Method for increasing production flexibility of an air separation unit

An apparatus for the production of air gases by the cryogenic separation of air, the apparatus comprising:

• a) a main air compressor configured to compress air to a pressure suitable for the cryogenic rectification of air to produce a compressed humid air stream, the compressed humid air stream having a first pressure Po;
• b) a front end purification system configured to purify the compressed humid air stream of water and carbon dioxide to produce a dry air stream having reduced amounts of water and carbon dioxide as compared to the compressed humid air stream;
• c) a booster compressor in fluid communication with the front end purification system, wherein the booster compressor is configured to compress a first portion of the dry air stream to form a boosted air stream, the boosted air stream having a first boosted pressure PB1;
• d) a cold box comprising a main heat exchanger, a system of columns having a double column composed of a lower pressure column and a higher pressure column, a condenser disposed at a bottom portion of the lower pressure column, and a liquid oxygen pump, wherein the cold box is configured to receive the boosted air stream and a second portion of the dry air stream under conditions effective to separate air to form an air gas product, wherein the air gas product is selected from the group consisting of oxygen, nitrogen, and combinations thereof;
• e) a first conduit in fluid communication with the front end purification system and the cold box, wherein the conduit is configured to transfer a second portion of the dry air stream to the cold box;
• f) a valve disposed on the first conduit, the valve being configured to adjust a flow rate of the second portion of the dry air stream into the cold box;
• and
• g) a process controller configured to choose between a first mode of operation and a second mode of operation, wherein the first mode of operation results in increased gas production, wherein the second mode of operation results in increased liquid production.