Date of Award

1989

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Lalit R. Verma

Abstract

A study on modeling, simulation, and automatic control for optimum drying and storage of rough rice in a farm-bin system was conducted to address some aspects of rice post-harvest technology. Resistance-type moisture sensors and temperature and humidity sensors were evaluated for continuously monitoring the conditions of air and grain. Models to predict rice moisture models during drying and storage were developed. Based on accuracy and predictability, the use of the capacitance-type humidity sensor is recommended over the resistance-type moisture sensor. A pressure drop model of airflow through rough rice was developed to aid in determining the optimum size and type of fan for aeration. The effect of rice moisture on the pressure drop was statistically significant at the 5% level. A respiration model for rough rice was developed to predict the carbon dioxide produced during storage and to determine the dry matter loss of the stored rice. The effects of gas modulating control and air recirculation on the energy savings in a bin-drying system of rough rice were analyzed by a computer simulation using SLAM II/PC. The gas modulating system saved 25% of total energy in August, and 8% in December, while the effect of air recirculation without dehumidification was negative in saving energy. Air recirculation with dehumidification saved much more drying energy in December as the air recirculation ratio increased, but the air recirculation was never necessary during August due to high drying potential in southwest Louisiana. The control criteria for an automatic aeration system of rough rice based on the temperature of air and grain, relative humidity of air, rice moisture, deterioration index, and dry matter loss were determined. This aeration control criteria adequately controlled air and rice conditions, and maintained the rice at a high level quality. The total economic benefits could add to more than 30 million dollars annually to the rice industry in the U.S. if the systems developed in this research for optimum drying and storage of rough rice are applied to the existing on-farm rice drying and storage.

Pages

273

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