System to cold compress an air stream using natural gas refrigeration
AssigneeAir Products and Chemicals, Inc.
InventorsDouglas Paul Dee, Donn Michael Herron, Jung Soo Choe
Life of this patent
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Abstract
An air stream is compressed in multiple stages using refrigeration derived from a refrigerant comprising natural gas for inter-stage cooling. The possibility of natural gas leaking into the air stream is reduced by use of an intermediate cooling medium (“ICM”) to transfer the refrigeration from the refrigerant to the inter-stage air stream. The compressed air stream can be fed to a cryogenic air separation unit that includes an LNG-based liquefier unit from which a cold natural gas stream is withdrawn for use as said refrigerant.
Claims17
A process for compressing a feed air stream to an air separation unit (“ASU”) including a liquefied natural gas based (“LNG-based”) liquefier unit, comprising:
- cooling an intermediate cooling medium (“ICM”) stream by indirect heat exchange against a refrigerant stream comprising natural gas;
- compressing the air stream using multiple compression stages;
- and
- cooling the air stream to a sub-ambient temperature between at least two of the multiple compression stages by indirect heat exchange against the ICM stream;
- wherein the LNG-based liquefier unit is synergistically integrated into the process by using a cold natural gas stream withdrawn at a temperature of −20° C. to −120° C. from an intermediate location of the liquefier unit as the refrigerant stream used to cool the ICM.
A process for compressing a feed air stream to an air separation unit (“ASU”), comprising:
- cooling an intermediate cooling medium (“ICM”) stream by indirect heat exchange against a refrigerant stream comprising natural gas;
- compressing the air stream in multiple compression stages;
- cooling the air stream to a sub-ambient temperature between at least two of the multiple compression stages by indirect heat exchange against the ICM stream;
- separating the air stream, in the ASU, into at least one nitrogen product stream and an oxygen product stream after the cooling and compressing steps;
- cooling the at least one nitrogen product stream in a liquefier by heat exchange against the refrigerant stream;
- and
- drawing off from an intermediate section of the liquefier a portion of the refrigerant stream at a temperature of −20° C. to −120° C. and using said portion of the refrigerant stream for the step of cooling the ICM stream.
An apparatus comprising:
- a compressor that compresses an air stream in multiple stages, the multiple stages comprising an initial stage, at least one intermediate stage and a final stage;
- a first heat exchanger that cools the air stream between the initial stage and the at least one intermediate stage against an intermediate cooling medium (“ICM”) stream,
- a second heat exchanger that cools the air stream between the at least one intermediate stage and the final stage against the intermediate cooling medium (“ICM”) stream;
- an air separation unit (“ASU”) that separates the air stream into at least one nitrogen product stream and at least one oxygen product stream;
- a liquefier that liquefies the at least one nitrogen product stream by heat exchange against a natural gas stream;
- and
- a third heat exchanger that cools the ICM stream by heat exchange against a portion of the natural gas stream withdrawn from an intermediate section of the liquefier.
Dependencies are inferred from the claim text.