微波-热风振动流化床干燥机设计与试验

针对微波干燥中场强分布不均、物料微波能吸收能力不同导致的微波加热不均匀现象,结合微波干燥的高效性、流态化干燥的均匀性以及热风干燥辅助去除水汽的功能,设计了一种实现干燥均匀性的微波-热风振动流化床干燥机,主要由振动流化床系统、热风系统、微波加热系统、测温系统和控制系统等组成。采用Ansoft HFSS软件对微波加热仓磁控管不同开口位置进行仿真分析,得到多馈口激励最佳方案。结果显示,物料高度距离箱底不变的情况下,4个微波馈入端口的位置相对于原始端口位置外移30 mm,物料表面场强分布更加均匀。以新鲜毛豆仁为例,对该机的性能和加热均匀性进行试验验证,结果表明:设计方案和控制系统方案可靠,微波-热风振动流化床干燥下毛豆仁的干燥时间为54 min,比单独微波流化床干燥的干燥时间缩短34. 1%,比微波-热风组合干燥的干燥时间缩短12. 9%且产品均匀性显著提高。

Design and Experiment of Microwave-Hot-airflow Vibrating Dryer

The non-uniform distribution of microwave field and the non-uniform absorption in fresh food during microwave drying lead to the uneven quality. Combining the advantages of the high efficiency of microwave drying with the uniformity of fluidized drying, water vapor was removed by hot airflow. A microwave-hot-airflow vibrating dryer (MAVD) was developed based on drying uniformity. The MAVD device mainly included a fluidized bed system, a hot air heating system, a microwave heating system, a temperature measurement system and a control system. The positions of magnetron in drying chamber were simulated and optimized with the software of Ansoft HFSS. The results showed that when the height of the tray was constant from the bottom of the box, the positions of the four microwave feed ports were 30mm away from the original port position, thus the surface electromagnetic field distribution of the material was more uniform. The performance of the device was tested with green soybean. The results showed that the design and control system of the drying test platform were reliable. The drying time of MAVD was 54min, which was 34.1% shorter than that of microwave fluidized bed drying alone, and the uniformity of products was significantly improved. The research results provided reference for microwave drying equipment to improve the uniformity of microwave heating.