US2250536A - Steam generating apparatus - Google Patents

Description

July 29, 1941. J. E. KENNEDY STEAM GENERATING APPARATUS Filed June 10, 1938 5 Sheets-Sheet l ATTORN EY y 1941-- J. E. KENNEDY 2,250,536

' STEAM GENERATING APPARATUS Filed June 10, 1958 5 Sheets-Sheet 2 INVENTO R J. E; Kennedy ATTORNEY 5 Sheets-Sheet 3 J. E. KENNEDY STEAM GENERATING APPARATUS Filed June 10, 1938 July 29, 1941.

INVENTORI J. EKemwa/y ATTORNEY A J1 1 i w 5 fi y l941- J. E. KENNEDY 2,250,536

STEAM GENERATING APPARATUS Filed June 10, 1958 5 Sheets-Sheet 4 INVENTOR ATTORNEY July 29, 1941. J. E. KENNEDY STEAM GENERAT ING APIARATUS Fild June 10, 1958 5 Sheets-Sheet 5 I o a a Q oooeooooooec o oo ooooo oo ooooofoo oooo 00 000000000 .INVENTORI ATTOl RNEY Patented July 29, 1941 UNiTED srtrmz;

or ric STEAM GENERATING APPARATUS Application June 10, 1938, Serial No. 212,926

16 Claims.

' This invention relates to apparatus for generating steam by heat generated particularly from thecombustion of pulverized or other fluent fuel, and it is an object of the invention to provide an improved construction and arrangement of boiler elements and boiler furnace whereby there is a maximum exposure of the fluid conducting elements' of the boiler, and a maximum heat transfer to said elements of the radiant heat of combustion with an eflicient combustion of the fuel as well as an efficient utilization of the developed heat of combustion, and to provide a compact steam generating apparatus having a large steam generating capacity relative to the size of the apparatus and that is inexpensive to construct and maintain. 1 V

It is another object of the invention to provide a Water tube steam generating boiler, having, an improved system of connecting steamgand water conducting tubes with water and steamldrums utilizing a minimum number of headers to effect free and unrestricted circulation of the Water,

subjected to changes in pressure and temper-,

ature.

It isafurther object of the invention to pro-,

vide an improved water tube boiler including a steam and water drum withsteam and water con ducting tubes connected in circulation with'isaid drum to effect separation of the steam and water discharged from the tubes into the drum without setting up turbulent action of the water in the drum and producing an extremely dry steam.

It is a further object of the invention to provide a steam generating boiler including a furnace having front and side walls and an air preheater a wall of which is arranged to constitute the reariwallof the burner furnace, and battles arranged to provide a continuous passage for the heated gases without gas or soot pockets to effect a streamline flow of the heated gases therethrough with a plurality of passes thereof substantially at right angles to the Water and steam conducting tubes of the boiler and so proportioned that the mass velocity of the heated gases is increased in their passage through the successive passes and thus insuring maximum transfer and absorption of the heated gasesby the boiler'elements, and said passage having an exit outlet for said gasesat the rear of the boiler furnace in communication with an inlet for the gases into the air 'preheater.

It is another object of the invention to provide an improved construction and arrangement of water tube boiler furnace having upright side and front Walls and an arch or roof with asteamvand' water drum supported in elevated positio-nreare wardly of the furnace arch to permit of free and unrestricted expansion and contraction thereof. without transmitting the expansion ,and con traction forces thereof to the boiler setting, and, a mud and water drum connected in circulation with and suspended from the steam and water. drum by steam and water conducting tubes to; permit of free and unrestricted expansion and contraction of said drum and tubes, and arrang ing the boiler furnace with a water cooled bottom supported by cooling water conductingtubesv connected in circulation with the mud drum and headers at the bottom of the side and front fur -S nace walls with water wall tubes connected in circulation with said headers and the steam and Water drum extending in spaced relation .to the side and front walls and arch .of the boiler furnace to expose the entire' surface of the tubes to the radiant heat of combustion and permit expansion and contraction of the tubes without transmitting. the expansion and contraction forces to the walls of theboiler furnace. I

In the drawings accompanying and forming part of this application, a

Figure 1 is a longitudinal, sectional view of a steam generator embodying the invention, the

section being taken on the line I-l of Figure 5; looking in the direction of the arrows;

Figure 2 is a sectional detail view to show th brick;

means and method of supporting" the fire of the arch of the generator furnace;

Figures 3 and 4 are sectional views taken substantially on the lines 3-3 and 4'4-,- respectively, of Figure 1, looking in the direction of the arrows;

Figure 5 is a sectional view taken substana tially on the line 5-5 of Figure 1, looking in the direction of the arrows and showing the 'manner' of supporting thefurnace'wall and headers by the boiler setting, with a portion of the headers arranged with hand holes exterior of the boiler setting;

Figure 6 is a sectionalview taken substantially on the line 66 of Figure 1, looking in the direction of the arrows; 4 7

Figure '7 is a sectional view showingthe ar generator; H

Figure 8 is a sectional view taken substantially water drum of the steam;

on the line 8-8 of Figure 1, looking in the direction of the arrows;

Figure 9 is a sectional detail view taken substantially on the line 9-9 of Figure 8, looking in the direction of the arrows, and showing the mounting of a header relative to the boiler setting at the side wall of the boiler furnace, and showing the connection thereto of water wall tubes for the furnace and screen bottom water cooling tubes; and

Figure 10 is a sectional, detail view taken substantially on the line l-l0 of Figure 9, looking in the direction of the arrows.

In carrying out the embodiment of the invention shown in the drawings, a steam and water drum D is supported in elevated position to extend transversely of the top and rear of the boiler furnace upon saddles H mounted on horizontal girders l2, fixed on and carried by vertical structural steel members [3, the drum being supported upon the saddles to permit it to have free expansion and contraction movement in all directions. The water and mud drum D, of smaller size than the drum D, is connected in circulation with and suspended from the drum D to extend transversely of the rear lower portion of the boiler furnace by a bank of down comer tubes T, whereby the mud drum and tubes are adapted to have free and unrestricted expanding and contracting movements in all directions. The bank of tubes T is in the nature of an economizer section of the steam generator, and comprises a series of laterally spaced parallel rows of tubes disposed about and connected at one end to the drum D, below the center of the same, and connected at the opposite ends of the drum D above the center thereof, as shown in Figure 1. The drums and the tubes T are arranged at the rear of the combustion space of the boiler furnace.

The furnace comprises vertical front and side walls of brick I4, l and I6, respectively, having an inner lining of refractory material, such as fire brick, and a rear wall I! disposed below the mud drum D. The front and side walls are supported upon a base or setting S, by plates 18 supported on chairs l9 in the form of sections of I beams, as shown in Figures 9 and 10. The roof or arch of the furnace inclines slightly upwardly from the front wall to the steam and water drum D, and comprises fire brick suspended in rows extending transversely of the furnace by hangers. The two rearmost rows of brick are suspended by hooks, as shown at 20 in Figure 2, mounted on members 2| fixed upon and extending transversely of channel members 2|, extending between and fixed to the structural steel members l3, the remainingbrick being suspended by hangers, as at 20 in Figure 2, from transverse members 22 fixed to and extending between girders 22' fixed at one end on the channel member 2 l and at the opposite end to structural steel members I 3 disposed at the outer side and opposite ends of the front furnace wall M. The upper portion of the steam and water drum D is enclosed in a layer of heat insulating material 24 and a wall 24' declines rearwardly from below the axis of the drum to a vertically disposed layer of monolithic material 25 extending between the side walls at the rear of the furnace for a purpose hereinafter described. A baffle 26 curves downwardly from the layer of material 25 with the concave side uppermost and then declining forwardly to a point within the second row of the bank of tubes T with the other tubes extended through openings in said baflle. To provide a circuitous passage for the hot gases from the combustion space of the furnace to the outlet, a battle 21, substantially of U shape in cross section, extends between the side walls of the furnace with an end of one portion extending substantially tangentially to the top of the mud drum D and diverges upwardly and forwardly, and to the rear of the combustion space of the boiler furnace, and then curved rearwardly and extending rearwardly and inclining upwardly from the horizontal in spaced relation to the declining portion of the baffle 26, and terminates within the second rearmost row of tubes of the bank T, with the remainder of said tubes extended through openings in said bafile, as shown in Figure 1. By this arrangement of the bafiles there is provided a circuitous passage for the hot gases of combustion from the combustion space without sharp corners and gas and soot pockets, and providing three passes for the flow of gases at substantially a right angle to the bank of tubes T. This arrangement and proportionment of bafiles increases the mass velocity of the hot gases as they pass through the successive passes which insures a maximum transfer and absorption of the heat of the gases of combustion by the boiler elements. From this passage the gases flow to and from the outlet of the passage to a hopper bottom 28 of an air preheater juxtaposed to the vertically disposed wall 25 constituting the rear wall of the boiler furnace, and serving to insulate said wall of the air preheater from the heat of the gases in their passage over the baffle 21 to above the bafiie 26. The air preheater is shown as comprising a casing having a header plate at the opposite ends, as 30, with the ends of spaced tubes 31 fixed in said header plates and opening to the hopper bottom and a chamber 32 in the casing connected to the stack for the exhaust of the waste gases of combustion, the easing 29 having an air inlet and an air outlet for the flow of air therethrough, preferably in a direction reverse to the flow of the gases through the tubes 3|. The boiler is adapted to be fired by fluent fuel, particularly pulverized coal, and a burner or burners, shown as two in number, B, are arranged in burner mountings 32' in superposed openings in the front wall of the burner furnace. The combustion chamber of the furnace is arranged with a water-cooled screen bottom disposed above the furnace setting S, to be hereinafter described.

The rear of the combustion chamber of the furnace is defined by a bank of riser steam and water conducting tubes T, connected in circulation with the drums D, D' and shown as comprising three rows of tubes spaced transversely of the furnace, and the rows of tubes spaced rearwardly of the combustion chamber. The tubes T are connected at one end to the drum D at and above the center of the drum, diverge forwardly and upwardly toward the combustion space from the drum, then extend upwardly, inclining slightly forward from the vertical to adjacent the top of the furnace, then curved rearwardly through an arc of substantially and inclined slightly upwardly from the horizontal and connected to the drum D above the horizontal center of the drum and level of the water therein, thereby permitting discharge of water and steam from said tubes across the level of the water in the drum and producing a separation of water from the steam, the steam rising and the water falling by gravity, effecting a natural separation of the water from the steam and producing. a substantially dry steam. The tubes of bank T are of larger diameter than the tubes of bank T, and as there is a larger number of tubes in the latter bank there is a greater surface for the transfer and absorption of the heat of the hot gases of combustion, said bank of tubes in effect functioning as an economizer section of the steam generator unit.

The front and side walls, as well as the top of the combustion space of the boiler furnace, are arranged with water walls. The water wall of the front wall is defined by a row of laterally spaced riser tubes '1' having a portion extending vertically of and spaced from the front wall of the combustion chamber to adjacent the top of the furnace, then curved laterally substantially through an arc of 90 and extend along and in spaced relation to the top of the furnace. The tubes are secured at one end in communication with a manifold or header 34, extending transversely of the bottom of the front wall of the furnace, and supported at the .ends upon the furnace setting and intermediate the ends upon the chairs l9, so that a portion of the header is arranged within the combustion chamber, and preferably covered with a refractory -material, so that the header is not exposed directly to the radiant heat of combustion. A portion of the header is exposed to the exterior of the furnace and arranged with hand holes having removable covers, as at 35, to readily gain access to the interior of the header for removing and securing of the tubes and cleaning the same, as shown in Figure 5.

The tubes T are connected at the opposite end to the drum D above the horizontalcenter and level of the water therein, whereby the water discharged with the steam from said tubes into the drum will be separated from the steam and fall by gravity. By the arrangement of the tubes '1 there is provided a free and unrestricted fiow of fluid through the tubes from the header 34 to the drum D, and the tubes are arranged to have free and unrestricted expansion and contraction, without the possibility of exerting the expansion and contraction forces to the furnacewall. To permitlof the free and unob-' structed discharge of fuel into the combustion chamber, the center tubes of the row of tubes "1 are offset laterally to opposite sides intermediate the ends, as at 39 in Figure 5, and the four successive tubes outwardly from said center tubes are offset progressively to a less extent than the tubes 30, and maintained out of engagement with each other, as clearly shown in said Figure 5. The header 34 is in a lower plane than the mud drum D, and circulation of water is from the mud drum to the header by tubes 31 extending forwardly and downwardly from the mud drum, and then extending substantially in a horizontal plane below the bottom of the boiler furnace.

Each of the side walls l5, l6 of the combustion chamber is arranged with a water wall comprising a row of riser tubes T and T extending relative to the walls and spaced laterally from each other and the walls. are complemental to each other and disposed in a lateral recess portion of the side walls of the furnace, as shown in Figures 6 and 8. The first tube 38 of each of said rows of tubes, as shown in Figure 1, is connected'to the front header 34, extends vertically of the'side wall to adjacent the top'of the furnace, then curves'rearwardly These rows of tubes through an arc of substantially and then extends transversely of the side wall and connected to the drum D. The remaining tubes 38 of the rows of tubes T3 and T are connected to manifolds or headers 34' and 34 extending transversely of the lower portion of the side walls. The headers are supported at the opposite ends by the boiler setting and intermediate the ends by the chairs l9, similar to supporting the header 34, with a portion of the headers arranged within the furnace, preferably provided with a covering of refractory material so-they will not be exposed directly to the radiant heat of combus tion. A portion of the headers is exposed exterior of the furnace and arranged with hand holes having removable covers 35, similar to the header 34, for gaining ready access to the interior of the headers to remove and secure the tubes therein, and clean the same. The headers 34, 34 as well as the header 34, are provided with a drain outlet leading from thebottom thereof, and as shown at 35' in Figures 9 and 10, extended through the boiler setting. H V

The rows of tubes T and T successive to the first of said tubes each have a vertically extending portion and such portion of successive tubes rearwardly is of progressively" decreasing length. The tubes at the termination of the vertical portion are curved rearwardly through an arc of substantially 90 with a' portion extending transversely of the furnace wall parallel to the corresponding portion of the first of said tubes 38; and

spaced from each other, as shown at 38 in Figures '3 and 4, and connectedin circumferentially spaced relation about the ends of the drum D. The portions 38' of the tubes. from intermediate said rows of tubes T and T toward the rear of the combustion space are curved reversely upon themselves, as shown at 38* in Figure 1. Circulation'of water to the headers and tubes" T and T is from the mud drum B through tubes 39 connected at one end to and spaced longitudinally of the drum, as shown in Figure 8, the tubes extending forwardly and downwardly from the drum to extend in a plane below and parallelly ofthe tubes 31 for a portion of the length thereof, as'shown in Figure 4, and then. curved laterally andconnected to the headers 34, 34 In the present instance, as shown in Figure 8, the tubes 39 are shown as twelve in numberfsix of the tubes inwardly from one end of the drum being connected to the header 34' and the six tubes inwardly from the opposite end of the drum connected to the header 34 The tubes 39' are arranged in pairs, similar to' the tubes3l, a portion of the tubes extending parallelly of and below thetubes 31, the outer pair of t'ubes39 extending parallel to the associated tubes '31 to a less extent than the remaining- The tubes 39 are curved laterally through tubes. an arc of substantially 90-from" the portion extending parallelly of the tubes 31 and with the tubes successively inward fromthe first'tube being spaced longitudinally of the headers. By:v

through anarc' of 90,they are adapted to have free and unrestricted expansion and contraction as well as'free and unrestrictedcirculation of water andsteam therethrough." By the connec: tion of the tubes T and water. wall. tubes with:

the steam and water drum D, without any interposed header, it permits of an increased velocity in the flow of the steam and water, making it possible to generate an extremely dry steam, and producing a highly efficiently operating steam generator, in view of the dry steam, which is determined by the fact that the concentrates of feed water for the headers of the water wall tubes and the generator builds up equally, the dryness of the steam obtained and maintaining a stable water level. Furthermore, by the arrangement of the bank of economizer tubes T and the arrangement of the baflles to effect free passage of the exit gases substantially at right angles to said tubes, efliciency is obtained from the low temperature exit gases.

By the arrangement of fixedly supporting the headers and connecting the tubes 31 and 39 to the front and side headers and the drum D whereby the tubes diverge downwardly from said drum and emerge in a curved portion with a portion of the tubes extending substantially in a horizontal plane, and, connecting the rows of tubes T T and T to the fixed headers and arranging said tubes intermediate the connection thereof with the drum D with a curved portion and spaced from each other and the front and side walls of the furnace, permits of expansion and contraction of all of the tubes without exerting stresses and strains on the tubes to loosen the connection thereof with the headers or the drums D and D.

- The bottom of the boiler furnace is arranged above the tubes 3! and 39 and cooled by the water flowing therethrough, as shown, strips of refractory material or brick are mounted upon and supported by pairs of the tubes 31 to extend longitudinally thereof, the strips of refractory material being spaced laterally of the bottom of the boiler furnace and thus arranging the same as an ash screen bottom, as shown at 40 in Figure 4. The ash settles to the bottom of the furnace and passes through the spaces or slots between the refractory material into troughs arranged below the furnace bottom, the walls of the trough being arranged to converge toward the bottom thereof to direct the ash to the bottom of the troughs. The ash collected in the troughs is removed therefrom by suitable means, and shown as a screw conveyer 4| rotatable in each trough. The drum D is provided with a suitable inlet adapted for connection with a water supply and V steam outlet means 42, and arranged with pressure and water level indicating gauges P and W, and the drum D is provided with a drain outlet.

While I have illustrated and described one embodiment of steam generating apparatus for carrying out my invention, it will be obvious that various modifications may be made in the construction and arrangement of the parts without departing from the scope of the invention, and that portions of the invention may be used without others and come within the scope of the invention.

Having described my invention, I claim:

1. In a steam generating unit, a furnace having upright front and side walls, upper and lower horizontal drums, down comer tubes connecting said drums in water circulation at the rear of the combustion space of the furnace, a fixed header extending transversely of the lower portion of the front wall of the furnace with a peripheral wall portion disposed within the furnace chamber, a horizontal row of laterally spaced tubes at the bottom of the furnace connecting said header in water circulation with the lower drum, a row of riser tubes connected to said header through the wall portion thereof within the furnace chamber, said tubes having a vertical portion extending in parallel and spaced relation to each other and the front wall of the furnace to adjacent the top of the furnace, and then curved rearwardly and extending in parallel spaced relation to each other and the top of the furnace and connected to the upper drum above the axis thereof.

2. In a steam generating unit, a furnace having upright front and side walls, upper and lower drums and tubes connecting the drums in water circulation and suspending the lower drum from the upper drum, said drums and tubes being arranged at the rear of the combustion space of the furnace, fixed headers extending transversely of the lower portion of the front and side furnace walls, rows of tubes below the bottom of the furnace chamber connecting said headers in independent water circulation with the lower drum and with the row of tubes connected to the front header superposed to the tubes connected to the side headers, a row of tubes disposed relative to the front wall and top of the furnace connected in circulation with the front header and the upper drum above the axis thereof, and a row of riser tubes disposed relative to each side furnace wall, one of said latter rows of tubes connected to one side header and the upper drum in circumferentially spaced relation about one end thereof and the other of said rows of tubes connected to the other side header and the upper drum in circumferentially spaced relation about the other end thereof, and the tubes of each row of tubes disposed relative to the front wall and top and side walls of the furnace being arranged in spaced relation to each other and the walls of the furnace to expose the entire surface of the tubes to the radiant heat of combustion and to permit of unrestricted expansion and contraction of the tubes without exerting stresses on the tubes to loosen the connections of the tubes with the headers and drums.

3. A steam generating unit as claimed in claim 2, wherein a peripheral wall portion of each header is disposed within the furnace and the tubes connected to said wall portion of the headers.

4. In steam generating units, a furnace having upright front and side walls, upper and lower horizontal drums, tubes connecting said drums in water circulation and said drums and tubes arranged at the rear of the combustion space of the furnace, headers fixed upon supports and extending transversely of the lower portion of the side and front walls of the furnace arranged with a peripheral wall portion disposed within the furnace chamber and a peripheral wall por tion exterior of the furnace arranged with hand holes, rows of tubes disposed below the bottom of the furnace chamber connecting said headers in independent water circulation with the lower drum, a row of tubes connected to the wall portion of the front header disposed in the furnace chamber having an upright portion disposed relative to the front wall and extending adjacent to the top of the furnace, then curved rearwardly and having a portion disposed relative to the top of the furnace and connected in circulation with the upper drum above the center thereof, and a row of tubes connected to the wall portion of each side header disposed within the furnace chamber relative to the side furnace walls, each tube of each of said rows of tubes having an upright portion, then curved rearwardly with a portion extending transversely of the furnace wall, the upright portion of the forward tube of each ofsaid rows of tubes extending adjacent to the top of the furnace and the upright portion of the tubes successively inwardly of said first tube being of progressively decreasing length and said upright portion of the tubes rearwardly from the tube midway the rows of said tubes curved reversely and connected in circulation with the upper drum in circumferentially spaced relation about the ends and below the axis of the drum, and the tubes of each row of tubes disposed relative the front and side walls of the furnace arranged in spaced relation to each other and the furnace walls to expose the entire surface thereof to the radiant heat of combustion in the furnace, and said rows of tubes and the tubes connecting the header to the mud drum arranged to permit of unrestricted expansion and contraction of the tubes without exerting stresses on the tubes to loosen the connection of the tubes with the drums and headers.

5. A steam generating unit asclaimed in claim a 2, wherein the headers are supported in fixed position on chairs supporting the furnace walls mounted on the furnace setting with a peripheral wall portion of the headers disposed within the furnace in which wall portion of the headers the tubes are mounted, and a peripheral wall portion of the headers disposed exterior of the furnace and arranged with hand holes having removable closures to facilitate connecting the tubes to and disconnecting the tubes from the headers.

6. In a steam generating unit, a furnace having upright front and side walls, upper and lower horizontal drums and tubes connecting said drums in water circulation at the rear of the combustion space of the furnace, fixed headers extending transversely of the lower portion of the front and side walls of the furnace, a row of tubes disposed relative to the front wall and top of the furnace connected at one end to the front header and the opposite end connected to the upper drum above the axis thereof, a row of tubes disposed relative to each side furnace wall, each of said rows of tubes connected at one end to a side header and connected at the opposite ends to the upper drum in circumferentially spaced relation about an end thereof, and a row of tubes connecting each header in independent water circulation with the lower drum and exe tending below the bottom of the furnace, and the tubes of each row of tubes shaped to permit of unrestricted expansion and contraction of the tubes without exerting stresses to loosen the connections of the tubes with the headers and drums.

7. In a steam generating unit, a furnace having upright front and side walls, upper and lower drums, tubes connecting said drums in water circulation and suspending the lower drum from the upper drum at the rear of the combustion space of the furnace, a fixed header extending transversely of the lower portion of the front wall of the furnace, a horizontal row of tubes' spaced laterally of and extending below the bot-' tom of the furnace connecting said header in water circulation with the lower drum and said 'tubes shaped to permit of unrestricted expansion and contraction of the tubes without exerting stresses on the tubes to loosen the connections of the tubeswith the drum and header,

and .tubesyconnected' in a spaced row to said header, said tubes having an upright portion extending in parallel spaced relation to each other and the front-furnacejwall to adjacent the top of the furnaceand aportion extending in parallel 4 spaced relation to each other and the top of the furnace'connected tothe upper drum in a row spaced.longitudinallyof the drum above the axis thereof, and said. tubes arranged with a curved portion connecting the, Portions of the tubes extending relativexto the front wall and top of the furnace whereby said tubes are adapted to have expanding and contracting movement without exerting stresses on the tubes to loosen the connections of said tubes with the drum and header and without transmitting the expansion and contraction forces of the tubes to the furnace wall.

.8. In a steam boiler, a furnace having upright front and side walls, upper and lower drums, tubes connecting said drums in water circulation and suspending the lower drum from the upper drum'at the rear of the furnace chamber, fixed headers extending transversely of the lower portion of the front and side walls of the furnace, horizontal rows of superposed tubes spaced laterally of and extending-transversely of the bottom of the furnace chamber connected at one end to the lower drum, the upper row of said tubes connected :at the opposite ends to the front header and the other row of tubes connected at the opposite ends to and spaced longitudinally of the side headers, a row of tubes connected at one end to the front header disposed relative to and spaced from the front wall and top of the furnace and connectediat the opposite ends to the upper drum" above the center thereof, a row of tubes connected at one end to each side header and disposedrelative to and spaced from each other and the side walls of the furnace and connected at the opposite end to the upper drum, the

connections of one of said rows of tubes with the upper drum being circumferentially spaced around one end of the drum and the connections of the opposite end of the other of said rows of tubes with the upper drum being circumferentially spaced about the opposite end of the drum,and said rows of tubes connected to the headers and the upper drum being arranged to expose the entire surface thereof to the radiant heat'of combustion in'the furnace, and said rows of tubes and the rows of tubes connecting the headers with'the lower drum arranged to have unrestricted expansion and contraction without the expansion and contraction forces loosening the'connections of the tubes with the headers and the drums.

9. In a steam generating unit, a furnace having upright'front and side walls, an upper drum, a lower'drum and a bank of tubes connecting said drums in water'circulation at the rear of the furnace; a header extending transversely of the lower portion of'the front furnace wall, tubes connected in a horizontal spaced row to said header and the lower drum, strips of refractory material supported-on said tubes in laterally spaced relation and arranging the furnace with a water cooled screen bottom, and a row of riser tubeslconnected at'the ends in openings spaced longitudinally of said header and upper drum arranged in parallelly spaced relation to the front said drums in Water circulation at the rear of the furnace, a header extending transversely of the lower portion of the front furnace wall, a row of horizontal spaced tubes connected to said header and the lower drum, strips of refractory material supported on said tubes in laterally spaced relation and arranging the furnace with a water cooled screen bottom, a row of riser tubes connected to said header and the upper drum arranged in parallelly spaced relation to the front wall and top of the furnace, headers extending transversely of the lower portion of the side furnace walls, a row of tubes disposed relativeito each side wall of the furnace connected to said headers the upper drum in circumferentiall-y spaced relation about the ends thereof, and tubes connecting said headers to the lower drum, said latter tubes being connected to the drum in a row spaced longitudinally of the drum with half the tubes inwardly from one end of the drum connected to one side header and the tubes inwardly from the other end of the drum connected 'to' the other header, the successive tubes inwardly from the ends of the drum having a portion of progressively increasing length extending parallelly below the tubes connected to the front header and then curved laterally and connected to the headers.

11. In a steam generating unit, a furnace having upright front and side walls, an upper drum, a lower drum and a bank of tubes connecting said drums in water circulation in the rear portion of the combustion space of the furnace, headers extending transversely of the lower portion of the side furnace walls, a horizontal row of tubes connected at one end in openings spaced longitudinally of the lower drum, said tubes inwardly from one end of the drum to midway the drum connected at theopposite ends in openings spaced longitudinally of one side header, and the tubes of said row of tubes inwardly from the oppositeend of the drum to midway the drum connected at the opposite end in openings spaced longitudinally of the other side header, and a row of riser tubes disposed relative to each side wall of the furnace, the tubes of each of said rows of tubes being connected at one end in openings spaced longitudinally of a side header and connected at the opposite end in openings spaced circumferentially about an end of the drum below the axis thereof, and the tubes of said rows of tubes spaced from each other and the side walls of the furnace and arranged to permit expansion and contraction of the tubes without exerting forces thereon to loosen the connections of the tubes with the headers and drums and without transmitting said forces to the side walls of the furnace.

12. In a steam boiler, a furnace having upright front and side walls, an air preheater including a vertically disposed casing arranged with a wall at and constituting the rear wall of the furnace, said air preheater having an inlet at the lower end for the products of combustion exiting from the furnace, heat resisting material on said wall of the air preheater within the furnace, upper and lower horizontal drums connected in water circulation by a bank of downcomer tubes disposed with one side of the bank of tubes opposed to said rear furnace wall and the opposite side of the bank of tubes opposed to the combustion space of the furnace chamber, a bank of riser tubes connected to said drums forwardly of the downcomer tubes in the combustion space-of the furnace, a bafile extendthe top of the lower drum and then upwardly be; tween the banks of riser and downcomer tubes to substantially midway the drums and then extended rearwardly transversely of the bank of downcomer tubes and terminating in spaced relation to the rear furnace'wall, and abafiie ex.- tended forwardly from the rear. furnace wall transversely of the bank of downcomer tubes intermediate the first baffle and lower drum and terminating in spaced relation to the upwardly extending portion of the first baflle, said baffles forming a passage for the flow ofthe gases of combustion from the combustion space'of the furnace having a series of passes extending substantially at right angles to the bank of downcomer tubes, and said passage having an inlet from the combustion space of the furnace chamber at the upper end of said bank of tubes and an outlet at the lower portion of said tubes in communication with the inlet to the air preheater.

13. In a steam generating unit, a furnace having upright front and side walls, upper and lower horizontal drums and downcomer tubes connecting the drums in water circulation and suspending the lower drum from the upper drum, said drums and tubes being arranged at the rear of the combustion space of the furnace, a fixed header extending transversely of the lower portion of each side wall of the furnace, a horizontal row of laterally spaced tubes at the bottom of the furnace connected at one end in openings equidistantly spaced longitudinally of said lower drum, and said tubes inwardly from one end to midway the drum connected at the opposite ends in openings spaced equidistantly longitudinally of one side header and the tubes inwardly from the opposite end to midway the drum connected at the opposite ends in openings spaced equidistantly longitudinally of the other side header, and a row of tubes connected at one end in openings spaced equidistantly longitudinally of each header, the tubes of each of said rows of tubes having an upright portion extending in parallel and spaced relation to each other and a side wall of the furnace, the upright portion of the first tube in each row being adjacent the front furnace wall and extending substantially to the top of the furnace, and the upright portion of the successive tubes inwardly from said first tube to the rear of the furnace being of progressively decreasing lengths, and the tubes curved rearwardly from the upright portion with a portion extending transversely of the furnace wall and said latter portion of the tubes midway of the rows of tubes to the rear of the furnace curved in a reverse direction and extending upwardly, and said rows of tubes connected in openings circumferentially spaced about the ends of the upper drum below the axis thereof and arranged in spaced relation to each other and the side walls of the furnace.

14. In a steam generating unit, a furnace having upright front and side walls, upper and lower ing intothe combustion space of the furnace'from horizontal drums, tubes connecting said drums in water circulation in the rear of the furnace chamber, a header disposed relative to the lower portion of the front furnace wall, a horizontal row of laterally spaced tubes connecting the lower drum and said header in water circulation, a row of tubes connected at one end to said header disposed relative to the front wall and top of the furnace and connected at the opposite ends to the upper drum, refractory material extending longitudinally above and bridging the spaces between successive pairs of tubes of the horizontal row of tubes and arranging the furnace with a screen bottom, a pair of troughs below and adapted to collect ash therein passing through the screen bottom, the walls of said troughs extending parallelly of the horizontal row of tubes with one wall of each trough declining from the bottom and a side wall of the furnace and the other walls declining from the bottom of the furnace midway the side walls of the furnace toward the bottom of the troughs, and a screw conveyor disposed in the bottom of each trough operative to deliver ash from the troughs.

15. In a steam generating unit, a furnace having an outlet for Waste gases of combustion in the rear wall adjacent the bottom of the furnace, upper and lower horizontal drums connected in Water circulation by a bank of downcomer tubes disposed with one side of said tubes opposed to the combustion space of the furnace chamber, a bank of riser tubes connected to said drums forwardly of the downcomer tubes in the combustion space of the furnace, a baffle extending into the combustion space of the furnace from the top of the lower drum and then upwardly between the banks of riser and downcomer tubes to substantially midway the drums and then extended rearwardly transversely of the bank of downcomer tubes and terminating in spaced relation to the rear furnace wall, and a baffle extended forwardly from the rear furnace wall transversely of the bank of downcomer tubes intermediate the first baiile and lower drum and terminating in spaced relation to the upwardly extending portion of the first baflie, said bafiles forming a passage for the flow of the gases of combustion from the combustion space of the furnace having a series of passes extending substantially at right angles to the bank of downcomer tubes, and said passage having an inlet from the combustion space of the furnace at the upper end of. said bank of downcomer tubes and an outlet at the lower portion of said tubes in communication with the outlet of the furnace.

16. In a steam generating unit, a furnace having upright front and side walls, upper and lower horizontal drums and tubes at the rear of the combustion space of the furnace connecting the drums in water circulation, a row of riser tubes having a vertical portion disposed relative to and extending substantially for the height of the front furnace Wall and a portion disposed relative to the top of the furnace connected in independent Water and steam circulation with the drums, a row of riser tubes disposed relative to each side wall of the furnace connected in independent water circulation with the drums, the row of tubes disposed relative to the front wall and top of the furnace and the rows of tubes disposed relative to the side Walls of the furnace arranged in spaced relation to each other and the furnace Walls to expose the entire surface of the tubes to the radiant heat of combustion in the furnace and permit of expansion and contraction of the tubes without transmitting the expansion and contraction forces to the walls of the furnace.

JOSEPH E. KENNEDY.

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