(517d) Effects of Preprocessing Parameters on Material Attributes and Flow Behavior of Loblolly Pine

The inhomogeneous, elastic and cohesive nature of biomass poses several feeding and handling challenges during granular flow which create issues when transporting material through biorefinery unit operations (hoppers, silos, screw conveyors, etc.). It is therefore essential to study the mechanical and physical properties of these materials and accurately characterize bulk flow to ensure uniform handling and prevent issues of segregation, agglomeration, plugging, ratholing, stagnant material, arching, etc. This work is aimed at understanding and solving the flow challenges that biorefineries are faced with, through extensive experimental investigation of the mechanical properties and flow behavior (resulting from shear-failure of the bulk sample) of industrially relevant mature loblolly pine wood. Shear tests are conducted on a rotary shear tester (Schulze-style tester) at the different consolidation stresses (approximately 1 – 10 kPa) that the material might experience in an industrial scale hopper to obtain mechanical properties of the sample. This project investigates the linkages between material attributes (particle size and shape, mechanical properties arising largely from the biological cellular structure and biopolymer composition, and moisture content manifesting as enhanced particle cohesion due to capillary forces, preprocessing method, etc.), and resulting flow performance. Step wise explanatory regression of the shear test data provided a preliminary prediction estimate for apparent cohesion (output flow response) with respect to the preprocessing and material attributes (prediction parameters) discussed above. Smaller particles are seen to have higher cohesion and lower flowability. This is hypothesized to be an observational result of the interparticle forces exceeding gravitational forces in finer particles. Further, the measured properties depend on the consolidation forces. These results indicate that material might stagnate and cause mechanical locking at certain particle sizes and consolidation stresses, preventing flow. These observations imply careful consideration of operational conditions and material properties on equipment design and operation is essential to avoid material flow issues.