GB1577896A

GB1577896A - Heat exchanger

Info

Publication number: GB1577896A
Application number: GB828977A
Authority: GB
Original assignee: CF Braun and Co
Current assignee: CF Braun and Co
Priority date: 1977-02-28
Filing date: 1977-02-28
Publication date: 1980-10-29

Description

(54) HEAT EXCHANGER (71) We, C.F. BRAUN & CO., a corporation organised according to the laws of the State of Delaware, of 1000 South Fremont Avenue, Alhambra, California 91802, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a heat exchanger.

The present invention provides a heat exchanger comprising an elongate outer shell, a shroud extending longitudinally within, and being spaced from the shell, a bundle of heat exchange tubes within the shroud, the shell having at one end an inlet nozzle, the shroud extending within, and being spaced from the nozzle and being sealingly attached to the mouth of the nozzle so that any fluid entering the nozzle, in use, passes into the interior of the shroud, and the shell having an outlet nozzle at the said one end which is in communication with the space between the shroud and the shell, the exchanger further comprising a tube plate at the other end of the shell the space between the shroud and the shell communicating, near the plate, with the interior of the shroud so that fluid flowing, in use, from the interior of the shroud to the said space passes across the plate.

This construction ensures that the temperature differential across the tube plate is substantially reduced and that the shell (including the inlet nozzle) is subjected to a relatively uniform temperature along its length.

By passing hot gas through the inlet nozzle and into the shroud and cold water through the tubes the exchanger can be used not only to cool the gas but also as a steam generator.

A heat exchanger constructed in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a partially sectioned side view of the heat exchanger.

Figure 2 is a top view, in partial section, of the heat exchanger shown in Figure 1.

Figure 3 is a section view taken along lines 3-3 of Figure 2.

Figure 4 is a sectional view taken along lines 44 of Figure 2.

Referring to the accompanying drawings and first to Figure 1, a shell and tube type heat exchanger having an outer shell 2, has at one end an inlet nozzle 4 through which the incoming, hot gases are passed. In a typical ammonia synthesis process, hot gases at temperatures of from 700O to 1200do may be generated in the catalyst bed, and the effluent gas temperature from modern design synthesis converters generally ranges from 800 F to 1,000 F. Concentrically spaced within the shell and attached to the mouth of the inlet nozzle 4 is a shroud 6, which extends longitudinally inside the shell between the heat exchange tubes 1 0 and the shell 2 to form an annular passage 12.The passage so formed by the shell and the shroud is sealed from the incoming gas by seal 14 which sealingly connects the shroud and the inlet nozzle. Thus, the hot gas from inlet nozzle 4 passes into the interior of the shroud containing heat exchange tubes 10. For clarity of illustration, only one heat exchange tube is shown, but of course the usual bundle of tubes is used. The tubes pass through a tube plate 16, which in turn abuts a spherical channel generally designated 18. The advantages of such a channel, especially when the heat exchanger is used for high pressure service, are full described in our United States Patent 2,919,906. The fluid which passes into the tubes enters through inlet 20, flows through the tubes and back to the channel and exits from the heat exchanger via outlet 22. Pass partition 24 separates the incoming fluid from the outgoing fluid.Removable panel 26 provides access to inlet 20 and a removable enclosure assembly 28 'pm- vides access to the interior of the spherical channel and facilities maintenance or repair. It will be understood that various other designs for the inlet and outlet of fluid to the tubes may be used.

Tube plate 16 is integrally connected with shell 2 by weld seam 30. The connection be tween the tube plate 16 and the shell 2 is leak proof so that the gas being passed, through the shell cannot escape at that end of the heat exchanger and is thus forced to flow in a direc tion counter-current to the direction of the in coming gas along annular passage 12 and finally through exit nozzle 34. Additional weld seam 36 connects the main body of shell 2 to the end portion containing gas inlet and outlet nozzles 4 and 34 respectively. Shroud 6 is supported and centered along annular passage 12 by shroud guides 40, while the heat exchanger itself stands on supports 42.

The hot gas, after passing through inlet nozzle 4, flows first through baffles 44 and 46 which contain a plurality oflloles to permit the gas to pass tllerethrough, but prevents damage to tubes due to direct impingeiuent. As can be seen best in figures 2 and 3, the gas then passes arotllld inipingemcIit baffle 48 which is supported by cross bars 50 and 52, and then in a geocrally longitudinal direction past baffles 54 placed at intervals along the length of the heat cxcllange tubes. Tulle tube plate end of shroud 6 is stopped short of tlie tube plate to allow for greater longitudinal growth of the shroud than the shell uiider operatiug conditions.

It should be notcd, as call best be seen in figures I and 2, that tlic shroud 6 is cut back from tlic tube plate 16 to create outlet ports 58. This permits the cooled gas, after having passed along the length of the heat exchanger tubes, to flow along back side 16a of the tube plate 16.By passing the hot gas into the heat exchanger at the end remote from the tube plate the gas must pass along the entire length of the heat exchanger tubing, with a resultant drop in tenlpelature, before contacting the tube plate. The temperature difference across the two faces of the tube plate is thus reduced.

After passing tile length of the tube, the cooled gas then flows through ports in the shroud and through annular passage 12 and outlet nozzle 34. As best seen in figure 4, the cylindrical shroud 6 is supported at the inlet end and properly positioned within shell 2 by shroud guides 40.

The cooled gas, after being passed along the heat exchange tubing, will have a resultant tem- perature drop of several hundred degrees depending upon the efficiency of the system.

Typically, hot ammonia gas entering at about 900"F will exit at about 635 F. Thus, by passing the cooled gas along or across tlie back face of the tube plate, the temperature differential is substantially reduced since the temperature of the incoming water is typically about 595 to 6000 F. By the same token, the shell is contacted only by the cooled gas and coiisequently instead of being subjected to temperatures ranging from 953 F at the gas inlet end to 6500F at the tube plate end is subjected to a relatively uniform temperature of about 650"F along its entire length.

Further, cooled gas can pass into the space between the shroud 6 and the inlet nozzle 4 so that the nozzle too is kept relatively cool.

The invention having been particularly shown and described with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in forms and details may be made therein, without departing from the scope of the invention. Although the heat exchanger has been described with specific reference to heat exchange of ammonia gas, it is to be understood that it is intended for use in other environments and in the heat exchange of liquids as well as gases.

WHAT WE CLAIM IS: 1. A heat exchanger comprising an elongate outer shell, a shroud extending longitudinally within, and being spaced from the shell, a bundle of heat exchange tubes within the shroud, the shell having at one end an inlet nozzle, the shroud extending within, and being spaced from the nozzle and being sealingly attached to the mouth of the nozzle so that any fluid entering the nozzle, in use, passes into the interior of the shroud, and the shell having an outlet nozzle at tlie said one end which is in comlnunication with the space between the shroud and the shell, the exchanger further comprising a tube plate at the other end of the shell the space between the shroud and the shell communicating, near the plate, with the interior of hue shroud so that fluid flowing, in use, from the interior of the shroud to the said space passes across the plate.

2. A heat exchanger as claimed in claim 1, wherein each of the shroud and shell converges towards tlie inlet nozzle.

3. A heat exchanger substantially as hereinbefore described with reference to, and as illustrated by tlic accompanying drawings.

4. A process of cooling a fluid using the heat exchanger as claimed in any one of claims 1 to 3, the process comprising passing the fluid through the inlet nozzle and collecting it at the outlet nozzle and passing cooling fluid through the tubes.

5. The process of claim 4, wherein the fluid to be cooled is a mixture of synthesis gas and ammonia from an ammonia synthesis process at a temperature from about 700"F to 10000F and is cooled to a temperature from about 500"F to 700"F.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

tween the tube plate 16 and the shell 2 is leak proof so that the gas being passed, through the shell cannot escape at that end of the heat exchanger and is thus forced to flow in a direc tion counter-current to the direction of the in coming gas along annular passage 12 and finally through exit nozzle 34. Additional weld seam

36 connects the main body of shell 2 to the end portion containing gas inlet and outlet nozzles 4 and 34 respectively. Shroud 6 is supported and centered along annular passage 12 by shroud guides 40, while the heat exchanger itself stands on supports 42.

The hot gas, after passing through inlet nozzle 4, flows first through baffles 44 and 46 which contain a plurality oflloles to permit the gas to pass tllerethrough, but prevents damage to tubes due to direct impingeiuent. As can be seen best in figures 2 and 3, the gas then passes arotllld inipingemcIit baffle 48 which is supported by cross bars 50 and 52, and then in a geocrally longitudinal direction past baffles 54 placed at intervals along the length of the heat cxcllange tubes. Tulle tube plate end of shroud 6 is stopped short of tlie tube plate to allow for greater longitudinal growth of the shroud than the shell uiider operatiug conditions.

It should be notcd, as call best be seen in figures I and 2, that tlic shroud 6 is cut back from tlic tube plate 16 to create outlet ports 58. This permits the cooled gas, after having passed along the length of the heat exchanger tubes, to flow along back side 16a of the tube plate 16.By passing the hot gas into the heat exchanger at the end remote from the tube plate the gas must pass along the entire length of the heat exchanger tubing, with a resultant drop in tenlpelature, before contacting the tube plate. The temperature difference across the two faces of the tube plate is thus reduced.

After passing tile length of the tube, the cooled gas then flows through ports in the shroud and through annular passage 12 and outlet nozzle 34. As best seen in figure 4, the cylindrical shroud 6 is supported at the inlet end and properly positioned within shell 2 by shroud guides 40.

The cooled gas, after being passed along the heat exchange tubing, will have a resultant tem- perature drop of several hundred degrees depending upon the efficiency of the system.

Typically, hot ammonia gas entering at about 900"F will exit at about 635 F. Thus, by passing the cooled gas along or across tlie back face of the tube plate, the temperature differential is substantially reduced since the temperature of the incoming water is typically about 595 to 6000 F. By the same token, the shell is contacted only by the cooled gas and coiisequently instead of being subjected to temperatures ranging from 953 F at the gas inlet end to 6500F at the tube plate end is subjected to a relatively uniform temperature of about 650"F along its entire length.

Further, cooled gas can pass into the space between the shroud 6 and the inlet nozzle 4 so that the nozzle too is kept relatively cool.

The invention having been particularly shown and described with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in forms and details may be made therein, without departing from the scope of the invention. Although the heat exchanger has been described with specific reference to heat exchange of ammonia gas, it is to be understood that it is intended for use in other environments and in the heat exchange of liquids as well as gases.

WHAT WE CLAIM IS: 1. A heat exchanger comprising an elongate outer shell, a shroud extending longitudinally within, and being spaced from the shell, a bundle of heat exchange tubes within the shroud, the shell having at one end an inlet nozzle, the shroud extending within, and being spaced from the nozzle and being sealingly attached to the mouth of the nozzle so that any fluid entering the nozzle, in use, passes into the interior of the shroud, and the shell having an outlet nozzle at tlie said one end which is in comlnunication with the space between the shroud and the shell, the exchanger further comprising a tube plate at the other end of the shell the space between the shroud and the shell communicating, near the plate, with the interior of hue shroud so that fluid flowing, in use, from the interior of the shroud to the said space passes across the plate.
2. A heat exchanger as claimed in claim 1, wherein each of the shroud and shell converges towards tlie inlet nozzle.
3. A heat exchanger substantially as hereinbefore described with reference to, and as illustrated by tlic accompanying drawings.
4. A process of cooling a fluid using the heat exchanger as claimed in any one of claims 1 to 3, the process comprising passing the fluid through the inlet nozzle and collecting it at the outlet nozzle and passing cooling fluid through the tubes.
5. The process of claim 4, wherein the fluid to be cooled is a mixture of synthesis gas and ammonia from an ammonia synthesis process at a temperature from about 700"F to 10000F and is cooled to a temperature from about 500"F to 700"F.