Dual fuel boiler

Abstract

A dual fuel boiler has a granular fuel burner and a fluid fuel burner. The fluid fuel burner is movable between a retracted stored position at a side of a combustion chamber-of the boiler and an extended operative position in which it extends out over a brazier of the granular fuel burner. Thus in the operative position substantially all of the flame and hot combustion gases generated by the fluid fuel burner in use are directed away from the brazier to prevent damage to the brazier.

Claims

1. A dual fuel burner assembly for a boiler having a combustion chamber, comprising: a granular fuel burner mounted on a side wall of the combustion chamber; a granular fuel brazier associated with the granular fuel burner, said granular fuel brazier being mounted on the side wall of the combustion chamber and projecting outwardly therefrom into the combustion chamber; a canopy mounted within the combustion chamber above the granular fuel brazier to promote full combustion of granular fuel in the granular fuel brazier; a fluid fuel burner mounted above the granular fuel brazier on the same side wall of the combustion chamber as the granular fuel brazier; an air supply duct and associated fan for feeding the granular fuel burner and associated granular fuel brazier and the fluid fuel burner; wherein the fluid fuel burner is mounted adjacent the granular fuel brazier on the side wall of the combustion chamber with the fluid fuel burner mounted above the granular fuel brazier between the granular fuel brazier and the associated canopy, and the fluid fuel burner is movable within the combustion chamber between a retracted stored position on the side wall of the combustion chamber at a side of the combustion chamber and an extended operative position in which the fluid fuel burner projects outwardly from the side wall of the combustion chamber into the combustion chamber extending out over the granular fuel brazier in which flame and combustion gases generated by the fluid fuel burner in use when it is in the extended operative position are directed away from the granular fuel brazier.

2. The dual fuel burner assembly as claimed in claim 1 wherein the fluid fuel burner locates outside the combustion chamber when in the stored position.

3. The dual fuel burner assembly as claimed in claim 1 wherein the fluid fuel burner is slidably movable between the stored position and the operative position.

4. The duel fuel burner assembly as claimed in claim 1 wherein an actuator is connected to the fluid fuel burner, said actuator being operable for moving the fluid fuel burner between the stored position and the operative position.

5. The duel fuel burner assembly as claimed in claim 4 wherein the actuator comprises a rack attached to the fluid fuel burner and an associated drive pinion which operably engages the rack and a drive motor driveably connected to the pinion.

6. The dual fuel burner assembly as claimed in claim 1 wherein the fluid fuel burner is mounted on a telescopic support for movement between the stored position and the operative position.

7. The dual fuel burner assembly as claimed in claim 6 wherein an actuator is connected to the fluid fuel burner, said actuator being operable for moving the fluid fuel burner between the stored position and the operative position, and the telescopic support comprises a blast tube slidably mounted within an outer support tube, the blast tube being movable through said outer support tube by means of the actuator which is connected to the blast tube, a fluid fuel burner nozzle being mounted at an outer end of the blast tube.

8. The dual fuel burner assembly as claimed in claim 7 wherein the blast tube forms an air duct for delivery of combustion air to the nozzle.

9. The dual fuel burner assembly as claimed in claim 8 wherein the blast tube has at least one air inlet opening which communicates with the air supply duct when the blast tube is in an extended operative position corresponding to the operative position of the burner.

10. The dual fuel burner assembly as claimed in claim 1 wherein the air duct has an outlet communicating with the brazier, a valve mounted at the outlet and being operable to close the outlet when the fluid fuel burner is in the operative position.

11. The dual fuel burner assembly as claimed in claim 10 wherein the valve is biased into an open position and is movable against said bias into a closed position by means of a ram.

12. The dual fuel burner assembly as claimed in claim 11 wherein the ram is operably connected to the fluid fuel supply for the fluid fuel burner such that pressurisation of the fluid fuel for delivery to the fluid fuel burner operates the ram to close the valve.

13. The dual fuel burner assembly as claimed in claim 10 wherein the fluid fuel burner is mounted on a telescopic support for movement between the stored position and the operative position, an actuator is connected to the fluid fuel burner, said actuator being operable for moving the fluid fuel burner between the stored position and the operative position, and the telescopic support comprises a blast tube slidably mounted within an outer support tube, the blast tube being movable through said outer support tube by means of the actuator which is connected to the blast tube, a fluid fuel burner nozzle being mounted at an outer end of the blast tube, wherein the valve is mounted on the blast tube such that the valve is closed when the blast tube is in the extended operative position and the valve is open when the blast tube is in the retracted position.

14. A dual fuel burner assembly for a boiler having a combustion chamber, comprising: a granular fuel burner mounted on a side wall of the combustion chamber; a granular fuel brazier associated with the granular fuel burner, said granular fuel brazier being mounted on the side wall of the combustion chamber and projecting outwardly therefrom into the combustion chamber; a canopy mounted within the combustion chamber above the granular fuel brazier to promote full combustion of granular fuel in the granular fuel brazier; a fluid fuel burner mounted above the granular fuel brazier on the same side wall of the combustion chamber as the granular fuel brazier; an air supply duct and associated fan for feeding the granular fuel burner and associated granular fuel brazier and the fluid fuel burner; wherein the fluid fuel burner is mounted adjacent the granular fuel brazier on the side wall of the combustion chamber with the fluid fuel burner mounted above the granular fuel brazier between the granular fuel brazier and the associated canopy, and the fluid fuel burner is slidably movable within the combustion chamber between a retracted stored position on the side wall of the combustion chamber at a side of the combustion chamber and an extended operative position in which the fluid fuel burner projects outwardly from the side wall of the combustion chamber into the combustion chamber extending out over the granular fuel brazier such that flame and combustion gases generated by the fluid fuel burner in use when it is in the extended operative position are directed away from the granular fuel brazier.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a side diagrammatic view of a boiler incorporating a dual fuel burner assembly according to the invention, in a position in which granular fuel is being burned;

(3) FIG. 2 is a view similar to FIG. 1, in which a fluid fuel burner is being used;

(4) FIG. 3 is a view similar to FIG. 1 showing another boiler according to a second embodiment of the invention; and

(5) FIG. 4 is a view similar to FIG. 2 of the boiler of FIG. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(6) Referring to the drawings, and initially to FIGS. 1 and 2 thereof there is provided a dual fuel boiler, indicated generally by the reference numeral 1, comprising a base 2 and upstanding side walls 3. The boiler 1 is divided into a combustion chamber 4 and a heat transfer and condensing unit 5, containing conventional boiler tubes and, for example, including water-filled walls. Mounted on the base 2 is an ash pan 6. All of this is conventional.

(7) There is further provided a dual fuel burner assembly, indicated generally by the reference numeral 10, comprising a granular fuel burner indicated generally by the reference numeral 11, and a fluid fuel burner, indicated generally by the reference numeral 12, and more clearly illustrated in FIG. 2. The whole of the granular fuel burner 11 is not, strictly speaking illustrated fully as the electrodes are mounted behind the fluid fuel burner 12 in an air chamber which will be described hereinafter.

(8) A wood pellet supply duct 20 feeds an air chamber 21 which in turn is fed by a fan 22. The air chamber 21 is connected to a brazier 23 through an outlet 24 having an associated valve 24a. The side valve 24a is connected by a con rod 25 and return spring 26 to a hydraulic ram 27 fed by oil through an oil line 28 from a combined motor and oil pump 29. The construction of brazier 23 is described in more detail in our co-pending European Patent Application No. 08169363.2 previously referenced.

(9) The fluid fuel burner, in this embodiment an oil burner 12, comprises an injector nozzle 30 mounted in a blast tube 31. The blast tube 31 includes air supply openings 32 and is in turn mounted in a support tube 33. The support tube 33 further houses a rack 34 and pinion 35 driven by a motor 36. A flexible oil supply line 37 feeds, from the combined motor and oil pump 29, fuel to the injector nozzle 30. The motor 36 is operable to drive the pinion 35 which in turn drives the rack 34 for sliding the blast tube 31 within the support tube 33. Thus, the fluid fuel burner 12 can be moved between a retracted stored position as shown in FIG. 1 and an extended operative position as shown in FIG. 2. As can be seen in the drawings, when in the retracted stored position, the fluid fuel burner 12 locates at a side of the combustion chamber 4 outside the combustion chamber 4 and when in the extended operative position, the fluid fuel burner 12 projects into the combustion chamber 4, extending out over the brazier 23. The rack 34, pinion 35 and motor 36 together form an actuator for slidably moving the fluid fuel burner 12 between the stored position and the operative position.

(10) The blast tube 31 and associated support tube 33 together form a telescopic support for the fluid fuel burner 12. It will be noted that when the blast tube 31 is in the extended position as shown in FIG. 2 a number of circumferentially spaced-apart air supply openings 32 in a side wall of the blast tube 31 communicate with the air chamber 21 for supply of combustion air through the blast tube 31 to the injector nozzle 30. Similar openings may be provided in the support tube 33 for through-passage of air, or alternatively the air supply openings 32 may be positioned outwardly of an outer end of the support tube 33 when the blast tube 31 is in the fully extended position.

(11) As the oil pump 29 is switched on to supply pressurised fuel to the injector nozzle 30, pressurised oil is delivered through the oil line 28 to the ram 27 which overcomes spring 26 bias to close the valve 24a cutting off air supply to the brazier 23.

(12) Finally, it will be noted that above the brazier 23, there is mounted a canopy 40, which canopy 40 is to make sure the combustion in the brazier 23 is full combustion and that there is not residual carbon monoxide (CO) in the boiler to be subsequently exhausted to atmosphere.

(13) In operation, and referring firstly to FIG. 1 where the boiler 1 is shown in operation as a wood pelletted boiler, namely, with the granular fuel burner 11 in operation, wood pellets are delivered through the wood pellet supply duct 20 into the brazier 23 in conventional manner. Simultaneously, air is delivered by the fan 22 into the air chamber 21 and through the outlet 24, the valve 24a of which is now open, and into the brazier 23 for normal combustion. The air in the air chamber 21 bypasses the support tube 33 and blast tube 31.

(14) In operation, when it is desired to use the fluid fuel burner, in this case, the oil burner 12, the motor 36 is operated and the blast tube 31 is extended from a retracted stored position within the support tube 33. The air supply openings 32 in the blast tube 31 are exposed and air is delivered from the air chamber 21 through the blast tube 31 to the burner 12 injector nozzle 30. The valve 24a is shut by the hydraulic ram 27 closing the outlet 24 to the brazier 23.

(15) It will be noted that now the combustion flame and gases generated by the injector nozzle 30 are injected into the combustion chamber 4 remote from the brazier 23 and are directed away from the brazier 23.

(16) Referring now to FIGS. 3 and 4, there is illustrated another duel fuel boiler indicated generally by the reference numeral 50. It is largely similar to the boiler 1 described previously and like parts are assigned the same reference numerals. In this case the valve 24a is mounted by an arm 52 on the blast tube 31 such that the valve 24a is closed when the blast tube 31 is in the extended operative position shown in FIG. 4 and the valve 24a is open when the blast tube 31 is in the retracted position shown in FIG. 3. A suitable opening is provided in the support tube 33 for through-passage of the arm 52. Other than this the construction and operation of the boiler 50 is similar to that for the boiler 1 described previously.

(17) In this specification, the terms comprise, comprises, comprised and comprising and the terms include, includes, included and including are deemed totally interchangeable and should be afforded the widest possible interpretation.

(18) The invention is in not limited to the embodiments hereinbefore described but may be varied in both construction and detail, within the scope of the appended claims.