Process for air fractionation by low-temperature rectification
First Claim
1. In a process for air fractionation by low-temperature rectification comprising a rectification step from which nitrogen and product oxygen streams are obtained and a cooling stage wherein a process gas of the air fractionation is employed as working gas to produce refrigeration by compression and expansion of at least a portion of said working gas, the improvement comprising:
- compressing said working gas in said cooling stage and thereafter dividing said working gas into a first partial stream and a second partial stream, both of which are at least partially cooled and at least partially subjected to engine expansion, said first partial stream being expanded at a temperature higher than that at which the second partial stream is expanded;
compressing at least said second partial stream, prior to expansion, wherein work gained during expansion of at least a part of one of said partial streams is utilized in the compression of said second partial stream, said compression of said second partial stream being performed in two compression stages; and
introducing at least a portion of at least one of said partial streams to the rectification step.
1 Assignment
0 Petitions
Accused Products
Abstract
In a system for air fractionation by low-temperature rectification, refrigeration is produced in a cooling stage by compression and expansion of the feed air or of nitrogen from rectification. By using the work gained during expansion for compressing only a partial stream of the gas passed through the cooling stage, the system according to this invention operates with increased efficiency and lower operating costs.
22 Citations
36 Claims
-
1. In a process for air fractionation by low-temperature rectification comprising a rectification step from which nitrogen and product oxygen streams are obtained and a cooling stage wherein a process gas of the air fractionation is employed as working gas to produce refrigeration by compression and expansion of at least a portion of said working gas, the improvement comprising:
-
compressing said working gas in said cooling stage and thereafter dividing said working gas into a first partial stream and a second partial stream, both of which are at least partially cooled and at least partially subjected to engine expansion, said first partial stream being expanded at a temperature higher than that at which the second partial stream is expanded; compressing at least said second partial stream, prior to expansion, wherein work gained during expansion of at least a part of one of said partial streams is utilized in the compression of said second partial stream, said compression of said second partial stream being performed in two compression stages; and introducing at least a portion of at least one of said partial streams to the rectification step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
-
-
35. An apparatus for air fractionation by low-temperature rectification comprising:
-
(a) compression means for compressing the air to be fractionated; (b) means for dividing resultant compressed air into a first partial stream and a second partial stream; (c) heat exchange means for cooling said first partial stream; (d) expansion means for expanding the cooled first partial stream to remove mechanical energy therefrom; (e) recycle means for recycling the expanded first partial stream to a point upstream of said compression means (a); (f) two serially connected compression stages for compressing said second partial stream; (g) heat exchange means for cooling resultant compressed second partial stream; (h) expansion means for expanding at least a portion of said second partial stream to remove mechanical energy therefrom; (i) a two-stage rectification column comprising a first high-pressure stage and a second low-pressure stage, said first stage and said second stage being in heat exchange relation by a condenser-evaporator; (j) delivery means for delivering said second partial stream to said first stage of said rectification column; and (k) product delivery means for removing gaseous and liquid product nitrogen and gaseous and liquid product oxygen from said second pressure stage of said rectification column; wherein said two serially connected compression stages are in connection with expansion means (d) and (h) whereby mechanical energy obtained in said expansion means (d) and (h) is utilized to operate said two serially connected compression stages.
-
-
36. An apparatus for air fractionation by low-temperature rectification comprising:
-
(a) heat exchange means for cooling air to be fractionated; (b) a two-stage rectification column comprising a first high-pressure stage and a second low-pressure stage, said first stage and said second stage being in heat exchange relation by a condenser-evaporator, said first stage having an inlet means for delivery of cooled air to be fractionated, said second stage having product delivery means for removal of gaseous and liquid product nitrogen and gaseous and liquid product oxygen therefrom; (c) outlet means for removing nitrogen-enriched gas from an upper portion of said first stage of said rectification column; (d) compression means in fluid communication with said outlet means (c) for compressing said nitrogen-enriched gas; (e) means for dividing the compressed nitrogen-enriched gas into a first partial stream and a second partial stream; (f) cooling means for cooling said first partial stream; (g) expansion means for expanding said first partial stream to remove mechanical energy therefrom; (h) recycle means for recycling the expanded first partial stream to a point upstream of said compression means (d); (i) two serially connected compressed stages for compressing said second partial stream; (j) cooling means for cooling the compressed second partial stream; (k) expansion means for expanding at least a portion of said second partial stream to remove mechanical energy therefrom; and (l) delivery means for delivering at least a portion of said second partial stream to said first high-pressure stage of said rectification column; wherein said two serially connected compression stages are in connection with expansion means (g) and (k) whereby mechanical energy obtained in said expansion means (g) and (k) is utilized to operate said two serially connected compression stages.
-
Specification