US2192642A - Furnace construction - Google Patents

Description

March 5, 1940. R. E. GRIFFITH FURNACE conswaucnofi I-iled March 3, 1939 3 Sheets-Sheet 1 March 5, 1940. R. E. GRIFFITH FURNACE CONSTRUCTION Filed Iarh 3, 1939 3 Sheets-Sheet 2 ATTORNEY.

Mud! 1940- R. a. GRIFFITH 2,192,642

FURNACE cons'riwc rlon 11m; larch s, 1939 s Sheets-Sheet s ATTORNEY.

of the fact that such walls are often irregular or Patenfe an. 5, 194% r raNr 2,192,642 FURNACE CONSTRUCTION Raymond E. Griflith, Mount Lebanon, Pa, assignor to E. 3. Lavino and Company, Philadelphia,'i?a., a corporation of Delaware Appiication March 3, 1939, Serial No. 259,629

15 Claims.

This invention relates to furnace lining .oonstructions and more particularly, to a manner of and means for use in constructing furnace linings whereby expansion of the refractory units comprising the lining, particularly of the hot ends of such units, is compensated for, to the end that crushing and spalling of the refractory units during periods of service is eliminated or at least reduced to a minimum. I

An important object of the invention is to provide a metallic spacer for use with refractory construction materials by virtue of which (1) there are eliminated many of the difficulties encountered in the installation of the refractory linings in metallurgical furnaces and (2) there is a'method of compensating for the strains developed in refractory linings because ofthe expansion of the refractory materials during periods of service.

In the construction of some curved sections of furnace linings, such as, for example, the walls of an electric furnace having a circular cross-sectional shape or the lining of a rotary kiln, with shaped refractory units it is often diflicult to correctly proportion the shaped units so that they will accurately fit the kiln walls, especially in view have irregularities at intervals which increase the difiiculty of installing the lining. This resulltl is a lining which fits the furnace shell loosely w en cold and which may be damaged considerably (especially in the case of a rotary kiln) before it is actually subjected to the service for'which it is intended.

It is among the objectsof my invention to provide a means for tightening such linings; making them firm and rigid before the furnace is heated, and this object is accomplished by-the insertion of wedge shaped metal plates between the faces of the brick as required. I may use the plates between each pair of adjacent faces, between the faces of alternate brick, or in contact with every third brick, every fourth brick, etc. may be slightly smaller than the brick faces with which they are in contact, and may be inserted wholly'or partially, as required to give the neces-' sary rigidity to the lining. The plate is so designed, however, that no dimension thereof is sumciently great to permit the expansion of the plate to cause'it .to extend beyond the brick face with which it is in contact in a direction which will place a strain upon adjacent brick. It is common practice in laying up brick work for furnace linings to break the joints, that is, to lay up the brick so that joints are not continuous,

The plates and in the practice of my invention care must be taken not to have the expansion of the plate in heating place a strain upon any of the adjacent brick. v

The thickness of the metal used to form the a plate and the typeof ofiset to give the plate a wedge-shaped contour must be determined with several objects in view. The plate must have sufficient strength when cold to support the weight ofthe lining as previously described. However, go it is also among the objects of this invention to compensate for the expansion of the refractories on heating, and particularly for the difierential expansion between theends of the brick exposed to the source of heat of thefurnace and the opi6 'posite ends. Forthis purpose I have provided a plate which is rigid when cold, butwhich is collapsible under the influence of pressure and heat. The plate must be so designed therefore that its yieldpoint is lower than the -yiel point of the refractory brick with which it is used, so that as the brick expands, the plate is. flattened, but the. rigidity of the structure is maintained, with no undue strain placed upon the refractory structure.

Although face to face contact of the refractory units provides a very desirable weight distribution in the cold refractory lining, such an installation is subjected to unusual and irresistiblestrains during periods of service. The faces of the brick or other refractory construction units exposed to 'the source of heat of-the furnace are naturally at a higher temperature than the faces not so exposed, and therefore undergo a greater percentage of total expansion. The differential expansion causes a pinching-off or a shearing-off of the hot ends of the brick, and as a result fragmerits of the brick spell or drop from the furnace structure, and the effective thickness of the refractory lining is reduced, and the life shortened.

In structures of magnesitebrick, or of brick 40 containing magnesite, it has been found that the loss of spalls' can be partially overcome by the use of flat steel plates in the joints between the brick. In furnace walls built in this fashion, the flat plates, when exposed to the heat and atmosphere of the furnace, are oxidized to iron oxide, and tend to combine with the adjacent portion of the brick, forming a cementitious interface or mortar which helps hold the pinched-off fragments in place. The construction previously developed' does not compensate for the differential expansion of the brick nor prevent the fracturingof the refractories during periods of service. Moreover, oxidation of the plates in the above type of installation is accompanied by expansion 5 and crystal growth to the detriment of the furnace lining. The use of corrugated plates, or plates having offset portions comprising a prime feature of the present invention, provides a space to compensate for the volume increase due to oxidation of the iron plate and crystal growth caused by theiron oxide and other compounds which may be formed.

Furthermore, the greatest need for compensation is at the faces of the brick exposed to the source of heat of the furnace, because these faces, being higher in temperature than the opposite faces, have a greater percentage of total expansion. The plates'of my invention are designed to ential expansion because the offsets are greatest in magnitude at the points where expansion is greatest.

From the foregoing it will be understood that the general over-all shape of the plates which form a part of my invention is such that the plate is flat at one end and Wedge-shaped at the opposite end. The wedge-shaped effect is obtained by the use of corrugations or other offset portions of increasing magnitude. The advantages of this design are many, both in the cold, newly built furnace and in the furnace subjected to heat during periodsof service.

In order to fully illustrate my invention I have shown, in the accompanying drawings, several examples of the various forms and shapes which the spacing-plates of the invention may assume and I have also illustrated some manners of utilizing these plates in a furnace construction composed of refractory units. In these drawings,

for the purpose of example, there have been illustrated the best embodiments of the invention now known to me, but such embodiments are to be regarded as typical only of many possible embodiments, and the invention is not to be limited thereto.-

In the drawings- Figs. 1, 2 and 3 are perspective views of spacing plates embodying features of the invention and which may be readily utilized in constructing a furnace lining which will have the features and advantages hereinbefore discussed.

Fig. 4 is a vertical sectional view through the lining of a circular furnace or kiln showing how and also showing further features of the invention.

Fig. 7 is a perspective view of? one of the refractory bricks shown in Figs. 4 to 6 and showing how a corrugated wedge-shaped plate cooperates with the various faces of the brick.

Fig. 8 is a perspective view of a portion of a furnace lining and representing a vertical end.

- presents a perfectly flat plane; surface.

wall construction in which spacing plates of the present invention maybe profitably utilized.

The preferred form of spacing plate of theof longitudinal wedge-shaped offset areas or corrugations l2, herein shown to be three in number, although obviously any desired number of such offset areas may be provided within the scope of the invention, The oifset areas I2 are greatest in magnitude along the edge AB of the plate and the magnitude of the ofisets becomes gradually less in the direction toward the fiat portion In, tapering onand'fading into the face of the plate approximately along the line C-D, the balance of the plate being flat as previously indicated. The rate of taper may be such as 'to cause the wedge-shaped areas to extend from one-third to two-thirds of the length of the plate. While the width of the offset areas l2 has been shown to be substantially constant from end to end of the ofisets, it is obvious that the width may also progressively decrease in the direction toward the fiat portion I0 so that the general appearance of the offset portions l2 would be more or less that of a section of a cone.

Another form of spacing plate embodying features of the invention will be seen in Fig. 2. In this form the plate has a plurality of rows of offset portions l3, l4, l5 and IS. The offset portions l3 in the first row nearest the edge'A-B of the plate have the greatest magnitude of offset and the offset portions l4, l5 and I6 in the succeeding rows have gradually decreasing degrees of offset so that the offset portions H5 in the row furthest from the edge -A'--B taper or fade into the fiat portion ID of the plate. The offset portions are arranged so that they cover from one-third to two-thirds of the plate extending from the edge AB.

Still another form of spacing plate of the invention is shown in Fig. 3. In this form the plate is provided with a plurality of transverse corrugations I1, I 8, l9 and 20, extending across the width of the plate. The corrugation l1 nearest the edge AB of the plate is the greatest in magnitude and the succeeding corrugations l8, l9 and 20 are of decreasing magnitude respectively so that the corrugation 20 tapers oif or fades into the flat portion 10.

One manner of utilizing the spacing plates of the present invention in the construction of a furnace lining is illustrated in Figs. 4, 5,6 and 7 of the drawings, These figures represent portions of a circular refractory lining construction composed of refractory units which are wedgeshaped in section to provide the necessary circular construction. In utilizing the spacing plates of my invention, between certain of the refractory units 2|, spacing plates, many of the forms described herein, are driven to their full length. These spacing plates thus positioned are indicated by the reference numeral 22 and it will be seen that their outer edges, corresponding to the edge AB, as previously described, are substantially flush with the inner wall of the lining.

In fact some or all of the plates 22 may be perfectly flat plane metal plates, although it is preferable that some be wedge-shaped plates of this invention. To make the lining rigid, between other of the refractory units 2| there are inu and brace the whole structure into a rigid aggreate.

Fig. 5 illustrates, in somewhat enlarged fashion, the relative positions of the bricks 2| and the spacing plates 22 and 23. and shows how the greater expansion of the hot ends of the brick, that-is, the ends exposed to the source of heat of the furnace, is compensated for. In other words, at the rear fiat portion ll] of the spacing plate very little expansion occurs in the brick and compensation therefore is not an important item. The offset portions l2, progressively in creasing in magnitude away from the flat portion III will obviously wedgethe composite construction into a rigid mass while cold, and expansion of the hot ends of the brick 2| due to service temperatures will be readily accommodated by the corrugations or offset portions which will cause the spacing plate to yield coincident with the pressure of the expanding brick. Since the amount of this expansion is a function of distance from the source of heat it is obvious that tendency of the brick to expand decreases progressively away from the heat source. Thus the magnitude of the corrugations l2 may progressively diminish in a direction away from the source of heat and still adequately compensate for expansion of the brick.

For the purposes of better illustration, the manner in which a rotary kiln lining is constructed is indicated in Fig. 4 by showing the lining only partially in place. It will be understood that approximately one-half the circumference of the kiln proper is laid up by the bricks 2| being placed in position as shown within the steel furnace shell 25 and the whole structure braced to preserve the exact internal diameter by means of the screw jack 26 The plates 23 are then rammed or driven solidly into position so as to wedge the structure securely and firmly. Thereafter the kiln may be rotated a quarter or a half turn and the remainder of the brick work laid in similar fashion.

Fig. 6, looking at the interior wall of the kiln lining, shows how spacing plates of the present invention may be used between all brick interfaces. In other words, it is generally preferable that there be no direct contact of one wall of a brick with the adjacent wall of an adjoining brick. To that end the brick 2| are separated from adjoining. bricks at all interfaces, either with offset wedge-shaped plates of the present invention, or with flat metal plates. As clearly indicated, a relatively large spacing? plate 21 may be utilized along the relatively long longitudinal wall of the brick while narrower plates 23 may occupy the space between the smaller end walls of the brick. The same is likewise true of any flat plates that maybe used, such as the larger plates 29 and the smaller ones 30.

The manner in which these plates cooperate with adjacent brick faces is clearly seen in Fig. '7 which shows the bri'ck'2l to be wedge-shaped to fit into the necessary circular construction. The plate 21 lying alongside of the longitudinal face of the brick will substantially coincide with that face because the same is substantially rectangular in plan. The end wall 3| of the brick,

however, has the form, of a trapezium. This,"

however, does not interfere with the employment of a spacing plate 28 generally rectangular in plan. The plate 28 need not cover the entire surface of the end 3|, it being sufllcient that it serve the purpose of spacing it from the corresponding end-of the adjacent brick and capable ofthe furnace wall.

of exerting a wedging effect while also being able to compensate for expansion of the bricks 2| at their hot ends or edges which will be the inner curved face 32 of the brick.

corrugations decreasing in magnitudeand taper ing into fiat portion as previously described. The numeral 45 represents a filler placed in the corrugations on one side of the plates only. The filler 45 may be a refractory material to supply a bonding mortar with the brick being used. Or the filler may be a mixture'of a refractory material with a heat softening material, in which case the softening of the fusible material will permit the movement of the spacer to compensate for any movement in the refractory structure. Again the filler may be a mixture of a refractory material with a combustible material, for example ground magnesia and tar so proportioned that the shrinkage due to the removal of the combustible material compensates for the expansion of the refractory material. Or I may use for the filler 45 a pressure softening or resilient material which will permit movement of the plates 21 and 23 without imposing a strain on the structure while at the same time keeping a full joint. Various combinations of the above fillers are possible. It is a particular feature of my invention that the filler is used on only one side ofthe corrugated plate, that is only onehalf the available space contains filler, the re-- when the furnace is heated to service tempera ature. Thus the lining will then present a smooth and unbroken surface.

In the construction of other curved furnace sections with shaped refractory units, such as,

forinstance, an arched roof in an open hearth furnace, it is often. difficult to get the desired curvature and still so proportion the shaped units to obtain full face to face contact between them and thus obtain an even distribution of the dead weight of the span over the faces of the brick. If such full face to face contact is not obtained, the weight of the span will be concentrated at the points of contact and cause undesirable and frequently damaging strains in the. masonry. The above description shows how such a condition'is eliminated by the use of my invention.

Fig. 8'shows how spacing plates of the present invention, or slight modifications thereof, may.

be utilized in constructing a vertical end wall of the furnace. In this view the reference numeral 33 indicates a vertical I-beamwhich in technical terminology is known as a buckstay. It is understood, of course, that there are a plurality of buckstays 33arranged in spaced intervals back In the illustrated instance the furnace wall 34 is constructed of a plurality of refractory bodies or bricks 35 the opposite faces of which are substantially parallel, the.

bricks being laid one upon another. Since there are frequently unavoidable irregularities in the brick it is sometimes dimcult to have the wall absolutely tight and rigid. To this end it is a feature hereof to employ, in addition to the bricks 35, one or more refractory bricks 36, the upper and lower faces of which are not parallel, that is, the bricks 36 are substantially wedge-shaped with the thinner portion toward the interior of the furnace.

Between each of the flat bricks 35 thereare interposed plane flat metal spacers 31 which project beyond the interior face of the wall and are provided with'perforations or openings 38 for a purpose presently to be described. Wherever the wedge-shaped bricks 36 are present there is inface of the wall and are provided with perforations 38, the same as are the fiat plates 31. The purpose of these perforations is to serve as a binding or foundation for the retention of plastic refractory cement or mortar 4B, The refractory cement 40 is placed over the irmer edge of all of the bricks 35 and 36 to fill the space between the projecting ends of each of the spacing plates. The openings 38 provide communication from one side to the other. of the plates whereby the cement lining 40 may be strengthened and made practically a monolithic construction after the furnace is fired in service. Asfurther means of strengthening and supporting the wall, metal rods or bus bars GI of substantial size are welded at each end to adjacent buckstays 33, extending from one buckstay to the 'next. The spacing plates 31 and 39 extend completely through the wall and project beyond the outward exterior of the same and are provided-with aligned openings 42 through which metal ties 43 may be threaded and then secured at either end to upper and lower bus bars 4!, for instance, by being looped around the bus bars as shown in the drawings. If desired the spaces between the outwardly projecting ends of the spacing plates may also be filled with cement or other plastic as indicated at 44.

The structure just described provides -avertical furnace wall which is thoroughly and rigidly 'braced and held in position. The provision of the date and compensate for any expansion of the hot ends of the brick after the furnace is heated up to service temperatures. The inwardly projecting portions of the spacing plates provide a convenient means for applying a plastic refractory lining to the furnace wall and of assuring that the liningwill beheld securely and firmly in place when first inserted in plastic condition as well as after firing under service temperatures.

Thus the ofiset wedge-shaped spacing plates cf the present invention find novel and desirable use in the construction of furnace linings of a curved or a circular nature as well as in vertical wall construction. The spacing plates will likewise find other utility obvious to those, skilled in the art wherever expansion of refractory bodies under the influence of heat is a detrimental factor and which expansion will be compensated for by the employment of spacing plates of this instruction comprising, a metallic plate having off-v set areas throughout a substantial portion thereof, said offset areas being of greatest magnitude adjacent one edge of said plate and gradually and progressively decreasing in magnitude toward the opposite edge thereof.

2. A spacing member according to claim 1 wherein the offset areas extend not further than two-thirds the distance from one edge of the plate to the opposite edge thereof, the remainder of said plate being fiat.

3. A spacing member for interposition between contiguous refractory bodies in a furnace construction comprising, a metallic plate having corrugations extending longitudinally throughout a substantial portion thereof, said corrugations be ing 'of greatest magnitude adjacent one edgeof said plate and gradually and progressively decreasing in magnitude toward the opposite edge thereof.

4. A spacing member according to claim 3 wherein the corrugations extend not further than two-thirds the distance from one edge of the plate to the opposite edge thereof, the remainder of said plate being flat.

5. In furnace construction, a plurality of con tiguous refractory units, and substantially wedgeshaped spacing plates between the juxtaposed faces of said units, said plates having'ofiset areas throughout a substantial portion thereof, said areas being of greatest magnitude at that edge of said plate which is adjacent the portion of said refractory units nearest to the source of heat in said furnace, whereby expansion of the said ends of said refractory units under high temperatures is compensated for, said offset areas gradually decreasing in magnitude toward the edge of said plate furthest removed from the source of heat. 6. In furnace construction, a plurality of contiguous refractory units having metal plates between juxtaposed faces of certain of said units, and substantially wedge-shaped metallic plates between juxtaposed faces of other of said units, said wedge-shaped plates being in the formof a member having offset areas throughout a substantial portion thereof, said offset areas being of greatest magnitude adjacent one edge of said plate and gradually and progressively decreasing in magnitude toward the opposite edge thereof.

7. The method of constructing a furnace-lining of curved contour, comprising: laying a plurality of substantially wedge-shaped refractory units in contiguous fashion to form the desiredcontour, and driving substantially 'wedgehaped prising a plurality of refractory units laid onev 76 upon the other; metallic spacing plates between juxtaposed faces of said units and extending inwardly beyond the interior surface of said wall, the inwardly extending portions of said plates being provided with aligned perforations, and refractory material filling the spaces between the inwardly projecting portions ofsaid plates and extending through said openings.

10. In fumace'construction, 'a furnace wall comprising a plurality of refractory units laid one upon another, certain of said units having their upper and lower faces substantially parallel, other of said units having non-parallel upper and lower faces so that said units are substantially wedge-shaped, and spacing members between juxtaposed faces of said wedge-shaped units, said spacing members being in the form of metallic plates having oifset areas throughout substantial portions thereof, the offset areas being of greatest magnitude adjacent one end of the plate and gradually and progressively decreasing in magnitude toward the opposite edge thereof.

11. In furnace construction,-a plurality of contiguous refractory units, metallic spacing members between the juxtaposed faces of said units;

said spacing members having ofiset areas throughout a substantial portion thereof, said oflset areas being of greatest magnitude adjacent one edge of said spacing members and gradually and progressively decreasing in magnitude shaped spacing plates between the juxtaposed facing of said units, said"plates having offset areas throughout a substantial portion thereof, said areas being of greatest magnitude at that edge of said plate which is adjacent the portion of said refractory units nearest to the source of heat in said furnace, whereby expansion of the said ends of said refractory units under high temperatures is compensated for, said ofiset areas gradually decreasing in magnitude toward the edge of said plate furthest removed from the source of heat, and plastic material in said offset areas at one side of said plates.-

RAYMOND E. GRIFFITH.

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