US2962005A

US2962005A - Forced flow vapor generating unit

Info

Publication number: US2962005A
Application number: US735819A
Authority: US
Inventors: Paul H Koch
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1958-05-16
Filing date: 1958-05-16
Publication date: 1960-11-29
Anticipated expiration: 1977-11-29
Also published as: GB907192A

Description

Nov. 29, 1960 P. H. KOCH 2,962,005

FORCED FLOW VAPOR GENERATING UNIT Filed May 16, 1958 7 Sheets-Sheet 1 IN VEN TOR.

BY Paul H. Koch AT TORNEY Nev. 29, 1960 KOCH 2,962,005

FORCED FLOW VAPOR GENERATING UNIT Filed May 16, 1958 7 Sheets-Sheet 2 /1so I INVENTOR.

BY Paul H .Koc h mam,-

ATTORNEY Nov. 29, 1960 P. H. KOCH FORCED FLOW VAPOR GENERATING UNIT 7 Sheets-Sheet 3 Filed May 16, 1958 ATTORNEY NOV. 29, 1960 p, KOCH FORCED FLOW VAPOR GENERATING UNIT '7 Sheets-Sheet 4 Filed May 16, 1958 FIG. 4

INVENTOR.

. Paul H. Koch BY wow/W ATTORNEY 7 sheets sheet 5 II I P. H. KOCH FORCED FLOW VAPOR GENERATING UNIT FIG. 5

Nov. 29, 1960 Filed May 16, 1958 H 2 I 9 1 A 2 A III 1 1 6 w w 1 M m 2 m. w 1 9/ V 1 l NOV. 29, 1960 KOCH 2,962,005

FORCED FLOW VAPOR GENERATING UNIT Filed May 16, 1958 7 Sheets-Sheet 6 FIG.6

I'M Hwl-l W il i l -j IN V EN TOR.

Paul H. Koch AT TORNEY Nov. 29, 1960 P. H. KOCH FORCED FLOW VAPOR GENERATING UNIT 7 Sheets-Sheet 7 Filed May 16, 1958 INVENTOR.

Paul H. Koch ATTORNEY FORCED FLUW VAPOR GENERATING UNIT Paul H. Koch, East Orange, N.J., assignor to The Babcock & Wilcox Company, New York, N.Y., a corporation of New Jersey Fiied May 16, 1958, Ser. No. 735,819

13 Claims. (31. 122-47s This invention relates to the construction and operation of a forced flow fluid heating unit and more particularly to improvements in the construction and operation of a forced circulation one-through vapor generating and superheating unit.

The general object of the present invention is the pro vision of a commercial size forced circulation oncethrough vapor generating and superheating unit adapted to produce superheated vapor from a vaporizable fluid over a wide range of high pressures and temperatures without use of tempering equipment and characterized by its adaptability for use at capacities commensurate with that of the prime mover served, operability with available commercial fuels at high combustion efiiciencies, and rapid response to load changes.

A further and more specific object of the invention is the provision of a steam generating unit of the character described so constructed and arranged as to require a minimum of expensive structural supporting members; to assure an optimum distribution of fluid to all fluid flow paths; to assure an optimum relation of fluid velocity within the tubes to heat input into the tube walls to effect adequate cooling of the tube walls to a safe temperature; to provide a division of the fluid heating surface between the radiant and convection heated sections of the unit whereby the water heating surface is mainly confined to the boundary walls of the furnace chamber and a substantial portion of the superheating of the fluid is accomplished in the furnace; and to provide superheating and reheating of the fluid in tube banks disposed in parallel convection gas passes of the unit.

The various features of novelty which characterize my 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, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of my invention.

Of the drawings:

Fig. l is a partially diagrammatic sectional elevation of a forced circulation once-through steam generating unit constructed and operable in accordance with the invention;

Fig. 2 is a plan section taken along the line 2-2 of Fig. 1

Fig. 3 is a plan section taken along the line 3-3 of Fig. 1;

Fig. 4 is a plan section taken along the line 44 of Fig. 1;

Fig. 5 is a partly diagrammatic plan section, one half of which is partly broken away to show the secondary superheater supply tubes and upper headers, taken along the line 5-5 of Fig. 1;

Fig. 6 is a sectional elevation taken along the line 6-6 of Fig. 1;

Fig. 7 is a sectional elevation similar to Fig. 1 showice ing a diagrammatic representation of fluid flow paths in a side wall of the furnace; and

Fig. 8 is a sectional elevation taken along the line 8-8 of Fig. 7.

In the drawings the invention has been illustrated as embodied in a top-supported forced flow once-through steam generating unit intended for central station use.

The particular unit illustrated is designed on oil and gas firing for a maximum continuous steam output of 1,63 8,- 000 pounds of steam per hour at a pressure of 2450 p.s.i'.g. and a total temperature of 1050" F. at the superheater outlet, based on feed water being supplied at a pressure of 3070 p.s.i.g. and a temperature of 536 F-.; and a maximum continuous steam output of 1,339,000 pounds steam per hour at a pressure of 533 p.s.i.g. and a total temperature of 1000" F. at the reheater outlet. While the fluid heating unit construction illustrated and hereinafter described is specifically designed and particularly adapted for theproduction of superheated steam at pressures and temperatures below the critical pressure of 3206 p.s.i. and the critical temperature of 705 F., it will be understood that the fluid heating unit illustrated may be adapted for operation at temperatures in excess of critical pressures and temperatures.

The main portions of the unit illustrated include an upright furnace chamber 10 of substantially rectangular horizontal cross-section defined by front 12, rear 14, side 16 walls and a roof 18 and having a gas outlet 20 at its upper end opening to a horizontally extending gas.

pass 22 of rectangular vertical cross-section formed by extensions of the furnace roof 18 and side walls 16 and a floor 24. The gas pass 22 communicates at its rear end with the upper end of an upright gas passage 24 of rectangular horizontal cross-section defined by a front.

wall 26, a rear wall 28, side walls 30, and a roof 32. The furnace 10 is divided into a pair of

compartments

34, 36 by a vertical partition wall 38, each compartment opening at its upper end to the gas outlet 20. The lower portions of the front and rear Walls of the furnace slope inwardly and downwardly and cooperate with the furnace side walls to form a hopper 4t) and a rectangular throat passage 42 for discharging ash into an ash pit, not shown. A secondary superheater 44 is disposed in. part in the upper portion of the furnace chamber 10 adjacent the gas outlet 20 thereof, with the remainder occupying the furnace end of the gas pass 22. The portion of the gas pass 22 downstream of the secondary superheater 44 is divided into parallel heating gas passes or

' sections

46 and 48 by a vertical baffle 50; and the upright gas passage 24 is divided into parallel heating passes or

sections

52 and 54 by a vertical baffle 56, the

passes

52 and 54 being continuations of

passes

46 and 48, respectively. The gas pass 52 is occupied by a convection primary superheater 58, the gas pass 46 by an intermediate convection primary superheater 60, the gas pass. 54 by a primary reheater 62, and the gas pass 48 by a secondary reheater 64. Both of the gas passes 54, 52 are occupied by an economizer 66 disposed downstream gas-wise of the primary superheater 58 and the reheater. 62. The heating gases from the gas passes 52 and 54 respectively flow to

ducts

67 and 69 from which the gases discharge into a common duct leading to an airheater, notshown. The proportioning of the gas flow between the

passes

46, 52 and 48, 54 is controlled by sets of dampers 71 and 73 in the

ducts

67 and 69. From the airheater the gases pass to an induced draft fan, and then to a stack.

The vapor generator setting is top-supported by structural steel members including upright members 61 and cross beams 63 from which hangers 65, of which only a few are illustrated, support all walls. I

The lower portion of the

compartments

34, 36 of the furnace are fired by horizontally extending burners 68 arranged to direct fuel and air in mixing relationship into the compartments through corresponding burner ports in the boundary walls of the furnace. The front, rear and side walls of the furnace each include two vertically spaced rows of burners, each row having two burners symmetrically arranged at opposite sides of the vertical centerline of the wall. Preheated air is supplied to the burners by a forced draft fan, not shown, which passes air under pressure through the airheater and a duct 70 to a vertically extending windbox 75 enclosing the burners 68 and the lower portion of the boundary walls of the furnace 10.

Feedwater at a pressure of 3070 p.s.i.g. is supplied by a feed pump, not shown, to the economizer 66 wherein it is partially heated. The economizer comprises two sections of horizontally arranged multiple-looped nested return bend tubes disposed across the path of heating gas flow and connected at their opposite ends to outlet and inlet headers '72 and 74 disposed on the centerline of the baflle wall 56 and extending normal to the front and

rear walls

26 and 28. From the outer header 72 the fluid flows through a downcomer 76 and supply tubes 77 to the inlet headers for the fluid heating tubes lining the front, rear and side walls of the furnace 10, as shown in Fig. 1. p

The front, rear and side walls of the furnace 10 and the side walls of the gas pass 22 are formed by insulation covered metallic casing lined by fluid heating tubes secured thereto. Each of the boundary walls of the furnace 10 is lined by a row of vertically extending parallel tubes arranged in groups to form coplanar radiant heat absorbing tubular panels extending between a corresponding number of horizontally arranged upper and lower headers, the front wall 12 having a row of tubes 80 forming tubular panels extending between upper and lower headers 82 and 84, the rear wall 14 having a row of tubes '87 forming tubular panels extending between upper and

lower headers

86 and 88, and each side wall 16 having a row of tubes 90 forming tubular panels extending between upper and

lower headers

92 and 94. The tubes 90 also line the portion of the side walls of the gas pass 22 opposite the secondary superheater 44. The rear wall tubes 87 have their upper portions bent inwardly and upwardly to form a nose arch 96; then rearwardly and upwardly to form the floor 24 of the gas pass 22; and then vertically for connection to the headers 86 and to form a part of a screen 98 disposed downstream gaswise of the intermediate primary superheater 60 and reheater section 64 and at the rear end of the gas pass 22. Intermediate portions of some of the tubes of the front, rear and side walls of the furnace are suitably bent to form the openings or ports for the burners 68. The furnace 10 has its corners beveled to promote heat absorption in the fluid heating tubes thereat, these tubes constituting the end tubes of the front and rear walls of the furnace.

In accordance with the present invention, the furnace boundary wall fluid heating surface is so proportioned and arranged that the distribution of flow to all fluid flow paths is at an optimum; that the maximum temperature difierential between adjacent tubes is below a predetermined critical limit, thereby maintaining difierential ex pansions in the walls within safe limits; that fluid flow unbalances in the tubes are minimized; that the tube surfaces in different zones of heat intensity in the furnace are sufficient in quantity to carry away the heat at a rate adequate to prevent overheating of the tubes; and that the tubes are of suflicient inside diameter along their lengths to provide adequate fluid circulation velocities. Accordingly, each of the panel

fluid supply headers

84, 88, 94 is connected to the downcomer 76 by one of the supply tubes 77. Each supply tube 77 is provided with a flow resistor 97, diagrammatically illustrated in Fig. l, at a point where it joins the downcomer 76. These resistors impose a resistance to water flow which has a proportioning and equalizing effect on the amount of water entering each panel. The size of the flow resistors may be varied for different panels, depending on their length, arrangement and heat absorption. The flow resistors are of predetermined size to regulate the amount of water flowing to each panel in accordance with these variables. For the sake of clarity, Figs. 7 and 8 diagrammatically show the flow path of the vaporizable fluid to, through and from some of the tubes of one of the tube panels of one of the side walls 16, the fluid flow path through the other tube panels of this wall and of the tube panels of the other side wall, the front wall 12 and the rear wall 14 being substantially similar. Each side wall includes tube panels A A and A Tube panel A comprises a group of tubes A arranged in equal number on opposite sides of the vertical centerline of the panel A and in parallel relationship, with each tube 90A having, as clearly illustrated for the panel A an upflow leg portion B extending in the furnace below the level of the upper end of the hopper 40, upflow and downflow leg portions C extending between the level of the upper end of the hopper and the upper end of the windbox 75, and an upflow leg portion D extending in the furnace above the level of the upper end of the windbox. Since the tube lengths in the burner zone are exposed to gases of higher heat intensity than those above and below the burner zone, their total absorption is highest and the quantity of heating surface presented by the tube lengths in the burner zone and the velocity of the fluid flowing through these tube lengths must be greater than that above and below the burner zone to carry away the heat at a rate sufiicient to prevent overheating of the tubes. Thus the upflow legs B of the tubes 90A below the upper end of the hopper 40 are spaced about a tube diameter apart and are of a relatively small inside diameter. The portions C of the tubes 90A extending in the burner zone between the upper end of the hopper 40 and the upper end of the windbox 75 are of the same inside diameter as the upflow legs B. The tube portions C of each of the tubes 90A consists of an initial upflow leg C, on one side of the centerline of the panel A forming a vertical continuation of a tube leg B, a downflow leg C and a final upflow leg C on the opposite side of the centerline and spaced therefrom a distance about the same as the distance of the leg C, from the adjacent end of the tube panel A The upflow legs C are spaced about one tube diameter apart. The inlet ends of the upflow legs C of the tubes 90A disposed on one side of the centerline of the panel A, are connected to the discharge ends of the tube legs B on the same side of the centerline; and the discharge ends of these upflow legs C are connected to the inlet ends of the upflow legs C disposed on the opposite side of the centerline by the downflow legs C which extend downwardly and laterally within the windbox 75, with the legs C disposed between the legs C on the opposite side of the centerline and contacting the legs C throughout the height of the burner zone. Each tube of the panel A is formed and routed similar to those of the panel A the discharge ends of the initial upflow legs C of half of the tubes disposed on one side of the centerline of the panel A being connected to the inlet ends of the final upflow legs C disposed between the initial upflow legs C of the other half of the tubes on the same side of the centerline by downflow legs C extending downwardly and laterally within the windbox 75. The same pattern is repeated for the tubes on the other side of the centerline of the panel A The tubes of the panel A in the burner zone are routed and formed in substantially the same manner as those of the panel A The tube lengths D of the side wall panels above the windbox 75 are connected at their opposite ends to the discharge ends of the final upflow legs C of the tubes in the burner zone and to the upper headers 92, are spaced a tube diameter apart, are of a greater inside diameter than the tube lengths in the burner zone to minimize the fluid flow unbalances that may result from the relatively high pres: sure drop of the fluid in flowing through the tube legs in the hopper and burner zone; and are of suflicient diameter to provide the fluid velocity necessary to prevent overheating.

By way of example, and not of limitation, the furnace wall tube portions below the burner zone are OD. x .391" ID. on 1%" centerlines; the tube portions in the burner zone are .73" OD. x .391 ID. and substantially tangent to each other; and the tube portions above the burner zone are OD. x .54 ID. on 1 /2 centerlines.

The

outlet headers

82, 86 and 92 of the tube panels of the furnace front, rear and side walls are connected for series flow of the vapor-liquid mixtures generated in the tube panels to a header 1% by tubular connectors 101, as shown in Fig. 5. The header 100 constitutes the leg of a horizontally arranged T-shaped header having its cross-portion 1110A extending parallel to the front wall 12 and its leg portion 1% in the plane of the centerline of the furnace 1d. The vapor-liquid mixtures are mixed in passing through the T-shaped header so that the enthalpy, and thereby the temperature, will be substantially uniform upon discharge therefrom. The header 100A is connected for flow of the vapor-liquid mixtures to a horizontally arranged fluid distribution header 102 by a row of tubes 104 forming the roof of the furnace and the gas pass 22.

The header 1112 is arranged to supply fluid to the tubes forming the baflle walls of the gas pass 22 and the upright gas passage 24 and to tubes lining the side walls of the gas pass 22 and the boundary walls of the gas passage 24. The portion of each of side walls of the gas pass 22 downstream of the secondary superheater 44 is lined by a row of vertically extending closely spaced parallel tubes 103 arranged in groups to form tubular panels extending between a corresponding number of horizontally arranged upper headers 106 and a horizontally extending common lower header 108 disposed between the rear wall 1198 and the front wall 26, with the headers 106 being connected to the header 102 by tubes 110 and the header 103 being connected at one end to a header 112A. As shown in Fig. 3, the header 112A constitutes one leg of a continuous horizontally arranged collecting header 112 disposed along the periphery of the gas passage 24 at a position intermediate the economizer 66 and the primary superheater 58. The lower portions of the tubes 103 cooperate with the rear wall 14, front wall 26 and a floor 114 to form an idle compartment 116. The baflie wall 50 is formed by a row of vertically extending closely spaced parallel tubes 11% arranged in groups to form tubular panels extending between a corresponding number of horizontally arranged upper headers 120 and. a horizontally extending common lower header 122 disposed in the compartment 115, with the headers 120 being connected to the header 1112 by tubes 124 and the header 122 connected to the header 112A by tubes 126.

The front wall 26 of the gas passage 24 is formed by a row of vertically extending spaced parallel tubes 128 having their intertube spaces closed by metallic webs; their upper ends connected to the header 1112; lower ends connected to the header 112A; and their upper portions bent to form, along with the upper portions of the tubes 87, the screen 98. The roof 32 is formed by and the rear wall 28 is lined by a row of upwardly extending closely spaced parallel tubes 1% having their upper ends connected to the header 1112 and their lower ends to a leg 11213 of the header 112. Each side wall 30 is lined by a row of tubes 132 arranged in groups to form coplanar tubular panels extending between a corresponding number of upper headers 134 and a leg 112C of the header 112, with the upper headers 134 being connected to the header 102 by tubes 136. The bafllle wall 56 is formed in part by a row of vertically extending closely spaced parallel tubes 13% arranged in groups to form coplanar tubular panels extending between a corresponding number of horizontally arranged upper headers and a common horizontally extending lower header 142, with the upper headers being connected to the header 102 by tubes and the lower header 142 having its opposite ends connected to the

headers

112A and 112B, respectively. The remainder of the baflle 56 is formed by a metallic wall 56A suitably secured to the header 142 and the

economizer headers

72 and 74 and extending downwardly from the bottom of the header 142 to the ducts 71 and 73. Thus the header 1612 is connected for parallel downflow of fluid to tubes of the side and baffle walls of the gas pass 22 and the boundary walls of the upright gas passage and the header 112 is connected to receive the fluid discharging from all of the these tubes. The vapor-liquid mixtures flowing through the header 112 are mixed therein so that the enthalpy, and thereby the temperature, will be substantially uniform upon discharge therefrom. The fluids thus mixed pass to the primary superheater 58.

The primary superheater 58 comprises three groups of horizontally disposed nested multi-looped tubes arranged in laterally spaced panels serially connected to define parallel flow paths for fluid flow between the headers 112A and 11213 and a transverse external outlet header 144 in counterflow heat transfer relation to the gases flowing through the parallel gas pass 52. From the header 144 the partly superheated vapor passes to the intermediate primary superheater 60 which comprises a group of pendently supported vertically disposed nested multiple-looped tubes arranged in laterally spaced panels to define parallel flow paths for vapor flow between the header 144 and a transverse header 14$ disposed in the compartment 116, with the tubes being arranged so that vapor flows first in counterflow heat transfer relation to the gases and then in parallel flow heat transfer relation.

The additionally superheated vapor then flows through a downcomer and supply tubes 152 to the final primary vapor superheating tubes forming the partition wall 38 of the furnace.

The partition wall 38 extends normal to the front and

rear walls

12 and 14 of the furnace 10 and is formed by two coplanar tubular panels E and F, each panel being formed by final primary vapor superheating tubes 154 contacting each other along their lengths and extending vertically throughout the height of the furnace. The panel E extends between a horizontally arranged upper outlet header 155 and a pair of lower headers 156 which are disposed parallel to and outside of the front wall of the hopper 40. As shown in Fig. 5, the header 155 constitutes one leg of a horizontally arranged cross-shaped header and extends subjacent and in the same vertical plane as the header 1%, the other leg 155A extending normal to the leg 155 and parallel to the front wall 12. The panel F extends between the header 15S and a lower header 158 which is disposed parallel to and outside of the rear wall of the hopper it The panel B is spaced from the front wall 12 and the panel F is spaced a slight distance from the nose arch 96 and from the panel E to provide openings 16th for the flow of gases between the

compartments

34, 36 of the furnace. The

headers

156 and 158 are connected to the clowncomer 1511 by the tubes 152 to provide parallel upflow of vapor through the panels E and F. The vapor thus further superheated passes from the header 155 to the header 155A, and then through tubes 162 to the secondary superheater 44.

The secondary superheater comprises two

groups

44A and 44B of tubes. Group 44A includes horizontally spaced pendantly supported radiant heat absorbing tube platens arranged in vertical planes in the direction of gas flow, with each platen having a multiplicity of nested return bend tubes connected at their opposite ends to a horizontally arranged inlet header 164 and a horizontally extending inlet-outlet header 166, with the inlet headers 164 being connected to the header 155A by the tubes 162..

Group 44B comprises pendantly supported vertically dis posed nested multiple-looped tubes arranged in laterally spaced panels to define parallel flow paths for vapor flow between the header 166 and a transverse header 170 disposed in the compartment 116, with the tubes being arranged so that the vapor flows first in parallel flow heat transfer relation with the gases flowing through the gas pass 22 and then in counterflow heat transfer relation. The vapor receives its final superheating in this group of tubes and is discharged to outlet header 170 from which it passes through a conduit 172 to the high pressure stage of a vapor turbine, not shown.

The primary reheater 62 comprises horizontally extending nested multiple-looped tubes arranged substantially similar to the tubes of the primary superheater and in contrafiow relation with the heating gases and having their opposite ends connected to a lower inlet header 17d and an upper transverse outlet header 176, with the inlet header 174 receiving partially expanded vapor from the turbine. From the header 176 the partly reheated vapor passes to the secondary reheater 48 which comprises vertically disposed nested multiple-looped tubes arranged substantially similar to the tubes of the intermediate primary superheater 46 and having their opposite ends connected to the header 176 and a transverse outlet header 178 disposed in the compartment 116. The finally reheated vapor then passes from the header 178 through a conduit 179 to the turbine for final expansion.

Thus in operation the high pressure fluid supplied by the feed pump passes through the economizer 66; then flows in parallel through the radiant heat absorbing tube panels of the front, rear and side walls of the furnace; then through the tubes 104 forming the roof of the furnace and the gas pass 22; then in parallel through the convection heat absorbing fluid heating tubes of the side and baffle walls of the gas pass 22 and the boundary and baflle walls of the gas passage 24; then successively passes through the primary superheater vapor superheating tubes 58, the intermediate primary vapor superheating tubes 69, the primary final vapor superheating tubes forming the division wall 38 of the furnace 10 and the secondary vapor superheating tubes 44; and then flows to the high pressure stage of the turbine. Partially expanded steam from the turbine successively passes through the primary vapor reheating tubes 62 and the secondary vapor reheating tubes 64, from which it returns to the turbine for final expansion.

Combustion air and fuel are supplied through the burner ports to the lower portion of each of the

compartments

34, 36. The resulting heating gases flow upwardly through the

compartments

34, 36 and over the radiant heating absorbing portion 44A of the secondary superheater to the gas inlet of the gas pass 22; then flow horizontally through the furnace end of the gas pass 22 in contact with the convection heat absorbing portion 44B of the secondary superheater; and then divide into parallel streams, with one stream successively passing through the gas section 46 and the gas section 52 in contact with the intermediate primary vapor superheating tubes 60 and the primary vapor superheating tubes 58, and the other stream successively passing through the gas section 48 and the gas section 54 in contact with the secondary vapor reheating tubes 64 and the primary vapor reheating tubes 62. The proportioning of the gas flow between the

gas sections

46, 52 and the

gas sections

48, 54 is controlled by the sets of dampers 71 and 73.

The superheating and reheating surfaces are propor tioned and arranged to provide the required final or ou let steam temperatures at full steam load. The proportion of the heating gases flowing through the

gas sections

48, 54 and 46, 52 are respectively increased and decreased by means of the dampers 73 and 71 as the rate of steam generation decreases to hold the reheater outlet steam temperature constant over a wide range of steam loads, while the final superheater outlet steam temperature is maintained constant by controlling the firing rate of the t 8 burners. The vapor generating and superheating surfaces are proportioned and arranged so that the portion of the heated fluid circuit in which the transition of the water from a liquid to a vapor condition occurs will always be located in the relatively low temperature primary superheater 58 throughout the operating range.

While in accordance with the provisions of the statutes illustrated and described herein a specific form of the invention now known to me, those skilled 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 covered by my claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. A once-through forced circulation vapor generator comprising walls including radiant heat absorbing fluid heating tubes in the form of panels arranged for parallel flow of fluid therethrough defining an upright furnace chamber having a heating gas outlet, means forming a gas pass serially connected to said gas outlet, a bank of vapor superheating tubes positioned in said gas pass in the path of gas flow leaving said furnace chamber, means including a row of vapor superheating tubes dividing said furnace chamber into a pair of gas flow compartments each opening to said gas outlet, means for burning fuel in said furnace chamber, means for supplying a vaporizable fluid to said radiant heat absorbing fluid heating tubes under a substantial pressure, and means for interconnecting said fluid heating and vapor superheating tubes to provide a serial flow of fluid successively through said radiant heat absorbing fluid heating tubes, vapor superheating tubes dividing said furnace chamber, and bank of vapor superheating tubes.

2. A once-through forced circulation vapor generator comprising walls including upwardly extending radiant heat absorbing fluid heating tubes in the form of panels arranged for parallel flow of fluid therethrough defining an upright furnace chamber having a heating gas outlet at its upper end and its corners beveled to promote heat absorption in the fluid heating tubes thereat, means forming a gas pass opening to said gas outlet, a bank of vapor superheating tubes positioned in said gas pass in the path of gas flow leaving said furnace chamber, means including a row of vapor superheating tubes dividing said furnace chamber into a pair of intercommunicating gas flow compartments each opening at its upper end to said gas outlet, means for burning fuel in the lower portion of each of the compartments of said furnace chamber, means for supplying a vaporizable fluid to each of said tube panels under a substantial pressure, and means for interconnecting said fluid heating and vapor superheating tubes to provide a serial flow of fluid successively through said radiant heat absorbing fluid heating tubes, vapor superheating tubes dividing said furnace chamber, and bank of vapor superheating tubes.

3. A once-through forced circulation vapor generator comprising walls including radiant heat absorbing fluid heating tubes in the form of panels arranged for parallel flow of fluid therethrough defining an upright furnace chamber having a heating gas outlet, means forming a gas pass serially connected to said gas outlet, a bank of vapor superheating tubes positioned in said gas pass in the path of gas flow leaving said furnace chamber, means including a row of vapor superheating tubes dividing said furnace chamber into a pair of gas flow compartments each opening to said gas outlet, means for burning fuel in said furnace chamber, a plurality of tubular conduits each supplying fluid to one of said tube panels, means for supplying a vaporizable fluid to each of said tubular conduits under a substantial pressure, a flow resistor in each of said tubular conduits proportioned to regulate the amount of fluid entering each of said tube panels, and means for interconnecting said fluid heating and vapor superheating tubes to provide a serial flow of fluid successively through said radiant heat absorbing fluid heating tubes, vapor superheating tubes dividing said furnace chamber, and bank of vapor superheating tubes.

4. A-once-through forced circulation vapor generator comprising walls including upwardly extending radiant heat absorbing fluid heating tubes in the form of panels arranged for parallel flow of fluid therethrough defining an upright furnace chamber having a heating gas outlet, means forming a gas pass serially connected to said gas outlet, a bank of secondary vapor superheating tubes positioned in said gas pass in the path of gas flow leaving said furnace chamber, a bank of primary vapor superheating tubes positioned downstream gas-wise of said secondary vapor superheating tubes, means including a row of vapor superheating tubes dividing said furnace chamber into a pair of gas flow compartments each opening to said gas outlet, means for burning fuel in said furnace chamber, means for supplying a vaporizable fluid to each of said tube panels under a substantialpressure, and means for interconnecting said fluid heating and vapor superheating tubes to provide a serial flow of fluid successively through said radiant heat absorbing fluid heating tubes, bank of primary vapor superheating tubes, vapor superheating tubes dividing said furnace chamber, and bank of secondary vapor superheating tubes.

5. A once-through forced circulation vapor generator comprising walls including upwardly extending radiant heat absorbing fluid heating tubes in the form of panels arranged for parallel flow of fluid therethrough defining an upright furnace chamber having a heating gas outlet, means forming a gas pass serially connected to said gas outlet, a bank of secondary vapor superheating tubes positioned in said gas pass across the full width thereofin the path of gas flow leaving said furnace chamber, means dividing said gas pass downstream of said secondary vapor superheating tubes into a pair of parallel flow gas sections, a bank of primary vapor superheating tubes positioned in said gas pass in one of the parallel gas flow sections thereof, a bank of vapor reheating tubes positioned in said gas pass in the other of the parallel gas flow sections thereof, means including a row of vapor superheating-tubes dividing said furnace chamber into a pair of gas flow compartments each opening to said gas outlet, damper means arranged to proportion the heating gas flow through said parallel gas flow sections, means for burning fuel in said furnace chamber, means for supplying a vaporizable fluid to each of said tube panels under a substantial pressure, and means for interconnecting said fluid heating and vapor superheating tubes to provide a serial flow of fluid successively through said radiant heat absorbing fluid heating tubes, bank of primary vapor superheating tubes, vapor superheating tubes dividing said furnace chamber, and bank of secondary vapor superheating tubes.

6. A once-through forced circulation vapor generator comprising walls including upwardly extending radiant heat absorbing fluid heating tubes in the form of panels arranged for parallel flow of fluid therethrough defining an upright furnace chamber having a heating gas outlet, means including convection heat absorbing fluid heating tubes forming a gas pass serially connected to said gas outlet, a bank of secondary vapor superheating tubes positioned in said gas pass in the path of gas flow leaving said furnace chamber, a bank of primary vapor superheating tubes positioned downstream gas-wise of said secondary vapor superheating tubes, means including a row of vapor superheating tubes dividing said furnace chamber into a pair of gas flow compartments each opening to said gas outlet, means for burning fuel in the lower portion of each of the compartments of said furnace chamber, means for supplying a vaporizable fluid to each of said tube panels under a substantial pressure, and means for interconnecting said fluid heating and vapor superheating tubes to provide a serial flow of fluid successively through said radiant heat absorbing fluid heating tubes, convection 10 heat absorbing fluid heating tubes, bank of primary vapor superheating tubes, vapor superheating tubes dividing said furnace chamber, and bank of secondary vapor superheating tubes.

7. A once-through forced circulation vapor generator comprising walls including upwardly extending radiant heat absorbing fluid heating tubes in the form of panels arranged for parallel flow of fluid therethrough defining an upright furnace chamber having a heating gas outlet at its upper end and its corners beveled to promote heat absorption in the fluid heating tubes thereat, means including convection heat absorbing fluid heating tubes forming a gas pass serially connected to said gas outlet, a bank of secondary vapor super-heating tubes positioned in said gas pass in the path of gas flow leaving said furnace chamber, means including convection heat absorbing fluid heating tubes dividing said gas pass downstream of said secondary vapor superheating tubes into a pair of parallel flow gas sections, a bank of primary vapor superheating tubes positioned in said gas pass in one of t the parallel gas flow sections thereof, a bank of vapor reheating tubes positioned in said gas pass in the other of the parallel gas flow sections thereof, means including a row of vapor superheating tubes dividing said furnace chamber into a pair of gas flow compartments each opening to said gas outlet, damper means arranged to proportion the heating gas flow through said parallel gas flow sections, means for burning fuel in the lower portion of each of the compartments of said furnace chamber, means for supplying a vaporizable fluid to each of said tube panels under a substantial pressure, and means for interconnecting said fluid heating and vapor super-heating tubes to provide a serial flow of fluid successively through said radiant heat absorbing fluid heating tubes, convection heat absorbing fluid heating tubes, bank of primary vapor superheating tubes, vapor superheating tubes dividing said furnace chamber, and bank of secondary vapor superheating tubes.

8. A once-through forced circulation vapor generator comprising walls including upwardly extending radiant heat absorbing fluid heating tubes in the form of panels arranged for parallel flow of fluid therethrough defining an upright furnace chamber having a heating gas outlet at its upper end, means including convection heat absorbing fluid heating tubes forming a horizontally extending gas pass opening at one end to said gas outlet, a bank of secondary vapor superheating tubes positioned in said gas pass in the path of gas flow leaving said furnace chamber, means including convection heat absorbing fluid heating tubes forming an upright gas passage laterally adjacent and opening to the opposite end of said gas pass, means including convection heat absorbing fluid heating tubes dividing said upright gas passage and said gas pass downstream of said secondary vapor superheating tubes into a pair of parallel flow gas sections, a bank of primary vapor superheating tubes positioned in said upright gas passage in one of the parallel gas flow sections thereof, an intermediate bank of. primary vapor superheating tubes positioned in said gas pass in said one parallel gas flow section intermediate said banks of primary and secondary vapor superheating tubes, a bank of primary vapor reheating tubes in said upright gas passage in the other of the parallel gas flow sections thereof, a bank of secondary vapor reheating tubes positioned in said gas pass in said otherparallel-gas flow section and connected for series flow of vapor from said bank of primary vapor reheating tubes, means including a row of final primary vapor superheating tubes dividing said furnace chamber into a pair of intercommunicating gas flow compartments each opening at its upper end to said gas outlet, damper means arranged to proportion the heating gas flow through said parallel gas flow sections, means for burning fuel in the lower portion of each of the compartments of said furnace chamber, means for supplying a vaporizable fluid to each of said tube panels under a Substantial pressure, and means for interconnecting said fluid heating and vapor superheating tubes to provide a serial flow of fluid successively through said radiant heat absorbing fluid heating tubes, convection heat absorbing fluid heating tubes, bank of primary vapor superheating tubes intermediate bank of primary vapor superheating tubes, vapor superheating tubes dividing said furnace chamber, and bank of secondary vapor superheating tubes.

9. A once-through forced circulation vapor generator comprising walls including upwardly extending radiant heat absorbing fluid heating tubes in the form of panels arranged for parallel flow of fluid therethrough defining an upright furnace chamber having a heating gas outlet at its upper end, means including convection heat absorbing fluid heating tubes forming a horizontally extending gas pass opening at one end to said gas outlet, a bank of secondary vapor superheating tubes positioned in said gas pass in the path of gas flow leaving said furnace chamber, means including convection heat absorbing fluid heating tubes forming an upright gas passage laterally adjacent and opening to the opposite end of said gas pass, means including convection heat absorbing fluid heating tubes dividing said upright gas passage and said gas pass downstream of said secondary vapor superheating tubes into a pair of parallel flow gas sections, a bank of primary vapor superheating tubes positioned in said upright gas passage in one of the parallel gas flow sections thereof, an intermediate bank of primary vapor superheating tubes positioned in said gas pass in said one parallel gas flow section intermediate said banks of primary and secondary vapor superheating tubes, a bank of primary vapor reheating tubes in said upright gas passage in the other of the parallel gas flow sections thereof, a bank of secondary vapor reheating tubes positioned in said gas pass in said other parallel gas flow section and connected for series flow of vapor from said bank of primary vapor reheating tubes, means including a row of final primary vapor superheating tubes dividing said furnace chamber into a pair of inter-communicating gas flow compartments each opening at its upper end to said gas outlet, damper means arranged to proportion the heating gas flow through said parallel gas flow sections, means for burning fuel in the lower portion of each of the compartments of said furnace chamber, a plurality of tubular conduits each supplying fluid to one of said tube panels, means for supplying a vaporizable fluid to each of said tubular conduits under a substantial pressure, a flow resistor in each of said tubular conduits proportioned to regulate the amount of fluid entering each of said tube panels, and means for interconnecting said fluid heating and vapor superheating tubes to provide a serial flow of fluid successively through said radiant heat absorbing fluid heating tubes, convection heat absorbing fluid heating tubes, bank of primary vapor superheating tubes, intermediate bank of primary vapor superheating tubes, vapor superheating tubes dividing said furnace chamber, and bank of secondary vapor superheating tubes.

10. In a forced circulation fluid heating unit, walls defining a furnace chamber for the flow of heating gases, burner means supplying high temperature heating gases to said chamber and establishing a gas flow zone intermediate the height of said chamber and in the vicinity of said burner means of higher heat intensity than exists in the portions of said chamber above and below said zone, at least one of said walls including a plurality of laterally contiguous tubular panels arranged for parallel flow of fluid therethrough, each of said panels comprising a group of upwardly extending tubes arranged for parallel flow of fluid therethrough, each of said tubes of each panel including continuous initial upflow legs extending below and throughout said zone of high heat intensity and second upflow legs extending throughout and above said zone of high heat intensity, means for supplying a vaporizable fluid of substantially the same enthalpy in parallel flow relation directly from a common source to the lower inlet ends of said initial upflow legs of each of said panels, said initial upflow legs being arranged in parallel spaced relation to provide intertube spaces, said second upflow legs being disposed in the spaces between and contiguous to said initial upflow legs along the height of said Zone so that the number of tube legs presented to the gases in the zone of high heat intensity is double that below and above said zone, and downflow tubular means disposed externally of said one wall and arranged to connect the upper discharge ends of said initial upflow legs for series flow of fluid to the lower inlet ends of said second upflow legs.

11. In a forced circulation fluid heating unit, walls defining a furnace chamber for the flow of heating gases, burner means supplying high temperature heating gases to said chamber and establishing a gas flow zone intermediate the height of said chamber and in the vicinity of said burner means of higher heat intensity than exists in the portions of said chamber above and below said zone, at least one of said walls including a plurality of upwardly extending laterally contiguous tubular panels arranged for parallel flow of fluid therethrough, each of said tubes of each panel including a continuous initial upflow leg extending below and throughout said zone of high heat intensity and a second upflow leg extending throughout and above said zone of high heat intensity, and means for supplying a vaporizable fluid of substantially the same enthalpy in parallel flow relation directly from a common source to the lower inlet ends of said initial upflow legs of each of said panels, said initial upflow legs being arranged in parallel spaced relation and having their upper discharge ends connected for series flow of fluid to the lower inlet ends of said second upflow legs by downfiow tube legs disposed externally of said one wall, said second upflow legs being disposed in the spaces between and contiguous to said upflow legs along the height of said zone so that the number of tube legs presented to the gases in the zone of high heat intensity is double that below and above said zone.

12. In a forced circulation fluid heating unit, walls defining a furnace chamber for the flow of heating gases, burner means supplying high temperature heating gases to said chamber and establishing a gas flow zone intermediate the height of said chamber and in the vicinity of said burner means of higher heat intensity than exists in the portions of said chamber above and below said zone, each of said walls including a plurality of upwardly extending coplanar laterally continguous tubular panels arranged for parallel flow of fluid therethrough, each of said panels comprising a group of upwardly extending tubes arranged for parallel flow of fluid therethrough, each of said tubes of each panel including a continuous initial upflow leg extending below and throughout said zone of high heat intensity and a second upflow leg extending throughout and above said zone of high heat intensity, and means for supplying a vaporizable fluid of substantially the same enthalpy in parallel flow relation direction from a common source to the lower inlet ends of said initial upflow legs of each of said panels, said initial upflow legs being arranged in parallel spaced relation to provide intertube spaces and having their upper discharge ends connected for series flow of fluid to the lower inlet ends of said second upflow legs by downflow tube legs disposed externally of said chamber, said second upflow legs being disposed in the spaces between and contiguous to said initial upflow legs along the height of said zone so that the number of tube legs presented to the gases in the zone of high heat intensity is double that below and above said zone, the portions of said second upflow legs above said zone having a greater inside diameter than the portions of said second upflow legs in said zone to minimize fluid flow unbalances in the tubes.

13. In a forced circulation fluid heating unit, walls defining a furnace chamber for the flow of heating gases, burner means supplying high temperature heating gases to said chamber and establishing a gas flow zone intermediate the height of said chamber and in the vicinity of said burner means of higher heat intensity than exists in the portions of said chamber above and below said zone, each of said walls including a plurality of upwardly extending coplanar laterally contiguous tubular panels arranged for parallel flow of fluid therethrough, each of said panels comprising a group of upwardly extending tubes arranged for parallel flow of fluid therethrough, each of said tubes of each panel including continuous initial upflow legs having their lower inlet ends connected to a fluid distribution header and extending below and throughout said zone of high heat intensity and second upflow legs extending throughout and above said zone of high heat intensity, a tubular conduit connected to the fluid distribution header of each panel, means for supplying a vaporizable fluid of substantially the same enthalpy in parallel flow relation directly from a common source to each tubular conduit, and a flow resistor in each tubular conduit proportioned to regulate the amount of fluid entering each panel, said initial upflow legs being arranged in parallel spaced relation and having their upper discharge ends connected for series flow of fluid to the lower inlet ends of said second upflow legs by downflow tube legs disposed externally of said chamber, said second upflow legs being disposed in the spaces between and contiguous to said initial upflow legs along the height of said zone so that the number of tube legs presented to the gases in the zone is double that below and above said zone, the portions of said second upflow legs above said zone having a greater inside diameter than the portions of said second upflow legs in said zone to minimize fluid flow unbalances in the tubes.

References Cited in the file of this patent FOREIGN PATENTS 857,965 Germany Dec. 4, 1952 663,892 Great Britain Dec, 27, 1951 744,797 Great Britain Feb. 15, 1956