Abstract:

Abstract:  Open system nonisothermal pyrolysis experiments at a heating rate of 1 K/min were performed on immature coal samples (Ro=0.4%) from the Tarim Basin, NW China, and on their isolated macerals (vitrinite, exinite, fusinite and semifusinite) in order to determine the kinetics of gas generation (CH4 and N2). Assuming that the generation rate of CH4 and N2 was described by 25 single firstorder reactions with a single preexponential (Ao＝1.0×1013 s-1), a discrete distribution of activation energies was computed by data processing for CH4 and N2. When the activation energies were distributed between 42 and 90 kcal/mol, a model occurred with the dominent activation energy of 60, 52, 50, 70, and 66 kcal/mol for CH4 from coal, vitrinite, exinite, fusinite and semifusinite, respectively; the dominant activation energy for N2 was 74, 108, 100, 108 and 102 kcal/mol respectively when the activation energies were in the range of 60108 kcal/mol. Based on the kinetic parameters derived from laboratory experiments, CH4 transformation ratios were calculated for geological heating rate of 5.3 K/Ma. Gas containing more than 80% of CH4 was formed under these conditions at temperatures in excess of 160 ℃ from coal, whereas the percentage of methane generation from vitrinite and exinite was higher than that from coal.

Key words:

Key words: Tarim Basin; coal and maceral; utrahigh temperature pyrolysis; activation energy; kinetic modelling