US2606017A - Furnace roof and wall structure - Google Patents

Description

Aug. 5, i952 L.. s. I ONGENECKER FURNACE RooF AND WALL STRUCTURE 2 SHEETS--SHEET l .Filed Feb. 5. 1949 AIA l5l X23 Hg 23 m l HvVENToR. Lew' SLongeneclrer BY //wwfl J- VHIS ATTORNEYS ug 5, 1952 L. s. LONGENECKER 2,606,017

FURNACE ROOF AND WALL STRUCTURE Filed Feb. A5. 1949 2 SHEETS- SHEET 2 1N VEN TOR. Lew S. Longenec/rer BY /zuhfl%gl(nnm HAS ATTORNEYS atented ug. 5, 15952 UNETE smi-:ss sereni cl2-Fics] 2,606,017 FURNACE ,RQQF AND WALL- vSQERJJCTUltE Levi- S. Longenecker, Mount Lebanonrlia. Alpiicationlebrnary 5, 19.45% Serial No.-

9 Claims. (C1. 26S- 43) stood, vbut Awhich materially shortens ytheir efo fective life. -For example, a vfurnace chamber wall or roof when new loses layer'after vlayer from the furnace chamber side thereof. These layers vary in thickness fromZl/g inches downto 3A; of an inch, depending somewhat :upon the original thickness of the wall' as well as on'the furnace chamber temperatures and pressures. The loss or peeling off of these-layers yseems to follow some sort of a time cycle, since peeling does not occur immediately on heating up the furnace, but startsV later on when the inside surface ofthe wall or roof, as the'case maybe, becomes saturated with vapors-from the furnace atmosphere. After-the first Alayer falls away-the lnewr -surfacetakescn a glaze or vapor coating which persists for a time or until the structure loses another layer in a similar manner. "The time between -peeiings seems `to increase and the thickness of the peeled layers appearsv to Adecrease. as the wall becomesthin'ner. -li'orinstance, this peeling, if it can be called peeling, in a roof or wall 131/2 inches thick, disappearsY or ceases .when the structure A(wall orfroof) .arrives atfa thickness of, from 4.-.5v inches. From here on, while the structure becomes thinnerwith each successive heat, no morevpeeling occurs.

Such a wall or roof vin an open hearth furnace, afterk it has reached thel` point l,at-which, it` no .1911561 peels PIOUCCS ,en average f @913.31150 heats per inch Yof wear. A 1731/2 inch wall or roof therefore before it burns downto a; thickness of l1/2 inches ought to have a useful thickness of 12 inchesnand on the basis of` 60 heats per inch of thickness, such' a structure (Waller roof) shouldproduce 720 heats. Atthepresent time, however, due to this peeling"A phenomenon, such a wallonlyproduces around 3.60 heats.v

From a study of brick ends taken.from the slag pocket of an open hearth furnacehaving `chemically bonded basic refractories it isfapparent that the pieces (-peelings) of f each of thev llayers are of fairly uniform thickness throughout;their entire cross 'sectionalarea. `I'n other words, the plane of the fracture face =`of such brick ends parallels that ofthe original inner or furnace chamber --fla'cve-'of tliebricl.

" These pieces (brick`ehds)' have iairly`-s`quare Yedges, and measurements of the same adjacent their fracture facelshowV that the originalithicklinchesN 1- with a a' corresponding -i-ncarease-` l'the width las4 well. -Aierently the-whole innerend 5 has swelled 'or' lgrown'l kiue' to the ai furnace vapors' 4which penetrated. its structur U2-his swelling or growth of-lyinch per eve l inches means `a growth 'of 1- inch-*per foot; 1T 's `vapor or liquid" penetration `should follow seineT'is'ot of a gradient line. :Theaniount 'ofpenetration should be greatest at the inner or furnace'chamberfface and should taper oitolzerosornewhere Vback .Withimthebrickl AThe swelling ,or 'growth of the brick,therefore, should begrcate'stf'at .the inner or furnaceicharnber 'faoe and should `taper, olfvv to zero somewhereback'o'f such'faceff lain' convinced 'frommystudy ofthe broken brick ends/takenl from .theslagtpocket that'the pieces Vnfiaking lupi each of theibroken `away-or peeled on" layers have grown or swelled lat' the rateof..aboutfoneinchV .per foot. This swelling isy localized .andY is confined f' to. a zone' which' Ais relatively Vnarrow. vwith 'relation` to the' thickness of a 13% inch bricklwallV and since the remainder of the wall has not grown or; swelled'andlisltoo heavy to` berraised oralifted byanyof the'. ela- ,tivelyv narrow `zones `as. suchzonesY swell 'orlgrow, the swelled portions buckle for relief :andt'ea'r themselves. loose from Vthe remainderv ofi theo-wall.

I am of the belief that as the thickness/of thewall, duetothe lpeeling. oifof successive layers, approaches a thickness of from -iinches,

the weight .of thel unswelledilortonihas. fdecreased tosucha vpoint that. vrsuch ,portion .can teV raised bv the, swellcdnortons,,withcut tearf swelled portions.

Magnesite bricks on the other hand under continued heating at high temperatures shrink and continue to shrink until they apparently reach zero porosity. Iron oxide in the furnace atmosphere under furnace operating temperatures may retard or somewhat reduce the amount of shrinking but it will not cause any growth or swelling of magnesite bricks.

Chrome ore is apparently added to the magnesite for the purpose of making a more stable brick structure and reducing its burning shrinkage. Since a valuable brick structure is obtained by proper balancing of magnesite and chrome ore, we apparently are forced to accept its growth or swelling which occurs immediately adjacent the furnace chamber face when such structure is used in furnaces having iron oxide in the furnace chamber atmosphere, and one object of this invention is to produce a furnace wall or roof structure a portion at least of which is made up of chemically bonded or burned magnesitechrome refractories in which the effects of such growth behavior are offset and rendered harmless.

Another object of this invention is to produce Va. chemically bonded or burned basic refractory wall or roof structure for open hearth furnace u se in which the service life will be materially increased over what it has heretofore been.

Another object is to produce a chemically bonded basic refractory wall or roof structure for open hearth furnaces in which the service life is doubled over what it has heretofore been.

Another object is to provide a method of making a furnace wall or roof structure from basic refractory blocks or bricks in which the peeling phenomenon above referred to does not occur.

AV still further object is to produce a furnace wall or roof structure comprising at least some chemically bonded or burned basic, refractories which increase their cross sectional dimensions immediately adjacent their furnace chamber end faces under the influence of open hearth furnace temperatures and atmospheres and in which such growth behavior is offset by the shrinking characteristics of other refractories included in such structures.

These and other objects, I attain bymeans of the structure described in the specification and illustrated in the drawings accompanying and forming part of this application.

In the drawings:

Figure 1 is a view in front elevation of a fragmentary portion of a furnace wall embodying this invention;

Fig. 2 is a top plan view of a larger section of Such wall;

Fig. 3 is a sectional View taken on line III-III of Fig. 1

Fig. 4 is an enlarged view in front elevation of three of the courses of bricks disclosed in Fig. 1 after the wall has reached furnace operating temperature under operating conditions;

Fig. 5 is an enlarged perspective view of one of the magnesite-chrome bricks used in the makeup of the wall of Figs. 1-3 inclusive;

Fig. 6 is an enlarged perspective view of a steel reinforcing bar which may be used in the makeup of the wall structure of this invention; and

Fig. 7 is an enlarged perspective view of one of the load carrying expansion compensatingshimlike members which are preferably used in the wall structure of this invention.

A typical wall for open hearth furnaces embodying this invention comprises groups of chemically bonded or burned bricks part of which swell immediately adjacent their furnace chamber end faces and part shrink a corresponding amount immediately adjacent their furnace chamber end faces under furnace operating conditions and temperatures. These two types of bricks are alternately arranged as in a checkerboard so that the swelling of one type is offset by the shrinking of the other type; the composition of the bricks being such that the amount of shrinking of one type will as nearly as possible oifset the amount of swelling of the other type.

In the preferred form of wall of this invention. the bricks are preferably chemically bonded. The swelling bricks are magnesite-chrome bricks, while the shrinking bricks are preferably magnesite with very little, if any, chrome in their make-up. I have marked the magnesite bricks M and the magnesite-chrome bricks C.

While bricks of usual shape and dimensions 3 x 41/2 x 131/2 can be used provided each of the C bricks along at least two of its longitudinally extending edge portions is modied or shaped so as to provide space for accommodating lengthening of the diagonals of the C bricks as is bound to occur under furnace operating temperatures and conditions, I prefer to use bricks that are generally square in cross section and are fl- X 4 X 131/2.

While each M brick may be and preferably is square in cross section, each C brick has at least two of its longitudinally extending edge portions so modified or shaped as to provide spaces for accommodating lengthening of the diagonals of the C bricks which occurs under furnace operating temperatures and conditions. This modifying or shaping preferably is accomplished by forming depressions ID, which as shown in Fig. 5, extend along the upper longitudinally extending edges of the C bricks (the swelling bricks). When these bricks are alternately arranged as in a checkerboard, these depressions provide the necessary space to accommodate the increase in length of their diagonals due to the localized swelling which occurs under furnace operating temperatures and conditions. When the wall is laid up, these recesses are preferably filled with a magnesia'carbonate mortar which shrinks at a temperature below the brick swelling temperature.

In some cases, it may be desirable to provide ferrous metal reinforcing members for the bricks, and if desired, these can take the form of steel f rods I3 having their outer ends I4 bent over as shown in Figure 6 so as to lie against the outer face of the C bricks. The sides of depressions I0 in bricks of the size here used are preferably 1/2 inch wide when the reinforcing rods are used. The rods will be embedded in the magnesia carbonate mortar which shrinks at a temperature below the oxidizing temperature of the rods.

The groups of bricks making up a wall or roof strucutre may each comprise as many bricks as desired, but in the drawings I have limited each group to 12 bricks.

The swelling or growth of the C bricks is localzed being limited to a relatively narrow zone adjacent the inside or furnace chamber face of the wall or roof and develops during a constantly held temperature in the presence of iron oxide in the furnace atmosphere such as encountered under open hearth furnace operating temperatures and conditions.

The thermal expansion to which basic refrac- :tori'es are subject is an entirely different Vphenomenon from thisy localized vswelling or vgrowth ldue*to the effect of iron oxidel on theic'hrome of 'the C bricks, and has no relation Awhatever thereto. v

Thermal expansion affects. the Ventire brick.

vthickness and causes the bricks tobecome Wedgeshaped; Ythe thicker section thereof beingadjacent the -inner or furnace chamber AIface of the Wall andthe thinner section being adjacent the outside face. yUnder these conditionsY due tothermal expansion, the wall. bowsoutwardly unless restrained or compensated for. Iprevent this eutwardlybowing -by tyingcertainof the bricks `in each-bundle toltherbuckstays ior steel- 'work of the furnace structure. In this connection. each of etheb'ricks, both C -and`M,l-attheir outer-ends, is provided in both its topi-and bottom sides with T-shaped slots l-forreceiving the T-shaped ends i6 of wall tying Amembers Il `vvhi`ch,rin thecase of vertical Vwalls,canbe -secur-edito the furnace buckstays |18.

4In-the case of furnace roofs embodying this invention, thesev tying members can be supported by overhead beams and' used `as suspension means for the bricks informing a suspended roof structure. ThevT-shaped ends of these :tying members fit into two-adjacent Vbricks so that the `bricks are suspended from opposite sides, L that Vis, 'each brick is supported by two T-shaped supports of thetying members.

In the case of vertical walls,.I preferably only tie the top and bottom rows of bricks in each bundle or group to thebuckstays or steel structure of the furnace.

If the bricks are chemically bonded 4and are used in an open hearth furnace, the furnace operating temperatures will be such that the inside face of the furnace wall or roof as the case may be, reaches 3000* F. when the wall is soaked through and temperature equilibrium is obtained. The maximum expansion will occur about L1/2 inches in from the furnace chamber j face. jAt the point of this maximum expansion ahump is'formed and such humpmust carry the y entire wall load, since the'wall is bucked ,up from the outside by tyingniembers H. In order to prevent the wail under'such conditionsV from teetering on such-hump (there being voids inthe wall both-insideand outside of such hump) I preferably remploy load carrying expansion compensating shim-like members such as dis- 'closed'in an application iiled by me on `May 22, "1948,'and serially numbered 28,600, now Patent One such member which is numbered i2 is disclosed in Figure 7, its design, however diiers somewhat from that disclosed in my said application. It is preferably produced from copper strip of le or 16 gauge and is provided with prongs I9 as in said application. Itis preferably of such length as to embrace four oi' the bricks and of such Width as to extend from a point adjacent the outer face of the wall to the high point of the hump which, as pointed out, isv

about 4%/2 inches from the inside or furnace chamber face of the furnace wall as disclosed in Figure 3.

'I'he forward or inner edges of these load carrying expansion compensating members l2 are bent up as shown at 2G preferably about 1/4 inch. The rear portion of each of these members has T-shaped slots 2l punched therein to accommodate the T-shaped tie members H.

lio

6 The edgportions Y22 between such siots'are :also bent up-IA -inch-asshown in Figure 7.

Prongs I9 are vformed by ypunching and vthis punching is performedf'bya pointed vpunch which forms a hole and forces thedisplaced metaloutwardly-to provide theY-prong-like protuberances around -sueh holes. VThese protuberances or prongsproj ect-about L1A; inch vbeyond-the pronged faceof the member, so that their height plus the thickness of Athe Vmetal strip. will .equal vthe heightofthe-bent up innerandouter edges of the members.

In laying up a wall,-these copper expansion compensating members are preferablyplaced s0 that eachof thesame extends from thelcenter of one bundle or group'fto the center of the next adjacent bundle .ore group. The bent up ends serve as seals for the spaces or gaps between the bricks above and -below the same, causedby prongs I9.

In'laying up the-wall, vertical Awood strips 23 are used to space apart the groups `orbundles of bricks for the purpose of providing room for the bundles to growtransversely. These Vstrips are removed after the wall is completed,since 'they might notb-urn laway rapidly enough to accommodate such expansion.

'Instead of using wood strips as -jspacers for the vertical joints between the groups, I may make use-'of spacers made from copper strip ma." `teriai such as used'forthehorizontal load carrying shim-like members of Figure 7, but without the notches '2L In otherwords the strip-will have two4 continuous lips llike `lip 2d whichact as seals; the effective` thickness "of the Istrip being determined'by the length of ,fthe prongs and the heightof'thelips 2t." These strips' can 'be-widder two narrow strips canb'ejused, one

adjacent the furnace chamber face of #the wall and one adjacent the outside face ofthe' wall.

' It wiiLof course, vbe understood thatthis wall and roof yconstruction is applicable to sprung roofs as well as lsuspended roofs and may be utilizdin forming the lining of rotaryfkilnsas -.we11 as the hear-tbs of'iurnaces.

A WhatV I claimis:

l'. 4A furnace side walloor roof structure comprising two types of generally rectangular refractory members ofsubstantially the same size alternately arranged as in a checkerboard, the.

members of one type being subjectrtolocalized swelling immediately Yadjacent their furnace chamber faces under furnace4 operating temprising two types of generally rectangular refractory members of substantially the same size, the members of one type being subject to localized swelling immediately adjacent their furnace chamber faces under furnace operating temperatures and conditions and the members of the other type being subject to localized shrinking a corresponding amount immediately adjacent their furnace chamber faces under the same furnace operating temperatures and conditions, the members of such two types being alternately arranged as in a checkerboard, but 'with at least two of the longitudinallyl extending corner portions of each refractory member of the swelling type being so shaped that space is provided to accommodate the increasing length of their diagonals occuring under such furnace operating temperatures and conditions.

3. A furnace side wall or roof structure comprising two types of generally rectangular members of substantially the same size, those of one type being subject to localized swelling immediately adjacent'their furnace chamber faces under furnace operating temperatures and conditions and those of the other type being subject to localized shrinking a corresponding amount immediately adjacent their furnace chamber faces under the same furnace operating temperatures and operating conditions, the members of such two types being alternately arranged as in a checkerboard but with the two upper longitudinally extending corner portions of the refractory members of the swelling type being so shaped that spaces are provided to accommodate increase in the length of their diagonals occurring under furnace temperature and operating conditions.

4. A structure as dened in claim 1, in which the refractory members of the swelling type are chemically bonded and contain chrome.

5. A structure as defined in claim 1, in which the refractory members of both types are chemically bonded and those of the swelling type contain both magnesite andchrome.

6. A structure as defined in claim 1, in which the spaces for accommodating lengthening of the diagonals of the refractory members of the swelling type are formed by providing grooves which extend lengthwise of and include at least two of its longitudinally extending corner edges.

7. A structure as defined in claim 1, in which the grooves forming the spaces for accommodating lengthening of the diagonals of the refractory members of the swelling type extend along the upper longitudinal edge portions of such refractory members.

8. A furnace side wall or roof structure comprising two types of chemically bonded generally rectangular refractory members of substantially the same size, those of one type being subject to localized swelling immediately adjacent their furnace chamber faces under-furnace operating temperatures and conditions and those of the other type being subject to localized shrinking a corresponding amount immediately adjacent their furnace chamber faces under the same furnace operating temperatures and conditions, the members of such two types being alternately arranged as in a. checkerboard; two of the longitudinally extending edge portions of each refractory member of the swelling type being so shaped as to provide spaces for accommodating lengthening of the diagonals of two adjacent refractory members of the same type under such furnace operating temperatures and conditions.

9. A furnace side wall or roof structure comprising two types of chemically bonded generally rectangular refractory members of substantially the same size alternately arranged as in a checkerboard, the members of one type comprising magnesite and sufficient chrome ore to cause localized swelling immediately adjacent their furnace chamber faces under furnace operating temperatures and conditions and those of the other type containing magnesite and little if any chrome ore so that localized shrinking in corresponding amount will occur immediately adjacent their furnace chamber faces under the same furnace operating temperatures and conditions; each refractory member of the swelling type having at least two of its longitudinally extending edge portions so shaped as to provide spaces for accommodating lengthening of the diagonals of the refractory members of such type due to localized swelling under furnace operating temperatures and conditions.

LEVI S. LONGENECKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Swindell July 26, 1887 Gray Dec. 19, 1922 Heuer June 15, 1948 Fairchild June 7, 1949 FOREIGN PATENTS Country Date Germany Sept. 1, 1921 OTHER REFERENCES Refractories, published 1949 by the General Refractories Co., Philadelphia, Pa., pages 173 and 175.

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