EP0864834B1 - Heat exchanger with dense fluidized bed combined with a reactor with circulating fluidized bed - Google Patents

Abstract

The fluidised bed exchanger has a casing (1) whose longitudinal vertical walls (1A,1B) are formed from tubes which transport a fluid. The tubes are divided lengthways into chambers separated from each other by a low wall (10) of liquid circulating tubes. The longitudinal walls comprise horizontal tubes (11A,11B,12A,12B) and the low wall extends from the inner wall of the casing to a height less than that of the casing. This low wall is made up of superposed, transversal extensions of the tubes (11A,11B) for each of the faces of the longitudinal vertical walls, in the form of hair clips, perpendicular to the tubes and extending upto the opposite longitudinal face.

Description

The present invention relates to a dense fluidized bed exchanger to be associated with a circulating fluidized bed reactor.

It relates more specifically to a dense fluidized bed exchanger comprising a box whose vertical longitudinal walls consist of tubes carrying a heat transfer fluid and divided in the direction of its length in separate chambers from each other by a spill wall constituted a wall consisting of tubes carrying a heat transfer fluid.

US Patent 3893426 describes such an exchanger.

Such an exchanger is generally intended for a combustion plant comprising a circulating fluidized-bed exchanger comprising a gas outlet opening into a separation cyclone whose recovered solids are treated in this dense fluidized bed before being at least partially reinjected into the circulating fluidized-bed exchanger.

• une chambre de réception des solides dans laquelle sont introduits des solides par un orifice,
• au moins une chambre intermédiaire dans laquelle se déversent les solides après leur passage au-dessus d'un premier muret,
• une chambre de sortie des solides recevant les solides après leur passage au-dessus d'un second muret et comportant un orifice d'évacuation des solides.

In a conventional manner, the dense fluidized-bed exchanger comprises in a box a number of chambers:

• a solids reception chamber in which solids are introduced through an orifice,
• at least one intermediate chamber in which the solids discharge after passing over a first wall,
• a solids outlet chamber receiving solids after passing over a second wall and having a solid discharge port.

The intermediate chamber is equipped with a lower fluidization air supply box, fluidization air injection nozzles arranged on the lower wall of the chamber and a heat exchanger generally consisting of a plurality of parallel arrangements of tubes carrying a coolant, for example steam, arranged transversely to the chamber and suspended from the upper wall of the chamber, each tube arrangement being connected in the lower part to an inlet manifold of the heat transfer fluid and in the upper part to an outlet manifold of this heated fluid.

In this chamber there is therefore the dense fluidization of the solids and heat recovery by the exchanger.

It is known to produce the longitudinal walls of the box and the spill walls by means of tubes carrying a heat transfer fluid to increase heat exchange, heat recovery and thus the efficiency of the installation.

Such known walls consist of walls of vertical tubes extending over the entire height of the box and having windows distributed over their width at the desired discharge height.

This spill arrangement does not allow the passage of solids over the entire width of the box and, the windows to be of clean width limited given the continuity of the vertical tubes from the bottom of the wall to the top of it, this The arrangement does not allow continuous and optimal flow of solids from one chamber to another.

The invention solves this problem by proposing a tube wall arrangement which can be achieved over a given height and thus allows a continuous and undisturbed discharge of the solids above the wall.

To do this, according to the invention, said vertical longitudinal faces consist of horizontal tubes and said wall consists of transverse and superimposed extensions of tubes of each of the vertical longitudinal faces, in the form of a hairpin, perpendicular to said tubes and extending to the opposite vertical longitudinal face.

It is thus possible to make a low wall of desired height.

According to the preferred embodiment, these extensions are vertically alternating from one face to the other, to allow mechanical stability and flow balancing of the heat transfer fluid.

In order to achieve the hydrostatic behavior, preferably, the wall consisting of a double cased wall is internally reinforced with spacers.

According to a preferred embodiment, one tube out of two of each vertical wall comprises such an extension directed towards the other wall and between two such extensions, is intercalated an extension of the other wall which is on the same horizontal plane as the tube of the other wall having no extension.

Advantageously, the upper part of the wall is shaped as a bevel of reducing section.

The invention is described below in more detail with the aid of figures representing only a preferred embodiment of the invention.

The figure 1 is a schematic perspective view of a dense fluidized bed exchanger box.

The figure 2 is a perspective view of detail of an exchanger according to the invention.

The figure 3 is a partial sectional view along II-II of the figure 2 .

The figure 4 is a partial perspective view, partially broken away, of an exchanger according to the invention.

• une chambre de réception 2 des solides dans laquelle sont introduits des solides par un orifice 3,
• au moins une chambre 4, 5 dans laquelle se déversent les solides après leur passage au-dessus d'un premier muret 10A et séparées l'une de l'autre par un muret du même type 10B,
• une chambre de sortie 6 des solides recevant les solides après leur passage au-dessus d'un autre muret 10C et comportant un orifice 7 d'évacuation des solides.

In a conventional manner, a dense fluidized bed exchanger schematized on the figure 1 has in a box 1 a number of rooms:

• a solids reception chamber 2 in which solids are introduced through an orifice 3,
• at least one chamber 4, 5 in which the solids discharge after passing over a first wall 10A and separated from each other by a wall of the same type 10B,
• an outlet chamber 6 solids receiving solids after passing over another wall 10C and having a 7 solid evacuation port.

As visible on the figure 2 according to the invention, the vertical longitudinal walls 1A, 1B consist of horizontal tubes 11A, 12A and 11B, 12B.

The wall 10 consists of transverse and superposed extensions of tubes 11A, 11B of each of the vertical longitudinal walls 1A, 1B, in the form of a hairpin, perpendicular to said tubes and extending to the opposite vertical longitudinal face 1B, 1A.

More specifically, a tube on two 11A, 11B of each vertical wall 1A, 1B has such an extension directed towards the other wall 1B, 1A. Between two such extensions, is intercalated an extension of the other wall 1B, 1A which is on the same horizontal plane as the tube 12A, 12B of the other wall 1A, 1B having no extension.

The upper part of the wall 10 is shaped as a bevel of reducing section.

It is thus realized a constant pitch between tubes, whether on the vertical walls or on the wall and this without intersecting tubes.

Conventionally, metal fins close the walls of tubes thus formed connecting all the adjacent tubes and the wall is covered externally with a layer of concrete 13 ( figures 3 ).

The holding of this tube structure is mechanically reinforced by spacers arranged inside the wall.

The upper part of the wall 10 is visible on the figure 3 in cross section.

A high spacer 14 is shown on the figure 3 . It is a bar welded between the two branches of the hairpin of an extension. Such spacers 14 are distributed over the height of the upper part and on the width of the wall, to obtain the desired mechanical stability.

In the lower part of the wall 10, as visible on the figure 4 spacers spread over the width of the wall provide mechanical stability and the connection to the bottom wall of the box.

This bottom wall called hearth also consists of horizontal tubes and, more specifically, an upper wall 15 consisting of tubes connected by horizontal fins. To each tube of this wall and below this, is connected another tube 16 by a vertical vane 17. Two tie rods 18 arranged at the right of the wall and longitudinally thereto, are welded to the floor, passing through the vertical fins 17. Connected to these tie rods 18, are placed spacers 19 of a maximum height equal to the height of the constant section portion of the wall and consist of a plate or equivalent having laterally notches receiving the tubes of extensions.

Claims (5)

1. Dense fluidized-bed heat exchanger comprising a box (1), the vertical longitudinal walls (1A, 1B) of which are formed by tubes conveying a heat-transfer fluid, said box being divided along its length direction into chambers separated from one another by an overflow divider (10) consisting of a wall formed from tubes conveying a heat-transfer fluid, characterized in that said vertical longitudinal walls (1A, 1B) are formed from horizontal tubes (11A, 11B, 12A, 12B) and said divider extends from the bottom wall of the box (1) up to a height below that of said box and is formed from superposed transverse extensions of tubes (11A, 11B) of each of the vertical longitudinal faces (1A, 1B), in hairpin form, which are perpendicular to said tubes and extend as far as the opposite vertical longitudinal faces (1B, 1A).
2. Dense fluidized-bed heat exchanger according to Claim 1, characterized in that these extensions alternate vertically from one face to the other.
3. Dense fluidized-bed heat exchanger according to either of the preceding claims, characterized in that the divider formed from a tubed double wall is internally reinforced by braces (14, 19).
4. Dense fluidized-bed heat exchanger according to Claim 2, characterized in that every other tube (11A, 11B) of each vertical wall (1A, 1B) has such an extension directed towards the other wall (1B, 1A) and in that inserted between two such extensions is an extension of the other wall (1B, 1A) that lies in the same horizontal plane as the tube (12A, 12B) of the other wall (1A, 1B) that does not include an extension.
5. Heat exchanger according to one of the preceding claims, characterized in that the top of the divider is bevelled so as to have a decreasing cross section.

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