| For the problem of germinated brown rice(GBR) dryer with low efficiency and poor quality, some researches were conducted to optimize the parameter of germinated brown rice microwave drying process, simulate and analyze the process of the microwave drying of the germinated brown rice. By meansof the analysis of distribution uniformity of electromagnetic field in the microwave drying chamber, a continuous drying microwave dryer was designed for the germinated brown rice to increase drying efficiency and ensure quality.In the microwave drying experiments of germinated brown rice the intensity of microwave, surface velocity, drying duration of per cycle were slected as influencing factors, and temperature, moisture content, fissuring rate, GABA were selected as the objective factors. Response surface design method with three factors and five levels was employed to establish regression models to describe the influcencing factors and objective factors. Optimization of germinated brown rice under conditions of continuous microwave drying were obtained as microwave intensity of 4 w/g, surface velocity of 2.50m/s, the drying time per cycle of 3.00 min.A heat-mass transfer model was built to describe the distribution of temperature and moisture of GBR under continous microwave drying condition. The verification test were done under microwave intensity of 1.16 W/g, 2.75 W/g, 4.34 W/g to deterimine the validity of model developed. Results from simulation and experiments showed the slow temperature increment at later stage of drying process. The control of microwave input rate may decrease of energy consumption of microwave energy, and increase the drying quality of GBR. Tempering stage following the drying stage may increase the temperature consistency within GBR to improve the drying uniformity and quality of GBR. These researches give the guidance for the determination and design of control system of continous microwave dryer.HFSS software was employed to simulate the electric-magnetic fileld within the drying cavity by means of the comparison of magnetron array at different modes. The distributions of electric-magnetic fileld were simulated under different distance of load location to the bottom of microwave dryer. The simulation results show the the distance of material surface and the wave guidance ports of magnetron has the obvious effect on the distribution and intensity of electric-magnetic field. Closed distance may result in the high intensity of electric-magnetic field. Side by side arrangement of magnetrons may generate the uniform distribution of electric-magnetric fileld at material surface under the distance of100 mm to the bottom of microwave dryer. If the distance of material surface to bottom of microwavedryer is in the range of 150-200 mm, n-type arrangement of magnetrons may generate the uniform distribution of electric-magnetic field. However, the distance of 100 and 150 mm had lower the Q-factor than that of 200 mm. The electric field intensity is in range of 3000-4000 V/m at distrance of 200 mm with high stored energy. These researches help to design the new microwave dryer to improve the drying uniform and energy utilization.Based on the results from the optimization and simulation of microwave drying technology, a new continous microwave dryer was designed including the ration feed, microwave drying section, tempeing section, control system. Three stages drying technologies were developed as drying stage, tempering stage and next drying stage considering the distribution uniform of electric-magnetric field and microwave energy utilization. A continous microwave drying process will be achieved by the new microwave dryer to gain the high efficient and qulity. |
