PYROLYTIC BEHAVIOUR OF CELLULOSE IN A FLUIDIZED BEDREACTOR

摘要

The literature devoted to the competitive and sequential kinetics of cellulose pyrolysis is quite controversial, because of the ambiguous relationship established among cellulose molecules, levoglucosan and other products. A fast pyrolysis system composed of a feeding system, a fluidized bed reactor, carbon filter, vapour condensing system and gas storage is created to quantitatively investigate the yield of bio-oil, syngas and char from cellulose pyrolysis, at different temperatures (from 430 to 730 °C) and residence times (from 0.44 to 1.2 s). The products in the bio-oil are characterized by GC-MS, while the gas sample is analyzed by GC. The relationship between levoglucosan and the other main products (5-HMF, FF, HAA and HA) is estimated versus the possible routes for primary cracking of the cellulose molecules and the secondary reactions of fragments. CO formation is seen as enhanced at high temperature and residence time, while the yield of CO? is slightly changed. Further on, an improved kinetic scheme is proposed, to describe the pyrolysis steps of cellulose, showing that levoglucosan acts not only as a product of cellulose cracking, but also as a precursor for the formation of almost all the other products.