US2013565A

US2013565A - Boiler

Info

Publication number: US2013565A
Application number: US611070A
Authority: US
Inventors: Lundgren Edwin
Original assignee: Foster Wheeler Inc
Current assignee: Foster Wheeler Inc
Priority date: 1932-05-13
Filing date: 1932-05-13
Publication date: 1935-09-03
Anticipated expiration: 1952-09-03

Description

E. LUNDGREN Sept. 3, 1935.

BOILER Filed May 13, 1932 5 Sheets-Sheet l INVENTOR 6/5 ATTORNEY Sept. 3, 1935- E. LUNDGREN 2,013,565

' BOILER Filed May 13, 1952 s Sheets-Sheet 2 INVENTOR W 61 BY 5/3 ATTORNEY E. LUNDGREN Sept. 3, 1935.

BOILER Filed May 13, 1952 3 Sheets-Sheet 5 ll IIIAILI AIIAIIAII IPIA 83\ JUPERHEATEE JUPf/PHE'ATER F 5 IINVIENTOR BY 011! /1/5 ATTORNEY Patented Sept. 3, 1935 UNITED STATES cornea Edwin Lundgren, Frederick, Md., assignor to Foster Wheeler Corporation, New York, N. Y., a

18 Claims.

This invention relates to steam generators and more particularly relates to boilers and to novel means for controlling the furnace temperatures of boilers.

In its broad aspect, the invention contemplates the provision of means for closely and selectively controlling the temperature of fluids passing through radiant heat absorption bodies disposed in or forming part of the furnace walls of a boiler. More specifically, the invention aims to provide novel means for readily, eficiently and selectively controlling the degree of superheat and reheat of steam passing through radiant superheating and reheating tubes located in one or more walls of the furnace of a boiler.

The nature of the invention will become apparent from the following description considered in connection with the accompanying drawings forming a part hereof and which illustrate preferred means for carrying out the invention. In-

asmuch as other means and other arrangements and combinations of the several parts may be varied without departing from the spirit of the invention, it is understood that no intention is entertained to limit the scope of the invention except by the claims appended thereto.

In the drawings:

Fig. l is a view partly in longitudinal section and partly in elevation, of a high pressure boiler constructed in accordance with, and utilizing, the present invention;

Fig. 2 is a transverse sectional view of the boil er taken substantially on line 22 of Fig. 1;

Fig. 3 is a fragmentary view in elevation of the lower portion of the front of the boiler on an enlarged scale;

Fig. 4 is a sectional view on an enlarged scale taken substantially on line 4-4 of Fig. 3;

Fig. 5 is a sectional view on an enlarged scale taken substantially on line 55 of Fig. 3;

Fig. 6 is a fragmentary sectional view taken substantially on line 6--6 of Fig. 3 and on an enlarged scale; and 7 Figs. '7, 8, 9 and 10 are diagrammatic transverse sectional views of the boiler furnace similar to Fig. 2 which illustrate the manner in which the desired degrees of superheat and reheat may be selectively obtained in accordance with this invention.

Like characters of reference refer to like parts throughout the several views.

Generally speaking, the aims and objects of the invention are attained by disposing the tubes of primary and secondary or reheat radiant superheaters in one or more of the walls of the furnace of the boiler and utilizing a plurality of jet fuel burners and suitably disposed air conduits in the lower part of each wall and controlling the operation of each of the burners and the quantity .of air introduced through each of the air conduits to thereby control the position, shape and intensity of the flame issuing from each burner so that substantially any desired degree of superheat and reheat may selectively be obtained.

Referring to the drawings, reference character l0 designates the setting of a high pressure, bent water tube, boiler having a front wall ll, side walls I2 and I3, rear wall I4 and a roof l5. The boiler is substantially symmetrical with respect to the dot and dash line indicated XX in Fig.- 1, consequently for convenience of illustration, only one side of the boiler has been shown in detail. As shown, two mud drums l6 and I! are mounted in the setting adjacent and parallel to the side walls l2,-and l3 and two steam and water drums l8 and l9 are mounted in the upper part of the setting.' A bank of boiler tubes 20, a bank of downcomers 2| and a bank of tubes 22, part of which serve'as downco'mers, connect mud drums l6 and H with the steam and water drums l8 and I9 respectively. A single dry steam drum 23 is connected to each of the steam and water drums l8 and H) by banks of

tubes

24 and 25 respectively. Two saturated

steam collecting headers

26 and 21 are disposedalong each side of the dry steam drum 23 and are connected to the latter by tubes 28 and 29 respectively. A convection superheater 30 is mounted between the

tube banks

20 and 22 on each side of the boiler. These superheaters are each provided with an inlet header 3I and an outlet header 32.

As illustrated, the boiler furnace is rectangular in form and has vertical end or front and

back walls

33 and 34 respectively andvertical side walls 35 and 36, all of which are formed of suitable refractory material. Broadly speaking, all of the walls are lined or covered with radiant heat absorbing surfaces. More specifically, the

end walls

33 and 34 are formed, lined or covered with primary radiant superheater tubes 3'! and the side walls 35 and36 are formed, lined or covered with secondary radiant superheater or reheater tubes indicated 38. The tubes of both the primary and reheater superheaters are vertically disposed and are preferably placed close together to form substantially continuous walls of radiant heat absorbing surfaces. As shown, the radiant superheater and reheater each consists of a plurality of tube loops with the ends of the tubes connected to inlet and outlet headers.

=b oiler, as shown in Fig. 1.

For example, the reheater in sidew all 35, Fig. 1, consists of inlet and outlet headers '39 and 40 respectively and a plurality of loops of the tubes 38, looped at their upper ends, the loops being designated 4|, so that'the path of the steam through the reheater is from the inlet header 39 upwardly in a vertical direction through the tubes 38 to the loops 4| and downwardly in a vertical direction to the outlet header 40. The reheater in side wall 36 is arranged substantially in the same manner with inlet and

outlet headers

42 and 43 respectively. The radiant superheaters in

end walls

33 and 34 are also arranged in substantially the same manner as the radiant reheaters in side walls and 36. The radiant superheater in end wall 34 has inlet and outlet headers 44 and 45 respectively, with the inlet header 44 connected by a steam pipe 46 with the saturated steam collecting header 26 and with its outlet header 45 connected by steam pipe 41 to the inlet header 3| of convection superheater 30 disposed on the right hand side of the boiler, as viewed in Fig. 1. The radiant superheater in end wall 33 is arranged similarly to the radiant superheater in end wall 34 and has its inlet header 48 connected by steam pipe 49 with saturated steam collecting header 21 and with its outlet header 5!] connected by a steam pipe 5|, Fig. 2, to inlet header 3| of convection superheater 30 located on the left hand side of the It is understood of coursethat in lieu of the connections just described any other suitable or desirable connections between the saturated

steam collecting headers

26 and 21 and the radiant and convection superheaters may be utilized, and if desired, the steam from the saturated

steam collecting headers

26 and 21 may be caused to pass through the convection superheaters prior to its passage through its radiant superheaters.

The furnace is fired by means of a plurality of burners 54 adapted to burn pulverized coal, oil, gas or other jet fuel and which will be termed jet fuel burners for convenience. In the form shown, the burners are supplied with pulverized coal and the burners are arranged and disposed in the walls of the furnace in accordance with the present invention. The burners are substantially like the inter-tube type of burner disclosed in the pending application of Martin Frisch, Serial No. 444,906, filed April 17, 1930, but with slight modifications to make them suitable for firing through a refractory wall. As shown, each burner comprises a fan tail distributing nozzle 55, each of which is connected to a plurality of nozzles arranged in two series, an upper series 56 and a lower series 51. As shown in Figs. 1 and 2, the nozzles in each series are arranged alternately, the nozzles in the upper series 56 being adapted to direct the flames issuing therefrom in a downwardly inclined direction and the nozzles in the lower series 51 being adapted to direct the flames issuing therefrom in an upwardly inclined direction. In the form disclosed, three burners, each having a plurality of nozzles, are disposed in each wall of the furnace in the ,lower part thereof and are arranged closely adjacent each other and adjacent one end of the wall as clearly shown in Figs. 1 and 2. The burners 54 are preferably arranged so that the flames issuing therefrom will ordinarily be directed at substantially right angles or normally from the wall in which the burners are mounted.

The pulverized coal and air are delivered to the burners 54 through conduits 58 from feeders 59, one of which is provided for each burner. These feeders are substantially of the type shown in Patent No. 1,896,354, granted to Martin Frisch, February 7, 1933, but any other desired form of feeder may be utilized. In the form shown, each feeder consists essentially of a stationary cell plate 60 secured to a cylindrical pulverized coal housing 6| and having a plurality of substantially rectangular openings or cells 62 arranged circumferentially about the center of the cell plate. A housing 63, which forms an air chamber, is secured below the plate 60 and the outlet end of an air conduit 64 controlled by a damper 65 is connected to this housing. A rotatable member 66 having an inclined cylindrical passage 61 which registers with the cells 62 in plate 68 as it is rotated, and a central air passage 68 which opens into the housing 63 at its lower end, has a circular plate-like portion 69 at its upper end which has an axially extending boss 10 which engages in a central aperture in the cell plate 66. A substantially circular plate 1| overlies the cell plate 60 and is secured to the boss 16 of the rotatable member 66 for rotation therewith. This plate 1| has a segmental portion cut away at 12 to expose certain of the cells 62 but except for the cutaway portion, the plat-e overlies and covers all the cells 62. The plate 1| has a curved air passage 13 which connects at its central end with air passage 68 and at its outer end registers with the cells 62 in plate 60, one at a time as the member 66 is rotated. A rod 14 carried by the plate 1| moves through the pulverized coal in the housing 6| to insure that the cells are properly filled. Rotatable member 66 has a contrally disposed sleeve 15, to which is secured a gear 16 which is driven by a worm 11, whichin turn is driven by a variable speed electric motor 18 or other suitable variable speed driving means.

The operation of the feeder is as follows: Pulverized coal is delivered from a hopper or other suitable source of supply into the housing 6| and fills the cells 62 which are intermittently uncovered by the rotation of plate 1|. Preheated air is forced from a source and by means presently to be described, into the housing 63 through conduit 64 and flows through passages 68 and 13 and as the member 66 is rotated, forces the pulverized coal from the cells 62 into the passage 61. The coal and air are forced through passage 61 and sleeve 15 into conduit 58 which is connected to one of the burners 54. It is thus apparent that the quantity of coal delivered to each burner may be closely controlled by controlling the speed of the motor 18 and that the quantity of air delivered to each burner may be controlled by means of the damper 65. In this manner the capacities of the burners are controlled and the intensity of the flame issuing from each burner ,may be precisely controlled as desired.

At this point it is deemed desirable to describe the course of the gases or products of combustion on leaving the furnace. From the furnace ihe economizers 8| and then pass through the tubes of air heaters 82 after which they are delivered to a stack or stacks by force draft fans 83.

Preheated air is delivered to the burner 54 in the following manner: Atmospheric air is delivered by blowers or fans 84 into conduits 85,

whence it is forced over the tubes of the air heaters 82 which may or may not be provided with suitable baffles to direct the course of the air over the tubes. From the heaters 82 the heated air passes into air ducts 86 which deliver it to points adjacent the burners 54 as will presently appear. A duct 81 which connects at one end with the duct 86, delivers part of the preheated air flowing through the duct 86 to

primary air fans

88 and 89, Fig. 3, through short connecting ducts 90 and 9|. The

air fans

88 and 89 deliver the heated air through

ducts

92 and 93 respectively to a manifold 94 from which the air is delivered through conduits 64 previously described to eachof the feeders 59. As indicated in Fig. 3, each air duct 81 delivers air to two primary air fans which supply the air manifold 94 from which air for six feeders and burners is delivered. In other words, with the form disclosed two such air supply units are employed for supplying the twelve burners disposed in the four furnace walls.

Air ducts 86 deliver preheated air into ducts 95, one of which extends horizontally along the lower part of each furnace wall and for preferably the full length thereof in the zone of the burner nozzles 56 and 51.

Air direction tiles 96 are provided above and below each pair of nozzles of the burners, each of the tiles being .provided with a plurality of superposed air passages 91, which in the tiles above the burner nozzles have their central portions above their inlet and outlet ends and in the tiles below the burner nozzles have their central portions below their inlet and outlet ends, as shown in Fig. 4. At the rear or inlet ends of the tiles 96 and disposed in suitable cages 98 are dampers 99 which may be operated by any suitable means, such as the worm and gear mechanism shown. This mechanism consists essentially of a worm gear I00 mounted on a shaft IOI carrying an operating hand wheel I02, and a worm wheel I03 driven by the worm gear and having a crank arm I04 connected to a rod I05 which is connected to crank arm I06 rigidly secured to the damper 99. With this operating means it will be apparent that the quantity and velocity of the air passing through the direction tiles 96 may be varied and controlled at will and that the air passing through the tiles above the burner nozzles will tend to lower the direction of the flames issuing from the nozzles and that the air streams passing through the tiles below the burner nozzles will tend to raise the direction of the flames issuing therefrom. The upward or downward direction of the flames may thus be controlled as desired.

Additional air direction tiles I01 extend horizontally along the lower part of each of the Walls of the furnace, preferably in the plane or zone of the tiles 96 disposed above the burner nozzles. These tiles I01 preferably extend from the burners to the ends of each wall as shown in Figs. 1 and 2 and are similar to the tiles 96 disposed above the burners 54 with similar air passages 91 therethrough. Dampers I08 are mounted back of the tiles I01 in a manner similar to the manner in which the dampers 99 are mounted and thesedampers are similarly operated. Air is delivered to the tiles 96 and I01 through the conduits 95 previously described. The air streams passing through the tiles I01, together with the air streams passing through the tiles 96, aid in controlling the degree of superheat and reheat by modifying the shape, position and intensity of the flames issuing from the several burners in the .walls of the-furnace, as will be described.

pits I08 are provided burners are mounted. Burners C, F, W and Z are operated at minimum or low capacity to provide very short flames and substantially little heat. Burners B, E, V and Y are operated at intermediate capacities to provide flames of lengths and intensities intermediate the lengths of the flames issuing from the burners A and C, D and F, and so forth. No air is admitted into the furnace through the air direction tiles I01 which extend from the burners to the ends of each wall,

this being indicated in Fig. 7 by the closed position of the dampers in what will be termed air conduits G, H, J, K, L, M, N and 0. With the arrangement of the radiant superheater and reheater tubes in the

walls

33, 34, and. 36 of the furnace as previously described, it will be perceived that with the manner and intensity of firing just described and as indicated in Fig. 7, a high degree of superheat and reheat will be obtained. As indicated in this figure the gases or products of combustion whirl about in the furnace in a single column in the center of the furnace with the peripheral portions of the column at substantially the same distance from both the superheater and reheater tubes.

To obtain a high degree of superheat and a low degree of reheat, the burners should be operated in the manner indicated diagrammatically in Fig. 8. As indicated in this figure, burners C, F, U and X are operated at maximum capacities; burners B, E, V and Y are operated at intermediate capacities and burners A, D, W and Z are operated at minimum capacities. Air is introduced into the furnace through the conduits G and H in streams which flow along the walls 35 and 36 which are formed of tubes of the radiant reheater. These streams of air provide relatively cool insulating layers and prevent the absorption of a large amount of radiant heat in these reheater tubes. No air is introduced along the walls formed of the superheater tubes as indicated by the closed position of the dampers in conduits J and K, and air may or may not, as desired, be introduced through the conduits L, M, N and 0. With this manner of firing it will be readily seen that the superheater tubes will absorb a relatively large amount of radiant heat and that the reheater tubes, due to the air streams described and to the fact that the flames issuing from the burners C and F are at some distance from the reheater tubes, will absorb but a relatively small amount of heat. As indicated in this figure, due to the action of the flames upon each other, the gases tend to swirl about in a column of irregular, transverse cross-sectional configuration as compared with the swirling column of gases of substantially circular, transverse cross-sectional configuration which is obtained by the method of firing indicated in Fig. '7. For example, the flame issuing from burner C tends to carry the end of the flame issuing from burner X and the products of combustion carried thereby toward the center of the furnace as clearly indicated, and the flame from burner F likewise tends to carry the end of the flame from burner U toward the center of the furnaceto provide a swirling column of products of combustion having a cross-sectional configuration which resembles a distorted ellipse with the peripheral portions of the column closer to the superheater tubes than to the reheater tubes.

Conversely, to obtain a high degree of reheat and a low degree of superheat the firing should conform to that indicated in Fig. 9. As indicated in this figure burners A, D, W and Z are operated at their maximum or high capacities, burners B, E, V and Y are operated at intermediate capacities and burners C, F, U and X are operated at minimum or low capacities. .Air is admitted through certain of the air direction tiles I01 as indicated by the open position of the dampers in conduits J and K and the streams of air issuing from these conduits flow along the superheater

tubes forming walls

33 and 34 and provide a relatively cool insulating layer to prevent the absorption of much. heat by the superheater tubes. Air may or may not, as desired, be introduced through the conduits indicated L, M, N and O. The gases swirl about in the furnace in a column of irregular, transverse cross-sectional configuration which resembles a distorted ellipse as clearly indicated, this being due to the action of the flames issuing from the burners W and Z on the flames issuing from the burners A and D. In this instance, the peripheral portions of the column are closer to the reheater tubes than to the superheater tubes.

To obtain a low degree of superheat and reheat the firing should conform to that indicated in Fig. 10. As indicated in this figure burners A, D, U and X are operated at minimum or low capacities, burners B, E, V and Y are operated at intermediatecapacities and burners C, F, W and Z are operated at maximum or high capacities. Air, as indicated by the open position of the dampers, is admitted into the furnace through each of the conduits G, H, J and K, and may or may not be admitted through conduits L, M, N and 0. With the insulating layers provided by the air streams flowing along the superheater and reheater tubes as indicated, and with the burners in the central portions of each of the walls operating at max imum capacities and the other burners operating at intermediate and low capacities, it will be apparent that both alow degree of superheat and reheat will be obtained with this manner of firing. The gases swirl about in the center of the furnace in a cylindrical column of relatively small diameter and flow at approximately the same distance from both the superheater and reheater tubes.

While the manner in which high and low degrees of superheat and reheat may selectively be obtained has been described and illustrated herein, it willreadily be apparent to those skilled in the art to which this invention appertains, that to obtain any other degrees of superheat and/or reheat, it is merely necessary to operate the proper burners at the desired capacities and to admit the proper quantities of air through the desired air direction tiles I81. It will also be apparent that the air streams admitted through the air direction tiles 96 disposed above and below the nozzles of each of the burners will addrtionally materially aid in controlling the superheat and reheat by suitably modifying in the manner desired, the shape, position and intensity of the burner flames.

It will thus be perceived that the present invention provides means by which the degree of superheat and reheat may be closely and selectively controlled, it being necessary merely to operate the several burners in the manner indicated and at the desired capacities to obtain the desired degree of superheat and reheat.

Inasmuch as the structure, disposition and arrangement of the several parts of the boiler structure disclosed herein may be widely varied without departing from the spirit of the present invention, it will be understood that no intention is entertained to limit the extent of the invention except by the scope of the claims appended hereto.

What I claim is:

1. A boiler comprising a. furnace having one or more walls formed of steam heating tubes, a plurality of burners disposed in each wall of the furnace and arranged to direct the flames issuing therefrom substantially normallylto the wall in which the burners are mounted, means for introducing air into the furnace from each Wall adjacent and parallel to an adjacent wall and means for controlling the burners and the quantity of air introduced into the furnace to control the degree of heat of the steam in said steam heating tubes.

2. A boiler comprising a furnace having one or more walls formed of radiant heat absorption surfaces, a plurality of jet fuel burners disposed in one or more walls of the furnace, means fcr supplying fuel and air to said burners, means for introducing air laterally of one of the burners in each wall of the furnace, means for controlling the number of burners active in each wall in which burners are mounted and for controlling the amount of fuel and air admitted to each of said burners and means for controlling the quantity of air introduced adjacent one or more walls of the furnace for controlling the amount of heat absorbed in said radiant heat absorption surfaces.

3. A boiler comprising a setting, a rectangular furnace in the setting, opposed walls of said furnace being formed of steam superheating tubes, the other opposed walls of said furnace being formed of steam reheating tubes, a plurality of jet fuel burners disposed in each wall of the furnace and means for selectively controlling the quantity of fuel and air admitted to each of the burners for selectively controlling the degree of superheat and reheat of the steam in said superheating and reheating tubes.

4. A boiler comprising a setting, a rectangular furnace in the setting, opposed walls of said furnace being formed of steam superheating tubes, the other opposed walls of said furnace being formed of steam reheating tubes, a plurality of jet fuel burners in each of the walls of the furnace, an air conduit having an outlet at one end of each wall of the furnace, means for controlling the quantity of fuel and air admitted to each of outlet at said end of each of said walls, means for controlling the quantity of fuel and'air admitted to each of said burners and means for controlling the quantity of air introduced into the furnace through each of said air conduits to thereby control the degree of superheat and reheat respectively of the steam in said superheating and reheating tubes.

6. A boiler comprising a setting, a rectangular furnace in the setting, opposed walls of said furnace being formed of steam superheating tubes, the other opposed walls of the furnace being formed of steam reheating tubes, a plurality of jet fuel burners disposed in each wall adjacent one end thereof and directed so that the flames issuing therefrom are directed substantially normally from the wall in which the burners are located, an air conduit in each wall having an outlet at the said end of each of said walls, means for controlling the quantity of fuel and air delivered to each of said burners and means for controlling the quantity of air introduced into the furnace through each of said air conduits for controlling the degree of superheat and reheat respectively of the steam in the steam superheating and reheating tubes.

'7. A boiler comprising a setting, a rectangular furnace in the setting, opposed walls of said furnace being formed of steam superheating tubes, the other opposed walls of said furnace being formed of steamreheating tubes, a plurality of jet fuel burners disposed in the lower part of each of the said walls and adjacent one end thereof and directed so that the flames issuing therefrom are directed toward the opposite wall,

an air conduit having an outlet in the lower part of each wall and at said end of each wall and arranged so that the air delivered therefrom is directed along the wall adjacent said end of each wall, means for controlling the quantity of jet fuel and air admitted to each of said burners and means for controlling the quantity of air delivered along each wall by said air conduits for selectively controlling the degree of superheat and reheat respectively of the steam in said steam superheating and reheating tubes.

8. A boiler comprising a furnace having one or more walls formed of radiant heat absorption surfaces, a plurality of jet fuel burners disposed in one or more walls of the furnace, means for controlling the number or burners active in each of the walls in which burners are mounted and for controlling the amount of fuel and air admitted to each of said burners, means for introducing air above and below each of said burners, means for controlling the quantity of air introduced above and below each of said burners, and means for introducing air at one side of one or more burners, whereby the amount of heat absorbed in said radiant heat absorption surfaces is controlled.

9. A boiler comprising a furnace having one or more walls formed of radiant heat absorption surfaces, a plurality of jet fuel burners disposed in one or more walls of the furnace, means for controlling the number of burners active in each of the walls in which burners are mounted and for controlling the amount of fuel and air admitted to each burner, means for controlling the shape, position and intensity of the flames issuing from said burners comprising air conduits having outlets above and below each of said burners and at one side of one or more of the burners to thereby control the amount of heat absorbed by said radiant heat absorption surfaces.

10. A boiler comprising a setting, a rectangular furnace in the setting, opposed walls of said furnace being formed of steam superheating tubes, the other opposed walls of said furnace being formed of steam reheating tubes, a plurality of jet fuel burners in each of the walls of the furnace, means for controlling the quantity of fuel and air admitted to each of said burners, air conduits having outlets above and below each of said burners and outlets at the ends of each of the walls of the furnace, whereby the amount of heat absorbed in said steam superheating and reheating tubes is selectively controlled.

1 1. -A boiler comprising a furnace having opposed walls formed of steam heating tubes, burners in the furnace discharging products of combustion approximately parallel and normal to said walls, and means for regulating said burners to control the flow of products of combustion through the furnace to control the distance of the stream of said products of combustion from the said tubes to/thereby control the degree to which the steam in the said tubes is heated.

12. A furnace having walls provided with vapor heating tubes exposed to heat radiated from 7 products of combustion flowing through the furnace, means for producing a plurality of laterally disposed streams of products of combustion in each of a plurality of walls of the furnace, the streams being directed to form a whirling column of products of combustion in the furnace and means for controlling the volume of the several streams of products of combustion to control the transverse cross-sectional configuration of said column to vary the distances of the peripheral portions of said column from said walls and tubes to control the amount of heat absorbed by the vapor in said tubes.

13. A furnace having walls provided with vapor heating tubes exposed to heat radiated from products of combustion flowing through the furnace, means for producing a plurality of streams of products of combustion in the furnace so directed as to form a whirling column of products of combustion in the furnace, means for controlling the volume of the several streams of products of combustion to control the transverse cross-sectional configuration of said column to vary the distances of the peripheral portions of said column from said walls and tubes to control the amount of heat absorbed by the vapor in said tubes, and means causing air to flow along one or more of the walls having tubes to reduce the quantity of heat absorbed by the vapor in said tubes.

14. A furnace having walls provided with vapor heating tubes exposed to heat radiated from products of combustion flowing through the furnace, means for producing a plurality of laterally disposed streams of products of combustion in each wall of the furnace, the streamsbeing directed to form a whirling column of products of combustion in the furnace and means for controlling the volume of the several streams of 15. The method of operating a furnace having walls provided with vapor heating tubes exposed to heat radiated from products of combustion flowing through the furnace which comprises producing a plurality of laterally disposed streams of products of combustion in each of a plurality of walls of the furnace, directing said streams so as to form a whirling column of products of combustion in the furnace and controlling the volume of the several-streams of products of combustion to control the transverse crosssectional area of the column to control the distances of the periphery of the column from the tubes in the walls of the furnace whereby the amount of heat absorbed by the vapor in the tubes may be regulated.

16. The method of operating a furnace having walls provided with vapor heating tubes exposed to heat radiated from products of combustion flowing through the furnace which comprises producing a plurality of laterally disposed streams of products of combustion in each of a plurality of walls of the furnace, directing said streams so as to form a whirling colunm of products of combustion in the furnace and controlling the volume of the several streams of products of combustion to control the transverse cross-sectional area of the column to control the distances of the periphery of the column from the tubes in the walls of the furnace whereby the amount of heat absorbed by the vapor in the tubes may be regulated, and causing air to flow along one or more of the walls having tubes to reduce the quantity of heat absorbed by the vapor in said tubes.

17. The method of operating a furnace having a plurality of walls provided with vapor heating tubes exposed to heat radiated from products of combustion flowing through the furnace-which comprises producing a plurality of laterally disposed streams of products of combustion in each of a plurality of walls of the furnace, directing said streams to form a whirling column of products of combustion in the furnace and controlling the volume of the several streams of products of combustion to control the transverse cross-sectional configuration of the column to provide an irregular configuration whereby portions of the periphery of the column are closer to one wall than another.

18. The method of operating a furnace having walls provided with vapor heating tubes exposed to heat radiated from products of combustion flowing through the furnace which comprises producing laterally disposed streams of products of combustion in each wall, directing the streams substantially normally from the walls in which they are produced whereby a whirling column of products of combustion is formed in the furnace, and selectively controlling the volume of the streams to vary the transverse cross-sectional area of the column to control the distance of the periphery of the column from the tubes in the walls of the furnace whereby the amount of heat absorbed by the vapor in the tubes may be regulated.

EDWIN LUNDGREN