New generation microwave vacuum dryer
Mild Steel Coil,Hot Rolled Mild Steel Coil,Steel Hot Rolled Coil,Hot-Rolled Coil Steel Jiangyin Mitoo Precise Co.,Ltd. , https://www.mitoosteel.com
In industrial production, there are many items that cannot be dried under high temperature conditions, such as some medicines, chemicals, nutritious foods, and high-end Chinese herbal medicines such as ginseng and velvet. In order to ensure product quality, the drying process must be performed at a temperature below 100°C or Under room temperature conditions, it is known that the gas pressure decreases and the boiling point of water also decreases. For example, at an atmospheric pressure (101.3 kPa), the boiling point of water is 100°C, and at 0.073 atm (7.37 kPa), the boiling point of water is 40°C. Under vacuum conditions, heating the object causes the internal moisture of the object to evaporate without any temperature rise. Since the convective heat transfer of air under vacuum conditions is difficult to perform, it is only by means of heat conduction that the material is provided with heat energy. The conventional vacuum drying method is slow in heat conduction, low in efficiency, and difficult to control the temperature. The heated material also generates internal and external temperature differences. Microwave heating is a type of radiant heating. It is the direct interaction between microwaves and materials. It is heated at the same time inside and outside, and does not need to transmit heat through convection or conduction. Therefore, the heating speed is fast, the drying efficiency is high, and the drying quality is high.
Developed countries such as the United States, France, and Japan began to develop industrialized microwave vacuum drying equipment in the 1980s. And achieved good results in practical applications. In collaboration with a company, the University of California, USA, used microwave vacuum drying equipment to process seedless raisins. The traditional process of 65 °C, 24-hour hot air drying to 50 °C, 5 hours microwave vacuum drying, greatly improving product quality. The Microwave Vacuum Dryer (2450MHz, 48KW) manufactured by French International Microwave Company is processing instant orange powder. The product not only maintains the original color, fragrance and taste, but its vitamin retention is much higher than that of spray drying. In the late 1980s, domestic research and development of microwave vacuum drying equipment began, and through years of efforts, around 2000, successfully solved the low pressure microwave field arc discharge, heating temperature difference between the material layer, non-contact temperature measurement in the microwave field, etc. A number of problems have crossed from the experimental stage to the industrialized production stage. For food engineering, pharmaceutical engineering, biological engineering, chemical engineering, materials engineering and deep processing of agricultural and sideline products, it provides a new type of high-efficiency drying equipment. Microwave vacuum drying features:
1. Efficient: In the conventional vacuum drying equipment (assuming a vacuum pressure of 7.37kpa, a material dehydration temperature of 40°C, and 1kg of water vaporization heat of 574 kcal), heat transfer through convection is very difficult under vacuum conditions, only Conduction can be conducted, the heating speed is slow, the drying cycle is long, and the energy consumption is large. The microwave vacuum drying equipment adopts radiation energy transmission, and it is the whole medium heating, no other heat transfer medium is needed, and the above shortcomings are avoided. Therefore, the speed is high, the efficiency is high, the drying cycle is greatly shortened, and the energy consumption is reduced. Compared with conventional drying technology, it can improve work efficiency by more than four times.
2, heating evenly: Because microwave heating is inside and outside the material at the same time heating, material inside and outside the temperature difference is very small, will not produce the conventional heating inside and outside the inconsistent heating conditions, and greatly improve the quality of the drying.
3, easy to control: easy to continuous production and automation, microwave power can be quickly adjusted and non-inertia features, easy-to-immediate control, easy adjustment and determination of process parameters.
4, the device is small, easy installation and maintenance.
5, the product quality is good: Compared with the conventional method, the quality of the processed product has been greatly improved.
6, in addition microwave equipment has the effect of disinfection, sterilization, product safety and health. Shelf life can be extended. From the above-mentioned features, energy efficiency, consumption reduction, product quality improvement, safety and health, and low investment in equipment can be seen in the significant economic and social benefits. In the processing of dehydrated vegetables, the comparison results of the technological performance, economic benefits, and product quality of various drying equipments are shown in Table 1:
Comparing the microwave vacuum drying equipment's efficiency by four times that of the conventional vacuum drying equipment, it can be seen that the microwave vacuum drying is a high-tech with significant economic benefits and high promotion value. At present, the new industrialized microwave vacuum drying equipment developed by our company has passed the appraisal of the relevant state units, and a series of products have been formed from 2KW to 100KW microwave vacuum drying equipment. This will provide a modern high-tech drying equipment for many fields and scientific research departments of China's national economy.