Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
Enzymatic hydrolysis of cellulose to fermentable sugars necessitates high solids loadings, at which these suspensions behave as non-Newtonian fluids, exhibiting a yield stress. During the hydrolysis, large reductions in slurry viscosity and yield stress are observed especially during the initial stages of digestion. In previous studies rheological properties were measured using conventional rheometers that require time-consuming off-line measurements and encounter challenges due to the large ratio between fiber length and the instrument gap. We use magnetic resonance imaging (MRI) to measure velocity profiles of various cellulose suspensions in tube flow. Coupling the flow profiles with pressure drop measurements, we calculated yield stress values for a variety of cellulose substrates. Our results showed that the MRI rheological measurement is in agreement with reported values from the literature, and has potential advantages such as reduced uncertainty due to averaging effects over large sample sizes.