There are many kinds of industrial desiccants such as silica gel, montmorillonite, molecular sieve and calcium chloride. More commonly used are white silica gel and color-changing silica gel and montmorillonite desiccant.

Main performance indexes of silica gel desiccant

A, moisture absorption capacity. The most important index to characterize the performance of silica gel desiccant. A-type silica gel desiccant has the requirement of moisture absorption ability under high humidity and low humidity, and generally the higher the better.

B, moisture content once (or thermal weightlessness). An important index to characterize the service state of silica gel desiccant refers to the amount of water (expressed by mass percentage) contained in the desiccant when it is dried at a certain temperature. Too high moisture content means that silica gel has absorbed moisture, and its moisture absorption ability is bound to be low; When the moisture content is too low, the drying cost is too high. The temperature of silica gel to remove adsorbed water is about 150℃.

C, the PH value of the aqueous solution ⑻, specific resistance ⑼. An important index to characterize the impurity content and quality stability of silica gel desiccant. The PH value of ordinary silica gel is between 4 and 8, and it is economical to control it at about 5; The indicator indicating silica gel needs to be stable in a strong acidic environment, so the PH value will be relatively low, around 2.5. The specific resistance of silica gel is generally in the range of thousands to tens of thousands of ω. cm。

D, specifications and particle size pass rate. Silica gel with different specifications (particle size range ⑾, shape) is used for different packaging needs (different packaging sizes, different packaging materials, different moisture absorption speed requirements, etc.); The number of particles that meet the specification requirements in raw materials is called particle size qualification rate (expressed as mass percentage).

E, bulk density. Represents the volume occupied by a certain amount of desiccant, in g/m3. Also known as bulk density and packing density. Bulk density plays an important role in the formulation of desiccant packaging specifications and the calculation of fixed volume desiccant dosage. The bulk density of type a silica gel is about 740 ~ 800 g/l.

Characteristics and application

A-type porous silica gel desiccant has stable chemical properties (it does not react with other substances except hydrofluoric acid and strong alkali), stable physical properties (high mechanical strength, good wear resistance and less impurities), no harm to human body (amorphous structure of silica gel makes it generally not cause stones and other diseases if it is not ingested in large quantities), good moisture absorption ability under high and low humidity, and relatively moderate price, so it is widely used in food, medicine, art, electronic products and so on. Discolored silica gel:

Color-changing silica gel is a commonly used functional silica gel desiccant product, also known as indicator silica gel, by adding a certain proportion of color-changing components (3~7%) to make silica gel change color after absorbing water, thus indicating the moisture absorption state of silica gel.

Because the color-changing silica gel contains a certain amount of indicator, part of the pores will be occupied, so the moisture absorption performance will be reduced to some extent, with a reduction range of about 2~4%.

Color-changing silica gel is also divided into several categories.

Name Blue Glue Indicator, Color Change

Color-changing silica gel) (low humidity-high humidity) blue-purple-light purplish red

(Light blue-purplish red-light red) Indicator main components: Cobalt chloride process is the most mature, the lowest cost, characteristics and application: it is generally required to be used in occasions.

Orange glue (silica gel with orange turning green,

Cobalt-free color-changing silica gel) orange-yellow-green-dark green

(Light orange-light yellow green-green) Indicator main component: ammonium ferrous sulfate.

Characteristics and application of copper chloride: cobalt-free, relatively safe, replacing blue glue.

Orange glue (orange white silica gel,

New cobalt-free color-changing silica gel) Orange-light orange-colorless indicator Main component: ammonium ferric sulfate.

Characteristics and application of ammonium ferrous sulfate: it does not contain harmful metal elements such as cobalt and copper.

European and American countries are widely used.

Main performance indexes of montmorillonite desiccant

A, moisture absorption capacity. The moisture absorption performance of high-quality montmorillonite desiccant is close to that of silica gel desiccant, and even better than silica gel desiccant at low humidity.

B, moisture content (or thermal weight loss). The temperature of montmorillonite to remove adsorbed water is slightly higher, about 180℃.

C. PH and conductivity of the aqueous solution. The PH of montmorillonite is weakly alkaline, generally between 7 and 8, which is closer to neutrality than silica gel. Similar to silica gel, the conductivity of montmorillonite indicates the impurity content of montmorillonite, and the conductivity is generally several ms/m.

D, specifications and particle size pass rate. Montmorillonite desiccant is made of bentonite ore by crushing and sieving, so it is generally irregular block. Wesson's montmorillonite mainly has two specifications: 0.5~2mm and 1~4mm. Compared with silica gel, the mechanical strength of montmorillonite is lower, and irregular particles are more likely to produce dust. There are two ways to solve this problem: First, packaging with better and denser packaging materials, but the denser the packaging materials, the worse their air permeability, which will affect the moisture absorption speed of products; The second is to make spherical particles by using the cohesiveness of montmorillonite itself, but the spherical montmorillonite will reduce its moisture absorption capacity because it limits the expansion space of montmorillonite. There are mainly two kinds of spherical montmorillonite, 1~2mm and 2 ~ 4 mm. It is necessary to use montmorillonite with appropriate specifications as raw materials according to different requirements.

E, packing density. The bulk density of montmorillonite is relatively high, ranging from 900 to 1000g/L, and the bulk density of spherical montmorillonite is higher, reaching more than 1000 g/L..

Characteristics and application

As a desiccant, montmorillonite does not need to add any other substances in the process of raw material mining and processing, and it will not corrode metals and other products. It is a safe and environmentally friendly desiccant raw material. Because its hygroscopicity is close to that of silica gel and its cost is relatively low, it is gradually replacing silica gel in many drying fields, especially in the packaging and transportation of large and medium-sized machinery, glass products, metal parts and other products, montmorillonite desiccant has occupied an absolute dominant position.

The general industrial desiccant mainly depends on what products you use, and these are the hopes that will play a role for you.