US1860363A - Steam generator - Google Patents

Description

May 31, 1932.

W. D. LA MONT QSTEAM GENERATOR Filed June 11, 1926 11 Sheets-Sheet l INVENTOR 14/4: 75/ DOUGLAS 1/7/7040" ATTORNEYS May 31,1932. w. D. LA MONT STEAM GENERATOR Filed June 11, 1926 ll Sheets-Sheet 2 I INVENTOR M4 75/? QOVEZAS [A lfo/vr BY I ATTORNEYJ May 31, 1932. w. D. LA MONT STEAM GENERATOR Filed June 11. 1926 11 Sheets-Sheet 3 INVENTOR il; 752 001/5145 xi/71w;

ATTORNEYLS y 1932- w. D. LA MONT ,860,363

STEAM GENERATOR Filed June 11. 1926 ll Sheets-Sheet 4 fwd , INVENTOR 14444715? 001/6243 ZA/Va/vr ATTORNEYS May 31, 1932. D LA M N 1,860,363

STEAM GENERATOR Filed June 11. 1926 ll Sheets-Sheet 5 m5 m2 m4 WWW / ATTORNEYS May 31, 1932. w. D. LA MONT STEAM GENERATOR Filed June 11'. 1926 11 Sheets-Sheet 6 INVENTOR M44751? Dal/ems ZA/Ya/vr m wcfw ATTORNEYLS y 1932. w. D. LA MONT I 1,860,363

STEAM GENERATOR Filed June ll. 1926 11 Sheets-Sheet 7 7M 7/ 7/74 I M5 M8 5% W :TTORNEYJ /77 i I... Q

May 31, 1932. w. D. LA MONT 1,850,363

' STEAM GENERATOR I Filed June 11. 1926 ll Sheets-Sheet 8 7 INVENTOR M44753 Dauauas [Alien/r BY M r W A ORNEYcS May 31, 1932.

w. D. LA MONT STEAM GENERATOR Filed June 11, 1926 ll Sheets-Sheet 9 INVENTOR M ALTE/E' 004164 AS [AM/v7 ATT R N EYJ May 31, 1932. w. D. LA MONT STEAM GENERATOR Filed June 11, 1926, ll Sheets-Sheet l0 INVENTOR #444 T5? flaw: ZA/Yo/vr BY Mw j ATTORNEY' May 31, 1932. w. D. LA MONT STEAM GENERATOR Filed June 11, 1926 11 Sheets-Sheet 11 m W m T N mm m Y M *A Patented May 31, 1932 UNITED STATES PATENT OFFICE WALTER DOUGLAS LA MONT, OF LARCHMOII'Z', NEW YORK, ASSIGNOR TO LA MON T v CORPORATION, A CORPORATION OF NEW YORK STEAM GENERATOR Application filed June 11, 1926. Serial No. 115,169.

This invention relates to the generation of steam or other vapors and has for its object the generation of steam or vapor under diffcrcnt pressures by generators which have a common series or series parallel water 01' liquid circulation. Other and further objects and advantages of the invention will appear from the detailed description which follows.

In my co-opending application, Serial No. 79,096, filed January 4. 1926, patented July 21,,1931, Patent No. 1,815,439 I have described steam generator installations in which generators of the film tube type which is have been described in my prior Patent No.

1,545,668, dated July 14, 1925, and in my copending application, Serial No. 32,064, filed May 22, 1925, are used in combination with boilers of conventional designs to increase the efi'iciency of these installations and to improve the operation and particularly the circulation of the conventional type boilers by connecting the positive circulation of the film tube generators in series. parallel, or series parallel with the water mass of or the convection circulation in the conventional type boilers. thereby not only increasing the overall cfliciency of the installation as a whole by adding highly efficient heat transfer surface m in the form of film tubes which permit operation with a much lower stack temperature than has hitherto been practicable but rendering the conventional type boilers themselves more efiicient as steam generators. The present invention is in part a continuation of my above referred to application. Serial No. 7 9.096, and embodies and includes improvements in the general type of installation therein described, as well as other features of novelty.

According to the present invention, two or more generators are provided with at least part of their circulation in common and the 5 installation is arranged so that steam or other vapors of different pressures can be generated from the different generators without disturbing the common circulation of water or other liquid. One or more of the gen- }0 erators may advantageously have positive. circulation. When one or more positively circulated generators are combined accord-v ing' to the present invention, particularly Where a series or series parallel water flow is provided, the circulation in all the generators is improved and this type of arrangement constitutes the preferred broad embodiment of the present invention.

In the ensuing descriptions, I will refer to steam enerators and to the generation of steam, ut it should be understood that the oo present invention is equally applicable to the generation of vapors from any liquid or any mixtures of liquids and that, therefore, the features which are described in connection with the generation of steam are in the main equally applicable to the generation of other vapors.

As the generatorhaving positive circulation, I prefer to use a film tube generator as described in my above referred to prior applications and patent. In its broadest aspect, however, the present invention is not limited to combined installations in which one or more La Mont film tube generators are utilized, and, on the contrary, any generator with positive circulation may be substituted for the La Mont film tube generator with a corresponding decrease in heat transfer etliciency. The film tube generator, however, presents so many advantages with regard to ease of construction and installation, heat transfer efficiency and the like, that it eonstitutes the preferred positive circulation generator in installations according to the K present invention and while the broad concept of the present invent-ion is notlimited to combinations utilizing this type of generator, in its more specific aspects the combination with one or more common typeszof convection circulated boilers, operatinglto generate steam at different pressures, is an, important feature of the preferred embodiment of the present invention."

Under the term positive circulation include pumps of all kinds and other devices which positively and definitely circulate water. I do not, in this application, claimthe use of generators in which a geyser ac-- tion is effected in the generating tubes, this forming part of the subject-matter of my 00- application, Serial N 0. 116,305, filed 5 11 1 1 1926 patented Oct. l3, 1931, Patent No.1,82 7,244. 1

When twogenerators are to be operated at different ressures and a series or series parallel circisation of water through the generators is to 'be, provided, it is. necessary to rovide two pressure transformers, one to reguce the pressure of waterfed from the high pressure nerator to the low pressure enerator an one, to'increase the presure o the water fed from the low pressure gfmngator into the high pressure generator. latter pressure transformer must, of necessity, be a positive circulation means; that is to say, a means which adds energy to the'medium circulated. This means is usually one or more pumps, in series or in parallel. The pressure transformer for reducing feed pressure from the high pressure generator to the low pressure generator may be a simple throttling device in which pressure reduction is effected by the speed of flow of the water or energy absorbing means such as water turbines and the like ma be used in order to bring about the desire equalizatlonjof pressure. In many cases where the high pressure generator is much smaller in capacity than the low pressure generator, a throttlevalve may be unnecessary as a pipe connection of small size may exert sufiicient throttling action and minor variations will be compensated for by the large volume of water in the low pressure generator. valve is omitted it should be understood that the feed tube itself is acting as a throttle or pressure transformer.

Connection between the two generators may be entirely in series, that is to say, all of the circulating water is circulated in series through both generators or a series parallel arrangement can be provided whereby all of the water in one generator is circulated in series through the other generator but this water does not include the whole of the circulating water in this latter generator. In some cases, a complete series circulation is not necessary or desired and either the high or low pressure boiler may be caused to feed water into the other without any return. Thus, the low pressure generator may act to heat the feed water for the high pressure generator in addition to its function as a steam generator and conversely, of course, the high pressure generator may feed into the low pressure generator through a. suitable throttle valve.

The heating gas flow through the generators can be in various forms. Thus, for example, the gases may circulate first through one generator and then through a second and may strike either the high pressure generator first or the low pressure generator first. Parallel gas flow through the two generators is also possible and frequently desirable and Where a throttle flows can be used and may be desirable under certain structural or operating conditions.-

Se arately fire generators may also be used, an as a matter of fact, they can be considered really as a special case of pure arallel gas flow since it is thermally, alt ough not structurally, immaterial whether two gases are generated by separate flames or whether a single flame is used and the gases are divided into two parts. Accordingly hereafter the ex ression parallel flow of heating gases Wlll be used to include separate firing of the generators as well as utilizing part of the gas from a single fire for one generator and part for the other.

While the invention is not limitedto any particular heating gas flow or to any'particular combination, for certain purposes a series flow of heating gases possesses notable economic and thermodynamic advantages. Thus, for example, a film tube generator can be easily and simply installed in the stack of an ordinary generator furnace which position is particularly advantageous as it permits the use of very long tubes with a corresponding high efiiciency in the film tube generator. Owing to the fact that the film tube generator has a very high heat transfer capacity, it is easily possible in most cases to produce a zero heat head or a heat head actully less than zero. That is to say, the stack gases, on leaving the film tube generator, may be reduced to a temperature equal to that of the steam generated or even less, since the water circulation in a film tube generator is from top to bottom and is, therefore, counter to the gas flow, making it possible in some favorable installations to bring down stack temperatures to a oint intermediate between the temperature 0 the steam generated in the film'tube generator and the temperature of the water introduced into the top of the film tubes. Such an arrangement is structurally and thermally very efficient and advantageous and is included as a specific feature of novelty of the present invention in some of its preferred embodiments.

The film tube generator and analogous positive circulation generators may be used as the high pressure or low pressure members.

When used as the low pressure member in the coldest heat zones with a series heating gas flow, the greatest thermal efilciency can be achieved and this arrangement is peculiarly suited to the structural features of the film tube generator which requires forgreatest efiiciency long, small tubes, readily fitting into the stack of boiler furnaces. On the other hand, the small tubes and high heat transfer capacity of film tube generators make them peculiarly suitable for generatinghigh pressure steam, particularly where they are placed in the hottest zone of the furnace. When so placed, the thermal efliciency of the whole installation is decreased, if the generator in the low temperature zones is of the convection type. However, the structural and operating advantages of the film tube generator when used to generate high pressure steam in zones of high heat, may, and frequentl will render this arrangement very desira le even though it maybe necessary in some cases to sacrifice some thermal efii ciency due .to higher stack temperatures. \Vhere a plurality of film tube generators are used, some in hot zones and others in cold zones, of course, there is no loss in thermal efficiency and the advantages of the film tube generator both from the standpoint of low heat head and high steaming capacity may be enjoyed. It should be understood that in every case it is necessary to make some compromise between ideal thermal efiiciency and structural and economic factors. The best compromise for any particular plant installation may be determined by the engineer designing the installation and itis one of the. important advantages of the present invention that it is applicable to a wide variety of installations and this flexibility of arrangement and construction makes it possible to re-design existing boiler units with a minimum of rebuilding and to so increase the efficiency of the installation as to, in many cases, add-years of life to obsolescent units, which, however, frequently represegit a very large capital investment.

The present-invention is also of importance in connection with water walls; thus, for example, a film tube generator arranged as a water wall can be used very effectively for the generation of very high pressure steam, as it is exposed to the radiant heat of the flame and possesses,therefore, a very great steaming capacity while the high heattrans fer efliciency of the generator adds a very desirable factor of safety against burning out. Installations in which one or more generators are operating as water walls are included in the present invention and are important embodiments thereof.

While the present invention is particularly concerned with installations in which a film tube generator is associated in series with a generator of the convection circulation type, it should be understood that two film tube generators can be connected together according to the present invention in order to generate steam of different pressures. Such installations can frequently be very efliciently arranged and where the difference in pressure is not too great, the drop in pressure through the injection orifices of the low pressure film tube generator may, in many cases, be sufficient to efi'ect the desired drop in pressure between the two generators. In other cases, additional throttle valves must be provided and can be with advantage controlled by the amount of steam generated in the low pressure generator by various control means such as water level controls and the like. A similar automatic control throttle many common accessories such as safety valves, blow-offs and the like have been omita ted in some cases and it should be understood that the drawings which are simplified to bring out the fundamentals of the present invention arenot to be considered as limiting the invention to generators as illustrated, and, on the contrary, all the usual accessories will be employed wherever they are desirable.

The drawings also show various circulation features associated with different-types of conventional boilers. It should be understood that the association of one type of gas or water circulation with a particular type of conventional boiler in no sense limits the invention, as the drawings have merely been chosen to illustrate the most important types of circulation and a number of conventional boilers have been used in these illustrations in order to show the applicability of the present invention to these various types of, boilers. It should be understood that features of flow shown in one figure as associated with "one type of common boiler may be used with other types of boilers shown in other figures with a different type of circulation and vice versa.

The boilers of the present invention are illustrated in a purely diagrammatic form in the drawings, in which Figure 1 is a section through two La Mont boilers showing cross feed from the low pressure to the high pressure boiler without return,

Figures '2 and 3 are sections through high pressure inclined water tube boilers associated with low pressure La Mont boilers, Figure 2 illustrating cross feed from the low pressure to the high pressure boiler and Figure 3 series parallel circulation through the two boilers; v

Figure 4: is a section showing a combination of a high pressure La Mont boiler, having tubes placed in the fire tubes of a low pressure fire tube boiler;

' Figure 4a is a horizontal section along the line ia-4a of Figure 4;

Figure is a section showing a combination ofa bent tube cross drum boiler with a low pressure La Mont boiler illustrating cross sin 1e pass water tube boiler associated with I I feed from the high pressure to low pressure rately fired high pressure La Mont boiler;

Figure 9 is a section through an Edgemoor hig pressure La Mont water wall boilers;

Figure 10 is a section through three La Mont generators illustrating a pure series flow.

Figure 11 is a section through two inclined tube water tube boilers having a series gas flow Figure 12 is a section throu h a multiple unit Ladd type. water tube boi or associated with a high pressure La Mont generator;

Figure 13 is a section through a cross drum inclined water tube boiler associated with two La Mont generators with parallel and series gas flow respectively; and Figure 14 is a detail in perspective showing one of the headers broken away to show the jet orifices.

In the construction'shown in Figure 1 two separate La Mont generators consisting in upper headers 1 and 2, lower headers or pots 3 and 4 and tubes 5 and 6 are arranged in the same furnace. Each generator has an independent circulating system. Thus, water and steam discharged from the lower header 3 flow through the pipe'7 into the pot 8, where steam is separated and taken off through the pipe 9 provided with a valve 10 and the water ows through the pipe 11, pump 12 and pipe 13 into the upper header 1, thus completing the circuit for the high pressure boiler. Suitable valves 14 and 15 may be provided to rogulatethe flow in this circuit. In a similar manner the steam and water discharged from the lower low pressure header 4 flow through the pipe 16 into the pot 17 where steam is separated and passes off through the pipe 18 controlled by the valve 19 and the water separated flows through the pipe 20, pump 21 and pipe 22 to the upper low pressure header 2. A complete circulation is therefore provided for each boiler.

In addition to the separate circulations for the two boilers a pipe 23, provided with a valve 24, connects the water space of the-high pressure pot 8 with the water space of the low pressure pot 17 and water tends to feed through t is pipe into the low pressure circulating system. The flow of water is controlled by the valve 24 which is in turn actuated by the water level control 25 on the pot 17, the amount of water fed being adjusted to the evaporation of the low pressure boiler. Feed water for .both boilers is taken in 1,seo,aes

through a pipe 26 controlled .by a valve 27 which is actuated by the water level control 28 on the high pressure pot 8. All of the feed for both boilers therefore is introduced into the high pressure system and is controlled both by the evaporation of the high pressure generator and by the amount of feed which passes from the high pressure pot to the low pressure pot.

Gas flow through the two boilers is in series, first through the high pressure boiler and then through the low pressure boiler, resulting in a very economical action since the highly efficient heat transfer of the film tube generators brings the temperature of the gases substantially down to thetemperature of the low pressure steam generated in the tubes 6. A single feed passes directly into the high pressure circulation and supplies both high pressure and low pressure generators with the amount of make-up water needed. The feed from the high pressure pot to the low pressure pot is automatically adjusted in accordance with the steam demands of the low pressure generator and in fact, actually enhances the steam capacity of this latter unit, since the water in the pot 8 may frequently be at a temperature above the boiling point of water under the pressure existing in the pot 17. Accordingly when the pressure is reduced in passing from pot 8 to pot 17 through the throttle valve 24, steam is formed which is added to the amount of low pressure steam generated by the low pressure boiler and passes oil through the pipe 18. The operation of the two boilers is independent of their relative steam demands and the feed is automatically proportioned to the boilers in. accordance with their demand, a steady uninterrupted feed is obtained irrespective of the relative steam demands on the two boilers and a very eflicient utilization of the heating gases is achieved.

y In the drawing, the feed is shown as introduced in to the suction of the La Mont circulating pump. This is a convenient and advantageous location for feed introduction, but the feed can be introduced into any other portion of the outside circulation of the La Mont generator or feed can be introduced into the high pressure water tube boiler.

Instead of feeding water from the high pressure unit to the low pressure unit the converse is also possible and is frequently desirable. This flow is shown in Figure 2, where a low pressure La Mont generator consisting in upper header 2, lower header 4 and tubes 6 is arranged in the stack or flue of an inclined tube boiler operating at a higher pressure. The water tubes are shown at 29 passing from rear headers 30 to front headers 31. The drum 32 is connected to the front headers through the pipes 33 and to the rear headers through the pipes 34, completing the circulating circuit of the boiler. The circula is heated up so that the Water tube boiler 013- tion of the La Mont unit is from the header 4 through the pipe 16 to the pot 17 and thence through the pipe 20, pump 21 and pipe 22 back to the upper header 2. Steam is taken off from the pot through the pipe 18 controlled by the valve 19. Part of the excess water of the La Mont circulation is pumped fromthe water space of the pot 17 into the back header of the high pressure boiler by means of the pump drawing water through the pipe 36, and discharging it through the pipe 37, valves 38 and 39 being provided in the respective pipes for control.

Feed water for both boilers is injected into the circulation of the La Mont boiler through thefeed pipe 40 controlled by the valve 41 which, in turn, is actuated by the water level control 42. In operation all of the feed water for both boilers is circulated through the low pressure La Mont boiler and crating at high pressure receives only heated feed water. The La Mont generator, therefore, not only serves the purpose of an efiicient source for low pressure steam but it also serves to heat up all of the feed water which is introduced'intothe high pressure boiler. Owing to the largeamountiof cold feed water which is injected into the circulation of the La Mont generator, thetmperature of the water in the upper header2 is comparatively low. and it is therefore readily possible to operate with a heat head on the La Mont tubes which is less than zero; that is to say,

I the stack gases after leaving the La Mont generator are at a temperature below that of the low pressure steam generated. p

In addition to increasing the over-all efiiciency of the boiler installation by generating low pressuresteam by means of what may really be considered as thewasteheat from the high pressure boiler, and particularly in carrying stack temperatures down'to an eX-- ceedingly low point by operating theLa Mont generator as a feed water heater as well as a gcnerator,.a further advantage is inherent in the construction shown in Figure 2, namely, the increased efficiency of circulation in the water tube boiler.

The water injected through the pipe 37 possesses considerable velocity and can, if desired. be so directed as to flow into the water tubes in the form of jets at considerable speed. A semi-injector action results which greatly enhances the ef fectivencss of the ordinary convection circulation which exists in inclined tube boilers oi pressure La. Mont generator and merely feeding the excess water into the hi h pressure water tube boiler, a series para lel circulation is provided, waterunder high pressure being taken from the forward end of the drum 32, through the pipe 43, into the up per header 2 of the La Mont generator. In other words, the water for the La Mont generator is circulated through the water tubes of the inclined tube generator and thence in series through the La Mont generator. This greatly enhances the circulation efiiciency in the inclined water tube generator itself and at the same time omits the additional pump required in the modification shown in Figure 2 in order to provide for a separate circulation in the La Mont generator. Feed can be introduced through the pipe 44 and the La Mont generator can be utilized therefore as a feed water. heater as well as a generator, effecting the economical savings described in connection with the modification shown in Figure 2.

Figures 4 and 4a represent a very advantageous combination of a La Mont generator with a relatively inefiicient and at the present time almost obsolete or obsolescent type of vertical fire tube generators. The fire tube generator consists in a shell 45 extending down to form water legs 46 and 47 separated by bafiles or partitions 217, and provided with fire tubes 48'. The La Mont generator, which is operated at a higher pressure than is the fire tube boiler, consists in an upper header 51, lower header 53 and tubes 55, which tubes pass through the fire tubes, resulting in a very markedly decreased hydraulic mean depth and increased velocity of heating gases through the fire tubes. Steam and water is discharged from the lower header 53 into pot 54, where steam is separated, the steam passing oil through the pipe 49 controlled'by the valve 50 and the water flowing into the leg 46 of the fire tube boiler through the pipe 52 provided with the valve 225, controlled by the water level control 226. Water is taken from the leg 4. through the pipe 56.and

pipe 49, the excess water flowing into the other leg of the fire, tube boiler. Thus, the circulation of water through the La Mont generator passes in series through the fire tube boiler and enhances the circulation of the latter in addition to Very greatly increasing the efiiciency of both units, due to the fact that the La Mont tubes pass through the fire tubes and therebypermit a verylow hydraulic mean depth and high gas velocity with a correspondingly increased heat transfer efficiency. Low pressure steam is taken from the fire tube boiler through the pipe 61 controlled by the valve 62.

In the modification shown in Figure 5, a low pressure La Mont generator isinstalled -in the stack of a bent tubecross drum boiler .installation of the Stirling type, which boiler I in this modification operates at a considerably higher pressure than does the La Mont generator. he Stirling boiler consists in upper .drums .63, 64 and 65 and lower drums 66,

which is connected with the drum 63 by the J tubes 67 and to the drums 64 and 65 by thetubes 68 and 69. Steam aces of the upper drums are connected b t e tubes 70 and 71 and the water spaces 0 the drums 64 and 65 are connected by the tube 72.

' The La Mont generator consists in upper header 73, lower header 74 and tubes 75. Water and steam from theheader 74 of the La Mont generator pass through the pipe 76 into the not 77 where the steam is separated and passes off through the pipe .78 controlled by the valve 79. Water from the water space of the pot is pumped through the suction pipe 80, pump 81 and pipe 82 into the upper header 73, thus pI'OVldl% a separate com lete circuit for the La ont generator. alves 83 and 84 control the speed of circulation.

Feed water is introduced into the drum 63 of the Stirling boiler through the pipe 85 and the feed is controlled by the valve 86 actuated through the water level control 87 connected to the drum 64. Water is also fed from the drum 65 through the pipe 88 into the pot of the La Mont generator andserves as make-up water to replace the steam generated in the La Mont generator. The flow through the pipe 88 is controlled by the throttle valve with a minimum of redesigning and rebuilding, and a large increased overall eflicienc-y results,,both from the more efiicient utilization of the heat in the heating gases and from the increased circulation in the Stirling boiler which correspondingly increases its steaming capacity and im roves its operation. The water discharge through the pipe 88 is usually at a temperature considerably'above the boiling point corresponding to the pressure which exists in the 0t 77 and therefore, a considerable amount 0 water is turned into steam and passes oil as low pressure steam through the pipe 78. A sudden increased demand for low pressure steam, therefore, 1ow-.

' the result that an ad-v La Mont generator 0 small and economical size. Only a single pump'is used and the system is sun le andrelia'ble in operation and lends ltsel tomany industrial applications.

A combination of. a Scotch marine boiler and a separately fired La Mont generator is shown in Figure 6. The Scotch boiler which is of conventional design, consists in'a shell 91 extending in the form of a leg 92 surrounding the firebox, and provided with fire tubes 93. Feed is introduced through the pipe 94 controlled by the valve 95 and steam is taken oil from the steam space through the 'pipe 96 controlled by the valve 97. The

Scotch marine boiler which may advantageously operate at a moderate steam pressure is associated with ahigh pressure separately fired La Mont generator consisting in an upper header 219, lower header 220 and tubes 221, the circulation being from the header 220 through the pipe 222 into the pot 223 and thence through the pipe 224, pump 98 and pipe 99 into the upper header of the La'Mont generator. Valves 100 and 101 are also provided for" controlling the flow.

In addition'to the separate circulations of v the La Mont boiler and the ordinary convection circulation of the Scotch boiler means are provided for feeding water from the leg 92 of the Scotch boiler into the pot 223 by means of the pump 102 drawing water from the bottom of the leg 92 through thepipe 103 and discharging it through the pipe 104, valves 105 and 106 being provided for control purposes.

A relatively clean, hot feed is thus provided for the La Mont generator which is advantageous when it is desired to generate large quantities of high pressure steam in a La Mont generator of-economical size. Owing to its high heat transfer capacity it is also possible to use heat sources of great intensity without danger of burning out the tubes. Not only is a hot feed water of desirable purity assured for operation of the La Mont enerator at high pressure but the circulation 1n the Scotch marine boiler is very greatly enhanced as the flow through this boiler is from the feed pipe 95 backward and down through the leg 92 and then out through the pipe 103 into the pot of the La Mont generator. The flow of water thus roughly is counter to the flow of heating gases up through the combustion space and through the fire tubes resulting in an effective heat transfer and decreasing the stack temperatures of the ases leaving the Scotch boiler. This counter ow can, in some cases, materialas water walls or radiant heat boilers and an eflicient and desirable combination of water wall boiler and conventional inclined Water tube boiler is shown in Figure 7. In this figure, the water tube boiler consisting-in a drum 107 rear header 108, front header 109 and tubes 110 and bafiies 111, preferably oper ates under moderate pressure, steam being taken oflf from the steam space of the drum through the pipe 112 controlled by the valve 113. The low pressure La Mont water wall boiler consists in upper header 114, lower header and pot'115 and tubes 116. High pressure water from the rear header 108'fl0WS to the header 114 through the pipe 117 con trolled by the throttle valve 118. After passing through the genei ator tubes 116, the mixture of steam and water is separated in thepot 115, the steam passing ofl through pipe 119 controlled by valve 120 and the water being pumped by the pump 121 through the pipes 122 and 123 into the water s ace of the drum 107, suitable valves 124 an 125 being provided to control flow.

The La Mont generator, efiiciently shields the walls and serves as an eflicient source of low pressure steam. 'At the same time the circulation through the main boiler is enhanced due to the fact'that water is pumped into one end of the drum and taken out from the rear header 108'at the other end of the drum. 'A further important advantage lies in the fact that the danger of burning out the tubes '116 is minimized due to the fact that a large volume of high pressure water is avaiL able for feeding these tubes directly and is instantly controlled by the valve 118 which is actuated by the water level control 126. There is therefore, little or no danger of burning out these tubes even with very marked and sudden variations in the temperature of the fire and in the demandsffor .1; low pressure steam.

iii

If desired, the water wall can be operate as a full tube water wall instead of a film tube struction may be cheaper and where the de mand for low pressure steam is not'great, it may be economlcally advantageous to construct full tube water wall stead of film tube generators.

In Figure 8, a separately fired high pressure La Mont generator is shown associated with an ordinary Wickes boiler designed to generate steam at a lower pressure. The lVickes boiler consists in an upper drum 127, lower drum 128 connected b rear circulating tubes 129 and front circulating tubes 130. A baflie 131 separates the two sets of tubes. The steam is taken 01f from the steam space of the upper drum through the pipe 132 controlled by the valve 133 and a feed pipe 134 generators, 1n-

-provided with a valve 135 is also connected to the water space of the upper drum. This feed pipe is used for auxiliary feeding, as will be described below.

The separately fired high pressure La Mont generator consists in anupper header 1 36, lower header-137 and generating tubes 138.

VVater and steam from the lower header 137- pass through the pipe 139 to the pot 140,

valve 142. Excess Water from the water spaceof the pot is circulated through the pipes 143 and 144 by the pump 145 which forces the water into the upper header136.

Valves 146 and 147 are provided to regulate flow and feed water isintroduced through the pipe 148 controlled by the Valve 149,

which is actuated by the Water level control 158.

Some of the high pressure steam from the pot 140 is passed through the pipe Y150 and injector 151 where it picks up feed water from the tank 152 through the pipe 153 and.

injects this feed water at high velocity through the pipe 154 and nozzles155 into the bottom of the water tubes 130 of the Wickes boiler, thereby very greatly enhancing the speed of circulationin the Wickes boiler and Q correspondingly increasing its steaming capacity. The amount of feed water injected into the Wickes boiler by. the high pressure steam is controlled by means of the throttle valve 156 actuated from the'water level control 157 associated with the upper drum of the W'ickes boiler. Feed .into the La Mont generator is similarly controlled by a water level control 158 associated with the pot 140.

In operation the circulation through the La Mont generator is substantially inde endent from that of the Wickes boiler as ar as the water is concerned, and high pressure steam 1 can begenerated in varying amounts according to demand. The demand for low gressure steam fromthe Wickes boiler prouces variations in thewater levelin the upper drumand this in turn actua-tes the throttle valve 156, causing the injection of the necessary feed water by means of high pressure steam from the La'Mont generator. Particularly where there isa large difference in pressures between'the two boilers a veryti l violent injection will take place and the naturally sluggish convection circulation of the \Vickes boiler is greatly accelerated. The

' of water in the Vickes boiler is not necessary, a. somewhat cheaper and simpler construct-ion-cau be used in which the nozzles arev omitted and the feed water is simply injected into the bottom of thedrum below the tubes 130. This will increase the circulation due to the fact that the velocity of the injected water continues into the circulating tubes.

The arrangement of a Wiclres boiler with a separately fired La Mont generator is very flexible and the relative sizes of the two units can be varied within wide limits. It is also possible to operate either generator separately from the other; thus, for example, if connection to the Wickes boiler is shut off by closing the valve 156 the La Mont generator can be operated entirely independently and in the same way the VVickes boiler can als'obe operated independently, utilizing a separate feed through the pipe 134 controlled by the valve 135. In some cases, it may be desirable to provide a very small La Mont generator where the demands for high pressure steam are low or the La Mont generator may be run at varying loads and. at times the steam production may be insuflicientto inject suflicient feed water into the \Vickes boiler even when the whole of the high pressure steam is used for this purpose. The deficiency can then be made up by introducing some additional feed water through the pipe 134 if desired. In general, it should be understood that control of feed water which has been illustrated as automatic in some fi ures and as manual in others can be widely varied between the limits of full automaticcontrol and full manual control.

The combination of two La Mont water wall generators for high pressure steam with a lower pressure Edgemoor single pass boiler is shown in Figure 9. The front water wall consists in an upper header 159, generatingtubes 160 and lower header or pot 161 and the rear water wall similarly consists in an upper header 162, generating tubes 163 and a lower header or pot 164. The Edgemoor boiler is provided with an upper steam and water drum 165, a lower drum 166. generating tubes 167, a rear steam and water drum 168, a water heater 169 and a superheater 170. The steam space of the drum 165 is connected to the steam space of the drum 168 by means of the pipe 171 and the water spaces of these two are similarly connected by the tube 17 2. Saturated steam at low pressure can be taken off through the pipe 173 controlled by the valve 174 or it can be passed through the superheater passing out through the superheated steammain 175 controlled by the valve 176. Feed water is introduced through'the pipe 177 controlled.

164 to the drum 166 of the Edgemoor boiler through the pipe 184 controlled by the throttle valve 185. High pressure steam is taken off from the pots 161 and 164 through the pipes 186 and 187 controlled by the valves 188 and 189. Valves 190 and 191 are also provided in the pipes 182 and 183 in order to control the delivery of water to the La Mont generators. These valves may be operated manually or, as shown in the drawing, may be connected to suitable water level controls on the pots 161 and 164. These water level controls are shown at 192 and In operation feed water for both of the boilers is introduced through the pipe 177 heated in the feed water heater 169, whence it passes into the drum 168 and down through the pipe 179. The pump then delivers the water at a considerably higher pressure into the La Mont generators where part of the water is evaporated and steam and water are separated in the pots 161 and 164. The excess water is then circulated through the pipe 184 into the bottom drumof the Edgemoor boiler and-thence positively upward through the generating tubes 167 into the upper drum 165, where steam and water are partially separated, the steam and water passing through pipes 171 and 172 into the steam separating drum 168. The water then circulates down through the pipe. 179 and again through the La Mont generators.

It will be seen that the water circulation through the generators at diiferent pressures is purely in series, every bit of the circulating water being required to pass through the generators at both pressures in series. This provides for an extremely efiicient circulation through the Edgemoor boiler and very greatly increases its steaming capacity. At the same time the large feed water heater of the Edgemoor boiler serves to heat up feed water for both the Edgemoor and the La Mont generators. Only a single pump is required in this system and yet a full positive circula tion isassured in all three generators.

' Figure 10 illustrates three-La; Mont generhigh pressure generator.

ators arranged in series inthe same furnace and possessing a pure series circulation; The high pressure generator which is arranged in the hottest zone of the furnace con.- sists in upper header 194, tubes 195 and lower header or pot 196. Correspondingly the intermediate pressure generator includes upper header 197, tubes 198 and lower header or pot 199, whereas the low pressure generator which is in the coolest zone is shown as provided with upper header 200, tubes 201 and lower header or pot 202. Each of the pots is provided with steam pipes from their steam space, the high pressure pot discharging high pressure steam through the pipe 203 controlled by the valve 204, the intermediate pot through pipe 205 controlled by valve 206 and the low pressure pot through pipe 207 controlled by valve 208.

Water from the low pressure pot 202 passes through a pipe 209 into reservoir 227 from which it is drawn by pump 210 and forced through a pipe 211 into the upper header 194 of the high pressure generator. A large excess of water is circulated through this generator, a certain amount being evaporated and the steam separated in the pot 196. The water which remains unevaporated passes then from the water space of the pot 196 through the pipe 212 into the upper header 197 of the intermediate pressure generator, whence it circulates down through the film tubes 198, a still further portion of water being evaporated and the steam separated in the pot 199. The unevaporated water andalso some steam passes from the water space of the pot 199 into a reservoir 8 which is similar to that shown in Figure 1, where steam and water are separated, the water passing thence through the pipe 213 into the upper header 200 of the lower pressure generator, where a still further amount is evaporated and the steam separated in pot 202. The excess water is recirculated through pipe 209 into reservoir 227 where any entrained steam is separated and passes into the steam main 207 through the pipe 228. Feed water may be introduced into the reservoir 227 directly but preferably such introduction is controlled by means of an injector 151 operated from steam from the V This feed water is taken from a tank 152 and passes into the system through the pipe 153 to an injector 151, the steam for which is led from the reservoir 8 by the pipe 150. A water level con- I trol 216 acts upon valve 215 in the pipe 150 posed to the most intense heat they receive the maximum protection. The intermediate generator is correspondingly protected by its proportionate excess of water.

The drop in pressure between the generators is produced in the modification shown 1 in Figure 10 by the restriction of the inlet orifices in the headers 197 and 200 when the difference in pressure between the various generators is not excessive. This arrangement is very simple and economical, as it involves no moving parts or valves.

Owing to the fact that all the water is circulated in series through the three generators a stoppage in either the high or intermediate pressure generators might cause the low pressure generator to run dry and burn out and in order to prevent this possibility by- pass pipes 216 and 217 can be provided leading from the pump outlet to the upper headers 197 and 200 and controlled by the valves 218'and 219. In case of a partial or total stoppage of flow'through the high pressure or intermediate pressure generator, one or more of these valves can be opened to produce a parallel circulation through the intermediate or low pressure generators and prevent their burning out.

In a similar manner, these valves may be used to modify the pure series circulation and produce in part a series parallel circulation. This may be desirable where the demands for low pressure or intermediate pressure steam may vary and may, at times, be disproportionately large in comparison to the demands for high pressure steam. The exact combination of controls, automatic, semiautomatic or manual, which is most desirable under the operating conditions in any particular installation will, of course, be chosen by the skilled steam engineer.

Figure 11 illustrates the combination of two inclined cross drum water tube boilers operating under diiierent pressures. The high pressure boiler consists in drum 229, front headers 230 and 231, rear headers and 233, the headers being connected respectively by two decks of generator tubes 23% and 235. The upper rear header 232 is connected to the drum 229 by the tubes 236 and the respective front and rear headers are connected by the pipes 238 and 237. A superheater consisting in intake header 289, superheater tubes 240 and outlet header 241, is connected to the steam space of the drum 229 by the pipe 242 and discharges high pressure superheated steam through the pipe. 243 into a

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