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Your Location: Home >> News >> Technical support >> How to adjust the temperature of vacuum freeze drying

How to adjust the temperature of vacuum freeze drying

Release Date: 2018/7/25 17:46:41 .
Browse: 976

How to adjust the temperature of vacuum freeze drying
The vacuum freeze dryer is an excellent drying method. Under dry conditions, the dry product can be stored for a long time without the need of additives at normal temperature. The structure of the freeze-dried product is porous and crisp, and the rehydration is fast when used. The color, fragrance, taste, shape and activity of the articles after rehydration are basically unchanged, and the vacuum freeze dryer is especially suitable for the food, health care products and pharmaceutical industries. The vacuum freeze dryer freezes the wet material or solution to a solid state at a lower temperature (-10 ° C ~ -50 ° C), and then directly sublimes the moisture into a gaseous state without a liquid under vacuum (1.3 to 13 Pa). The drying technique that ultimately dehydrates the material. Vacuum freeze dryer technology is the core guarantee for enterprise innovation transformation, and quality is also the guarantee of product fate. Vacuum freeze dryer manufacturers always adhere to the enterprise tenet of "survive by quality, develop by benefit", dare to be the first, be brave in innovation, and strive to improve product quality, so as to better serve our customers.
The working principle of the vacuum freeze dryer is to freeze the dried object to below the triple point temperature, and then directly sublimate the solid water (ice) in the article into water vapor under vacuum conditions, and remove the article from the article to make the article dry. After the material is pretreated, it is firstly frozen, then vacuum dried and sublimed, and then packaged in a post-treatment workshop. The vacuum freeze dryer heating system provides sublimation latent heat to the material, and the refrigeration system provides the required amount of cooling to the water trap and the drying chamber. The quality requirements for freeze-dried products are: constant biological activity, uniform appearance and color, full shape, firm structure, fast dissolution rate and low residual moisture. To obtain high quality products, a comprehensive understanding of the theory and process of lyophilization should be obtained. The freeze-drying process of the vacuum freeze dryer includes three stages of pre-freezing, sublimation and re-freezing. The vacuum freeze dryer has a reasonable and effective shortening of the freeze-drying cycle and has obvious economic value in industrial production.
During the lyophilization process, the temperature pre-freezing of the liquid articles and the subsequent sublimation of the moisture in the solid matter need to control the temperature within a certain range of the process requirements, which requires the vacuum freeze dryer to have a certain precision temperature adjustment function. Under the premise of not setting the temperature control unit, the temperature regulation problem of the vacuum freeze dryer is better solved. The specific scheme is as follows:
1. In order to meet the cooling capacity of the refrigeration compressor, add a cooling branch that can provide appropriate cooling capacity to the refrigeration system before the vacuum freeze dryer to meet the cooling capacity of the temperature adjustment. ;
2. At the same time, due to the temperature adjustment, the refrigeration compressor supplies cooling to two evaporators with different evaporation temperatures. The difference in working conditions may cause a large impact on the refrigeration compressor due to the delay of the expansion valve control. In severe cases, It will cause the liquid pressure of the refrigeration compressor to cause a failure, which requires a good grasp of the control of the return steam pressure. The technicians now add an electromagnetic valve to the steam return line of the front tank evaporator, and the electromagnetic valve is passed through the pressure controller. The monitoring of the differential pressure before and after to control the opening or closing of the valve reduces the load shock during the temperature adjustment, and ensures the smooth operation of the compressor of the vacuum freeze dryer;
3. In order to prevent the pressure in the front tank evaporator from rising due to the closing of the electromagnetic valve, the temperature adjustment effect is not guaranteed, and the vacuum freeze dryer technician adds a steam return to the steam return line in front of the electromagnetic valve. The branch pipe, which is connected to the secondary compressed suction pipe of the refrigeration compressor, has been proved to be practical by the practice on multiple vacuum freeze dryers, which can avoid the increase of the cost of adding the temperature control unit. Moreover, the capillary temperature adjustment which is generally used nowadays is caused by the unsatisfactory temperature regulation effect and the load shock to the compressor.
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