US2796048A - Gas tube vapor generator - Google Patents

Description

June 18, 1957 E. A. KAzMlERsKl 2,795,048

GA3 TUBE VAPOR GENERATOR Filed oct. 8, 1953 ATTO R N EY GAS TUBE VAPOR GENERATOR Elias A. Kazmierski, Bernardsville, N. J., assignor to The Babcock & Wilcox Company, New York, N. Y., a corporation of New Jersey Application October 8, 1953, Serial No. 384,999

2 Claims. (Cl. 122-7) This invention relates in general to Vapor generators and particularly to improvements in upright gas tube vapor generators, of a type in Which hot gases are passed 'through tubes which are disposed inside and coextensive with the length of an upright liquid containing shell.

Current operation practice indicates that gas tube vapor generators of the above type are required to operate at higher rates of heat absorption and with higher ternperature heating gases than heretofore. The heating gases which in most cases are industrial waste gases, are available at temperatures high enough to cause overheating of the parts of the unit subject to direct exposure thereto unless adequate cooling of these parts is insured.

When high temperature heating gases are introduced into re, or hot gas tubes which are connected into a top tube sheet of the upright liquid containing shell of such units and which extend downwardly through this shell, the vapor which is formed normally rises to the top of the shell Ifrom whence it is passed through risers extending from the side of the shell to a liquid and vapor drum arranged above the shell. In units where the heating gas temperatures are l500 F. or more, the vapor which for-ms in the shell may tend to collect in stationary pockets adjacent the top tube sheet. In such cases it may happen that neither the liquid in the shell nor the generated vapor Vformed along the inside surface of the tube sheet will circulate `fast enough to wet the sheet and thereby absorb the heat input to which the tube sheet is subjected.

In order to electively use high temperature heating gases in yunits of this type, the invention includes an up right gas tube vapor generator with riser tubes extending from the top tube sheet of the liquid containing shell to the liquid and vapor drum. The risers connect to the places inside the liquid shell where vapor pockets may tend to form and provide a positive liquid supply to these areas. These riser tubes provide a steam and water flow which prevents the `formation of vapor pockets by providing an exit `for the vapor as it is lformed and also by providing a constant supply of cooling liquid to the top of the liquid drum.

With the foregoing in mind, it is an object of the present invention to provide a novel gas tube vapor generator construction in which the metal surfaces of the liquid shell are constantly cooled by liquid or vapor, or a mixture of the two, and which unit will operate eiciently within a wide range of heating gas temperatures.

The various features of novelty which characterize the 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, its operating advantages and specic objects attained by its use', reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a specific embodiment of the invention.

Of the drawings:

Fig. 1 is a sectional elevation of a gas tube boi-ler States Patent fi? ICC constructed in accordance with the invention, taken on the line 1-1 of Fig. 2;

Fig. 2 is a front elevation of the gas tube boiler shown in Fig. l;

Fig. 3 is a partial sectional view taken on the line 3 3 of Fig. l; and

Fig. 4 is an enlarged sectional view of the top tube sheet of the boiler of Fig. 1 showing lgas tube and steam riser tube connections to the water shell.

The upright gas tube boiler shown in Figs. 1 to 3 comprises, in general, a horizontally disposed cylindrical steam and water drum 10, and a vertically elongated cylindrical liquid containing shell 12, which is inclined slightly from the vertical, in .this instance 10, positioned below and to one side of the steam and water drum 10, and connected to the steam and water drum by downcomer tubes 14 and groups of riser or vent tubes 16 and 18 which interconnect the dr-um and the top of the shell. The drum 10 and the shell 12 are supported on a structural framework, comprising vertical columns 20 interconnected by cross bracing such as 22, 24 and 26. The drum 10 is horizontally disposed upon and supported on the cross members 22, as by means of brackets 28. The shell 12 extends generally upwardly, but with its axis inclined, from the vertical, and has secured thereto brackets 30 whichsupport it on cross members 24 and 26. The described supporting arrangement permits substantially unrestricted relative expansion and contraction of the drum and the shell and their associated iiuid interconnections.

A plurality of downcomer or fwater make-up tubes 14 extend from the bottom water space of the steam and water drum to the bottom portion of the water shell. Two groups of these downcomer tubes, .14a and 14h, are bent around each side of, and connected into, the lower portion of the water shell on the side opposite the steam and water dnurn. Another group, 14C, is connected into a lower portion of the water shell on the side adjacent to the steam and water drum.

A plurality `of heating gas, or tire tubes 32 are disposed inside of, and extend the `full length of the shell 12. These tubes are connected into upper and lower circular end plates, or tube sheets, 34 and 36 respectively. Holes of a diameter large enough to permita gas tube to extend therethrough are cut into each tube sheet and the gas tubes are arranged to extend through corresponding upper'and lower tube sheet holes parallel to the elongated shell axis.

A cylindrical Wall 3i with an inside refractory liner 33 is arranged to define a heating gas supply passage or upper vestibule 35 above the tube sheet 34, and a similar cylindrical wall 37 with a refractory liner 39 defines a lower cooled gas exit passage or vestibule 41 below the tube sheet 36. The upper cylindrical wall encompasses portions of the length of the riser tubes 16 and 18. The remaining portions of these riser tubes extend through the cylindrical wall 31, through holes cut therein for that purpose. The tubes are surrounded by asbestos gaskets 43 at the Wall holes.

The steam and water drum `10 is supplied with water through a feed connection 38 and the water level inside the drum is indicated by a gage glass which maybe connected to ttings 4i). The water level of the whole unit normally extends above the t-op riser tube connection in the steam and water drum. Steam which is generated in the unit is collected in the upper portion of the drum lll and discharged through a steam outlet 42 to a point of use. Safety valves 44 are provided in the upper portion of the drum 10 to permit a b-loW off of steam in the event the steam pressure exceeds a safe operating limit.

In accordance with the invention, a plurality of riser tubes 16 and 18 are arranged to interconnect the steam and water drum and the upper portion of the liquid space of the shell. The riser tubes comprise a plurality of tubes arranged Vin two groupsl and ltotaling, in `this instance, fifty-two tubes, but a number more o r less than fifty-two can be used. The tubes in y.group 16 -are composed of rise'r tubes which connect into the steam and water drum `at the side thereof which is adjacent Vthe shell, and the tubes of the group 18 are composed of the riser tubes on the opposite side `of the drum 1t) which are connected into the top of the water shell 12. These tubes are arranged to connect into the shell top tube sheet on either side of tire tube connections thereto and are spaced so that they connect at points distributed over the whole tube sheet, with the major portion of them being connected into the uppermost or highest portion.

Heat transferred from the heating. gas flowing through tubes 32 generates steam in the water kspace of the shell 12, and the mixture of steam and water thus formed is discharged through riser tubes 16 and 18 to the drum 1t). The connections of the ends of the riser tubes 16 an-d 18 to the upper tube sheet 34 are so arranged as to spacing and attachment that the ow of a mixture entering the tubes from the sheet wets the inner or lower surface' 48 of the tube sheet. Heat which is transferred into the metal of the sheet from the heating gases passing through the passage 35 into gas tubes 32 is absorbed by the flow of the mixture of steam and water below the inclined tube sheet.

Referring to Figs. l and 3 the majority of the riser tubes are positioned toward the highest part of the inclined shell head. They are perpendicular to the top tube sheet and extend parallel to the shell sides for a portion of their length above the top tube sheet. The riser tube intermediate portions are arranged at an inclination from the horizontal, and the top end portions are bent for radial connection to the drum 10. The described arrangement of riser tubes insures the discharge of streams of steam and water mixture from transversely spaced positions within the upper portion of the shell. With the lowermost portion of tubes 16 and 18 extending normal to the tube sheet optimum liquid and vapor ow conditions into and through the tubes are produced. The expedient of extending the tubes normal to the tube sheet and parallel to the heating gas ow also contributes to optimum gas flow conditions approaching the entrance to the gas tubes 32 and provides additional heat absorbing surface, thereby reducing the gas temperature at the tube sheet 34.

A refractory gas-deflecting ring 45 completely encircles the top of the tube sheet. A portion of this ring extends above the uppermost riser tube 18a at the highest point on the shell. It prevents hot gas irnpingement on an uncooled portion of the upper tube sheet above the highest liquid source from the riser tube 18a.

Referring to Figs. 3 and 4, both the riser tubes 16 and 18 and the gas tubes 32 are connected into the top tube sheet 34. The gas tubes extend slightly beyond each tube sheet, when in place, and the overlapping portions are held in position in the sheets by pressure tight seal welds 46 which are applied to the outside projecting edges. Similar gas tube connections are made at the lower tube sheet 36. The riser tubes 16 and 18 are inserted into the tube sheet 34 to -a position slightly short of the' inner tube sheet surface 48 and beyond annular grooves 50, which are previously cut around the inside circumference of the walls of the holes in the tube sheet. When the tubes are in such a position, they are expanded into the tube sheet holes so that tube metal extends into the annular grooves 50 for a tight fit. The tubes are then seal welded, as at 52, around the outside tube portions adjacent the tube sheet, and re-expanded. Care is exercised to insure that the riser tubes do not extend below the tube sheet inner surface 48. Vapor pocket formation on the inner surface of the tube' sheets at positions in back of n'ser tube projections, which might occur if the riser tubes 4 extended beyond the inside of the sheet, are thus avoided.

In operation, hot heating gases are directed toward the top tube sheet through the' gas passage 35 and around the riser tubes 16 and 18 and into the gas tubes 32. These hot gases then pass downwardly through the gas tubes and out through the gas passage 41. Heating gases are normally passed through from top to bottom. However, the unit may be operated -by lpassing heating gas from the passage 41 upwardly through the re tubes and out through the passage '35. In the described arrangement the hottest portion of the .unit is at the top of the shell 12, around the top tube sheet 34 which is ordinarily exposed to the high temperature incoming gases. A mixture of liquid and steam is generated by the heat of the gases passing through the gas tubes.

The described construction is characterized by a plurality of riser tubes 16 and 18 which connect from the liquid portion of the steam and water drum directly into the top of the water shell. Thus, these tubes are always filled with Water, or waterl and vapor mixture, which water or mixture acts to absorb heat from the contacted surrounding metal parts. Any steam that forms is conducted up through these riser ltubes `and into the steam and water drum. With the riser tubes thus arranged, steam vapor does not accumulate beneath the top tube sheet. All the metal surfaces, including the tube sheets, are constantly cooled by the ywater vor a mixture of water and the steam that is generated. There are no hot spots caused by a vapor accumulation which might fail to adequately cool the contracted lmetal surfaces and, as a result, the parts of the unit have a much longer life, with no tendency to overheat.

While in -accordance with the provisions of the statutes, there is illustrated and described herein a specific form of the invention, thoseskilled 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 as covered by the claims, and that certain features of the invention may sometimes be used to advantagev without a corresponding use -of other features.

What is claimed is:

l. A vapor generator comprising an upper elongated horizontally varranged vapor-liquid separating drum, a lower vertically elongated boiler shell inclined slightly from the vertical having upper and lower parallel inclined at tube sheets constituting the ends of said shell, a plurality of heat transfer tubes extending between and connected to said upper and lower tube sheets for the flow of a heating uid therethrough, said tubes uniformly arranged to substantially ll .the interior of said shell, means for supporting said upper drum and said boiler shell in offset relation to provide independent thermal expansion between said drum and said shell, a plurality of iiexible downcomer tubes connecting the liquid space of said drum to the lowermost portion of said boiler shell at circumferentially and uniformly distributed positions, and a plurality of exible riser tubes connecting said upper drum to the uppermost portion of said boiler shell at uniformly distributed Vpositions over the entire area of the upper fiat inclined tube sheet.

2. A vapor generator comprising an upper elongated horizontally arranged vapor-liquid separating drum, a lower vertically elongated boiler shell inclined slightly from the vertical having upper and lower parallel inclined flat tube sheets constituting the ends of said shell, a plurality of heat transfer tubes extending between and connected to said upper and lower tube sheets for the flow of a heating Huid therethrough, said tubes uniformly arranged to substantially fill the interior of said shell, means for supporting said upper drum and said boiler shell in ottset relation to provide independent thermal expansion between said drum and said shell, a plurality of liexible downcomer tubes connecting the liquid space of said drum to the lowermost portion of said boiler shell at circumferentially Vand uniformly ydistributed positions, a plu- S 6 ralty of flexible riser tubes connecting said upper drum References Cited in the le of this patent to the uppermost portion of said boiler shell at uniformly UNITED STATES PATENTS distributed positions over the entire area of the upper at inclined tube sheet, and means for connecting said 119731968 Welgel et al Sept' 18 1934 boiler shell at said tube sheets in a heating iluid duct for 5 FOREIGN PATENTS gell? flow 0f heafmg uld through Sald heat trans- 187,567 Great Britain Feb. 22, 1923 146,927 Austria Sept. 10, 1936 843,698 Germany Iuly 10, 1952

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