US2386565A

US2386565A - Open hearth furnace

Info

Publication number: US2386565A
Application number: US488071A
Authority: US
Inventors: Nissim Raoul
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-05-16
Filing date: 1943-05-22
Publication date: 1945-10-09
Anticipated expiration: 1962-10-09

Description

.0d- 9, 1945. R. NlsslM 2,386,565

OPEN HEARTH 'FURNAGE Filed Mayg22. 1943 5 Sheets-Sheet 5 OCL 9, 1945. n R, NlsslM .l 5 2,386,565

OPEN HEARTH 'FURNACE Filed May 22, 1943 y 5 sheets-sheet 4 Patented Oct. 9, 1945 FricE 2,386,565 y OPEN nm'rn FURNACE Raoul Nissim, London, England Application May 2&2, 1943, Serial No;

In Great Britain May 16, 1942 8 Claims. `(Cl. -26d-,27)

The present invention relates to open hearth furnaces of the stationary and tilting. types'.

At present the normal open hearth furnace is chargedthrough doors in the side walls of the furnace by` means yof a travelling charging machine which may'serve a battery of four or five furnaces. The time `taken to charge each furnace mayamount tol as much as between one and two hours, which in addition to involving the disadvantage of very serious loss in smelting time, also givesrise to the disadvantage that the charging and melting cycles of the several furnaces are out of phase so that they require separate and individual'regula'tion and working; furthermore the quality of the `metal produced in the several furnaces may be slightly different.

Thisdiiculty can be'minimised by making the charging 'doors as large as possible but the latif greatly increased.

er expedient introduces the further difiicult'yr thatwhilst the'doors are open cold air is aspirated into the furnace tending to cool the furnace and thus to damage the skewbacks and disintegrate the furnace lining particularly inv the neighbourhood of the doors. Owing to the cooling ofthe furnace vthe fuel consumption is also For ythese reasons it is usual to avoid charging anopen' hearth furnace with a light scrap since the lighter the scrap the longer is the time taken to charge :it unless thelscrap is given a preliminary conditioning treatment.

With a view toobviating these difficulties it has alreadyy been proposed to charge an open hearth furnace from above by hinging the whole furnace roof'at one'sideso that it can'be hinged upwardlytoallow the charging from above.

A furnace'built on these lines would, however, r.have :the disadvantage that the stresses in the brickwork of the roof would bevery different in the open position when `the roof is up ended from those in the closed position, with the consequence that the brickwork would tend to disintegrateveryyrapidly. Furthermore, the under sidefof the roof 'when in the open position would be cooled to a very great extent whilst the height :of they structure required tolift the whole roof in this mannerwouldbe very considerable.

suffers from the disadvantage that the removable charging section, each time it is swung away from the furnace, is thoroughly cooled, with A the consequence that it rapidly deteriorates owing to the alternate heating and cooling to which it is subjected. Furthermore, it is not easy to crane the section back into place on the roof unless thereis provided excessive clearance between the removable charging section and the adjacent fixed portions of the roof. e

It is an object of the present invention to provide means whereby a furnace having an arched roof may be charged from above without introducing the disadvantages mentioned above.

With this-end in view and in accordance with the invention there is provided an open hearth furnace having at least one charging section of its roof formed separately from the hearth It is alsoknown toconstruct an openA hearthv z furnacev with asection of its roof removable. In the operation of such a furnace, charging is efl fected from above by first displacing the `removable section ofthe roof right away from theA furnace with the ald of a crane or the like, after which the charge is insertedinto the furnace through theopening in the roof. Such a process and from the remainder of the roof; and means for transferring the said charging section longitudinally of the furnace from its normal or closed position so as to lie above another portion of the furnace, roof thus leaving an opening in the roof through which \the furnace may be charged from above.

The` fact thatl the charging section is moved longitudinally of the furnace so as to be located immediatelyabove another hot portion of the roof ensures firstly that the charging section'is not unduly cooled, as it is kept comparatively hot by heat ra iated from the roof, and secondly that the static condition of the sectionA remains unchanged during the displacement. v

A furnace constructed in accordance with the invention preferably comprises two charging sections located at the centre of the roof, each being a complete span, and if desired the remain-- ing portion of the roof may also be constructed in sections each being a complete span .separate from lthe charging sections and from the furnace hearth. By this means any one or more of these removable sections can :be quickly and easily removed from the furnace roof for repair or replacement.

In charging the furnace each charging section (if there be more than one) is first lifted, so as to be clear of the remaining adjacent parts of the roof, andls then transferred longitudinally of the furnace softhat it liesabove another portion jof the furnace roof, whereupon the furnace is charged from above by means of abasket-'type charger. f

The time taken to charge is, by this'means,.

, these sections will be nace may be formed with one or since abattery of four or ve furnaces are all charged within twenty minutes or so, the charg-` ing and smelting cycles are substantially in phase, thus simplifying the regulation and working of the several furnaces by virtue of the fact that they can be controlled as one.

Preferred embodiments of the invention will now be described with reference to the accompanying diagrammatic drawings in which:

Figure 1 is a longitudinal sectional elevation of an open hearth furnace constructed in accordance with the present invention,

Figure 2 is a perspective view of one charging section of a furnace roof,

Figures 3 and 4 are similar plan views-of a furnace showing two charging sections in their closed and opened positions respectively,

Figure 5 is a longitudinal sectional elevation of a furnace having a modified form of roof,

Figure 6 is a longitudinal sectional elevationl of a portion of the roof of a furnace and showing another modification of a charging section,

Figure 7 is a View similar to that of Figures l, l

5 and 6 but showing a roof having charging sections so constructed and arranged that they need not be lifted before being transferred longitudinally of the furnace, and

Figure 8 is a transverse section of an open hearth furnace having one or more of its roof sections formed with three hinge points.

In Figure 1 is illustrated a normal type of open hearth furnace with the exception that the centre portion of the arched roof is constructed in the form of two sections IUA and IDB, each of which comprises a complete span over the furnace from walls. Henceforth each of termed a charging section since it is by displacement of one or both of these sections that charging is effected. Each section can be lifted vertically so as to clear the remaining adjacent portions I of the roof and can be transferred longitudinally of the furnace into the position such as that shown at I (IA so as to allow a charging basket II to be lowered into the furnace from above( The sections IIIA and IBB can both be removed separately or together in which latter case a larger basket is employed.

It will be seen that when a charging section, such as IDB, is in its closed position the inner face of the charging section lies substantially fiush with the inner face of the remaining portions I0 of the roof and when a charging section, such as IDA, is in its opened position it lies immediately above a hot part of the furnace roof and is `thus prevented from cooling unduly.

Each charging section is constructed of refractory bricks enclosed preferably within a metallic framework and each section rests freely upon the longitudinal front and back walls of the furnace hearth; preferably in sand seals formed at the tops of these walls.

As illustrated in Figure 1, a hydraulic piston and cylinder I2 is used to rotate the wheels I3, around each of which run chains I4 by which the section IDA is lifted, whilst a hydraulic piston and cylinder I is used to transfer the trolley I6 which runs on rollers I1 and which carries 'the section IUA. The lifting` and transferring mechanism may be operated pneumatically, electrically, by steam or in any other suitable manner. The furmore small side doors, one of which is shown at I8, for fettling the hearth or for the introduction of refining and correcting agents and for the working of the furnace generally.

the front to the back In place of the hydraulic lifting and transferring mechanism illustrated in Figure 1 ordinary cranes may be used, and in any case the transferring and charging mechanism may serve a battery of furnaces.

One of the sections 10A and IBB is illustrated in perspective in Figure 2.

Figures 3 and 4 are diagrammatic plan views of the furnace illustrated in Figure 1, Figure 3 showing the charging sections IDA and IDB in their closed positions and Figure 4 showing the sections IIIA and IUB in the opened positions.

Referring now to Figure 5, the whole roof of the furnace here illustrated is constructed in several sections, I9, 20, 10A, 2l, IDB, 22 and 23, each of which is preferably a complete span across the furnace and two of which, the charging sections IDA and IDB, are removable for charging.

The longitudinal edges of all the sections may be provided with sand seals formed along the tops of the longitudinal front and back walls of the furnace. As each section is framed it may be lifted off the hearth for repairs. It will be seen that the whole of the roof in this modification is made up of a plurality of sections each of which is separate vfrom the hearth and the remainder of the roof. The term roof section is used herein to describe any or all of these sections, the expression removable section is used to denote sections sucir as I9 which are removable for repair but which are not normally used for charging the furnace whilst the expression charging section is used to denote those sections which are normally used for charging. In order to complete the prevention of the escape or inlet of gas or air to and from the furnace the transverse edges of each section are provided with sand seals as shown in Figures 5, 6 and 7.

As in the case of Figure 1 the sections IllA and IDB of Figure 5 can be raised up from the remainderof the furnace roof by means of chains I4 and may be transferred horiontally by means of hydraulic jacks I5. Either one or both of the charging sections IIJA and IDB can be transferred longitudinally of the furnace so that when the furnace is open for charging each section lies on top of another part of the furnace so that it is prevented from cooling rapidly and the life of the brickwork is thereby prolonged. The section IOA may be raised to the position shown in broken lines and is thereafter transferred to the left so as to li above the removable sections I9 and 20.

The lifting and transferring mechanism may be of any known or suitable kind and preferably are inter-locked, so that only one can be operated at a time, by means of the apparatus described in United States Patent 2,313,837 when hydraulically operated. The same principle of interlocking may be applied when the lifting mechanism is other than hydraulic.

That portion of the roof above which lies a transferred section may tend to become over hot and therefore it may be necessary to provide means for cooling it. When this is done it is possible to relate the cooling of the roof with the movement of the charging section by an outerlocking arrangement similar to that described above.

When either one or both charging sections have been transferred to one side a charging basket is lowered into the furnace with the aid of a suitable crane.

When one of these charging sections has to be taken away for repairs the chains I4 are disconnetted. from that Section and the latter..is .re;

" moved with. the .aid of a crane, while the ref' edges of the sectionand the 'transverse-members, thereof are bridged by girders 25 by, which the seotionfcan be lifted. Mechanicalstresses set up in tho bri'okw'ork due to the weight of the brick-.- work and: thermal, expansionlare taken by this.

frame 24 so that the usual buckstaysmay Alie dispensed with.

The chargingsection illustrated .in Figures 5,. 6'a1'1df74` are constructed in such a way that the, lng'itudinal thrust ofl the expanding refractory.

material A is -supported bythe metallic ,frame 24 which is itself protected byan adequate thickness offre'fractory material. Thus .for example in Figure bricks 49 are lstepped up so as to raise the resultant thrust to the height of the metallic, frame 24, whilstthe frame 24 is protected from heat bythe refractory Vbricks 49. .If .desired the metallicfframework may itself be. water-cooled.

AFigure G illustrates another arrangement in which'the underside of the chargingsection IUA liesflu's'hwith the briCkWQrk of an adjacentsectioxlil'oi'- the roof. As in the case of Figure 5 bricks. 49 are stepped up so that the longitudinal thrust;`v

in ther refractory bricks may be taken by the metallic frame 24 which is water-cooledv as shown.

Inthve arrangement illustrated, in Figure 7 the. charging sections |0A and HIB are adjacentme,r another as in .the case of .Figure 1 Aand are so constructed andvarranged that they need not vbe f. lifted before being transferred. Hinged anges 26 on the charging lsections are rotated so as. to.

of uneven thermal expansions, with respect to another."v l i l Eachcharging .section may be lifted neither" from above with the aid of chainssecuredto. rings` on the framework of thesection .or'from .below with the aid ofjacks .bearing against the under.-

side of the longitudinal edges'of the section.`

.As mentioned above, each roof section is heldin a .steelroof ring-or frame so that when the "re-.- fractory bricks of the roof expand as a result of.v an increase in temperature the apex ofe'ach roof.. section tends to rise. 'I'he resultant reactiveforce in ,each brick in these. circumstances. is, as. .is knownfshifted .so that it passes outside themiddle third ofthe vbrick-.iso long as-the resultantforcef lieswithin the middle third of the brick tneiatterl' remains .whollyunder compression, but as soon as the resultant force is shifted outside the middle .thirda portion of the'brick is-put under be withdrawn fromsand seals 21 formed in the.

transyerse edges of the adjacent portionsl of the roof, after which the charging section ,is

transferred vlongitiilinaliy into 'the position shown .45

It will be"appreciatedv that, with this arrangement, and also that of Figure 6, all the metal framework is protected from the main heat of the furnace by a protective refractory lining. The

metal framework serves to hold the bricks together and prevent them from disintegrating andA falling into the furnace.

In order to preserve gas-tight seals between a charging section e. g. I 0A and an adjacent removable portion e. g. 20 (Figure 5) of the roof,

or along the joints formed between adjacent.v

charging sections (Figures 1 and 7) or again between adjacent charging sections and a xed portion of the roof, a trough is formed along the top of the transverse edge of one member into which dips a flange formed upon the adjacent member.- The ange may be angularly rotatable so that it can be lifted out lof the sand seal, before moving one or other of the adjacent sections.

In all cases the transverse sand seals are continuations'of longitudinal sand seals formed between the longitudinal edge of a roof section and the hearth wall. Since each section, whether it be a charging section `or a removable section, is protected by sand seals, any slight distortions of the roof do not affect the functioning of the `furnace in any way, Whilst the transverse sand seal-joints permit one section to Arise, as a result nsv tension-:with the* .result that portions of the bricks tend to come apart-and leave' cracks, and the roof generally tends to disintegrate rapidly'.'-

-As shown in Figure 8,-it Ais proposed to avoid' this-diilcultyby, as it were, hinging eachy roof section both at its' longitudinal rimsv 34V and 35 and along a longitudinal line at or near its pole' or apexy 36. Adjacent bricks 31'and 38running along .the apex are formed so as to be respectivelyconcave and convex so that, when the crown ofthe furnace rises, as a result of thermal expan# sion, the two halves 39A and 39B of the roof-f;

section may pivot at the-'hinge point 36. At 40 is shown a iiexible metal protective cover serving f to .prevent sand or the like falling into the :"Ihe hingepoints 34 and 35 at the longitudinal edges of the section are substantially simllar. AThe section is supported by a frame 'or skew backqfM :(correspondingwith'24 of Figure 5) which maybe hollow and formed with an aperture to allow a free flow of air within. Alternatively, it;.may.bez'.wateracooled.i The skew back or frame 4l isformed internally-with a-'convex portion 42 co-operating with ametal liner^43 secured to the outer brick-44 of the roof section'. 'The liner 43 isI externally-concave of large` radius' of .curvature than that of the frame curve 42 so that, as the crown of the roof section rises under thermal expansion, the two halves 39A and 39B of the section pivot not only along the joint 36 but also at the longitudinal edges 34 and 35. A few bricks near each transverse edge are stepped up so that these edgesKl may each dip into a sand seal 45 formed between the skew back or frame 4l and an upstanding portion 46 at the inner face of the Secured to the skew back 4| is a flexible protective metal cover plate 49.

As shown, the frame 4| is formed with the convex surface 42 andthe edge of the roof section with a concave-portion 43. The curvatures may, however, vbe reversed.

In United States Patent 2,313,837 there is described a furnace comprising a hearth and a roof either of which can be,` displaced laterally to allow for charging from above. The roof is loosely boxed within an auxiliary ring which in turn rests freely upon the hearth walls. 'Ihe section ofthe auxiliary ring comprises an upstanding portion, spaced from but retaining the roof and two co-planar horizontal portions the inwardly directed one of which rests upon the top of the hearth walls and the outwardly directed one of which receivesjacks located below the auxiliary ring. .In the present invention the charging and removable sections of the furnace roof may be located upon the furnace walls in the manner described in United States Patent 2,313,837, that is to say, with the aid of an auxiliary ring, and these sections may be lifted and transferred in any of the ways described in the same patent.

The sections may also rest on the hearth Walls without the intermediary of an auxiliary ring and be lifted as described in the. Same patent specification.

What is claimed is:

1. An open hearth furnace including a hearth, a roof thereon having at least one roof section thereof formed separately from the hearth and from the remainder of the roof, said section being arched and formed in two parts which are hinged together along a longitudinal line in the neighbourhood of the crown of the furnace and along each of their longitudinal edges, means being provided for transferring at least one of said sections longitudinally of the furnace from its normal or closed position so as to lie above another portion of the furnace roof thus leaving an opening in the rooi:` through which the furnace may be charged from above. i

2f. A furnace as claimed in claim l, wherein adjacent bricks of the said two parts along the centre hinge line are formed respectively with co-operating cylindrically concave and convex surfaces.

3. A furnace as claimed in claim 1, wherein each roof section is encased by a metallic skewback formed with cylindrically curved internal faces along its longitudinal members, which faces co-operate with correspondingly' curved edge bricks of the roof section.

4. A furnace as claimed in claim 1, wherein each roof section is encased by a metallic skewback which is hollow so that it may be cooled with suitable fluid.

5. A furnace as claimed in claim 1, including a protective cover over each of said hinge lines.

6. An open hearth furnace including a hearth, a roof thereon, having at least one charging section and at least one removable section, each formed separately from the hearth and from the remainder of the roof, means for transferring the said charging section longitudinally of the furnace from its normal or closed position so as to lie above another portion of the furnace roof thus leaving an opening in the roof `through which the furnace may be charged from above, a refractory roof section encased by a metal skewback, and the brickwork of the section adjacent its transverse edges being stepped up` in order that longitudinal thrusts due to thermal expansion are transmitted to the said skewback while the latter may be set back and thus protected from the heat of the furnace by a portion of the refractory brickwork.

7. An open hearth furnace including a hearth surmounted by a transversely arched roof having at least one charging section which is formed separately from the hearth and from the remainder of the roof, and which is of substantially the width of and the same transverse curvature as the roof, and means for transferring the said charging section longitudinally of the furnace from its normal or closed position, so as to lie above another portion of the furnace roof, thus leaving an opening in the roof approximately equal to the width of the roof, through which opening the furnace may be charged from above.

8. An open hearth furnace including a hearth surmounted by a transversely arched roof having at least one charging section and at least one other section, each of which is formed separately from the hearth and from the remainder of the roof, and is ofsubstantially the width of and the same transverse curvature as the roof, means for mounting said other section so thatsaxne is in position of useduring furnace operation, but is otherwise removable as a unit for repair or inspection. andmeans for transferring the said charging section longitudinally of the furnace from its normal or closed position so as to lie above another portion of the furnace roof, thus leaving an opening in the roof approximately equal to the width of the roof, through which opening the furnace may be charged from above.

- y RAOUL NISSIM.