EP0787946B1 - External fluidized bed for equipping a circulating fluidized bed furnace - Google Patents

Description

The present invention relates to a fluidized bed external intended to equip a circulating fluidized bed hearth.

It relates more precisely to a dense fluidized bed comprising in a box a chamber in which is pour solids and equipped with a lower box fluidization air supply, injection nozzles fluidizing air disposed on its lower wall and a heat exchanger made up of a plurality parallel arrangements of tubes conveying a fluid coolant hanging from the upper wall of the chamber, each arrangement of tubes being connected to a heat transfer fluid inlet manifold consisting of a tube placed longitudinally in the box and in the upper part, inside the chamber to an outlet manifold of this heated fluid constituted a tube arranged longitudinally in the box and equipped with at least one outlet pipe for the heated heat transfer fluid passing through a wall of the chamber.

Such a fluidized bed is known from document US-A-3983927. In this document, the heat exchanger tubes are arranged vertically with bent returns at the top and bottom, and the inlet and outlet manifolds outlet are located parallel in the upper part inside the chamber.

The present invention provides an arrangement for operating in natural circulation and offering great ease of assembly and disassembly during repair operations.

The present invention consists into a bed of compact shape and the manufacture and repairs are particularly easy and quick.

To do this, according to the invention, said parallel tube arrangements are arranged transversely in the bedroom, the inlet manifold being housed, at the bottom, in the bottom wall of the chamber.

According to the preferred embodiment of the invention, the outlet manifold is arranged under the upper wall of the chamber and said tubing passes through this wall superior.

Preferably, the two collectors are arranged in the longitudinal central plane of the chamber.

Advantageously, all the tubes of each arrangement of tube are of substantially identical length.

Preferably, the inlet manifold is housed in a slot made in the lower wall of the chamber and coated with sand.

Advantageously, a supply line for heat transfer fluid passes through the fluidization box and is connected to the input manifold.

The invention also relates to an installation for combustion comprising a circulating fluidized bed hearth comprising a gas outlet opening into a cyclone of separation whose recovered solids are treated in a external fluidized bed as specified above.

The invention is described below in more detail at using figures representing only one embodiment preferred of the invention.

Figure 1 is a perspective view of a bed according to the invention, its wall being partially torn off.

Figure 2 is a cross-sectional view of this bed.

• une chambre de réception des solides 11 dans laquelle sont introduits des solides par un orifice 12,
• une chambre 2 dans laquelle se déversent les solides après leur passage au-dessus d'un premier muret 13,
• une chambre de sortie 15 des solides partiellement représentée sur la figure 1, recevant les solides après leur passage au-dessus d'un second muret 14 et comportant un orifice d'évacuation des solides non visible sur la figure.

The dense fluidized bed comprises, in a box 1 consisting of a metal sheet 20 reinforced with stiffeners and a layer of internal concrete 21, three chambers:

• a solid receiving chamber 11 into which solids are introduced through an orifice 12,
• a chamber 2 into which the solids are poured after their passage over a first low wall 13,
• an outlet chamber 15 for the solids partially shown in FIG. 1, receiving the solids after their passage over a second wall 14 and comprising a solids evacuation orifice not visible in the figure.

Bedroom 2 is equipped with a lower box fluidizing air supply 3, nozzles 4 of fluidization air injection arranged on the wall lower 2A of the chamber 2 and of a heat exchanger 5 consisting of a plurality of parallel arrangements of tubes conveying a heat transfer fluid, for example steam, arranged transversely to chamber 2 and suspended from the upper wall 2B of chamber 2, each arrangement of tubes being connected at the bottom to an inlet manifold heat transfer fluid 6 consisting of a tube arranged longitudinally to the casing 1 and in the upper part to a outlet manifold of this heated fluid 7 consisting of a tube placed longitudinally in the box 1.

In this chamber 2 therefore takes place the dense fluidization solids and heat recovery by the exchanger 5.

Such a bed is generally intended for an installation combustion system comprising a circulating fluidized bed hearth comprising a gas outlet opening into a cyclone of separation whose recovered solids are treated in this external fluidized bed before being at least partially reinjected into the circulating fluidized bed hearth.

The inlet manifold 6 is housed in the wall lower 2A of chamber 2 and arranged in the plane central of bedroom 2. More specifically, it is housed in a slot 9 made in the bottom wall 2A of the chamber 2 and coated with sand or concrete 16, which ensures its fixation and its protection. A supply line in heat transfer fluid 10 passes through the fluidization box 3 and is connected to the inlet manifold 6 by a connector You.

To this input collector 6, the arrangements of heat exchange tubes which are so classic essentially horizontal and hairpin hair and extend to the height of the walls 13, 14. The fixtures are hung in pairs on the wall upper 2B of chamber 2 by two supporting tubes vertical 17, 18 which are connected to the inlet manifold 6, pass through the upper wall 2B and return via return sections 17A, 18A connect to the manifold outlet 7 to which the tubes of the connection arrangements are connected tubes. Advantageously, these support tubes 17, 18 can be of the type described in patent document FR-2 622 963 and be joined to the horizontal sections by connecting parts providing both support mechanical and hydraulic connection, support tubes constituting an extension of one of the pin tubes to hair. The horizontal hairpin tubes are all the same length which eliminates any tension _differential in the support tubes 17, 18.

The concrete collector outlet 7 is arranged inside bedroom 2, in the central plane longitudinal of chamber 2 and more precisely under the upper wall 2B of chamber 2 and is equipped with at least an outlet pipe for the heated heat transfer fluid 8 passing through this upper wall 2B and connected to the outlet manifold 7 by a tee fitting ensuring also the suspension of the outlet manifold 7 on the wall upper 2B.

Several sets of collectors and fittings tubes as previously described can be installed in chamber 2, aligned in the longitudinal direction of it.

Such a bed allows a particularly manufacturing improved, which reduces manufacturing and assembly on site.

Indeed, the box 1 without its upper wall can be made in a first set, like an open box. The upper wall with collectors 7, 6 and the suspended tube arrangements 5 can be prefabricated in a second set, in the workshop or on site. It is enough during the final assembly, introduce the second from above set in the first set, the input manifold 6 being installed in the slot 9, placed on the metal sheet 20 then coated with sand or concrete.

The complete disassembly of the device is carried out by destruction of any concrete 16 and removal from above of the second set.

The sanding of the inlet manifold 6 facilitates disassembly of the latter and any intervention on this one.

In the event of a leak and necessary repair, a partial disassembly is carried out by cutting off the pair damaged tube arrangements and the support tubes 17, 18 correspondents just above and just below the pair of tube arrangements and translating this pair of arrangements in the box up or down in order to carry out the repair on the tube arrangements cleared.

In the upper part, disassembly requires less space than in known beds and it is thus possible to make a bed with less height and size.

Thanks to this new design of the bed, the exchange thermal takes place as soon as the fluid leaves the collector inlet 6 in the exchange tube arrangements thermal 5, all of these arrangements being inside from bedroom 2.

Claims (7)

1. Dense fluidized bed comprising in a vessel (1) a chamber (2) into which solids are tipped and provided with a fluidization air feed box (3) at the bottom, fluidization air injector nozzles (4) disposed on its bottom wall (2A) and a heat exchanger (5) made up of a plurality of parallel tube arrangements conveying a heat exchange fluid suspended from the top wall (2B) of the chamber (2), each tube arrangement being connected to a heat exchange fluid inlet manifold (6) in the form of a tube disposed longitudinally to the vessel (1) and at the top, inside the chamber (2), to a heated fluid outlet manifold (17) in the form of a tube disposed longitudinally to the vessel (1) and provided with at least one heated heat exchange fluid outlet pipe (8) passing through a wall of the chamber (2), characterized in that said parallel tube arrangements are disposed transversely to the chamber (2), the inlet manifold (6) being housed at the bottom in the bottom wall (2A) of the chamber.
2. Bed according to claim 1, characterized in that the outlet manifold (7) is disposed under the top wall (2B) of the chamber (2) and said pipe (8) passes through said top wall (2B).
3. Bed according to either of the preceding claims, characterized in that the two manifolds (6, 7) are disposed in the longitudinal central plane of the chamber (2).
4. Bed according to claim 3, characterized in that all the tubes of each tube arrangement are of substantially the same length.
5. Bed according to any one of the preceding claims, characterized in that the inlet manifold (6) is housed in a slot (9) in the bottom wall (2A) of the chamber (2) and covered with sand.
6. Bed according to any one of the preceding claims, characterized in that a heat exchange fluid feed pipe (10) passes through the fluidization box (3) and is connected to the inlet manifold (6).
7. Combustion installation comprising a circulating fluidized bed furnace having a gas outlet feeding into a separator cyclone, the recovered solids from which are treated in an external fluidized bed according to any one of the preceding claims.

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