Discussion on Microwave Vacuum Low Temperature Drying Technology

Microwave vacuum drying equipment is a new type of microwave energy application equipment which combines microwave energy technology with vacuum technology. It combines a series of advantages of microwave and vacuum drying, and overcomes the shortcomings of long cycle and low efficiency of conventional vacuum drying. Microwave vacuum drying has the advantages of high yield, good quality and low processing cost. Microwave vacuum drying equipment consists of microwave generator (also called magnetron), vacuum drying chamber, material rotating disk, vacuum system and electronic control system. In the industrial production of

, many articles can not be dried at high temperature. For example, some medicines, chemicals, nutritious food, ginseng, antler and other high-grade Chinese herbal medicines, in order to ensure the quality of products, the drying treatment must be carried out under 100 C or room temperature. It is well known that the boiling point of water decreases with the decrease of air pressure. For example, at one atmospheric pressure (101.3 kpa), the boiling point of water is 100 degrees C, while at 0.073 (7.37 kpa), the boiling point of water is 40 degrees C. Under vacuum conditions, heating the object can evaporate the moisture inside the object without temperature rise. Conventional vacuum drying method has slow conduction speed, low efficiency, and difficult temperature control. The heated material will also produce internal and external temperature difference. Microwave heating is a kind of radiation heating, which is the direct action of microwave and material. It can be heated both inside and outside at the same time without convection or conduction to transfer heat, so it has fast heating, high drying efficiency and good drying quality. It provides a new and efficient drying process for food engineering, pharmaceutical engineering, biological engineering, chemical engineering, material engineering and deep processing of agricultural and sideline products.

uses microwave vacuum drying equipment to produce seedless raisins, and changes the traditional technology of 65 to 24 hours dry air drying to 50 degrees, 5 hours microwave vacuum drying. Processing instant orange powder, the product not only keeps its original color and fragrance, but its vitamin retention is much higher than that of spray drying. The efficiency of microwave vacuum drying equipment on dehydrated vegetables is four times as high as that of conventional vacuum drying equipment. It can be seen that microwave vacuum drying is a high-tech with remarkable economic benefits and high popularization value.