MXPA96002055A - Pre-heating furnace for baked amorphous carbon bodies - Google Patents

Abstract

The present invention describes apparatus (10) for pre-heating a carbon body (12,12') prior to pitch impregnation, utilizing electrical current flow through the carbon body (12,12') along their longitudinal axes. The apparatus comprises a framework (34,30,32,40,34'32'40') on which first and second electrical contact means (60,70,60',70') are movably supported. In use the carbon body is supported on the framework (34,30,32,40,30',32'40') by stationary roller assemblies (46) and the electrical contact means (60,70,60',70') are pressed against opposite ends of the carbon body (12,12') by respective adjustable pressing assemblies (64,74).

Description

PREHEATING OVEN FOR AMORPHOUS BODIES AMORFO CARBON HORN EADO BACKGROUND OF THE INVENTION The present invention relates to a furnace for preheating baked amorphous carbon bodies, which must be densified by impregnation with liquid tar. In the manufacture of carbon and graphite electrodes, it is common practice to extrude a mixture of coke and tar particles to form an amorphous, shaped carbon body. This body of amorphous carbon, subsequently baked, at a temperature in the order of 800 ° C in a baking oven, v. gr. , a gas-fired oven to increase its resistance.

In the course of baking, part of the tar is volatilized leaving a large number of small sized pores in the amorphous carbon body. It is important to densify the body of amorphous carbon by filling these pores with tar. This is commonly accomplished, by means of an additional preheating step at a temperature of approximately 275 ° C, at said temperature, the porous, evacuated baked carbon body is submerged in tar or liquid in an autoclave under pressure. Under these conditions, the tar has a viscosity that allows filling of the pores in the baked charcoal body. After this impregnation step, the amorphous carbon body can be graphitized by well-known techniques, e.g. , the process of Graphitization ^ Longitudinally (GLM) which is described in the Patent of E. U.A.

The "preheating" of a porous baked coal body has been previously achieved in gas-fired furnaces since the desired preheat temperature, e.g. , approximately 275 ° C, is relatively low and can be easily achieved in such furnaces. However, due to the relatively large size of baked carbon bodies intended for use as electrodes in electric arc furnaces, "preheating" required a relatively long time, and the "preheating" from "outside in", results in a non-uniform temperature condition in the baked charcoal bodies. Therefore, it is an object of the present invention to provide an apparatus for rapidly and uniformly "preheating" a baked charcoal body at a temperature suitable for impregnating the tar in the body. Other objectives will be evident from the following description and claims. BRIEF DESCRIPTION OF THE DIAMETERS Figure 1 is a side elevational view of the apparatus of the present invention; Figure 2 is a plan view of the apparatus of Figure 1; Figures 3 and 4 are front elevational, partial views of portions of the apparatus of Figure 1; 'Figures 5, 6 and 6a, show isolation devices Alectric of the prior art, which are used with the apparatus of Figure 1. Figure 7 shows an electrode contact plate of the apparatus of Figure 1; and Figure 8 shows, in some schematic form, an insulating shell for the apparatus of Figure 1. SUMMARY OF I NVENTION The present invention is an oven for heating a body of longitudinally extending amorphous carbon, having the shape of an electrode in cylindrical cross-section, at a temperature which is below the graphitization temperature of the body, using an electric current that passes longitudinally, lengthwise, through the body of coal. 5 The electric current is around 40,000 A, at approximately 30 volts and only enough time is applied for the carbon body to be heated to approximately 275 ° C, much less than the temperature required for graphitization, that is, 2200-3000 ° C. DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, the elevational view of the Figure 1 shows the preheating apparatus of the present invention at 10, which is adapted to preheat an amorphous carbon body 12 cylindrically configured, passing electric current 5 from the power cable 16, longitudinally through of the carbon body 12, to cross over the power cable 18. The power cable 18, applies electric current to the carbon body 12 ', placed along the carbon body 12, shown more clearly in the plan view of Figure 2. The electric current passes longitudinally through the carbon body 12 'to the power cable 22. The apparatus of the present invention includes a working frame of structural steel members, e.g. , beams I. A vertical steel member 30 is disposed opposite to and separate from the vertical steel member 22, both of which are fixed, at 31 and 33, a steel base member 34, horizontal, which is supported on a concrete base 35. The horizontal steel member 40, extends on vertical members 30 and 32, and is fixed thereto at 42 and 44, to provide a rigid structure. The stationary roller assemblies 46, shown in Figure 3, comprise individual rollers 47 and 49, mounted in line on the base member 34, extended between the vertical steel members 30 and 32. An amorphous carbon body 12, is placed on roller assemblies 46, eg. , using a forklift or other conventional device. The rollers 47 and 49 can be grooved, as shown at 41 in Figure 3, in such a way that the carbon body 12 is sheltered therein and restricted from lateral movement, but can move axially on the rollers 47 and 49. As shown in Figure 3, the roller 47 (49) is pivotally mounted at 50 in a steel frame 52 which is fixed to the steel base member 34 as indicated in amorphous carbon body 12 supported on the electrical contact plate 60 is brought into contact with an end 62 of the carbon body 12 by actuating the set 64 of adjustable hydraulic press means, which is fixedly mounted on the vertical steel member 30. The electrical contact plate 70, is placed concurrently in contact with the end 72 of the carbon body 12, driving the .set 74 of adjustable hydraulic press means, which is fixedly mounted on the vertical steel member 32. The plates of contact 60, 60 'and 70, 70', are completely and abuttingly in contact with the entire surface of the carbon body at the ends 62 and 72, respectively, as shown in Figure 7. The electrical contact plate 60, it is pivotally supported at 80 by the expanded horizontal member 40, through the steel washer 76, hanging downward, which, by itself, is pivotally connected to the electrical contact plate 60 in the shackle 78. The plate electrical contact 70, is connected pivotally to the steel rod 80 in shackle 82 and plate 70 is mounted horizontally in a rolling manner, on expansion member 40, by roller assembly 90 engaging steel rod 80 as shown in Figure 4, in which the roller 91 is shown supported on the flange 93 of the expansion member 40. Due to what has been described above, the pivotal and rolling support of the electric contact plates 60 and 70, and the roller support of the carbon body 12, form excellent electrical contact with carbon 12 since the differences in length of Carbon bodies are easily compensated by the flexible performance of the adjustable press means 64 and 74, and the free longitudinal movement of the carbon body 12. Since it is well known that the electrical continuity must be interrupted in metal members of the frame, electrical isolation devices, ie joints 1 16, are provided in the roller support frames 52. The isolation device 1 16 shown in Figure 5 is conventional and is described in the patent of E. U.A. 4, 916,714, comprising a rectangular plate 132 provided with holes and welded to the ends 131 and the adjoining joints between both 132, are provided by a bolt and a nut designated by 133 and 134, respectively. To interrupt the electrical continuity, a flat, rectangular, perforated plate 135, of an electrically insulating material, is disposed between the plates 132. As also the bolts must be insulated, they are provided with a sleeve having the shape of a cylinder with two washers from electrically insulating material designated 136 in Figure 5. Electrical insulation 161 for supporting rods 76 and 80, is in the form of a commercially available tension rod insulator, shown in Figure 6, comprising a pair of metal inserts 170 and 172, threaded separately, which are embedded in the electrical insulator 174 and receive the threaded portions of the steel rods 76 as shown in 180 and 182. The electrical insulation is also provided in 181 between the plates contact 60 and 70, and sets 64 and 74 of respective press media. This is shown in Figure 6a, for the contact plate 60, where the thrust plate 182 is electrically separated from the contact plate 60 by the electrical insulator 184, and 5 is held in place by the bolts 186 going to through electrical insulation sleeves 188 and washers 189. The apparatus of the present invention, in a preferred embodiment, shown in Figures 1 and 2, includes a side-by-side duplicate arrangement, having support members 95 and 97, of transverse bar, for simultaneously preheating a second body of carbon 12 'that receives electric current as a transversal conductor. The roller assembly, electrical contact plates and press means for the duplicate arrangement for the carbon body 12 ', operate independently from the arrangement of the carbon body 12, in such a way that the differences in the lengths of carbon bodies 12 and 12 'are easily accommodated. The carbon bodies 12 and 12 'are exposed to air environmental on all sides and the furnace apparatus of the present invention is preferably placed with an enclosure of thermal insulation, as illustrated at 100 in Figure 8, such that the carbon bodies are heated and surrounded by a static environment of ambient air to ensure rapid uniform heating. The envelope 8 is suitably made of highly insulating laminated wall sheets, one of its sides being Removable (as indicated at 102) to allow placement and removal of carbon bodies 12 and 12 '.

Claims (3)

1. A CLAIMS v 1. Apparatus for preheating an amorphous carbon body, cylindrically shaped, comprising: a) a frame formed of structural steel members, including i) a first vertical steel member arranged opposite to and separate from, a second member of vertical steel ii) a horizontal steel member expanding the first and second vertical steel members and fixed thereto to provide a rigid structure; b) a first stationary roll assembly extending horizontally in line, between the first and second vertical steel members, adapted to support a cylindrically shaped amorphous carbon body, extending between the first 15 and second steel members and to allow said amorphous carbon body to be rolled back and forth on said roller assembly between the first and second steel members verticals; c) a first electrical contact means 20 pivotally supported and hanging downwardly of said horizontal member adjacent to said first vertical support member; d) a second electric contact means rotatably supported and hanging downwardly of said horizontal member adjacent to said second vertical support; e) a first adjustable press assembly, mounted *, fixedly on said first vertical support member, to apply a pressing force on said first electrical contact means; f) a second adjustable pressing assembly, fixedly mounted on said second vertical support member, for applying a pressing force on said second electrical contacting means; said apparatus being configured in such a way that it can be receiving a carbon body configured on said roller assembly, between the first and second electrical contact means and can be brought into contact by said first and second contact means by adjusting the first and second press assemblies.
2. 2. Apparatus according to claim 1, wherein a) said frame formed of structural steel members includes i) a third vertical steel member disposed opposite to and separated from a fourth vertical steel member ii) a horizontal steel member expanding the third and fourth vertical steel members and attached thereto to provide a rigid structure; b) a second stationary roller assembly extending horizontally in line between the third and fourth vertical steel members adapted to support a body of amorphous carbon cylindrically shaped, extending between and fourth steel members and to allow said amorphous carbon body to be rolled back and forth on said roller assembly between the third and fourth vertical steel members; c) a third electrical contact means pivotally supported and hanging downwardly of said horizontal member adjacent to said third vertical support member; d) a fourth electric contact means supported roladamente and hanging downwardly of said horizontal member adjacent to such fourth vertical support; e) a third adjustable pressing assembly, fixedly mounted on said third vertical support member, for applying a pressing force on the third electrical contact means; f) a fourth adjustable pressing assembly, fixedly mounted on said fourth vertical support member, for applying a pressing force on said fourth means of electrical contact; g) means for electrically connecting said second and third electrical contact means; said apparatus being configured in such a way that said first and second roller assemblies are in a side-to-side relationship and such that a shaped carbon body can be received on said roller assembly between said third electrical contact means and can be connected by means of said third and fourth means, by adjusting said first and second press assemblies.
3. 3. The apparatus according to claim 1, in combination with a thermally insulating envelope, which substantially surrounds said apparatus.