When the air is out of the air compressor, due to the compression, the moisture in the air is in the saturated state. After the water cooling column decreasing the temperature, the water content in the saturated state decreases, and the excess water condenses into the water. The water volume in the air cooling column increases and the water temperature rises. But not only is the temperature of the air reduced, but also the moisture content of the air. In the water cooling column, the crude nitrogen is used to cool the water. After passing through the main heat exchanger from the fractionator, the temperature of the crude nitrogen is close to the normal temperature, but it is very dry. The dry crude nitrogen contacts with the water, and a large amount of water is evaporated into the crude nitrogen by using the unsaturation of the crude nitrogen, which absorbs the heat of the water and reduces the water temperature.
