US2399234A - Pulverized fuel burner - Google Patents

Description

April 30, 1946. H. KREISINGER ETAL PULVERIZED FUEL BURNER 2 Sheets-Sheet 1 Filed Feb. 14', 1942 INVENZOR; Hqn g lii'ezsnger Wjgmms t'aracnlsh' HTTORNEY.

April 30, 1946. H. KREISINGER ET AL PULVERIZED FUEL BURNER Filed Feb. 14, 1942 2 Sheets-Sheet 2 m m y w m Wggzhiqs t'aracnsit Patented Apr. 30, 1946 mm rum. BURNER Henry Kreisinx lf, Plermont, and Virglnius Z.

Csracristi, Bronxville, N. Y., assignors to Combustion Engineering Company, Inc., New York,

Application February 14, 1942, Serial No. 430,936

' 4 Claims. (01. 110-104) This invention relates to pulverized fuel burners and particularly to improved means for uniformly supplying finely ground coal etc., to horizontally disposed burners.

In horizontally disposed pulverized fuel burners the fuel and air mixture is given a rotative movement in passing through the burner because of a volute entrance into the fuel nozzle and spiral riding in the latter. The rotative movement imparted to the fuel and air mixture produces turbulence and causes it to bush out" or spread into a flame cone upon its entrance into the furnace. Seen through an observation door in the furnace wall opposite the burner the flame from a well designed and operated horizontal burner appears to radiate from the center of the burner forming an annular disk.

Even distribution of fuel and air to a furnace with a horizontally disposed burner is more diflicult than with burners disposed vertically and firing downwardly'into the furnace. Ordinarily there are fewer burners and therefore the streams of fuel entering the furnace are larger; the path of the burning mixture between the tip of the burner andthe generating bank also is usually shorter than with vertical flring. Consequently,

. the distribution of coal and air over the entire cross section 'of the moving stream of burning mixture from the burner wall to the generating bank must be accomplished in a short distance from the burners and the distribution must be uniform throughout this section. If the distribution is not uniform, certain parts of the furnace et too much fuel and too little air and other parts get too much air and too little fuel. It will readily be seen that the more bushy the flame is the shorter the distance from the burner in which the fuel and air can be spread uniformly across the entire cross section of the furnace. To make bushing of the flame effective, it is necessary that the pulverized coal should be uniformly distributed around the periphery of the tip of the coal nozzle and this is a most difiicult problem to solve because it is affected not only by burner design but by the shape and arrangement of the fuel p ping.

Feeding the coal and air mixture to the volute entrance of a horizontally disposed burner and the rifling therein impart a rotative movement to the coal and air mixture causing the coal to be concentratedalong the inner wall of the nozzle so that it is discharged from the nozzle tip in an annular ring. Some segments of this ring may contain more coal than others because bends in the piping to thebumer and the direction of approach of the piping with respect to the burner inlet may cause'the coal and air mixture to be introduced to the inlet at one side or the other of the latter so that some segments of the annular 5 ring at the nozzle tip receive less coal than others. Consequently, when the coal in these segments is discharged approximately radially into the furnace, certain parts of the furnace get too much fuel and too little air while other parts get too much air and too little fuel.

- 'An object of this invention is to provide an improved means in the fuel pipe supplying a burner which will cooperate with the burners to produce a uniform distribution offuel at the tip into a furnace;

Figure 2 is an enlarged sectional view on the 7 line 2-2 in Fig. 1 showing adjustable deflecting I means in the fuel supply pipe for directing the fuel stream so as to cause the fuel to be introduced to the inlet of the burner uniformly to attain a uniform discharge of the fuel and air mixture from the tip of the burner;

Figure, 3 is a sectional view on the line 3-3 in Fig. 2 illustrating the manner of introduction of fuel stream to the inlet of the burner to effect uniform discharge from the burner tip; v

Figure 4 is a sectional view on the line 4-5; in

Figure 1 or 2 with the adjacent part of the cylindrical inlet portion of the burner developed into the plane of the sheet;

Figure 5 is a plan view ofthe burner shown in Fig. l with diagrammatic illustrations of several angular positions for the fuel pipe in ap- 40 proaching a bend therein leading to the burner .and show the consequent effect upon the flow and distribution of the fuel produced by the bend in the piping;

Figures 5a, 5b, 5c, 5d and 5e are sectional views form feeding of the coal across the inlet to the burner.

of the latter so as to effect a more efflcient com- In Fig. 1 the numeral ill designates a vertical wall of a furnace having an opening 12 therein into which the tip of a horizontally disposed fuel burnerv designated as a whole by the numeral I 4 extends for introducing fuel and air into the furnace. The burner I4 projects through an air duct I 6 supplying secondary air for the combustion of the fuel around the tip is of the burner ll. The burner H has a volute entrance section 20 as shown in Fig. 3 to which the fuel and aid mixture is supplied through the fuel pipe 2i having a bend 22 therein near the burner. Pipe 2| may approach the burner ll from various positions, such as those designated by the reference letters a, b, c, d, and e in Fig. 5.

The fuel pipe 2! may begcylindrical as shown while near the entrance portion 24 of the burner the volute section thereof i rectangular so that it has a fiat horizontal undersurface 26 extending parallel to the burner axis for the width of the entrance 24. The interior wall of the cylindrical burner 14 is provided with a plurality of helical ribs 80 extending from adjacent tip l rearof the coal being thrown against the outer wall in the fuel pipe in passing around the bend when the pipe approaches the burner from a position in front but to one side thereof as indicated at b andd in Fig. 5. As contrasted with such uneven distribution of fuel at the inlet of the wardly throughout nearly the length of the burner nozzle. Ribs 30 terminate short of the outer end wall 3| of the burner; progressing clockwise around the burner the end of each successive helical rib extend further across the inlet opening 28 than its predecessor which is nearer the oiftake. Coal entering the inlet 28 of the burner in a uniform ribbon indicated by the dots A on the flat bottom surface 28 of the volute flows into the burner and encountering successive helical ribs 30 is sheared off or diverted axially through the burner in the form of a number of smaller ribbon indicated by the dot B,

.each of these ribbonlike streams travelling in a helix between two adjacent ribs 30 to the tip i5 of the burner nozzle. The rotative movement of the coal mixture through the burner concentrates the coal along the walls of the nozzle so that on reaching the nozzle tip a large part of the'coal distributed uniformly across the inlet 28 on the flat surface '26 it will be uniformly discharged into the furnace as indicated in Fig. 6.

However, if some sectors of the ring of coal at the nozzle tip contain more coal than others, the adjacent part of the furnace receives more coal than parts of the furnace opposite the sectors having the smaller amounts of coal as indicated in Fig. 7. For example, if the section of the fuel supply pipe ahead of bend 22 approaches the burner in a position in front thereof as indicated at C in Fig. 5, the coal in passing around the bend 22 concentrates against the outer wall thereof as indicated by the dots. In passing around the bend the coal enters inlet 28 concentrated against the opposite wall of the pipe and upon reaching the burner the coal is concentrated against the side wall 25 of the volute section 20 at the inlet 28 to the burners a's indicated by the dot in Fig. 50. Consequently, in the ribbons of coal passing between helical ribs 30 near the burner inlet there is a relatively large amount of coal while between the ribs further around the burner wall and remote from the inlet there is much less coal, if any. Figs. 5b and 5d also indicate unequal distribution of fuel across the inlet to the burner as a consequence burner, Fig. 5c shows the distribution at the inlet when the coal in passing around the bend concentrates against the outer wall of the fuel pipe approaching from the left of the burner in Fig. '5 and in passing around the bend reaches the position shown in Fig. 5 where it is uniformly distributed across the inlet to the burner and thus equal amounts of fuel will be sheared off by-successive helical ribs 30 that it encounters as a result all of the segmental ribbons of coal travelling spirally to the tip it of the burner contains equal amounts and therefore the annular ring of coal at the burner tip has substantially equal amounts of coal in it different seg ments. Thus substantially uniform amounts of coal are discharged all around the tip I5 as indicated in Fig. 6. When the fuel feed pipe 2! comes in from the right hand side of the burner as shown by the position a in Fig. 5, the fuel concentrating on the outer side of the bend after passing the latter will reach the inlet concentrated against the top wall 21 of the outlet a indicated in 131g. 5a but will pass across the outlet opening 28 and thus flow towards the spiral ribs 30 in the same manner as when forming a ribbon on the flat bottom 26 of the inlet to the burner.

However, it is not always possible to locate the fuel piping so that it approaches the burner from a position which produces a uniform distribution in a ribbon across the inlet to the burner. In many installations it is necessary to install the feed pipe, or it is found to be installed in some position resulting in an unequal distribution across the inlet opening to the burner as outlined above.

To overcome such uneven distribution and delivery of fuel to the inlet of the burner when the fuel pipe is installed in such unfavorable positions, the present invention provides an adjustable sleeve section All in the part of fuel supply pipe 2| adjacent the burner ll. Sleeve 40 is provided on part of its inside wall with a series of deflecting vanes 42 capable of intercepting the stream of coal passing along the wall of the supply pipe at one side thereof in an undesirable location and turning the stream angularly about the axis of the supply pipe into a position on -another part of the pipe wall from which it will pass on to the burner inlet 28 distributed substantially evenly across the width of the'latter. As shown in Fig. 2 a section ll of feed pipe adjacent the volute inlet portion 20 of burner I4 is belled at its open end and receives the lower end of the adjustable sleeve 40. The upper end of the latter is also belled to receive preceding section 2la and is rotatable about the axis of the feed pipe of which the section 2ia is a part.

7 Packing 43 is mounted between the bell portion of the section 4! and the adjustable deflector sleeve 48 and between the latter and the outer wall of the lower end of the section 2la. There are also provided collars 44 having flanges 45 tion for interrupting the stream of coal flowing along the pipe wall in an undesirable location and angularly displacing itabout the pipe axisinto a position on the inner pipe wall such that it will flow as a uniform ribbon across the flat portion 26 -of the volute entrance section 20 of the burner.

Thus in fuel supply pipes provided with a deflector section in accordance with the present invention the deflecting sleeve 40 may be adjusted to a position in which its deflecting vanes 42 intercept a stream of coal flowing along the pipe and direct it by deflection into a location such that the coal is distributed uniformly across the inlet to the burner. It has been found that if a heavy concentration in the stream of fuel enters the burner inlet near the middle-of wall 26 it distributes itself more or less evenly over the full width of the inlet. This is becausewhen the mass of material enters the volute section 20 in a central position on its outer wall 26 the action of centrifugal force tends to spread the mass laterally to form a ribbon of substantially uniform thickness or depth across the inlet. If, however, the heaviest concentration moves toward one side of the inlet as in the position shown in Figs. 51), c or d, the fuel does not adjust itself evenly across the inlet and the flames in the furnace are one-. sided. In such cases the concentration of the fuel stream may be shifted and dispersed by adjusting sleeve 40 so that the vanes 42 deflect the coal towards the middle of the inlet 28 to the burner.

The deflecting vanes 42 are placed at a suitable angle to the axis of the sleeve 40 to effect suflicient rotation of the coal stream about the axis of the fuel supply pipe to concentrate the coal along the lowenflat wall 26 at the inlet to, the burner as indicated in Fig. .3. The deflecting vanes 42 may project from the inner wall of the adjustable sleeve 40 so as to occupy approximatelyhalf of its cross-sectional area or may intercept more or less of this area according to the amount of correction of-the angular position of the fuel stream within the pipe that has to be effected.

While the adjustable deflector vanes 42 are particularly applicable to fuel supply systems having horizontally disposed burners, they may also be utilized to angularly displace the coal stream about the axis of a fuel pipe leading to a vertically disposed burner so that a uniform dissively further across said inlet passage so that adjacent ribs deflect substantially equal amounts of material axially of the nozzle from a stream of material distributed substantially uniformly across said inlet opening. v

2. In apparatus for supplying a mixture consisting of pulverized material in flotation in a current of air having a cylindrical nozzle provided with a volute inlet passage adjacent its outer end causing the mixture to flow tangentially into the nozzle and to impart a. rotary movement to the mixture; longitudinally extending helical ribs equally spaced peripherally on the inner wall of said nozzle for maintaining a rotary movement of'the mixture in its travel axially of the nozzle, the rib nearest said inlet passage in the direction of material flow terminating adjacent the nozzle side of the passage and successive ribsabout the wall of said nozzle P in the direction of material flow extending progressively further across said inlet passage so that adjacent ribs deflect substantially equal amounts of material axially of the nozzle from a stream of material distributed substantially uniformly across said inlet opening; a material supply conduit connected to said inlet passage; and deflecting vanes disposed on only a part of the inner wall of said conduit and occupying a portion of the cross-sectional area thereof and adjustable for positioning themperipherally of said conduit to dispose them to intercept a stream of material flowing in concentrated form in one location on the inner wall of said conduit and to tribution of coal across the burner inlet is effected.

What we claim is:

sisting of pulverized material in flotation in a current of air having a cylindrical nozzle pro-. vided with a volute inlet passage adjacent its outer end causing the mixture to flow tangentially into the nozzle and to impart a rotary movement to the mixture; longitudinally extending helical ribs equally spaced peripherally on the inner wall of said nozzle for maintaining a rotary movement of the mixture in its travel axially of the nozzle, the rib nearest said inlet passage in the direction of material flow terminating adjacent the nozzle side of the passage and successive ribs about the wall of said nozzle in the direction of material flow extending progresangularly shift said stream about the axis of said conduit to another location from which it may flow along the wall of said conduit to enter said inlet portion of said nozzle distributed substantially uniformly across the Wall of said passage that parallels the nozzle axis.

3. In apparatus for supplying pulverized material in flotation in a current of air having a cylindrical nozzle provided'with a volute inlet passage adjacent its outer end; a material supply pipe connected to said inlet passage; and deflecting vanes disposed on only a part of the inner wall of said pipe and occupying only a portion of the cross-sectional area thereof for angularly displacing a major portion of the material flowing therethrough toward the middle of the outerwall of said inlet passage parallelling the axis of said nozzle.

4. In a conduit for carrying pulverized material in flotation in a current of air, a plurality of deflecting vanes inclined with respect to the axis of said conduit and circumferentially spaced in contiguous relation to form a group located on only a part of the inner wall of said conduit and occupying only a portion of the cross-sectional area thereof and adjustable for positioning them peripherally of said conduit to dispose them to intercept a stream of material flowing in concentrated form in one location on the inner wall of said conduit and to angularly shift said stream about the axis of said conduit to another location from which it may flow along the wall of said conduit distributed substantially uniformly across the latter.

, HENRY KREISINGER.

VIRGINIUS Z. CARACRISTI.

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