(36a) Biological Degradation and Moisture Effects on Corn Stover Comminution

Biomass comminution is the most energy intensive unit operation during preprocessing behind drying. This size reduction stage is simple in concept, but the resulting particle fragments’ size and morphology depend on complex interactions of biomass properties, mill operations, and their natural variabilities. These resulting particle sizes and morphologies, contribute to feeding and handling performance as well as convertibility in terms of biological access or thermal transport, etc. In previous developmental work, a predictive population balance model (PBM) was developed for knife milling of corn stover stalks and scaled up from bench to pilot scale. Based on a breakage probability and breakage function, the milled particle size distribution was predicted as a function of variation in mill tip speed, moisture content, initial particle size, and retention screen size. This work presents further developments to the predictive model to probe more complex factors impacting stover stalk strength properties and breakage behavior in a knife mill, including non-linear effects of moisture and material biological degradation. Linkages between pectin and moisture in the middle lamella of the stalks, are parametrically explored for their impact on strength properties and comminution behavior. This work focuses on changing pectin and moisture levels of the corn stalks to further probe these correlations and their effect on breakage behavior. Particle size and distribution shape metrics are matched between experimental measurements and model predictions. Particle size metrics studied include passing diameters and distribution shape metrics include relative span, kurtosis and skewness.