真空干燥機(jī)與傳統(tǒng)干燥機(jī)的區(qū)別在哪里呢？

傳統(tǒng)干燥泛指從濕物料中除去水分或其他濕分的各種操作。如在日常生活中將潮濕物  料置于陽(yáng)光下曝曬以除去水分，工業(yè)上用硅膠、石灰、濃硫酸等除去水蒸氣、工業(yè)氣體或  有機(jī)液體中的水分。在化工生產(chǎn)中，干燥通常指用熱空氣、煙道氣以及紅外線等加熱濕固  體物料，使其中所含的水分或溶劑汽化而除去，是一種屬于熱質(zhì)傳遞過程的單元操作。

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.

傳統(tǒng)干燥，在被干燥物料表面形成流體邊界層，受熱汽化的水蒸氣通過流體邊界層向  空氣中擴(kuò)散，干燥物內(nèi)部水分要向表面移動(dòng)。如果其移動(dòng)速度趕不上邊界層表面的蒸發(fā)速  度，邊界層水膜就會(huì)破裂，被干燥物料表面就會(huì)出現(xiàn)局部干裂現(xiàn)象，然后擴(kuò)大到整個(gè)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.

而真空干燥機(jī)在真空環(huán)境下，水分的沸點(diǎn)降低了，可以實(shí)現(xiàn)低溫干燥，為熱敏性物料  的干燥提供了有利條件；氧分壓降低了，避免了物料在干燥過程中的氧化變質(zhì)現(xiàn)象，保障  了被干燥物料的質(zhì)量，在缺氧狀態(tài)下殺死了一些細(xì)菌，抑制了一些細(xì)菌的繁殖生長(zhǎng)；真空  干燥過程可以回收一些有毒有害的氣體，防止了環(huán)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.

傳統(tǒng)干燥使被干燥物料內(nèi)部和表面形成很大的溫度梯度，促使被干燥物料中某些成分  散發(fā)出去。尤其是食品，會(huì)散失香氣，影響其味道。

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.

而真空干燥時(shí)物料內(nèi)外溫度梯度小，由逆滲透作用使得作為溶劑的水獨(dú)自移動(dòng)，克服  了溶質(zhì)散失現(xiàn)象。真空干燥也容易實(shí)現(xiàn)產(chǎn)品多樣化。以食品干燥為例，可以通過控制溫度  和真空度，使產(chǎn)品發(fā)泡，膨化，生產(chǎn)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.

真空干燥物料內(nèi)和表面之間壓力差較大，在壓力梯度作用下，水分很快移向表面，不會(huì)出現(xiàn)表面硬化。同時(shí)能提高干燥速率，縮短干燥時(shí)間，降低真空干燥機(jī)運(yùn)轉(zhuǎn)費(fèi)用。

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.