Microwave vacuum drying equipment is a new type of microwave energy application equipment that combines microwave energy technology and vacuum technology. It combines a series of advantages of microwave and vacuum drying. Flash drying machine overcomes the disadvantages of long cycle and low efficiency of conventional vacuum drying. In the general material drying process, it can improve work efficiency by 4-10 times compared to conventional methods. The microwave vacuum flash drying machine has the advantages of high drying yield, good quality, and low processing cost. It is a high-tech product that integrates electronics, vacuum science, mechanics, thermodynamics, programming, and other disciplines. It is a new technology and process developed based on in-depth research on the physical transformation of substances, internal and external heat and mass exchange, and water migration under vacuum conditions during the drying process. In industrial production, many items cannot be dried under high temperature conditions, such as some medicines, chemicals, nutritional foods, and high-end Chinese herbal medicines such as ginseng and deer antler. In order to ensure product quality, the drying treatment must be carried out under conditions below 100 ℃ or room temperature. It is well known that when the air pressure decreases, the boiling point of water also decreases. For example, at one atmospheric pressure (101.3 kPa), the boiling point of water is 100 ℃, while at 0.073 atmospheric pressure (7.37 kPa), the boiling point of water is 40 ℃. Under vacuum conditions, heating an object can cause the internal moisture of the object to evaporate without heating up. Due to the difficulty of convective heat transfer in air under vacuum conditions, thermal energy can only be provided to materials through thermal conduction. The conventional vacuum drying method has slow heat transfer speed, low efficiency, and difficult temperature control. Microwave heating is a type of radiation heating that directly interacts with materials, heating both inside and outside without the need for convection or conduction to transfer heat. Therefore, it has fast heating speed, high drying efficiency, and easy temperature control.
Developed countries abroad began developing industrialized microwave vacuum drying equipment in the 1980s and achieved good results in practical applications. French International Microwave Company uses microwave vacuum drying equipment to process seedless raisins, transforming the traditional process of 65 ℃ and 24-hour hot air drying into 50 ℃ and 5-hour microwave vacuum drying, greatly improving product quality and yield. In the late 1990s, our unit began to develop microwave vacuum equipment in China. After several years of effort, we completed the industrial development of a 10KW microwave vacuum drying equipment in 2000. This provides a new and efficient drying equipment for pharmaceutical engineering, biotechnology, chemical engineering, materials engineering, and deep processing of agricultural and sideline products.
2、 The advantages of microwave vacuum drying equipment
1. Efficient
Conventional vacuum drying equipment uses steam for heating, which requires heating from the inside out. The heating speed is slow and requires a large amount of coal consumption. However, microwave vacuum drying equipment uses electromagnetic wave heating, which does not require heat transfer media and directly heats the interior of the object. The heating speed is fast. A 1 kW microwave can heat water at room temperature to 100 ℃ in 3-5 minutes, avoiding the above drawbacks. Therefore, it is fast, efficient, greatly shortens the drying cycle, and reduces energy consumption. Compared with conventional drying techniques, it can improve work efficiency by more than four times.
2. Uniform heating
Due to microwave heating, materials are heated simultaneously from the inside out, and the temperature difference between the inside and outside of the materials is very small, which does not result in inconsistent heating between the inside and outside in conventional heating. This results in a puffing effect, which is beneficial for crushing and greatly improves the drying quality.
3. Easy to control, convenient for continuous production and automation. Due to the characteristics of fast adjustment of microwave power and no inertia, it is easy to control in real time and can operate between 40 ℃ and 100 ℃
Adjusting temperature
4. Small backup volume, convenient installation and maintenance
5. The product quality is good, and compared with conventional methods, the processed product quality has been significantly improved.
6. Microwave has the effects of disinfection and sterilization, and the product is safe and hygienic. Long shelf life.
7. Significant economic benefits.
From the characteristics introduced above, significant economic and social benefits can be seen in terms of energy conservation, consumption reduction, improving product quality, safety and health, and low equipment investment costs.
3、 Basic structure and working principle
1. Flow Chart of Microwave Vacuum Drying Equipment Applied in the Processing of Precious Medicinal Materials (Omitted)
4、 Circuit control design
1. Circuit composition diagram (omitted)
5、 System design
1. Vacuum pump selection
2. Material turntable design
3. Whole machine thermal balance design
4. Power regulation design
6、 Economic Benefit Analysis
A comparison was made on the process performance, economic benefits, and product quality of various drying equipment processed by a pharmaceutical factory in Jiangxi. The comparison of drying indicators is as follows:
Project dynamic microwave drying spray drying flash dryer
Drying time 45-70 minutes 3-5 seconds 20-45 hours
Drying temperature 45-60 degrees (arbitrary setting), inlet air 180 degrees, 50-60 degrees (difficult to control)
Ointment loss of 0.2~5% and above 3%
Moisture content: 4-5%, 2-4%, 4-6%
Content loss increases by 20-30% compared to other devices, decreases by 20-30%, and decreases by 20-30%
Under the same production conditions, one unit requires 3 units and 5 units
The cost per kilogram of dry cream is 0.4~0.5 yuan/kg, 3-4 yuan/kg, 3-4 yuan/kg
Drying method: Process configuration
It can be seen from the above that the drying cost is low, the benefit is good, and the equipment occupies a small area, which is equivalent to 20% of the area of the steam vacuum dryer and 30% of the spray drying equipment, greatly saving the purification plant. The dynamic vacuum microwave dryer is not only suitable for traditional Chinese medicine extracts, but also for health products, food and chemical products, especially for paste like and high viscosity materials; It can also play a better role in killing bacteria.
7、 Conclusion
The successful development of industrial microwave vacuum drying equipment has filled the gap, and this high-tech equipment has greatly promoted the development of national technology, especially the development of China's pharmaceutical industry, which will have a profound impact. At the same time, its successful development has opened up a broader field for the application of microwave energy.
The successful development of this product has made breakthroughs in many key technologies, and has also proposed some theoretical basis and methods for design. It has also gained valuable experience in practice, laying a solid foundation for the further development of this technology.
The actual operation shows that the equipment has excellent performance, advanced technology, and reasonable design. It is a new technology and product with significant economic benefits, good social benefits, and high promotion value.
