US1739594A

US1739594A - Furnace protection

Info

Publication number: US1739594A
Application number: US692460A
Authority: US
Inventors: George P Jackson
Original assignee: COMBUSTION ENG CORP
Current assignee: COMBUSTION ENG CORP; COMBUSTION ENGINEERING Corp
Priority date: 1924-02-13
Filing date: 1924-02-13
Publication date: 1929-12-17
Anticipated expiration: 1946-12-17

Description

1360- 17, 1929. a. P. JACKSON FURNACE PROTECTION Original Filed Feb. 13, 1924 3 Sheets-Sheet v INVENTOR BY 45, 0.

WI 777555 w 1380- 1929- G.'P. JACKSON FURNACE PROTECTION Original Filed Feb. 13, 1924 3 Sheets-Sheet fINVE/VTOR 7 BY 6 l 9" MW ATTORNEV$ may be taken from the stack or chimney of a Patented Dec. 17, 1929 I UNITED STATES PATENT OFFICE GEORGE I. JACKSON, OF FLUSHING, NEW YORK, ASSIGNOR TO COMBUSTION EN GINEER- ING- CORPORATION, A CORPORATION OF',NEW YORK FURNACE PROTECTION Application filed IsebruarylS, 1924, Serial No. 692,460. Renewed May 9, 1929.

My invention relates tofnrnace protection, and is more especially concerned with furnaces for burning fuel in'suspension, such as pulverized or powdered coal, or even oil. However, the invention is also adaptable, in its broader aspects, to other types of furnaces, fired by automatic stokers or by hand. I aim to obviate rapid wastage or deterioration of furnace linings by excessively high temperatures; to provide against troublesome slag formations or deposits on the furnace walls and bottom in a novel manner, without the necessity for admission of air in any considerable excess over the requirements for complete combustion of the fuel; and to improve the furnace efficiency in other ways.

I have found that these and other'advantages can be realized by a cooling medium suitably introduced into the combustion chamber, so as to afford a cool layer or curtain over the areas requiring protection, or

even to lower the temperature of the furnace generally to a considerable degree.

I prefer an inert cooling agent, and especially fiue gases: i. e., products of combustion that have been sufficiently cooled for my purposes by contact with boilertubes, or with other heat-absorbing agencies. Such gases power plant, from uptakes or flues leading to the stack, or even from some point within a boiler itself where the gases have become sufficiently cool.

For the sake of greater clearness, I have hereinafter first explained my invention in connection with illustrative forms of pow- 'dered fuel furnaces wherein the fuel is admitted in a downward stream, and afterward described the application of the invention to a somewhat similar furnace equipped with one ormore side burners. It will be under.-

stood, however, that the invention is not limited to these particular applications and embodiments, but can be otherwise carried out and applied.

In the drawings, Fig. 1 shows a verticalsection through a steamboiler furnace for burning powderedcoal, adapted for operation in accordance with my invention.

Fig. 2 shows a vertical section through a furnace somewhat differently equipped for operation in accordance with my invention.

Fig. 3 shows a vertical section through a somewhat different type of steam boiler furnace, also adapted for operation in accordance with my invention.

Fig. 4 is a fragmentary sectional view, on a larger scale than Figs. 1-3, illustrating a somewhat different construction applicable to the furnaces shown in those figures.

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 4. i

The furnace shown in Fig. 1 has a large, deep, unobstructed combustion chamber 7 enclosed by upright walls that slope outward slightly, so that the chamber as a whole expands upward. It has an outlet 8 for productsof combustion from its upper region at the rear. One or more powdered fuel burners 9 are directed downward into the combustion space or chamber 7 near its front wall 10, through the roof 11. As shown, such a burner 9 comprises an inner fuel pipe or nozzle with circumjacent damper-controlled air intakes. Powdered fuel with somewhat more than carrying air (for example about to percent of the total air required for proper combustion, more or less) is fed in or admitted through the burner 9, and is continually ignited by the heat of the front wall 10 and of the furnace generally. This fuel may conveniently be supplied from an elevated bin 12 and a subjacent feeder 13. Air additional to that entering at the burner 9- may be supplied along the outer side of the descending flame and fuel stream, through damper-controlled inlet openings 14 at various heights in the front Wall 10. With the air entering at the burner 9, thissupplemental supply affords sufficient air to assure complete combustion,and may even, indeed, suffice to form a cooling zone .15 in the bottom region of the chamber 7, above, its floor 16, according to the now familiar practice with furnaces of this type. The progressive admission of this supplemental air prolongs the I draft in the chamber. It then bends upward and ascends through the rear of the chamber 7, and the products of combustion finally pass through the outlet 8 to the heating surfaces of the boiler 20, and ultimately to the uptake or flue 21 leading to the stack 22. (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 course of, the flames is about as indicated b the dash lines. Complete combustion (o stream line character) is obtained in the combustion chamber 7, and high temperatures are developed.

.The relatively heavy incombustible residue from the fuel falls or precipitates toward the floor 1 6 and toward the rear" and side walls of the chamber 7, in a finely divided and molten condition. The refuse particles falling directly to the floor 16 encounter and pass through the cooling zone in the lower region 15 and are there effectually cooled 1 below fusion or slag-forming temperature,

so that the do not run together into a solid mass on t e floor, but simply collect as a deposit of dust,-easily sucked out, or otherwise removed, at front and rear clean-out doors 23. The cooling zone 15 also absorbs radiant heat from the deposit and from above, and so prevents refusion of the deposit. The temperatures easily attainable in the combustion chamber 7 above the cooling zone 15 are so great that a wall or inner linlng of even the most refractory materials commercially available tends to become fused over its inner surfaoe and to run under theweight or drag of the molten refuse particles continually passing from the flames to the wall and adhering; also, the highly'heated walls tend to scour and erode under the action of the refuse-laden gas currents. Such tendencies are especially marked at the rear wall 24, owing to the sweep of the flames toward and against it as they turn upward and ascend; While the front wall 10 is in a measure protected by the cooling and deflecting action of the air admitted at its inlets 14.

As indicated above, I have found that these difficulties can be obviated, and various improvements in operation realized, by suitable introduction of a cooling medium into the chamber 7.. In Fig. 1, provision is made for doing this at the outer side of the ascending fuel and flame stream, by continually admitting a curtain or film of furnace gases at a multiplicity of inlets 25 dispersed over the rear wall 24. These inlets 25 are preferably sheltered (as against stoppage by refuse or slag striking the wall or running down it) close under shoulders or ledges 26, here shownzas marking the lower edges of a series of shingle-like upright surfaces of the wall 24, each overhanging the upper edge of that below it. In the present instance, the inlets 25 discharge downward, so that the gas film not only tends downward by reason of its relatively low temperature, but also by virtue of its initial downward momentum'as discharged into the chamber 7. The inlets 25- open at the roots of the shoulder 26 parallel with the subjacent wall surfaces, so that the gas issuing from the inlets acts very effectually to blow off refuse particles or dust from the furnace lining before it accumulates sufliciently to assume a troublesome, slaggy form, or to interfere with the gas discharge. For supplying the inlets 25 with flue gases, there is'a conduit 27 leading off from the uptake flue 21 and delivering, through branch pipes 28, into horizontal ducts 29 in the Wall 24 that communicate with the gas inlets 25. The conduit 27 may be provided with a centrifugal blower 31 as a means of sucking the gases from the flue 21 and forcing them into the chamber 7, so as to assure ample supply and downward flow over the furnace lining. As here shown, the rear wall 24 is built of a series of horizontal sections each containing one or more of the ducts 29 and overhanging the face of the section below it to afford one of the shoulders 26.

Besides cooling the refuse particles striking the wall 24 and the wall itself to the point where trouble from slagging or erosion will not arise, the downflowing gases admitted as'just described act to keep the flames sweeping upward at the rear of the chamber- 7 from impinging on the wall. Ultimately reaching the lower region 15 of the chamber 7 and spreading out over its floor 16, the gases help to maintain the cooling zone 15 at a suitably low temperature,-and may even, indeed, permit operation with just suflicient secondary air admission at the inlets 14 to assure complete combustion, or with admission of all the air required for this purpose at the burner 9. This continual supply of cool gases to the cooling zone 15 also prevents it from becoming a mere dead pocket of hot gas; and the relative (or even absolute) inertness of the atmosphere thus maintained at 15 serves to control the flame level 1n the.

chamber 7, and tends to prevent encroachment of the flame stream on the cooling zone. Mingling with the fuel and flame stream at every region of contact,'the flue gases act as a cooling diluent to reduce the flame temperature; and as the gases can be admitted in practically any amounts desired, the general furnace temperature can be controlled and reduced to a point where slagging or erosion cannot occur at any, of the walls.

The flue gases afford several advantages over admission of steam or a1r for like purposes, in that they are always conveniently available in ample Volume, and at a temperature low enough for the purpose, yet not so low as to require extreme nicety of regulation in order to guard against overchilling the furnace; in that they are inert, and hence cannot exert any effect as a supporter of combustion; and in that they-are already at a suitable temperature, without extra expenditure of heat on them.

Fig. 2 illustrates the extension of ducts 29 and inlets 25 from the rear wall 24 along the furnace sides and across its front wall 10. As here shown, the supplemental air inlets 14 are omitted from the wall 10, and all the air required for complete combustion is admitted at the burner 9. Thus the flue gases flowing down over the lining all around the chamber 7 are alone relied on to maintain the cooling zone 15 in the lower portion of the chamber.

Ample amounts of gas'can be admitted to control and reduce the general furnace temperature'to any degree desired.

Fig. 3 illustrates the employment of my invention in afurnace with a side burner 32 in its front wall 10. In the present instance, the furnace is associated with a Ster ling type of boiler instead of that shown in Fig. 1, and flue gas inlets are provided in the combustion chamber floor 16, and in,-

lets 25 in its rear or bridge wall 24.

As here shown, the overhanging rear wall sections are built up of a series of horizontal highlyrefractory courses forming the inner shell or lining of the wall 24, including extra wide courses 33 serving as septa between the gasducts 29. The outer shell or layer 34 of the wall 24 may be built up of ordinary fire brick, or of material even less refractory. As shown, there are upright buckstays 35 of I section at the outer side of the wall 24, with horizontal angle bar braces 36 secured to them at the levels of the extra wide inner courses 33. The inner refractory shell or lining is braced to the firm structure formed by

themembers

35 and 36 by attachment of the extra wide courses 33 to the braces 36, by means of U shaped ties or clips 37 engaged in suitable openings in courses 33 and members 36. The inlets 25 from the wall ducts 29 start as grooves in the upper sides of brick at the bottoms of the ducts and then extend downward through the thickness of these bricks, discharging just in front of and along the inner surfaces of the wall 24, as in Figs. 1 and 2. In Fig. 3, the brick with the inlets 25 are those next above the extra wide courses 33, and overhang the latter to form the shoulders 26.

As here shown, the furnace floor 16 is built in a step-like conformation, with riser shoulders 26 and gas inlets 25 extending up through the floor and discharging rearward from the shoulders along the treads. Thus the gas issuing from the inlets 25 blows rearward and prevents the falling refuse par ticles from blocking the inlets, and moves on rearward in a horizontal film or layer. I

Besides maintaining the cooling zone at 15 and alfording the rear wall 24 somewhat the same protection as in Figs. 1 and 2, the gases admitted at the

various inlets

25 and 25 mingle with the flames and reduce and control the general furnace temperature. Instead of being extended as in Figs. 1 and 2, the flame stream from the burner 32 is comparatively short and broad, merely dipping down somewhat below the level of the burner and then rising to the combustion chamber exit at 8. By the cooling action of the gases, the short flame is rendered soft like the long flame of Figs. 1 and 2, instead of an extremely hot,

White flame such as would ordinarily result from complete burning of the fuel in a short flame. Also, the flue gases modify the form of the flame, and thus shorten and spread it out, and reduce its tendency to impinge and beat on the rear wall 24.

Figs. 4 and 5 show a wall construction somewhat different from those shown in Figs. 1-3, but applicable to the furnaces there shown, and especially to walls of the furnaces shown in Figs. 1 and 2. As shown in Figs. 4. and 5, the brick outer shell 34 of Fig. 3 is replaced by an all-metallic hollow structure 40, comprising horizontal I beam members 36 with

metal plates

41, 42 secured against their inner and outer heads by C bent ties 43 that attach the wide wall courses 33 to the former and by hook clamps 44 engaging the latter. Thus the structure 40 affords horizontal air ducts 45 paralleling the gas ducts 29 and separated from them only by the thin metal septa 41, so that the air in these ducts 45 may be preheated by the gas in the ducts 29 At either side of the gas supply connections 28 (which are equivalent to the connections 28 from the conduit 27, shown in Fig. 1), the air ducts 45 are completely blocked off by upright partitions 46 extending between the I beams 36%, to afford passage for the gases from the gas openings 47 in the outer plates 42 to corresponding openings 48 in the inner plates 41. Air is admitted to the ducts 45 through. damper-controlled openings 49 in the outer plates 42 at either side of the gas connection openings 47, beyond the corre bered 14 in Fig. 1. Thus flue gases are admitted at numerous points, and dispersed over the wall lining in a downward moving curtain or film, while at the same time supplemental air for combustion is heated, by its passage around the furnace from the back to the front in proximity to the flue-gas ducts, and admitted to the furnace through the front wall.

As shown in Figs. 4 and 5, the gas inlets 25 start as grooves in the lower sides of the lining courses next above the extra wide courses 33, and then extend downward through the latter, opening in the same relation to the wall surfaces as in Figs. 1-3. The extra wide courses 33, however, overhang to form the shoulders 26.

In each of Figs. 2-5, various parts and features are marked with the same reference characters as corresponding ones in preceding figures, as a means of dispensing with merely repetitive description in -each instance.

I claim:

1. Themethod of lowering furnace temperature and protecting the furnace wall from erosion and slagging, which comprises continually admitting and maintaining a film of inert cooling medium thereover.

2. The method of lowering the temperature attained in a pulverized fuel furnace' and protecting its wall from erosion and slagging, which comprises continually admitting a film of flue gases at a multiplicity of inlets dispersed over the wall.

3. The method of protecting the wall of a pulverized fuel combustion chamber from erosion and maintaining in its lower region a cooling zone for falling refuse from fuel burned thereabove, so as to prevent slagging of such refuse; which method comprises continually introducing over the wall a downward moving film of inert cooling medium.

4. A combustion chamber wall comprising a series of horizontal sections each having a horizontal duct for cooling medium and overhanging the inner surface of that below, with discharge from each duct opening substantially vertically downward under the shoulder 'of its wall section.

5. A furnace wall constructed with a stepped inner surface, each step overhanging the wall surface subjacent to it, an inlet in each step discharging downwardly across said sub acent surface, and means associated with said inlets and delivering an inert cooling medium thereto.

6. 'A furnace wall constructed with a stepped inner surface, each step overhanging the wall surface subjacent to it, an inlet in each step discharging downwardly across sa 1d subjacent surface, and means associated with said inlets and delivering an inert cool- 1ng.med1 um thereto, said means including a connection from a flue gas passage.

signed my name.

GEORGE P. JACKSON.

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