Characterization of particle size and moisture content effects on mechanical and feeding behavior of milled corn (Zea mays L.) stover

Interest in biofuels has grown in recent years. Unfortunately, biofuel refineries are unable to operate at full capacity due to handling and feeding issues as the feeding systems for biomass are often poorly designed. To inform more effective and reliable handling and feeding systems, this study presents mechanical (moisture, particle size/distribution, bulk density, compressibility, and elastic recovery) and flow characterization (critical arching distance and feed rate in a wedge hopper and screw feeder) of corn (Zea mays L.) stover. Results showed that particle size has the most significant effect on flowability, while moisture content plays a role for a sample with large particles. For example, the feed rate of a sample with a nominal particle size of 3 mm and 10% moisture content was 44 lb./h, compared a feed rate of 24 lb./h for a sample with the same moisture content but larger nominal particle size of 25 mm. Samples with nominal particle sizes of 3 mm and moisture contents of 10% and 30% exhibited much smaller differences in feed rate. The feed rate of the former sample was 44 lb./h, and the feed rate of the latter 46 lb./h, such that the difference was within experimental measurement uncertainty. Additionally, the critical arching distance increases with increasing particle size and exhibits a small dependence on moisture content. The overall study concludes that milled corn stover feedstocks with smaller particles exhibit substantially better flowability.