US2602433A - Superheating and reheating of vapor - Google Patents

Description

July 8, 1952 J. D. KUPPENHEIMER 2,602,433

SUPERHEATING AND REHEATING OF VAPOR l Filedmay e. 1949 Patented July 8, 1952 l SUPERHEATING AND REHEAT'ING OFWPOR Jolinl D# 'Kuppenireimeri Worcester; s'gnorrto Rilemstoken Corporation,

Mass., f as. l Worcester,v

Mass., a corporation of Massachusetts ApplicationMax'Si1949;.Serialho91g77'5 y Thls= inventionlrel'atesf to fthef-superlreating andi reheatingof vapor; and more particularlyfto f an apparatuswherebyvapor, suchas'steam` maybei superh'eatedfor-useein the' high :pressure stages off aturbineand then reheated" for'use inA the' lowA pressurestagesf'of(the-Lturbine.

` Apparatus heretofore'V provided forv` this purpose'oftenincludes-fa vapor generatorhaving a combustion chamberwithin which fuel is burned' to produce hot gases; These het gases" are utilize'd" notonljv'fonvaporgeneration but also forA the superheating and reheating of the steam.` For'thi'sipurpose'thereare usually provideda'low temperature' superheater; a'V high temperature. superheater; and a reheater locatedv betweenL the two' superheaters'; the' arrangement beingY- such" thatthe hot'gasesv/ill flow' irr contactv with` thev high` temperaturesuperheater', .thereheaten` and the' lowv temperature superheater, in the order named. Suchv an apparatus has certain serious' disadvantages. For the most'. ef'cientf genera.- tion of'power it is desirable that the temperature oflthevapor leavingthe reheatershould be high. and approximately the same as the temperatureV of.the.vaponleavn'g';the high temperature superheater. However, aeonsiderablereduction inthe temperature of the hot gases takesplace. as .theyilovv in contact .With .thehigh temperature. superheaten. and-.bythetirne thegases reach the reheater the heat .head or. difference lneijvveen the. temp er ature .of .thexhotg asesandthetemper ature. of.. the vapor inthe reheateri. is comparatively.v low. Consequently` itisneeessary-v toprovide a: rela-tively largesreheater in order.. that.the vapor. may' be.- reheantedf to.r the. required temperature. Sucliat largeA reheater isv very expensive, it oc.- eupiesvaluablespace;A and it` produces an excessiveHdropf-in the pressure of'thevapor ilovvingT therethrough. Furthermore, if the size oftthehigh; temperature: superheaterr'is. altered in order.' tof-effect an adjustment inzthe temperai'f'urezof.` the vaporleaving the same, thisvvvilly changethe temperature of the f gase'szreachingf the reheater and thus' alter thetemp'erature of? the. vaporY leaving: ther-reheaterr; which'. is? undesirable;

It: is accordinglyone: obj eetwo'f the vinvention to` provide a relativelyv simple; inexpensive; andrdependablee apparatus fon' superheating, and re heating vapor.

Itf is a2 furtherobject'vof the invention to'. provide a-l n'eW- andi highly.'v advantageous. apparatus for? utili'zingi:A the heat'v of hot gasesf t'o` generate vapor; tofsup'erhe'at the vapor; and. to-r'eheat' the vapori With these; and" other' objects in=` View;Y as will relatie; (c1. 12a-479.).

beapparentzto those skilledYr-inthe. art,...the;.in

vention..residesin the combination ofipartsset forth: in the= specification. and. coveredm by. the claimzappended hereto. A f -v Referring` tothe drawings. illustratingone.- embodiment-of1 the invention, andv in. whichvlike. reference numerals indicatelike parts,

Eig. 1r is. axlongitudinal yvertical.section through. an; apparatus-for: the: generation, superheatingf. andfreheatingfof vapor, suchas-steam. Y v

Irrliigl. thereis. show .a-. boilersetting com: prising; a front. wall I-Il1 .af reariwa'll. II .arcor-I 2., and two sidewallsiIA (one-.only.o;fvvhich.iappears)f.. Aiy transverse steam-and-waten drum. I5; isflo-f catedin.theupperrear.portonofthesetting,.and a.A transverse water. drum I6. is .-spaceda substantial distancegbelovv theV drum .I5.- yAv transverse. Water drum or header I8 is locatedinthe upper. front portion of the/setting.v Abank.of..-upright waterA tubes IBfis located immediately.. in. front off. thev rear vvallv I I and connects the. drums s I 5v and'rI; Thesedrums arey also connected -by a row ofupright-Water tubes 2liF which are.. spaced forwardly,r a-.Ysubstantialdistance from the..tubes. I9.- A-` rowf of Water. tubes 2;.rv extendupwardly from the; drum I Ii-` in front of..the` tubes 2.0.. for a. portion ot the height of. the latter f tubesuand then arerbentvforwardly-to connect `,With v.theft-ront drums. I8; Other; Waterrtubesf23- arelocatedin frontvoffand beneathfthe tubes 22gand likewise connect ati their-"upper ends-v with: the. header I8: Azrow ofzW-ater tubes-24 extend upwardlyalong theffront Wall I0 andare connectedtorthe `front section; taken onA drum I 8'5 A"v rovvfof watertubes. 25 lie. directly beneath thereofv I2 and-connect the drumsvland I The space. 2 1 l'behind the front wall lI Ill provides. a: combustion.' chamber: in which a .suitable` fuel; suchasfoil orrpulverzedcoal; iseburned to pro-` duce -hotfgasesi Inorderto direct these gases in a desired manner, certain bailes are provided; A4 baiilei- ZBfeXtends' "upwardly` from the lower Water? drum I tzr-part". Wayl along. the Water"r tubes 2'0 andiy then'i forwardly along. theV tubes.v 22', this baie? terminating af substantial distancefto. the rear? of' then front durm I8. A" bailley 3l)y extends downwardly from .the steam-and-water drinnr I5- alongthefront'row oi water tubes I9-V and-tenv initiates a substantial:distancel above the lower drum'v4 I6. Other' baflesi 3|' extend: across the Water.' tubes I 9; toi direct ;th'e.1gases l in..a-':tortuous course. A soot hopper 32 is located behind the lower drum i6, and a gasoutlet duct 33 with the usual damper 34 therein is located adjacent the upper drum l5. The space 36 beneath the roof I2 and above the upper forwardly extending portions of the water tubes 22 forms a passage through which hot gases from the comb-ustion chamber 21 may flow in a generally rearward direction. The space 31 between the baiiles 28 and 30 forms a passage through which the gases leaving the passage 35 may flow downwardly.V The space 38 between the rear Awall ||A andthebaiiie 30 forms a passage through which the gases leaving the lower end of the passage?! may 'new i y upwardly to the'outlet duct 33.

The hot gases'heat the various 'water tubes and generate steam therein, this steam being released in the steam-and-water drum l5. This will be saturated steam,-its temperature Vbeing the temperature of boiling water corresponding to the pressure within the drum. 1f this pressure is say 1050 pounds per square inch, the steam temperature will be 552 degrees Fahrenheit. Before such steam can be used e'lciently for the generation of power in a steam turbine, it is necessaryY to superheat the steam to a comparatively high temperature, such as 1000 degrees F. This superheating is preferably done in two separate stages. For this purpose a low temperature superheater 40 is mounted Within the passage 31 and arranged to receive steam directly from the drum l5, and a high temperature superheater 4| is mounted Within the'passage 36. The superheater 4| is arranged to receive steam from the superheater 40' and to deliver the steam to a header 42 frompwhich it may flow to a steam turbine (not shown) for the production of power. Each of the superheaters 40 and 4| comprises a plurality of tubes spaced apart laterally and .each bent into sinuous form to provide a plurality of upright loops lyingin a vertical plane.

It is important to maintain the temperature of the steam in the header 42 as closely as possible to the desired value of 1000 degrees. For this purpose the superheaters 40 and 4i are made large enough to heat the steam to a somewhat higher temperature under most conditions, and means is provided to desuperheat the steam Yslightly after it leaves the superheater 40 and before it enters the superheater 4|. The particular means illustrated comprises 'a desuperheater 44 immersed in the boiler water in the lower drum I and having an inlet header 45 and an outlet header 46. The low temperature superheater 40 is provided with an outlet header 48 which is connected to the desuperthe pipe 5| to the header `50.

heater inlet header by a pipe 49. The high Y temperature superheater 4| is provided with an inlet header which is connected to the desuperheater outlet header 48 by a pipe 5 I. The headers 48 and 50 are connected to one another by a pipe 53 having a diaphragm actuated valve 54 o f well-known type therein tov control the iloW.

The valve 54 is controlled in response to variations in the temperature of the steam within the superheater outlet header 42, in order to minimize such variations. This may be brought about by apparatus of a Well-known type comprising a temperature responsive bulb 56 located within the header 42 and connected by a tube 51 to a relay 58 which in turn is connected by a tube 60 to the diaphragm chamber of the valve 54. Air or other suitable fluid under pressure is supy plied to the relay 58 through a tube 6|.

parts are so constructed and arranged that if the temperature of the steam reaching the header 42 should increase and slightly exceed the desired value of 1000 degrees, the bulb 55 will respond to such increase and cause the relay 58 to transmit a slightly increased fluid pressure to the diaphragm chamber of the valvei54, thereby closing this valve slightly and causing a larger portion of the steam from the header 4S to flow through the pipe 4S, the desuperheater 44, and This will reduce the temperature of the steam entering the high temperature superheater 4|, and thereby reduce the temperaturer of the steam-reaching the outlet-header 42. Similarly, upon a slight reduction in temperature within the header 42, the relay y53 will open the valve 54 slightly and cause a smaller proportion of the steam to pass through the desuperheater 44, thereby raising the ternperature of the steam entering the high temperature superheater 4|. j Thus the steam temperature at the outlet header 42 is maintained at the desired value, and at no point in thesystem is the steam heated to a temperature .exceeding the maximum temperature desired at the said header 42. Because of theV resistance to steam flow through the superheaters and the desuperheaters, the pressure of the steam at the header 42 may be approximately 1000 pounds,

i. e., 50 pounds less than the pressure in the drumA The steam from the header 42 is delivered toA -these stages, its pressure will have been reduced to say 500 pounds, and its temperature willhave dropped to say 500 degrees. Thisis somewhat above the saturation temperature for this pressure, so that the steam will be dry. Before this steam enters the low pressure stages of the turbine it is desirable to reheat the steam and thereby prevent, or at least minimize, condensation within the turbine. Preferably the steam is .reheated to approximately the same temperature as that to which it was originally superheated, i. e. 1000 degrees F'.

Referring once more to the drawings, it will be seen that a header 65 is provided to receive the steam to be reheated, and the tubes 6B of a low temperature reheater are connected to this header to receive steam therefrom. These tubes 66 are bent into the form of upright loops located within the downow gaspassage 31, and they deliver the steam into a desuperheater 68 of the well-known spray type having a spray pipe 68 therein. The spray pipe 69 receives substantially pure water, such as condensate, at a suitable pressure from a pipe 1| under the control of a diaphragm valve 12. From the desuperheater 08 the steam enters a high temperature reheater 14 located within the gas passagev 35 and-arranged to deliver the reheated steam to an outlet header 15 from which it may flow to the low pressure stages of the turbine. The reheater 14 comprises a plurality of tubes spacedv apart laterally and each bent into sinuous form to provide a plurality of upright loops lying in a vertical plane.

The temperature of the steam'in the outlet header 15-is preferably maintained substantially constant and approximately equal to that of the steam Within the header 42, i. e. 1000 degrees F. For this purpose a temperature responsive bulb 11 is located within the header 15 and connected These of the valve 12. Air or other suitable fluid under pressure is supplied to the relay 19 through a tube 82. These parts are so arranged that uponv a slight increase in the steam temperature within the header 15, the bulb 11 will cause the relay 19 to transmit a slightly decreased uid pressure tothe diaphragm chamber of the valve 12, thereby causing this valve to open slightly and admit more water to the spray pipe 69 in the desuperheater 68. This will immediately lower the temperature of the steam entering the reheater 14, and thereby lower the temperature of the steam reaching the header 15. Similarly, a slight reduction in the temperature within the header 15, below the desired value, will cause the relay 19 to close the valve 12 slightly and reduce the rate at which water is sprayed into the desuperheater 69, until the desired temperature is restored in the header 15. At no point in the system is it necessary to reheat the steam to a temperature above that desired in the header 15. y

The high temperature superheater 4| and the high temperature reheater 14 are located within a common g-as passage 36 and subjected to heat from a common gas stream. Thus they are subjected to substantially the same heat head or temperature difference. Preferably the elements of these two heat exchangers are closely intermingled, so as to minimize the effect of any differences in the gas temperature across thepassage. As shown in Figs. l and 2, each reheater tube 14 may be located in a common vertical plane with an adjacent superheater tube 4|, the loops intermeshing within these planes. The flow of the steam through the superheater 4I and through the reheater 14 is in a generally forward direction toward the front drum I8 and opposite to the generally rearward direction of flow of theY hot gases in the passage 36. Thus the ow of the steam and the fiow of the gases are opposite, providing efficient transfer of heat. Also, the high temperature portions of the reheater and of the superheater are adjacent 6 l therethrough will be less than with prior constructions. The weight of the steamV flowing through the reheater 14 per hour will ordinarily be substantially the same as the weight of the steam iiowing through the superheater 4| per hour, since only a small quantity of water will be added at the d-esuperlieater 68. However, the pressure within the reheater will be considerably less, and the volume of the steam flowing therethrough per hour will accordingly be greater than in the case of the superheater. Hence it will ordinarily be desirable to make the reheater tubes 14 somewhat larger in diameter than the superheater tubes 4|, to avoid too great a pressure drop through the reheater.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

Apparatus for superheating and reheating vapor comprising means providing a passage for the flow of hot gas in a stream extending throughout the entire width of the passage, a superheater for vapor under pressure having a plurality of separate elements distributed substantially uniformly across the entire Width of the passage, and a reheater for vapor under a somewhat lower pressure having a plurality of elements which are intermingled substantially uniformly with the bent into sinuous form to provide a series of loops to one another and are equally exposed to the high temperatures of the gases entering the passage 36 at perhaps 180'() degrees F. Hence considerably less total heating surface will be required for the reheater than with prior constructions in which the reheater is located behind the superheater. Because of the reduced size of thereheater, the pressure loss in the steam flowing lying in a common plane, and each reheater element likewise comprises a tube bent into sinuous form to provide a series of loops lying in a common plane, all of said planes extending parallel with the general direction of the g-as flow in the passage, and .each reheater tube lies in a common plane with one of the superheater tubes, the loops of the tubes being intermeshed. JOHN D. KUPPENHEIMER.

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

UNITED STATES PATENTS i Number Name Date 1,952,542 Ehlinger Mar.27, 1934 2,035,763 Robinson Mar. 31, 1936 2,477,950 Bailey Aug. V2, 1949

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