US3089467A - Steam generator - Google Patents

Description

y 4, 1963 w. H. ARMACOST 3,089,467

STEAM GENERATOR Filed March 18, 1959 4 Sheets-Sheet 1 g Superheoi Wilbur H. Armucost ATTORNEY May 14, 1963 Filed March 18, 1959 W. H. ARMACOST STEAM GENERATOR Fig. 2.

4 Sheets-Sheet 2 INVENTOR Wilbur H. Armclcost ATTORNEY 1963 w. H. ARMACOST 3,089,467

STEAM GENERATOR Filed March 18, 1959 4 Sheets-Sheet 3 Superheot INVENTOR Wilbur H. Armucost ATTORNEY May 14, 1963 Filed March 18, 1959 W. H. ARMACOST STEAM GENERATOR 4 Sheets-Sheet 4 Water Well Panel 4 F I Radiant s. H. Panel I Flow; down 8| up gi g- L: 3 o: urner e E "s T, I w 2 Wafer Wall 5 -e 7 Panel e E 3 FM; 0 2: 0 1: 0 u i z *5 5 P 2 Superheaf 5 lClnLme ,5 a5 61? w Furnace 3-, Burner c 5 35 g 64 8 O "4- 'g f; g g 5 Water Wall %r g g s E W Panel g 5 S 2 To Radlant E G L o 5 S.H.Panel O "i Burner Radiant S. H. Panel 36 Flow down 8| up WaterWall 76 78 80 84 p l 24 Drum 20 22 24\ fig /8 From Turbine 8 I\ L: 7 g Water Wall Panel F Radiant Reheat Panel -I- c =F|w up g[ l '13 J g 28 Burner l. o I u E E 3 3 5 Water Wall 5 3 2 3 Panel 0- o 4I I: 5 (05' q 0 '0 g 1: o I 2: 21 o I0 Reheat 3 ,Clr.L|ne 2-0- F m 5, (I) E 62 Furnace Burner E 3 2 E 2- :3 E Wafer Wall E g 3 5 g 2 Panel 5 5 5 g .9 52 LL 0 2 a a8 Burner Radiant Reheat Panel 32 Flow up Water Wall L 76 78 82 84 Panel From Turbine INVENTOR Fig. 4.

Wilbur H. Armacost i A4 KW ATTORNEY 3,889,467 STEAM GENERATOR Wilbur H. Armacost, Scarsdale, N.Y., assignor to Cornhustron Engineering, Inc, New York, N.Y., a corporation of Delaware Filed Mar. 18, 1959, Ser. No. 896,316 (Iiaims. (El. 122--24) This invention relates generally to vapor or steam generators and has particular relation to high capacity high temperature and pressure generators as employed in the utility field.

The invention is directed to an improved steam generator organization employing so-called twin or separate furnaces which are independently fired but have their heat exchange surface interrelated and their steam generating surface interconnected with a common steam and water drum so as to form a steam generating organization or unit which may serve a single turbine generator unit. As embodied, one of the furnaces may be termed a reheat furnace since all of the reheating of the unit is accomplished in this furnace and the other furnace may be termed a superheat furnace since all of the radiant superheating surface is contained in this furnace. The reheat and superheat surfaces or, in other words, the reheat and superheat tubes are arranged in such a manner as to minimize the requirement for interconnecting piping which merely conveys the reheat or superheat steam from one section of reheat or superheat surface to another or to the turbine.

Each of the furnaces is vertically elongated and positioned in relatively closely spaced side by side relation, being fired adjacent its lower portion and having combustion gases passing through a suitable opening in the upper end of its rear wall. Extending from this opening is a suitable gas pass arranged in conventional manner so that it extends a short distance horizontally and then vertically downward in parallel relation with the particular furnace. In the upper end of each of these gas passes is positioned convection superheating surface which receives from the steam and water drum steam generated in the steam generating portion of the unit. This convection steam heating surface in each of these gas passes communicates with radiant steam heating surface disposed along the various walls of the superheater furnace. The arrangement is such that the steam from the convection steam heating surface enters this radiant steam heating surface at the upper end of the boiler, passes in a particular manner through this surface, traversing the full length of the boiler several times and finally is collected in a suitable outlet header at the lower end of the furnace from which it is conveyed to a turbine, which, of course, is also located in proximity to the lower end of the steam generator as is conventional.

The reheat furnace has various of its walls lined with radiant reheat tubes and the reheat steam, i.e., the steam to be reheated, is received in a suitable header at the lower end of the reheat furnace which communicates with the lower end of various of these tubes with the reheat steam passing up through these tubes and then down through other tubes where it is collected at an outlet header also located at the bottom of the reheat furnace.

Each of these furnaces is fired by horizontally arranged burners that project fuel through the front wall of the furnace and there are a plurality of vertically extending horizontally spaced tubular panels of steam generating tubes that extend from this front wall a short distance into the furnace with these panels dividing this portion of the furnace into chambers and with the burners being arranged to horizontally introduce fuel and air into these chambers. Each of the furnaces is independently fired and is provided with a hopper bottom formed by inclining the lower portion of the side walls of the furnace toward Patented May 14, 1963 one another and these side walls are lined with tubes which do not form part of the finishing stages or final portion of either the superheater or reheater so that the temperature will not be objectionally high so as to cause slagging difficulties.

Accordingly, it is an object of this invention to provide an improved steam generating unit operating on the reheat cycle having separated furnaces and with the steam heating, both reheat and superheat, surface being organized in an eflicient and expeditious manner so that connection piping is necessarily reduced to a minimum while at the same time the general arrangement of the steam heating surface is efficient and conducive to troublefree operation of the unit.

Other and further objects of the invention will become apparent to those skilled in the art as the description pro ceeds.

With the aforementioned objects in view, the invention comprises an arrangement, construction and combination of the elements of the inventive organization in such a manner as to attain the results desired as hereinafter more particularly set forth in the following detailed description of an illustrative embodiment, said embodiment being shown by the accompanying drawing wherein:

FIG. 1 is a vertical sectional view looking from the front of the unit and showing the superheat and reheat furnaces in spaced side by side relation with the burners and the steam generating partitions, which would normally not be shown in this section, being indicated in dotted lines;

FIG. 2 is a vertical sectional view of the reheat furnace organization looking from the side of the furnace;

PEG. 3 is a view similar to that of FIG. 2 but showing the superheat furnace; and 7 FIG. 4 is a diagrammatic representation in the nature of a flow diagram with the various elements being labeled.

Referring now to the drawings, wherein like reference characters are used throughout to designate like elements, the illustrated and preferred embodiment of the invention depicted therein comprises a vapor or steam generating unit having a pair of separately spaced vertically elongated furnaces with one of the furnaces being identified as 10 and indicated as the reheat furnace and the other identified as 12 and indicated as the superheat furnace. The steam generating surface of this unit comprises vertically extending steam generating tubes that line the front wall 14 of furnace 10 and the front wall 16 of furnace 12 as well as a portion of the side walls of each of these furnaces and also forming part of the steam generating surface are a pair of vertically extending tubular panels 52 that project into the furnace at the lower portion thereof and adjacent the front wall.

The steam generating circuit of the unit includes the steam and water drum 18 which is common to both of the furnaces and downwardly from which extends the downcomer 20 with this downcomer being connected at its lower end to pump 22. Extending from this pump are supply conduits 24 that are connected with headers 26 at the lower end of each of the furnaces 10 and 12. Extending up from each of these headers are steam generating tubes 23 which line the front walls 14 and 16 of the furnaces with these tubes extending up along these walls and across the roof of the furnace and being connected with header 30. The side walls 32 and 34 of furnace 10 as well as the side walls 36 and 38 of furnace 12 have their forward portion thereof lined with steam generating tubes 39 for a distance identified as 46 in FIGS. 2 and 3. These tubes extend up along these side walls and are connected at their upper ends with header 42 which is in turn connected by means of conduits 44 to header 30 and with this header being connected with conduits 4-6 to the steam and water drum .18. The front-to-back dimensions of the furnaces and 12 are greater at the lower portion of the furnace than at the upper portion as clearly indicated in FIGS. 2 and 3, and the tubes 39 that extend along the side walls of the upper portion are bifurcated generally at the incline 48 of the front Walls of the furnaces so that the number of tubes extending along the front portion of the side walls below this incline will be sufiicient to cover this portion of the furnace wall. In addition to the steam generating tubes 28 and 39 that line the front and side walls, respectively, of the furnaces 1i) and 12, each of the furnaces is provided with a pair of panels 52 that project into the furnace below the inclined front wall portion 48 with these panels extending generally down from this inclined front wall portion or extending forwardly or inwardly from the front wall as indicated in FIGS. 2 and 3.

1e tubes that make up these panels 52 may advantageously be formed by bifurcating the tubes lining the upper portion of the front furnace wall. The tubes of these panels extend out through the front wall of the particular furnace adjacent the lower end thereof and then down so that they connect with headers 26. The lower ends of tubes 39 on the side walls are connected with one of the supply headers 54 which is, in turn, connected by conduit 56 to header 26 so that pump 22 is effective to force water through all of the steam generating tubes and the steam and water mixture that egresses from these tubes passes to and is collected in steam and water drum 18.

Each of the furnaces 1t) and 12 is fired by means of a plurality of horizontally spaced rows of burners 58 and, as embodied there are four verticaly disposed burners in each row and there are three rows arranged so that the fuel together with combustion supporting air is projected horizontally between the panels 52 and between these panels and the side walls, or in other words, into the chambers formed by the panels. The combustion gases thus generated pass up through the furnace and out through outlet 60 located in rear wall 62 of furnace 10 and rear wall 64 of furnace 12. Extending from this outlet is a suitable and conventional gas pass which includes the horizontally disposed portion 66 and vertically disposed portion 68 that extends downwardly and parallel with the furnace and may communicate with a suitable stack. In the lower region of this gas pass portion 63 there is provided the usual heat exchange equipment which may include economizer surface 70 while in the upper portion thereof is positioned the convection superheating surface 72. This surface positioned in the gas pass of each furnace is in the form of conventional sinuously disposed tubes with steam being supplied thereto through conduit 74 and with the inlet header of this steam heating surface being identified as 76. The steam passes up through this surface to outlet header 78 and from this outlet header the steam passes through the additional convection steam heating surface 80 disposed in the horizontal gas pass portion 66 with the inlet header of this surface being identified as 82 and the outlet header being identified as 84. From outlet header 84 the steam is conveyed to the upper end of the superheat furnace 12 and particularly to the inlet header 86 one of which is disposed immediately above each of the side walls 36 and 38 of this superheat furnace. These side walls 36 and 38 are lined with superheater tubes 88 for the lateral distance identified as 90 (FIG. 3) and every other tube 38 is connected at its upper end with the adjacent inlet header 86 whereby steam flows down through these alternate tubes on the side walls 36 and 38. The lower end of tubes 88 are connected with header 92 so that this downwardly flowing steam upon reaching header 92 flows up through the remaining or alternate tubes 88 which have their upper ends connected with the adjacent leg of U-shaped header 92 that is disposed above the particular wall. Thus the steam flows down through and then up through alternate of the tubes 38. U-shaped header 92 is connected with the upper end of tubes 94 that line the rear wall 64 of furnace 12 so that the steam flows down through these tubes 94 and the lower end of 4 these tubes is connected with the final outlet header 96 of the superheater from which the steam is conveyed to the turbine which, as is conventional, is located in proximity to the lower end of the steam generator.

After having a portion of its energy utilized or removed the steam is returned to the unit for reheating, and as embodied, reheat furnace 10 has its side walls lined with tubes 98 and which are connected at their lower ends with one of the headers 160 there being one such header adjacent the lower end of each of the side walls 32 or 34. The steam to be reheated passes from the inlet header 100 up through the tubes 98 lining the side walls to the header 102. The upper ends of tubes 98 are connected at their upper ends with the adjacent leg of U-shaped header 102 which has its center portion 106 disposed above rear wall 62 and connected with the tubes 198 extending downwardly therealong. Thus steam flows up through tubes 98, through header 102 and down through tubes 108. This steam is collected in outlet header 110 to which the lower ends of tubes 198 are connected and which is disposed adjacent the lower end of wall 62.

It will be seen with this organization that there is very little connecting piping required solely for the purpose of conveying high temperature and high pressure steam from one steam heating section to another and it will be particularly noted that when the steam has been heated to at least an appreciable amount or extent of its desired temperature the requirement for connecting piping which would necessarily operate at a relatively high temperature is at a minimum. This is extremely desirable and important since this high temperature, high pressure piping is very costly.

With regard to the superheat steam, after leaving the intermediate stage of the superheater, i.e., the superheat surface identified as 80, and entering the radiant portion there is substantially no connecting piping required. Thus, with regard to the high temperature end of the superheat range connecting piping to convey the superheat steam from one section of the superheater to another is substantially eliminated and furthermore the outlet of the superheater is at the bottom of the furnace and accordingly near the point of use, i.e., the turbine, so that the extremely long pipe which is often utilized to convey the very highest temperature and pressure steam from the upper end of one of these units to the turbine is not required.

Likewise, with regard to the reheat furnace interconnecting piping is also substantially eliminated and the inlet and outlet of the reheater are located near the source of reheat steam and the point of use of the steam, i.e., the lower end of the reheat furnace, so that here also, there is no requirement for a long run of pipe to convey the reheat steam to or from the upper end of the unit.

By referring to the flow diagram of FIG. 4 it is believed that the flow path of the various fluids and the advantages obtained thereby will be very evident.

Both reheat furnace 10 and superheat furnace 12 are of the hopper bottom type where the side walls are sloped inwardly at their lower ends to form a restricted opening 112. The arrangement of the surfaces in these furnaces is such that the tubes that line and make up the inclined walls of the hopper do not have the highest temperature steam passed through them, or, in other words, are not the final steam heating stages of either the reheat or the superheat furnaces. Accordingly these tube portions that make up this sloping hopper are relatively cool with this being desirable so that ash particles that slide down these slopes will have less tendency to adhere to them than would otherwise would be the case. With regard to the reheat furnace 10, tubes 98 that make up the greater portion of the hopper, are the tubes that initially receive the steam to be reheated and accordingly are the coldest portion of the entire reheat surface. Of course the steam generating tubes 39 that form the front portion of the side walls 32 and 34 are at a relatively low temperature. Also with regard to superheat furnace 12 the tubes 88 that form a substantial portion of the sloping walls of the hopper are the first portion of the radiant section of the superheater with the final portion or finishing section of the superheater being the tubes 94 that line the rear wall 64 of the superheat furnace. Accordingly the steam passing through the tubes 88 and the tubes themselves are not at the high final superheat temperature but are relatively low intermediate temperature. Here also the tubes 39 that line the front portion of the side walls 36 and 38 of the superheat furnace are a relatively low temperature.

It will thus be seen that with the particular organization of this invention a novel circuit arrangement and interconnection of heat exchange surface is provided so as to produce an efficiently operating unit.

While I have illustrated and described a preferred embodiment of my invention it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made without departing from the spirit and scope of the invention. I therefore do not Wish to be limited to the precise details set forth but desire to avail myself of such changes as fall within the purview of my invention.

What is claimed is:

l. A vapor generator operating on the reheat cycle comprising a pair of upright furnaces generally polygonal in transverse section and disposed in side by side spaced relation, one of said furnaces comprising a reheat furnace and the other a superheat furnace, said furnaces having combustion gas outlets at the upper end of their rear wall, passageway means extending from said outlet, vertically extending steam generator tubes lining the front wall of each furnace and the front portion of each side wall thereof, a steam generating circuit into which these tubes are connected and which includes a steam and water drum positioned intermediate said furnaces adjacent the upper end thereof, each furnace having panel means formed of vertically extending steam generator tubes positioned adjacent said front wall at the lower region thereof with said panel means extending into the furnace from said front wall and disposed in spaced relation across said front wall thereby forming horizontally spaced chambers in the furnace, means for horizontally introducing fuel and air into said horizontally spaced chambers, convection heat exchange surface disposed in said passageway means and including superheating surface for superheating steam generated in said steam generating tubes, said superheater furnace :having the remaining portion of its Walls lined with superheater tubes extending vertically throughout the length thereof, means for conveying steam from said convection superheater surface to a given number of these superheater tubes on the side walls so that the steam is conveyed down therethrough with these tubes being iutercalated among the remaining superheater tubes on the side Walls, means for conveying this steam after passing down through these superheater tubes on the side walls up through the remaining superheater tubes, the rear furnace wall being lined with vertically extending superheater tubes that extend from the upper to the lower end of the furnace, means for conveying the steam after traversing said remaining superheater tubes down through these tubes lining the rear wall, header means at the lower end of the furnace communicating with these last mentioned superheater tubes, said reheater furnace having the remaining portion of its side walls lined with reheater tubes that extend vertically from the lower end to the upper end thereof, header means receiving steam to be reheated and communicating with the lower end of these reheater tubes so that the steam is conveyed upwardly therethrough, the rear furnace wall being lined with reheater tubes that extend vertically from the upper to the lower end thereof, means for conveying this steam after passing up through the reheater tubes in the side walls to the upper end of the reheater tubes on the rear wall for passage downwardly therethrough, and header means at the lower end of the furnace communicating with the last mentioned reheatertubes and receiving the steam therefrom.

2. The organization of claim 1 wherein the superheater tubes on the furnace side walls are alternately arranged with regard to steam fiow.

3. The organization of claim 1 wherein each of the furnaces is of the hopper bottom type with the tubes lining the side walls being sloped inwardly at the lower region of the walls to form said hopper bottom.

4. A vapor generator operating on the reheat cycle comprising a pair of separate upright furnaces of generally rectangular transverse section providing a front, rear and two side walls with each of said furnaces having radiant vapor heating surface lining some of the walls thereof and with each furnace being fired in the lower region thereof, the radiant vapor heating surface of one furnace being comprised of superheating surface and that of the other furnace being comprised of reheating surface, said superheating surface including tubes extending verti-cally along the inner surface and throughout the length of each of the side walls of said one furnace, means for delivering vapor to the upper ends of about one half of these tubes on each side Wall, a common header for the tubes of each side wall and to which the lower ends of the superheating tubes on the respective side Walls are connected, the rear furnace wall of said one furnace having its inner surface lined with vertically extending superheating tubes, means delivering the vapor from the upper ends of the other half of the superheater tubes on each side wall and to the upper end of these rear wall tubes, means for conveying vapor from the lower end of these last-mentioned tubes to a point of use, said reheating surface including tubes extending vertically along the inner surface of each side wall and the rear well, these side wall tubes being in serial flow relation with the rear Wall tubes and with the arrangement being such that the steam to be reheated enters the lower ends of the side Wall tubes passes up therethrough and down through the rear wall tube and then to a point of use.

5. A vapor generator operating on the reheat cycle comprising a pair of separate upright furnaces of generally rectangular transverse section providing a front, rear and two side walls with each of said furnaces having radiant vapor heating surfaces lining some of the walls thereof and with each furnace being fired in the lower region thereof, vapor generating tubes disposed on at least some of the Walls of said furnaces and connected into a vapor generating circuit, said furnaces being in spaced relation for the interposition of a vapor and liquid drum therebetween, a vapor and liquid drum mounted in the space between said furnaces at the upper region thereof with the axis of the drum horizontal and parallel with the furnace walls delineating said space and with the drum forming part of the vapor generating circuit, the radiant vapor heating surface of one furnace being comprised of superheating surface and that of the other furnace being comprised of reheating surface, said superheating surface including tubes extending vertically along the inner surface and throughout the length of each of the side walls of said one furnace, means for delivering vapor to the upper ends of about one half of these tubes on each side Wall, a common header for the tubes of each side wall and to which the lower ends of the superheating tubes on the respective side walls are connected, the rear furnace wall of said one furnace having its inner surface lined with vertically extending superheating tubes, means delivering the vapor from the upper ends of the other half of the superheater tubes on each side wall to the upper end of these rear wall tubes, means for conveying vapor from the lower end of these last-mentioned tubes to a point of use, said reheating surface including tubes ex- 7 8 tending vertically along the inner surface of each side wall References Qlted in the file of this patent and the rear wall, these side wall tubes being in serial flow relation with the rear wall tubes and with the arrange- UNITED STA 1 ES PATENTS merit being such that the steam to be reheated enters the 2,609,798 nerly Sept. 9, 1952 lower ends of the side wall tubes passes up therethrough 5 2,737,160 AfmaCOSt 6t 1 M i 1956 and down through the rear wall tubes and then to a point 2,731,745 Armfl s 6 31 1957 of use. 2,863,424 Koch Dec. 9, 1958

Claims (1)

1. A VAPOR GENERATOR OPERATING ON THE REHEAT CYCLE COMPRISING A PAIR OF UPRIGHT FURNACES GENERALLY POLYGONAL IN TRANSVERSE SECTION AND DISPOSED IN SIDE BY SIDE SPACED RELATION, ONE OF SAID FURNACES COMPRISING A REHEAT FURNACE AND THE OTHER A SUPERHEAT FURNACE, SAID FURNACES HAVING COMBUSTION GAS OUTLETS AT THE UPPER END OF THEIR REAR WALL, PASSAGEWAY MEANS EXTENDING FROM SAID OUTLET, VERTICALLY EXTENDING STREAM GENERATOR TUBES LINING THE FRONT WALL OF EACH FURNACE AND THE FRONT PORTION OF EACH SIDE WALL THEREOF, A STREAM GENERATING CIRCUIT INTO WHICH THESE TUBES ARE CONNECTED AND WHICH INCLUDES A STREAM AND WATER DRUM POSITIONED INTERMEDIATE SAID FURNACES ADJACENT THE UPPER END THEREOF, EACH FURNACE HAVING PANEL MEANS FORMED OF VERTICALLY EXTENDING STEAM GENERATOR TUBES POSITIONED ADJACENT SAID FRONT WALL AT THE LOWER REGION THEREOF WITH SAID PANEL MEANS EXTENDING INTO THE FURNACE FROM SAID FRONT WALL AND DISPOSED IN SPACED RELATION ACROSS SAID FRONT WALL THEREBY FORMING HORIZONTALLY SPACED CHAMBERS IN THE FURNACE, MEANS FOR HORIZONTALLY INTRODUCING FUEL AND AIR INTO SAID HORIZONTALLY SPACED CHAMBERS, CONVECTION HEAT EXCHANGE SURFACE DISPOSED IN SAID PASSAGEWAY MEANS AND INCLUDING SUPERHEATING SURFACE FOR SUPERHEATING STREAM GENERATED IN SAID STREAM GENERATING TUBES, SAID SUPERHEATER FURNACE HAVING THE REMAINING PORTION OF ITS WALLS LINED WITH SUPERHEATER TUBES EXTENDING VERTICALLY THROUGHOUT THE LENGTH THEREOF, MEANS FOR CONVEYING STREAM FROM SAID CONVECTION SUPERHEATER SURFACE TO A GIVEN NUMBER OF THESE SUPERHEATER TUBES ON THE SIDE WALLS SO THAT THE STREAM IS CONVEYED DOWN THERETHROUGH WITH THESE TUBES BEING INTERCALATED AMONG THE REMAINING SUPERHEATER TUBES ON THE SIDE WALLS, MEANS FOR CONVEYING THIS STREAM AFTER PASSING DOWN THROUGH THESE SUPERHEATER TUBES ON THE SIDE WALLS UP THROUGH THE REMAINING SUPERHEATER TUBES, THE REAR FURNACE WALL BEING LINED WITH VERTICALLY EXTENDING SUPERHEATER TUBES THAT EXTEND FROM THE UPPER TO THE LOWER END OF THE FURNACE, MEANS FOR CONVEYING THE STREAM AFTER TRANVERSING SAID REMAINING SUPERHEATER TUBES DOWN THROUGH THESE TUBES LINING THE REAR WALL, HEADER MEANS AT THE LOWER END OF THE FURNACE COMMUNICATING WITH THESE LAST MENTIONED SUPERHEATER TUBES, SAID REHEATER FURNACE HAVING THE REMAINING PORTION OF ITS SIDE WALLS LINED WITH REHEATER TUBES THAT EXTEND VERTICALLY FROM THE LOWER END TO THE UPPER END THEREOF, HEADER MEANS RECEIVING STREAM TO BE REHEATED AND COMMUNICATING WITH THE LOWER END OF THESE REHEATER TUBES SO THAT THE STEAM IS CONVEYED UPWARDLY THERETHROUGH, THE REAR FURNACE WALL BEING LINED WITH REHEATER TUBES THAT EXTEND VERTICALLY FROM THE UPPER TO THE LOWER END THEREOF, MEANS FOR CONVEYING THIS STREAM AFTER PASSING UP THROUGH THE REHEATER TUBES IN THE SIDE WALLS TO THE UPPER END OF THE REHEATER TUBES ON THE REAR WALL FOR PASSAGE DOWNWARDLY THERETHROUGH, AND HEADER MEANS AT THE LOWER END OF THE FURNACE COMMUNICATING WITH THE LAST MENTIONED REHEATERTUBES AND RECEIVING THE STREAM THEREFROM.

Images