一、工作原理及應(yīng)用范圍介紹Introduction of Working Principle and Scope of Application

真空冷凍干燥（也稱“凍干"）是先將濕物料凍結(jié)到冰點(diǎn)以下，使水分變成固態(tài)的冰，然后在較高的真空度下使冰直接升華為水蒸汽，再用真空系統(tǒng)中的水汽凝結(jié)器將抽出的水蒸汽冷凝，從而達(dá)到將需干燥物料中的水分脫除獲得干品的工藝過程。凍干技術(shù)現(xiàn)廣泛運(yùn)用于醫(yī)藥工業(yè)（如血 清、血漿、疫苗、酶、抗 生素）食品工業(yè)（如草莓、整蝦、雞丁、蘑菇片、蔬菜等）生物體的存活保存等。

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、特點(diǎn)Characteristics

1. 干燥是在水的三相點(diǎn)壓力以下進(jìn)行的，物料處于高度缺氧狀態(tài)；干燥又是在低溫下進(jìn)行，物料不會過熱。因此，這種方式特別適于極為熱敏和極易氧化的物料的干燥。例如，用于干燥食品，可以保留新鮮食品的色、味、香和等營養(yǎng)物質(zhì)。

2.   由于物料在升華脫水以前先經(jīng)凍結(jié)，形成穩(wěn)定的固體骨架，所以水分升華汽化后，固體骨架基本保持不變，干制品不失原有的固體結(jié)構(gòu)，保持著原有的形狀。多孔結(jié)構(gòu)的制品具有很理想的速溶性和快速復(fù)水性。

3.   由于物料中水分在預(yù)凍以后以冰晶的形式存在，原來溶于水中的無機(jī)鹽類溶解物質(zhì)被均勻地分配在物料之中。升華時，溶于水中的溶解物質(zhì)就析出，避免了一般干燥方法中因物料內(nèi)部水分向表面遷移所攜帶的無機(jī)鹽在表面析出而造成表面硬化的現(xiàn)象。

4.   因物料處于凍結(jié)狀態(tài)，溫度很低，所以供熱的熱源溫度要求不高，采用常溫或溫度不高的加熱器即可滿足要求。如果冷凍室和干燥室分開時，干燥室不需絕熱，不會有很多的熱損失，故熱能的利用很經(jīng)濟(jì)。

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、工藝流程圖Process flow diagram

四、技術(shù)參數(shù)（下表中數(shù)值僅供選型時參考）

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