With the rapid development of national economy, cryogenic air separation plant has been widely used in petrochemical, glass, tire, polysilicon, carbon fiber and other industrial fields. The nitrogen production process consists of air compression and purification, air separation and liquid nitrogen vaporization.
1.Air compression and purification: after the dust and mechanical impurities are removed by the filter, the air enters into the air compressor, compressed to the required pressure, and then sent to the air cooling columnto reduce the air temperature. Then it enters the molecular sieve adsorption device 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 fractionator and is cooled to the saturation temperature by the reflux gas (product nitrogen, waste gas), and then sent to the bottom of the distillation column, where nitrogen is obtained at the top of the column. After throttling, the liquid air is sent to the condensing evaporator for evaporation. At the same time, part of the nitrogen from the fractionator is condensed. Part of the condensed liquid nitrogen is used as the reflux of the distillation column, and the other is the reflux of the distillation columnPart of the product is used as liquid nitrogen product from the fractionator.
The waste gas from the condensing evaporator is reheated by the main heat exchanger to about 130K, and then it is sent to the expander for expansion refrigeration to provide cooling capacity for the fractionator. Part of the expanded gas is used for regeneration and purging of molecular sieve, and then discharged into the atmosphere through the muffler.
3.Vaporization of liquid nitrogen: the liquid nitrogen from the fractionating columnis stored in the liquid nitrogen storage tank. When the air separation plantis overhauled, the liquid nitrogen in the storage tank enters the vaporizer to be heated and then sent to the product nitrogen pipeline.
