GB2079910A

GB2079910A - Solid fuel burner

Info

Publication number: GB2079910A
Application number: GB8022250A
Authority: GB
Original assignee: DALBY HARRY ROBERT
Current assignee: DALBY HARRY ROBERT
Priority date: 1980-07-08
Filing date: 1980-07-08
Publication date: 1982-01-27
Also published as: GB2079910B

Abstract

A solid fuel burner has a cylindrical burner chamber 1 rotated in use about its axis which is inclined to the horizontal. Fuel is fed from its lower end, and air to support combustion is forced in through apertured sides. Waste products, especially clinker, are automatically discharged from an open mouth at the upper end of the burner chamber, this being a natural consequence of the rotation of the chamber. <IMAGE>

Description

SPECIFICATION Solid fuel burner The invention relates to solid fuel burners for central heating plant, and to central heating plant incorporating such burners. The invention is particularly concerned with such heating plant for heating industrial premises, where the savings associated with the use of the lower priced solid fuels, rather than electricity, oil or gas, will be of great benefit.

Problems which have traditionally been associated with the design of solid fuel burners have been their need for constant tending; the difficulty of ensuring uniform and efficient combustion; the difficulty of removing the ash and clinker that is formed; and the high carbon monoxide content of the flue gases. These problem are to a large extent interdependent.

Taking a coal burner by way of example: there is a tendency for coal to swell and fuse during combustion; this leads to inefficient burning due to the failure of the air supply to support combustion at the centre of the fused mass; inefficient burning means a higher carbon monoxide content in the flue gases; and the fusing results in the formation of larger pieces of clinker.

Traditionally clinker is removed by being allowed to fall downwardly through a fire grate, but if the individual clinker pieces are too large to pass through the grate they collect in the burner and have to be removed periodically when the burner is shut down and cool enough for access.

The invention adopts a novel and inventive solution which enables solid fuels, including coal, to be burned efficiently and the clinker removed automatically. The invention provides a solid fuel burner comprising a rotatable burner chamber which has an open mouth at one end thereof, means for introducing solid fuel axially into the chamber from the other end thereof, means for passing air through the chamber and means for rotating the chamber during combustion of the solid fuel therein.

One effect of rotation of the chamber is to move or stir the burning solid fuel continuously, ensuring efficient combustion and breaking up of the clinker as it forms. However perhaps the most surprisingly effective feature of a burner according to the invention is the facility of automatic clinker removal. As the burner chamber rotates, fresh fuel is supplied to the end remote from the open mouth and the ash and the pieces of clinker collect, not at the bottom of the fire bed, but at the top, where they spill out of the open mouth of the chamber. Combustion can therefore continue for prolonged periods without the need for attention.

Preferably the burner chamber is cylindrical, with a frusto-conical mouth through which the ash and slag issues. The axis of rotation is advantageously inclined at an acute angle to the horizontal, with the open mouth of the chamber at a higher level than the other end.

Preferably the air is blown through a plenum chamber surrounding the rotating chamber, and enters the chamber through apertures in its side and/or end walls. In this way some of the air passes through the mass of burning fuel to support combustion there, and the remainder of the air passes over the burning fuel where it provides for complete oxidation of the combustion gases. In addition, the plenum chamber provides thermal insulation of the bearings on which the burner chamber rotates.

The fuel feed may conveniently be a screw feed from a hopper. The thermal output of the burner may be controlled in use by varying the rate of solid fuel feed and/or the air feed, even to the extent of reducing the thermal output to a purely standby capacity.

For example, to cut back the thermal output from full output to a standby capacity the fuel feed could be switched off; the air feed could be continued for several minutes to burn off volatiles from the fuel and thus avoid smoke; and then the air feed could be interrupted. Thereafter it is necessary periodically to switch on the fuel/air feed cycle for brief intervals to keep the fuel bed alight. This may be achieved by a time-controlled switch which switches the air supply on for a short period say once every hour. In this way it has been possible to keep the burner at its standby capacity continuousiy for as long as may be desired.

To light a burner according to the invention it is necessary only to ignite a firelighter in the fuel bed and to start up the airflow and the rotation of the burner chamber. For a more automated start-up, however, it may be thought desirable to incorporate gas burners and igniters so that a simple switch depression, possibly at a remote location, is sufficient to ignite the gas burners until the fuel is well alight.

The invention also proves central heating plant in which such a burner has its mouth directed into an after-combustion chamber leading to a heat exchange chamber for heating a central heating fluid. In use when the fuel is burning in the rotating burner chamber, a tongue of flame extends out of the mouth of the burner chamber into the after-combustion chamber. The ash and clinker also issue out of the mouth of the burner chamber where they fall to the floor of the aftercombustion chamber and are removed either by means of an ash and clinker tray provided for the purpose or by means such as a scraper or conveyor for automatically transporting away all that falls from the burner mouth.

The drawing is a diagrammatic section through a coal-fired central heating plant incorporating a burner according to the invention. The burner comprises a cylindrical double-walled burner chamber 1 mounted on bearings (not shown) with its axis inclined to the horizontal. At the upper end of the burner chamber 1 is an open mouth 2 facing into an after-combustion chamber 3.

The inner wall of the burner chamber 1 is apertured and the space between the inner and outer walls acts as a plenum chamber for air which is fed as indicated by the single-headed arrows both through and over the fire bed 4 in the burner chamber 1. The fire bed 4 is formed by feeding solid fuel, such as coal, axially from the lower end of the chamber 1 in the direction of the double-headed arrow. This feed may be, for example, a screw feed from a fuel hopper.

In use the chamber 1 is driven for example via a ring gear 5 and the solid fuels burned in the air passing through and over the fire bed 4. Waste and clinker 6 form, and are thrown to the top of the fire bed 4 by the rotation of the chamber 1. When the fuel feed is sufficient to fill the chamber 1 to the level shown, this waste and clinker 6 spills out of the open mouth 2 onto a pile 7 at the bottom of the after-combustion chamber 3. From there they can be removed for example in a removable tray or container provided for the purpose.

The after-combustion chamber 3 leads to a heat exchange section 8 which may be air or water cooled depending on the nature of the central heating plant.

All other features of operation will be readily apparent from the above general description of the invention.

Claims

1. A solid fuel burner comprising a rotatable burner chamber that has an open mouth at one end thereof, means for introducing solid fuel axially into the chamber from the other end thereof, means for passing airthrough the chamber and means for rotating the chamber during combustion of the solid fuel therein.

2. A burner according to claim 1, wherein the axis of rotation of the burner chamber is inclined at an acute angle to the horizontal with the open mouth of the chamber at a higher level than the other end.

3. A burner according to claim 1 or claim 2, wherein the burner chamber is cylindrical with a frusto-conical mouth.

4. A burner according to any preceding claim, wherein the means for passing air through the burner chamber comprises a plenum chamber surrounding the burner chamber and communicating with the burner chamber via apertures in the side wall and optionally the end wall thereof opposite to the open mouth.

5. A burner according to any preceding claim, wherein the means for introducing the solid fuel axially into the chamber comprises a screw feed from a fuel hopper.

6. A burner according to any preceding claim, wherein the means for introducing the solid fuel axially into the chamber is operable at a variable speed.

7. A burner according to any preceding claim, wherein the means for passing air through the chamber is operable to provide a variable rate of air flow.

8. Central heating plant comprising a burner according to any preceding claim, the mouth of which is directed into an after-combustion chamber leading to a heat exchange chamber for heating the central heating fluid.

9. Plant according to claim 8, wherein an ash and clinker tray is provided on the floor of the after-combustion chamber beneath the mouth of the burner for collecting and periodically removing the ash and clinker.

10. Plant according to claim 8, wherein on the floor of the after-combustion chamber beneath the mouth of the burner there is provided means for automatically transporting away ash and clinker falling from the mouth of the burner.

11. Central heating plant substantially as described herein with reference to the drawings.