JP3397155B2 - Method for treating exhaust gas from vapor grown carbon fiber - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vapor grown carbon fiber,
More specifically, the present invention relates to a reaction exhaust gas generated when carbon fibers are produced by thermal decomposition of an organic compound by a vapor phase growth method and a method for treating exhaust gas such as a heat treatment exhaust gas at the time of post-process firing and heat treatment for graphitization, and an incinerator thereof.

[0002]

2. Description of the Related Art A method for producing vapor grown carbon fiber is disclosed in Japanese Patent No. 27.
As shown in Japanese Patent No. 78434, an organic compound containing a transition metal such as iron serving as a catalyst is dissolved in a raw material liquid such as benzene, and the solution is heated in a reaction furnace heated to 800 to 1300 ° C. toward a heating furnace wall surface. There is a method of spraying and pyrolyzing. Specifically, a fiber metal compound such as ferrocene is used as a catalyst, dissolved in a liquid organic compound such as benzene, and hydrogen is used as a carrier gas to be sprayed on the inner wall of the reaction tube.
It is used for seeding and pyrolyzing an organic compound to produce fine crude fibrous vapor grown carbon fiber. (Hereinafter, this step is referred to as a pre-step.) The exhaust gas after the reaction generated in this pre-step is mainly hydrogen used as a carrier gas and contains benzene which is an unreacted carbon source and organic compounds such as ferrocene which is a catalyst. Compounds, hydrogen, benzene, methane generated during the production of vapor grown carbon fiber,
It contains reaction products such as ethylene, which are generally flammable gases. (Hereinafter, this is called reaction exhaust gas). This reaction exhaust gas is flammable because it contains hydrogen as a main component and is explosive. Therefore, conventionally, the reaction exhaust gas was diluted to below the explosion range with a blower and released into the atmosphere.

Further, the crude carbon fibers produced in the reaction tube are usually scraped off and collected, but these carbon fibers contain unreacted organic substances, non-fibrous carbides and tar components. Therefore, in the next step, heat treatment is performed in a non-oxidizing atmosphere, for example, the final product is required in a non-oxidizing atmosphere of nitrogen, helium, argon, etc. in a closed furnace as shown in JP-A-8-60444. Heat treatment such as firing and graphitization is performed at a temperature suitable for the properties. (Hereinafter, this step is referred to as a post-step.) The exhaust gas generated in the post-step is mainly an inert gas such as argon and nitrogen, and naphthalene, anthracene,
It is flame-retardant because it contains high molecular substances such as tar. (Hereinafter, this is referred to as heat treatment exhaust gas.) This heat treatment exhaust gas was inevitably discharged as it was because it was flame retardant.

[0004]

DISCLOSURE OF THE INVENTION The present invention, in order to safely treat and discharge the flammable reaction exhaust gas as described above,
It also develops a method of incinerating flame-retardant heat-treated exhaust gas in a furnace at low cost. In particular, organic compounds such as benzene are regulated from being exposed to workers by the Industrial Safety and Health Act, and because they are harmful substances, their emission to the atmosphere must be prevented, and hydrogen and methane must be prevented. Since ethylene, etc. are flammable substances, there is a danger of explosion if leaked. In addition, the tar component is viscous in terms of its physical properties and is troublesome to collect. The method of condensing or adsorbing these with activated carbon or the like requires a large amount of handling in terms of equipment and has a problem of waste treatment. In addition, it is necessary to handle these tars carefully because of hygiene, and it is preferable to incinerate them, but since they are high-molecular substances and also contain an inert gas, they cannot be burned by themselves. . In order to solve this, the present inventors considered a method of burning reaction exhaust gas, but the reaction of the previous process may be stopped for maintenance, and only the post process may be operated, or the post process may be operated. In the heat treatment, the amount of carbon fiber is not constant because the amount of carbon fiber varies. Therefore, in the method of simply burning these gases, not only stable incineration cannot be achieved, but conversely, a backfire to the reactor and the apparatus for heat treatment occurs, which causes a problem of damaging the apparatus and the like . In addition, there is a risk of high-concentration reaction exhaust gas being filled when there is a misfire for some reason, and there is a problem during re-ignition.

[0005]

The method for treating exhaust gas of vapor grown carbon fiber according to the present invention is as follows. (1) In the method for producing vapor grown carbon fiber, the exhaust gas of the production process is incinerated in a dedicated incinerator. (2) The reaction exhaust gas which is combustible as exhaust gas and at the time of firing or graphitization. The method is to incinerate the generated flame-retardant heat treatment exhaust gas at the same time, or incinerate either of them in this incinerator. The features of this method are (3) Flame of pilot burner that burns using combustible gas The method (1) or (2) is characterized in that the reaction exhaust gas in the reaction exhaust gas supply pipe is incinerated at the end of the reaction of the vapor grown carbon fiber for safety. The vapor grown carbon fiber according to the above (1) to (3), characterized in that it is purged into the furnace and incinerated, or the heat treated exhaust gas in the heat treated exhaust gas pipe at the end of heat treatment is purged into the incinerator and incinerated. An exhaust gas treatment method, and (5) a safety feature of a manufacturing apparatus is enhanced by providing a flashback prevention device in a supply pipe of a reaction exhaust gas and a heat treatment exhaust gas to an incinerator (1) to ( It is a method of treating vapor grown carbon fiber of 4). Furthermore, (6) Incinerating by constantly monitoring the flames of the pilot burner and the main burner, switching the reaction exhaust gas to the atmosphere discharge pipe when these flames are misfired, and stopping the reaction exhaust gas supply to the incinerator. The above object was achieved by the method for treating exhaust gas of vapor grown carbon fiber according to (1) to (5), which improves the safety of the furnace. As an incinerator for achieving the above method, (7) a vapor grown carbon fiber equipped with a main burner for supplying a reaction gas, an auxiliary burner for supplying a heat treatment exhaust gas, and a pilot burner for igniting with a combustible gas Devised an incinerator for exhaust gas treatment.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION To explain the present invention in more detail, the method for treating the reaction exhaust gas and / or the heat treatment exhaust gas of the vapor grown carbon fiber according to the present invention uses a vertical incinerator in an incinerator. Combustible gas is always burned by a pilot burner, reaction exhaust gas is supplied there through the main burner, and is ignited by the flame of the pilot burner for incineration. The combustible gas may be a commercially available one such as propane or city gas. This reaction exhaust gas is flammable,
Can be incinerated. However, during the incineration, since the reaction exhaust gas is flammable, the ignition method when the reaction starts and the reaction exhaust gas starts to be generated, and the pressure fluctuation of the reaction exhaust gas during the reaction and the reaction exhaust gas Care must be taken to prevent flashback when the outbreak stops. Therefore, as a method of igniting the reaction exhaust gas, the pilot burner is always burned in the incinerator so that the reaction exhaust gas can be immediately ignited when the reaction exhaust gas is supplied. The reaction exhaust gas is supplied through the main burner, and the structure is such that resistance is provided at the nozzle of the main burner and flashback does not occur even if there is a slight pressure fluctuation. Also, when the reaction exhaust gas supply is stopped due to the end of the reaction, etc., the reaction exhaust gas in the reaction exhaust gas supply pipe is purged into the incinerator with non-combustible gas, and the reaction remaining in the reaction system or the reaction exhaust gas supply pipe By incinerating the exhaust gas, it is possible to prevent a flashback into the reaction exhaust gas supply pipe. In addition, the flame of the pilot burner and the combustion flame of the reaction exhaust gas of the main burner are constantly monitored in the incinerator, and if there is a misfire for any reason, the reaction exhaust gas cannot be ignited, so the reaction exhaust gas supply piping must be connected to the incinerator. To supply air to the atmosphere, and stop the reaction exhaust gas supply to the incinerator. At that time, the reaction is also immediately stopped, and purging with an incombustible gas is performed. In addition, a check device such as a flame arrester or a water sealing device may be provided in the supply pipe of the reaction exhaust gas to the incinerator. Furthermore, the reaction in which flammable reaction exhaust gas is generated can be sequenced so that it cannot be performed unless the pilot burner of the incinerator is combusted. One of the features of the present invention is that a flame-retardant heat treatment exhaust gas supply pipe is separately provided and supplied from the auxiliary burner into the furnace. As a result, by combusting at the same time hydrogen, methane, ethylene, and other highly volatile, highly flammable organic compounds, and tar, which are highly viscous and relatively incombustible at room temperature, the heat treatment exhaust gas of the heat treatment exhaust gas is mixed with the mixed gas. It is possible to incinerate and increase combustion efficiency. Ignition method using the reaction exhaust gas,
Flashback prevention method, purge method, and response method at the time of misfire,
The same method can be applied to the combustion exhaust gas. Further, even when the reaction exhaust gas is stopped, since the combustible gas is used as a fuel, it is possible to introduce only the heat treatment exhaust gas, and it is possible to burn efficiently, while the pilot burner of the incinerator is always burned, the reaction exhaust gas, Combustion is performed stably even when the amount of heat treatment exhaust gas changes.

[0007]

EXAMPLES The present invention will be described in more detail below with reference to examples. (Example) An outline of an incinerator for reaction exhaust gas of vapor grown carbon fiber is shown in FIG. A carbon fiber is grown by spraying a liquid of benzene containing 4 wt% of ferrocene from the top of a vertical heating furnace as shown in Japanese Patent No. 2778434 on a furnace wall at 1200 ° C at a hydrogen gas flow rate of 100 L / min. Let This was scraped off from the furnace wall to obtain carbon fiber. The carbon fiber obtained by the reaction is compression-molded and disclosed in JP-A-8-60.
Heat treatment heat treatment was performed in a heat treatment continuous furnace as shown by 444 under flowing argon. The time and temperature for heating the molded body in the furnace were 1400 ° C. and about 30 minutes. At that time, the reaction exhaust gas was about 130 L / min and 30 L / min from the main burner and the heat treatment exhaust gas from the auxiliary burner, respectively, and the reaction exhaust gas was about 75% hydrogen, benzene as a carbon source of other raw materials, and by-produced organic matter. The heat treatment exhaust gas contained a compound and contained mainly tar and a tar content. Before the reaction was started, the inside of the system including the heat treatment continuous furnace was purged with nitrogen gas to start the reaction. The reaction exhaust gas was combusted and incinerated through the main burner into the burning incinerator of the pilot burner using LPG as a fuel. The heat treatment exhaust gas was simultaneously burned by an auxiliary burner. Benzene in the incineration waste gas at that time was 0.25 ppm or less as the lower limit of detection. At the end of the previous step, the inside of the reaction tank was purged with nitrogen gas to remove the reaction exhaust gas, and then the main valve was closed. After completion of all the steps, the flame of the main burner was extinguished by purging the inside of the continuous furnace system with nitrogen gas and purging the heat treatment exhaust gas with nitrogen gas.

[0008]

According to the method for treating exhaust gas of vapor grown carbon fiber according to the present invention, a combustible gas is constantly burned by a pilot burner in an incinerator, and the reaction exhaust gas from the main burner contains tar and the like. By supplying combustible heat treatment exhaust gas from the auxiliary burner and igniting it with the flame of the pilot burner to incinerate it, combustible reaction exhaust gas such as benzene used as a raw material can be safely incinerated. In addition, tar components that are difficult to handle can be burned and incinerated at the same time. As described above, it is possible to contribute to the industrial production of vapor grown carbon fiber.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for an exhaust gas incineration method according to the present invention.

[Explanation of symbols]

1 pilot burner 2 main burner 3 flame detector 4 Waste gas sampling port 5 auxiliary burners 8 incinerator

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshihisa Sakamoto, Yoshihisa Sakamoto, 5-1 Okawa-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa, Production Research Center, Research Institute, Waseda Electric Works Co., Ltd. (72) Kaoru Matsumoto, Kawasaki, Kanagawa 5-1 Okawa-cho, Kawasaki-ku, Awadako Co., Ltd., Research Institute, Production Technology Center (56) References JP-A-4-308225 (JP, A) JP-A 59-142826 (JP, A) JP-A 56-24022 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F23G ⁷ /00-7/06 D01F 9/133

Claims (10)

(57) [Claims] 1. A method for producing a carbon fiber by a vapor phase method, wherein a carbon fiber is obtained by thermally decomposing an organic compound in a pyrolysis furnace using a transition metal or a compound thereof as a catalyst, which is combustible in the production step in the pyrolysis furnace. Reaction gas and / or the flame-retardant heat-treated exhaust gas generated during firing or graphitization in the subsequent step is incinerated in an incinerator. 2. The method for treating exhaust gas of vapor grown carbon fiber according to claim 1, wherein the reaction exhaust gas is an explosive gas containing hydrogen as a main component. 3. Treatment of exhaust gas of vapor grown carbon fiber according to claim 1, wherein the exhaust gas is burned by igniting with a flame of a pilot burner using a combustible gas as a fuel, the exhaust gas supply burner being provided. Method. 4. A reaction and / or reaction in a process for producing a vapor grown carbon fiber.
Alternatively, at the end of the heat treatment in the heat treatment step, the reaction exhaust gas in the reaction exhaust gas supply pipe and / or the heat treatment exhaust gas in the heat treatment exhaust gas supply pipe is purged into an incinerator and incinerated. 5. A method for treating exhaust gas from a vapor grown carbon fiber according to 1. 5. The gas phase method according to claim 1, wherein a supply line for supplying the reaction gas exhaust gas of the gas phase method carbon fiber and the heat treatment exhaust gas to the incinerator is provided with a flashback prevention device. Carbon fiber exhaust gas treatment method. 6. The flames of a pilot burner and an exhaust gas supply burner are constantly monitored, and when the flames are misfired, the reaction exhaust gas and / or the heat treatment exhaust gas is switched to an atmosphere discharge pipe,
The method for treating exhaust gas of vapor grown carbon fiber according to any one of claims 1 to 5, wherein the exhaust gas supply to the incinerator is stopped. 7. A method for treating exhaust gas of vapor grown carbon fiber, comprising a main burner for supplying a combustible reaction exhaust gas, an auxiliary burner for supplying a flame-retardant heat treatment exhaust gas, and a pilot burner for igniting with a combustible gas. Incinerator for exhaust gas of vapor grown carbon fiber. 8. A step of thermally decomposing an organic compound in a thermal decomposition furnace using a transition metal or a compound thereof as a catalyst to obtain a vapor grown carbon fiber, a step of separating reaction exhaust gas generated from the step from the carbon fiber, and A method for producing carbon fiber, comprising: a step of heat-treating carbon fiber in a non-oxidizing atmosphere; and a step of incinerating heat-treated exhaust gas generated in the heat-treatment step and / or reaction exhaust gas separated in the separation step. 9. The method for producing carbon fiber according to claim 8, wherein the reaction exhaust gas contained in the carbon fiber is separated. 10. A method for incinerating the heat treatment exhaust gas generated in the heat treatment step and / or the reaction exhaust gas separated in the separation step is a method for treating exhaust gas of vapor grown carbon fiber according to any one of claims 1 to 6. The method for producing a carbon fiber according to claim 8, which is a method.