US2239662A - Furnace - Google Patents

Description

Ap E. G BAILNEIY FURNACE Original Filed June 23, 1925 fr /12 4650/16 2 5 07. fi%m flficwzziy Patented Apr. 22, 1941 OFFICE FURNACE Ervin G. Bailey, Easton, Pa., assignor, by mesne assignments, to The,Babco'ck & Wilcox Company, Newark, N. J., a corporation of New Jersey Application June 23, 1925, Serial No. 29,010 Renewed April 6, 1931 11 Claims. This invention relates to furnaces and is shown embodied in the construction of the walls of boiler furnaces with a view to increasing the durability of such walls while maintaining proper temperature conditions for efficient combustion of the fuel. Other embodiments or applications of the invention are also shown having a similar or analagous purpose in view.

Much trouble has been experienced, especially in large furnaces and where pulverized coal or liquid or gaseous fuel is used, owing to' the rapid destruction of the walls by the high temperature and high velocity of flame travel, as well as the rapid destruction or burning out of tubes or metallic parts of the boiler located in the .more exposed places.

Constructions have been devised with a view to overcoming or mitigating this objection in the wall construction, among which is the emtionable for other reasons.

l'his objection is overcome by the present invention in which water circulating lining tubes are provided with numerous projecting ribs, studs, or blocks secured to the tubes, preferably integrally, as by welding, these projections serv ing as an anchorage or means for holding a covering of refractory material which may be applied thereto in a plastic condition or otherwise. forming a layer or covering which constitutes the inner or exposed face of the wall which is directly subjected to the effect of the combustion going on in the furnace.

The said refractory covering is of much lower heat conductivity than the metallic walls of the circulating tubes and furthermore increases the thickness of material between the surface exposed to the heat and flame. and the water or 1 face of the tubes when directly exposed, and a sufilciently high temperature for u effectivecombustion is thus attainable, while the masonry wall at the back of the tubes is equally well protected, and the tubes themselves are protected from the burning effect of the combustion in the furnace.

By this construction the temperature of 'the inner face of the furnace wall may be maintained about as high as the refractory material can withstand without melting and wasting away, and the slag from the melting ash tends to accumulate and become united to the tubes or refractory material thereon and may in some cases serve to provide the requisite refractory covering for the tubes.

fractory material upon said metallic surface may be applied to furnace structures already erected, the projections being-united to the tubes, or other metallic containers, while in the furnace by spot welding, for example, or by a mechanical connection or fastening where feasible. rho invention may also be employed in new structures, in which case a simpler and a less expensive wall may be made than the usual wall composed of masonry built outside of the tubes.

The invention is also applicable to portions of a steam boiler and furnace construction other than the furnace walls, as for example in connectioii with certain of the circulating portions of the boiler proper which are excessively exposed to the fire. The invention ,'iS also applicable to the wholeor any part of either the floor or roof of a furnace. Hence; it is to be understood that the term wall, in the appended claims, unless otherwise limited, connotes any part of the enclosing boundaries of a furnace chamber,

Fig. 1 is a sectional plan of a furnace wall embodying this invention, showing an example of a construction which may be employed in new installation;

Fig. 2 is an elevationof the front. face of the wall shown in Fig. 1, being the face which is exposed to. the fire at the inside of the combustion. chamber Figs. 3 and 4 are similar views showing the embodiment of the invention as it may be applied to furnaces already erected of the type in which the walls are composed of circulating water tubesancl masonry;

Fig. 5 is a sectionaiplan of another modifica tion of the construction in-which the walls are composed of water tubes and masonry;

Fig. 6 is a detail view illustrating a method of forming the illustrative studs;

Fig. 7 is a sectional plan showing a modification of the construction indicated in Figs. 3 and 4 of the drawing.

In the construction shown in Figs. 1 to 4 and ,7.

the circulating tubes 2 are of a kind which has monly constructed at the outside of the tubes, as

indicated at 4 in Fig. 3, and act to protect said masonry from attaining a sufliciently high temperature to cause rapid deterioration.

In order to prevent too great cooling of the inner surface of the furnace wall, which results in inefficient combustion of the fuel, and may be otherwise objectionable, the said tubes are, in accordance with the present invention, provided with a plurality of metallicextensions or projections such as ribs, studs, or blocks 5 which, as shown in Figs. 1 and 2, are also provided on the fins 3, said blocks being preferably integrally united with the walls of the tubes and to thefins by welding.

Said metallic extensions or projections 5, serve as means for holding a covering or lining of refractory material upon the surfaces of the tubes at the inside of the furnace, as indicated at 6, which material having a rate of thermal conductivity lower than that of the walls of the tubes 2 and also aifording additional thickness of material between the inner exposed face of thewall and the cooling medium circulating in the tubes 2 permits the temperature at the inner surface to rise to a point at which the effective combustion of the gases and fuel material impinging against said surface is not impaired.

At the same time the protectionaflorded to the masonry portion 4 of the wall is equal to or greater than that afforded by the naked tubes alone.

tions are shown as mechanically connected to the fins 3 by having shanks or stems driven or screwed into holes formed in the fins to receive .them.

This construction enables the temperature at the inner face of the wall to be very materially increased as compared with that attainable when the surfaces of the tubes and fins at the inside of the combustion chamber are exposed directly to the fire, and the refractory material 8 which is securely anchored by the projections to the fins 8 of the tubes may be extended fully overt e tubes, or a refractory covering will in some cases accumulate and build upon the said tubes, as hereinafter explained; The refractory covering applied and held as in the construction shown in Fig. 5 will enable the temperature at the inner surface of the wall to be greatly increased and will in many cases meet the requirements satisfactorily.

I The construction shown in Figs. 1 and 2 is such as may be employed where the invention is to be embodied at the outset in new construction. In such cases the tubes may be provided with anchoring projections ii on their outer surfaces similar to the projections 5 and, as shown. longer projectionslf, 53 are applied to the fins and extreme outer portion of the tubes, all of which projections 5!. 52, it serve as a secure anchorage for the wall material Ill which may be any suitable concrete or mortar applied in plastic condition by spreading over or moulding upon the outer sides of the tubes and fins with their anchoring projections.

At the right hand portion of Figs. 1 and 2 the anchoring projections ill are shown as in the form of ribs which 'in some cases may be more desirable than the round pin form of projection 7 shown at the left hand in Figs. 1 and 2 or the pyramidal form shown in the other figures.

In Fig. 5 construction similar to that already described is shown, except that the tubes 2 in this case are not provided with longitudinal fins such as are shown at 3 in Figs. 1 to 4 and '1, and the masonry wall, or a portion thereof, indicated at I may be of a more refractory material than that required for and commonly used in the outer masonry walls such as indicated at l in Fig. 3 in connection with the circulating tubes provided with longitudinal fins 3 which fins not only serve approximately to close the spaces between the tubes but also to enhance the conduction of heat away from said space to the tubes and the circulating material therein so that the masonry at the back or outside of said fins does not acquire so high a temperature as the masonry indicated at I in Fig. 5.

The cooling medium in the tubes will serve to conduct the heat from the refractory coating and the tube walls sufliciently rapidly to enable the refractory material to withstand the action of the fire without destruction, but the temperature at the surface of the metal will be substantially less than when exposed directly to the fire and oxidizing or chemical action on the metal will be prevented so that the metal surfaces will be adequately protected against burning out.

In order better to serve their pu pose as an anchorage for a coating of refractory material the said projections may be made tapering, or of approximately frusto-pyramidal shape, as shown, and applied with their smaller ends againgst the surface of the tube, thus having a dovetailing or interlocking action in conjunction with the refractory coating.

As shown in Fig. 6, the projections may be cut from a bar with the shearing planes at a slight angle to the length of the banand with the inclination alternating from out to cut.

The refractory material may be applied in plastic condition, and any suitable refractory compound or material such as commonly employed for thebricks of refractory masonry may When the tubes with their projections .are un- 7 covered, or have only a comparatively thin covering of refractory material, the slag from the ash in the fuel will accumulate and will itself form a suitable coating upon the' tubes to produce the temperature conditions required, the rapidity and effectiveness of this action varying somewhat according to the nature of the fuel being used, so that it is not in all cases necessary to apply a coating of refractory materialto the tubes before the furnace is put into operation, although such building of a refractory coating from the slag and its eillcient adherence to the tubes and "blocks is enhanced by a preliminary covering of suitable refractorymaterial on the tubes.

After the furnace is in operation there will be to a greater or less extent an automatic adjust-- ment of the thickness of the refractory covering upon the metal containing the cooling circulating medium, since if the covering becomes too thick the temperature will exceed the melting point, or

will result in a wasting away of the material at the exposed surface until it is reduced to a thickness at which the cooling effect of the circulating material reduces the temperature of the exposed surface to a point at which the fusion or softening and wasting of the material is checked. On the other hand, when the coating of refractory is comparatively thin the lower temperature at-its surface results in the congealing and accumulation of slag material from the ash which increases thethickness of the covering until the temperature is reached at which particles of molten ash no longer adhere to and accumulate on the lining material.

Whether the refractory material is originally applied in plastic form upon and between the tubes or is deposited thereon from the products of combustion, or is applied in any other suitable way, the conjoint or cornbinative effect of the tubes with their projections, with or without fins in the spaces between the tubes. and the coating of refractory materialsecured upon the tubes or other metal containing aheat abstracting me dium and effectively anchored to the metal by the projections, is to produce an effective wall, or an eiiective inner wall or lining for the usual masonry wall having the effect of adequately protecting the masonry portion and refractory covering from the wasting effect of the. combustion, while at the same time maintaining a high temperature at the surface exposed to the fire so that the eiflciency of the combustion is not impaired by the cooling action of the medium which protects the structure from the destructive effect of the fire. I

I claim:

1. A wall comprising a plurality of spaced tubes, pins on saidtubes, a sheet of continuous slag extending across and between said tubes and embedding said pins whereby they cooperate to keep said sheet in place. 4

2. A wall comprising a plurality of spaced tubes, pins on saidtubes, and a sheet of continuous slag extending across and between said tubes, and having reverse bends therein and embedding said pins whereby they cooperate to keep said sheet in place.

3. Fluid heat exchange apparatus acting as a embedding the projections to am a shield between the tubes and the burning fuel, the projections acting as supports or anchors for-holding the deposited slag layer in operative position, said row of tubes absorbing a preponderance of heat on one side of the row.

4. In a tubular heat exchanger adapted as a part of a furnace 'wall to transmit to a contained fluid the heat received radiantly from fuel burning in the furnace; said tubular heat exchanger having a row of tubes constituting a metallic inner part in contact with the contained fluid; and a composite outer structure exposed to radiant heat from the burning fuel; said outer structure comprising metallic projections extendlng' outwardly from the inner part and rigidly connected therewith, with the projections on at least some of the tubes independent of the proiections on others of the tubes, and refractory material contacting with the inner part and located between the projections, said refractory material being of greater thermal resistance than the material of the remaining structure, thereby preventing overheating of the exchanger metal and contributing to higher furnace temperatures.

5. A boiler having a hollow part carrying water 6. In a tubular heat exchanger adapted as a part of a furnace wall to transmit to is contained fluid the heat received radlantly from fuel hurn-' ing in the furnace, said tubular heat exchanger having a metallic inner structure consisting of a new of aligned tubes in contact with the contained fluid: and a composite outer structure exposed to radiant heat from the burning luel;

said composite outer structure including metallic projections joined with the metal of the tubes and distributed over and around the furnace faces oi the tubes, and refractory material contacting with the inner structure and extending across the furnace faces of the tubes between the projections to form a shield between the tubes and the burning fuel, said refractory mafurnace wall and comprising, in combination, an

inner structure consisting of army of aligned tubes conducting a fluid past a heating zone wherein the fluid receives heat transmitted from burning fuel through the tube walls: and an outer composite structure including metallic projections on the tubes, and a slag layer deposited by the products of combustion moving from the burning fuel and extending across the tubes and teriai being of greater thermal resistance than the material of the remaining structure to there by prevent overheating of the exchanger metal and contributeto higher furnace temperature, some of said projections irorn a pair of adjacent tubes extending towards each other across the spaces between the tubes with their ends in close proximity.

7. Steam boiler apparatus comprising; in combination; an inner structure consisting of a row of aligned tubes conducting a fluid past a heating zone wherein-the fluid receives heat transmitted from the burning fuel through the tube walls; and an outer composite structure consisting of fiat and wide longitudinal fins arranged on opposite sides of each tube with the adjacent ends oi the fins on adjacent tubes in proximity so as to delineate with the tubes a wall structure for the furnace, separate metallic projections joined with the tubes and the fins and distributed over and around the furnace sides ofsaid parts, and refractory material extending across the spaces between the projections to form a shield fits snugly against the tube between the tubes and the burning fuel, the projections acting as supports or anchors "to hold the refractory in operative position, said refractory and the tubes absorbing a preponderance of heat.

the tube, and rigid refractory material positioned on said structure while in a non-rigid condition and which extends from the inner face of said wall into contact with said tubes and into the spaces between the tubes and which fits snugly against the tube surfaces and all of said lateral surfaces and is cooked by said surfaces and which interlocks with and is reinforced by the tubes and projections whereby the tendency of portions of the refractory materialto break away from-said structure is minimized.

9.1 vertically disposed boiler furnace wall comprising a metallic structure including cooling tubes spaced away from the inner face of the wall and projections integrally connected to each of said tubes and extending therefrom toward said face, and rigid refractory material positioned on said structure while in a non-rigid con- (iition and which extends from the inner face of said wall into contact with said tubes and which surfaces and the lateral surfaces 0: ma projections, as latter being distributed both'horizontally and vertically throughout the portions of said material ad'- jacent said face, whereby said material is cooled and supported, :and the downflow tendency of molten material on said face is retarded.

10. In a furnace .wall the combination of a plurality of tubes in line with each other spaced apart and having opposite longitudinal flns in the spaces between them, the 'tubesbeing connected into a fluid system, retainingmeans on the fins desi ed and adapted to make a keyed engagement with a plastic-coating and to hold it'to the inner face of the wall, and means for burningfuei within the furnace.

11. In fluid heat exchange apparatus, a furnace, a plurality of armed tubular sections adapted to be disposed along a boundary of the furnace, means for connecting the tubular. elements into a fluid circulation, metallic extended surface elements welded to the tubular sections and extending from opposite sides of each tubular section toward an adjacent tubular section, and ceramicrefractory material disposed between adjacent tubular sections and closing the spaces therebetween and disposed in contact with the metal of said extensions,-said metallic extensions on the respective tubular sections being separate and distinct from the extensions on the adjoining tubular sections. the metallic extensions being in the nature of studs distributed longitudinally of the tubular sections.

navm o. earner.

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