Radiant flash pyrolysis of cellulose pellets:: products and mechanisms involved in transient and steady state conditions

The present paper reports the results of an experimental study of the flash pyrolysis of cellulose pellets (prepared from microgranular cellulose powder) subjected to concentrated radiation delivered by an imaging furnace. The masses and chemical compositions of the gaseous, liquid and solid products are studied as functions of the heat flux density and of the time of exposure to the radiation (between 0.05 and several seconds). The mass balances are very good despite the very low quantities involved (10(-6)-10(-7) kg). All experiments confirm the primary formation, on the surface of the pellets, of a short lifetime (around 20 ms) intermediate liquid compound (ILC) whose thickness reaches rapidly a steady state value. The condensable vapors and the gases appear to be formed from ILC, as well as char in the case of low flux densities. The HPLC and HPLC/MS analysis of ILC and of the vapors show the unique presence of anhydrooligosaccharides containing only small amounts of levoglucosan and cellobiosan. (C) 2002 Elsevier Science Ltd. All rights reserved.