1、 Preparation before operation
1. Equipment inspection: Close the drainage/inflation valve, check the oil level of the vacuum pump (to be filled to the centerline of the window) and whether the vacuum pipeline connection is tight. Ensure that the interior of the cold trap is clean and free of residual frost.
2. Material handling: Slice the materials (such as chicken breast and drug solution) evenly (recommended thickness<15mm) and spread them flat on the material tray or penicillin bottle to avoid excessive accumulation and affecting drying efficiency.
3. Probe installation: Insert the temperature probe into the material center or place it tightly to ensure accurate monitoring of the core temperature of the material.
2、 Pre freezing stage
1. Loading materials: Place the material tray/penicillin bottle on the pre freezing rack, put it into the cold trap, and cover it with a tight seal.
2. Start pre freezing: Select the pre freezing program in the control system, set the temperature below the eutectic point of the material (usually ≤ -40 ℃), and set the pre freezing time according to the characteristics of the material (usually 8-10 hours).
3. Complete judgment: Wait for the material to fully solidify (no liquid flow observed by the naked eye), and the cold trap temperature to stabilize to the set value (such as -55 ℃) before ending the pre freezing process.
3、 Vacuum drying stage
1. Switch drying rack: Quickly transfer pre frozen materials to the drying rack, connect multiple manifolds (if applicable), and ensure that the vacuum glass cover/freeze-drying chamber sealing ring is installed in place.
2. Activate the vacuum system:
Turn on the refrigeration unit to maintain the low temperature of the cold trap (≤ -50 ℃).
Start the vacuum pump and observe the vacuum degree continuously decreasing to the set value (usually<100Pa).
3. Sublimation drying (one-time drying):
The system automatically executes the preset program: the cold trap maintains low temperature to capture water vapor, and the partition provides controllable heat to promote ice crystal sublimation.
The duration is about 10-36 hours, depending on the amount and thickness of the material.
4. Desorption drying (secondary drying):
After sublimation, gradually increase the temperature of the partition (such as reaching 35 ℃) to further analyze the bound water.
Determine the endpoint by monitoring the material temperature curve (with no fluctuations for 2-3 hours) or tactile sensation (crispy and non sticky).
4、 End process
1. Breaking through the void for material retrieval:
Turn off the refrigeration unit and vacuum pump, slowly open the inflation valve to restore normal pressure.
Remove the vacuum hood/open the compartment door, quickly take out the freeze-dried finished product and seal the packaging to prevent moisture absorption.
2. Equipment maintenance:
After defrosting the cold trap, drain the water and clean the remaining ice water inside.
Close all valves and power supply, and check the status of the vacuum pump.