US 5,049,174 AGranted

Hybrid membrane - cryogenic generation of argon concurrently with nitrogen

AssigneeAir Products and Chemicals, Inc.

InventorsRobert M. Thorogood, Wilman Tsai, Robert F. Weimer, David H. S. Ying

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Abstract

The present invention involves an efficient process for separating selected components of a gas stream by integrating a cryogenic separation unit and a membrane separation unit. Two embodiments provide for the concurrent generation of an argon-rich stream in the gas or liquid phase, along with a nitrogen-rich product stream, both being produced from a stream normally comprising oxygen, nitrogen, and argon, e.g., air. Broadly, the novel system uses a membrane means to preferentially reject the oxygen component from the recycle stream of the cryogenic unit, concurrently accumulating the argon component to allow its separation as an argon-enriched product stream.

Claims20

Dependent claims

A process for the concurrent production of gaseous and/or liquid nitrogen and crude argon from a feed gas stream comprising oxygen, nitrogen, and argon, said process comprising providing an added degree of freedom for adjusting the process parameters by:

(a) feeding said gas stream to a hybrid cryogenic air separation unit comprising a main and a secondary cryogenic unit and a membrane system to process said gas stream and yield a nitrogen product and crude argon product;
(b) withdrawing at least a portion of the treated gas which is argon-enriched from the main cryogenic distillation unit;
(c) feeding the argon-rich portion to the secondary distillation unit wherein said stream is separated to form a nitrogen-enriched distillation overhead vapor stream which is returned to the main cryogenic separation unit, and a product crude argon and oxygen bottoms liquid stream which is removed from the hybrid separation system for possible further purification;
(d) withdrawing a substantially pure gaseous nitrogen stream from the upper section of said main cryogenic distillation unit as product;
(e) compressing a second gaseous oxygen-enriched stream from the upper reboiler section of said main cryogenic distillation unit combining with the fresh compressed feed stream, and feeding the resulting stream to a first membrane unit, wherein said stream is split into a relatively argon and nitrogen-rich reject stream which is recycled after cooling to the bottom of said primary distillation unit, and a relatively oxygen-rich permeate stream;
(f) compressing said oxygen-rich permeate stream and feeding same to a second membrane unit wherein said stream is split into an oxygen-rich vent stream, and a relatively argon and nitrogen-rich stream which is recycled to the lower section of said distillation zone for condensation in the reboiler/condenser component thereof;
(g) withdrawing said condensed stream from said reboiler/condenser component of said secondary cryogenic unit and recycling same to the bottom section of said main cryogenic unit;
and
(h) providing refrigeration for the operation of the cryogenic process by work expansion of a process gas stream within the cryogenic system.

6 more elements

A process for the concurrent production of gaseous and/or liquid nitrogen and crude argon from a feed gas stream comprising oxygen, nitrogen, and argon, said process comprising

(a) feeding at least a major percentage of said feed gas directly to the bottom section of said main cryogenic distillation unit to produce a high-purity nitrogen vapor stream, an oxygen-rich vapor stream for internal processing, and an argon-rich liquid side stream;
(b) feeding the argon-rich side stream to the upper section of a second cryogenic distillation unit, wherein said stream is separated to form a nitrogen-enriched vapor stream that is returned to the main cryogenic separation unit, and a crude argon and oxygen bottoms liquid, which is removed directly from the separation system for added processing to argon product;
(c) withdrawing said high-purity nitrogen vapor stream as a product;
(d) passing said second oxygen-rich vapor stream to the membrane zone wherein it is split into a relatively oxygen-rich permeate stream which is vented, and into a relatively argon and nitrogen rich reject stream;
and
(e) compressing and cooling said argon-rich and nitrogen-rich stream and recycling the compressed stream directly to the bottom section of said main cryogenic separation unit;
and
(f) providing refrigeration for the operation of the cryogenic process unit by work expansion of a compressed process gas stream within the cryogenic process unit.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/540,028Filed 18 Jun 1990
Granted: 17 Sep 1991
Term ends: Not estimatedThe source records don’t support an estimate.

Classification14 codes

B01D 53/229
By diffusion: integrated processes
F25J 3/04284
Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion: using internal refrigeration by open-loop…
F25J 3/04296
Of feed air, e.g. used as waste or product air or expanded into an auxiliary column: claude expansion, i.e. expanded into the main or high…
F25J 3/04636
For air: using a hybrid air separation unit, e.g. combined process by cryogenic separation and non-cryogenic separation techniques