| With the development of science and technology, the mechanization of grain drying has become a major research topic. Vacuum drying as a new drying method which can dry at low temperature, has been rapidly developed and applied in many fields. However, due to the lack of research on the vacuum drying characteristics of biological seeds, the application of vacuum drying in this field is still poor. Spherical shape as the most common form of biological seed, the research on its drying characteristics can provide a theoretical basis for the study of large grain vacuum drying equipment.Based on the potential theory of spherical biological seed, the mathematical model under conditions of vacuum drying heat and mass transfer process was established in this paper. The mathematical model equations were separated by finite difference method, and the model was simulated under different drying temperature and different vacuum conditions in the MATLAB environment. The influence of different vacuum drying conditions on drying rate and the reasons were analysed. Then, choosing the representative peanut seeds as the research object, the DZF-6090 type vacuum drying apparatus was used to do the vacuum drying experiment and the experimental data was recorded. The theoretical calculation of drying curves were compared with The experimental data in order to verify the reliability of the calculation results. In this paper, the unit energy consumption of vacuum drying process was estimated, and was compared with the traditional hot air drying process. Finally, the quality of the seeds after vacuum drying was verified by experiments.Through the above research on vacuum drying process, this paper draws the following conclusions:Drying temperature has a great influence on the drying rate, and the effect of vacuum degree on drying rate is relatively small. From the unit energy consumpution estimation of vacuum drying, it is concluded that the average unit energy consumption of evaporating 1Kg water by vacuum drying process is 5000KJ-6500KJ. Compared with the traditional hot air drying and vacuum drying, it is concluded that at the beginning of the equipment procurement, a daily working capacity of 300 tons of vacuum drying oven spends about 300 thousand more than the equivalent drying capacity of hot air drying oven does. But in the specific operation of the late processing, the traditional hot air drying costs 2632-8404 yuan more than the vacuum drying does per day, so the vacuum drying is suitable for long term use. In environmental protection, vacuum drying can effectively reduce the dust pollution to the environment compared with the traditional hot air drying. From the experimental analysis of seed drying quality, it is concluded that the drying temperature has great effect on the germination rate of the seeds, and the vacuum degree has little effect on the germination rate of the seeds, so the vacuum drying process can effectively ensure the quality of the seeds. |
