There are many types of vacuum drying equipment, and the application fields are extensive and the development is relatively rapid. This paper expounds the development of several kinds of vacuum dryers at home and abroad, in order to realize the exchange of information, find out the problems that need 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: low oxygen content when dry at low pressure, can prevent oxidative deterioration of dried materials, dry flammable and explosive dangerous goods; can vaporize moisture in materials at low temperature, easy to dry heat sensitive materials; Recycling valuable and useful ingredients in the dried material; preventing the emission of toxic and harmful substances in the dried material, and becoming an environmentally friendly type of green drying. Therefore, the application of vacuum drying equipment is increasingly widespread.
The main disadvantage of vacuum drying is that a vacuum system capable of pumping steam is needed, which makes the equipment investment cost high and the operation cost high; the equipment production efficiency is low and the output is small. In order to overcome these shortcomings, many scientific and technological workers have made many efforts. At the same time, due to the many advantages of vacuum drying, some products have to use vacuum drying equipment. Therefore, the development of vacuum drying equipment will be promising.
1. The variety of vacuum drying equipment at home and abroad is increasing. Various new types of vacuum drying equipment have been developed for different purposes.
1), microwave vacuum drying equipment to save energy and increase drying rate.
2) The combination of spray freeze-drying equipment spray 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 spray freezing, it forms micro-nano scale particles, which increases the drying rate and improves the product. Production.
3) Vacuum vapor phase drying equipment is a device specially designed for drying large oil-immersed transformers and other similar electrical equipment. Switzerland developed this product in the 1970s. China introduced this kind of equipment in the 1980s. After the 1990s, it has basically completed the introduction and digestion, and now it can be produced in sets.
4) Small-scale experimental freeze-drying equipment In order to meet the needs of schools and scientific research units, several small-scale experimental freeze-drying equipments with different functions have been developed at home and abroad.
5) Freeze-dried and separated pharmaceutical lyophilizer.
Food lyophilizers are separately cooled and dried to save energy, save time and increase production. Traditional medical freeze dryers are all frozen and dried in the machine at one time. Some companies in Western Europe and the United States pre-freeze the drug for the same purpose as food lyophilization, and then send it to a dryer for drying.
2. Unbalanced development of continuous vacuum drying equipment at home and abroad
In order to improve equipment production and ensure product quality, a variety of continuous vacuum drying equipment have been developed abroad more than ten years ago. However, due to the limitations of the technical level and people's perceptions, the development is relatively slow.
1), belt continuous vacuum drying equipment
The WL-VAQ belt type continuous vacuum drying equipment produced by Nippon Seisakusho Co., Ltd. is suitable for liquid materials, mud-like, paste-like concentration and high viscosity drying. Japan's BV-100.5 vacuum belt continuous drying device uses steam and conduction heating, the temperature of each section is adjustable, and the belt tension and speed are adjustable. The Swiss company has developed a range of belt-type continuous vacuum drying units with automatic cleaning.
Since 1995, he has been engaged in the design, manufacture, installation and service of belt continuous vacuum drying equipment, and the technology is relatively mature.
Domestic belt continuous vacuum drying equipment is rare. In 2004, a small research facility was successfully developed in a research institute in Guangdong Province for the drying of banana powder. The effect is very good.
2), grain continuous vacuum drying equipment
The amount of grain dried is large and continuous drying equipment must be used. In the past, many countries have developed a number of grain drying equipment, and vacuum dried grains are mostly used for seed drying because the vacuum drying cost is too high. In fact, this is a misunderstanding. According to the senior engineer of Zhengzhou Food Science and Design Institute He Xiang, 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, running cost and hot air. Dry and flat. If considering the quality of the dried product, the breakage rate of the drying process, the waisting rate, etc., the total cost of vacuum drying at low temperatures is not higher than that of hot air drying.
3) Continuous vacuum freeze drying equipment
The food is rich in raw materials and the output of the products that need to be lyophilized is large. Therefore, continuous food freeze-drying equipment appeared earlier. A Danish company produced CONRAD– 800 continuous freeze-drying equipment in 1985 for lyophilized coffee production with a capacity of 13 tons per day.
The first continuous vacuum freeze-drying equipment made in China was successfully developed by a research institute in Shenyang in 2000. The vacuum chamber adopts a rectangular structure, and a separator is arranged between the inlet and outlet bins and the drying bin, and an automatic weighing system is provided in the inlet and outlet bins, which can determine the drying rate, the water output and the final drying degree of the freeze-dried food. Two external water traps work alternately to achieve continuous water trapping and ice melting.
Understand the development trend of vacuum dryer series drying equipment
2018 12/25
