Working Principle Of Nitrogen Generator

PSA pressure swing adsorption nitrogen production principle
Carbon molecular sieve can adsorb oxygen and nitrogen in the air at the same time, and its adsorption amount also increases with the increase of pressure, and there is no obvious difference in the equilibrium adsorption amount of oxygen and nitrogen at the same pressure. Therefore, it is difficult to complete the effective separation of oxygen and nitrogen by pressure changes alone. If the adsorption rate is further considered, the adsorption characteristics of oxygen and nitrogen can be effectively distinguished. The diameter of oxygen molecules is smaller than that of nitrogen molecules, so the diffusion rate is hundreds of times faster than that of nitrogen. Therefore, the speed of carbon molecular sieve adsorbing oxygen is also very fast, and the adsorption reaches more than 90% in about 1 minute; while the adsorption amount of nitrogen is only about 5% at this time, so the adsorption at this time is mostly oxygen, and the rest is mostly nitrogen. In this way, if the adsorption time is controlled within 1 minute, oxygen and nitrogen can be initially separated. In other words, adsorption and desorption are achieved by pressure difference, adsorption when pressure increases, and desorption when pressure decreases. The distinction between oxygen and nitrogen depends on the difference in the adsorption rate of the two, which is achieved by controlling the adsorption time. If the time is controlled to be very short, oxygen has been fully adsorbed, and nitrogen has not yet been adsorbed, the adsorption process is stopped.
Principle of Cryogenic Air Separation Nitrogen Production
Cryogenic nitrogen production can produce not only nitrogen but also liquid nitrogen, which meets the process requirements of liquid nitrogen, and can be stored in liquid nitrogen storage tanks. When there is an intermittent nitrogen load or the air separation equipment is repaired, the liquid nitrogen in the storage tank enters the vaporizer and is heated, and then sent to the product nitrogen pipeline to meet the nitrogen demand of the process unit. The operating cycle of cryogenic nitrogen production (referring to the interval between two large heatings) is generally more than 1 year, so cryogenic nitrogen production is generally not considered as a standby. However, pressure swing adsorption nitrogen production can only produce nitrogen, without standby means, and a single set of equipment cannot guarantee continuous long-term operation.
Principle of Membrane Air Separation Nitrogen Production
After being compressed and filtered by a compressor, the air enters the polymer membrane filter. Due to the different solubility and diffusion coefficients of various gases in the membrane, the relative permeation rates of different gases in the membrane are different. According to this characteristic, various gases can be divided into "fast gas" and "slow gas".
When the mixed gas is under the action of the pressure difference on both sides of the membrane, gases with relatively fast permeation rates, such as water, hydrogen, helium, hydrogen sulfide, carbon dioxide, etc., pass through the membrane and are enriched on the permeation side of the membrane, while gases with relatively slow permeation rates, such as methane, nitrogen, carbon monoxide and argon, are retained and enriched on the side of the membrane, thereby achieving the purpose of mixed gas separation.