A freeze dryer, also known as a freeze dryer, is a type of equipment that uses vacuum freeze sublimation drying technology to dehydrate materials. Its core advantage is that it can complete the drying process in a low temperature and vacuum environment, and retain the active ingredients, physical structure, nutrients and appearance of the material to the greatest extent.
type
According to the application scenario, structural design and processing scale, freeze dryers can be divided into the following categories
Divided by treatment scale and purpose
Laboratory type - small size, high temperature and pressure control accuracy, processing capacity of several grams to several kilograms, suitable for R&D and lyophilization of small batches of samples.
Pilot type - processing capacity of thousands of grams to tens of kilograms, used for process verification, connection between R&D and mass production.
Industrial production type - processing capacity of tens of kilograms to several tons, high degree of automation, suitable for large-scale mass production.
According to the structure, the plan is divided
In-situ type - the whole process of material freezing, sublimation and analysis is completed in the same cavity, without pollution, suitable for aseptic scenarios.
Shelf type - simple structure, low cost, need to transfer materials manually, mostly used for drying non-sterile materials.
Bell type - composed of lyophilization chamber and cold trap, compact size, suitable for lyophilization of small samples in the laboratory.
Test principle
The freeze dryer is based on the three-phase change law of water, maintaining a vacuum environment throughout the process, and the drying process is divided into three steps:
1. Pre-freezing stage: The temperature of the material is reduced below the eutectic point, and the free water and partially bound water are converted into solid ice crystals.
2. Sublimation drying stage: Vacuum below the three-phase point pressure, low-temperature heating directly sublimates the ice crystals into water vapor, which is captured and frozen by the cold trap to remove more than 90% of the water.
3. Analytical drying stage: increase the heating temperature (lower than the material tolerance value), maintain a high vacuum, and resolve the residual bound water to reduce the moisture content of the material to 1%-5%.
Fields of application
Laboratory research field - preservation and pretreatment of animal and plant tissues, microorganisms, soil samples to ensure the stability of physical and chemical properties of samples.
Food processing field - production of freeze-dried fruits and vegetables, probiotics, instant soups, etc., with less nutrient loss and long shelf life.
New materials - nanomaterials, special ceramics, lithium battery materials are dried to avoid structural damage caused by high temperatures.
In the field of cosmetics - freeze-dried masks, essence production, preserving the efficacy of active ingredients.
Common faults and solutions
1. The vacuum degree is not up to standard
Causes: aging sealing ring, abnormal vacuum pump oil, valve not fully open, contaminants in the cavity.
Solution: Replace the sealing ring; Refill/replace vacuum pump oil; Fully open valve; Clean the cavity.
2. The water content of the material is too high
Reasons: Insufficient drying time, low heating temperature, high cold trap temperature.
Solution: Extend the resolution drying time; moderately warm up; Overhaul of the cold trap refrigeration system.
3. Poor cooling effect
Causes: Refrigerant leakage, compressor failure, condenser blockage, fan stalling.
Solution: Repair leakage and replenishment; overhaul compressors; Clean the condenser; Replace the fan.
4. Uneven shelf temperature
Causes: Damaged heating pipe, insufficient thermal conductivity medium, uneven material placement.
Solution: Replace the heating pipe; supplementary media; Place the material evenly.
How to choose
heat-sensitive/aseptic materials are selected as in-situ freeze dryers with precise temperature control; High moisture materials value cold trap capacity and cooling speed.
laboratory research and development of small bell jar/in-situ machine; pilot production selected trial in-situ machine; Large-scale mass production selects industrial automation models.
Laboratory model vacuum ≤ 10Pa, industrial model ≤ 1Pa; The temperature of the cold trap for conventional materials is -50°C~-60°C, and the temperature of the freeze-drying material is -80°C; The temperature control accuracy ≤± 1°C.
Online monitoring, automatic defrosting, and sterilization functions are selected as needed; Give priority to manufacturers with many after-sales outlets and installation training.
summary
Freeze dryer is a high-efficiency dehydration equipment based on vacuum freeze sublimation technology, and its low-temperature drying characteristics can retain material activity and structural integrity to a large extent, and meet the differentiated needs of laboratory research, food processing and other fields. The selection needs to closely follow the material characteristics, processing scale and core performance parameters, and timely troubleshoot common faults such as vacuum degree and refrigeration system in daily use to ensure the stable operation of the equipment and give full play to the advantages of the freeze-drying process.
