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US 4,224,045 AGranted
Cryogenic system for producing low-purity oxygen
AssigneeUnion Carbide Corporation
InventorsWalter J. Olszewski, John H. Ziemer
Life of this patent
Estimating the term…
Abstract
Low-purity oxygen is produced by fractional distillation of liquefied air. A gas turbine, powered in part by waste nitrogen from the distillation, supplies energy to compress the feed air. Compressing the waste nitrogen prior to turbine expansion provides an increase in energy efficiency.
Claims22
A process for producing low-purity oxygen by low-temperature rectification of air comprising:
- (a) compressing feed air to at least 85 psia,
- (b) dividing the compressed air into a first part and second part,
- (c) mixing said first part as oxidant for a combustion stream with fuel,
- (d) igniting said combustion stream in a combustion zone at ignition pressure of at least 80 psia to heat said combustion stream,
- (e) expanding the heated combustion stream in a power turbine to lower pressure with the production of external work,
- (f) recovering at least part of said external work as energy for said compressing of feed air,
- (g) cooling said second part of compressed air,
- (h) introducing the cooled air to a higher pressure rectification stage having its upper end in heat exchange relation with the lower end of a lower pressure rectification stage,
- (i) separating said cooled air into oxygen-enriched and nitrogen-rich liquids in said higher pressure rectification stage,
- (j) transferring at least part of said liquids from step (i) to said lower pressure rectification stage for separation into low purity oxygen and nitrogen-rich gases,
- (k) operating said lower-pressure rectification stage at pressure at least 20 psi lower than the step (d) ignition pressure,
- (l) discharging a low-purity oxygen product stream and at least one nitrogen-rich gas stream from said lower pressure rectification stage,
- (m) compressing at least part of the nitrogen-rich gas discharged in step (l) to pressure at least equal to the step (d) ignition pressure, and
- (n) flowing the compressed nitrogen-rich stream into the combustion stream, upstream of said power turbine.
11 more elements
Apparatus for producing low-purity oxygen by low temperature rectification comprising:
- (a) a compressor for compressing feed air to pressure of at least 85 psia,
- (b) a combustion system comprising a combustion chamber, conduit means for flowing a first part of compressed feed air from compressor (a) to said combustion chamber, means for introducing fuel to said combustion chamber, and conduit means for flowing combusted gas from said combustion chamber to,
- (c) a turbine for expanding the combusted gas to lower pressure so as to produce external work,
- (d) means for transferring external work of turbine (c) to compressor (a),
- (e) means for cooling a second part of compressed feed air,
- (f) a double rectification column comprising a higher-pressure stage for operation at at least about 85 psia, a lower-pressure stage, and a heat exchanger joining the upper end of the higher-pressure stage and the lower end of the lower-pressure stage, separate conduit means for transferring oxygen-enriched and nitrogen-rich liquids from the higher-pressure stage to the lower-pressure stage,
- (g) conduit means for flowing the cooled second part of the compressed feed air to the higher-pressure stage for rectification therein,
- (h) a compressor for compressing nitrogen-rich gas to pressure of at least 85 psia,
- (i) conduit means for flowing nitrogen-rich gas from the lower-pressure rectification stage to compressor (h),
- (j) conduit means for flowing compressed nitrogen-rich gas from compressor (h) to combustion system (b), and
- (k) conduit means for discharging low-purity oxygen from said power-pressure rectification stage.
8 more elements
A process for producing low-purity oxygen by low-temperature rectification of air comprising:
- (a) compressing feed air to at least 85 psia,
- (b) dividing the compressed air into a first part and second part,
- (c) mixing said first part as oxidant for a combustion stream with fuel,
- (d) igniting said combustion stream in a combustion zone at ignition pressure of at least 80 psia to heat said combustion stream,
- (e) expanding the heated combustion stream in a power turbine to lower pressure with the production of external work,
- (f) recovering at least part of said external work as energy for said compressing of feed air,
- (g) cooling said second part of compressed air,
- (h) introducing the cooled air to a higher pressure rectification stage having its upper end in heat exchange relation with the lower end of a lower pressure rectification stage,
- (i) separating said cooled air into oxygen-enriched and nitrogen-rich liquid in said higher pressure rectification stage,
- (j) transferring at least part of said liquids from step (i) to said lower pressure rectification stage for separation into low purity oxygen and nitrogen-rich gases,
- (k) operating said lower-pressure rectification stage at pressure at least 20 psi lower than the step (d) ignition pressure,
- (l) discharging a low-purity oxygen product stream and at least one nitrogen-rich gas stream from said lower pressure rectification stage,
- (m) compressing at least part of the nitrogen-rich gas discharged in step (l) to pressure at least equal to the step (d) ignition pressure, and
- (n) injecting said compressed nitrogen-rich stream into the combustion stream prior to the step (d) ignition.
11 more elements
Apparatus for producing low-purity oxygen by low pressure rectification comprising:
- (a) a compressor for compressing feed air to pressure of at least 85 psia,
- (b) a combustion system comprising a combustion chamber, conduit means for flowing a first part of compressed feed air from compressor (a) to said combustion chamber, means for introducing fuel to said combustion chamber, and conduit means for flowing combusted gas from said combustion chamber to,
- (c) a turbine for expanding the combusted gas to lower pressure so as to produce external work,
- (d) means for transferring external work of turbine (c) to compressor (a),
- (e) means for cooling a second part of compressed feed air,
- (f) a double rectification column comprising a higher-pressure stage for operation at at least about 85 psia, a lower-pressure stage, and a heat exchanger joining the upper end of the higher-pressure stage and the lower end of the lower-pressure stage, separate conduit means for transferring oxygen-enriched and nitrogen-rich liquids from the higher-pressure stage to the lower-pressure stage,
- (g) conduit means for flowing the cooled second part of the compressed feed air to the higher-pressure stage for rectification therein,
- (h) a compressor for compressing nitrogen-rich gas to pressure of at least 85 psia,
- (i) conduit means for flowing nitrogen-rich gas from the lower-pressure rectification stage to compressor (h),
- (j) conduit means for flowing at least part of the compressed nitrogen-rich gas into combustion system (b) upstream of said combustion chamber, and
- (k) conduit means for discharging low-purity oxygen from said lower-pressure rectification stage.
8 more elements
Dependencies are inferred from the claim text.