Energy saving measures for small freeze dryer from freeze-drying process

Energy saving measures for small freeze dryer from freeze-drying process

The small freeze dryer plate type cold trap includes a liquid supply manifold, a liquid supply cross box, a cold trap main board, a return air cross box and a return air main. The advantages of small freeze dryers are high thermal conductivity, low energy consumption of small freeze dryers; there are several reciprocating channels in the cold trap main board, which makes it easy to distribute the working medium in the cold trap evenly, and the temperature of each cold trap is uniform, which is beneficial to the evaporation or refrigerant of the working medium. In the case of the same evaporation or heat exchange surface, the cold trap has a large amount of cold transfer and high heat exchange efficiency, and the small freeze dryer can realize the gravity supply of the working medium, and the direct expansion of the working medium can be simplified. Refrigeration system, reduce equipment investment; reduce pump power when using pump forced circulation supply.
The outer surface of the cold trap main board can also be corrugated, which not only increases the heat transfer area, but also promotes the disturbance of the heat transfer medium and improves the heat exchange efficiency; without the leeward side, the small freeze dryer facilitates the uniformity of water vapor on the outer surface of the cold trap. Condensed, the effective heat exchange area is fully utilized; in the case of the same water trapping area of ​​the cold trap, the occupied volume of the dry cold trap can be reduced, the manufacturing cost of the small freeze dryer can be reduced; the reduction of the warehouse body can also shorten the material Pre-evacuation time after entering the warehouse, avoiding material temperature melting, ensuring the quality of freeze-dried products, reducing the capacity of evacuated vacuum units, reducing vacuum unit investment, and reducing operating costs; vertical cold trap plate during defrosting, ice layer is easy The whole piece falls off, and the small freeze dryer can shorten the defrosting time.
In summary, the small freeze dryer has the advantages of small volume, low energy consumption, high water-trapping efficiency, easy defrosting, low manufacturing cost, and direct expansion of the lyophilizer cold trap. Less is not good for increasing the unit freeze-drying area and unit time production. Therefore, choosing the right tray loading and cooling rate can reduce energy consumption.

1. Shape processing and concentration adjustment of materials
For solid materials, if there is no excessive shape requirement, the heat transfer mass transfer area can be increased by cutting treatment, thereby speeding up the freeze-drying rate and reducing the freeze-drying time; if the shape of the material is high, cutting is not allowed, and puncture can be taken. The treatment is to facilitate the escape of water vapor inside the material, and the lyophilization rate is enhanced by strengthening the mass transfer process.
For liquid raw materials, if there are more colloidal substances, when the concentration is higher, appropriately lowering the concentration of the materials will help to increase the freeze-drying rate. However, the material concentration should not be too low, otherwise the energy consumption will be increased due to too much moisture removed, and the water vapor diffusion pores may be clogged and the freezing rate may be lowered. If the liquid material has a high water content, such as a water content of more than 80%, it should be concentrated as much as possible before lyophilization to increase the drying rate.
2. Vacuum freeze drying system
For vacuum freeze-drying systems, energy-saving measures should be taken from three aspects: maintenance of vacuum, refrigeration system and drying system. First, the low vacuum is beneficial for the outward diffusion of heat, but at the same time the resistance to outward diffusion of water vapor increases; the result is reversed at high vacuum. The higher the vacuum of a small freeze dryer, the greater the energy required to maintain the vacuum. Therefore, choosing the right degree of vacuum is conducive to reducing consumption. Secondly, reducing the condensation temperature, increasing the evaporation temperature, adopting a scientific and reasonable heat transfer method, adopting an automatic system, and achieving comprehensive energy utilization are all conducive to the reduction of energy consumption in the freeze-drying process.
3. Improve heating method and heating temperature
The control of the heating temperature includes temperature control of the frozen layer and the dried layer. In the case of ensuring that the material does not melt, the higher the temperature of the frozen layer, the better. Under the premise of not denaturation of the material or disintegration of the dried layer structure, a higher dry layer temperature is used as much as possible to shorten the drying time.
4. Control pre-freezing speed and tray loading
When studying the vacuum freeze-drying process, the relevant people found that the pre-freezing speed affects the formation of ice crystals, and the faster freezing rate is smaller, which is not conducive to sublimation, long dehydration time, but dissolves quickly after drying. The slower freezing rate is larger for ice crystals, which is good for dry dehydration, but slower after drying. In addition, the thinner the thickness of the material piled up on the unit area tray, the faster the heat transfer and mass transfer rate, and the shorter the drying time. However, the thinner material thickness is the advantage of the small-sized freeze-drying plate type cold trap for each batch of dry material per unit freeze-drying area.