US2840048A - Grate organization - Google Patents

Description

June 24, 1958 H. SCHROEDER cam: oacmxzmxon 2 Sheets-Sheet 1 2 INVENTOR Henry Schroeder {Le/M A4 .Jd/

ATTORNEY Filed June 29, 1956 Fig. l.

GRATE ORGANIZATION Henry Schroeder, Jackson Heights, N. Y., assignor to Combustion Engineering, Inc., New York, N. Y., a corporation of Delaware Application June 29, 1956, Serial No. 594,744

6 Claims. (Cl. 122-435 1 This invention relates to grates employed in the lower portion of the furnace of boilers and the like, and has particular relation to the support of such a grate em-' ployed with a furnace that is hung from its upper end and expands downwardly as a result or the thermal expansion caused by increases in the temperature of the furnace structure.

In modern furnaces of the type employed in steam generators and wherein the inner surface of the furnace walls are lined with generally vertically disposed heat exchange tubes it is the practice, for ease of construction and simplicity of design, to hang these furnaces or steam generators, if they are of any appreciable size, from their upper ends with their lower ends being. free and moving up and down a ratherlarge distance in response to the high temperature differential that prevails between the material of the furnace in its cold or shut down condition when the furnace is not in operation and in its hot condition when the furnace is in operation. With these furnaces it has heretofore been the practice, when a grate was required with the particular type of fuel for which the furnace was designed, to mount the grate upon a stationary foundation independent of the lower end of the furnace and provide a suitable seal between the grate or grate housing and the lower end of the furnace with this seal accommodating the dilferential movement between the stationary grate and the lower end of the furnace with the expansion'and contraction of thefurnace resulting in thismovement being as much as eight inches. These seals were necessarily located somewhat above the upper surface of the grate and because of the high tem-' perature prevailing at this location it was impossible to use the desirable and efficient water type of seal and resort had to be made to a mechanical seal which was difiicult to maintain reasonably tight and was susceptible of becoming clogged and jammed by fuel particles dispensed into the furnace because of the turbulent condition that prevails in the furnace.

The present invention provides an improved grate organization which successfully eliminates these difficulties and troublesome conditions that heretofore prevailed. In accordance with the invention there is provided an upright elongated furnace of rectangular transverse section and which has the-inner surface of its walls lined with vertically disposed side-by-side heat exchange tubes. The furnace is supported from above by means of a structural steel framework which surrounds and extends above the furnace with certain of the tubes being supported from the upper end of this framework by means of suitable hangers and with the lower end of the furnacebeing free sothat it may expand and contract vertically in response to temperature increases and -decreases, respectively. The lower end of a pair of opposed walls are inclined inwardly to form a basket type of bottom and generally at the throat of this bottom is-provided a chain grate for receiving upon itsupper run a layerof fuel which is to be burned. This grate is supported by means of a suitable structural support frame which is in turn connected to and supported by the lower ends of the tubes so that the grate is effectively supported from and moves with the lower end of the furnace.

The grate is enclosed within a housing which. is also.

supported from the lower end of the furnace and has a discharge opening at the discharge end of the grate for the conveying of ash to a suitable pit or the like. Im-

mediately below this discharge opening is provided anash collecting pit or the like which'is stationarily mounted independently of the furnace and has. an 'upwardly open trough formed at andextending about its upper end into which extends a plate member which is positioned about the discharge opening formed in the housing with liquid being disposed in the trough and together with the plate member forming a liquid seal between the ash pit and the lower end of the furnace with this seal being in a relatively low temperature zone and being free of difliculty'with relation to clogging. Air is supplied both beneath the upper run of the grate for passage through the grateand immediately above the grate at the throat portion of the basket bottom of the furnace, with the inwardly inclined walls of the furnace being constructed so as to have openings therein adjacent the throat for the admission ofair, with this arrangement providing rapid and efficient combustion and reducing the size of the rather expansive grate that is required.

It is an object of this invention to provide an improved grate organization employed with furnaces which are supported generally'from their upper end and expand downwardly.

Other and further objects of the invention will become apparent to those skilled in the art as the description proceeds.

With the aforementioned objects in view, the invention comprises an arrangement, construction and combination of the elements of the inventive organization in such a manner as to attain the results desired as hereinafter more particularly set forth in the following detailed de scription of an illustrative embodiment, said embodiment being shown by the accompanying drawing where- Fig. l is a longitudinal vertical sectional view of a steam generator fired with a suitable fuel which requires a grate for complete combustion and with a chain grate being disposed in' the lower end of the furnace and organized in accordance with the present invention.

Fig. 2 is a sectional view of the lower part of the furnace only and is taken generally along line 22 of Fig. 1.

Fig. 3 is an enlarged fragmentary view of the liquid seal connection between the hopper and the lower portion of the furnace.

Fig. 4 is also an enlarged fragmentary view of .the portion of furnace generally included in the circle 4 of Fig. 2 and showing in detail the mounting of the grate.

Referring now to the drawings, wherein like reference characters are used throughout to designate like elements, the illustrative and preferred organization depicted therein comprises furnace 10 which is vertically disposed and is fired through burners 12 with the combustion gases passing upwardly through the furnace and out the lateral outlet provided in its upper end. Extending from this outlet is the gas pass 14 within which is located steam generating tubes 16 which are connected between the upper and lower boiler drums 18 and 20, respectively, with. the hot combustion gases from furnace 10 passing overthese tubes and then down through passageway 22 within which there may be located economizer and air heater heat exchange surface as is well known. The furnace is of generally rectangular transverse section and has its inner surface lined with steam generating tubes Patented June 24, .1958

24 which communicate at their upper ends with the upper drum 18 and at their lower ends with the lower drum 20 with the latter being effected by means of the downcomers 26 which are connected. to the ring distribution header 28 with this. header in' turn being connected through the conduits-or-spurs 30 to the headers 32 located at thebottom of the furnace walls an'd into which the tubes 24 are connected. 7 r r The fuel that is'fired into furnace 10 may be a combination such as oil and bark'bwith one of the fuels being of a type thatrequires' a grate order to obtain completecombustion orla single fuel of this latter type may be employed with the burners 12' in the illustrative organization being arranged to fire two fuels with ports 12a being adaptedfor the firing .of oil and ports 12]; for the firing of bark with the bark being introduced through these ports by means of apneu atic distributor or other suitable conveying'means. The entire furnace and boilerare supported from above with the lower end of the furnace being free to expand and contract as required toaccommodatetthe movement 7 resulting from temperature changes of the furnace structureand for this purpose a structural steel framework which ismounted upon a firm fixed foundation 25 surrounds the furnace and boiler and extends somewhat above the same. This framework includes vertically extending columns or I-beams27 which are interconnected by suitable I,-beams .29 with these beams having channels or additional I-beams such as 31 interposed therebetween and connected therewith as shown in Figs. 1. and 2 Extending downwardly from this support structure which includes be'ams29 and 31 that aredisposed .above the furnace and boiler are hanger members-33 which support the drums, tubes and entire steam generator structure from above with certain of these hangers being connectedwith one .or more of the f vertically. disposed tubes 24. in a manner known in the art. and so as to support the furnace from its upper end to 'permit it to expand vertically downwardwith this movement being several inches, as

for example eight inches,.with modern high capacity boilers. i t r The bottom of furnace 10 is preferably of the basket type having a pair of opposed walls inclined inwardly toward each other at their lower end, as shown in Fig. 2 to form a somewhat restricted throat 34 that extends across the width of the furnace and immediatelybelo'w this throat is provided a chain grate 36 upon the upper run 4 over the rear end of the grate by baffle 62 which extends downwardly from thefurnace wall into close proximity of the upper run of the grate. However fine fuel particles may find their way past this baflie so that hopper 64 is positioned below this end of the grate and is provided with a normally closed discharge passage 66 through which ash and fuel may be periodically removed.

The ash which falls from the discharge end of chain grate 36 passcsthrough opening 68 formed in floor 60 and into hopper orash pit 70 which is stationarily mounted independently of the furnace and may take the form of a concrete enclosure having an open upper end.' The upper end of hopper 70 is effectively sealed to the housing or enclosure that is provided about the chain grate in a fluid tight maner but in a manner which permits the required relative movement between the hopper and the lower end of the furnace in both vertical and lateral direction due to thermal expansion and contraction of the furnace. This is accomplished through a fluid or waterseal which includes trough 72 formed around the upper end of hopper 70 and into which extends the seal plate or baffle member 74 which extends downwardly from and about the opening 68 in wall 60 with trough 72 being filled with liquid and being sufliciently deep to permit the required relative movement without withdrawal of the bafile or seal plate from the liquid. Foreign matter is prevented from entering the trough by means of plate 76 which is disposed within seal plate or baffle 74 and extends downwardly beyond th'eupper end of hopper 70.

Combustion supporting air is admitted to furnace 10 at three locations, one being the location of burners 12 which are spac'ed a substantial distance above the bottom of the furnace with the other two locations being adjacent the furnace bottom and are for the purpose of 38 of which the portion of the fuel, such as bark,- that I is not burned in suspension is deposited and burned. This chain grate is supported from the lower end of tubes 24 through a suitable structural steel support which includes transversely extending I- beams 40 and 42 which extend between and are connected to the respective channels 44 and 46. These channels'have their web portion in engagement with the tubes extending along the innersurface of the boiler walls and are secured to certain of these tubes by any suitable meanssuch as bolts 48 shown in Fig. 2. This support framework for the chain grate is thus effectively secured to the lower end of the furnace and moves therewith. The chain 50 of grate 36 is positioned between the two spaced sprockets 52a and 52b which are also supported by the furnace with the support shaft of these sprockets being journaled in bearing blocks that are connected to the channels 44. The chain grate is driven through sprocket 52a by conventional drive mechanism and is moved in the direction indicated by arrows 54. The lower run 56 of the chain grate rests uponlongitudinally arranged support bars 58 which are in turn supported by the I-beams 42. The entire grate is positioned within an enclosure with the furnace walls forming the side walls and the front wall of the enclosure while below the grate there is provided floor 60 which is supported from Ibeams'4 2 and at the rear is wall 62 supportedfrom tubes' 24. Fuel is" prevented from passing supporting the combustion of fuel disposedon the upper run 38 or the grate with one of these locations admitting air immediately above this upper'run and another admitting air below this upper run for passage upwardly therethrough. In the illustrative organization air which is preferably preheated by passing in indirect heat exchange relation with the combustion gases passing downwardly through passage 22 is supplied through duct 78 to the distribution manifold 80 with this preheated air being introduced beneath upper run 38 of the grate by means of downwardly extending duct 82 with the outlet of this duct being positioned below metering plate 84 which is effective to regulate the air passing upwardly through't'he grate and comprises a stationary plate member having a plurality of passages therethrough with a the effective size of the openings in the metering plate may be varied as desired. Combustion supportingair is admitted immediately above chain grate 36 through ducts 90 which also extend downwardly from manifold 80 and into chamber 92 formed by the wall 94 and the lower end'of tubes 24 and which extends across the width of the furnace. Certain of the tubes 24 at the location of throat 34, such as every other or every third tube, are laterally bent with relation to its adjacent tubes so as to form a series of openings 96 across the width of the furnace at throat 34 which openings permit combustion supporting air to be admitted into the furnace at the throat from chamber 92 with it having been found that this lateral admission of air through these openings 96 in this type furnace bottom in combination with the upward passage of air through the grate results in a somewhat turbulent condition at the grate which enhances the combustion process with the throat of the basket bottom causing increased air velocity and reduced pressure for admission of airthrough openings 96.

fold upwardly through duct 98 to the several burners admitted into; the furnace 'together'with out departing from the spirit and scope of the invention.

I therefore do not wish to be limited to the precise details set forth but desire to-avail myself of such changes as fall within the purview of my invention.

What is claimed is: t

1. In a vapor generator the combination of avertically disposed furnace, the inner surfaceof the walls of the furnace being lined with vertically disposed heat exchange tubes in side-by-side relation, a fixed foundation a support framework secured thereto and extending above said furnace, means interconnecting said framework with the upper portion of certain of said tubes to effectively support said furnace generally from its upper end and permit the same to expand downward, means operative to introduce into said furnace an ash bearing fuel of the type wherein at least portions of the fuel must be deposited and burned upon a grate in order to obtain complete combustion, a grate positioned at the bottom of the furnace operative to receive the fuel portions to support the same for burning and thereafter discharge the ash, said grate being supported by said tubes so as to move therewith, means for admitting air beneath the grate for passage upwardly through the grate, means disposed below said grate to receive said ashes and fixedly supported independently of the furnace, means in,- terconnecting said last mentioned means and the lower end of the furnace in a substantially fluid tight manner and in a manner permitting limited relative movement therebetween in a vertical and horizontal direction, said seal means including a water seal.

2. In a furnace which is vertically disposed and has' its walls lined with vertical, side-by-side heat exchange tubes and which is suspended from its upper portion so that it extends down with its lower end being free for this purpose the combination of a grate disposed across the lower end of the furnace to receive fuel and have the same burn thereupon thereafter discharging the remaining ash, said grate being effectively connected to and supported from the lower end of the heat exchange tubes and accordingly the lower end of the furnace wall so as to move therewith, means provided below said grate and stationarily supported independently of the furnace to rcceivethe ash from the rate,- said means and the lower end of the furnace being movable relative to each other in a vertical and lateral direction, said means having formed at its upper end immediately below the lower end of the furnace a channel extending horizontally thereabout and having a liquid disposed therein, plate means extending downward from the furnace below the grate and into said channel and liquid and effectively sealingly interconnecting the furnace and said means while permitting said relative movement therebetween.

3. In an organization of the type described a vertically disposed furnace of generally rectangular transverse section and having vertical side-by-side heat exchange tubes lining the inner surface of its walls, a fixed foundation, a support framework secured thereto and extending above the furnace and interconnected therewith in a manner to permit the furnace to expand downward with the lower end of the furnace being free for this purpose, the lower portion of a pair of opposed walls of the furnace being inclined inwardly toward each other to form a basket type bottom having a restricted throat portion extending across the furnace, certain of the tubes lining these inclined walls being laterally bent relative to their adjacent through said openings into thefurnace, means for introducing an ashbearing fuel into the furnace and=which requires a grate in order to obtain complete combustion, a grate disposed across the furnace immediately below said throat to receive fuel and have the same burn thereupon thereafter-"discharging the remaining ash, said grate being effectively connected to and supported from the lower end of said tubes and accordingly said'furnace walls so as to move therewith,,means for introducing air below and forcing it up through said grate, means provided be-. low said grate and stationarily supportedindependently of the furnace to receive ash from the grate with this 7 means and'the furnace being movable relative to each other a predetermined distance in. a vertical and horizontal direction, an upwardly open trough provided at and extending about the upper end of the last mentioned 7 means and substantially filled with a liquid, a perimetrical wall extending downward from the bottom of the furnace and received within said trough to form a seal while per- 'mitting relative movement between the furnace and this last mentioned means.

4. In combination, a vertically disposed furnace of generally rectangular transverse section, the walls of said furnace including vertical heat absorbing tubes disposed along their inner surface, a framework disposed about said furnace and interconnected generally with the upper end thereof so that the furnace may expand downward with the lower end of the furnace being free for this purtube at the location of the throat to form passages for pose, the lower portion of a pair of opposed walls of the boiler being inclined inwardly toward each other to provide a reduced cross section at'the lower end of the furnace, means for introducing an ash bearing fuel into the furnace which requires a grate in order to obtain complete combustion, a chain grate disposed in the lower end of the furnace for supporting a layer of burning fuel, said grate being effectively supported from the lower end of said tubes and accordingly said wall so that it moves therewith, means for introducing and passing air upwardly through the grate, means below said grate and stationarily supported independently of the furnace to receive ash from the grate the last named means and the lower end of the furnace being movable relative to each other in a vertical and lateral direction, and means providing a seal between this last mentioned means and the lower end of the furnace that is substantially fluid tight but permits such relative movement.

5. In a furnace which is vertically disposed and has its walls lined with vertical side-by-side heat exchange tubes and which is suspended from its upper portion so that it expands downward with its lower end being free for this purpose, the combination of a chain grate disposed across the bottom of the furnace and the upper run of which is adapted to have fuel disposed and burned thereon, said grate being connected to and supported by the lower end of the furnace walls so that it moves therewith, an enclosure disposed about the grate with an ash discharge opening being provided in the enclosure at the discharge end of the grate and with the enclosure being secured to and forming a portion of the furnace, means providing an ash pit below said discharge opening and stationarily supported independently of the furnace to receive said ash, said means and said furnace being relatively movable a predetermined distance in a vertical and horizontal direction, means operative to effectively interconnect the ash pit means and said enclosure about the outlet formed therein in a substantially fluid tight manner permitting said predetermined relative movement.

6. In an organization of the type described the combination of a vertically disposed furnace having vertical side-by-side heat exchange tubes lining the inner surface of its walls, a fixed foundation, a support framework secured thereto and positioned about the furnace and interconnected therewith in a manner to permit the furnace to expand downward with the lower end of the furnace being free for this purpose, a chain grate disposed across the a lower end of" the furnace so the upper runfthereof is adapted to have fuel disp'osedland burned thereon, said grate being connected :to and-supportedby the loweinend of 'the furnaceso'that itiinovestherewith, anenclosure disposed'about the grate with the enclosure being secured to andforrning a portionof-the; furnace and having an ash discharge opening at the discharge end of the grate,

end of the ash pit means within which said wall is loosely received to permit said relative movement, said trough having a liquid disposed thereinin engagement with said wall .and forming a seallbetween'the furnace and the ash pit while permitting the required relative movement therebetween. I

References Cited in the file of this patent UNITED STATES PATENTS I Bailey Q. June 14, 1932 1,863,181 2,337,634 Berry Dec. 28, 1943 Schoessow Jan. 29, 1952

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