PSA full name: Pressure Swing Adsorption (PSA).PSA is a new gas separation technology, which has been developed rapidly in foreign countries since the late 1960s and early 1970s. Its principle is to separate the gas mixture by the difference of the "adsorption" performance of different gas molecules by molecular sieve. It takes air as raw material.The nitrogen and oxygen in the air are separated by the selective adsorption of nitrogen and oxygen with a high efficiency and high selection of solid adsorbent.

At present, carbon molecular sieves and zeolite molecular sieves are used more in the field of nitrogen and oxygen production.The separation of oxygen and nitrogen by molecular sieve is mainly based on the different diffusion rates of the two gases on the surface of molecular sieve. Carbon molecular sieve is a carbon-based adsorbent with some characteristics of activated carbon and molecular sieve.Carbon molecular sieves are composed of very small micropores with pore sizes ranging from 0.3nm to 1nm.The smaller diameter of the gas (oxygen) diffuses faster and more into the solid phase of the molecular sieve, so that nitrogen enrichment can be obtained in the gas phase.After a period of time, molecular sieve on oxygen adsorption balance, according to the carbon molecular sieve under different pressure on the adsorption of different gas adsorption characteristics, reduce the pressure to remove the carbon molecular sieve on oxygen adsorption, this process is called regeneration.PSA usually uses two towers in parallel, alternately pressurized adsorption and decompression regeneration to obtain a continuous flow of nitrogen.

With air as raw material, with carbon molecular sieve as adsorbent, the use of pressure change adsorption principle, the use of carbon molecular sieve on oxygen and nitrogen selective adsorption and separation of nitrogen and oxygen method, commonly known as PSA nitrogen.This method is a new technology of nitrogen production which developed rapidly in 1970s.Compared with the traditional method of nitrogen, it has simple process, high degree of automation, produce gas quickly (15 ~ 30 minutes), low energy consumption, product purity can be adjusted according to user needs in a wide range, convenient operation and maintenance, low operating cost, good adaptability device etc., in 1000 nm3 / h the following competitive in nitrogen making equipment,PSA is more and more popular among medium and small nitrogen users, and has become the choice method for medium and small nitrogen users.

Process flow and equipment introduction of PSA nitrogen making machine

1. Brief introduction to the technological process

Air through the air filter to remove dust and mechanical impurities into the air compressor, compressed to the required pressure, after strict oil removal, water removal, dust removal and purification treatment, the output of clean compressed air, the purpose is to ensure the service life of the molecular sieve adsorption tower.There are two adsorption towers with carbon molecular sieve.
One tower is operated while the other tower is decompressed and desorbed.Clean air into the working adsorption tower, through the molecular sieve oxygen, carbon dioxide and water are absorbed by it, flow to the outlet end of the gas is nitrogen and trace argon and oxygen.Another tower (desorption tower) allows adsorbed oxygen, carbon dioxide and water to escape from the pores of the molecular sieve and discharge into the atmosphere.In this way, the two towers take turns to complete nitrogen and oxygen separation and continuously output nitrogen, as shown in Fig. 2.The purity of nitrogen produced by pressure change  adsorption is 95%-99.9%. If higher purity nitrogen is needed, nitrogen purification equipment should be added.Psa nitrogen making machine output 95% 99.9% of the nitrogen into the nitrogen purification equipment, at the same time through the flowmeter to add just the right amount of hydrogen gas, hydrogen and nitrogen in the purification equipment of deoxidization tower of trace oxygen in catalytic reaction, and then by water to remove oxygen condenser cooling, in addition to water, water separator, and then through the depth of the dryer drying (two adsorption drying tower used interchangeably:One is adsorbed and dried for water removal, the other is heated for desorption and drainage) to obtain high purity nitrogen. At this time, the purity of nitrogen can reach 99.9995%. At present, the maximum production capacity of nitrogen production by pressure swapping adsorption in China is 3000M3N /h.