(207b) The Nature of Torrefaction Effect On Producing High-Quality Fuel Intermediate Via Fast Pyrolysis

Session T4 08 Thermochemical Conversion I

AIChE 2013

November 3 ~ 8, 2013

San Francisco, CA

The Nature of Torrefaction Effect on Producing High-Quality Fuel Intermediate via Fast Pyrolysis

Jiajia Meng,¹ Junyeong Park,¹ Andrew Moore,¹ David Tilotta,¹ Sushil Adhikari,² Stephen Kelley,¹ Sunkyu Park¹

¹ Department of Forest Biomaterials, North Carolina State University, Raleigh, NC 27695

² Biosystems Engineering Department, Auburn University, Auburn, AL 36849  

*Presenting author: jmeng@ncsu.edu

As a new rising pretreatment technology for making high quality bio-oil via fast pyrolysis, torrefaction pretreatment has attracted increasing attention last years. This simple thermal pretreatment was expected to reduce oxygen content as well as associated water and acids in the resulting bio-oil, therefore bringing significant benefits (reducing hydrogen consumption and coking formation) to the further oil upgrading process, i.e. hydrotreating. Understanding the effect of torrefaction treatment on bio-oil properties and pyrolysis chemistry is critical to fulfill these expectations. In this study, fluidized-bed fast pyrolysis was performed on torrefied loblolly pine with different degrees of torrefaction severity. With the bio-oils made from this integrated process, the effect was investigated via: (1) comparing the physical and chemical properties, including oxygen content, water content, viscosity, average molecular weight, acidity (TAN number) heating value and chemical composition (determined by GC/MS and solvent fractionation) of bio-oil made from torrefied wood to that made from non-treated wood; (2)  semi-quantifying the carbon and hydrogen distribution between the bio-oils made from the pretreated wood and the raw wood with ¹H and ¹³C NMR characterization; (3) accessing the time and thermal stability of bio-oil made from pretreated wood by accelerated aging and natural aging methods. The results show that torrefaction pretreatment can significantly reduce the oxygen and water content of the bio-oil as well as varying the chemical composition of bio-oil with concentrated pyrolytic lignin and levoglucosan. Less polymerization occurred during the aging process for bio-oil made from torrefied wood. All these effects are attributed to the structural and compositional change of torrefied wood induced by the thermal treatment. Possible cellulose pyrolysis mechanism was proposed to explain the increased levoglucosan concentration in the torrefaction-based bio-oil. In addition, the torrefaction effect on fast pyrolysis process was accessed by separated and integrated torrefaction and pyrolysis mass balance, elemental balance, and energy balance. With these understanding, an integrated process, including torrefaction pretreatment, fast pyrolysis, and oil upgrading to produce hydrocarbon fuel, is proposed.