Study On Reaction Properties Of Rapid Coal Liquefaction In Methane Atmosphere

On the basis of kinetic analysis of coal pyrosis in methane atmosphere and gas-liquid equilibrium analysis of methane-solvent, rapid liquefaction of Longkou lignite coal was studied in a novel laboratory scale tubular reactor. The effect of several parameters on the liquefaction reaction has been investigated, moreover, the mechanism of rapid liquefaction has also been preliminarily studied.Thermogravimetric analysis (TGA) was carried out for Longkou lignitic coal with four different heating rates of 25, 40, 55 and 70 oC.min-1. The experimental results indicated a synergistic effect during methane and coal. The kinetic parameters, activation energies (E) and pre-exponential factors (k0), of thermal pyrolysis for coal at different conversion levels were correlated from the thermogavimetric data. The conversion dependent E and k0 values were obtained. The compensation effect was clearly observed from the straight line of the plot of ln(k0) versus E. It indicated that many parallel reactions with different rate parameters occur simultaneously during the pyrolysis of coal. The distribution functions, f(E) and k0(E), were then established satisfactorily by the distributed activation energy model (DAEM).A set of experiment apparatus for determining gas solubility in liquids at high pressures was designed and established. Its reliability was confirmed with literature data. The solubility of methane in the solvent at high pressures was measured exactly and then the Peng-Robison EOS coupled with two kinds of mixing rules was adopted to calculate the GLE data under high pressure by correlation. The calculated results showed that the data of the system were well described by the Peng-Robison EOS.Liquefaction experiments were performed at a temperature ranging from 400 to 800 0C, a residence time ranging from 4.5 to 11.2 seconds and 10-15 MPa (without catalyst). Reactions were also carried out under nitrogen gas atmosphere at the same reaction conditions. The results indicated that there were synergism effects between coal and methane at the temperature over 6000C, and the temperature and residence time were the main factors influencing the coal conversion and products distribution. The oil yield reached a maximum of 21.97 (wt.% daf) at 750 0C during 9.0 seconds. The results indicated that the liquefaction process was reasonable and rapid liquefaction was feasible.Raw coal and liquefaction residue were characterized by scanning electron microscope (SEM), Fourier transformation infrared microspectroscopy (FTIR), Temperature-Programmed Thermogravimetry instrument, X-Ray Diffractometer (XRD) and Elemental Analyzer. These results have provided a scientific basis for improvement of the novel technology.