GB2108617A

GB2108617A - Improvement in and relating to fluidized bed combustion systems

Info

Publication number: GB2108617A
Application number: GB08231074A
Authority: GB
Inventors: Raymond Wright
Original assignee: TI Accles and Pollock Ltd
Current assignee: TI Accles and Pollock Ltd
Priority date: 1981-11-05
Filing date: 1982-10-29
Publication date: 1983-05-18
Also published as: GB2108617B

Abstract

A nozzle 12 for a fluidized bed combustion system comprises a tubular element with an annularly bulged portion 16. The nozzle is releasably secured in an aperture 18 through a component 11 of the combustion system by trapping the bulged portion between clamping means 20 and the periphery of the aperture. <IMAGE>

Description

SPECIFICATION Improvements in and relating to fluidized bed combustion systems The present invention relates to fluidized bed combustion systems and in particular to a nozzle for such systems.

In a fluidized bed combustion system, air is pumped into a particulate material within the combustion chamber, in order to fluidize the material. The air may be introduced by means of air injection nozzles which pass through the base plate of the combustion chamber, pressurised air being fed to these nozzles from a plenum chamber positioned on the external side of the combustion chamber base plate. Alternatively, the air may be fed into the combustion chamber through one or more supply tubes, these tubes passing along the length of the combustion chamber and being provided with a plurality of air injection nozzles spaced along their length. It has been proposed to weld the air injection nozzles to the base plate of the combustion chamber or to the supply tubes.

However, under the combustion conditions, the air injection nozzles have a limited life and must be replaced from time to time. It has also been proposed to provide screw-threaded air injection nozzles, which are screwed into the base plate or the supply tubes. While such nozzles may be replaced relatively easily, they are produced by maching from hexagonal stock and are consequently relatively costly to produce.

According to one aspect of the present invention, a nozzle for a fluidized bed combustion system comprises a tubular element with an annularly bulged portion; said bulged portion forming an abutment one surface of which is adapted to be clamped about the periphery of an aperture through a component of the combustion system, by a clamping means which engages an opposed surface of the abutment.

The nozzle may be produced from plain cylindrical tube. The annularly bulged portion may be formed by any suitable process, for example by means of a radially expanding mandrel. The end of the tube which is disposed within the combustion chamber is preferably closed with an end plate and a series of holes or slots are formed in the tube adjacent to the end plate, to form an outlet from the tube into the combustion chamber.

According to a further aspect of the present invention, a fluidized bed combustion system includes a nozzle in the form of a tubular element having an annularly bulged portion, said nozzle or injector being clamped to a component of the combustion system by clamping means which engages one surface of the bulged portion of the nozzle and forces an opposed surface of the bulged portion into engagement with the periphery of an aperture through the component.

In order to ensure good continuous contact of the bulged portion of the nozzle about the periphery of the aperture of the component, the periphery of the aperture may be contoured.

Furthermore, a gasket or sealing compound may be interposed between the bulged portion of the nozzle and the periphery of the aperture.

The clamping means may be in the form of a plate which may be used to secure the nozzle individually, but is preferably used to secure two or more nozzles. For convenience, the clamping plate is formed with open ended slots which engage about half the periphery of the bulged portion of the nozzles. However, the clamping plate may alternatively be provided with holes which fit over the nozzle and engage the whole of the periphery of the bulged portion thereof.

The clamping plates may be secured to the component by releasable fastening means, such as bolts, which may be tightened to clamp the plate down onto the bulged portion of the nozzle and thus clamp the bulged portion of the nozzle to the component. Alternatively, the clamping plate may be mounted rotatively on the component and provided with cam surfaces, these cam surfaces engaging the bulged portion of the nozzle, so that as the clamping plate is rotated into a clamping position, the cam surfaces will gradually force the bulged portion of the nozzle against the periphery of the aperture in the component.

The invention is now described, by way of example only, with reference to the accompanying drawings, in which:~ Figure 1 shows a sectional elevation of a pair of air injection nozzles, formed in accordance with the present invention, secured to the base plate of a fluidized bed combustion chamber; Figure 2 shows a sectional elevation of a modification of the construction shown in Figure 1: Figure 3 shows a plan view of a "tile" assembly for forming the base plate of a fluidized bed combustion chamber; utilizing injection nozzles, formed in accordance with the present invention; Figure 4 shows a cross-sectional elevation of a sparge tube for a fluidized bed combustion system, with injection nozzles formed in accordance with the present invention; Figure 5 shows a part sectional side elevation of the embodiment shown in Figure 4; and Figure 6 shows a plan view of the embodiment shown in Figure 4; Figure 7 shows a sectional elevation of an alternative embodiment of the invention; Figure 8 is a plan view of Figure 7; and Figure 9 shows a sectional elevation of a further embodiment of the invention.

As illustrated in Figure 1, a fluidised bed combustion chamber 13 has a base plate 1 1, a plurality of air injection nozzles 12 (only two shown) pass through the base plate 11 into the combustion chamber 13. These air injection nozzles 12 are closed at their inner ends by end plates 14 and each injection nozzle 12 has a series of holes or slots 1 5 adjacent to the end plate 14 which provide an outlet for air into the combustion chamber 13.

In use, the combustiuon chamber is filled with particulate material, for example sand, to a level above the end plates 14 of the air injection nozzles 12. Air is fed through the injection nozzles 12 from a plenum chamber (not shown) which is formed against the outer surface of the base plate 11, into the combustion chamber and fluidizes the particulate material.

The air injection nozzles 12 are formed with a bulged portion 1 6 which is spaced slightly from the inlet end 17 of the nozzle 12 and is of greater diameter. Counter sunk holes 18 are provided in the base plate 11, through which the ends 1 7 of the nozzles 1 2 are inserted, so that the bulged portions 1 6 of the nozzles 12 abut the countersunk portions of holes 1 8, with the interposition of a gasket 1 9. A clamping plate 20 is fastened to the base plate 11 and clamped down on the upper surface of the bulged portions 1 6 of the two adjacent nozzles 12, by means of a nut 21 which engages bolt 22. For convenience, the bolt 22 is welded to the base plate 11.The clamping plate 20 has a pair of open ended slots 23, one on either side of the hole 24 through which the fastening bolt 22 passes, these open ended slots 23 engaging something over 50% of the periphery of the bulged portions 1 6 of each of the nozzles 11. The portions of the slots 23 which abut the bulged portions 1 6 of the nozzles 12, are also counter sunk in order to increase the contact area therebetween.

The arrangement descirbed above provides a fluid tight joint between the air injection nozzles 12 and base plate 11 of the fluidized bed combustion chamber 1 3, which may easily be dismantled when, for example, replacement of the air injection nozzles 12 is necessary.

In the embodiment described above, clamping plates 20 and fastening nuts 21 are positioned inside the combustion chamber 1 3 and consequently access is required to the chamber 13 when initially fitting or replacing the air injection nozzles 12. Furthermore, these components will also be subjected to conditions in the chamber, with the possible risk of damage.

This problem is overcome by the modification illustrated in Figure 2.

In the embodiment illustrated in Figure 2, the air injection nozzles 12 are inserted from below the base plate 11. In order to do this, the holes 1 8 must be made large enough to allow the end plates 14 of the nozzles 12 to pass therethrough.

In turn, the bulged portions 16 of the nozzles 12 must be made larger in diameter than the end plates 14, so that they will abut against the counter-sunk portions of the holes 1 6. The injection nozzles 12 are then clamped to the base plate 11 in the manner described above, with the clamping plate 20 and fastening nut 21 on the outside of the combustion chamber.

The base plate 11 of the combustion chamber 13 may be constructed from pre-formed "tile" asssemblies 30 of the form shown in Figure 3.

Each of these tiles 30 is provided with sixteen air injection nozzles 1 2 which are mounted through a plate 31 in the manner described above. In the example illustrated, the injection nozzles 12 are clamped to the plate 31 in groups of four, by means of clamping plates 32. Several such tiles 30 may be bolted together to form the base plate of a fluidized bed combustion chamber.

As illustrated in Figures 4,5 and 6, where are is supplied to a fluidized bed combustion chamber through one or more supply tubes 40, which run within the chamber along its length, the air injection nozzles 12 are located in holes 41 in the supply tube 40 in the manner described with reference to Figure 1. The nozzles 1 2 are however bulged to form a retaining portion 42 which conforms to the curvature of the tube 40 and the clamping plate 43 is also curved to the contour of the tube 40. The clamping plate 43 is fastened to the tube 40 by means of a nut 44 which engages a correspondingly threaded stud 45 welded to the outer surface of the tube 40.

For certain applications, particularly to cater for conditions during light-up of the fluidized bed, the combustion chamber 1 3 is provided with a base plate 11 which is water cooled. Figures 7, 8, and 9 show examples of such water cooled base plates.

In Figures 7 and 8 the base plate 11 is formed of parallel water tubes 50, between which tubes there are welded strips 51 to complete the base plate 11. The holes 1 8 are provided in the strips 51, which thus function in the same manner as the plate 11 in Figure 1. In Figures 7 and 8 the air injection nozzles 12 are clamped by perforated strips 52 overlying the strips 51, and bearing on the upper surfaces of the bulged portions 1 6 of the nozzles 12. Bolts or screws 22, between adjacent nozzles 12, clamp the strips 52 into the bulged portions 16. Alternatively clamping plates 43 of the type shown in Figures 5 and 6 may be used for each pair of nozzles 12.

In Figure 9 the base plate 11 is fully water cooled by a water jacket 53 formed between the base plate 11 and a lower plate 54. At the location of each nozzle 12 a tube 55 is welded through the lower plate 54 and to the underside of the plate 11. The nozzle 12 has an elongate section 56 extending below the bulged portion 1 6 to a level below the lower plate 54. A collar 57 fills the gap between the tube 55 and the section 56 of nozzle 12. The lower part of the section 56 and the collar 57 may be expanded somewhat after installation to ensure a generally gas-tight fit.

Claims

1. A nozzle for a fluidized bed combustion system comprising a tubular element with an annularly bulged portion; said bulged portion forming an abutment, one surface of which is adapted to be clamped about the periphery of an aperture through a component of the combustion system by a clamping means which engages an opposed surface of the abutment.

2. A nozzle according to Claim 1 in which the tubular element is a plain cylindrical tube with a bulged portion adjacent one end and a cover plate covering the other end, at least one hole or slot being provided in the tube adjacent the cover plate, to form an outlet from the nozzle.

3. A fluidized bed combustion system including a nozzle as claimed in Claim 1 or 2, said nozzle being clamped to a component of the combustion system by clamping means which engage one surface of the bulged portion of the nozzle and forces an opposed surface of the bulged portion into engagement with the periphery of an aperture through the component.

4. A fluidized bed combustion system according to Claim 3 in which a plurality of nozzles are provided, these nozzles serving as air injection nozzles by means of which pressurised air may be introduced into a combustion chamber, in order to fluidize a particulate material within the chamber.

5. A fluidized bed combustion system according to Claim 3 or 4 in which the component is the base plate of a combustion chamber.

6. A fluidized bed combustion system according to Claim 5 in which the base plate is made up of a plurality of tile assemblies, each tile assembly having a plurality of nozzles mounted thereto.

7. A fluidized bed combustion system according to Claim 3 or 4 in which the component is a supply tube which is disposed within a combustion chamber.

8. A fluidized bed combustion system according to any one of Claims 3 to 7 in which the clamping means is a plate which clamps one or more nozzles to the component of the combustion system.

9. A fluidized bed combustion system according to Claim 8 in which the clamping plate is fastened to the component by means of a releasable fastening which may be tightened down to force the clamping plate against the abutment on the nozzle and trap the abutment between the clamping plate and the component.

10. A fluidized bed combustion system according to Claim 8 in which the clamping plate is mounted rotatively on the component and is provided with cam surfaces, these cam surfaces engaging the bulged portion of the nozzle, so that as the clamping plate is rotated into a clamping position, the cam surfaces will gradually force the bulged portion of the nozzle, against the periphery of the aperture through the component.

11. A fluidized bed combustion system according to any one of Claims 3 to 10 in which the periphery of the aperture through the component is contoured so as to provide good continuous contact between the bulged portion of the nozzle about the periphery of the aperture.

12. A fluidized bed combustion system according to any one of Claims 3 to 11 in which sealing means is interposed between the bulged portion of the nozzle and the periphery of the aperture.

13. A fluidized bed combustion system, according to Claim 5, in which the base plate includes a plurality of substantially parallel cooling ~liquid tubes, the space between adjacent tubes being closed by a strip sealed to both adjacent tubes, and the aperture engaged by the bulged portion of the nozzle is formed through the closing strip.

14. A fluidized bed combustion system, according to Claim 13, including a plurality of said nozzles clamped by a further elongate strip formed with apertures which engage on top of the bulged portions of the nozzles.

1 5. A fluidized bed combustion system, according to Claim 5, in which the base plate comprises a tank bounded by upper and lower walls, through which tank cooling fluid may be passed in contact with the walls, a plurality of tubular passages extending through the tank and opening through the walls, the interior of each passage being sealed from the cooling fluid, each nozzle extending through the upper plate, onto which the bulged portion is clamped, through one of the tubular passages and through an aperture in the lower wall.

1 6. A fluidized bed combustion system, according to Claim 15, in which the lower end of the nozzle is expanded after fitting to form a substantial seal against the component surrounding the lower end.

17. A nozzle for a fluidized bed combustion system, substantially as described herein, with reference to and as shown in the accompanying drawings.

18. A fluidized bed combustion system substantially as described herein, with reference to and as shown in the accompanying drawings.