US3256842A

US3256842A - Multiple fuel burner

Info

Publication number: US3256842A
Application number: US356239A
Authority: US
Inventors: Vigneron Claude Charles Eugene; Stoufilet Robert
Original assignee: Babcock and Wilcox Ltd
Current assignee: Babcock International Ltd
Priority date: 1963-04-02
Filing date: 1964-03-31
Publication date: 1966-06-21
Anticipated expiration: 1983-06-21
Also published as: FR1360793A; GB1038002A

Description

June 1966 c. c. E. VIGNERON ETAL 3,256,842

MULTIPLE FUEL BURNER 5 Sheets-Sheet 1 Filed March 31v 1964 INVENTORS Claude C.E. Vigneron Roberr Sfouff lei ATTORNEY June 21,1966

C. C. E. VIGNERON ETAL MULTIPLE FUEL BURNER 3 Sheets-Sheet 2 Filed March 31. 1964 IIHHI June 1966 c. c. E. VIGNERON ETAL 3,

MULTIPLE FUEL BURNER Filed March 31. 1964 3 Sheets-Sheet 5 United States Patent 3,256,842 MULTIPLE FUEL BURNER Claude Charles Eugene Vigneron and Robert Stoufilet,

Paris, France, assignors to Babcock & Wilcox, Limited, London, England, a corporation of Great Britain Filed Mar. 31, 1964, Ser. No. 356,239 Claims priority, application France, Apr. 2, 1963, 930,093, Patent 1,360,793 6 Claims. (Cl. 11022) The present invention relates generally to burners, and more particularly to burners which are used in connection with vapor generators and which burn pulverized carbonaceous fuel and/ or a supplementary fuel such as fuel oil.

When pulverized coal is used as the primary fuel in the combustion chamber of a vapor generator, it is necessary to provide an auxiliary fuel system, the auxiliary fuel being used not only to ignite the pulverized coal, but also to sustain the main flame at certain operational conditions, e.g., at low loads. The auxiliary fuel must be of the easily ignitable class, such as light fuel oil or natural gas, since combustion is usually initiated by a high voltage electrical spark. In order to minimize consumption of the relatively expensive auxiliary fuel, it is desirable that the auxiliary fuel system be capable of variable load operation so that the firing rate of the auxiliary system may be kept as low as possible in relation to the requirements of sustaining combustion of the main fuel stream.

If the vapor generator is to additionally be operated with an alternate or supplementary main fuel such as heavy oil,

it becomes necessary to provide an additional (third) fuel system in order to be able to insure the attainment of full load conditions on the vapor generator when using either or both primary fuels. Normally, the full load capacity of the primary fuel system is about ten times greater than the capacity of the auxiliary fuel system.

The present invention provides for the realization of a combined burner having incorporated therein an auxiliary fuel system capable of igniting and sustaining a pulverized coal flame, and a supplementary heavy fuel oil system which can alternately assume the full load of the vapor generator, either alone or in combination with the pulverized fuel system. To efi'ect these purposes, the inventive burner comprises a pulverized coal burner having an inlet channel of annular form defined by fixed inner and outer concentric tubes. An axially movable eccentric tube assembly isdisposed within the inner conduit and contains an electrically ignited auxiliary fuel system and flame detection means therefore, and a supplementary fuel oil nozzle assembly and a separate flame detection means therefor.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the specification. For a better understanding of the invention, its operating and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a partially sectioned elevation view of the combination burner disclosed herein;

FIG. 2 is a partially sectioned view of the burner taken along line 2-2 of FIG. 1;

FIG. 3 is a rear end view taken along line 3-3 of FIG.

FIG. 4 is a sectional view taken along line 44 of FIG. 1; and

FIG. 5 is an enlarged front end view taken along line 5-5 of FIG. 1 and having portions thereof removed.

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As shown in the drawings, the subject inventive burner includes a pulverized coal burner which includes an outer tubular member 1 having its forward end opening into the combustion chamber 2, the outer tube 1 being suitably connected at its rearward end with an elbow 3 to which is connected a coal and primary air feeding conduit 4. It should be recognized that the tube 1 traverses a pressurized windbox 5, and that separate provisions (not shown) are made for introducing secondary air into the combustion chamber 2. The elbow 3 is internally formed with a supporting sleeve 7 connected to a circular flange 8 which is suitably connected to the body of the elbow 3. The internal bore 9 of the supporting sleeve 7 is provided with two raised bearing surfaces 10 on which is supported the tube 11. An upwardly extending flanged inlet pipe 12 is integrally formed as part of the sleeve 7, and connects with an air supply pipe 13, through which air is supplied from the windbox 5 to the air chest 14 for passage through the internal portions of the burner as will be described hereinafter.

It should be noted that the external tube 1 and the concentrically disposed inner tube 11 cooperate to define an annular pulverized fuel inlet channel opening into the combustion chamber 2, the pulverized fuel and primary air being supplied to the annular channel from the conduit4. The forward end of the inner tube 11 carries a coal diffuser or impeller 33 which extends in front of the open forward end of the annular pulverized fuel inlet channel.

An axially movable tube 15 is arranged on the interior of the inner tube 11 and is displaced eccentrically upwardly in relation to the co-extensive longitudinal central axis of the inner and

outer tubes

1 and 11, thus forming a longitudinally extending crescent shaped space 47. Lugs 17, fastened to the inner tube 11 (FIG. 5) serve to support and guide the movable tube 15. At its rearward end, the tube 15 supports a connecting case 16 to which are attached the electrical cables A and D of the ignitor and flame detector devices operatively associated with the ignition system to be described hereinafter.

A substantially horizontal partition 18 (FIG. 5), extending longitudinally of the interior of the tube 15, divides the volume enclosed by the tube 15 into the mutually isolated upper and

lower chambers

19 and 20, containing respectively, a gas ignitor 21 and a fuel oil supply assembly 22. The ignitor 21 includes a pilot burner 23 and two

gas nozzles

24 and 25 disposed on opposite lateral sides of the pilot burner 23. The

nozzles

24 and 25 and the pilot burner 23 are all connected with a supply tube 26 which extends rearwardly and connects with an inlet gas tube 27 arranged on the connecting case 16. Calibrated orifices 28 are provided to appropriately proportion the gas between the pilot burner 23 and the

nozzles

24 and 25. The pilot burner is provided with a spark-producing igniting electrode 30 and a separate flame sensing electrode 31 which is connected to a flame detector (not shown) of the type responsive to the immersion of the electrode 31 in a flame. An air inlet pipe 32, near the rearward end of the tube 15, is connected with a suitable supply of air for sweeping the upper chamber 19 (including the gas ignitor 21) with air. The fuel oil supply assembly 22 and the nozzle 22A disposed at the forward end thereof are preferably of the type capable of operating over a wide load range, e.g., ten-to-one. Suitably this may be of the type employing mechanical atomization at high loads and utilizing high pressure steam or air for atomization at low loads. The assembly 22 is contained substantially concentrically within a tube or distance piece 35 which is disposed in the lower chamber 20 of the tube 15 so that the axis of the assembly 22 is substantially co-extensive with the centerlines of the inner and outer tubes 1 and 11 (FIG.

The tube 15 is axially movable inside the inner tube 11, the axial position of which may be adjusted and fixed by means of set screws 37. It should be understood that once adjusted to meet the particular conditions of the installation, the inner tube 11 is kept in the same axial position and is for all practical purposes stationary, i.e., it is not contemplated that the axial position of the inner tube 11 -will be changed during normal operation. The rearward end of the inner tube 11 supports two laterally disposed hydraulic-

jacks

38 and 39 by means of a connecting flange 40. The piston rods 42 of the

hydraulic jacks

38 and 39 are connected to a driving flange 43 which is in turn connected to the axially movable tube 15 through adjusting screws 44 and lugs 45 which are aflixed to the tube 15. It should be recognized that the adjusting screws 44 may be used to alter, within limits, the forwardmost position of the tube 15. A packing gland 46, at the rearward end of the inner tube 11 insures the tightness of connection between the fixed-position inner tube 11 and the axially movable tube 15.

The sighting space 47, having a crescent shaped cross section extending around and mainly below the movable tube 15 within the inner tube 11, is used for inspection of the flame of the burning fuel oil issued from nozzle 22A. A light-sensitive flame detecting device 51 is preferably arranged at the rearward end of the space 47 at the lower portion thereof.

Air delivered to the air chest 14 through the air supply pipe 13 is admitted consecutively into the space 47, the chamber 20, and the annular space between the fuel oil supply tube 22 and the distance piece 35 through substantially aligned pairs of

openings

48, 49, and 50 formed respectively in the walls of the inner tube 11, the movable tube 15, and the distance piece 35. Thus, all the inner chambers (space 47, upper and

lower chambers

19 and 20, and the annular space inside the distance piece 35) are swept with air which serves the dual purposes of supporting combustion and preventing the back-flow of gases from the combustion chamber 2 through the burner.

In operation, to start the burner, the movable tube 15, containing the ignitor 211 and the oil nozzle 22A, is advanced to its forwardmost position by the

hydraulic jacks

38 and 39. The ignitor 21 is then put into operation by initiating the flow of gas into the inlet gas tube 27 and effecting a spark by the ignition electrode 30. Having detected the presence of the gas flame with the ignitor flame sensing electrode 3 1, the flow of fuel oil to the nozzle 22A is started, the necessary steps being taken to insure proper fuel oil atomization. As soon as the detector 51 senses a stable oil flame, the gas ignitor 21 may be extinguished, and the flow of pulverized fuel may be commenced. The oil flame insures ignition of the coal and sustains the coal flame while the coalflow is being increased. As soon as the coal flow rate is sufficiently high so that the coal flame is self-sustaining, the flow of fuel oil may be terminated, and the movable tube 15 can be withdrawn by means of the

hydraulic jacks

38 and 39 to its inactive retracted position where the ignitor 21 and fuel oil nozzle 22 are protected from the damaging effects of direct radiation from the combustion chamber. If desired, a separate flame detection system (not shown) may be used to prove the stability of the coal flame, or the flame detector -51 may be used for this purpose.

In the event that the coal flame becomes unstable, it is possible to put the gas ignitor 21 and the oil nozzle 22A into service with a minimum of delay. Also, during periods when the supply of coal is low, the fuel oil burner may be used to carry a substantial part of, or the entire load requirements of the vapor generator.

While in accordance with the provisions of the statutes there is illustrated and described herein a specific embodiment of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.

What is claimed is:

1. In combination with a combustion chamber wall having a burner port formed therein, a multiple fuel burner comprising an outer tube and a substantially concentric inner tube, said tubes defining therebetween an annular passageway opening at its forward end for the discharge of pulverized carbonaceous fuel through said burner port into said combustion chamber, an axially movable longitudinal tubular housing disposed within said inner tube and having its longitudinal axis substantially parallel with the axis of said inner tube, a. liquid fuel supply assembly disposed within and connected with said housing and terminating at its forward end in a spray nozzle disposed substantially co-axially with respect to the longitudinal axis of said outer tube for directing a stream of liquid fuel into said combustion chamber, an ignitor assembly disposed adjacent said liquid fuel supply assembly within and connected with said housing and arranged in igniting relationship to said stream of liquid fuel, and means for axially moving said tubular housing between a forward operative position and an inactive retracted position, said liquid fuel supply assembly and said ignitor assembly being arranged to move axially with said tubular housing.

2. In combination with a combustion chamber wall having a burner port formed therein, a multiple fuel burner comprising an outer tube and a substantially concentric inner tube, said tubes defining therebetween an annular passageway opening at its forward end for the discharge of pulverized carbonaceous fuel through said burner port into said combustion chamber, a liquid fuel supply assembly disposed within said inner tube and terminating at its forward end in a spray nozzle disposed substantially co-axially with respect to the longitudinal axis of said outer tube for directing a stream of liquid fuel into said combustion chamber, means forming an elongated unobstructed sighting space along one side of said inner tube, said sighting space having its forward end open to said combustion chamber, a flame detector element of the light-sensitive type arranged within said inner tube at the rearward end of said sighting space to detect the presence of a flame from said burner within said combustion chamber, an ignitor assembly arranged in igniting relationship to said stream of liquid fuel, and

a flame detection device operatively associated with said ignitor assembly to detect the presence only of an ignitor flame.

3. In combination with a combustion chamber wall having a burner port formed therein, a multiple fuel burner comprising an outer tube and a substantially concentric inner tube, said tubes defining therebetween an annular passageway opening at its forward end for the discharge of pulverized carbonaceous fuel through said burner port into the combustion chamber, an axially movable longitudinal tubular housing disposed within said inner tube and having its longitudinal axis displaced to one side of and substantially parallel with the longitudinal axis of said inner tube so as to provide a sighting space on the opposite side of said inner tube, a liquid fuel supply assembly disposed within said housing and terminating at its forward end in a spray nozzle disposed substantially co-axially with respect to the longitudinal axis of said outer tube for directing a stream of liquid fuel into said combustion chamber, a flame detector element of the light-sensitive type arranged to sight along said sighting space to detect the presence of flame within said combustion chamber, an ignitor assembly disposed within said housing and arranged in igniting relationship to' said stream of liquid fuel, a flame detector operatively associatcd with Said ignitor assembly for detecting the presence of an ignition flame within said housing, and means for axially moving said tubular housing between a forward operative position and an inactive retracted position.

4. In combination with a combustion chamber wall having a burner port formed therein, a multiple fuel burner comprising an outer tube and a substantially concentric inner tube, said tubes defining therebetween an annular passageway opening at its forward end for the discharge of pulverized carbonaceous fuel through said burner port into the combustion chamber, a longitudinal tubular housing disposed within said inner tube and having its longitudinal axis displaced to one side of and substantially parallel with the longitudinal axis of said inner tube so as to provide an unobstructed sighting space on the opposite side of said inner tube, a partition longitudinally dividing the inner volume of said tubular housing into a first chamber and a second chamber, said chambers being isolated from one another, a liquid fuel supply assembly disposed within said first chamber and terminating at its forward end in a spray nozzle disposed substantially co-axially with respect to the longitudinal axis of said outer tube for directing a stream of liquid fuel into said combustion chamber, a flame detector element of the light-sensitive type arranged to sight along said sighting space to detect the presence of flame within said combustion chamber, an ignitor assembly disposed within said second chamber and arranged in igniting relationship to said stream of liquid fuel, a flame detector operatively associated with said ignitor assembly for detecting only the presence of an ignition flame within said housing, and means for passing air forwardly through said second chamber and said sighting space.

5. In combination with a combustion chamber wall having a burner port formed therein and a pressurized windbox on the outer side thereof, a multiple fuel burner comprising an outer tube traversing said windbox, an elbow connected to the rearward end of said outer tube, an inner tube substantially concentrically arranged within said outer tube and extending rearwardly through a wall of said elbow, said inner and outer tubes defining therebetween an annular passageway opening at its forward end for the discharge of pulverized carbonaceous fuel through said burner port into said combustion chamber, an axially movable longitudinal tubular housing disposed within said inner tube and extending rearwardly beyond said inner tube, said housing having its longitudinal axis displaced to one side of and substantially parallel with the longitudinal axis of said inner tube so as to provide an unobstructed sighting space on the opposite side of said inner tube, a partition longitudinally dividing the inner volume of said tubular housing into a first chamber and a second chamber, said chambers being isolated one from the other, a liquid fuel supply assembly disposed within said first chamber and terminating at its forwardend in a spray nozzle disposed substantially coaxially with respect to the longitudinal axis of said outer tube for directing a stream of liquid fuel into saidcombustion chamber, a flame detector element of the light-sensitive type arranged to sight along said sighting space to detect the presence of flame within said combustion chamber, an ignitor assembly disposed within said second chamber and arranged in igniting relationship to said stream of liquid fuel, a flame detector operatively associated with said ignitor assembly for detecting the presence of an ignition flame within said housing, a passageway arranged to conduct air from said windbox to said inner tube for passage forwardly through said sighting space, means for passing air around said ignitor assembly, and fluid operated jack means interconnecting said inner tube and said housing for axially moving said housing between a forward operative position and an inactive retracted position.

6. In combination with a combustion chamber wall having a burner port formed therein, a multiple fuel burner comprising an outer tube and a substantially concentric inner tube, said tubes defining therebetween an annular passageway opening at its forward end for the discharge of pulverized carbonaceous fuel through said burner port into said combustion chamber, a longitudinal tubular housing disposed within said inner tube and having its longitudinal axis displaced to one side of and substantially parallel with the axis of said inner tube so as to provide a sighting space on the opposite side of said inner tube, a liquid fuel supply assembly disposed within said housing and terminating at its forward end in a spray nozzle disposed substantially coaxially with respect to the longitudinal axis of said outer tube for directing a stream of liquid fuel into said combustion chamber, an ignitor assembly disposed adjacent said liquid fuel supply assembly within said housing and arranged in igniting relationship to said stream of liquid fuel, a flame detector of the light sensitive type arranged to sight along said sighting space to detect the presence of flame within said combustion chamber.

References Cited by the Examiner JAMES W. WESTHAVER, Primary Examiner.

CHARLES J. MYHRE, FREDERICK L. MATTESON,

JR., Examiners.

4/1927 Great Britain.

Claims

1. IN COMBINATION WITH A COMBUSTION CHAMBER WALL HAVING A BURNER PORT FORMED THEREIN, A MULTIPLE FUEL BURNER COMPRISING AN OUTER TUBE AND A SUBSTANTIALLY CONCENTRIC INNER TUBE, SAID TUBES DEFINING THEREBETWEEN AN ANNULAR PASSAGEWAY OPENING AT ITS FORWRD END FOR THE DISCHARGE OF PULVERIZED CARBONACEOUS FUEL THROUGH SAID BURNER PORT INTO SAID COMBUSTION CHAMBER, AN AXIALLY MOVABLE LONGITUDINAL TUBULAR HOUSING DISPOSED WITHIN SAID INNER TUBE AND HAVING ITS LONGITUDINAL AXIS SUBSTANTIALLY PARALLEL WITH THE AXIS OF SAID INNER TUBE, A LIQUID FUEL SUPPLY ASSEMBLY DISPOSED WITHIN AND CONNECTED WITH SAID HOUSING AND TERMINATING AT ITS FORWARD END IN A SPRAY NOZZLE DISPOSED SUBSTANTIALLY CO-AXIALLY WITH RESPECT TO THE LONGITUDINAL AXIS OF SAID OUTER TUBE FOR DIRECTING A STREAM OF LIQUID FUEL INTO SAID COMBUSTION CHAMBER, AN IGNITOR ASSEMBLY DISPOSED ADJACENT SAID LIQUID FUEL SUPPLY ASSEMBLY WITHIN AND CONNECTING WITH SAID HOUSING AND ARRANGERD IN IGNITING RELATIONSHIP TO SAID STREAM OF LIQUID FUEL, AND MEANS FOR AXIALLY MOVING SAID TUBULAR HOUSING BETWEEN A FORWARD OPERATIVE POSITION AND AN INACTIVE RETRACTED POSITION, SAID LIQUID FUEL SUPPLY ASSEMBLY AND SAID IGNITOR ASSEMBLY BEING ARRANGED TO MOVE AXIALLY WITH SAID TUBULAR HOUSING.