(334e) Quantitative Assessment of Milled Woody Biomass Attributes Impact on the Performance of Compression Screw Feeder Using Modeling and Experiment

Lignocellulosic biomass is an abundant and cheap source of renewable energy that can play a strategic role in shaping the clean energy portfolio to meet increasing global energy demands while satisfying the proposed measures to mitigate climate changes. However, biomass recalcitrance to decomposition to release sugar content for fermentation or upgrading adversely affects economic and efficient production of biofuels and biochemical products. This recalcitrant nature is attributed to the complex internal structure of the plant in its raw form, which gives rise to unfavorable properties, e.g., high variability, high cohesiveness, low bulk density, and characteristic flow behavior that involves complex localized elastic and plastic deformation patterns with strong dependency on the stress history. Accordingly, biomass pretreatment is mandated to change the physical properties and chemical composition of the biomass feedstocks using different mechanical, thermal, and chemical processes. Biomass poor flowability renders materials handling and feeding to the biorefinery a substantial challenge in the supply system. The unique characteristic of the lignocellulosic biomass feedstocks dictates developing dedicated design practices for handling and feeding unit operations beyond the conventional methods that are based on decades-long accumulated experience from other industries dealing with particulate materials with substantially better flow properties. Current design practices lead to operation under average feeding rates much lower than the design capacity and significantly higher operation cost due to frequent system interruptions and process upsets. Promoting an adequate understanding of the characteristic nature of the granular biomass flow behavior and the underlying transport mechanisms is still needed to reduce the overall cost and enable commercial-scale deployment of bioenergy technologies. Preprocessing and materials handling involve energy intensive processes. Thus, developing mitigating strategies requires identifying the underlying mechanisms controlling the flow behavior of this biomass feedstocks to determine critical parameters. This can aid in the optimization of preprocessing unit operations and engineering favorable flowability of biomass in feeding and handling. The present work seeks quantitative assessment of the effect of particle characteristics of milled white pine on the performance of a compression screw feeder unit that is part of the Chemical Preprocessing System (CPS) at Idaho National Laboratory using an integrated computational and experimental approach. Following quality-by-design approach, the impact of different Critical Material Attributes (CMAs) and Critical Process Parameters (CPPs) on the performance of the considered unit is studied. Three critical quality attributes (CQAs) are used as performance metrics: 1) mass flow rate, 2) shaft driving torque, and 3) specific energy consumption. Experiments and discrete element model (DEM) simulations are conducted to evaluate the impact of two CMAs – particle size and moisture content, on the chosen CQAs. The impact of a CPP, namely, shaft rotational speed (rpm) is also investigated. The results shed light on the relation between material attributes, operation parameters, and screw feeder blockage mechanisms as well as the quality of the formed plug seal.