Microwave in honeycomb ceramics is mainly used for shaping drying of honeycomb ceramics, foam ceramics and special ceramics. The drying of ceramics is one of the most important processes in the ceramic production process. A large part of the quality defects of ceramic products are caused by improper drying.
Due to the strong penetrating power of the microwave, it can penetrate deep into the sample, first making the sample center temperature rise rapidly.
Through the practical application of the manufacturer, the microwave ceramic drying and setting equipment has the following advantages:
1. The product is dry and stereotyped with good quality, no cracking, and uniform foam aperture.
2, easy to control, easy to operate, flexible; because the microwave output power is adjustable, the conveyor belt speed is adjustable, so products of different materials can be used.
3, save time, high output, low energy consumption; through the actual production of the manufacturer, the drying time is 1/5 of infrared drying, saving energy 1/3.
4, the production intensity is small, labor-saving, provincial process, especially easy to connect with the front and rear process into an automatic production line, reducing the number of handling; saving manpower, labor efficiency is greatly improved.
5, environmental protection, clean, no pollution, and will not produce the "three wastes" problem.
Drying technology classification:
According to whether the drying system is controlled, it can be divided into natural drying and artificial drying. Since artificial drying is an artificial control of the drying process, it is also called forced drying.
According to the different drying methods, it can be divided into:
1 convection drying, which is characterized by using gas as a drying medium to blow the surface of the body at a certain speed to dry the body.
2 Radiation drying, which is characterized by the use of radiant energy of electromagnetic waves such as infrared rays and microwaves to illuminate the dried body to be dried.
3 Vacuum drying, which is a method of drying a blank under vacuum (negative pressure). The blank does not need to be heated, but it needs to use the pumping equipment to generate a certain negative pressure, so the system needs to be sealed and it is difficult to continuously produce.
4 joint drying, which is characterized by comprehensive use of two or more drying methods to exert their respective characteristics, complementary advantages, often can obtain a more ideal drying effect.
There are also some drying methods, which are divided into batch dryers and continuous dryers according to whether the drying system is continuously. The continuous dryer can be divided into downstream, countercurrent and mixed flow according to the direction of movement of the drying medium and the blank: it is divided into a chamber dryer and a tunnel dryer according to the shape of the dryer.
Microwave drying technology:
Microwave refers to an electromagnetic wave between high frequency and far infrared ray. The wavelength is O.001-1m and the frequency is 300-300000MHz. Microwave drying is to irradiate the wet body with microwave. The direction and magnitude of the electromagnetic field change periodically with time, so that the polar water molecules in the body change with the alternating high-frequency electric field, causing the molecules to rotate violently and the friction is converted into heat. The whole body is uniformly heated to achieve the purpose of drying. The penetration of microwaves is much greater than that of far infrared rays, and the smaller the frequency, the greater the half power depth of the microwave. Features of microwave drying:
(1) Uniform and fast, which is the main feature of microwave drying. Since the microwave has a large penetrating power, heat can be directly generated inside the medium when heated. Regardless of the complexity of the shape of the blank, the heating is uniform and rapid, which makes the green body dehydrate quickly, the mold release is uniform, the deformation is small, and cracks are not easily generated.
(2) It is selective. Microwave heating is related to the nature of the material. In a microwave field of a certain frequency, water is much larger than other materials because of its dielectric loss, so the moisture is much larger than that of other dry materials. The microwave heating is carried out simultaneously in the surface, and the internal moisture can be quickly heated and directly evaporated, so that the ceramic body can be demolded by heating in a short time.
(3) High thermal efficiency and sensitive reaction, since the heat directly comes from the inside of the dry material, the loss of heat in the surrounding medium is very small, and the microwave heating chamber itself does not absorb heat, does not absorb microwaves, and all the emission acts on the green body, and the thermal efficiency high.
Microwave heating equipment is mainly composed of DC power supply, microwave tube, connecting waveguide, heater and cooling system. The microwave heater can be divided into standing wave field resonant heater and traveling wave field waveguide according to the action of heating object and microwave field. Heaters, radiant heaters, slow-wave heaters, etc.
Therefore, in order to better utilize the advantages of microwave technology, in addition to the use of mixed heating or mixed drying technology, strengthen the study of the mechanism of interaction between ceramic materials and microwaves, and enhance the dielectric properties, dielectric consumption and microwave frequency of ceramic materials. The basic data test of the temperature relationship, and the improvement of the microwave drying process and equipment, make this technical committee serve the ceramic industry.
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