As a pretreatment process for compressed air in ambient temperature air separation equipment, it is not only necessary to filter out mechanical impurities, but also to remove the moisture contained in the compressed air.

The most common compression equipment used to provide raw compressed air sources for ambient temperature air separation units is the oil injected screw compressor. Some users may use oil-free screw compressors, or large units may use centrifugal air compressors as a supporting equipment. Regardless of the type of compression machinery, when compressed air is cooled after being compressed, the water content in the compressed air tends to be saturated (except during particularly dry and cold seasons in northern regions). If the compressed air is cooled to 40 ℃ and is in a state of water saturation, the absolute water content in the compressed air will reach 50.9g/m ³, which refers to the water content per cubic meter of compressed air. With such a high water content, for a pressure swing adsorption system, a large amount of water enters the molecular sieve, which will preferentially adsorb water and not play a role in air separation. It will also greatly reduce the strength of the molecular sieve, causing it to pulverize and ultimately leading to system failure; For membrane separation systems, the entry of saturated compressed air containing water into the membrane fibers can also cause membrane system failure. Especially when the compressed air comes from an oil injected screw compressor, moisture can carry oil into the system, causing poisoning of the molecular sieve or unexpected damage to the membrane fibers. Therefore, in ambient temperature air separation equipment, regardless of the process method used, a drying step needs to be set up. For pressure swing adsorption nitrogen production equipment, it is usually necessary to reduce the pressure dew point of compressed air to below 8 ℃, at which point the water content in the compressed air is equivalent to less than 8g/m ³; For membrane systems, it is recommended to reduce the relative humidity of compressed air to below 60%, which is crucial for ensuring the long-term stable operation of the device.