The vacuum unit of medical vacuum dryer is composed of two rotary mechanical vacuum pumps and one roots vacuum pump. Vacuum freeze-drying is a better method for dehydration of substances. It can freeze the freeze-dried substances in advance, and then sublimate the moisture of substances under low temperature and pressure to achieve the purpose of dehydration. The sublimated water vapor is collected by condensation. After the vacuum freeze-drying operation, the material becomes dehydrated.
The freeze-dried solid materials present porous structure due to the sublimation of tiny ice crystals, and maintain the volume of the original frozen, and are easy to dissolve and recover after adding water. The temperature of the products is kept at a lower temperature state (generally lower than – 250) during the sublimation process, so it is particularly suitable for the drying of those materials that are not heat-resistant, such as enzymes, hormones, nucleic acids, blood and immune products. The result of drying can discharge more than 95-99% water, which is beneficial to the long-term preservation of products. The drying process of products is carried out under vacuum condition, so it is not easy to oxidize. In view of the chemical, physical and biological instability of some biochemical drugs, the application of Roots vacuum pump in medical vacuum freezing has been proved to be a very effective method.
After vacuum freeze-drying, the enzyme action of the material is weak, the original chemical and physiological properties are basically unchanged, the dried material is porous structure, the volume is basically unchanged, easy to recover. Especially, the material after vacuum freeze-drying can be preserved for several years without deterioration.
With the rapid development of biochemical drugs and biological agents, medical vacuum freezing technology will show its importance and superiority more and more.
The vacuum unit is connected with drying box and condenser through vacuum pipeline and vacuum valve to form a sealed vacuum system. The vacuum unit is equipped with electric contact vacuum gauge, which can automatically control the start of Roots vacuum pump according to the pre selected vacuum level. A vacuum butterfly valve is installed in the vacuum pipeline between the drying box and the condenser, which can be opened and closed at any time according to the use requirements. The bottom of the condenser is equipped with a branch vacuum pipeline to the hot air blower, and the middle valve is separated by a 50 butterfly valve. This valve and the branch pipeline are used for defrosting and drying of the condenser. The vacuum branch pipe on the roots pump is the path when the mechanical vacuum pump is used alone, and the upper part is equipped with a solenoid valve. When the roots vacuum pump is started, the width will be automatically closed. The vacuum pipeline is equipped with the electromagnetic belt air release stop valve. When the vacuum pump stops, the vacuum pipeline can be automatically closed. At the same time, the air will be put into the pump to prevent the vacuum pump oil from rushing into the vacuum pipeline due to the negative pressure. A corrugated hose is arranged between the connecting pipes of the vacuum pump to prevent the vibration from being transmitted to its components during operation.
The application of Roots vacuum pump in medical vacuum freezing is described. Roots vacuum pump has the advantages of quick start, low power consumption, low operation and maintenance cost, large pumping speed and high efficiency. It is not sensitive to a small amount of water vapor and dust contained in the extracted gas. It has a large pumping speed within the pressure range of 100-1 PA, and can quickly remove the suddenly released gas. This pressure range is just between the oil sealed mechanical vacuum pump and the diffusion pump. Therefore, it is often connected in series between the diffusion pump and the oil sealed mechanical vacuum pump, which is used to improve the pumping capacity of the intermediate pressure range.