There are many types of vacuum drying equipment, a wide range of applications, and rapid development. This article only elaborates on the domestic and foreign development trends of several vacuum drying equipments in order to achieve the exchange of information, find out the problems to be solved in the development of vacuum drying equipment, and improve the level of vacuum drying equipment in China. Vacuum drying has many advantages: it has low oxygen content when dried under low pressure, can prevent oxidation and deterioration of the material to be dried, can dry flammable and explosive dangerous goods; it can vaporize the moisture in the material at low temperature, and it is easy to dry heat sensitive materials; Recover valuable and useful ingredients from the dried material; prevent the release of toxic and hazardous substances from the dried material, which can be an environmentally friendly type of “green†drying. Therefore, vacuum drying equipment is increasingly used. The main disadvantage of vacuum drying is the need for a vacuum system capable of pumping steam, which results in high equipment investment costs, high operating costs, low equipment production efficiency, and low output. To overcome these shortcomings, many scientific and technological workers have made many efforts. At the same time, vacuum drying has many advantages. Some products have to use vacuum drying equipment. Therefore, the development of vacuum drying equipment will be promising. 1. Continuous development of vacuum drying equipment at home and abroad is unbalanced In order to increase the output of equipment and ensure product quality, a variety of continuous vacuum drying equipments have been developed abroad more than ten years ago. However, due to the limitations of the technology level and people's perceptions, the development is slow. 1) Continuous vacuum drying equipment Japan Risen Production WL-VAQ type belt type continuous vacuum drying equipment, suitable for liquid materials, mud, paste paste reported concentration and high viscosity boring drying. The BV-100.5 type vacuum belt type continuous drying device produced by Japan's Okawara Plant uses steam and conductive heating. The temperature in each zone can be adjusted, and the tension and speed of the Conveyor Belt can be adjusted. The Swiss company Bucher-Gade developed a series of continuous vacuum drying equipment with automatic cleaning devices. Since 1995, he has been engaged in the design, manufacture, installation and service of belt continuous vacuum drying equipment. The technology is mature. Domestic belt-type continuous vacuum drying equipment is rare. In 2004, the Guangdong Academy of Agricultural Sciences successfully developed a small-scale test equipment for the drying of banana powder with good results. 2) Grain continuous vacuum drying equipment The amount of dried grain is large and continuous drying equipment must be used. In the past, all countries in the world developed a lot of grain drying equipment. Vacuum dried grains are used in seed drying because vacuum drying costs are too high. In fact, this is a misunderstanding. According to He Xiang, senior engineer of Zhengzhou Institute of Grain Science and Design, the continuous corn vacuum drying equipment developed by them has a production capacity of 60t/d. The fixed investment is slightly higher than hot air drying, and the running cost and hot wind Dry and flat. If the quality of the dried product is taken into consideration, the breakage rate of the drying process, the waist rate, etc., the total cost of the vacuum drying at a low temperature is not higher than the hot air drying. 3) Continuous vacuum freeze-drying equipment Food raw materials are abundant, and the product that needs to be lyophilized is very large. Therefore, the continuous food freeze-drying equipment appeared earlier. Danish ATLAS company produced CONRAD-800 continuous freeze-drying equipment in 1985, used for freeze-dried coffee production, with a production capacity of 13t per day. Figure 2 is a schematic diagram of the equipment. Figure 3 is a continuous lyophilizer produced in Germany. The first domestic continuous vacuum freeze-drying equipment was successfully developed by Shenyang Refrigeration Technology Institute in 2000. The vacuum chamber adopts a rectangular structure. There is a spacer between the in-out silo and the drying chamber. The in-out silo is provided with an automatic weighing system, which can determine the drying rate, the amount of water output and the final drying degree of the freeze-dried food. Two external water traps work alternately to achieve continuous catching and melting. There is a big gap between the sales volume of continuous freeze-drying equipment at home and abroad. Danish ATLAS Corporation sold 18 continuous freeze-drying equipments from 1985 to 1990, among which Taiwan was purchased in Taiwan. However, the mainland provinces and cities have not yet introduced such equipment. Only one domestically-made equipment has not been sold yet. Go out. 2. Vacuum drying equipment at home and abroad are all increasing For different purposes, various new types of vacuum drying equipment have been developed. 1) Microwave vacuum drying equipment Save energy and increase the drying rate. 2) Spray freeze-drying equipment The combination of spraying and freeze drying is determined by the nature of the material and the output of the product. The material must be a liquid slurry. After being sprayed and frozen, micro-nano-scale particles are formed, which increases the drying rate and improves the product's Yield. 3) Vacuum Vapor-phase Drying Equipment It is a device specially used for drying large-scale oil-immersed transformers and other similar electrical equipment. Switzerland developed this product in the 1970s. China introduced such equipment in the 1980s. After the 1990s, it has basically completed its introduction and digestion. Now it can produce complete sets. 4) Freeze-drying equipment for small experiments In order to meet the needs of schools and research institutes, several small-scale experimental freeze drying equipments with different functions have been developed at home and abroad. Figures 4~7 are several small-scale experimental lyophilizers produced by the Martin Christ Company of Germany. They are small in size, light in weight and have many functions. Basically can meet the freeze-dried experiment of various materials. Domestically, several manufacturers such as Haimen Light Industry Machinery Factory have begun to digest, absorb and introduce designs, and have developed new products, but their performance is not yet stable. Single cavity system Under aseptic conditions, pre-freezing and drying are performed in the condensing chamber. Double cavity system The pre-freezing is performed in a low-temperature refrigerator or a rotary chiller, and drying is performed in a drying chamber above the condensing chamber. 5) Freeze-dried separation medicine freeze-dryer The lyophilizers used in foods are frozen and dried separately to achieve the purpose of energy conservation, time savings, and production increase. The lyophilizer used in traditional medicine is frozen and dried in the machine at a time. Some companies in Western Europe and the United States, in order to achieve the same purpose as food lyophilization, pre-freeze drugs and then send them to a dryer for drying. As a brand-new processing method, laser processing has gradually been widely used in the leather, textile and garment industries due to its advantages of precision, speed, simple operation, and high degree of automation. Compared with the traditional cutting method, the laser laser cutting machine is not only low in price and low in consumption. 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