Process and plant for separating air by cryogenic distillation
AssigneeL'Air Liquide, Societe Anonyme a Directoire et Conseil de Surveillance pour l'Etude et l'Exploitation des Procedes George Claude
InventorJean-Pierre Tranier
Life of this patent
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Abstract
An air separation plant producing pressurized gaseous oxygen includes at least one column having a bottom reboiler. The column is fed with a stream of air. The bottom reboiler is warmed by a nitrogen-enriched gas compressed in a cold compressor and pumped liquid oxygen is withdrawn from the bottom of the column, pumped and vaporized. The refrigeration for the process is produced by air expansion in a turbine.
Claims23
Process for separating air by cryogenic distillation in an apparatus comprising at least one column, comprising the steps of:
- compressing the air, purifying the air and sending at least one portion thereof to a first column;
- separating air in the column at cryogenic temperature;
- compressing at least one portion of a fraction containing at most 30 mol % of oxygen extracted from the column in a compressor, the intake temperature of which is below room temperature;
- at least partially cooling the compressed fraction and condensing the compressed fraction by vaporizing an internal fluid of the first column or a fluid extracted therefrom;
- and
- extracting an oxygen-rich liquid fraction from the first column, pressurizing the oxygen-rich liquid fraction to a pressure above that of the column and vaporizing the oxygen-rich liquid fraction by direct or indirect heat exchange with a portion of the feed air in order to from an oxygen-rich pressurized gas product.
Plant for separating air by distillation in at least a first column (17) having a bottom reboiler (19), comprising means (7) for sending compressed and purified air to the first ( or the) column, a compressor (21) for compressing a gas (25) containing at most 30 mol % of oxygen coming from the column having as inlet temperature of at most 5° C. warmer than a temperature of the first (or the) column, means for sending the compressed gas to the bottom reboiler, means (33) for sending the at least partially compressed gas condensed in the bottom reboiler (19) back to the column, optionally means for enriching the compressed gas with nitrogen upstream of the reboiler, means (27) for withdrawing an oxygen-enriched liquid from the bottom of the column, means (23) for pressurizing it and means (19, 47) for vaporizing the pressurized liquid by direct or indirect heat exchange, characterised in that it includes means for vaporizing the pressurized liquid by direct or indirect heat exchange and, if the exchange is direct, the heat exchange takes place with air (9) intended for the first column.
Dependencies are inferred from the claim text.