US2140522A - Combustion apparatus - Google Patents

Description

. Dec 20, 1938- R. A. FoRE'sMAN coMUsTIoN APPARATUS lFiled June 18 2 Sheets-Sheet lA R. A. FoREsMAN v COMBUSTION APPARATUS Dec. 20, 1938,.'

2 sheets-sheet 2 Filed June v18, 1936 lNvENToR Rosan-r AF-onzsM/fw ATTORNZYJ v*Patented Dec. 20,1938

ooMUsTIoN APPARA'IUS Robert A. Foresman, Prospect Park, Pa., assignor f 'to Westinghouse Electric & Manufacturing Y ofPennsylvania.

ytion y.c :hamber rupon a travelling grate and passes `througlri' successivestages of combustion as itis 5V conveyedfthrough thechamber by the grate. An objectgof myinvention is to provide an improved f furnace of this kind;

l liurtlier objects of invention are `to assist bustionof the ueladjacentthefuel admission end ofvthe bed during periods when the furnace isshllidown- These and other objects are eifectedby my inl ,vx'erition as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:v Y

Fig. lluis a sectional plan view of a boiler fur- 20 nacear-rangedin accordance with my invention 1i f and istaken along the line I-I of Fig. 2;

Figslg and 3 are sectional views of the appa- '1ra us'and are taken, respectively,V along the lines 2d Fig.- fi is a sectional view taken along the line Fig. 6 is a partial view of a boiler furnace simiy `.'irOflaJr to thatof Figl 1 having a second embodiment -offmy-invention applied'thereto. f

in ,practicin'g my invention, I provide a travellingfgrate `Stoker having a fuel magazine so disposed v that it deposits fuel thereon by gravity. A

`lwall lmeinberis spaced above the grate for der iiningtherewith a fuel discharge opening through which fuel from the magazine passes as the grate isadvanced The fuel is levelled off by the Wall Landa bed of fuel of predetermined depth is car- 40 Vvfied bythe grateinto ra combustion chamber y I ,wheregit passes throughsuccessive stages of combus'tion.; Refuse of combustion or ash is removed f froinfthegrate in any suitable manner.

f With this type of furnace, difliculty may arise 45?in' maintaining combustion adjacent the fuel disvcharge opening, particularlyduring heavy loads whenfuel is being fed to the combustion chamf berat a high rate. At this time, the zone of ignirv'tion' rtends to move away from the vfuel opening 50,1due to therapid feeding of fuel. During'shutdown periods, this undesirable condition may also prevail,` as thesupply of lair to the grate is subfst'antially reduced and tends to pass through relatively thin portions of the fuel bed, whereby insuflicient air passes through the thick end of the Vitionpf the fuel as it Venters the Ycombustion ilo chamber during operationv and to maintaincom- Company, East Pittsburgh, yPa., a corporation Application June 1s, 1936, serial No. 85,851

l1o claims. (ci. 11o-36) invention relates tol furnaces of thetype in rwhich fuel is admittedto one Aendl of the combusbed where it enters the combustion chamber to sustain combustion at this point. Accordingly, when operation ofthe furnace'is initiated after a shut-down period, difficulty arises in effecting combustion of the relatively thick end of the bed 5 and, if 4the grate yis started, simultaneously, with the iiow of air, fuel may be carried to the ash removal zone only partly consumed. This, of

course, represents inefficient operation.

In @accordance with my invention, I propose to vl0 effect a relatively small flow of heated gas from the combustion chamber through a portion of the thick end of the fuel bed Within the fuel dischargev opening at all times, so that ignition of the fuel therein is assisted during operation and combus- 1,6 tion is slowly effected `during shut-down periods. VA conduit that communicates with the fuel bed in or adjacent to the fuel discharge opening may be provided for effecting this flow of gas, which conduit connects with a zoneV of relatively low pressurein the gas otake. Means are provided for adjusting the flow of gas through the conduit to the' desired value. kWith this arrangement, the furnace may be operated at a high rate of combustion and ignition of the fuel in the thick end of the bed within the fuel opening is readily effected by the ilow of hot gases therethrough.

Referring now to Figs. l to 4, inclusive, of the drawings,1 show my invention applied to a boiler furnace of the typedisclosed in my copending application, Serial No. 658,334, filed February 24, 1933, although it may be applied equally well to `other forms of furnace structure employing either Water-cooled'or refractory walls.

In the drawings, a boiler structure, indicated generally at I0, is carried by a base II that provides a support for arotatable annular grate I2. The boiler I0 includes an outer wall I3 having a Water space I4 formed therein, the lower portion I5 of the wall I3 being substantially cylindrical 40 linxform and disposed above the outer periphery of lthe grate I2'. is'substantially semi-circular in shape to provide An upper portion 23 of the wall I3 space for rthe fuel magazine as will be described later. The lower circular portion I5 of the Wall 45 4I3 is cut away to'dene an opening IB for the discharge of ashfrom the grate as best shown in Figs. 1 and 2. Further reference to the discharge tending from the outer wall |3 inwardly as best shown in Fig. 2. A water space 22 is. formed in the horizontal wall 2| and communicates with the spaces i4 and i8 for the circulation of water therebetween.

The upper semi-cylindrical portion 23 of the outer wall |3 has its end portions connected to the center column l1 by means of radial walls 24 and 25 having water spaces 25 and 21, respectively, that provide communication between the spaces I4 and I8. The lower end of the radial Wall 25 connects with the horizontal wall 2|, the Water spaces 21 and 22 thereof being in communication.

The lower edge 28 of the radial wall 24 is disposed in spaced relation with the grate |2 for defining an opening 29 which determines the depth of fuel carried by the grate |2. This function will be referred to hereinafter.

Arranged beneath the horizontal wall 2| and transversely of the grate l2 is a vertical wall 3| extending horizontally from the outer wall to the' inner column f |1 and extending vertically from' the horizontal wall 2| downwardly towards the grate and terminates adjacent to the latter (Fig. 2). A water space 32 may be provided in the' wall 3| which affords communication between ,t'he' lower portions of the space |4, the space I8 and the space 22. A vertically-extending opening or passage 33 isV formed in the horizontal wall'l between radial walls 24 and 3| for the passage of fuel to the grate. A fuel magazine 34 is disposed above the horizontal wall 2| andadjacent tothe radial walls 24 and 25 for the gravitational feeding of fuel through the opening 33to the grate. This arrangement of the magazine 34 and boiler structure l0 is disclosed in my copending application, Serial' No. 57,332, filed January 3, 1936, and assigned to the Westinghouse Electric & Manufacturing Company. The bottom 35 of the magazine 34 is sloped toward the opening 33 for facilitating movement of fuel thereto.

y An arcuate space 36 is defined by the wall I3 and the column l?, within which arcombustion archf31 is disposed as best shown in Figs. 2 and 3. The arch 31 divides the space 36, vertically, into a combustion chamber 38 and a gaspassage 39. The arch 31 extends from the radial wall 25 toward the wall 24 but terminates at 4l) (Fig. 1) in spaced relation with the Wall 24 to definea passage 4| for the flow of gas' from the combustion chamber 38 to the gas passage 39. A top wall 42 covers the gas passage 39 and is provided with an outlet 43 for the products of combustion (Figs. l and 3). A damper 44 may be arranged in the outlet 43 for regulating the draft through the furnace.

As best shown in Fig. 3, a support for the lgrate may be provided by an annular flange 45 formed on the inner ring |9 of the base andby a plurality of radial walls 41 to 49, inclusive, (Fig. 4) formed in the base The walls 41 and 49 divide the base into a windbox and an vash receiving chamber 52, the former being disposed beneath the combustion chamber 38 and determines the length of the grate receiving air. A

Y portion of the wall 49 is shown in dotted lines in Fig. 1 and indicates the portion of the combusa damper 54 disposed therein. It will be understood that, where forced draft is employed, a suitable blower (not shown) may be connected to the wndbox. An opening 55 is provided in the wall 48 for providing continuity of the windbox.

The grate l2 is rotated in any suitable manner as by a pawl and ratchet mechanism 56 which may include a shaft 51 journalled in the base and oscillated by a crank 58. A pawl 59 which oscillates with the shaft 51 engages ratchet teeth 65 formed in an under surface of the grate l2 and effects step by step rotation of the grate E2 as the shaft is oscillated. The grate moves in clockwise direction as viewed in Fig. 1.

Suitable means may be provided for removing ash from the grate adjacent the opening |6. Accordingly, a plate 6| may be tangentially disposed with respect vto the grate and having its lower edgecontiguous thereto whereby ash is moved radially of the grate as the latter passes beneath the' plate 6|. The removed ash passes through opening i3v and drops into the ash receiving chamber 52a Suitable containers 62 may be disposed in-'the chamber 52 for receiving the ash. The chamber 52v may loe-provided with a dusttight h'cusing's having a door 64 for providing access to the containers 62.

Referring now to the operation of -such a fluid heater, assume that thefmagazine 34 islled with coal and that the grate is rotated by the mechanism 55. Fuel passes by gravity from the magazine 34 through the opening 33 upon the gra-te and is leveled off to a predetermined depth by the bottom edge 28 of the wall 24. The fuel on the grate l2 is progressively burned as it passes through Athecombustion chamber 38 and combustion is substantially complete as it passes the region of the combustion chamber over the wall 49 of the windbox. Ash is removed by the plate 5| and deposited in the containers 62. Products of combustion-pass in a direction counter to the movement of the grate I2 and pass through the opening 4| into the gas passage 39 and thence to the gas offtake 43.

In a furnace of thistype, it may be diflicult, during period of high load, to effectv ignition of the green fuel being fedto the combustion chamber at a relatively high rate through the fuel discharge opening 23 because, as shown in Fig. 5, a substantialY portion of the hot gases passing from beneath the arch 31 into the opening V4| flow adjacent to the end ofthe` arch 31 and out of contact with the surfacerk of the fuel as it emerges from beneath the wall 24. -The ignitingeffect of these gases is, therefore, lost. Fig. 5 discloses in' dotted arrows thev normal path of the gases flowing from the combustion chamber to the opening 4|. Furthermore, during shut down-periods or periods when the grate-is stationary and the supply of 'air to the windbox is substantially reduced,fthe fire burns away from the thick portion of the fuelbed or wall 24 within the opening 29 toward thinner portions of the bed, that is, inthe direction of thewall 25. This is ydue tothel aforementioned condition and to the fact that air will flow through a thinner portion or more consumed portion of the fuel bed than throughv a thickerv or less consumed portion of the fuel bed. Accordingly, when operation vof the gr'atef is initiated and the supply of air in` creased, ignition of the 'fuel in the thick portion of the bed is -difcult and fuel may be carried to the ash removal end Vof the combustion chamber 'prior toits complete combustion. f

In accordance with my invention, I obviatethis l j condition' by inducing a flow of hot gases fro'mvthe r combustion chamber throughv the thick portion of the bed of fuel in or adjacent to the fuel discharge opening 29, as best sho-wn by the solid arrowfs'of Fig. 5, vIgnition of the fuel is, therefore, L assisted during operation and, during shut down periods, combustion is slowly effected in the fuel Y'bed within the opening 29. Accordingly, when yoperation is initiated yzagftera shut down period, "ignition Aof the fuel entering the opening y29 is y'readil'y'eilected by the relatively hot coals therein A. andby thehot gases from'th'e combustion cham- 1 Lber.

` 'One' form of effecting the'flowof hot gases `from the'combusticn chamber 38 isv kshownin Figs; 1 to .f3 and 5.v 'A conduit vB6 is disposed'on thefside of tthe wall Zladjacent to the fuel inthe magazine 13M This conduit terminates in the bed ofr fuel adjacentrto the opening .29, as best shown in Figs. V20, 2 and :5. Preferably, the conduit is made flat and substantially. coextensive with the width ofthe fwall T24. VThe other end of the conduit terminates .in a region of relatively lowpressure', suchas. for

example, in the gas oftakeforinducing a flow ofheate'd gases from the .combustion "chamber through the; fuel in the-opening 2,9 as shown by j v1@solidarrowsin Fig. Y5. A damperG'l may be employed for regulating the fiow of gas through 'the anfponduitss.

' Preferably.v the conduit is disposed in heat ex-r v. changing relation with. the vwall. 2'4 so ythat the v i Vheat abstracted from thegas conveyed thereby is i A1 conducted to the Vwall 24. This conduit B6 radiatesrsome'heatalso to the fuel in the magazine 134 .whereby some advantageous preheating of the fuel isobtained, but thequantityrof heat radig thetombusnon chamber.k n; ,win be understood ythatthetubes sa terminate at oneens in the bed `Aof fuellying within the opening.v 29- ybeneaththe vvalrlfzfi` and, at their other, ends, in a region of .low'pressure as described inconnection with the priOrQembo'diment. In this embodiment. heat is rabstractedfrornthe tubes directly by the water in thespace 26. From the foregoing, it will befapparent that I y have'kprovided improved operation cfa furnace t havingra travelling grate, uponwhichV a bed of fuel is deposited forfprogressive combustion as it passes through a combustion chamber. While I k have shown my invention applied to a furnace ofthe rotating grate type.V it will be understood {thatit maybe applied to other forms of furnace structure. Furthermore, my invention is disclosed applied to a boiler furnace havingwater walls,

' kbut it is applicable also to furnaces for other purposes employing other forms of wall structure.l

"f f While I have shown my invention in two forms,Y itwill be obvious to those skilled inthe art that it isnot so limited, but is susceptible of `various other'changes and modifications without depart- "ing 'from the spirit tlrereoffk and I desire,lthere `fore,"thatv only such limitations shall be yplaced thereupon as are imposed by the prior art or as jarespecificallyr set forth inthe appended claims. d l WhatIclaim is: t

1. In combustion apparatus, the combination `of a furnace structure having a combustion charnber thereima movable ygrate defining, atleast in part, thebottom of the combustion chamber,

means vfor depositing fuel upon a portion of said grate, a wall member'having a fluid space formed therein and disposed transversely of the grate, said wall member having its bottom edge spaced vabove the grate for leveling the fuel and determining the depth thereof as it is carried by the grate into the combustion chamber, means for supplying air to the underside of said grate, means 'nular grate disposed at the bottom of said space,

a wall member extending transversely of the grate 'andfdividing said space into a combustion zone and a fuel receiving zone, said wall member being spaced .above the grate for defining therewith an opening for the discharge of fuel to the combustion zone as the grate is rotated, means for passing 'air through'the bed of fuel in the combustion zone, and means for passing heated gases from the combustion zone through a portion of the kbedof fuel in said fuel receiving zone.

3, In combustion apparatus, the combination of a furnaceV structure having spaced inner and outer rsubstantially concentric wall members d efiningan annular space therebetween, a rotatable annular grate disposed at the bottom of vsaid space,wa1l members extending transversely of the grate and dividing said space into a combustion chamber and a fuel receiving chamber, one of said transversely extending Walls being spaced above the grate for defining an opening through which fuel is carried into the combustion charnberY as the grate is rotated, means for passing airV ,throu'ghthe portion` of the fuel bed within the .combustion chamber,y for effecting combustion thereof, meansv for passing heated gas from the rcombustion chamber through a portion of the fuel in the fuel receiving chamber, and means for adjusting the amount of gas passed through the fuel in the fuel receiving chamber.

4. In combustion apparatus, the combination of a furnace structure having spaced inner and outer substantially concentric wall members defining an annular space therebetween, a rotatable annular grate disposed at the bottom of said space,

first and'second Wall membersy extending transfuel is carried into the combustion chamber as the grate is rotated, means disposed adjacent the second transversely extending wall member for deecting ashfrom the grate, means for supplying air to the under side of the grate, means defining a passage communicating with the combustion chamber for removing gases therefrom, a conduit communicating with the bed of fuel disposed in said fuel discharge opening and with said gas removing passage for promoting a ow of heated gas through a portion of the fuel in the opening and means for adjusting the amount of heated gas flowing through the opening to said conduit.

5. In combustion apparatus, the combination of a boiler structure having spaced inner and outer,substantially concentric wallsn defining an annular space therebetween, said walls having spaces therein for fluid to be heated, a rotatable annular grate disposed 4at lthe bottomv of said space, first and second walls extending trans versely of the grate and having fluid spaces therein communicatingr with the vspaces of the inner and outer' walls `for dividing said annular space into va combustion and a fuel receiving chamber, said first transversely extending Wall having its bottom edge spaced above the grate for defining an opening through which fuel of a predetermined thickness` passes into the combustion chamber as thevfgrate is rotated, Ymeans for removing ash from the gratev arranged adjacent said second transversely spaced wall, means for withdrawing gas fromr the combustion chamber, a windbox for supplying air for combustion beneath the grate, andY a conduit communicating withthe fuel within said opening and with the gas withdrawing means for promoting a flow of gas through the opening, said conduit being disposed in heat exchanging relation with said first transversely extending wall. Y

6. In combustion apparatus, the combination of a rotatable circular grate, a furnace structure associated with the grate and defining a combustion chamber above a segment of the grate, means defining a fuel conduit above a second segment of the grate and yincluding members extending transversely of the grate, one of said members being spaced vabove the grate for defining an opening through which fuel is carried by the grate as itis rotated, means for conveying gases of combustion from the combustion chamber, and means for passing a portion of the combustion gases through the fuel in said opening for preheating the same and thence in heat transfer relation with the fuel in said fuel conduit.

'7. In combustion apparatus, the combination of a rotatable circulargrate, a furnace structure associated with the grate and defining a combustion chamber above a segment Vof, thegrate,

means defining a fuel vconduit above a second Y segment of the grate and including members extending transversely of the grate, one of said members being spaced' above the grate for defining an opening through which fuel is carried by the grater as it is rotated,km`eans for conveying gases of combustion from the combustion chamber, andmeans for passing a portion of the combustion gases through the fuel in said opening for preheating the same and thence in heat transfer relation with the fuel in said fuel conduit, and means for'adjusting` the quantityof ygases of'combustion that is passed through the fuel in the opening. t

8. In combustion apparatus, the combination of a rotatable circular grate, a structure associated with the grate for defining a combustion chamber yabove a segment of the grate, said structure having .a space formedtherein for medium tobe heated, a conduit for fuel disposed above a second segment of the grate for feeding ,5 j

fuel thereto by gravity, means spaced above the grate for providingan opening through which fuel is carried by the grate to the combustion chamber, means for conveying gases of combustion from the combustion chamber, and second 3 ,i

conduit means communicating Awith theffuel on the grate adjacent said opening for providing flow of a portion of the gases of combustion from the combustion chamber through the fuel in said ciated with the grate for defining a combustion chamber above a segment thereof, a magazine for fuel elevated with respect to the grate lfor depositing fuel by gravity on a second segment of the grate, means spaced above the grate for dening a fuel orifice through which fuel is passedk from the lmagazine to the combustion chamber as the* grate is actuated,.means for conveying a portion ofthe gases of combustion from the combustion chamber and means for passing a second portion of the gases of combustion through the` fuel in said orice for preheating the ,same and thence in heatrtransf'er relation Ywith the fuel in said magazine.

l0. In combustion apparatus, thecombination of a movable grate, a boiler associated with they,

grate andl having water kcooled Walls defining a combustion chamber above a segment of the grate, a magazinetfor depositing fuel by gravity on a second segment ofthe grate, meansn spaced above the grate for defining aV fuel orifice through which fuel is passed from the magazine toV the combustion chamber as the grate lis actuated. means for conveyingr a portion of ,the gases of combustionr A,from the combustion chamber and means for passing a second portion of the gases of combustion through the fuel in said-orifice for preheating the same and thence in heat transfer relation with one of said water cooled Walls.

ROBERT A. FORESMAN.

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