GB1597118A - Fludised bed distributor plate assemblies - Google Patents

Description

(54) FLUIDISED BED DISTRIBUTOR PLATE ASSEMBLIES (71) We, NORTHERN ENGINEERING IN DUSTRIES LIMITED, a British Company, of Regent Centre, Newcastle upon Tyne NE3 3SB, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to fluidised bed distributor plate assemblies and to apparatus incorporating such assemblies.

Fluidised bed apparatus has a container in which the bed of particulate material is located. The base of such a container is generally formed by a distributor plate having a plurality of apertures or nozzles through which fluidising medium is passed.

In some constructions of fluidised bed apparatus, the container has a sidewall or sidewalls inclined or curving away from the distributor plate'base. An example of such an apparatus is a fluidised bed shell boiler. The combustion tube of this type of boiler is generally substantially cylindrical, the distributor plate being located in the tube below the horizontal diametral plane of the tube.

In this type of apparatus, the part of the bed of particulate material supported by the inclined or curved sidewall(s) has a tendency not to fluidise or to only partially fluidise.

This can cause the particles of that part of the bed to fuse under operating conditions owing to overheating.

This can also happen, although to a lesser extent, in corners of the container where the supply of fluidising medium from the plate may not be adequate to support proper fluidisation.

It has been proposed to overcome this problem by introducing sparge pipes, connected to a source of fluidising medium, into such parts of the bed to fluidise them properly. This is not a very satisfactory solution, however, owing to the sparge pipes overheat; p and distorting; and, because they overheat, they are starting surfaces for particle fusing. It is also difficult to achieve uniform distribution of the fluidising medium along the sparge pipes without resorting to using relatively high pressures which cannot be readily supplied by fans or blowers suitable for fluidising the bed.

According to the invention, a fluidised bed distributor plate assembly comprises a distributor plate supporting a plurality of fluidising medium distribution nozzles which have fluidising medium outlets, at least some of the nozzles located adjacent the periphery of the assembly being inclined to the distributor plate in a direction away from the centre of the plate, the fluidising medium outlets of the inclined nozzles being at substantially the same height above the upper surface of the plate as the fluidising medium outlets of the remainder of the nozzles.

Also according to the invention, fluidised bed apparatus comprises a container for a bed of particulate material, the base of the container comprising a distributor plate assembly as set forth in the preceding paragraph, the inclined nozzles being located at a part of the periphery of the assembly adjacent an inclined or curved sidewall or a corner portion of the container.

Preferably, the nozzles comprise stub pipes secured in apertures in the distributor plate, cap members having fluidising medium outlets being secured over the ends of the stub pipes.

Preferably, the distributor plate assembly comprises a lower arcuate structure forming with the plate a fluidising medium chamber.

The lower structure preferably comprises two arcuate plate portions secured to opposed edges of the distributor plate and secured to a fluidising medium distribution duct, the ends of the chamber being closed by segment-shaped plates.

Preferably, the distributor plate has gaseous fuel distribution ducts extending beneath it, the ducts having feed pipes extending into at least some of the nozzles.

A fluidised bed distributor plate assembly will now be described to illustrate the invention by way of example with reference to the drawings accompanying the provisional specification, in which: Figure 1 is a plan of the distributor plate assembly; Figure 2 is a vertical sectional view of the lower structure of the assembly shown in Figure 1; Figure 3 is a view of an upper structure of the assembly on line Ill-Ill in Figure l; and Figure 4 is a view as seen in the direction of the arrow IV in Figure 1.

The drawings show a fluidised bed distributor plate assembly 10 which comprises an upper structure 12 for supporting a bed of particulate material which structure is secured to and supported by an arcuate lower structure 14 which typically is mounted in a substantially cylindrical combustion tube of, for example, a fluidised bed shell boiler (not shown).

The upper surface 12 includes a rectangular plate 16 having a series of rows of vertical bores 18 into which are secured stub pipes 20 (only some of which are shown in Figure 1).

Adjacent to each longitudinal edge 22 of the plate 16 there is a row of bores 24, which have mutually parallel central axes inclined to the upper surface of, and in a direction away from the centre of, the plate 16. Stub pipes 26 are secured in the bores 24 and have their lower ends flush with the lower surface of the plate 16, while their upper ends are substantially normal to their longitudial axes.

The stub pipes 20 and 26 are welded in the respective bores 18 and 24 at 28.

The stub pipes 20 and 26 each have external screw-threaded portions 30 and 32, respectively, onto which cap members 34 (see Figure 3) are screwed. The cap members 34 have fluidising medium outlet apertures 36 (not shown in Figure 4).

A rectangular plate 38 is connected to the plate 16 by a vertical trapezium-shaped plate 40 (see Figure 4).

Vertical support plates 42 are welded to the lower surface of the plate 16 and carry square-sectioned U-shaped pipes 46 (only one shown in Figures 1 and 4 for clarity) welded into apertures in the support plates 42 (see Figure 3). Outlet pipes 48 extend upwardly from the pipes 46 into each of the stub pipes 20. The limbs of the U-shaped pipes 46 are bent to take into account the change in levels between the plates 16 and 38. Inlet pipes 44 (Figure 4) are connected to the pipes 46.

The pipes 46 are of square section for ease of fabrication, but could be of normal circular section if desired.

The lower structure 14 comprises segment sped front and rear support plates 50 and 52, respectively, and a central portion 54 (Figures 1, 2 and 4).

The front plate 50 has an upper flange 56 extending away from the central portion 54.

Below the flange 56 are apertures 58 through which the inlet pipes 44 pass. Surrounding each aperture 58 is an internally-threaded boss 60. The front plate 50 also has a central aperture 62 in which a duct 64 is welded.

The duct 64 extends to the rear plate 52 to which it is welded. The duct 64 has apertures 66 along the length of its sides 68. The front of the duct 64 has a flange 70 by which it can be connected to a fluidising medium, for example, air, supply means.

The central portion 54 of the lower structure 14 is made up of the duct 64 and two opposed curved plates 72. The curved plates 72 are welded to the duct 64 and to the front and rear plates 50 and 52, respectively. The curved plates 72 are stepped at 74.

An inwardly-extending flange 76 extends around the whole of the upper periphery of the lower structure 14.

The upper structure 12 is secured to the lower structure 14 by bolts 80 passing through apertures (not shown) in the peripheral edges of the upper structure 12 and the flange 76 of the lower structure. An asbestos gasket can be positioned between the structure 12 and the flange 76 to ensure that sealing engagement between them is obtained. Alternatively, the upper structure 12 can be welded to the lower structure 14.

The inlet pipes 44 pass through apertures 58 in the front plate 50 of the lower structure 14 and a sealed relationship is obtained therebetween by externally-threaded sleeve nuts 82 engaging the bosss 60 and compressing sealing rings between themselves and the bosses 60.

The upper and lower structures 12 and 14 together form a substantially gas-tight chamber having outlets formed by the stub pipes 20 and 26.

The distributor plate assembly is fitted to a shell boiler (not shown) by being slid into the combustion tube of the boiler to form the base for a bed of particulate material. The plate assembly 10 is secured to the front of the boiler by bolts passing through apertures 86 provided in the front plate 50 of the lower structure 14. The rear wall ofthe container of the bed is a firebrick wall extending partially across the tube. The front wall of the container is formed by a door having a firebrick lining which engages the flange 56 of the front plate 50 of the lower structure 14 and extends substantially the whole length of the stepped portion 74 in the assembly 10.

The sidewalls of the container are formed by the combustion tube wall.

The door of the boiler can have solid, liquid and gaseous fuel supply means secured to it.

The front end of the distributor plate assembly 10 has been designed so that the assembly can be fitted into an existing shell boiler but could clearly be modified for other boiler designs.

The invention has been particularly described with reference to fluidised bed boiler apparatus having a substantially cylindrical combustion tube, but it is clear that it is applicable to other types of fluidised bed apparatus by suitable positioning of the inclined nozzles adjacent to an inclined or curved sidewall or a corner.

WHAT WE CLAIM IS: 1. A fluidised bed distributor plate assembly comprising a distributor plate supporting a plurality of fluidising medium distribution nozzles which have fluidising medium outlets, at least some of the nozzles located adjacent the periphery of the assembly being inclined to the distributor plate in a direction away from the centre of the plate the fluidising medium outlets of the inclined nozzles being at substantially the same height above the upper surface of the plate as the fluidising medium outlets of the remainder of the nozzles.

2. An assembly according to claim 1, in which the nozzles comprise stub pipes secured in apertures in the plate, cap members having fluidising medium outlets being secured over the ends of the stub pipes.

3. An assembly according to claim 1 or claim 2, in which the plate has a lower at least partially arcuate structure forming with the plate a fluidising medium chamber.

4. An assembly according to claim 3, in which the lower structure comprises two arcuate plate portions secured to opposed edges of the distributor plate and secured to a fluidising medium distribution duct, the ends of the chamber being closed by segmentshaped plates.

5. An assembly according to claim 4, in which gaseous fuel distribution ducts extend beneath the distributor plate, the ducts having feed pipes extending into at least some of the nozzles.

6. Fluidised bed apparatus comprising a container for a bed of particulate material, the base of the container comprising a distributor plate assembly as claimed in any

Claims (1)

1. preceding claim.

   7. Apparatus according to claim 6, in which the inclined nozzles are located at a part of the periphery of the assembly adjacent an inclined or curved sidewall or a corner portion of the container.

   8. A fluidised bed distributor plate assembly substantially as described herein with reference to the drawings accompanying the provisional specification.