The capping type freeze dryer (also known as a freeze dryer or freeze-drying equipment) is widely used for drying processes in the fields of biological products, pharmaceuticals, food, etc., especially for drying thermosensitive substances. The process usually includes steps such as sample freezing, sublimation (vacuum drying), and capping and packaging. The following is the common process flow of the capping type freeze dryer:
1. Sample preparation
Preparation of samples: Prepare the solution or suspension to be dried according to the substance that needs to be dried. It can be liquid drugs, culture media, food ingredients, etc.
Loading samples: evenly distribute the prepared samples on the sample tray of the freeze dryer. Usually, samples should be evenly distributed and stacked to ensure even freeze-drying.
2. Low temperature freezing stage
Sample freezing: Place the sample in a freeze dryer and rapidly freeze it through a low-temperature system. The freezing temperature is usually controlled between -40 ° C and -80 ° C, which can quickly freeze the moisture in the sample and form solid ice.
Freezing time control: During the freezing process, it is necessary to ensure that the moisture of the sample is completely frozen. If the sample is a biological product or drug, special attention should be paid to temperature control to avoid excessive ice crystals caused by too low a temperature, which can damage the structure of the sample.
3. Vacuum sublimation stage
Entering the vacuum state: After the freezing process is completed, the freeze dryer will enter the vacuum state. At this point, the air pressure inside the device will be reduced to a level close to zero, generally controlled between 10-100Pa. Under low-pressure conditions, solid ice begins to sublime directly into water vapor without going through the liquid phase.
Sublimation process: Through vacuum and moderate heating, ice crystals gradually sublime and evaporate. This process is the core of freeze-drying. During the sublimation process, the moisture in the sample is directly converted from solid to gas and collected through the condensation system of the equipment.
Sublimation temperature control: During the sublimation process, it is necessary to precisely control the heating temperature, usually between -20 ° C and -40 ° C, to ensure that the sample is not damaged by overheating and to ensure smooth sublimation of moisture.
4. Secondary drying stage (finished product drying)
Secondary drying: After sublimation, the sample may still contain a small amount of crystalline water or free water, so secondary drying is required. At this point, the freeze dryer continues to evaporate the moisture in the sample by gently heating and maintaining a low temperature and vacuum state until the moisture content drops to an extremely low level (usually less than 1%).
Temperature control: Temperature control during the secondary drying stage is very important and should generally be set between 10 ° C and 40 ° C according to the properties of the substance. Avoid excessive temperature to prevent damage to the properties of the sample.
5. Capping and packaging stage
Cap sealing: After the drying process is completed, the dried sample usually needs to be sealed to prevent moisture from reabsorbing. In the working principle of the capping type freeze dryer, the "capping" process is a key link.
Capping operation: After completing freeze-drying, sample containers (such as ampoules, medicine bottles, aluminum foil bags, etc.) will be sealed and capped in a vacuum environment to ensure that the samples are completely unaffected by external moisture and air.
Sealed container: Some freeze dryers are equipped with an automatic capping system, which can accurately press the sealing lid onto it to form a sterile and sealed packaging.
6. Complete drying
Take out the sample: After the sealing is completed, the freeze-dried sample can be taken out. At this point, the sample has completely dehydrated and maintained its original structure and biological activity (especially in biological products).
Storage conditions: The freeze-dried sample should be stored in a low-temperature, dry environment, usually between -20 ° C and -80 ° C, to prevent moisture absorption or deterioration of the sample.
7. Control system and monitoring
Temperature and pressure monitoring: Modern freeze-drying equipment is equipped with temperature and pressure sensors, which can monitor various parameters of the freeze-drying process in real time, ensuring that each stage of operation is within a reasonable range.
Automated control: Many capping freeze dryers use automated control systems that can automatically adjust parameters such as temperature, pressure, and vacuum degree, achieving unmanned operation and reducing human errors.
8. Cleaning and maintenance
Cleaning: After use, the freeze dryer needs to be cleaned, especially the sample tray, cooling system, sealing components, etc., to ensure that they will not be contaminated during the next use.
Regular maintenance: Regularly inspect and maintain components such as the capping system, refrigeration system, and vacuum system of the equipment to ensure long-term stable operation.
summary
The process flow of the capping type freeze dryer includes multiple steps such as sample freezing, sublimation, secondary drying, capping and packaging. Each step requires precise control to ensure that the final drying effect meets quality requirements and maintains the stability and effectiveness of the sample. During use, operators should strictly follow the equipment instructions and process requirements to ensure the success of the freeze-drying process and the high quality of the samples.