Principle and application of modular dryer？

Compressed air is used in various aspects of the industrial field as an important production power. In the production process of compressed air, moisture in the air will enter the compressed air system along with the compressed air. Moisture in the compressed air will cause corrosion of the compressed air pipeline and the reproduction of microorganisms; if the moisture is not removed, the condensate formed will accumulate at the low point of the system, which will pose a potential threat to industrial production, such as failure of air control components, increased equipment wear, or directly leading to the top of the production process.

Traditional refrigeration dryers and adsorption dryers have long been well-known products. Most of these dryers are installed in air compressor stations, and after the compressor, they dry the compressed air of the entire system. We know that each different user has different requirements for the dryness of compressed air at the compressed air use point. There will also be different dryness requirements in the compressed air system of the same user. Therefore, the compressed air drying method is to dry only the actually required part according to the required dryness. Whether it is test air, production workshop, or field air, whether it is mobile air or fixed air, compressed air users have higher requirements for the immediacy and reliability of compressed air drying. It is based on the need to dry compressed air at the point of use that the membrane-type compressed air dryer was born. The membrane dryer was originally a solution for small gas usage points, and later evolved into various suitable application fields. 2. Molecular membrane characteristics Polymer membrane materials have the characteristics of water molecule penetration and diffusion. As shown in Figure 1, if there is a gas partial pressure (different concentrations) at both ends of the molecular membrane, the gas molecules will diffuse through the membrane from the side with a larger partial pressure to the side with a smaller partial pressure. The diffusion rate of gas molecules through the polymer membrane depends on three aspects: a. The structure of the membrane material through which the diffusion needs to pass; b. The size of the gas molecules c. The evaporation temperature of the gas Through continuous laboratory experiments, scientists have found that there is a synthetic polymer membrane. At room temperature, as shown in Figure 2, the diffusion rate of water vapor molecules through the polymer membrane is 20,000 times faster than that of oxygen molecules. This synthetic molecular membrane is an ideal material for separating water molecules from other gas molecules. This characteristic makes this synthetic polymer membrane the basic material for manufacturing membrane dryers. 3. Structure of polymer membrane

At the beginning of the use of polymer membranes, because only the basic material of the membrane was used, the selectivity of the molecular membrane to gas was relatively low. As shown in Figure 3, this means that gases with a lower diffusion rate can also pass through the membrane matrix material, including nitrogen, especially oxygen (penetration can reach 5%). In other words, low-selectivity permeable membranes will form a large amount of leakage and change the composition ratio structure of various gases in the air composition, which is not suitable for use in breathing air.

At the same time, gas molecules directly pass through the membrane wall, which will cause the dirt in the compressed air to accumulate on the membrane surface, affecting the service life of the membrane. The permeation of other gases on the membrane surface is used as backwash gas, so the backwash gas volume is constant based on pressure. The backwash gas volume cannot be adjusted, and the flexibility is low. Therefore, it cannot be adapted to large flow applications, and the backwash gas volume loss is also large.

With the advancement of technology, laboratories are working hard to solve the problems of low-selectivity permeable membranes. A few years later, high-selectivity permeable membranes with different technologies were manufactured. Taking the high selective permeability membrane of BEKO as an example, a layer of coating is adhered to the inner side of the high selective permeability membrane, as shown in Figure 4, which basically achieves the ideal effect that only water molecules can penetrate the permeable membrane.

Since the low selective permeability membrane is low in cost and simple to manufacture, there are a large number of low selective permeability membrane dryers on the market. The method to distinguish low selective permeability membrane dryers is to close the dryer outlet and measure whether there is still compressed air consumption. If there is still compressed air consumption, the low selective permeability membrane is used. If there is no compressed air consumption, the high selective perm