Article pubs.acs.org/EF
Biomass Pyrolysis in Sealed Vessels. Fixed-Carbon Yields from Avicel Cellulose That Realize the Theoretical Limit Sam Van Wesenbeeck,*,† Charissa Higashi,† Maider Legarra,† Liang Wang,‡ and Michael Jerry Antal, Jr.† †
Hawaii Natural Energy Institute, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States SINTEF Energy Research, Sem Saelands vei 11, 7034 Trondheim, Norway
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S Supporting Information *
ABSTRACT: In agreement with prior experimental work, thermodynamics predicts differences in the outcome of biomass pyrolysis conducted in sealed, constant-volume systems as opposed to constant-pressure systems. In particular, much higher values of the fixed-carbon yield can be expected in constant-volume systems. Avicel cellulose is known to give very low char and fixed-carbon yields; thus, char and fixed-carbon yields from cellulose have been given primary attention in this work. Our tubing bomb results reveal (i) fixed-carbon yields that realize the theoretical “limiting” values when the vessel is pre-pressurized to a modest pressure with N2 gas, and (ii) a gas product composed of steam (water) and CO2, with traces of CO and virtually no tars. Above a small range of modest temperatures and pressures, the char endures a molten phase and becomes a hard coke. The ash content of the char/coke reflects the composition of the glass wool and kao wool materials used to hold the Avicel powder in place.
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4. Charcoal at 300 °C was said to resemble coking coal having undergone melting: glossy, shiny, brittle, and bonded to the glass tube. 5. Violette measured ash contents of 3−4% vs 0.5% in the case of ordinary charcoal. Unfortunately, in the 1850s, the temperature scale was not well defined (for example, Violette believed that antimony melted at 432 °C, whereas its true melting point is 631 °C); consequently, in some cases the temperatures mentioned in Violette’s papers were underestimates of the true temperature. The promise of pyrolysis in sealed vessels languished for 140 years until Mok et al.11 reported differential scanning calorimetry (DSC) studies of the pyrolysis of small (
