US2255086A - Fluid heat exchange apparatus - Google Patents

Description

Sept. 9, 1941'. c. u. sAvoYE FLUID'HEAT EXCHANGE APPARATUS Filed Sept. 14, 1938 2 Sheets-Sheet l .lolonono' lalanne' ...www1-0U.

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ATTORNEY.

Patented Sept. 9, 1941 UNiTsD r 2,255,086 runny nella: EXCHANGE e'rrAleA'rUs'v 'f Application September 14, 1938, Serial No. ,229,801

5 claims. y(ci. 122-4235) This invention relates to uid heat exchange apparatus operating at high temperatures. It is more particularly concerned with apparatus of this type in which heat is transmitted from a furnace which is fired by burning of fuel at temperatures above the fusion point of the ash ofthe fuel.

The invention may be considered as exemplified by a water tube steam boiler. Such a boiler has one or more banks of closely spaced tubes exposed externallyy to the furnace gases so that the uid within the tubes is heated. When the boiler furnace is provided withV water walls the steam may be generated in. the tubes of those walls, and when the steam pressure is high and ash particles in the gases from being soft enough to stick to the closely spaced tubes and obstruct the gas flow spaces between them. f

When the furnace temperature is higher than the allowable entrance temperature to the tube bank, as is good practice in the interests of effective combustion, the furnace exit gases-must be cooled before they reach the tube bank, and the means for cooling the gases must be such that there will be no excessive obstruction to gas flow by the collecting of slag or ash.

When the furnace gases approach a superheater tube bank they must be limited in their temperature to such a value that the superheater tube metal will not be overheated, `and the gases must be cooled to such a temperature range When previously they have had a higher temperature. In some cases, there is a bank of steam generating tubes in front of the Superheater forthis purpose, but in other cases they are not needed because of the steam generating capacity of the furnace water walls, and then the cooling of the hot exit'gases to the allowable superheater gas temperature` must be otherwise accomplished. Y

The invention relates to means for accomplishing the above indicated results, said means being of wide application to a variety of boilers including those with straight tubes between headers.

Other objectsof the invention will appear'as the following description proceeds. l

The invention will be described with reference to the preferred embodiments thereof which are shown inthe accompanying drawings. In the drawings: Y Y

Fig. 1 is a view vin the nature of a verticalsection lthrough-a steam boiler embodying the invention;

Figure 2-is .ai transverse section ron theline 2-2 of'Fig. 1, and looking'fin the direction ofthe arrows;

Fig. 3 is a transverse, Vertical sectionr on the section line 3--3 of Fig. 1, looking 'in the opposite direction, as indicated by the arrows;

Fig. 4 is a diagrammatic view illustrating another embodiment of the invention in transverse vertical ,sectionj Fig. 5 isa transverse vertical section on the line 5 5 of Fig.v 6; and

Fig. 6 is a vertical section through a boilerl employing the invention.

In carrying out'the invention there'are provided sets of watertubes such as those indicated steam by the reference characters lill-l5, inclusive, in

Fig.` 5,of the drawings. These tubes extend acrossthe furnace gas stream'` andfthey are connect'ed intothe boiler 'circulation tofand from the drum I8 so as tobe supplied with water for the generation of steam. K

The sets; of tubes lli-l5, inclusive, are arranged so as to cool the furnace gases and theyfare arranged in rows, with widespacesbetween the rows. 1 The tubesr of each set extend upwardly fromxthe cross header 20 (Fig. 1 and Fig. 6) and are bentso that their major portions provide a widely. spaced arrangement ,of longitudinal rows. The' outlet ends of these tubes extend upwardly and are connected to the uptake headers '22 as indicated in thedrawings, 1

kThe wide spacing of thesets or rows -of tubes lll-l5, inclusive, Vprovides gas bodies, radiating to allof the tubes withinV sight of them, and the greater the mean thickness of each gas body, or equivalent mean length of radiating rays, the greater willy be the hourly gas radiationl rate per square foot of tube surface.l The illustrative arrangement provides separate gas ,bodies of considerable mean thickness, so that the length of path ofgases radiating tothe widely spaced tubes andthe surfaces of such tubes receiving such radiation are such'that the'furnace gases are cooled to the temperatures required at the tube'bank 24 beyond thegas cooling, or slag screen tubes.

55 The Wide spacing of the tubes of the sets lll-l5,

increased thermal resistance and constant tube temperature. This action continues until the outer face of the slag accumulation reaches the temperature at which the slagis fluid. and runsA off by gravity. This xes a maximum thickness of slag on the sides of the tubes below the bank 24, and by making the horizontal spaces between these tubes a large multiple of this thickness,. a most substantial reduction of gas ow area is possible. l

In the installation indicated inI Fig. 6l ofA the drawings the furnace 30 is providedv with Water cooled walls such as those indicatedat 32 and 34, and it is fired by pulverized fuel burners 36 and 38. In the zone of the-furnace` adjacent the burners 36- and 38 thev walls of the furnace may be lined with ceramic refractoryv material held in place by the wall cooling tubes such as those-indicated. at 40 and 42. This burner zone 44 may have the' wall' tubes within that zone provided with metallic studs or other extensions welded-to the tubes anddistributed over the inner facesthereof in such a. manner asto maintain the ceramic refractory'material in position.

In the furnace-zone-abovethebur-ners 36 and 38 theV furnace walls may be lined with wall blocks secured to the wall cooling tubesandthe hopper 46 below the zone 44 may have its sides formed by metallic blocks secured. to the: wall cooling tubes and closing theV spaces 'between them.

The furnace gases pass upwardly through the furnace and into. the cavity radiation chambers between the sets of tubes Ill-I5 inclusive. These tubes are indicated.v as horizontally inclined: tubes extending` acrossfthe upper portion-of the furnace from the header. 20.. and enteringthe sectional headers 48l at theirlower ends. 'Ihe sectional headers 48 communicate with the outlet ends of the steam. generating tubes of. they bank 24, and these tubes are supplied with water at their lower ends by downtake headers 50. having. their upper ends inv direct communication with the water space of. the drumy I8. byV the conduits 52. The cross header. 20A is. supplied with water byv reason.` of its direct connection. with the lower ends. of the downtake headers, 50,. afforded. by the tubes 54. v

The upper ends of the sectionalheaders 48 are connected with` the steam spaceof. the drum I8 by the risers 56, the upper parts of. which form the horizontal. circulators. 58..

Irrthe particular installation indicated in Fig. 6 of the draw-ings the furnace gases pass upwardly beyond` the bank. of steam generating. tubes24in two parallel. passes 60 and 62. These passes are separatedv by abaiile 64 defined by. the upper row of. tubes. 66 of the bank. 24. tubes extend from the-tops of-'the sectional headers. 58 to an intermediate header 10.. which. is connected to the steam. spaceof thedrum I8 byy other tubes defining. the upper part of the baille 64.

V.A superheater 'i4A is: arrangedin. the gas, pass These.

60 and an economizer section 16 is positioned within the gas pass 62. Another economizer section 18 is disposed in the upper parts of the gas passes 60 and 62, and above this section dampers 80, 8l, and 82 are arranged so as to control the proportioning of the ow of furnace gases between the two parallel passes 60 and 62.

With reference to Fig. 2 of the drawings, it will be noted that the set I0 of slag screen tubes have their inlet ends bent laterally at different distances above the cross header 20. For instance, the second tube from the left, has its portion 92 bent to the left so that the steam generating portion 94 of that tube is in line with the steam generating portion 96 of the rst tube, andsimilarly the inlet portions of tubes 98 and IIJU are bent so as to bring their steam generating portions |02 and |84 into alignment with the steam generating portions of the lower tubes. A succeeding group of the screen tubes Hi8-H28, inclusive, are similarly bent so that. they may'form the set.. of tubes Hf. This arrangement is continued across the entire furnace.

Fig. 3 of the drawings shows the manner in which thescreen tubes comprising the sets Ill-I 5 inclusive are bent at their outlet ends. In a sense, the bends of these tubes are reversely arranged with respect to the bends of the.y inlet ends ofthe same tubes.

Fig. lindicatesthegas tight seal H0 between theheader 28 and the water'wall defined by the tubes 42. It also: shows a similar seal H2l at the opposite side of the'l furnace so as to prevent gas leakage between the water wall defined by the tubes 4Dv and the uptake headers- 48 above that wall. Both sealf constructions permit relative movement betweenthe water wallsI and the headersv 2Dfand 48;

Fig. 4- of` the drawings shows another arrangement of the screen tubes below the bank of tubes 24. In this instance, the screen tubes are arranged in rows I28-'l28,. inclusive, disposed. obliquelyfwith reference tov the direction of. fi'owA o the furnace gases.

While the invention has been described with reference to the particular? embodimentsshown in the drawings, it is to be appreciated'that. it is not limited to al1 off the details thereof. These may be modiedin different combinationswitliin the'scope of thesub-joined claims.

I claim:

l. In a water tube steam boiler, a furnace'iired with a slag formingfuel, a bank of spaced' fluid heating tubes extending across the flow of hot gases from the furnace, an uptake communicating with the discharge ends of the tubes, a downtake communicating with the inlet ends of the tubes, a cross header below said tubes, means connectingV the downtake with the header, and slag screenY tubes connected. to the header inA a row longitudinally' of' the header, said screen tubes having steam. generating portions extending in parallelism across the iiow of gases, at a position forwardly of said bank of tubesv andarranged in rows, in planes transversely related to the horizontal axis ofthe header, the ends. ofthe slag screen tubes remote. from` the header being bent upwardly toward the.uptake.

2`..In a water tube-steam. boiler, afurnace, means associated with the furnace for burninga slag forming fuel at temperatures above the fusion pointv of theash, and a bank of convection; heated tubes extending across the path of= thev combustion products passing from the furnace.;

the combination therewith of sectional uptake and downtake headers at opposite ends of the tubes of said bank, a cross headerl disposed at the downtake header side and at a level considerably below the lower ends of the downtake headers, tubular means connecting the lower ends of the downtake headers with said cross header, and slag screen tubes having their inlet ends connected to the cross header and their intermediate portions widely spaced and arranged in parallelism across the gas pass at a position between the rst mentioned tubes and the fur- IlaCe, Sad Slag screen tubes having upwardly eX- tending discharge ends communicating directly with the lower ends of the sectional uptake headers.

3. In a water tube steam boiler, a furnace, means associated with the furnace for burning a slag forming fuel at temperatures above the fusion point of the ash, and a bank of horiri zontally inclined tubes extending across the path of the combustion products passing from the furnace, the combination therewith of uptake and downtake header constructions at opposite ends of the tubes of said bank, a cross header disposed at the downtake header side and at a level considerably below the downtake header structure, tubular means connecting the downtake header construction with said cross header, and slag screen tubes having their inlet ends connected to w the cross header and their inclined intermediate portions widely spaced and arranged in parallelism across the gas pass at a position between the first mentioned tubes and the furnace, said slag screen tubes having upwardly extending discharge ends communicating directly with the uptake header construction,

4. In a water tube steam boiler, a furnace, means for burning fuel in the furnace, and a bank of convection heated tubes extending across the path of the products of combustion passing from the furnace, the combination therewith of uptake and downtake means at opposite ends of the tubes of said bank, a cross header in the nature of a tubular unit extending transversely of said bank of tubes and disposed at the downtake side and at a position below the downtake means, tubular means for connecting said cross header into the fluid system of the boiler, and other tubes having their inlet ends connected to the cross header and their intermediate portions arranged in parallelism across the gas pass at a position between the first mentioned tubes and the furnace, said other tubes having upright discharge ends leading directly upwardly to the lower end of the uptake means.

5. In a steam boiler, a furnace, fuel burner means associated with the furnace, means forming a gas pass leading from the furnace, a plurality of spaced and parallel groups of convection heated tube sections extending across the gas pass tc form a bank, the tube sections of each group being spaced from each other and arranged in an upright row, and means including integral extensions of said tube sections at opposite sides of the gas pass for connecting the sections intov the water circulation of the boiler, the integral extensions having straight upright portions disposed in upright rows at opposite sides of the gas pass, the axes of the straight portions being transversely related to the longitudinal axes of the associated sections.

CHARLES U. SAVOYE.

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