Air separation
AssigneeThe BOC Group, Inc.
InventorThomas Rathbone
Life of this patent
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Abstract
Compressed, purified, vaporous air and liquid air streams are introduced into a higher pressure rectification column. A stream of oxygen-enriched liquid flows from an outlet of the higher pressure rectification column via a reboiler and an expansion valve into a vessel. The oxygen-enriched liquid is partially vaporised in a boiler located in the vessel. The residual liquid flows from the vessel and a condenser to a lower pressure rectification column in which oxygen and nitrogen products are separated. A stream of vapour flows from the boiler through an outlet from the vessel to a pipeline which leads the air back for compression with incoming air. A greater yield of oxygen, and, if separated, argon is made possible by this recycle.
Claims18
A method of separating air comprising:
- introducing a part of the air into an arrangement of rectification columns in a liquid state and taking a liquid nitrogen product therefrom;
- compressing a flow of air and introducing a part of the compressed air flow in vapour state into a higher pressure rectification column of said arrangement and separating the air therein into a nitrogen fraction and an oxygen-enriched liquid fraction;
- withdrawing a stream of the oxygen-enriched liquid fraction from the higher pressure rectification column;
- passing a first part of the oxygen-enriched liquid stream along a first route that leads to a lower pressure rectification column, and separating an oxygen product in the lower pressure rectification column;
- and
- passing a second part of the oxygen-enriched liquid stream along a second route leading back to the compression of the air.
An apparatus for separating air, comprising:
- a higher pressure rectification column for separating air into a nitrogen fraction and an oxygen-enriched liquid fraction;
- a lower pressure rectification column;
- an air liquefier;
- an inlet for liquid air into one or more of the rectification columns;
- a nitrogen outlet from one of the rectification columns for liquid nitrogen product;
- at least one compressor for compressing a flow of air;
- an air inlet to the higher pressure rectification column for air in vapour state;
- a product outlet from the lower pressure rectification column for an oxygen product;
- and
- an oxygen enriched liquid outlet from the higher pressure rectification column for a stream of the oxygen-enriched liquid fraction;
- the oxygen enriched liquid outlet from the higher pressure rectification column communicating with a first route for the oxygen-enriched liquid that leads to the lower pressure rectification column;
- the oxygen enriched liquid outlet communicating with a second route for the oxygen-enriched liquid that leads back to the said compressor.
Dependencies are inferred from the claim text.