US2602432A - Apparatus for effecting combustion - Google Patents

Description

July 8, 1952 E. s. BAILEY APPARATUS FOR EFFECTING COMBUSTION Filed Apri1 8, 194's INVENTOR l: rfz'n GBai/ey ATTORNEY Patented July 8, 1952 APPARATUS FOR-.EFFECTING OOMBUSTION Ervin G Bailey, E'aston, Pa., assignor to The Babco'ck: &. Wilcox: Company; Newr Yorla. N'. Y.," acorporationrof; New-Jersey- Application April8, 1949; SerialNo. 86,172

V 1' This invention relates to; pulverized' fuel burners, and more particularly to apparatus for burn ing pulverized coal.

The particular'burner involved in this invention isiof'a pre-mix type wherein the fuel and the supply of combustionair are brought together in mixingrelation'ship before introduction to the furnace.

Morespecifically it is a high capacity pro-mix burner adapted to an arrangementof'spaced furnace wall coolingtubes.

With pre-mix burners the mixture of fuel and airas itentersthe-furnace is a highly combustible mixture; and the specific P mixture. depending on thecharacter' of the fuel, the proportion and temperature of the" air, aswell as the extent of mixing, will have a so-called rate of flame propagation which is the velocity at which flame will move through the mixture. An intimate mixture of fuel and air will of course give a higher rate-of-flame propagation than a poorer mixture of the same fuel and air of the same proportion. In attainment of high capacities essential in confined furnace spaces, an intimate mixture promotes a condition wherein there will be a short flame, with respect to the burner port. on the'other hand, the attainment of an intimate mixture prior to introduction into the furnace and the delivery of all the fuel and air mixture at a velocity in excess of its rate of flame propagation in order to avoid burning back into the burner structure is a problem which is particularly'involvedin the operation of pre-mix burners, and particularly with pulverized fuel burners.

The effective operation of a pre-Inix burner with pulverized coal as fuel is more difficult than the operation of a pre-mix burner with a gas or vapor as a fuelbecause it handles fine solid material which is abrasive and which may collect and coke in low velocity or hot metal zones.

The pre-mix burner of this invention is particularly advantageous in that it solves the problemsinvolved while being adaptable to a furnace wall comprising spaced water cooling tubes.

In the operation of theburner of the invention air-borne pulverized fuel is introduced into the secondary air in an elongated stream issuing from an elongated nozzle which is ofiset and out of alignment with the burner port, so that it is subject to a minimum of radiated heat from the furnace through the port.

To deflect the fuel and air stream a layer of secondary air at high velocities is introduced between it and an inclined deflecting wall to minimize abrasive impingement" of pulverized material and consequent wear.

6 Claims. (Cl. 122-235) Mixing is accomplished in a converging passage into which the fuel nozzle discharges, the fuel stream issuing from the nozzlebeing em braced by secondary air. A converging-passage, with increasing velocities, induces turbulent mixing flow, so that when the mixtureflows through the parallel walled extension of the mixing passage between the furnace wall tubes a mixture is delivered through the ports to the furnace which is readily ignitable, and burns fairly close to theface-of the burner wall.

The invention is related to the construction and arrangement of elements-forming the mixing passage, and the' arrangement of the offset nozzle and air deflector.

The various features of novelty which characterize the invention are pointed out with. particularity in the claims annexed to andforming a part of this specification. For a better understanding ofthe invention, reference should'be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

In the drawings:

Fig. l is a partial vertical section of, a furnacev roof showing the arrangement of burners and burner tubes;

Fig. 2 is a vertical section on the line 2-2.. of Fig. 1, showing the arrangement of the burner tips and the mixingpassages formed by the. deflector elements which are supported bythe tubes forming components of the circulatory system ofthe fluid heat exchange apparatus including the furnace; and

Fig. 3-- is a plan of the burner tubes and a burner tip showing the structure and arrangement of an associated deflector.

The fuel burner construction ofthepresent invention is particularly adapted for application to high capacity furnaces for steam generators.

The'laoundary wallsof. the illustrated furnace are lined with spaced steam generating tubes such as In. The upper portions of these tubes are bent to form horizontally inclined furnace roof sections such as indicated-at 12. Several othernroof tube sections are indicatedat 12, and I l-l8, inc., in Fig. 2.

The steam generating. tubes are connected to a steam and Water drumv 20 and they are supplied at their lower ends with Water through a circulatory system including tubular downoomers 22 having roof sections such as 24, 2.6, and 28 (Fig. 2). v

Long, narrow and rectangular burner. ports are provided in the horizontally inclined portion of the furnace roof, between the-groupsrof the:

roof tube sections indicated in Fig. 2. Such burner ports are indicated at 30-32 in Fig. 2.

The walls of the fuel and air mixing passages leading to successive burner ports are formed between successive deflectors 3'638 (Fig. 2), these deflectors preferably being formed of metal. They flare outwardly from their upper or air entrance ends, as shown, with their vertically inclined front walls 4B42 welded to tubes l2, l5, and H and their vertical rear walls 44-48 welded to the tubes [4, l6 and It.

To maintain the deflectors 35-38 in their operative positions their end walls, such as 48 and 49, and their intermediate stiffeners 50, are cut out as clearly indicated at 52-54, the cut out portions embracing the roof tube sections 24, 2c and 28 of the downcomers.

The vertical walls of the deflectors, -44 i6 (Fig. 2) are continued downwardly beyond the tubes l4, l6, and I8 by the side walls 56 of box-like constructions welded to tubes, such as M. Each of these box-like constructions also has a side wall 58, end walls, and a transverse middle wall formed to fit the tubes and to facilitate welding said constructions to the tubes from positions within said side and end walls. The spaces between the side walls 55 and 58 and the end walls are filled with refractory material 60.

Abovethe burner ports and the deflector constructions there is a secondary air chamber 62, a wall of which is shown at 64 and a portion of the roof at 66. This chamber is connected to a suitable source of preheated air under pressure which is caused to flow from the chamber and through the burner ports into the furnace.

Within the secondary air chamber 62 are disposed a plurality of tubes ML-ll, corresponding in number to the number of burners. These tubes supply air borne pulverized fuel to the burners, and for that purpose they are connected to an air swept pulverizer (not shown). These tubes terminate at positions above the burner ports 30-33 where they are fitted with burner nozzles such as 8082. Each nozzle is tapered as indicated by the walls 84 and 85 of the nozzle 82 in Fig. 2, and, in the opposite plane, is flared as indicated by the walls ti l and 85' (Fig. 1) to provide-a wide discharge opening '88 discharging primary air and pulverized fuel asa thin sheet, in a direction such as that indicated at 90 in Fig. 2.

With this construction and arrangement of burner nozzles and burner ports an elongated stream of secondary air from the chamber 62 is caused to flow along the inclined surface (i.e. 4042) of each deflector in a direction such as that indicated by the arrow 82 and at a position between theburner nozzle outlet 88 and the inclined wall 42 of the deflector. These interposed streams of secondary air, while flowing in such relation to the stream of primary air and fuel as to promote effective mixing of fuel and air, also act to scrub and protect the inclined surfaces 4U l2 of the deflectors and to minimize contact of pulverized material with those surfaces.

To maintain the correct operative relationships of the burner nozzles 8i382 and the Walls 7 The spaces between the end walls of the deflectors, the drum 20, and the wall 64 are closed by thermal insulation and refractory bodies H0 and H4 acting to confine the flow of secondary air to the burner ports.

The present invention provides a multiple tip pulverized fuel burner arranged to discharge streams of pulverized fuel and air through burner ports between spaced roof tubes of a fluid cooled furnace construction. It provides a particular construction of deflectors and burner nozzles which accomplishes effective mixing of the fuel and air and at the same time prevents coking on the surface of the burner ports. The combined flow of primary air and suspended pulverized coal is directed in wide, thin sheets at a small angle to inclined surfaces of the passageways leading to burner ports with a wide thin sheet of secondary air interposed relative to each sheet of fuel and primary air and each inclined surface. A wide stream of secondary air also passes along the opposite side of each entering sheet or stream of primary air and fuel to substantially envelope the latter with secondary air in a manner to further promote effective mixing of fuel and air, for resultant complete and rapid combustion of the fuel within the furnace.

While in accordance with the provisions of the statutes I have illustrated and described herein the best form of my invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departin from the spirit of the invention covered by my claims, and thatcer tain features of my invention may sometimes be used to advantage without a correspondingv use of other features.

What is claimed is:

1; In a furnace, spaced means forming fuel and air mixing passages leading to burner ports at the furnace face, metallic deflectors forming walls of said passages converging toward said ports, burner nozzle means each angled toward one wall of its associated passage and directing a stream of primary air and fuel toward a deflector and through the associated burner port into the furnace, and means interposing a stream of secondary air between each deflector and the stream of primary air and fuel.

2. In a pulverized fuel fired furnace, spaced fluid conducting tubes defining the boundaries of the furnace, some of said tubes defining burner ports, metallic deflectors mounted on the tubes and presenting opposite walls which converge toward the burner ports and the interior of the furnace, said converging walls defining fuel and air mixing passages leading to the burner ports, burner tips presenting thin wide outlet passages each disposed off center within a mixing passage and directed toward one of the converging walls of the mixing passage, each burner tip directing a mixture of pulverized fuel and primary air toward the interior of the furnace and toward one of the converging walls of the mixing passage, and means including a secondary air chamber supplying wide streams of secondary air for flow on opposing sides of each burner tip outlet.

3. In a pulverized fuel fired furnace, spaced fluid conducting wall cooling tubes defining a furnace boundary surface, some of said tubes defining burner ports at the face of a furnace boundary, deflectors disposed exteriorly of thelatter tubes and presenting opposite mixing. passage walls which converge toward the burner ports, burner nozzles or tips each presenting a thin wide tip being set well back from the associated burner,

port, and means including a secondary air chamber supplying a thin wide stream of secondary air between the nozzle outlet and the mixing passage wall toward which the mixture of fuel and V I primary air is directed.

4. In a fluid heat exchange installation, fluid heating tubes defining a furnace boundary, some of said tubes being spaced apart to provide burner ports and parts of burner port passages leading to the ports, a premix burner nozzle for each passage with each nozzle having its tip substantially spaced rearwardly from the associated tubes, each nozzle also being angled toward a target wall forming one side of its burner port passage, a heat resisting deflector for eachburner port passage having a side forming said target wall disposed transversely of the direction of the associated nozzle and across the projection of the initial part of the path of the fuel and primary air stream issuing from the nozzle, the deflectors also covering the sides of the tubes forming the burner port passage opposite the tube sides toward the interior of the furnace and presenting opposite walls of the burner port passages, and means causing a stream of secondary air to move along the target wall toward which the efflux from the associated nozzle is directed, said stream of secondary air being interposed relative to the target wall and the tip of the associated burner nozzle.

5. In a fluid heat exchange installation, fluid heating tubesdefining a furnace boundary, groups of said tubes being sufficiently spaced apart to provide burner ports and downwardly extending and tapering parts of fuel and air mixing burner port passages, a downwardly directed premix burner having a primary air and fuel nozzle for each passage with each nozzle having its tip substantially spaced rearwardly from the associated tubes, each nozzle also being angled toward a target wall forming one side of its burner port passage, a heat resisting deflector for each burner port passage having a side forming said target wall disposed transversely of the direction of the associated nozzle and across the projection of the initial part of the path of the fuel and primary air stream issuing from the nozzle, each deflector also covering the sides of a group of said tubes opposite the interior of the furnace and presenting walls of the burner port passages, and means causing a stream of secondary air to move along the burner port target walltoward which the efilux from the associated nozzle is directed, said stream of secondary air being interposed relative to the target wall and the tip of a burner nozzle.

'6. In a fluid heat exchange installation, fluid heating tubes defining a furnace roof, some of said tubes being spaced apart to provide a burner port and parts of a downwardly extending and tapering fuel and air mixing passage leading to the port, the walls of said passage diverging upwardly from the furnace faces of the tubes, a downwardly elongated premix burner nozzle in the passage with the nozzle having a transversely elongated outlet tip spaced rearwardly from the associated tubes, each nozzle also being disposed in off-center relation to the burner port passage and angled toward a target wall forming one side of its burner port passage, the nozzle being directed toward the target wall at a small acute angle to direct a stream of primary air and fuel toward that wall, a superposed pulverized fuel and air conduit connected to the nozzle, a heat resisting metallic deflector having ,a side forming the target wall disposed transversely of the direction of the associated nozzle and across the projection of the initial part of the path of the fuel and primary air stream issuing from the nozzle, the deflector also covering the sides of fluid heating and burner port passage forming tubes opposite the interior of the furnace, and means causing a stream of secondary air to move parallel to and along the target wall toward which the eiilux from the associated nozzle is directed, said stream of secondary air being interposed relative to the target wall and the tip of the burner nozzle.

ERVIN G. BAILEY.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS 7 OTHER REFERENCES Power Magazine, page 6, vol. 6, No. 1, July 1,

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