There are many problems when purchasing freeze dryer equipment. From the user's point of view, Shanghai Haozhuang instrument introduces the selection technology of some experimental series freeze dryer.
Freeze drying machine freeze-drying is to pre freeze water-containing substances into solid state, in vacuum state to sublimate water from solid state to gas state, in order to remove water and preserve material. The original chemical and biological characteristics of the products obtained by this drying method are basically unchanged, and they are easy to be preserved for a long time. After adding water, they can return to their original morphology before freeze-drying, and keep their original biochemical characteristics. It is a high-quality drying method. The main uses of modern freeze-drying technology include: the freeze-drying storage of in vitro biological tissues; the freeze-drying preservation of living bacteria and live toxins; the freeze-drying of Chinese herbal medicine, western medicine, biological drugs and blood products; the freeze-drying storage and transportation of convenient food, health food and functional food; the freeze-drying preparation of nano ceramic materials and various metal powder materials. Therefore, freeze drying technology has been widely used in chemical industry, food, materials, medicine, biological products and other fields. Vacuum freeze dryer (referred to as freeze-drying machine) is a kind of equipment to realize freeze-drying technology. It is a kind of machine with complex structure. It involves the knowledge of refrigeration, vacuum, thermal engineering, machinery, fluid, electrical control and pressure vessel.
Classification of experimental series freeze-drying machines:
The performance indexes of the experimental series freeze dryer are small volume, light weight, multi-function, stable performance and high accuracy of the test system. It is better to use one machine for multiple purposes, which can adapt to the freeze-drying experiment of various materials. The main classification methods of experimental series freeze-drying machines are as follows:
1. In terms of structure
L bell jar type freeze-drying machine: the freeze-drying chamber and cold trap are separate upper and lower structures, and the freeze-drying chamber has no pre freezing function. This type of freeze-drying machine needs manual operation when it is transferred to the drying process after the pre freezing of materials. Most of the experimental lyophilizers are bell jar type with simple structure and low cost. Most of the freeze-drying chambers use transparent plexiglass cover, which is convenient to observe the freeze-drying situation of materials.
L in situ freeze-drying machine: the freeze-drying chamber and cold trap are two independent chambers. The shelf in the freeze-drying chamber has refrigeration function. After the material is put into the freeze-drying chamber, the pre-freezing and drying process of the material does not need manual operation. The manufacturing process of this type of freeze-drying machine is complex and the manufacturing cost is high. However, the in-situ freeze-drying machine is the development direction of freeze-drying machine, and it is an ideal choice for the exploration of freeze-drying process, especially suitable for the freeze-drying of pharmaceutical, biological products and other special products.
a. Common type B, multi manifold type C, gland type
2. In terms of function
Common shelf type: the materials are packed in bulk in the material tray, which is suitable for freeze-drying of food, Chinese herbal medicine and powder materials.
Device with cap: it is suitable for the drying of the materials in the bottle. When preparing for freeze-drying, the materials are packed into the vials according to the needs. After the cap is covered, the freeze-drying is carried out. After the drying, the capping mechanism is operated to compress the bottle cap, which can avoid secondary pollution, re absorb moisture, and is easy to be stored for a long time.
Multi manifold type: a flask is installed outside the drying chamber to dry the materials frozen on the inner wall of the bottle. At this time, the flask is connected to the manifold outside the drying box as a container. The materials in the flask are heated by room temperature. Through the multi manifold switch device, the flask can be removed or loaded at any time as needed without shutdown.
With the function of pre freezing: in the process of material pre freezing, the cold trap is used as the pre freezing chamber to pre freeze the materials. In the drying process, the cold trap is a water trap to capture the water overflowing from the material. The freeze-drying machine with pre freezing function can complete the pre freezing and drying of materials in the freeze-drying process. The freeze-drying machine has high efficiency and saves the cost of low-temperature refrigerator.
Several parameters should be paid attention to when choosing and purchasing the freeze dryer
1. Freeze dried area
The number in the freeze-drying machine model represents the freeze-drying area of the model freeze-drying machine. For example, the freeze-drying area of fd-1a-50 freeze-drying machine is 0.12 m2. According to their own needs, users should determine how much freeze-drying area the freeze-drying machine needs through calculation. For example, for each batch of products with 1.2 kg (L) liquid volume, the loading area of freeze-dried plate can be calculated by loading materials in material tray with thickness of 10 mm
A (area, M2) = V (volume, m3) / h (height, m) = 0.0012m3/0.01m = 0.12m2
It is necessary to select a freeze-drying machine with a loading area of 0.12 m2.
2. Cold trap temperature
In theory, the lower the cold trap temperature is, the stronger the water catching capacity of the cold trap is. However, the lower the temperature of the cold trap is, the higher the refrigeration requirement is, and the higher the machine cost and operation cost are. The cold trap temperature of the experimental series of freeze dryers is mainly about - 50 ℃ and - 80 ℃. The freeze-drying with cold trap temperature of - 50 ℃ is suitable for some products which are easy to freeze-drying, and the freeze-drying with cold trap temperature of - 80 ℃ is suitable for the freeze-drying of some special products. The effect of cold trap temperature on the water catching capacity shows that the cold trap temperature decreases from - 35 ℃ to - 55 ℃, and the water catching capacity of the cold trap is improved obviously, but the cold trap temperature is lower than - 55 ℃. Therefore, in the case of no special needs, the cold trap temperature of about - 50 ℃ is an ideal choice.
3. Cooling rate
The cooling rate reflects the refrigeration capacity of the refrigeration system. Under no-load condition, the cold trap temperature should reach the minimum temperature specified in the index within 1 hour. For example, for the freeze-drying machine with cold trap temperature less than - 50 ℃, the time when the cold trap temperature reaches - 50 ℃ should not be more than 1 hour when the machine starts refrigeration.
4. Limit vacuum
The limiting vacuum degree reflects the leakage of freeze-drying machine and the pumping efficiency of vacuum pump. In the past, the higher the vacuum degree is, the better it is. Now, it is considered that the vacuum degree should be within a reasonable range. If the vacuum degree is too high, it is not conducive to heat transfer, and the drying speed will decrease. However, the no-load limit vacuum degree of freeze-drying box should be more than 15 PA.
5. Vacuum time
The no-load pumping speed of freeze-drying box should be pumped from atmospheric pressure to 15pa within half an hour.
6. The temperature uniformity and flatness of the plate layer are as follows
The uniformity and smoothness of the plate temperature have a great influence on the uniformity of product quality. The better the temperature uniformity and flatness, the better the homogeneity of freeze-dried product quality. The shelf temperature control of freeze-drying machine includes heater type and middle flow type. The temperature uniformity and flatness of freeze-drying machine shelf with intermediate fluid control layer is good. The plate layer of this freeze-drying machine is hollow sandwich structure, and the cooling and heating of the plate layer are realized by the circulation of the intermediate fluid in the flow channel inside the plate layer, so the plate temperature is uniform and uniform. Lgj-50c freeze dryer in the four ring freeze-drying machine adopts the technology of shelf intermediate fluid. The shelf temperature control of bell jar freeze-drying machine is basically using heater, and the consistency of plate temperature is slightly poor. However, in general, the temperature difference between the plates of the freeze-drying machine for medicine should be controlled at ± 1.5 ℃, and the temperature difference within the plate should be ± 1 ℃. The food freeze-drying machine can be appropriately relaxed.
7. Control system
The control system types and functions of freeze-drying machine are different. For the experimental series of freeze-drying machine, it is mainly used for material freeze-drying process exploration and a small amount of pilot production. Therefore, the control system should be able to display the freeze-drying process parameters in real time and automatically record; set, modify and effectively implement the freeze-drying process program; have communication interface to facilitate data acquisition and storage.
On 2018-08-08 11:45:46
