The small freeze-drying machine has the function of layer temperature control, vacuum adjustment function, pulse backfill function, can display and view the freeze-drying curve, can detect the sample temperature, and has functions such as one-key defrosting.
Three common energy-saving methods for small freeze dryers:
1. Control the freezing point vacuum monotonic method
The vacuum monotonic method of controlling freezing point uses the respective advantages of freeze-drying and vacuum monotonicity, and strictly controls the temperature of food close to the freezing point, but cannot freeze, which not only saves refrigeration energy consumption, but also avoids the problem of thermal denaturation of food. Damage to biological cells during phase transition;
2. Change the structure of the material tray
The material tray can be improved from the thermal conductivity of the tray material and the contact heat transfer surface between the material tray and the material. Selecting materials with good thermal conductivity can effectively strengthen the freezing process;
3. Control the pre-freezing speed and the loading capacity of the tray
When discussing the vacuum freeze-drying process, Wang Jie et al. found that the pre-freezing rate affects the composition of ice crystals. The faster freezing rate is smaller for ice crystals, which is not conducive to traveling. The dehydration time is long, but it dissolves quickly after drying.
The slower freezing rate has larger ice crystals, which is beneficial to monotonic dehydration, but dissolves slowly after drying. In addition, on the unit area of the material tray, the thinner the thickness of the material accumulation, the faster the heat transfer and mass transfer speed, and the shorter the monotonic time.
Energy-saving operation of small freeze dryer:
For liquid raw materials, if there are more colloidal substances, when the concentration is high, appropriately reducing the concentration of the material will help to improve the freeze-drying rate. However, the material concentration should not be too low, otherwise the energy consumption will be increased due to too much water removed, and the water vapor diffusion channels will be easily blocked, reducing the freezing rate.
If the liquid raw material has a high water content, such as more than 80% water content, it should be concentrated as much as possible before freeze-drying to improve the drying rate. For solid materials, if there is no excessive shape requirements, the heat and mass transfer area can be increased by cutting, thereby accelerating the freeze-drying rate and reducing the freeze-drying time;
if the shape of the material is required to be high, cutting is not allowed, and puncture In order to facilitate the escape of water vapor inside the material, the freeze-drying rate can be improved by strengthening the mass transfer process.
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