COMBUSTION AND GASIFICATION REACTIVITIES OF HYDROPYROLYSIS CHARS - EFFECT OF PRESSURE AND HEATING RATE

The combustion and CO2-gasification reactivities of chars from Linby (UK) and Pittsburgh No.8 (USA) coals have been determined in an atmospheric pressure TGA-apparatus. The chars have been prepared in a newly configured high-pressure wire-mesh reactor under pressures ranging from atmospheric to 150 bar, at heating rates between 1 and 1000 K s(-1). Yields of tar, total volatile and char are presented and discussed. The combustion reactivities of chars prepared under hydrogen have been observed to go through a minimum around pyrolysis pressures of 20 bar. By contrast, the C0(2) gasification reactivities of chars prepared under H-2 at 700 degrees C have been observed to increase initially as a function of pressure and to stabilise above 40 bar: however, reactivities of chars prepared at 850 degrees C were found to increase with H-2 pressure only up to about 20 bar and then to drop sharply. Limited data for pyrolysis under He are also presented for comparison with the effect of H-2 on the process.