Air separation method and plant
AssigneeL'Air Liquide, Societe Anonyme a Directoire et Conseil de Surveillance pour l'Etude et l'Exploitation des Procedes Georges Claude
InventorsFrancois Fuentes, Richard Dubettier
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Abstract
The pressurized waste nitrogen (11) from a column of an air separation unit (10) is sent, optionally after being compressed, to a combustion chamber (15) where it is heated, to a turbine (17) in which it is expanded and again to the combustion chamber (15) where it is mixed with the flue gases in order to give up waste heat thereto.
Claims17
An air separation process in which a stream of compressed and purified air is separated in an air separation unit (10) in order to produce a nitrogen-enriched gas stream (11) at between 2 and 7 bar, the nitrogen-enriched gas stream is expanded in a turbine (17) and the expanded gas stream (19) is sent to a convection region located downstream of a combustion chamber (15), characterized in that the gas stream is expanded without having been mixed with a stream of fuel and it is not mixed with a stream of air after its expansion.
The process as claimed in one of the preceding claims, in which the air is purified in a purifying means (7) before being sent to the separation unit, the purifying means is regenerated by a nitrogen-enriched gas stream (11) and at least one portion of the stream that has served for the regeneration is sent to the expansion turbine (17).
The process as claimed in one of the preceding claims, in which the nitrogen-enriched stream (11) is withdrawn from a single column or from the medium-pressure column and/or the low-pressure column of a double column or from the high-pressure column and/or the intermediate-pressure column and/or the low-pressure column of a triple column.
The process as claimed in one of the preceding claims, in which the nitrogen-enriched stream (11) contains at least 50 mol % nitrogen and between 0.5 and 10 mol % oxygen.
The process as claimed in one of the preceding claims, in which a nitrogen-enriched stream (20, 23, 24, 31), preferably containing at least 50 mol % nitrogen, coming from an external source, is mixed with the nitrogen-enriched stream (11, 19) coming from the air separation unit (10), upstream of the expansion turbine (17).
An air separation plant comprising:
- i) an air separation unit (10) operating by cryogenic distillation,
- ii) a combustion chamber (15) followed by a heat-recovery region comprising at least one convection region,
- (iii)an expansion turbine (17),
- (iv) means (3) for sending air to the air separation unit operating by cryogenic distillation,
- (v) means for withdrawing a nitrogen-enriched gas stream (11) from the air separation unit operating by cryogenic distillation,
- (vi) means for sending the nitrogen-enriched gas stream to the expansion turbine and
- (vii)means for sending the nitrogen-enriched gas stream from the expansion turbine to the convection region located downstream of the combustion chamber characterized in that it comprises neither means for mixing air with the nitrogen-enriched gas downstream of the turbine and upstream of the combustion chamber nor means for mixing fuel with the nitrogen-enriched gas before its expansion.
Dependencies are inferred from the claim text.