US1795317A - Steam plant - Google Patents

Description

March l0, 1931.

J. H. sENGsTAmEN STEAM PLANT F1ed Sept. 7. 1929 INVENTOR Patented-'Mal'. 10, 1931 PATENT- oFFl'cE.

JOHN H. SENGSTAKEN, OF BROOKLYN, NEW YORK, ASSIG-NOR TO FOSTER WHEELER CORPORATION, F NEW YORK, N. Y., A CORPORATION OFNEW YORK STEAM PLANT Application filed September steam in the boiler proper and more heat must be taken'out of the products of combustion after they leave the boiler proper.

Devices for absorbing this lower temperature range of heat .are generally known as economizers. Economizers include both air preheaters, in which products of combustion heat air supplied to the furnace,and feed Water heaters, in which the feed water is preheated before entering the boiler proper. Air preheaters may be used alone and feed water heaters may be used alone.

Air preheaters have steel plates which are heated to high temperatures by the products of combustion- With high temperatures of products of combustion entering the air preheater, there is danger of corrosion. Plants are now being designed with temperatures of over 1,000o F. for the gas leaving the boiler proper. This temperature is likely to oxidize the plates of an air preheater. The gas inlet temperature for an air preheater should preferably be under 800 F.

The large amount of heat available in products of combustion of 1,000 F. or over,

, when applied entirely to the heating of feed water, has a tendency to cause excess steam formation in a feed water heater particularly when the feed water is supplied to the economizer at high temperatures as is becoming usual practice.

In order to obtam a maximum effect from the products of combustion and, at the 'samej time, eliminate these diiiculties, I propose to f suitable pressure through conduit 21 into combine a feed water heater and' an air preheater in a boiler installation in such a manner that the feed water heater eliminates the above described difficulty as to the-'preheater and the preheater eliminates the above described difficulties as to the feed water heater.

In accordance with this purpose, I arrange the air preheater between two lsections'of a feed water heater so that the temperature 7, 1929. serial Nt. 390,945.

tering the feed water heater proper.

The invention is diagrammatically illustrated on the accompanying drawing-wherep invention On the drawing, reference character 104 designates a boiler comprising the usual water tubes 11 and steam and water drum 12. The tubes are situated within a combustion or -furnace chamber 13. A stoker 14 is indicated as a source of products of combustion.

Air for combustion is supplied through air duct 15. Solid or liquld fuel co-acts with the air to formvhot products of combustion which heat the water tubes and produce steam. The products of combustion leave the boiler proper through Hue 16, having been partially cooled by contact with the boiler surfaces. l

Other factorsremaining constant, the higher the pressure of steam withdrawn from the boiler, the higher the exit temperature of the products of combustion. This is because saturated steam must have higher temperature at higher pressure'. .Assume that the temperature of gases entering flue l16 is 10700 In flue 16 is a feed water heater composed of a first section 17 and a second section 18.

Between these sections isy an air preheater 20. Feed, water is supplied from apuinp at individually connected to vindividual tubes of rowv 24 by members 25.' Section 18 'of the Fig. 1 is a diagrammatic view'of a steamfeed water heater comprises a plurality .f

vrows of tubes, 'each row containing the -same numbei1 of tubes and the rows being connected for series flow in a plirality of parallel paths. Extended surface rings may be applied to the feed water heater tubes. The parallel paths of flow through section 18 join again at header 26.

A conduit 27 connects header 26 with a header 28. Header 28 is part of first feed water heater section 17. Another conduit 33 connects header 26 with steam and water drum l2. A valve 84 is interposed in conduit 27. A valve 35 is interposed in conduit 33. Assume that valve 34 is open and that valve 35 is closed. l

Section 17 likewise is made up of a plurality of rows of tubes connected to give series flow between corresponding tubes of the respective rows and parallel flow in the rows. Feed water after passing through the tubes of section 17 enters header 29 and thence passes through one or more conduits 30 into the steam and water drum 12 of the boiler proper. A valve 36 is interposed in conduit 30' The number of rows of tubes in section 18 is appreciably greaterthan the number of rows of tubes in section i7. 'With like tubes ,and like rows in the two sections, the number of rows in the second section is preferably at least twice the number in the first section.

The air preheater may beef any of various types, a plate type air preheater being indicated by way of example. Referring' to Fig. 2, productsof combustion pass downwardly through passages Si. .dir enters through duct 32, passes through passages 38 and thence passes through duct l5 to the boiler furnace. Heat is `transferred from the products of .combustion to the fresh air through the folates of the air preheater.

T e various surfaces are preferably calculated and designed so that, with an exit Hue gas temperature of about 1070O F., the first feed water heater section will reduce the teniperature of the roducts of combustion to about 7 50 l*1 which is below the temperature which will cause oxidation and so that the temperature of the products of combustion leaving the air preheater and entering the second vfeed water heater section will be about 675 l?. Even though the temperature of feed water supplied .through conduit 2l is 300 F. or more, the feed water heater will not form steam or -form steam to any excessive extent. Bue to the air pre-heater, the temperature of the water entering the first feed water heater section is sufficiently low so that, pg' .providing e a suitable velocity of dow, earning is prevented r diminished.

Instead of having series dow, .the feed water Vmay :pass in parallel through sections 17 and .18. In such case water passes 4through conduit 21 into feed heater section 18 and thence Vthrough conduit 33 to the steam and c ,water drum, the valve 34 being closed. Feed maaar? temperature may be maintained in liuc l at the hot gas entrance to the air prehcatcr by controlling the relative rates of flow of water through conduits 2l and 37.

. lt will also be evident that the feed heater sections may be connected in series and have feed water supplied both at inlet 2l and inlet 37 in which case desired temperatures can also be maintained by suitable regulation of the flow of feed water.

llt will be understood that the invention is not limited to particular structure. The boiler proper may be of any type and it may be heated in any manner. ri`he flow through the feed water heatermay be down instead of u though l prefer counter-flow. Tubes may e bare or have extended surface and may be otherwise connected than above described. instead of one connection 27, there may be as many connections as tubes in a row so that there is full series flow between headers 22 and 29.

l/Vhat l claim is:

l. A steam plant comprising a boiler, a flue for conducting products of combustion from said boiler, an air preheater interposed in said flue and feed water heater sections vin said flue on each side of the air preheater, one of said sections being in advance of said preheater and the other of said sections being behind the preheater with respect to gas dow through said flue.

2. steam plant comprising a boiler, a flue for conducting products of combustion from said boiler, an air preheater interposed in said flue, a first feed water heater section in said flue, a second feed water heater section in said flue, means to supply feed water to said second feed water heater section, means to conduct feed water from said second feed water heater section to said first feed water heater section and means to conduct feed water from the iirst feed Water section to the boiler, the arrangement being such that the products of combustion first heat feed water in the first feed water heater section, then heat air for combustion in the air preheater and then heat feed water in the second feed water heater section.

3. A steam plant comprising a boiler, a flue for conducting products of combustion from said boiler, an air preheater interposed in said due, a `first feed water heater ysection in said flue., a second feed water heater section in said flue, means to supply feed water to said second feed water heater section, means to yconduct feed water from said second feed water heater section to said first feed water heater secien and means to conn duct feed Water from the first feed water section to the boiler, the arrangement being such that the products. of combustion first heat feed water in the first feed water heat# er section, then heat air for combustion 1n the'air preheater and then heat feed water in the second feed water heater section, the heat transmitting surface of the second feed water heater section having an area appreclably greater than the surface area ofthe first feed water heater section.

` 4. The method of'extracting heat from a stream of flue gases which comprises succes` sively extracting high temperature heat due to cooling by feed water, extracting intermediate temperature heat due to cooling by air and extracting lower temperature heat due to cooling by feed water.

5. A steam plant comprising a boiler, av iue for conducting products of combustion from said boiler, an air preheater interposed in said iue, feed water 'heater sections in said 'lue gases which .comprises passing said gases into heat exchange relation with feed waterfor a given length of time to extract high temperature heat, then passing said gases into heat exchange relationwith air to extract intermediate temperature heat and then passing said gases into heat exchange relation with feed water for'an appreciab y longer length of time than the aforesaid vlength of time to extract lower temperature heat.

' J OHNI-L SENGSTAKEN.

iue on each side of the air preheater, one of y.

said sections bein in'advance of said preheater and the oter of said sections being behind the preheater withrespect to gas iow through said iue and conduits connecting the feed water heater sections with each other and with the boiler and valves in said conduits providin vflow of feed `waterin parallel through t e feed water heater sectlons and to the boiler and in series thro h the feed waterl heater sections and to the oiler.

6. A steam plant'comprisin a boiler, a

flue forv condncting products o combustion from said--' boi1e r,` an 'air preheater interposed v in said Hue,` a first feed-water heater section in said flue, a second feed water heater section in said Hue means to supply. feed waterA water heater section, means to saidfrst feed to supply feed water t0 said second feed water heater section, means to conduct feed water from said second feed-water heater section fto said'irst feed water heater section, means to conduct feed water from said second feed water heater section to said boiler andmeans to conduct feed water fromv the i'rst feed Awater heater section tothe boiler, the arrangement l being such that the products-of combustion first heat feed water in the first feed waterA heater section, then heat air'for combustion vin the air preheate'r and then heat feed water in" the second feedwater heater section.

7. A.' steamy/'plant comprisin' a boiler, lav l iue for conducting products o combustion fromv said boiler, an air preheater interposed in said flue and feed waterheater sections in said flue o nv each side of the air preheater one of said sections belng 1n advance of sai preheater vand the other -of said sections being behindthe preheater with respect to gas How through said iue and the latter of said sections having a heat transmitting surface of appreciably greater area than the surface` area of the former section.

8. The method of extracting heat from

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