Thermogravimetric study on the pressurized hydropyrolysis kinetics of a lignite coal

Hydropyrolysis of coal is considered to be a third coal conversion technology between the coal liquification and gasification technologies. It is also the primary process for coal hydrogasification (CHG). However, the detailed kinetic characteristics of coal hydropyrolysis (CHP) are still rarely studied, which is adverse to the further development of the CHP and CHG technologies. In this work, the hydropyrolysis kinetics of a lignite coal is studied in a pressurized thermogravimetric analyzer (P-TGA). The non-isothermal thermogravimetric method is used and the effect of pressure on the pyrolysis kinetics of the lignite coal is detected. Finally, some useful results are found from the analyses for the lignite hydropyrolysis under P-TGA. With the increment of the pyrolysis pressure, the initial pyrolysis temperature increases when the pressure is higher than 1 MPa; the temperature span of the pyrolysis process shrinks; the weight loss peak value position of the derivative thermogravimetric (DTG) curve shifts rightwards when the pressure is lower than 1 MPa, while it shifts leftwards when the pyrolysis pressure is higher than 1 MPa; the reaction process will be restrained when the pressure is lower than 2 MPa. In addition, the kinetic triplets including the pre-exponential factor, the activation energy and the kinetic mechanism function are defined for the hydropyrolysis process under different pressures.