US1676246A - Furnace-wall construction - Google Patents

Description

July 1o, 192s.

1,676,246 B. BROIDQ V FUmiAE WALL CONSTRUCTION v i AFilm June so, yms l :sheets-sheen r ATTORNEY.

Patented July 1go, 192s,

UNITED' s'l'ra'rlzs.'A PATENT OFFICE..

BENJAMIN BBOIDO, F NEW YORK, N. Y., ASSIGNOB, T0 '.lHESUPEBH-EATEB COMPANY, OF NEW YORK, N. Y. l

FUnNAcn-WALL coNs'rnuc'rroN.

vApplicatie nieu :une ao, 1925. serial no. 40,605.

My invention relates to furnaces and has particular reference to the type of furnace adapted to be used under steam boilers, and

in which one-orV more of the combustionchamber walls are lined either with water screens, or radiant heat superheaters, or both.

In modern installations of this character very large combustion chambers are provided, necessitating the placing'of the boiler at a considerable height above the grate level or the bottom of the furnace, and this latter consideration necessitates the use of high furnacewalls which are expensive to con-v' i struct. In structures of this type where the combustion rate 4is usually very hi h,J the walls of the combustion chamber or urnace are frequently lined with screens formed of heat absorbing tubes and my invention con- ,20 templates the arrangement of such tubes so that they will form-a lateral support for the furnace walls and thereby permit the use of a wall construction which is not only much lighter and' more inexpensive to construct than the usual form, but which may also be made in a readily removable form, so that easy access may be had to the tube structures for the purposeof repairs or replacement.

The tubes forming the screen lining the furnace walls are subjected to the intense direct radiant heat of the combustion chamber and as a consequence, the heat transfer rate through these tubes is relatively high as compared with the rest of the boiler. They are also subjected, in many cases, to accumulations of slag, particularly in installations where' the combustion rate is high'l and a considerable quantity of slag is carried up with the combustion gases. This condition is more particularly pronounced in cases where pulverized fuel is employed, as in such cases the slag particles, because of their minute character, are carried by the i combustion gasesin larger quantities than is thecase withyhand or Stoker fired coal burning installations. My invention con templates a structure which will tend to eliminate or minimize the trouble due to slag accumulation, which will in the case of water. screens improve the generating performancethereof, and which will also` rovide other and further advantages w 'ch will appearmore fully in connection with l the following detailed description of my invention.

As illustrative of my invention, I have shown in the accompanying drawings, a standard boiler ot the cross drum ty e, to the'furnace of which has been applied) both water screens and a radiant type superheater constructed in accordance with my invent1on.

Figure 1 is a diagrammaticelevation of the boiler setting with a portion of the casmg broken away toshow the position of the tu es.

Figure 2 is a diagrammatic vertical section taken along the lines 2-2 of Figure 1. Figure 3 is a section on an enlarged scale taken on the line 3 3 of Figure 2, and,

F1gure 4 is a section on an `enlarged scale taken on the line 4--4 of Figure 2, showing l a modified` form of wall construction.,v

Referring to Figure 2, the numeral l0,

indicates the drum of aconventional emes drum water tube boiler, connected in the usual manner by suitable circulators 11, with p the bank of generating tubes 12, and as the 'specific form of 'boiler to which my invention may be applied' is immaterial it is not believed necessa to describe the boiler in any detail. Therhoiler is shown as mounted above thev combustion chamber 13, which is of the type adapted for firing by means of a pulverized fuel urner shown at 14, although 1t is to' be understood that the invention is not limited to use with this method of firing, but maybe employed in connection with any of the known forms. In they embodiment shown, chosen for illustrative purposes only, the combustion chamber is rectangular in form and is provided with. water screens forming a lining for the two side Walls thereof, and withia radiant type super-heater lining the rear wall. It will be' obvious,v

however, that the invention is equally applicableto combustion chambers having curvi- "line'ar as well asy plane Walls, and `thatvthe l' |disposition Vof, either 4the water screens or superheaters or both may be varied with reference to the wall surfaces as the requirements ofthe individual installation dictate. Itwill be further apparent that the inclusion of both water screens and superheater in the combustion chamber is notessential to the susv A similar top or outlet header 17, which is.

also slightly inclined to the horizontal, is connected by means of a suitable up-ilow pipe 18 to the boiler drum 10, and the screen itself is formed by a plurality of parallel water tubes 19, suitably connected at their ends into the headers and 17. As heretofore pointed out, thev invention is concerned entirely with the specific disposition of the screen and as the particular manner in which the screen is connected into the Vboiler is immaterial, in so far as the invention is concerned, the necessary water circulation through the screen may be provided` by connection to some source other than that of the boiler, if desired, without departing from the scope of the invention. Headers 15 and 17' are preferably placed outside the boiler wall in order to remove the joints between the screen tubes and headers from exposure to the high temperatures existing within the combustion chamber and to make them readily accessible, but this position of the headers is not essential.

The superheater is constructed in much the saxnevmanner as are the water screens, comprising a bottom inlet-header l20, and an upper outlet header 21, the two headers being connected by a plurality of parallel tubes 22, forming the su erheater. The inlet header 20 is connected) with the steam space of the drum 10 by means of the steam pipes` 46 23 and 24, andthe superheated steam is delivered through the outlet 25 in the header 21. As in the case of the water screen and for the same reasons, the headers 20 and 21 are preferably, but not necessarily, placed outside the boiler casing.

In the exercise of my invention, the tubes forming either a water screen or superheater, instead of being placed placed at an angle to the vertical and slope inwardly over the combustion chamber. In

the form illustrated the projection of the tubes 19 as viewed in Fig.y 1 is vertical, but it vwill be readilyapparent that these tubes might e ually well be' placed at an inclination to t e vertical in this direction in addition to their inclination tothe vertical plane of the furnace wall indicated in Fig. 2. Likewise the tubes 22 are shown as lying in the plane of the paper in Fig. 1, but this is i also a matter of choice as these tubes may,

'per boiler wall section 27. As previously vertically, are

Lemme if1 desired, be inclined with respect to this ane.

The desired inclination may .be given to the tubes, while retaining the headers outside tlie furnace walls, in a number of 'derent ways, and I have shown two ways in which this 4may be accomplished. yIn Figure 1, I have shown the inclination accomplished by bending the tubes 22 outwardly at each end from an intermediate inclined section, so that the ends of the tubes may be joined to the headers out-side the boiler in any desired manner', such for example as that described in my Patent No. 1,363,713, issued December 28, 1920. In Figure 2, the inclination of the tubes of the water screen is accomplished by placing the lower header with its cross section at such an angle that the upper face thereof is at an angle to the horizontal, and the screen tubes which enter this face normal thereto, with respect to the plane of the paper in Figure 2, are consequently positioned at an angle to the vertical. Header 15 is preferably placed outside of the lower section 26 of the furnace wall, and as will bre noted from Figure 2, the inward inclination of the tubes will bring the upper ends of the straight portions thereof within the line of the upnoted, it is desirable to have the headers outside the boiler setting and in order'to make this disposition of the header 17 possible, the upper ends of the tubes 19, are curved,

as at 19, and enter the header 17 outside 100 the furnace wall. yIt will be readily understood, however, that various other forms of connections may be used to accomplish this result.

The Wall construction above and below the screen headers may be of any of the usual forms. The inclined screen tubes 19 or 22, however, make possible the use of a more advantageous form of wall over the area cov-l ered by the tubes, as the latter may be emllo ployed as a support against which the wall may be placed and held in position by gravity.

As indicated in Figure 1, this portion of the wall may comprise a number of refractory blocks or slabs 28 covered by an outer insulating covering 29 of any suitablematerial. A suitable supporting memberv such as the angle 30 serves to support the lowermost series of the sections which form this portion ofthe wall surface and which ,are supported laterally by the 'tubes 19 or 22. rlhe upper sections of this portion of the wall surface also receive lateral support. from the tubes and may either rest directly 125 upon the series of sections directly below or may rest upon additional transverse supporting members, similar to the angles 30. While it is not essential that this section of the wall be built up in separate units, such construction affords the advantage of ready removability for access-to the screen tubes 'in case repair or replacement of the latter 41S necessary.

In Figure 4 I have shown a modified form Y of wall construction las applied to one of the screens, although it will be obvious that this construction may also be applied to a superheater. In this form the tubes have interposed between them on the side away from the combustion chamber, a series of removable plates 31, of the type which vare described in4 myv copending' application Serial No. 752,374, tiled November 26, 1924.' This form of construction provides a continuous metallic wall against which af suitable 'refractory wall. may be supported in the manner just described in 'connection with Figure 1.

In the forms which I have illustrated the inclination of the tubes is shown as comparatively slight, but the amount of inclination is to bezdetermined in each case by specific boiler conditions where the application is made and it may be at 'a much greater angle than is indicated in the particular application shown herein. In any case, however,

the inclination of the screen offers 'a support for. the outer part of the wall, whereby the latter may be more readily andcheaply installed than is 'the case where the wall vmust be self supporting, and this construction furthermore admits more readily ofthe furnace walls being made in removable units. This feature is of great practical,

importance as with this 'construction the si'de walls may be made at a very considerable reduction in cost and the small and readily removable units of the wall, which are merely laid against the inclined tubes, afford easy access for the purpose of repair or replacement of any o f the tubes which may have been burnt or otherwise damaged.'

' The inclination of the side wall tubes, particularly in cases where a substantial inclination is employed, will zresult, in the cases Where grates are used and an incandescent fuel bed is positionedat the bottom of the furnace, ina better rate of heat transfer through the tubes than would be the case if they were vertical. as the radiant heat lwill strike the tubes in a line more nearly normalv to the surface thereof than would be the case will. instead of tending to flow in amolten 'condition down the length of the tubes, tend to drop from the lower surface thereof. directlyto the fuel bed,'or to the iioo'r of the combustion chamber.v` A f In addition to the advantages previously mentioned, which apply both to water screens -and the over-heating of the tubes, in the case of the superheater, is prevented by so locating or protecting the superheater that the amount of heat which the tubes can absorb is properly limited. 0n the other hand,l screen tubes, being water. lled and capable of absorbing heat at .a much higher Vrate than steam filled tubes, are usually placed where` the temperature conditions are eX- tremely severe. As a result, large quantities of steam are produced in these Vscreen tubes and the steam thus formed, displacing a portion of the water, which has a higher capacity for heat absorption and for which capacity the screen is designed, tends to cause the tubes to become overheated and in many instances burned.

By inclining the screen tubes, the steam, rising vertically as formed, will break away from the surface on the innerside of the tubes which is exposed directly to the combustion chamber, and travel upward through the outer portion of the tubes into'the outlos.

lower face of th'e screen tubes will also tend to preventthe formation of,v steam bubbles or pockets which, occupy the full cross section of the tubes, and which in moving up-v ward carry large slugs of water into the boiler drum. By minimizing this tendency to form steam pockets in the'tubes and instead, to discharge the steam in a more or less continuous column along the outer face of the tube, the discharge of large slugs of water from the screen linto the drum is reduced, and the`water level in the latter is thereby kept more nearly even than would be the case if a straight vertical screen were used.

I claim:

1. In l'combination a boiler,ysetting walls enclosing the boiler and extending therebelow to enclosea combustion chamber, there being an aperture in one of said walls, a

outer wall of refractory material resting upon said tubes, maintaining contact therewith by gravity, and closing said aperture.

2. In a boiler and furnace-setting, a wall comprising an upper section, a lower section space-d therefrom` and an intermediate por-V tion closing said space, saidintermediate portion comprising a plurality of upwardly inclined heat absorbing tubes, and an outer refractory wall portion resting upon said tubes and deriving its sole lateral support therefrom.

3. A boiler and furnace setting comprising a wall having an upper section, a lower section spaced therefrom, and an intermediate portion closing'sai-d space, said intermediate portion comprising a plurality of upwardly inclined heat absorbing tubes, top and bottom headers to which said tubes are connected, said headers being located outside the boiler setting, the exterior of said intermediate portion being formed of refractory material resting upon and laterally supported by said inclined tubes.

4. In a boiler and furnace setting a lower wall section, a header lying adjacent to and outside said lower section, .a plurality of heat absorbing tubes connected to'said header and rising therefrom at an inward inclination from the vertical, an upperwall sectionq a secon-d'header outside said upper sec-v tion, said tubes being curved outwardly at Atheir upper ends to connect to said second header, and a refractory wall resting upon and laterally supported by said tubes intermediate said headers.

5. In a boiler and furnace setting a lower wall section, a header lying adjacent toI and outside said lower section, a plurality of heat Lemme absorbing tubes connected into the top of said header and rising therefrom at an inward inclination from the vertical, an upper wall section, a secon-d header outside said upper section, said tubes being curved outwardly at their upper ends to connect into the side of said second header, and a refractory wall resting uponl and laterally supported by said tubes intermediate said headers.

6. In a boiler and furnace setting, a wall having spaced upper and lower sections, a pair of inclined headers outside said wall and adjacent sai-d space, a plurality of heat absorbing tubes connecting said headers and bridging said space, said ltubes being inwardly inclined throughout the major portion of their length, and a refractory wall closing said space and resting upon and laterally supported by said inclined tubes.

7 In a boiler and furnace setting, a wall having spaced. upper and lower sections, a water screen comprising a plurality of upwardly and inwardly inc-lined water tubes bridging said space, and a refractory wall resting upon and laterally supported by said inclined tubes, the portion of the wall supported by said tubes comprising a plurality of removable sections.

8.` In a boiler and furnace setting, a wall having an aperture therein located opposite the combustion chamber below the boiler, headers located adjacent the upper and lower boundaries of said aperture, a plurality of`

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