US2018179A - Fuel burner - Google Patents

Description

M. H. KUHNER Oct. 22, 1935.

FUEL BURNER Filed Feb. 29, 1932 2 Shee'ts-Sheet 2 .INVENTOR Nfx H. KUHNER c i ATTORNEY Patented Oct. 22, 1935 UNITED STATES PATENT oFFicE Application February 29, 1932, Serial No. 595,739

1 Claim.

This invention relates to fuel burners, and more particularly to burners for fuels such as gas, pulverlzed coal, or saw dust, which are suitable for burning in suspension in the combustion chamber of a furnace. I

In burning fuels of this type, it is desirable to produce a rapid and thorough mixture of the fuel and air within the furnace, so that combustion will be rapid and the flame will occupy as small a space as possible. Attempts have been made to obtain this result by introducing the fuel stream into the furnace within .a surrounding annular stream of air, and whirling both the air and the fuel about the axis of the fuel stream. This has resulted in an outwardly fiaring flame which cannot be used satisfactorily in a narrow furnace, since it impinges on the furnace side walls and causes slagging troubles, incomplete combustion, and rapid destruction of the walls. Moreover, a burner of the whirling type tends to throw the coarser particles of fuel out of the flarn'e under the influence of centrifugal force, and these particles drop to the furnace floor and remain unconsumed. This separation of coarse particles is more pronounced in the case of saw dust and wood shavings, because of the comparatively large size of the individual pieces, and great diliiculty has been experienced in burning wood refuse of this character in suspension, even though no whirling motion is imparted to the fuel.

It is accordingly one object of the invention to provide a burner for fuel which will cause the fuel and air to mix rapidly and thoroughly within the furnace chamber and produce immediate and emcient combustion in a comparatively small space.

It is a further object of the invention to provide a burner which will produce a short flame without appreciable flaring, so that it may be used satisfactorily in connection with a narrow furnace chamber.

It is a further object of the invention to provide a burner which will produce rapid ignition of the fuel, and which is so constructed that it will be capable of withstanding the heat of the ame without injury.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claim appended hereto.

Referring to the drawings illustrating one embodiment of the invention, and in which like reference numerals indicate like parts,

Fig. 1 is a vertical section through a furnace wall having a wood refuse burner and a pulverized coal burner associated therewith;

Fig. 2 is a perspective'view of the burner plate for the wood refuse burner. showing the plate prior to the application of the refractory mate- 5 rial;

Fig. 3 is an enlarged perspective View of one of the frusto-conical .air valves for the Wood refuse burner;

Fig. 4 is an enlarged perspective view of one of 10 the fuel stream defiectors used on the pulverized coal burner;

Fig. 5 is a section on the line 5-5 of Fig. 1;

Fig. 6 is a section on the line 6 6 of Fig. 1;

Fig. '7 is a perspective View of the burner plate l5 for the pulverized coal burner, showing the plate prior to the application of the refractory material; and

Fig. 8 is a small scale side elevation of the two burners, showing the operating mechanism for 20 the damper and valves.

The embodiment illustrated comprises a. cornparatively thick furnace wall I0 constructed of non-metallic refractory material and provided with a rectangular opening II and a second rec- 25 tangular opening I2 located beneath the rst opening. A burner I4 for wood refuse is arranged to discharge through the upper opening II, and a burner I5 for pulverized coal is arranged to discharge through the lower opening I2. 30

The wood refuse burner I4 comprises a fiat rectangular burner plate I6 having a rib I8 projecting from the rear face` thereof toward the furnace. This rib is spaced inwardly from the outer edge of the plate and ts within the opening II in the 35 furnace wall, the plate contacting with the wall around the opening. The plate I6 is provided with a number of openings I9, preferably circular in shape, through which fuel and air may be discharged into the furnace. As shown in Fig. 2, 40 these openings I9 are located in two horizontal rows with the openings in the lower row staggered with respect to the openings in the upper row. In order to protect the burner plate from the radiant heat of the furnace and to provide an increased in- 45 candescent surface which will facilitate ignition and combustion of the fuel, I form a comparatively thin lining 20 of non-metallic refractory material over the rear face of the plate. I have found that chrome ore, applied in plastic form, is a suitable 50 material for this lining, but it will be apparent that other refractories may be employed within the scope of my invention. By using a plastic material I provide a monolithic lining. The application and supporting of the refractory lining is facilitated by surrounding each opening I 8 with a rearwardly projecting annular rib 2 I.

A jet of fuel is projected through each opening I8 by means of a horizontal tube 23. These tubes 5 are mounted coaxial with the openings, and their rear or discharge ends are preferably in substantially the same vertical plane as the front surface of the burner plate I8. The front or inlet ends of the tubes are bent downwardly at an angle into l a common plane and connected to a flat laterally flaring fish-tail distributing conduit 24 having a flanged inlet connection 25 at its lower end. The conduit 24 serves to spread out the stream ofwood refuse and primary or carrying air, and distribute it among the tubes 23. Small angle irons 28 are provided between the inlet ends of adjacent tubes to aid in splitting the fuel stream. While I do not wish to be limited to any specific size of fuel tubes, I have found that tubes having an internal diameter of approximately three inches are satisfactory for burning wood refuse consisting of saw dust and shavings. Such refuse contains some rather large particles, and it is not desirable to use tubes much smaller than this, since they would become plugged too easily.

Each jet of fuel is surrounded by an annular stream of air to support the combustion thereof. This secondary air is preferably supplied under pressure, and for this purpose I provide walls forming an air chamber 28, and deliver air to this chamber by means of a duct 29 from a suitable fan or other apparatus (not shown) The burner plate I8 forms the rear wall of the air chamber and the openings I9 in the burner plate are therefore supplied with air directly. These openings I8 are considerably larger in diameter than the fuel tubes, so that ample area is available for the air to flow into the furnace with the fuel.

The rate of air flow into the furnace must be varied to correspond with the rate at which fuel is being supplied. For this purpose I preferably utilize a separate damper or valve 30 at each opening I9, and provide a suitable mechanism for adjustlng all the valves simultaneously. Each valve 30 as illustrated is frusto-conical in shape, with its smaller end at the rear, and provided with a forwardly projecting hollow cylindrical portion 3i which is slidable on the outer surface of the corresponding fuel tube 23. The frusto-conical shape has an important advantage in that it directs the air stream inwardly at an angle toward the central fuel stream and thus promotes rapid and thorough mixing of the fuel and air. The

' front edge of each opening I9 may be beveled as shown at 32 (Fig. 1), to provide a seat for the valve.

The air control valves are preferably arranged for simultaneous adjustment, and for this purpose I have shown a transverse horizontal bar 34 lo- 00 cated between the upper and lower rows of fuel tubes 23. Each valve 30 is provided with a T- shaped bracket 35 which is secured to this bar. The ends of the bar 34 project through horizontal slots 38 in the side walls of the air chamber 28 and are connected to arms 38, the lower ends of the arms being connected by a transversely extending rotatable shaft 39. The arm 38 at one side of the burner may be manually actuated by means of a hand wheel 40 (Fig. 8) mounted on a horizontal rotatable shaft 4 2. The shaft 42 is screw threaded for a portion of its length and carries a nut 43 which engages the upper end of the arm 38. By turning the hand wheel 40, the shaft 42 will be rotated, causing the nut 43 to travel along the shaft and thereby swinging the arms 38.

'I'his serves to slide the bar 84 along the slots 38 and to adjust the air valves 30 to or from the. burner plate I8. Various other mechanisms may be employed for adjusting-these valves.

The pulverized fuel burner I5 is in many re- 5 spects similar to the wood refuse burner, and comprises a flat rectangular burner plate 48 having a rib 4'I projecting from its rear face. This rib fits within the furnace wall opening I2. The plate 48 has a number of circular openings 48 therein, 10 these being located in four horizontal rows with the openings in the different rows aligned vertically. The openings 48 are surrounded by rearwardly projecting annularV ribs 50, and the rear face of the plate is protected by a comparatively 15 thin lining 5I of chrome ore or other refractory material.

A jet of pulverized fuel is projected through each opening 48 by means of a horizontal tube52. The tubes 52 are coaxial with the openings, and 20 their forward portions are brought together both horizontally and vertically and connected to a distributing chamber 54 .having a rectangular cross-section. The forward'part of the chamber 54 is curved downwardly and provided with. a 25 flanged inlet opening 55. Curved vanes 58 maybe mounted in the curved portion of the chamber 54 to prevent excessive segregation of the'fuel due to centrifugal force. Since pulverized coal is usually ground exceedingly fine, the tubes-52 can 30 be and preferably are considerably smaller than the tubes 23. I have found that tubes having an internal diameter of approximately one and onequarter inches are satisfactory for fuels such as pulverized coal or gas.

Air is supplied to the fuel jets from an air chamber 58 which communicates with the air chamber 28 thereabove. .Frusto-conical air valves 59 are slidably mounted on the rear portions of the tubes 52, and cooperate with beveled 40 seats onthe burner plate 48 to control the air ow through the openings 48. These air valves 58 are fastened to transverse bars 82, one located between the two upper rows of fuel tubes and one located between the two lower rows of 45 fuel tubes. The bars are horizontally slidable in slots in the side walls of the air chamber 58, and their ends are connected to bell crank levers 84 which are joined by vertical links 85. The corresponding levers at opposite sides of the 50 burner are connected by transverse rotatable shafts 88. 'I'he damper mechanism may be operated by means of a hand wheel 88 mounted on a vertical screw threaded shaft 89 which carries a nut 'I8 connected to one of the bell crank le- 55 vers.

In some cases it is found desirable to interpose defiecting surfaces in the path of the fuel jets issuing from the tubes 52, thereby causing a more rapid mixture of the fuel and air.- I have shown 60 a deflector in the form of a flat annular plate 12 slightly larger in outside diameter than the fuel tube and mounted coaxial with and slightly in the rear of each tube. 'Ihis plate 12 may be welded or otherwise secured to a thin rectangular strip I3 55 which fits tightly within the tube 52. A part of the fuel stream will pass through the central opening 'I4 in the deilector, while the remainder will be deflected laterally into the surrounding air stream. 70

It may at times be desirable to operate one of the burners alone, the air and fuel supplies to the other burner being shut off. vWhile the valves 30 and 58 may be used for this purpose, I have illustrated an auxiliary damper mechanism which 75.

can be adjusted to direct the entire air stream to either burner desired. This comprises a wall or plate 16 extending vertically through the central part of the air chamber 28 and rearwardly beneath the air control valves 30. At the. upper i edge of the wall 16 I provide a damper 11. This damper is mounted on a horizontal rotatable shaft 18, so that it can be swung to either side desired and thus shut off the air flow to either one of the burners. With the damper in the position shown, both burners will be supplied with air. The shaft 18 may be adjusted by means of the mechanism illustrated in Fig. 8, which comprises a worm gear segment 80 mounted on the shaft and a worm 8| in mesh therewith. A shaft 82, provided with a handwheel 83, is connected to the worm 8l.

The operation of the invention will now be apparent from the above disclosure. A stream of pulverized coal and primary air is supplied to the inlet connection of the burner I5, and a stream of saw dust and primary air is supplied to the inlet connection 25 of the burner I4. Secondary air is delivered by a suitable fan to the duct 29. The fuel issues from the rear ends of the tubes 23 and`52, and each fuel jet is surrounded by an annular stream of secondary air. The frustoconical valves 3d and 59 direct the air inwardly toward the fuel stream, thus promoting rapid mixing and thorough combustion. By adjusting these valves, the air fiow can be varied to correspond with the rate of fuel supply. Since the air control valves are located at the point of air discharge, the air velocity can be maintained high even at low combustion rates. This makes it possible to ensure satisfactory mixing of fuel and air though the demand for heat be low. 5

v The fuel as it enters the openings ll and I2 is surrounded by the refractory surfaces of the wall I0 and is directly exposed to radiation from these surfaces as well as from the refractory linings 20 and 5l. This is of great value in obtaining 10 immediate ignition and a comparatively short flame. The linings 20 and 5I furthermore protect their respective burner plates I6 and 4B from warping and burning. Since no whirl is imparted to the fuel, there is no tendency for the coarser 15 particlesof fuel to be thrown out of the flame by centrifugal force. Moreover, because of this lack of whirl, the ame does not flare laterally to any great extent, and hence will not impinge upon the side walls of a narrow furnace.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

A burner for fuel comprising a flat burner plate having a plurality of openings therethrough 25 tubes mounted in front of the openings to discharge jets of fuel therethrough, an air valve slidably mounted on each tube to controlthe air flow through the adjacent opening, and means to operate the air valves simultaneously. 30

MAX H. KUHNER.

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