US2614541A

US2614541A - High temperature fluid heater

Info

Publication number: US2614541A
Application number: US716346A
Authority: US
Inventors: Wilbur H Armacost; David M Schoenfeld
Original assignee: Combustion Engineering Superheater Inc
Current assignee: Combustion Engineering Inc
Priority date: 1946-12-14
Filing date: 1946-12-14
Publication date: 1952-10-21
Anticipated expiration: 1969-10-21

Description

Oct. 21, 1952 w. H. ARMACOST ETAL 2,614,541

HIGH TEMPERATURE FLU ID HEATER Filed Dec. 14, 1946 INVENTORS Wilbur H. Armocost David Schoenfeld BY M IIEHW Patented Oct. 21, 1952 UNITED STATES PATENT OFFICE HIGH TEMPERATURE FLUID HEATER Wilbur H, Armacost, Scarsdale, and DavidM, Sehoenfe d, New Y rk, N- ssi ors, y

mesne assignments, to Combustion Engineering-Superheater, Inc., a corporation of Delaware Applioa'tion'llecember 4, 19%, Serial. No; 7 6 3.46. 1

3' Claims.

bust on or a m lt or y a com na on i b By so doing the product o combu n o not contaminate the fluid ing heated.- At pr s.- sures up. to about 50 lb. per sq. in. gage, and temperatures up to about 850 deg. FE, the art for accomplishing these ends is wellunderstood and developed, H wever, wh n it. is nec y toheat. fluids at pressures'of up to 450 lb per sq. in. absolute or higher to temperatures of 11300 deg. F. or higher, special precauticnsmust be observed. I p p v p These precautions have to do with the selection of materials comprising the tubes and headers carrying the fluid to be heated to secure proper strength and life at the elevated temperatures, the arrangement of the tubes of different materials in order to secure the greatest economy in design and construction, and the duality of the fuel or fuels used to provide the heat. Toheat fluids underpressur e to temperatures in excess of about 850 deg}. it is necessary to employ for the tubing heat resistant steel alloys in which the principal alloying components arevarying percentages of chromium and nickel.

Up to temperatures in the range 1100-1150 deg. F. the character of the fuel used does not become of importance. Above this temperature range, however, the character of the fuel is of the utmost importance since it has'been found that certain ingredients in the fueLsuch'aS sulphur which becomes a component of .theJfiue gases of combustion, react wlththenickel in such alloys. This combination with the nickel-reduces 2 In racticing this nv ntio e ivide th o a fl id h atine suriaoe. nto t o por ions; We n f e hefirst. portion to conven na su phu eontainiug products. of furuaoe u combustio and ther by bring h flu d e p tur up to some'given. value su h to 1.150 eg- R;

and We expose he sec d po i n to sub nthe strength, ductilityand temperature resistant properties of the. alloys to the...point where the original material's, now-modified, are no longer suitabieior the purpose intended Thus the life of the equinmenti's shortened to the point where it is no longer safe and must be dis arded or replaced. r It is an objectbfrthis invention to provide novel means for overcoming theabovedifliculty. other obj cts and. advantages. w l "b com apparent as .t edeser ntion hereof proceeds.

or the-drawinssbigures 1,2 and arevertical br s seotion f through. uid h t t a ,eorporate illustra egforrns o thei vention, and Figure 4 is a cross-s cti n through one oi the hes-tens fluid conduits,

daily s lphuree furna e c bus on gases and the eby fu her raise th luid. temperatur to 30.0 d g F, or h e rhe here-disclosed emodime t of th s ar ang ment ifeoti el avo deteriora i o he heat-resis an al y stee in the fluid heater parts due to high-tempera. ture combination of certain combustion-gas ingr n uch as s phur) with nic e or o er ingredients of the alloy.

InFigure 1 there is shown a first furnace I compr n com ustio cham e W ls 2 an provided with a burner or burners 3 for intro ducing a fuel, such as pulverized coal, to be burned within the furnace for the'production of combustion gases that contain sulphur in customary amounts. This. first furnace is provided with an off-take 4 surrounded by upper walls. 5. In the illustrative arrangement shown the offtake- 4 terminates in an ir heater 6 of thetubular form in which the gases pass upwardly through a multiplicity of tubes 1 arranged in parallel, while the air for combustion to be heated enters through duct 8, passes aroundtubes. I and leaves thr u h du t 9- The r he e bi en l s d b walls I 0 which. Connect to flue ll. Flujell is provided with a branch duct l2,

he pparatus of Fi ure 1 further include a se nd ur ac I surrounded by walls I and p v e Witha burn or burners for .intro-,

uoine fuel, s h as il or natur wh ch heated air from theair heater 6 to therespemtive burners 3.. and. i 5 of both furnaces I- and i 3; and each of these two furnaces is provided with a nozzle. I! connected to a duct l8v which in turn is connected to duct I9 for conducting flue gases from the flue H tn said nozzles.

The fluid to be heated is delivered to header .2!) from which it isbarried through a multia plicity of parallel tubes 2| (here represented diagrammatically but each having the circular contour shown in'Figure 14;) upwardly along a wall 2 of furnace 'l oppositejthe burners 3 thence across the top of furnace, I and back to header 22. Qbviously'some tubesmay-b arranged along the side wall of the furnace. From header 22 the fluid passes upwardly through conduit or conduits 23 into header 24. From header 24 a multiplicity of parallel tubes 25 (again shown diagrammatically but actually having the Figure 4 contour) conduct the fluid through offtake 4 in a number of sinuous passes back and forth thereacross to header 26. From header 25 the fluid is conducted via conduit or conduits 21 to header 28. From header 28 it passes through a multiplicity of parallel tubes 29 (each again of the Figure a contour) which pass across the roof of furnace l3 thence down and up along wall Hi of said furnace l3 opposite burners l to header 3!). From header 3E] fluid is conducted by a conduit 3| to the point of use.

In operation of the Figure 1 apparatus, the fluid tubes 2! and '25 in the first furnace receive from the sulphur-containing combustion gases therein heat only suflicient to raise the fluid temperature (as at header 26) to not higher than some given range such as 1100 to 1150 deg. F. Below this temperature range the combination of combustion-gas ingredients (such as sulphur) with nickel and other ingredients of the alloy-steel tubes is not objectionable.

Fluid tubes 29 in the second furnace l3 further extract from the sulphur-free combustion gases therein more heat which additionally raises the fluid temperature to 1300 deg. F. or higher.

This flexibility is accomplished by providing a number of by pass circuits enabling the operator to control the flow of fluid through some of the heating surfaces. Accordingly a by pass is provided by conduit 34 to by pass heating surface 2| and by conduit 3! and by tubes 2|a to by pass heating surface 25. There is also provided a by pass by

conduits

38 and 36a to by pass only a portion of heating surface 25.

Thus in Figure 2 the basic arrangement of furnaces and I3 and air heater for combustion air is the same as in Figure 1. The arrangement of the fluid heating tubes 2|, 25 and 29 which are connected serially in Figure 1 are in part connected in parallel or in series-parallel in Figure 2. The fluid to be heated enters header through conduit or conduits 32 provided with valve 33. A branch from conduit or conduits 32 conducts a portionof the fluid through a valved conduit or conduits 34 to header '24. From header 20 a portion ofthe fluid passes through a multiplicity of parallel tubes 2| along a wall of furnacel to header 22.

From header 24 the remaining portion of the fluid passes through a multiplicity of tubes in the ofltake 4 downwardly through one group in counter flow with respect to the rising gases from the furnace thence through another group upwardly in parallel flow to the. gases to header which are in counter and parallel flow. A multiplicity of tubes 2|a from header 35 pass across the top of furnace I to header 262' From header 26 the fluid heating tubes 29 are connected to

headers

26, 28 and 3|] and are arranged the same as in Figur 1.

By closing connection 38 and opening connection 3?, portions of the fluid to be heated flow in parallel from intake conduit 32 to header 23 via tubes 25 and via tubes 2| and 2|a. By opening connection 38, closing connection 31 and removing tubes 2|a, portions of the fluid to be heated flow in parallel from intake conduit 32 to tubes 36a via the counterflow group of tubes 25 and via tubes 25. Thereafter the parallel flowing fluid portions join at the junction of

tubes

25 and 36a and flow together through the remaining parallel flow group of tubes 25 to header 2%. Optionally the valves may be omitted and the resistances through the circuits so balanced that the desired flow of fluid is obtained through the respective tubes 2|, 2| a and/or 25.

In Fig. 3 is illustrated a third arrangement of an apparatus for practicing applicants impoved method of heating fluids to a comparatively high temperature. The Fig. 3 variation is again an improvement over the basic form shown in Fig. l. The distinction between Fig. 3 and Fig. 1 is three fold; first, an idle pass 39 is provided between heating surfaces 2| and 25; second, provision is made for the heated fluid to flow in a parallel flow relationship through heating surfaces 2| and 25 instead of in a serial flow relationship as shown in Fig. l; and third, air instead of gasis used toestablish a blanket between heating surfaces 2| and 29 to protect same from direct flame impingement of the hot flame issuing from burners 3 and I5 respectively. The two first named distinguishing features are designed to afiord a closer control over the flow and temperature of the heated fluid and to result in a more thorough mixing of combustion gases (coming from duct l9, furnace and furnace I3) in idle pass 39 before passing over heating surface-25. 7

Thus in Figure 3 furnaces and I3 are arranged as in Figures 1 and 2 and again interconnected by conduit 16. The offtake from furnace delivers the'products of combustion into an idle pass 39 from which the products pass through offtake 4, the air heater for combustion airii andv flue As in Figure 1, the hot air leaving theair heater 6 passes through duct 9 tothe burners 3 and I5. A branch duct 9a from duct 9 delivers air to a duct 91) which in turn is connected to each of the nozzles IT. The branch duct l2 from flue connectsvia duct l9 directly-into the furnace pass 39.

Inthis Figure 3 organization the fluid to be heated passes through the fluid heating tubes 25 and "2| in parallel, that portion passing through tubes 25 from header 24 discharges into header 28a, thence passes via conduit or conduitsZBb to header 26 and the remaining portion passes through conduit or conduits 32 and valve 33 to header 20 and thence through heating tubes 2| to header 26.' Leaving header 25 the two fluids join and pass through conduit or conduits 2'! to header 28, through heating tubes 29, to header 3B and through conduit or conduits'3l to the point of use.

By the arrangement shown in Figure 3 the products of combustion leavingthe furnace I may be-t'empered within the down pass 39" by admixture of flue gases delivered through duct l9 into said pass. In the Figure 1 organization such tempering may be effected by taking a branch duct 9a off of duct |9 which delivers flue seses itc't tqp ef furnace lthroush openings 11911. is al t-mean of-admltting the temperpl -r g gases, however, is not aseffective-asthat sh w -i F ure 8.

in the Figure 3 "organization 'l-ivered from duct 9 via ducts 9a and 9b to the nozzles H. In Figure 1 flue gasesare admitted to the nozzles l1. In either case, whether heated air or flue gases are used, the nozzles H function to throw a "blanket ofrelatively cool gas or air across the surface of the heating tubes 2| and 29 to shield them against direct impingement of the hot flame leaving the burners ,3 and l5. Preferably hot air is so passedthroughthe nozzle l1 discharging into furnace It? so as to avoid the impingement of a sulphur-containing gas onto the tubes 29 therein "or to dilute it a.

all of the foregoing organizations of Figs. :1, 1.2 nd 3 th total amount of h at su face for heating the fluid is divided 'soglihat that .DQrtion of the-heating surfaces (tubes25, -2l and May in whicht flu is br h 1 p to th ap rox ma temperature range of 1100-1150 deg. F, may be heated by the products of combustion of fuels burned-in the first furnace 1| that may contain appreciable quantities of sulphur and that portion of the heating surface (tubes 29) in which the fluid is heated from the aforementioned temperature range up to temperatures of about 1300 deg. F. or higher is provided with heat from the products of combustion from fuels burned in the second furnace I3 containing substantially no sulphur.

By this unique arrangement deterioration of heat-resistant alloy steels from combination with sulphur (or other ingredients) from the fuel with nickel (or other ingredients) in the alloy is avoided as earlier indicated. It will be evident, moreover, that the flue gases from the second furnace may be discharged into the first furnace at any convenient location; also that the two furnaces may be combined into a single setting adjacent to each other, or may be separate if desirable.

For steel alloys resistant to higher temperatures greater percentages of chromium and nickel are used than for similar alloys resistant. to lower temperatures. As a result the prices for the alloys resistant to higher temperatures are higher than the prices of alloys resistant to lower temperatures. The arrangement using two furnaces and two fuels to provide longer life of the alloy materials also permits arrangements of heating surfaces and selection of materials therefor in order to use the least amount of expensive alloy material and the greatestamount of inexpensive alloy material to accomplish a given result. v

Also in the accomplishment of these ends the disposition 'of the heating surfaces may be such that some of the heat is imparted to the surfaces by radiation and some by convection from the flue gases of combustion flowing over the surfaces, or by a combination of these two means.

The gases of combustion may flow over the tubes in relation to the fluid flowing through the tubes eitherin countercurrent, in parallel, or in a combination of countercurrent and parallel flow, in order to take advantage of the tempering differential existing between gases of combustion and'fluid being heated to hold the temperature hot as is' de- 3'6 an; commands-and airmay be*made' without ide- 1.11 1 a method for heating a fluid under pressure to an elevated temperature in a heat exchanger fabricated of material including heat resisting and nickeksteel alloytubing and-exposed in part-to-combustion gas containing sulphur ingredients which at metal temperatures below a.; given range fail to substantially affect 'the nickel contained 'in said alloy-tubing but which -at metal temperaturesabove-said given range -en ter into 'a =-ehernical reaction with the nickel contained "in said alloy rendering said alloy-tubing unsuitable for service under high pressure and high temperature conditions; the stepswhich comprise flowing said fluid through the nickel-steel alloy tubing of a first portion of said heat exchanger while exposing said first portion tubing to said combustion gas sulphur ingredients, the cooling action of said fluid serving tomaintain the metal temperature of said first portion nickel-steel alloy tubing below said given range whereby, said combustion gas sulphur ingredients are; substantially prevented from entering into chemical reaction with the nickel contained in said first portionalloy tubing; and flowing the partially heated fluid from said first portion tubing through the tubing of a second portion of said heat exchanger while exposing said second portion alloy steel tubing to combustion gas that is substantially free of the aforesaid sulphur ingredients and at elevated temperatures causing the metal temperature of said second portion alloy tubing to rise above 'changer fabricated of material including heat resisting and nickel-steel alloy tubing and exposed in part tocertain combustion gas containing sulphurous compounds which at metal temperatures below a given range fail to substantially affect the nickel contained in said alloy tubing but which at metal temperatures above said given range enter into a chemical reaction with the nickel contained in said alloy rendering said alloy tubing unsuitablefor service under high pressure and high temperature conditions; the steps which comprise flowing said fluid through the steel tubing of a. first portion of said heat exchanger while exposing said first portion tubing to combustion gas containing sulphurous compounds, the cooling action of said fluid serving to maintain the metal temperature of said first portion steel tubing at a degree which is below said given range; and flowing the partially heated fluid from said first portion tubing of the metal in the tubes to a degree suitable to through the tubing of a second portion of said heat exchanger said tubing being composed of heat resisting nickel-steel alloy while exposing said second portion alloy steel tubing to combustion gas that is substantially free of any sulphurous compounds and at elevated temperatures causing the, metal temperature of said second portion alloy tubing to rise above said given range whereby said combustion gas is substantially prevented from affecting the strength and heat resisting qualities of said second portion alloy steel tubing.

3. In a method for heating a fluid under pressure to an elevated temperature in a heat exchanger fabricatedof material including heat resisting and nickel-steel alloy tubing and exposed in part to certain combustion gas containing sulphurous compounds which at metal temperatures below 1l00-1150 F. fail to substantially affect the nickel containedin said alloy tubing but which at metal temperatures above 1100-1150 F. enter into chemical reaction with the nickel contained in said alloy rendering said alloy tubing unsuitable for service under high pressure andhigh temperature conditions; the steps which comprise flowing said fluid through the nickel-steel alloy tubing of a first portion of said heat exchanger while exposing said first portion tubing to combustion gas containing sulphurous compounds, the cooling action of said fluid serving to maintain the metal temperature of said nickel-steel alloy tubing below 1100-1150 F. whereby the sulphurous compounds in said combustion gas are substantially prevented from entering into chemical recation with the nickel contained in said first portion alloy tubing; and flowing the partially heated'fiuid from said first portion tubing through the tubing of a second portion of said heat exchanger while exposing said second portion alloy steel tubing to com-- bustion gas that is substantially free of any sulphurous compounds and at elevated temperatures causing the metal temperature of said second portion alloy tubing to rise above 1100-1150 F. whereby said combustion gas is substantially prevented from affecting the strength and heat resisting qualities of said second portion alloy tubing.

WILBUR H. ARMACOST;

DAVID M. SCHOENFELD.

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

UNITED STATES PATENTS Number Name Date 1,342,073 Trinks June 1, 1920 1,936,699 Weaver Nov. 28, 1933 1,979,639 Robber et al. Nov. 6, 1934 2,041,364 Miller May 19, 1936 2,090,504 Schutt et al. 1 Aug.- 17, 1937 2,103,719 Harnesberger Dec. 28, 1937 2,146,497 Barnes Feb. 7,1939 2,174,663 Keller Oct. 3,1939 2,288,749 Schulze July 7, 1942 2,333,331

Oberstad Nov. 2, 1943