US1522917A - Underfeed stoker - Google Patents

Description

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.1. s. SKELLY UNDERFEED S TOKER 'Filed July 26, 1920 rama-.a aan. is, teas.

JOHN S. SKELLY, OF-M:ONIONGrAl-IEIM, PENNSYLVANIA, ASSIGNOR T0 INTER- NATIONAL COMBUSTION ENGINEERING CORPORATION, A CORPORATION OF "DELAWARE Application ale'd July 2e,

To ZZ ywhom it may concern.'4

Be it known that I, JOH S. SKELLY, a citizen of the United States, and a resident of Monongahela, in the county of Washington and State of Pennsylvania, have made a new and useful Invention in Underfeed Stokers, of which the following is a specification.

This invention relates to furnaces and l0 particularly to furnaces in which automatic means are employed for delivering the fuel to the furnace and for propelling it across the fuel supporting elements of the furnace. An object of the invention is to produce a furnace of the type specified in which improved means are employedfor.effectively propelling the fuel rearwardly through the furnace and for effectively controlling combustion throughout different portions of the fuel bed.

A further object is to produce a furnace of the type specified, vwhich is provided with a transversely extendingretort at the front of the `furnace and in which new and improved means are employed for breaking up or agitating the fuel contained within the retort, for. propelling the fuel rearwardly' from the retort to the ash receiving or discharging mechanism, and for controllingcombustion throughout the fuel bed.

A further object is to produce an under feed stoker of improved construction in which a new and improved arrangement of fuel supporting and fuel propelling elements are employed, whereby a better distribution of fuel through the fuel bed is obtained and a better operation of the furnace is insured under widely varying operating conditions.

A .further object is to produce an under feed sto'ker employing improved vdetails of construction so combined and associated as lo produce a stoker having a wide range of, fuel burning capacity and one which is efficient and effective while operating under widely varying operating conditions.

These and other objects, which will be Y made more apparent throughout the further description, are attained by means of a Stoker embodying the features herein described and illustrated in the drawings accompanying and forming a part hereof.

In the drawings', 1Figure 1 is a diagrammatic, longitudinal, sectional View of a stoker embodying my invention.` Figures 2 UNDERFEED STOKER.

1920. serial No. 398,897.

and 3 are each fragmental sectionall views illustrating details of construction ernployed in connection vwith a 'Stoker such as is illustrated in Figure 1. Fig. 4c is a fragmental sectional view along the line 4 4 of Fig. 1. f

The stoker illustrated is provided with a` 'retort 5, which extends transverselyT *across the front of the furnace and is so arranged and constructed that the fuel delivered to it is retained therein a suflicient period to loccasion a partial distillation of the volatile material. It is also so arranged and c'onstructed that the incoming fuel enters the retort below .the-surface of the fuel contained therein and occasions abreaking up of the mass of fuel within the retort and an upward movement of the fuel as it moves transversely across the retort and is fed ontofuel supporting elements or grate bars forming -a part of the furnace structure. In the embodiment of the invention illustrated, the rear wall of the retort is, in effeet, made up of the forward ends of a series of grate bars which receive the fuel as it issues from the retort. The grate bars of this series are preferably alternate` moving and stationary bars, so constructed and located that the longitudinal movement of the `moving bars not only occasions a. breaking up of the fuel issuing from the retort, but also occasions a displacement of the fuel in such a way that combustion of the fuel leaving the'retort is facilitated. In addition. the mot-ion of the' grate bars occasionsor aids the propulsion of the fuel toward the rear of the furnace. The furnace also includes a second series of grate bars, which is preferably 'composed of alternately, ar-

lranged moving and stationary bars` located between the first series of bars and the ash or refuse receiving or discharging mechavnism. As shown, the rear ends of these bars are so located and arranged that they discharge the ash or refuse material Ainto an 1 open well or pit which may be provided with well known clinker grinder roll or rolls ora conveyor adapted to break up and discharge the refuse material delivered to the well.. 'I The movement of the movable bars of the 7 second series is preferably capable of adjustment, independently of the bars of the tirstseries. as shown in my application Se- -rial No. 330,953. tiled October 16, 1919, now PatentNo. 1,393,979, granted October 18,

" dependently controllable means 1921, and each series is associated with infor delivering air to the fuel bed.

i Referring more particularly to the drawings: Thestoker illustrated is provided with a' reciprocating plunger 6 which, operating l in conjunction with a hopper 7, 1s adapted to feed fuel from the hopper across a fiat horizontal Hoor or plate 8. This plate 8 extends through the front wall ofi the furnace and at its inner end forms the fioor of the retort 5. Any suitable means may be employed for reciprocating the plunger 6, and in the drawings I have'diagrammatially illustrated a mechanism 6 for accomplishing this. Thefuel fed across the "plate 8 by the plunger 6, traverses .a

' l by side and extend downwardly in parallel relation toward the rear of the Ifurnace. As shown, the forward end of each grate bar is supported on the rear edge of the plate 8, whereas, the rear end is supported on a bracket 12"", which forms a part of the frame work vof the Stoker' structure. As has been said, the forward -ends of the grate bars 11 and 12, in effect, form the rearwall of the retort 5. The bars are lso located and arranged that 'the fuel in leaving the retort must pass upwardly over the forward ends of the tbars as it moves ontov the fue'l supporting surfaces thereof. This rearward movement of the fuel is facilitated by a periodic longitudinal motion of the moving grate bars 11.

As shown, each of the moving grate bars is provided with a bearing surface 13 at its forward end and a corresponding bear ing surface 14 at its rear end. These surfaces are so located with relation to the major axis of'the bar that they are substantially,horizontal when thebar is mounted in place on the frame of the stoker structure; With this arrangement, the reciprocations of the bar are such that each point of the bar moves substantially horizontallyv. Consequently, the forward end of the bar is ushed substantially horizontally into'tie mass of4 fuel contained with-inthe retort during each forward reciprocationv and is then withdrawn horizontally away from and even out of the confines'. of the retort, as defined by the forward fa' es of the stationary bars. For the sake ol 'simplicity of manufacture and standardization of parts, the stationary `Leseaem' bars, are substantially similar tothe mov# ing bars, except that each stationary bar' is provided at itsforward end with downwardly projecting lugs 15, which-engage opposite sides of a transversely extending flange 16 ,formed on the rear edge of the plate'S.' (See Fig. 2.) As shown, the forward end of' each moving-and stationary grate bar is wedgedl shaped with the apex of the wedge located adjacent to the upper surface of the plateS. 'With this arrangement, a forward movement of the moving bars into the mass of rearwardly moving fuel withinrthe retort 5 breaks up the mass by causing portions thereof to .move upwardly across the inclined forward face of the bar and onto the bar. This motion ofl each bar also vadvances the position of the fuel bed proper-with relation to the forwardly moving grate bars and causes an agitation of the fuel bed, sincethe forward movement of the bar causes itsrearwardly inclined, fuel supporting surface to. in effect, move out from under Oneway from the fttlfsupportedf by it. vThis occasions Lsettling of the fuel bed to fill the space vacated by the forwardly moving bars, and as these bars move rearwardly, they positively displace theportion of the fuel bed supported by them, by carrying it toward the rear of the furnace and at the same time move it upwardly with relation to the 'portions of the fuel bed supported by the: stationary bars. As the forward ends of these moving bars move out of the mass f of partially coked fuel contained within the retort 5, they occasion a -settlementI ofthe mass of fuel and a consequent agitation and breaking up of the mass contained within the retort. It will, therefore, be apparent that the fuel contained within thel retort and the fuel located on thev grate bars is positively broken j up by the reciprocations of the moving bars, and at the-same time is positively propelled toward the rear of the furnace.

As shown in Figure 1l the moving bars are actuated by means of a rocker bar 17, which extends transversely of the grate liars 11 and 12 and is mounted in suitable bear- 1 ings supported by the supporting frame of thestoker and located substantially inidway between the ends of the bars l1 und "i12, As illustrated, the roclvr bar 1,7 is pro- Lvided with a longitudinall' extending rib *18, which projects upwardly and isadaptod to be engaged by lugs 19 fornied on the lower faces ofthe moving grate bars l1, l`herocker bar 17 is preferably oscillated by means of the actuating mechanism of the l plunger (5, as clearly illustrated in my patent, aforesaid.

@s shown, the bars 11 and 12 of the first series are adapted to feed fuel onto a second seriesof alternately arranged moving and maaar? stationary bars 2l'and 22. The bars 2l and 22 extend rearwardly of the furnace and are located side by side. The forward end of these bars preferably projects under the -rearwardly projecting ends of the. bars ll or 12 of the i'stseries and the upper face of each bar 2l and 22 maybeengaged by the horizontally disposed bearing surfacel4 of thebar under which it projects. Each of the bars 2l and 22 is so formed that the fuel supporting surface at the end of the bar adjacent tol the first series extends at such an angle to the major portion of the fuel supporting surface that Iit occupies a liori zontal position when the grate is in place on -the supporting structure; whereas, the major portion of the fuel supporting sur'- face is inclined downwardly toward the rear of the furnace. Each grate bar of this sei-iles'is also provided with front and rear bearing surfaces 23 and 24, so inclined with relation tothe longitudinal axis of the bai that they occupyr substantially horizontal positions whenthe bar is in place on 4the` supporting structure. lVith thi arrangement. the moving bars move horizontally, as

described in connection with the bars 11 and l2. This motion is imparted to them by a rocker bar 25, which illustrated as eX- tending transverselyof' the bars and located intermediate their ends. The mechanism for actuating the rocker bar 25 and the operating connections between it and the moving bars 21 may be substantially as illustrated in my before mentioned copend ing application.

For convenience in manufacture, the stationary and moving bars 2l and 22 are substantially ,similar in details of construction, except that each stationary bar is provided with lugs V26 and 2T which engage the to) flange of a partition 28 on which their lower ends are supported. (See Fig.' As

shown. each bar is hollow. having a passage located on the forward portion of the bar.V

All these ports communicate with the in terior passage Ht). The forward end of each bar is shown as rectangular in vertical scction. that is, the foiwvard end face .extends substantially at right angles to the adjacent portion of the top and bottom surfaces of the bar. The rear end of each bar is similai'ly constructed. except ythat the upper edge projects beyond the lower edge. I

As shown, the bars 21 and 22 partially overhang a well or pit 34 forineel.between the bridge wall 35 and the partition 28. In

the drawings, I have diagrammatically illustrated a refuse crushing and discharg# 'ing mechanism 34,- wliieli.inay be continuously or periodically operated for the purpose of crushing and discharging such ash and refuse material as collects in the well 34,

One of the features of this invention is i the means employed for delivering air under pressure to the incoming fuel and the fuel supported by the grate bars. As illustrated. the space below the grate bars :is divided into separate fuel delivery passages in order thatthe air supply to the furnace may be more readily controlled for the purpose of `maintaining the desiredcondition of comwhich may receive air under pressure fi'oin The bracket 39 extends -1 a fan or blower. transversely of the grate bars ll and l2, and with the front plate 37 or an auxiliary plate secured thereto forms a passage which extends transversely of 'the grate bars and communicates with the air admission ports 40 of the grate bars. The space located below the grate bars and between the plate 38 and a partition wall 4l, forming a part of the frame work of the stoker, is what may be termed a secondary air chamber,

since it receives air from the air delivery passages 42 through discharge ports- 43 of the grate bars and delivers it, to the fuel bed through the spaces between the adjacent grate bars 1l and l2.

For the purpose of supplementing this air supply in suoli a way that the thickerporsoA tion of the fuel bed receives a greater quantity of air under pressure than the thinner portions, I have provided ports 47 iii-the fuel supporting surface of each grate bar adjacent the forward end of the bar. These ports 47 communicate with the. interior pas- -sage 42 and are so arranged that some of them deliver air to the fuel issuing from the retort 5 and moving up the wedge shaped ends of the bars: whereas, some of them de-` liver air to the fuel located on the forward portion of the downwardly inclined support ing surface of the bar. lith this arrangement, the fuel bed receives air which has traversed the passages 42 of the grate bars and the air chamber 44, and a portion of the-- fuel bed also receives air directly from the passages 42. The saine is true of the fuel issuing from the retort, since the spaces between the grate bars permits some air under pressure to pass' into the retort from the secondary air chamber 44 and also from the passage 3G. In addition, the fuel issuing lll) from the retort also receives air from the ports 47 located in t-he wedge shaped-forward end of each bar.'

Inasmuch as the forward ends of the bars ll. and l2 act as a detlector, the fuel bed supported 'byfthese bars will be thickest at points adjacent to the forward ends-of the bars, and as a result, this thick portion willA require a greater amount of air than the thinner portions of the bed and can be supplied with a greater amountof air without 'i danger of blowing holes in the fuel bed and thereby cut-ting down the efficiency' of the furnace. In the stoker illustrated., combustion is accelerated as the fuel issues from the 'retort by the arrangement ofthe grate bars with relation to the retort and also by the arrangement of the air admission pase sages for delivering` air to the retort and that portion of the fuel bed immediately adjacent .the retort. As previously pointed` out, the movement of the moving grate bars agitates and breaks up the mass of fuel issuing from the retort, and this agitation is continuously taking place due to the periodic action of the moving Agrate bars burning fuel immediately adjacent the retort. This feature I believe is new, since so far as I know,V no stokers now on the market supply air. in the manner above described, to an agitated portion of the fuel bed located immediately adjacent to the retort. As a result of this method ofoperating the stoker. the partial coking of the fuel contained within the retort is more effectively accomplished with my stoker than with others known to me, and the partial volatilization of the fuel takes place immediately adjacent to an extremely hot and rigorously burning portion of the fuel bed. These distillates are alsothoroughly mixed with the excess air delivered through the ports 47 and through the spaces between the grate hars. It will` of course, be understood that any excess air so delivered to the distillatie is highl \v heated by its passage through -the ilu-andescent and vigorously burning fuel and that consequently, the distillates will be thoroughly consumed as they pass lnick'wardly through the combustion chamber to the stoker.

Another feature of my invention is that the forward portions of the grate bars 11 and 12 or those portions which support the vigorously burning part of the fuel bed, receive the largest amount of air and are consequently adequately cooled. In 'the first place, the air traversing the longitudinal passage Lt2 takes up heat from the grate bars llaaaaeiv and this heat is subsequently returned to the l parent tha't the volume of air traversing the forward portion of each grate bar is materially greater than'the volume traversing the remainder of the grate bar; consequently, the air traversing the forward portionsof the individual grate bars has great heat absorbing capacity and is capable of keeping theforward ends ofthe grate bars cool under theextreme conditions of combustion encountered. From the-foregoing, it. will be apparent that the greatest cooling action is encountered at the portion of each grate bar most likely to be burned away and consequently, theV life of the bar is materially increased.

Substantially the same conditions exist at the forward ends of the second, series 0f grate bars. In the drawings, I have Shown the lower ends of the bars l1 and 4l2 so formed that the moving bars, in effect, act as pushers in lpropelling fuel across the bars 2l and 22. This pusher action, accomplished as it is by ahorizontal reciproca*-` tion of the moving bars 11, tends to cause the fuel bed to thicken at the forward ends of the bars 21. This thickening tendency is augmented by the fact that the forward ends of the fuel supporting surfaces of the' bars 2l and 2 2 are substantially horizontal: Consequently, it is desirable to supply suiiicient air to the fuel bed at this point to'ni sure thorough combustion from the front to the rear endof the bed. This is accom- 'l plished by providing the ports 33 in the bars 21 and 22 and by locating these ports in the forward ends of the bars.

s has been describefhthe bars 2l and 22 are hollow and are provided'with ports 3l and 32. As shown, the ports 31 receive air from a passagetl; which extends upwardly from the floor of thefurnace structure and is located between suitably positioned par tition plates'l and 52. This passage also communicates directly with an lair duet `which may receive airfrom the duct 39 or from a separate source of supply. It the duct 53 receives air from the duct 39, it is desirable toemploy a damper or other controlling means in the duct 53. .so that ,the supply of air through the passage 50 may be regulated independently ofthe supply of air through the 'passage 36.

The passage 50, like the passage 3G, ex-

tends transversely1 of'the' grate bars as llO sociated with it and delivers air to the ports 31 of those bars.A A portionof the air so delivered traverses the passages 30 'ofthe grate bars and' is received by a secondary air chamber 53, located below the major portion of the hars 2l and 22. This air is heated in'its passage through the grate bars I3() l and in the preheatedstate is delivered to the fuel bed through the spaces between wliereas,"that portion 'of' the fuel bed located. immediatelyiadja'cent to the first series of bars also receives air direct from the ports 33. .f

Even though the arrangement and the operation of the grate bars may not occasion a thickening or a material thickening of the fuel bed at the 'forward ends of the bars 21-and 22, it is desirable to accelerate combustion at this point by thebreaking up of the fuel bed and by thede'livery of adequatequantiti'es of air to support vigorous combustion.. It will be apparent that the fuel, after having traversed the bars 11 and 12, is comparatively low in combustible: material; consequently, it is desirable to maintain, if possible, a hot zone through which this fuel must pass before being delivered M to the ash pit or well 34. By providing this hot Zone in which combustion -is a second time accelerated, I am able to maintain combustion throughout substantially the entire fuel bed and to deliver ash and'refuse material in which the carbon content is exceedingly low.

In the drawings,.I have illustrated separate doors 55 and 56 which give access to the respective chambers 44 and 53 for the pur pose of removing siftings from these chambers.

The voperation of the furnace illustrated is briefly as follows: The hopper? is filled with fuel, whichis fed across theplate 8 and into `the retort 5 through the rearwardly expanding passage 9. V"This passage 9 is preferably so designed that itpermits the coal traversing it to lform a seal between the interior vand the exterior of the Stoker,

' but it is also so formed that it prevents packing of the coal and a resultant detrimental effect on the operation ofthe stolzer. ItA will bc-noted that the inclination of the bars 21 and 22 is somewhat less than the inclination of the bars 11 and l2.' This maintains a thicker fuel bed throughout tha-n would be the case if the bars 21 and 22 were inclined the same amount as the bars ofthe first series. The fact that a relatively thick fuel bedis maintained from the front to the rear of the furnace'enables the furnace to be operated under higher lconditions of air pressure than would bethe case if the fuel bed thinned out toward the rear. 'As a result, the stoker may be operated under high capacities by speeding up the fuel feeding mechanism and the moving grate bars and by increasing the blast or forced draft-to the fuel bed; rlhe air supply to`the portion of the fuel bed supported by the grate bars 21 and 22 may also be controlled independently of -the air supply to the remaining portion of the fuel bed, and in this way, the combustion throughout the entire bed'may be controlled and a hot zone may be attained at a point substantially midway between the front and rear ends Iof the stoker.

For `this purpose I may employ a dam. per 53a in the air duct 53.

It will, of course, be understood that whilex groups.

ilhile I have illustrated and described but one embodiment of my invention, it will be apparent to those skilled in the art that various changes, modifications, additions,

omissions, and substltutions may be made 1n the apparatus illustrated without departing 'from the spirit and scope of the invention as set forth by theA appended claims.

What I claim is:

1. In combination in a furnace, a fuel feeding mechanism, a-iiooracross which fuel fed by said mechanism is moveda. series of grate bars extending longitudinally of the furnace and associatedwith said floor to v form a retort extending transversely across the front of the furnace, a second series of grate bars onto which fuel moves from the first series,I a bridge wall spaeed'from the second series of bars to form an ash receiving well, and means for imparting a fuel impelling motion to grate bars of both series.

2. In combination in a furnace, a fuel feeding mechanism, a floorv acrosswhich fuel fed by said mechanism; is impelled, a series of alternately arranged moving and stationary grate bars, associated with said.

floor to form a retort at the front of the furnace, a bridge wall, a second series of alternately arranged stationary and movable grate bars between said bridge wall and said first series and spaced from the bridge wall to form an ash receiving well into which fuel impelled across said Lsecond series of bars is discharged, and means located in the bottom of said well for discharging the ash and refuse mechanism received thereby.

3. In combina-tion in a furnace, a fuel feeding mechanism, a floor vacross which fuel is fed .by'said mechanism, a series df downwardly inclined hollow grate bars having wedge-shaped forward ends associated with said floor to form a coking retort at the front of the furnace, and having apertures formed in the `wedge-shaped ends thereof and in the fuel supporting surface thereof intermediate the ends of the bars for delivering air from the interior of the bar to fuel issuing from said retort and fuel located on said bars, a second series of hollow grate bars located below and extending rearwardly from said first series, and having apertures formed in the fuel supporting surfaces thereof adjacent said first series of bars for delivering airl to the fuel Ireceived from saidrfirst series of bars 'and means for deliveringI air under'pressure to said bars.

4. In combination in a furnace, a fuel feeding mechanism, a floor across which fuel is fed by said mechanism, a. series of alternately arranged downwardly inclined moving and stationary grate bars, associated with said floor to form a retort at the fro-nt of the furnace, a bridge-wall, a second seseries of spaced, alternately arranged, mo-vf able and stationary grate bars extending in parallel relation from said retort toward the rear' of the furnace, each bar, provided with a wedge shaped forward end and having air delivery' apertures in its wedge shaped forward end and in its upper face intermediate its ends, a second series of spaced, downwardly inclined, alternately arranged, movable and stationary grate bars, extending in parallel relation from the rear ends of said 'first series toward the rear of the furnace,

ward the rear of the furnace and so ar- ,5

ranged thatthe forward ends of the bars form an extension ofthe fuel delivery side of the retort and the moving bars move into and out of the confines of the retort as defined by the forward ends of the stationary bars, each bar having air delivery apertures formed inthe forward end of the fuel supporting surface thereof, -a second series 0f alternately arranged, moving and stationary air delivering grate bars, located in parallel relation, overlapped by the first series, and extending toward the rear of the furnace. each of said second seriesof bars having apertures `formed in theforward end of the fuel supporting surface thereof and means for delivering air under pressure through the bars of both series and through said apertures for maintaining zones oi increased combustion adjacent to the forward ends of the bars of each series.

In testimony whereof, I have hereunto subscribedmy name this 22 day of July, l1920. o

JOI-IN S. SKELLY.

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