US1782096A - Superheater boiler - Google Patents

Description

Nov. 18,

W. F. KEENAN, JR., ET AL SUPERHEATER BOILER Filed April 10. 1928 4 Sheets-Sheet l INVENTORS MLTER /T K55/VAN JR.

HAROLD E EDDY fg@ #M4/@iff Nov. 18, 1930. w. F. KEENAN, JR., ET AL 1,782,096

SUPERHEATER BOILER Filed April 10, 1928 4 Sheets-Sheet 2 lNVENTOR WALTER K55/VAN JR.

HAROLD fam' BY d ATTORNEY Nov. 18, 1930. w. F. KEENAN, JR., ET AL 1,782,095

SUPERHEATER BOILER Filed April 1o, 1928 4 sheets-sheet s "Wi- M 1 1 l x n l l INVENTORS WALTER E /fEENA/v JR HAROLD E EDDY I Nov. 18, 1930. w. F. KEENAN, JR., ET AL 1,782,096

SUPERHEAT'ER BOILER Filed April l0, 1928 4 Sheets-Sheet 4 lNVENTORS HAROLD EDDY WAL T51? E /ffE/VAN Jn.

Patented Nov. 18, 1930 UNITED STATES PATENT ol-rlclaz WALTER EHEENAN, JB., or PELHAJM,- NEW Yoan, AND HAROLD E. EDDY, or JAcxsoN, MICHIGAN, AssIGNoEs :ro FOSTER WHEELER coEPoBATIoN, or' NEW YoEx,.N. Y., A

CORPDRATlON F NEW YORK SUPEBHEATEB BOILER Application led April 10,

The general object of our present invention is to provide a superheater boiler with improved means for utilizing radiant heat,

absorbed from the combustion chamber of 6 the boiler, in superheating steam. Our present invention is characterized by features of construction and arrangement differentiating it from radiant heat superheaters heretofore in use, and giving it certain distinct and char- 10 acteristic advantages'. v

While other forms of radiant heat superheater constructions have been proposed there are, so far as we are aware, but two forms or types of such superheaters which have been 16 found to be practical, or at least have been put into successful commercial use.

Of these, the form most important and successful from thecommercial standpoint, is characterized by the fact that the walls of 2 0 the superheater conduit elements are thick, the wall thickness being several times that ofasteeltubestrongenough to resist the bursting tendency of the internal. steam pressure.

l. Ordinarily, these thick walled radiant heat superheater elements are arranged side by side so as to form a practically continuous and smooth wall furnace exposed to the combustion chamber.` Such elements need to be anchored' at their-backsto a substantial reinforcing frame to prevent objectionable distortion of the conduit elements by the expansion and contraction stresses to which .they

are subjected. Those stresses are of considerablema itude because ofthe high rate of heat to heat radiation, and because all of this heat must be absorbed at one side onl of ,each element. The exposed side of eac 1 element is therefore at a considerably higher temperature than the opposed side of the element, and this sets up unbalanced internal stresses which would cause excessive and prohibitive bowing of the elements if the latter were not anchored at points along their length to an external supporting structure of sufficient strength to keep the bowing' within practical limits.

'The temperature diiference between the front and rear faces of each such superheater element is minimized, and the effective heat absorption per unit of suface area exposedv 1928. Serial No. 268,908.

absorption increased by the thick walls of the elements which conduct a considerable amount of heat from the radiant heat absorbing sections of the elements to the side and rear portions, of the walls surrounding the steam channels in the elements. But while the relatively great wall thickness thus tends to minimize temperature differences between different portions of the conduit walls, the

. difference in temperature between the front and rear walls of each conduit is nevertheless substantial, and the ve thickness of the walls provided to minimize the temperature difference, augments the stress creating tendency of the temperature dierence which is not eliminated. The approximately continuous and smooth heat absorbing face of a superheater of this type is of an advantage in that it is comparatively easy to remove furnace dust and ash deposits on said surface, such deposits ybeing especially heavy, and of series consequence if not removed, with certain coals, and especially 's in the case of powdered coal burning furnaces.

The second type of radiant heat superheater which has had some successful commerical application, is one consisting of tubular vertical elements placed in back of a screen formed byl water cooled tube elements which are spaced apart so that the superheater elements are exposed to radiation from the combustion chamber only through comparatively narrow spaces between water cooled tubes in front of the superheater elements.

It is one of the practical advantages of the prior type of superheater last mentioned, that the superheater elements are thin walled round tubes. The last mentioned type of superheater is o pen to the disadvantage, however, thatits capacity is inherently low because of the relatively small surface area of each superheater element effectively exposed to radiant heat from t-he combustion chamber. The effective capacity of such a superheater is reduced; moreover, by the fact that the superheater elements radiate heat to, and are cooled by the screening water tubes. In such a superheater, the s acing of the screening waterl tubesand of t e superheater tube' elements is prescribed lwithin.

vtil) .relatively narrow limits by the conditions of use. The water tubes must be spaced far enough apart to permit a substantial penetration of radiant heat to the superheater tubes, and must not be spaced far enough apart to seriously impair the water screen protective effect which is a characteristic of this type of superheater. The spacing of the water tube elements and of the superheater elements is necessarily inter-related, and unless the superheater elements, in a superheater of this type are spaced fairly closely, it is impossible to secure a superheater capacity which is adequate from the commercial standpoint. p

Thel presence of the water screen tubes in front of the su erheater elements and the characteristic re atively close spacing of the tubes, is conducive to the accumulation of furnace dust and ashes in t-he spaces between the Water tubes and the superheater tubes to an extent permitting the furnace dust and ash deposits to bridge across the spaces between the superheater and water cooled tubes. The effective removal of such furnace dust and ash deposits by means of steam or air jets is a much more difficult matter than is the removal of the deposits forming on the smooth walled superheater types lirst de* scribed, particularly when ashes tend to form a somewhat plastic form of slag as occurs with some kinds of coal.

In4 accordance with the present invention, we employ superheater elements which are preferably round thin walled tubes, and which are Widely spaced away from one another, and from the furnace wall in front ofwhich they are disposed, so that while more i heat is necessarily absorbed at the combustion chamber side of each tube than at its oppositeside, the absorption at the rear is high enough to reduce internal stresses due to unequal absorption to an amount which is unob'ectionable in the case of such thin walled tu es.

The relatively wide spacing of the tubes permits a substantial heat absorption by the rear sides of the latter, and permits of a greater amount of heat absorption by an element of given steam flow capacity than is possible with either of the two prior types of radiant heat superheaters mentioned above. The increased capacity per element is especially marked, o course, as com ared with the rior type of superheater emp oying thin wa ed tube elements. Furthermore, our in'- vention eliminates, or greatly minimizes, the troubles due to furnace dust and ash accumulations experienced with the last mentioned pior type of superheater, since the distances tween adjacent tubes, and between the tubes and furnace wall back of the tubes, are too great to permit of any bridging across of slag or ash deposits from tube to tubefor from tubes to wall. Furthermore, the invention permits of ample room for suitable cleaning provisions, and the cleaning operation is relatively simple and easy, since all, or the major portion of the work to be done on the superheater consists merely in the removal of deposits on the thin walled elements themselves. Such deposits are of relatively minor importance because the smooth circular surfaces of the suprheater elements gives minimum opportunity for the adherence of slag or furnace dust to the metal, particularly when the tubes are vertically disposed as is ordinarily desirable. Furthermore, the slight movements lof the elements due to expansion and contraction when heating and cooling', combine to produce an intermittent crac'liing action on any slag that may have deposited on the superheater elements. rllhe effect of said cracking action obviousl tends to increase with the thickness of the eposit. When the tubes are vertically disposed, slag loosened by the cracking action described, falls clear of, and away from the superheater elements.

When it is desired to obtain amaximum superheating capacity with superheater tubes .arranged in accordance with the present invention, those tubes will ordinarily form the only cooling screen immediately associated with the furnace wall in front of which they are disposed. llnsome cases, however, li may advantageously combine such tubes with a water cooled lining for the furnace wall back of the tubes, or with a superheater lining for that wall formed by superheater elements of either of the prior types described above, where a greater furnace wall cooling eect, or an additional superheating eiect, or both, are considered necessary or desirable. rlhe use of a water cooled wall lining back of superheater tubes arranged in accordance with the present invention, provides the additional advantage of protecting the tubes in vstarting a boiler into operation, or in other conditions of operation in which the superheater tubes are not protected against overheating by'an adequate flow of steam through the latter. The use of such a water cooled furnace wall lining is advantageous, also, because of the lower temperature of the water cooled walls which of itself practically eliminates any tendency to slag or ash to deposit on the -hning to any signicant amount.

As previously pointed out, a limited amount of such movement of the tubes of our improved superheater as results from expansion and contraction, is of itself desirable. Where the exposed lengths of the tubes are comparatively short, say live feet long, or so, the tube elements are preferably supported at their ends only, and the end portions of each element are ordinarily bent at right angles to the length of the body portion o the 'element and project through the furnace wall for connection to external headers. Where conditions make it desirable to employ substantially longer superheater tube elements, the latter may well be anchored to the furnace wall at one or more intermediate points in the length of each element. Such intermediate anchorage with long tubes is not intended or relied upon to prevent such movements, in response to temperature changes, as occur with the shorter elements which are not anchored except at their ends.

The various features of novelty which characterize our invention are pointed out with particularity-in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, and 'the advantages possessed by it, reference should be had to the accompanying 'drawings and descriptive matter in which we have illustrated and described preferred embodiments of the invention.

f Of the drawings:

Fig. 1 is a sectional elevation of a portion l of a boiler furnace in which a preferred form vof the present invention is incorporated;

Fig. 2is a front combustion'chamber side view of the apparatus shown in Fig. l; v

Figs. 3 'and 4 are views taken similarly to Figs. 1 and .2, respectively, illustrating a modified construction;

Fig. 5- is a partial section on the line 5-5 lof Fig. 4;

Figs. lGrand 7 are views taken similarly to Figs. 1 and 2, respectively, illustrating a third modification; v

Fig. 8 is a somewhat diagrammatiorepresentation of the external headers employed vin the construction shown in Figs. 6 and 7;

Figs. 9, 10 and 11 are views each taken similarly to Fig. 1, and illustrating adiiferent arrangement of means for anchoring a tube element at points intermediate its ends;

Figs. 12 yand 13 are plan and elevation views respectively of a further modification (ill having intermediate anchoring means.

In the constructlon shown 1n F1gs. 1 and 2,

l Ay represents a combmstion chamber wall in which is mounted a'fradiant heat superheater embodying a preferred form of the present invention, and comprising superheater elements in the form of round thin walled tubes B. The body portions of the tubes B are parallel to, and are spaced away from the f inner surface of the furnace wall A. The end portions of each tube element extend transversely to the length of the body ortion through openings A and A2 in the urnace wall, and are connected to external' headers C and D. As shown, each'element end portion passes longitudinally through the central portion of the corresponding opening A or A2. The inner end of each opening A and A2, adjacent the combustion chamber, is partially j filled by refractory bricks E. The weight of each element B is mainly supported by means of a metallic' block or chair F anchored at the bottom of the corresponding passage A. Gas leakage through the pas-v, 1

sages A and A2 may bey prevented in any usual or suitable manner, for example, by

packing the joints with kieselguhr or analogous relatively non-rigid refractory material y adapted to yield to accommodate such relative movements of the partsfas result from thermal expansion and contraction. i l

With the described construction, the body l portions of the tubes B are spaced away from,

the face of the wall A an appreciable dis-jv tance, so lthat a portion of the heating gases may flow between the wall and said body-por- I tions which therefore absorb l'radiant `heat from the gases at all sides. In addition, when the wall A is of refractory material, as inthe construction shown in Figs. 1 and`2, the wall absorbs radiant heat from all portions of the combustion chamber and re-radiates heat to the adjacent sides of the tubes B. In any event, moreover, the tubes B, owing to the` fact that they are separated from one another by an appreciable distance, each receives'radiant heat from the main portion ofthe com-l bustion chamber through a circumferential arc portion of its surface ofappreciably lmore than 180 F. In con/sequence, while the rate v of heat absorption by the tubes B is greatest atthe side of each tube B directly vfacing, the combustion chamber, the heat absorption by the remaining surface of each tube is'substam tial, and large enough to greatly reduce the distortion tendency experiencedwhentheheat `absorption is confined wholly or mainl to a limited portion of the tube directly acing f ters inches or greater, and the distancebe-f tween the furnace wall B and the adjacent sides of the tubes B varies between four and twelve inches. It will be understood, how'- 'ever, that a wide variation in the spacing of the tubes relative. to one another and to the adjacent furnace wall is possible, and that the dimensions stated, are given by way of example and illustrative discription, and not by way of-positive limitation. y

With the adjacent tubes B separated from one another and the wall A by substantial distances as described, there is no tendency in ordinary practice, for furnace dust and ashes to bridge across the spaces between adjacent tubes, and between the tubes and the furnace wall A. Furnace dust and ashes depositing on the tubes and between the tubes all suitable openings K in the combustion cham-.s

tion of the tubes is of small consequence owing to the length of the transverse end connections and the flexibility of the latter re sulting from their substantial length and the Afact that they are thin walled tubes. Minor distortion or bowing of the elements, w1ththe spacing described, does not result in disadvantageously changing the relative spacy ing of the tubes relative to -one another or to the wall A.

In some case s superheater tubes B of the character shown in Figs. 1 and 2, may advantageously be combined, as shown in Figs. 3, 4

. 4and 5, with other heat absorbing elements G which may themselves constitute part of a furnace wall superheater or may form part of the water circulating system of the boiler to' which the furnace pertains. In the particular arrangement shown in Figs. 3, 4 and 5, the tubes G comprise body (portions longer than the tubes B and exten ng above and below the transverse end portions of the latter, and vthemselves having transverse end portions extending through the furnace wall `A into engagement withupper and lower headers G and G2, respectively. As shown, the header' G is seated upon a furnace wall bracket A10 through which the superheater header C is suspended by connections C. The header G2 is shown as suspended from the header D bya connection G3 and strap D2 encircling the header D, the latter being suspended through said strap D2 and a suspension' member D from a Wall vcarried bracket A11. As shown, the suspension'member D acts on the bracket A11 through a compression spring D3, thus permitting some movement of approach and separation of the headers D and G2 relative to the headers C and G', respectively, as the tubes B and G contract and elongate with changes in temperature, thereby reducing the bending stresses impressed on the transverse end connections of the tubes B and G.

' In the particular arrangement shown in Figs. 3, 4 and 5, the tubes G are thin walled water tubes of an external diameter slightly less than the distance between the adjacent tubes B, and the body portion of each tube G is seated in a metallic wall lining portion formed by sectional saddle blocks H. The latter are interposed between the tubesand refractory material A8 arranged between the saddle blocks H and an outer wall casing A.

Advantageously the saddle blocks H engagf ing each tube G, are welded to the latter. As'shown in Fig. 5, the saddle blocks for adjacent tubes G meet edge to edge and battens L close the joints between the adjacent saddle blocks and thereby prevent the maf the tubes B is less than with the construction v shown in Figs. l and 2, there is nevertheless, an appreciable absorption ofheatat the sides of the tubes B adjacent the furnace wall.

In lieu of using a water wall lining for the furnace wall in front of which the superheater tubes B are disposed, a wall liningformed by superheater elements,`such as the elements I of the construction shown in Figs. 6, 7 and 8, may be employed, especially where additional superheating beyond -'that furnished by the tubes B is desirable. `As shown; the superheater elements I are of the standard heavy Wall type, each element being rectangular in cross section and bein at its ends to headers J and JA t rough relatively iexible transverse I. As shown, theelements are horizontally disposed and the headers J and JA are correspondingly vertical. f

As previously explained, the arrangement shown in Figs. 6, 7 and 8 is especia sirable where a relatively high superheating elfect is desired and to this end the super.- heater elements I and B may be connected for lsteam flow therethrough in series. In the arrangement shown in Figs. 6, 7 and 8, an inlet J to the header J ,constitutes the steam inlet to the compound su erheater.; From the header J the steam flows '1n parallel 4through the diferent elements I to the opposite header JA. From thence it flows through dividedoutlet pipes J 2 to-inlets D', opening to the header DA atone side of a partition D3 which separates the latter into two steam chambers. The steam thus supplied to one half of the header DA passes through the corresponding tubes B to the other header CA. From Y'the latter the steam passes to the other half of the header DA- through the corresponding tubes B. The outlet 'connection D2 to said other half of the'header DA,

constitutes the superheater steam outlet from the compound superheater. D"represents a safety valve connection.

As previously pointed out, when the tubes' B are of moderate length they do not need to be reinforced or supported except b their connected 1pipes or` nipples connections to the headers. When suoli tubes w are appreciably longer, however, they may advantageously be supported at points intermediate their ends. For examp1e,.as shown in Fig. 9, the elements BB may have lugs B5 welded thereto at their rear sides to which are attached bolts L extending outward through the adjacent furnace Wall and suitably counected to external framework shown as comprising channel bars M. In Fig. 9, the masonry furnace wall AB is shown as corbelletl out to provide seats A12, for the body portion of the elements BB at each side of each lug B5. j

In order to reduce the bendingstresses to which the transverse end connections are subjected as a result of the expansion and contraction of the body portions of the tubes, particularly when the latter are relatively long, said body portions may be bent. For

example, as shown in Fig. 10, the elements l may be bent tubes BC, shaped to provide two shown in Fig. 10, the tubes BCmay or may not be supported intermediate their ends, as by connecting the overlapping portions of 85 adjacent tubes, or by means of anchor coniections LA analogous to those employed in Another example of a construction employing long tubes is shown in Fig. 11. In the 'latter figure the tube elements BD have their body portions bowed to provide a central portion which approaches the furnace wall A, andmay or may not be anchored tol the latter by tie bolts L as conditions require or 'make desirable'.

While the special arrangements shown in Figs. 9, 10 and 11 give more opportunity for the lodging of furnace dust or ashes in the l superheater, and between the latter and the furnace wall than with the simple Yconstruction of Figs. 1 and 2, the general arrangement lis such. that it is vcomparatively easy to dis'- l'odge deposits of furnace dust and ashes by steam lances or the like. The removal of dust and ashes from the tubes proper is ordinarily facilitated by a vertical disposition of the tubes, but with such arrangements as are shown in Figs. 9, 10 and 11, it is sometimes advantageous to have the elements horizon.

tally disposed since this makes it easier to minimize and'to eliminate accumulationsof furnace dust and ashes between the elements j and the furnace wall, where the elements extend into `proximity with the latter, and, in the case of the construction shown in Fig. 10,

to get rid of dust and ashes tending to accuf mulate where the portions of adjacent elements cross one another adjacent their centers.

In Figs. 12 and 13, a further modification is shown vin which vertically spaced'pairs of bare tube elements BE are extended horizontally in front of the furnace wall AC. The elements are of great length and in one installation were made approximately twent three feet long. Each element is preferab divided into two sections, the opposite endys of which are connected to the headers C and D and the adjacent ends of which pass through the masonry wall AC. The adjacent tube ends are connected by a flanged return bend BE externally of the furnace wall. The middle portion BE2 of each section is mounted in a metallic wall box W, which ex tends through the masonry section of the wall AC. The looped ortions BE2 are anchored in position by .bolts W secured to angle beams W2. .The spaces between and around the legs of the loops BE2 are filled with plastic fire-brick Y and refractory cement Y. The outer side of the furnace wall is covered by refractory cement AC? which can be easily removed to make the loop anchoringmeans accessible fromthe outside. Similarly the adjacent ends of the` tube sections pass through a wall box W andare h ld by U-bolts W', the space between the l gsV being filled with removable .refractory material.

While in accordance with the provisions of the statutes, we have illustrated`and described the best form of embodiment of our invention now known to us, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus r'bent into the form of a loop or bight and disclosed without departing from the spirit A of our invention as set forth in the appended claims and that in some'cases certain features of our invention may be used to advantage without a corresponding use of other features.

Having now described'our invention, what we claim as new and desire to secure by' Letters Patent, is:

1.' The combination with'the combustion chamber wall of a boiler furnace, of thin walled radiant heatsuperheater tube elements adjacent said wall at the furnace chamber side of .the latter and freely exposed to. heat radiation from the portion of the' combustion chamber in front of said elc- 'ments, said elements being spaced apart from one another and from said wall to avoid -slag bridging action between said elements and between the latter and said wall, and to permit of substantial radiant heat absorption from gases between said elements, and between saidl` elements and said wall as Well as from the latter.

2. The combination with the combustion chamber wall of a boiler furnace, of thin walled radiant heat superheater tube elements adjacent said wall at the furnace chamber side of the latter and freely exposed to heat radiation from the portion of the combastion chamber in front of said elements,

*Y said elements being spaced apart from one another and from said wall to avoid slag bridging action between said elements and between the latter and said wall, and to permit of `substantial radiant heat absorption from gases between said elements, and between said elements and said wall as we`ll as from the latter, said elements having outturned end portions projecting through said walls and external headers to which said end portions are connected.

3. The combination with the combustion chamber wall of a boiler furnace, of thin walled radiant heat superheater tube elements adjacentsaid wall at the furnace chamber side of the latter and freely exposed to heat radiation from the portion of the combustion chamber in front of said elements, said elements being spaced` apart from one another and from saidwall to avoid sla bridging action between said elements and between the latter and said wall, and to permit of substantial radiant heat absorption ments adjacentsaid wall at the furnacechamber side of the latter and freely exposed to heat radiation from the portion of the combustion chamber in front of said elements, said elements being spaced far enough apart from one another and from said wall to avoid slag bridging action between said elements and between the latter and said wall and to permit of substantial radiant heat absorption from gases between said elements, and between said elements and said walls, and other wall cooling conduit elements lining said walls.

5. The combination with the combustion chamber Vwall of a boiler furnace, of thin walled' radiant heat superheater tube elements adjacent said wall at the furnace chamber side of the latter and freely eX- posed to heat radiation from the portion of the combustion chamber in front of said elements, said elements being spaced far enough heater conduit elements .lining said walls and connected to the first mentioned conduit elements for steam vflow in. series through conduits in the two sets.

6. Thev combination with a `combustion chamber wall of a boiler furnace, of thin walled radiant heat superheater elements adjacent said wall on the combustion chamber side of the latter, said elements being spaced apart from one another and from said wall to avoid slag bridging action between said elements and between the latter and said wall and to permit of radiant heat absorption from gases between said elements, and between said elements and said wall as well as from the latter and from the portion of the combustion chamber in front of said elements, said elements being bent between their ends to provide outwardly extending bights or loops extending into said wall, and means for anchoring said loops in place.

7 The combination with a combustion chamber vwall of a boiler furnace, of thin wal-led radiant heat superheater elements adjacent said wall on the combustion chamber side of the latter, said elements being spaced apart from one another and from said wall to avoid slag bridging action between said elements and between the latter and said wall and to permit of radiant heat absorption from gases between said elements and be` tween said elements and said wall as well as from the latter and from the portion of the combustion chamber infront of said elements, metallic boxes mounted in said wall, and said elements being bent between their ends to provide bights or loops extending through said wall boxes, and means for anchoring said loops in place.

8. The combination `with a combustion chamber wall of aboiler furnace, of a row of thin walled radiant heat superheater tube elements adjacent said wall at the furnace chamber side of the latterand freely exposed to heat radiation from the portion of the combustion chamber in front of said elements, said elements being substantially spacedapart from one another and from said' wall to avoid. slag bridging action between said elements and between the latter and said wall, and to permit'of substantial radiant heat absorption from gases between said elements, and between said elements and said wall as well as from the latter, said elements having outturned end portions projecting through said walls, external headers to which said end portions are connected, and means for supplying .a cleaning fluid under pressure to the space between said row of tube elements and said wall.

9. The combination with a combustion chamber wall of a boiler furnace, of a row of thin walled 'radiant heat superheater tube elements adjacent said wall at the furnace chamber side of the latter and freely exposed to heat radiation from the portion of the i combustion chamber in front of said elements, said elements being substantially -spaced apart from one another and from said wall to avoid slag bridging action between said elements and between the latter and said wall, and to permit.of substantial radiant heat absorption from gases between said elements, and between said elements and said wall as well as from the latter, said elements having outturned end `portions rojecting through said Walls, external hea ers to which said end portions are connected, soot blower openings in a second wall of said I chamber normal to said first mentioned wall,

and soot blowers mounted in said openings and arranged to supply a cleaning Huid under pressure to thespace ,between said row of tube elements and said lirst mentioned wal Signed' at New York city, in the county of New York and State of New York, this 31st day of March, A. D. 1928.

WALTER F. KEENAN,- JB. Signed at Jackson, in the county of Jackson and Stateof Michigan, this 5th day of April, 1928.

HAROLD F. EDDY.

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