US1649121A - Furnace-wall protection - Google Patents

Description

Nov. 15, 1927.

H. KRElSlNGER FURNACE WALL PROTECTION 2 Sheets-Shet l Filed Aug. 2-3, 1923 INVENTOR WWA/555' A TTORNE Y mmm Www. v

H. KREISINGER FURNACE WALL PROTECTION Filed Aug, 2.5, 1925 2 Sheets-Shee'b 2 NVENTOR atented Nov. 1 5, 1927.

" NITED STATES I 1,649,12 PATENT OFFICE.

HENRY KREIINGER, OF PIEBMONT, NEW YORK, ASSIGNOR TO COMBUTON ENGI- NEERNG CORPORATION, OF NEW YORK, N. Y.,A CORPORATION OI' NEW YORK.

FURNACE-WALL PBOTECTON.

Application filed August 23, 1923. Serial No. 658304/ My invention relates to furnace Wall protection, and is more especially concerned with furnaces adapted for burning fuel in suspension, such as pulverized or powdered coal, or even oil.

deterioration or wasting away of the furnace walls through high temperatures and slagging; to prevent permanent fouling or incrustation of the wallslwith slaggy coating lo or other accretions of troublesome character; and to provide for prompt and easy removal of such refuse -deposits on the walls as may occur.

F or the sake of greater clearness, I have hereinafter explained my invention with special reference to the particular embodiment illustrated in the accompanying drawngs, wherein is shown a furnace with'powdered fuel burner directed downward into ae the combustion chamber adjacent one of the uprght walls of the latter. It will be understood, however, that the invention is not limited to the particulars f the embodiment here illustrated, but can be otherwise carried out and applied.

In the drawings, Fig. 1 shows a vertical section through a steam boiler furnace for burning powdered coal, with provisions for the application of my invention therein.

Fig. 2 shows a vertical section through the combustion chamber at right angles to Fig. 1, taken as inclicated by the line 2-2 in Fig. 1.

Fig. 3 is a fragmentary View of certain 3:, devices for removing. deposits from the furnace walls.

Fig. 4 shows a cross section at right angles to lFig. 3, taken as indicated by the line 4-4 in Fig. 3.

As shown in Figs. 1 and 2, the furnace combustion chamber 10 is a large, deep, unobstructed chamber, enclosed by upright walls that slope outward slightly, so that the chamber as a whole expands upward. One or more powdered fuel burners 11 are directed downward into the combustion space or chamber 10 near its front wall 12, through the roof 13. As shown, such a burner 11 comprises an inner fuel pipe or nozzle with circumjacent air intakes. Powdercd fuel with somewhat more than carrying air (preferably say, about of the total air required for proper combustion) is fed in or admitted through the burner 11, and is continually ignted by the heat of the front ll&

I aim to obviate rapid -completecombuston, and even, if desred,

wall 12 and of the furnace generally. Air additional to that entering at the burner 11 s (or may be) supplied through inlet openings 14 at various heights in the front wall 12, so as to afford sueient air to assure to form a cooling zone in the bottom region 15 of the chamber 10. The burning stream (of mingled air, fuel, combustible gases from the fuel, and products of combustion) descends in the front of the chamber 10 until its momentum is overcome by the upward draft through the boiler. It then bends upward and ascends through the rear portion of the combustion chamber 10, finally passing upward therefrom to the boiler heating surfaces. (Here and elsewhere, I have used the terms front and rear in reference to the regions where the furnace is fired and whence the products of combustion make their exit from the main combustion chamber, respectively.) The size and depth of the chamber 10, the contiguity of the downward and upward fuel streams, and their change of direction as described assure rapid and complete combustion :in the chamber 10; and high temperatures are developed.

The air admitted at the front wall inlets 14 may preferably be preheated. For this purpose, the combustion chamber walls may be built hollow With. a narrow space between the very highly refractory inner lining or curtain 20 and the outer shell 21, and the air may be passed through 'this intramural space on its way to the inlets 14,-thus ill) 'also cooling the walls somewhat, and reducing the loss of heatby conduction through them. In the present instance, extra wide courses of the inner lining 20 serve as septa to divde the intramural space into dampercontrolled and regulated horizontal ducts 22 at the levels of various inlets 14, as a means of controlling and regulating the distribution of this air over the lining 20 and to the inlets. Opposite the air supply openings 14 in the lining 21 are damper-controlled and regulated air intakes 23 in the outer shell 21, by means of which outside air can be admitted directly through the openings 14, in lieu of the heated air or in admixture -therewth, either to Supplement it or to regulate its temperature and assure adequate cooling in the zone 15. In the present 1nstance, the rear wall 24 of the chamber 10 is shown solid, without intersp aee or ducts 22, but with a correspndingly thcker nner lining of very'hg y refracto material. The relatively heavy incombust le resdue from the fuel falls or precptates toward the floor and toward the walls and 26 of the chamber 10, inya finely divided and molten condition. The refus`e partcles falling directly to the floor'25 encounter and pass through the ,cooling zone n the lower region 15. This cooling zone 15 ma be maintained either by an excess of ar a tted as already described, or by u water screen consisting of a bank of water tubes 27 (sloping upward toward the rear) at a suitable height above ;the floor 25,- or by both. In the coolingacne 15 (however t be maintained), the partcles are efi'ectually cooled belowfjuson or slag-forming temperature so that they do not run together into a solidmass-on the floor 25, but sim ly collect 'as' dust that can be easly suo ed out (or 'otherwise removed) at cleanout doors 28 at the rear. gQr they may be raked back and allowed ,to fall through a dump opening 29 ;in the floor 16 'at the rear. The screen 27 also absorbs 'radant heat from the subjacent deposit on the floor 25, and prevents rcfusion thereof by such heat from the region of combustion above the screen. The water tube boiler shown n Fg. 1 s

- of a familiar type, comprisinga transverse drum 30 connected to vertical front and rear headers 31, 32 themselves interconnected by banks of water tubes 33 inclined upward toward the rear. The water tubes 33 overle an opening in the top or roof `13 of the chamber 10, and the furnace 'gases take a crcuitous course' amongst them (as defined by the baflling shown, and indicated by the arrows) on their-way to the furnaceuptake and the stack. In the present instance the ends of the screen tubes 27 are connected into front and rear headers 34 and 35, which are themselves connected to the lower ends of the corresponding boiler headers 31 and 32 by downtake pipes' 36 at the front and by uptake means including tubes 37, headers 38, and pipes 39 at the rear.' Thus the water screen s connected into the' general .boiler circulation in parallel with thawater tubes 33, and acts to reinforce the circulation through the lowermostoftlfeglatter`.

The temperature& obtainjng jiithe 'com- 'bustion chamber 10 `abovethe cooling zone 15' are so great'that if no provisions were made to revent, a wall or nner lining 20 of even the most refradtory materials com mercially available would be-kept continually fused over its innersurface, and would run under the weight or 'drag of the molten refuse particles or slag continually passing from the flames to the walls and ad ermg. Also, it would be subject to scourng and erosion by the refuse-laden gas currents. Hence the refractory furnace walls or lining would be speedily destroyed,-except, perhaps, at the front wall 12, which is cooled and protected somewhat by the air admitted through its inlets 14. The deterioration would tend to be especially severe at the rear wall 24, owing to the sweep of the flames toward and over the latter as they turn upward and ascend.

Or, again, if the cooling of the inner lining 20 by the ntramural air circulation at 22 were suficiently eflective, the lining 20 might itself be kept from fusion, and instead acq'uire a coating of slag solid at the back, but fused and runny at its own exposed inner surface. Furthcr accretions of the refuse would then run down to freeze and build up in masses above the coolin zone 15. Such masses would remain an grow larger until forcibly brokenway and removed. This ac`tion, again, would be most pronounced at the rear wall 24.

Now I have discovered that such wastage and fouling difliculties of powdered fuel practice prior to my invention can be overcome by causing such refuse particles as adhere to the upright walls to assume or deposit in a readily removable form,-for in some places and under some conditions, many, at least, of the particles striking the walls may simply bounce ofl` without adhering, and so fall to the floor 24. Under suitable conditions, initial deposit structures of fragile mossy or whiskery character can be realized: in fact, formations so loose as to -be quite friable and even pulverulent. Such character or formation can be given the refuse deposits by cooling etfected substantially at the innermost wall surface as contrasted with mere ,cooling eflected be tweentle general planes of the innermost and outermost surfaces of the wall. (Cf. the ducts 22 in Fgs. 1 and 2.) In practice, a most favorable condition seems to be the maintenance of a cool gaseous skin or lining on the internal surfaces of the walls. It is not generally necessary to admit or maintain over the wall a special layer of outside air: on the contrary, cooling of the thin outermost layer of the combustion chamber atmos phere answers the purpose quite well.

-As here shown, the coohn is done by water tubes ranged along t e innermost wa'll surfaces of the chamber 10. At the rear, the vertical tubes '37 that carry the upward circulation from the water screen 27 are arranged substantially against the wall 25 inside; at the sides, vertical tubes 41 are arranged substantially against the walls 26 on the inside. At ther upper and lower ends, these side tubes 41 bend outward throughthe side walls 26 (like the upper ends of the rear tubes 37) and are connected to lower and updper headers 44, 45, which may slope upwar to the rear like the screen 4 At the front, the lower ends of the lower headers 44 are connected to the boiler drum 30 by downtake pipes 46; while to the rear, the upper ends of the upper headers are connected by uptake pipes 47 and doublefaced headers 48 into some of the horizontal return tubes 49 from the rear headers 32 to the front drum 30. 41 are connected into the general boiler circulation in parallel with the boiler tubes 33,-very much like the water screen tubes 27 and the rear tubes 37.

While consider-able variation is admissible or required under the various conditions of different installations, for that illustrated 3" to 4" tubes spaced 14" on centers represents fair practice for the tubes 27, 37, and 41.

lBy these tubes 37 and 41, therefore, a cool, thermo-protective gaseous lining of rather peculiar characteristics is maintained over the internal wall surfaces. First, this gaseous lining causes adherent refuse particles to depost on the rear wall 24 in easily removable forms, instead of in hard, adherent, runny-surfaced coating and mass formationsof slag,-as already mentioned above. Secondly, this gaseous lining. reduces the absorption of heat by the surfaces of walls 24, 26 that it protects,--besides, incidentally, cooling them somewhat from the inside. (In other words, the tubes 37 and 41 cool the inner wall surfaces indirectly,

through the thern'o-proteetive gaseous line lining is necessarily quite thin, owing to the vigorous, free sweep of the flames through the interier of the chamber 10, and especially over the area of the rear Wall 24. To the extent of its limited thickness, this thermo-protective lining is not involved in the conbustion, since it is at rather too low a temperature. owever, it is so thin and so stabilized (so to speak) by the friction and shelter of the walls 24, 26 and the tubes 37, 41, that its existence does not really affect the over-all ecieney of the furnace.

Where the cooling is especially thorough, or the sweep of the 'flames less vigorous, an even more favorable action than just stated will result: i. e., the refuse particles will all be so much cooled as to bounce ofi from the conbustion ehainber walls 'Without adhering at all, so 'that there will be no deposit. This 'is notably the case over the side walls 26; in the cornersof the combustion chamber; across the portion of the rear wall 24 behind where the flames are curving diagonally upward and-rearward, and the cooling efiects of screen 27 and rear tubes 37 overl`hus the side tubes lap; and toward the top of the back wall 24, i

idly. If this growth were allowed to go on i unchecked, the highly' thermo-insulatve nossy structure 'would eventually attain a' thickness between the tubes 37 such that the cooling eifect of the latter would be more or less lost. The deposit would then become harder and more cohesive, and would eventually begin to fuse and run at its inner surface,-just as in the case described above,-and runny masses of slag would build up above the cooling zone 15. Owing to the inherent weakness of the nossy structure, masses of the slag-surfaced deposit would from time to time break loose and fall to the floor 25,-always, of course, with the chance of lodging on the screen tubes 27 and interfering with the fall of refuse particles between them. In any case, the slagging at the inner surface of the deposit would prove objectionable and troublesome.

To obviate such` difiiculties, I prefer to remove the deposit more or less continually or periodically, before it attains sufiieient thickness to become runny at its exposed inner surface, or to assume any form more troublesome or difficult of removal than its initial one. This makes it a very easy Inatter to keep the walls clean; because initially the deposits formed under the influence of the cooling at the inner surfaces of the furnace walls are so loose and even pulverulent in structure as to be detached or precipitated with the utnost ease,-either in fragile, friable fragmente, or in a loose dust. It is not generally necessary to resort tocontinuous percussion or vibration of the furnace wall: the loose fo'nation may simply be periodically blown oti' the walls and thus dissipated,-very much as soot deposits are blown ofl' boiler tubes. ln many installatons (as already intimated), this need not be resorted toregularly except for the rear Wall 24.

In Figs. 1 to 4, a steam blower system 50 is shown for this purpose, comprising a lower header 51 with valved steam supply connection 52, individually valved vertical pipes 53 ranged across outside the rear wall 24 at intervals oorresponding to the spacing of the rear tubes 37, and rows of blower tubes 54 extending` through the wall 24 midway between the tubes 57. Asshown, there are three such tubes 54 to each pipe 53. At its inner end, each tube 54 is provided with a flat blower head 55 that lies snug against the wall 24, and has nozzle holes 56 arrangedto discharge along the wall surface, obliquely toward and along the cooling tubes 37. The angle of discharge may vary considerably: e. g., 22 or to the vertical, or even less.

The manner of burning the fuel has some bearing on the process described, for by virtue of the admission of only part of the air with the fuel and the balance at successive points, a long, soft flame results whichhas a. lower temperature than a, short, clear, white flame and therefore there is less heat transmitted by radiation as between the flame and any surface where there is deposit, and consequently the deposit'of the refuse in the rcadily 'en'ovable form described is facilitated. The use of water cooled tubes outs down the air necessary in excess of the theoretical, and thus decreases the volume of gases to be landled, and increases the efficiency and the amount of CO, in the stack gases.

What I claim is:

upright refractory furnace walls which consists in absorbing heat at spaced regions adjacent said wall by the indirect action of a cooling medium in order to cool the inter- V 1 2; The method of obviating fouling of upright refractory furnace walls which consists in absorbing heat at spaced regions adjacent said wall by the indircct action of a cooling medium in order to cool the intervenng spaces sufliciently to cool the molten refuse particles passing the-ethrough from the flame to the walls to 'such condition that they will adhere on lodging and assume a. friable,`mossy 'condition but will not form a solid mass, matntaining the deposit in such condition by the action of said cooling medium' and periodically dislodging t by blowing it off before the deposit has built 1. The method of obviating foulmg of out in the furnace to a point where it will run.- e

I In testimony whereof, I have hereunto signed my name.

4 HENRY KREISINGER.

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