Cryogenic rectification process-based method for producing air product, and air separation system

A cryogenic rectification process-based method for producing an air product, comprising:

• a. providing an air separation system for preparing a nitrogen product and/or an oxygen product, which comprises:
• a rectification column, at least one air boost system, at least one air pre-cooling apparatus, at least one air purification apparatus and at least one heat exchange apparatus, wherein the rectification column comprises a first column with a first pressure, a second column with a second pressure and a main condensation and evaporation apparatus arranged at the bottom of the second column;
• and the air boost system comprises a main air compressor and at least one air booster;
• b. after passing feed air sequentially through the main air compressor for pressurization to a first pressure range, the air pre-cooling apparatus for pre-cooling and the air purification apparatus for purification, splitting off one portion thereof as a first air stream for heat exchange through the heat exchange apparatus with a gas or liquid product produced by rectification, and then introducing the first air stream after cooling down into the first column for rectification;
• and the other portion passing through the air booster for pressurization to a third pressure range before being split into a second air stream and a third air stream, the second air stream passing through the heat exchange apparatus for heat exchange with the gas or liquid product produced by rectification and being discharged from a middle part of the heat exchange apparatus into an air expander for depressurization to the first pressure range before being introduced into the first column for rectification;
• and the third air stream passing through the heat exchange apparatus for heat exchange with the gas or liquid product produced by rectification, and after cooling down, being depressurized to the first pressure range for introduction into the first column or depressurized to a second pressure range for introduction into the second column;
• c. providing a liquid nitrogen line and an oxygen-enriched liquid air line which introduce liquid nitrogen at the top of the first column and oxygen-enriched liquid air at the bottom of the first column, respectively, into the second column as reflux for rectification;
• and
• d. providing an air product outlet line in which at least one liquid air booster pump is arranged, and discharging the oxygen-enriched liquid air or at least partially liquefied feed air of the third air stream from the bottom of the first column through the air product outlet line, into the liquid air booster pump for pressurization to a target pressure, and then into the heat exchange apparatus for vaporization via heat exchange so as to obtain the required air product.

An air separation system for producing an air product based on a cryogenic rectification process, the air separation system comprising:

• a. a rectification column, which comprises:
• a first column with a first pressure, a second column with a second pressure and a main condensation and evaporation apparatus arranged at the bottom of the second column;
• and a liquid nitrogen line for guiding liquid nitrogen from the top of the first column through a throttle valve into the second column and an oxygen-enriched liquid air line for guiding oxygen-enriched liquid air from the bottom of the first column through the throttle valve into the second column arranged between the first column and the second column;
• b. at least one air boost system, at least one air pre-cooling apparatus, at least one air purification apparatus, at least one heat exchange apparatus, at least one air expander, at least one liquid oxygen booster pump, at least one liquid air booster pump and a plurality of pressure reducing apparatuses, the air boost system comprising a main air compressor and at least one air booster;
• c. a first air inlet line for guiding feed air through the main air compressor, the air pre-cooling apparatus, the air purification apparatus and the heat exchange apparatus into the first column;
• a second air inlet line for guiding feed air through the main air compressor, the air pre-cooling apparatus and the air purification apparatus, out of the heat exchange apparatus and then through the air expander into the first column;
• and a third air inlet line further branching off from the second air inlet line before the second air inlet line enters the heat exchange apparatus, the third air inlet line passing through the heat exchange apparatus directly and being connected to the first column or the second column via the pressure reducing apparatus;
• d. a liquid oxygen product outlet line for discharging liquid oxygen from the main condensation and evaporation apparatus through the at least one liquid oxygen booster pump and then through the heat exchange apparatus;
• and
• e. an air product outlet line connected to the bottom of the first column or the third air inlet line, the air product outlet line being provided with the at least one liquid air booster pump to pressurize at least partially liquefied feed air from the third air inlet line or the oxygen-enriched liquid air discharged from the bottom of the first column to a target pressure for vaporization via heat exchange through the heat exchange apparatus so as to output the required air product.