Heat exchanger assembly and system for a cryogenic air separation unit

Abstract

A sub-cooler type heat exchanger assembly and system for use in a cryogenic air separation plant is provided. The sub-cooler type heat exchanger includes at least two separate heat exchange segments within the same housing or shell and is configured to concurrently cool two or more upward flowing cryogenic liquids using nitrogen-rich streams from the lower pressure distillation column.

What is claimed is: 
     
         1 . A heat exchanger assembly for a cryogenic air separation unit, comprising:
 a housing having a shell, at least two cryogenic liquid inlets, at least two cryogenic liquid outlets, at least one nitrogen-rich stream inlet and at least one nitrogen-rich stream outlet, the housing configured to receive a flow of at least one nitrogen-rich stream of the air separation unit at the at least one nitrogen-rich stream inlet and separate flows of at least two cryogenic liquids at the at least two cryogenic liquid inlets;   a first heat exchange segment disposed within the housing and configured for receiving a first flow of at least one cryogenic liquid of an air separation unit and for channeling the first flow of the at least one cryogenic liquid in a cross flow orientation or a counter-cross flow orientation from at least one of the cryogenic liquid inlets to at least one of the cryogenic liquid outlets;   the first heat exchange segment further configured for receiving a portion of the flow of the at least one nitrogen-rich stream and for channeling a portion of the flow of the at least one nitrogen-rich stream in a first direction within the first heat exchange segment from the at least one nitrogen-rich stream inlet to the at least one nitrogen-rich stream outlet to sub-cool the first flow of the at least one cryogenic liquid and wherein the first direction is generally orthogonal to the first flow of the at least one cryogenic liquid;   a second heat exchange segment unit disposed within the housing and configured for receiving a second flow of at least one cryogenic liquid of an air separation unit and for channeling the second flow of the at least one cryogenic liquid within the second heat exchange segment from another of the cryogenic liquid inlets to another of the cryogenic liquid outlets; and   the second heat exchange segment further configured for receiving a portion of the flow of the at least one nitrogen-rich stream and for channeling the portion of the flow of the at least one nitrogen-rich stream in a second direction within the second heat exchange segment from the at least one nitrogen-rich stream inlet to the at least one nitrogen-rich stream outlet to sub-cool the second flow of the at least one cryogenic liquid.   
     
     
         2 . The heat exchanger assembly of  claim 1  wherein the housing further comprises at least two nitrogen-rich stream outlets and the flow of at least one nitrogen-rich stream exiting the housing is split into at least two streams. 
     
     
         3 . The heat exchanger assembly of  claim 1  wherein the first flow of at least one cryogenic liquid comprises a flow of kettle liquid from the higher pressure column. 
     
     
         4 . The heat exchanger assembly of  claim 1  wherein the first flow of at least one cryogenic liquid comprises a flow of shelf liquid from the higher pressure column. 
     
     
         5 . The heat exchanger assembly of  claim 1  wherein the first flow of at least one cryogenic liquid comprises a flow of liquid oxygen from the lower pressure column. 
     
     
         6 . The heat exchanger assembly of  claim 1  wherein the first flow of at least one cryogenic liquid comprises multiple flows of cryogenic liquids. 
     
     
         7 . The heat exchanger assembly of  claim 6  wherein the multiple flows are selected from the group consisting essentially of a flow of kettle liquid from the higher pressure column; a flow of shelf liquid from the higher pressure column; a flow of liquid oxygen; and a flow of liquid air. 
     
     
         8 . The heat exchanger assembly of  claim 1  wherein the second flow of at least one cryogenic liquid comprises a flow of kettle liquid from the higher pressure column and wherein the second direction is generally orthogonal to the second flow. 
     
     
         9 . The heat exchanger assembly of  claim 1  wherein the second flow of at least one cryogenic liquid comprises a flow of shelf liquid from the higher pressure column and wherein the second direction is generally orthogonal to the second flow. 
     
     
         10 . The heat exchanger assembly of  claim 1  wherein the second flow of at least one cryogenic liquid comprises a flow of liquid oxygen the lower pressure column and wherein the second direction is generally orthogonal to the second flow. 
     
     
         11 . The heat exchanger assembly of  claim 1  wherein the flow of at least one nitrogen-rich stream in the second direction is a gravity assisted flow in a downward orientation. 
     
     
         12 . The heat exchanger assembly of  claim 11  wherein the flow of the at least one nitrogen-rich stream further comprise waste nitrogen or product nitrogen or both from a lower pressure column of the air separation unit. 
     
     
         13 . The heat exchanger assembly of  claim 11  wherein the second flow of at least one cryogenic liquid comprises liquid air and wherein the second direction is generally parallel to the second flow. 
     
     
         14 . The heat exchanger assembly of  claim 11  wherein the second flow of at least one cryogenic liquid comprises liquid air and wherein the second direction is in a counter-flow orientation with respect to the second flow. 
     
     
         15 . The heat exchanger assembly of  claim 1  wherein the cryogenic liquid inlets are disposed vertically below the corresponding cryogenic liquid outlets such that the overall flow of the cryogenic liquids is in an upward flow orientation. 
     
     
         16 . The heat exchanger assembly of  claim 1  wherein the spatial volume of the first heat exchange segment within the housing and the spatial volume of the second heat exchange segment within the housing are substantially equal. 
     
     
         17 . The heat exchanger assembly of  claim 1  wherein the width or spatial volume of the first heat exchange segment within the housing and the width or spatial volume of the second heat exchange segment within the housing are different. 
     
     
         18 . A heat exchanger system for an air separation unit, comprising:
 a primary heat exchanger having a plurality of heat exchanging units, the primary heat exchanger configured to cool a compressed and purified incoming air stream to temperatures suitable for cryogenic rectification of the air stream in distillation columns via indirect heat exchange with return streams from the air separation unit; and   a sub-cooling heat exchanger fluidically coupled to one or more of the heat exchanging units in the primary heat exchanger, the sub-cooling heat exchanger configured to sub-cool at least two cryogenic liquid streams via indirect heat exchange with a nitrogen-rich stream selected from the group comprising a waste nitrogen stream, a product nitrogen stream, or other nitrogen-rich return stream, the sub-cooling heat exchanger comprising:   (i) a housing having a shell, at least two cryogenic liquid inlets, at least two cryogenic liquid outlets, at least one nitrogen-rich stream inlet and at least one nitrogen-rich stream outlet, the housing configured to receive a flow of the nitrogen-rich stream at the at least one nitrogen-rich stream inlet and separate flows of at least two cryogenic liquids at the at least two cryogenic liquid inlets;   (ii) a first heat exchange segment disposed within the housing and configured for receiving a first flow of cryogenic liquid and for channeling the first flow of the cryogenic liquid in a cross flow orientation or a counter-cross flow orientation from at least one of the cryogenic liquid inlets to at least one of the cryogenic liquid outlets; the first heat exchange segment further configured for receiving a portion of the nitrogen-rich stream and for channeling the portion of the nitrogen-rich stream in a first direction within the first heat exchange segment from the at least one nitrogen-rich stream inlet to the at least one nitrogen-rich stream outlet to sub-cool the first flow of cryogenic liquid and wherein the first direction is generally orthogonal to the first flow of cryogenic liquid; and   (iii) a second heat exchange segment unit disposed within the housing and configured for receiving a second flow of cryogenic liquid and for channeling the second flow of cryogenic liquid within the second heat exchange segment from another of the cryogenic liquid inlets to another of the cryogenic liquid outlets; the second heat exchange segment further configured for receiving a portion of the nitrogen-rich stream and for channeling the portion of the nitrogen-rich stream in a second direction within the second heat exchange segment from the at least one nitrogen-rich stream inlet to the at least one nitrogen-rich stream outlet to sub-cool the second flow of the cryogenic liquid;   wherein the sub-cooling heat exchanger is separated and disposed apart from the primary heat exchanger.   
     
     
         19 . The heat exchanger system of  claim 18  further comprising:
 an inlet manifold disposed upstream of the sub-cooling heat exchanger and fluidically coupled thereto and configured to deliver the nitrogen-rich stream from a lower pressure distillation column of the air separation unit to the at least one nitrogen-rich stream inlet; and 
 one or more exhaust manifolds disposed downstream of the sub-cooling heat exchanger and fluidically coupled thereto, the one or more exhaust manifolds configured to deliver the warmed nitrogen-rich stream from the sub-cooling heat exchanger to one or more of the heat exchanging units of the primary heat exchanger as a portion of the return streams.