The investment of microwave drying equipment is relatively high.Deoiling microwave dryer machine consumes high-quality energy, electric energy, and the conversion rate from electric energy to electric energy is only about 50%. Therefore, this technology is only suitable for drying products with high added value. For example, for products that take a long time to meet the water removal requirements by other methods, or products that cannot obtain the desired quality (such as color, etc.) by other methods. So microwave drying is only suitable for some special cases. Microwave is mainly used to improve the drying ability (quickly remove moisture without producing temperature gradient inside the material) or for terminal drying. It is used to remove several percentage points of moisture which takes a long time to come out in the later drying stage. Generally speaking, microwave heating can be combined with convection or vacuum drying to reduce energy consumption. At present, microwave vacuum drying and microwave freeze drying have been commercialized.
Microwave dryer machine combined with microwave system and vacuum system has the advantages of both. It not only reduces drying temperature but also speeds up drying speed. It has the characteristics of fast, high efficiency and low temperature. It can better retain the original color and fragrance of materials such as dried food or medicines. Moreover, the loss of thermosensitive nutrients or active ingredients such as vitamins is greatly reduced and better drying is obtained. Dry quality. This technology is especially suitable for drying heat-sensitive materials such as food, medicine, biological products, and has low equipment cost and operation cost.
Microwave vacuum drying has great potential in dehydration of fruits and vegetables, which has a large moisture content and a high cost of freeze drying. Many studies have shown that microwave vacuum drying of fruit and vegetable products, its color, flavor and thermal components retention rate is very close to freeze-drying. Although the texture is hard and there is a certain gap with freeze-drying, the drying time and cost can be greatly reduced. The University of California has studied microwave vacuum drying technology to produce dehydrated and puffed grapes, which can keep the flavor and color of fresh grapes well and keep their shape from shrinking. Because of the low temperature and short drying time of microwave drying, vitamin B1, B2 and C can get high retention rate. If this new technology can be applied to the production of raisins in Xinjiang, the wrinkled shape of raisins in China will be completely changed, and the situation that only sweet flavor, quality and nutritional components can be changed, while vitamins are almost completely lost.
Microwave can be applied to a variety of other dryers in both atmospheric and vacuum environments. For example, in fluidized bed, spouted bed, vibrating bed or tray dryer to improve drying speed. All of these technologies can lead to a significant reduction in drying time, but unfortunately, the initial investment and operating costs are so large that the increased speed and reduced usage cannot compensate for the increased costs. The experiment proves that microwave convection dryer is very effective in drying grapes, but the cost is quite high.See the news list>>