Method and equipment for producing air product based on cryogenic distillation

Abstract

The invention discloses a method and equipment for producing an air product based on cryogenic distillation. Raw material air and nitrogen compressed by a compressor are cooled by a main heat exchanger and then fed into a distillation system for low-temperature separation. In a rectification system, products such as oxygen and nitrogen are obtained through low-temperature separation, and meanwhile, oxygen-enriched liquid air is obtained at the bottom or near a rectification tower. Oxygen-enriched liquid air or liquid air in the rectification system is sent out after being increased to target pressure through a low-temperature liquid air pump, and then air products with various pressures are produced by mixing with circulating nitrogen in a gas phase. By the adoption of the method, the problem that in the prior art, liquid nitrogen and the oxygen-enriched liquid air or the liquid air are mixed in a liquid phase, and the required proportion of the obtained air product cannot be determined after vaporization can be solved; and meanwhile, the air product can be obtained in a more accurate and safer manner on the premise of using a nitrogen circulation internal compression process.

Description

technical field [0001] The invention relates to the field of cryogenic air separation, in particular to a method and equipment for producing air products based on cryogenic distillation. Background technique [0002] Cryogenic separation, also known as low-temperature rectification, usually uses mechanical methods, such as throttling expansion or adiabatic expansion, to compress and cool the gas, and then use the difference in boiling point of different gases to carry out rectification to separate different gases . [0003] The principle of cryogenic air separation is to use air as raw material, after compression, purification, and heat exchange, the air is liquefied into liquid air. Air liquid is mainly a mixture of liquid oxygen and liquid nitrogen. Using the different boiling points of liquid oxygen and liquid nitrogen, they are separated by rectification to obtain nitrogen and oxygen. [0004] In a specific coal chemical project, especially a synthetic ammonia plant, a...

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Problems solved by technology

In theory, there is no problem in adjusting the nitrogen and oxygen content in the liquid phase according to the prior art, but it is more difficult in actual operation, because it cannot be determined that the obtained air product is just in the required ratio after vaporization, and the saturated liquid nitrogen and Oxygen-enriched liquid air or liquid air will produce bubbles after mixing, so it is not suitable to be directly fed into the pump for pressurization

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