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A particulate medium thermal Processor was designed and fabricated to dry, roast, disinfest and de-germinate cereal grains. The components are: a particulate heater, medium and grain mixer, separation unit and aeration unit. Comparative tests showed that particulate medium heating was 5 times faster and 87% more efficient than convective heating. Although the drying efficiency was 95% higher in the convection system, the overall use of input energy was 28% higher in the Processor. / Drying of corn was investigated at 500kg/h. High moisture removal was achieved at initial moisture contents of 19% and 24% using salt at initial medium temperature of 250ºC. The highest moisture removal achieved was 6.17% (w.b.) with a corn flow rate of 500 kg/h, initial moisture content of 19%, initial medium temperature of 250°C, and a 60 s contact time. / Soybean was roasted in the Processor at 500 kg/h. Initial medium temperatures of 175, 200 and 250°C resulted in grain temperatures of 104, 107 and 127°C, respectively, for a contact time of 60 s. An average of 4.11% (w.b.) moisture reduction was achieved from commercially dried soybean at 6.8% initial moisture content. / A preliminary study showed grain temperatures over 67°C was sufficient to achieve 100% insect mortality of Sitophilus granarius for a 30 s exposure. These temperature and contact time data were used for evaluating the possibility of thermal disinfestation using the Processor. Tests on wheat processed at 1000 kg/h showed that grain temperatures rose to between 69.8°C and 72.9°C for exposure times of 60s. These results were achieved at thermal efficiencies of 43% and 49% respectively. Estimated cost of disinfestation using the machine was CAN$ 0.385/t. / Seed quality wheat was processed to determine parameters leading to total thermal de-germination. Tests were conducted at 40, 60, 80 and 100°C. Total de-germination of the wheat seed was found to occur at temperatures over 80°C for an exposure time of 60 s.

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Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

The results of a theoretical and experimental investigation into the drying of wheat and barley in two stages with an intervening rest period are presented. The reduction in drying time, excluding rest period, has been determined in comparison with the conventional continuous drying for various drying requirements. The effect of airflow rate and the temperature difference between grain and air on the reduction in moisture content and the time required to cool the grain during dryeration is also included. The moisture diffusion equation was solved numerically assuming a spherical grain. The variable grid spacing, Crank-Nicolson approximation technique and the Gauss-Seidel iterative procedure was employed. The theoretical predictions were compared with experimental results. The drying and resting was performed on a thin layer at a temperature of 60°C. An automatic micro-computer based system was developed to record and store the experimental data. The results indicate that the moisture redistribution during resting is well advanced after a period of two hours for wheat and one hour for barley. The extent of redistribution was measured by the increase in drying rate observed as the rest period was extended. An optimum moisture content for commencing resting is specified, which is a function of initial, final and equilibrium moisture contents. This optimum was chosen to minimise the actual drying time. There is good agreement between the theoreticaaand experimental predictions. It was found that the incorporation of a surface resistance into the diffusion model improves the description of the experimental results. The results enable a drying strategy to be specified that reduces the actual drying time by as much as 39%. - iv For dryeration experiments, the grains pre-heated to different temperatures were put into a well insulated aluminium cylinder and aerated at various airflow rates. An airflow rate of about 60-120 m3/hr/m3 of grain was found to be optimum. The moisture reduction during cooling was observed to be 0.65 to 0.78% (db) per 10°C temperature difference. It was noticed that moisture reduction also depends on initial moisture content of the grain. The practical implications of two-stage drying are discussed.

Two slotted two-dimensional spouted bed units with flexible bed dimensions were designed and fabricated. Static vertical pressure of grains (shelled corn, soybean, and wheat) on the air entry slots in the pilot scale unit indicated that the silo theories are not applicable to predict this pressure accurately without including the bed to air inlet aspect ratio, slant angle, and sphericity of grains. A grain quantitative factor accounting for emptying angle of repose and sphericity of particles was proposed and included with the collected data to develop an empirical regression model. / Aerodynamics of grains (shelled corn, soybean, and wheat) were found to be affected by slant angle, spout width, separation distance, length of bed and the bed geometrical similarity. Mathematical models for the design parameters of the spouted beds were developed following the principles of dimensional analysis and similitude. Model predictions agree closely with the data. / The drying rate of shelled corn in the geometrically similar two-dimensional spouted beds with draft plates was found to depend on the bed geometry and operating parameters. The drying characteristics of corn in the investigated spouted beds was found to be of the thin layer type. The performance of dryers was modeled in the form of the Page's equation. Expressions for the model parameters accounting for bed geometry, grain moisture content, and drying conditions were developed. The developed model predictions agree well with the data from both beds.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1985. / Bibliography: leaves 101-106. / Microfilm. / xxiv, 193 leaves, bound ill. 29 cm