Excessive air humidity can cause discomfort to people and induce diseases; it also affects the preservation of materials and certain technological processes, as well as instruments and meters that require low humidity conditions, such as underground engineering, weapon warehouses, tunnels, and precision In occasions such as instrument operation, high-humidity environment will cause the accuracy of precision electronic devices to decrease, seriously affect the use of ammunition and other problems, and even cause major accidents and cause losses to the national economy. Therefore, people must take effective measures to ensure that the air humidity meets the requirements. At present, the commonly used air dehumidification methods include cooling dehumidification, solid adsorbent dehumidification, and rotary dehumidification. Although these traditional dehumidification methods are widely used, they still have disadvantages such as low dehumidification efficiency, complex equipment, and secondary pollution. Membrane dehumidification technology is a new type of dehumidification technology developed in recent decades. It has entered the field of air purification scientific research and industrial applications, and has become a research frontier and application hot spot. Advantages of membrane dehumidification: continuous dehumidification process, no pollution problems, high dehumidification efficiency, simple equipment and easy maintenance, etc. It can be divided into hydrophilic membrane dehumidification and hydrophobic membrane dehumidification according to the dehumidification mechanism. This article will introduce the domestic and foreign research progress of membrane dehumidification technology for air dehumidification from these two aspects.
Working principle of hydrophilic membrane dehumidification technology
Hydrophilic membrane dehumidification technology is mainly based on the dissolution-diffusion mechanism. For a specific membrane material, the permeation rate of water vapor in it is relatively large, and its permeability coefficient is at least two orders of magnitude higher than that of nitrogen, oxygen and other trace gases in the air. When the humidified air flows through the hollow fiber membrane (intake on the left side), it is absorbed by the membrane surface, which creates a concentration gradient on both sides of the membrane. Water vapor diffuses in the very thin membrane wall to the other side of the membrane (permeate side). And a small part of the dry purge air is blown out of the membrane dryer, and the obtained dry air is discharged from the outlet of the hollow fiber membrane to complete the water vapor separation. During the whole process, the water vapor partial pressure difference that always exists inside and outside the membrane ensures that water molecules continue to diffuse outward, forming a continuous drying process, as shown in the figure below.