The effect of drying corn, rice and wheat seed in two stages was studied, using germinability as a measure of quality. For the first stage, fluidised bed dryer (FBD) and spouted bed dryer (SBD) were used to dry seed from 20-25%wb to 18%wb while in-store dryer (ISO) was used in the second stage for drying from 18%wb to below 14%wb. The drying air temperature range of 40-80??C was studied for the first stage while 18-30??C and relative humidity 60-70% were for the second stage. It was found that dryer type, drying temperature, initial moisture content of seeds and drying time had significant effects on the seed germination. From the result, the drying air temperature of 40??C was safe for corn and rice in FBD while 60??C was acceptable for wheat. In SBD, the 40??C was the maximum drying temperature for rice and wheat without quality deterioration. Meanwhile the second stage drying in an ISD under all specified conditions was safe. In this work, the thin-layer drying models were developed. The results showed that the modified Page's model and modified two-compartment model were the best-fitted models with the root mean square (RMS) of the differences between the predicted moisture ratio and the measured values below 0.03. Besides, the existing ISD simulation program provided the RMS of 0.3, 1.1, and 0.9%wb for corn, rice and wheat respectively. The germination models for FBD and SBD were also developed. As a result, the modified Giner's models 1&2 were the best-fitted models for FBD with the RMS of the differences between predicted and measured germination percentages of 7.9, 4.2 and 3.4% for corn, rice and wheat while the modified Giner's models 2&3 were for SBD with the RMS of 5.5 and 6.1% for rice and wheat respectively. The comparison between FBD and SBD revealed that FBD had faster drying rate while SBD consumed less energy. Ultimately, the energy cost analysis showed that single-stage drying in a fixed bed dryer using ambient condition consumed less energy than two-stage drying using a FBD and ISD but lower energy cost must be weighed against the faster drying rate, flexibility, portable design, and product uniformity of FBD.
| Identifer | oai:union.ndltd.org:ADTP/234314 |
| Date | January 2007 |
| Creators | Jittanit, Weerachet, Chemical Sciences & Engineering, Faculty of Engineering, UNSW |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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