Effect of pressure on char formation during pyrolysis of pulverized coal

Char samples prepared in a pressurized entrained flow reactor (PEFR) at a pressure of 2.0 MPa and in a drop tube furnace (DTF) at atmospheric pressure have been examined. Chars generated in the PEFR show characteristics (e.g., morphology and internal structure) similar to those produced in a pressurized drop tube furnace (PDTF) over the pressure range of 0.5-1.5 MPa but differ significantly from those of chars prepared in a DTF at atmospheric pressure. Consistent with previous work, high pressure favors the formation of a foam type of char structure while the number of both cenospheric and solid char particles decreases under pressurized conditions. Swollen chars with higher porosities are produced from pyrolysis at elevated pressures. These experimental measurements agree with the results that are predicted using a char formation model developed previously by the authors, demonstrating an optimum pressure range for maximum swelling