GB2321099A

GB2321099A - Solid fuel boiler.

Info

Publication number: GB2321099A
Application number: GB9800086A
Authority: GB
Inventors: Dennis George Cornwell
Original assignee: CORNWELL HEAT Ltd
Current assignee: CORNWELL HEAT Ltd
Priority date: 1997-01-10
Filing date: 1998-01-06
Publication date: 1998-07-15
Also published as: GB9800086D0

Abstract

An Anthracite boiler including a combustion chamber having an apertured floor (42) through which primary air (PA) is blown into a burning fuel bed (18), the boiler also having an ejector ram (46) for ejecting a clinker/ash layer from beneath the fuel bed forwardly on to a shelf-like front extension of the combustion chamber floor, the major part of the burning fuel mass being held back by a crosspiece (70) extending across the combustion chamber.

Description

Solid Fuel Boiler This invention relates to a solid fuel boiler and, in particular, a boiler which uses Anthracite, e.g. Anthracite beans, as the solid fuel, which is gravity fed into the combustion chamber.

According to the invention, there is provided a gravity feed Anthracite boiler having a combustion chamber, a ram for ejecting a clinker/ash layer forwardly from beneath the fire bed, and a crosspiece in front of the fire bed at a height to hold back at least the greater part of the fire bed when the clinker/ash layer is ejected.

Typically, in a solid fuel boiler of this general type, the primary air enters the firebed by two methods, i.e. through an apertured grate then through the clinker layer and also directly through the clinker, thus bypassing the apertured grate.

According to a further feature of the invention, the boiler has a combustion chamber with an apertured floor, and primary combustion air is blown upwardly into the Anthracite in the combustion chamber through the apertured floor, in such a way as to create a regular and repeatable clinker mass.

In a solid fuel boiler of the general type under consideration, the floor of the combustion chamber terminates at a front edge over which clinker and ash is pushed to drop into an ash box by means of an ejector ram which is periodically operated, usually manually, typically about every 10 hours. After 10 hours a semi-solidified layer of clinker/ash has formed under the mass of burning fuel, and this semi-solidified layer is pushed out by the ram from beneath the burning fuel mass, to drop over the front edge of the combustion chamber floor into the ash box.

In the boiler according to the present invention, however, a shelf-like forward extension of the combustion chamber floor is provided, as well as an ejector ram, so that when the later is operated, again typically about every 10 hours, a clinkerlash layer beneath the mass of burning fuel is pushed forward on to the shelf. This clinker/ash layer is then pushed into the ash box after a further period of operation, i.e. typically 10 hours. This is desirable because for a clinker to be ejected in a single operation, excess fuel would be pushed out of the firebed in front of the clinker: also this would seriously disturb the firebed, resulting in a slow recovery period.

Preferably, secondary air, mainly used for the burning of fuel gases such as carbon monoxide, is injected into the forward region of the combustion chamber in front of the crosspiece, for example above the shelf-like extension of the combustion chamber floor.

The boiler preferably has a fire door giving access to the ash box at the bottom front, whilst air is fan blown from the bottom back into a space behind the ash box beneath the combustion chamber floor, primary air then being directed upwardly through the apertures in the floor whilst a portion of the air blown into the space is tapped off to serve as secondary air. The apertured portion of the combustion chamber floor may take the form of a removable floor portion.

A preferred water jacket is provided to the interior of both side walls of the boiler and these side portions of the jacket are interconnected by a transverse portion to the interior of the front wall of the boiler above the fire door. This transverse portion may lie beneath a portion of a fuel hopper, which allows fuel to drop down the back of the boiler from a loading point at the back of the top of the boiler.

The hopper preferably tapers to a bottom exit immediately in front of the back wall of the combustion chamber, so that the fuel being burnt adopts a downwardly and forwardly sloping front face. This sloping front face is maintained when the ram is operated to push the clinker/ash layer, surmounted by a small amount of fuel still being burned, on to the shelf-like extension of the combustion chamber floor.

Preferably, the crosspiece is constituted by a transverse pipe connecting the side portions of the water jacket forwardly of the sloping front face of the burning fuel mass. The crosspiece, in addition to holding back a major part of the fire bed, also enables a more uniform overall shape and quantity of burning fuel mass, including that on the shelf-like extension, to be maintained.

Combustion gases preferably exit from the combustion chamber on both sides thereof, being divided into two ducts which extend upwardly within the two side portions of the water jacket to emerge into an insulated flue chamber at the top of the boiler to which an exit flue connects.

In front of and connecting at the back with the transverse water pipe, an L-shaped arrangement of plates closes off the combustion chamber from the fire door, which is openable to enable emptying of the ash box of the semi-solidified clinker/ash layer pushed over the front edge of the shelf-like extension of the combustion chamber floor. The typically L-shaped plate arrangement prevents cold air being drawn in through the opened fire door into the aforesaid ducts leading to the flue.

The invention is further described with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side view of the boiler; Figure 2 is a diagrammatic front view; and Figures 3a to 3d are explanatory diagrams.

Referring to the drawings, the illustrated boiler is a boiler for solid fuel, in particular Anthracite such as Anthracite beans, and comprises a combustion chamber 10 gravity fed with solid fuel via a hopper 12 to which access for loading is provided by a lid 13 at the top of the boiler. The hopper tapers to a reduced cross section at the delivery point 14 into the combustion chamber 10.

This delivery point lies immediately forward of the rear wall 16 of the combustion chamber, so that the fuel 18 being burnt forms a rear triangular mass with a front face 20 sloping forwardly and downwardly.

Above the combustion chamber 10 the boiler has a water jacket which has portions 22 to the interior of the side walls of the boiler and a transverse interconnecting portion 24 formed beneath the sloping bottom wall of the hopper to the forward side of the water jacket. Ducts 26, 26A for the flow of the hot gases of combustion pass upwardly through the two side portions of the water jacket, leading from apertures in the roof of the combustion chamber on opposite sides thereof to an insulated flue chamber 28 at the top of the boiler, to which the flue 30 connects. Inlets 32 for cold water and outlets 34 for hot water are provided near the bottom and the top of the boiler. Sometimes only two will be used, an inlet on one side of the boiler and an outlet on the opposite side.

Primary and secondary air blown by a fan 36 are injected into the combustion chamber 10. The fan 36 is preferably located at the top of the boiler at the back, with a duct 38 connecting the fan down to an air box 40 beneath the combustion chamber 10.

The floor 42 of the combustion chamber 10 has a removable central section 43 with slit-shaped apertures for directing fan blown primary air PA upwardly, directly into the mass of burning fuel 18 in the combustion chamber. Secondary air SA is injected into the combustion chamber via an apertured transverse pipe 44 above the forward end of the floor of the combustion chamber, over which clinker and ash can be pushed by a periodically operable manual ram 46 into an ash box 48 in front of the air box 40. The pipe 44 receives air tapped off through pipe 45 from the duct 38. Secondary air is primarily used for burning fuel gases such as carbon monoxide.

Access to the ash box 48 is by means of a fire door 50 at the bottom front of the boiler.

Due to the injection of primary air into the combustion chamber 10 through the floor thereof, the ram is periodically operated, typically every ten hours, to eject clinker and ash, which forms a semi-solidified layer at the bottom of the mass of burning fuel, in a unique manner from the combustion chamber 10 into the ash box 48.

Thus, the floor of the combustion chamber is extended to form a shelf-like extension 52 thereof in front of the mass of burning fuel 18, as shown in Figure 3.

In Figure 3a, the boiler is recently lit, and a mass of burning fuel 18, devoid of any underlying clinker/ash layer, is supported on the floor 42 of the combustion chamber 10 above the series of slit-shaped apertures 54 through which primary air is injected to support combustion. The division between the burning fuel 18 and the "green" Anthracite 56 is adjacent the bottom of the taper of the hopper 12.

Figure 3b shows the condition after about 10 hours, when a layer 58 of clinker/ash has formed at the bottom of the mass of burning fuel 18.

The ram 46 is now operated (by an accessible manual lever on the outside of the boiler) to push the clinker/ash layer on to the shelf-like extension 52 at the forward end of the floor of the combustion chamber 10. Due to the injection of primary air from below, some burning Anthracite 64 remains on top of the clinker/ash layer 58, but most of this is not carried forward with the clinker/ash layer, as described with reference to Figure 3c.

As can be seen in Figure 1, as well as in Figure 3c, the two side portions of the water jacket are extended downwardly to enable connection thereof by a transverse water pipe 70 positioned in front of the mass of burning fuel 18 at a height such that the fire bed constituted by still burning Anthracite 64 is mostly held back when the clinker/ash layer 58 is pushed forward on to the shelf-like extension 52. In this way, relatively little still burning fuel is pushed forward eventually to enter the ash box, possibly still not fully burnt, and the overall shape and quantity of the burning fuel mass, including that on the shelf-like extension 52, is maintained more uniform, which is beneficial to efficient running of the boiler.

In front of the water pipe 70, an L-shaped plate arrangement 72, connecting at the back with the water pipe, effectively shuts off the fire door from the combustion chamber.

Riddlings pan 74 is also shown in Figure 3 for completeness.

The condition after a further ten hour period, i.e. a normal ten hour run period in continuous use of the boiler, is shown in Figure 3d. Some unburnt Anthracite 66 remains on top of the clinker/ash layer 58 on the shelf 52, and a fresh clinker/ash layer 58A has formed at the bottom of the main mass of burning fuel 18.

Operation of the ram 46 now pushes forward the clinker/ash layer 58A, together with relatively little still burning Anthracite on top of it, on to the shelf 52, thereby to push the first clinker/ash layer 58 into the ash box 48. De-clinkering then takes place substantially regularly in this way, say every ten hours, while the boiler remains in continuous use. When the fire door is opened for declinkering, the isolation of the door from the combustion chamber by the Lshaped plate arrangement 72 prevents cold air being drawn in through the door by the updraught in the flue ducts.

The ash box 48 is emptied periodically by opening the fire door 50 and, in order to prevent air being drawn in through the opened door and into the flue ducts 26, 26A, the fire door is closed off from the combustion chamber (from which gases enter the ducts 26, 26A) by the L-shaped plate arrangement 72.

The injection of primary air through an apertured floor only results in a regular shaped clinker mass, which can easily be ejected by the ram. As the clinker formed during each period has a relatively flat upper surface, when it is forced beneath the transverse water tube the bulk of the burning fuel on the clinker is scraped off. Efficient burning of fuel gases such as carbon monoxide takes place due to the injection of secondary air, generally in the space behind the L-shaped plate arrangement.

Claims

1. A gravity feed Anthracite boiler having a combustion chamber, a ram for ejecting a clinker/ash layer forwardly from beneath the fire bed, and a crosspiece in front of the fire bed at a height to hold back at least the greater part of the fire bed when the clinker/ash layer is ejected.

2. A boiler according to claim 1, wherein the combustion chamber has an apertured floor and primary air is blown upwardly into the Anthracite in the combustion chamber through the apertured floor.

3. A boiler according to claim 1 or claim 2, wherein the floor of the combustion chamber supporting the fire bed has a shelf-like extension on to which the clinker/ash layer is pushed by the ejector ram, which layer is pushed into a fire box by the next clinker/ash layer pushed out from under the fire bed the next time the ejector ram is operated.

4. A boiler according to any of claims 1 to 3, wherein secondary air is injected into the forward region of the combustion chamber in front of the crosspiece.

5. A boiler according to claim 4, wherein secondary air is tapped off from the supply of primary air to the combustion chamber.

6. A boiler according to any of claims 1 to 5, having a water jacket to the interior of both side walls of the boiler interconnected by a transverse portion to the interior of the front wall of the boiler above a fire door.

7. A boiler according to claim 6, wherein the transverse portion of the water jacket lies beneath a portion of a fuel hopper, allowing fuel to drop down the back of the boiler from a top loading point

8. A boiler according to any of claims 1 to 7, wherein the crosspiece is constituted by a transverse tube containing water and communicating with a water jacket.

9. A boiler acording to claim 8 when appendant to claim 6 or claim 7, wherein the transverse water tube connects between the two side portions of the water jacket.

10. A boiler according to any of claims 1 to 9 when appendant to claim 6 or claim 7 or claim 9, wherein combustion gases exit from the combustion chamber on both sides thereof, divided between two ducts extending upwardly within the side portions of the water jacket.

11. A boiler substantially as hereinbefore described with reference to the accompanying drawings.

11. A boiler according to any of claims 1 to 10, wherein a fuel hopper tapers to a bottom exit immediately in front of the back wall of the combustion chamber, so that fuel being burnt adopts a downwardly and forwardly sloping front face.

12. A boiler according to any of claims 1 to 11, wherein, in front of and connecting with the crosspiece, an L-shaped plate arrangement closes off the combustion chamber from a fire door operable to enable emptying of an ash box.

13. A boiler substantially as hereinbefore described with reference to the accompanying drawings.

Amendments to the claims have been filed as folows

1. A gravity feed Anthracite boiler having a combustion chamber which has an apertured floor and primary air is blown upwardly into the Anthracite in the combustion chamber through the apertured floor, a ram for ejecting a clinker/ash layer forwardly from beneath the fire bed, and a crosspiece in front of the fire bed at a height to hold back at least the greater part of the fire bed when the clinker/ash layer is rejected, wherein the floor of the combustion chamber supporting the fire bed has a shelf-like extension on to which the clinker/ash layer is pushed by the ejector ram, which layer is pushed into a fire box by the next clinker/ash layer pushed out from under the fire bed the next time the ejector ram is operated.

2. A boiler according to claim 1, wherein secondary air is injected into the forward region of the combustion chamber in front of the crosspiece.

3. A boiler according to claim 2, wherein secondary air is tapped off from the supply of primary air to the combustion chamber.

4. A boiler according to any of claims 1 to 3, having a water jacket to the interior of both side walls of the boiler interconnected by a transverse portion to the interior of the front wall of the boiler above a fire door.

5. A boiler according to claim 4, wherein the transverse portion of the water jacket lies beneath a portion of a fuel hopper, allowing fuel to drop down the back of the boiler from a top loading point.

6. A boiler according to any of claims 1 to 5, wherein the crosspiece is constituted by a transverse tube containing water and communicating with a water jacket.

7. A boiler acording to claim 6 when appendant to claim 4 or claim 5, wherein the transverse water tube connects between the two side portions of the water jacket.

8. A boiler according to any of claims 1 to 7 when appendant to claim 4 or claim S or claim 6, wherein combustion gases exit from the combustion chamber on both sides thereof, divided between two ducts extending upwardly within the side portions of the water jacket.

9. A boiler according to any of claims 1 to 8, wherein a fuel hopper tapers to a bottom exit immediately in front of the back wall of the combustion chamber, so that fuel being burnt adopts a downwardly and forwardly sloping front face.

10. A boiler according to any of claims 1 to 9, wherein, in front of and connecting with the crosspiece, an L-shaped plate arrangement closes off the combustion chamber from a fire door operable to enable emptying of an ash box.