Files
Abstract
Production of pelleted biomass is an emerging industry in the United States. A primary quality attribute of pelleted biomass is moisture content. This parameter is critical in pricing, binding, combustion, and storage of pelleted biomass. To produce pellets of high quality, moisture content must be tightly controlled. In this work, the effects of temperature and pellet material type on the dielectric properties were investigated. The resulting information was used to develop temperature- and material-independent moisture prediction equations. Further work was performed in investigating the dielectric properties of pine, peanut-hull, and hardwood pellets. A unified calibration for pellets at 20C was developed that provides moisture content for the materials with a standard error of calibration between 0.48% and 0.56%. Additionally, a microwave system designed for moisture sensing in flowing bulk material was used to determine feasibility in sensing biomass from measurement of the dielectric properties. Moisture content of the flowing material was predicted by using a permittivity-based density-independent moisture calibration function. Finally, a novel open transverse-slot substrate-integrated waveguide sensor is presented. The sensor is designed and fabricated for dielectric measurements on sawdust at 8GHz. The permittivity of the material was determined by fitting the voltage standing wave ratio and phase with a normalized two-dimensional polynomial with known dielectric values. The permittivity determination model was tested by using independent sets of training and validation measurements on sawdust at different bulk densities and moisture contents between 6.8% and 39%. The predicted dielectric properties values showed linear relationships with moisture content.