Thursday, August 14, 2008 - 2:30 PM
S163

Heat and mass transport issues in lignocellulose conversion

Sridhar Viamajala, Biological and Irrigation Engineering, Utah State University, 4105 Old Main Hill, Logan, UT 84322-4105

Biomass pretreatment and enzymatic hydrolysis involve challenging transport processes due to the presence of multiple phases, non-Newtonian slurry rheology and the porous nature of biomass particles. For example, in dilute acid pretreatment, acid catalyst in an aqueous solution (liquid phase) is mixed with biomass (solid phase), which is then heated to 180-200 °C for 2-5 min by direct injection of high pressure steam (gas phase), resulting in a highly complex, multiphase reaction system likely limited by heat transfer rates. As a first step towards understanding pretreatment reaction kinetics as a function of heat transfer rates, slurry-phase experiments were performed on corn stover and kinetics of the reaction were determined as a function of thermal gradients.

Effective transport is also critical during enzymatic digestion, both to achieve and maintain target temperature(s) and enzyme distribution(s) and to prevent localized accumulation of products (sugars) to minimize feedback product inhibition of the enzymes. Studies were performed to characterize the rheological properties of untreated and dilute-acid pretreated corn stover slurries at high solids concentrations under continuous shear using plate-plate type measurements. Slurry rheological behavior was examined as a function of insoluble solids concentration (10 to 40%), extent of pretreatment (0 to 75% removal of xylan) and particle size (-20 and -80 mesh). The slurries behaved as shear-thinning, yield-stress fluids with the fluid rheology dependent depending upon availability of free water, particle size and chemical composition of the material.

Results highlighting these transport process examples during biomass conversion will be presented.  


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