GB1565247A

GB1565247A - Burners for kilns

Info

Publication number: GB1565247A
Application number: GB330077A
Authority: GB
Original assignee: CROMARTIE KILNS Ltd
Current assignee: CROMARTIE KILNS Ltd
Priority date: 1978-01-25
Filing date: 1978-01-25
Publication date: 1980-04-16

Description

(54) IMPROVEMENTS IN OR RELATING TO BURNERS FOR KILNS (71) We, CROMARTIE KILNS LIMITED, a British Company of Park Hall Road, Longton, Stoke-on-Trent, Staffordshire do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to burners, especially burners which are known as gas and air burners for use particularly but not exclusively in kilns wherein clayware is to be fired.

In one previously proposed type of gas and air burner air and gaseous fuel is completely premixed before being delivered to the burner nozzle but this type of burner suffers from flame blowback in a low turndown condition which is particularly applicable to firing kilns.

According to the present invention there is provided a burner apparatus comprising a housing having an internal chamber communicating with a nozzle, an inlet in said housing for admission of air, first inlet means in said chamber for admission of gaseous fuel thereto under pressure, and second inlet means in said chamber arranged such that inflow of pressurised gaseous fuel draws a proportion of air from the housing inlet into the chamber to enable air and the gaseous fuel to be mixed in desired proportions in said chamber, and outlet means through which the air and the gaseous fuel mixture can pass from said chamber out of the nozzle, the remaining proportion of air from the housing inlet being arranged to be delivered through the housing to a location adjacent to the nozzle.

Preferably the area of the outlet means is greater than the area of the second inlet means in said chamber.

Preferably also said chamber is supported coaxially within the housing and defines an annular channel between the chamber and the housing for passage of said remaining proportion of air. Advantageously, said second inlet means in said chamber comprises a plurality of holes arranged around the periphery of said chamber adjacent to said first inlet means for communication between said chamber and the annular channel. Also said outlet means preferably comprises a plurality of holes located around the periphery of the nozzle.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawing, the single figure of which shows a burner apparatus according to the invention in longitudinal section.

Referring to the drawing a burner for use particularly in kilns wherein clayware is to be fired comprises a housing 10 which is of cylindrical cross-section and which has an enlarged section 12 at one end thereof, preferably formed of high temperature metal e.g.

stainless steel, titanium. A circular mounting plate 14 extends across the section 12 towards the inner end thereof in a plane normal to the longitudinal axis of the housing 10 and is retained in position by means of locating screws 16 so as to define an annular passage between the periphery of the plate 14 and the inner wall of the housing section 12.

The plate 14 is provided with an axial through aperture 18 and mounts, on an outer face 20, a nozzle 22 which has a mushroom head and which has a central cavity 24 opening at the face 20 in axial alignment with the aperture 18 in the plate 14. Outlet means is provided for the cavity 24 in the form of an axially extending hole 25 and twelve radially extending holes 26 in the nozzle 22 communicating between the cavity 24 and externally of the nozzle 22, the holes 26 being arranged in axially aligned groups of three at 90" intervals round the periphery of the nozzle 22. The latter is preferably made of a high temperature metal, e.g. stainless steel, titanium.

The plate 14 also mounts on its inner face 28, i.e. the face remote from the nozzle 22, a tubular member 30 which is open ended and opens at one end in axial alignment with the aperture 18 in the plate 14 and at the other end opens into a chamber 32, pref=- ablv formed of a high temprature metal, e.g.

stainless steel, titanium. The member 30 and the chamber 32 extend coaxially within the housing 10 so as to define an annular channel therewith. At the other end of the chamber 32 there is located one end of an inlet tube 34 for admission of gaseous fuel under mains pressure to the chamber 32, the tube 34 being further supported in the housing by an annular support plate 36. Means (not shown) is provided to control the flow of gaseous fuel into the tube 34.

A pair of electrodes 38, 40 are located within the housing 10 and extend longitudinally thereof, at diametrical opposed locations, to the nozzle 22. The electrodes 38, 40 extend through, to be supported by, the plates 14 and 36 and form a spark gap at the nozzle 22. The function of the electrodes as seff ignition and flame failure devices for a gas and air burner is well established.

At a location in the wall of the housing 10 towards that end of the chamber 32 remote from the nozzle 22 an air inlet 42 is provided. A low pressure fan or the like (not shown) is provided for delivery of the air.

Towards the same end of the chamber 32 the latter is provided with an inlet arrangement through which a proportion of the air being delivered to the inlet 42 can pass into the chamber 32. The inlet arrangement is preferably in the form of radially extending holes 44 around the periphery of the chamber 32 and spaced from one another by 900.

The total area of the holes 44 is less than the total area of the holes 26 in the nozzle 22.

In operation, air is delivered through the inlet 42 to the housing 10 and gaseous fuel is delivered to the chamber 32 under pressure through the tube 34. The latter opens into the chamber 32 at the location of the holes 44 such that inflow of the pressurised gaseous fuel draws a proportion of air through the inlet holes 44 into the chamber 32. This proportion of air is mixed with the gaseous fuel in the chamber 32 and passes through the member 30 to the cavity 24 of the nozzle 22 and therefrom through the outlet holes 26.

Simultaneously the remaining proportion of air delivered through the inlet 42 passes through the annular channel defined between the member 30 and chamber 32 and the inner wall of the housing 10, through the annular channel defined by the plate 14 to a location adjacent to the nozzle 22.

The controlIed premixing of the air and gaseous fuel provides a more stable flame closer to the nozzle and along with the nozzle mushroom head which creates turbulence, prevents the formation of unburnt carbon which would otherwise cause failure of the self ignition and flame failure devices. Also in low turn down conditions flame blowback is prevented. It will be appreciated that the size of the flame produced can be varied by varying the relative proportions of the air/gas jets and the amount of air delivered externally of the nozzle. The burner is capable of operating within a wide range of temperatures and operates more efficiently than known burners in oxidising conditions.In all conditions the flame can be maintained efficiently at all times thereby eliminating nuisance shut down of the burner, In another known type of gas and air burner wherein a partial pre-mix takes place, the air is required to entrain the gaseous fuel and therefore has to be supplied at a significantly higher pressure than the air in the present invention, requiring auxiliary means for so pressurising the air. Unlike the present invention such an arrangement does not adequately perform in reducing atmospheres as required in pottery kilns, preferably at any stage of turndown, and cannot achieve an over-gassed situation which is often required in kilns to affect glaze, without the use of an involved system using bypasses and governors etc.Also, unlike the present invention, stable conditions cannot be achieved with flame turndown, which can be in excess of 50:1 as required in kilns, because of the high air pressure.

Various modifications may be made without departing from the invention as defined in the claims. For example the burner as hereinbefore described may be used in ap plications other than firing kilns.

WHAT WE CLAIM IS:- 1. Burner apparatus comprising a housing having an internal chamber communicating with a nozzle, an inlet in said housing for admission of air, first inlet means in said chamber for admission of gaseous fuel thereto under pressure, and second inlet means in said chamber arranged such that inflow of pressurised gaseous fuel draws a proportion of air from the housing inlet into the chamber to enable air and the gaseous fuel to be mixed in desired proportions in said chamber, and outlet means through which the air and the gaseous fuel mixture can pass from said chamber out of the nozzle, the remaining proportion of air from the housing inlet being arranged to be delivered through the housing to a location adjacent to the nozzle.

2. Apparatus according to Claim 1, wherein the area of the outlet means is greater than the area of the second inlet means in said chamber.

3. Apparatus according to Claim 1 or 2, wherein said chamber is supported coaxially within the housing and defines an annular channel between the chamber and the housing for passage of said remaining proportion of air.

4. Apparatus according to any of the pre

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. other end opens into a chamber 32, pref=- ablv formed of a high temprature metal, e.g. stainless steel, titanium. The member 30 and the chamber 32 extend coaxially within the housing 10 so as to define an annular channel therewith. At the other end of the chamber 32 there is located one end of an inlet tube 34 for admission of gaseous fuel under mains pressure to the chamber 32, the tube 34 being further supported in the housing by an annular support plate 36. Means (not shown) is provided to control the flow of gaseous fuel into the tube 34. A pair of electrodes 38, 40 are located within the housing 10 and extend longitudinally thereof, at diametrical opposed locations, to the nozzle 22. The electrodes 38, 40 extend through, to be supported by, the plates 14 and 36 and form a spark gap at the nozzle 22. The function of the electrodes as seff ignition and flame failure devices for a gas and air burner is well established. At a location in the wall of the housing 10 towards that end of the chamber 32 remote from the nozzle 22 an air inlet 42 is provided. A low pressure fan or the like (not shown) is provided for delivery of the air. Towards the same end of the chamber 32 the latter is provided with an inlet arrangement through which a proportion of the air being delivered to the inlet 42 can pass into the chamber 32. The inlet arrangement is preferably in the form of radially extending holes 44 around the periphery of the chamber 32 and spaced from one another by 900. The total area of the holes 44 is less than the total area of the holes 26 in the nozzle 22. In operation, air is delivered through the inlet 42 to the housing 10 and gaseous fuel is delivered to the chamber 32 under pressure through the tube 34. The latter opens into the chamber 32 at the location of the holes 44 such that inflow of the pressurised gaseous fuel draws a proportion of air through the inlet holes 44 into the chamber 32. This proportion of air is mixed with the gaseous fuel in the chamber 32 and passes through the member 30 to the cavity 24 of the nozzle 22 and therefrom through the outlet holes 26. Simultaneously the remaining proportion of air delivered through the inlet 42 passes through the annular channel defined between the member 30 and chamber 32 and the inner wall of the housing 10, through the annular channel defined by the plate 14 to a location adjacent to the nozzle 22. The controlIed premixing of the air and gaseous fuel provides a more stable flame closer to the nozzle and along with the nozzle mushroom head which creates turbulence, prevents the formation of unburnt carbon which would otherwise cause failure of the self ignition and flame failure devices. Also in low turn down conditions flame blowback is prevented. It will be appreciated that the size of the flame produced can be varied by varying the relative proportions of the air/gas jets and the amount of air delivered externally of the nozzle. The burner is capable of operating within a wide range of temperatures and operates more efficiently than known burners in oxidising conditions.In all conditions the flame can be maintained efficiently at all times thereby eliminating nuisance shut down of the burner, In another known type of gas and air burner wherein a partial pre-mix takes place, the air is required to entrain the gaseous fuel and therefore has to be supplied at a significantly higher pressure than the air in the present invention, requiring auxiliary means for so pressurising the air. Unlike the present invention such an arrangement does not adequately perform in reducing atmospheres as required in pottery kilns, preferably at any stage of turndown, and cannot achieve an over-gassed situation which is often required in kilns to affect glaze, without the use of an involved system using bypasses and governors etc.Also, unlike the present invention, stable conditions cannot be achieved with flame turndown, which can be in excess of 50:1 as required in kilns, because of the high air pressure. Various modifications may be made without departing from the invention as defined in the claims. For example the burner as hereinbefore described may be used in ap plications other than firing kilns. WHAT WE CLAIM IS:-

1. Burner apparatus comprising a housing having an internal chamber communicating with a nozzle, an inlet in said housing for admission of air, first inlet means in said chamber for admission of gaseous fuel thereto under pressure, and second inlet means in said chamber arranged such that inflow of pressurised gaseous fuel draws a proportion of air from the housing inlet into the chamber to enable air and the gaseous fuel to be mixed in desired proportions in said chamber, and outlet means through which the air and the gaseous fuel mixture can pass from said chamber out of the nozzle, the remaining proportion of air from the housing inlet being arranged to be delivered through the housing to a location adjacent to the nozzle.

4. Apparatus according to any of the pre

ceding claims. wherein said second inlet means in said chamber comprises a plurality of holes arranged around the periphery of said chamber adjacent to said first inlet means for communication between said chamber and the annular channel.

5. Apparatus according to any of the preceding claims wherein said outlet means comprises an axially extending hole and a plurality of holes located around the periphery of the nozzle.

6. Apparatus according to any of the preceding claims, wherein the nozzle and the chamber are formed of a high temperature metal.

7. Burner apparatus substantially as hereinbefore described with reference to the accompanying drawing.