US 4,152,130 AGranted

Production of liquid oxygen and/or liquid nitrogen

AssigneeAir Products and Chemicals, Inc.

InventorAlan Theobald

Life of this patent

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Abstract

Liquid oxygen and/or liquid nitrogen are made by removing carbon dioxide and water vapor from air, compressing the purified air in a re-cycle compressor and dividing the purified compressed air into first and second streams. Part of the first stream is expanded in a first expander and the refrigeration produced is used to cool both the first and second streams in a first heat exchanger. On leaving the first heat exchanger, the second stream is expanded in a second expander and the refrigeration produced is used to liquify at least part of the remainder of the first stream. The liquid stream is expanded and introduced into a fractionation column from which liquid nitrogen and/or liquid oxygen can be withdrawn. Expanded air from the first and second expanders is returned to the re-cycle compressor although part of the expanded air from the second expander is preferably introduced into the fractionation column. The invention is particularly suited to installations producing in excess of 100 tons of liquid per day and, at this size, preferred designs offer an estimated 51/2 to 9% power savings over the known prior art.

Claims1

Dependent claims

A method for producing at least one liquid product from the group of liquid oxygen and liquid nitrogen comprising the steps of:

(a) drying and removing carbon dioxide from a feed air stream to form a dry, carbon dioxide-free feed air stream;
(b) compressing said dry, carbon dioxide-free feed air stream in at least one recycle compressor to a pressure above 425 psia;
(c) dividing said compressed feed air stream into first and second feed air streams;
(d) dividing said first feed air stream into a sidestream and a remaining stream;
(e) expanding said sidestream to a lower pressure and temperature, and cooling said remaining stream and said second stream in heat exchange relationship with said expanded sidestream;
(f) expanding said second stream, after cooling in clause (e), to a lower pressure and temperature, and further cooling said once cooled remaining stream in heat exchange relationship with a first portion of said expanded second stream;
(g) expanding said twice cooled remaining feed air stream to a lower pressure, and injecting said expanded and cooled remaining feed air stream at least partially as a liquid, into a distillation column as a first feed air stream to the column;
(h) injecting a second portion of said expanded second stream into said distillation column as a second air feed stream to said column;
(i) recycling the exapnded streams of steps (e) and (f) to said recycle compressor as recycled feed air streams along with said initially dry carbon dioxide-free feed air stream;
(j) separating said first and second feed air streams in said distillation column and producing both liquid oxygen and liquid nitrogen in said column;
and
(k) withdrawing at least one of said liquid oxygen and liquid nitrogen from said distillation column as liquefied product.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/887,101Filed 16 Mar 1978
Priority: GB 11755/7719 Mar 1977
Granted: 1 May 1979
Term ends: Not estimatedThe source records don’t support an estimate.

Classification20 codes

F25J 3/04412
Using a dual pressure main column system: in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the…
F25J 3/04157
Purification and cooling of the feed air; recuperative heat-exchange with product streams: afterstage cooling and so-called "pre-cooling" of the…
F25J 3/04181
By adsorption of the impurities: regenerating the adsorbents
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…