Title page for ETD etd-04132012-174640

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
  • sorghum bagasse
  • dielectric properties
  • microwave drying
  • thermal properties
  • chinese tallow tree seeds
  • biofuels
Date of Defense 2012-03-30
Availability unrestricted
Due to limited supply of traditional fossil based fuels, and increased interest in air and

water 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 55C) 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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