Freeze-drying is a method of first freezing water-containing substances into a solid state, then sublimating the water in it from a solid state to a gaseous state, to remove the moisture and preserve the substance. Vacuum freeze-drying technology has a wide range of applications in the fields of bioengineering, the pharmaceutical industry, the food industry, material science, and deep processing of agricultural and sideline products.
The composition of the freeze dryer
Freeze dryer consists of a refrigeration system, vacuum system, heating system, and electrical instrument control system. The main components are a drying box, condenser, refrigeration unit, vacuum pump, heating/cooling device, etc.
The refrigeration system is the most important part of the freeze dryer and is called the “heart of the freeze dryer”. Its refrigeration system is mainly composed of the following components: compressor, refrigerant, oil separator, water condenser, filter drier, intercooler, sight glass, solenoid valve, hand valve (top cover valve), expansion valve, evaporation (plate exchanger, rear box condenser coil), vapor-liquid separator, return air filter, pressure gauge, pressure control relay, CPCE (energy regulator), safety valve, refrigeration pipeline, etc.
The key “3 elements” for the success of the freeze dryer
Determining the recipe is the most important step. The composition of the solution is related to the implementation of steps such as freezing and sublimation.
The formulation includes active ingredients; excipients; processed water.
After the formula is determined, strictly speaking, the eutectic point temperature and eutectic point temperature of the product have been determined, and in a certain sense, the freeze-drying process of the product has been determined. Antifreeze and activity retention ability.
2. Important thermodynamic properties (lyophilization process curve)
degree of supercooling; degree of crystallization; disintegration temperature or eutectic temperature; phase change of interstitial species in the metastable state; the heat of crystallization of solution; melting temperature of interstitial species.
3. Freeze dryer with excellent performance
Freeze dryer/freeze dryer should have excellent performance; can be adjusted at will; strong repeatability.
How to use a freeze dryer？
1. Before each startup, first check whether the pump oil in the vacuum pump is sufficient.
2. Unscrew the drain valve and let the remaining water flow out. Tighten the valve after draining.
3. Check whether the contact part between the freeze-drying chamber of the freeze-drying machine and the cold trap is in good condition, and clean and readjust if necessary.
4. Close all valves. Close the valve where you want to connect the cold trap to the vacuum pump.
5. Turn on the power switch of the cold trap and the power switch of the vacuum pump.
6. After 15 minutes, open the valve connecting the cold trap to the vacuum pump.
7. After 1 minute, the pre-frozen sample (already in the freeze-drying bottle) can be hung on the holder, and the freeze-drying process can be performed after opening the corresponding valve.
8. After the freeze-drying is completed, close the corresponding valve and remove the freeze-drying bottle.
9. After all freeze-dried bottles are removed, turn off the power of the vacuum pump and the cold trap in turn.
10. After the frost in the cold trap has melted, open the drain valve for drainage, and then close it.
Daily maintenance method of freeze dryer
1. Under normal circumstances, the freeze dryer shall not be used continuously for more than 48 hours;
2. The sample must be frozen into ice, if there is residual liquid, it will cause a vaporization jet;
3. The surface area of the prepared sample should be expanded as much as possible, and it should not contain acid-base substances and volatile organic solvents;
4. During the freezing process of the sample, the temperature gradually decreases, and the partition heating program can be selected to speed up the drying efficiency and shorten the drying time;
5. Note that the cold trap of the freeze dryer is about minus 50 degrees and below, it can be used as a low-temperature refrigerator, but you must wear thermal gloves to prevent frostbite;
6. Before starting the vacuum pump, check whether the inflation valve is closed and whether the contact surface between the plexiglass cover and the rubber ring is clean and free of dirt, and is well sealed.