US2325318A - Pulverized coal burner - Google Patents

Description

ucalul \UUIH INVENTOR flaw/an fiU/mdrzx ORNEY 2 Sheets-Sheet 1 H. W. HENDRIX PULVERIZED COAL BURNER Filed March 10. 1941 July 27, 1943.

45l-lt55 UNITED Search Roorr STATES PATENT OFFICE 13 Claims.

This invention relates to burners and more particularly to burners of the type used for burning pulverized coal.

An object of the invention is to provide a novel and improved burner of the above type in which the entering coal and carrier air is divided into a plurality of separate streams which are individually advanced to the burner throat.

Another object is to provide a burner of the above type in which each of such fuel streams is fed positively along the burner tube with a predetermined helical movement.

Another object of the invention is to provide a burner of the above type suited to effect delivery of the individual streams of coal and carrier air at equal intervals around the entire periphery of the burner throat.

Another object is to provide for an adjustable delayed admittance of the secondary air at the burner throat.

Another object is to provide a burner of the above type having means to regulate the velocity of the carrier air and suspended fuel at the burner throat so as to adapt the burner for fuel supplies having different quantities of carrier air or different ratios of volatile matter in the fuel.

Another object is to provide a burner of the type above indicated in which a rich, uniformly distributed mixture of fuel and carrier air is supplied to the secondary air at the burner throat. I

Another object is to provide a burner of the above type which is eflicient and stable in operation at 'various capacities.

Another object is to provide a burner of the above type having novel and improved details of construction and features of operation.

Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

Although the novel features which are believed to be characteristic of this invention are pointed out more particularly in the claims appended hereto, the invention itself may be better understood by referring to the following description, taken in connection with the accompanying drawings, in which a, specific embodiment thereof has been set forth for purposes of illustration.

In the drawings,

Fig. 1 is a longitudinal section through a burner embodying the present invention;

Fig. 2 is a transverse section taken on the line 22 of Fi 1;

Fig. 3 is a partial horizontal section taken along the line 3-3 of Fig. 2;

Fig. 4 is a longitudinal section similar to Fig. 1 illustrating a further embodiment of the invention; and

Figs. 5 to 8 are detail views illustrating different embodiments of the invention.

In the following description and in the claims certain specific terms are used, for convenience, in referring to various details of the invention. These terms, however, are to be given as broad an interpretation as the state of the art will permit.

Referring to the drawings more in detail, the invention is shown as applied to a burner comprising a burner tube [0, which is mounted in registration with a burner throat I I in a furnace wall I2 forming a part of a combustion chamber. The burner tube I0 is shown as provided at its outlet end with a flange l3 which is secured by suitable means, shown as bolts 14, against the outer surface of the furnace wall I2. The inlet end of the burner tube I0 is shown as provided with a flange [5 secured against the inner wall I6 of a wind box or plenum chamber H. The wind box I! comprises the inner wall [6 and an outer wall [8 spaced to receive an air register Hi, to be described.

A fuel inlet duct 20 is positioned to admit fuel tangentially to the burner tube I 0 through an opening 2| therein. The duct 20 is shown as connected to a fuel supply pipe 22 which may be provided with suitable means, not shown, for controlling the quantity of fuel supplied and may be provided with means, such as cones or baffles 23, for effecting a uniform distribution of fuel and carrier air across the area of the burner inlet.

The air register I9 is provided with a plurality of peripheral air doors 25 adapted to receive air from the plenum chamber I! and to discharge air through an air discharge opening 26 in the register back plate 21. The air doors 25 are adapted to control the rotation of the air supplied through the register. The particular form of air register, however, forms no part of the present invention and is accordingly not set forth in detail.

An inner cylinder 3!] is mounted within the burner tube HI in registration with the opening 26 of the air register l9 and is spaced from the burner tube NJ to provide an annular passage 3| for fuel and carrier air therebetween. The cylinder 30 extends to a point near the burner throat ll and is provided with a sleeve 32 which telescopes in the cylinder 30 and is adjustable longitudinally to vary the area of the passage to the burner throat H for controlling the exit velocity of the coal and carrier air. The sleeve 32 may be adjusted by suitable means, shown as a rod 33 extending to the outside of the plenum chamber I1 and provided with an adjusting handle 34.

The outlet end of the burner tube I is shown as provided with a deflection cone 35 which is adapted to deflect the fuel stream inwardly toward the axis of the tube. This cone 35 may be made replaceable, if desired. The tile 36 at the burner throat may be provided with a surface forming a continuation of the surface of the cone 35 so as to protect the latter from the heat of the flame.

In the embodiment shown in Figs. 1 and 2, a plurality of helical vanes 40 are provided in the annular passage 3| between the burner tube l0 and the inner cylinder 30. These vanes 40 are spaced axially to provide helical fuel passages 4| therebetween and extend from the 'zone at which fuel is received from the fuel supply duct 20 to the outlet end of the cylinder 30 so that the fuel streams in the passages 4| are advanced uniformly and are discharged at uniform intervals around the periphery of the burner throat. The vanes 40 are shown as secured to the burner tube I0 and as extending inwardly to the cylinder 30. They may, however, be spaced somewhat from the cylinder 30 to provide a slight clearance or equalizing passage as shown in Fig. 6, or may be carried by the cylinder 30 as shown in Fig. 5. In Fig. 5 the vanes 400. are shown as attached to the cylinder 30 and extending outwardly. In the embodiment of Fig. 6 vanes 40b are shown as attached to the tube l0 and extending inwardly but terminating short of the cylinder 30 to provide clearance therebetween.

In certain instances it may be desired to burn gaseous or liquid fuel in addition to or in place of the solid fuel above mentioned or to use such gaseous or liquid fuel for ignition purposes. For this purpose, the burner is shown as provided with a fluid fuel supply barrel 42 which extends axially of the burner tube l0 and is provided at its inner end with an atomizer tip 43 of any desired type. A diffuser 44 is likewise mounted on the barrel 42 but may be withdrawn into the air register if desired when pulverized fuel is burned. The barrel 42 extends outwardly through the air register I9 and may be connected to any suitable source of fluid fuel, not shown.

Operation In the operation of this device, finely divided fuel, such as pulverized coal suspended in a stream of primary or carrier air and uniformly distributed therein as by cones 23, is received from the feed pipe 22 and passes through the inlet duct 29 and the opening 2| into the annular pasage 3| between the burner tube l0 and the inner cylinder 30. As the fuel enters the annular passage 3| it is divided into several streams, each of which is confined, by the vanes 40, in a passage 4| and is caused to advance helically to its point of discharge at the burner throat. The vanes 40 prevent any relative shifting of the carrier air and fuel streams and accordingly maintain the fuel and air distributed as received from the inlet duct 2|].

With a fixed quantity of carrier air, the velocity of the carrier air and fuel stream at the burner throat may be controlled by-adjusting the position of the sleeve 32, or if the quantity of carrier air varies, the velocity of fuel and carrier air supplied to the burner throat may be maintained constant by said adjustment.

Secondary air for combustion passes from the plenum chamber through the air register I9 to the interior of the inner cylinder 30 and emerges from the cylinder 30 at the burner throat. Hence, the carrier air and fuel stream remains out of contact with the secondary air until it reaches the burner throat. The passages 4| between the vanes terminate at uniform intervals around the periphery of the cylinder 30 at the outlet end thereof. Consequently, the fuel is discharged in a series of streams which are uniformly spaced around the entire throat periphery. By separating the secondary air from the fuel stream until it is thus discharged at the burner throat, a rich mixture of fuel and carrie air is obtained at the burner throat which tends to stabilize ignition.

The sleeve 32 may be adjusted with respect to the burner throat in accordance with the volume of primary air carrying the fuel stream, so as to maintain any desired velocity of the fuel and carrier air at the burner throat. The secondary air may be adjusted by means of the air doors 25 of the air register I9 or by varying the air pressure in the plenum chamber IT, as is well known in the art. The invention accordingly provides means for obtaining a uniform delivery of fuel at the burner throat under conditions for efiicient combustion. The burner is {dependable in operation and is well suited to commercial use.

Fig. 4

In the embodiment shown in Fig. 4, the various parts similar to Fig. 1 have been given the same reference characters and will not be redescribed. In this embodiment the vanes 4|) have been replaced by staggered vanes 50 and 5| mounted respectively on the burner tube Ill and on the inner cylinder 30. These vanes substantially span the space 3| between the burner tube and the cylinder 30 to provide passages 52 which act similarly to the passages 4| of Figs. 1 to 3. The clearance between adjacent vanes, however, provides means for equalizing any inequalities in the air-fuel stream as it passes helically around the cylinder 30. It is to be understood, of course, that the vanes 50 and 5| may be arranged in registration instead of in staggered relation if desired as shown in Fig. 7. Furthermore, the vanes 50 and 5| may overlap radially as shown in Fig. 8 or may be spaced apart radially as shown in Figs. 4 and 7 to provide for direct passage of air and fuel from one passage 52 into the adjacent passage for diffusion purposes. Fig. '7 discloses vanes 50a and 5|a attached respectively to the tube H) and cylinder 30 similar to those disclosed in Fig. 4 except that the vanes 50a and 5|a are in registration to provide a substantially closed passage except for the clearance between the two sets of vanes. In the embodiment of Fig. 8 the vanes 50b and SH) are in staggered relation, as shown in Fig. 4, but overlap so as to eliminate a direct axial through passage therebetween. Various other changes and modifications will be apparent to a person skilled in the art.

Although certain specific embodiments of the invention have been shown for purposes of illustration, it is to be understood that the invention may be varied as to details of construction and method of operation and is only to be limited in accordance with the scope of the following claims.

What is claimed is:

1. A pulverized fuel burner comprising a burner tube having an open outlet end adapted to be connected with a burner throat, an inner tube in said burner tube having walls spaced therefrom to form an annular passage therebetween, tangential fuel inlet means including an inlet port in the peripheral wall of said burner tube to supply to said annular passage a stream of pulverized fuel suspended in carrier air under conditions to cause the air-fuel stream to rotate peripherally in said passage, a central axial air admission means supplying a stream of secondary air to said inner tube to advance axially therein, and a plurality of helical vanes in said annular passage spaced apart axially along said inlet port to form a plurality of separate helical passages extending from said inlet port to divide the air-fuel stream into a plurality of individual streams and terminating in uniformly spaced relationship around the periphery of the burner tube at the outlet end thereof whereby the fuel is discharged in a plurality of streams uniformly spaced around the periphery of the burner throat at which point it is brought into contact with the secondary air from within the inner tube.

2. A burner according to claim 1 in which said helical vanes are mounted on said burner tube and extend inwardly into approximate engagement with said inner tube.

3. A burner according to claim 1 in which said helical vanes are mounted on said inner tube and extend outwardly into approximate engagement with said burner tube.

4. A burner according to claim 1 in which said helical vanes comprise inwardly extending vanes mounted on said burner tube and outwardly extending vanes mounted on said inner tube.

5. A burner according to claim 1 in which said helical vanes comprise inwardly extending vanes mounted on said burner tube andoutwardly extending vanes mounted on said inner tube, said inwardly and outwardly extending vanes being relatively offset to provide clearance for equalization of flow in the various passages.

6. A burner according to claim 1 in which said helical vanes comprise inwardly extending vanes mounted on said burner tube and outwardly extending vanes mounted on said inner tube, said inwardly and outwardly extending vanes being relatively offset to provide clearance for equalization of flow in the various passages, and being overlapped to prevent direct axial passage of air and fuel between adjacent fuel passages.

'7. A burner according to claim 1 in which said helical vanes comprise inwardly extending vanes mounted on said burner tube and outwardly extending vanes mounted on said inner tube, said inwardly and outwardly extending vanes being in registration and being spaced apart radially to provide clearance for equalization of flow in the various passages.

8. A pulverized fuel burner comprising a burner throat, a burner tube of greater diameter than said burner throat and open at its outlet end thereto, an inner tube in said burner tube having walls spaced therefrom to form an annular passage therebetween, said inner tube being spaced at its outlet end from said throat to form a restricted annular fuel passage therebetween, tan gential fuel inlet means including an inlet port in the peripheral wall of said burner tube to supply to said annular passage a stream of pulverized fuel suspended in carrier air under conditions to cause said stream to rotate peripherally in said burner tube, means causing said. rotating stream to advance helically therein to the burner throat, and axial air admission means admitting a secondary air stream to said inner tube to advance axially therein, said inner tube causing said peripherally rotating fuel stream to contact with said secondary air stream substantially at the burner throat, whereby a rich, uniform fuel mixture is obtained.

9. In a burner according to claim 8, means to adjust the inner tube relative to the burner throat for varying the area of the annular fuel passage therebetween in accordance with flow requirements.

10. In a burner according to claim 8, a sleeve carried by saidinner tube and means for adjusting said sleeve relative to the burner throat for varying the area of the annular fuel passage therebetween in accordance with flow requirements.

11. In a burner according to claim 8, means in the annular passage between said burner tube and said inner tube to cause said air-fuel stream to advance helically therein from said inlet means to said burner throat and to discharge said fuel stream uniformly around the entire periphery of said burner throat.

12. In a burner according to claim 8, a plurality of helical vanes in said annular passage between said burner tube and said inner tube, said vanes being spaced axially to provide a plurality of separate helical passages therebetween and extending from a zone to receive the air-fuel stream directly from said inlet means and to divide the same into a plurality of individual streams traversing the respective helical passages and terminating in uniformly spaced relationship around the periphery of the burner tube at said throat, whereby the fuel is discharged in a plurality of streams uniformly spaced around the periphery of the burner throat at which point it is brought into contact with the secondary air from within the inner tube.

13. In a burner according to claim 8, a plurality of helical vanes in said annular passage between said burner tube and said inner tube, said vanes being spaced axially to provide a plurality of separate helical passages therebetween and extending from a zone to receive the air-fuel stream from said inlet means and to divide the same into a plurality of individual streams traversing the respective helical passages and terminating in uniformly spaced relationship around the periphery of the burner tube at said throat, whereby the fuel is discharged in a plurality of streams uniformly spaced around the periphery of the burner throat at which point it is brought into contact with the secondary air from within the inner tube, and means to adjust the inner tube relative to the burner throat for varying the area of the annular fuel passage therebetween in accordance with flow requirements.

HOUSTON W. HENDRDI.

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