JP6230945B2 - Two-stage heating type vertical graphitization furnace 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, isotropic graphite) is generally used as a material that can withstand such heating at 2200 ° C. or higher, and various members (shaft, Used in heaters and heat insulating materials).

  Industrially, an Atchison furnace (for example, Patent Document 1) is used to perform graphitization in batch mode, but it is also attempted to perform it continuously in order to produce it efficiently. 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 part materials for the equipment, and it may be difficult to take measures against exhaust gas and manage the heat at the entrance and exit. For this reason, the structure becomes complicated, and it takes time to install and operate.

  In recent years, 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 2 and 3). 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. Simple wiring is not required and operation is simple.

JP-A-5-78111 Japanese Patent Laid-Open No. 11-209114 JP 2002-167208 A

  However, in the continuous graphitization furnace described in Patent Document 2, the present inventor gradually heats the carbon material as a raw material, so that impurities present in the carbon material become an inappropriate compound. It was found that desorption and evaporation may occur. In particular, when the carbon material is petroleum coke derived from petroleum or a calcine product (calcine coke) of petroleum coke, sulfur contained as impurities is desorbed as hydrogen sulfide or sulfur at 1500 to 2200 ° C. In other words, when the inner wall of the graphitization furnace is a carbon material (graphite material), the desorbed sulfur content such as hydrogen sulfide reacts with the carbon constituting the inner wall of the graphitization furnace and wears the inner wall. I found it. Furthermore, it discovered that sulfur content, such as hydrogen sulfide which permeate | transmitted the inner wall, also reacts with the carbon of the various members (heat insulating material, heater) which comprise a furnace, and carries out deterioration wear.

  On the other hand, the continuous graphitization furnace described in Patent Document 3 can be rapidly heated by energization heating. Since the raw material carbon material itself generates heat in electric heating, the sulfur content such as hydrogen sulfide described above reacts with the raw material carbon material, so that the furnace body such as the inner wall of the furnace, the heater, and the heat insulating material is worn out and deteriorated. There is no. However, the present inventor has found that when the raw material is a fine powder of 5 to 30 μm, the product obtained is not uniform because it is insufficient for uniform heating. Patent Document 1 describes a method of graphitizing a fired body by electric heating. In this method, a graphitized material is produced by kneading carbide with a binder such as pitch to form a cylindrical solid. In other words, it is a method aimed at graphitization of the fired body and is not suitable for graphitization of powder.

  From the above, the object of the present invention is to wear the furnace and its inner wall, various members (shaft, heater, heat insulating material), etc., with carbon materials (graphite materials), etc., due to gas containing sulfur content of these members. Further, the present invention provides a vertical graphitization furnace that is extremely little deteriorated and that can uniformly apply heat to a carbon material that is a raw material, thereby obtaining homogeneous graphite.

The present invention, according to one aspect, is 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 furnace body, and an electric heating cylinder connected to the upper end of the furnace body,
The energization heating cylinder is a cylindrical member that is charged by charging the carbon material from above,
At least two electrodes, which are placed on the inner wall of the cylindrical member opposite to each other via the carbon material and form an energization region for heating the carbon material by energization,
The furnace body is provided on the outer periphery of the furnace body, and a heat source that forms an external heat source region that heats the carbon material from the outside of the furnace body;
A cooling jacket provided on the outer periphery of the furnace main body 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 carbon material is introduced from above into the inside of the current heating cylinder of the vertical graphitization furnace, which includes a furnace main body and a current heating cylinder connected to the upper end of the furnace main body. Passing the charged carbon material through an energized region in which at least two electrodes installed on the inner wall of the cylindrical member of the energization heating cylinder are energized and heated to 1700-2300 ° C., and A step of converting to graphite by passing through an external heat source region heated to 2300 to 3000 ° C. with a heat source provided on the outer periphery of the furnace body, a step of cooling the graphite, and the cooled graphite into the furnace And a method for producing graphite including at least a step of removing from the lower part of the steel.

  According to the vertical graphitization furnace of the present invention, an energization region that includes a furnace body and an energization heating cylinder connected to the upper end of the furnace body, and energizes at least two electrodes in the energization heating cylinder to heat the carbon material. By forming an external heat source region that heats the carbon material from the outside in the furnace body, even when powder is used for the carbon material, heat can be applied uniformly, so that homogeneous graphite can be obtained. Is possible. Specifically, by directly energizing the carbon material in an energization heating cylinder connected to the upper end of the furnace body, the temperature of the carbon material is rapidly increased, and impurities remaining slightly in the carbon material are desorbed. . As a result, the gas containing sulfur derived from impurities in the furnace is not a carbon material (graphite material) such as a shaft, a heater, or a heat insulating material, but a raw material carbon. Reacts with materials. For this reason, even when the furnace body, its inner wall, and various members (shafts, heaters, heat insulating materials), etc. are made of graphite, these members are very unlikely to be worn out and deteriorated by the gas containing sulfur, and damage the furnace. Hateful. Furthermore, by providing an external heat source region after the energized region, there is no insufficient reaction in the fine carbon material, and the heating unevenness of the carbon material is extremely reduced. Can do.

  In addition, when the furnace body is made of a graphite material, the furnace body can be directly energized or grounded by constituting the cylindrical member of the current heating cylinder connected to the upper end of the furnace body with an insulating material. In addition, the damage to the furnace can be extremely reduced. Furthermore, since the insulating substance is more excellent in heat dissipation than the graphite material, it makes it difficult for heat to accumulate in the electrode material and prevents deterioration of the electrode, thereby extending the life of the electrode.

1 is an example of a graphite production system using a vertical graphitization furnace according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS In the vertical graphitization furnace of one embodiment which concerns on this invention, (a) The cross-sectional simplified view of a longitudinal direction in an electricity supply area | region, (b) The conceptual diagram of electrode arrangement | positioning. It is a conceptual diagram of another electrode arrangement | positioning in an electricity supply area | region in the vertical graphitization furnace of FIG. In the vertical graphitization furnace of another embodiment according to the present invention, (a) a simplified sectional view in the longitudinal direction in the energized region, (b) a conceptual diagram of electrode arrangement, and (c) a perspective view of electrode arrangement. . In a vertical graphitization furnace of another embodiment concerning the present invention, (a) a section simple figure of a longitudinal direction in an energization field, and (b) a conceptual diagram of electrode arrangement. It is a conceptual diagram of another electrode arrangement | positioning in an electricity supply area | region in the vertical graphitization furnace of FIG. 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 electric heating cylinder connected to the upper end of the cylinder, and the electric heating cylinder is installed on the inner wall of the cylindrical member opposite to the carbon member with the carbon material being charged from the top and charged. And at least two electrodes that form an energized region for heating the carbon material, and the furnace body is provided on the outer peripheral portion of the furnace body, and an external heat source region for heating the carbon material from the outside of the furnace body. A heat source to be formed, a cooling jacket provided on the outer periphery of the furnace body under the external heat source region and forming a cooling region for cooling the generated graphite, and an outlet for taking out the graphite provided under the cooling region It is equipped with.

  FIG. 1 shows an example of a graphite production system 1a using a vertical graphitization furnace according to an embodiment of the present invention. The carbon material M is charged into the tubular member 4a by a certain amount from the measuring feeder 6 through the hopper loading port 7 provided on the upper part of the tubular member 4a constituting the energization heating cylinder. The cylindrical member 4a is installed in a cap shape at the upper end of the furnace body 2a. In the energization heating cylinder, at least two electrodes 3a-1, 3a-2 are provided on the inner wall of the cylindrical member 4a so as to face each other through the carbon material M, and the electrodes 3a-1, 3a-2 are energized. Thus, an energized region for heating the carbon material M is formed. Further, a heating device 8 is provided as a heat source on the outer peripheral portion of the furnace body 2a below the energization heating cylinder, and an external heat source region for heating the carbon material M from the outside of the furnace body 2a is formed. The carbon material M is converted into graphite G by passing through the energization region and the external heat source region. Furthermore, a cooling jacket 11 is provided on the outer peripheral portion of the furnace body 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 main body include a carbon material (preferably graphite, more preferably isotropic graphite), a ceramic material such as alumina, a refractory metal such as tungsten and tantalum, or an alloy material. In particular, since the furnace body is required to have heat resistance, a carbon material (preferably graphite, more preferably isotropic graphite) is preferable, and at least the inner wall of the furnace body (including the shaft of the shaft furnace) is preferably graphite, More preferably, it is made of isotropic graphite.
An electric heating cylinder is connected to the upper end of the furnace body, and a carbon material is introduced from the upper part of the electric heating cylinder. A Taber-shaped hopper may be installed on the upper part of the electric heating cylinder. Furthermore, a weighing feeder may be installed on the hopper, and a certain amount of carbon material may be charged. The charged carbon material is heated and converted into graphite in a sufficiently charged state in the energization heating cylinder and the furnace body. In addition, an inert gas (for example, nitrogen, argon, helium, or the like) is allowed to flow as a sealing gas at the upper part of the energization heating cylinder and the lower part of the furnace body. This gas is for preventing air and the like from being mixed in the upper part of the energization heating cylinder and the lower part of the furnace body. The flow rate of the inert gas is, for example, 5 to 40 L / min, preferably 10 to 30 L / min at the upper part of the energization heating cylinder. Moreover, in the lower part of a furnace main body, it is 0.5-10L / min, Preferably it is 1-5L / min.

  The energization heating cylinder is installed on the inner wall of the cylindrical member opposite to the carbon material through which the carbon material is charged from above and filled with the carbon material, and forms an energized region for heating the carbon material by energization. At least two electrodes. An energized region is formed by energizing at least two electrodes, and the carbon material is heated. By energization, Joule heat corresponding to the specific resistance of the carbon material is generated in the carbon material between the electrodes, thereby heating the carbon material. The electrodes may be energized using direct current or alternating current. 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.

  In the energized region, it is preferable to heat the carbon material so that the temperature becomes 1700 to 2300 ° C. When the temperature is lower than 1700 ° C., impurities such as sulfur are not desorbed from the raw material carbon material. When the temperature is higher than 2300 ° C., when the raw material carbon material is a 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. In the heating by energization, the center part between the electrodes becomes the highest temperature. For this reason, it is preferable to arrange | position an electrode so that a carbon material can be heated efficiently in a cylindrical member. The temperature and range of the high temperature portion of the carbon material that appears between the electrodes when energized can be set by adjusting the power supplied to the energization. The high temperature part is preferably a maximum temperature of 2300 ° C. Specifically, it is achieved by adjusting the voltage at 30 to 3000 V and the current at 30 to 3000 A. By setting it as this range, it becomes possible to raise a high temperature part to a desired temperature within a short time, for example, within 5 minutes, preferably within 3 minutes.

  The cylindrical member is preferably made of an insulating material having heat resistance of about 2000 to 2500 ° C. Examples of the heat-resistant insulating material include ceramics, and silicon carbide is particularly preferable. Ceramics generally have a limit of about 2000 ° C. as a heat-resistant temperature, but heating by this method heats the central part between electrodes to the highest temperature. For this reason, heat should be dissipated to some extent in the vicinity of the electrodes, and even ceramics have sufficient heat resistance.

  The cylindrical member is provided with an electrode on its inner wall in order to form an energization region. For this reason, the cylindrical member has a through-hole for installing an electrode. The number and size of the through holes are designed according to the number and size of the electrodes, but preferably have at least two through holes. In some cases, in order to hold the electrode more stably, a holding member may be provided on the contour portion or the outer peripheral portion of the through hole. When the holding member is used, the size of the through hole needs to be designed in consideration of a space for installing the holding member. The position of the through hole is not particularly limited, but when it has at least two through holes, one through hole is made at a certain distance from the upper end of the cylindrical member, and the other through hole is The cylindrical member can be manufactured at a position facing the previously formed through hole with a central axis extending vertically and passing through the center of the cross section of the cylindrical member.

  The holding member is preferably made of a heat-resistant insulating material. Examples of the heat-resistant insulating material include ceramics, and silicon carbide is particularly preferable. The holding member can be disposed between the cylindrical member and the electrode, or in the contour portion or the outer peripheral portion of the through hole, and may be disposed on all surfaces of the electrode in contact with the through hole of the cylindrical member. It is preferable to arrange at least between the through-hole portion of the cylindrical member and the bottom surface of the electrode. The shape of the holding member is not particularly limited, but it is preferable to design the holding member so as not to create a gap when the electrode is inserted into the through hole of the cylindrical member. The holding member desirably has a thickness suitable for stably holding the electrode. The length of the holding member is not particularly limited, but is preferably in the range from the thickness of the cylindrical member to the length in the direction of insertion into the through hole of the electrode. By using the holding member, the electrode can be installed more stably. Thus, by making the cylindrical member and the holding member into an insulating substance (ceramic), there is little leakage of current from the electrode installed in the through hole of the cylindrical member, and when the carbon material as a raw material is heated Erosion due to generated sulfur-containing gas is difficult to occur.

  The electrodes use at least one positive electrode and at least one negative electrode to form at least one pair. Examples of the material for the electrode include carbon materials (isotropic graphite). The shape of the electrode is not particularly limited, and may be a cylindrical shape or a rectangular parallelepiped, and both may be the same shape or different shapes. Although the size of the electrode is not particularly limited, it is preferable to use a size suitable for obtaining a desired high temperature range, and both of them may be the same size or different sizes. It is preferable that the area of the electrode which acts as a positive electrode or a negative electrode is equal. The electrode is installed in the through hole of the tubular member so as to be inserted from the outside to the inside of the tubular member. Inside the cylindrical member, the inner side of the electrode (the surface facing the central axis of the cylindrical member) is connected to the cylinder so that the carbon material can be heated more uniformly and at the same time the carbon material can be passed through by a certain amount. It is preferable to fix along the inner wall of the shaped member, for example, in accordance with the position of the inner wall surface or at a position slightly entering the central axis side from the inner wall surface.

  As one aspect of the arrangement of the electrodes, at least one pair of electrodes are arranged on the inner wall of the cylindrical member so as to face each other with a carbon material interposed therebetween. For example, each pair of electrodes is arranged so as to be fitted into a portion (through-hole) that has been punched into the wall surface of the cylindrical member in advance according to the size of the electrode via a carbon material filled in the cylindrical member. To do. In this case, it is preferable that the cylindrical member is designed so that the center of the line connecting the pair of electrodes matches or is aligned with the central axis inside the cylindrical member. Moreover, you may install the holding member for hold | maintaining an electrode in the through-hole part of a cylindrical member. In some cases, in order to avoid static electricity, measures against static electricity such as grounding may be taken as necessary.

  2A and 2B show the size of the electrode of the cylindrical member 4a in advance through the carbon material M in which the two rectangular electrodes 3a-1 and 3a-2 are filled in the cylindrical member 4a. The example of arrangement | positioning which fits into the part 4h-1, 4h-2 cut through according to the thickness (through-hole) is shown. In this case, the center of the line connecting the electrodes 3a-1 and 3a-2 is arranged to coincide with the central axis inside the cylindrical member 4a. FIG. 3 shows the cylindrical member 4b in advance through a carbon material M in which two pairs (four) of electrodes 3a-1, 3a-2, 3a-3, 3a-4 are filled in the cylindrical member 4b. The example of arrangement | positioning fitted to the through-hole parts 4h-1, 4h-2, 4h-3, 4h-4 according to the magnitude | size of the electrode is shown. A straight line connecting the pair of electrodes 3a-1, 3a-2 and a straight line connecting the other pair of electrodes 3a-3, 3a-4 are perpendicular to each other on the central axis inside the cylindrical member 4b. Next, the through hole of the cylindrical member 4b is designed. When the electrodes 3a-1, 3a-2, 3a-3, 3a-4 are positive electrodes, the electrodes 3a-2, 3a-4 are negative electrodes. 4A, 4B, and 4C show a holding member 14 for holding the electrodes 3a-1 and 3a-2 in the through-hole portions 4h-11 and 4h-12 of the cylindrical member 4c. An example of an arrangement in which is installed.

  As another aspect, at least one of the pair of electrodes is disposed on a part or all of the inner wall of the cylindrical member, and the other of the at least one pair of electrodes is disposed on the central axis inside the cylindrical member. Is done. For example, one electrode with wiring for transmitting electricity from the outside is arranged on the central axis inside the cylindrical member, and another electrode serving as a counter electrode is inserted through a carbon material filled in the cylindrical member. It arrange | positions so that it may fit in the through-hole part match | combined with the magnitude | size of the electrode of the wall surface of a cylindrical member previously.

  5 (a) and 5 (b), one electrode 3a-5 provided with wiring 5 for transmitting electricity from the outside is arranged on the central axis inside the cylindrical member 4a and filled into the cylindrical member 4a. An arrangement is shown in which the other electrodes 3a-1 and 3a-2 are fitted into the through-hole portions 4h-1 and 4h-2 that have been adjusted to the size of the electrode in advance on the wall surface of the cylindrical member 4a through the carbon material M. In this case, the electrodes 3a-1, 3a-2 are counter electrodes to the electrode 3a-5 disposed on the central axis inside the cylindrical member 4a. FIG. 6 shows four electrodes 3a-1, 3a-2, 3a-3, 3a- in the through-hole portions 4h-1, 4h-2, 4h-3, 4h-4 on the wall surface of the cylindrical member 4b. 4 shows an arrangement in which 4 is inserted. In this case, the electrodes 3a-1, 3a-2, 3a-3, 3a-4 are counter electrodes to the electrode 3a-5 arranged on the central axis inside the cylindrical member 4b.

  The carbon material moves into the furnace body after being heated by the electric heating cylinder. The furnace main body 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. The heating zone is provided with a heat source on the outer peripheral portion of the furnace body, includes an external heat source region for heating the carbon material from the outside of the furnace body, and may include an intermediate region at 1900 to 2100 ° C. after this region. 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, assuming that the heating zone is 1. Moreover, the ratio of the length of the energization region and the external heat source region in the energization heating cylinder is preferably 2 to 10 when the energization region is preferably 1. In addition, when an intermediate region is included after these two regions, preferably the length of the energizing region is 1, the external heat source region is 2 to 10, and the intermediate region is 1 to 5.

  The external heat source region includes a heat source on the outer peripheral portion of the furnace body, and is formed by heating from the outside of the furnace body to heat the carbon material. Examples of the heat source include a heater made of carbon material (isotropic graphite). With these heat sources, it is possible to heat the carbon material by heating from the outer periphery of the furnace body to a high temperature. As another heat source, a coil is provided on the outer peripheral portion of the furnace body, and an alternating current is applied to induce induction heating of the carbon material. In this case, the applied alternating current may be a high frequency. If necessary, the outside of the heating wire that is a coil is insulated by a heat insulating material or the like. 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 body may further include an intermediate region where the carbon material is 1900 to 2100 ° C. after 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 main body. 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 homogeneous graphite can be obtained.

  After converting the carbon material into graphite in the heating zone of the furnace body, 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 body 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 a certain amount may be taken out.

  FIG. 7 shows an example of a graphite production system 1b using a vertical graphitization furnace which is another embodiment of the present invention. The carbon material M is charged into the tubular member 4a by a certain amount from the measuring feeder 6 through the hopper loading port 7 provided on the upper part of the tubular member 4a constituting the energization heating cylinder. The cylindrical member 4a is installed in a cap shape at the upper end of the furnace body 2b. In the energization heating cylinder, at least two electrodes 3a-1, 3a-2 are provided on the inner wall of the cylindrical member 4a so as to face each other through the carbon material M, and the electrodes 3a-1, 3a-2 are energized. Thus, an energized region for heating the carbon material M is formed. Further, a heating device 8 is provided as a heat source on the outer peripheral portion of the furnace body 2b below the energization heating cylinder, and an external heat source region for heating the carbon material M from the outside of the furnace body 2b is formed. In addition, the heat insulating material 10 is provided on the outer peripheral portion of the furnace body 2b under the external heat source region, and the temperature is set to 1900 to 2100 ° C. The carbon material M is converted into graphite G by passing through the energization region, the external heat source region, and the intermediate region. Furthermore, a cooling jacket 11 is provided on the outer peripheral portion of the furnace body 2b below the external heat source region, and a cooling region for cooling the generated graphite G is formed. The cooled graphite G is taken out from the collection unit 13 through the take-out port 12 provided below the cooling region.

According to the vertical graphitization furnace of the present invention, by directly energizing the carbon material with an energization heating cylinder connected to the upper end of the furnace body, the temperature of the carbon material is rapidly increased and slightly left in the carbon material. The impurities to be evaporated are evaporated. As a result, the gas containing sulfur derived from impurities can be discharged without stagnation in the furnace, so the furnace body, its inner wall, various members (shaft, heater, heat insulating material), etc. are composed of graphite. 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 energized region, an insufficiently reactive 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.
In addition, when the furnace body is made of a graphite material, the furnace body can be directly energized or grounded by constituting the cylindrical member of the current heating cylinder connected to the upper end of the furnace body with an insulating material. In addition, the damage to the furnace can be extremely reduced. Furthermore, since the insulating material is more excellent in heat dissipation than graphite, it is difficult for heat to accumulate in the electrode material, so that deterioration of the electrode can be prevented, resulting in a longer life of the electrode.

  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 from above into the current heating cylinder of the vertical graphitization furnace, comprising a furnace main body and a current heating cylinder connected to the upper end of the furnace main body, and the charged carbon A step of passing the material through an energized region in which at least two electrodes installed on the inner wall of the cylindrical member of the energization heating cylinder are energized and heated to 1700-2300 ° C., and further provided on the outer periphery of the furnace body. At least a step of converting to graphite through an external heat source region heated to 2300 to 3000 ° C., a step of cooling the graphite, and a step of removing the cooled graphite from the lower part of the furnace This is a method for producing 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. Then, it dried until the water | moisture content became 1 mass% or less using a hot-air circulation furnace at 150-200 degreeC, and it was set as the powder of the average particle diameter of 12 micrometers with the rotor mill.
<Calcined coke A> (used in Example 1)
After calcining coke A obtained by calcining raw coke A at about 1500 ° C. using a rotor kiln to a size of 3 mm or less with a vibrating sieve or the like, it was made into a powder having an average particle size of 12 μm with a rotor mill.
<Raw coke B>
After sieving commercially available coke to 3 mm or less with a vibration sieve, it is dried at 150 to 200 ° C. using a hot air circulating furnace until the water content becomes 1% by mass or less, and a powder with an average particle diameter of 12 μm is obtained with a rotor mill. did.
<Calcined coke B> (used in Example 2 and Comparative Example 1)
After calcining coke B obtained by calcining raw coke B at about 1500 ° C. using a rotary kiln to a size of 3 mm or less with a vibrating sieve or the like, a powder having an average particle size of 12 μm was obtained with a rotor mill.

(2) Graphitization The obtained carbon material was converted into graphite using a vertical graphitization furnace. The graphitization furnace has a cylindrical furnace body with an inner diameter of 20 cm and a total length of 4.5 m provided with an inner wall made of graphite, and a take-out port is provided at the lower part of the furnace. The carbon material charged from the top of the furnace body was heated to convert it into graphite. A cooling jacket was installed 1 m above the bottom of the furnace body to cool the material converted to graphite. The cooled graphite was recovered in the recovery section through the outlet of the furnace body. The substantial graphitization time was 7-10 hours.

In Examples 1-2, as shown in FIG. 7, the heating was performed in a furnace provided with an electrically heated cylinder at the upper end of the furnace body. The cylindrical member of the electric heating cylinder was made of silicon carbide, and had an inner diameter of 20 cm, a thickness of 5 cm, and a height of 0.5 m. A through hole was formed so that the upper side of a 10 cm ² square shape was located 20 cm from the upper end of the cylindrical member. Furthermore, another through hole was produced so as to face this through hole with the central axis inside the cylindrical member being separated. A 10 cm ³ rectangular parallelepiped electrode was placed in the two through holes produced so as to be fitted from the outside to the inside of the cylindrical member. A current of 2700 A and a voltage of 30 V were applied to the electrode, and the current was passed through the carbon material filled in the furnace body, and the high temperature part was heated to 2200 to 2300 ° C. (baking part). Next, the carbon material passed through the energized region was processed in the furnace body. First, on the outer periphery of the furnace main body under the cylindrical member, a heating element was installed in a range of 1.1 m to form an external heat source region, thereby heating the carbon material to 2500 to 2600 ° C. (firing part). . Next, on the outer periphery of the furnace main body under the external heat source region, a heat insulating material was installed in a range of 1.1 m, and the heat given to the carbon material by the above two heatings was set to 1900 to 2100 ° C. (annealing) Part or first cooling part).

  In Comparative Example 1, a furnace body having an external heat source area of 1.1 m was used instead of the current heating cylinder used in Example 1 being installed. The conditions in the external heat source region were the same as in the example. This furnace body is used in the same manner as conventionally used.

(3) Evaluation of graphitization furnace The inside of the used graphitization furnace was observed to evaluate the presence or absence of damage.

  When the inside of the graphitization furnace used in Examples 1 and 2 was confirmed, no damage was found, and no problem was found.

  When the inside of the graphitization furnace used in Comparative Example 1 was confirmed, damage was observed, and it was scooped at the top of the furnace, which is a position corresponding to the energization region of the example.

  As shown in the above results, as a result of converting petroleum coke, etc. into graphite in a state close to powder or fine powder using a conventional graphite graphitization furnace, the wall surface (made of graphite) in the graphitization furnace is scooped out. The situation that has occurred. In the comparative example, unlike the graphitization furnace used in the examples, heating by direct energization is not used, so that the desorbed sulfur reacts with the carbon material (graphite material) that is a constituent member of the furnace and wear occurs. Estimated. On the other hand, in the embodiment, since the carbon material of the raw material is heated directly by energization, the temperature of the raw material carbon material becomes higher than that of the structural member of the furnace. It is presumed that the hindrance of the furnace was prevented by inhibiting it.

1a, 1b: Graphite production system using a vertical graphitization furnace 2a, 2b: Furnace body 3a-1, 3a-2, 3a-3, 3a-4, 3a-5: Electrodes 4a, 4b, 4c: Tubular 4h-1, 4h-2, 4h-3, 4h-4, 4h-11, 4h-12: Through-hole part of cylindrical member 5: Wiring 6: Weighing feeder 7: Hopper insertion port 8: Heating device 10: Thermal insulation material 11: Cooling jacket 12: Extraction port 13: Collection part 14: Holding member M: Carbon material G: Graphite

Claims (7)

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 furnace body, and an electric heating cylinder connected to the upper end of the furnace body,
The energization heating cylinder is a cylindrical member that is charged by charging the carbon material from above,
At least two electrodes, which are placed on the inner wall of the cylindrical member opposite to each other via the carbon material and form an energization region for heating the carbon material by energization,
The furnace body is provided on the outer periphery of the furnace body, and a heat source that forms an external heat source region that heats the carbon material from the outside of the furnace body;
A cooling jacket provided on the outer periphery of the furnace main body 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. As a counter electrode of the at least two electrodes, further comprising one electrode with wiring for transmitting electricity from the outside,
One electrode marked with the wiring is provided on the central axis inside of said tubular member, said at least two power poles, claim 1 is part of or all the provided et the inner wall of the tubular member The vertical graphitization furnace described in 1.   The vertical graphitization furnace according to claim 1 or 2, wherein the electrode forms the energization 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.   The vertical graphitization furnace according to any one of claims 1 to 4, wherein an inner wall of the furnace body is made of graphite, and the cylindrical member is made of an insulating material.   The vertical graphitization furnace according to any one of claims 1 to 5, wherein the insulating substance is silicon carbide. A step of introducing a carbon material from above into the inside of the current heating cylinder of the vertical graphitization furnace, comprising a furnace main body, and a current heating cylinder connected to the upper end of the furnace main body,
Passing the charged carbon material through an energized region in which at least two electrodes installed on the inner wall of the cylindrical member of the energizing heating cylinder are energized and heated to 1700-2300 ° C .;
Furthermore, with a heat source provided at the outer peripheral portion of the furnace body, passing through an external heat source region heated to 2300 to 3000 ° C. and converting to graphite,
Cooling the graphite;
Removing the cooled graphite from the lower part of the furnace.