

Type of Document Master's Thesis Author Picou, Laura A. URN etd-04132012-174640 Title Rapid Microwave Drying of Non-Food Agricultural Feedstock for Improved Biofuel Production Degree Master of Science in Biological & Agricultural Engineering (M.S.B.A.E.) Department Biological & Agricultural Engineering Advisory Committee
Advisor Name Title Boldor, Dorin Committee Chair Aita, Giovanna Committee Member Lima, Marybeth Committee Member Keywords
- sorghum bagasse
- dielectric properties
- microwave drying
- thermal properties
- chinese tallow tree seeds
- biofuels
Date of Defense 2012-03-30 Availability unrestricted Abstract Due to limited supply of traditional fossil based fuels, and increased interest in air andwater quality along with other environmental concerns, there has been a rise in the utilization of
biomass based energy sources. Many agricultural materials can be used for the production of
biofuels, including materials that are typically underutilized such as sweet sorghum bagasse and
otherwise nuisance species such as Chinese tallow tree seeds. The goal of this project was to
examine the relationship between the dielectric properties of sweet sorghum bagasse and Chinese
tallow tree (CTT) seeds, respectively, and frequency and moisture content; to determine pertinent
thermal properties of these materials, and to optimize process parameters of a continuous belt
microwave drying system for improved biofuel production.
Prior to microwave drying, the elemental composition, fatty acid composition, oil
content, and various thermal properties for each of the component layers of CTT seeds were
investigated. These tests revealed dramatic differences between each of the component layers of
CTT seeds. For both sorghum bagasse and CTT, the dielectric properties across a range of
moisture contents and frequencies were measured. The values obtained here were applied to the
calculation of the penetration depth of microwaves through the materials in order to illustrate
how these materials would behave when exposed to microwave energy. The dielectric properties
for each material were found to be dependent on both frequency and moisture content.
For microwave drying tests, the parameters investigated include microwave power levels
(300W, 750W, and 1.2kW) and ambient air temperatures (room temperature and 55°C) with total
residence time of 5 minutes. Data collected included humidity, temperature, sample surface
temperature, moisture content, and absorbed microwave power. The moisture removed when
microwaves are used is greatly in excess of the internal air moisture holding capacity, due to
forced removal of water from the samples via pressure gradients generated by direct interaction
with the water molecules in the matrix. Results indicate that microwave drying achieves results
better than the control with respect to moisture removed per unit energy input.
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