangerous are tectonized zones in which naturaly crushed coal exists. As we studied with this-year laboratory investigations of CO2 adsorption, such coal can adsorb much greater quantities of gas than normal compact coal varieties.
COBISS.SI-ID: 26647335
This study dealing with possibilities for energy exploitatin of landfill gasses in Slovenia was not a direct object of our project but is connected with it indirectly. Our mining and geotechnology profession is now already for a considerable time (last 15 years or so) interested in so called waste material mining and manegement from different aspects: restoration of waste material dumping zones, protection of environment (especialy waters), extraction of beneficial substances etc. Capture of gas from decaying organic matter, which is gathered and deposited to more and more extent separately in the last 10 years, is also an activity how to use landfill material-s potential. For our project it is welcome and important that we have contacts with this field of gas capture and usage in the sense of exchange of information, results, knowledge and analytical equipment.
COBISS.SI-ID: 1097566