MXPA00010221A - Method for producing elongated carbon bodies - Google Patents

Abstract

The present invention relates to a method for continuous production of elongated carbon bodies, particularly carbon electrodes which are produced in direct connection with the smelting furnace wherein the electrodes are consumed, where a metallic casing containing unbaked carbonaceous electrode paste comprising a particulate solid carbon material and a carbonaceous binder is continuously or substantially continuously lowered through a baking furnace which is heated to a temperature between 500 and 1200°C, whereby the unbaked electrode paste is baked into a solid carbon body and where the casing is extended by joining new sections of casing on the top of the casing as the casing is lowered through the baking furnace, where the lower part of each section of casing has an outer diameter that is equal to or smaller than the inner diameter of the upper part of each section of casing, said method being characterized in that each new section of casing is mounted upon the section of casing below in such a way that the lower part of the new section of casing is positioned inside the casing of the upper part of the section of casing situated below the new section of casing and where the length of the lower part of each section of casing has such an extension that the new section of casing during baking freely can slide downwards in relation to the section of casing situated below the new section of casing a distance which at least compensates for the shrinkage of the electrode paste contained in the casing during baking of the carbon body in the baking furnace.

Description

METHOD FOR PRODUCING LONG CARBON BODIES FIELD OF THE INVENTION The present invention relates to a method for the continuous production of elongated carbon bodies, and more specifically, to carbon electrodes that are produced in direct connection to a melting furnace, where the electrodes are used, wherein a meta coating, consisting of electroless paste, carbonaceous without cooking consisting of a particulate carbon material, and a carbon binder, is baked in a solid carbon body by lowering the metal coating containing the electrode paste, carbonaceous downwards through a cooking oven.

PRIOR ART From Norwegian Patent No. 154860 a method for the continuous production of elongated carbon bodies is known, wherein a perforated metal coating containing electrode paste, carbonaceous without cooking consisting of a solid particulate carbon material and a carbonaceous binder, in A continuous or almost continuous mode is lowered through a melting furnace that is heated to a temperature between 500 and 1300 ° C. The electrode, carbonaceous paste without cooking is at this temperature baked in a solid carbon body. As the coating is lowered through the baking furnace, new sections of the coating are welded to the top of the metal coating and more electrode paste, carbonaceous, without cooking is filled into the coating. The method described above can be used for the continuous production of elongated carbon bodies which after being baked in the baking oven are cut into suitable lengths and which can be used as coating blocks for melting furnaces, lower blocks for cathodes in electrolytic cells for the production of aluminum and the like; or the method can be used for the production of continuous carbon electrodes in direct connection with a melting furnace, where the electrodes are being used. In the last mentioned case, the baking oven is arranged on the melting furnace in such a way that the produced electrodes extend towards the melting furnace where these are consumed. The elongated carbon bodies produced can have any convenient cut. Carbon electrodes that are produced in direct connection with melting furnaces usually have a circular cross section. By the known method new coating sections, as already mentioned, are welded to the upper part of the coating. This is an operation that requires intense labor. In addition, when the electrodes are produced in direct connection with a melting furnace, where the electrodes are consumed, the welding operation takes place in a hot gas atmosphere and often contaminated. For electrodes where the coating is removed when the electrodes have been baked, welding the sections of the coating together means that the coating has to be cut horizontally to remove it. With the heating, the viscosity of the electrode paste decreases so that the electrode paste softens and with more heating at a temperature between 500 and 1300 ° C. The electrode paste is baked to a solid carbon body. During heating, the electrode paste shrinks and thus occupies a smaller volume. By known methods where coating sections are used which are connected to each other by welding, the electrode paste will not have a downward flow to compensate shrinkage in view of the electrode paste sticking to the inner surface of the coating. Thus, there is a possibility that the baked carbon body contains cavities, which increases the possibility of rupture of the electrode when the carbon body is used as an electrode. Also with the shrinkage of the electrode paste that adheres to the inner surface of the coating, the coating can be deformed locally. This will also be improved as the coating, during the other heating in the baking oven, extends in the axial direction, whereby it is possible to introduce a tensile stress into the electrode paste. In relation to the traditional self-baking electrodes for steel ovens, the zueca patent number 112236 discloses a method for the use of coating sections that are filled with electrode paste, carbonaceous without cooking. According to the zueca patent, each coating section is filled with electrode paste prior to the assembly of the sections on the top of the electrode column. The lower part of each coating section has a diameter somewhat smaller than the remaining part of the coating. When a new section of the lining is mounted on top of the electrode column, the bottom of the new section is installed in a telescopic shape in the section of the lining located below the new section. To join the new section of the cladding to the electrode column, the area between the bottom of the new cladding section and the top of the electrode column is heated, whereby the electrode paste in this area melts or softens , whereby the electrode paste in the lower part of the new section of the coating flows together with the electrode paste in the upper part of the electrode column. Then, the new section of the liner is welded to the lower liner. Baking the electrode takes place in the area of electrical power supply to the electrodes in the same way as for traditional self-baking electrodes. The method described in the patent zueca number 112236 for joining sections of curing [sic] filled with electrode paste, however, does not solve the problems described above in connection with the electrode produced according to Norwegian patent number 154860. Thus, , the use of the method for joining coating sections according to the patent zueca in connection with the method described in the Norwegian patent number 154860, will not solve the problem of shrinkage of the electrode paste during cooking or the problem caused by the expansion of the coating when the coating is heated in the baking oven. Furthermore, by using the method described in the patent zueca it will still be necessary to cut the coating horizontally to remove the coating below the baking oven since it is a prerequisite according to the patent zueca that the new sections of the coating are welded to the coating under the new coating.

DESCRIPTION OF THE INVENTION An object of the present invention is to provide a method where, by using the method according to Norwegian Patent No. 154860, it is not necessary to weld new sections of the coating to the coating below the new section of the coating, and where an automatic compensation is obtained for the shrinkage of the electrode paste and for the extension of the coating during cooking. Accordingly, the present invention relates to a method for the continuous production of elongated carbon bodies, particularly carbon electrodes that are produced in direct connection to the melting furnace, where the electrodes are consumed, where a metallic coating containing an electroless paste, carbonaceous without cooking, consisting of a particulate solid carbon material, and a carbonaceous binder is lowered continuously or almost continuously through a baking oven which is heated to a temperature between 500 and 1200 ° C, with which the electrode without cooking is baked in a solid carbon body, and where the coating is spread by the new sections of the coating on the upper part of the coating as it is lowered through the cooking oven, where the part bottom of each section of the liner has an outer diameter that is equal to or smaller than the internal diameter of the upper part of each liner section, the method being characterized in that each new liner section is mounted in the lower liner section in such a way that the lower part of the new liner section is located within the lining of the upper part of the liner. section of the liner located below the new section of the lining, and where the length of the lower part of each lining section has such an extension, that the new lining section during firing can slide freely downward relative to the section of the lining located below the new section of the coating a distance that at least compensates for the shrinkage of the electrode paste contained in the coating during cooking of the carbon body in the baking oven. According to a preferred embodiment, coating sections are used consisting of an upper cylindrical portion and a lower cylindrical portion, where the diameter of the lower cylindrical portion is equal to, or smaller than, the inside diameter of the upper cylindrical portion. It is preferred that the ratio between the length of the upper part and the lower part of the coating section be between 1: 1 to 1000: 1, and more preferably, between 3: 1 and 12: 1. According to another embodiment, cladding sections are used where at least the lower part of each cladding section has a conical space, so that the external diameter of the conical part of the cladding section is smaller than the diameter of the cladding section. the upper part of the coating. By the method of the present invention each lining section is thus not rigidly fixed to the section of the lower lining, but is only loosely placed on top of the section of the lining located below. As the electrode paste in the section below the upper section shrinks during cooking, the weight of the upper section of the liner will cause the section of the liner to slide freely downward towards the lining in the section of the lining located below. The shrinkage of the electrode paste, in this way, will not cause local deformation of the coating. By the method of the present invention, the separation of the coating sections after cooking the electrode in the baking oven is substantially simplified as it is only necessary to cut the coating in the vertical direction. According to another embodiment of the present inventionEach coating section is filled with electrode paste without baking to such a level that the distance from the level of the electrode paste to the top of each coating section is less than the length of the bottom of the coating sections. The sections of the coating can be filled with electrode paste without cooking before or after the sections are installed. In this way, the lower part of the cladding sections, when assembled, will rest on the electrode paste without firing in the section of the cladding located below.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a vertical section through a cladding section for use in the method of the present invention. Figure 2 shows a vertical section through an electrode column extending through a baking oven with the upper part of the coating being freshly assembled, and where. Figure 3 shows a vertical section through a second embodiment of a coating section for use in connection with the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION In Figure 1 there is shown a liner section 1 consisting of an upper part 2 and a lower part 3. the lower part 3 of the section of the liner has a diameter slightly smaller than the upper part 2 of the section of the coating. The outer diameter of the lower part 3 is equal to or slightly smaller than the inner diameter of the upper part 2. When a new coating section 1 is installed, a section of coating having the shape as shown in Figure 1 is placed telescopically in the section below. The coating section 1 is preferably filled with uncooked electrode paste at a level as shown by reference number 4 in Figure 1, such that the distance from level 4 to the top 5 of the top of the coating is less than the length of the lower part 3 of the coating section. Otherwise, the section of the liner is filled with electrode paste without firing to level 4 after the section of the liner has been placed in telescopic connection with the section of the liner located below. In figure 2 there is shown schematically a cooking oven 6 that can be heated by means of a suitable heating means such as heating with electric resistance, induction heating, gas burners, oil burners, and so on. An electrode coating consisting of a number of telescopically arranged sections of the liner 1 having a shape as shown in Fig. 1 and containing electrode paste without cooking, is lowered continuously or almost continuously through the cooking oven 6. in the baking oven, the electrode without cooking is baked in a solid carbon body maintaining a temperature between 500 and 1300 ° C in the baking oven. The boundary between the uncooked electrode paste and the cooked carbon body is shown with the reference numeral 7 in FIG. 2. When a new coating section is assembled, the new section is placed with the lower part 3 of the coating within the lower or lower coating. The lower edge of the new coating section hereby will rest on the electrode paste in the coating section located below. In view of the fact that sections of coatings containing uncooked electrode paste are being lowered through the baking oven, the electrode paste will heat up and begin to soften and during cooking the electrode paste will shrink. Due to the weight of the coated sections of the coating with the electrode paste located above the cooking oven, the soft electrode paste within the cooking oven will be compressed together and the section of the coating will slide down relative to the lower coating. When the joint between the two coating sections has entered the cooking oven, the telescopic connection between the coating section will be sealed. By the method of the present invention, the coating sections are not joined together by welding or by any other kind of rigid connections, but rest freely on the electrode paste in the lower coating section. In view of the fact that the individual sections of the coating filled with electrode paste rest on the electrode paste in the lower coating section, the electrode paste without cooking will always be under pressure so that any cavity will be filled with the electrode paste will automatically be compensated as the sections of the coating are released to move relative to one another. In addition, the elongation of the lining due to heat will not be transferred to the other lining section as this elongation is compensated by the telescopic connection. Lengthening a coating section by this means will not transfer any force to the sections of the coating above or below a certain section of the coating. In view of the fact that it is possible to fill the sections of the coating with electrode paste without firing before the assembly of the sections of the coating, the gases that are released in the electrode paste during the cooking in the baking oven can not escape through the upper part of the electrode column as the top of the electrode column will always contain cold electrode paste. Even if the method of the invention has been described for the embodiment where the lower part of the section of the liner has a smaller diameter than the upper part of the lining, it is within the scope of the present invention to mount the lining sections with the part top down. In this case, only a telescopic connection will be had between the sections of the liner where the part of the section of the liner having the largest diameter is mounted in such a way that the larger diameter is placed outwardly from the lower liner. In Figure 3 there is shown an embodiment of a coating section that can be used in connection with the method of the present invention. Parts of figure 3 which correspond to parts of figure 1 have identical reference numbers. The section of the liner shown in Figure 3 has a cylindrical upper part 2 and a conical lower part 8 where the outer diameter of the lower conical part 8 is smaller than the internal diameter of the upper cylindrical part 2. when mounted In a new lining section, the section of the liner is positioned in such a way that the conical bottom 8 fits into the section of the liner below. The coating used in the present invention may be perforated to allow the gases that come off during cooking to flow into the cooking oven. As the coating sections, according to the method of the present invention, are not rigidly fixed to each other by welding or the like, it is easy to separate the coating after the electrode has been baked. It is only necessary to cut the lining in the vertical direction. The method according to the present invention gives a substantial simplification of the work necessary for the assembly of new coating sections, at the same time that the environment for the operators is substantially improved. In addition, a better quality of the carbon bodies produced is obtained, as the possibility of cavities in the cooked carbon bodies is effectively eliminated.

Claims (1)

1. CLAIMS A method for the continuous production of elongated carbon bodies, particularly carbon electrodes that are produced in direct connection with the melting furnace, where the electrodes are consumed, where a metallic coating containing an electrode paste, carbonaceous without cooking, consisting of in a particulate solid carbon material and a carbonaceous binder it is lowered in a continuous or quasi-continuous manner through a baking oven which is heated to a temperature between 500 and 1200 ° C, whereby the electrode paste without cooking is cooked in a solid carbon body, and wherein the coating is extended by joining new coating sections in the upper part of the coating as the coating is lowered through the baking oven, where the lower part of each coating section has an outer diameter that is equal to or smaller than the internal diameter of the top of each section of r coating, it is characterized in that each new coating section is mounted on the section of the lower coating in such a way that the lower part of the new section of the coating is located within the coating of the upper part of the coating section located underneath. the new coating section, and wherein the length of the lower part of each coating section has such an extension that the new coating section during cooking can freely slide down relative to the section of the coating located below the new one. coating section, a distance that at least compensates for the shrinkage of the electrode paste contained in the coating during the firing of the carbon body in the firing oven. The method according to claim 1, characterized in that each coating section, before assembly, is filled with electrode paste without firing at such a level that the distance from the level of the electrode paste to the top of each coating section it is smaller than the length of the lower part of the sections of the lining, whereby the lower part of the sections of the lining, when assembled, will rest on the electrode paste without firing in the section of the lining located below. The method according to claim 1, characterized in that each coating section, after assembly, is filled with electrode paste without firing at such a level that the distance from the level of the electrode paste to the top of each coating section it is smaller than the length of the lower part of the lining sections, whereby the lower part of the lining sections, when assembled, will rest on the electrode paste without firing in the section of the lining located below. The method according to claim 1, characterized in that coating sections are used consisting of an upper cylindrical portion and a lower cylindrical portion, where the external diameter of the lower cylindrical portion is equal to or less than the internal diameter of the cylindrical portion. higher. The method according to claim 1, characterized in that cladding sections are used where at least the lower part of each cladding section has a conical shape such that the external diameter of the conical part of the cladding sections is smaller than the diameter of the upper part of the coating. The method according to claim 1, characterized in that the ratio between the length of the upper part and the lower part of the coating section is between 1: 1 to 1000: 1. The method according to claim 6, characterized in that the ratio between the length of the upper part and the internal part of the coating section is between 3: 1 and 12: 1. SUMMARY OF THE INVENTION The present invention relates to a method for the continuous production of elongated carbon bodies, particularly carbon electrodes that are produced in direct connection to the melting furnace, where the electrodes are consumed, where a metallic coating containing electrode paste, carbonaceous without cooking consisting of a solid particulate carbon material and a carbonaceous binder is it goes down continuously or almost continuously through a baking oven which is heated to a temperature between 500 and 1200 ° C, whereby the electrode without cooking is cooked in a solid carbon body, and where the coating it extends by attaching new sections of the liner to the top of the liner as the liner is lowered through the baking oven, where the bottom of each liner section has an outer diameter that is equal to or smaller than the internal diameter of the liner. upper part of each coating section, the method being characterized because each new revelation section The section is mounted on the lower liner section in such a way that the lower part of the new liner section is located within the lining of the upper section of the lining located below the new lining section, and where the length of the lower part of each coating section has a section such that the new coating section, during cooking, can slide freely downward relative to the coating section located below the new coating section a distance which at least it compensates for the shrinkage of the electrode paste contained in the coating during the cooking of the carbon body in the baking oven.