US3534713A - Flow circuit for division wall - Google Patents

Description

, United States Patent a corporation of New York [54] FLOW CIRCUIT FOR DIVISION WALL 4 Claims, 1 Drawing Fig.

[52] U.S.Cl 122/240,

122/406 [51 Int. Cl ..F22b37/70 [50] FieldofSearch.. 122/235,

[56] References Cited UNITED STATES PATENTS 2,255,086 9/1941 Savoye 122/235 2,758,574 8/1956 Kuhner 122/240 3,324,837 6/1967 Gorzegno et al 122/406 FOREIGN PATENTS 1,059,287 11/1953 France 122/235 Primary Examinerl(enneth W. Sprague Att0rneys- Richard H. Thomas, John Maier Ill and Marvin A.

Naigur ABSTRACT: A flow circuit for a once through subcritical vapor generator including a division wall of the type in which vertically oriented parallel tubes of the division wall are substantially in the same plane and are bent near the bottom thereof to penetrate a sidewall of the furnace at approximately a 3(l-slope from the horizontal, the tubes penetrating the sidewall being one above the other. The tubes are connected to an inlet header disposed outside the furnace in a horizontal plane to provide along its length essentially the same quality fluid, the tube connections between the inlet header and division wall tuhes being bent and routed so that the tube lengths from the inlet header to the outlet header of the division wall are kept approximately the same.

FURNACE WALL Patented Oct. 20, 1-970 FURNACE WALL INVENTOR. WALTER F? GORZEGNO ATTORNEY FLOW CIRCUIT FOR DIVISION WALL The present invention relates to a flow circuit for a oncethrough vapor generator, and in particular, to a flow circuit including a partial division wall of a subcritical generator which is located in the generator circuitry so that it receives a vapor and liquid mixture.

A division wall is a panel of vertically extending parallel tubes disposed within a furnace enclosure about in the middle of the furnace. The division wall has the same heat absorption function as other walls or panels of the vapor generator, but design features of the wall may vary for different generators depending upon the position of the wall in the overall generator circuitry and the quality of the fluid which the wall receives. For instance, the division wall may be used for super heating a fluid vaporized elsewhere in the generator, or it may be used between the economizer and vapor generating components. It may also be used as a vapor generating surface, between furnace circuits and superheating circuits of the generator.

As vapor generators and furnace cross sections increase in size in accordance with today s trend, the use of a division wall for additional furnace absorption becomes almost mandatory. The present invention contemplates a division wall which is located in the furnace circuitry of a subcritical vapor genera tor at a point where it receives a vapor and liquid mixture.

Also in accordance with the invention, the division wall is only partial, extending from above the burners to the top of the furnace coextensive with only the upper part of the furnace enclosure. This has the advantage that the vapor and liquid mixture enters a pass which is in a low heat absorption area of the furnace. In addition it is possible to fit more burners in the furnace than with a full division wall so that burner clearance is not a concern. Further the need for stainless and high chrome ferritic steel, required where higher tube metal temperatures are involved, such as with a steam cooled full division wall, is not present when departure from nucleate boiling is avoided by design. Preferably, the division wall follows or is downstream of the furnace and convection pass enclosure circuits and upstream of the primary superheater.

In that the division wall is only partial, and is positioned only in the part of the furnace above the burners, connections with the lower end of the division wall to the rest of the generator circuit are made by bending the panel of tubes near the bottom of the division wall so that they extend, still as a panel, in a 30-slope from the horizontal direction penetrating the front or rear wall of the furnace enclosure. This means that the division wall tubes on the inside of the bend will be shorter in overall length than those on the outside of the bend. The resultant differences in pressure drop in the tubes could cause a flow upset in the division wall.

In a subcritical vapor generator, the fluid may be either in a vapor phase or a liquid phase, or it may be a mixture thereof. Every panel of tubes, including division wall tubes, requires a header to transmit the flow to the tubes, and if the header is vertically oriented, in the case of a subcritical unit, a steam phase will exist at the top of the header, and the heavier liquid phase at the bottom. This means that some of the connections disposed longitudinally along the header will receive a liquid flow, and some will receive a vapor flow, resulting in uneven fluid flow and enthalpy distribution in the division wall panel resulting in high tube temperatures, temperature differences, and stresses within the panel. To avoid these conditions requires that a horizontal header be used.

In accordance with the invention, it was found that such a horizontal header could advantageously be connected with a partial division wall in a way to overcome the problem of different tube lengths in the division wall.

Accordingly, by the invention, for a once-through vapor generator flow system, there is provided a furnace which includes front rear and side walls defining an upright furnace enclosure. A division wall within the furnace enclosure is positioned in the generator circuitry to receive a steam and water mixture. The division wall comprises a plurality of tubes defining a vertically oriented panel which has a lower section extending at an angle thereto penetrating the furnace enclosure front or rear wall. Overall, the division wall panel is approximately l shaped with the tubes on the inner side of the bend of the division wall being progressively shorter than the tubes on the outer side of the bend. A horizontal header for the division wall is positioned outside of the furnace enclosure, centered with the plane of the division wall, and connecting tubes are provided between the header and division wall tubes connected to the header spaced along the length thereof extending upwardly and then sideways to connect to selected tubes of the division wall. Centermost connecting tubes will be shorter in length than those removed from the center of the header, and the progressively longer connecting tubes will be routed to the progressively shorter division wall tubes so that the overall tube lengths between the inlet and outlet headers for the division wall are kept approximately the same.

Successive tubes of the division wall are alternately connected to left and right connecting tubes from the inlet header so that the quality of flow across the division wall remains as uniform as possible.

The invention and advantages thereof will become apparent upon further consideration of the specification, with reference to the accompanying drawings, in which:

The FllG. is a schematic section view illustrating a flow circuit in accordance with the invention.

Referring to the FIG., there is illustrated a furnace enclosure 12 comprising a plurality of parallel tubes 14, the enclosure encompassing an upwardly extending division wall 16 also made up of a plurality of parallel tubes 18. The furnace enclosure generally will have four walls, a front wall, a rear wall, and side walls, and will be rectangular in cross section. The division wall tubes will extend upwardly in the furnace enclosure as a panel centered between the enclosure side walls and lying in a plane going from the enclosure front wall to the enclosure rear wall. The tubes of the division wall may be welded together as required along their lengths so that the panel is essentially rigid.

In accordance with the present invention, the division wall contemplated is only a partial division wall, extending from a plane above the burners of the furnace enclosure (not shown) to the top of the enclosure. Accordingly, the division wall tubes 118 will be bent outwardly near the bottom of the division wall so that they extend on approximately a 30-slope from the horizontal through a generator wall, in this instance penetrating the generator front wall. The significant aspect of the partial division wall is that the tubes of the division wall will penetrate the furnace wall enclosure at an angle thereto, and will thereby define an upper vertical extent 20 and a lower sloped extent 22, together defining an approximate L shaped configuration. e

Usually the division wall tubes will be aligned into a single plane, with the vertical extent and horizontal extent both lying in the same vertical plane. In this way the tubes on the inner side 24 of the bend of the division wall will be shorter than the tubes on the outer side 26 of the panel bend; or, referring to the panel array outside of the generator enclosure wall, the upper tubes of the division wall will be shorter than the lower tubes.

Outside of the furnace wall, but parallel to the wall and below the division wall tubes, there is provided a horizontally disposed cylindrical header 28. The length of the header depends upon the number of tubes in the division wall, and numbers of connections 30 between the header and division wall. As illustrated in the FIG., the header is centered with the plane of the division wall, and the connections 30 between the header and division wall are longitudinally aligned and spaced along the top of the header in fluid communication with the inside of the header. Preferably the connections extend vertically from the header in a single plane aligned with the axis of the header to define a span parallel to the generator wall, and then are bent horizontally to connect with selected tubes of the division wall. In that the middle or center of the header is aligned with the plane of the division wall, it can be described as having righthand connections to the right of center (facing the enclosure wall l2), and lefthand connections to the left of center. The centermost connection centered along the header simply extends upwardly a short distance until it is at a level with the lowermost tube of the division wall, and then is connected to that tube. The first connection to the left of the centermost connection extends a slightly greater distance upwardly and then to the right for connection with the next highest tube of the division wall. Similarily, the first tube on the righthand side of the centermost tube extends even further upwardly until it is at the same level with the third tube from the bottom of the division wall, and then is bent towards the plane of the division wall for connection with that tube. The fourth connection is on the lefthand side of the centermost connection, and the fifth connection is on the righthand side, and so forth, with left and righthand connections being joined alternately with successive tubes of the division wall.

Above the division wall, the tubes thereof are connected to outlet header 29.

lt is apparent that the shortest connections near the center of the header will be connected to the longest division wall tubes, i.e., the lowermost tubes or those on the outside of the division wall bend; and that the longest connections will be connected to the shortest division wall tubes, or tubes on the inside of the division wall bend. By suitably dimensioning the connections, the overall tube lengths between the division wall inlet and outlet headers can be kept approximately the same. In this way flow upsets caused by variations in total tube length are avoided in the division wall,

To introduce a fluid into the horizontal inlet header, a downcomer 32 spaced from the surface of the generator and coming from convection wall enclosure passes or other suitable surface is connected to a bottle 34, which in turn is provided with legs 36 leading to intermediate bottles 38 provided with connections 40 between the intermediate bottles and the header 28. The latter connections are evenly spaced lengthwise of the header, so that a fluid entering the downcomer is distributed evenly to the header.

Since the header 28 is disposed on a horizontal plane and supplied at frequent locations along its length, there will be no major separation of fluid in the header into liquid and vapor phases. Accordingly, a connection on the righthand side of the header furthermost removed from the centerline thereof should receive essentially the same quality fluid as a connection on the lefthand side furthermost removed from the header centerline. By connecting successive tubes of the division wall alternately to the right and lefthand sides, should there be a difference in distribution of fluid in the header 28 from center to an end, there will be a similar distribution created in the division wall from rear to front. A final balancing of outlet fluid enthalpy leaving each portion of the division wall can then be achieved by orificing the division wall tubes in groups.

Some of the other advantages accruing from the invention have been mentioned. For instance, a water and steam mixture enters a furnace pass which is in a low heat absorption area of the furnace. In addition, it is possible to fit more burners in the furnace than with a full division wall so that burner clearance is not a concern. Finally the use of stainless and ferritic high chrome steels used in full steam cooled division walls is not required when departure from nucleate boiling is avoided by proper design considerations.

Although the invention has been described with reference to a specific embodiment, variations within the scope of the following claims will be apparent to those skilled in the art.

lclaim:

l. A once-through vapor generator flow system comprising a furnace including at least one wall defining an upright furnace enclosure, burners disposed in said furnace enclosure, a

division wall within the furnace enclosure positioned in the generator circuitry to receive a vapor and liquid mixture, the division wall comprising a plurality of tubes defining a vertically oriented panel, the panel being disposed in a plane at right angles to the enclosure wall and including a section thereofwhich is bent in said plane so that the tubes thereof extend toward and penetrate the enclosure wall, a horizontal header for the division wall, a plurality of connection tubes spaced along the length of the header in flow communication therewith connected with preselected tubes of the division wall, the connecting tubes being dimensioned lengthwise thereof and routed to compensate for differences in lengths of the division wall tubes said header being beneath the lowermost tube of the division wall lower extent. the connecting tubes being spaced uniformly along the top surface of the header and extending upwardly and then horizontally to connect to the division wall tubes the horizontally disposed header being at right angles to the plane of the division wall tubes and including a center aligned with the plane of the division wall tubes, the connecting tube centered on the header being connected to the lowermost tube of the division wall, successive connecting tubes removed from said centered tube being connected to the division wall tubes above said lowermost tube, left and righthand connections being connected alternately with successive tubes of the division wall.

2. A once-through vapor generator flow system comprising:

a furnace including at least one enclosure wall defining an upright furnace enclosure;

a division wall within the furnace enclosure positioned in the generator circuitry to receive a steam and water mixture;

the division wall comprising a plurality of parallel tubes defining a panel, said panel including an upper vertical extent and a lower approximately 30-slope from horizontal extent, each tube of the division wall having an approximately L shaped configuration;

both said extents lying in the same vertical plane, the 30- slope from horizontal extent penetrating said enclosure wall;

a cylindrical horizontal inlet header for the division wall positioned in a horizontal plane lower than the lowermost tube of the division wall, at right angles with the plane of the division wall, said header including a center between the header ends lying in the same vertical plane as the division wall;

means to distribute a vapor and liquid mixture to said division wall inlet header;

an outlet header for the division wall;

tube connecting means connecting the inlet header with the division wall tubes comprising a plurality of connecting tubes at spaced intervals along the header in flow communication with the header each including a vertical leg extending upwardly from the inlet header and a horizontal leg extending to connect with a selected tube of the division wall, the vertical and horizontal legs of the connecting tubes defining a vertical plane aligned with the axis of the inlet header;

left and righthand connecting tubes being connected alternately to successive tubes of the division wall; and

the innermost shorter connecting tubes relative the center of the inlet heater being connected to the lowermost and longer division wall tubes, the connecting tubes being dimensioned lengthwise to compensate for difference in tube lengths in the division wall tubes.

3. A flow system according to claim 2 further including a burner centerline wherein the division wall is above said center line.

4. A flow system according to claim 3 wherein said division wall is sized to produce a vapor flow at the outlet header thereof.

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