US2590712A

US2590712A - Steam generator with double outlet furnace

Info

Publication number: US2590712A
Application number: US22643A
Authority: US
Inventors: Joseph A Lacerenza
Original assignee: Combustion Engineering Superheater Inc
Current assignee: Combustion Engineering Inc
Priority date: 1948-04-22
Filing date: 1948-04-22
Publication date: 1952-03-25
Anticipated expiration: 1969-03-25

Description

March 25, 1952 J. A. I AcERr-:NzA

STEAM GENERATOR WITH DOUBLE OUTLET FURNACE Filed April 22, 1948 2 SHEETS-SHEET l P m U 2f 4 M9 w \|V3 4, M4 M a zzm wwwa@ 6 `045 5 5 f WWW 7 5 v A 3 0900. s |11 7 \/|M .32m/ 4 0 J. :OJ 5

/9 mlm J. A. LACERENZA March 25, 1952 A STEAM GENERATOR WITH DOUBLE OUTLET FuRNAcE I 2 SHEETS-SHEET 2 Filed April 22, 1948 INVENTOR J. A. Lucerenzo non Fig. 5.V

Fig. A4.

ATTORNEY Patented Mar. 25, 1952 GENERATOR WITH DOUBLE OUTLET FURNACE Joseph A. Lacerenza, New York, Ne Y., assignor t0 Combustion Engineeringeuperheater, I nc., a corporation of Delaware Application April Z2, 1948, Serial No. 22,643

11 Claims. (C1-lmfao This invention relates to improvements in steam generators and particularly to steam .generators provided with superheaters and reheaters and having improved means for regulating the temperatures of the steam leaving said heaters.

High capacity steam generators working at high pressures and delivering steam at high temperatures may have a major portion or al1 of the steam returned to be reheated in the steam generator to a high temperature. For example, if the steam is delivered to a steam turbine at a temperature such as'about 950 F. a major portion, such as about 90%, may be returned from an intermediate stage of the turbine to the steam generator to be reheated to a high temperature, such as about 950 F., `and thence returned to the subsequent stages of the turbine.

When in such a generating plant the superheater and reheater are placed within the steam generator in series with respect to the gas flow through the generator, and with all of :the gas flow flowing over both heaters, the reheat temperature will be `too high at the high loads, if the reheater is designed to provide the proper temperature at the lower loads, -or it ywill fbe too low at the low Vloads if the reheater is .designed to provide the proper reheat at 4the higher loads.

To correct these departures from the desired steam temperatures by means of `by.passir-1g some of the gases around eitherof lthe heaters involves more `than necessary heat yabsorbing surface in said respective heaters and additional vheat absorbing surface to reduce the excess `temperature of the byfpassed gases.

When the superheater and reheater are placed in parallel passes for the furnace leaving gases, the relative amounts of gas flowing over the heaters may be shifted from `one pass to the other in accordance with the Vheat requirements of the heaters, whereby the above mentioned ob.- jections may be substantially overcome.

It is an object .of this invention to provide in a highY capacity steam -generator having steam heating surfaces within parallel passes for the furnace leaving gases, novel arrangementsof fuel burning means and heat absorbing ysurfaces to more efficiently lregulate the temperature and flow of said gases through said passes for superheating and reheating vthe steam from the generator Vto its Vproper 4temperatures.

Additional objects of the invention will appear from the following description `of one preferred embodiment of the invention when taken in conjunction with the accompanying drawings wherein: c

Figure 1 is a diagrammatic vertical section through a steam generator embedying the lne vention.;

Figure 2 is a cross section teken Yon line 2-2 of Figure v.1;

Figure@ is a cross section taker 91.1 lille 3f? of .Figure 1; and.

Figure e .is a fragmentary vertical section through e typical burner 0f the tilting tyre,-

\ Figure .5 is a diagrammatic illustration af e vsurerheeter 'with a. desuperheatsr arranged the steam line to the rrirremover es illustratively Shown .ir-1 Figure ,1 my improve@ S''lellll generali@ COKlDlSQS a lllllf? Wllll may ,include three generally vleslellelsl es A' .l5 and .C- .At the top of the ,furnace ,1S ,er Outlet U and at the bottom of the furnace another outlet 1.,. The furnace may be provided with two af A,burners en. upper Set l and e lower ,Set 2. ,Preferably the burners are of the tilting type as disclosed in the U. S. Patent to Kreisinger `et al. No. 12,363,875. The upper set of burners I may be arranged to be tilted independently of the lower set of burners 2. t

Preferably the furnace is completely lined on all sides with steam generating tubes 3 which vare connected for circulation of water there,- through to the steam and water drums ,4 and 5 Yvia risers l and 3. Risers 6 and 1 connect respectively the :fr- Ont and rear walls of the fur.- nace to drum 4 while risers 8 connect the Yside wallsthrough yheaders 9; there being two headers 9, one for each side wall. A multiplicity of downcomer tubes 'l0 connect the steam drums 4 and 5 to headers lvl and `I2 from which the downfcomer tubes yI3 and l4 carry water from the drums tothe bottom headers l 5, I6, Il, :L8 and IS Iof the water walls. There yare similar headers 15 l1 and I9 for the side wail opposite that shown.

The offtakes U and L direct the gases Aleaving the vfurnace Vinto two passes -20 and 2l. Upper pass 20 is provided with an outlet -2'2 while Vlower pass 2| is provided with an outlet 23. Preferably said outlets 22 and 2-3 are adjacent one another and are provided -wit-h dampers 124 and 25 for throttling gas 4flow therethrough.

Preferably the passes 20 and 2 l have-Wallslined with steam generating tubes connected into circulation with the steam drums 4 and 5. Ad-

Ijacent the offtake U some of the water wall tubes 3 1a extend via risers 1 into drum 4. The horizontal portions of these risers 1 serve as a support for the roof 21 of the furnace and for the upper end of the pass 20. The remaining of the water wall tubes 3 may pass upwardly across offtake U and join risers 1 into the drum 4.

Adjacent the lower oitake L of the furnace some of the water Wall tubes 3a rise from header I8 upwardly and rearwardly along the bottom of pass 2| thence rise in open formations across the pass, thence extend forwardly toward the furnace while supporting the upper wall of the pass, and thence rise in alignment with the remaining tubes 3 of the rear wall of the furnace. The remaining tubes 3a from header I8 rise vertically across oitake L and join the former tubes 3 in alignment with the rear wall of the furnace.

The walls of the vertical portion of passes 2U and 2| are preferably lined with steam generating tubes which are supplied from the bottom headers I8 and 28. The tubes 29 rising from header 28 extend upwardly adjacent the front Wall of pass 2| for a short distance, thence some of the tubes 29 extend into the pass and upwardly to form a by-pass 30. Above by-pass 30 the tubes 29 adjacent the front wall extend inwardly to join the remaining tubes and thence continue upwardly in alignment again along the front wall of pass 2| and up into pass 20. After passing upwardly for a distance in pass said tubes 29 again spread apart into a lower group 3| and an upper group 32 forming the walls of a jby-pass 33. At the upper end of said by-pass 33 the lower group of tubes 3| bend upwardly to cross the by-pass 33 and connect to header 26. lThey discharge through risers 1a, 1 to the steam drum 4. At the upper end of said by-pass 33 theI upper group of tubes 32 bend upwardly as tubes 32a across the pass 20 and thence continue to discharge into drum 5. By-passes 3U and 33 are provided with dampers a and 33a.

The rearward sides of passes 2| and 20 are lined with tubes 34 which are continuations of tubes 35 rising from header I8 and extending 'across pass 2| to the rear wall thereof. Thence 'tubesl 35 continue upwardly as tubes 34 through both the passes 2| and 20 and at their upper ends bend forwardly to form the roof tubes 36 of pass 20. The upper ends of said roof tubes 36 bend upwardly and thence continue astubes 36a into drum 5.

Within the upper portion of pass 20 is a superheater divided into three

sections

31, 38 and 39. `Steam from drum 5 is conveyed via tubes 4U into the superheater inlet header 4| whence it flows lserially through

sections

31, 38 and 39 to superheater outlet header 42.

The

superheater sections

31, 38 and 39 may constitute the entire superheater surface required.

vShould more superheat be required than can be eiciently provided by these sections, it may be desirable to locate a further superheater section -43 within the lower portion of pass 2| which re- -ceives the steam from outlet header 42 Via con- -nection 44 into its inlet header 45. Steam leaves superheater 43 via outlet header 46.

Adjacent said superheater 43 and located within the lower portion of pass 2| is a portion of a reheater 41 the remaining portion 48 of which is located within the vertical portion of pass 2|'. Steam from an intermediate expansion stage of a prime mover, such as a steam turbine, is con- 'ducted to the inlet header 49 of the reheater by a conduit not shown, thence passes downwardly rthroug'h'reheater 48 comprising a bank of sinuous tubes and connected to the sinuous tube bank of reheater portion 41 via tubes 50; Steam leaves the reheater 41 via outlet header 5| to be returned to a later stage in said prime mover.

Within the vertical portions of passes 2| and 20 and adjacent the

outlets

23 and 22 thereof is llocated an economizer having lower and

upper sections

52 and 53 respectively. Feed water enters the lower portion of lower economizer section 52 thence flows upwardly through the tubes of the economizer into thelower portion of the upper section 53 thence upwardly through that section and out of the top thereof into the drum 4 through connections not shown.

Figure 2 shows one preferred arrangement of the burners and 2 with respect to the furnace. located adjacent or at the corners thereof. The fuel streams issuing from each set of these burners are directed tangentially toward the surface of an imaginary vertically disposed cylinder within the furnace and may selectively be directed upwardly and downwardly as taught by Kreisinger et al. Patent 2,363,875 earlier identified.

Referring to Figure l, the groups of burners and 2 are preferably connected each group to one mill 54 or mill 55, or sets of separate mills, and the fuel is delivered from the mills through conduits 56, 451 to fans 58, 59 and thence via.

conduits

68, 6| to the groups of burners and 2 respectively. Only two mills are shown by way of example, each connected to one set of burners. Obviously the remaining burners are similarly connected although not so shown. By such grouping of mills and burners, the amount of fuel delivered by burners may be varied from that delivered by burners 2 by regulating the fuel output of the respective mills by controlling the speed of each mill motor MI and M2. In the illustrative embodiment shown in Fig. 1 a speed adjuster SI is interposed in the line between the power source and mill motor MI. Similarly a speed adjuster S2 is interposed in the line between the power source and mill motor M2. Each motor drives its respective mill 54 or 55 as well yas fan 51 or 58 which delivers the fuel to the burner or 2 respectively.

Figure 3 is a plan section through the furnace and the upper pass 2U showing the

superheater sections

31, 38 and 39 within said pass. Preferably the by-pass 33 extends for the full width of the pass 29, as this drawing view shows.

Figure 4 shows a typical fragmentary sectional view through one of the burners. It comprises an air casing or housing 62 and pulverized fuel nozzle I, 2 extending therethrough. Only one such fuel nozzle is shown in this disclosure. The

fuel nozzle comprises a conduit 63 which is provided with an end piece or tip 64 rotatable vertically about horizontal supporting bearings 65 on the end of conduit 63. The tip 64 and conduit v63 may be formed at their juncture to a socket type of joint as shown.

' vSurrounding the nozzle tip 64 and mounted thereon is a tubular air deflecting vane 66, the whole when tilted upwardly or downwardly, directing the fuel and air stream accordingly into the furnace. The tip 64 and vane 66 are rotated by means of a rod 61 connected at one side of the tip by an arm 68 fixed to the pin of bearing 65 on which the tip 64 rotates. 'Ihe other end of rod 61 is connected to a bell crank 68 which is yconnected to a vertically movable member 69. Vlhen the vertical member'89 is moved upwardly or downwardly it tilts the burner either downwardly or'upwardly.

Above and below each of the fuel pipes there are provided air chambers J .having tips 1| which rotate upwardly anddownwardly together with the fuel nozzles 64 and through .the same angularity. The tips 1| are pivoted at 12 and connected by rod 13 to the end of the bell crank 14 similar to the bell crank for operating the fuel nozzles, the bell crank 14 being lin turn .connected to the vertically movable member 69.

According to the invention the steam generator is .provided with two parallel passes with respect to the flow of furnace leaving gases, one pass 20 being connected .to an offtake U adjacent one end of the furnace and the other pass 2| being connected to an offtake D adjacent the other end of the furnace. One or more heaters are placed within each of these passes as already described, the heaters absorbing relatively variable amounts of heat from the gases in order to heat the respective fluids passing through them to the proper temperatures at the various ratings of the steam generator. To meet these variations in heat absorption, the amount of gases flowing through each pass 2U and 2| is varied and/or the entering temperature of the gases to each of the passes is varied, supplemented by the control dampers in each of the passes.

The heat in the furnace leaving gases entering each pass 2i) and 2| may be regulated by varying the amounts of fuel delivered by the various burners to the furnace. By varying the fuel delivered by the mills 54 associated with the upper burners the heat flowing into the upper pass 2D with the gases may be varied to suit and by varying the fuel delivered by the mills 55 associated with the lower burners 2, the heat flowing into the lower pass 2| may be varied to suit.

The temperature of the furnace leaving gases may also be varied by tilting the burners by means disclosed in the U. S. patent to Henry Kreisinger et al. No. 2,363,875. By tilting the upper burners I upwardly, the mass of flame therefrom will move into the upper portion of the furnace to zone B and consequently less heat will be absorbed from the flame" by the portions of the furnace below the llame resulting in relatively hotter furnace leaving gases to the upper pass 20. By tilting the lower burners 2 downwardly to zone C the mass of flame from the fuel delivered by these burners will move into the lower portion of the furnace and less heat will be absorbed from said llame vby the portion of the furnace above the flame, resulting in relatively hotter furnace leaving gases to the bottom pass. Should the upper pass require substantially more heat both the upper and lower burners may be tilted upwardly and should it require substantially less heat both the upper and lower burners may be tilted downwardly.

The flow of gases through the respective passes is controlled by

dampers

24 and 25 to supplement the burner control. Obviously any combination of angularity of the burners may be used and/or any variations in fuel supply by the various burners may be used to obtain the desired steam temperatures of the steam leaving the respective heaters.

The by-passes 3l! and 33 and the regulation of dampers Sila and 33a may serve to care for minor fluctuations in temperatures not covered by the manipulation of the burners and/or

dampers

24 and 25. Furthermore desuperheating of the steam by means well known, such as desuperheater 80 (Fig. l), may be employed to iron out small variations in steam temperatures leaving the heaters due to heat lag caused by the large mass of metal in the heaters. In the preferred embodiment .of my invention .shown in Fig. l the desuperheater is arranged betweerstages 31 and 38 of the superheater. .In some cases, especially in .cases where a single :stage superheater is utilized as diagrammatically indicated in Fig. 5 a desuperheater 8l is located in the steam line connecting the superheater with the turbine. In other cases such as in connection with a reheatsuperheater 4l, 48, Fig. l, a desuperheater 82 is preferably located in the steam line between the intermediate expansion stage of the steam turbine and the reheater. Each

desuperheater

30, 8| vand 82 is connected to a supply of spray water or cooling fluid (not shown) in a manner well known in the art. f

By advantageously dividing the heaters and placing them within the two parallel passes with respect to gas flow a relatively lower resistance to gas flow may be obtained.

Should the resistance to gas flow through the heaters within the two

passes

20 and 2| be materially different, the overall resistances may be substantially balanced by shifting some of the economizer heating surface from the pass of high resistance into the pass of low resistance.

Should the heat absorption from the gases by the heaters within the two passes 20 and 2l be materially different, the overall absorption of each pass may be substantially .balanced by shifting some of the economizer heating surface from the pass of high heater absorption to the one of low absorption.

By placing the reheater and the second stage of the superheater in the bottom pass both will be located adjacent the operating iloor at a level nearer the steam turbine which they serve and the superheater connection to the turbine will involve shorter high pressure and high temperature piping.

A further advantage is in having two sets of superimposed burners, the upper set burning one fuel Whose products of combustion rise to ilow into the upper furnace offtake and pass, and the lower set burning another fuel whose products of combustion flow downwardly into 'the lower furnace oiftake and pass. In this manner the two flames and products of combustion of Athe separate fuels avoid being mixed. Such mixture may result in slag deposits on lall of the heating surfaces, both upper and lower, if one ofthe fuels contains slag producing elements. By separating the flow of the products of combustion lfrom each fuel according to the invention, the heating surfaces in the path of the products of combustion from the non-slagging fuel will remain lfree from slag. .For example, such fuels Aas blast furnace gas or oil may be delivered to the upper set of burners while pulverized coal may be delivered to the lower set.

While the preferred embodiment of my invention has been shown and described, it will be understood that changes in construction, combination and arrangement of parts may be made without departing from the spirit and scope of the invention as claimed.

I claim:

1. In a steam generating unit having a generally vertical furnace associated therewith; steam generating tubes lining the walls of the furnace; a top offtake adjacent the upper end of the furnace and a bottom offtake adjacent the lower end of the furnace; means forming two passes for the flow of furnace leaving gases therethrough, the first of said passes being connected tto said top offtake and the second pass being connected to said bottom oftake; damper means in.

at least one of said passes adjustable to govern the apportionment between those two passes of the total gases leaving the furnace therethrough; at least one fluid heater arranged in each of said first and second passes; burner means located between said top and bottom offtakes in the furnace walls and arranged for delivering fuel and air to be burned into the furnace tangenltially to an imaginary vertically disposed cylinder in said furnace; and means for tilting said burners for directing the fuel and air streams therefrom .withn the furnace toward said top oiftake or toward said bottom oflltake tov vary the relative amount of heat absorbed by said steam generating tube portions in both the upper and lower portions of the furnace.

2. In a steamI generating unit having an associated furnace; steam generating tubes lining the walls of the furnace; an offtake adjacent one end of the furnace and another offtake adjacent the other end of the furnace; means forming two passes for the flow of furnace leaving gases therethrough, the first of said passes being connected to one of said offtakes and the second pass being connected to the other oiftake; dampers in said passes adjustable to govern the apportionment therebetween of the total gases leaving the furnace therethrough; a steam superheater and a steam reheater arranged one in each off said first and second passes; burner means located between said offtakes in the furnace walls and arranged for delivering fuel and air into the furnace to be burned therein; and means for tilting said burners for directing the fuel and air streams therefrom within the furnace either toward one offtake or rtoward the other offtake to vary the relative amount of heat absorbed by said steam generating tubes located in that part of the furnace which is adjacent to said one offtake and that part of the furnace which is adjacent to said other offtake.

3. In a steam generating unit having a generally vertical furnace associated ltherewith; steam generating tubes lining the walls of the furnace; an upper oiftake adjacent the upper end of the furnace and another lower offtake adjacent the lower end of the furnace; means forming two passes for the flow of furnace leaving gases therethrough, the first of said passes being connected to the said upper offtakes and the second pass being connected to the said lower offtake; dampers in said passes adjustable to govern the apportionment therebetween of the total gases leaving the furnace therethrough; a rst stage steam superheater arranged in said rst pass and a second stage steam superheater plus a steam reheater arranged in said second pass; burner means located between said upper and lower offtakes in the furnace walls and arranged for delivering fuel and air into the rfurnace to be burned therein; and means for tilting said burners for directing the fuel and air streams therefrom upwardly within the furnace and toward said upper offtake or downwardly within the furnace and toward said lower offtake, to vary the relative amount of heat absorbed by said steam generating tube portions in the upper and lower portions of the furnace.

4. In a steam generating unit having an associated furnace; a steam and water drum; steam generating tubes lining the Awalls of the furnace connected for circulation to said drum; an upper oiftake adjacent the upper end of the furnace and another lower otake adjacent the lower. @dei the .www means forming two passes for the flow of furnace leaving gases therethrough, the flrst of said passes being connected to the said upper offtake and the second pass being connected to the said lower oiftake, the rearward portions of said passes with respect to gas flow therethrough being in substantial vertical alignment; steam generating tubes extending through both said rearward pass portions and lining the walls off said passes and connected for circulation to said drum; dampers in said passes adjustable to govern the apportionment therebetween of the total gases leaving the furnace therethrough; at least one steam superheater arranged in one of those passes and a steam reheater arranged in the other; burner means located between said upper and lower offtakes in the furnace walls and arranged for delivering fuel and air into the furnace to be burned therein; and means for tilting said burners for directting the fuel and air streams therefrom upwardly within the furnace and toward the upper offtake or downwardly within the furnace and toward said lower oiftake to vary the relative amount of heat absorbed by said steam generating tubes in the upper and lower portions of the furnace.

5. In a steam generating unit having an associated furnace; steam generating tubes lining fthe walls of the furnace; an upper oitake adjacent one end of the furnace and another lower oiftake adjacent the other end of the furnace; means forming two passes for the flow off furnace leaving gases therethrough, the first of said passes being connected to the said upper offtake and the second pass being connected to the said lower offtake; dampers in said passes adjustable to govern the apportionment therebetween of the total gases leaving the furnace therethrough; at least one steam superheater arranged in one of fthose passes and ea, steam reheater arranged in the other; means forming a by-pass for the flow of some of the furnace gas'es around at least one of said heaters; a damper in said bjr-pass for regulating said ow; burner means located between said two offtakes in the furnace walls and arranged for delivering fuel and air into the furnace to be burned therein; and means for tilting said burners for directing the rfuel and air streams therefrom within the furnace upwardly and toward the upper offtake or downwardly and toward the lower offtake to vary the relative amount of heat absorbed by said steam generating tubes in the upper and lower portions of the furnace.

6. In a steam generating unit having an associated furnace; steam generating tubes lining the walls of the ffurnace; a top offtake adjacent the upper end of the furnace and a bottom offtake adjacent the lower end of the furnace; means forming two passes for the flow of furnace leaving gases therethrough, the first of said passes being connected to the said top offtake and the second pass being connected to the said bottom offtake; dampers in said passes adjustable to govern the apportionment therebetween of the total gases leaving the furnace therethrough; at least one fluid heater arranged in each of said first and second passes; upper and lower burner means located between said upper and lower offtakes in the furnace walls for delivering fuel and air into the furnace to be burned therein; and means for tilting said upper and lower burners for independently directing Within the furnace the upper and lower fuel and air streams issuing therefrom upwardly and towardl 9 said tcp oiftake or downwardly and toward said bottom offtake to vary the relative amount of heat absorbed by the steaml generating tube portions adjacent the top offtake and the steam gen- `@rating tube portions adjacent the bottom 01T- haake;

7. In a steam generating unit having an lassociated furnace; steam generating tubes lining l the walls of said furnace; `an offtake adjacent one end of the furnace and another offtake adjacent the other end of the furnace; means forming two passes for the flow of furnace-leaving gases therethrough, the first of said passes being connected to one of said offtakes and-the second pass .being connected to the other offtake; damper means in at least one of said passes adjustable to govern the apportionment therebetween of the total gases leaving the furnace therethrough; at least: one fluid heater arranged in each of said first and second passes; burner means located between said offtakes in the furnace walls for delivering air and fuel into the furnace to be burned therein; and means for tilting said burners for directing the fuel and air streams therefrom within the furnacel eilther toward one offtake or toward the other offtake, to vary the relative amount of heat yabsorbed by the furnace wall portion adjacent the said one oiftake and the furnace wall portion adjacent lthe said other offtake.

8. In a steam generating unit Ihaving an associated furnace; a top offtake adjacent the upper end of the furnace and a bottom offtake adjacent'the lower end of the furnace; means forming two passes for the flow of furnace-leaving gases therethrough, the first of said passes being connected to the said top offtake and the second pass being connected to the said bottom offtake; at least one fluid heater arranged in each of said first and second passes; at least two burners located in the furnace `walls intermediate said upper and lower offtakes for there delivering air and fuel streams into the furnace, the aforesaid fuel and air from eaoh individual burner creating a mass of high temperature burning gas within the furnace interior; individual tilting means for each of said burners for independently directing the fuel and air stream issuing therefrom eifther upwardly within the furnace and toward said top offtake or downwardly within the furnace and toward said bottom offtake so as to bring the location orf each burner-produced mass of burning gas within the furnace walls either closer to said top oftake and more remote from said bottom offtake or closer to said bottom offtake and more remote from said top oiftake and, by reason of the velocity head created by said tilted up or tilted down stream of air and fuel from each burner, to increase the gas pressure adjacent the particular offtake towards which each burner is tilted and thereby cause the gas flow through that oiftake correspondingly to increase; and steam generating tubes lining the walls of said furnace for absorption of heat from each of said burner-produced masses of high temperature gas, the quantity of heat so absorbed by said walllining tubes from each of said burner-produced masses of high temperature gas varying with the veritical location of that gas mass within the furnace whereby the aforesaid tilting of each furnace burner alters the total heat leaving both the top and the bottom furnace offtakes and varies both the quantity and lthe temperature of the gases leaving said top offtake and of the gases leaving said bottom offtake thereby to control the heat absorbed by each of the aforesaid uid heaters in said top and bottom oiftake passes` 9. In a steam generating unit having an associated furnace; an offtake adjacent one end of the furnacev and another offtake adjacent the other end ofthe furnace; means forming-two passes for the flow of furnace-leaving gases therethrough, the first of said passes being connected to the said one yofftalre and thesecond pass being connected to the said other offtake; at least one superheater arranged in each of said rst and second passes; burner means located in the furnace walls intermediate said two oiftakes for there delivering into lthe furnace streams of fuel and air creating a mass of high temperature burning gas within the furnace interior; means for tilting said burner means to direct saidfuel and air streams issuing therefrom either toward the furnaces said one oitake or toward the furnaces said other offtake so as to bring the location o-f said high temperature nrass of burning gas within the furnace walls either closer to said one offtake and more remote from the other offtake or closer to said other offtake and more remote from said one offtake and, by reason of the direction given by said burner tilt to the velocity head inherent in said streams of air and fuel from the burner means, to increase the gas pressure adjacent the particular offtake towards which the burner means is tilted and thereby cause the gas flow through that offtake correspondingly to increase; steam generating tubes lining the walls of said furnace for absorption of heat from said mass of high temperature gas, the quantity of heat so absorbed by said wall-lining tubes varying with the location of said high tem-'- perature gas mass within the furnace along the length thereof between said one end offtake and said other end offtake whereby the aforesaid tiltingv of said burner means alters lthe total heat leaving both the one and the other furnace offtake and varies both the quantity and the temperature of the gases leaving said one offtake and of the gases leaving said other offtake thereby to control the heat absorbed by each of said superheaters in the said one and other oiftake passes; and desuperheater means associated with at least one orf said superheaters to effect final control in the temperature of steam passed therethrough.

10. In a steam generating unit having an associated furnace; an offtake adjacent one end of the furnace and another offtake adjacent the other end of the furnace; means forming two passes for the flow of furnace-leaving gases therethrough, the rsit of said passes being connected to the said one offtake and the second pass being connected to the said other offtake; at least one fluid heater arranged in each of said first and second passes; burner means located in the furnace walls intermediate said two offtakes for there delivering into the furnace a stream of combustible mixture creating a mass of high temperature burning gas within the furnace interior; means for tilting said burner means to direct said stream of combustible mixture issuing therefrom eit'her toward the furnaces said one offtake or toward the furnaces said Aotherl offtake so as to bring the location of said mass of burning gas within t-he furnace walls either closer to said one offtake and more remote [from the other offtake or closer to said other offtake and more remote from said one offtake land, by reason of the direction given by said burner tilt to the velocity head inherent in said stream of combustible mixture, to increase the gas pressure adjacent the particular offtake towards which 1 the burner means is tilted and thereby cause the gas ow through that offtake correspondingly to increase; means for varying the quantity of the combustible mixture being discharged from said tiltable burner means whereby to vary the velocity head and gas pressure in said gas mass as well as the quantity of gas flowing through each of said oftakes; and steam generating tubes lining the walls of said furnace for absorption of heat from said mass of high temperature gas, the quantity of heat so absorbed by said wall-lining tubes varying with the location of said high temperature gas mass within the furnace along the length thereof between said one end oitake and said other end oiftake whereby the aforesaid tilting of said burner means alters lthe total heat leaving both the one and other furnace oii'takes and varies both the quantity and the temperature of the gases leaving said one oitake and of the gases leaving said other oiftake thereby to control the heat absorbed by each of said fluid heaters in the said one offtake and said other oiftake passes.

11. In a steam generating unit having an associated furnace; an oiftake adjacent one end of the furnace and another offtake adjacent the other end of the furnace; means forming two passes for fthe ow of furnace-leaving gases therethrough, the rst of said passes being connected to the said yone oiftake and the second pass being connected to the said other offtake; at least one fluid heater arranged in each of said first and second passes; burner means located in the furnace walls intermediate said two offtakes for there delivering into the furnace a stream of combustible mixture creating a mass of high temperature burning gas within the furnace interior; means for tilting said burner means to direct said stream of combustible mixture issuing therefrom either toward the fur- Vnaces said one offtake or toward the furnaces said other offtake so as to bring the location of said mass of burning gas within Ithe furnace walls either closer to said one offtake and more remote from the other offtake or closer to said other olftake and more remote from said one oitake and, by reason of the direction given by said burner tilt to the velocity head inherent in said stream of combustible mixture to increase the gas pressure adjacent the particular offtake towards which the burner means is tilted Iand thereby cause the gas iiow through 'that oitake correspondingly to increase; and steam generating tubes lining the walls of said furnace for absorption of heat from said mass of high temperature gas, the quantity of heat so absorbed by said walllining tubes varying with rthe location off said high temperature gas mass within the furnace along the length thereof between said one end offtake and said other end oiftake lwhereby the aforesaid tilting of said burner means alters the total heat leaving both the one and the other furnace offtakes and varies both the quantity and the temperature of the gases leaving said one 01T- take and of the gases leaving said other oitake thereby to control the heat absorbed by each of said iiuid heaters in the said one oiftake and said other oiTta-ke passes.

JOSEPH A. LACE'RENZA.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,975,268 ,Grady Oct. 2, 1934 2,100,190 Jackson Nov. 23, 1937 '2,109,840 Gordon Mar. 1, 1938 2,431,177 Iager et al Nov. 18, 1947