US2583265A - Grate fired fluid heating unit - Google Patents

Description

Jan. 22, 1952 R. c. HUSTON GRATE FIRED FLUID HEATING UNIT 2 SHEETS-SHEET 1 Filed March 6, 1948 INVENTOR {imp/ C Hus zon 01W ATTORNEY Jan. 22, 1952 R. c. HUSTON CRATE FIRED FLUID HEATING UNIT Filed March 6, 1948 ATTORNEY Patented Jan. 22, 1952 GRATE FIRED FLUID HEATING UN IT Ralph "C. Huston, Wadsworth, Ohio, assignor to The 'Babcock & Wilcox Company, Rockleigh, N..J., a corporation of New Jersey Application March 6, 1948, Serial'No.,13,369

7 Claims.

' l The present invention relates in general to the construction and operation of a fluid heater having a grate-fired furnace, particularly with ref- Hence to the disposition of fluidiheating surface associated with the :furnace walls.

In fluid heaters of the vapor generator or steam boiler classification, it is common practice to employ grate-fired furnaces having fluid cooled side walls in which rows of upright fluid conducting tubes are connected .to headers ar.-'

ranged marginally of the grate, make-up liquid being fed to the headers at intervals along their lengths. Such headers are necessarily of relatively large cross section and for the higher boiler operating pressures are .necessarily of heavy wall thicknesses. When thick walled headers are installed marginally of a grate, it is found that heat cracks often develop in header surfaces directly exposed to the burning bed of fuel, sometimes after onlylimited periods of service. This is due to the high temperature gradient through i the thick header wall which causes the wall metal to become overheated. The effect is accentuated when the furnace is operated under forced draft, .as a result of the higher rtemperatures involved, and particularly when blow holes are .formed in thin areas of the bed and localized zones of intense heat are created, the risk of damage to metals adjacent the firing zone ordinariiy being increased when coals of a bituminous character are :employed.

A purpose of my invention therefore is to provide a grate .fired fluid heating unit .in which .fluid cooled furnace wall areas may bedirectly eX- ,posed to the burning bed of fuel with a minimum risk of injury to the metal of fluid conducting elements, irrespective of the character of fuel being burned. I

. Another object pertainingmore particularly to the construction .of a grate fired fluid heater furnace, having fluid conducting elements of relatively large cross section marginally of the grate, is to provide a fluid cooledmetallic barrier or shield betweensuch elements and the bed of fuel, the barrier to be formed of tubes .of relatively small cross section so as to enable tubes having relatively thin walls to be used for a "given operating pressure as compared with the relatively thick walled fluid'conducting elements "of larger cross section.

A further object isto arrange the tubularheat fbarrier'in such manner as to be more readily "renewable than the fluid cooled element shielded thereby.

.An object is also to support the tubular barrier unit from theshielded element and to pro- .vide for the circulation of fluid therethrough in parallel-with the main circulatory system of the fluid heating unit.

The various features of novelty which characterize my'invention are pointed out with particularity in the claims annexed to and forming a 'part'of this spectification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have :illustratedand describedselected embodiments of my invention.

Of the drawings: Fig. 1 is .an elevational View in section of a sicker fired vapor generating unit including an illustrative embodiment of my invention;

Fig. 2 is a partial vertical section of the unit shown in Fig. 1,-taken :along line 2-2;

Fig. 3 is a fragmentary detailed enlargement of Fig. :1 featuring the fluid-cooled structure ad jacent the grate;

Figs. 4, 5 and 5 are transverse .sections taken respectively along lines 4-4, 5-5, and 6-6, of

Fig. 3; and

Fig. 7 is a fragmentary enlargement of Fig. 3, rotated through 90'.

The vapor generating unit as illustrated in Fig. 1 comprises a steam boiler of the bent tube type having its major convection heating surface provided by banks of tubes I2, 13, [4 extending between and connected to an upper, steam and water drum l5 and a lower, muddrum .16, a

superheater ll havingsteam inlet connections ill from drum l5 being disposed between the front tube bank 12 and the intermediate tube bank 43. A stoker'fired boiler furnace l9, having its combustion chamber 21 arranged forwardly of the front boiler bank l2, is provided with fluid cooled boundary walls comprising side walls 23, of which one only is shown, airont wall -24, a rear wall 25, and a roof 26. The stoker firing apparatus includes a traveling chain grate 21 having its top run 28 movable from front to rear across the bottom of combustionchamber 2i and receiving coal or other solid fuel delivered thereto from stoker apparatus 29 arranged exmriorly of the furnace adjacent the lower end of its front wall 24. Air for combustion is delivered under pressure in suitable known manner to the space between the upper and lower runs of the grate. A chain guide member 3i, or series of such members, is disposed along each margin of the top run 23 and mounted in known manner on the grate supporting structure. An ash discharge hopper or pit 32 is provided adjacent the rear end of the grate.

Furnace walls 23, 24 and 25 are cooled by fluid conducting tubes 23a, 24a, and 25a, respectively, while the roof 26 is cooled by upper extended portions of the front wall cooling tubes 24a, and all furnace wall cooling tubes are connected into a natural circulatory system which includes boiler drums I and I6 in a manner hereinafter more fully described.

A lower portion of front furnace wall 24 is inclined upwardly and rearwardly to provide an ignition arch 34 above a front portion of the grate 21, while a lower portion of the rear furnace wall 25 is inclined upwardly and forwardly to provide an arch 35 above a rear portion of the grate, the arches 34 and 35 cooperating to define a throat passage 36 of smaller gas flow area than the combustion regions immediately upstream and downstream thereof. A wall 31 extends from the upper end of rear arch 35 to the lower boiler drum I6 to provide an outer boundary wall portion of the boiler tube space.

The front wall tubes 24a are connected at their lower ends to a header 38 which extends horizontally above the grate 21, in upwardly spaced relation thereto adjacent the lower end of the front ignition arch 34, the lower portions of tubes 24a extending upwardly adjacent the inner face of the arch and having their exposed surfaces protected by a layer of heat refractory material 39 applied thereto. The upper ends of tubes 24a are connected to the upper boiler drum I5.

The rear wall tubes 25a are connected at their lower ends to a header 4I disposed rearwardly of the grate 21, beyond the ash pit 32, and extending horizontally at an elevation below the top run of the grate, the header 4I having tubular make-up water connections 42 with the lower boiler drum I6. The upper ends of tubes 250. are connected to the upper boiler drum I5 between the connections provided for the tubes of boiler banks I2 and I3. The lower portions of tubes 25a extend upwardly adjacent the inner face of the rear furnace wall 25 where they are directly exposed to furnace heat whereas, above the wall 25, intermediate portions 25b of these tubes are inclined rearwardly and upwardly to provide support for a bafiie 43 which defines,

with roof 25, a passageway 45 through which heating gases are directed into contact with convection heated surfaces of the boiler and superheater. An upright bafiie 41, disposed adjacent the forward side of tube bank I3 and constituting an upper extension of baflie 43, terminates in downwardly spaced relation to the upper boiler drum I5 to define an entrance for gases into the space containing tube banks I3 and I4, the gases discharging from the space through outlet 48.

In each side wall 23, a circular lower side wall header 56 extends horizontally adjacent the top run 28 of the grate, each header 5!! having the lower ends of tubes 23a of the associated wall 23 connected thereto, and having tubular makeup water connections 5! with the lower boiler drum I6, the make-up connections or tubes 5| having their lower ends connected to the respective headers 50 at spaced intervals therealong as indicated in Fig. 3. The upper ends of tubes 23a in each side wall 23 are connected to an upper header 52 from which riser tube connections 53 extend to the upper boiler drum I5.

Each header 5!) is supported at intervals along its length by means of support members 54 and 56 mounted on a plate 51 associated with the 4 grate supporting structure. As shown, each member 54, adjacent the rearward end of each header 50, is in the form of a rectangular plate vertically aligned with the centerline of the header and having its upper edge secured by welds 58 to the header and its lower edge secured by welds 59 to plate 51. 7 Each member 56, as shown, includes a rectangular base plate portion 6I together with integral upright plate like portions 62 and 63 arranged at right angles to each other, the portion 62 being arranged longitudinally of header 50, in vertical alignment with the centerline thereof and having its straight upper edge secured thereto by welds 64, and the portion 63 extending transversely of the header and having its arcuate upper edge conforming to the circular contour of the header and being secured thereto by welds 65. Each support member 56 is permitted to move relative to plate 51 in unison with the longitudinal movement of header 50, each base plate portion 6I being disposed between spaced guide bars 61 suitably secured as by welds 68 to plate 51. Each header 56 is thus free to expand forwardly from its point of stationary support on member 54 adj acent its rearward end.

Each lower side wall header 50 is shielded from contact with the moving bed of burning fuel on the grate by means of a group of tubes II extending longitudinally of the header adjacent the furnace side thereof, the tubes II being of relatively small diameter as compared with the diameter of a header 50, for example, in a ratio of an order of about 1:3. In each side wall 23, the header protecting tubes II have their intermediate length portions straight and parallel to each other, and also parallel to the header 50 with which each group is associated, these intermediate straight length portions also extending beyond the respective headers 50 at both ends. Tubes II have their rearward end portions bent downwardly and connected to the rear wall downtake header 4|, and have their forward end portions bent upwardly and connected to the front wall uptake header 3B. As thus connected, the tubes II receive water fed from transverse header M and act as water supply tubes to the transverse front header 38, a natural circulation through tubes II being induced by the head differential resulting from steam generation in the front wall cooling tubes 24a which extend from the header 38 to the steam and water drum I5.

The tubes II are arranged in groups of threes, for example, in the pattern indicated in Figs. 4, 5 and 6, with the lowermost tube of each group resting on asbestos rope I2, or the like, received in a groove in the upper edge of chain-guide 3|. As herein illustrated, each tube II is in contact with the tube next adjacent, while the uppermost tube is additionally in contact with header 50. Tubes II are retained in position adjacent each header 50 by means of tie bolts I3 having their outer ends bent to engage tie loops I4 which are welded to the respective tubes II, and having their inner ends threaded and received in slots I5 in the respective angle members 16 which are arranged in longitudinally spaced groups as shown in Fig. 3, with the members of each group secured to the headers 50 in longitudinally and circumferentially spaced relation. The inner end of each bolt I3 is fitted with a nut I8 bearing against a washer I9 which is preferably tackwelded to the respective angle member I6 after the associated tube II is tied in place. Although not illustrated. the outer bent end of each tie bolt 33 may be arranged at right angles to the body portion of the bolt and fitted with a nut to facilitate assembly and also to prevent disengagement from within the loop 14. Thus the tie bolts hold the tubes H in predetermined parallel relationship to the furnace face of the side wall header while providing for differential expansion with respect thereto. The space between the assembled tubes H and each header 59 and support plate '5'? is enclosed at its outer side by a plate member BI having its upper edge portion overlapping and secured to a bar, or bars, 82 attached to header 50, the space thus enclosed being filled with loose asbestos 83, or the like, to provide a seal against the escape of furnace gases.

While in accordance with the provisions of the statutes I have illustrated and described herein the best form of my invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

I claim:

1. In a furnace having a grate associated with the combustion chamber thereof, a fluid conducting header arranged marginally adjacent the fuel supporting surface of said grate, a group of fluid conducting tubes paralleling said header at the side toward said grate, and means tying said tubes to said header and maintaining successive tubes of said group in contacting relationship.

2. In a furnace having a grate associated with the combustion chamber thereof, a fluid conducting header arranged marginally adjacent the fuel supporting surface of said grate, a group of fluid conducting tubes arranged in vertical superj acent succession alongside of and parallel to said header at the side toward said grate, and means tying said tubes to said header and maintaining successive tubes of said group in said superjacent relationship.

3. The combination as defined in 'claim 2 wherein the tying means is formed of separate components each having a connection to said header and a connection to one of said tubes.

4. The combination as defined in claim 2 wherein the tying means is formed of separate components individually engaging one of said tubes and comprising a loop member secured to the tube and a tension member having one end in engagement with said loop.

5. The combination as defined in claim 4 comprising a group of members secured to said header at circumferentially spaced positions for engagement by said tension member components.

6. In a furnace having a grate in the combustion chamber thereof, a fluid conducting header associated with a wall of said chamber and extending marginally adjacent the fuel supporting surface of said grate, a group of fluid conducting tubes arranged longitudinally of said header at the side adjacent said grate, said tubes being tied to said header by means holding said tubes in predetermined transverse relationship while permittin longitudinal movement thereof relative to said header, and means for supporting said header at longitudinally spaced points by means maintaining said header fixed at one of said points while permitting longitudinal movement thereof at other points therealong.

7. In a furnace having a combustion chamber defined in part by an upright wall arranged at one side of a grate extending across said chambar, a fluid conducting header associated with said wall and extending longitudinally of said grate at an elevation adjacent the fuel supporting surface thereof, a group of fluid conducting tubes arranged at successive elevations alon the inner face of said header, means tying said tubes to said header at spaced points therealong while permitting longitudinal movement of said tubes relative to said header, and means for supporting said header at longitudinally spaced points by means maintaining said header fixed at one of said points while permitting longitudinal movement thereof at other points therealong.

RALPH C. HUSTON.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,456,649 Poppenhusen May 29, 1923 1,456,650 Poppenhusen May 29, 1923 1,999,984 Bailey et al Apr. 30, 1935 2,005,082 Greenawalt June 18, 1935 2,159,557 Heller May 23, 1939 2,186,919 Bailey Jan. 9, 1940 2,196,889 Bailey Apr. 9, 1949 2,250,536 Kennedy July 29, 1941 2,333,078 Wallis et al Oct. 26, 1943 2,333,644 Ebbets et al Nov. 9, 1943 2,412,568 Donahue et a1 Dec. 17, 1946 FOREIGN PATENTS Number Country Date 109,565 Australia Jan. 25, 1940 500,882 Great Britain Feb. 16, 1939

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