Microwave vacuum drying equipment, which combines microwave energy technology and vacuum technology, is a kind of new type microwave energy application equipment. It not only has advantages of microwave and vacuum drying but also has overcome shortcomings of general vacuum equipments, such as long drying cycling time and low efficiency. As for general drying courses, microwave vacuum characterizes big drying output, good quality and low cost of processing etc. It is well known, when air pressure reduces, water boiling point will reduce too. For example, water boiling point is 100℃ under the circumstance of atmospheric pressure (101.3kpa); while water boiling point is 40℃ under the circumstance of 0.073 atmospheric pressure (7.37kpa). In the condition of vacuum, heating materials can make water within materials vaporize in the state of no temperature rise. And, it is very difficult to process air convection heat-transfer in the condition of vacuum. Only by the method of heat conduction, hot energy can be supplied to the materials. According to the general vacuum drying way, heat conduction velocity is very slow, inefficiency and hard to control temperature. Further, it is likely to appear temperature difference between inside and outside of materials. Microwave heating is a kind of radiation heating, which microwave directly effects on the materials and makes the inside and outside of materials be heated at the same time. There is no need to transfer heat quantity through convection or conduction. So, microwave heating has advantages of rapid heating, high-efficiency drying and good qualityof drying. Microwave vacuum drying equipment is a hi-tech product integrated multiple sciences as a whole.
Microwave vacuum drying equipment is mainly made up of microwave signal generator, vacuum drying chamber, material tray, vacuum pumping system and controlling system.