GB2205635A

GB2205635A - Solid fuel furnace

Info

Publication number: GB2205635A
Application number: GB08713032A
Authority: GB
Inventors: Ronald John Young
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-06-03
Filing date: 1987-06-03
Publication date: 1988-12-14
Also published as: GB8713032D0

Abstract

A solid fuel furnace for large-scale industrial use, e.g. steam generation, includes a fuel feed 31 which terminates in a combustion zone 32 in which fuel is to be fed in an upward direction, the combustion zone being bounded by a plurality of tuyere elements 33, 34 for admission of combustion air into the combustion zone. The combustion zone is preferably surrounded by dead plates 37, 38 which serve to receive slag, ash and partially-combusted fuel split over from the top of the combustion zone and also define the upper end of supply ducting for combustion air. The side and corner tuyere elements 33 and 34 are shown in more detail in Figs. 1 and 2. <IMAGE>

Description

SOLID FUEL FURNACES This invention relates to solid fuel-fired furnaces, especially of the type for providing heat for generating large quantities of high-pressure steam, for example in power stations.

In furnaces of the type described above, it is usual to utilize a mechanical stoker for supplying the solid fuel to the combustion zone. One commonly-used form of mechanical stoker is the chain grate, which comprises a slowly moving endless chain of grate bars traversing the combustion zone. Fuel is fed on to the chain at the upstream end of the grate, burnt in the combustion zone, and slag and ash fall off at the other end to collect in the ash pit. Combustion air is blown through the grate from below, to control the combustion process. However, such grates do not permit efficient combustion and hence tend to be extravagant in the use of fuel.Furthermore, due to incomplete combustion, noxious gaseous combustion by-products are produced and it is widely believed that these by-products, as well as contributing to atmospheric air pollution such as industrial haze and smog, also are a major contributing factor in the production of "acid rain" which poses a major global environmental threat.

It is an object of the present invention to provide a solid fuel furnace for large-scale industrial use in which combustion proceeds substantially to completion, whereby the combustion products are substantially environmentally harmless, and which is more economical in fuel consumption than existing furnaces.

According to the invention, a solid fuel furnace (as hereinbefore defined) includes a fuel feed pipe terminating in a combustion zone in which fuel is fed in an upward direction, the combustion zone being bounded by a plurality of tuyere elements for admission of combustion air into the combustion zone.

A furnace according to the invention is preferably surrounded by dead plates arranged in a substantially horizontal plane at or towards the upper end of the combustion zone, to receive slag, ash and partially-combusted fuel spilt over from the top of the combustion zone. The dead plates may also serve to define the upper end of supply ducting for combustion air, the ducting surrounding the fuel feed pipe, so that combustion air is constrained to flow through the tuyere elements into the combustion zone.

In use, fuel is fed upwardly to the combustion zone and air is ducted upwardly around the fuel feed pipe and is blown into the combustion zone through the tuyere elements, so that the combustion zone is constituted by a bed of burning fuel which substantially fills the cross-sectional area of the upper end of the fuel feed pipe, fresh fuel moving upwardly into the combustion zone and spent or partially-spent fuel spilling over from the top of the combustion zone on to the dead plates. To control the combustion process and ensure substantially complete combustion, either the rate of fuel feed and/or the pressure of combustion air may be varied.

The use of tuyere elements in furnaces according to the invention enables a combustion zone constituted by an upwardly-moving fuel feed to be achieved for large-scale industrial furnaces, in that individual tuyere elements may be removed for servicing or replacement. The tuyere elements are arranged side by side around the periphery of the combustion zone and each tuyere element preferably comprises, as a front face, ranks of teeth extending outwardly from a common support bar, the teeth defining open-ended slots therebetween such that two such tuyere elements, when placed side by side with the ends of one rank of teeth of one tuyere element in contact with the facing ends of a rank of teeth on the other tuyere element, define closed slots or ducts for the passage of combustion air into the combustion zone.The support bar is preferably extended above, below and behind the front face to provide a closed frame enclosing a central chamber. Lugs may be attached to the frame for locating the tuyere element around the edge of the fuel feed pipe and for locating dead plates thereon.

The external wall of the supply duct for combustion air may comprise a brick wall and the dead plates, which preferably have a shallow trough formed therein, may bridge the gap between the upper edge of the wall and the tuyere elements, thereby forcing combustion air through the slots or ducts defined by adjacent tuyere elements. Suitable tuyere elements containing ranks of teeth mutually at an angle may be provided for forming a corner to the combustion zone.

According to the invention, the entire combustion zone is bounded by a continuous array of tuyere elements, adjacent elements defining combustion air slots or ducts, and any one or more of the tuyere elements may be removed for servicing or replacement without disturbing adjacent tuyere elements.

In use, solid fuel is fed continuously to the combustion zone, for example by a screw or worm feed mechanism disposed in the fuel feed pipe.

Conveniently, according to a further feature of the invention, the screw mechanism may extend directly into the fuel bunker without the need to pass it via an intermediate hopper. For this purpose, the fuel bunker may be situated adjacent the furnace or boiler-room.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 shows side, front and rear elevations of tuyere elements for use in a furnace according to the invention; Figure 2 shows side elevations of corner tuyere elements; Figure 3 is a view from above of a furnace according to the invention and Figure 4 is a cross-sectional side view in diagrammatic form of a furnace according to the invention.

Referring to Figure 1, tuyere elements are shown as side elevation in la, front elevation in ib and rear elevation in ic and consist of a closed frame 11 enclosing a central chamber 12. Lugs are provided at 13 and 14. At the front, the frame constitutes a common support bar 15 from which extend sideways ranks of teeth 16, 17 which define open-ended slots 18, 19 therebetween.

Figure 2 shows corner tuyere elements having ranks of teeth 21, 22 and 23, 24 mutually at right angles.

Figure 3 shows the screw fuel feed mechanism 31 of a furnace according to the invention for delivering solid fuel through the fuel supply pipe which terminates in a combustion zone 32 bounded by a continuous array of tuyere elements 33 of the type shown in Figure 1 and corner tuyere elements 34 of the type shown in Figure 2. Dead plates 35-38 surround the tuyere elements.

Figure 4 shows the arrangement of. Figure 3 when viewed as a diagrammatic vertical section along the line IV-IV. The dead plates 37, 38 are shown supported between the tuyere elements and a brick wall 41 which define a chamber for receiving combustion air from a compressor (not shown). Lines 42 represent the closed slots between adjacent tuyere elements and through which combustion air is ducted to the combustion zone.

Claims

1. A solid fuel furnace for large-scale industrial use and including a fuel feed pipe which terminates in a combustion zone in which fuel is to be fed in an upward direction, the combustion zone being bounded by a plurality of tuyere elements for admission of combustion air into the combustion zone.

2. A furnace according to Claim 1, in which the combustion zone is surrounded at or towards the upper end thereof by dead plates arranged in a substantially horizontal plane.

3. A furnace according to Claim 2, in which the dead plates define the upper end of supply ducting for combustion air, to constrain the said air to flow through the tuyere elements into the combustion zone.

4. A furnace according to any preceding claim, in which each tuyere element comprises, as a front face, ranks of teeth extending outwardly from a common support bar, the teeth defining open-ended slots, whereby two tuyere elements when placed side by side with the ends of one rank of teeth of one tuyere element in contact with the facing ends of teeth in a rank of the other tuyere element define closed slots or ducts for the passage of combustion air into the combustion zone.

5. A furnace according to Claim 4, in which the support bar of each tuyere element extends above, below and behind the front face to provide a cage structure defining a central chamber.

6. A furnace according to any preceding claim, including means to feed fuel continuously to the combustion zone.

7. A furnace according to Claim 6, in which the said means comprise a screw or worm feed mechanism which extends directly between the fuel bunker and furnace.

8. A method of operating a solid fuel furnace, in which fuel is fed continuous and upwardly to the combustion zone of said furnace, the combustion zone being bounded by a plurality of tuyere elements for admission of combustion air.

9. A method according to Claim 8, in which the combustion zone is defined by tuyere elements and dead plates as defined in any of Claims 2 to 5.

10. A solid fuel furnace substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.