JPH03330B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for graphitizing a carbon fired body having an isotropic high-density structure with high yield. [Prior Art] Graphite articles are manufactured by kneading aggregate raw materials such as coke powder with a binder such as tar pitch, and then molding the kneaded product through the following steps: calcining, graphitizing, and processing. The graphitization process involves filling a resistance electric furnace called an Acheson-type graphitization furnace with a carbon fired body as a processing material, surrounding it with a heat-insulating packing material such as coke or silica sand, and then passing it through a terminal electrode. It is carried out by raising the temperature to a high temperature of 2,800 to 3,000 degrees Celsius through high voltage and current, and by the resistance heat of the carbon thermal compact and packing material in the furnace. At this time, the carbon fired bodies are usually packed in the furnace by arranging them in one or two rows at regular intervals in the furnace length direction. Electric current flows in series between the fired carbon bodies packed in the furnace, but graphitization is mainly carried out through resistance heating of the packing material present in the current path. [Problems to be solved by the invention] As mentioned above, the main heat source that contributes to the heating of carbon fired bodies depends on the gap resistance heat generation of the packing material between the corresponding surfaces of each fired body, so the heat transfer temperature is is greatly affected by gap disparity. For example, when cylindrical carbon fired bodies are arranged vertically at right angles to the furnace length direction, the gap lengths differ because the mutually corresponding surfaces are circular, and the center of the current path with the smallest gap A significant temperature difference occurs between the portion (high heat generation portion) and both end portions (low heat generation portion) where the gap is large. Recently, high-density graphite materials with an isotropic structure formed using a hydrostatic press (rubber press) have been used in various fields, but this type of high-density compact is particularly susceptible to internal distortion due to thermal stress. There is a problem that cracks or breakage occur relatively easily due to the above-mentioned heat transfer temperature difference. [Means for Solving the Problems] The present invention eliminates the drawbacks of the conventional methods described above, and
The object of the present invention is to provide a graphitization method that can process even a carbonaceous fired body with a high density structure with good yield. That is, the method for graphitizing a carbon fired body according to the present invention involves arranging a large number of carbon fired bodies having an isotropic high-density structure obtained by firing a molded body using a rubber press in series and at regular intervals in the furnace length direction of an Acheson furnace. In this method, the fired carbon body is embedded in a packing material with good thermal conductivity and loaded into a cylindrical surrounding section made of carbonaceous material, and the surrounding area is covered with a normal packing material. Its structural feature is that it is energized. Hereinafter, the present invention will be explained in detail based on the drawings. FIG. 1 is a partial vertical sectional view of an Acheson graphitization furnace showing an example of application of the graphitization method according to the present invention, and FIG. 2 is a sectional view taken along line A-A' in FIG. A furnace wall, 2 a hearth, and 3 a terminal electrode to which a conductor 11 is attached. Reference numeral 4 denotes cylindrical surrounding sections made of a carbonaceous material such as carbon or graphite, which have the same shape and are arranged in series at equal intervals in the furnace length direction. The cylindrical surrounding section 4 can be formed by integrally processing a carbonaceous block, or by appropriately combining plate-shaped or rod-shaped carbonaceous members such as by cutting them.
Also, the shape can be either square or cylindrical, but
In the case of a cylindrical shape, there is a tendency for local gap differences to occur between the facing cylindrical surrounding sections, which weakens the heat uniformity effect. Therefore, in the case of a cylindrical shape, as shown in FIG. , 6' preferably have a planar shape with substantially the same surface area. The carbon fired body 7 to be treated is filled in the cylindrical surrounding section 4 while being embedded in a packing material 8 with good thermal conductivity such as graphite powder, and the periphery thereof is covered with a normal coke grain packing material 9. It is packed in a furnace. Finally, the upper layer of the furnace is covered with silica sand 10 for shielding, and electricity is applied to the furnace via the terminal electrode 3. [Function] According to the graphitization method of the present invention, the fired carbon body is loaded into the carbonaceous cylindrical surrounding section while being embedded in the packing material with good thermal conductivity, so that gap resistance heat generation is caused by the gap resistance generated by these partition wall members. The heat is indirectly transferred to the carbon fired body through the carbon sintered body. Due to this indirect heat transfer effect, local temperature distribution differences in the carbon fired body and fluctuations in temperature increase rate are alleviated, and an excellent heat uniformity effect is exhibited. This heat-uniforming effect is particularly remarkable when each corresponding surface of the cylindrical surrounding section has a planar shape with the same surface area, and serves to greatly improve the yield. Example 1 Molded product by rubber press (bulk density 1.45g/
A ^cylindrical carbon fired body having an isotropic high-density structure and having a diameter of 600 mm and a height of 700 mm was prepared. 900mm on each side, constructed by combining graphite plates (200mm)
Square cylindrical surrounding sections with a height of 1000 mm and a height of 1000 mm were set in series at equal intervals in the furnace length direction of the Acheson graphitization furnace.
Two pieces of the above-mentioned fired carbon bodies were embedded in graphite powder packing and loaded into the center. The furnace was filled with coke powder packing to enclose the cylindrical surrounding section, and the upper layer was shielded with silica sand 10. Next, power was transmitted to the terminal electrode, and the temperature was raised to 2800°C over 80 hours to perform graphitization. Table 1 shows the yield results of the graphitized product obtained. Example 2 A cylindrical surrounding section consisting of two stacked cylinders having an outer diameter of 900 mm, an inner diameter of 700 mm, and a height of 500 mm, which were integrally machined from a graphite block, was set in series at equal intervals in the furnace length direction of an Acheson type graphitization furnace. Two carbon fired bodies having the same characteristics and shape as those of Example 1 were loaded into this cylindrical surrounding compartment in a state where they were embedded in graphite powder packing. Then, graphitization treatment was performed in the same manner as in Example 1. The yield results of the graphitized product obtained are also listed in Table 1. Example 3 As shown in FIG. 3, round graphite rods were attached to the periphery of the cylindrical surrounding compartment set in the furnace in Example 2, so that the surfaces corresponding to each compartment were formed into a substantially planar shape. Graphitization treatment was otherwise performed under the same conditions as in Example 2. Table 1 shows the yield results of the graphitized product thus obtained.
Published in . [Comparative Example] A carbon fired body having the same characteristic shape as in Example 1 was directly charged into an Acheson type graphitization furnace without using the cylindrical surrounding section according to the present invention. Other conditions were the same as in Example 1 for graphitization. The yield results of the graphitized products obtained are shown in Table 1 in comparison.

[Table] [Effects of the Invention] According to the present invention, cracking and breakage phenomena of the carbon fired body during the graphitization process are effectively reduced based on the heat-uniforming effect of the cylindrical surrounding section. Therefore,
Even a carbon fired body with a high density structure can be graphitized with a high yield.

[Brief explanation of drawings]

FIG. 1 is a partial vertical sectional view of an Acheson graphitization furnace showing an example of application of the present invention, and FIG.
FIG. 3 is a sectional view taken along line A'. FIG. 3 is a partially enlarged cross-sectional view showing one example of a cylindrical surrounding section. 4... Cylindrical surrounding section, 5... Rod-shaped carbon member, 7
... Carbon fired body, 8 ... Packing material with good thermal conductivity.

Claims (1)

[Claims] 1. A large number of carbon fired bodies having an isotropic high-density structure obtained by firing a molded body using a rubber press are arranged in series and at equal intervals in the furnace length direction of an Acheson furnace and graphitized. The method is characterized in that the fired carbon body is embedded in a packing material with good thermal conductivity and loaded into a cylindrical surrounding section made of a carbonaceous material, and the periphery thereof is covered with a normal packing material and energized. A method for graphitizing a fired carbon body. 2. Claim 1 in which the cylindrical surrounding section is formed by integrally processing a carbonaceous block or by combining plate-shaped or rod-shaped carbonaceous members.
A method for graphitizing a carbon fired body as described in . 3. The method for graphitizing a carbon fired body according to claim 1, wherein the cylindrical surrounding section is configured such that each corresponding surface has a planar shape with substantially the same surface area.