CO 2-speicherung in kohleflözen: Adsorptions/desorptions-experimente mit CO 2/CH 4-mischungen im Rahmen des EU-RECOPOL projektes

While sorption data for single gases such as CO ₂, CH ₄, and N ₂ on coal at various temperatures and pressures are increasingly available, the number of data records for experiments with gas mixtures, above all with consideration of selective or preferential sorption of individual gas components is still limited. With this as background, this study was made of gas mixture sorption experiments on various coal samples, different thermal maturity, source, age, and maceral composition. Measurements were made of adsorption/desorption with CO ₂/CH ₄ mixtures at 45°C and ≤ 180 bar. The experimental setup consists of a sequential arrangement of a calibrated reference and measurement cell and a sample loop for the transfer of gas samples to a GC. A flowrate apparatus was used to guarantee the complete equilibration between gas and adsorbed phases. The discussion covers introduction; the samples and where they came from; methodology (sample treatment, experimental setup, carrying out a preferential sorption experiment); sorption experiments with CO ₂/CH ₄ gas mixtures (Dutch coal samples, Argonne premium coal samples); and conclusion and inferences. The preferential adsorption of CH ₄ occurred only at pressures ≤ 90 bar. This corresponds to a depth of 900-1000 m. For the RECOPOL project in Poland, this phenomenon is insignificant because the injection of gas is to occur at ∼ 1100 m depth. If, however, shallow lying coalbed seams are considered such as occur in the USA and Canada the preferential adsorption of CH ₄ could have an unfavorable effect on this CO ₂ storage concept. The RECOPOL project relates to the Upper Silesian hard coal area in the region of Katowice and the first European pilot test to store CO ₂ there in non-destructible, untouched coal bed seams. The goal of this project is to achieve a storage concept and the possibility of use of CO ₂ injection to enhance the obtaining of coal bed methane. The sorption of CO ₂ is known to be double that of CH ₄ on coal such that it is to be expected that from a CO ₂/CH ₄ mixture under competitive conditions CO ₂ adsorbs preferentially on the coal.