US2976857A - Vapor generator with panel superheating means - Google Patents

Description

March 28, 1961 C. J. HEROLD VAPOR GENERATOR WITH PANEL SUPERHEATING MEANS Filed Dec. 5, 1958 2 Sheets-Sheet 1 INVENTOR Conrad J. Herold Km A. vim

ATTORNEY March 28, 1961 c. J. HEROLD 2,976,857

VAPOR GENERATOR WITH PANEL SUPERHEATING MEANS Filed Dec. 5, 1958 2 Sheets-Sheet 2 Fig. 3.

INVENTOR Conrad J. Herold J} K M A4 f ATTORNEY VAPOR GENERATOR WITH PANEL SUPERHEATIN G NmANS Filed Dec. 3, 1958, Ser. No. 777,960

1 Claim. (Cl. 122-478) This invention relates to vapor generators and particularly to modern high capacity generators which employ panel type radiant superheaters which extend into the furnace of the vapor generator.

With the steadily increasing capacity that is being called for in modern utility boilers it has been necessary to employ a substantial amount of radiant superheating surface in order to obtain the steam temperature for which these units are designed. It is the general practice to provide this steam heating surface in the form of radiant panels that extend down into the vertically disposed furnace to an area of rather intense heat with the panels being formed of sinuously bent, internested tubes. The panels are spaced across the furnace in rows and because of the length of the panels it is necessary that there be some means to laterally support the lower ends since otherwise they would vibrate and move around to an extent that could not be tolerated. One of the most widely used methods of supporting these panels is to extend a thick walled water cooled tube, across the furnace with the tube being provided with spacers between which is embraced one of the tubes of each panel and with the tubes of each panel themselves being connected together by suitable connectors which prevent relative lateral movement of adjacent tubes. This horizontal thick walled support tube, however, is itself a source of trouble in the steam generator since the furnaces of these high capacity steam generators are 40 or more feet across and this horizontal tube is necessarily in a zone where it is subjected to very intense heat. Stratification will occur in this tube with steam occupying the upper portion while water occupies the lower portion and this causes the upper portion to overheat and accordingly fail and also causes internal erosion in the upper portion of the tube with this erosion occurring particularly in the lengths of the tube between the panels where the spacer tube is exposed to extreme heat and high combustion gas flow. While a spinning device may be positioned in the tube to eliminate the Stratification this adds a considerable pressure loss which is detrimental in natural circulation boilers and in forced circulation boilers would require that the pump for the circulating system be of such a size as to overcome the pressure loss or drop which will exist in this tube and which would be greater than that in other tubes of the steam generator with it being very uneconomical to size a pump for this particular support. The present invention is directed to eliminating these difiiculties.

In accordance with this invention lateral support for the superheater panels that extend down into the furnace of the steam generator is provided by suitably bending a pair of adjacent tubes that line the furnace wall next to the panel so these tubes extend from this wall into the furnace forming a generally horizontally disposed U or loop, with the upper run of this loop having the panel snuggly but slidably embraced between the pair of tubes while the outer end or web and lower run are positioned in relatively closely spaced relation to the end of the atent F 2,976,857 Patented Mar. 28, 1961 panel. With this arrangement not only is the lower end of this panel restrained from moving laterally but this U-shaped support provides, to an appreciable degree, a shield from the intense heat in this zone of the furnace. This is extremely important when it is considered that the return bends that make up the lower ends of the panels have the poorest heat dissipating capacity or heat transfer of the entire panel and are located in the most intense zone of heat of any part of the panel. They have the poorest heat dissipating capacity because these return bends act, to an extent, as separators for foreign material with this material being deposited against thevtube Wall as the direction of steam flow is reversed thereby causing a thin scale of this material to form on the inside of the tube reducing the rate of heat transfer and accordingly the cooling effect of the steam. This may result in the metal at this turn overheating and eventually cause 'a tube failure. Accordingly, partially shielding the return beads of these panels is extremely desirable in order that this likelihood of tube failure may be greatly reduced if not completely eliminated.

it is an object of this invention to provide an improved vapor generator organization employing radiant vapor heating panels extending longitudinally into the furnace, with the furnace being lined with heat exchange tubes.

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 description of an illustrative embodiment said embodiment being shown by the accompanying drawings wherein:

Fig. l is a somewhat diagrammatic illustration in the nature of a vertical section through a high capacity vapor generator within which is embodied the present invention;

Fig. 2 is a detailed fragmentary elevational view showing the furnace wall tubes at the location where the tubes are bent laterally from the wall to provide the lateral Fig. 4 is a fragmentary perspective view showing two of the superheater panels embraced within the support tubes which are bent from the adjacent furnace wall.

Referring now to the drawings, wherein like reference numerals are used throughout to designate like elements, the illustrative and preferred embodiment of the invention shown therein includes an upright furnace 10 which is fired with a suitable fuel generally in its lower region through burners 12 with the combustion gases generated by the burning fuel passing upwardly through the furnace and out through the lateral discharge passageway 14. The furnace is of the usual rectangular transverse section and may be 30 ft. deep and 40 ft. wide with the inner surface of the furnace walls being lined with steam generating tubes 16 which are connected at their lower ends to header 18 and communicate at their upper end with steam and water drum 20. Water from this drum passes down through downcomer 22 which is connected at its lower end with pump 24 and this pump is effective to force the water through the steam generating tubes.

The steam generated in the steam generating tubes is superheated by means of the superheater designated generally 24 and which includes the radiant panels 26 and the convection panels 28. Each of these panels are made up of a group of tubes that are connected between inlet header 30 and outlet header 32 with the tubes extending down from the inlet header 30 through the roof of the furnace to a zone in the furnace of intense radiant heat where they are reversely bent and extend back up to the upper end of the furnace with the downwardly extending and upwardly extending runs of ,these tubes forming the radiant panel 26 of the superheater and with the returnbends being internested. These tubes extend from this radiant panel laterally adjacent the upper end of the,

furnace to the passageway 14 where they again extend downwardly and then upwardly and through the roof to header 32 and from the convection panel 28.

Radiant panels 26 are normal to and spaced across front wall 34- of the furnace and the pair of vertically extending steam generating tubes that line the inner surface of this front wall immediately adjacent each radiant panel and at the location of the lower end ofthe panels are bent outwardly to form a 'U or loop extending from the wall and which is arranged to provide lateral support for the lower end of panels 26 and to shield the return bends of these panels from some of the intense radiant heat in the furnace. These .U bends, designated generally 36, comprise upper run 38, lower run 40 and interconnected web portion 42. As clearly shown in Fig. 4, the upper run 38 of the pair of tubes bent from the wall 34 adjacent panel 36 snugly embraces the panel therebetweenwhile the web 42 and the lower run 40 are in relatively closely spaced relation with the return bends at the lower end of the panel so as to partially shield the panel from the flame in the furnace. Wehportions 42 of the pair of tubes are provided with laterally extending fins 44, as shown, with the fins that extend toward each other abutting and being welded together throughout their" length thereby providing a rigid construction. While the upper runs 38 of the U bends which embrace the panel 26 therebetween are effective to substantially prevent,

lateral movement or vibration of the panel they permit the panel to slide vertically so that the tubes of the panel may expand and contract as required.

At the location of the U bends 26, the tubes that line wall 34 and that are adjacent to the tubes that are bent from this wall have a portion (40 in Figs. 2 and 3) bent slightly towards each other so as to occupy a portion of I the space normally occupied by the pair of tubes that form the superheater support and are provided with fins 41- While I have illustrated and described a preferred embodiment of my invention it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without 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 3 within the'purview of my invention.

What I claim is:

A vapor generator including an upright furnace of generally rectangular transverse section having front, rear and side walls with the furnace exit for combustion gases being in the upper end of said rear wall, burner means including tubularpanels extending down into the furnace ofthe furnace and providing a lateral support for the I from the upper end thereof with the panels being adjacent and normal to said front wall and disposed in spaced relation thereacross, each of the panels being formed of a plurality of immediately adjacent tubes that extend vertically down into the furnace from the top thereof to a pre. determined distance where they are reversely bent in in-;

H 1 lower end of the panels comprising a pair of front wall tubes adjacent each panel having adjacent portions bent in unison from the wall and extending into the furnace to form generally a loop with the lower leg of each pair a being in adjacent relation to and below the lower end of the panel while the upper leg of the pair forms an entube portions forming the outer end of the loops with 'the fins being in abutting relation and welded together,

the wall'tubes adjacent each of the pair of tubes bent to extend into the furnace being finned at the location of the bent tube portion to fill the space left thereby.

References Cited in the file of this patent UNITED STATES PATENTS 2,803,227 Marshall Aug. 20, 1957 r V FOREIGN PATENTS 1,065,921 France Jan..l3, 1954

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