A vacuum freeze dryer (vacuum freeze dryer) is a specialized device that utilizes the principle of sublimation to convert water from a solid state to a gaseous state in a low-temperature vacuum environment, yielding a dried product.
I. Core Working Principle
Pre-freezing Stage: The material is rapidly frozen at low temperatures (typically -40°C to -80°C), causing the water to form ice crystals, thus solidifying the material's structure.
Sublimation Drying: Under a high vacuum (maximum vacuum level of 0.0006 mbar), the ice crystals directly sublime into water vapor, which is captured and discharged through a cold trap, dehydrating the material.
Desorption Drying: This further removes any remaining bound water from the material, ensuring a final moisture content below 5% while preserving the active ingredients and their morphology.
II. Equipment Components and Functions
Refrigeration System: Provides a low-temperature environment, supporting single-stage or dual-stage refrigeration modes. The cold trap temperature can reach as low as -80°C, ensuring rapid freezing of the material. Vacuum System: Equipped with a multi-stage Roots water ring vacuum unit, the system boasts a pumping rate of up to 5.0 m³/h, quickly establishing a high vacuum environment and accelerating the sublimation process.
Heating System: Utilizes silicone oil heating or steam circulation to provide a uniform heat source for the material, promoting water sublimation.
Control System: Supports programmable freeze-drying curves, capable of storing ≥20 programs, and provides real-time monitoring of parameters such as temperature and vacuum level for automated operation.
Material Bin and Condenser: The material bin is used to store the material to be dried, while the condenser captures sublimated water vapor to prevent it from re-entering the material.
III. Technical Features and Advantages
Low-Temperature Drying: The entire drying process is performed at low temperatures, preventing denaturation of heat-sensitive materials and preserving bioactive components (such as enzymes, vitamins, and proteins).
High-Vacuum Environment: Inhibits microbial growth and enzymatic reactions, preventing oxidation and deterioration, and extending the shelf life of the material.
Structural Preservation: After drying, the material exhibits a sponge-like, porous structure with unchanged volume, excellent rehydration, and rapid dissolution. Energy-saving and High-Efficiency: Select models feature an energy-saving design, resulting in lower total power consumption than comparable products, and support customizable designs.
Flexible Operation: Supports intermittent or continuous operation modes, adapting to diverse needs from laboratory R&D to industrial production.
IV. Application Areas
Food Industry: Used for drying fruits, vegetables, meat, poultry, aquatic products, condiments, convenience foods, and specialty products, preserving their color, aroma, flavor, shape, and nutritional content for long-term storage and transportation.
Medical: Used for dehydrating and preserving biological products such as vaccines, serum, plasma, antibiotics, and hormones, ensuring the stability of active ingredients.
Biological Research: Used for long-term storage of blood, bacteria, and tissue samples, restoring their activity by simply adding water.
New Material Preparation: Used in applications such as graphene drying and aerospace thermal insulation ceramic production, utilizing vacuum freeze-drying technology to create unique material structures.
Other Applications: Used for archaeological preservation of wooden and silk artifacts, specimen preparation, and specialized material preparation.
V. Equipment Classification and Selection
By Structure:
Bell-Jar Freeze Dryers: Separate freeze-drying chamber and cold trap require manual material transfer, making them suitable for small-scale laboratory experiments. In-situ freeze dryer: The freeze-drying chamber and cold trap are integrated, automating the material pre-freezing and drying process. It is suitable for demanding applications such as pharmaceuticals and biological products.
By Function:
Laboratory Type: Small freeze-drying area (e.g., 0.12 m2), supporting small-scale and pilot-scale research.
Production Type: Large freeze-drying area (covering 1-30 m2), supporting large-scale industrial production.
Selection Parameters:
Freeze-drying area: Select based on production scale. For example, the LGJ-18C has a freeze-drying area of 0.18 m2.
Cold Trap Temperature: The general standard is -60°C, with -80°C optional for special needs.
Ultimate Vacuum: The unloaded ultimate vacuum should be above 15 Pa to ensure drying efficiency.
Plate Temperature Uniformity: The temperature difference between the plates of a pharmaceutical freeze dryer should be controlled within ±1.5°C.
VI. Typical Case Studies
Food Processing: A biotechnology company in Hangzhou uses the GZL-2CIP freeze dryer to prepare freeze-dried powder, preserving the nutritional content and flavor of the food. Pharmaceutical Production: A pharmaceutical company in Jilin purchased GZL-5 equipment for the production of traditional Chinese medicine preparations, ensuring the stability of active ingredients.
Biological Research: A laboratory in Shanghai uses a high-vacuum freeze dryer to process pathogenic microbial samples, enabling long-term storage and convenient transportation.
