Q Q: 506615608
传统干燥泛指从湿物料中除去水分或其他湿分的各种操作。如在日常生活中将潮湿物 料置于阳光下曝晒以除去水分，工业上用硅胶、石灰、浓硫酸等除去水蒸气、工业气体或 有机液体中的水分。在化工生产中，干燥通常指用热空气、烟道气以及红外线等加热湿固 体物料，使其中所含的水分或溶剂汽化而除去，是一种属于热质传递过程的单元操作。
Traditional drying generally refers to various operations to remove moisture or other moisture from wet materials. For example, in daily life, wet materials are exposed to the sun to remove moisture. In industry, silica gel, lime and concentrated sulfuric acid are used to remove water in steam, industrial gas or organic liquid. In chemical production, drying usually refers to heating wet solid materials with hot air, flue gas and infrared ray to vaporize and remove the moisture or solvent contained therein. It is a unit operation of heat and mass transfer process.
传统干燥，在被干燥物料表面形成流体边界层，受热汽化的水蒸气通过流体边界层向 空气中扩散，干燥物内部水分要向表面移动。如果其移动速度赶不上边界层表面的蒸发速 度，边界层水膜就会破裂，被干燥物料表面就会出现局部干裂现象，然后扩大到整个外表 面，形成表面硬化。
In traditional drying, a fluid boundary layer is formed on the surface of the material to be dried. The water vapor vaporized by heating diffuses into the air through the fluid boundary layer, and the moisture in the dried material moves to the surface. If its moving speed can't catch up with the evaporation speed of the boundary layer surface, the water film in the boundary layer will break, and the dry material surface will appear local dry cracking phenomenon, and then expand to the whole outer surface to form surface hardening.
而真空干燥机在真空环境下，水分的沸点降低了，可以实现低温干燥，为热敏性物料 的干燥提供了有利条件；氧分压降低了，避免了物料在干燥过程中的氧化变质现象，保障 了被干燥物料的质量，在缺氧状态下杀死了一些细菌，抑制了一些细菌的繁殖生长；真空 干燥过程可以回收一些有毒有害的气体，防止了环境的污染。
In the vacuum environment, the boiling point of water is reduced, which can realize low-temperature drying, which provides favorable conditions for the drying of heat-sensitive materials; the oxygen partial pressure is reduced, which avoids the oxidation and deterioration of materials in the drying process, ensures the quality of the materials to be dried, kills some bacteria in the anoxic state, and inhibits the growth of some bacteria Some poisonous and harmful gases can be recovered in the drying process to prevent environmental pollution.
The traditional drying makes the internal and surface of the dried materials form a large temperature gradient, which makes some components in the dried materials emit. In particular, food will lose its aroma and affect its taste.
而真空干燥时物料内外温度梯度小，由逆渗透作用使得作为溶剂的水独自移动，克服 了溶质散失现象。真空干燥也容易实现产品多样化。以食品干燥为例，可以通过控制温度 和真空度，使产品发泡，膨化，生产出酥脆、速溶等食品。
In vacuum drying, the temperature gradient inside and outside the material is small, and the reverse osmosis makes the water as the solvent move alone, which overcomes the phenomenon of solute loss. Vacuum drying is also easy to achieve product diversification. Taking food drying as an example, the product can be foamed and expanded by controlling temperature and vacuum degree to produce crisp and instant food.
There is a big pressure difference between the inner surface and the surface of vacuum dried materials. Under the effect of pressure gradient, the moisture will move to the surface quickly, and the surface hardening will not occur. At the same time, it can improve the drying rate, shorten the drying time and reduce the operating cost of the vacuum dryer.