Cryogenic air separation nitrogen/oxygen is a traditional nitrogen production method that has been developed in recent decades. It uses air as a raw material, compresses and purifies it, and then uses heat exchange to liquefy the air into liquid air. Liquid air is mainly a mixture of liquid oxygen and liquid nitrogen. The boiling point of liquid oxygen and liquid nitrogen is different (-183℃& -196℃). Let them separate to obtain nitrogen. The cryogenic air separation nitrogen/oxygen production equipment is complex, covers a large area, has high capital construction costs, has a large investment in equipment, high operating cost, slow gas production (12 to 24 hours) after startup, high installation requirements and long cycle. Comprehensive equipment, installation and infrastructure factors, equipment below 3,500Nm3/h, the investment scale of PSA units of the same specifications is 20% to 50% lower than that of cryogenic air separation units. The cryogenic air separation nitrogen/oxygen plant is suitable for large-scale industrial N2/O2 production, while for medium and small scale N2/O2 production it is uneconomical.
In molecular sieve air separation nitrogen/oxygen systems, air as raw material, carbon/zeolite molecular sieve as adsorbent, using the principle of pressure swing adsorption, adopting carbon/zeolite molecular sieve’s selective adsorption of oxygen and nitrogen to separate nitrogen and oxygen, commonly known as PSA N2/O2. This method is a new nitrogen/oxygen-producing technology that was rapidly developed in the 1970s. Compared with the traditional nitrogen/oxygen production method, it has simple process flow, high automation, fast gas production (15 to 30 minutes after startup), low energy consumption, product purity can be adjusted according to user needs in a wide range, easy operation and maintenance, operation low cost and strong adaptability of the device, so it is competitive in nitrogen/oxygen production equipment below 1,000Nm3/h. It is more and more popular among small and medium-sized nitrogen/oxygen users. PSA nitrogen/oxygen has become the first choice for medium and small nitrogen/oxygen users.
Membrane air separation nitrogen/oxygen, air as raw material, under different pressure conditions, different properties of oxygen and nitrogen gas in the membrane with different permeation rates to separate oxygen and nitrogen. Compared with other nitrogen/oxygen-making equipment, it has the advantages of simpler structure, smaller volume, no switching valve, less maintenance, faster gas production (≤3 minutes after startup), convenient capacity increase, etc. It is especially suitable for nitrogen purity ≤ 98% of medium and small nitrogen users with the best price/performance ratio. When the purity of nitrogen is above 98%, it is 15+% higher than the PSA nitrogen generator of the same specification in capital, operation and maintenance costs.