Performance comparison of cryogenic separation nitrogen production, PSA Nitrogen Generator and membrane separation nitrogen production
(1) The process flow of PSA pressure swing adsorption and membrane separation nitrogen production is simple, the number of equipment is small, the operation is simple, and it can be shut down at any time and can be shut down for a long time. Cryogenic nitrogen production not only has a complicated process flow and a large number of equipment, but also needs to be operated in a cryogenic and low temperature state. Before the equipment is put into normal operation, there is a pre-cooling start-up process, and the start-up time is generally not less than 12h from the start of the expander to the time when the nitrogen purity reaches the required level. Before the equipment enters the overhaul, there must be a period of heating and thawing time, generally 24h. Therefore, cryogenic separation nitrogen production is not suitable for occasions with frequent start and stop. Compared with PSA pressure swing adsorption, membrane separation nitrogen production not only has simpler equipment structure, but also has no switching valve, which makes operation and maintenance easier and the time required for gas production is shorter.
(2) Cryogenic separation of nitrogen production can simultaneously obtain gas nitrogen and liquid nitrogen, which is suitable for the technological process that requires liquid nitrogen. Liquid nitrogen can also be stored in a liquid nitrogen storage tank as a backup. When there is a short-term sudden increase in nitrogen demand or a minor repair of Nitrogen Production Equipment, the liquid nitrogen in the storage tank can be vaporized and sent to the nitrogen pipe network to meet the requirements of the process device for nitrogen. Continuity requirements. PSA pressure swing adsorption and membrane separation nitrogen production Pressure swing adsorption nitrogen production can only produce nitrogen gas, and there is no backup means. It is difficult for a single set of equipment to ensure continuous long-term operation of the process unit.
(3) When the nitrogen purity volume fraction is less than or equal to 97%, the nitrogen extraction rates of PSA pressure swing adsorption and membrane separation nitrogen production processes are basically the same; when the nitrogen purity volume fraction is greater than 99%, the nitrogen extraction rate of the cryogenic separation nitrogen production process is adopted. The highest, followed by PSA pressure swing adsorption, and the nitrogen extraction rate of membrane separation nitrogen production process dropped sharply. At the same time, to produce nitrogen at the same pressure, the air pressure at the outlet of the cryogenic separation nitrogen production air compressor is equivalent to that of PSA pressure swing adsorption nitrogen production, while the membrane separation nitrogen production pressure requires higher air pressure. The main energy consumption of the three nitrogen production processes is in the air compressor. Therefore, when the purity of nitrogen produced is relatively high, the air compressor required for membrane separation nitrogen production is large in scale, high in power, and the total energy consumption is the highest. In addition, the energy consumption of nitrogen production by cryogenic separation is relatively low.
(4) The nitrogen separation adsorption-desorption-adsorption process of PSA pressure swing adsorption nitrogen production has pressure fluctuations, and the nitrogen pressure is unstable; while the nitrogen separation process of cryogenic separation and membrane separation nitrogen production is continuous, and the product nitrogen pressure is relatively stable. Therefore, PSA nitrogen production must add a nitrogen buffer tank at the nitrogen outlet of the PSA adsorption tower to buffer nitrogen and adjust the gas pressure to ensure the stability of the nitrogen product pressure.
(5) There are many cryogenic separation nitrogen production equipment, long process, large area and high investment. Compared with PSA pressure swing adsorption nitrogen production, membrane separation nitrogen production requires a large amount of air, a high pressure ratio, and a large compressor scale. The corresponding air purification components (filters, dryers, degreasers, etc.) The adsorption is large, the investment is high, and the cost of the membrane module of the core component of nitrogen production is also higher than that of the PSA adsorption tower. Therefore, PSA pressure swing adsorption nitrogen production has the lowest investment.
