US2268560A

US2268560A - Vapor generator

Info

Publication number: US2268560A
Application number: US253255A
Authority: US
Inventors: Ervin G Bailey
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1939-01-28
Filing date: 1939-01-28
Publication date: 1942-01-06
Anticipated expiration: 1959-01-06

Description

Jan. 6, 1942. E. e. BAILEY '7 2,268,560

VAPOR GENERATOR Filed Jan. 28, 1939 4' Sheets-Shet 1 first 0 en ass Primary Furnace eraiure f Tmp 1 2 3 4 5 Surface, Thousand [Fl 1'1? G Bailey INVENTOR.

- BWM ATTORNEY.

Jan. 6, 1942. E. G. BAILEY VAPOR GENERATOR Filed Jan. 28, 19:59

4 Sheets-:Sheet 2 V IWENTOR'. [win 6 Bailey BY ATTORNEY.

E. G. BAILEY VAPOR GENERATOR Filed Jan. 28, 1939 Jan. 6, 1942.

4 Sheets-Sheet 3 Erw'n G. Bailey, INVENTOR.

ATTORNEY.

Jan. 6,1942. 5, G, BAILEY 2,268,560

VAPOR GENERATOR Filed Jan. 28, 1939 4 Sheets-Sheet 4 ATTORNEY.

i-Patented Jan. 6, 1942 UNHT'ED STATES PATENT OFFICE VAPOR GENERATOR Ervin G. Bailey, Easton, Pa., assignor to The Babcock & Wilcox Company, Newark, N. J., a corporation of New Jersey Application January 28, 1939, Serial No. 253,255 11 Claims. (01. 122-235) The present invention relates in general to the construction and operation of vapor generating.

or seam, vary very considerably between coals from different deposits. The ashes of all coals, however, in passing from the solid to the liquid phase pass through a transition zone defined by three temperature points, usually referred to as 1. Initial deformation temperature, 2. Softening temperature, and Y 3. Fluid temperature, which can be determined in the laboratory by well known standard methods, the ash residue from a slowly burned out coal sample being formed into a cone-shaped briquet, and the specific temperatures being dete'rmined in a mufile furnace. The initial deformation is that temperature at which the cone starts to distort and is indicative of when the lower fusing temperature particles of the heterogeneous mixture comprising the ash begin -.to soften and cement the higher fusing temperature particles. The softening temperature is that at which the cone .has fused down to a spherical lump. The fluid temperature is that at which all ingredients of the ash become molten. The specific temperatures and the ranges between any two temperatures vary considerably with ashes of coals from different locations.

In burning pulverized coal in the furnaces of the steam generating units of my invention I desire to obtain the maximum practical thermal efficiency of the unit, or in other words, to utilize to the greatest possible extent the heat units in the coal being burned. This necessitatesa consideration of many factors, but one of the most essential factors is the eflicient and substantially complete combustion of the coal with the least practicable amount of excess air to attain these results. With these combustion conditions I naturally obtain the least weight of gases containing the maximum obtainable heat units from the coal, which results in high furnace temperatures. These furnace temperatures are in excess of the fluid temperatures of many of the individual constituents of the heterogeneous coal; ashes, with 55 factorily disposed of, as, for example, in a slag the result that upon combustion of the combustible material in the individual particles of pulverized coal the individual ash particles contained therein are exposed and raised in tempera- 5 ture, so that many of them become molten, and

as the combustion of the combustiblematerial proceeds small individual ash particles, some liquid and others plastic or solid, depending on their composition and fusion temperature, are

0 liberated and carried away in the gases of combustion.

In the utilization of the combustion gases thus formed heat is abstracted therefrom, and from the solid particles of slag in suspension therein, 5 eitherby radiation to a cooler surface bounding the gas flow, as, for example, water-cooled walls of a furnace, or by convection in passing over a bank of tubes at lower temperature, as, for example, a bank of boiler, superheater,economizer or air heater tubes, or by a combination of both radiation and convection heating. As the heat is abstracted fromthe gases'the temperature of the gases and also the slag particles in suspen sion therein is decreased so that the'slag passes through a range of temperature to below the initial deformation temperatureat which point it is in solid condition.

Where the temperature of, the gases andtheslag particles in suspension therein is at or above 9 the ash fluid temperature, the handling of such slag is relatively simple. The individual particles liberated from the coal and in suspension in the gases impact to some extent against each other butmostly against thewalls of the furnace,

5 and as the surfaces of these furnace Walls, either because of their construction or due to a prior accumulation of slag thereon are maintained :ata temperature also above the slag fluid temperature, the slag deposited thereon is maintained molten and runs down so that it can be satistap furnace. I

Similarly, when the slag particles in suspension 45 in the gases have been cooled down to a temperature definitely below the initial deformation temperature of the ash, the handling is a relatively simple matter, as the slag is solid and and will not adhere'to any cool surface with ample, a bank of tubes. Not only. can these solid particles of slag be handled in a satisfactory mancan be obtained.

which it might come into contact, as, for ex-' flow within certain temperature ranges. This not only makes more difficult the problem of handling, but results in theformation of an insulating layer over whatever heat absorbing surface the slag is adhering to and materially reduces the absorption of heat. This condition is particularly serious if, for example, it is permitted to occur in a bank of tubes spaced relatively closely together, as there is a tendency for the slag accumulation on one tube to join with the slag accumulation on an adjoining tube and thereby not only eifectively insulating those surfaces and reducing heat absorption, but also obstructing the passageway between the tubes to the passage of gas. As has been previously mentioned, the specific initial deformation and fluid temperatures of ash not only vary in ashes of different coals, but the ranges between these temperatures vary quite widely. As examples of these conditions, with specific coal ashes with which I have had experience, one coal has a relatively low initial deformation temperature of 2020 deg. F. with a relatively low fluid temperature of 2420 deg. F., the range being 400 deg. F. Another coal ash has a higher initial deformation temperature of 2350 deg. F., and a corresponding higher fluid temperature of 2750 deg. F., with an equivalent range of 400 deg. F. Still another coal ash' has a relatively low initial deformation temperature of 2180 deg. F. and a relatively high fluid temperature of 2860 deg. F., with a wider range between these temperatures of 680 deg. F.

A further very important factor in connection with the physical characteristics 'of coal ash is that there .is a selective separation of ash those of the' original coal ash will prevail in various and different locations.

A steam generating unit of the type particularly applicable for the burning of pulverized coals having wide ranges of ash fusion temperatures is disclosed in my prior application Serial No. 88,285 filed July 1, 1936. One installation of the steam generating unit disclosed in said prior application has been successfully operated at a steam output of 225,000 lbs. of steam per hour with a steam pressure of 1260 lbs. per sq. in. and a steam temperature of 923 deg. F. burning a pulverized coal having an initial deformation temperature of 2180 deg. F., and an ash fluid temperature of 2860 deg. F. with a heat liberation in the primary furnace of 61,800 B. t. u. per cu. ft. per hour. The.same unit has also been successfully operated at a steam output of 342,- 000 lbs. of steam per hour with a steam pressure of 1225 lbs. per sq. in. and a steam temperature of 910 deg. F., burning a pulverized coal having an initial deformation temperature of 2350 deg. F-., and an ash fluid temperature of 2680 deg. F. with a heat liberation in the primary furnace of 98,000 B. t. u. per cu. ft. per hour. In the operation of this unit under both of these sets of conditions, the first set being indicative of medium rating, and the second set indicative of high rating with, incidentally, coals of different characteristics, the pulverized coal is burned in suspension in the primary furnace chamber by a turbulent type of burner at temperatures well above the fluid temperature of the ash, the adiabatic temperature being in the neighborhood of 3600 deg. F. and the tempera- .ture 'of the gases leaving the primary furnace throughout the distance of travel of the gases.

Coal ash is, by virtue of its formation, a heterogeneous mixture of individual constituents including oxides, carbonates, sulphides, sulphates, silicates, and the like of various metals, each with its own individual initial deformation and fluid temperatures, so that the temperature determinations made for any specific coal ash or sla sample are composite in nature. In the passage of the gases through a steam generating unit, the various individual ingredients of the heterogeneous mixture are not necessarily deposited at the same rate, as for example, a greater percentage of the larger and/or denser constituents is more likely to be deposited onthe floor of the furnace and lower furnace walls early in the travel of the gases. than would be some of the other less F. with medium rating high rating. In other the primary furnace ranging from 2920 deg. to 2950 deg. F. with the words, the gases leaving chamber are at temperatures above the ash fluid temperature, thus permitting some ofv the ash that has been liberated from the coal in molten condition during combustion of the combustible material to be separated in the primary furnace and "be removed in the liquid state. Combustion is substantially complete in the primary furnace.

In'order to obtain steam temperatures of this order the superheating surface must receive gases at relatively high temperatures. The cost limitation of superheater construction, however, makes the use of small, closely spaced superheater tubes desirable. The distribution of steam and gas contact with the superheater elements must be substantially uniform to avoid overheating of these elements. These requirements necessitate dense ingredients, and this results in a modiflcafurnace, but to the contrary will certainly notprevail, and composite temperatures other than the reduction of the high gas temperatures leaving the primary furnace to a temperature range at which the gases may safely contact with the superheater elements and yet be sufiiciently high to obtain the desired heating effect. At the same time the slag particles in suspension must be removed or their temperature reduced below the slag initial deformation temperature before reaching the closely spaced superheater tubes in order to avoid slag in the plastic condition of the intermediate range between initial deformation and fluid temperatures contacting with and adhering to the superheater tubes, decreasing the heat transfer thereto, and accumulating to a point where the passage of gas therethrough is obstructed.

For these reasons on leaving the primary furnace chamber the hot gases and slag particles remaining in suspension therein are caused to fiow through an elongated narrow substantially unobstructed passage or "open pass in which the gas and slag temperatures are reduced mainly by radiant heat absorption by the fluid cooled walls of the passage. With the first section of this passage verticallyarranged for an upflow of the hot gases the slag separating out in this section, being still above the plastic point of the ash, flows down the walls thereof to the bottom of the passage, from which it is removed through a slag outlet along with the liquid slag separated out in the primary furnace itself. During the passage of the gases through the remaining or downflow section of the passage the gas temperature is further reduced through the plastic range,

between fluid and initial deformation temperatures. Such slag and gases that contact with the walls of this section of the pass being in a sticky or semi-sticky condition, may adhere to the'walls and build up a spongy accumulation thereon.

The construction of the walls in this portion of the passage however, is such as to present an essentially smooth surface so that a cleavage plane is provided between the surface and the slag thereon, with the result that there is a tendency for the accumulated slag to break away and fall tothe bottom of this section of the passageway not only because of gravity actingon the accumulated mass itself, with the cleavage plane facilitating breaking away from the walls,

but also due to the scrubbing action of the gases passing vertically downward at high velocity. Further than this, the surfaces of this portion of the passage are made readily accessible for cleaning, so that despite the fact that the slag in the gases is in the plastic range and tends to accumulate on the surfaces these surfaces can, nevertheless, be kept relatively clean, so that the heat is transferred from the gases and slag particles in suspension to the water tubes forming the passage walls or boundary, thus maintaining a high rate of heat transfer .and conversely a rapid reduction in temperature both of the gases and the slag in suspension, so that as the gases pass from this portion 'of the passageway the slag particles remaining in suspension are cooled to a solid or dry state below the initial deformation temperature of the passageway,

of the slag. This open pass section of the unit is suitably proportioned as to length, cross-section and effective heat absorbing surface so as to ensure a reduction in gas temperature through the desired temperature range and the suspended slag being in a solid condition below its initial deformation temperature when the gases enter the convection section of the unit containing the closely spaced superheater tubes.

The general object of my present invention is to provide an improved construction of steam generating unit of the type described, which is particularly characterized by an improved arrangement of the pressure parts, permitting of a substantial reduction in the number of drums and headers required, a higher rate of circulation in the steam generating section, greater accessibility-of the surface for cleaning and renewal, a top or bottom support construction of the unit, and in general, improved operation at a substantially lower cost of construction 'and erection.

The various features of novelty which characterize myinvention are pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention.

its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter, in which I have illustrated and described preferred embodiments of my invention.

0f the drawings:

Fig. 1 is a graph showing the relationship between gas and ash temperatures throughout a steam generating unit extended to a point where the gases and slag particles in suspension therein are at a temperature below the initial deformation temperature of the slag;

Fig. 2 is a somewhat diagrammatic sectional elevation of a steam generating unit constructed in accordance with the invention;

Fig. 3 isa horizontal section taken on the line 3-3 of Fig. 2;

Fig. 4 is a horizontal section through one of the outer walls of the primary furnace;

Fig. 5 is a horizontal section through one of the partitions; and

Fig. 6 is a view similar to Fig. 2 illustrating a modified construction.

In Fig. 1 I have illustrated in graph form the relationship between gas and ash temperatures in operating the steam generating 'unit disclosed in.

.. which the gases pass, each division representing 500 sq. ft. At the top of the graph additional divisions are indicated dividing this surface into the primary furnace, first open pass, secondgopen pass and cavity below superheater-the superheater being the first bank of convection heated tubes in the unit. From this graph it will be observed that the primary furnace, in the walls and roof, contains approximately 1800 sq. ft. of surface exposed to the gases, the first open pass 1100 sq. ft., and so on. The ordinate of the graph indicates temperatures from 1600" F. to

3100 F., each division representing 100 F.

On the zero ordinate are indicated the initial deformation, softening and fluid temperatures for the ash in the coal of 2180 F., 2250 F., and 2860 F. respectively, these temperatures being determined from a laboratory sample of the coal ash in the manner previously described. Corresponding temperatures determined for slag samples takenfrom various locations in the unit with respect to gas travel are also indicated, and lines drawn joining the equivalent temperatures, and it will be noted, as previously described, that these temperatures are not consistent but. vary due to the selective separation of the various amounts ofthe individual constituents of the total heterogeneous mixture. The shaded area between the lines of initial deformation temperatures and fluid temperatures so drawn represents the varying range of plastic or stickiness temperatures of the slag at various locations in the steam generating unit.

In the zone indicating the primary furnace the adiabatic temperature, which will be in the neighborhood of 3600" F. is not shown, but the temperature of the gases leaving the primary furnace as determined by optical pyrometer is 2920 F., or above the ash fluid point. It is desirable to maintain this temperature in the primary furnace, not only to facilitate the removal of some of the slag separated in molten form, but also to insure substantially complete combustion, and the water-cooled walls of the furnace are so constructed, as for example, employing partial stud tubes with refractory, as shown in Fig. 4, to insure this condition. In the first and second open passes the rapidly decreasing temperature of gases as determined by optical pyrometer and high velocty thermocouple is clearly shown, as is also the fact that the gas temperature is definitely below the initial deformation temperature before leaving the second open pass and entering the cavity below the superheater, so that the slag particles carried in the gases are definitely cooled to a solid condition as they contact with the first bank of tubes, or superheater, located above the cavity.

Referring to Figs. 2 to 5 the steam generating unit illustrated has its setting divided into a primaryfurnace chamber ID, a laterally spaced convection section II connected thereto by an intervening substantially unobstructed vertically elongated passage comprising upflow and downflow sections or open passes" l2 and I3 respectively. The furnace chamber I0 is preferably of rectangular horizontal cross-section and defined by a front wall l5, opposite side walls Ii, inclined roof", and floor B. The furnace chamber is separated from the upflow passage section l2 except at its lower rear side by a partition wall 20 extending downwardly from the rear end of the furnace roof H. The upflow and downflow passage sections are separated except at their upper ends by a partition wall 2| extending upwardly from the bottom of the setting. The downflow passage section 13 and convection secas hereinafter described to permit its walls to withstand the maintenance therein of a normal mean temperature above the ash fluid temperature. The molten slag particles separating out in the primary furnace deposit on the roof, walls and floor thereof in a fluid condition and are removed through one or more slag discharge openings 28 located in the partition 2| slightly above the floor level in the primary furnace and passage section l2. The slag flowing through the slag outlet or outlets 28 drops into a water filled ash hopper 42 below the down pass IS.

The vertically arranged open passage sections l2 and I3 subsequent to the furnace in the direction of gas flow are made relatively narrow longitudinally of the setting, but are of such height that the combined distance of gas travel through them in series, together with the degree of cooling obtained by the specific construction of fluid cooled walls employed, is such as to ensure the gases entering the first open pass l2 from the primary furnace chamber l0 having slag particles in suspension and being at a temperature above' the the time they are discharged from the bottom of the second open pass I: to a temperature at which the slag particles still remaining in suspension are below their plastic or stic temperature. On entering the .flrst upward flow open pass l2, the slag particles, being still above their fluid temperature, will adhere to the walls of the passage and will flow downwardly thereon 1 to the floor II which is common to the primary tion H are also separated except at their lower ends by a partition wall 22 extending downwardly from the top of the' setting. The rear side of the convection section is formed by a panel wall 23 and the tops of the passages closed by a roof 24. The unit is advantageously of uniform width throughout, as shown in Fig. 3. with this division of the setting, the heating gases leaving through the lower rear side of the furnace chamber I0 flow upwardly through the passage l2, downwardly through the passage l3, and upwardly through the convection section II, the upper end of which is connected to an induced draft fan (not shown).

.In accordance with my invention the furnace chamber is made relatively narrow longitudinally of the setting, and the one or more burner ports 25 extending transversely of the portion of the roof closely adjacent 5 to the front wall l 5. A combustion air box 28 receiving a supply of air from a forced draft fan (not shown) opens to the'bumer port 25. A plurality of pulverized coal burners 21 of a suitable turbulent type, such as shown in U. S. Patent 2,055,722, are mounted in the air box 26 so as to discharge streams of primary air and pulverized coal in suspension downwardly through corresponding burner ports into the f mace chamber Ill. The narrow formation of t primary furnace and the described arrangement-of the fuel burners relative to the furnace front wall and gas outlet results in an effective use of substantially the entire volume of the primary furnace. The entering fuel rapidly ignites and flows downwardly in a stream which tends to hug the front wall I5 during its downward travel,

distance so roof l1 constructed with furnace l0 and pass l2, and thence be discharged with 'the molten slag separated in the primary furnace through the slag discharge opening 28.

On passing from the top of the pass l2 into the second downward flow open pass l3, the slag particles in the gases are at such a temperature as to be in the lower portion of the plastic or "stic range between initial deformation and fluid temperature. The tubes in the screen between the flrst and second open passes are spread apart in the screen formation a suflicient that such slag as might accumulate on them will not do so to an extent that will unduly restrict the gas flow area. The boundary walls of this second open pass are constructed in such a manner as to present cool and essentially smooth surfaces to the flow of gases, as the sticky nature of the slag is such ,as to necessarily result in the slag adhering to and accumulating on these surfaces, and the smoothness of them provides a natural cleavage plane that enhances the removal of the accumulations by their own weight. Furthermore, the gas flow in a downward direction facilitates and assists the removal of' slag from the walls depositing it in the dry the lower 'end of the partition wall 20. The priash removal chamber immediately beneath this second passage and the convection section, from which the slag is also removed in the solid and dry state. Botli of the open passes are unobstructed by tube banks or the like, so that such slag accumulations that occur must necessarily be upon the passag walls from which they can be readily remov and there is no tendency toward obstructing the gas flow. Furthermore, the vertical positioning of these open passes is most conducive to the removal of slag separated thereinin the first open pass in the molten state and in the second open. pass in a solid or spongy state. The walls of both passes are susceptible to theapplication of cleaning means such as steam blowers or the like, to facilitate mary furnace chamber In is entirely fluid cooled and expedite the removal of slag accumulations plastic range are cooled by ation and located in the the deheaders and downcomer connections located out of the path of the heating gases. As shown, a horizontally elongated elevated steam and water drum 39 extends transversely of the unit directly above the partition wall 20 and above the level of the roof 24. The drum 30 is supported from the superjacent steel work by U-shaped straps 3|. A horizontally elongated water drum 32 extends transversely of the unit below the upfiow pass |2.

The steam generating surface consists substantially entirely of tubes heated mainly by radi portion of the setting in front of the convection section II. The steam generating tubes include a row of tubes 33 extending from the drum 32 along the floor I8, front wall l5, roof I1, and front wall of the upflow section l2, to the drum 30, and supported from the underside of the drum 39 by hanger rods 33 A second row of tubes 34 extends from the drum 32 across the lower end of the upfiow passage section |2, along the partition 20 and front Wall of the passage |2 to the drum 30. The inclined tube portions 34 extending across the lower portion of the upfiow passage are bent and spaced to form an inclined fluid cooled screen extending from the furnace floor to the lower end of the partition 20. The tube portions 34* and the superjacent tube portions forming the partition wall 20 are studded and covered with refractory to the extent desired for most efiicient operation of the unit. The upper portions 34 of most of the tubes 34 arebent rearopposite side of the drum 30. A third row of generating tubes 35 extends vertically from the drum 32 along the partition wall 2|, with the tube portions 35 above the upper end of the partition wall bent and arranged to form a screen between the upfiow and dcwnfiow passages l2 and I3 respectively. The tubes 35 are also provided with metallic studs and refractory material, as shown in Fig. 5 to define the partition wall 2|. The partition wall is continued downwardly at the rear side of the front wall of the ash hopper 42 flow passage l3. A fourth row tends upwardly from a header 3'! along the inclined lower portion of the wall 23, across the lower-end of the convection section, along the partition wall 22 and the roof 24 to the drum 30. The lower inclined portions of the tubes 35 are block-covered to form an inclined hopper floor terminating at the ash pit 42. The portions 3|; of the tubes 36 extending across the lower end of the upfiow convection section are bent and spaced to form an inclined screen across the lower end of the convection section between the rear wall 23 and the lower end of the partition wall 22. The portions of the tubes 35 above the below the downscreen are provided with stud extensions and redrum 32 to theheating gases first contact fractory material, as shown in Fig. 5, to define the partition wall 22. The side walls of the furnace chamber H) are each defined by a row of partially studded tubes 40 extending between horizontally arranged upper and lower headers 38 and 39 respectively. The side walls of the passage section l2 and 3 are defined by similar tubes 40 extending between upper headers 4| adjacent the drum 30 and the headers 39. Tubes 43 defining opposite side walls of the convection section extend between the headers 39 andupper headers 44. The headers 38, 4| and 44 are connected to the upper drum 30 by riser tubes 45 which are hung from the superjacent steelwork and in turn top support the side walls of the unit.

As shown, the

drums

30 and 32 and headers '31, 38, 39, 4| and 44 are located out of the path The fluid circulation through the described generating elements is enhanced by the elevated position of the drum 30 and the external location of the various supply connections to the generating elements. As

shown in Fig. 3, the drum nected by large standpipes outer side of the side walls nections to the drum 30 are along opposite sides of the water in the bottom of the standpipes 46 open, will be The headers 39 are supplied from the standpipes 46 by tubes 41, the header 3'! by external tubes 48, and the drum 32 by tubes 49.

The described construction is adapted for a higher heat liberation per front foot of furnace than the unit disclosed in my said priorapplication, so that the temperature in the primary furnace will be correspondingly higher. The final gas temperature entering the convection section must be approximately the same, however, and in the present construction the open passes are made considerably higher to insure a greater heat absorption in those sections of the unit. The present construction avoids any possibility of the lower end of the downflow passage becoming plugged by slag accumulations deposited from the walls of the passage, by arranging the tube screen 36 across the entrance to the convection section, and thus leaving a free area from the downflow passage to the ash hopper formed below both the downfiow passage and convection section. The relatively large fluid cooled cavity resulting in this portion of the unit further reduces the gas temperature, and affords an ample gas turning space in which suspended slag particles can separate and the gases more uniformly enter the convection section. The tube screen 36 forms the final cooling zone before the gases enter the convection section.

The convection section of the unit is utilized solely for the location of the auxiliary heating surface of the unit. As shown, the entering with a steam superheater consisting of vertically spaced serially connected tube sections 5| extending between inlet and

outlet headers

52 and 53 respectively arranged externally of the rear wall 23. Adjacent tubes in the lowermost superheater section are arranged in nested rows to permit a greater transverse spacing'between adjacent tube coils in the superjacent superheater sections. The superheater tube coils are supported at their inner ends from the partition wall tubes 36 in a well known manner and at their outer ends from 30 and 32 are con- 46 arranged at the IS. The tube conpreferably arranged drum, whereby the drum, to which the relatively quiescent.

a cross-beam 54 through the header 52' and tube engaging elements.

A plurality of vertically spaced serially connected downflow economizer sections 60 are arranged in-the convection section above the superheater sections. The economizer tube coils are also supported at their inner ends by the tubes 36 and at their outer ends from the vertical pore tions of the superheater tubes extending along the rear wall. A'by-pass passage 10 containing additional economizer surface 11- is arranged along one side of the convection section to per-; mit regulation of the superheater temperature, as described in my said prior application. The panelled construction of the wall 23 and the .absence of downcomer tubes or other heat absorbing tubes along that wall facilitates the inspection, repair and renewal of the auxiliary'heating surface in the convection section. The modified steam generator construction illustrated in Fig. 6 is particularly designed for the high capacity generation of steam at high pressures and steam temperatures of about 950 F.

In units of this type, provisions may advantageously be incorporated for reheating the steam after a predetermined passage through an associated turbine. In the Fig. 6 unit, the heat absorbing surface defining the side walls of the downfiow passage section l3-and the partition wall.22 is employed as a steam reheater. As shown, the steam to be reheated is supplied to the hopper header 31', and flows through the tubes 36' along the hopper wall, through the screen-tubes 3&3 and partition wall 22 to an upper header 80. The reheated steam is then passed to side wall headers 4|, from which it flows downwardly through the side wall tubes Ml to outlet headers 42'.

While in accordance with the provisions of the statutes I have illustrated and described herein the preferred forms of the invention now known to me, those skilled in the art will understand thatv changesmay be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my inventio may sometimes be used to advantage without a corresponding use of other features. While the constructions illustrated are particularly designed for and especially useful for burriing-slag-forming pulverized coal, itis apparent that other fluid fuels, such as oil and gas, can be used therein.

I claim:

1. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally of and connected to the furnace chamberby a substantially unobstructed vertically elongated connecting passage arranged between said furnace chamber and convection section, means for burningfuel in suspension in said furnace chamber, a relatively large diameter main' steam and water drum arranged-at the furnace chamber side of said convection section, the steam generating surface of the steam generator consisting mainly of rows of vertically disposed tubes chamber and connecting passage and receiving heat mainly by radiation,-downcomer conduit means confined to the furnace chamber side of said convection section arranged to supply water fromsaid drum to all of said radiantly heated tubes, and a bank of horizontally arranged steam superheating tubes extending across the path of the gases flowing through said convection secing across the path of the gases tion and connected to receive steam directly from said drum.

2. A steam generator comprising a setting including a furnace chamber and a convection section arranged laterally of and connected to the furnace chamber by an inverted U-shaped substantially unobstructed means for burning fuel in suspension in said furnace chamber, a relatively large diameter main steam and water drum arranged above said furnace. chamber and laterally of said convection section, steam generating surface consisting mainly of rows of vertically disposed radiantly heated tubes defining walls of said furnace chamber and connecting passage and discharging to said drum, downcomer conduit means confined to the furnace chamber side of said convection' section arranged to supply water from said drum to all of said radiantly heated tubes, and a bank of steam superheating tubes extendflowing through said convection section and connected to receive steam directly from said drum.

3; A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, a substantially unobstructed connecting passage between and connected to said furnace chamber and convection section, means for burning fuel in suspension in said furnace chamber, an upper steam and water drum arranged at the furnace chamber side of said convection section and externally of said connecting passtream of slag-forming pulverized fuel into said defining 'walls of said furnace sage, a lower water drum arranged at the furnace chamber side of said convection section, the steam generating surface of the steam generator being connected to said upper and lower drums and consisting mainly of rows of vertically disposed radiantly heated tubes defining walls of said furnace chamber and connecting passage, conduit means confined t6 the furnace chamber side of said convection section for supplying water from said upper drum to all of said radiantly heated tubes, and a bank of horizontally arranged fluid heating tubes in the path of the gases flowing through said convection section.

4. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, a substantially unobstructed connecting passage having its opposite ends connected to said furnace chamber and convection section respectively, means for introducing a downwardly directed furnace chamber and burning the same in suspension therein at a normal mean furnace chamber temperature above the fuel ash-fusion temperature, a fluid cooled slag-impervious floor for said furnace chamber, an outlet for molten sla in the lower part of said furnace chamber, an upper horizontally elongated main steam and water drum arranged at the furnace chamber side of said convection section, the steam generating surface of the steam generator discharging to said upper drum and consisting mainly of rows of vertically disposed radiantly heated tubes defining walls of said furnace chamber and connecting passage, conduitmeans confined to the V furnace chamber side of said convection section for supplying water from said upper drum to all of said radiantly heated tubes, and a bank of steam superheating tubes in the path of the gases flowing through said convection section and connected to receive steam directly from said drum.

connecting passage,

' means for burning through said convection section,

, above the fuel ash-fusion 5. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, an inverted U-shaped substantially unobstructed connecting passage having upflow and downfiow sections with their lower ends connected to the lower portions of said furnace chamber and convection section respectively, pulverized fuel in suspension in said furnace chamber at a normal mean temperature therein above the fuel ash fusion temperature, an upper steam and water drum, a lower water drum, steam generating surface connected to said upper and lower drums and consisting mainly of rows of vertically disposed radiantly heated tubes defining walls ofsald furnace chamber and connecting passage, conduit means for supplying water from said upper drum to said radiantly heated tubes, a bank of fluid heating tubes in the path of the gases flowing means forming passage section, molten slag sepinto said downan ash pit below said downfiow and an outlet for the passage of arated in said furnace chamber flow passage section and ash pit.

6, A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, an invertedU-shaped substantially unobstructed connecting passage having vertically elongated upflow and downfiow sections extending a substantial distance above the top of said furnace chamber with their lower ends connected to the lower portions of said furnace chamber and convection section respectively, means for introducing a downwardly directed stream of slag-forming pulverized fuel into said furnace chamber and burning the same in suspension therein at a normal mean furnace chamber temperature temperature, an outlet for molten slag in the lower part of said furnace chamber, an upper steam and water drum arranged at the furnace chamber side of said convection section and externally of said connecting passage, a lower water drum arranged at the furnace chamber side of said convection section, steam generating surface connected to said upper and lower drums and consisting substantially only of rows of vertically disposed raidiantly heated tubes defining walls of said furnace chamber, connecting passage and convection section, means for top supporting said drums and connected tubes, conduit means combined to the furnace chamber side of said convection section and connected to said steam and water drum and forming water supply connections to all of said tubes, and a bank of fluid heatradiantly heated ing tubes in the path of the gases flowing upwardly through said convection section.

7. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, an inverted U-shaped substantially unobstructed connecting passage having upflow and downfiow sectionswith their lower ends connected to thelower portions of said furnace chamber and convection section respectively, means for burning fuel in suspension in said furnace chamber, an upper horizontally elongated main steam and water drum arranged laterally of said convection section and externally of said connecting passage,

' consisting mainly mainly of vertically disposed tubes heated mainly by'radiation arranged at the furnace chamber side of said convection section, said steam generating tubes including a row of tubes defining the front wall and roof of said furnace chamber, a second row of tubes defining a partition wall between said furnace chamber and upflow passage section, and a third row of tubes'defining a partition wall between said upflow and downfiow passage sections, conduit means at the furnace chamber side of said convection section for supplying water from said upper drum to all of said radiantly heated tubes, and a bank of fluid heating tubes in the path of the gases flowing upwardly through said convection section.

8. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, an inverted U-shaped substantially unobstructed connecting passage having upflow and downfiow sections with their lower ends connected to the lower portions of said furnace chamber and .convection section respectively, means for burning fuel in said furnace chamber, an upper steam and water drum arranged laterally of said convection section, steam generating surface discharging to said upper drum and of vertically disposed tubes heated mainly by radiation and defining walls of said furnace chamber and connecting passage, means forming an ash separating chamber below said downfiow passage section and convection section and having an unobstructed connection a lower horizontally elongated water drum arranged at the furnace chamber side of said convection section, charging to said upper drum and consisting steam generating surface dis-- withsaid downfiow passage section, and a bank of fluid heating tubes extending across the path of the gases flowing upwardly through said convection section.

9. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, an inverted -U-shaped substantially unobstructed vertically elongated connecting passage having upflow and downfiow sections with their lower ends connected to the lower portions of said fur nace chamber and convection section respectively, means for burning fuel in suspension in said furnace chamber, an upper horizontally elongated steam and water drum arranged laterally of said convection section, a lower water drum arranged at the furnace chamber side of said convection section and externally of and below said connecting passage, steam generating surface discharging to said upper drum and con+ sisting mainly of vertically disposed tubes heated mainly by radiation arranged at the furnace chamber side of said convection section, said steam generating tubesincluding a row of tubes defining the front wall and roof of said furnace chamber, a second row of tubes defining a partition wall between said furnace :chamber and upflow passage section, a third row of tubes defining a partition wall between said upflow and downfiow passage sections, and a fourth row of tubes defining the rear wall of said downfiow passage section, conduit means confined to the furnace chamber side of said convection section upflow and downflow sections with their lower ends connected to the lower portions of said furnace chamber and convection section respectively, means for introducing a downwardly directed stream of pulverized fuel into said furnace chamber and burning the same in suspension therein, an external horizontally elongated steam and water drum arranged at the furnace chamber side of said convection section, and steam generating surface discharging to said steam and water drum and consisting mainly of vertically disposed tubes heated mainly by radiation arranged at the furnace chamber side of said convection section, said steam generating tubes including a row of tubes defining the front wall and roof of said furnace chamber, a second row of tubes defining a partition wall between said furnace flow passage section and an inclined wall cooled by said fourth row of tubes, and a horizontally arranged bank of fluid heating tubes in the path of the gases flowing upwardly through said convection section. a

11. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, an inverted U-shaped substantially unobstructed connecting passage having upflow and downflow sections with their lower ends connected to the lower portions of said furnace chamber and convection section respectively, means for'burning fuel in suspension in said furnace chamber, an upper steam and water drum arranged at the furnace chamber side of said convection section, steam generating surface directly connected to said upper and lower drums and consisting of vertically disposed tubes heated mainly by radiation arranged at the furnace chamber side of said convection section and defining walls of said furnace chamber and connecting passage, a bank of steam superheating tubes in the path of the gases flowing upwardly through said convection section, and steam reheating surface including rows of tubes defining the rear and side walls of said downflow passage section.

ERVIN G. BAILEY.

I CERTI FICATE OF C ORRECTI ON Patent No. 68,560 January 6, 1914 ERVIN .G. BAIIEY.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: 'Page 6 0nd column, line 'Yziclaimlp, before "steam" insert horizontally arranged";

page 7, first column, line 53, claim- 6, for "combined" read confinedand that the said Letters Patent shouid be read with thiscorrection therein that the same may confonn t0 the record of the case in the Patent Office.

Signed and sealed this 1st day of September, A. D. 1911?.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.