Influence of Pressure on Coal Pyrolysis and Char Gasification

Coal char structure varied greatly with pyrolysis pressure, which has a significant influence on the gasification reactivity. In this study, the influence of pressure on the behavior of coal pyrolysis and physicochemical structure and gasification characteristics of the resultant coal char was investigated using a pressurized thermogravimetric analyzer combined with an ambient thermogravimetric analyzer. First, the pyrolysis of Shenfu (SF) bituminous coal was performed in a pressurized thermogravimetric analyzer (TGA) at different pressures (0.1, 0.8, 1.5, 3, and 5 MPa). The volatile mainly evolved out at 400–800 °C. The gas products are mainly CO2, CO, CH4, and light aliphatics with some water. It was observed that the pyrolysis of coal was shifted to lower temperature (50 °C) with pressure increasing from ambient to 5 MPa, and the devolatilization rate of coal pyrolysis was decreased and the coal char yield was increased slightly. The structure of solid coal char was analyzed using FTIR, ASAP2020, and CNHS. In the solid char, the main organic functional groups are mainly C═O, C–C (alkane), C–H ar, C–O–C, and C═C ar. The carbon content was increased while H content decreased. Finally, the gasification of the solid char was preformed at ambient pressure with CO2 as gasify agent. The gasification process of coal char can be divided into postpyrolysis and char gasification. Higher pressure accelerated the initial stage of char gasification, and higher gasification reactivity was observed for char derived at 5 MPa.