SOLID WASTE COMPACTOR AND EJECTOR TRANSFER SYSTEM PERFORMANCE WITH BULK SWITCHGRASS

摘要

A solid waste compactor and ejector transfer system provided alternative bulk compaction and hauling for switchgrass (SG) either field chopped with a forage harvester (FC) or with bales size-reduced with a tub grinder as coarse (CTG) and fine (FTG) materials. Bulk-compacted biomass was envisioned for an average depot-to-biorefinery transport distance of 56 km to take advantage of moderately increased bulk densities and efficient loading and unloading. The compactor increased bulk densities, although bulk densities were less than values reported for large packaged bales, either round or square. Maximum bulk densities observed were 168 kg m-3 (wet density) or 139 dry kg m(-3) (Dkg m(-3)). Bulk density differences were observed among SG materials, although the increased bulk density values for FC and FTG were statistically the same. Some variations were noted between bulk densities determined with ejector trailer loads and laboratory universal test machine measurements, which had a volumetric factor difference of over 33,000. Although bulk density values were less than those reported for bales, advantages were noted with bulk compaction loading and ejection unloading, such that FC loading a full over-the-road semi-trailer required a minimum of 24 min, as limited by the supply system, and unloading only required 5 min. If the supply to the compactor did not limit the compaction rate, a load time of 5 min was calculated for a theoretical maximum compaction rate (128.4 DMg h(-1)) of FC based on compactor displacement and FC "loose" dry bulk density of 124.8 Dkg m(-3). Volumetric efficiency and other factors would potentially reduce the theoretical maximum compaction rate in practice. Low energy requirements for bulk compaction and ejection indicated an economy of scale, with compaction and unloading ejection energies as low as 1.05 and 0.05 kWh DMg-1 for FC, respectively. Bulk compaction consumed energy that was orders of magnitude less than some agglutination techniques and offered a compromise to easily increase bulk density for moderate transport distances. Spillage between the compactor and ejector trailer should be addressed for commercial applications, especially for FC materials that flow well. Bulk compaction proved viable with off-the-shelf designs, and there is potential to improve designs with reduced-friction internal surfaces and integration of compaction and ejection functions into a dedicated vehicle.