In the air separation unit of molecular sieve adsorption purification process, after the air is compressed at the last stage of the air compressor, the temperature out of the air compressor reaches 80-90 ℃. Since the adsorption capacity of molecular sieve is inversely proportional to the temperature, in order to improve the working efficiency of molecular sieve adsorber and ensure the purification effect, the compressed air from the air compressor must be cooled to reduce the temperature of the compressed air before entering the purification system.
The pre cooling system is composed of water chiller, water cooling column, air cooling column, cooling chilled water pump, water filter, etc. the pre cooling system must have enough cold source to cool the air. The heat exchange device is used to realize the heat exchange between the air and the cold source. The water separator separates the water when the temperature drops, so as to ensure that the dry air enters the purification system.
1.In the air cooling column, the cooling water and compressed air exchange heat through direct contact between gas and liquid. There are two sources of cooling water, onepartis the normal temperature water of the water cooling column, which is cooled by sewage nitrogen, after the temperature is reduced, the water is supplied to the air cooling column by water pump, and the other one part is the chilled water provided by the chiller.
2.After the air is cooled to 40 ℃ by the end cooler of the compressor, the air enters the evaporator of the refrigerator. The air is directly cooled by the evaporation heat absorption of the refrigerator without indirect cooling by chilled water.
3.The manufacturers with surplus crudenitrogen can make full use of the heat absorption potential of the crudenitrogen discharged from the cooling box, absorb the latent heat of evaporation of water in the water cooling column, reduce the temperature of the cooling water, and then enter the air cooling column to cool the air.
4.When the pressure swing adsorption regeneration purification system is used, the air temperature is required to be less than 40 ℃. At this time, the design margin of the aftercooler can be larger, and then the air can be directly cooled to 37 ℃ by the aftercooler.