Effects of Mixing Quality On the Kinetics of Biomass Liquefaction

Tuesday, October 18, 2011: 9:45 AM
211 B (Minneapolis Convention Center)
David M. Lavenson1, Emilio J. Tozzi1, Tina Jeoh2, Michael J. McCarthy3 and Robert L. Powell1, (1)Chemical Engineering and Materials Science, University of Calfiornia Davis, Davis, CA, (2)Biological and Agricultural Engineering, University of Califonrnia, Davis, Davis, CA, (3)Biological and Agricultural Engineering, University of Calfiornia Davis, Davis, CA

Abstract: Biochemical conversion is a promising route to produce fuels and chemicals from cellulosic biomass. A key step in the process is biomass liquefaction, where enzymes are used to break down pretreated cellulosic particles. During this process, drastic changes in the mechanical properties of the cellulosic slurry cause a transition from a solid-like material to a pumpable liquid. A fast liquefaction is desirable to achieve reductions in equipment size and cost. To assess the effect of
mixing quality on the speed of liquefaction, cellulases were added to static fiber beds in vials. Different initial mixing conditions were used. One of the conditions was a well-mixed slurry where the enzyme is uniformly distributed in the slurry. The opposite extreme condition was addition of a thin layer of enzymes on one end of the vial, representing a completely unmixed enzyme. Samples were incubated for 96h at 50C. The state of liquefaction of the fiber beds was assessed using a mechanical penetrometer test. Large differences in the force-displacement curves were observed between untreated control slurries and enzymatically treated slurries. More importantly among the treated ones, the liquefaction times were much shorter for well-mixed slurries than for poorly mixed ones. Liquefaction data was also compared with reducing sugars measured throughout the incubation period to correlate with product yields.

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