Graphite furnace

Abstract

The graphite furnace of the present invention comprises a body portion including a receiving space in which a raw material crucible is received, an inner wall portion installed on one side of the body portion, and an electrode module installed on the inner wall portion and arranged such that one end facing the receiving space protrudes from the inner wall portion.

Description

Technology Field

[0001] The present invention relates to a graphite furnace. Background Technology

[0002] The four major components of a secondary battery are commonly referred to as the cathode, anode, electrolyte, and separator. Among these, the cathode, anode, and separator are considered core materials because they determine the overall performance of the secondary battery.

[0003] Secondary batteries, such as lithium-ion batteries, generally generate electricity through the chemical reaction of lithium ions moving between the cathode and the anode. Here, while the cathode determines the overall capacity and voltage of the battery, the anode plays the role of storing and releasing lithium ions from the cathode.

[0004] As such, the anode material, which stores lithium ions, affects the battery's charging speed and lifespan. It is no exaggeration to say that battery performance varies depending on the performance of the anode material. Furthermore, as the development of cathode materials has recently reached its limits, the development of anode material technology has become an even more critical factor in improving battery performance.

[0005] The cathode material production facility includes a furnace that grinds and heats the raw material powder. Conventional graphite furnaces have a problem of low conductivity efficiency because the tip of the electrode is located flush with the inner wall. The problem to be solved

[0006] The present invention aims to overcome the aforementioned conventional problems, and the objective of the present invention is to provide a graphite furnace capable of improving conductivity efficiency. means of solving the problem

[0007] A graphite furnace according to one embodiment of the present invention includes a body portion having a receiving space in which a raw material crucible is received, an inner wall portion installed on one side of the body portion, and an electrode module installed on the inner wall portion and arranged such that one end facing the receiving space protrudes from the inner wall portion.

[0008] The inner wall portion may include a carbon block located adjacent to the electrode module and a heat-resistant member located adjacent to the carbon block.

[0009] The above heat-resistant member may be a high-alumina refractory brick.

[0010] The thickness of the carbon block may be in the range of 600mm to 650mm.

[0011] The electrode module may further include a thermal conductive layer applied to at least a portion of the surface facing the receiving space.

[0012] The above electrode modules are plurality of, and the plurality of electrode modules may include a first electrode located at the center of the inner wall portion and a second electrode located around the first electrode.

[0013] The thickness of the thermal conductive layer applied to the second electrode may be half the thickness of the thermal conductive layer applied to the first electrode.

[0014] The length of the electrode module protruding from the inner wall may be included in the range of 50 mm to 65 mm.

[0015] The above electrode module may further include a refractory member installed between the ends protruding from the inner wall portion.

[0016] The above-mentioned refractory member may include a base portion and a protrusion that protrudes from one side of the base portion and is positioned at regular intervals along the longitudinal direction of the base portion. Effects of the invention

[0017] The graphite furnace according to the present invention is arranged so that one end facing the receiving space in the electrode module protrudes from the inner wall portion, thereby improving conductivity efficiency.

[0018] In addition, the graphite furnace according to the present invention includes a heat-resistant member, thereby preventing melting from occurring at the inner wall during the process of energizing the graphite furnace. Brief explanation of the drawing

[0019] Figure 1 is a flowchart illustrating a general process for manufacturing artificial graphite. FIG. 2 is a plan view illustrating a graphite furnace according to one embodiment of the present invention. Figure 3 is a cross-sectional view taken along line A-A' in the graphite furnace of Figure 2. Figure 4 is a cross-sectional view taken along the B-B' line in the graphite furnace of Figure 2. Figure 5 is a cross-sectional view taken along the C-C' line in the graphite furnace of Figure 2. FIG. 6 is a cross-sectional view illustrating a graphite furnace including an electrode module according to a modified example. FIG. 7 is a cross-sectional view illustrating a graphite furnace according to another embodiment of the present invention. FIG. 8 is a perspective view showing an excerpt of a refractory member. Specific details for implementing the invention

[0020] The embodiments of the present invention are provided to more fully explain the invention to those skilled in the art, and the following embodiments may be modified in various different forms, and the scope of the invention is not limited to the following embodiments. Rather, these embodiments are provided to make the disclosure more faithful and complete and to fully convey the spirit of the invention to those skilled in the art.

[0021] Additionally, in the drawings below, the thickness or size of each layer is exaggerated for convenience and clarity of explanation, and like reference numerals in the drawings refer to like elements. As used herein, the term "and / or" includes any one of the listed items and all combinations of one or more thereof. Furthermore, in this specification, the meaning of "connected" refers not only to cases where Member A and Member B are directly connected, but also to cases where Member C is interposed between Member A and Member B so that Member A and Member B are indirectly connected.

[0022] The terms used herein are for describing specific embodiments and are not intended to limit the invention. As used herein, the singular form may include the plural form unless the context clearly indicates otherwise. Additionally, as used herein, "comprise, include" and / or "comprising, including" specify the presence of the mentioned features, numbers, steps, actions, parts, elements, and / or groups thereof, and do not exclude the presence or addition of one or more other features, numbers, actions, parts, elements, and / or groups.

[0023] Although terms such as "first," "second," etc. are used in this specification to describe various components, parts, regions, layers, and / or parts, it is obvious that these components, parts, regions, layers, and / or parts should not be limited by these terms. These terms are used solely to distinguish one component, part, region, layer, or part from another region, layer, or part. Accordingly, the first component, part, region, layer, or part described below may refer to the second component, part, region, layer, or part without departing from the teachings of the present invention.

[0024] Additionally, spatial terms such as "beneath," "below," "lower," "above," and "upper" may be used to facilitate understanding of one element or feature depicted in the drawings and another element or feature. These spatial terms are intended to facilitate understanding of the invention according to various process or usage conditions of the invention and are not intended to limit the invention. For example, if an element or feature in the drawings is inverted, an element or feature described as "beneath" or "below" becomes "upper" or "on top." Therefore, "beneath" is a concept that encompasses "upper" or "below."

[0025] Before describing the graphite furnace according to one embodiment of the present invention, a general process for manufacturing artificial graphite will be described.

[0026] Figure 1 is a flowchart illustrating a general process for manufacturing artificial graphite.

[0027] Referring to Fig. 1, a typical artificial graphite manufacturing process includes a grinding step, an assembly step, a heating step, and a coating step.

[0028] The grinding step is a step of grinding coke particles to a particle size that exhibits optimal performance as a cathode material.

[0029] In the grinding step, carbon-based raw materials are ground. The carbon-based raw materials may include needle cokes, mosaic cokes, coal tar pitch, resin pitch, or two or more of these.

[0030] The average particle size (D50) of the above-mentioned pulverized carbon-based raw material may be 1 μm to 20 μm, or 5 μm to 15 μm. The average particle size (D50) of the above-mentioned pulverized carbon-based raw material can be measured using a particle size meter (DC24000 UHR, CPS Instrument) via the laser diffraction method after preparing a sample by diluting it in deionized water to 1 wt%.

[0031] When grinding the above carbon-based raw material, grinding conditions and a grinder can be appropriately selected by paying attention to the grinding characteristics of the carbon-based raw material, such as high abrasion, hygroscopicity, lubricity, and impact strength, and low specific gravity and elastic modulus.

[0032] The assembly stage is the stage where coke is combined with a binder to form particles.

[0033] The above grinding and aggregation steps involve grinding the coke raw material using a jet mill until the average particle size (D50) becomes 10㎛, and then aggregating the resulting product using a horizontal aggregation device at 800℃ for 24 hours.

[0034] The heating step is a step of structurally changing the coke raw material into graphite by heat treatment with heat at 3,000 degrees. In the heating step, the aggregated product is graphitized by heat treatment at 2,800°C for 400 hours, including heating and cooling times, using an Etchison graphitization furnace device.

[0035] More specifically, the graphitization step can be carried out using devices such as an Acheson graphitization furnace, a box-type graphitization furnace, or a lengthwise graphitization furnace.

[0036] The processing temperature for graphitization is not particularly limited, but graphitization can be performed in a range of, for example, 2,000 to 3,500°C, 2,500 to 3,500°C, 2,800 to 3,500°C, or 2,800 to 3,200°C. When the graphitization treatment satisfies the above temperature range, crystallization of the graphite proceeds, and the resulting artificial graphite has ductility and can be easily processed, and since sublimation of the graphite surface is minimal, the temperature can be easily raised.

[0037] Although various methods can be applied for the above graphitization, the assembled product can be embedded in a furnace, and an Acheson furnace, which generates heat by passing an electric current from an electrode to the sintered body, or an induction furnace, which generates heat by flowing an induced current through an induction coil to the sintered body, can be used.

[0038] The coating step is the step of uniformly coating the artificial graphite surface with pitch.

[0039] The coating step involves mixing 100 parts by weight of the graphitized product and 5 parts by weight of pitch (solid pitch), which is a carbon coating material, using a mixing homogenizer (vertical / horizontal mixer), and carbonizing the mixture for 24 hours at a temperature of 1,500°C to perform carbon coating.

[0040] Artificial graphite is finally manufactured by performing a second iron removal treatment to remove magnetic foreign matter by mixing it with the carbonized product under magnetic force conditions of 36,000 Gauss using an electronic iron removal device.

[0041] The above method for manufacturing a cathode material is explained in more detail as follows.

[0042] a) a step of pulverizing; b) a step of mixing the pulverized natural graphite from step a) with a liquid pitch containing a solvent and pitch ('mixing step'); c) a step of removing all or part of the solvent from the mixture from step b) after mixing is completed ('solvent removal step'); d) a step of manufacturing pulverized graphite by pulverizing the solvent-removed mixture from step c) ('pulverization step'); e) a step of heat-treating the pulverized graphite from step d) ('heat treatment step'); and f) a step of classifying the heat-treated pulverized graphite from step e) ('classification step').

[0043] Below, steps a) through f) above are explained in detail.

[0044] In the above method for manufacturing the cathode material, the 'natural graphite' in step a) may have an average particle size of 5㎛ to 500㎛, preferably 5㎛ to 100㎛, and if the average particle size exceeds 500㎛, the overall manufacturing time increases, which is not economically desirable.

[0045] In the above method for manufacturing the cathode material, the pulverization of natural graphite in step a) is performed using a high-speed mechanical milling device such as a hammer mill, jet mill, bead mill, or a mixture thereof, preferably using a jet mill. At this time, the operating pressure of the hammer mill, jet mill, and bead mill is the pressure required for each mill used, and the pressure when pulverizing using a jet mill is 5.5 bar to 9.9 bar.

[0046] In addition, the pulverized natural graphite product obtained by undergoing a pulverization process using a jet mill or the like from the natural graphite described above is classified using an ultrafine classifier such as a Turbo to select and classify only natural graphite particles with an average particle size of 1 μm or less and a tap density of 0.2 g / cc to 0.3 g / cc. Natural graphite particles with an average particle size of 1 μm or less that are classified and selected in this way are called 'pulverized natural graphite'.

[0047] The SEM of the above 'micronized natural graphite' has acute-angled regions on its surface, although not shown in the illustration.

[0048] In the 'mixing step' of step b) of the above method for manufacturing the cathode material, the amount of solvent and pitch used in the 'liquid pitch containing solvent and pitch' is in the range of 80:20 to 50:50 in weight% ratio.

[0049] The above solvent is any solvent capable of dissolving pitch, preferably one or more selected from the group consisting of mineral oils such as kerosene, heavy oil, and light oil; hydrocarbon solvents such as toluene and decane; heteroatom-containing solvents such as acetone, tetrahydropurine and pyridine; and mixtures thereof, more preferably mineral oils such as kerosene, light oil, and heavy oil.

[0050] The above pitch is a petroleum pitch-based, coal-based pitch, or polymer resin, and preferably a petroleum pitch.

[0051] The viscosity of the above liquid pitch is 2,000 to 20,000 cP.

[0052] In the 'mixing step' of step b) of the above method for manufacturing the cathode material, the amount of 'finely pulverized natural graphite and liquid pitch' used is in the range of 80:20 to 50:50 in weight% ratio.

[0053] At the above range of mixing ratios, the spheroidization of finely pulverized natural graphite, which mostly exhibits a flake-like form, is well achieved. If the usage ratio of liquid pitch is less than 20% by weight, the spheroidization of finely pulverized natural graphite is partially not achieved, which may result in a large amount of un-granulated natural graphite fines, thereby reducing the manufacturing efficiency of granulated spheroidal graphite. Additionally, if the usage ratio of liquid pitch is greater than 50% by weight, the difference in the average particle size of the manufactured granulated spheroidal graphite increases, which may cause problems in the manufacturing yield of granulated spheroidal graphite particles with particle diameters suitable for use as negative electrode active materials for secondary batteries.

[0054] In the 'mixing step' of step b) of the above method for manufacturing the cathode material, the mixture of liquid pitch and finely pulverized natural graphite is mixed by stirring at a speed of 100 to 800 rpm for 2 to 8 hours at a temperature of 50 to 200°C using a mixer such as a screw mixer.

[0055] If the above mixing time is exceeded, the manufacturing efficiency of the granular graphite decreases, and as shown in Comparative Examples 1 and 2 below, the manufacturing efficiency of the granular graphite is also significantly lowered even if step b) is not performed (see Comparative Examples 1 and 2).

[0056] In the above method for manufacturing the cathode material, the solvent removal in the 'solvent removal step' of step c) is performed under reduced pressure. The degree of reduced pressure used may be such that it can remove at least 50%, preferably at least 70%, and more preferably at least 80% of the solvent used, and the time required may be determined in conjunction with the reduced pressure. As a preferred example, at least 80% of the solvent was removed for one hour under a reduced pressure of 50 torr. The removal of the solvent using the above vacuum pressure is performed at room temperature.

[0057] A graphite furnace according to one embodiment of the present invention heats coke raw materials in the heating step of the artificial graphite manufacturing process to structurally transform them into graphite.

[0058] A graphite furnace according to one embodiment of the present invention is configured to produce artificial graphite by graphitizing the raw material inside a raw material crucible, and graphite furnaces such as a direct current furnace or an Acheson furnace may be applied.

[0059] Here, taking the Acheson Furnace as an example, carbon black and insulating material are sequentially filled into a rectangular container with an open top, raw material crucibles are stacked on top with resistance material filling the gaps, raw material crucibles are stacked again on top of the raw material crucible layers with resistance material filling the gaps again, and finally, the top is covered with insulating material. Then, the raw material inside the crucibles is graphitized by indirectly heating them using the resistance heat generated by passing an electric current.

[0060] Furthermore, the graphite furnace is installed inside a base structure (not shown) provided for the installation of a workspace for workers and various equipment. Additionally, a shielding cover (not shown) may be installed on the graphite furnace to block high-temperature heat emitted upward.

[0061] Hereinafter, a graphite furnace according to one embodiment of the present invention will be described in detail with reference to the attached drawings.

[0062] In the present invention, carbon black, thermal insulation, and resistance materials charged into the graphitization furnace for graphitization treatment are referred to as "auxiliary materials," a crucible filled with raw materials in which all materials that can be used to produce artificial graphite are mixed in a powdered state is referred to as a "raw material crucible," a crucible containing artificial graphite produced after heat treatment in the graphitization furnace is referred to as a "graphite crucible," and the raw material crucible and the graphite crucible are collectively referred to as a "crucible."

[0063] FIG. 1 is a flowchart illustrating a general process for manufacturing artificial graphite, FIG. 2 is a plan view illustrating a graphite furnace according to an embodiment of the present invention, FIG. 3 is a cross-sectional view taken along the line A-A' in the graphite furnace of FIG. 2, FIG. 4 is a cross-sectional view taken along the line B-B' in the graphite furnace of FIG. 2, and FIG. 5 is a cross-sectional view taken along the line C-C' in the graphite furnace of FIG. 2.

[0064] As illustrated in FIGS. 1 to 5, a graphite furnace (100) according to one embodiment of the present invention includes a body portion (110), an inner wall portion (120), and an electrode module (130).

[0065] The body portion (110) includes a receiving space (111) in which a raw material crucible is received. The raw material in the raw material crucible is graphitized in the body portion (110). Auxiliary materials such as carbon black, thermal insulation, and resistance material may be stacked from the bottom of the body portion (110) for graphitization treatment.

[0066] Also, although the graphite furnace (100) is not shown in the drawing, the process can be carried out automatically by an automated device.

[0067] More specifically, a crucible working robot and a filling material working robot can feed raw materials into the receiving space (111) and discharge the heat-treated artificial graphite produced to the outside. The automation device can automatically perform the loading of raw material crucibles and the output of graphite crucibles to the graphite furnace, as well as the supply and discharge of auxiliary materials.

[0068] The process in the graphite furnace (100) can be carried out automatically by an automation device as described above. Accordingly, the efficiency and stability of the operation are improved, and the time for receiving and releasing crucibles from the graphite furnace (100) can be shortened. A detailed explanation of this is omitted.

[0069] The inner wall portion (120) is installed on one side of the body portion (110). An electrode module (130), to be described later, may be installed on the inner wall portion (120). That is, the inner wall portion (120) may be installed to occupy the central portion of each of the two ends of the body portion (110). A detailed description of such an inner wall portion (120) will be provided later.

[0070] The electrode module (130) is installed on the inner wall portion (120), and one end facing the receiving space (111) is positioned to protrude from the inner wall portion (120). Accordingly, conductivity efficiency can be improved. To this end, the length (T) of the electrode module (130) protruding from the inner wall portion (120) may be included in the range of 50 mm to 65 mm.

[0071] Meanwhile, the electrode module (130) may be in the plurality. The plurality of electrode modules (130) may include, for example, a first electrode (131) and a second electrode (132).

[0072] The first electrode (131) can be located in the center of the inner wall portion (120).

[0073] The second electrode (132) is located around the first electrode (131). More specifically, there may be eight second electrodes (132). Eight second electrodes (132) may be arranged around the first electrode (131). However, the arrangement of the first electrode (131) and the second electrode (132) is not limited to that described above.

[0074] Meanwhile, the aforementioned inner wall portion (120) may include, for example, a carbon block (121) and a heat-resistant member (122).

[0075] The carbon block (121) is positioned adjacent to the electrode module (130). The thickness of the carbon block (121) may be in the range of 600 mm to 650 mm. Here, the thickness of the carbon block (121) is the vertical distance relative to the direction shown in FIG. 5.

[0076] The heat-resistant member (122) is positioned adjacent to the carbon block (121). The heat-resistant member (122) may be a high-alumina refractory brick. The high-alumina refractory brick is a refractory brick with an Al2O3 content of 45% or more, a refractory degree of SK35 or higher, high hot strength, and excellent spalling resistance, corrosion resistance, and alkali resistance.

[0077] Such a heat-resistant member (122) can prevent melting from occurring in the inner wall (120) during the process of energizing the graphite furnace (100).

[0078] FIG. 6 is a cross-sectional view illustrating a graphite furnace including an electrode module according to a modified example.

[0079] Referring to FIG. 6, the electrode module (230) may further include a thermal conductive layer (133) as a variation example.

[0080] The heat conductive layer (133) can be applied to at least a portion of the surface facing the receiving space (111).

[0081] Since the temperature difference between the end portion protruding from the electrode module (130) and the electrode module (130) buried in the inner wall portion (120) is large, the amount of heat transfer is inevitably reduced relatively, and the amount of heat released may be limited due to the thermal boundary layer phenomenon occurring between the protruding electrode module (130) and the buried electrode module (130).

[0082] The heat conductive layer (133) can resolve the above-mentioned problems by neutralizing the temperature difference to facilitate heat dissipation. The heat conductive layer (133) can be applied to the portion protruding from the electrode module (130) into the receiving space (111). At this time, the corners of the portion protruding from the electrode module (130) into the receiving space (111) may be rounded.

[0083] The rounded portion of the electrode module (130) disrupts the fluid flow of the graphite furnace (100), thereby facilitating more active heat exchange and increasing the resilience against thermal shock of the inner wall portion (120) of the graphite furnace (100). Since the electrode module (130) is formed in a rounded shape, it has the effect of increasing durability due to the thermal boundary layer phenomenon.

[0084] Meanwhile, at the point where the fluid meets the high-temperature electrode module (130), the rate of change of the fluid's temperature is high, but as it moves away from the electrode module (130), it forms a boundary of a region where the rate of change of the fluid's temperature gradually decreases. As this thermal boundary layer becomes thicker along the length direction of the electrode module (130), heat transfer to the fluid does not occur, and heat is inevitably transferred to the inner wall (120). As described above, this can be improved by placing the thermal conductive layer (133) at an angle between the electrode module (130) and the inner wall (120).

[0085] The heat conduction layer (133) may be, for example, an amorphous refractory. Refractories can be classified into shaped refractories and amorphous refractories according to their physical form. A shaped refractory refers to a refractory that has a fixed shape, while an amorphous refractory is a refractory that can be constructed in any shape according to the part or mold to be constructed.

[0086] The amorphous refractory material used as the heat conductive layer (133) may include, for example, alumina, graphite phosphate, metallic aluminum powder, and stainless steel fiber.

[0087] More specifically, the amorphous refractory material may comprise 76 to 84 weight percent alumina, 10 to 15 weight percent graphite phosphate, 2 to 3 weight percent metallic aluminum powder, and 4 to 6 weight percent stainless fiber based on the total weight. Such amorphous refractory material has advantages such as ease of construction and a long service life.

[0088] Meanwhile, the heat conductive layer (133) may be applied to both the first electrode (131) and the second electrode (132), and the thickness of the heat conductive layer (133) applied to the second electrode (132) may be half the thickness of the heat conductive layer (133) applied to the first electrode (131). This may be because the temperature difference in each part of the first electrode (131) is relatively large compared to the second electrode (132).

[0089] As described above, the second electrode (132) has a relatively smaller amount of thermal conductive layer (133) applied than the first electrode (131), so that the heat release effect can be achieved while reducing the cost of using the thermal conductive layer (133).

[0090] FIG. 7 is a cross-sectional view illustrating a graphite furnace according to another embodiment of the present invention, and FIG. 8 is a perspective view illustrating a refractory member.

[0091] Referring to FIGS. 7 and FIGS. 8, a graphite furnace (200) according to another embodiment of the present invention may further include a refractory member (140).

[0092] The refractory member (140) is installed between the ends protruding from the inner wall portion (120) in the electrode module (130). More specifically, the refractory member (140) is positioned between the ends of the first electrode (131) and the second electrode (132), respectively, and can be in close contact with the inner wall portion (120).

[0093] Such a fire-resistant member (140) may include, for example, a base portion (141) and a protrusion (142).

[0094] The base portion (141) may be in the shape of a block. The material of the base portion (141) may be, for example, a refractory brick.

[0095] The protrusion (142) protrudes from one side of the base portion (141). The protrusion (142) may be positioned to face the receiving space (111) of the body portion (110).

[0096] The protrusions (142) are positioned at regular intervals along the longitudinal direction of the base portion (141). The material of the protrusions (142) may be selected from, for example, carbon black bricks, high-alumina bricks, and clay.

[0097] The empty space between the protrusions (142) as described above can improve the thermal conductivity within the graphite furnace (200). The heat generated while heating the raw material crucible is transferred through the protrusions (142), and the transfer to the electrode module (130) can be minimized. That is, the refractory member (140) can prevent the electrode module (130) from being damaged by high heat.

[0098] Although various embodiments of the present invention have been described above, the drawings and the detailed description of the invention referenced so far are merely illustrative of the present invention and are used only for the purpose of explaining the present invention, not to limit the meaning or the scope of the present invention as defined in the claims. Therefore, those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims. Explanation of the symbols

[0099] 100, 200: Graphite furnace 110: Body part 111: Storage space 120: Inner wall section 121: Carbon block 122: Heat-resistant member 130: Electrode module 131: First electrode 132: Second electrode 133: Thermal conductive layer 140: Refractory member 141: Base part 142: Protrusion part

Claims

Claim 1 A graphite furnace comprising: a body portion including a receiving space for receiving a raw material crucible; an inner wall portion installed on one side of the body portion; and an electrode module installed on the inner wall portion, wherein one end facing the receiving space is arranged to protrude from the inner wall portion; and wherein the electrode module comprises a heat conductive layer applied to the surface of at least a portion of the end facing the receiving space. Claim 2 A graphite furnace according to claim 1, wherein the inner wall portion comprises: a carbon block located adjacent to the electrode module; and a heat-resistant member located adjacent to the carbon block. Claim 3 In paragraph 2, the heat-resistant member is a graphite furnace made of a high-alumina brick (High Al Refractory Brick). Claim 4 In paragraph 2, the thickness of the carbon block is included in the range of 600mm to 650mm, a graphite furnace. Claim 5 delete Claim 6 In claim 1, the electrode modules are plurality of, and the plurality of electrode modules include a first electrode located at the center of the inner wall portion; and a second electrode located around the first electrode; a graphite furnace. Claim 7 In claim 6, the thickness of the thermal conductive layer applied to the second electrode is half the thickness of the thermal conductive layer applied to the first electrode. Claim 8 A graphite furnace according to claim 1, wherein the length of the electrode module protruding from the inner wall is included in the range of 50 mm to 65 mm. Claim 9 A graphite furnace according to claim 1, further comprising a refractory member installed between the ends protruding from the inner wall portion in the electrode module. Claim 10 In claim 9, the refractory member comprises: a base portion; and a protrusion portion protruding from one side of the base portion and positioned at regular intervals along the longitudinal direction of the base portion; a graphite furnace.

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