JP6215112B2 - Two-stage heating type vertical graphitization furnace using high frequency and method for producing graphite - Google Patents

Description

  The present invention relates to a continuous vertical graphitization furnace.

  Graphite is excellent in lubricity, conductivity, heat resistance, acid resistance and alkali resistance, and is used for electrode pastes, casting paints, dry batteries, pencils, refractories, heat insulating materials for steel ropes, rubber resins, solid lubricants, crucibles. , Packing, heat-resistant, heat-resistant products, conductive paint, pencil, electric brush, grease, powder metallurgy, brake pads, linings, clutches, mechanical seals, rubber resin additives, etc. In recent years, it is sometimes used as an electrode material of a lithium ion battery by utilizing a phenomenon that Li ions enter a laminated structure portion of graphite crystals. Thus, graphite is used in various fields, and it can be said that establishment of an efficient manufacturing method is extremely important.

  When producing artificial graphite, generally, a raw material made of a carbon material such as coke must be pulverized and heated at about 2200 ° C. or more for a long time. A carbon material (graphite material) is generally used as a material that can withstand such heating at 2200 ° C. or higher, and is used for a furnace and its inner wall, or various members (shaft, heater, heat insulating material) constituting the furnace. Has been.

  Industrially, it is often graphitized batchwise (for example, Patent Documents 1 and 2) like the Atchison furnace, but it is also being attempted to perform it continuously for efficient production (for example, Patent Document 3). In order to perform graphitization in a continuous manner, there is a method in which a furnace is installed in a horizontal direction, and a tray on which a raw material for graphitization is placed is moved in a horizontal direction by a conveyor in a furnace made of graphite. Since this method requires work at a high temperature, it is necessary to select the material of parts for the equipment, and it may be difficult to take measures against exhaust gas and manage the heat at the entrance and exit. As a result, the structure becomes complicated and it takes time and effort to install and operate.

  For this reason, recently, a continuous vertical graphitization furnace in which a furnace is placed vertically, a raw material is charged from the upper part and heated inside, and graphite is taken out from the lower part has been tried (Patent Documents 4 and 5). In a continuous vertical graphitization furnace, the raw materials are stacked and heated from the bottom to the top inside the furnace, and the raw material corresponding to the amount taken out while taking out the graphite from the lower port is always charged from the upper port. A certain amount of raw material is present in the furnace and graphitizes. In this method, only the inside of the furnace is heated, and there is no need for trays or conveyors that can withstand heating, so the structure is relatively simple and there is no need for equipment or power for movement. Operation is also simple because no extra wiring is required.

JP-A-5-78111 JP-A-5-294725 International Publication No. 2012/043402 Japanese Patent Laid-Open No. 11-209114 JP 2002-167208 A

  Since the continuous graphitization furnace described in Patent Document 2 is heated only by induction heating, the heating rate is fast and the efficiency is good. However, the present inventor has found that in the continuous graphitization furnace described in Patent Document 2, there are places where the influence of electromagnetic waves is strong and weak where heat unevenness is generated. Further, it has been found that if a carbon material is graphitized only by induction heating, the cost becomes higher than other methods and the efficiency becomes worse. Furthermore, it has been found that various members constituting the furnace, for example, the graphite material of the shaft, retain heat and deteriorate.

  On the other hand, the continuous graphitization furnace described in Patent Document 5 can be rapidly heated by energization heating. However, the present inventor has found that in this method, a part to be heated and a part which is very little but not sufficiently heated may be produced, resulting in a non-uniform product.

  As a heating method used for graphitization, Patent Document 1 describes a method of graphitizing a fired body by energization heating. This method kneads carbide with a binder such as pitch to produce a graphitized material by converting it into a cylindrical solid, and is a method for the graphitization of a fired body. Is not suitable. Patent Document 2 and Patent Document 3 describe an apparatus for producing graphite by high-frequency heating. The inventor described in Patent Document 2 uses high-frequency heating in a batch-type container under vacuum conditions, so that the heating of the graphitized material in the container is partially uneven or only high-frequency is used. It has been found that heating may be economically disadvantageous. Moreover, since the apparatus of patent document 3 is only a means to heat the upper surface of a crucible secondary, it discovered that a carbon material might not be heated to high temperature. Thus, with the conventional heating method, it is difficult to uniformly heat the entire raw material, and thus it was difficult to obtain homogeneous graphite.

  In view of the above problems, as a result of intensive studies, the inventors rapidly heated the carbon material as a raw material in the upper part of the furnace to evaporate and remove volatile impurities including sulfur contained therein. Thus, it was found that homogeneous graphite can be obtained by preventing damage to the inner wall of the furnace.

That is, according to one aspect of the present invention, there is provided a continuous vertical graphitization furnace in which a carbon material charged from the upper part is heated and graphitized, and the obtained graphite is taken out from the lower part.
A charging port provided at the top of the furnace for charging the carbon material;
A coil that is spirally wound around the outer periphery of the furnace under the inlet and forms an induction heating region that heats the carbon material by passing an alternating current;
An external heat source region that is provided on the outer periphery of the furnace below the induction heating region and is a heat source that is not a coil that forms the induction heating region, but is a heater , and heats the carbon material from the outside of the furnace A heat source to form,
A cooling jacket provided on the outer periphery of the furnace under the external heat source region, and forming a cooling region for cooling the generated graphite;
It is possible to provide a vertical graphitization furnace including a take-out port for taking out the graphite provided under the cooling region.
According to another aspect of the present invention, a step of charging a carbon material into a vertical graphitization furnace, and an induction of heating the charged carbon material to 1700-2300 ° C. by induction heating from the outside of the furnace. A step of passing through the heating region, and further, a heat source comprising a heater provided on the outer periphery of the furnace that does not form the induction heating region and passes through an external heat source region that is heated to 2300 to 3000 ° C. There is provided a method for producing graphite including at least a step of converting into graphite, a step of cooling the graphite, and a step of taking out the cooled graphite from the lower part of the furnace.

According to the vertical graphitization furnace of the present invention, in the furnace, the carbon material is heated from the outside of the furnace, and the induction heating region in which the carbon material is heated by passing an alternating current through a coil spirally wound around the outer periphery of the furnace. By providing the external heat source region, even when powder is used for the carbon material, heat can be applied uniformly, so that homogeneous graphite can be obtained. Specifically, by rapidly raising the temperature of the carbon material in the induction heating region installed at the top of the furnace and providing an external heat source region after the induction heating region, there are insufficiently reacted parts in the carbon material. It does not occur and the heating unevenness of the carbon material is extremely reduced, so that desired graphite can be obtained efficiently.
Moreover, it becomes possible to promote the crystal growth of graphite by combining induction heating by high frequency and external heat source heating. Furthermore, high-frequency induction heating is not likely to cause the high-frequency coil itself to reach a high temperature, so that the life of the furnace can be improved without causing deterioration of various members and peripheral members constituting the furnace.

1 is an example of a graphite production system using a vertical graphitization furnace according to the present invention. It is an example (a) and another example (b) of the coil in the induction heating area | region with which the vertical graphitization furnace which concerns on this invention is equipped. It is another example of the graphite manufacturing system using the vertical graphitization furnace which concerns on this invention.

  Hereinafter, the best mode which is an example for carrying out the present invention will be described in detail, but the scope of the present invention is not limited to this mode.

  The present invention, according to one embodiment, relates to a continuous vertical graphitization furnace. The vertical graphitization furnace of the present invention is a continuous vertical graphitization furnace in which a carbon material charged from the upper part is heated to be graphitized, and the obtained graphite is taken out from the lower part. An induction port provided at the top of the furnace, a coil that is spirally wound around the outer periphery of the furnace under the injection port, and forms an induction heating region for heating the carbon material by passing an alternating current, and induction heating A heat source provided on the outer periphery of the furnace under the region, forming a heat source region for heating the carbon material from the outside of the furnace, and cooling provided on the outer periphery of the furnace under the external heat source region A cooling jacket for forming a cooling region for cooling the generated graphite, and a take-out port for taking out the graphite provided under the cooling region.

  FIG. 1 shows an example of a graphite production system 1a using a vertical graphitization furnace 2a according to an embodiment of the present invention. The carbon material M is charged into the furnace 2a by a certain amount from the measuring feeder 6 through the charging port 2a-1 provided with the hopper 7 provided in the upper part of the furnace 2a. In the furnace 2a, an induction heating region for heating the carbon material through an alternating current is formed in the coil 3 spirally wound around the outer periphery of the furnace 2a. In addition, a heating device 8 is provided as a heat source on the outer periphery of the furnace 2a below the induction heating area, and an external heat source area for heating the carbon material M from the outside of the furnace 2a is formed. The carbon material M is converted into graphite G by passing through the induction heating region and the external heat source region. Furthermore, a cooling jacket 11 is provided on the outer peripheral portion of the furnace 2a below the external heat source region, and a cooling region for cooling the generated graphite G is formed. The cooled graphite G is recovered by the recovery unit 13 through the takeout port 12 provided below the cooling region.

Examples of the material constituting the furnace include carbon materials (preferably graphite, more preferably isotropic graphite). In particular, the furnace is preferably a carbon material (preferably graphite, more preferably isotropic graphite) because heat resistance is required, and at least the inner wall of the furnace (including the shaft of the shaft furnace) is preferably graphite, and more preferably Is made of isotropic graphite.
The charging port is provided in the upper part of the furnace, and a Taber-shaped hopper may be installed on the upper part. Furthermore, a weighing feeder may be installed on the hopper, and a certain amount of carbon material may be put into the furnace. The carbon material charged from the charging port is heated in a sufficiently filled state in the furnace and converted into graphite.

  The furnace may have a cylindrical shape, for example, a cylindrical shape having a height of 4.5 m and an inner diameter of 20 cm, and is preferably divided into a heating zone and a cooling zone from the top to the bottom. If necessary, a preheating zone may be provided above the heating zone. The heating zone has a coil wound in a spiral around the outer periphery of the furnace, an induction heating region that heats the carbon material through an alternating current through the coil, and a heat source on the outer periphery of the furnace to heat the carbon material from the outside of the furnace Including an external heat source area. Furthermore, you may include the intermediate area | region which becomes 1900-2100 degreeC after these two area | regions. After converting the carbon material to graphite in the heating zone, a cooling region for cooling the obtained graphite to, for example, 30 to 200 ° C. is provided as a cooling zone. The ratio of the length of the heating zone and the cooling zone is preferably 0.2 to 0.5 when the heating zone is 1. The ratio of the length of the induction heating area and the external heat source area is preferably 1 to 2 when the induction heating area is preferably 1. Further, when an intermediate region is included after these two regions, preferably, the length of the induction heating region is 1, the external heat source region is 1-2, and the intermediate region is 0.5-1.

  The furnace also flows an inert gas (such as nitrogen, argon or helium) as a sealing gas at the top and bottom of the furnace. This gas is for preventing air and the like from being mixed in the upper and lower parts of the furnace. The flow rate of the inert gas is preferably 5 to 40 L / min, more preferably 10 to 30 L / min, for example, in the upper part of the furnace. is there. In the lower part of the furnace, it is preferably 0.5 to 10 L / min, more preferably 1 to 5 L / min.

  The induction heating region is formed by passing an alternating current through a coil spirally wound around the outer periphery of the furnace to heat the carbon material. Induction heating is a non-contact heating method. By passing an alternating current through the coil, an alternating magnetic field that changes with time is generated, thereby generating Joule heat according to the specific resistance of the carbon material to perform heating. When the carbon material is a powder, the heat conductivity is generally small and the carbon material itself functions as a heat insulating material, so that heat is difficult to escape from the carbon material, and as a result, it can be kept at a high temperature.

  The induction heating region is provided with a coil that is spirally wound around the outer periphery of the furnace. Furthermore, a power source for supplying an alternating current to the coil and a frequency control device for the alternating current are provided outside the furnace. The alternating current supplied from the power source is converted to a current having a desired frequency by the frequency control device, and supplied to the coil using the wiring.

  The coil used is preferably composed of a conductor such as a copper wire. Examples of the cross-sectional shape of the coil include a perfect circle and an ellipse. The thickness of the coil when provided in the furnace is not particularly limited, but may be wound twice or more at the same position.

  Although arrangement | positioning of the coil with which the outer peripheral part of a furnace is equipped is not specifically limited, For example, when a furnace is a cylinder, you may arrange | position so that it may wind around the outer peripheral part of a furnace. In some cases, the coil may be installed inside the furnace so that the central axis of the coil coincides with the central axis of the furnace. In this case, all of the furnace portion that becomes the induction heating region may be covered with the coil, or the coil may be arranged at a constant interval. When the coils are arranged in the furnace at regular intervals, the coil intervals are not particularly limited as long as the induction heating region can be heated to a desired temperature. For example, the coils may be arranged apart from each other by the outer diameter of the coil. . Moreover, you may provide a heat insulating material or a space between a furnace and a coil so that a coil may not be heated with the heat | fever emitted from a furnace.

  FIGS. 2A and 2B show examples of the arrangement of the coils in the induction heating region in the vertical graphitization furnace. In FIG. 2 (a), the coil 3 is arranged so as to cover the entire range of the induction heating region of the furnace 2a. On the other hand, in FIG. 2B, the coils 3 are arranged at regular intervals in a range that becomes an induction heating region of the furnace 2a.

  In the induction heating region, heating is performed so that the carbon material is preferably 1500 to 2300 ° C, more preferably 1700 to 2300 ° C. When the temperature is lower than 1500 ° C., impurities such as sulfur are not sufficiently desorbed from the raw carbon material. When the temperature is higher than 2300 ° C., when the raw carbon material is powder, the amount of electric power for heating increases and the cost increases. On the other hand, when the temperature is higher than 2300 ° C., temperature control becomes difficult, and desired uniform graphite cannot be obtained. The heating temperature can be adjusted by the frequency of the alternating current applied. The frequency of the applied current is not particularly limited, and an alternating current having a wide range of frequencies can be used, but a high frequency is preferable. Specifically, the frequency is preferably 30 to 1000 Hz, and more preferably 35 to 500 Hz. If it is 30 Hz or less, heating is not sufficient, and if it exceeds 1000 Hz, the cost increases. By adjusting the frequency of the applied current, the carbon material can be raised to a desired temperature within a short time, for example, within 5 minutes, preferably within 3 minutes. By applying a current of a specific frequency to the coil, the temperature of the carbon material in the furnace is rapidly increased, and impurities (S, N, etc.) remaining in the carbon material are evaporated. This makes it possible to discharge the gas containing sulfur derived from impurities in the furnace without stagnation, so when the furnace, its inner wall, various members (shaft, heater, heat insulating material), etc. are made of graphite material However, the deterioration of these members due to the gas containing sulfur is extremely small, and the furnace is hardly damaged.

  The external heat source region includes a heat source on the outer peripheral portion of the furnace and is formed by heating from the outside of the furnace to heat the carbon material. Examples of the heat source include a heater made of carbon (isotropic graphite). It is possible to heat the carbon material by heating the outer periphery of the furnace to a high temperature with these heat sources. In this region, the carbon material is preferably heated at 2300 to 3000 ° C. When the temperature is lower than 2300 ° C., graphitization of the raw material carbon material does not proceed, and the capacity as the electrode material of the lithium ion battery becomes small. When it is higher than 3000 ° C., the characteristics (initial efficiency) as an electrode material of the lithium ion battery are lowered.

  The heating zone of the furnace may further include an intermediate region where the carbon material is 1900 to 2100 ° C. after the induction heating region and the external heat source region. This region is not particularly heated, and retains the amount of heat generated by heating in the previous steps. For this reason, it is preferable to attach a heat insulating material to the outer peripheral part of a furnace. By providing this region, even when the carbon material is powder, the temperature gradient with respect to the external heat source region can be moderated, the flow of the raw material can be made smooth, and more uniform graphite can be obtained.

  After converting the carbon material into graphite in the heating zone of the furnace, the obtained graphite is cooled to, for example, 30 to 200 ° C. in the cooling region of the cooling zone. A cooling jacket is attached to the outer periphery of the furnace for cooling.

  The graphite obtained in this way is recovered by the recovery unit through the take-out port provided under the cooling region. The recovered graphite may be taken out without any separation or may be taken out by a certain amount.

  FIG. 3 shows a graphite production system 1b using the vertical graphitization furnace 2b of one embodiment of the present invention. The carbon material M is charged into the furnace 2b by a certain amount from the measuring feeder 6 through the charging port 2b-1 provided with the hopper 7 provided in the upper part of the furnace 2b. In the furnace 2b, an induction heating region for heating the carbon material through an alternating current is formed in the coil 3 spirally wound around the outer periphery of the furnace 2b. In addition, a heating device 8 is provided as a heat source on the outer periphery of the furnace 2b below the induction heating area, and an external heat source area for heating the carbon material M from the outside of the furnace 2b is formed. In addition, the heat insulating material 10 is provided on the outer peripheral portion of the furnace 2d below the external heat source region, and an intermediate region of 1900 to 2100 ° C. is formed. The carbon material M is converted into graphite G by passing through the induction heating region, the external heat source region, and the intermediate region. Further, a cooling jacket 11 is provided on the outer peripheral portion of the furnace 2b below the intermediate region to form a cooling region for cooling the generated graphite G. The cooled graphite G is recovered by the recovery unit 13 through the takeout port 12 provided below the cooling region.

  According to the vertical graphitization furnace of the present invention, the temperature of the carbon material is rapidly increased in the induction heating region installed in the upper part of the furnace, and impurities (S, N, etc.) slightly remaining in the carbon material are evaporated. Let This makes it possible to discharge the gas containing sulfur derived from impurities in the furnace without stagnation, so when the furnace, its inner wall, various members (shaft, heater, heat insulating material), etc. are made of graphite material However, the deterioration of these members due to the gas containing sulfur is extremely small, and the furnace is hardly damaged. Furthermore, by providing the external heat source region after the induction heating region, an insufficiently reacted portion does not occur in the carbon material, and the heating unevenness of the carbon material is extremely reduced, so that desired graphite can be obtained.

  The carbon material that is a raw material is a substance mainly composed of hydrocarbons, and graphitizes when heated. Specific examples include petroleum coke, petroleum coke calcine (calcine coke), coal coke, and pitch. Preferably, it is a raw material oil obtained from a vacuum distillation oil or bottom oil of a residue fluidized fluid contact device (RFCC) at the time of crude oil processing, and has an initial boiling point of 300 ° C. or more and a total content of asphaltene component and resin component of 25 It is petroleum coke obtained by delay coking a mixture of heavy oil having a mass content of 40% by mass or less and a heavy oil having an aromatic index fa of 0.3 or more and an initial boiling point of 150 ° C. or more. A scaly graphite powder is obtained. Further, calcine coke (calcined coke) which is a calcine product of this petroleum coke is also preferred. Such petroleum coke contains more sulfur than coal coke and other carbon sources, but it is homogeneous, excellent in crystallization, and easily available. It is very preferable for use in graphite.

The vacuum distilled oil is obtained by subjecting crude oil to an atmospheric distillation apparatus to obtain gas, light oil, and atmospheric residual oil. Then, the atmospheric residual oil is heated at a furnace outlet temperature of 320 to 360 under a reduced pressure of 10 to 30 Torr, for example. It is a distilled oil of a vacuum distillation apparatus obtained by changing in the range of ° C. The residual oil fluid catalytic cracking unit (RFCC) uses residual oil (normal pressure residual oil, etc.) as a raw material oil and selectively performs a cracking reaction using a catalyst to obtain a high-octane FCC gasoline. Is a fluid catalytic cracking device of the type. As the bottom oil of the residual oil fluid catalytic cracker, for example, the residual oil such as atmospheric residual oil is changed in the reactor reaction temperature (ROT) range of 510 to 540 ° C., and the catalyst / oil mass ratio is changed in the range of 6 to 8. The bottom oil manufactured by letting it be mentioned is mentioned. Here, as an operating condition of the residual oil fluid contact device (RFCC), for example, an atmospheric distillation residual oil having a density of 0.9293 g / cm ³ and a residual carbon of 5.5% by mass is reacted at 530 ° C., Fluid catalytic cracking can be achieved at a total pressure of 0.21 MPa and a catalyst / oil ratio of 6. The initial boiling point is a thermometer reading (° C.) when the first drop of distilled oil falls from the lower end of the condensing tube according to JIS K 2254.

  The contents of the saturated component, the resin component, and the asphaltene component can be measured by the TLC-FID method. In the TLC-FID method, a sample is divided into four components by a thin layer chromatography (TLC) into a saturated component, an aroma component, a resin component, and an asphaltene component, and then each is detected by a flame ionization detector (FID). The component is detected, and the percentage of each component amount with respect to the total component amount is used as the composition component value. First, a sample solution is prepared by dissolving 0.2 g ± 0.01 g of a sample in 10 ml of toluene. Use a microsyringe to spot 1 μl at the lower end (0.5 cm position of the rod holder) of a silica gel rod-like thin layer (chroma rod) that has been baked in advance, and dry it with a dryer or the like. Next, 10 microrods are taken as one set, and the sample is developed with a developing solvent. As the developing solvent, hexane is used for the first developing tank, hexane / toluene (volume ratio 20:80) is used for the second developing tank, and dichloromethane / methanol (volume ratio 95: 5) is used for the third developing tank. The saturated component is eluted and developed in the first developing tank using hexane as a solvent. About an aroma component, it elutes and develops in the 2nd development tank after the 1st development. Asphaltene components are developed by elution in a third development tank using dichloromethane / methanol as a solvent after the first development and the second development. The developed chroma rod is set in a measuring instrument (for example, “Iatroscan MK-5” (trade name) manufactured by Diatron (currently Mitsubishi Chemical Yatron)), and each flame ionization detector (FID). Measure the amount of ingredients. The total amount of each component is obtained by summing the amounts of each component.

The fragrance index fa can be determined by the Knight method. In the Knight method, the distribution of carbon is divided into three components (A1, A2, A3) as an aromatic carbon spectrum by the 13C-NMR method. Here, A1 is the aromatic ring internal carbon number, half of the aromatic carbon that is not substituted with the substituted aromatic carbon (corresponding to a peak of about 40-60 ppm of 13C-NMR), and A2 is not substituted. The remaining half of the aromatic carbon (corresponding to a peak of about 60 to 80 ppm of 13C-NMR) A3 is the number of aliphatic carbon (corresponding to a peak of about 130 to 190 ppm of 13C-NMR), from which fa is expressed as fa = (A1 + A2) / (A1 + A2 + A3)
Is required. The 13C-NMR method is the best method for quantitatively determining fa, which is the most basic amount of chemical structural parameters of pitches, as described in the literature ("Pitch Characterization II. Chemical Structure" Yokono, Sanada (Carbon, 1981 (No. 105), p73-81).

  The delayed coking method is a method of obtaining raw coke by heat-treating heavy oil with a delayed coker under pressurized conditions. As conditions for the delayed coker, a pressure is preferably in a range of 0.5 to 0.7 MPa and a temperature in a range of 500 to 530 ° C. The raw coke of this delayed coker process contains a large amount of moisture, so it is dried and then crushed and classified.

  The carbon material as the raw material is pulverized as necessary before being introduced into the graphitization furnace. The average diameter of the carbon material powder is preferably 5 to 50 μm. If it is smaller than 5 μm, the fluidity is deteriorated, and the continuous processing may be difficult because the fluid does not flow smoothly in the furnace. If it is larger than 50 μm, there may be a case where sufficient thickness cannot be obtained when a sheet is used as a lithium ion battery electrode material. The average particle diameter can be measured using a laser diffraction / scattering method. The method of pulverization is arbitrary, but when petroleum coke is used, the petroleum coke is preferably made to about 1 mm to 5 mm with a vibrating sieve or the like and then dried. In general, petroleum coke contains volatile oil components for recovery and moisture when used, and therefore needs to be dried, and the moisture is preferably dried to 1% by mass or less. If necessary, the volatile oil component may be removed by heating at a temperature of preferably about 600 ° C. for 1 to 2 hours. Thereafter, it is made into powder using a jet mill, a ball mill, a hammer mill or the like. If the carbon material is petroleum coke, coal coke, etc., it may be graphitized as it is. However, since the properties of the subsequent processing and the resulting graphite powder are improved, it is preferably calcined at a temperature of about 900 to 1500 ° C. once. It is good to do. Such calcination is generally performed using a rotary kiln.

  According to another embodiment of the present invention, a method for producing graphite using the above vertical graphitization furnace. That is, a step of charging a carbon material into a vertical graphitization furnace, a step of passing the charged carbon material through an induction heating region where the carbon material is heated to 1700-2300 ° C. by induction heating from the outside of the furnace, and A step of converting to an external heat source region heated to 2300 to 3000 ° C. with a heat source provided on the outer periphery of the furnace, converting the graphite, a step of cooling the graphite, and a step of cooling the cooled graphite into the furnace A method for producing graphite including at least a step of removing from the lower part of the graphite.

  By this method, even when powder is used for the carbon material, heat can be applied uniformly, so that homogeneous graphite can be obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention, this invention is not limited to an Example.

[Examples 1 and 2 and Comparative Example 1]
(1) Preparation of carbon material The carbon material which is the used raw material is as follows.
<Raw coke A>
A mixture of heavy oil having an initial boiling point of 335 ° C., an asphaltene + resin content of 27% by mass and a saturated content of 43% by mass and a heavy oil having an aromatic index of 0.4 or more and an initial boiling point of 168 ° C. has an average temperature of 450 Raw coke subjected to delayed coking at 0 ° C. was sieved to 3 mm or less with a vibrating sieve. Thereafter, it was dried at 150 to 200 ° C. using a hot air circulating furnace until the water content became 1% by mass or less, and then a powder having an average particle diameter of 12 μm was obtained by a rotor mill.
<Calcined coke A> (used in Example 1)
Raw coke A was calcined at about 1500 ° C. using a rotary kiln, and the obtained calcined coke was sieved to 3 mm or less with a vibration sieve or the like, and then powdered with an average particle size of 12 μm with a rotor mill.
<Raw coke B>
Commercially available raw coke was sieved to 3 mm or less with a vibrating sieve, and then dried at 150 to 200 ° C. using a hot air circulating furnace until the water content became 1% by mass or less. Then, it was set as the powder with an average particle diameter of 12 micrometers with the rotor mill.
<Calcined coke B> (used in Example 2 and Comparative Example 1)
Raw coke B was calcined at about 1500 ° C. using a rotary kiln, and the obtained calcined coke was sieved to 3 mm or less with a vibrating sieve or the like, and then powdered with an average particle size of 12 μm by a rotor mill.

(2) Graphitization The obtained carbon material was graphitized using a vertical graphitization furnace. The graphitization furnace has a cylindrical furnace having a height of 4.5 m and an inner diameter of 20 cm with an inner wall made of graphite, and a charging port is installed at the upper part of the furnace and an outlet is installed at the lower part of the furnace. The carbon material charged into the furnace from the charging port was heated in the furnace and converted into graphite. A cooling jacket was installed 1 m above the bottom of the furnace to cool the material converted to graphite, and the material was recovered at the recovery part via the outlet. The substantial graphitization time was 7-10 hours.

  In Examples 1 and 2, a furnace in which the heating zone is divided into three regions is used like the vertical graphitization furnace 2b of FIG. Each area is 1.1 m. The first region was an induction heating region, and a coil was installed on the outer periphery of the furnace as shown in FIG. The frequency of the alternating current to be applied was set to 50 Hz, and the carbon material was heated to 2000 to 2100 ° C. (baking part). The second region was an external heat source region, and a heater was installed on the outer periphery of the furnace, thereby heating the carbon material to 2500 to 2600 ° C. (firing part). The third region is an intermediate region, and a heat insulating material is installed on the outer periphery of the furnace below the external heat source region, and the heat applied to the carbon material in the above two regions is set to 1900 to 2100 ° C. (Annealed part or first cooling part).

  In Comparative Example 1, a furnace having an external heat source area of 2.4 m was used in place of the dielectric heating area of the furnace used in Example 1 being installed. The conditions in the external heat source region were the same as in the example. This furnace is used in the same manner as conventionally used.

(3) Evaluation of graphite and graphitization furnace The properties of the obtained graphite powder were observed, and the sulfur content thereof was measured using a fluorescent X-ray analyzer. Further, the inside of the used graphitization furnace was observed to evaluate the presence or absence of damage, and the carbon dioxide concentration in the exhaust gas was measured using a gas chromatograph.

  The graphite powders obtained in Examples 1 and 2 were 1.0 ppm and 0.90 ppm, respectively, when the sulfur content was measured. In both Examples 1 and 2, the concentration of carbon disulfide in the exhaust gas from the furnace was 50 ppm, and when the inside of the graphitization furnace was confirmed, no damage was found and no problem was found.

  The graphite powder obtained in Comparative Example 1 was 3.0 ppm when the sulfur content was measured. In addition, compared with Examples 1 and 2, Comparative Example 1 took about 1.2 to 1.5 times longer to graphitize.

DESCRIPTION OF SYMBOLS 1a, 1b: Graphite manufacturing system using vertical graphitization furnace 2a, 2b: Furnace 2a-1, 2b-1: Input port 3: Coil 6: Weighing feeder 7: Hopper 8: Heating device 10: Insulating material 11: Cooling jacket 12: Extraction port 13: Collection part M: Carbon material G: Graphite

Claims (5)

A continuous vertical graphitization furnace in which a carbon material charged from the upper part is heated and graphitized, and the obtained graphite is taken out from the lower part,
A charging port provided at the top of the furnace for charging the carbon material;
A coil that is spirally wound around the outer periphery of the furnace under the inlet and forms an induction heating region that heats the carbon material by passing an alternating current;
An external heat source region that is provided on the outer periphery of the furnace below the induction heating region and is a heat source that is not a coil that forms the induction heating region, but is a heater , and heats the carbon material from the outside of the furnace A heat source to form,
A cooling jacket provided on the outer periphery of the furnace under the external heat source region, and forming a cooling region for cooling the generated graphite;
A vertical graphitization furnace comprising a take-out port for taking out the graphite provided under the cooling region.   The vertical graphitization furnace according to claim 1, wherein the alternating current is 30 to 1000 Hz.   The vertical graphitization furnace according to claim 1 or 2, wherein the coil forms the induction heating region of 1700 to 2300 ° C, and the heat source forms the external heat source region of 2300 to 3000 ° C.   The vertical graphitization furnace according to any one of claims 1 to 3, wherein an intermediate region of 1900 to 2100 ° C is formed between the external heat source region and the cooling region. A step of introducing a carbon material into a vertical graphitization furnace;
Passing the charged carbon material through an induction heating region for heating to 1700-2300 ° C. by induction heating from the outside of the furnace;
Furthermore, the step of converting to graphite by passing through an external heat source region heated to 2300 to 3000 ° C. with a heat source comprising a heater provided on the outer peripheral portion of the furnace, which does not form the induction heating region ;
Cooling the graphite;
Removing the cooled graphite from the lower part of the furnace.