Principles of Freeze Dryer
- Freeze drying, or lyophilization, involves freezing the material and then reducing the surrounding pressure to allow the frozen water to sublimate directly from solid to gas phase.
- This method preserves the structure and composition of the material.
Construction of Freeze Dryer
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- Freezing Chamber: Where material is frozen initially.
- Vacuum Chamber: Encloses the frozen material and reduces pressure.
- Shelves/Trays: Hold the material to be dried.
- Vacuum Pump: Creates a vacuum in the chamber.
- Condenser: Captures and freezes the sublimated vapor.
- Heating System: Provides controlled heat to the material during drying.
Working of Freeze Dryer
- Freezing: Material is frozen solid.
- Primary Drying (Sublimation): The chamber is evacuated, and controlled heat is applied, causing ice to sublimate into vapor.
- Secondary Drying (Desorption): Remaining bound moisture is removed by slightly increasing the temperature under vacuum.
- Condensation: Sublimated vapor is captured and condensed on a cold surface.
- Unloading: The dried material is removed from the chamber.
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Uses
- Drying pharmaceuticals, biological products, food products, and delicate materials.
Merits
- High Quality: Preserves the structure, activity, and quality of the material.
- Long Shelf Life: Dried products have extended shelf life without refrigeration.
- Gentle Process: Suitable for highly sensitive and delicate materials.
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Demerits
- High Cost: Expensive equipment and high operational costs.
- Complex Process: Requires precise control and monitoring.
- Energy Intensive: Significant energy consumption, particularly during the freezing phase.
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