US2912942A - Pulverized fuel burner - Google Patents

Description

Nov. 17, 1959 G. C.'WHlTNEY, JR, ETAL 2,912,942

PULXERIZED FUEL BURNER Filed July 29, 1954 United States Patent PULVERIZED FUEL BURNER Gilbert C. Whitney, Jr., and Jay L. Clark, l )ansville, N.Y., assignors to Foster Wheeler Corporation, New York, N.Y., a corporation of New York Application July 29, 1954, Serial No. 446,532

5 Claims. (Cl. 110-104) The present invention relates to a fuel burner and more particularly to a fuel burner which uses pulverized solid fuel.

In the usual fuel burner for pulverized solid fuel, a mixture of air and pulverized fuel is introduced as a stream through a volute inlet section into a cylindrical burner body. Upon entering the cylindrical body, the solid fuel particles in the mixture are thrownto the outside of the stream against the inner surface of the cylindrical body. Thereafter, both the separated fuel particles and stream of air from which the particles separate, move toward the burner bodys outlet with a velocity that is the resultant of the axial velocity component of the mixture and a circumferential velocity component imparted to the mixture in the volute inlet section. The separated stream of air moves centrally of the burner body toward the bodys outlet while the fuel particles, move along the inner surface of the body toward the outlet. Where the scroll of the volute fades into the diameter of the burner body, another stream of air moves axially forward, as well as circumferentially,

in the burner body toward the bodys outlet. This other 1 stream of air is of materially higher velocity than the average velocity of the above-mentioned stream of air and persists down through the burner body in the form of a spiral air rope. Since it is a characteristic of dust laden streams that the majority of the dust is transported in the high velocity areas of the carrier stream, the net effect in the conventional burner where coal is the fuel and air is the carrier stream, is the formation of a spiralshaped rope of coal dust which delivers, for example, A of the pulverized coal in approximately of the circumference of the tip or outlet of the burner body. It has also been found that this effect persists practically unchanged regardless of the distribution of air-coal stream in the supply conduit leading to the burner.

In accordance with the present invention, a fuel burner for pulverized fuel is provided with novel means for uniformly distributing the pulverized fuel around substantially the entire circumference of the burner outlet.

The present invention further provides a novel fuel burner for pulverized fuel and wherein internal recirculation of the fuel and overheating of the burner is prevented.

The invention, together with its various features and objects will be understood by reference to the accompanying drawing, in which:

Fig. 1 is a longitudinal sectional view, in elevation, of the burner of the present invention; and

Fig. 2 is a sectional view of the burner taken along line 22 of Fig. 1.

Like characters of reference refer to similar parts throughout the views.

Referring to the drawing, the reference character designates a fuel burner for pulverized fuel comprising a main body 11 with an inlet 12 and an outlet 13, and a volute inlet section 14 having an inlet 15 and an outlet 2,912,942 Patented Nov. 17, 1959 3 16. Body 11 comprises a frusto conical shaped casing i and a horizontally disposed cylindrical portion 19.

Volute portion 18 has a scroll 25 (Fig. 2) which joins portion 19 to form a scroll inlet 26 (Fig. 2) which scroll inlet is not unduly restricted by reason of the COHStl'llC.

tion of such portions. A cylindrical sleeve 27 extends axially within cylindrical portion 19 and body 11 of the burner. Sleeve 27 is of a smaller diameter than portion 19 and body 11 and together with the latter define a generally tapered annular passage 28 between the outer periphery of said sleeve and the inner surface of said portion and body. An inner tube 29 is disposed concentric with and in sleeve 27 and provides means for lighting off the burner.

Disposed on the inner surface of body 11 are a plurality of vanes or bars 30 which are circumferentially spaced apart and which extend substantially longitudinally of burner 10. Bars 30 are triangular-shaped in crosssection and have their apexes facing toward the burner axis. The opposite ends ofbars 30 are spaced from inlet 12 and outlet 13, respectively, of the body 11.

.In operation, when a mixture of pulverized fuel and air, as for example, a mixture of coal and air, is supplied to burner volute section 14 by conduit 17, the mixture enters inlet 15 and impinges against scroll 25 whereby a tangential or circumferential velocity is imparted to the mixture due to its change in direction. As the mixture leaves scroll 25, the coal particles are thrown to the outside of the coal-air mixture against the inner surface of cylindrical portion 19 by centrifugal force and the coal particles separate from the air stream. Thereafter, the coal particles move along the inner periphery of portion 19 and body 11 toward body outlet 13 while part of the separated air stream moves centrally of por-' tion 19 and body 11 toward outlet 13. Another part of the separated air stream moves in the form of a spiral and at a higher velocity than the first-mentioned part of the separated air stream toward the bodys outlet 13 in portion 19 and body 11. The separated coal dust travelling along the inner periphery of portion 19 and body 11 moves into this high velocity area and is transported in the high velocity carrier stream thereby forming a spiral rope of coal dust.

'In accordance with the present invention, when the spiral rope of coal, carried in the air stream, passes forward of body inlet 12 toward outlet 13, the coal rope.

impinges against bars 30, which are at substantially right angles to its flow path, and is dispersed or broken up. After the coal and high velocity carrier stream are dispersed by impingement against a bar 30, the carrier stream tends to reform and the coal tends to move into said stream to form another coal-air rope. However, before a coal-air rope can be again formed, the dispersed coal and carrier stream impinges on another bar 30 at substantially right angles to the flow path, until the coal and Air supply means 21 is attached to a fill the low pressure area or void extending along the axis of the burner. This low pressure area or void is caused by air having no velocity along said axis moving outwardly toward the inner surface of burner body 11. Thus, in the present invention, since the burner flame extends outwardly into the furnace when the burner is fired and not inwardly of the burner, overheating of the burner is prevented.

Optimum results are obtained in accordance with the present invention when the opposite ends of bars 30 are positioned in spaced relationship with the inlet and outlet of body 11, as shown in Fig. 1. If the ends of bars 30, nearest inlet 12, are extended rearwardly in the burner to scroll 25, a portion of the coal-air mixture entering inlet section 14 will slide alongthe sides of the barstoward body outlet 13 instead of impinging against the barsto be uniformly dispersed thereby, as above described; Conversely, if the ends of bars 30, nearest inlet 12, are moved too far away therefrom, and toward body outlet 13-, the density of the coal-air rope spiral increases and the rope becomes so compact that when the rope strikes the side of a bar 30, it slides over the top of the bar and down the other side of the bar without being dispersed, as above described.

If the ends of bars 30, nearest outlet 13, are extended toward said outlet, the coal-air mixture discharged through outlet 13 will be in the form of jets equal to the number of bars 30 disposed in the burner since the. coal-air rope does not have sufficient time to be uniformly dispersed. Conversely, if the ends of bars 30', nearest outlet 13, are moved away from said outlet too: great a distance, the coal-air rope spiral will reform since the. high velocity carrier stream reforms resulting in a non-uniform distribution of coal-air mixture from said outlet.

Inasmuch as various modifications may be made in the embodiment of the invention herein disclosed without departing from the principles thereof, it will be understood that the invention is not to be limited excepting by thescope of the appended claims.

What is claimed is:

1; An apparatus for introducing a mixture of pulverized fuel and air into a furnace, comprising a hollow body having an inlet to receive a mixture of pulverized fuel and air and an outlet for discharging said mixture therefrom, means for supplying a mixture of pulverized fuel and air to said body inlet for providing a helicoidal stream of said mixture flowing through said hollow body, and a plurality of spaced straight vanes secured to the inner surface of said body, each of said vanes being disposed in the same plane as the longitudinal, axis of said hollow body and extending substantially the length-of the body from a point in spaced relationship withsaid body inlet to a point spaced from the body outlet for continuously disrupting the helicoidal stream of pulverized fuel to effect substantially uniform distribution of the pulverized fuel across the flow area of the body at. said outlet and a substantially uniform discharge of pulverized fuel from the outlet.

2. An apparatus for introducing a mixture of pulverized fuel and air into a furnace, comprising a substantially cylindrical hollow body having an inlet to receive a mixture of pulverized fuel and air and an outlet to discharge said mixture therefrom, means. for

supplying a mixture of pulverized fuel and air to said body inlet for providing a helicoidal stream of said mixture flowing through said body, and a plurality of straight vanes spaced from each other circumferentially around the inner peripheral surface of said body, each of said vanes being disposed in the same plane as the longitudinal axis of said body and extending from a point in relatively close spaced relationship with the body inlet to a point in relatively close spaced relationship with the body outlet for continuously disrupting the helicoidal stream of pulverized fuel by impingement against said vanes thereby providing substantially uniform distribution of pulverized fuel across the flow area of the body at said outlet and a discharge of pulverized fuel from the outlet of substantially uniform distribution.

3. The apparatus of claim 2, wherein the vanes are triangular shaped in cross-section and are disposed with their apexes facing toward the longitudinal axis of the body,

4'. A burner nozzle for introducing a mixture of pulverized fuel and air into a furnace, comprising a main hollow body having an inlet and an outlet, a voluteshaped inlet section having an inlet for receiving a mixture of pulverized fuel and air and having an outlet, said volute outlet being in communication with said main body inlet to pass said mixture of pulverized fuel and air tangentially into said body inlet for providing a helicoidal stream of pulverized fuel flowing through said body, a plurality of spaced straight vanes secured to the inner surface of said body, each of said vanes being disposed to lie in the same plane as the longitudinal axis of said body, the opposite ends of each of said vanesbeing spaced inwardly from said body inlet and said body outlet for continuously dispersing said heli'coidal stream of pulverized fuel and uniformly distributing the pulverized fuel across the flow area of the body outlet.

5. An apparatus for introducing a mixture of pulverized fuel and air to a furnace, comprising a frusto-conical shaped hollow body having an inlet and an outlet, a volute outlet sect-ion forming a plenum chamber having an inlet to recevie a mixture of pulverized fuel and air and an outlet, said volute outlet being in communication with said hollow body inlet to pass said mixture of pulverized fuel and air tangentially to said hollow body inlet for providing a spiral flow of said mixture through said hollow body, a plurality of spaced straight vanes disposed circumferentially around the inner peripheral surface of said hollow body, each of said vanes disposed to lie in the same plane as the longitudinal axis of said hollow body and extending substantially the entire length of said hollow body from a point in relatively close spaced relationship with the body inlet to a point in relatively close spaced relationship with the body outlet for continuously disrupting the spiral stream of pulverized fuel to effect a uniform distribution of pulverized fuel across the flow area of said hollow body at said body outlet and a discharge of pulverized fuel from said body outlet of substantially uniform distribution.

References Cited. in the file of this patent UNITED STATES PATENTS 1,843,662 Craig et al Feb. 2, 1932 1,870,013 Keenan Aug. 2, 1932 2,615,407 Ragusan Oct. 28, 1952-

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