Shell and tube heat exchanger

Patent metadata

Field	Value
Publication number	US-11828542-B2
Application number	US-201916975383-A
Country	US
Kind code	B2
Filing date	Mar 7, 2019
Priority date	Mar 22, 2018
Publication date	Nov 28, 2023
Grant date	Nov 28, 2023

Abstract

A shell and tube apparatus (1) includes an outer shell (2); a first tube bundle (3) and a second tube bundle (4) coaxial with each other; a first inner shell (5) and a second inner shell (6); the first inner shell surrounds the first tube bundle and is arranged between the two tube bundles; the second inner shell surrounds the second tube bundle and is arranged in the space between the second tube bundle and the outer shell (2); the first tube bundle (3) operates as a preheater; the second tube bundle (4) operates as a boiler; the coaxial inner shells (5, 6) define a counterflow path for a hot fluid which passes through the shell side.

First claim

What is claimed is:

1. A shell and tube heat exchanger apparatus comprising:
an outer shell, a first tube bundle and a second tube bundle coaxial with each other, wherein:
the tubes of said first tube bundle are straight;
said second tube bundle is arranged externally around the first tube bundle, and the tubes of said second bundle are U tubes comprising straight sections and straight return sections which are parallel to the tubes of the first bundle;
the apparatus comprises a first inner shell and a second inner shell,
said first inner shell surrounds said first tube bundle and is arranged between said first tube bundle and said second tube bundle;
said second inner shell surrounds said second tube bundle and is arranged between said second tube bundle and said outer shell;
said first and second tube bundles form a single tube side of the apparatus, which is passed through by a fluid;
the apparatus comprises first inlet and outlet interfaces for a first fluid circulating in the shell side on the outside of the tubes of said first and second tube bundles, and second inlet and outlet interfaces for a second fluid circulating in said tube side;
the apparatus is configured such that:
the first fluid flows along the shell side passing in sequence through a first space enclosed by the first inner shell and a second space defined between the first inner shell and the second inner shell;
the second fluid flows along the tube side passing, in sequence, first through the second tube bundle and then through the first tube bundle;
said shell and tube heat exchanger apparatus comprising a plurality of chambers for collecting and distributing the second fluid;
wherein said plurality of chambers comprises:
a first chamber which receives the second fluid entering the apparatus and which communicates directly with an inlet side of the second tube bundle;
a second chamber which is arranged to receive the fluid flowing out from the second tube bundle and which communicates directly with an inlet side of the first tube bundle;
a third intermediate chamber which communicates directly with an outlet side of the first tube bundle, collecting an at least partially evaporated flow from said first tube bundle,
wherein the third chamber is situated underneath the second chamber and said second chamber and third chamber are divided by a baffle and communicate via a vertical riser tube, so that the effluent of the first tube bundle passes from the third chamber to the second chamber via said riser tube.

2. The apparatus according to claim 1 , wherein at least one of the first inner shell and the second inner shell comprises a plurality of longitudinal sections.

3. The apparatus according to claim 1 , wherein at least one of the first inner shell and the second inner shell cooperates structurally with at least one tube bundle, resting against at least one baffle of said tube bundle.

4. The apparatus according to claim 1 , comprising an inlet for said first fluid communicating with the space defined by the first inner shell inside which the first tube bundle is housed, and said first inner shell comprises passages able to distribute said first fluid in the interspace between the first and second inner shells, the second tube bundle being housed in this interspace such that the first fluid runs over the first tube bundle and the second tube bundle in sequence.

5. The apparatus according to claim 1 , wherein the first tube bundle and the second tube bundle operate respectively as boiler and as preheater of the second fluid, the second fluid flowing out from the first tube bundle at least partially evaporated.

6. The apparatus according to claim 5 , arranged so as to:
distribute said second fluid, entering the apparatus, into said second tube bundle;
collect the second fluid flowing out from the second tube bundle and distribute it in the first tube bundle;
collect the at least partially evaporated fluid flowing out from the second tube bundle;
separate the steam phase from the liquid phase in said outgoing fluid;
reintroduce the liquid phase inside the second tube bundle.

7. The apparatus according to claim 1 , wherein said riser tube terminates with an end inside the second chamber and said end is situated above the inlet of the first tube bundle, said second chamber thus being able to operate as a gravity separator of the liquid phase and the steam phase contained in the fluid flowing out from the first tube bundle.

8. The apparatus according to claim 7 , comprising a first tube plate and a second tube plate, the third intermediate chamber being defined between said two tube plates, and the second tube plate further forming the bottom of the second chamber.

9. The apparatus according to claim 8 , wherein the tubes of the first tube bundle are bayonet tubes, each of the bayonet tubes comprising a respective tube fixed to said second tube plate and a respective return tube which is coaxial with and on the outside of the tube, the return tube being fixed to the first tube plate, each bayonet tube having an inlet of the tube which is open towards the second chamber and an outlet of the return tube which is open towards the third intermediate chamber.

10. The apparatus according to claim 8 , wherein the tubes of the second tube bundle are U tubes fixed to an outer ring region of said first tube plate.

11. The apparatus according to claim 1 , wherein:
the apparatus is vertical, the bottom part of the apparatus houses the two coaxial tube bundles, the top part of the apparatus houses the second chamber operating as a steam collection chamber.

12. The apparatus according to claim 11 , characterized by natural circulation between the first tube bundle, the intermediate chamber, the riser tube and the second chamber.

13. A method for revamping a chemical plant, in particular a plant for ammonia synthesis, in which:
the plant to be revamped comprises a water preheater and a steam generator which use the heat of a process gas as heat source,
the method is characterized by replacing both said preheater and said steam generator with a single new apparatus according to claim 1 .

14. The method according to claim 13 , comprising:
redirecting said process gas to a hot gas inlet of said apparatus and redirecting a flow of water, initially directed to said preheater, to a water inlet of said apparatus.

Assignees

• Casale Sa

Inventors

• Caselli Cristiano
• Redaelli Luca

Classifications

• F28D7/12 Primary

  the surrounding tube being closed at one end, e.g. return type (F28D7/14 takes precedence) · CPC title

• F28D7/06

  the conduits having a single U-bend (F28D7/10 takes precedence){(F28D7/0016 and F28D7/0033 take precedence)} · CPC title

• F28D7/0075

  with particular circuits for the same heat exchange medium, e.g. with the same heat exchange medium flowing through sections having different heat exchange capacities or for heating or cooling the same heat exchange medium at different temperatures · CPC title

• F28D7/0091

  the supplementary medium flowing in series through the units · CPC title

• F28D7/1676

  with particular pattern of flow of the heat exchange media, e.g. change of flow direction · CPC title