Masters Theses

Date of Award

5-1989

Degree Type

Thesis

Degree Name

Master of Science

Major

Biosystems Engineering

Major Professor

Zachary A. Henry

Committee Members

Luther R. Wilhelm, Bobby L. Bledsoe

Abstract

Burley tobacco absorption data were collected for environmental conditions experienced in the burley belt during October through December. These data were needed to describe the physical characteristics of the burley leaf in order to apply the information to a moisture determination system. The exponential drying equation was used to model absorption data experimentally determined at temperatures of 0, 5, 10, and 15°C. Samples were preconditioned in a 12% relative humidity environment, then introduced to either a 55, 75, or 85% relative humidity for absorption until equilibrium was closely approached. An evaluation of the leaf character (order) was determined for each test by physically handling the leaf and comparing it to a scale rating for 'order'.

Drying tests were conducted using a hot-air-blast oven. Preliminary drying tests were developed to investigate the drying characteristics of burley samples containing different moisture contents, particle sizes, and stalk positions. The results of the preliminary tests were used to establish the parameters for the main drying experiments. The samples for the main experiment were initially conditioned in relative humidities of 12, 55, 75, and 85% with particle sizes of 1, 3, 6, and 25 mm from three stalk positions. The times of drying were 3, 5, 7, 9, and 11 min. A limited test was made to compare the hot-air-blast oven determinations to a 24-h convection oven test.

The moisture absorption results showed that, under the conditions of this experiment, the exponential equation was adequate for describing moisture absorption in the cured burley tobacco leaf. It was concluded that relative humidity has a greater effect on equilibrium moisture content and that temperature has the greater effect on the slope of the absorption curve. It was also concluded that the established character scale could be used to estimate moisture content of samples.

The 3-mm particle size was the optimum size for use in a quick-dry oven. Particle size had a significant effect on the time required to release all moisture in the hot-air-blast oven. The 25-mm shred size was found unacceptable for use in a quick-dry test. Initial sample moisture content had the greatest effect on the amount of moisture removed. It was concluded that a good estimate of the initial sample moisture content would enhance the drying results from a quick-dry oven.

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