US2921542A - Fluid fuel burner - Google Patents

Description

Jan. 19, 1960 J. H. KIDWELL ETAL 2,921,542

FLUID FUEL BURNER Filed June 5, 195a INVENTORS John H. Kidweli BY George Musaf 5 ATTORNEY United States Patent 'FLUID FUEL BURNER John H. "Kidwell and George Musat, Canton, Ohio, as-

;signors to The Babcock & Wilcox Company, New York, 'N;X., a corporation of New Jersey Application June 5, 1956, Serial No. 589,546 4 Claims. (Cl. 1-10-w28) The present :invention relatesto fuel burning apparatus, :and more particularly .to a fuel burner having adyustable skimmer elements positioned in a scroll shaped primary 'air and pulverized material supply chamber which is arranged to discharge the air and material in a substansubstantially tangential direction into a scroll chamber.

The coaland primary air delivered to the chamber is thus given ,a circular motion with the swirling fuel and air lea ing the chamber in a direction axially of the circular movement through a discharge nozzle and into a movi-ng mass of secondary combustion air.

The stream of pulverized coal and primary air discharged substantially tangentially into the scroll chamher is uniformly distributed for discharge by means of a plurality of curved skimmer vanes or plates which are pivotally connected with the opposite side walls of the ,scroll chamber. The skimmers are adjustable so that the upstream end of each skimmer plate is selectively projected into the swirling stream of coal and air moving in a circular direction about the interior of the scroll chamber. A frusto-conical nozzle is attached to one side of the scroll chamber, with the base of the nozzle merging with an opening in the sidewall of the chamber, with the discharge end of the nozzle extending to a burner port positioned in the wall of a furnace. The nozzle through which the pulverized coal and primary air stream moves with a circular motion from the scroll chamber is preferably provided with a cylindrical member of lesserdiameter than the outlet end of the nozzle where the cylindrical member extends axially of the chamber and nozzle.

The various features of novelty which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, refer- ,ence should be had to the accompanying drawings and descriptive matter in which we have illustrated and de- .cludes a nozzle 11 of frusto-conical shape extending through an air register 12 and associated with a burner port 13 formed in a'wall 14 of a furnace 15. The nozzle to the scroll chamber.

Patented Jan. 19, 1960 is supplied with air-borne pulverized fuel which is delivered to a scroll chamber 16 through an inlet duct 17 opening tangentially to the chamber and arranged substantially normal to the axis of the frusto-conical nozzle.

As shown in the drawings, the inlet duct '17 is of rectangular cross-section reducing in area from the flanged connection 18 with a supply pipe to the tangential inlet The outer wall 21 of the scroll chamber is in the form of a volute and the parallel side walls 22 and 23 of the scroll chamber are provided with openings therein which are co-axial with the central axis of the nozzle and the scroll chamber 16.

With a substantially rectangular cross-section, the inlet duct is ordinarily provided with a transition section 24 which is attached to the flange 18 of the duct and converts the usual circular cross-section of a fuel supply pipe (not shown) to the cross-section of the inlet duct. The cross-sectional area of the rectangular inlet duct is selected to be at most equal to the total cross-section area of the transport line, and preferably somewhat less so as to maintain flow velocities in the stream entering the scroll chamber 16.

As shown in Fig. 2, the inlet duct is arranged for generally downward introduction of coal and air. With such an arrangement, a transition pipe section 24 is not absolutely essential to convert the circular cross-section of the transport line to the rectangular cross-section of the inlet duct since this can be accomplished in the flanged connection therebetween. This is possible with a downward introduction of fuel and air since no shelves will be formed in the connections, for the deposition of pulverized fuel. It will also be noted that insofar as the scroll chamber 16 and nozzle 11 arrangement are concerned, the inlet duct may be positioned at any angle to the axis of the burner 10 as may be convenient with respect 'to the fuel and air source.

The frusto-conical nozzle 11 is constructed and arranged with its base 25 attached to the marginal portion of a circular opening 26 in the side wall 23 of the scroll chamber 16. The circular opening and the inside dimension of the nozzle base are selected to be substantially the same diameter and to be so positioned that the radius of the circular opening 26 is slightly less than the radius of the cut-off point 27 of the scroll. The nozzle and chamber can, of course, be constructed in one piece, as by casting, or may be manufactured in separate piece; and bolted or welded together.

The nozzle 11 is advantageously constructed with a length sufiicient to extend through the air supply housing and air register 12 in the assembly of the burner in connection with the burner port 13. However, insofar as operations are concerned, the frusto-conical nozzle can be considerably shorter than illustrated in Fig. 1. In general, the length of the nozzle will be at least twice the diameter of its base. In the embodiment shown, the nozzle base 25 is approximately 18" in diameter while the tip of the nozzle is approximately 10" in diameter and the length of the nozzle is approximately 5.

As shown in Fig. l, the air register 12 associated with the burner of the invention is constructed with a circumferential combustion air opening 30 located outwardly adjacent the wall 14 of the furnace 15. The air inlet opening 30 is provided with a circumferential series of leaves or louvers 31 which are pivotably supported between an inner annular plate 32 positioned normal to the axis of the nozzle 11 and parallel outer annular plate 33 which is attached along its inner circumferential edge to the exterior of the burner nozzle. The inner plate 32 of the air register is provided with a central opening 34 for the discharge of secondary combustion can occur.

air from the space between the plates 33 and 34 and into of approximately 20", and a'base diameter of approximately 36". Thus, combustion air entering throughthe louvers 31 in an inward direction acquires a tangential motion and moves in a' generally horizontal direction through the opening 34 and through the burner port 13 into the furnace 15. The position of the louvers 31 is ad ustable through an extension rod 35 extending through an outer insulated wall 36 which forms the outer boundary of an air inlet box 37. The extension'rod 35 is provided with a crank 40 with all of the louvers rotatably ad usted by movement of the crank through the extension rod to a system of gears and levers (not shown) mounted on the annular plate 33. The outer 'wall 36 of the air inlet box 37 is provided with at least one view port 41 which consists of a short section of pipe 42- extending through the wall 36 and matching a pipe 43 of larger diameter which extends from the exterior surface of the outer wall through the annular plate 33 of the air register. The outer end of the view port is provided with a closure member 44 having a glass insert 45 through which the operation of the burner and the condition of the flame within the furnace 15 may be observed.

Whenever coal segregation occurs in the entering coal and air stream, there will be an unequal distribution of the fuel discharged from the nozzle of a burner. When this occurs, the flame conditions within the furnace may be such as to cause an exceptionally heavy flame in one sector of a furnace while one or more of the other sectors may have an insuflicient supply of fuel, in comparison with the combustion air supplied. Under these conditions, incomplete combustion and high carbon loss To avoid such conditions, the burner of the present invention is provided with a plurality of curvilinear skimmer plates 46 which are individually adjustable and so arranged as to permit even distribution of the pulverized coal discharging from the burner nozzle 11.

In the illustrated embodiment of the invention, the

skimmer plates 46 are constructed of curved steel plates, and are three in number. Each of the plates correspond in length to one of the quandrants of a circle having a diameter substantially equal to thediameter of the opening 26. The width of each plate is slightly less than the spacing between the parallel side walls 22 and 23 of the chamber 16. For example, the side width of the chamber 16 is approximately 13" and each plate 46 is 12% in width, thus providing a clearance between the edges of the plates and the side walls of the chamber when the plates are installed in the chamber. Each plate is pivotally supported at one end by pins 47 which are welded on opposite sides at the end of the plate. The pins 47 are positioned to project beyond the edges of the plate so as to engage sockets which are drilled in the side walls 22 and 23 of the chamber. The sockets are located on a circle of slightly greater diameter than that of the opening 26, and are positioned approximately 90 on each side of the cut-off point 27 of the chamber and at a position approximately 180 from the cut-E point.

The pins 47 have a length sufficient to project beyond the sides of the chamber so that the pinon the side 23 of the chamber adjacent the nozzle 11 is of sulficient length to project through the wall of the chamber and to be flush with the exterior surface of the wall. The opposite pin 47 projects through the side wall 22 of the chamber and is engaged by a hollow cap 51 which is welded to the exterior surface of the chamber side wall.

In their installed position, each of the skimmer plates 46 will have a free end 52 facing upstream ofthe coal .and air mixture entering the scroll chamber 16. Since v the distribution characteristics of the skimmer plates is stream, the plates are adjustably supported so that the free end thereof may be adjusted transversely of the entering air-borne coal stream. This is accomplished by means of a threaded rod 53 which is pivotally attached to the convex surface of each of the skimmer plates 46. The rod is threaded in its outer portion and projects through the outer surface 21 of the scroll chamber to engage locking nuts 54 threaded on the rod on opposite sides of an L-shaped support 55. The support is welded at its lower end to the plate 21 of the scroll chamber and provides a fixed position through which the threaded rod 53 extends so that the position of the rod, and the attached skimmer plate, may be adjusted by manipulation of the threaded nuts 54. The rod is provided with a hollow seal member 56 which is welded to the exterior surface of the plate 21 of the scroll chamber. The construction is such as to prevent loss of air-borne coal through the openings in the scroll chamber as necessary for the movement of the skimmer plate adjusting rods 53.

As shown in the drawings, the scroll chamber 16 and nozzle assembly 11 is provided with a hollow tube 57 of lesser diameter than the discharge end of the nozzle. For example, with the 10" diameter nozzle discharge end of the nozzle illustrated, the tube 57 is selected for a diameter of 5". The tube is arranged co-axially with respect to the nozzle and is co-extensive with the nozzle and scroll chamber assembly. As shown in Figs. 1 and 2, the tube is provided with pin-like spacing arms 60 near the discharge end of the nozzle so as to maintain the coaxial relationship between the tube 57 and the nozzle 11. The tube is provided with a plate flange 61 which is bolted to the exterior side of the scroll chamber wall 22. The construction of the flange and the spacing members is such as to maintain the co-axial relationship of the tube and nozzle while at the same time providing an arrangement whereby the tube may be removed from the assembly, if such removal becomes desirable.

With the tube 57 described, the scroll chamber 16 in effect is provided with an inner circular wall so that the core of the swirling mass of air-borne coal is filled and any tendency to form a vacuum or a zone of low pressure at the core of the cyclonically moving coal and air stream is avoided. Moreover, with the tube extended throughout the length of the nozzle, the swirling stream of coal and air moving through the nozzle 11 passes through a flow path of annular section which diminishes in area throughout the length of the nozzle. The stream of airborne coal discharged from the nozzle tip intimately mixes with the surrounding mass of secondary combustion air entering the burner port 13 from the opening 34. The discharge of the coal and air stream in a tangential direction causes an immediate intimate mixing of coal dependent upon the relative position of the free end 52 and air for high efficiency combustion. A zone of relatively low pressure forms on the furnace side of the nozzle tip, with the zone causing a re-circulation of air and some of the inner marginal fringe of the vcoaland air stream, to create good ignition conditions so that the flame entering the furnace is propagated along an inner conical shape to maintain ignition of the fuel and air stream.

The burner 10 of the present invention may be used with liquid or gaseous fuels and for this purpose, a liquid fuel assembly 64 may be inserted in the tube 57 with the atomizing tip 65 terminating substantially at the.tip 66 of the nozzle 11. A gaseous fuel may be introduced through a burner ring 68 positioned adjacent the burner port 13 and on the furnace side of the tip 66 of the nozzle 11. The burner ring discharges gaseous fuel radially inwardly into the secondary combustion air passing from the annular opening 34 into the burner port 13.

While in accordance with the provisions of the-statutes we have illustrated and described herein the best form and mode of operation of the invention now known to us, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by our claims, and that certain features of our invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. Fuel burning apparatus which comprises a scroll chamber, means for tangentially introducing air-borne pulverized fuel into said chamber to maintain a confined circular movement of said air-borne pulverized fuel in said chamber, means for discharging said circularly moving fuel axially of said chamber including a frusto-conical outlet conduit having a length greater than its diameter opening to one end of said chamber, and a plurality of curved skimmer plates transversely extending across said scroll chamber, each of said skimmer plates being pivotably mounted at one end to the side walls of said chamher at positions equally spaced from the common axis of said chamber and nozzle and having substantially the same radius as the base of said nozzle, each skimmer plate having its free end individually radially adjustable into the moving stream of tangentially introduced airborne coal in said chamber.

2. A burner comprising a scroll chamber having spaced parallel side walls, means for introducing airborne pulverized fuel into said chamber substantially tangentially thereof, a frusto-conical nozle having a length greater than its diameter coaxially attached to said chamber with one end of said nozzle merging into a corresponding opening in one of said chamber side walls, a member of substantially uniform circular crosssection axially coextensive with said chamber and said nozzle and having a diameter less than said nozzle, and a plurality of individually adjustable curvilinear plates formed of segments of a circle having a diameter substantially equal to that of said nozzle and extending across said chamber for deflecting differentially selected portions of said air-borne pulverized fuel into different circumferential portions of said nozzle.

3. A burner comprising a scroll chamber having spaced parallel side Walls, means for introducing air-borne pulverized fuel tangentially into said chamber, a nozzle hav ing a length greater than its diameter coaxially attached to said chamber with one end of said nozzle merging into a corresponding opening in one side of said scroll chamber, a cylindrical member coaxial with said scroll chamber and axially coextensive with said scroll shaped chamher and said nozzle, and a plurality of curved skimmer plates transversely extending across said scroll chamber, each of said skimmer plates being pivotably mounted at one end to the side walls of said chamber at positions equally spaced from the common axis of said chamber and nozzle and having substantially the same radius as the nozzle, and means for individually radially adjusting the opposite end of said skimmer plates into the moving stream of air-borne coal in said chamber.

4. A burner comprising a scroll chamber having spaced parallel side walls, means for introducing air-borne pulverized fuel tangentially into said chamber, a frusto-conical nozzle having a length greater than its diameter coaxially attached to said chamber with the base of said nozzle merging into a corresponding opening in one side of said scroll chamber, a cylindrical member coaxial with said scroll chamber and axially coextensive with said scroll shaped chamber and said frusto-conical nozzle, and a plurality of curved skimmer plates transversely extending across said scroll chamber, each of said skimmer plates being pivotably mounted at one end to the side walls of said chamber at positions equally spaced from the common axis of said chamber and nozzle and having substantially the same radius as the base of said nozzle, each skimmer plate having its free end individually radially adjustable into the moving stream of tangentially introduced air-borne coal in said chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,738,176 Dyer Dec. 3, 1929 2,096,765 Saha Oct. 26, 1937 2,284,708 Woolley June 2, 1942 2,329,468 Hardgrove Sept. 14, 1943 2,341,682 Andrews Feb. 15, 1944 FOREIGN PATENTS 343,177 Great Britain Feb. 19, 1931

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