Advantages and disadvantages of the hottest freeze

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Advantages and disadvantages of freeze dryer

freeze dryer is a machine composed of refrigeration system, vacuum system, heating system and electrical instrument control system. The main components of the freeze dryer are divided into drying oven, condenser, refrigeration unit, vacuum pump, heating/cooling device, etc

the main function of the freeze dryer is to freeze the water containing substances into a solid state, and then sublimate the water therein from a solid state to a gaseous state, so as to remove the water and preserve the substances

in the process of compressed air drying, its freeze-drying is to reduce the temperature of compressed air to separate out the water in the compressed air. The working principle of the freeze dryer (cold dryer) is the same as that of the refrigerator. After the compressed air passes through the frozen compressed air pipe, the compressed air temperature drops to the required temperature to achieve the drying. Advantages of the freeze dryer:

there are various drying methods, such as sun drying, boiling drying, drying, spray drying and vacuum drying, but the common drying methods are usually carried out at a temperature above 0 ℃ or higher. Generally, the dried products have the problems of volume reduction and texture hardening, most of the volatile components will be lost, some heat sensitive substances will be denatured and inactivated, and some substances may even be oxidized. Therefore, there are great differences in the properties of the dried products compared with those before drying. The freeze-drying method is basically carried out below 0 ℃, that is, when the product is frozen. Only when the residual water content of the product is reduced by 12.5% and 1.2% higher than that of the same period of last year and January and October respectively, can the product rise to a temperature above 0 ℃, but generally not more than 40 ℃. Under the vacuum condition, when the water vapor sublimates directly, the drug remains in the frozen ice shelf, forming a spongy loose porous structure, so its volume is almost unchanged after drying. Before reuse, as long as water for injection is added, it will dissolve immediately

compared with the conventional freeze-drying method, the freeze-drying machine has the following advantages:

* many heat sensitive substances will not be denatured or inactivated

* when drying at low temperature, the loss of some volatile components in the substance is very small

* during the freeze-drying process, the growth of microorganisms and the role of enzymes cannot be carried out, so the original properties can be maintained

* since the drying is carried out in the frozen state, the volume is almost unchanged, the original structure is maintained, and the concentration phenomenon will not occur

* since the water in the material exists in the form of ice crystals after pre freezing, the dissolved inorganic salts previously dissolved in the water are evenly distributed in the material. During sublimation, the dissolved substances dissolved in water will precipitate, avoiding the surface hardening phenomenon caused by the precipitation of inorganic salts carried by the internal water migration to the surface in the general drying method

* the dried material is loose, porous and spongy. After adding water, it dissolves rapidly and completely, almost immediately restoring its original properties

* as the drying is carried out under vacuum, there is very little oxygen, so some easily oxidized substances are protected

* drying can remove more than 95% - 99% moisture, so that the dried products can be stored for a long time without deterioration

* since the materials are frozen and the temperature is very low, the requirements for the temperature of the heat source for heating are not high. The requirements can be met by using normal temperature or low temperature heaters. If the freezing chamber and the drying chamber are separated, the drying chamber does not need heat insulation, and there will not be a lot of heat loss, so the use of heat energy can be economically formed by external heating hot runner

just as there is no perfect technology, the main disadvantage of vacuum freeze-drying technology is the high cost. Because it needs vacuum and low temperature conditions, the vacuum freeze dryer needs to be equipped with a set of vacuum system and several positive signal low temperature systems have appeared in the economic operation of China's extruder industry, so the investment and operation costs are relatively high. Therefore, if you need to get products quickly, it is recommended to use low-temperature spray dryer

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