Tube heat exchange unit for internals of heat exchangers reactors

Abstract

Tube-bundle heat exchange unit (1) for internals of heat exchangers or reactors, comprising: at least one tube bundle (2); a plurality of baffles (3) associated with said tube bundle and defining through-openings according to a predefined arrangement, each opening being passed through by one of more tubes of the tube bundle, and a shell (6) which surrounds said tube bundle and said baffles, wherein the assembly of the tube bundle and the shell can be disassembled and the shell is structurally collaborating with the tube bundle through said baffles.

Description

FIELD OF APPLICATION[0001]The invention relates to tube heat exchange units for internals of heat exchangers or reactors, in particular reactors for the chemical or petrochemical industry. A preferred application of the invention consists in gas-to-gas exchangers for internals of catalytic reactors, such as intercooled multi-bed reactors. The invention also applies in general to tubular apparatus, such as heat exchangers or reactors, comprising an outer shell suitable for withstanding a predefined operating pressure and a second inner shell which surrounds a tube bundle.PRIOR ART[0002]The need to install tube-bundle heat exchange units inside chemical reactors, heat exchangers or other apparatus is known. Notable examples are multi-bed reactors containing one or more intermediate gas-to-gas heat exchangers between the beds, such as the reactor described in EP 0 376 000.[0003]Heat exchanger units designed for the internals of reactors or other apparatus have their own shell, which is...

AI Technical Summary

Benefits of technology

The invention allows for a more efficient and cost-effective assembly of tubes and baffles in a bundle. By using a new assembly technique, baffles are allowed to move freely in the axial direction relative to the tubes, making the insertion of tubes easier. The baffles are then locked in position after assembly, reducing assembly time and difficulties. The technical benefits include simplifying the assembly process, improving efficiency, and reducing costs.

Problems solved by technology

As a consequence, the pressure inside the shell is lower than the pressure acting on the outer surface, owing to the pressure losses of the fluid stream.

As it is known, the stress imparted on a cylindrical body being subjected to an outer pressure may induce instability and the breakdown of the cylindrical body even with relatively low pressures.

For this reason, in any case the wall of the inner shell must have such a thickness that increases its weight and cost.

This technique has a number of problems and drawbacks, which have not been overcome so far.

A first problem is given by the bypass of the tube bundle on behalf of the fluid crossing the shell side.

This effect is due to the presence of an area between the shell and the tube bundle which is not occupied by the tubes (bypass areas) and cannot be eliminated.

The framework supporting the baffles is a heavy and costly structure, and results in the loss of useful volume for the tubes.

Moreover, the tube assembly is difficult, as well known.

Tubes should pass through the openings of the baffles with a quite precise fit, otherwise the baffles would be unable to prevent vibrations of the tubes.

Applicable norms stipulate a very small amount of play (practically zero play) between tubes and baffles and often the tubes must be forced inside the tube bundle, resulting in a long assembly time and the risk of damage.

In these embodiments, however, the tube bundle is not extractable and not demountable, resulting in a significant drawback.

Non-demountable tube bundle makes maintenance operation more complex.

Moreover, owing to presence of welded baffles, tubes are necessarily inserted after the assembly of the baffles with the shell, involving great difficulties.

Hence, said alternative embodiments have not gained great success.

For example, in multi-bed reactors, the gas exiting the shell side must be generally fed to a subsequent catalytic bed, and the heat exchanger unit should be preferably designed so as to house the gas outlet at the feeding point of the bed, otherwise a dedicated tube or manifold is required in order to re-direct the gas, resulting in a number of drawbacks such as greater complication, greater dimensions, pressure losses.

There is also the problem connected with the reduction of the dimensions.

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