US3015319A

US3015319A - Radiant tubular heat exchanger

Info

Publication number: US3015319A
Application number: US710508A
Authority: US
Inventors: Steinert Gerhard
Original assignee: Kohlenscheidungs GmbH
Current assignee: Kohlenscheidungs GmbH
Priority date: 1958-01-22
Filing date: 1958-01-22
Publication date: 1962-01-02
Anticipated expiration: 1979-01-02

Description

Jan. 2, 1962 G. STEINERT 3,015,319

RADIANT TUBULAR HEAT EXCHANGER Filed Jan. 22, 1958 2 Sheets-Sheet 1 INVEN'IIQIQNERT GERHARD S {27 2s s4 s5 HG. 2 BY 55 29 503132 23 A AGENT Jan. 2, 1962 G. STEINERT RADIANT TUBULAR HEAT EXCHANGER 2 Sheets-Sheet 2 Filed Jan. 22, 1958 M m w 1/ uucmuodno/w cn H00 :0 one 00 00 0a 000: "0000000;

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IN VEN TOR. GERHARD STEINERT mafia AGENT M m Mn.

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United States Patent 3,015,319 RADIANT TUBULAR HEAT EXCHANGER Gerhard Steinert, Stuttgart, Germany, assignor to Kohlenscheidnngs-Gesellschaft m.b.H., a corporation of Germany Filed Jan. 22, 1958, Ser. No. 710,508 2 Claims. (Cl. 122-478) The invention relates to a radiant tubular heat exchanger more specifically to a radiant tubular steam heater as provided in a steam generator having furnace walls that are lined with water-cooled tubes, and comprising parallelly disposed tubular wall panels spaced from each other a substantial distance to prevent the bridging over of slag.

In a steam boiler having a furnace equipped with fluid cooled walls, undesirable peaks of temperature are encountered in the combustion gases produced in the lower portion of the furnace, as these gases rise and pass through the upper portion of the furnace. These peaks of temperature are the result of the cooling effect of the tube lined furnace walls in the vicinity thereof, and cause unequal heat absorption in the panel heat exchanger disposed in the upper part of the furnace chamber. Such unequality in temperature not only necessitates the employment of a greater amount of heating surface because of the less efficient use made thereof, but also requires a more liberal use of costly tube material that is capable of withstanding higher gas temperatures, all of which is highly undesirable both from the standpoint of first cost as well as maintenance costs.

Various means have been employed heretofore to eliminate or reduce temperature peaks in the rising gas stream. One design proposes an increase in the distance between the tubular panels as these panels approach the side walls of the furnace. However, since a minimum distance of approximately two feet is required between the panels to prevent the bridging over of the slag deposited thereon during operation of the furnace, it follows that the larger spacing employed near the furnace walls will reduce the total amount of heating surface that can be installed in a given furnace width thereby increasing the temperature of the gases entering the succeeding convection heating surfaces and causing undesirable slag deposits thereon.

In attempting to solve the present problem it was also proposed in the past to lengthen those tube panels which are located at or near the central portion of the furnace chamber. However, to be fully efiective such lengthening must be extensive and calls for an increase in furnace height in order to avoid the overheating and burning of the thusly extended tube portions, unless costly higher temperature alloy materifl is made use of in the tubes to a greater extent.

The present invention has as its primary object a solution of the above problem without the need of taking into the bargain the above-recited disadvantages. This is expediently accomplished by providing a heat exchanger in the upper portion of the furnace chamber which comprises a row of widely spaced tubular panels parallelly disposed with respect to each other and to the side walls, and in which each panel adjacent the side walls is being formed by a row of tubes having a sum total of tubular circumferences which is smaller than the combined circumferences of the tubes comprising each of the remaining panels, i.e., those which are located in the central zone of the furnace chamber.

Another related object of the invention is to provide a steam heater in the upper portion of the furnace constructed of widely spaced tubular panels, each panel adjacent the side walls comprising a row of tubes that are spaced a greater distance apart than the tubes that form the panels more remotely located from the side walls.

Patented Jan. 2., 1962 Still another object of the steam heater in the upper portion of the furnace chamber of a radiant steam generator in which the outer tube panels, those located near the side walls have a smaller total horizontal width than the tube panels located near the center of the furnace chamber.

Other objects and advantages of the invention will become apparent from the following description of illustrative embodiments thereof when taken in conjunction with the accompanying drawings wherein:

FIG. 1 shows an elevational diagrammatic view of a steam power plant operating under the reheat cycle and being equipped with the herein disclosed inventive improvement;

FIG. 2 is a fractional front elevational section of the radiation chamber and steam heater of the steam boiler illustrated in FIG. 1 when taken on line 2-2 thereof;

FIG. 3 is a plan view taken on line 3'3 of FIG. 2;

FIG. 4 is another elevational front section of a furnace and a. steam heater similar to that shown in FIG. 2 but disclosing my invention as applied to a. single superheater;

FIG. 5 is a diagrammatic plan view taken on line 5-5 of FIG. 4;

FIG. 6 represents a front elevational section of a furnace and radiant single superheater wherein the direction of steam flow has been reversed from that shown in the embodiment of FIGS. 4 and 5;

FIG. 7 is a diagrammatic plan view taken on line 7--7 of FIG. 6;

FIGS. 8, 9, 10 and 11 show various cross sections taken through steam heaters embodying the basic feature of my invention, i.e., that of providing the tube panels near the side walls with a smaller, circumferential total dimension than the tube panels remote from the side walls.

Referring now to the drawings wherein like reference characters are used throughout to designate like elements, "FIG. 1 illustratively shows a steam generating power plant having a furnace 2 including a lower combustion chamber 3 and a top-jacently adjoining radiation chamber 4. The walls of the furnace 2 include front wall 6, rear wall 8 and

side walls

10 and 12. Fuel and air are discharged into the combustion chamber 3 for burning by way of burners 13 which preferably are arranged for tangential firing. The hot gases produced rise upwardly giving off heat to the

furnace walls

6, 8, 10 and 12 which are lined with water carrying and steam generating tubes 14. These gases are further cooled by passing consecutively over other heating surfaces disposed in the upper portion 4 of the furnace, in an adjoining horizontal gas ofitake 15 and in a vertical gas pass 16. The gases are finally discharged into the atmosphere by way of induced draft fan 17 and stack 18. Water wall tubes 14, terminate in a steam and water drum 19 and deliver a mixture of steam and water into the drum wherein the steam is separated from the water by means, not shown. The water flows downwardly through downcomers 20 and enters the water wall tubes 14 by way of

headers

21 and 22 thereby completing the circulation circuit. The steam separated from the water is conducted from drum 19 to a convection superheater 24 located in the horizontal gas pass 15 and then to a radiant superheater 26 which is disposed in the upper portion of the furnace or radiation chamber 4. In the embodiment shown in FIG. 2, radiant superheater 26 comprises a series of spacedly disposed

panels

29, 30, 31, 32, 33 located in the central portion of chamber 4 and arranged in parallel relation with each other and with the

side walls

10, 12 of the furnace.

Each of the panels 29 to 33 comprises a plurality of closely spaced U-tubes nested to form a panel wall as indicated in FIG. 1. Each vertical leg of these tubes is connected to an inlet header 38 or an outlet header 40 invention is to provide a.

respectively. Inlet header 38 receives steam from con- 42 by'way'ofan outlet header 40 and steam pipe 44.

Having expended some of its energy in the turbine, the steam is conduced to a convection reheater 46 disposed in thevertical gas pass 16, from whence the steam flows via pipe 41 to inlet header 43 of radiant reheater 48 located in the radiation chamber 4.' Reheater '48 is formed of two sections 48a and 481) (FIG. 2) having parallelly disposed spaced tubular walls similar to those used in constructing radiant superheater section 26. In the preferred embodiment'shown in FIG. 2 reheater section 4812 comprises

tubular panels

27 and 28 and reheater section 485 panels 34 and 35. After'being heated to the desired temperature the steam passes through outlet headers 45 and steam pipe 42 to the low pressure stageof steam turbine 42. i

In accordance with the present invention the reheater panels are disposed adjacentthe side walls and 12 each panel being formed of tubes-having a smaller total circumference when measured in a horizontal plane than the tubes which form

superheater tube panels

29, 30, 31, 32 and 33 located remotely from the side walls.

FIGS. 4, '5, 6 and 7 illustratively show twoembodiments of my'invention as applied to a single superheater 50 occupying the entire width of the radiation chamber 4. Superheater 50-is divided into two

sections

51 and 52, one half of section 51 being located adjacent each

side wall

10,12 and section 52 being located in the central zone of radiation chamber'4. In accordance with the inventionsuperheater portion 51 comprises

tubular wall panels

53, 55 each being formed of a plurality of closely spacedtubes the combined circumferences of these tubes being smaller than the combined circumferences of' the tubes-that form the ubular panels of the centrally located portion 52. r w i More specifically, in FIGS. 4 and 5, there ,is shown a superheater in which the steam to be heated enters the outer sections 51 by way of headers 54. After having passed through the tubes of sections 51 the steam enters headers 56 and is conducted via pipes 58 to the header 60 of the centrally located section 52. While passing through the tubes of section 52 the steam is heated to the final temperature and is conducted to a source of'use byway of header 62 and suitable piping, not shown.

The single superheater illustrated of a design similar to that shown in FIGS. 4 and 5, however, distinguishes therefrom by a reversal of the direction of flow of the steam as indicated by arrows. Thus the steam enters header 62, flows through the U-shaped tubes of section 52 and leaves by wayof header 66 to be conducted via steam pipe 58 and headers 56 into superheater portions 51 where the steam is heated to its final temperature and conducted to a point of use; by way of headers 54 and suitable steam piping, not shown.

I As earlier set forth wherein the superheater portions 51 adjacent the

side walls

16 and 12 are formed of tubes having a smaller combined circumference for each tubular panel Wall than the tubes forming the panels of the centrally located portion 52.

Similarly, as earlier stated, the reheater

tubular panels

27, 28,34 and 35 of FIG. 2 each comprise a plurality of'tubes having a smaller sum total of circumferences than the tubes forming the centrally located

superheater panels

29, 30, 31, 32 and 33.

FIGS. 8, 9, l0 and 11 illustrate some preferred design features of the tube panels of a radiant steam heater,

which is in accordance with my invention, and which fulfill the design conditions set'forth in the two preced- 1 ing paragraphs, design conditions which must be met to accomplish the, objects of my invention.

Thusin the embodiment of FIG. 8, this is accomplished by a steam heaterarrangement having uniform in FIGS. 6 and 7 is 4 tube spacing wherein the outermost panels 64 are of a horizontal width which is substantially less than the width of the centrally located panel 70. The

panels

66 and 68 located

intermediate panels

64 and 70 have a width which gradually increases with the distance of these panels from the nearest side wall,

Panels

64, 66 and 68 can be arranged symmetrically about axis A-A as illustratively shown in FIG. 8, or these panels can be arranged adjacent the gas otftake 15 as indicated in FIG. 9.

Or, the width of the vided into two or more between front wall 6 and FIG. 10.

Furthermore, in accordance with my invention and as illustratively shown in FIG. 11, the spacing of the

tubes forming panels

64, 66 and 68 increases as the location of these panels approaches the

nearest side wall

10 or 12, thereby presenting to the gases a sum total of circumferences in each panel which is not only smaller than the combined circumferences of the

tubes forming panels

64, 66 and 68 can be diportions which are distributed gas oiftake 15 as illustrated in a centrally located panels 70 but which gradually decreases as the nearest side wall is approached.

The various arrangements shown in FIGS. 8, 9, l0 and 11 can equally well be applied to;a reheat steam generator such asthat illustrated in FIGS. 1, 2 and 3, or to a steam generator equipped with a single superheater such as thatshownin FIGS. 4, 5, 6 and 7.

In FIGS. 4, and 5 is shown a steam heater in which the relatively cool steam "first flows through the outer sections:51 and is heated to the final temperature by passing through the central section 52. Such an arrangement advantageopsly leads to a more uniform flow velocity of the steam through all of the tubes because the progressive increase of the steam volume due to heating is accompanied by a progressive increase in flow area.

On the other hand, FIGS. 6 and 7 illustrate a steam heater organization wherein'the flow ofsteam is reversed, i.e., the relatively cool steam first flows through the centrally located, highly heated section 52 and is brought to the final temperature by passingthrough the outer sections 51. Such a flow arrangement advantageously permits the'final heatingstage to takeplace in a moderate temperature zone which results in economical advantage with respect to the use of hightemperature alloy material. In-addition the higher flow velocities attained in the outer section tend to promote a more elfective cooling of the tube walls.

In conclusion, the problem precipitated by the cooling efi'ect of the

side Walls

10 and 12 upon the gases causing non-uniform temperature distribution across the furnace width and the width .of the gas ofltake 15 is successfully metby my inventively improved-design of a panel type radiant steamheater as herein disclosed. My invention imposes a heat absorption pattern upon the gas steam which largely erases these inequalities in gas temperature and eliminates to a substantial degree the disadvantages resulting therefrom.

such changes, as fall within the purview of my invention.

What I claim is:

1. In a radiant heat exchanger having a combustion chamber for the generation of hot gases by the burning of fuel and a ton-jacently adjoining radiation chamber having two parallel side walls lined with heat absorbing. tubes, said heat absorbing wall'tubes creating parallellyflowing vertical zones of gas of non-uniform temperature characteristic when .measured 'in a horizontal plane, with the temperature of. the-centrally located. gas zonebeinghigherthan the temperature of the side wall adjacent gas zones, the combination of a row of upright tubular wall panels spacedly disposed across the upper portion of said radiation chamber in parallel relation to the heat absorbing tubes lining said side walls and to each other, each panel comprising a plurality of parallelly spaced tubes carrying a gaseous medium to be heated by absorbing radiant heat from the hot gases generated in said combustion chamber, the lineal circumference when measured in a horizontal plane, per rated gas flow area, of the tubes forming the said tubular panels that are adjacent said side walls being substantially smaller than the corresponding lineal circumference of the tubes forming the tubular panels located adjacent the centre of saidv radiation chamber, and said upright tubular panels being divided into serially connected groups including a first group located adjacent said side walls and a second group occupying a central location Within said radiation chamber, said first group having means for receiving said gaseous medium to be heated, means for progressively increasing the temperature thereof while advancing said medium thro'ughthe tubes of said first group, said second group having means for receiving said medium from said first group, means for progressively increasing the temperature thereof while advancing said medium through the tubes of said second group, and means for discharging said gaseous medium from said second group after having been heated.

2. in a radiant steam generator having a combustion chamber for the generation of hot gases by the burning of fuel and a top-jacently adjoining radiation chamber having two parallel side walls lined with heat absorbing tubes, said heat absorbing Wall tubes creating parallelly flowing vertical zones of gas of non-uniform temperature characteristic when measured in a horizontal plane, with the temperature of the centrally located gas zone being higher than the temperature of the side Wall adjacent gas zones,

the combination of a row of upright tubular wall panels spacedly disposed across the upper portion of said radiation chamber in parallel relation to the heat absorbing tubes lining said side Walls and to each other, each panel comprising a plurality of parallelly spaced tubes carrying steam to be heated by absorbing radiant heat from the hot gases generated in said combustion chamber, the lineal circumference when measured in a horizontal plane, per rated gas flow area, of the tubes forming said tubular panels that are adjacent said side walls being substantially smaller than the lineal circumference of the tubes forming the tubular panels located adjacent the centre of said radiation chamber, and said upright tubular panels being divided into serially connected groups with respect to steam flow including a first panel group solely occupying the space adjacent said side walls and a second panel group solely occupying a space remote from said side walls within said radiation chambensaid second group having inlet means for receiving primary steam, exclusive of reheat steam, from said steam generator for superheating and outlet means for discharging said steam after superheating to a turbine, and said first group having means for receiving steam, exclusive of primary steam, from the high pressure stage of said turbine for reheating.

References Cited in the file of this patent UNITED STATES PATENTS 1,996,099 Cooper Apr. 2, 1935 2,075,067 Snyder Mar. 30, 1937 2,685,279 Caracristi Aug. 3, 1954 2,821,175 Seidl Ian. 28, 1958 FOREIGN PATENTS 624,769 Germany I an. 29, 1936 899,503 Germany Dec. 14, 1953