US2762345A

US2762345A - Heat exchange system for vapor generators

Info

Publication number: US2762345A
Application number: US365928A
Authority: US
Inventors: Julius H Bayard
Original assignee: Foster Wheeler Inc
Current assignee: Foster Wheeler Inc
Priority date: 1953-07-03
Filing date: 1953-07-03
Publication date: 1956-09-11
Anticipated expiration: 1973-09-11

Description

y J. H. BAYARD HEAT EXCHANGE SYSTEM FOR vAPoR GENERATORS Filed July s, 195s 000C WOOO fm-f JUL/us H BAYARD Sept. 11

United States Patent HEAT EXCHANGE SYSTEM FOR VAPOR GENERATORS Julius H. Bayard, New York, N. Y., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application `uly 3,1953, Serial No. 365,928 6 Claims. (Cl. 122-1) This invention relates to heat exchange apparatus and more particularly to a preheater system for a vapor generator.

It is usual in vapor generators to heat feed water therefor in an economizer positioned in heat exchange relationship with gases from the furnace of the vapor generator which, in turn, lowers the temperature of said gases. If the temperature of the feed water entering the economizer is of-such degree that the heat removed from the gases does not lower the gas temperature to the desired degree an air heater is positioned in heat exchange relationship with gases beyond the economizer in the direction of ow of the gases. Since the specific heat of the exhaust gases in relationship to the air is low, the size of the air heater is normally very large.

In accordance with the present invention a portion of the feed liquid from a feed pump is passed to the inlet of the lower section of an economizer having a lower, middle and upper section. Another portion is passed to the middle section of the economizer. The middle sec-` tion of the economizer is located beyond the lower section of the economizer in the direction of ow of combustion gases from the furnace so that said gases pass in heat exchange relationship with said lower section, prior to passing in heat exchange relationship with said m-iddle section. The upper section lof the economizer is located beyond the middle section of the economizer in the direction of ow of combustion gases from the furnace so that said gases pass in heat exchange relationship with said middle section, prior to passing in heat exchange relationship with said upper section. The feed liquid passing through said lower and middle sections of the economizer is heated by passing in in-direct heat exchange relationship with gases of combustion flowing from-.the furnace, the portion of feed liquid in the lower section of the economizer being heated to a higher temperature than the portion of feed liquid owing through the middle section of the economizer. This is due to the greater mean temperature difference between the hot exit gases passing in heat exchange relationship with the relatively cool feed liquid flowing through the lower section, than the temperature difference between the exit gases which have already given up some of their heat, thereafter passing in heat exchange relationship with the other portion of relatively cool feed liquid in the middle section.

The relatively hot feed liquid thereafter flows out of the outlet of the lower economizer section to the inlet of an air heater. Here the feed liquid is passed in indirect heat exchange relationship with cold air to be used to support combustion in the furnace of a vapor generator thereby decreasing the temperature of said feed liquid and heating the air to a relatively hot temperature. Since the mean temperature difference between the air and feed liquid is large, the air heater provided can be small and the air can be heated to a high temperature therein. The heated air is thereafter passed to the vapor generator to support combustion and the relatively cool feed is passed out of the outlet of the air heater to the inlet of the Part-,meel sept. 11, s

from the furnace of the vapor generator. These gases are relatively cool since some of their heat content has been given up by being previously passed in indirect heat' exchange relationship with the liquid owing through the lower and middle sections yof the economizer., as hereinbefore described. The feed liquid thereafter ows to the outlet of said upper economizer section and joins the portion of feed liquid owing to the inlet `of the middle section of the economizer further regaining heat given up to the air, by passing in indirect heat exchange relationship with gases of combustion flowing from the furnace, as hereinbefore described. All of the feed liquid then leaves the outlet of said middle section and flows to the feed liquid inlet of the vapor generator.

The present invention provides apparatus for preheating feed water and preheating air for a vapor generator in which the temperature of the flue gases of a vapor generator may be controlled and in which expansion tanks and the like are not necessary.

This invention also provides apparatus for preheating air and feed water for a vapor generator in which separate feed water pumps are not required and in which the possibility -of air heater tires are greatly reduced and in which the air heater may be positioned in any desired location. Y

Theinvention will be understood from the following description when considered in connection with the'accompanying drawing forming a part thereof and in which comprising a setting 10 having vapor generating surface therein with an upper steam and water drum 11 associated therewith together with a lower water drum 12 in' the lower part of the setting in substantial vertical alignment with said upper drum. Drums 11 and 12 are connected Aby a substantially vertical bank of steam gener;

ating tubes 13 having a central bale 14 extending from said lower drum upwardly to a point short of the upper drum. At one side of the bank of tubes 13 is a furnace or combustion chamber 15 red, as of burners 16. The roof and side wall of chamber 15 is lined by water tubes 17. At the opposite side of bank 13 is a gas outlet passage 18 which communicates with gas inlet 19 of ilue or stack 20. The flue has a gas outlet 21 which acts as a gas outlet for the setting.

An economizer 22 having an upper section 23 with a feed Water inlet 24 and a feed water outlet 25 is positioned in flue 20. Economizer 22 has a middle section v 26 over which gases from gas passage 18 pass prior to flowing in heat exchange relationship with upper section i As shown, feed water to be used in the vapor generator, which feed water may -be condensate from acondenser, not illustrated, is discharged by a feed pump 33 through an economizer inlet conduit 34 having one end in communication with said pump and the other'end in communica-tion with inlet 31 of lower section 30 of the economizer.- A portion of the feed passes into section30 through its inlet 31, and another portionpasses intoJmid-i'.

shown, by a plurality" die section 26 of'the economizer through inlet 27 by conduit35whch communicates at one end with conduit 34 and at the opposite end with; inlet 27. The portion of feed water which enters lower section 30 through inlet 31 flows therethrough and thenpassesout. therefrom b`y outlet- 32t0. an air heater 36 by heater inlet conduit 37 having one end in communication' with outlet 32 and the opposite endLin communication with heater. inlet 38.

heater 36 comprises aplurality of tubes 39 extending transversely of'air conducting means or air conduit 4Q. A'dace'nt tubes are connected-.by return bends 4i and' 42s'o that feed water enteringthe air heater through inlet 38pass`es in a continuous path of ilow fromv the lower tube. to the upper tube thereafter tofpass from the heater' at'outlet 43; As shown tubes 39': have extended surface' members 44 thereon.. Airconduit 40-is incommun'i'cationv above air heater, 36 with a source of air to be he'ated'and extends' below saidair heater and into cornmu'r'iicationwith` the furnace 15, through burners 16.

Fe'ed.water whichhaspassed through air heater 36' iiows' therefrom throughoutlet 43 and into upper. section 23 of the economizer 22through heater outlet conduit #l-'which communicates at one end with. outlet 43 and. at the" opposite end with inlet 24 of economizer section 23. Feed water whichy enters section23 of economizer 22 `through' inlet 24 ows therethrough and thence into middle Section 26 of the economizer throughk outlet 25 and conduit 46 which communicates at one end with outlet 25 and at the opposite end with .conduit 35.

In. operation,gases. of combustionfrom combustion chamber 1 5 How therefrom. into bankof tubes 13 andare directed' upwardly by baille 14 over some of the tubes thence downwardly overA the remainderot thek tubes and into gas passagelSr Fromgas passage 18, the gases flow through out1`et.19 thence in heat exchange-relationship with the tubes of lower economzer section 30, thereafter in' heat exchange relationship with` the tubes: ofV middle economizer... section 26, and thereafter in-A heatY exchange relationship withthe tubes of economizer section 231.

Feed'water to be. heated for the vapor generator passes by feed pump .33 through an economizer inlet conduit 34. A portion of the feed waterthereafter passesinto lower section 30,. ofeconomizer22l byyconduit 34 and another portion .passes into middle section 2601i said economi-zer by conduit 35. The. feed water passinginto sections. 30 and '26; is heated. by passing inA indirect heat exchangerelationship with the combustion gases flowing from the` furnace through outlet 19. AThe portion voffeed water passing into the lower section` 30 of the economizer isV heatedtoamuch higher .temperature than the; portion of feedwater flowing through the middle. section since: the

temperature.- difference. between the gases and feed wateris greater.

The relatively hot feed. waterv thereaftern ows out of economizersection by conduit 3.7 to air heater 36 and passes in indirect.heatexchangerelationshiptwith cold air flowingV through air conduit 4t)r of` the heater.. Since the mean temperature diierencebetween the coldfair passing. through.` the heater and: the hotfeed-Ywater is large,- Vthe 'air canbe heated to .a high. temperature withasmall, air heater. The heated air. thenfpassesto burners lsto sup= port combustion in` the vapor generatorand the feedv Waterzwhich-,is now relatively cool passes-to upper sec-V tion.2'3ofthe economizer hy'conduit 45.V In-.section 23, therfeed-.water regains part ofthe .heat given-mttothe` air by, passing inY indirect heat exchange relationship with combustion gases owing'fromithe Ifurnace which'havehad. ...their temperature previously reduced.-.by passing.;- in

heatfexchauge relationship withy-feedwater inth'elowerandmiddle sections tot" the.v economizer. Feedwater their. flows. out. of. section 22t-l by conduit; 46 l and joins feed water flowinginto the middlesection 26 of the-econornizer: through. conduitSSs Here; further: pasagetfofzther teeth waters; and'rcornbustion: gases.- flovszingifrorrrl theifurn'acel. chamberzin indirectheatexchange 'relationship withaone'- another provides an increase in temperature of the feed water and correspondingly decrease in temperature of the exit gases in the stack. The heated feed water thereafter is passed to the steam and water drum 11 of the vapor generator by conduit 29.

Inasmuch as changes may be'rnade in the form, location and relative arrangement of the several parts of the apparatus disclosed Without departing from the' essential characteristics oftheV invention, it will `be understood that the inventionisnot to be limited `excepting by the scope of the appended claims.

What is claimed is:

1. In a vapor generating apparatus comprising a vapor generator'havin'g a setting, a'furnace in the' setting; means for tiring the furnace, said settingA having a gas outlet in communication with the furnace and through which gases of combustion flow from the setting, vapor generating surface in the setting in heat exchange relationship-with said gases of combustion prior to -the flow of saidgases-` from the setting gas outlet, a source of feed liquid, an economizer disposed-in said setting beyond said generating surface and in heat exchange relationship with gasesA ofcombustion owing to said gas outlet, said economizer' having a plurality of sections disposed in the path of flow of the gases passing to the gas outlet and havingliquid from said source tlowing therethrough, one of said sec'- vtionsbeing soY disposed in relation with the other sections and with said path of gases of combustion to provide al higher. temperature of feed liquid in said onesection than inthe other sections, an air heater comprising air conductingrnea-ns through which air tlows and a tubular ovtfpathV communicating with said one section to receive the-feed liquid. after passingl through. said one section to provide ow of liquid through said tubular path, saidtubular' tlow path beingdisposed in heat exchange relationship with'said vair conducting means, said air conducting. meanscommunica-tinglwith said iiringfmeansto provide the la-tter withV preheated air, and meanscommunicating the other gases of combustion prior tothe-flow of said gases fromv the-setting,- gas outlet, a-source of feed-liquid, an economizer disposed in said setting beyond said generatingv surtace-an'din heat exchange-'relationship withi gases otcom-1 bustion. flowing tol said. gas outlet, said econornizer' having" a .rst, second, and third section disposed in the pathwofA flow of the gases passing-to theI gas outlet and havingliquid from' said source ilowing.` therethrough, the third' of-saidl sections being. so` disposedzin relationl with the first and second sections andiwith'said path-of. gases of combustion topro'vide'fa highertemp'eratureo'f feed liquid inrsa'id' third section than; in the iirst-and-Lsecond4 sections; the second ot said' sectionsbeing so-.disposed in: relation withn said rst. sectionrandl/with saidpath of gas'es ofcombustion'- to provide a high'e1temperature'V of.' feedliquidinsaidseco'nd section thanzin saidftirst/'se'ctiong an air heater comprising-- air'conductingmeans thronghwhich1 airflo-ws` and-a tubulapilowfpath communiea't-ingv withsaid thirdl section t'o receive-.theifeed liquidafter passing-through said one s'ection t'oap'rovide flow ofliquidVV through saidljtubular' path; sadt'ubular` flow pathfbeing disposed'in heat' exchange relationship with said air' conducting means, said airlcon'-A ducting meanscommunicatihgmm said tiring means: toA providefthe'f latter with preheated air', and meanscommu? nicatingfwith'the f'rstandi' second'sect'ions of' 'said econo-v mizer withl said vaporgenerat'or-to provide-theda'tter with; preheatedffeed liquidi 321 Ina'lva'por generating-apparatuscomprising a` vapor generator hav-inglase'tting'; a'furnaceinthesetting; m'e'ansf for tiring the furnace, said setting having a gas outlet in communication with the furnace and through which gases of combustion flow from the setting, vapor generating surface in the setting in heat exchange relationship with said gases of combustion prior to the flow of said gases from the setting gas outlet, a source of feed liquid, an economizer disposed in said setting beyond said generating surface and in heat exchange relationship with gases of combustion owing to said gas outlet, said economizer comprising a first, second and third section having liquid from said source iiowing therethrough, said first and second sections being disposed beyond said third section in the path of flow of the gases passing to the gas outlet to provide a higher temperature of feed liquid in said third section than in the first and second sections, an air heater comprising air conducting means through which air flows and a tubular ow path communicating with said third section to receive the feed liquid after passing through said one section to provide ilow of liquid through said tubular path, said tubular ow path being disposed in heat exchange relationship with said air conducting means, said air conducting means communicating with said firing means to provide the latter with preheated air, and means communicating the first and second sections of said economizer with said vapor generator to provide the latter with preheated feed liquid.

4. In a vapor generating apparatus comprising a vapor generator having a setting, a furnace in the setting, means for tiring the furnace, said setting having a gas outlet in communication with the furnace and through which gases of combustion ow from the setting, vapor generating surface in the setting in heat exchange relationship with said gases of combustion prior to the flow of said gases from the setting gas outlet, a source of feed liquid, an economizer disposed in said setting beyond said generating surface and in heat exchange relationship with gases of combustion flowing to said gas outlet, said economizer comprising a rst, second, and third section disposed beyond one another respectively in the path of ow of the gases passing to the gas outlet and having liquid from said source owing therethrough to provide a higher temperature of feed liquid in said third section than in the first and second sections, an air heater comprising air conducting means through which air flows and a tubular ow path communicating with said third section to receive the feed liquid after passing through said one section to provide oW of liquid through said tubular path, said tubular ow path being disposed in heat exchange relationship with said air conducting means, said air conducting means communicating with said firing means to provide the latter with preheated air, and means communicating the first and second sections of said economizer with said vapor generator to provide the latter with preheated feed liquid.

5. In a Vapor generating apparatus comprising a vapor generator having a setting, a furnace in the setting, means for ring the furnace, said setting having a gas outlet in communication with the furnace and through which gases of combustion flow from the setting, vapor generating surface in the setting in heat exchange relationship with said gases of combustion prior to the flow of said gases from the setting gas outlet, an economizer disposed in said setting beyond said generating surface in heat exchange relationship with gases of combustion owing to said gas outlet, said economizer comprising a lirst section, a second section, and a third section disposed beyond one another respectively in the path of flow of the gases passing to the gas outlet, said economizer sections each having an inlet through which liquid enters the section and an outlet through which liquid passes from the section after ow therein, means for supplying feed liquid to the inlets of said second and third sections, an air heater comprising air conducting means through which air to vbe heated fiows'and a tubular flow path having a liquid inlet and a liquid outlet, a first conduit means in communication with the outlet of said third economizer section and the inlet of said tubular flow path, said tubular flow path being disposed in heat exchange relationship with air flowing through said air conducting means, said air conducting means communieating with the tiring means to provide heated air thereto, a second conduit means in communication with the outlet of said tubular ow path and said rst economizer section inlet, a third conduit means in communication with the outlet of the first economizer section and the inlet of said second economizer section, and a fourth conduit means in communication wtih the outlet of said second economizer section and said vapor generator.

6. In a vapor generating apparatus comprising a vapor generator having a setting, a furnace in the setting, means for ring the furnace, said setting having a gas outlet in communication with the furnace and through which gases of combustion flow from the setting, vapor generating surface in the setting in heat exchange relationship with said gases of combustion prior to the ow of said gases from the setting gas outlet, a source of feed liquid, an economizer disposed in said setting beyond said generating surface and in heat exchange relationship with gases of combustion owing to said outlet, said economizer comprising a first section, a second section and a third section, said sections being disposed beyond one another respectively in the path of flow of the gases passing to the gas outlet so that the gases pass first over the third section, thence over the second section and thence over the first section, the second and third sections being both connected to said feed liquid source lto provide for flow of feed liquid therethrough, an air heater comprising air conducting means through which air flows and a tubular flow path communicating with said third section to receive the feed liquid after passing through said third section to provide flow of liquid through said tubular path, said tubular flow path being disposed in heat exchange relationship with said air conducting means, said air conducting means communicating with said tiring means to provide the latter with preheated air, the first section connected to the tubular flow path of said air heater to receive the feed liquid therefrom, means for conducting the feed liquid from said rst section to said second section, and means for conducting the feed liquid from said second section to said vapor generator.

References Cited in the tile of this patent UNITED STATES PATENTS 1,911,501 Grady May 30, 1933 FOREIGN PATENTS 931,632 France Nov. 3, 1947