Rheology of corn stover slurries at high solids concentrations – Effects of saccharification and particle size

• Published in: Bioresource technology Vol. 100; no. 2; pp. 925 - 934
• Main Authors: Viamajala, Sridhar, McMillan, James D., Schell, Daniel J., Elander, Richard T.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-01-2009; [New York, NY]: Elsevier Ltd; Elsevier
• Subjects: Agronomy. Soil science and plant productions; biofuels; Biological and medical sciences; biomass; Biomass slurries; Carbohydrates - chemistry; cellulose; chemical composition; Computer Simulation; corn stover; Food industries; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; glucans; High solids; lignin; lignocellulose; mathematical models; Models, Chemical; Particle Size; Particle slurries; physical properties; Plant Components, Aerial - chemistry; Pretreatment; renewable energy sources; rheological properties; Rheology; saccharification; Solutions; Use and upgrading of agricultural and food by-products. Biotechnology; Use of agricultural and forest wastes. Biomass use, bioconversion; Viscosity; xylan; Zea mays - chemistry; Particle slurries; Pretreatment; Rheology; High solids; Biomass slurries; Monocotyledones; Particle size; Zea mays; Animal slurry; Saccharification; Biomass; Cereal crop; Straw; Particle; Gramineae; Angiospermae; Concentration effect; Spermatophyta; Corn by product
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2008.06.070

The rheological characteristics of untreated and dilute acid pretreated corn stover (CS) slurries at high solids concentrations were studied under continuous shear using plate–plate type measurements. Slurry rheological behavior was examined as a function of insoluble solids concentration (10–40%), extent of pretreatment (0–75% removal of xylan) and particle size (−20 and −80 mesh). Results show that CS slurries exhibit shear-thinning behavior describable using a Casson model. Further, results demonstrate that the apparent viscosity and yield stress increase with increasing solids concentration (which corresponds to a decrease in free water). Dilute acid pretreatment leads to lower viscosity and yield stresses at equivalent solids concentrations, as does smaller particle size. Taken together, these findings are consistent with the hypothesis that the availability of free water in the slurry plays a significant role in determining its rheological behavior. In particular, as the free water content of the slurry decreases, e.g., with increasing solids concentration, the greater interaction among particles likely increases the apparent viscosity and yield stress properties of the slurry. The results also suggest that the availability of free water, and thereby slurry rheological properties, depend on the chemical composition of the corn stover as well as its physical characteristics such as particle size and porosity. Hydrophilic polymers within the cell wall, such as xylan or pectin, or larger pores within bigger particles, facilitate sequestration of water in the solid phase resulting in decreased availability of free water. Thus, dilute acid pretreated slurries, which contain smaller size particles having significantly lower xylan content than slurries of untreated milled stover, exhibit much lower viscosities and yield stresses than untreated slurries containing large particles at similar solid concentrations.