Typical process flow of cryogenic nitrogen production:
The whole process consists of air compression and purification, air separation and liquid nitrogen vaporization.
1. Air compression and purification
The air is removed by the air filter after dust and mechanical impurities into the air compressor, compressed to the required pressure, and then into the air cooler to reduce the air temperature. Then enter the air drying purifier to remove water, carbon dioxide, acetylene and other hydrocarbons in the air.
2. Air separation
The purified air enters the main heat exchanger in the air separation tower, is cooled to the saturation temperature by the reflux gas (product nitrogen, waste gas), is sent to the bottom of the rectification tower, and nitrogen is obtained at the top of the tower. The liquid air is throttled and sent to the condensing evaporator to evaporate. At the same time, part of the condensed nitrogen sent by the rectification tower is used as the reflux liquid of the rectification tower. The other part comes out of the air separation tower as liquid nitrogen product.
The exhaust gas from the condensing evaporator is reheated to about 130K by the main heat exchanger into the expansion machine expansion refrigeration to provide cold capacity for the air separation tower, and part of the expanded gas is used as regeneration and blowing cold of the molecular sieve, and then discharged into the atmosphere by the silencer.
3. Liquid nitrogen vaporization
The liquid nitrogen from the air separation tower is stored in the liquid nitrogen storage tank. When the air separation equipment is repaired, the liquid nitrogen in the storage tank is heated into the carburetor and sent into the product nitrogen pipeline.
Cryogenic nitrogen can produce nitrogen with purity of ≧99.999%.