Vacuum drying has many advantages: drying under low pressure, low oxygen content, can prevent dry material oxidative deterioration, drying the inflammable and explosive dangerous goods; material in the water vaporization under low temperature, easy to dry heat sensitive materials; can be recycled material drying in the valuable and useful ingredients; can prevent dry materials, toxic and harmful substances in emissions, can become a environmental protection type "green" drying. Therefore, the application of vacuum drying equipment has become increasingly widespread.

Vacuum drying main disadvantage is the need a capable of pumping the vacuum system of steam, the equipment investment cost is high, the high cost of running; low efficiency of production equipment, production of small. In order to overcome these shortcomings, many scientific and technological workers have made a lot of efforts. At the same time, because there are many advantages of vacuum drying, some products have to use vacuum drying equipment. Therefore, the development of vacuum drying equipment will be very promising.

1. The development of continuous vacuum drying equipment at home and abroad

1) belt type continuous vacuum drying equipment

Japan Japan Osaka produced by the production WL-VAQ belt type vacuum continuous drying equipment, suitable for liquid material, slurry, paste sued concentration and high viscosity boring dry. Japan Okawa original plant production of BV-100.5 type vacuum belt continuous drying device, the use of steam and conduction heating, district temperature can be adjustable, belt tension and speed adjustable. The Swiss - Booher gaide company has developed a series of belt type continuous vacuum drying equipment with automatic cleaning device.

Began to engage in design, cinctured continuous vacuum drying equipment manufacture, installation and service from 1995, mature technology.

Rich food raw materials, the need for a large quantity of freeze-dried products. Therefore, the continuous food freeze drying equipment appears earlier. Denmark ATLAS company in 1985 on the production of CONRAD - 800 continuous freeze drying equipment, used for freeze dried coffee production, production capacity of 13T per day, figure 2 is a schematic diagram of the device. Figure 3 is a continuous freeze drying machine made in Germany.

The first vacuum freeze drying equipment made in China was successfully developed in 2000 by the Shenyang Institute of refrigeration technology. Vacuum chamber with rectangular structure, import and isolation piece is arranged between the silo and dry warehouse, import and silo are equipped with automatic weighing system, can judge the drying rate freeze dry food, water and final drying. Two external water traps work alternately to achieve continuous water capture and melting of ice.

1) Microwave vacuum drying equipment, energy saving, improve the drying rate.

2) Spray freeze drying equipment spray and freeze drying combination is determined by the properties of the materials and the product yield, essential material is liquid slurry, by spray freeze after the formation of micro / nano scale particles and increased the drying rate, improve product yield.

3) Vacuum vapor phase drying equipment is designed for large oil immersed transformers and other electrical equipment drying device. Switzerland developed this product in 1970s. Our country introduced this kind of equipment in 1980s, after 90s has been basically completed the introduction of digestion, and now can complete sets of production.

The pre freezing is carried out in a low temperature refrigerator or freezer, and the drying chamber is carried out on the top of the condensing chamber.

5) freeze dry separation type freeze drying machine for medicine

With the development of electronic and computer technology, the control system and display function of vacuum drying equipment are generally increased. Zhengzhou Grain Science Research Institute, has developed a corn vacuum drying equipment with automatic control and simulation screen display function; Shanghai tofflon, Beijing speed and other manufacturers of vacuum freeze a freeze-dried endpoint determination, design freeze drying curve, view the operation status, storage a plurality of freeze-drying curve, print production information for multiple functions.

1) innovation is the fundamental way for the development of vacuum drying equipment

At present of vacuum drying equipment development is slow, one important reason is mutual imitation, hovering at the same level of technology, lack of innovation. Imitation of the ability of strong, fast, innovative ideas, less investment. The focus of the competition in the market to grab the market, pull relations, price war. A good point of practice is in the quality and after-sales service, the next few. But these are not a good way to develop vacuum drying equipment, must invest human, material and financial resources to innovation.

2) energy saving is the key to the development of vacuum drying equipment

The on a reasonable design, selection and use of vacuum system.

Pumping the vacuum system of steam is not a lot. At present, there are mainly two categories, a class is directly pumping steam pump, main water jet pump, steam jet pump, water ring pumps and wet roots pump; another kind is by way of condensation water catching. These two methods are relatively high energy consumption, the first type of energy saving direction should be to improve the pumping efficiency of the pump; after a type of energy saving direction is designed such as gas solid phase transformation of the structure and thermal efficiency of the heat exchanger.

3) continuous vacuum drying equipment is an important method to improve product yield, energy saving

Compared with the continuous vacuum drying equipment and the cycle type vacuum drying device, less auxiliary time, saving time and improve the yield. At the same time, he does not have to be like the cycle of vacuum drying equipment, each production cycle, equipment temperature changes once, causing some of the energy wasted in the repeated heating of the device components. Therefore, saving energy.

4) combined vacuum drying equipment and other drying methods should be promoted mode of production