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一、工作原理及应用范围介绍Introduction of Working Principle and Scope of Application

真空冷冻干燥（也称“冻干”）是先将湿物料冻结到冰点以下，使水分变成固态的冰，然后在较高的真空度下使冰直接升华为水蒸汽，再用真空系统中的水汽凝结器将抽出的水蒸汽冷凝，从而达到将需干燥物料中的水分脱除获得干品的工艺过程。冻干技术现广泛运用于医药工业（如血 清、血浆、疫苗、酶、抗 生素）食品工业（如草莓、整虾、鸡丁、蘑菇片、蔬菜等）生物体的存活保存等。

The vacuum freeze drying (also called “freeze-drying”) refers to the process firstly freezing the wet materials to below the freezing point and the water into solid ice, then directly sublimating the ice into water vapor at higher vacuum degree, condensing the pumped water vapor by the vaporcondenser in the vacuum system, and finally obtaining the dry materials with water removed. Now, the freeze-drying technology is widely applied in the survival storage of living bodies in the medical industry (such as serum, plasma, vaccine, enzyme and antibiotic) and food industry (such as strawberry, shrimp, diced chicken, sliced mushroom and vegetable).

二、特点Characteristics

1. 干燥是在水的三相点压力以下进行的，物料处于高度缺氧状态；干燥又是在低温下进行，物料不会过热。因此，这种方式特别适于极为热敏和极易氧化的物料的干燥。例如，用于干燥食品，可以保留新鲜食品的色、味、香和等营养物质。

2.   由于物料在升华脱水以前先经冻结，形成稳定的固体骨架，所以水分升华汽化后，固体骨架基本保持不变，干制品不失原有的固体结构，保持着原有的形状。多孔结构的制品具有很理想的速溶性和快速复水性。

3.   由于物料中水分在预冻以后以冰晶的形式存在，原来溶于水中的无机盐类溶解物质被均匀地分配在物料之中。升华时，溶于水中的溶解物质就析出，避免了一般干燥方法中因物料内部水分向表面迁移所携带的无机盐在表面析出而造成表面硬化的现象。

4.   因物料处于冻结状态，温度很低，所以供热的热源温度要求不高，采用常温或温度不高的加热器即可满足要求。如果冷冻室和干燥室分开时，干燥室不需绝热，不会有很多的热损失，故热能的利用很经济。

1.The drying is carried out below triple point pressure of water, and the materials are under high anaerobic condition; in addition, the drying is carried out at low temperature, so there is no overheat of materials. Therefore, this mode is especially applicable to drying of material very sensitive to heat and easy to oxidize. For example, for the food dried by using this technology, its color, taste, smell, vitamin C and other nutrient substances of fresh food will be reserved.

2.As the materials are frozen before sublimating and dehydration with stable solid frame formed, the solid frame will keep unchanged basically after the water is vaporized, so the solid structure and original appearance of dry materials will not be changed. The finished products with porous structure have ideal instant solubility and fast reconstitution property.

3.As the water in the materials exists in the ice crystal form after pre-freezing, the inorganic salt substances dissolvedin water will be distributed in the material uniformly. During the sublimation, thesubstances dissolved in water will be precipitated, avoiding the surface hardening due to surface precipitation of inorganic salt carrying by water of material while moving to the surface.

4.The materials are in frozen state with very low temperature, the heat source temperature for heat supply may be normal temperature, or the heater with low temperature can meet the requirement. If the freezing chamber and drying chamber are separated, it is not required to insulate the drying chamber, and little heat loss may be caused, so it is very economical to recycle the heat energy.

三、工艺流程图Process flow diagram

四、技术参数（下表中数值仅供选型时参考）

Technical parameters (the values in the table below are for reference in type selection only)