Introduction of industrial microwave drying technology

Microwave is a kind of high-frequency electromagnetic wave with a frequency of 300 MHz to 300000 MHz and a wavelength of 1 mm to 1 m Microwave has the characteristics of electric field, such as short oscillation period, strong penetration ability, and specific effect of interaction with matter Traditional drying methods, such as flame, hot air, steam, electric heating, etc., are all external heating drying After the surface of the material absorbs heat, through heat conduction, the heat penetrates into the interior of the material and then heats up for drying Microwave drying is quite different It is an internal heating method Wet materials are in the microwave high-frequency electric field with very short oscillation period The water molecules in the wet materials will polarize and arrange in order along the direction of the microwave electric field Then they will rotate rapidly with the interactive change of the direction of the high-frequency alternating electric field, and generate violent collision and friction (up to a hundred million times per second) As a result, part of the microwave energy will be converted into molecular motion energy, which is expressed in the form of heat Now, the temperature of water rises and leaves the material, thus drying the material That is to say, after microwave enters the material and is absorbed, its energy is converted into heat energy in the dielectric of the material Therefore, microwave drying is a drying method which uses electromagnetic wave as the heating source and the dried material itself as the heat generator The core of microwave drying equipment is microwave generator At present, the frequency of microwave drying is mainly 2450 MHz It is mainly used for drying chemical industry, food, agricultural and sideline products, wood, building materials, paper and other industries, and also for sterilization of food, agricultural and sideline products In the traditional drying process, in order to improve the drying speed, it is necessary to increase the external temperature, increase the temperature gradient, but it is easy to produce the phenomenon of coke outside the material However, when microwave heating is used, the heat can permeate evenly regardless of the shape of the material, and the expansion effect can be produced, which is conducive to crushing Under the action of microwave, the drying rate of the material tends to be the same and the heating is even Moreover, microwave drying technology does not affect the color, fragrance, taste and organizational structure of the dried materials, and the effective components are not easy to be decomposed and destroyed In order to solve the problem of uneven drying, microwave drying is being used instead of traditional drying Microwave equipment has less supporting facilities, less land occupation, convenient operation, continuous operation, and is convenient for automatic production and enterprise management (PLC programmable control and temperature adjustable) Microwave drying process has a high energy utilization rate, because the heat of microwave is directly generated in the interior of wet materials, with less heat loss, high thermal efficiency and no environmental and noise pollution, which can greatly improve the working environment.