US2636484A - Steam generator - Google Patents

Description

Ap 28, 1953 E. e. BAILEY ETAL STEAM GENERATOR 7 Sheets-Sheet 1 Filed April 8, 1949 INVENTOI QS Erv/n G Halley & BY Ro/p/r M Hardgrove AfiORNEY Q c F owm lllllllnvll l ||||l||| & i1

April 28, 1953 E. G. BAILEY ETAL STEAM GENERATOR '7 Sheets-Sheet 2 Filed April 8, 1949 MQ mg m% w% 5 Mr Em M EQ e y w mww mm w m m m I. n Y B ATTORNEY '7 Sheets-Sheet .3

E. G. B'HLEY ErAL STEAM GENERATOR NE. ww\ 0% 0w 0% Mam 000000000000000000000009 000000000000000000000000000 O0O00000000000000000000000000 000000000000000000000 00000000000000000000000000 0000000000000000000000000 00000000000 0000000000000 O000000000000000000000000 0000000000000000000000000 00000000000000000 000000000000000000 00000000000 April 28, 1953 Filed April 8, 1949 INVENTORS' Erv/n G. Ba/leg 5 ATTORNEY A ril 28, 1953 5;. e. BAILEY EI'AL STEAM 'GENERATOR 7 Sheets-Sheet 4 Filed April 8, 1949 & w

m W NM -Nm D" Y B ATTORNEY April 3, 1953 E. e. BAILEY ETAL 2,636,484

' STEAM GENERATOR Filed April 8, 1949 7 Sheets-Sheet 6 v I N 1- KO g INVENTORS Ervin G. Bar/72y &

f Y Ralph M. Hardgrove WW ATTORNEY April 28, 1953 E. G. BAILEY EI'AL STEAM GENERATOR Filed April 8. 1949 7 Sheets-Sheet 7 m NK g fi Q we 0 Q Q DON II u 11 5 m 1 i MM mmw am m o w 1 N w INVENTORS Erv/n G Bailey 3 BY Ralph M Hardgrove ATTORNEY which would interfere with Patented Apr. 28, 1953 STEAM GENERATOR Ervin G. Bailey, Easton, Pa., and Ralph M. Hardgrove, Canton, Ohio, assignors to The Eabcock & -Wilcox Company, Jersey City, N. J., a corporation of New Jersey Application April 8, 1949, Serial No. 86,174 V a This invention relates to a steam generating installation of the water tube type.

The invention, more particularly, relates to a water tube steam generator adapted for operation at high capacities and high steam pressures and for the effective use of pulverized fuel in the furnace of the installation.

'The steam generator of the invention is particularly adapted for the efficient generation of steam at high capacities, with effective use of minimum space requirements for the furnace and the convection components of the installation, these characteristics making the steam generator advantageous for use in a locomotive.

The steam generator of the installation involves a water cooled furnace used in conjunction with steam generating water tubes, some of which form the boundary walls of the furnace which is particularly adapted for the burning of pulverized coal as fuel.

' In the interest of high ignition temperatures, and of complete combustion of fuel, high furnace temperatures are maintained in the primary .or high temperature zone of the furnace. The combustion of the coal in this zone results in the liberation of ash which is raised to a temperature above its fusion point or the fusion point of any of its several constituent chemicals. Consequently, the individual particles of molten ash or slag, and larger particles resulting from the coalescing of several individual particles exist in suspension in the gases in the high temperature zone of the furnace and, somewhat beyond that zone. Some of these particles contact the furnace boundary surfaces and adhere thereto. They are at first chilled and solidified by the proximity of the cooler surfaces of the water tubes of the furnace, the lower temperatures of these tubes being maintained by fluid circulated through them. As a stratum of this chilled slag is built up from the wall surface, a condition is ultimately reached which, due to the thermal resistance of the layer so formed, and due to the high temperature existing in the furnace, results in the surface stratum which normally remains at the fusion temperature of the slag. Additional particles are deposited thereon in molten condition, flow down the surfaces of the stratum on the furnace walls and, at high capacities, result in a considerable flow of moltenash to the furnace floor. This flow of excess molten ash is, in the illustrative installation continuously dis posed of so as to prevent such an accumulation the'efiicient operation of the furnace.

15 Claims. (Cl. 122--328) Other particles of molten slag remain in suspension in the gases as they flow from the furnace and through succeeding gas passages. Some of these remaining particles contact the walls of these passages which, in the illustrativ installation, are formed by heat absorbing fluid conducting tubes. Under these conditions heat is radiated from the suspended particles as well as from the gases in which the particles are suspended. This heat is radiated to the walls and is absorbed and the degree of radiation and absorption varies with the temperature differential between the particles and the heat receiving wall surfaces. Also, this differential is, in turn, dependent upon the cleanliness of the wall surfaces, or the freedom of those surfaces from slag accumulation and the attendant thermal resistance and higher surface temperatures caused thereby.

Some of these conditions are beneficial to one stage of the combustion and heat absorption process, but, are detrimenta1 to other stages. In the stage or zone where combustion is taking place there are important advantages resulting from the high temperature of the furnace boundary surfaces. Examples of such advantages are the expedition and the completion of combustion. In stages or zones beyond the primary combustion zone, and after substantially complete combustion is effected, the major consideration is a high rate of heat absorption. This necessitates boundary walls at relatively low temperatures in order to effect high temperature differentials between the water or other fluid cooling the walls, and th combustion components transmitting heat thereto.

The present invention contemplates a steam generator which utilizes a convection section and a furnace gas tempering section in combination with a furnace, all operating in such a manner as to effectively meet the above indicated conditions and operating with a high availability factor under different conditions such as those involved by the use of coals from different sources. Goals from different seams or different sources used in pulverized form in furnaces all contain ash in greater or lesser amounts and the 'ashes from the different coals not only differ in chemical constituency but also differ in fusion temperatures.

One object of the invention is to provide a steam generating installation in which combustion gases and their suspended solids are effectively cooled after. they leave the high temperaturezone of the furnace and before then-reach the heat absorption zone formed by the spaced tubes of the convection section. Such tempering action is associated with means providing for the elimination of the cooled ash solids separated in the tempering zone, both of these actions preventing the tubes of the convection section from receiving suchv accumulations of. ash thatthey would soon become covered thereby to such an extent that the installation would lose its optimum steam generating capacity as a result of the closing of the gas passages between adjacent tubes.

The invention will be described with reference to an illustrative embodiment shown in the accompanying drawings, and further objects of the invention will appear as the description proceeds.

In the drawings:

Fig. 1 is a longitudinal vertical section through the illustrative installation;

Fig. 2 is a partial sectional plan, or horizontal section, on the line 2-2' of Fig. 1. This view shows only part of the installation involving the high temperature zone of the furnace and the gas tempering section of the installation immedi ately adjacent the furnace and receivingfurnace gases directly therefrom;

Fig. 3 is a partial sectional plan complementar-y to Fig. 2, taken on the same plane as Fig. 2 and showing the arrangement of the elements of the convection section, rearwardly of the gas tempering section shown in. Fig. 2;

Fig. 4 is a vertical section on the line 5-4 of 1 and looking in the direction of the arrows. This figure shows the arrangement of the steam generating tubes. delineating. the walls, roof, and

floor of the high temperature section. of the furnace;-

Fig". 5 is; a vertical section on. the; multiple plane line 55 of Fig. 1, looking in the direction of. the associated arrows and with: parts of some of. the tubes lid-bl: being: omitted for the sake of clarity;

Fig. 6 is a vertical section. through the installation on. the line E-5. of Fig; 1,. indicating the construction. of the, superheater;

Fig.7 is a transverse vertical section; on. the line t-'l of Fig- 3., showing the construction; and arrangement of the tubes for the main. bank. M of steam. generating tubes;

8 is a transverse vertical section on the line: 8-tt of Fig. 1. showing the. arrangement of the more. closely spaced tubes of the screen section', immediately rearwardly of. the: screen: sec.- tion. illustrated in Fig. 9:;

Fig. 9 is a transverse vertical section on the line 9-9 of Fig. 1. showing the arrangement of the more widely spaced. screen tubes disposed lust forwardly of. the screen tubes shown: in Fig. 8:;

Fig.. 10= is a multiple plane transverse, vertical section on the: line ill-4:0 of Fig. 1 showing the floor continuations oi the, wall tubes just. for.- wardly of. the lower: ends of the tempering fluid ducts; and

Fig; 1-1 is a: transversevertical section on; the line ll-H of Fig. 1 showing: the wall cooling tubes of the front transverse wall of the furnace and also showing the arrangement of the burner tubes relative to the: steam and: water drum and relative to the roof of the furnace.

The steam generator shown particularly in Figs. 1-, 2 and. 3 involves a. furnace Ill. the walls of which are defined. by steam generating tubes connected at their upper ends to the steam and water d-rum 12. The steam and water drum ill.

(which may also be termed an upper fluid chamber) extends over the furnace gas tempering section disposed immediately rearwardly of the furnace Ill, and beyond the gas tempering section the drum extends over the convection section which includes the main bank i l of steam generating tubes. and the superheater E6. The furnace is fired by burnerssuch as those indicated at 28-25. These are pulverized fuel burners supplied with a mixture of fuel and primary air through tubes such as those indicated at and 2'5.

In the operation; of. the installation, the flames from the burners 20-25 impinge against a stratum of molten slag upon the rearwardly inclined furnace floor 30, the floor being formed by the floor tube sections such as those indicated at 32 and 3d of Fig. 4, and their refractory covering 35-. The combustion products then pass rearwardly from the high temperature zone of the furnace and between. the upright shadow tubes such as those indicated. at AilinFigs. l and 2. Each of. these shadow tubes has a refractory covering. such asthat indicated at 462. The upper ends of these tubes are directly connected to the steam; and water drum #2 and their lower ends are connected to headers which are in turn connected. to the drum i2 by appropriate downcomers' to be later referred to.

As the furnace gases contact the shadow tubes. some of the molten ash. particles suspended in the gases a h pon the refractory coverings of these tubes and. flow downwardly along these surfaces to the rearwardly inclined. extension 41 of. the. furnace floor. this extension directin the particles to aslag outlet opening. 48- above a. slag disposal zone. Accumulations of slag upon the surfaces of the tube refractory covering. forming the margins of this outlet are periodically removed by the operation of the. swinging element 49 (Fig. ll pivoted at 59 and connected to a fluid pressure cylinder '53 by a link. 56. This cylinder is pivoted; at its forward end to a fixed bracket 55.

After passing the shadow tubes 48-45 the gases are caused to flow through the tempering passages 68 and Bi (Figsean-d 1 01. These passages, are formed between spaced groups of. inclined steam generating tubes such as 65.-8J, the groups or these tubes forming downwardly inclined ducts 9:2-94- (Fig. 2) for movement at a tempering. fluid such. as steam. or. air, transversely of. thepassages 6B and 61. $om-e of. these tubes form the central duct 93,, and the. remainder of the tubes form the remaining lateral: ducts 92 and. 9112 for the tempering nuid. This fluid passes to these ducts from appropriate tubular. connections or ducts. 'I-he fluid then passes. horizontally intoand across the tempering passages Git-81; through upright.- slots or openings such as 98. 8d,. llllt and. illl Wig-.2) to lower the tempera.- ture of the furnace: gases and their suspended solids and thereby cause the solids to coalesce for downward separation from the gases in. the tempering zone. This zone may be considered as part. of. a slag separation zone extending rearw-ardly from the. shadow tubes to a position rearwardl-y of the: tempering. ducts.

The: tempering fluid is distributed to the; ducts 92,. 93, and; 94. from a. transverse duct nee (Fig.1) which. is formed by the upper parts of the shadow tubes, the. tubes forming the walls of the ducts 912-94.. and the roof of the installation. The upper ends of the shadow tubes are: bent so as to extend rearward-1y between the tubes forming. the ducts, as indicated in Fig. 1. 'Ihere is thus formed a transverse tempering fluid passage conmeeting the top ends of the three tempering fluid ducts. The passage is in communication with an appropriate source of tempering fluid. It is also to be noted that the transverse tempering fluid passage 450 is formed in the space directly beneath the unprotected portion of the steam and water drum. This permits the tempering fluid, such as air, to pass between the roof tubes from the air duct 45I passing alongside the drum, see Figs. 4 and 5.

The tubes 65-81 forming the tempering fluid ducts are connected at their lower ends to a transverse header I05 integrally joined at its ends to the side headers I62 and I64 which are appropriately connected by downcomers to the water space of the steam and. water drum I2. The upper ends of the tubes 658I are connected directly to the steam and water drum I2 as indicated in Fig. 4. The middle duct 63 for tempering fluid has its front wall formed by the steam generating tubes I60I, the spaces between these tubes being closed by a non-metallic refractory covering such as that indicated at IIO. This refractory material is installed in a semi-plastic condition over theforward surfaces of the tubes and preferably between radial metallic studs welded to the tubes. This construction is well known in the art as a stud tube wall. These tubes are also so arranged that the wall presents a concave face toward the oncoming gases. The tubes 'I0-'I5 delineating the rear wall of the middle duct 93 are similarly arranged. This wall is also a stud tube wall including the refractory material H2. This wall is so spaced from the front wall of the duct that on one side the narrow upright slot I00 is formed for the discharge of tempering fluid across the flow of furnace gases and other products of combustion through the passage 60. At the other side of the duct 94 is a similar slot 99 for the flow of tempering fluid to combustion products in the tempering passage 6|.

The tempering fluid duct 92 at the outer side of the passage 60 and opposite the slot or opening I00 is similarly formed by stud tubes 65-69 and space closing refractory material as indicated at I I6 and H8 to present an upwardly inclined slot or opening ml for tempering fluid flow into the stream of combustion products flowing rearwardly through the passage 60. In like manner, the duct 94, at the opposite furnace wall of the installation is formed by similarly arranged stud tubes 82-07, with the spaces between these tubes closed by a refractory material indicated at I20 and I22. The discharge slot 98 for tempering fluid flow across the passage 6I is formed between the tubes 82 and 81.

The forward walls for the tempering fluid ducts 92 and 94 also present concave faces forwardly toward the oncoming combustion products, the marginal tubes 8! and 6! being disposed forwardly of the remainder of these walls to provide forwardlyfacing rims, or marginal surfaces, similar to those provided by the tubes I6 and 8| for the forward wall of the middle gas duct 93.

Directly rearwardly of the tempering passage 6I is a platten I26 formed by the forwardly inclined portions of the tubes I30I35. The upper ends of these tubes are directly connected to the steam and water drum I2 and their lower ends are appropriately connected into the fluid circulation of the installation. The platten terminates at the position indicated in Fig. lat I39. jlo provide-this construction, the lower parts of tubes I35,. I33-and I3I are bent to extend outwardly to the wall tubes I35A and I3IA (Fig. 2) to which they are joined by welding. The remaining platten tubes are welded to these bent lower ends at I30A, I32A, and I 34A.

A platten I40, similar to the platten I26, above described, is disposed directly rearwardly of the passage 60. It is formed by similarly arranged tubes I4I-I46 and they are similarly connected into the fluid circulation of the installation. The tubes of'the plattens I26 and I40 are substantially contiguous and they form; radiant heat shields and gas flow deflectors between the furnace I0 and the tubes of the widely spaced screen I (Figs. 3 and 9) and the more closely spaced tubes of the secondary screen I52 (Fig. 8) disposed at the entrance of the convection section. The plattens divide the chamber between the screens I50I52 and the tempering passages and BI into two zones, the rearward zone being free of the tubes, to promote the separation'of ash and the collection of solidified ash in a subjacent ash disposal zone.

After passing the widely spaced tubes of the screen I50 and the tubes of the succeeding screen I62, the furnace gases pass through the flow equalizing space I54 just forward of the superheater I6.

The tubes of the screen I50 are connected at their lower ends to a header I66 and their upper ends are in communication with the steam and water drum I2 (Fig. 9). The header I00 preferably communicates directly at its opposite ends with the lower side wall headers I62 and I64. These headers are indicated in Fig. 3, as terminating just rearwardly of the header I60 but they are connected to the rearward headers I66 and I68 by tubular connections I10 and I12.

The bank of tubes constituting the tubular screen I50 is three deep as indicated particularly in Fig. 3 of the drawings. There is a front row of tubes such as I50A, an intermediate transverse row of tubes such as I503, and a rear row of tubes I50C. Each of these tubes is directly connected at its upper end to the steam and water drum (or upper fluid chamber) I2 and the vertical lower portions of the tubes I50B and I50C are weld connected to the rearwardly inclined lateral portion I50D ofeach of the front tubes 'I56A. Such connections are provided at the positions indicated at I50F and I50H, in Fig. 1. Thus, the water supply for the tubes I 503 and I560 is afforded by their connections to the inclined lateral I50D which, in turn, is directly connected to the lower transverse header, or

lower fluid chamber, I60, in the arrangement particularly indicated in Fig. 1. The inclined laterals I561) are shown as connected to the side of the header I60, while the upper part of this header is directly connected to the upright tubes of the screen I52.

The side headers I62 and I64 are also integral with a furnace front wall transverse header I6I (Figs. 1 and 11) from which the front wall cooling tubes such as I63 and I65 extend upwardly to the drum l2, in the arrangement specifically shown in Fig. 11.

The more closely spaced tubes of the screen section I52 are vertically disposed directly above the header I60, as indicated in Figs. 3 and 8.

.Some of these tubes such as II82, are united by welding with other tubes of this screen section, such as I8 4-I86, in quasi-bifurcated tube constructions to provide an adequate number of .Wb si the s ree I w o ne e s tat n an the chambers for periodic removal of ash therefrom: i

The particular arrangement of the vertical junction headers such as 202 and 2| 2 (Fig. 6) and the construction and arrangement of the tubes and lower headers l 66 and I68 of the steam generating bank of tubes !4 (Fig. 7) are such as to promote the deposition of combustion solids in the ash receiving chambers 362--364 by avoiding obstructions to the falling of solids into the chambers.

While in accordance with the provisions of the statutes we have illustrated and described herein the best form of our invention now known to us,

those skilled in the art will understand that changes may be made in the form of the invention covered by our claims, and that certain features of our invention may sometimes be used to advantage without a corresponding use of other features. Y

What is claimed is:

1. 'In a fluid heat exchange installation, a furnace having its boundary surfaces defined by fluid conducting tubes, burners, means supplying pulverized fuel and air to the burners which fire the furnace at temperatures above the fusion temperature of the non-combustible residue of the fuel, said boundary surfaces including a floor receiving said residues to form a molten slag layer, the furnace floor being provided with a slag discharge opening, and a slag clearer including a member normally disposed out of the path of falling slag but periodically movable into and upwardly through said slag discharge opening to clear away solidified slag which tends to -tubes are exposed, and convection steam generating and superheating surfaces arranged beyond the slag separation zone in the direction of gas flow, the steam generating surfaces being presented by upright tubular elements connectedinto fluid circulation of the generator and the shadow tubes having their upper ends bent so as to cooperate with the steam generating tubes in forming a transverse tempering fluid passage from which fluid passes to the tempering fluid duct.

3. In a steam generator, a horizontally elongated and vertically restricted primary furnace, a fuel burning system including a set of fuel burners downwardly firing the furnace at high combustion rates with an ash forming solid fuel, fluid cooled tubes defining the floor and other boundaries of the furnace, the furnace floor having a slag discharge opening to which molten slag may flow from a position beyond the burners, the fuel system with its burners being so co-ordinated with the furnace floor that flames from the burners impinge upon a molten ash or slag stratum on the floor, a convection section heated by the furnace gases, means providing for the solidifying of slag particles in gas suspension before the gases pass to the convection section, said last named means including vertically inclined steam generating tubes constructed and-arranged to form furnace gas passages with ducts at opposite sides thereof, vertically inclined shadow tubes disposed forwardly of said gas passages, and means supplying said duets with a tempering fluid which is injected into and mixed with the furnace gases.

4. In a steam generator, a horizontally elongated and vertically restricted primary furnace, steam generating tubes delineating the floor and other boundary surfaces of the furnace, a fuel burning system including a set of pulverized fuel burners downwardly firing the furnace at high combustion rates with an ash forming solid fuel, the furnace floor being inclined downwardly away from a position opposite the burners for the flow of molten slag away from that position, forwardly inclined and refractory covered steam generating shadow tubes extending across the gas outlet of the furnace, such shadow tubes being individually spaced transversely of gas flow, other upwardly and forwardly inclined steam generating tubes extending across the flow of gases and connected into the fluid circulation system of the installation, said last mentioned tubes being constructed and arranged to provide tempering fluid ducts through which a tempering fluid passes for mixture with the furnace gases and consequent cooling of the ash particles suspended in the furnace gases, means at the lower part of the installation for receiving solidified ash particles deposited from the furnace gases,

chamber, means including tubes presenting water cooled slag collecting surfaces defining a molten slag removal zone, means including steam generating water tubes arranged to form tempering fluid ducts for the introduction of steam into mixing relationship with thestream of furnace gases leaving the slag removal zone, individually spaced shadow tubes disposed across furnace gas flow forwardly of the point of introduction of the tempering fluid, and means presenting convection steam generating and superheating surfaces arranged beyond the slag removal zone in the direction of gas flow, the shadow tubes having their upper ends bent so as to cooperate with the steam generating tubes in forming a trans"- verse tempering fluid passage from which fluid passes to the tempering fluid duct.

6. A steam generator including apparatus for conditioning the products of combustion of pulverized coal flowing rearwardly in a gas pass from a high temperature furnace to a convection section including spaced fluid heating tubes, said apparatus including a water cooled furnace having a floor normally covered with molten ash from the combustion of the coal, a tempering fluid system including fluid cooled ducts for introducing and mixing a tempering fluid with the stream of furnace gases, said ducts being inclined and extending upwardly and forwardly of said gas pass and through the furnace gases and having elongated longitudinally narrow tempering fluid discharge ports opening toward the stream'of furnace gases, and individually spaced shadow tubes connected into a fluid Oil! 11 solution system and disposed forwardly of fluid cooled ducts, the shadow tubes having their upper ends bent so as to cooperate with the steam generating tubes in forming a transverse tempering fluid passage from which fluid passes to the tempering fluid duct.

7. Apparatus for conditioning products of combustion of pulverized coal flowing rearwardiy in a gas pass from a high temperature furnace "to a convection section including spaced fluid heating tubes, said apparatus including a water cooled furnace (having a floor over which a slag stratum flows to a slag discharge opening, a tempering fluid system including fluid cooled ducts for introducing and mixing a tempering fluid with the moving furnace gases, said ducts being inclined upwardly and forwardly of said opening through the furnace gases and having elongated longitudinally narrow tempering fiui-d discharge ports opening toward the stream :of furnace gases, and spaced shadow tubes inclined in a manner similar to that or the .ducts and disposed in a transverse zone spaced forwardly of the ducts i 8. In a "water tube steam generator, a primary furnace having means associated therewith for burning pulverized fuel at fiurna'ce temperatures above the fusion temperatures of the noncomrbustible in the fuel, the primary furnace having a horizontal extension formed by wall cooling steam generating tubes, groups of forwardly inclined steam generating tubes connected into the cirmutation of the generator and arranged to pre sent a furnace gas cooling barrier across the furnace with an opening between the groups of tubes for the exit of furnace gases, groups of tubes being :also arranged relative to other similarly idlSDGSBd tubes to form tempering fluid ducts of relatively large free flow area exten ing into the furnace and having tempering .iiuid noon-ts laterally of said passage, means "for supplying said duets with tempering flu-id for flow of that fluid through said ports into mixing relationship with the furnace gases flowin through said massage, a group of vertically inclined and individually spaced fluid cooled shadow tubes disposed transversely of the extension of the ,primary furnace at a position forwardlt of said passage, an upright ,platten consisting of a plurality cf upright steam generating tubes in contiguous relation and installed directly rearwardily of the gas passage between the tempering fluid d'ucts, said platten acting as a target wall to catch sprays of slag shot and acting to shield subsequent heat absorbing surfaces from the primary furnace, and a convection section including bank of steam generating tubes and a convection superheater disposed rearwardly of said platten.

:9. a fluid heat exchange installation, a furnace having its boundary surfaces defined by :tluid conducting tubes, burners, means supplying pulverized fuel and air to the burners tor firing the -furnace at temperatures above the fusion temperature of the non-combustible residue of the fuel, said boundary sort-aces including a floor receiving said residues to dorm a molten "slag layer, the furnace floor being provided with a slag discharge opening, a slag receiver beneath said opening, a slag clearer normally disposed out of the path of slag moving downwardly through said opening, and means for periodically moving the clearer upwardly through said slag discharge opening to clearaway solidified slag which tends .to close said opening. 7

1-0. Ina steam generator, :a longitudinally extended elevated steam and water drum, a fur"- nace beneath the drum, "wall "means "providing a gas pass leading from the furnace and dis.- posed beneath the drum, :a bank of upright steam generating tubes exposed to the furnace gases in said gas pass, superheater tubes of inverted U-s'hape disposed within the gas pass and nested to form a bank of spaced tubes, inlet header means disposed at one side of the gas pass out of the path of the furnace gases and connected with the corresponding ends of a plurality of the superheater tubes, and outlet header means "disposed at the other side of the gas pass out of the path "of the furnace gases and connected to the corresponding outlet ends of the plurality of superheater tubes.

'11. In combustion and fluid heat exchange apparatus, means providing a flow of furnace gases with solids in suspension therein, -upright tempering fluid ducts extending across said how in a direction oblique to the direction of the now, means for supplying said duct with a tempering fluid at a temperature lower than that of said now or the solids in suspension therein, and individually spaced fluid cooled shadow tubes disposed transver ely of said flow and forwardly said ducts, said ducts having side outlets for the discharge of the tempering fluid into :said the upper ends 'of'the shadow tubes being so cent as to oo-act with other elements including the walls of said ducts to form a transverse inlet passage or chamber from which the tempering fluid flows :to said ducts.

. apparatus vfor conditioning products of combustion of pulverized coal flowing horizontally in-a :gas pass from a high temperature furnace :to a convection section including spaced fluid heating tubes, said apparatus including a water cooled furnace having a floor over which a slag stream flows to :a slag discharge opening, :a tempering fluid system including fluid cooled ducts .i-or introducing and mixing a tempering ,rl'uid with the horizontally flowing stream of furmace gases, said ducts :beiug inclined and extending upwardlyand forwardly from said opening through the furnace gases and having elongated longitudinally narrow tempering fluid discharge ,ports opening toward the stream of Jim- .naoe gases, and rearwardly and downwardly Lin- :clined fluid cooled shadow tubes disposed transversely or said flow of combustion products an at a position forwardly of said ducts.

lnra water tube steam generator, a primary furnace having means associated .therew ithlfor burning pulverized fuel at furnace temperatures above the fusion temperatures of the non-com.- bustib'le in the fuel, the primary furnace having ahorizontal extension formed by Wall cooling steam generating tubes, groups of forwardly inciined steam generating tubes connected into the circulation of the generator andarranged to present a furnace cooling barrier across the vertical extent .of the furnace with. an opening 'between the groups of tubes for the exit of furnace gases ,from the furnace, said groups of tubes being also arranged to forrultempering fluid ducts of relatively large free flow area extending into the furnace and having tempering fluid ports at the sides of said passage, means for supplying said duets with tempering fluid for how or" that fluid through said ports into mixing relationship with the furnace gases (flowing through said passage, a group of verticaily inclined and individually spaced .fluid cooled shadow tubes across the extension of the primary furnace at a position forwardly of said passage, an upright platten consisting of a plurality of upright steam generating tubes in contiguous relation and installed as a canopy directly rearwardly of the gas passage between the tempering fluid ducts, said platten acting as a target wall to catch sprays of slag shot and acting to shield subsequent heat absorbing surfaces from the primary furnaces, a convection section including a bank of upright steam generating tubes and a bank of upright superheater tubes disposed rearwardly of said platten, and lower headers disposed along the sides of the installation in the zone of the convection section, the tubes of said convection section having their lower parts bent outwardly for direct connection with said last mentioned headers.

14. In a fluid heat exchange installation, a furnace having its boundary surfaces defined by fluid conducting tubes, burners, means supplying pulverized fuel and air to the burners for firing the furnace at temperatures above the fusion temperature of the non-combustible residue of the fuel, said boundary surfaces including a floor receiving said residues to form a molten slag layer, the furnace floor being provided with a slag discharge opening, a slag clearer including a member normally movable into said slag discharge opening to clear away solidified slag which tends to close said opening, a convection section heated by the furnace gases, and a bypass construction including conduit means causing some of the furnace gases to pass through said opening and join the remainder of the gases at a position rearwardly of the convection section.

15. In a furnace having an opening at its lower part for the discharge therethrough of molten slag, means firing the furnace with a slag forming fuel at temperatures above the fusion temperature of the slag, a slag clearer having a part constructed and arranged to impact and remove slag bodies accumulated at said opening, means for movably mounting said part externally of and beneath the furnace, and means for moving said part upwardly toward said opening and across the path of slag flow downwardly from said opening.

ERVIN G. BAILEY.

RALPH M. HARDGRO-VE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 707,021 Schulz Aug. 12, 1902 863,597 Freeman Aug. 20, 1907 1,298,530 Mann Mar. 25, 1919 1,548,834 Foresman Aug. 11, 1925 1,729,217 Hufschmidt Sept. 24, 1929 1,826,029 Smith Oct. 6, 1931 1,858,451 Coutant May 17, 1932 1,874,487 Franklin Aug. 30, 1932 1,887,891 Roosen Nov. 15, 1932 1,925,026 Austin Aug. 29, 1933 1,947,225 Pflager et al Feb. 13, 1934 2,231,970 Toomey et a1 Feb. 18, 1941 2,242,762 Shellenberger May 20, 1941 2,346,715 Woodard et a1. Apr. 18, 1944 2,393,205 Tiemeier Jan. 15, 1946 2,399,884 Noack May 7, 1946 2,551,945 Harvey May 8, 1951 FOREIGN PATENTS Number Country Date 13,960 Great Britain July 6, 1905

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