EP0129486B1 - Compact boiler with fluidized bed - Google Patents

Abstract

A boiler comprising a fluidized bed combustion chamber which communicates with an exchange enclosure containing water tubes heated by the combustion tubes and within which is arranged an exchange and dust removal chamber equipped with water tubes and containing a vertical internal partition dividing it into two half chambers communicating with one another. One of these half chambers communicates with the upstream part of the enclosure through an inlet orifice situated at the top part and constrains the fumes to follow a descending path along the partition, while the other communicates with the downstream part of the enclosure through an outlet orifice situated at the top part and constrains the fumes to follow an ascending path.

Description

The present invention relates to a boiler comprising a fuel combustion chamber with a fluidized bed which communicates with an exchange enclosure containing water tubes heated by combustion fumes and within which is an exchange chamber and dedusting system which is equipped with water tubes and contains a vertical internal partition dividing it into two half-chambers communicating with each other and at their lower part and one of which communicates with the upstream part of the enclosure by an inlet orifice located in the upper part and constrains the flue gases to carry out a descending path and the other of which communicates with the downstream part of the enclosure by an outlet orifice situated in the upper part and constrains the fumes to effect a ascending route. Such a boiler is known from EP-A-0005965.

Fluidized bed boilers include a combustion chamber where the fuel is introduced and suspended, by an ascending stream of combustion air entraining a more or less significant part of ash which it is interesting to recycle to facilitate the adjustment of the bed temperature and / or to ensure perfect combustion. The ash recovery is generally carried out before the exchange beam by convection in order to protect the latter from erosion phenomena. In this case, ash collection is usually ensured by dust removal equipment not integrated into the boiler. The design of these boilers is bulky and leads to the use of relatively long ducts.

The present invention aims to provide a fluidized bed boiler with an integrated dedusting system providing a reduction in the size and length of the ducts and a particularly effective dedusting.

This object is achieved, according to the invention, by the fact that the inlet orifice is located laterally with respect to the interior partition and faces a perpendicular wall of the chamber so that the fumes enter substantially parallel to said partition and are stopped by said wall so as to change direction and be dusted.

According to another characteristic, the exchange and dedusting chamber includes a hopper at the lower part.

• La figure 1 est une vue générale, en coupe verticale, de la chaudière.
• La figure 2 représente schématiquement, en perspective, la chambre d'échange et de dépoussiérage faisant partie de la chaudière.

The invention will now be described in more detail with reference to an embodiment given by way of example and represented by the accompanying drawings.

• Figure 1 is a general view, in vertical section, of the boiler.
• Figure 2 shows schematically, in perspective, the exchange and dust removal chamber forming part of the boiler.

The boiler comprises a combustion chamber 1 of the fluidized bed type. It consists of a refractory enclosure 11 which contains the fluidized bed 12 of carbon. This is introduced into the enclosure by a supply mouth 13. The bed is suspended by an ascending air stream which is injected at the bottom of the enclosure by injection nozzles supplied with air. Combustion is initiated by the start-up burner 15. The enclosure is equipped, in the lower part, with a lateral outlet mouth 16 which allows the ash to be removed and, above, a lateral inlet mouth 17 which allows the introduction of recycled ash.

The combustion chamber 1 communicates with an exchange enclosure 2 containing water tubes 6 and 7 housed inside an external envelope 21 and heated by the combustion fumes which are channeled towards the outlet 22.

The fumes flow successively in an exchange chamber 3 then in an exchange and dedusting chamber 4 then in a terminal exchange chamber 5 which leads to the outlet 22.

The exchange chamber 3 which overhangs the fluidized bed forms a chimney lined with vertical tubes 6. These tubes are integrated into walls 31 which are formed by sheets closing the gaps between the tubes. A thermal insulation is interposed between the walls 31 and the casing 21. The tubes 6 are connected at their lower end to a lower supply belt and at their upper end to a vapor release manifold. The tubes of the wall 31 are interrupted on the side of the chamber 4 so as to provide an inlet orifice 46.

The exchange and dust removal chamber 4 is delimited by a common wall 31 forming the inlet orifice and by walls 41. Tubes 6 are integrated in the walls 41 made of sheets closing the gaps between the tubes.

This chamber contains a vertical interior partition 42 which can be produced by means of water circulation tubes. It divides the chamber into two half-chambers 43 and 44, these two half-chambers communicating at the bottom of the partition by a communication orifice 45. The upstream half-chamber 43 communicates with chamber 3 by the inlet orifice 46 located in the upper part. The downstream half-chamber 44 communicates with the terminal chamber 5 via an outlet orifice 47 located in the upper part.

Vertical tubes 6 are integrated in the walls 41 and in the partition 42 which consist of sheets closing the gaps between the tubes. The tubes of the interior partition open out at their ends into a supply manifold and into a clearance manifold. The tubes of the walls open at their ends into a supply manifold and into a release tube. The exchange and dusting chamber has a hopper 48 at the bottom for recovering the ash for recycling to the mouth 17 and / or for evacuating it.

The inlet port 46 is located laterally with respect to the internal partition 42 and faces a wall 41 perpendicular so that the fumes enter substantially parallel to the partition and are stopped by said opposite wall 41. The smoke descends in the half-chamber 43 along the partition 42 and passes through the orifice 45 then rises in the half-chamber 44 towards the outlet orifice 47.

Due to the sudden changes in direction of the fumes in chamber 4, they separate from the ashes they contain.

The position of the partition 42, as well as its height have been defined so that the ashes retained and collected in the hopper 48 are not taken up by the fumes.

By way of example, the table below groups together the capture yields of the dedusting chamber, obtained on a model, as a function of the ash load of the fumes and the height of the partition 42 when the latter is positioned close inlet 46.

The terminal chamber 5 contains vertical tubes 6 which are connected to a collecting tank 8 equipped with devices for drying the steam and located at the top and to a tank 9 located at the bottom.

The steam collected in the release manifolds is led to the collecting tank 8 which also receives the steam produced by the tubes of the chamber 5-The bundle 7 constitutes a superheater.

Claims (3)

1. A boiler comprising a fluidized bed combustion chamber (1) which communicates with an exchange enclosure (2) containing water-tubes (6, 7) heated by the combustion fumes and within which is disposed an exchange and dust-removing chamber (4) which is provided with water-tubes (6) and contains a vertical internal partition (42) dividing it into two semi-chambers (43, 44) communicating with each other in their lower part, one of which communicates with the upstream part (3) of the enclosure (2) through an inlet orifice (46) located in the upper part and constrains the fumes to follow a descending path while the other communicates with the downstream part (5) of the enclosure (2) through an outlet orifice (47) located in the upper part and constrains the fumes to follow an ascending path, characterised by the fact that the inlet orifice (46) is located laterally relative to the internal partition (42) and is in facing relation to a perpendicular wall (41) so that the fumes entering in a direction substantially parallel to said partition (42) are stopped by said wall (41) so as to change direction and have dust removed therefrom.

2. A boiler according to claim 1, characterised in that the internal partition (42) comprises water-tubes (6).

3. A boiler according to any one of the preceding claims, characterised in that the exchange and dust-removing chamber comprises, in the lower part, a hopper (48) for collecting the ashes.

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