GB2086755A

GB2086755A - Fluidised bed boilers

Info

Publication number: GB2086755A
Application number: GB8127581A
Authority: GB
Original assignee: Worsley G P & Co Ltd
Current assignee: Worsley G P & Co Ltd
Priority date: 1980-09-11
Filing date: 1981-09-11
Publication date: 1982-05-19
Also published as: GB2086755B

Abstract

A fluidised bed furnace (15) which fires or drives a boiler has a bed support 11 which is hollow or incorporates hollow components traversing its area and which is traversed through its hollowness by a medium also associated with the boiler, and has gas distribution pipes, tubes or ducts 27 passing through its thickness for bed fluidisation purposes. The medium may be a heat-exchange medium, and the bed support (11) may form part of an overall circulation system for both furnace and boiler portions, such as outer jacketing common to both portions. <IMAGE>

Description

SPECIFICATION Fluid-bed fired boilers The invention relates to boilers fired or driven by fluid-bed furnaces.

Our British Patent Specification No.

1 592846 and our copending patent applications nos. 79/04789 and 8029448 make proposals for bed supports of fluid-bed furnaces, which supports are cooled, generally by supply therethrough of combustion promoting-gas on its way to or as a feed to a system that pressurises and distributes that gas to and release it into incombustible particulate bed material for the purposes of fluidisation and combustion of fuel added to the fluidised bed material.

The primary aim of those fluid-bed furnaces is to produce high temperature exhaust gases as the media via which heat is produced for utilisation externally of the furnaces. Also, the bed support proposals of the above-mentioned applications have endeavoured not only to provide for bed traversal by the combustionpromoting-gas but also to strengthen and/or facilitate bed construction.

Recently, we have been investigating the development of unified fluid-bed furnace/boiler designs. It is to the results of those investigations that this invention is particularly directed.

According to this invention there is provided a fluid-bed furnace fired or driven boiler wherein a bed support for the fluid-bed furnace portion, which bed support is hollow, or incorporates hollow components or fabricated provisions traversing its area, and which also has gas distribution pipes, tubes or ducts passing through its thickness for bed fluidisation purposes, is actually traversed through its hollowness by a medium that is common to an associated boiler portion, say as the heat exchange medium therefor, preferably with the bed support structure incorporated into an overall circulation system for both boiler and furnace portions, advantageously as or in an enclosure or outer jacketing common thereto.

Particular embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of an integrated fluid-bed furnace/boiler hereof; Figures 2 and 3 are sections of wall and fluid-bed support constructions; Figure 4 is a diagrammatic view of a fluidbed support/bottom leader arrangement; and Figure 5 is a diagrammatic representation of another fluid-bed/boiler arrangement hereof.

In Fig. 1, furnace and heat exchange or boiler elements are integrated with the latter effectively formed as the casing of the furnace with top and bottom header tanks 10, 11 interconnected by walls 20, 21 of sides and/or ends of the furnace chamber 1 5.

The bottom header tank 11 actually comprises the support for the fluid-bed 1 8 and has spaced upper and lower plates 24, 25 through which pass fluidising pipes 27 from a plenum chamber 30 below the bed. The plenum chamber 30 houses a burner 32 for causing hot gases to be supplied to the bed material during initial heating up and fluidisation of incombustible bed material to temperatures at which fuel, usually coal, will burn when added to the bed, say at 36. Air will normally be supplied to the plenum chamber 30 from a fan, not shown, at least via the burner 32 but perhaps also otherwise at least after the burner is extinguished when it has served its purpose.

In operation, thermal fluid such as suitable oil will be supplied at 37 to the bottom header tank/bed support 11 and will be taken off for utilisation or storage at 38 from top header tank 10.

Exhaust gases from the furnaces chamber 1 5 are shown taken off at 1 6 through the top header tank and may serve to drive a further heat exchanger. The whole casing above the bottom header tank/bed support 11 is shown externally lagged at 1 9.

Such an arrangement is highly effective for utilisation of the very high efficiencies of fluidbed furnaces, even for low grade fuels, in socalled clean-air applications where the very high temperature exhaust gases from air fluidbed furnaces cannot be used directly.

Because of the very high working temperatures of out fluid-bed furnaces, we prefer a wall construction such as shown in Fig. 2 and comprising an assembly of conjoined tubes 41 that will have to be of heat resisting metal such as stainless steel. The bed support may then be of similar such tubes 42, see Fig. 3, spaced by webs 43 through which the fluidising and combustion promoting gas tubes 27 are passed.

As such tubes 42 may not afford sufficient capacity to act as a bottom header tank, an arrangement such as that of Fig. 4 may be used. There, the tubes 42 extend between bottom corner tanks 45, 46 having suitable connections both to the tubes 42 and to side or end wall tubes 41. Similar connections will, of course be made to the top header tank 10, which may thus be a separate initial fabrication, thereby facilitating assembly from fabricated components for sides, ends, bottom and top of the overall casing.

In Fig. 5, a combined fluid-bed furnace/boiler has a furnace element 51 and a boiler element 51 separated by a wall 52 through which exhaust gases may pass at 53 from the combustion chamber of the furnace to the chamber housing the boiler's heat exchanger 55 which is assumed, for simplicity, to act directly on a medium, such as water, steam or oil, to be heated and utilised and, for that purpose, being fed in at 56 to a lower chamber 57 and taken off at 58 from an upper chamber 59 to an accumulator 60 in a continuous circulation system via connections 61, 62 to the heat exchanger 55 and outer-walls 63, 64 even walls 52 of the overall casing, jacket or the like.

Between the lower chamber 57 and the outer wall 64 is a fluid-bed support structure 65 that permits, see arrow 66, flow of boiler medium therethrough via a connection or coupling 67.

The entire structure is mounted on supports such as 68, 69, 70, those (69, 70) flanking the bed support structure 65 having between them a plenum chamber 71, having an ignition burner 72 and serving for the supply of combustion-promoting and fluidising gas, usually air under pressure, to incombustible particulate material of bed 75 of the furnace element via tubes, pipes or ducts 76 passing upwardly through the bed support structure to terminate in release heads 77, or simply perforations therein, at a level above which the particulate material is to be fluidised during burning of fuel, usually coal, added to the bed material through a side or end of the furnace element, say at 78.

Claims

1. A fluid-bed furnace fired or driven boiler wherein a bed support for the fluid-bed furnace portion, which bed support is hollow or incorporates hollow components or fabricated provisions traversing its area, and which also has gas distribution pipes, tubes or ducts passing through its thickness for bed fluidisation purposes, is actually traversed through its hollowness by a medium which is common to an associated boiler portion.

2. A fluid-bed furnace fired or driven boiler as claimed in claim 1, wherein the medium is the heat exchange medium for the boiler portion.

3. A fiuid-bed furnace fired or driven boiler as claimed in claim 1, or 2, wherein the bed support structure is incorporated into an overall circulation system for both boiler and furnace portions.

4. A fluid-bed furnace fired or driven boiler as claimed in claim 3, wherein the overall circulation system is or is in an enclosure or outer jacketing common to the boiler and furnace portions.

5. A fluid-bed furnace fired or driven boiler substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 4 or Fig. 5 of the accompanying drawings.