The chemical properties of nitrogen are not active, and it is very inert in its ordinary state, and it is not easy to react chemically with other substances. Therefore, nitrogen is widely used as a protective gas and sealing gas in the metallurgical industry, electronics industry and chemical industry, and the purity of the general protective gas is 99.99%, and some require 99.998% or more of high purity nitrogen. Liquid nitrogen is a convenient cold source and has been widely used in food industry, medical treatment and semen storage in animal husbandry. In the production of synthetic ammonia in the fertilizer industry, if the raw material gas of synthetic ammonia - hydrogen and nitrogen mixture is washed and refined with pure liquid nitrogen, the content of inert gas can be extremely small, and the content of sulfur monoxide and oxygen does not exceed 20ppm.

PSA is a new gas separation technology, since the late 1960s and early 1970s in foreign countries has been rapid development, its principle is the use of molecular sieve on different gas molecules "adsorption" performance differences and separate the gas mixture, it is based on air as raw material, Nitrogen and oxygen in the air are separated by the selective adsorption of nitrogen and oxygen by a high-efficiency and highly selective solid adsorbent.

Pure nitrogen cannot be extracted directly from nature and is mainly separated by air. Air separation methods include: cryogenic method, pressure swing adsorption (PSA) method, membrane separation method. Now nitrogen is the main industrial gas, has a great commercial, there are many nitrogen machine manufacturers are also producing this nitrogen, and as long as the production is also a professional nitrogen machine, although there are several nitrogen machine manufacturers in the country. Cryogenic nitrogen production because it is in use, the equipment is complex, and the field area is very large, so it is not the mainstream equipment, accordingly, molecular sieve air nitrogen production has a great maturity, especially it is very convenient to use, can achieve automated operation, and its field area is relatively small, the operating cost has been greatly reduced.

Process overview

At present, carbon molecular sieve and zeolite molecular sieve are used more in the field of nitrogen and oxygen generators. The separation of oxygen and nitrogen by molecular sieve is mainly based on the different diffusion rates of the two gases on the molecular sieve surface. 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 pores with pore sizes ranging from 0.3nm to 1nm. The smaller diameter gas (oxygen) diffuses faster and enters the molecular sieve solid phase more, so that nitrogen can be enriched in the gas phase. After a period of time, the adsorption of oxygen by the molecular sieve reaches equilibrium. According to the characteristics of the adsorption amount of adsorbed gas by the carbon molecular sieve under different pressures, the pressure is reduced to remove the adsorption of oxygen by the carbon molecular sieve, which is called regeneration. The pressure swing adsorption method usually uses two towers in parallel, alternating pressure adsorption and decompression regeneration, so as to obtain a continuous flow of nitrogen.

Scope of action

With air as raw material, carbon molecular sieve as adsorbent, the use of pressure swing adsorption principle, the use of carbon molecular sieve on oxygen and nitrogen selective adsorption and nitrogen separation method, commonly known as PSA nitrogen production. This method is a new nitrogen production technology developed rapidly in the 1970s. Compared with the traditional nitrogen production method, it has the characteristics of simple process, high degree of automation, fast gas production (15 ~ 30 minutes), low energy consumption, product purity can be adjusted in a large range according to the needs of users, easy operation and maintenance, low operating cost, and strong adaptability of the device, so it is very competitive in the nitrogen production equipment below 1000Nm3 / h. More and more popular with small and medium nitrogen users, PSA nitrogen machine has become the preferred method for small and medium nitrogen users.