Where is refrigeration dryer applicable?

2020-11-22 17:06:33 admin1 1

The refrigeration dryer is suitable for the drying of high-end raw materials, Chinese herbal medicine, biological, wild vegetables, dehydrated vegetables, food, fruits, chemicals, pharmaceutical intermediates and other materials. Refrigerated vacuum drying is a new type of cabinet structure developed by refrigeration dryer that combines refrigeration system, vacuum system, heat transfer oil heating system, and moisture removal system, which makes use of the material storage space in the cabinet for drying.

1. Working principle Freeze drying: also known as sublimation drying. A drying method in which the water-containing material is frozen below the freezing point, the water is converted into ice, and then the ice is converted into vapor under a higher vacuum to remove it. The material can be frozen in the freezing device first and then dried. But it can also be frozen directly in the drying chamber by quickly vacuuming it. The water vapor generated by sublimation is removed by the condenser. The vaporization heat required in the sublimation process is generally supplied by thermal radiation. The working principle of the freeze dryer is to freeze the dried items to below the triple point temperature, and then directly sublime the solid water (ice) in the items into water vapor under vacuum conditions, remove them from the items, and dry the items . After pre-processing, the materials are sent to the quick-freezing warehouse for freezing, then sent to the drying warehouse for sublimation and dehydration, and then packaged in the post-processing workshop. The vacuum system establishes low-pressure conditions for the sublimation drying chamber, the heating system provides sublimation latent heat to the material, and the refrigeration system provides the required cold energy to the cold trap and the drying chamber. This equipment adopts high-efficiency radiant heating, and the material is heated evenly; it adopts high-efficiency water trap and can realize rapid defrost; adopts high-efficiency vacuum unit, and can realize oil-water separation; adopts parallel centralized refrigeration system, multi-channel cooling on demand, working conditions Stable and energy-saving; using artificial intelligence control, high control precision and easy operation.

(1) High-temperature humid air with a temperature of 45°C is discharged from the air compressor, and enters the pre-cooler through the humid air inlet ① and exchanges heat with the low-temperature dry air that has been cooled and dried into the dryer (the two have their own circulation The pipes are isolated from each other) to pre-cool the air at the inlet; (2) The pre-cooled cold air enters the cooler ④. Under the instant strong cooling of the evaporator of the refrigeration system, the air temperature drops sharply to 1.7°C. At this time, the water in the air The gas and oil gas quickly reach saturation, and separate from the air and condense into water droplets and oil droplets; (3) The air flowing out of the cooler enters the oil-water separator (11), where it separates from the air under the action of the oil-water separator The water droplets and oil are separated from the air and discharged out of the machine through the automatic drain ⑤. The dried air flows into the pre-cooler again through another pipe ③; (4) At this time, the temperature and pressure dew point of the dry air flowing into the pre-cooler can reach 1.7°C, and the pre-cooler exchanges heat with the inlet moist air. Increase the temperature appropriately, and then discharge it through the air outlet ②. (The temperature of the air discharged after the drying process is too low, which will cause condensation on the surface of the air equipment and affect the normal operation of the equipment).

2. Structure The freeze dryer is composed of refrigeration system, vacuum system, heating system, electrical instrument control system. The main components are drying box, condenser, refrigeration unit, vacuum pump, heating/cooling device, etc. 3. The freeze-dried product of the freeze-drying curve biological product needs to have a certain physical form, uniform color, qualified residual moisture content, good solubility, high survival rate or potency, and long shelf life. Therefore, it is not only necessary to control the preparation process and the sealed storage after lyophilization. What's more important is to fully control the parameters of each stage of the freeze-drying process to get high-quality products. The freeze-drying curve and time sequence are the basic basis for freeze-drying process control. The freeze-drying curve is the relationship curve that represents the temperature and pressure of the product during the freeze-drying process with time; the freeze-drying sequence is the opening and closing operation of various equipment at different times during the freeze-drying process. The most important process parameters in freeze-drying processing are the temperature of the product and the pressure in the drying box. For a specific freeze-drying machine, because the temperature of the product has a certain dependence on the temperature of the shelf or the temperature in the box, and many devices cannot control the pressure on the surface of the product, the freeze-drying curve often uses the shelf temperature (or The temperature inside the box) and the relationship curve of time. In order to monitor the main parameters of the freeze-drying process, freeze-dryers equipped with automatic recorders generally automatically record the four parameters and time curves of shelf temperature, product temperature, water vapor condenser temperature, and freeze-drying tank pressure. These curves are all freeze-drying curves.

A typical freeze-drying curve divides the temperature of the shelf into two stages. The shelf temperature remains low during a large amount of sublimation. According to the actual situation, it can generally be controlled between -10°C and +10°C. The second stage is to adjust the shelf temperature appropriately according to the nature of the product. This method is suitable for products with a lower melting point. If the performance of the product is not clear, the performance of the machine is poor or the work is not stable enough, this method is relatively safe.

In fact, the shape of the freeze-drying curve is related to many factors such as the performance of the product, the amount of filling, the type of packaging capacity, and the equipment conditions. The following factors should be considered when formulating the freeze-drying curve: ① Variety of products: some products are more affected by freezing, and some products are less affected; general bacterial products are more affected by freezing, and viral products are affected by freezing Smaller. Products with a low eutectic point require a low pre-freezing temperature, and the temperature of the slab during heating should be correspondingly lower; in order to store the product for a long time, the product with a low residual moisture content requires a longer freeze-drying time. For products that require high residual moisture content, the freeze-drying time can be shortened; ②Liquid volume: the total liquid volume and the volume of the product in each container. If the volume is large, the freeze-drying time will be longer; ③Types of containers: A flat bottom provides better heat transfer. If the bottom is uneven or the glass is thicker, the heat transfer is poor. The latter obviously takes longer to freeze-dry; ④The performance of freeze-drying machine: different manufacturers have different freeze-drying curves. During production, the best freeze-drying curve should be worked out according to their specific conditions. 4. How to use (1) Turn on the main power switch on the left side of the freeze dryer chassis, and the air pressure digital display is 110 pk; (2) Press and hold the main switch on the control panel of the freeze dryer for more than three seconds, and the temperature digital display Is the actual temperature of the cold trap; (3) Start the freeze dryer and pre-cool for more than 30 minutes; (4) Put the sample into the sample rack, cover the plexiglass cover, and start the vacuum pump; (5) Wait for the freeze dryer After the air pressure is stable, record the temperature and air pressure. Shutdown operation:

(6) Record the temperature and air pressure values before shutdown; (7) Press and hold the inflation valve on the control panel of the freeze dryer, and immediately turn off the vacuum pump; (8) When the air pressure is displayed as atmospheric pressure, open the plexiglass cover and take out the sample; ( 9) Turn off the refrigerator of the freeze dryer, press and hold the main switch for more than three seconds, and finally turn off the main power switch; (10) After the ice in the cold trap is completely melted into water, open the water outlet valve on the left side of the chassis to drain the water and dry Clean the inner wall of the cold trap with a cloth and cover it with a large piece of filter paper to prevent dust. 5. Precautions (1) The surface area of the sample prepared by the freeze dryer should be expanded as much as possible, and it must not contain acid-base substances and volatile organic solvents; (2) The sample must be completely frozen into ice, if any residual liquid will cause vaporization Spray; (3) Note that the cold trap of the freeze dryer is about minus 65 degrees, which can be used as a low-temperature refrigerator, but must wear insulation gloves to prevent frostbite; (4) Before starting the vacuum pump, check whether the water outlet valve is tightened and whether the inflation valve is closed. Whether the contact surface between the plexiglass cover and the rubber ring is clean and free of dirt and well sealed; (5) Generally, the refrigeration dryer should not be used continuously for more than 48 hours; (6) The temperature of the sample is gradually reduced during the freezing process, and the After the sample is taken out to warm up for a period of time, continue to dry to shorten the drying time.

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