US3796326A

US3796326A - Cupola furnace having a closure arrangement

Info

Publication number: US3796326A
Application number: US00213636A
Authority: US
Inventors: E Buhrer
Original assignee: Individual
Current assignee: Georg Fischer AG
Priority date: 1970-12-31
Filing date: 1971-12-29
Publication date: 1974-03-12
Anticipated expiration: 1991-03-12
Also published as: BE777538A; DE2162057A1; FR2120007B1; GB1372590A; IT944241B; AT317452B; DE2162057B2; CA964057A; FR2120007A1; SE377181B; DD94875A5

Abstract

Apparatus for charging a cupola furnace through an upper opening whereby a charging bucket comprising a bottom closure member is placed upon the charging opening in sealing engagement with the rim thereof. A cupola closure member is situated interiorly of the cupola furnace and operates to seal the charge opening from within the furnace. After the charging bucket is lowered into engagement with the rim of the upper opening, the cupola closing member is withdrawn from the charging opening in a direction interiorly of the furnace, and the bucket bottom closure is opened to effect charging. The size of the charging throat of the cupola furnace is made larger than is customary, and the device is structured to enhance discharge of waste gases therefrom.

Description

United States Patent 91 Biihrer CUPOLA FURNACE HAVING A CLOSURE ARRANGEMENT Inventor: Erwin Biihrer, Vogelingasschen 40,

Schafthausen, Switzerland [451 Mar. 12, 1974 3,653,647 4/1972 Carr et al 266/31 Primary Examiner-Robert G. Sheridan Attorney, Agent, or Firm--Toren and McGeady [5 7] ABSTRACT Apparatus for charging a cupola furnace through an upper opening whereby a charging bucket comprising a bottom closure member is placed upon the charging opening in sealing engagement with the rim thereof. A cupola closure member is situated interiorly of the cupola furnace and operates to seal the charge opening from within the furnace. After the charging bucket is lowered into engagement with the rim of the upper opening, the cupola closing member is withdrawn from the charging opening in a direction interiorly of the furnace, and the bucket bottom closure is opened to effect charging. The size of the charging throat of the cupola furnace is made larger than is customary, and the device is structured to enhance discharge of waste gases therefrom.

PATENTED MAR 12 1974 saw 1 or g Fig.1

PAIENTED MR 1 2 I974 sum 2 or a Fig. 2

PATENTEDNAR 12 mm SHEEI 8 (IF 6.

CUPOLA FURNACE HAVING A CLOSURE ARRANGEMENT FIELD OF INVENTION The present invention relates to a cupola furnace having an upper charging hole or opening located above the furnace throat and provided with a closure arrangement whereby a charging bucket can be placed on the rim or margin of the opening to effect charging of the cupola by activation of the closure arrangement.

BACKGROUND OF THE INVENTION A variety of constructions have been proposed for cupola furnaces comprising closure arrangements through which the cupola can be charged.

According to one particular embodiment of a cupola furnace, the upper portion of the throat or top of the furnace is constructed in the manner of a container having a configuration similar to those found in blast furnaces. With the top of the container open, an inclined elevator mechanism conveys a charge into the container by means of a tiltable bucket. After the charging opening of the container has been closed, a bottom closure of this container can be opened whereupon the charge falls into the melting zone of the eupola furance.

This embodiment has the disadvantage that the material to be charged must be of relatively small particle size in order to prevent bridge formations during the charging. This bridge formation, which is to be avoided, is a consequence of the restricted crosssection through which the material to be charged must pass when it moves from the upper container space into the throat of the cupola furnace.

Another disadvantage of this known construction is that the required repeated pouring or charging movements to which the charge is subjected result in unmixing of the charge. This in turn makes it necessary that, on the one hand, the coke and the slag forming agents, and on the other hand, the metallic components must be charged to the cupola furnace in separate and alternating stages.

It has also been proposed to construct a cupola furnace wherein a charging bucket can be placed onto a top charging hole or opening in such a manner that the bucket closes the opening. A closure device is arranged in this construction below the opening. This closure device is built into the throat of the furnace and is a twopart mechanism constructed in the form of a slide. This closure mechanism is actuated after the bucket has been placed on the opening. After this two-part closure mechanism has been opened, the bottom closure of the charging bucket can be opened and thus the material to be charged is supplied to the cupola furnace. After the bottom closure of the bucket has been actuated, the two-part closure device built into the throat of the furnace can again be closed.

This latter mechanism is presently employed in a variety of applications. In order to improve the closure arrangement, these two-part slide-like flap arrangements are also used in the form of a cylindrical surface.

As is well known in this art, a cupola furnace during start-up and when it is to be closed down, to wit, when it is to be blown empty, generates extremely hot waste gases. This, of course, results in considerable temperature differentials in the structure of the charging elements. These considerable temperature fluctuations cause, as a general rule, a deformation of the charging elements which can be avoided only if the elements have a very stiff or rigid configuration. Experience has demonstrated that plane or cylindrical iron plates are unsuitable for this purpose. Slide plates additionally require considerable play in their guides, the required play often times amounting to several centimeters. This required play is independent of the configuration of the slide plates.

Moreover, such embodiments require repeated and very careful service in order to assure proper operation.

A cupola furnace which is fitted with a throat closure device of the kind indicated above, has moreover the disadvantage that the waste gases are withdrawn from the melting zone or column through an annular surface. This creates extremely high gas velocities so that the unpurified cupola waste gases contain a very high amount of dust. This disadvantage applies to most of the prior art cupola furnaces which are charged through the throat.

It is a primary object of the present invention to overcome the disadvantages of prior art top charging arrangements for cupola furnaces.

Briefly, the cupola furnace of the present invention is characterized in that at least one throat closure member is movable from the interior of the cupola furnace to close the charging hole or opening and that the throat, which is situated above the melting column or zone of the cupola furnace, has a diameter which is en larged beyond customary dimensions.

In accordance with the invention, the throat and the charging opening above the melting column of the eupola are enlarged to such an extent that enables very bulky portions of the metallic components of the charge to be easily fed without obstruction into the interior of the cupola.

Another advantageous embodiment of the invention is characterized in that the throat consists of a coneshaped filling space which becomes narrower towards the cupola and that this cone-shaped filling space merges into an approximately cylindrical upper shaft or chute whose cross-section is at the most equal to the cross-section of the lower shaft and that the discharge by suction of the waste gas emanating from the top of the furnace is arranged to occur in the annular space between the upper and lower shaft.

The passage of the cupola waste gases through the gas discharge can be effected with such a low velocity that the dust content of the gas is only a fraction of the dust content of waste gases discharged from prior art cupola furnaces wherein the gases exit through an annular opening at the level of the melting column.

In the type of device to which the present invention relates, it may be found that after many years of use, the position of the charging opening relative to the throat of the furnace may, due to deformation, be displaced. It is also feasible that the holding arm of the closure body which bears against the opening from below will become warped after prolonged use. For this reason the invention provides a type of support which assures that the position of the closure member will adapt itself to the position of the opening so that even after prolonged use a satisfactorily sealing closure is assured.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understancing of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described the preferred embodiments of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. I is a sectional elevation of a first embodiment of a cupola furnace in accordance with the invention showing a filled charging bucket placed in position preparatory for charging;

FIG. 2 is a sectional elevation of the cupola furnace of FIG. 1 showing the arrangement after the closure mechanism has been actuated for charging;

FIG. 3 is a sectional view showing in more detail the mechanism of FIGS. 1 and 2;

FIG. 4 is a sectional elevation showing a second embodiment of the invention;

FIG. 5 is a sectional view showing in more detail the embodiment of FIG. 4; and

FIG. 6 is a sectional elevation showing a further embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and in particular to FIGS. 1, 2 and 3, there is shown a cupola furnace comprising a charge or column ll located within an inner wall 2. The level of charge in the melting column 1 is sensed in a known manner by a mechanism 3. When a predetermined level has been reached, a new charge is supplied to the cupola. The throat or top 4 of the cupola is formed by a conically shaped portion 5 which merges into a cylindrical portion 6. The cupola furnace gases are withdrawn through the pipe 7 in the direction of the arrow 8. A furnace throat closure 9 has an opening I0 (see also FIG. 3) onto which a charging bucket 11 can be placed. A closure body 32 rests on a pendu- I lum or pin support 13 which receives the closure body 12 in a bore 14 and which is supported on the bottom 15 ofa bore 16. The bore 16 is enlarged relative to the diameter of the pin support 13 by an amount conforming to the play which is required for proper functioning of the device.

The bore 17 in the closure body I2 is also larger in diameter than the diameter of the pin support holding means 18 in order to enable the necessary play therebetween. These plays which are provided between the components of the clsoure mechanism make it possible for the closure body 12 to adapt itself on all sides to the rim or edge of the charging opening 10 thereby assuring effective sealing engagement. At least three guide plates 19 guide the closure body 12 during the closure operation of the opening 10 into the correct position.

A U-shaped support arm 20., which is guided in a mounting 21 so that it can be raised and lowered but not rotated, is counterbalanced through arope 28 and rollers or pulleys 29 secured at a support structure 30, with a counterweight 22 in order to enable the closure body 12 to be pressed with the required closing pressure against the opening 10 by applying and relieving the weight of counterweight 22 to the support arm 2%.

During ordinary operation, when the closure body 12 closes the opening 10, the counterweight 22 is lifted a distance 24 from a support 23. An air cylinder 25 is connected during normal operation througha line 26 to a compressed air network and operates to lift the counterweight 22 the distance 24 from the support 23. When the cupola furnace is shut down, the compressed air cylinder 25 can be emptied through the valve 27 of the air line 26. When the counterweight 22 rests on the support 23, the support arm 20 is moved downwardly a predetermined distance thereby to open the opening 10.

When the cupola furnace is started up, the valve 27 of the air line 26 is again set in such a manner that compressed air is supplied to the cylinder 25. A structural member 31 on the cover 9 carries a floating closure plate 32 which adapts itself to each position of the support arm 20.

A lifting roller 33 of a charging trolley hoist (not shown) carries a coupling piece 34 which in a known manner can establish an automatic connection with a headpiece 35. The headpiece 35 is connected with a rod 36 whose lower end is connected with the bottom closure 37 of the charging bucket 11. Two jibs or traverses 38 and 39 are rigidly connected with the coupling piece 34. The

jibs

38 and 39 support, through flexible support members 410 and 41, the upper closure or cover 42 of the bucket i 1. The cover 42 lowers itself upon the charging bucket 11 and maintains a sealing engagement therewith when the coupling piece 34 is lowered or while it is in engagement with the headpiece 35 to maintain the bucket 11 suspended from the charging crane. When the bucket 11 is lifted by the charging crane, the closure 42 rests on the bucket 11 and the support members 49 and 41 are relieved. During this engagement, the bucket I1 may be placed on the rim of the opening 10 and will close the latter.

FIG. 3 shows that when the bucket 1 1 is placed in position, a safety distance 43 is formed between the bottom closure 37 and the closure body 12. If the coupling piece 34, by actuation of the charging crane, is lowered from the position in FIG. I into the position of FIG. 2, the closure body 12 and the parts l3, l5 l8 and 20, connected therewith, are also lowered in a vertical direction. The bucket 11 will open upon lowering of the coupling piece 34 for emptying of the charge material contained therein. During this lowering procedure, the bucket 11 remains closed by the upper closure 42. The material in the bucket falls over and around the cone of the bottom closure 37 and around the closure body 12 onto the melting column I in the cupola furnace. After the bucket has been emptied, the bottom closure 37 is lifted and at the same time the closure body 12 is pressed against the opening 10 by the counterweight 22. The various parts of the closure mechanism are constituted such that the force with which the closure body 12 is pressed against the opening 10 by the counterweight 22 is half of the weight of the

parts

35, 36 and 37.

FIGS. 4 and 5 show a further embodiment of the invention which differs from that of FIGS. 1 3 in that the round bucket 11 and the circular charging opening 10 are replaced by a charging bucket 50 and a charging opening 52 having a rectangular cross-section as viewed in a horizontal plane. The closure lid or cover 52 is, as shown in FIGS. 4 and 5, a part of the charging crane. A stirrup 53 is gripped in a usual manner by the charging crane and carries the bucket 50 through rods 54, rods 55 and a bottom closure 56. The bucket 50 is placed down onto the rim of the opening 51 by means of a guide (not shown) while hanging from the charging crane. As soon as the bucket 50 is placed on the cover 57, the bucket releases a blocking mechanism whereby the lifting

cylinders

58 and 59 are actuated in a known manner. The blocking mechanism is of conventional nature and is generally indicated by reference numeral 90. It may comprise a sensor 91 and a blocking control 92. The

closure bodies

60 and 61 are moved by means of the lifting

cylinders

58 and 59 and by means of two levers 63 from the closed position A into the opened position 13. By further lowering of the

parts

53, 54 and 55, the

bottom closures

56 and 62 of the bucket 50 are opened from the closed position C into the opened position D, and the charge thus falls into the melting column. By lifting the stirrup 53, the bottom flaps 56 and 62 are closed and release the actuation of the lifting

cylinders

58 and 59 whereby the

closure bodies

60 and 61 are moved into the position A.

FIG. 5 shows a closure body 61 in section according to FIG. 4. This rectangular closure body 61 has one of two levers 63 which holds the closure body 61 in a nonrotatable position. This is accomplished by the inserts 64 and the pendulum or pin support 65. The

closure bodies

60 and 61 can be pressed against the opening in a similar manner as disclosed in connection with the closure body 12 in FIG. 3.

From a practical point of view, it is required that the throat 4, which is enlarged in accordance with the invention, aswell as the adjoining pipes 7, be insulated in order to avoid large heat losses.

In FIG. 6, a melting column 71, a lower shaft 72 and an upper shaft 93 of the cupola furnace are shown. A throat 74 of the furnace consists of a conical portion 75 which is adjacent the cylindrical upper shaft 73. The throat closure consists of a closure body 76 which can be placed against the opening 77 from the interior of the cupola furnace. The upper shaft 73 is surrounded by an annular space 78 from which the waste gas discharge device 79 discharges the formed gases in the direction of the arrow 80.

The manner of operation of the cupola furnace hav' ing the charging arrangement of the present invention is as follows:

After the start-up of the cupola furnace, coke and charge is added through the bucket 85 and through the opening 77 for a period until the melting column 71 has filled the upper shaft 73. The volume of the upper shaft 73 is dimensioned such that more than one charge of the bucket 85 can be accommodated. The throat gases which are formed can escape only through the gas suction mechanism 79, through the annular space 78 into the line 80. This is so since the throat 74 is closed by the closure 76.

Advantageously, between the throat 74 and the gas suction device 79 there is arranged a connecting line 86. Since the pressure in the upper portion of the gas suction device 79 is somewhat lower than the pressure in the throat 74, there is a constant flow or scavenging of the throat 74 with gas.

If the temperature of the gases during empty melting of the furnace increases above a predetermined permissible limit value, the valve 84 opensThe amount of water which passes through the water line 87, the valve 84 and the connected nozzles 82 causes a cooling of the exiting gases down to a predetermined temperature and thus prevents damage which otherwise could occur due to too high gas temperatures.

A cupola furnace according to the present invention has the advantage that the dimensions of the throat and of the charging bucket can be chosen to be sufficiently large that the bulkiness of the material to be charged into the furnace can be selected taking into consideration merely the inner width of the cupola furnace but not that of the charging device.

The inventive closed cupola furnace thus described has the additional advantage that the amount of gas to be sucked off is lowered to a level of 50 65 percent as compared to prior art constructions.

The present invention insures that at no time, including charging, will cupola furnace gases exit to the atmosphere or leakage air be admixed with the waste gases. This is of particular importance if the dust removal from the cupola waste gases is to be effected by electrofilters.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

l. A charging mechanism for a cupola furnace having an upper charging opening comprising: a charging bucket adapted to be placed in sealing engagement with said opening; a bottom closure member for said charging bucket; a cupola closure member extending from within said cupola to be placed in sealing engagement with said opening; means for moving said cupola closure member in a direction interiorly of said cupola out of sealing engagement with said opening; said means for moving said cupola closure member including a U-shaped support arm having a pair of ends, means enabling said support arm to movably-extend from the interior to the exterior of said furnace while maintaining said furnace in a sealed condition, support arm actuating means located exteriorly of said furnace and engaging said support arm at one of said ends, and means connecting said cupola closure member to the other end of said support arm whereby said cupola closure member may be moved into and out of sealing engagement with said opening by operation of said actuating means; and means for opening said charging bucket bottom closure member while said bucket remains in sealing engagement with said opening whereby said cupola may be charged with the contents of said bucket.

2. A charging mechanism according to claim 1 wherein said charging bucket comprises an overhead supporting mechanism which includes said bottom closure member, said supporting member being configured such that the weight of said bucket rests upon said closure member to maintain a sealing engagement therebetween when said bucket is supported from above through said supporting mechanism, a charging bucket upper closure member, crane means including means for engaging said charging bucket supporting mechanism to transport said charging bucket, and flexible means for suspending said upper closure member from said crane means to locate and maintain said upper closure member in sealing engagement with said bucket when said crane means engages said supporting shaped throat section located proximate and below said charge opening, a cylindrically shaped charge melting column located below said comically-shaped throat, and a cylindrically shaped section adjacent said conical throat having a diameter not larger than said melting column, with said melting column and said cylindrical section being vertically juxtaposed to define an annular space therebetween for permitting escape of waste gases therethrough.

Claims

1. A charging mechanism for a cupola furnace having an upper charging opening comprising: a charging bucket adapted to be placed in sealing engagement with said opening; a bottom closure member for said charging bucket; a cupola closure member extending from within said cupola to be placed in sealing engagement with said opening; means for moving said cupola closure member in a direction interiorly of said cupola out of sealing engagement with said opening; said means for moving said cupola closure member including a U-shaped support arm having a pair of ends, means enabling said support arm to movably extend from the interior to the exterior of said furnace while maintaining said furnace in a sealed condition, support arm actuating means located exteriorly of said furnace and engaging said support arm at one of said ends, and means cOnnecting said cupola closure member to the other end of said support arm whereby said cupola closure member may be moved into and out of sealing engagement with said opening by operation of said actuating means; and means for opening said charging bucket bottom closure member while said bucket remains in sealing engagement with said opening whereby said cupola may be charged with the contents of said bucket.

2. A charging mechanism according to claim 1 wherein said charging bucket comprises an overhead supporting mechanism which includes said bottom closure member, said supporting member being configured such that the weight of said bucket rests upon said closure member to maintain a sealing engagement therebetween when said bucket is supported from above through said supporting mechanism, a charging bucket upper closure member, crane means including means for engaging said charging bucket supporting mechanism to transport said charging bucket, and flexible means for suspending said upper closure member from said crane means to locate and maintain said upper closure member in sealing engagement with said bucket when said crane means engages said supporting mechanism with said bottom closure member at or below a bucket sealing position.

3. A charging mechanism, according to claim 1, wherein said means connecting said cupola closure member to said support arm includes means enabling swivelled movement of said closure member to facilitate sealing engagement of said closure member with said charging opening.

4. A charging mechanism, according to claim 1, wherein said cupola furnace comprises a conically-shaped throat section located proximate and below said charge opening, a cylindrically shaped charge melting column located below said conically-shaped throat, and a cylindrically shaped section adjacent said conical throat having a diameter not larger than said melting column, with said melting column and said cylindrical section being vertically juxtaposed to define an annular space therebetween for permitting escape of waste gases therethrough.