Poor understanding of the flow behavior
of granular biomass material
poses great challenges for the bioenergy industry, as the equipment
functioning time is significantly reduced by handling issues like
screw feeder clogging and hopper arching. In this work, the flow behavior
of loblolly pine chips, including the mass flow rate and the critical
outlet width, in a wedge-shaped hopper is investigated by combining
physical experiments and numerical simulations. Comprehensive characterization
of the flow response affected by the two material attributes (initial
packing, particle density) and the three operational parameters (hopper
outlet width, hopper inclination, and surcharge) is conducted. The
results show that the hopper outlet width linearly controls the mass
flow rate, while the hopper inclination angle controls the critical
outlet size. The packing determines whether the flow is smooth or
surging, and the surcharge-induced compaction creates flow impedance.
The magnitude of these influences varies from a slender hopper with
a low inclination angle to a flat-bottom silo. These findings provide
guidance for hopper operation in the material handling industry and
shed light on the construction of a novel design method for material
handling equipment in biorefineries.
The bioenergy industry has been challenged by unstable flow and transport of milled biomass in material handling operations. Handling issues such as hopper clogging and auger jamming are attributed to knowledge gaps between existing handling units designed for bulk solids and their suitability for milled biomass with high compressibility. This work investigates various flow behaviors of granular woody biomass in wedge-shaped hoppers. Hopper flow physical experiments and numerical simulations are conducted to study the influence of the critical material attributes and critical processing parameters on the flow pattern, arching, and throughput. The results show that (1) the preferred flow pattern, mass flow, can be achieved by controlling the material's internal friction angle, hopper inclination, and hopper wall friction; (2) hopper arching, governed by the competing gravity-driven force against flow resistance from material internal friction and material− wall friction, can be controlled by the hopper wall friction angle and the inclination angle; and (3) flow throughput can be accurately estimated from our empirical equation with inputs of hopper outlet geometry and particle-scale to bulk-scale material attributes. This study elucidates woody biomass flow physics and provides guidance for industrial equipment design.
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