The operation of lignocellulosic biorefineries will likely involve difficult-to-transport biomass solids. The processing of high-solids slurries and/or granular materials will be necessary for achieving economies of scale.
Relevant to the biochemical conversion of biomass, the changing rheology of high-solids pretreated corn stover slurries were studied. Prior to saccharification, corn stover slurries with concentrations up to 20 wt% insoluble solids exhibited rheological properties characteristic of soft solids, including an apparent yield stress and shear-thinning. Both yield stress and viscosity were strong functions of concentration. During saccharification, the viscosity and yield stress of corn stover slurries diminished rapidly with conversion of cellulose to glucose. In addition, macromolecular additives altered the rheology and created more processable slurries.
Next, the feeding of wood chips is relevant to thermochemical processing. Wood particle transport occurs year-round, so understanding particle friction both wet and dry wood particles could assist in the design and modeling of equipment, including screw feeders. A tribo-rheometry method was developed using a commercial rheometer to measure torque needed to rotate two contacting millimeter-scale wood particles. Comparing ambient environmental conditions with controlled moisture content measurements using a custom-built humidity-controlled chamber found that the torque required to rotate wet wood particles was consistently higher than dry particles.
Overall, rheology provides a platform to help engineer biomass flows, which are needed to effectively scale-up the production of sustainable fuels and chemicals.
Matthew W. Liberatore is a Professor in the Department of Chemical Engineering at the University of Toledo. He earned a B.S. degree from the University of Illinois Chicago and M.S. and Ph.D. degrees from the University of Illinois at Urbana-Champaign, all in chemical engineering. From 2005 to 2015, he served on the faculty at the Colorado School of Mines. In 2018, he served as an Erskine Fellow at the University of Canterbury in New Zealand. His laboratory research involves unique rheology measurements of complex fluids from traditional and renewable energy materials to polymers and colloids. His educational research investigates problem solving related to student-written YouTube problems and learning analytics related to interactive textbooks. His interactive textbooks for Material and Energy Balances, Spreadsheets, and Thermodynamics are available from zyBooks – a Wiley brand. His website is: https://www.utoledo.edu/engineering/chemical-engineering/liberatore/.