Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10C—WORKING-UP PITCH, ASPHALT, BITUMEN, TAR; PYROLIGNEOUS ACID
  • C10C3/00—Working-up pitch, asphalt, bitumen
  • C10C3/002—Working-up pitch, asphalt, bitumen by thermal means
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/15—Nano-sized carbon materials
  • C01B32/182—Graphene
  • C01B32/184—Preparation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/20—Graphite
  • C01B32/205—Preparation
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10C—WORKING-UP PITCH, ASPHALT, BITUMEN, TAR; PYROLIGNEOUS ACID
  • C10C3/00—Working-up pitch, asphalt, bitumen
  • C10C3/06—Working-up pitch, asphalt, bitumen by distillation
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B7/00—Heating by electric discharge
  • H05B7/02—Details
  • H05B7/06—Electrodes
  • H05B7/08—Electrodes non-consumable
  • H05B7/085—Electrodes non-consumable mainly consisting of carbon
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/40—Electric properties
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/04—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of carbon-silicon compounds, carbon or silicon

Definitions

• the present invention relates to a method for producing a petroleum-based impregnation pitch used for producing a carbon material such as a graphite electrode or a carbon / carbon composite material.
• Graphite electrodes used in electric steel arc furnaces are extruded, fired, pitch impregnated (refilled), and then refired after crushing, classifying, and mixing needle coke with a predetermined particle size mixture together with a binder pitch. , Manufactured through various steps of graphitization.
• the graphite electrode is used in an electric steel arc furnace to generate an arc from its tip, reach a high temperature of over 2000 ° C., and melt a steel material or the like to produce an alloy steel.
• pitch impregnation and re-baking operations are performed several times in order to maintain high density and high strength.
• the purpose of this operation is to increase the electrical conductivity and thermal conductivity by binding aggregates such as needle coke to each other and reducing the porosity of the obtained carbon material to increase the density and strength. Is done for. Therefore, the pitch used in the pitch refilling step (referred to as "impregnation pitch") is indispensable for the production of carbon materials.
• the impregnation pitch it is important that (1) there is no quinoline insoluble matter (QI) and (2) the fixed carbon (FC) content is high for that purpose.
• QI quinoline insoluble matter
• FC fixed carbon
• the impregnation pitch contains a quinoline insoluble component (also referred to as “QI” in the present disclosure)
• QI quinoline insoluble component
• the fixed carbon content is low, the amount of components vaporized at the time of firing increases, and pores are generated. To compensate for this, the number of impregnation steps and re-baking steps must be increased.
• the pitch for carbon materials is roughly divided into those made from coal (coal tar) and those made from petroleum.
• coal tar pitch generally has a high fixed carbon content
• quinoline insoluble content is present in the raw material coal tar. Therefore, in order to use it as an impregnation pitch, a step of removing the quinoline insoluble component is required. ..
• the quinoline insoluble component is removed from the raw material pitch by a centrifugation method, and the light oil component is distilled off to produce an impregnation pitch having a quinoline insoluble content of 0.1 to 1%.
• the petroleum-based pitch as shown in Patent Document 3 does not contain quinoline insoluble matter in the raw material.
• An object of the present invention is to provide an impregnation pitch having a high fixed carbon content in spite of being a petroleum-based pitch.
• the present invention relates to the following [1] to [8].
• [1] A method for producing an impregnation pitch for producing a graphite electrode, which comprises heat-treating an ethylene bottom oil and distilling the heat-treated product to remove a low boiling point product.
• [2] The method for producing an impregnation pitch according to [1], wherein the amount of quinoline insoluble in the heat-treated product is 0.5% by mass or less.
• [4] The method for producing an impregnation pitch according to any one of [1] to [3], wherein the treatment time at the heat treatment temperature is 0.5 to 36 hours.
• [5] The method for producing an impregnation pitch according to any one of [1] to [4], wherein the amount of low boiling point removed by distillation is 20 to 80% by mass with respect to ethylene bottom oil.
• [6] The method for producing an impregnation pitch according to any one of [1] to [5], wherein the softening point of the produced impregnation pitch is 70 ° C. to 130 ° C. and the fixed carbon content is 45% by mass or more.
• the method for producing an impregnation pitch according to any one of [1] to [6], which does not include a step of removing the quinoline insoluble matter.
• the impregnation pitch used in the impregnation step is any of [1] to [7].
• a petroleum-based impregnation pitch having a high fixed carbon content and a desired softening point can be obtained without the need for a quinoline insoluble component removing step performed during the production of coal tar pitch.
• Kneading process A process of mixing and kneading both needle coke and binder pitch.
• Molding process 2. A process of molding the kneaded product by extrusion or the like to obtain a cylindrical molded body.
• Firing step 4 Step of calcining the molded product to obtain a fired product.
• Impregnation step 5. Step of filling the fired body with an impregnation pitch.
• Re-baking step 6 Step of re-baking the filled fired body to obtain a re-fired body.
• Graphitization process Graphitizing the refired product 7. Processing process A process in which a graphitized body is formed into a predetermined shape by cutting or the like to form a graphite electrode.
• the needle coke and the binder pitch which are crushed, classified, and blended in a predetermined ratio with a particle size, are mixed and kneaded together.
• the blending amount of the binder pitch is about 20 to 30 parts by mass with respect to 100 parts by mass of needle coke.
• the binder pitch is not particularly limited as long as it forms a paste by mixing with needle coke.
• petroleum-based pitch, coal-based pitch, coal tar pitch, and the like can be used.
• the kneaded product may contain iron oxide. Iron oxide has a puffing inhibitory effect.
• a commercially available mixer or stirrer can be used for mixing and kneading. Specific examples include a mixer such as a mixer and a kneader, and a kneader.
• the preferable kneading temperature is around 150 ° C., and then the temperature is cooled to a temperature suitable for molding (100 to 130 ° C.).
• Molding step The kneaded product is molded by extrusion or the like to obtain a cylindrical molded body having a predetermined size.
• the temperature of the molded product in the previous step is raised and fired at 700 ° C. to 1000 ° C. to obtain a fired product.
• the firing step is preferably performed in a combustion exhaust gas non-oxidizing atmosphere.
• the molded body softens at the initial stage of temperature rise, and a large amount of decomposition gas is generated by thermal decomposition and polycondensation of the binder pitch at 200 to 500 ° C., and pores are formed and volume shrinkage occurs.
• the binder pitch is carbonized at 500 to 600 ° C.
• the firing process often takes about one month including cooling.
• Impregnation step In the firing step, generally 35 to 45% of the mass of the binder is lost as volatile matter from the binder pitch. At that time, a large number of pores are generated in the fired body.
• the impregnation step is to fill the pores with the impregnation pitch. Impregnation is performed by, for example, putting a fired body in an autoclave, degassing under reduced pressure, injecting a melted impregnation pitch, and injecting the impregnation pitch into the pores at a gas pressure of about 1 MPa at about 200 ° C. ..
• Reburning step The filled fired body is fired again to obtain a refired body.
• the re-baking can also be performed under the same conditions as the firing step.
• the impregnation step and the re-baking step may be repeated as needed.
• the refired body is placed in a furnace (Achison furnace, LWG furnace, etc.) surrounded by an insulating material, and the refired body is subjected to heat treatment due to packing coke by energization or resistance heat generation of the refired body.
• the graphitization temperature is 2000-3000 ° C. This temperature is required to convert the amorphous carbon in the refired body to crystalline graphite. It is preferable to heat-treat for several days in order to convert the re-fired product into graphite.
• the graphitized body is machined such as by cutting to obtain a graphite electrode product with a predetermined shape.
• the method for producing an impregnation pitch of one embodiment includes at least a heat treatment step of heat-treating the ethylene bottom oil and an impregnation pitch of removing a low boiling point from the heat-treated ethylene bottom oil to have a desired fixed carbon content and softening point. Includes two distillation steps to produce.
• the fixed carbon content is a value measured by a measuring method based on the "fixed carbon content quantification method" of JIS K 2425: 2006
• the softening point is the "softening point” of JIS K 2425: 2006.
• the amount of QI is a value measured in accordance with JIS K 2425: 2006 "Method for quantifying quinoline insoluble matter of tar pitch".
• pyrolysis plants such as naphtha are often referred to as ethylene plants, the above-mentioned heavy fraction is called ethylene bottom oil.
• Naphtha pyrolysis plants are sometimes called naphtha crackers.
• ethylene bottom oil in addition to the ethylene bottom oil obtained by thermal decomposition of naphtha, a raw material further containing at least one selected from the group consisting of kerosene, light oil and a natural gas solution in addition to naphtha is heated.
• Ethylene bottom oil obtained by decomposition can also be used.
• Natural gas liquid (NGL: Natural Gas Liquid) is a high-boiling liquid component at the time of natural gas sampling, and is "a general term for liquid hydrocarbons separated and recovered from natural gas produced underground through a well" ( Oil and natural gas resource information glossary, https://oilgas-info.jogmec.go.jp/termlist/1001289/1001313.html).
• a raw material containing at least naphtha and, in some cases, further containing at least one selected from the group consisting of kerosene, light oil and natural gas liquid is referred to as a naphtha-containing raw material.
• a raw material containing at least one selected from the group consisting of kerosene, light oil and natural gas liquid is used as the naphtha-containing raw material in addition to naphtha
• the total content of kerosene, light oil and natural gas liquid is the total content of the naphtha-containing raw material. It can be 1 to 99% by mass in 100% by mass.
• the naphtha-containing raw material having a high total content contains at least one selected from the group consisting of kerosene, light oil, and natural gas liquid, which are cheaper than naphtha, and therefore contains more than one of the naphtha-containing raw materials having a low total content. It is economical.
• a large amount of ethylene bottom oil which is a heavy oil and whose use is limited, may be obtained, and the method of using the ethylene bottom oil may be a problem.
• the method for producing an impregnation pitch of one embodiment effectively utilizes ethylene bottom oil, even a naphtha-containing raw material having a high total content can be used as a raw material for thermal decomposition without any problem. ..
• the total ratio of kerosene, light oil, and natural gas liquid in the naphtha-containing raw materials is sometimes called the raw material diversification rate.
• the properties of ethylene bottom oil obtained by thermal decomposition of naphtha-containing raw materials depend on the type of naphtha-containing raw materials, thermal decomposition conditions, operating conditions of the refined distillation column, etc., but generally, the 50% distillation temperature is 200 to 200 or more. The temperature is 350 ° C., the aromatic carbon content is 50% by mass or more, the flash point is 70 to 90 ° C., and the kinematic viscosity at 100 ° C. is less than 10 mm 2 / s. However, since the ethylene bottom oil is a mixture of hydrocarbon compounds, the above values may vary slightly.
• the purpose of this step is to increase the degree of polymerization of the ethylene bottom oil and increase the fixed carbon content of the obtained impregnation pitch.
• the ethylene bottom oil obtained from the ethylene plant may be used as it is, or the ethylene bottom oil obtained by removing a part of the low boiling point by distillation may be used.
• ethylene bottom oil obtained from the ethylene plant
• the distillation method may be any of atmospheric distillation, vacuum distillation (vacuum distillation), and a combination of atmospheric distillation and vacuum distillation, and is appropriately selected.
• Ethylene bottom oil does not contain QI, but QI may be generated by the heat treatment.
• the QI amount of the heat-treated product of ethylene bottom oil is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and further preferably the heat-treated product substantially contains no QI (for example, 0.05). Mass% or less, or 0.01 mass% or less).
• the heat treatment temperature is preferably 360 to 450 ° C, more preferably 370 to 430 ° C, and even more preferably 380 to 400 ° C.
• the temperature is 360 ° C. or higher, the degree of polymerization of the pitch increases moderately.
• the temperature is 450 ° C. or lower, QI is difficult to generate.
• the heat treatment time is preferably 0.5 hours to 36 hours, more preferably 3 hours to 30 hours, and further preferably 5 hours to 24 hours from the time when the predetermined heat treatment temperature is reached. If the heat treatment time is 0.5 hours or more, the degree of polymerization moderately increases. If it is 36 hours or less, QI generation due to excessive heat treatment and caulking on the inner surface of the closed container are unlikely to occur.
• the following is an example of a specific method for performing heat treatment of ethylene bottom oil using a closed container.
• ethylene bottom oil is introduced into a closed container such as an autoclave.
• the atmosphere of the gas phase is not particularly limited, but as a nitrogen gas atmosphere, a mixed gas atmosphere of hydrogen gas and lower alkanes such as methane and ethane, or a mixed gas atmosphere of nitrogen gas, hydrogen gas and lower alkanes such as methane and ethane. good.
• the initial pressure is preferably 0 MPaG, but is not particularly limited.
• the ethylene bottom oil in the closed container is heated from room temperature to a predetermined heat treatment temperature, and heat treatment is performed for a predetermined time.
• rate of temperature rise There is no limit to the rate of temperature rise, but if the rate of temperature rise is excessively high and the surface temperature of the inner wall of the closed container becomes significantly higher than the predetermined internal temperature of ethylene bottom oil, caulking and caulking due to excessive heat treatment on the inner wall of the closed container It is not preferable because QI generation occurs.
• the pressure inside the closed container rises due to hydrogen gas generated by thermal decomposition that occurs during heat treatment and lower alkanes such as methane and ethane. There is no limit to this pressure, but it can be depressurized if necessary.
• This step is a step of removing a low boiling point substance by distillation from the heat-treated product of ethylene bottom oil obtained in the heat treatment step to produce an impregnation pitch having a desired softening point and a fixed carbon content.
• the distillation method may be any of atmospheric distillation, vacuum distillation (vacuum distillation), and a combination of atmospheric distillation and vacuum distillation, and is appropriately selected.
• the internal temperature of the distillation apparatus preferably does not exceed 360 ° C.
• the temperature is 360 ° C. or lower, QI generation due to a reaction such as polymerization and caulking on the inner wall of the distillation apparatus can be suppressed.
• the lower limit temperature does not affect the pitch characteristics, but if the temperature is low, the distillation pressure must be lowered in order to distill off low boiling point substances, so 200 ° C. or higher is preferable from the economical point of view. ..
• the low boiling point substance means a component that vaporizes under temperature and pressure conditions in the distillation step, and is an aggregate of many kinds of chemical substance species.
• the pressure during distillation is preferably 100 to 10000 Pa, more preferably 500 to 3000 Pa, and even more preferably 800 to 2000 Pa. Thereby, an impregnation pitch having a softening point of 70 ° C. to 130 ° C. can be obtained.
• the softening point of the impregnation pitch can be controlled by the amount of low boiling point removed. Generally, when the amount of low boiling point removed is large, it becomes a high softening point, and when it is small, it becomes a low softening point. In order to set the softening point of the impregnation pitch to 70 to 130 ° C., the amount of low boiling point removed is preferably 20 to 80% by mass, more preferably 40 to 70% by mass, and most preferably 50. It is ⁇ 70% by mass. However, the preferred removal amount may vary depending on the composition of the raw material.
• the softening point of the impregnation pitch is preferably 70 ° C. to 130 ° C., more preferably 80 ° C. to 120 ° C., and even more preferably 90 ° C. to 110 ° C. If the temperature is 70 ° C. or higher, the impregnated pitch is likely to be retained in the fired body in the re-baking step after impregnation. When the temperature is 130 ° C. or lower, the impregnation speed and impregnation property of the fired body can be improved.
• the fixed carbon content of the impregnation pitch is preferably higher because it can increase the density of the graphite electrode.
• the fixed carbon content of the impregnation pitch is preferably 45% by mass or more. When it is 45% by mass or more, the number of repetitions of the impregnation and re-baking steps for increasing the density of the graphite electrode can be reduced.
• the fixed carbon content of the impregnation pitch can be 45% by mass or more.
• Example 1 550 g of ethylene bottom oil was introduced into a 1.0 L SUS autoclave. The temperature inside the container was raised to 380 ° C. at a rate of 4 ° C./min while sealing and stirring in a nitrogen gas atmosphere. After 24 hours had passed since the temperature was raised, the mixture was allowed to cool to room temperature, and the heat-treated product inside was taken out. Using a vacuum distillation apparatus, the heat-treated product was distilled at 1000 Pa and a liquid temperature of 240 ° C. in a distillation pot to distill off a low boiling point component, and 237 g (yield 43%) of impregnated pitch sample 1 as a high boiling point component. Obtained. The amount of low boiling point removed was 57% by mass of the ethylene bottom oil.
• Example 2 550 g of ethylene bottom oil was introduced into a 1.0 L SUS autoclave. The temperature inside the container was raised to 380 ° C. at a rate of 4 ° C./min while sealing and stirring in a nitrogen gas atmosphere. After 8 hours had passed since the temperature was raised, the mixture was allowed to cool to room temperature, and the heat-treated product inside was taken out. Using a vacuum distillation apparatus, the heat-treated product was distilled at 1000 Pa and a liquid temperature of 257 ° C in a distillation pot to distill off low boiling point components, and 199 g (yield 36%) of impregnated pitch sample 2 as high boiling point components. Obtained. The amount of low boiling point removed was 64% by mass of the ethylene bottom oil.
• Table 1 shows the measurement data of Examples and Comparative Examples.
• the QI is 0% by mass and the fixed carbon content is maintained at around 50% by mass even without the QI removal step.
• the step of removing the quinoline insoluble matter which is indispensable in the production of the impregnation pitch for the conventional production of graphite electrodes, can be omitted.

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• 2021
  • 2021-01-21 EP EP21767136.1A patent/EP3971263A1/en not_active Withdrawn
  • 2021-01-21 CN CN202180003660.3A patent/CN113939577A/zh active Pending
  • 2021-01-21 JP JP2022505812A patent/JPWO2021181905A1/ja active Pending
  • 2021-01-21 US US17/595,653 patent/US20220220387A1/en not_active Abandoned
  • 2021-01-21 WO PCT/JP2021/002080 patent/WO2021181905A1/ja not_active Ceased

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