Desiccant is also called absorbent. It is used to prevent moisture and mildew and play a drying role. Desiccant is a kind of water removing agent that absorbs moisture from the atmosphere. Its drying principle is to physically adsorb water molecules in its own structure or chemically absorb water molecules and change their chemical structure to become another substance. )
The desiccants that use adsorption to remove water vapor include silica gel, alumina gel, molecular sieves, activated carbon, bone charcoal, charcoal or activated clay, etc.
Commonly used desiccants to remove water vapor by chemical absorption include calcium chloride, quicklime or phosphorus pentoxide, which have a high chemical affinity with water vapor.
There are currently five typical desiccant products in the desiccant industry:
1) Silica gel desiccant-the main component is silica, which is purified and processed from natural minerals into granules or beads. As a desiccant, its microporous structure (average 2A) has a good affinity for water molecules. The most suitable hygroscopic environment for silica gel is room temperature (20~32) and high humidity (60~90%). It can reduce the relative humidity of the environment to about 40%. Silica gel has a strong adsorption capacity and can produce a drying effect on human skin. Therefore, you should wear work clothes during operation. If silica gel gets into the eyes, rinse with plenty of water and seek medical treatment as soon as possible.
2) Clay desiccant (montmorillonite)-the appearance is a small gray ball, which is most suitable for absorbing moisture in an environment below 50°C. When the temperature is higher than 50℃, the degree of "water release" of clay is greater than the degree of "water absorption". But the advantage of clay lies in its low price.
3) Molecular sieve desiccant-it is a synthetic desiccant product with strong adsorption to water molecules. The pore size of the molecular sieve can be controlled by the different processing technology. In addition to adsorbing water vapor, it can also adsorb other gases. In the case of high temperature above 230℃, it can still hold water molecules well. Advantages: strong adaptability. Disadvantages: low moisture absorption rate, poor environmental protection (non-degradable).
4) Mineral desiccant-it is composed of several kinds of natural minerals, and the appearance is off-white small balls. It is non-toxic and harmless, and is a degradable environmentally friendly desiccant. The moisture absorption rate is more than 50%, which is twice that of ordinary silica gel.
5) Fiber desiccant-is made of pure natural plant fiber through special craftsmanship. Among them, the film-coated fiber desiccant sheet is convenient and practical, and does not take up space. Its moisture absorption capacity reaches 100% of its own weight, which is unmatched by ordinary desiccants. In addition, the product is safe and hygienic, and the price is moderate. It is an ideal choice for many biological, health food and medicines.
Quicklime desiccant
The main component of quicklime desiccant is calcium oxide, and its water absorption capacity is achieved through chemical reactions, so water absorption is irreversible. Regardless of the humidity of the external environment, it can maintain a moisture absorption capacity greater than 35% of its own weight, and is more suitable for low-temperature storage. It has an excellent drying and moisture absorption effect and is low in price. It can be widely used in food, clothing, tea, leather, shoemaking, electrical appliances and other industries.
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