Corn stover, a well-known example of lignocellulosic biomass, is a potential renewable feed for bioethanol production. Dilute sulfuric acid pretreatment removes hemicellulose and makes the cellulose more susceptible to bacterial digestion. The rheologic properties of corn stover pretreated in such a manner were studied. The Power Law parameters were sensitive to corn stover suspension concentration becoming more non-Newtonian with slope n, ranging from 0.92 to 0.05 between 5 and 30% solids. The Casson and the Power Law models described the experimental data with correlation coefficients ranging from 0.90 to 0.99 and 0.85 to 0.99, respectively. The yield stress predicted by direct data extrapolation and by the Herschel-Bulkley model was similar for each concentration of corn stover tested.
Corn stover is currently being evaluated as a feedstock for ethanol production. The corn stover suspensions fed to reactors typically range between 10 and 40% solids. To simulate and design bioreactors for processing highly loaded corn stover suspensions, the rheologic properties of the suspension must be measured. In systems with suspended solids, rheologic measurements are difficult to perform owing to settling in the measurement devices. In this study, viscosities of corn stover suspensions were measured using a helical ribbon impeller viscometer. A calibration procedure is required for the impeller method in order to obtain the shear rate constant, k, which is dependent on the geometry of the measurement system. The corn stover suspensions are described using a power law flow model.
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