US1843662A - Fuel burner - Google Patents

Description

2 Sheets-Sheet l,

O. CRAIG ET AL FUEL BURNER Filed Jan. 20, 1927 86 w S M Q n N 0 w o n NAM A ML 03 Feb. 2, 1932.

@VYlLi-ESS 0. CRAEG ET AL Feb. 2, 1932.

FUEL BURNER Filed Jan. 20, 1927 2 Sheets-Sheet 2 s m T N E V W L. I/. ANDRE W8 OLL/SON 67mm Q I (7% ch\ ATTOR Y WITNESS E C? Patented Feb. 2, 1932 PATENT oFFicE o msou Snare-hm) I. v. ANnREw or WORCESTER, MASSACHUS TTS, ASSIGNORS To .RILEY sToxnn-conrommon, or woncnSTER, MASSACHUSETTS, A CORPORATION or MASSACHUSETTS FUEL BURNER l A pplication filed January 20, 1927. Serial No. 162,371.

- j" This intent o fatesto fuel burners, and

more particularly to burners for pulverized fuel of the type in which the air necessary for. combustion isintroduced into the furnace through theburner.

One form of burner comprises a central pipe throughwhich the pulverized fuel and prlmary air are discharged and around the outside of whichthefsecondary airis delivered to the furnace. It is usually impossible .to avoid having several bends and elbows in the fuel pipe, and considerable segregation occurs as a result .of centrifugal force which throwsthe coarser fuel particles'to the outsidevo'f the bends; In prior burners of this type, this segregation has continued upto the time, the fuel and air enter the furnace, the fuel being distributed unevenly around the circumference of thedischarge nozzle. Obviously, unde r these conditions, it'is impossible to obtain *a, uniform mixture of coal and air, andfamunbalanced and inefficient flame is the-result.-

f i It is accordinglyloneobject of our invention to provide a. burner arranged to produce auniform distribution of pulverized fuel around the circumference of the discharge nozzle, regardless of any bends which may be present in the pipe line leading to the burner. It is very desirable in burning pulverized fuel to produce a high. degree of turbulence in the mixture of fuel and air leaving the burner. Such turbulence results in more rapid combustion and a shorter flame, permitting the use of a furnace having a smaller volume. Attempts have been made to produce turbulence by placing a helical screw thread or blade in the fuel discharge nozzle, causing the issuing fuel Stream to Whirl. Such prior devices have been unsatisfactory because they increase the fuel segregation, the fuel, tendingto flow along close to the surface of the blade and leave the nozzle in a concentrated stream.

It is therefore a further object of our invention to provide an improved type of spreader for a pulverized fuel burner, which is adapted togive a whirling movement to thefuel stream as it is discharged without causing appreciable segregation.

With burners for pulverized fuel, it is highly desirable to be able to cover a wide range of boiler ratings, that is, to burn efficiently a large or small amount of fuel as desired, depending on the load on the boiler being fired. Now in attempting tooperate at low ratings, it is necessary to "reduce the supply of fuel and of secondary air. The primary air cannot be reduced, as it is necessary to transport the fuel to the'burner. Therefore, the point is eventually reached Where the primary airis" sufficient for the amount .offuel being burned, and the secondary air is entirely out off. It has been impossible to operate satisfactorily under these conditions with prior burners, because they have depended upon the air flow to keep them 0001, and if this air supply is cut ofi ierious damage results from the radiant eat.

a It is accordingly a furtherobject of our invention to provide a ulverized fuel burner which can be operate efiiciently at all ratings, and which is so constructed and arranged that the suppl 'of secondary air may be entirely out o if desired without the radiant heat seriously damaging various parts of the structure defining the secondary air passage.

A still further object is to provide'a burner which will produce a uniform and highly turbulent mixture of air and fuel, and which will be inexpensive to manufacture, easy to install and simple to operate.

With these and other objects in view, as will be apparent to those skilled in the art. our invention resides in the combination of partsset forth in the specification and cov- 'ered by the claims appended hereto.

According to our invention, we provide a pipe or nozzle which is suitably located to discharge pulverized fuel and primary air into a furnace. In order to obtain a uniform discharge of fuel around the circumference of the pipe, we introduce the stream into the burner pipe through a tangential inlet. For this purpose the outer end of the pipe is preferably enlarged to form a substantially cylindrical chamber in which the fuel may whirl- Secondary air is introduced unirifts ng. bkeh my;

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,control mechanism formly around the discharge nozzle, prefertion, so that the secondary air is given a proably by vanes or louvers arranged to give nounced whirl or rotary motion. this air a rapid whirling motion, thereby aid- In the majority of installations it is desiring in the mixing effect. A spreading device able to utilize forced draft, and to deliver may be mountedat the discharge end of the thesecondary ainunderpressure froma suitfuel P pe. a his i ei b b e-r g radar p me "w p de a we series of uniformly spaced substantially raing 18 to forma plenumchamber around the dial blades each inclined at an angle; so'as" "leavers. This chamber is open at the bottom to givethe 'issuing -streamIanroutwardrms"shownrinrEig. 1; andmsuitahieductmay rotary motion: eThis spreader fiepreferablyiwbevconnected'ttheretmforthe delivery oi the mounted for adjustment longitudinally of air. In order to contmbthee azir pressure the fuel pipe on a smaller pipe coaxial there Fciwithin the casing 18, dampers 20 may be ar- With. This small pipe is useful particularly ran ed. As shown in Fig. 4, each damper in connection with aighus' er the 'fiiel 'sh'ir provided with a worm gear segstream, as it permits the ntroduction ofan ment 21 andthese mesh with worms 22 on 2. oil burner or other suitableQdevic e for this A"hand wheel 25 on purpose. Q i I v Q :this shaft'ca-n berotated to -opeii'br-elosethe Reierring to the drawings, iniwhi'chg i diifii pers as desired; fi v reference numeranind ue likepa s; v "The'louve'rs 16 ma be moiinted pivotally Fig. 1 isa vertical sebtionl' h wing o e eminthecasing 18, to permit themtobe adjusted bodimentoffour invention mounted on the to various angl s Itis'clear'that with'this front wall eta furnace, fihe sectio'nfbeing en agement -u1 y*}meyfb 'tiimed so as. to t'al'renfthrough the center foif t-h'ej burne land eausethfailfi? Whirlineithei. direction? By p b ne m t e or' hsi kee W i 1. 'h fi i i l fl y il u ti nswlj pea-i,regenerates vFig.2 isa'section on; thelii e- :1 Anew-annals]? member with ani riner dia 2st h lsai il. h t fiq 11 is taehed t the asing s theses-n xt to the wall; I member serves as assure-er for tlis'e insiefidrre id 's were gef h h igif lifassistance' to the brick mason in E iS aper p i ei' bf as -Aid vale; lay n -In h irf 'i jf ur b n'fi an 3i'1a section on Ztlie "sin .Fig. 4 is a 'side' elevation off Fig. 6 is aside elevation of'th spreading An annular" l nes (Fig. 1), is mounted device. v I i in the 'sp acef bet'yvecii 'th'e pipe 14 and the The -embodiment,' .of an inv entioni illus liduvers 16' toffoi' 'a: piOtec'tion'lfor the outer trated in the drawings comprises a vertical casing plate against'theradi'ant heat of the furnace walllO provided with a, circular furnace. This plate 33 i s'gpri bl p f opening 11 having'a flaring portion lzon the rated as shown to prevent cracking. I furnace side. A. horizontal pipeis ount As itis highly desirahle'to produce a unied concentric with the opening] 1,,' and is 'for1n distribution of the fuel around the adapted to discharge into the furnace a stream interior of pipe 14, we 'pi efer'to arrange an of pulverized fuel and primary air. enlarged} portion such as" the substantially The additional or secondary'air required circular chamber or receiving head 35 at the for combustion is supplied through thean; outer end of the pipe, and deliver the fuel nular space between the pipe 14; andthe. wall strehm thereto through'ataiigential inletpipe of opening 11-; In order' to ensure au niform conduitigfi, which inlay have a standard distribution of this airue provide a series pipe flange'BS for convenience in connectin g of guide vanes' .or;louvers 1Q, whichare'pref tofthe supply pipe. In this way, a rapidly erably arranged to form approximately a ,cylrotati'ng'inalss 'of air and pulverized fuel is inderco-axial with the pipe 14 and somewhat set up; in the chamber '35, and the mixture greater in diameterthan opening 151. Bythis the centralpi. l 'withoutsegconstruction, the vanes are .so mountedin rereg'ation. 'iThe chamber 3' I provides imperlation to the furnace ,wall 10. "ia t theynrc 'foi at'e connectionsbetween the inlet'36 and protected to? a large extent from the radiant the central pipel, so thatthe entire stream heat of the furnacegby the intervening reof fuel and primary air passes longitudinally fractories. -The pipc-l prei'erablyezitends through the pipe :as a mass whirling about beyond the inner. ends of theevanes. into the the axis thereof. opening 11, whereby the flame is. spaced tor v 'e have discovered that by placing a series a substantial distance f1'on1 the vanes and of guide vanes/l0 in proper positions around they willremain at a comparatively low temthe. exit passage of the chamber 35, an imperature even though there may he very lit.- provcment in operation is obtained. As tle secondary air flowing through the burner. shown clearly in. Fig. 3, these vanes are As shown clearly in Fig. 2. these vanes 16 are preferably inclined "to the radii extending placed in an approximately tangential posithereto, and are spaced u'niforml y around i the fuel supply pipe.

the burner axis. This construction aids in bringing about a more uniform distribution of fuel around the interior of pipe 14. Moreover we have found that the vanes reduce the pressure drop through the burner, thus permitting the fan which supplies the primary air to operate with less power consumption.

For convenience in manufacture and adjustment, the passages for fuel and primary air are constructed of several parts, as shown particularly'in Fig. 1. An annular member 45 is bolted to the casing 18, and the receiving head '35 is attached to this member by suitable fastening means, such as cap screws 46. It is to be noted that these cap screws do not pass through both of the connected parts, but are merely screwed into the receiving head 35. Each cap screw has a washer 48 beneath its head, and this washer overlaps the member 45, and is clamped thereagainst by tightening the screw. This construction permits the receiving head and inlet pipe 36 to be revolved about the axis of the burner to the most convenient angle for connection with It will be apparent that this adjustment is in no way affected by the spacing between adjacent screws 46. As shown, the receiving head-may be made symmetrical about the line 3-3, so that it may be reversed if desired to cause the fuel to revolve in the opposite direction. A closing plate 50 is mounted on the outer side of the receiving head. Each vane 40 is provided with an ear 52, and this ear is spot welded to the interior of pipe 14. This pipe is held in place in the member 45 by a set screw 54, and this construction permits the pipe to be rotated about its axis to vary the relation of the vanes 40 to the fuel inlet pipe 36.

In order to throw outward the fuel stream issuing from the nozzle 14 and increase the turbulent effect, we provide adjacent the end of the nozzle an improved fuel spreading de vice 56. This spreader comprises a large number of substantially radial vanes 57, each arranged at an angle to the general direction of the stream flow so as to whirl the primary air and fuel. We have found it advisable in a majority of instances to provide for opposite rotation of the fuel and secondary air, as this tends to increase the mixing effect and the turbulence. However, these directions of rotation may be made the same if desired by reversing the louvers 16. The spreader 56 may be conveniently constructed of a single circular piece of sheet metal, cut radially at a number of equally spaced points. the resulting vanes being suitably twisted to an acute angle with the plane of the sheet and shaped generally like the blades of one form of an air propelling fan, as illustrated. This construction provides a number of spaced thin vanes, presenting long edges extending substantially the full width of the fuel stream,

so that the fuel is caused to flow from the entire extent of said long edges in the form of thin sheets which are directed outwardly and distributed into the secondary air. A further advantage results from the use of our improved spreader in that the coarser particles of fuel are thrown by centrifugal force to the outside of the issuing fuel stream, where they are brought quickly into intimate contact-with the secondary air and are exposed to heat reflected from the adjacent refractories. This is very important, for obviously the coarse particles require a longer time for complete combustion, and in order to obtain a short flame it is essential that they start to burn immediately on leaving the nozzle.

The spreader 56 is shown attached by a. nut 58 to the inner end of a small pipe or tube 60 arranged concentric with the pipe 14. This pipe 60 is slidably mounted in a boss 62 on the plate 50, a screw 64 being used to hold it in any desired position. By this construction the spreader 56' may be adjusted along the axis of the burner as desired, thus varying the angle of flare of the-plane and controlling the position of the flame in relation to the furnace wall 10. At no position of-adjustment does the spreader seriously obstruct the flow of primary air and pulverized fuel.

The pipe 60 has a straight and unobstructed passage therethrough and it may be provided with a cap 65 on its outer end, held in place by a screw 66. This cap may have a small opening 68 therein for use as a peep hole, through which a clear view may be obtained of the flame interior. By removing cap 65, an oil burner or other suitable device may be inserted through the pipe 60 to initially light the issuing fuel stream. An inspection door 70 (Fig. 3) may be provided in the casing 18 to permit observation of the flame, or to ignite the oil burner which may be inserted through pipe 60.

The operation of our invention will now be apparent from the above disclosure. Pulverized fuel is delivered to the inlet pipe 36 on a current of primary air. This fuel may come directly from a suitable pulverizer of the unit type, or it may come from a storage bin. The fuel because of its tangential entry, whirls rapidly in the chamber 35, about the axis of the burner, and is uniformly distributed around the circumference of the nozzle pipe 14. This even distribution is aided by the series of guide vanes 40. The issuing fuel stream is given an outward whirling motion by the vanes 57 on the fuel spreader 56. Secondary air is delivered from a suitable fan to the chamber formed by casing 18, the pressure therein being controlled by dampers 20. This secondary air passes inward between the louvers 16, and is thereby evenly distributed, and given a rapid rotary motion. The secondary air contacts with the 'fuelinside the flaring opening 12, and the refractory surfaces of this opening reflect heat from the furnace directly on the fuel stream. A very high degree of turbulence is obtained, and the result-is rapid combustion and a flame only a few feet in length. When starting up with a cold furnace, suitable combustible materials, such as oil contained in a hand torch, maybe inserted through pipe to.bring, about ignition. By loosening screw 64, the pipe 60 and spreader 56- may be longitudinally adjusted to position the flame as desired. i

Having .thus described our invention, what we claim as new and desire to secure by Letters Patent, is:

1. Aburner for pulverized fuel comprising a central pipe having an enlarged portion substantially circular in. shape adjacent to its intake end, said enlarged portion beprovided with a tangential inlet for pulverized fuel and primary air, deflecting vanesarranged around; the interior ofsaid pipe in the path-offuel passing out of the enlarged portion, each vane being inclined withrespe'ct to ajradius extending; thereto, and means for @introducing secondary air uniformly around the discharge end ofthe P -H 1 v P 2. A burner for pulverized, fuel comprisin a central pipe having at its intake end a su stantially circular enlarged I portion, means for introducing fuel'and primary air tangentiallyinto said enlarged portion, defleeting vanes arranged around the interior of said pipe in the path'of the; fuel, each vanebeing inclined with respect to a radius extending thereto, and means for intrcduc ing secondary air around the discharge;end of the pipe. I v

. 3. A burner for pulverized fuel comprising a straight central imperforate burner pipe having an open discharge end, aninlet conduit for a stream of pulverized fuel and primary air arranged tangentially to said burner pipe and communicating therewith by imperforate connections so asto cause the entire stream of fuel and air to pass longitudinally through the burner pipe as a mass whirling about the axis of the pipe, and air admission means including an arrangement of louvres surrounding the central pipe for introducing secondary air uniformly around the burner pipe adjacent to its discharge end and into the whirling stream of fuel in the combustion zone beyond the burner pipe.

4:. Aburner for pulverized fuel comprising a straight central imperforate burner pipe having an open discharge end, an inlet conduit for a stream of pulverized fuel and primaryair arranged tangentially to said burner pipe and communicating therewith by imperforate connections so as to cause the entire stream of fuel and air to pass longitudinally through the burner pipe as a mass whirling about the axis of the pipe, said imperforate connections being shaped to provide a substantially circular'chamber larger in diameter than the central pipe and coaxial therewith, and air admission means including an arrangement of louvres surrounding the central pipe for introducing secondary air uniformly around the burner pipes adjacent to its discharge end and into the whirling stream of fuel in the combination zone beyond the burner pipe. r

5. A burner for pulverized fuel comprising a central pipe arranged to deliver directly into a furnace a stream of pulverizedfuel carried by a current of air, means for introducing. all of the secondary air into the furnace uniformly around the discharge end of the pipe, and a spreading device mounted axially of the pipe and at the discharge end thereofwhich hasa number of spaced thin vanes, each vane ext-ending outwardly and being. fixed at an angle to the general direction ofrthe stream flow, and the vanes presenting long edges extending substantially the full width of the fuel stream so that the fuel is" causedto fiow from theentire extent of said long edges and is thrown outwardly therefrom and distributed into the secondary air. 6. A burner for pulverized fuel comprising a central pipe arranged to deliver directly into a furnace ,a stream of pulverized fuel carried by a current of air, means for introducing all of the secondary air into the furthe pipe, a spreading device mounted axially of the-pipe and at'the discharge end thereof which has a number of spaced thin vanes, each vane extending outwardly andbeing fixed at an angle to the general direction of the stream flow, the vanes presenting long edges extending substantially the' full width of the fuel stream so that the fuel is caused to flow from the entire extent of said long edges and is thrown outwardly therefrom and distributed into the secondary air, and means to distribute the fuel substantially uniformly about the axis of the central pipe and cause it to be whirling when it strikes the deflecting vanes, thereby insuring proper distribution of the fuel into the secondary air.

7 A burner for pulverized fuel comprising a central pipe arranged to deliver directly into a furnace a stream of pulverized fuel carried by a current of air, means for introducing secondary air into the furnace uniformly around the discharge end of the pipe, a spreading device mounted axially of the pipe and at the discharge end thereof which has a number of deflecting vanes, each vane extending outwardly and at an angle to the general direction of the stream flow to throw the fuel outwardly into the surrounding secondary air, and an inlet conduit for puland) verized fuel and air arranged tangentially to said central pipe and communicating therewith by imperforate connections so as to cause the entire stream of fuel and air to pass longitudinally through the central pipe as a mass whirling about the axis of the pipe, said imperforate connection being shaped to provide a substantially circular chamber larger in diameter than the central pipe and coaxial therewith.

8. A burner for pulverized fuel comprising a pipe arranged to deliver into a furnace a stream of pulverized fuel carried by a current of air, a spreading device mounted axially of the pipe and adjacent to the dischar e end thereof which has a number of de ecting vanes, each vane extending substantially radially and at an angle to the general direction of the stream flow so as to throw the pulverized fuel outwardly, means for adjusting the spreading device along the axis of the pipe from a position within the pipe to a position beyond the end thereof, and means for introducing secondary air uniformly around the discharge end of the pipe and into the deflected fuel stream.

9. A burner for pulverized fuel comprising a pipe arranged to deliver into a furnace a stream of pulverized fuel carried by a current of air, a tube smaller in diameter than the pipe and mounted within the pipe and coaxial therewith, a spreading device mounted on the tube adjacent to the discharge end of the pipe, said spreading device having a number of deflecting vanes and each vane extending substantially radially and at an angle to the general direction of the stream flow so as to throw the pulverized fuel outwardly, and means for introducing secondary air uniformly around the discharge end of the pipe and into the deflected fuel stream, said tube having a straight and unobstructed passage therethrough to permit igniting material to be introduced to the whirling fuel stream and a view to be obtained of the flame interior.

Signed at Worcester, Mass, this 18th day of January, 1927.

OLLISON CRAIG. L. V. ANDREWS.

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