Combustion and gasification reactivities of hydropyrolysis chars: Effect of pressure and heating rate

Abstract

The combustion and CO 2-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 CO 2 gasification reactivities of chars prepared under H 2 at 700 °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 °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.