There are three kinds in the industry, i.e., deep cooling air separation, molecular sieve air separation (PSA) and membrane air separation.
A Deep-cooled Air Separation of Nitrogen
Deep-cooled air separation of nitrogen is a traditional method of nitrogen production, which has been used for nearly decades. It takes air as raw material, after compression and purification, and then uses heat exchange to make the air liquefied into liquid air. Liquid air is mainly a mixture of liquid oxygen and liquid nitrogen, using liquid oxygen and liquid nitrogen with different boiling points (under 1 atmospheric pressure, the boiling point of the former is -183 ℃, and the latter is -196 ℃), through the distillation of liquid air, so that they are separated to obtain nitrogen. Deep cooling air separation nitrogen equipment is complex, covers a large area, higher infrastructure costs, more one-time investment in equipment, higher operating costs, slow gas production (12 to 24h), high installation requirements, longer cycle. Comprehensive equipment, installation and infrastructure factors, 3500Nm3 / h below the equipment, the same specifications of the PSA device investment scale than the deep-cooling air separation device is 20% to 50% lower. Deep-cooled air separation nitrogen plant is suitable for large-scale industrial nitrogen production, while medium and small-scale nitrogen production is not economical.
B molecular sieve air separation of nitrogen
Air as raw material, carbon molecular sieve as adsorbent, using the principle of pressure change adsorption, the use of carbon molecular sieve on the selective adsorption of oxygen and nitrogen to make the separation of nitrogen and oxygen method, commonly known as PSA nitrogen. This method is a new nitrogen production technology developed rapidly in the 1970s. Compared with the traditional nitrogen production method, it has the features of simple process, high degree of automation, fast gas production (15-30 minutes), low energy consumption, product purity can be adjusted according to the user's needs within a wide range, convenient operation and maintenance, low operation cost, and strong adaptability of the device, etc. Therefore, it is quite competitive among the nitrogen production equipments of less than 1,000Nm3/h, and more and more welcomed by the medium-sized and small-sized nitrogen users. PSA nitrogen generation has become the preferred method for medium and small-sized nitrogen users.
C Membrane Air Separation Nitrogen Production
Taking air as the raw material, under a certain pressure condition, it utilizes the gases with different properties such as oxygen and nitrogen to have different permeation rates in the membrane to separate oxygen and nitrogen. Compared with other nitrogen equipment, it has the advantages of simpler structure, smaller volume, no switching valve, less maintenance, faster gas production (≤3 minutes), easy to increase capacity, etc. It is especially suitable for medium and small nitrogen users with nitrogen purity ≤98%, and has the best function-price ratio. When the purity of nitrogen is above 98%, the price of PSA nitrogen generator with the same specification is more than 15% higher than that of PSA nitrogen generator.