Heat exchanger and distillation column arrangement

Abstract

A shell and tube heat exchanger and distillation column arrangement for an air separation plant utilizing such heat exchanger in which tubes for passage of a liquid that is used in condensing a vapor are located within a cylindrical shell. The tubes are arranged in an inner array of tubes and an outer array of tubes surrounding the inner array of tubes and having more tubes than the inner array. The inner array of tubes present a larger average area, between tubes, for flow of the vapor in an outward, radial direction than tubes of the outer array to lessen pressure drop while allowing for more tubes to be located within the shell to increase the surface area available for heat exchange between the liquid and the vapor.

We claim: 
     
         1 . A shell and tube heat exchanger comprising:
 two opposed tube sheets;   a cylindrical shell connecting the two opposed tube sheets;   a central vapor inlet, centrally positioned with respect to a central axis of the shell, to introduce a vapor into the shell;   a central liquid outlet, centrally positioned with respect to the central axis of the shell, for discharging condensate produced by condensing the vapor;   tubes connecting the two opposed tube sheets for indirectly exchanging heat between a liquid flowing within the tubes and the vapor, thereby, condensing the vapor and producing the condensate within the cylindrical shell and, at least in part, inducing a flow of the vapor in an outward, radial direction toward the shell as a result of the condensation of the vapor;   the tubes arranged in an inner array of the tubes spaced apart from one another and surrounding the central vapor inlet and the central liquid outlet and an outer array of the tubes surrounding the inner array of the tubes and having a greater number of tubes than the inner array of the tubes; and   the inner array of the tubes and the outer array of the tubes spaced apart from one another to present areas between the tubes, the areas of the inner array of the tubes having an average of the areas greater than that of the areas of the tubes of the outer array of the tubes situated directly adjacent the inner array of the tubes to lower pressure drop of the flow of the vapor in the outward, radial direction.   
     
     
         2 . The shell and tube heat exchanger of  claim 1 , wherein:
 the central vapor inlet is located in one of the two opposed tube sheets; and   the central liquid outlet is located in the other of the two opposed tube sheets;   
     
     
         3 . The shell and tube heat exchanger of  claim 2 , wherein at least one support located within the shell supports the inner array of the tubes in an intermediate location of the inner array of the tubes between the tube sheets to inhibit vibration within the inner array of the tubes. 
     
     
         4 . The shell and tube heat exchanger of  claim 3 , wherein the at least one support includes:
 a plate having openings through which the inner array of the tubes pass and are thereby supported; and   the plate supported within the shell and tube heat exchanger at the intermediate location and opposite to the central vapor inlet so that the plate also acts as a baffle to also help in inducing the outward, radial flow of the vapor.   
     
     
         5 . The shell and tube heat exchanger of  claim 3 , wherein the plate has a star-like outer periphery having indentations located opposite to innermost tubes of the outer array of the tubes. 
     
     
         6 . The shell and tube heat exchanger of  claim 4 , wherein:
 the plate is supported by a set of supports connecting the plate to the one of the two tube sheets; and   a cylindrical member extends from the bottom of the plate towards the other of the two tube sheets to inhibit flow of the vapor around the plate in a direction taken from the one of the two tube sheets to the other of the two tube sheets.   
     
     
         7 . The shell and tube heat exchanger of  claim 1  or  claim 6 , wherein the inner array of the tubes is arranged in a circular pattern having an equal spacing between the tubes. 
     
     
         8 . The shell and tube heat exchanger of  claim 1  or  claim 6 , wherein the inner array of the tubes is arranged in a hexagonal pattern having an equal spacing between the tubes. 
     
     
         9 . The shell and tube heat exchanger of  claim 7 , wherein the outer array of the tubes is arranged in a repeating hexagonal pattern. 
     
     
         10 . The shell and tube heat exchanger of  claim 8 , wherein the outer array of the tubes is arranged in a repeating hexagonal pattern. 
     
     
         11 . A distillation column arrangement for an air separation plant comprising:
 a higher pressure distillation column configured to separate nitrogen from the air and thereby to produce a nitrogen-rich vapor column overhead and a crude liquid oxygen column bottoms;   a lower pressure distillation column configured to further refine the crude liquid oxygen and thereby to produce an oxygen-rich liquid and a lower pressure nitrogen-rich vapor column overhead;   a condenser reboiler for condensing at least part the nitrogen-rich vapor column overhead produced in the higher pressure column and for partially vaporizing an oxygen-rich liquid produced in the lower pressure column;   means for introducing the oxygen-rich liquid within tubes of the condenser reboiler; and   the condenser reboiler comprising;
 two opposed tube sheets; 
 a cylindrical shell connecting the two opposed tube sheets and located within a bottom region of the lower pressure column; 
 a central vapor inlet centrally positioned with respect to a central axis of the shell and connected to an inlet conduit communicating between the central vapor inlet and the higher pressure column to receive a nitrogen-rich vapor stream composed of the nitrogen-rich vapor column overhead and thereby introduce the nitrogen-rich vapor stream into the shell; 
 a central liquid outlet centrally positioned with respect to the central axis of the shell and connected to a piping network having a first conduit connected to the higher pressure column for introducing a reflux stream composed of the part of the nitrogen-rich liquid into the higher pressure column and a second conduit connected to the lower pressure column for introducing another reflux stream composed of another part of the nitrogen-rich liquid into the lower pressure column; 
 the tubes of the condenser reboiler connecting the two opposed tube sheets for indirectly exchanging heat between the oxygen-rich liquid flowing within the tubes and the nitrogen-rich vapor, thereby condensing the nitrogen-rich vapor and producing the nitrogen-rich liquid within the cylindrical shell, at least partially vaporizing the oxygen-rich liquid within the tubes and, at least in part, inducing a flow of the nitrogen-rich vapor in an outward, radial direction toward the shell as a result of the condensation of the nitrogen-rich vapor; 
 the tubes arranged in an inner array of the tubes spaced apart from one another and surrounding the central vapor inlet and the central liquid outlet and an outer array of the tubes surrounding the inner array of the tubes and having a greater number of tubes than the inner array of the tubes; and 
 the inner array of the tubes and the outer array of the tubes spaced apart from one another to present areas between the tubes, the areas of the inner array of the tubes having an average of the areas greater than that of the areas of the tubes of the outer array of the tubes situated directly adjacent the inner array of the tubes to lower pressure drop of the flow of the nitrogen-rich vapor in the outward, radial direction. 
   
     
     
         12 . The distillation column arrangement of  claim 11 , wherein:
 the central vapor inlet is located in one of the two opposed tube sheets; and   the central liquid outlet is located in the other of the two opposed tube sheets;   
     
     
         13 . The distillation column arrangement of  claim 12 , wherein:
 the oxygen-rich liquid is composed of the oxygen-rich liquid column bottoms produced in the lower pressure column; and   the oxygen-rich liquid circulation means comprises:
 the inner array of the tubes and the outer array of the tubes open at opposite ends thereof; 
 the condenser reboiler submerged within the oxygen-rich liquid column bottoms; 
 and the oxygen-rich liquid flowing within the inner array of the tubes and the outer array of the tubes through a thermosiphon effect. 
   
     
     
         14 . The distillation column arrangement of  claim 12 , wherein at least one support located within the shell supports the inner array of the tubes in an intermediate location of the inner array of the tubes between the tube sheets to inhibit vibration within the inner array of the tubes. 
     
     
         15 . The distillation column arrangement of  claim 14 , wherein the at least one support includes:
 a plate having openings through which the inner array of the tubes pass and are thereby supported; and   the plate supported within the shell and tube heat exchanger at the intermediate location and opposite to the central vapor inlet so that the plate also acts as a baffle to also help in inducing the outward, radial flow of the vapor.   
     
     
         16 . The distillation column arrangement of  claim 13 , wherein the plate has a star-like outer periphery having indentations located opposite to innermost tubes of the outer array of the tubes. 
     
     
         17 . The distillation column arrangement of  claim 16 , wherein:
 the plate is supported by a set of supports connecting the plate to the one of the two tube sheets; and   a cylindrical member extends from the bottom of the plate towards the other of the two tube sheets to inhibit flow of the vapor around the plate in a direction taken from the one of the two tube sheets to the other of the two tube sheets.   
     
     
         18 . The distillation column arrangement of  claim 11  or  claim 17 , wherein the inner array of the tubes is arranged in a circular pattern having an equal spacing between the tubes. 
     
     
         19 . The distillation column arrangement of  claim 11  or  claim 17 , wherein the inner array of the tubes is arranged in a hexagonal pattern having an equal spacing between the tubes. 
     
     
         20 . The distillation column arrangement of  claim 18 , wherein the outer array of the tubes is arranged in a repeating hexagonal pattern. 
     
     
         21 . The distillation column arrangement of  claim 19 , wherein the outer array of the tubes is arranged in a repeating hexagonal pattern.