US2878791A - Steam generating, superheating, and resuperheating plant - Google Patents

Description

March 24, 1959 A. LIEBERHERR STEAM GENERATING, SUPERHEATING, AND RESUPERHEATING' PLANT Filed Jan. 31, 1955 2 Sheets-Sheet l INVEN TOR.

A ETH we L IEBEEHEE/E.

A TTORNEJ arch 24, 1959 LIEBERHERR 2,878,791

STEAM GENERATING, SUPERHEATING, AND RESUPERHEATING PLANT Filed Jan. 51, 1955 2 Sheets-Sheet 2 INVENTOR. ,4 RTHUI? L [Ease/HERE.

United States Patent STEAM GENERATING, SUPERHEATING, AND RESUPERHEATING PLANT Arthur Lieberherr, Winterthur, Switzerland, assignor to Sulzer Freres, Societe Anonyme, Winterthur, Switzerland, a corporation of Switzerland Application January 31, 1955, Serial No. 485,061 Claimspriority, application Switzerland February 10, 1954 3 Claims. (Cl. 122-478) The present invention relates to a steam generating, superheating, and resuperheating plant.

The resuperheater of the plant according to the invention includes a heat transfer apparatus which is placed inside the steam generator and in which heat is indirectly exchanged between a high pressure operating fluid, which is heated in tubes forming part of the generator, and the steam to be resuperheated.

'The heat transfer apparatus is formed by a group of outer tubes or conduits and a group of tubes disposed inside the outer tubes. If the steam to be resuperheated, which is partly expanded, is conducted through the outer tubes and the high pressure fluid is conducted through "the inner tubes, the heat transfer apparatus is preferably disposed in a part of the steam generator where the apparatus is protected against radiant heat. In this case, "the partly expanded steam exchanges heat with the combustion gases and with the high pressure fluid. If the combustion gases and/or the high pressure fluid are hotter than the steam to be resuperheated, the resuperheating process requires less heating surface and is performed more quickly than in a resuperheating process in which a part of the heat is indirectly transferred outside of the steam generator from high pressure steam to the steam to be resuperheated, and in which another part of the heat is transferred inside the steam generator from hot combustion gases to the steam to be resuperheated. Radiation losses of an indirectly heated resuperheater portion'placed outside of the steam generator are avoided with "the "arrangement according to the invention. Aside from this, no additional space is required outside of the steam generator and pressure losses caused by the high pressure steam pipes connecting an indirect resuperheater with the tubularheating surfaces of the steam generator are eliminated.

"In certain cases, there is not enough room in the lines and in the parts of the steam generator where there is no radiant heat for accommodating the whole resuperheater. In such cases, the partly expanded steam is conducted through the inner tubes and the high pressure fluid is conducted through the outer tubes, and at least apart of the heat transfer apparatus is placed, to receive heat by radiation, for example in the combustion chamber of the steam generator. In this case, the steam to be resuperheated is indirectly heated by the high pressure fluid, the latter receiving heat by radiation. The tubes conducting the partly expanded steam are shielded against radiant heat by the conduits conducting the high pressure fluid. This is important because partly expanded steam does not always flow through the heat transfer apparatus, as is the case, for example, when the plant is started.

The heat transfer apparatus according to the invention may be used for regulating the resuperheat temperature. Control means may be connected with the tubular heating surfaces for the high pressure fluid, so that the high pressure fluid cools the partly expanded steam when the 2,878,791 Patented Mar. 24, 1959 latter is too hot, and heats the partly expanded steam when the latter is too cool.

Though it may appear advantageous to arrange a plurality of inner tubes in each outer tube of the heat transfer apparatus, for improving .heat transfer, pressure, and constructional conditions, it will be preferable in most cases to arrange only one tube inside each outer tube, particularly if the tubes are bent to a hair pin configuration. If several hair pin units are connected in series, the heat transfer apparatus may be in the form of a meander.

If the indirect heat transfer apparatus is placed outside of the steam generator, the individual heating tube of -the.latter must be connectedby means of a header or collector, and a conduit must be provided to connect .the header with a header connecting the individual elements of the indirect heat transfer apparatus. This is unnecessary, if the heat transfer apparatus is arranged inside the steam generator according to the invention, so that pressure losses and cost are reduced. In certain cases, for example, if the temperature of the fluid on one side of the heat transfer apparatus must be controlled by injecting water, the provision of a header may be advisable tointerconnect the tube sections conducting the fluid whose temperature must be controlled. The sectionsof the tubes conducting the other fluid, however, may be serially interconnected, avoiding headers. Colle'ctors are also desirable, if the different tube sections are .not uniformly heated. Since headers for this purpose are usually provided anyway in connection with the tubular heating surfaces of a steam generator, the tubes of individual sections of the heat transfer apparatus arranged according to the invention maybe connected in series.

'Though in this specification and in the claims the word steam is used to specify the operating fluid of the power plant, the invention is not limited topower plants using steam as operating fluid but is equally well applicable to plants using other vapors as operating fluid.

"The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, and additional objects and advantages thereof will best be understood from the following description of embodiments thereof when read in conjunction 'withthe accompanying drawing, in which Fig. 1 is a diagrammatic part sectional illustration of a power plant according to the invention;

Fig. 2 is a diagrammatic part sectional illustration of 'a'portio'n of a steam generator forming'part of a power plant according to the invention;

Fig. 3 is a part sectional diagrammatic illustration of a modification of the p'art shown in Fig. 2;

Fig. 4 'is an illustration of a detail of a power plant according to the invention;

Fig. 5 is a sectional'view of a detail of a power plant according to the invention.

The same numerals designate the same parts in all figures.

Referring more particularly to Fig. 1 of the drawing, numeral '1 designates a steam generator which is heated by a combustion apparatus 2. Numeral 3 designates a combustion'chamb'er in which radiant heat and combustion gases are produced. 'The combustion gases continue to pass through a flue '4. An operating fluid, such as water, is supplied to the steam generator through an inlet header 5. The water flows through tubes 27 and :7 forming acombustion gash'eated feed water preheater, generallyknown as an economizer. The preheatedfeed water enters a tubular heating surface 8 which :is used for lining the walls of the combustion chamber 3 land is exposed to radiant heat. The steam formed in the heating surface section 8 is conducted through a conduit 9 into a first superheater 10 and thereupon into a heat transfer apparatus 11 which forms a second superheater and a resuperheater which will be described later. The high pressure steam leaving the apparatus 11 passes through a third tubular superheating section 12 and therefrom through a steam main 13 into the high pressure part 14 of a prime mover, such as a steam turbine. The steam which is partly expanded in the prime mover 14 is conducted through a conduit 15 into a tubular resuperheating surface 16 and therefrom into tubes 21 which are arranged inside the tubes forming the second superheating surface for the high pressure steam. The resuperheated steam is conducted through a conduit 17 into a low pressure part 18 of the steam turbine plant. The high pressure turbine 14 and the low pressure turbine 18 have a common shaft for driving an electric generator 19. The steam exhausting from the low pressure turbine 18 is removed through a conduit 20. In the illustrated embodiment of the invention, the part of the steam generator, in which heat is transferred by conduction and convection and not by radiation, is too small to accommodate the total required resuperheating surface. It is therefore necessary to arrange a part of the resuperheater in the combustion chamber where it is exposed to radiant heat and where it is preferably used for lining a wall portion of the combustion chamber. Since resuperheaters are not always cooled by fluid passing therethrough, as is the case, for example, when starting the power plant, the portions of the resuperheating surface which are exposed to radiant heat must be especially protected. This can be done by means of complicated arrangements, including valves and the like, for passing high pressure fluid through the resuperheating tubes when no partly expanded steam is available. According to the invention, the protection of the resuperheater against radiant heat is eflected in a much simpler manner. The partly expanded steam is conducted through tubes 21, which are inside the tubes 22 of the heat transfer apparatus 11, the high pressure fluid being conducted through the annular space between the tubes 21 and 22. In the heat transfer apparatus 11, the resuperheating surface is heated by partly superheated high pressure steam, as is done in conventional indirectly heated resuperheaters which are arranged outside of the steam generator and which cause radiation losses. Such losses are avoided with the arrangement according to the present invention because the heating steam for the resuperheater gives off and receives heat simultaneously and the temperature outside of the tubes 22 is so high that no heat can radiate from the tubes 22 to the outside. A heat transfer apparatus arranged according to the invention can be much smaller to do the same work as does a conventional steam heated resuperheater. The heat transfer apparatus 11 includes a plurality of tubes arranged in parallel with respect to the flow of steam therethrough. The plant according to the invention can be so arranged that the superheaters 10 and 12, the resuperheater 16, and the heat transfer apparatus 11 all have the same number of parallelly arranged tubes. The number of headers can thereby be greatly reduced, because each outer tube of the apparatus 11 can be connnected with a tube of the superheaters for the high pressure steam, and each inner tube 21 can be connected with a tube of the resuperheater 16. Only the following headers are required: a header 23 at the inlet of the superheater 10, a header 24 at the outlet of the superheater 12, a header 25 at the inlet of the resuperheater 16, and a header 26 connected to the outlets of the inner tubes 21 of the heat transfer apparatus 11. The feed water preheater or economizer 27, 7 also includes a plurality of tubular elements arranged in parallel with respect to the flow of the fluid therethrough.

The part of the economizer formed by the tubes 27 is 4 constructed as a heat transfer apparatus 6 including outer tubes 27 through which the feed water is conducted, and inner tubes 28 arranged inside the tubes 27 for conducting a heating fluid which is supplied from a header 29 and returned into a header or collector 30. The heating fluid is preferably taken from the circuit of the operating fluid of the power plant at a point where the temperature of the operating fluid is higher than that of the feed water entering the heat transfer apparatus 6. The heating fluid may be steam bled from the turbine plant. The feed water passing through the outer tubes 27 is thus heated by the inner tubes 28. It may be heated simultaneously by the combustion gases passing outside of the tubes 27. The combustion gases pre vent any case heat radiation and losses to the outside.

Fig. 2 illustrates a modified arrangement according to the invention. The parts of the power plant not shown in Fig. 2 correspond to the respective parts shown in Fig. 1. Steam produced in the heating surface section 8 of the steam generator is conducted through a conduit 9 and a header 23 into a first superheater 31 from which the superheated steam flows through a header 44, a conduit 32, and a header 45 into inner tubes 33 of a heat transfer device 34. The high pressure steam leaving the tubes 33 is collected in a header 46 and passes through a conduit 35 and through an inlet header 24 into a second superheater 36. The high pressure steam superheated in the second superheater 36 is collected in a header 47 and conducted through a steam main 13 to a high pressure turbine. The partly expanded steam exhausting from the high pressure turbine is conducted through a conduit 15 and a header 25 into a first combustion gas heated resuperheater 37 and therefrom through outer tubes 38 of the heat transfer apparatus 34. The partly expanded steam leaving the tubes 38 is conducted through a second combustion gas heated resuperheater 39 at whose outlet a header 26 is provided which is connected, by means of a conduit 17, with the inlet of a low pressure turbine.

The heat transfer apparatus 34 constitutes a resuperheater which is heated by high pressure steam as well as by combustion gases. In the arrangement illustrated in Fig. 2, the combustion gases heat the partly expanded steam from the outside, whereas the high pressure steam flowing through the inner tubes 33 heats the partly expanded steam from the inside. The heat transfer apparatus can be used to serve not only as a normal resuperheater, but also as a temperature regulator for the steam to be resuperheated. The temperature of the high pressure steam can be controlled by injecting water from a conduit 40 into the high pressure steam conduit 32 which supplies heating steam to the heat transfer device 34, and by injecting water through a conduit 41 into the high pressure steam conduit 35 through which heating steam is removed from the heat transfer apparatus 34. The amount of water injected through the conduit 40 into the conduit 32 is so controlled that the temperature of the steam in the inner tubes 33 is lower or higher than .the temperature of the partly expanded steam flowing through the outer tubes 38 for cooling or heating, respectively, the partly expanded steam. The amount of water injected through conduit 41 into the conduit 35 is controlled to produce the desired steam temperature at the outlet of the high pressure superheater 36. A conduit 42 isprovided interconnecting the conduits 32 and 35, in which conduit a throttling means or valve 43 is arranged for controlling the flow of high pressure steam through the conduit 42. If the high pressure steam is cooled too much in the heat transfer device 34 and/or by injection of water from the conduit 40, hot high pressure steam from conduit 32 can be by-passed through the conduit 42 atound the device 34 and conducted into the superheater 3 Since the water injection must affect all parallelly arranged tubes of the heat transfer device and of the high pressure steam superheater, headers 44, 45, 46, and 47 must be provided in addition to the headers forming part of the system shown in Fig. 1. No headers are needed for interconnecting the tubular elements forming the resuperheater heating surfaces 37 and 39 with the outer tubes 38 of the heat transfer device 34.

Fig. 3 illustrates a modification of the heat transfer apparatus forming part of the system according to Fig. 2. If the individual parallelly arranged tubular elements of the heat transfer apparatus 34 and/or of the resuperheaters 37 and 39 are not uniformly heated, the provision of additional headers 48, 48a, 49, and 49a may be advisable. The header 48a mixes the steam coming from the tubes 37, and the header 48 distributes the mixed steam into the outer tubes 38. The header 49 mixes the steam heated in the tubes 38, and the header 49a distributes the steam into the tubes 39.

Fig. 4 illustrates an element 51 of a heat transfer apparatus. An inner tube 53 is inserted in an outer tube 52, both tubes being bent simultaneously to assume the con figuration of a hair pin. This method of manufacture is particularly suitable for elements in which only one inner tube is placed in the outer tube. A plurality of elements 51 may be arranged in parallel with respect to fluid flow. If large heating surfaces are required, several elements 51 may be arranged in series with respect to fluid flow.

Fig. 5 illustrates a connection of an inner tube 53 with an outer tube 52 and a direct connection, without header, of the outer tube 52 with a tube 55 of a consecutive heating surface. One arm of an angular hollow member 57 is pushed along the inner tube 53 until it abuts against the end face 56 of the outer tube 52 with which it is connected by a weld 59. The end face of the other arm of the member 57 is welded to the end face of the tube 55 at 58. The member 57 has a sleeve portion which is connected with the inner tube 53 by means of a weld 60.

The system according to the invention is particularly useful in connection with a forced flow steam generator of the once-through type. It can be applied to steam or Vapor power plants operating at, above, or below the critical pressure of the operating fluid. The elements of the heat transfer apparatus may be arranged in the form of packages or may be arranged in a plane, so that it can be used, for example, for lining or forming the combustion chamber wall or for forming baffles in large steam generators.

What is claimed is: I

1. A steam generating, superheating, and resuperheating plant comprising a combustion chamber, a flue connected with and receiving hot gases of combustion from said combustion chamber, heating tubes placed in said combustion chamber and in said flue for heating and evaporating water flowing through said tubes, a superheater connected with said heating tubes for receiving steam therefrom, said superheater including first tubes placed within said flue for receiving heat substantially by convection and second tubes connected in series relation with said first tubes and being placed in said combustion chamber for receiving heat substantially by radiation, and a steam resuperheater having a first portion placed within said flue for receiving heat from said hot gases and having a second portion connected in series relation with and downstream of said first portion with respect to the flow of the steam to be reheated, said second portion being placed inside of at least a portion of said second tubes of said superheater for exchanging heat with the steam in said second tubes of said superheater.

2. A steam generating, superheating, and resuperheating plant as defined in claim 1, including an inlet header and an outlet header interconnecting a plurality of said second tubes of said superheater for conducting operating medium in parallel relation through said tubes, said second portion of said resuperheater including a plurality of tubes individually disposed within the interconnected second tubes of said superheater and having inlet and outlet portions extending through said headers.

3. A steam generating, superheating, and resuperheating plant according to claim 2 in which said inlet portions extend through said outlet header and said outlet portions extend through said inlet header.

References Cited in the file of this patent UNITED STATES PATENTS 2,602,433 Kuppenheimer July 8, 1952 2,685,279 Caracristi Aug. 3, 1954 2,685,280 Blaskowski Aug. 3, 1954 FOREIGN PATENTS 275,236 Great Britain July 26, 1928 310,975 Great Britain June 12, 1930 383,569 Great Britain Nov. 17, 1932 662,102 Great Britain Nov. 28, 1951

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