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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Quality and Safety Assessment Research Unit » Research » Publications at this Location » Publication #316666
Title: Effects of temperature and material on dielectric properties of pelleted wood-based biomass

Author
item MCKEOWN, MURAT - University Of Georgia
item Trabelsi, Samir
item TOLLNER, ERNEST - University Of Georgia

Submitted to: Southeastcon, IEEE
Publication Type: Proceedings
Publication Acceptance Date: 3/9/2015
Publication Date: 4/9/2015
Citation: Mckeown, M.S., Trabelsi, S., Tollner, E.W. 2015. Effects of temperature and material on dielectric properties of pelleted wood-based biomass. Southeastcon, IEEE. 1:57-61.

Interpretive Summary: The production of biomass is a significant emerging industry in the United States with biomass energy consumption growing more than 60% between 2002 to 2013. A major part of this industry is the production of pelleted biomass which increases the density and permits more efficient handling and lower cost of transport. Material moisture content is a critical quality factor of pelleted biomass, and it is important for binding the material and in pricing, storage, and combustion optimization when it is burned as a fuel. Microwave measurements are useful for sensing bulk density and moisture content of particulate materials through use of their dielectric properties because of high correlations between these properties and the moisture content of the materials. Techniques have been developed for using microwave measurements to sense moisture content of particulate or granular materials independent of bulk density fluctuations. Since dielectric properties are dependent also on temperature, the nature of that dependence must be determined to take temperature variation into account when sensing moisture content. In this study, the temperature dependence of the dielectric properties of peanut-hull pellets and pelleted pine sawdust were investigated. The range of variables included temperatures between 0 °C and 50 °C, moisture contents between 6% and 16%, wet basis, and frequencies from 5 to 15 GHz, with three different bulk densities for each measurement. The effect of pelleted material was investigated by determining the dielectric properties of pine and peanut-hull pellets measured at 10 GHz. A unified calibration for sensing moisture content independent of density and with temperature compensation was developed that worked well for both pine pellets and peanut-hull pellets. This work paves the way for design of practical microwave sensors for monitoring moisture content of pelleted biomass materials, which would benefit producers of such biomass materials and consumers of these materials as fuel sources for various industrial applications.

Technical Abstract: The production of pelleted biomass represents a significant emerging industry in the United States. Solid biomass can be formed from the waste products of many different products. In this study, the effects of temperature and pellet material type on the dielectric properties were investigated. Temperatures of peanut hull pellets were increased in 10 °C increments ranging from 0 - 50 °C and dielectric properties at various moisture contents were determined. Further work was performed in investigating the dielectric properties of pine compared to those of peanut-hull pellets to determine whether a "unified" calibration for moisture content could be developed. Finally, the effect of pine-pellet degradation into sawdust was investigated to determine whether this would cause a change in the dielectric properties. Results showed that a temperature compensated calibration for moisture content could be developed for peanut-hull pellets. Additionally, a unified calibration for moisture content was achieved at 10 GHz.