US3299858A

US3299858A - Vapor generator wall construction

Info

Publication number: US3299858A
Application number: US453371A
Authority: US
Inventors: Franzmann Karl
Original assignee: Babcock and Wilcox Ltd
Current assignee: Babcock International Ltd
Priority date: 1965-05-05
Filing date: 1965-05-05
Publication date: 1967-01-24
Anticipated expiration: 1984-01-24

Description

1967 K. FRANZMANN VAPOR GENERATOR WALL CONSTRUCTION 2 Sheets-Sheet 1 Filed May 5, 1965 Y m R O z m T n N a R E r 0 W T .T 2 H .A a 2 9 1 2 H K 2 oooooomvdooooooooo F G Y F. w /0 B Jan. 24, 1967 K. FRANZMANN 3,299,858

VAPOR GENERATOR WALL CONSTRUCTION Filed May 5, 1965 2 Sheets-Sheet 2 United States Patent VAPOR GENERATOR WALL CONSTRUCTION Karl Franzmann, Oberhausen, Rhineland, Germany, as-

signor to Babcock & Wilcox, Limited, London, England, a corporation of Great Britain Filed May 5, 1965, Ser. No. 453,371 11 Claims. (Cl. 122-6) This invention relates generally to tubular fluid heat ing units and more particularly to a steam generator having a furnace or radiation chamber which is bounded by a wall formed with parallel contiguous fluid-cooled tubes, rigidly united along their lengths to form a gas-tight wall panel.

In a modern high capacity steam generator, there is a considerable pressure differential between the furnace or combustion chamber and the outside atmosphere. Where, as in the usual installation, the combustion air is pressurized sufiiciently to overcome the total fire-side draft loss of the unit, the combustion chamber or furnace will be operating at a substantial positive pressure. On the other hand, when gases are drawn through the unit, as by an induced draft fan, the furnace may be operating under negative pressure. In either instance, there normally results a considerable pressure differential across the boundary walls of the furnace. To prevent leakage of air or combustion gases into or out of the furnace, various types of gas-tight furnace wall casings have been developed and used; however, such casings have proven diflic'ult to design because of the many openings required to accommodate the passage of wall tubes, supply, discharge and mixing tubes through the casing. Accordingly, it. has become common practice to construct the furnace chamber of fluid-cooled boundary walls comprising a plurality of parallel, contiguous tubes rigidly interconnected, as by welding, along their lengths so as to form gas-tight wall panels.

Rigid panel walls of this type can be utilized in a zone of intense radiant heat emission only if the temperature of the fluid flowing through the plurality of tubes in each panel is substantially the same and the heat absorption rate across the width of the panel is substantially uniform. If these conditions are not met, severe thermal stresses may be induced in the wall panels. Moreover, the condition of substantially equal fluid temperature in all the tubes of a panel can most easily be achieved if the fluid flowing through the tubes is maintained at a level no higher than the saturation temperature corresponding to the fluid pressure within the tubes. It would therefore be desirable to construct the panel walls of the furnace chamber of evaporator or steam generator tubes only; however, this becomes increasingly diflicult as the operating pressure is increased because of the corresponding decrease in the heat of vaporization in the subcritical pressure range. Thus it is difficult to design the furnace chamber. walls of a high capacity, high pressure vapor generator so that all of the wall tubes exposed to the high radiating temperatures of the furnace chamber handle fluid at temperatures no higher than the saturation temperature corresponding to operating pressure.

So that the fluid in the tubes of the panel walls will not exceed saturation temperature, it is proposed according to the present invention, that the usual design of panel wall (tubes on centers equal to or less than about 1.5 times their outside diameter) be used in those portions of the furnace wall exposed to relatively low levels of radiant heat emission, and that the spacing between tubes in the portions of the furnace wall exposed to relatively intense radiant heat emission be spaced more widely (so that the center-to-center distance between adjacent tubes is about 4.5 times their diameter). Further, it is proposed that this latter (high radiation) portion of the furnace wall be protected from intense radiation by a shielding or anti-radiation wall formed of shielding tubes disposed on the gas side of the wall panel adjacent the more widely spaced tubes. The spacing of the shielding tubes should advantageously be closer than the spacing of the adjacent protected portion of the panel wall tubes to produce the desired radiation shielding effect. Moreover, in order that the radiation passing between the tubes of the anti-radiation wall does not project onto individual components of the panel wall, it is proposed that the shielding tubes be oriented so that their longitudinal axes are at intersecting angles with the longitudinal axes of the adjacent panel wall tubes, preferably at substantially right angles.

The anti-radiation tube wall shoulld be space-d sufliciently from the protected panel wall so that slag accumulations will not tend to form in the space between the adjacent walls, or so that if such accumulations do form therein, they can be easily removed by conventional means such as soot blowers. The anti-radiation wall may be secured in spaced relation to and supported by the shielded panel wall by means of suitable connectors, which are preferably attached directly by welding to the center of the intertube portion of the shielded panel wall so that heat absorbed by each connector is distributed as evenly as possible between the adjacent panel wall tubes.

So that the evaporating heating surface may be conserved for advantageous use in the panel boundary walls of the steam generator, it is contemplated that the shieldin g tubes of the anti-radiation wall will be vapor-cooled heating surfaces.

More specifically, according to the present invention, there is contemplated for use in a forced-circulation steam generator, a wall construction wherein first straight panel wall tubes are connected between a supply header and a collection header, and second panel wall tubes, having U- shaped legs disposed in the plane of the first panel wall tubes, are connected for serial flow with respect to the first panel wall .tubes between the collection header and an outlet header, the U-shaped bends of the second pan-- el wall tubes being in a zone of the panel wall shielded by the anti-radiation tube wall.

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 specific objects attained by its use, refer-- ence should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

FIG. 3 is a sectional view taken along line 3 -3 of;

FIG. 1;

FIG. 4 is a sectional view taken along line 4- 4 of FIG. 3;

FIG. 5 is a sectional view taken along line 55 of FIG. 4; and

FIG. 6 is a diagrammatic side view of a vapor generator showing a possible location on the wall construction of FIGS. 1 through 5.

As shown in the drawings, the tubular panel wall 10 includes an inlet header 11 and a parallel collection headerv 12, which headers are interconnected by a plurality of upwardly extending spaced, parallel wall tubes 13 forthe flow of coolant fluid upwardly therethrough. In

t the lower portion of the panel wall 10, adjacent tubes are rigidly interconnected, as by Welding, by plate means such as relatively wide fins or web members 14 positioned in the spaces between the tubes so as to render the panel wall gas-tight, the Weld preferably being on the side of the panel wall 10 that is not exposed to the radiant heat of the furnace chamber 9. g

In the upper portion of the panel wall 10, disposed between the panel wall tubes 13 are U-shaped tubes having upwardly extending

legs

16 and 17 connected in pairs at their lower ends by U-bend sections 19, the upper ends of the

tube legs

16 and 17 being respectively connected to the collection header 12 and an outlet header which is disposed parallel to and slightly above and to the rear of collection header 12. Panel wall tubes '13 and the

tube legs

16 and 17 are preferably of the same diameter, so that when constructed in the form of a planar wall, a uniform panel of the usual type is presented.

By arranging the tubes 13 on centers of about 4.5 times their diameter, the interposition of the

tube legs

16 and 17 will result in the upper portion of the panel wall 10 having tubes spaced on centers equal to about 1.5 times their diameter. The intert-ube spaces in the upper portion of the panel wall 10 are suitably closed to render the panel wall gas-tight by welding to the tubes along their lengths relatively narrow fin or web members 18. In the vicinity of the U-bend sections 19, the web members 14 may be connected as necessary to the Web members 18 so as to preserve the gas-tight integrity on the wall 10.

From the above, it can be seen that the fluid to be heated flows through the panel wall 10 as follows: fluid enters via the inlet or supply header 11, then flows upwardly in parallel flow relationship through the panel wall tubes 13 to the collection header 12 from whence it flow downwardly through tube legs 16, around the U- bend sections 19 and upwardly through tube legs 17 to the outlet header 20. It is contemplated, according to the present invention, that the fluid thus flowing through the panel Wall 10 will preferably not attain a temperature higher than the saturation temperature corresponding to the pressure within the pressure parts of the panel wall 10, and that the fluid will be passed from the outlet header 20 to some additional heat exchange means wherein the fluid temperature will eventually be increased into the superheat range.

Disposed on the gas side of and spaced from the panel wall 10 is an anti-radiation wall 22 comprising a plurality of horizontal, spaced, parallel shielding tubes 21, which tubes are preferably installed in coplanar fashion with relatively close spacing therebetween (tube centers of about 1.1 to 1.2 times the tube diameter) so as to effectively shield the wall tubes 13 from a major portion of the radiation from the furnace chamber 9. Fluid, preferably in the form of vapor, is passed through the shielding tubes 21 either serially or in parallel flow relation. It should be recognized that the interposition of the antiradiation wall 22 between the high radiant energy source (furnace chamber 9) and the panel wall 10, will materially reduce the total radiant heat absorption in the shielded area of the panel wall 10.

The shielding tubes 21 are attached to and supported by the panel wall 10 in spaced relation thereto by suitable connectors, which connectors may include vertical support plates 24 welded to the lateral centers of the web members 14 at spaced locations across the width of panel wall 10. The support plates 24 are formed with openings 25 arranged to accept U-shaped lugs 23 which are welded to the shielding tubes 21 on the sides thereof not exposed to the direct radiation of the furnace chamber 9.

Referring to FIG. 6, the above-described wall construction is preferably embodied in a vapor generator having boundary walls (including wall 10) defining furnace chamber 9 in confining high temperature radiant heating gases produced, for example, by burner means 29. Fluid flows from the vapor generating tubes of the furnace boundary walls to a superheater 28 and thence through the tubes 21 of the shielding wall 22.

While in accordance with the provisions of the statutes there is illustrated and described herein a specific embodiment of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.

What is claimed is:

1. In a fluid heating unit, upright boundary w'alls forming a heating chamber confining high temperature radiant heating gases, one of said upright boundary walls including a plurality of parallel contiguous vapor generating tubes rigidly united along their lengths'to form a rigid gas-tight Wall panel, means for passing fluid in parallel flow relation through said tubes at a temperature substantially equal to the saturation temperature corresponding to the pressure of the fluid within said tubes, and means for shielding a substantial portion of said one boundary wall from radiation within said furnace chamber including a shielding wall disposed on the gas side of said boundary wall and comprising a plurality ofshielding tubes arranged in side-by-side relation, and means for passing fluid through said shielding tubes.

2. In a high pressure fluid heating unit, upright boundary walls forming a heating chamber confining high temperature radiant heating gases, one of said upright boundary walls including a plurality of parallel contiguous vapor generating tubes rigidly united along their lengths to form a rigid gas-tight wall panel, means for passing a fluid in parallel flow relation through said tubes at a temperature substantially equal to the saturation temperature corresponding to the pressure of the fluid within said.

tubes, and means for shielding a substantial portion of said one boundary wall from radiation within said furnace chamber including a shielding wall disposed on the gas side of said boundary wall and comprising a plurality'of shielding tubes arranged in side-by-side relation, and

lel flow relation through said tubes at a temperature substantially equal to the saturation temperature corresponding to the pressure of the fluid within said tubes, and means for shielding a substantial portion of said one boundary wall from radiation within said furnace chamber including a shielding wall disposed on the gas side of said boundary wall and comprising a plurality of shielding tubes arranged in side-by-side relation, and means for passing a fluid through said shielding tubes at a temperature above the saturation temperature corresponding to the pressure of the fluid within said shielding tubes.

4. In a high pressure fluid heating unit, upright boundary walls forming a heating chamber confining high temperature radiant heating gases, one of said upright boundary walls including a plurality of parallel contiguous vapor generating tubes rigidly united along their lengths. to form a rigid gas-tight wall panel, means for passing fluid.

in parallel flow relation through said tubes at a temperature substantially equal to the saturation temperature corresponding to the pressure of the fluid'within saidl tubes, and means for shielding a substantial portion of side of said boundary wall and comprising a plurality of spaced substantially parallel shielding tubes arranged with their longitudinal axes disposed at intersecting angles with respect to the longitudinal axes of the tubes of said wall panel, and means for passing a fluid through said shielding tubes at a temperature above the saturation tempera ture corresponding to the pressure of the iluid within said shielding tubes.

5. In a high pressure fluid heating unit, upright boundary walls forming a heating chamber confining high temperature radiant heatin gases, one of said upright boundary walls including a plurality of spaced parallel contiguous vapor generating tubes, and metallic plate means rigidly uniting said tubes along their lengths to form a rigid gas-tght wall panel, means for passing fluid in parallel flow relation through said tubes at a temperature substantially equal to the saturation temperature corresponding to the pressure of the fluid within said tubes, and means for shielding a substantial portion of said one boundary wall from radiation within said furnace chamber including a shielding wall disposed on the gas side of said boundary Wall and comprising a plurality of spaced substantially parallel shielding tubes arranged with their longitudinal axes disposed at intersecting angles with respect to the longitudinal axes of the tubes of said wall panel, and means for passing a fluid through said shielding tubes at a temperature above the saturation temperature corresponding to the pressure of the fluid within said shielding tubes.

6. In a high pressure vapor generator, upright boundary walls forming a furnace chamber confining high temperature radiant heating gases. one of said upright boundary walls including a plurality of spaced parallel contiguous vapor generating and upright tubes, and metallic plate means rigidly uniting said tubes along their lengths to form a rigid gas-tight wall panel, means for passing fluid in parallel flow relation through said tubes at a temperature substantially equal to the saturation temperature corresponding to the pressure of the fluid within said tubes,

and means for shielding a substantial portion of said one boundary wall from radiation within said furnace chamber including a shielding wall disposed on the gas side of said boundary wall in spaced relation thereto and comprising a plurality of spaced parallel shielding tubes arranged with their longitudinal axes disposed at substantially right angles with respect to the longitudinal axes of the tubes of said wall panel, and means for passing a fluid through said shielding tubes at a temperature above the saturation temperature corresponding to the pressure of the fluid within said shielding tubes.

7. In a high pressure vapor generator, upright boundary Walls forming a furnace chamber confining high temperature radiant heating gases, one of said upright boundary walls including a plurality of spaced parallel contiguous vapor generating tubes, and metallic plate means rigidly uniting said tubes along their lengths to form a rigid gastight wall panel, means for passing fluid in parallel flow relation through said tubes at a temperature substantially equal to the saturation temperature corresponding to the pressure of the fluid within said tubes, and means for shielding a substantial portion of said boundary wall from radiation within said furnace chamber including a shielding wall secured in spaced relation to and supported by said boundary wall and disposed on the gas side thereof, said shielding wall comprising a plurality of spaced parallel shielding tubes arranged with their longitudinal axes disposed at substantially right angles with respect to the longitudinal axes of the tubes of said wall panel, the spaces betwewen said shielding tubes being less than the spaces between the tubes of the shielded portion of the boundary wall, and means for passing a fluid through said shielding tubes at a temperature above the saturation temperature corresponding to the pressure of the fluid within said shielding tubes.

8. In a high pressure forced-circulation vapor generator, upright boundary Walls forming a furnace chamber confining high temperature radiant heating gases, one of said upright boundary walls including a plurality of parallel contiguous and upright vapor generating tubes rigidly weld-united along their lengths to form a rigid gas-tight wall panel, means for passing fluid in parallel flow relation through said tubes at a temperature substantially equal to the saturation temperature corresponding to the pressure of the fluid within said tubes, and means for shielding a substantial portion of said one boundary wall from radiation Within said furnace chamber including a shielding wall disposed on the gas side of said boundary wall in spaced relation thereto and comprising a plurality of spaced substantially parallel shielding tubes arranged with their longitudinal axes disposed at intersecting angles with respect to the longitudinal axes of the tubes of said wall panel, and means for passing a fluid through said shielding tubes at a temperature above the saturation temperature corresponding to the pressure of the fluid within said shielding tubes, the tubes of said boundary wall and the shielding tubes being relatively serially arranged for the flow of fluid therethrough.

9. In a high pressure forced-circulation fluid heating unit having upright boundary walls forming a furnace chamber confining high temperature radiant heating gases, one of said upright boundary walls including a supply header, a collection header, a plurality of spaced parallel contiguous and upright tubes connected for parallel fluid flow between the supply header and the collection header, an outlet header disposed adjacent said collection header, a plurality of U-shaped tubes each having a pair of upwardly extending legs disposed in the plane of said upright tubes, said Ushaped tubes being connected for parallel fiuid flow between the collection header and the outlet header, the fluid flowing through said upright tubes and said U-shaped tubes being at a temperature no greater than the saturation temperature corresponding to the pressure of said fluid, and metallic plate means rigidly interconnecting the adjacent portions of said upright tubes and said U-shaped tubes along their lengths to form a gas-tight wall panel, the legs of said U-shaped tubes extending over only the upper portion of the height of said wall panel, and means for shielding a different portion of said wall panel from radiation within said furnace chamber including a shielding Wall disposed on the gas side of said boundary wall and in spaced relation thereto and comprising a plurality of spaced substantially parallel shielding tubes arranged with their longitudinal axes disposed at intersecting angles with respect to the longitudinal axes of the upright tubes of said wall panel, and means for passing a fluid through said shielding tubes at a temperature above the saturation temperature corresponding to the pressure of the fluid within said shielding tubes.

10. A fluid heating unit as claimed in claim 9 wherein said upright tubes and the legs of said U-shaped tubes are substantially the same diameter, the upright tubes are substantially straight in the plane of the boundary wall and are spaced on centers of about 4.5 times their diameter, the center of each leg of each U-shaped tube is spaced at about 1.5 times its diameter from the center of its adjacent leg, and the shielding tube centers are spaced less than 1.5 times their diameter.

11. The invention according to claim 7 wherein the shielding wall is secured to the Wall panel by plate members welded to the lateral centers of the metallic plate means at spaced locations across the width of the wall panel.

References Cited by the Examiner UNITED STATES PATENTS KENNETH W. SPRAGUE, Primary Examiner.

Claims

1. IN A FLUID HEATING UNIT, UPRIGHT BOUNDARY WALLS FORMING A HEATING CHAMBER CONFINING HIGH TEMPERATURE RADIANT HEATING GASES, ONE OF SAID UPRIGHT BOUNDARY WALLS INCLUDING A PLURALITY OF PARALLEL CONTIGUOUS VAPOR GENERATING TUBES RIGIDLY UNITED ALONG THEIR LENGTHS TO FORM A RIGID GAS-TIGHT WALL PANEL, MEANS FOR PASSING FLUID IN PARALLEL FLOW RELATION THROUGH SAID TUBES AT A TEMPERATURE SUBSTANTIALLY EQUAL TO THE SATURATION TEMPERATURE CORRESPONDING TO THE PRESSURE OF THE FLUID WITHIN SAID TUBES, AND MEANS FOR SHIELDING A SUBSTANTIAL PORTION OF SAID ONE BOUNDARY WALL FROM RADIATION WITHIN SAID FURNACE CHAMBER INCLUDING A SHIELDING WALL DISPOSED ON THE GAS SIDE OF SAID BOUNDARY WALL AND COMPRISING A PLURALITY OF SHIELDING TUBES ARRANGED IN SIDE-BY-SIDE RELATION, AND MEANS FOR PASSING FLUID THROUGH SAID SHIELDING TUBES.