The Design Of The Control System For Vacuum Freeze-dryer

Freeze-drying(lyophilization) is a process by which moisture content can be reduced in a product whilst also retaining the products characteristics for example odour, taste, enzyme activity. The water content is frozen; and the ice is then removed by sublimation (ice turning directly into vapor without transforming into water). By this method the twin advantages of freezing and drying are combined into one favorable means of preservation. Freeze-drying requires a frozen raw material. Heat and a vacuum are apllied to the frozen product. As heat is applied the moisture in the product is driven off as vapour (there is no liquid phase due to the low pressure). The vapour condenses out as solid ice onto the freezing coils located at the bottom of the dryer.Along with to freeze-drying study thorough and to the exaltation that the product quantity request, the people is also more high request to then automatic control degree of the freeze-dryer. The old control system of freeze-dryer is simple to open or close the devices seting on the machine, and the temperature and the vacuum is displayed only. The freeze-drying is a very complicated process. Along with freeze-drying technique, the request of recording automatically the data of the freeze-drying process is more and more outstanding.This control system is designed according to the new request of freeze-drying. It can satisfy at present mostly and in the future more complicated freeze-dryer. This control system can prepare to save various freeze-drying parameter and reload them, can examine and display the vacuum degree and temperature at the same time, can save automatically each parameter data. Each para can be browsed with curve form. It can control many layers' temperature at the same time, which let dry condition of each layer is as far as possible consistent.