Gas generation from coal: taking Jurassic coal in the Minhe Basin as an example

• Main Authors: Deliang Fu, Guosheng Xu, Li Ma, Fu Yang, Dan He, Zhonghui Duan, Yu Ma
• Format: Article
• Language: English
• Published: SpringerOpen 2020-04-01
• Series: International Journal of Coal Science & Technology
• Subjects: Jurassic coal; Pyrolysis; Gas generation; δ 13C; Stage evolution
• Online Access: https://doi.org/10.1007/s40789-020-00318-z
• ISSN: 2095-8293; 2198-7823

Abstract The gas generation features of coals at different maturities were studied by the anhydrous pyrolysis of Jurassic coal from the Minhe Basin in sealed gold tubes at 50 MPa. The gas component yields (C1, C2, C3, i-C4, n-C4, i-C5, n-C5, and CO2); the δ 13C of C1, C2, C3, and CO2; and the mass of the liquid hydrocarbons (C6+) were measured. On the basis of these data, the stage changes of δ 13C1, δ 13C2, δ 13C3, and δ 13CO2 were calculated. The diagrams of δ 13C1–δ 13C2 vs ln (C1/C2) and δ 13C2–δ 13C1 vs δ 13C3–δ 13C2 were used to evaluate the gas generation features of the coal maturity stages. At the high maturity evolution stage (T > 527.6 °C at 2 °C/h), the stage change of δ 13C1 and the CH4 yield are much higher than that of CO2, suggesting that high maturity coal could still generate methane. When T < 455 °C, CO2 is generated by breaking bonds between carbons and heteroatoms. The reaction between different sources of coke and water may be the reason for the complicated stage change in $$\delta^{{{13}}} {\text{C}}_{{{\text{CO}}_{{2}} }}$$ δ 13 C CO 2 when the temperature was higher than 455 °C. With increasing pyrolysis temperature, δ 13C1–δ 13C2 vs ln (C1/C2) has four evolution stages corresponding to the early stage of breaking bonds between carbon and hetero atoms, the later stage of breaking bonds between carbon and hetero atoms, the cracking of C6+ and coal demethylation, and the cracking of C2–5. The δ 13C2–δ 13C1 vs δ 13C3–δ 13C2 has three evolution stages corresponding to the breaking bonds between carbon and hetero atoms, demethylation and cracking of C6+, and cracking of C2–5.