Vacuum freeze-drying technology refers to the process of freezing materials at low temperature (generally below – 25 C) in vacuum to complete the transformation from solid to gaseous directly, so as to avoid the damage of temperature rise to the composition of heat-sensitive materials in the conventional drying process. 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, freeze-drying has been proved to be a very effective means. It is especially suitable for drying non-heat-resistant substances such as enzymes, hormones, nucleic acids, blood and immune products. Because of the high cost of freeze-drying equipment, enterprises generally use freeze-drying technology for relatively valuable powder injection preparations.
Freeze-dried solids exhibit porous structure due to sublimation of tiny ice crystals, and retain their original volume when frozen. They are easily dissolved and recovered after adding water. The result of drying can discharge more than 95%~99% water, which is beneficial to the long-term preservation of products. With the rapid development of biochemical drugs and biological preparations, freeze-drying technology will increasingly show its importance and superiority.
The refrigeration dryer used in pharmaceutical enterprises is generally composed of refrigeration system, vacuum system and heating system. The main components are drying box, condenser, refrigeration unit and vacuum pump. The liquid ring vacuum pump is connected in series with the Roots pump to vacuum the system. The freeze-drying of the products is carried out in the drying box. The shelf in the drying box is made of stainless steel plate. There are cold/heat medium tubes in the shelf. The products can be cooled or heated. Two refrigerators are used in parallel to ensure refrigerant supply. The heating system consists of an electric heating pipe, a medium (usually silicone oil), a circulating pump, etc. The silicone oil is heated by an electric heating pipe and then transferred by a circulating pump to a conduit in the shelf of a drying box to heat the products and provide sublimation heat. When frozen, the silicone oil is cooled by cooling exhaust pipes, and the pipes are conveyed by circulating pump to the inner shelf of the drying box to cool the products.
Freeze drying pump itself has low noise and energy saving, which has become one of the important equipment in many fields such as vacuum freeze drying industry, and plays an active role in improving work efficiency.