Desiccant Related Concepts And Principles

- Jan 16, 2017-

First, the concept

Adsorbent: It is commonly known as desiccant raw material and is the main component of desiccant. It absorbs water molecules in the air through its physical or chemical adsorption.

Packing material: For the bag desiccant, the material that acts as a bag for wrapping the raw materials needs to have certain gas permeability and dustproof performance, and in some cases, it needs to have certain waterproof property.

Silica gel: common adsorbent, transparent or translucent spherical, high mechanical strength, less dust, safe and non-toxic, but not degradable, the production process will pollute the environment. In recent years, developed countries are gradually restricting or prohibiting use.

Montmorillonite: also known as clay and bentonite, it is a natural mineral. As a desiccant, montmorillonite is irregular granules with various colors, safe and environmentally friendly. It is a new type of desiccant.

Relative Humidity: The percentage of the actual water vapor density in the air and the saturated water vapor density at the same temperature is called the "relative humidity" of the air. The degree of dryness and humidity of the air is related to the degree of saturation of the water vapor contained in the air, and is not directly related to the absolute amount of water vapor contained in the air. The sign of relative humidity is RH.

Moisture absorption rate: The ratio of the weight of the desiccant absorbed by water vapor to its own weight at a certain temperature and relative humidity, expressed as a percentage.

Water vapor transmission rate: The ability of a package of material per unit area to pass water vapor over a certain period of time, usually expressed in grams per square meter per day, ie g/m2/d.

UNIT: “unit”, when at (23 ± 2) ° C and 40% relative humidity in the air, the absorption of water vapor can reach at least 6.0g of the specified amount of desiccant as a "one unit" desiccant. The number of desiccant units is the total amount of desiccant bag moisture absorption capacity.

Second, the principle

Principle of silica gel absorption: The main component of silica gel is silica. The processed silica gel has a unique microporous structure with an average pore diameter of up to 24A. Its structure is very similar to a sponge. It consists of interconnected pores. The capillary adsorption system of surface area has good affinity for water molecules. Its microporous structure can adsorb and retain water vapor. It can absorb moisture even when the temperature is higher than 105 °C, but when the temperature is higher than 38 °C, its The moisture absorption rate begins to decrease, and its optimum moisture absorption state is between 21 ° C and 32 ° C. Even when the relative humidity is 60% to 90% higher, the relative humidity in the container can be maintained at 40%.

The principle of montmorillonite absorption: montmorillonite is a mineral composed of extremely fine aqueous aluminosilicate, which is a monoclinic aqueous layered silicate mineral. The montmorillonite particles are fine, about 0.2 to 1 micron, and have colloidal dispersion characteristics. Under the electron microscope, flaky crystals, color or white ash, or light blue or light red are visible. When the temperature reaches 100-200 ° C, the water molecules in the montmorillonite will gradually run away. The montmorillonite after water loss has a strong adsorption force on water molecules.