Ultra-low pressure single-column deep-cooling space division technique

Abstract

The invention discloses an ultra-low-pressure single-tower cryogenic air separation process. The process comprises the compression of air or oxygen-rich air, dewatering, purification and heat exchange of the air or the oxygen-rich air, compression and heat exchange of nitrogen, expansion refrigeration of nitrogen or air, preparation of liquid nitrogen or liquid air (or liquid oxygen-rich air), preparation of gas oxygen and gas nitrogen by ultra-low-pressure single-tower distillation and other steps. As the distillation is completely operated under the single-tower low pressure and a nitrogen compressor is provided, the purity of the liquid nitrogen is completely ensured, the distillation process is easy to operate, the resistance is small, the low liquid-gas ratio can be adopted, and the process can realize energy conservation, low project cost, convenient operation and regulation, flexible product proposal and easy formation of a large-scale combined oxygen-making unit with an oxygen-rich device, thereby reducing energy consumption, realizing large-scale devices and greatly improving nitrogen output under the same oxygen-making amount.

Description

technical field [0001] The invention relates to the technical field of air separation processes, in particular to the technical field of ultra-low pressure single-column cryogenic air separation processes. Background technique [0002] Oxygen and nitrogen are widely used in industrial production. The atmosphere is an inexhaustible source of nitrogen and oxygen. Therefore, both oxygen and nitrogen are produced by air separation in industry. The most widely used method is cryogenic air separation. At present, the common process of cryogenic air separation process is mostly full low-pressure double-column rectification separation process. [0003] Its technological process includes the following steps: [0004] a. Compression of air; [0005] b. Air removal, purification and heat exchange; [0006] c. Air expansion refrigeration; [0007] d. Preparation of liquid nitrogen and liquid air; [0008] e. Full low-pressure double-column rectification to produce gas oxygen and ga...

AI Technical Summary

Problems solved by technology

[0011] 1. All raw material air in this process needs to be compressed to 0.58~0.6MPa, which consumes a lot of power and energy

[0012] 2. The tower in this process operates under a pressure of 0.55-0.58MPa. At present, sieve plate towers are mostly used. Due to the high resistance, the number of trays should not be too many. In order to ensure the purity of liquid nitrogen, only high reflux ratio operation can be used. The working reflux ratio is 30-50% higher than the minimum working reflux ratio, and the oxygen content in liquid air is only 38-40%.

[0013] 3. The purity of gas nitrogen and oxygen in the double-tower process is limited not only by the number of trays and liquid-gas ratio of the lower tower, but also by the ratio of liquid-gas and the number of trays of the upper tower. In the case of no auxiliary tower It is difficult to produce high-purity nitrogen. Although high-purity nitrogen can be produced when an auxiliary tower is added (the purity of gas nitrogen is still restricted by the purity of liquid nitrogen in the lower tower), a large amount of polluted nitrogen needs to be drawn out. On the one hand, the extraction rate of oxygen is reduced. At the same time, the output of high-purity nitrogen is reduced

[0014] 4. The process is complicated, and there is a coupling relationship between the refrigeration and rectification processes. Due to the mutual constraints between the two processes, it is difficult to greatly increase the number of liquid products

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