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Chen R.,Key Laboratory Coal based CO2 Capture and Geological Storage | Chen R.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation History | Qin Y.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation History | Wei C.-T.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation History
Natural Gas Geoscience | Year: 2014

Based upon the data of mercury intrusion and methane isothermal adsorption of 5 sets of raw and two-step-extracted coals from western Guizhou and eastern Yunnan, the differences and influence factors of pore structure and adsorptivity between raw and solvent-extracted coals were comparatively discussed. The results show that the extraction changes vitrain pore structure. Coal rank controls the pore structure changes of carbon disulfide extracted coal, the extraction increases and enlarges the pore number and volume before and after the second coalification jump, respectively. The benzene extraction enlarges vitrain pore volume in all. The extraction also changes vitrain adsorptivity, but the change direction and magnitude depends on the coalification degree; the extraction of organic solvent enhances and reduces vitrain adsorptivity before and after the second coalification jump, respectively. It was found that the adsorptivity of extracted vitrain change has a positive relationship with the changes of the pore special surface area and/or volume, and it has a negative relationship to that of the total, macro, middle and transitional pore volume and special surface. It was considered that the second coalification jump plays a key role on the changes of the pore structure and the adsorptivity, and it evidenced that the methane adsorption happened in the surface area of coal micro pore. In addition, it was also suggested that the alteration of the organic extraction to the pore structure and adsorptivity of coal may involve the micro pore related to the macro-molecular structure of coal, which is worthy of further investigation. Source


Li W.,China University of Mining and Technology | Li W.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation History | Zhu Y.,China University of Mining and Technology | Zhu Y.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation History
Energy Sources, Part A: Recovery, Utilization and Environmental Effects | Year: 2014

Five vitrinite samples of various coal ranks from the Shanxi Formation, North China plate, were pyrolyzed using a Rock-Eval6 pyrolyzer and an improved micro-scale sealed vessel pyrolysis instrument to investigate the characteristics and kinetic behaviors of their pyrolysates. Cumulative formation of methane and C1-5 continuously increased as the pyrolysis temperature was increased. In contrast, the C2-5/C1-5 ratio is larger at a heating rate of 10 K/h heating than 30 K/h at the same temperature before the heavy gaseous components peak. Hydrocarbon generation from the vitrinite of various coal ranks that gaseous generation yield initially increases first and then decreases with increasing rank, with the maximum yield at Ro, max 2%. The results indicate that the activation energy of M1 ranges from 254.98 to 317.68 kJ/mol, with a peak of 3 kJ/mol in a diagram of activation energy distribution if its frequency factor of 7.890 × 1017/s is assumed. The activation energy of M2 ranges from 254.98 to 338.58 kJ/mol, with a peak of 313.50 kJ/mol in the diagram. The activation energy of M5 ranges from 213.18 to 246.62 kJ/mol, with a peak of 234.08 kJ/mol in the diagram. The activation energy of the total hydrocarbons of M4 in an open system is 217.36 kJ/mol. The light hydrocarbon (C6-14) content of M1, M2, M3, M4, and M5 are, respectively, 4, 110, 111, 104, and 38 mg/g·TOC. The temperatures corresponding to peak values of heavy gaseous hydrocarbon generation vary with coal rank and increase with an increase in coal rank as hydrocarbon generation and heavy hydrocarbon cracking in high-rank coals requires more energy. © 2014 Taylor and Francis Group, LLC. Source

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