US1600724A - Burner - Google Patents

Description

Sept. 21 A1926.

w. H. FvrrcH BURNER Filed' Nov. 22. 192s INVENTOR v TTORNEY Patented Sept. 21, v1926.

UNITED STATES `APATENT oFFlcE.

BURNER.

Application filed November 22, 1923. Serial No. 676,248.

This :invention relates to a burner for firing fuel in pulverized form, which is adapted for use in connection with furnaces generally, such as stationary boiler furnaces,

metallurgical furnaces, 'cement kilns, etc., although it has been ,found of particular value as a burner for metallurgical furnaces in which intensely high heat or, in other words, high CO2 is developed.

The burner is designed to produce a short flame of low velocity and high heat intensity and to prevent an accumulation of partly burned vfuel or coke about the discharge orifice of the burner. Dificulty with coking about the discharge orifice is a common fault with the present type of burners in use for firing pulverized fuel, the coke forming about the burner orifice and building up to an extent which results .eventually in the restriction or virtual. closing up of the orifice. This necessitates cleaning out the v burner periodically which is a troublesome operation and furthermore, cannot be done without a temporary suspension ofoperation, Moreover,- pulverized fuel burners, as

heretofore designed, and used in practice,

provide'in themselves no means of regulating the velocity of the mixture of pulverized fuel and air vwhichy they feed to the furnace; or if this is arranged for at all, the means employed have been ineffectual to accomplish the desired results. Generally speaking, such burners are designed to proyduce a combustible mixture of fuel and air by adding to the-fuel and primary air, or carrier'air for conveying the fuel into the furnace, a certain amount off-'secondary air to obtain better mixture. and'to furnishv additional air required for combustion. '.lhe secondary. airis usually brought'l into the burner mixing chamber by induction caused by the jet of `fuel and primary air. lIn

order thatth'e necessary amount of fuel may -be introduced to createthe high heat required, as for example, in metallurgical furnaces,r the mixture off,ue'l and air must 'be introduced into th'e furnace-at highQvelocity. v Such a jet produces along ain'e'fwith consequent wide distribution of heat 'oftlesser intensity and imping'ement of theflame on the opposite wall of the'furnace with resultant destruction' of the refractories.

The burner constituting the present invention comprises a chamber having the usual discharge orilicefrom which the mixture of fuel and air issues. Extending through the chamber, and iii-alignment with the discharge orifice, is a feed pipe forconveying the mixture of fuel and primary alrthrough the chamber for projection out of the discharge orifice. The rimary air, it will be understood, is air un er pressure, or

an air blast, customarily sup lied by a fan,

and this air. serves to carry t e fuel in suspension through the feedpipe in the burner.

erably in the form of a valve of approximately conical formation, which is capable of being moved toward and away from the discharge orifice of the burner chamber.

The secondary air is constrained by the valve, and the walls' of the chamber surrounding the discharge orifice, t0 flow into the path of the jet of fuel and primary air, and it will be readily seen that where this secondary air is under pressure a very thorough mixture of fuel and air is obtained in the burner before discharge from the outlet orifice thereof. Furthermore, by adjustment of the valve toward and away from the discharge orifice, the velocity as well as the volume of the secondary air entering the jet of fuel'and primary air is controlled in accordance. with the velocity of the latter stream and the requirements of combustion.

projected .at re atively high velocity the valve is adjustedv towarditsl extreme open positionh so that greater quantities of secondary air are added as combustion air, needed td consume the increased quantity of fuel; bntvvhere a small quantity of fuel is beingconsumed, the valve is .adjusted toward the discharge orifice to obtain a ,corre/spondingly smaller supply of secondary'fair' for combustion. 'Under either extreIneor intermediate conditions of operation,' the valve is adgusted in accordance with-the requirements. An important fea- .-ture of operation, however, is that the sec-v ondary air,jespeciallywhere under pressure, and directed against the fuel and primary air stream, as. described, cuts. down the ,ve-

locity thereof and the resultant fuel and air stream issuingfrom the discharge orifice is considerably reduced in velocity. Thus projected into the furnace, the fuel mixed with air entering at aireduced velocity produces a relatively short intensely hot flame with concentration or localization of heat and elimination of impingement on the walls of the furnace. The direction of the secondary air againstthe issuing fuel jet mixed with primary air, furthermore, ensures thorough mixture of the fuel and air within the burner prior to its injection into the furnace and also by virtue of its velocity and impingement against the inner walls of the chamber, prevents lodging'and accumulation of fuel around the burner opening and consequently the formation of coke. The form of burner at present preferred is illustrated in the `accompanying drawing, wherein the burner is shown positioned in the wall of the furnace which is simply indicated.

Referring to the drawing, the burner includes a casing 1 forming a chamber provided with a discharge orifice 2 at one end thereof, and is shown positioned in theopening 3 of the furnace wall 4. In alignment with the orifice 2 and extending through the chamber 1 is a supply or feed pipe 5 into which fuel and the primary or carrier air are introduced, from sources not shown, but which arrangements are well understood. The lower portion of the chamber 1 is provided with an -extension 6 which provides the connection to the source of the secondary air supply, also not shown, but likewise well understood. The. primary air supply or carrier air for the fu'el introduced into the feed pipe 5 is usually supplied by a centrifugal fan and the'inlet 6 for secondary air is also preferably connected to a source of air supply under ressure which may be a centrifugal fan. ounted on the feed pipe 5 is a valve 7 having an integral sleeve portion 8 which fits over the feed pipe 5 and is adapted to slide thereon. The lower part of the sleeve portion 8 is formed with rack'teeth 9 which are adapted to be engaged by a pinion 10 mounted on a shaft 11. The shaft 11 is supported, in the walls of the casing or chamber 1 and at its outer end carries a hand wheel 12 by which the valve member is adjusted.

The head portion of the valve is of approximate conical formation and is hollow as at 13 primarily to reduce its weight.

The valve head forms the incoming secondary air in the chamber 1 in a hollow conical body which is constrained by the valve and the confining walls of the chamber 1 to intersect at an' angle the fuel and primary -air issuing from the feed pipev5. The valve is adjustable by the `mechanism provided, toward and -away from the outlet opening 2 inaccordance with the requirements of combustion, and the space between the face of the. valve and the walls of the chamber serves as a small mixing chamber in 'which the secondary air flowing around the edges of the valve mingles with the fuel and air mixture passing outward through the opening in the valve. Owing to the angle at which the secondary vair intersects the stream offuel and primary air, a thorough mingling of the air and fuel is brought about in this mixing chamber, and the size 0f the mixing chamber and the effectiveness of the mixing action can be controlled by moving the valve and thus varying the angle at which the streams intersect. It will be seen also that the secondary air passing around the valve head 7 provides a constantly moving body of air in contact with the inside wall of the casing 1 about its outlet orifice 2, the velocity of this moving body of air depending upon the adjustment of the valve and the accumulation of fuel about the orifice with lconsequent colring is thus prevented. It has been found in practice that the burner described in the foregoing will roduce a most excellent mixture of fuel and air and a 'short intenselyv hot Haine without coking difficulties as before noted, and the CO2 obtainable has been in the neighborhood of 151/2 to 16%.

l claim 1. A burner for pulverized fuel comprising a casing having an outlet opening in one wall thereof, a feed pipe for delivering a mixture of pulverized fuel and air, this pipe terminating in the casing in alignment with the opening and at a distance therefrom, a valve member mounted on the pipe within-the casing and adjustable toward and away from4 the opening, this valve member having a diameter greater than that of the outlet opening in .the casing wall, and having a passage formed throughA it of substantially the same diameter as that of the feed pipe, the fuel and air mixture discharging from the feed pipe and passing through this passage to flow through the outlet opening of the casing, and means for introducing yinto the casing an additional supply of air which mingles with the fuel 1 and air mixture passing out of the valve member between the face of the latter and the outlet opening of the casing.

2. A burner for pulverized fuel comprising a casing having an outlet opening in one wall thereof, a Afeed pipe for delivering a mixture of pulverized fuel and air, this pipe terminating in the casing in alignment with the opening and at a distance therefrom, a valve member mounted on the pipe within the casing and adjustable toward and away from the opening, this valve member having a diameter greater than that of the outlet opening in the casing wall, and having a passage formed through it of substantially the same diameter as that ofthe `feed pipe, the fuel therefrom,

-diameter than the outlet opening mount- I means for introducing an additional supply ing, and means forintroducing an additional supply of air to the casing vat a point behind the valve member, the air so supplied being deflected outwardly toward the walls of the casing by the valve member and flowing past the latter in the form of an an.- nular stream which joins the stream ofthe fuel and air mixture between the -valve member and the outlet opening. v

3. A burnerv for pulverized fuel comprising a casing having an outlet opening in one wall thereof, a feed pipe fordelivering a mixture of pulverized fuel and air, this pipe terminating in the casing in alignment with the opening and at a distance a valve member of larger ed on the end of the pipe within the casing and with the walls of the casing defining a mixing chamber between it and the outlet chamber, this valve member having a passage through it of substantially the same diameter as the feed pipe` through which the fuel and vair mixture from the feed pipe is discharged linto the mixing chamber and means for., admitting an addi-y v tional supply of air into the casing at a'point such that this additional air iows around the valve member and into the said mixing chamber, mingling with the stream of fuel and air issuing'from the valve member and passing with. that stream out of the outlet opening. l

4. A burner for pulverized fuel comprise"v adjustment toward-and away from the outlet opening to vary the size of this mixing chamber, and having a passage through it of substantially the same diameter as the feed pipe through which the mixture -of fuel and air issuing from the feed pipe is discharged into this mixing chamber, and

of air into the casing at apoi'nt such that the additional air flows around the valve memberand into the mi-xingchamber, where it mingles with the fuel and air mixture and with thel latter'passes out through the 4'outlet opening. A

5. A burner for pulveri'zed fuel comprising acasing having an outlet opening in one I end wa1l thereof, a feed pipe projecting' 'through the other end walland `terminating within the casing, this feed pipe being in alignment.v with the outlet o ening aidadapted'v to deliver a` mixture o pulverized fuel andr air, means forV introducing an additional supply of air into the casing, and a valve member interposed betweenthe outlet opening and the point at `which this addiftional supply .of air is introduced, this vali e .member havingl a greater diameter than tha outlet opening and having a passagethere through of substantially the same4 size as th\v .feedvpipe, the fuel and lair mixture vissuing from .the feed. pipe owing through this passage and being discharged from'the latter into thev casing, in alignment with theoutlet opening.

6. A burnerv for pulverized fuel comprisi ing a casing having an outlet opening in one end wall thereof, a feed pipe projecting through the other end wall and terminating within the casing, this feed pipe being in alignment with the outlet o ening and adapted to deliver a mixture o pulverized lfuel and air, means for introducing an additional supply of air into the casing, a valve memberinterposed between the outlet opening and the point at which this additional supply of air is introduced, this valve member having a greater diameter than the outlet yopening and having a passage therethrough) of substantially the same size as the feed pipe, the fuel and air mixture issuing from the feed pipe flowing through this passage and being discharged from the latter into the casing in alignment withthe outlet opening, and means-for adjusting the valve member toward and away from the outlet opening. Y

7. A burner for pulverized fuel comprising a casing having a discharge opening, a feed pipe extending into the casing in alignment with the opening and terminating at a distance therefrom, this pipe being adapted to deliver a mixture of pulverized fuel and primary air, a cone-shaped valve member within the casing having a fiat base lying in opposition to the opening, the base being of greater diameter than the opening, and this valve member having a. passage through it of substantially the same diameter as the feed pipe through which the mixture of pulverized fuel and air issuing from the feed pipe flows in itspassage to the discharge opening, and means for admitting a supply of additional air into the casing at a point to the rear of the valve member, the additional air flowing along the inclined surfaces of the latter and around the edge of the base in the form ofan' annular stream surrounding the stream of pulverized fuel vand air, the two streams mingling between ing fa casing having a discharge opening, a feed pipe extending into the casing in alignment with the opening and terminating ata distance therefrom, this pipe being adapted to deliver a mixture of pulverized fuel and primary air, a Cone-shaped valve member lwithin the casing having a fiat base lying in opposition to the opening, the baseA from the feed pipe flows in its passage to the discharge opening, means for admitting a supply of additional air into the casing at a-point to the rear of the Valve member, the additional air flowing along the inclined surfaces ofthe latter and around the edge of the base in the form of an annular stream surrounding the stream of pulverize'd fuel and air, the two streams mingling between the base of the valve member and the outlet opening, and means for adjusting the Valve member toward and away from the opening.

In testimony whereof I aiiX my signature.

WILLIAM HENRY FITCH.

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