(280d) Kinetics of High Pressure Biomass Gasification

A major advantage of biomass gasification in thermochemical platform for biomass utilization is that any type of biomass can be converted to syngas, making it attractive for unmerchantable wood, harvest residue, and waste from forest and paper industry. The mechanism of biomass gasification is complicated and can be considered as the sum of two series processes - pyrolysis and char gasification. Several variables are important in the kinetics of biomass gasification, including ash content and composition, gasification temperature and pressures, and heating rates. One of the goals of present study is to develop kinetic models for high pressure biomass gasification. A combination of two complementary rate measurement techniques is being utilized in this study: (i) pressurized entrained flow reactor (PEFR) provides high heating rates (≥ 103 oC/sec) and short residence times (1-20 sec), and (ii) pressurized thermo-gravimetric analyzer (PTGA) provides lower heating rates (0.1-1 oC/sec), but larger residence times (5-100 min). The work presented here describes the results obtained with loblolly pine using both techniques. PTGA equipped with a mass-spectrometer provides important information on the evolution of gaseous species during pyrolysis. The char yield appears to be affected by the pyrolysis pressure. CO2 gasification of pyrolysis-generated char was studied at different pressures and temperatures. The reactivity of char (towards CO2) is influenced by the heating rates; in general the chars generated in PEFR (high heating rates) are more active than those generated in PTGA. The char gasification data are coupled with transport effects. However, at lower temperatures, it is possible to obtain intrinsic kinetics. Attempts to build mathematical models will be presented.