US2312375A - Vapor generator - Google Patents

Description

March 2,1943. G. c. WHITNEY JR 2,312,375

VAPOR GENERATOR Filed Dec. 7, 19:59 2 Sheets-Sheet 1' INVENTOR /LEf/QfC/I/lV/ T/VFK/.

ATTORNEY Ale/#14762 w w w w a u m 7 W 2 m m 2 w m 50 .F 2 6 5 Y7 Z 4 rw, a 2 a). d. m. a v. a 4 i 1 i 2 v c z MV ,0.

/rllll Milnjch Z, 19 3- cs. c. WHITNEY. JR 7 VAPOR GENERATOR Filed Dec 7, 1959 2 Sheets-Sheet 2 INVENTORQ 6/A6597 C. h/wr/v fe.

ATTORNEY Patented Mar. 2, 1943 VAPOR GENERATOR Gilbert 0. Whitney, Jr., New York, N. Y., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application December 7, 1939, Serial No. 307,957

17 Claims.

This invention relates to vapor generators, and more particularly pertains to the method of, and apparatus for, recovering heat in vapor generators. The invention will be disclosed in connection with steam generators, but it will be understood that it is applicable to vapor generators generally.

The major problem encountered in the operation of economizers in steam generators wherein some steam is formed in the economizer, has been the separation of the steam and water from the mixture thereof which is ordinarily present at; the economizer outlet, before the mixture enters the steam and water drum of the boiler. The need for this separation, aside from steam .washing, is primarily due to the practical limitations that are imposed on the diameter and wall thickness of the drums. The drums should be of sufficiently ample .dimensions to provide adequately for the separation of the mixture of steam and Water normally liberated therein by theboiler tubes, but the size of the drums becomes excessive if they are required to separate an additional mixture of steam and water received from a steaming economizer. Under these conditions, the use of a steam washer of adequate proportions in the drums would be practically impossible even though a mixture of steam and Water could be effectively used to wash steam.

However, there are numerous instances particularly in connection with modern high pressure steam generators, where various factors entering into the design and operation of such units make the joint use of both steaming economizers and steam washers highly desirable. The washers are necessary on account of the relatively high concentration of solids occurring in the boiler circulating water, and because of superheated steam requirements with respect to turbine operation, while steaming economizers are essential because of the high temperatures (1200-1400 F.) of the flue gases, and because ofthe relatively large amount of this heat that can be recovered most economically from these gases by a steaming economizer.

For example, in any such high pressure installation, the maximum heat recovery possible by air heating surface is limited by the maximum air temperatures permissible with the existing fuel burning equipment, while stage bleeding of turbines has reduced the heat recovery possible in non-steaming economizers by increasing feed ,water temperatures to levels regularly above 100" F. and at times as high as 500 F. at the economizer inlet. Ordinarily therefore, since furnace gas temperatures are substantially fixed by final steam temperature requirements, there would be a margin of several hundred degrees that would have to be absorbed by additional boiler heating surface ahead of the economizer in point of gas flow, or by a steaming economizer. However, in most cases the installation of additional boiler surface is very difficult due to drum limitations, and in all instances exceedingly expensive, based on the amount of heat recovery thus attainable, whereas additional economizer heating surface is much cheaper and more effective for the purpose specified. 1 The present invention provides means whereby steaming economizers may be advantageously used to recover heat which would normally be wasted in steam generators and the like. The invention. also provides means for controlling final steam temperatures by the-temperature of the steam leaving the steaming economizer. H In accordance with the method and apparatus of the invention, the major portion of the total feed water is withdrawn from an intermediate header in the economizer, which is located at a point in the economizer'where the water has almost, but not quite, reached saturation temperature at the pressure existing in the boiler drum. The solid water thus Withdrawn from the economizer is led directly to the steam washer in the steam and water drum of the boiler. The Water which is permitted to continue through the remainder of the economizer is of such an amount that by the time it reaches the outlet 0 header it is vaporized and is in the form of saturated or slightly superheated steam. This steam may be led either to a point in the drum below the steam washer or'directly to the inlet of the superheater. The intermediate header is so located in the economizer that regardless of operating conditionsonly solid water will be delivered to the'steam washer. The economizer'is thus divided into a steaming section, and anonsteaming section, with the steaming section containing sufficient heat absorbing surface so that the economizer as a whole will effect the desired reduction in the temperature of the flue gases.

The invention will be understood from the fol lowing description when considered in connection with the accompanying drawings forming a part thereof, and in which:

Fig. 1 is a partial vertical sectional view, illustrating more or less diagrammatically, a steam generator embodying'one form of the invention;

Fig. 2 is an enlarged transverse vertical sectional view of part of the boiler steam and water drum, and

Fig. 3 is a view similar to Fig. 1 but illustrat ing another form of the invention.

Like characters of reference refer to the same or to similar parts throughout the several views.

Referring to Figs. 1 and 2 of the drawings, reference character I designates generally the setting of a steam generator comprising an upper or steam and water drum H, and a main bank of steam generating tubes l2, which are vertically.

upper drum l l by means of a group of riser tubes I6, and headers l4 and I5 are connectedto drum n Water wall tubes 18,13

H by downcomers I1.

and also form a part of the steam generating surface and the circulatory system of the :unit". The combustion chamber 2| is lined by these .water wall tubes, and suitable fuel burning equip ment, not shown, produces the necessary prodnets of combustion in the furnace.

Suspended from the upper portion of thesetting and extending downwardly into the space between the tubes lii'and I1, is a superheater 22 having steam inlet and outlet headers 23 and 24 respectively. The inlet header 23 is connected to the steam and water drum by saturated steam line 25. Combustion gases leave the steam generating surface of the boiler through outlet'fiue 26 and flow through duct 21 to an economizer 28 which comprises a steaming section 29, and a non-steaming section 36. As shown, the gases after leaving the economizer, enter an air heater 3|, .which includes suitable air ducts, not shown, for conducting preheated air to the fuel burning apparatus in the lower portion of the combustion chamber 2!, while the spent flue gases are discharged to the atmosphere by a stack or any other means,also not shown.

As. shown more clearly in Fig. 2, the steam drum l I is provided with steam washing means 32 and'steam drying means 33. Any suitable type of steam washer may be employed, since the washing means forms no part of the invention. The washi'ngmeans shown includes a tray 34 horizontally dispo-sed'a'bovethe waterline in the drum, and

provided with a plurality ofp-arallel, elongated upwardly "extending nozzle-like ports '35; Ex tending over the top of each of these ports, and slightly spaced'therefromis a cap 'member 36, the lower edges of'the sides of which are serrated as indicated at 31. Feed water from the economizer is supplied to the tray- 34 by'a feedline 33. A body of this water flows across the tray between the ports to an outletpipe 39 the upper endof which is disposed so as to maintain the desired water level on thetray. Pipe 39 also conducts the overflow from the tray to the boiler circulating water in the lower portion of the drum. Stearnliberated in the space below the washer passes upwardly through the ports or nozzles 35 in the tray, is deflected by the cap members 36, and flows downwardly through the water on the tray and under the lower edges of the sides of the cap members, and then upwardly through the water to the space in the drum above the washer. The steam, which by its contact with the fresh feed water has been substantially freed of its'solid content, flows through the drier 33 to the steam line and thence to the supe'rheater.

Feed water is supplied tothe economizerfrom any suitable source by a feed'pump 49, which is controlledby the usual feed water regulator 4|, whereby the desired-water level ismaintained in the boiler drum at the various boiler ratings. This controlled amount of feed enters the economizer inlet header 43 through line 42, and flows through the non-steaming section to an intermediate header 44. The inlet end of the boiler feed line 38 is connected to the header 44, and as shown in Fig. 1, a fixed orifice is placed in this line at a point between the e'conomizer and the boiler drum. The diameter of the orifice is such that the major portion" of the total feed in the form of solid water flows from the header 44 through line 38 directly to the steam washer, while the smaller amount of the feed which continues through the steaming section 29 of the econ miaer will, atthe outlet thereof, be in the for'r nfof 'saturatIed'o-r slightly superheated steam. This steam is 'ledfrom outlet header 45 through line .4? to the'lowerportion of the boiler drum.

In theform of the invention illustrated in Fig. 3, the steam from the steaming section of the ec-onomizer instead of flowing 1130' the drllu'n, is conducted by line :4] directlyto the inlet header 23' of the superheater where, together with'ithe saturated steam from the boiler,"-'it'flows through the -superheater to the outlet header 2.4". thermostat bulb 48 'is dispose'd in' the header 24" and it is connected by a pressure lineA'EIwi-tha motor valve 55 in the feed line'38. By means of the thermostatbulb; the'motorwalve "is automatically regulated by the final temperature "of the superheated steam'in the header '2 4-,a1id th-us controls the flowthrough the feed line, 'and'the amount of water flowing through the steaming section of the economizer, to the end :that the temperature'of the steamflowingthroughline 41' may be controlledso as to effect the finaltemper ature of the superheated steam. It will be-understood that at all times, ah ample supply of solid water will be delivered to t'he steam washer, and that-normally only a'yery slight variation-inflow through the steaming section of the econom-izer will be sufficient to produce the required change in temperature of the steam generated therein to serveas a means for superheat'control. Obvious"- ly, if the ,alreadylimited amount of water flowing through the steaming sectionis reduced, theter'r'fperature'of 'the'steam therein will be readily in: creased by the-heat of the flue gases.

In operation thereforejwhen the final temperature of th superheated steam falls below see?- tain predetermined level, the thermostatbulb 43 will actuate the motor valve 53through the pres sure line-49 so a'sto withdraw more water from the intermediate header. through finesa'winch results in rapidly-increasing" the temperature of the steam in the steaming'sectio'n. The heating effect ofrthis' hottersteam when'introduce'd into the superheater header 'willincre'asethe final temperature 'Qfthe superheated; steam until it r'eturns to the desired level. The operation is reversed when the superheated 'steam temperature be omes oo h.

It Willjbfl apparent, that in accordance with the invention, steaming'economizers maybe adva'm tageously and economically employed from the standpoint of bothheat recovery'and'steam washing in modern high pressure steam plants. "The invention not only providesfor the admission of feed water containing no steam' to the steam washer, but also'pro'yides a ready m'eans'fofcontrolling superheat: i

Although-by way of 'exampleI have disclosed preferred embodiments of 'the' invention: it will be understood'that changes maybe made'in menarticular form' and arrangement of the various parts of the apparatus herein disclosed without departing from the principles of the invention, and that the invention is not to be limited excepting by the scope of the appended claims.

' What is claimed is:

1. In a vapor generator, a vapor generating section, a vapor and liquid drum connected to the vapor generating section, a vapor and liquid contacting device in the drum, a gas passage arranged to receive gases after flowing in heat exchange relationship with the vapor generating section, a heat exchange device in said gas passage having a portion in which liquid is heated and a connecting portion in which heated liquid is vaporized, means for deliveringliquid to the first mentioned portion of the heat exchange deyice, a conduit for delivering heated liquid from said liquid heating portion of the heat exchange device to the vapor and liquid contacting device in the drum, and a separate conduit for conductingvapor from the vaporizing portion of the heat exchange device to a point of use.

:2. In a vapor generator, a vapor generating section, a vapor and liquid drum connected to the vapor generating section, a vapor superheater for the generator, a gas passage arranged to receive gases after flowing in heat exchange relationship with the vapor generating section, a heat exchange device in said gas passage having a liquid heating portion and a liquid vaporizing portion, means for delivering liquid to the heat exchange device, a conduit for delivering heated liquid from said liquid heating portion to the drum, and a separate conduit connected to the outlet of the vaporizing portion and to the inlet of the superheater.

" 3. In a vapor generator, a vapor generating section, a vapor and liquid drum connected to the vapor generating section, a vapor and liquid contacting device in the drum, a gas passage arranged to receive gases after flowing in heat exchange relationship With the vapor generating section, a heat exchange device in said gas passage having a portion in which liquid is heated and a connecting portion in which heated liquid is vaporized, means for delivering liquid to the first mentioned portion of the heat exchange device, a conduit for delivering heated liquid from said liquid heating portion of the heat exchange device to the vapor and liquid contacting device in the drum, a flow controlling device in said conduit, and a separate conduit for conducting vapor from the vaporizing portion of the heat exchange device to a point of use.

4. In a vapor generator, a vapor generating section, a vapor and liquid drum connected to the vapor generating section, a vapor and liquid contacting device in the drum, a gas passage arranged to receive gases after flowing in heat exchange relationship with the vapor generating section, a heat exchange device in said gas passage having a portion in which liquid is heated and a connecting portion in which heated liquid is vaporized, means for delivering liquid to the firstmentioned portion of the heat exchange device, a conduit for delivering heated liquid from said liquid heating portion of the heat exchange device to the vapor and liquid contacting device in the drum, a flow controlling device having a fixed orifice in the conduit, the flow area of the orifice being such that all the liquid delivered to the heat exchange device is withdrawn therefrom through said conduit excepting for that part which will be vaporized in the vaporizing portion, and a separate conduit for conducting vapor from the vaporizing portion to a point "of use. 5. In a vapor generator, a vapor generating section, a vapor and liquid drum connected to the vapor generating section, a vapor superheater for the generator, a gas passage arranged to receive gases after flowing in heat exchange relationship with the vapor generating section, a heat exchange device in said gas passage having a liquid heating portion and a liquid vaporizing portion, means for delivering liquid to the heat exchange device, a conduit for delivering heated liquid from said liquid heating portion to the drum, avalve in the conduit, thermostatic means responsive to the temperature of the vapor leaving the superheater for controlling the valve to decrease the fiow of fluid to the vaporizing por tion when the temperature of the superheated vapor falls below a predetermined level and increase said flow when the temperature of the superheated vapor rises above a predetermined level, and a separate conduit for delivering vapor from the vaporizing portion to the superheater. 6. In a steam generator, a steam generating section, a steam and Water drum connected lto said section, a steam washer in the drum, a gas passage arranged to receive gases after flowing in heat exchange relationship with said section, an economizer in said passage having a portion in which water is heated and a connecting portion in which steam is generated, means for delivering feed water to the first mentioned portion of the economizer, a conduit for delivering heated Water from the Water heating portion of the economizer to the steam washer in the drum, and a separate conduit for conducting steam from the steam generating portion of the economizer to another part of the generator.

7. In a steam generator, a steam generating section, a steam and water drum connected to said section, a steam washer in the drum, a gas passage arranged to receive gases after flowing in heat exchange relationship with said section, an economizer in said passage having a portion in which water is heated and a connecting portion in which steam is generated, means for delivering feed Water to the first mentioned portion of the economizer, a conduit for delivering heated water from the water heating. portion of the economizer to the steam washer in the drum, and a separate conduit for delivering steam from the steam generating portion to the steam and water drum.

8. In a steam generator, a steam generating section, a steam and water drum connected to said section, a steam washer in the drum, a gas passage arranged to receive gases after flowing in heat exchange relationship with said section an economizer in said passage having a portion in which water is heated and a connecting portion in which steam is generated, means for delivering feed water to the first mentioned portion of the economizer, a conduit for delivering heated Water from the water heating portion of the economizer to the steam Washer in the drum, a fiow controlling device having a fixed orifice in said conduit, the flow area of the orifice being such that all the feed water delivered to the first mentioned portion of the economizer is withdrawn therefrom through said conduit excepting for a predetermined part which will be vaporized in the steam generating portion, and a separate conduit for withdrawing steam from the steam generating portion.

9. In a steam generator, a steam generating section, a'ste'am and waterdrum eonnectea to said section, a steam superheater for the generator, a steam washer in the drum, a gas passage arranged to receive gases after flowing in heat exchange relationship with said 'sec'tion,"an economizer in said passagehaving a water heat 'in'g portion and a steaming portion,'ineans for delivering feed Water to the economizer, a conduit for delivering heated water from the water heating portion to the steam Washer in the drum, a valve in the conduit, thermostatic means responsive to the temperature of the steam leaving the superheater for controlling the valve to de= crease the flow of Water to the steaming portion when the temperature of the superheated steam falls below a predetermined level and increase said how when the temperature of the superheated steam rises above a predetermined level, and a separate conduit for delivering steam from the steaming portion to the superheater.

10. The method of generating steam in a steam generator having a steam generating section, a steam and water drum and a steam Washer in the drum, which comprises flowing feed water through a heating zone and into a steam generating zone both zones being in heat exchange relationship with gases produced in fir ing the generator, separately conducting steam free Water from said heating zone to the steam washer in the drum, vaporizing the portion of the heated feed water passing into said steam generating zone, and conducting the vaporized portion to a zone of use.

11. The method of generating steam in a steam generator having a steam generating section, a steam and water drum and a steam Washer in the drum, which comprises flowing the feed water through a heating zone and into a steam generating zone both zones being in heat exchange relationship with gases produced in firing the generator, separately conducting steam free water from said heating zone to the steam Washer in the drum, vaporizing the portion of the heated feed water passing into the steam generating zone, and delivering thervaporized portion to the drum.

12. The method of generating steam in a steam generator having a steam generating'se'ction, a steam and water drum and a steam washer in the drum, which comprises flowing the feed Water through .a heating zone and into a steam generating zone both zones being in heat exchange relationship with gases produced in firing the generator, separately conducting steam free water from said heating zone to the steam washer in the drum, controlling the flow of steam free Water to the washer, vaporizing the portion of the heated feed waterpassing into the steam generating zone, and conducting the vaporized portion to a zone of use.

13. The method of generating steam in a steam generator having a steam generatingsection, a steam and water drum and a steam washer in the drum, which comprises flowing the feed water through a heating zone and "into "a steam generating zone both zones being in "heat exchange relationship with gases produced in firing the generator, separately conducting steam free water from said heating zone to the steam washer in the drum, regulating the flow of steam 14. The method of generating steam in a steam generator having asteam generating section, a steam and water drum, and a steam Washer in'the drum, which comprises flowing the feed water through a heating zone in heat exchange relationship with gases produced in f ring the generator, conducting heated water from said zone to the steam washer in the drum, v'a porizing a portion of the feed water in a steam ing zone disposed in heat exchange relationship with said gases,'delivering said vaporize-d portion of the feed water to a superheater, and regulating the flow of heated water to the Washer in response to the temperature of the steam leaving the superheater in such manner that the how is increased when said temperature falls below "a predetermined level and the flow is decreased when said temperature rises above a predetermined level.

15. The method of generating and superheating steam in a steam generator having a steam generating section and a steam and water drum, which comprises flowing the feed Water through a heating zone in heat exchange rela tionship with gases produced in firing the gen erator, conducting heated waterfrom said zone to the drum, vaporizing a portion of the feed water in a-steaming zone disposed in heat exchange relationship with said gases, delivering said vaporized portion of the feed water to a superheater, and controlling the temperature of the steam-leaving the superheater by regulating the quantity of feed water vaporized in said heating zone in response to the temperature of the steam leaving the superh'eater.

16. In a vapor "generator, a vapor generating section, a vapor and liquid drum connected to "the outlet of the vaporizing portion and to 'the inlet or -the superheater.

-17. The method of generating and superheatih'g steam in astea-m generator having a steam generatin section, a stea-mand water drum and a steam washer in the drum, which comprises flowing feed watertnrmi n 'a heating zone in heat exchange relationship with gases produced in firing the generator, conducting heatedwat'er from an initial portion of said zoneto the steam Washer in the drum, vaporizing heated water in a final portion of said zone, delivering said vaporized portion of the feed Water to .a superheater, and controlling the temperature of the steam leaving the superheater by regulating the quantity of feecl water vaporized in said heating zone in response to the temperature of the'steam leaving the superheate r V GILBERT C. WHITNEY, J a,

Images