US2371191A - Stoker - Google Patents

Description

March 13, 1945` R. A. SHERMAN STOKER Filed Feb. 1o. 1941 3 Sheets-Shea?, 1

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.ATTORNEYS March. 13, 1945.

R. A. SHERMAN s'roKER Filed Feb. 10, 1941 3 Sheets-Sheet 2 {f8-' of?) 7| "f 72 66 I' 77 "www -70 mVENroR. Ralph A. Sherman.

, BY i/w, ,LM

` ATTORNE YS.

March 13, 1945. R, A. SHERMAN STOKER Filed Feb. 1o, i941 3 sheets-sheet s Y* wVAM//, Il: E l A, 7 M9 u 4` s l l5... 7 5 n x Y v www INVENToR Ralph A. Sherman ,M7 ATIQRNEYS.

Patented Mar.` 13, 1.945

STATE PAT-ENT? oFFlce 'Ralph A. Sherman, Columbus, Ohio,A assigner to Battelle 'Memorial Institute; Columbus, Ohio, la

lcorporation of Ohio npelieationrebruary 1o, 191211, .seniamo'. 378,298 l "t claims; (01. 11e-45) My invention :relates :tc 1.a Stoker.;` It relates, more .'speciflca'1ly, to a combustion apparatus or .Stoker which is adapted to feed solid fuel to 1a furnace, .obtain efficient Y.cornbustiun `.of vthe fuel,

fand remove-*the ashes,1 withoutV the `disadvantages `of flthe. stakers Lnow .commonly in use. l `Stokers now"'inuse=comrnonly1a't the present -timeare all ofonesirriilar design. In these prior art sto-kers, the 'fuel "isied upwardly :through a retort :on thewinside' of which near .the Vtop iis .placed va irow or rows -el? :tuyres through which lair. lis 'supplied vfor the ibur-ning :of .the fuel. .All .bitumincuscoals rcoke to fawgre'ater or lesser lex- -tent in the .retort and l-many coke iso strongly that 4the .coke .isfslo'w :burning and may .ultimatelyli .the flrebcx Many ef the bituminous vcoals of 'highest grade fand :highest heating value fare un suited `to fsuch :stokers because of fthe coke which is `formed therefrom during combustion `in #such fstokers. Furthermore, because such stokers .the `xccrxibustibn occurs l1in' a narrow l"annularrlng, between the rcer-itral-cclreformation and an outer vent agglomeration .p Anothero-bjectof .my invention is Ato provide Aa. `Stoker which `is of sucha nature that the fuel bed is .maintained ,in such uniform condition `at all. times that ieicient 'combustion with a mini- -mumqcfexcess airisobtained. a

1;.- Tou'accomplish the .objectsyof my invention, .I provide a `Stoker ,fwhereinfthe ,total air required Afor combustion is divided intotwoparts. At v,theI

Aoi theg-air :necessary `for their combustion being kring of ashiwhere 'thefuel ycannot radiateto the heating surfaces -ef the boiler or 'fu-mace, exrcessi'velyhigh temperatures result which fuse the ash into a clinker that cannot 'be removed auto.

ma'tically.. fSuch stekels, therefore, 'require fre-'- quentmanualfattention; .Another dimculty with prior art fdesigns .ofstokersre'sults fremlthe heavy smoke which lis producedqwhen the stcker is stopped.v This is `caused by the coal lbelow fthe surface `:of 'the vhetfuelbedcontinuing to give -off volatile ligases', for 'burning of which -no air is availablethroug'h thestuyres.

` 'importa'nticibiect of "my invention iis to vprowide 'a1 Stoker. that `will ioperalte effectively -with a 4wide warietyfof coals, including :the ystrongly .-eolcfing-coals. A l 1 `Another object of my invention is toprcvide fa "stokerfwhich :is f of fsuch a nature fas .tc distribute #the combustion rover a'wde areawhere 'lheat'fcan radiate to lowfte'mperature surfaces `so as to fmaintalnsuchfazlow temperature Tin the ffuel bed `that the 'formation fof *clinker' isi prevented and automatic 'removal-Of the 'ash fis made possible. A-iurther robiect oi fmy invention `is to provide a Stoker wherein the supply of air forcombustion `is soldistributed 'that high `A`velocities lare .avoided and fthe fcarry-everb iii-y ash is prevented; l

.` vstilllanotherobject 'of lmy invention '-is 1to1protrcduced in such :a away xthat-,fair i'will 'be available for "the l combustion auf volatile matter even :after supplied through the grate. The uniformityeof the pieces of coke and of the .fuel :bed :assures complete combustion with :aminimum of excess air. t

tion consists Aof a vertical, cylindrical :fuel cham- .bento the bottomof `whichieoalis supplied by a .suitablegmeans such as .a screw ccnveyen from a -hopperfor fbin. [The coallifted 'in this cylindrical chamber by means of :a .centrally located screw, the core o-r supporting 1shaft of Awhich is hollow :and .through which lair .is .passed from .a plenum chamber, located below, to ports or -tuyres `at Vthe :periphery of` a :head which .is :disposed f on the upper end ofthe :liftingfscrew and rotates therewith. Allhis .head .is `spaced rabove the upper edgeviof the cylindrical fuel chamber. The ima-lis y.of-the fuel chamber vare hollow and lcommunicate with` the same lplenum .chamber asl the -central screwso 'thatair wllbesupplied to ports -or tuyres fat Athe top yof theduel chamber, The coal ,will pass upwardly and 4.outwardly through la :ring orifice,` .formed between the .upper `edge of the fuel chamber-:and `.the zhead, .between two streamsPofiair issuing from 'the ports `or `tuyres formed in the headand lthe'wall 'of the fuelzchamber. rI'he lair :supplied :at these 'two points is limited to that required .to bur-n fthe =volatile gases vzand thus asupply :the Iheat required `for cokng. While itiscolri-ng, the .coal is ina plastic condiftioniand, :by thero'tation of the head,A is `brclren up `into :small pieces that .are Vmoved outwardly .onto ;a xgrate'iwhich surrounds Ithe fuel chamber.

. :Combustion :of athe small "pieces Aof `coke is completediontheLoutersgrate-by air'that may be supplied-by either forced forinatural draft. Because theburning is .spread :over fa large area, provided i In its preferred eform, thesto-ker of this finveny important; features of my invention, is always above the fuel bed. The ports formed therein are, therefore, never restricted by particles of coal or coke and, consequently, a considerable flow of air can occur through natural draft even when the fan on the stoker is not operating. In automatically controlled stokers, this is enough I which is keyed on a horizontally disposed drive shaft I5. The pinions I4 and I5 and the shaft I6 are disposed in a chamber I'I formed at the bottom of the retort member I. The shaft I 6 is rotatably mounted in bearings formed in the wall of this chamber. The shaft IS extends through an opening in the wall of this chamber and is driven in a manner to be described laters-,The lower end of the main portion of the screw, lIIl'is provided with a bearing portion I8 which lits within a bearing I 9 formed on the lower end of the inner shell 3 of lthe retort I.

These portions I8 and I9 cooperate to close the lower end of the annular combustion chambery formed within retort I and tuyre ring to burn most of the volatile matter that continuesto be released from the coal just belowthe coke layer for some minutes after the stoker is stopped by the room thermostat control- In operation of my stoker, torch-like flames produced by air for combustion issuing from these ports into the streams of rich gas can be seen after the stoker is stopped. Because the air is distributed over a wide area and enters the furnace at all points at relatively low velocity, and because the ash is continuously shaken from the coke through the grate, with my stoker the fly ash is materially reducedl from that obtained with stokers of conventional design. i

vThe preferred embodiment of my inventlonis illustrated in the accompanying drawings wherein similar characters of reference designate corresponding parts and wherein:

Figure 1 is a vertical sectional View taken substantially along line I-I of Figure 4 through a stoker constructed according to my invention.

Figure 2 is a side elevation, partly broken away, of the stoker illustrated in Figure 1.

Figure 3 is,a perspective view, partly broken away, of my stoker.

Figure 4 is a horizontal sectional view taken substantially along line 4-4 of Figure 1.

With reference to the drawings,`I have illustrated the vpreferred form of my stoker as comprising 4a vcylindrical vertically disposed. retort memberl. This retort member I rests on a bottom plate 2 which is suitably secured thereto. The retort member I has an integral inner shell 3 disposed within the upper end thereof to form a 'vertically disposed annular air circulating space 4. The retort member I is capped by a tuyre ring 5 which has a substantially cylindrical outer shell 6 that interlocks with the outer wall of retort I and an outwardly flared inner wall 'I which rests on and interlocks with the upper edge of the inner shell 3 of the retort. Thus, the ring 5 is provided with an annular space 8 which is a continuation of the space 4. The walls 6 and 1 of the ring 5 are integrally. joined at their upper edges. Adjacent the upper edge of the outer wall 6 a plurality of tuyres or ports 9 and formed a circumferentially spaced intervals.

Disposed centrally within the retort I is a vertical coal lifting screw I0. This screw I0 includes a central shaft or support having iiights of helical form and fits within the inner shell 3. The shaft part of the screw III is of hollow construction forming an air passageway II. On its lower end `this screw I0 has a driving extension I2 which is rotatably mounted in a bearing carried at the center of a support I3. The lower end of this extension has a bevel pinion I4 keyed thereon. This pinion I 4 meshes with a similar bevel pinion 5. Air is supplied to the lower chamber Il through a large inlet 2| formed in the wall thereof. This inlet is connected to a tube 22 (Figure 4) which has its outer end connected, as at 23, to the outlet tubeIof a blower 24. As illustrated best in Figure l, the air will enter the chamber I'I and will pass upwardly` through openings 25 of support I3, into the annular chambers 4,l and 8 and will leave the chamber 8 through the tuyres 9. Some of the air will also pass upwardly through bearing member I8 of the lifting screw I0 through ports 26 into the interior of the screw. Preferably,

though not necessarily, the screw flights terminate at the lower edge of the tuyre ring 5. However, atuyre head 21 is mounted on the upper end of the hollow shaft of the screw. This head 21 is'of hollow construction and its lower edge interts with the upper edge of the screw I0, as indicated at 28, so that it will rotate therewith. The head 2'I has an outwardly flared lower` portion 29 and a cylindrical-enlarged upper portion 3U. It is provided with a removable cap 3|. At the bottom of the portion 30, an integral annular projecting shoulder 32 is formed. The Wall of the head at this shoulder 32 has a plurality of circumferentially spaced tuyres or ports 33 formed therein. These ports are downwardly directed, as indicated best in Figure 1. Thus, air will pass .rotate with the screw I0.

For feeding coal into the base of the combus tion chamber 20, a tangentially disposed coal inlet port 34 is provided in the wall of theretort at a. point spaced aboveair inlet 2|.- This inlet 34 is connected, as indicated in Figure 4, to a coal feed tube 35. This coal feed tube 35 has a coalfeeding screw 36 rotatably mounted therein. The tube 35 is located at the same side of the retort as the air tube 22 butextends'in an opposite direction and at a higher level. It may extend to a suitable bin or hopper. The tube 35 has its inner end extending beyond the inlet 34 to form a small cylindrical chamber 31. The end of the screwis rotatably mounted in the end wall of this chamber, asat 38, and extends through this wall. Dust will tend to collect in theA chamber 3Iand, therefore, in this chamber the Ascrew is provided with a reversely threaded portion 39, to force the dust rearwardly` back into the opening 34. The screw 3S is driven infa manner to be explained later. vv Surrounding the tuyre ring 5 is a, grate 40 which is made up of a plurality of segmental sections that interlock with each other, as indicated vatlll in Figure 3. These grate sections are horizontally disposed and each is provided at its innerend with a depending leg 42 whichfits into a socket 43 formed on a' grate-'supporting ring 44. I'he ring 44 surrounds theretort'jland'is otally connected, asat 11.

shaft l5. as at 18.

supported by means ofball bearings 45. (Figures l. and') on an annular flange 4S formed on the riphery and on its lower surface, the ring 44 has ratchet ,teeth 49 formed thereon jbymeans of which it may be rotated. v

. The ashes which .fall through the grate 40 will fall onto an .ash plate 50 whichis horizontally supported by the ring 44 for rotation therewith.

An ash trough of annular form is supported at the periphery of `the plate 5l) by means ,of radially extending arms 52 which have `their inner vends secured, as at 53, to the stationary flange `46. This ash trough 5| has an inner wall 54 which terminates just below the plate .5and

`an outer wa1l55 which terminates at the level of the` grate.. The plate 5u has a plurality of plow membersSG which extend down into thetrough 5l. These plow members 56 'serve to move the ashthrough the trough, upon rotation of `ring 44.,

until they drop .through an ash outlet 51. For causing the ash to pass from v the plate 50 into the .trough 5I, I provide plows `58 which are dis.- posed directly abovev plate 5D 'but which` are .se-7 cured to the outer wall 55,0f the trough, as vat 59, These plows 53 will serve to sweep the ash olf plate 50 into the trough llpon rotation of the ring 44 and the plate 50 relative .to the trough 5l and members 5.8.

The ash passes .downwardly through the outlet 5l into an ash removal tube 60. This tube 60 has an ash removal screw 6I disposed for rotation therewithin. vThissorew 6| will feed the ash through an outlet 62 into asuitable container for receiving it. l

Power to drive all parts of the stoker is transmitted from a motor 63. Blower 24 may be driven from motor 63 in any suitable manner. Motor 63 is connected to the outer end ofthe ash removal screw Bl through the medium of speedreducing gear unit 64. `The inner end of the screw 6l is rotatably carried ina bearing housing 65 which is bolted, as at 6,6, to the outer Wall ofthe retort member l. As shown best in Figures 2 and 4, the inner end of screw 6I has a` sprocket 61 keyed thereon. :This sprocket drives a sprocket chain. This chain tpassves around a sprocket wheel B9 keyed on the outer portion of shaft I6 which drives the coal-lifting screw IIJ. The chain 6B also passes around a sprocket wheel 16 which iskeyed on the end of the coal-feeding screw `36. Also on the end of the coal-feeding screw 36 is keyed a diskll. This disk 1| is provided with a plurality of openings 12 any of which may receive a pin 13. The

pin 13 will extend into a slot 14, formed vin the' outer end of a link.15. The opposite end of thisv link 15 is bifurcated and straddles the. upper end of the grate moving arm 16 to which it is piv' The arrn 16 has its lower end pivotedon the extreme outer end of It will be apparent that rotation of the disk 1|: willv swing the arm 116. lThe extent of this swing ing `movement may be changed `bychanging the pin Iffrom 'one opening 12 'to another. The armhas a'ratchet member 19 pvoted to the upper endthereof and which is normally in en, sagement with. the ratchet teeth 49 of grate sup; porting ring 44.y It will be apparent from lligurc'e 2, that when the arm 16 is swung to the right, the ring 44 will not be rotated. However, when `the arm 16 is swung to the left, the ring 44 will be rotated'tofa `predetermined extent. Rotation of disk 1I will oscillate' the arm 16. To preventstripping `of the teeth 49,` in oase the ring 44 fails to move, the pivot'l is of special construction. A block 8| isvsupported for sliding movementin a guide member `82. A spring 84 surrounds a pin .83 `and normally forces the block 8l 'to the right handend of member 82, as shown in Figure 2. When the link 15 pushes on arm 16 and itxfailslto moveto the left, the block 8l will be moved to the left in memberl 82 against the force of-spring 84. Thus, stripping of the teeth 49 iS, prevented.

In the operationof my apparatus, coal from a bin `or hopper is moved through the coal feed tube 35 ntothe' bottom of the chamber 20. It

islifted upwardly through this chamber by means of the rotating screw ID. The coal is fed up.- wardly through the tuyre ring 5 and outwardly over the upper edge of this ring between such edge and the 'rotating head 21. The airsupplied by blower 24 will issue 4through the tuyre ports 9 in ring 5v and tuyre ports 33V in head 21. This willburn the volatile matter of the coal thus supplying heat for the coking 'of the coal.` 'In this .manner a fuel plasticizing temperature zone is maintained within 'and immediately above the tuyre ring 5 of the retort causing the fuel par ticles to coalesce or agglomerato. Thus the up' yper end of the fuel column emerging from the ring 5 will be more or less self-sustaining so that r-4l) radial pressure internally exerted thereon by the outwardly flaring'wall 29 of the. head 21 will break up such agglomerations into particles of smaller size to be distributed outwardly over the fuel bed in the intermittent rotation of the grate-4D. y

, It will be noted that the upper end of the ring or. egresssection 5 of the retort and the upper Lend ofthe head wall 29 are of such relative diam eters ythat `the large pieces of plasticized fuel forced outwardly therebetween will be subjected to a severe crushing force which very effectively breaks down the plasticized fuel mass into comparatively small coke pieces of substantially uni form size. l

By terminatingthe feed screw nights at the upper end of the body section of the retort the fuel is not agitated within the top section 5 so that the individual fuel particles will readily plasticize or agglomerato therein, while possible cokingof the fuel on the screw flights is avoided. The small piecesfof coke form a thin fuel bed of substantially uniform thickness which is burned with a minimum. excess of air which may be supplied either by forced or natural draft beneath the grate .40. A draft chamber (not shown) will Vbe provided with a` casing enclosing the lower part of the Stoker. Draft from this chamber will` reach the grate 40 through the space vbetween plate 50 and the upper edge of the inner wall 54 of trough 5 I. i l The large area of the fuel bed on the grate, radiating tolow-temperature heat-receiving surfaces,.insures that excessive temperatures are not attained 'in the fuel bed'. The ash is not fused together'into .clinker' and removal through the perforated grate into a receiver below and then by automaticv means outside the'fu'rnacais made possible. During operating periods of the stoker the emission of high pressure air from the tuyres 33 produces a circularly moving flame sheet directed downwardly from the rotating head 21, which constantly drives olf the products of combustion emanating from thel fuel bed and directs the same outwardly and upwardly into vcontact with the walls or other heat transfer surfaces of the furnace. Thus the development of high ash fusing temperatures in the thin fuel bed is obviated while a substantially uniformly incandescent condition thereof is quickly established and maintained. During off periods of the stoker this flame sheet is subdued, thesupply of air to the tuyres 33 by natural draft being only suflicient to ignite the volatiles rising from the fuel chamber of the retort.

The features described make possible the use of a wide variety of coals including heavily coking coals without difliculty. Thin, uniform fuel beds are formed on the grate and clinker formation is`prevented. Air is supplied by natural draft at the point needed to reduce or eliminate smoke from the volatile gases released during the "off periods of intermittently operated stokers. The division of the air supply into two parts insures low velocities and elimination of diculties from fly ash. Other advantages in economy, flexibility, and convenience of operation and maintenance may be secured bymeans of this invention.

Various other advantages will be apparent from the preceding description, the drawings and the following claims.

Having thus described my. invention, what I claim is:

, 1. A coal-feeding and combustion device comprising a combustion chamber, a vertically disposed retort associated therewith, a grate surrounding said retort, said retort having a series of outwardly discharging air supply tuyres around the upper periphery thereof, coal feeding means in the retort including a centrally disposed vertical support spaced from the retort wall to form therewith a vertical fuel passageway, a tuyre head carried by the upper end of said support, said head being flared upwardly and outwardly to form an exit passageway above the retort having an axis substantially at right angles to the axis of the vertical passageway, said head also having a series of outwardlyand down` wardly discharging air supply tuyres for cooperation with the air supply tuyres of the retort to supply a portion of the air required for the combustion of the fuel, and means for supplying air to the tuyres in said retort and said head.

2. A coal feeding and combustion device comprising a combustion chamber, a retort associated therewith, a grate surrounding said retort, coal feeding means including a support disposed in the retort cooperating with the retort wall to form a vertical passageway, said retort having a series of outwardly discharging air supply tuyres around the upper periphery thereof, a tu- .yre head carried by the upper end of vsaid support, said head being flared upwardly and outwardly in such a manner that said head extends outwardly at least substantially vertically above the upper edge of said retort, the vertical clearance between said head and the upper edge of said retort being substantially assmallas the horizontal dimension of said passageway at the upper edge of said retort, saidhead also having a series of outwardly and downwardly discharging air supply tuyres for cooperation with the air supply tuyres of the retort to supply a portion of the air required for the combustion of the fuel, and means for supplying air to the tuyres in said retort and said head.

3. Ar coal feeding and combustion device comprising in combination a combustion chamber, a vertically disposed retort associated therewith having a series of outwardly discharging air supply tuyres around the upper periphery thereof, a horizontal grate surrounding said retort adjacent to said'air supply tuyres, means for feeding coal upwardly through said retort including a rotatable part, a tuyre head supported by said part and spaced a short distance above the upper edge of said retort and being flared upwardly and outwardly to deflect the coal outwardly over the upper edge of said retort at substantially right angles to the axis of the retort, said head also having a series of outwardly and downwardly discharging air supply tuyres for cooperation with the air supply tuyres of the retort, and means for supplying air to the tuyres in said 4retort and said head.

head on its upper end which is flared upwardly Y and outwardly in such a manner that said head extends outwardly at least substantially vertically above the upper edge of said retort, the vertical clearance between said head and the upper edge of said retort being substantially as small as the horizontal distance between the upper edge of said retort and said head, said head having downwardly and outwardly directed air -supply tuyre openings formed in the periphery thereof, said retort having outwardly directed vair supply tuyre openings formed in the periphery thereof adjacent to the upper edge for cooperation with the air supply tuyre openings of the head, means for supplying air to said tuyre openings, means for rotating said screw and head, and a grate provided around the retort adjacent to the air supply tuyre openings therein.

5. An under-feeding furnace stoker, comprising, in combination with the furnace grate, a vertical retort having an upper end section extending above the furnace grate and forming a fuel plasticizing chamber, means for feeding fuel into the lower end of the retort, a vertical feed screw rotatably mounted in the retort and having flights terminating at the lower end of said upper section thereof to feed the fuel upwardly into said plasticizing chamber, said feed screw including a hollow central shaft, and a rotating head on the upper end of said shaft having a part spaced above the retort and provided with a series of outwardly and downwardly discharging air supply tuyres communicating with said hollow shaft, said head, between said tuyres and the screw shaft, having an arcuately curved wall cooperating with the upper end of the retort wall to resist the passage of the plasticizedvfuel therebetween under feeding pressure and subject the same to crushing forces dividing said plasticized fuel Vinto particles of substantially uniform size.

6. The combination dened in claim 5, in which said upper end section of the retort is provided perature adjacent to the retort and above the grate, and means'is provided for directing air to the retort tuyres.

f 7. The combination defined in claim 5 in which means is provided to detachably interlock said rotating head with the upper end of the screw shaft.

RALPH A. SHERMAN.

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