JP2005221150A - Waste gas treatment device for carbon fiber manufacturing device by vapor-phase method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste gas treatment device for rendering carbon hydride and a sulfur compound in a waste gas generated in manufacturing carbon fiber by a vapor-phase method, harmless, and diffusing the waste gas to the atmospheric air preferably after reducing carbon dioxide. <P>SOLUTION: This waste gas treatment device 10 for discharging a discharged gas to the outside of a system constituting the carbon fiber manufacturing device by the vapor-phase method, using transition metal or a transition metal compound, and sulfur or a sulfur compound as catalyst, and manufacturing carbon fiber from a carbon source by the vapor-phase method in a reaction furnace 33, comprises a burning oxidizing means 11 for burning and oxidizing the incombustible discharged gas, generated in the reaction furnace 33 wherein the carbon fiber is manufactured by performing the heat treatment on a material gas in the presence of the catalyst, under a specific burning condition, a humidity absorbing means 12 and a circulation tank 13. An absorbent composed of the water or alkaline solution is supplied to the humidity absorbing means 12 to absorb specific harmful components from the burnt oxidized gas, and the absorbent after absorbing the harmful components in the circulation tank is partially discharged. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vapor grown carbon fiber (VGCF) that forms carbon fibers by thermally decomposing hydrocarbons as a raw material gas in the presence of a catalyst comprising a transition metal or a transition metal compound and sulfur or a sulfur compound. The present invention relates to an exhaust gas treatment apparatus of a vapor phase carbon fiber production apparatus for producing fine fibrous carbon fibers such as carbon nanotubes, carbon nanohorns, carbon nanocoils, and ribbon-like carbon fibers.

  The production of carbon fiber by the gas phase method involves the use of an organic solvent such as benzene or toluene as a carbon source, a transition metal such as iron as a catalyst or a transition metal compound, and sulfur or a sulfur compound as a catalyst. In addition, the carbon source is supplied into a reactor controlled to a temperature of 800 to 1500 ° C., the carbon source is thermally decomposed, and the decomposed carbon is grown with a transition metal as a nucleus to obtain a predetermined carbon fiber such as a carbon nanotube (CNT). Is manufacturing.

  When carbon fiber is vapor-grown by pyrolyzing the source gas, by-products such as hydrogen, chain hydrocarbons, aromatic hydrocarbons, and hydrogen sulfide are generated separately from the carbon fiber as the main product. The Of these by-products, most of the high-boiling components in aromatic hydrocarbons are recovered together with the main product carbon fiber, but some high-boiling aromatic hydrocarbons that are not recovered are also hydrogen and chain hydrocarbons. The low-boiling aromatic hydrocarbons and hydrogen sulfide need to be discharged out of the system as exhaust gas together with the carrier gas because of the material balance.

  Conventionally, these exhaust gases were directly released into the atmosphere or incinerated and released into the atmosphere, but high boiling point aromatic hydrocarbons are flame retardant and cannot be incinerated. At the same time, it was released into the atmosphere as it was.

  On the other hand, the carbon fiber produced in the reactor is subjected to heat treatment at 800 ° C. to 3000 ° C. in order to satisfy the quality requirements of the product user. As described above, this carbon fiber has a high boiling point among aromatic hydrocarbons. The transition metal used as a catalyst containing most of the components is present as sulfides (the carbon fiber in this state is called crude carbon fiber), and when this is heat-treated, one of the high-boiling aromatic hydrocarbons is present. The part is volatilized as it is, and further low boiling point hydrocarbons and hydrogen sulfide are generated by the thermal decomposition reaction. This heat-treated exhaust gas was also diffused into the atmosphere as it was, or was incinerated and diffused into the atmosphere, but the sulfur compound or sulfur oxide was diffused into the atmosphere as it was.

  In other words, since the production of carbon fiber by the gas phase method is currently performed on a small scale, by-products and exhaust gas are open to the atmosphere as they are without any particular restrictions. is there.

  However, considering the environmental aspects even in small-scale production, it is preferable to burn down by-products and heat treatment exhaust gas to reduce harmful substances. The situation is not going well.

  In response to such problems, in a gas phase carbon fiber manufacturing method for obtaining carbon fiber by thermally decomposing an organic compound in a reaction furnace using a transition metal as a catalyst, a vertical incinerator is used, such as propane or city gas. A combustible gas is always combusted by a pilot burner, a reaction exhaust gas or a heat treatment exhaust gas is supplied through a main burner, and an incineration treatment method is performed by igniting with a flame of the pilot burner (for example, Patent Document 1).

  As described above, in the production of carbon fiber by the vapor phase method, flame retardant high-boiling aromatic hydrocarbons cannot be completely decomposed even if incinerated and must be released to the atmosphere as they are. In addition, carbon dioxide is generated from chain hydrocarbons, low boiling point hydrocarbons and decomposed high boiling point hydrocarbons by incineration, and sulfur oxides are generated from hydrogen sulfide. At present, the amount of vapor-grown carbon fiber is small, so the amount of carbon dioxide, sulfur compounds, or sulfur oxides released to the atmosphere is relatively small, and the production facilities are located in a part of a large-scale chemical plant. Therefore, it fully satisfies the regulation value for the total amount of sulfur oxides stipulated in the Air Pollution Control Law.

  However, when the scale of the production facility is increased to increase the production amount of vapor grown carbon fiber, the amount of carbon dioxide, sulfur compound or sulfur oxide released into the atmosphere becomes large, and the production facility is independent. There is a possibility of becoming a location, and there is a risk that it will not be possible to meet the regulation value for the total amount of sulfur oxides stipulated in the Air Pollution Control Law. Furthermore, if a production facility that takes into consideration the prevention of global warming is aimed at, it is desirable to suppress as much as possible the carbon dioxide generated by the combustion of exhaust gas.

In the said patent document 1, there is no place touched on the response | compatibility to the said substance which is not processed also by a combustion process.
Japanese Patent No. 3397155

  The present invention relates to an exhaust gas after detoxifying hydrocarbons and sulfur compounds in exhaust gas generated in the course of vapor-grown carbon fiber production, and preferably after reducing carbon dioxide generated in the detoxification process. An object of the present invention is to provide an exhaust gas treatment apparatus that diffuses air.

  In order to solve the above-mentioned problems, the present invention introduces exhaust gas from a reaction furnace in the process of producing vapor grown carbon fiber into a combustion furnace and incinerates it. In the exhaust gas from the reactor, hydrogen gas generated as a carrier and hydrogen produced by the decomposition reaction of hydrocarbons as carbon fiber production raw materials exist as flame retardant high-boiling aromatic hydrocarbons and hydrogen sulfide. . In the present invention, in order to completely oxidize these flame-retardant high-boiling aromatic hydrocarbons and hydrogen sulfide, the combustion furnace exhaust gas temperature is adjusted to 400 to 600 ° C. with an auxiliary burner using city gas or the like as fuel. And oxidize by combustion. The gas subjected to the combustion oxidation treatment is introduced into a wet absorption means provided at the subsequent stage of the combustion furnace, and is absorbed and removed by contact with water as an absorbent, preferably an alkaline aqueous solution. The gas rendered harmless through the combustion oxidation treatment and the absorption removal treatment is released into the atmosphere.

  That is, the present invention constitutes a vapor-grown carbon fiber production apparatus for producing carbon fiber from a carbon source by a vapor phase method in a reaction furnace using a transition metal or a compound of a transition metal and sulfur or a sulfur compound as a catalyst. In an exhaust gas treatment apparatus that exhausts a gas to be discharged generated in a reaction furnace to the outside of the system, a gas generated in a reaction furnace for producing carbon fiber by heat-treating a raw material gas in the presence of a catalyst Of these, a combustion oxidation means for burning and oxidizing a flame-retardant gas under a predetermined combustion condition, and a harmful component removal apparatus for removing a predetermined harmful component from the gas burned and oxidized by the combustion oxidation means.

  Further, according to the present invention, in the above exhaust gas treatment apparatus, the harmful component removal apparatus has a wet absorption means and a circulation tank, and supplies an absorption liquid made of water or an alkaline solution to the wet absorption means from the combustion oxidizing gas. A predetermined harmful component was absorbed, and a part of the absorbing solution that absorbed the harmful component in the circulation tank was excluded.

  The present invention also provides a heat treatment of a carbon fiber produced by a vapor phase method in a reaction furnace from a carbon source using a transition metal or a compound of a transition metal and sulfur or a sulfur compound as a catalyst at a temperature of 800 to 3000 ° C. In the exhaust gas treatment apparatus for exhausting the gas to be discharged generated in the heat treatment furnace to the outside of the system, the combustion oxidation means for burning and oxidizing the hydrogen sulfide gas generated in the heat treatment and to be discharged under a predetermined combustion condition; A wet absorption means for absorbing a predetermined harmful component from the exhaust gas combustion-oxidized by the combustion oxidation means into an absorption liquid made of water or an alkaline solution, and a circulation tank for removing a part of the absorption liquid out of the system were provided. Furthermore, the present invention is the above exhaust gas treatment apparatus, further comprising a diffusion means for releasing the gas from which harmful components have been removed by the wet absorption means to the atmosphere.

  The present invention comprises a transition metal or a transition metal compound and sulfur or a sulfur compound as a catalyst, a gas to be discharged generated in a production process for producing carbon fiber from a carbon source by a gas phase method in a reaction furnace, and An exhaust gas treatment apparatus that exhausts at least one of the gas to be discharged generated when the carbon fiber manufactured by the manufacturing process is heat-treated at a temperature of 800 to 3000 ° C. in a heat treatment furnace is the discharge target. A harmful component removing device for removing predetermined harmful components from the gas was provided. Further, the harmful component removal apparatus has a wet absorption means and a circulation tank, and supplies the absorption liquid composed of water or an alkaline solution to the wet absorption means to absorb the harmful substances of the gas to be discharged into the absorption liquid. In addition, a part of the absorbing solution that has absorbed harmful substances is excluded from the system by a circulation tank. Further, the gas to be discharged contains hydrocarbon gas or hydrogen sulfide gas.

  The present invention relates to an exhaust gas treatment method in which exhaust gas generated in the production of vapor-grown carbon fiber is burnt and oxidized under appropriate combustion conditions, and the combustion oxidation gas is subjected to wet absorption treatment. It is possible to reduce the concentration to 100 ppm or less.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram for explaining the outline of the configuration of a vapor grown carbon fiber production apparatus equipped with an exhaust gas treatment apparatus according to the present invention. The vapor grown carbon fiber production apparatus includes a CNT production unit 30, a CNT purification unit 50, and an exhaust gas treatment unit 10.

  The exhaust gas treatment unit 10 includes a combustion oxidation tower 11 that functions as combustion oxidation means, a wet absorption tower 12 that functions as wet absorption means, a circulation tank 13, a circulation pump 15, and an exhaust blower 16. Means) are connected as shown in the figure using pipes 14-1 to 14-5.

  The combustion oxidation tower 11 includes an exhaust gas supply nozzle 113 that supplies the exhaust gas sent from the CNT production unit 30 via the pipe 14-1 into the tower, and an air supply nozzle that supplies air to the exhaust gas at an appropriate air ratio. 114, a pilot burner 111 that ignites a mixed gas of exhaust gas and air, and an auxiliary combustion burner 112 that uses city gas or the like as a fuel to completely oxidize flame-retardant high-boiling aromatic hydrocarbons or hydrogen sulfide. It is done. Gas that is burnt and oxidized in the combustion oxidation tower 11 (hereinafter referred to as “burning oxidation gas”) is supplied to the wet absorption tower 12 via the pipe 14-2.

  In the wet absorption tower 12, an absorption liquid made of water, preferably an alkaline solution, is distributed inside from the shower nozzle 121, and harmful components contained in the combustion oxidizing gas are absorbed by the absorption liquid. The absorbing liquid that has absorbed the harmful components is supplied to the circulation tank 13 through the pipe 14-3. The treated exhaust gas from which harmful components have been removed and detoxified is released into the atmosphere via the pipe 14-5 and the exhaust blower 16.

  In the circulation tank 13, a part of the absorption liquid that has absorbed the combustion oxidizing gas is discharged, and the absorption liquid after being added by the discharged amount is supplied to the wet absorption tower 12 via the circulation pump 15 and the pipe 14-4. Supply.

  The CNT manufacturing unit 30 includes a reaction furnace 31.

  The reaction furnace 31 is a furnace that thermally decomposes hydrocarbon as a raw material under a catalyst composed of a transition metal or a transition metal compound and sulfur or a sulfur compound to generate carbon nanotubes, and a raw material solution containing the catalyst and the raw material Supply pipe 311, hydrogen gas supply pipe 312, and vaporized gas discharge pipe 313. In the reaction furnace 31, a transition metal such as iron (Fe) or a transition metal compound (for example, ferrocene), an organic compound (for example, thiophene) containing sulfur (S) or a sulfur compound, and a raw material liquid (for example, ferrophene). , Toluene) and hydrogen gas.

  In the reactor 31, generated unreacted raw materials, unused catalyst residues, carbon fibers containing non-fibrous carbides, tars, and the like (hereinafter referred to as “crude carbon fibers”) and the like are passed through pipes 32 and 53-1. And supplied to the CNT purification unit 50.

  The CNT refining unit 50 is a part that refines crude carbon fiber to form a carbon fiber (carbon nanotube) as a final product, and includes a first heat treatment furnace 51 and a second heat treatment furnace 52. .

  The first heat treatment furnace 51 is a heat treatment means for removing volatile components from the crude carbon fiber and volatile components sent from the reaction furnace 31, and has a furnace section 511 and a gas discharge pipe 512. Composed. Of the crude carbon fibers and volatile components sent from the reaction furnace 31, volatile components are vaporized in a furnace section 511 maintained at, for example, 800 to 1500 ° C., and then removed from the gas exhaust pipe 512. Volatile components discharged from the gas discharge pipe 512 are burned and oxidized by the combustion oxidation recovery means similar to the exhaust gas processing unit 10, and then harmful substances are recovered, and only the harmless gas is released to the atmosphere. The crude carbon fiber from which the volatile components have been removed is sent to the second heat treatment furnace 52 via the pipe 53-2.

  The second heat treatment furnace 52 is a means for performing a heat treatment for graphitizing the crude carbon fiber from which the volatile components have been removed, and includes a furnace part 521 and a gas discharge pipe 522. The crude carbon fiber supplied from the first heat treatment furnace 51 to the furnace part 521 via the pipe 53-2 is graphitized by being maintained at, for example, 1300 to 3000 ° C. in the furnace part 521. The exhaust gas generated by the treatment is discharged from the gas discharge pipe 522. The exhaust gas discharged from the gas exhaust pipe 522 is burnt and oxidized by the combustion oxidation recovery means similar to the exhaust gas processing unit 10, and then harmful substances are recovered, and only the harmless gas is released to the atmosphere. In the present embodiment, the carbon fiber (CNT) produced from the composition carbon fiber is obtained through two-stage heat treatment (heat treatment), but the present invention is not limited to this. Depending on the desired carbon fiber (CNT), heat treatment at 800 to 3000 ° C. may be performed in at least one step.

  The reactor 31 for producing vapor grown carbon fiber has a hydrogen atmosphere, and the system pressure is controlled to 0.1 to 5 kPa for the purpose of preventing accidents caused by air intrusion. Even in the furnace section 511 and the furnace section 512 that perform the heat treatment, the system pressure is controlled to 0.1 to 5 kPa in order to prevent accidents due to air intrusion.

  The detailed configuration of the exhaust gas treatment unit 10 that performs wet absorption treatment after combustion and oxidation of exhaust gas containing hydrocarbons and hydrogen sulfide will be described with reference to FIG.

  The exhaust gas accompanying the reaction treatment and the heat treatment is pushed out of the system at the above system pressure and sent to the exhaust gas treatment unit 10 which is a combustion oxidation facility. The exhaust gas treatment unit 10 includes a combustion oxidation tower 11, a wet absorption tower 12, and a circulation tank 13, which are connected by pipes 14-2, 14-3, and 14-4, respectively. The pipe 14-2 is provided with a heat exchanger 17, the pipe 14-4 is provided with a circulation pump 15, and the pipe 14-5 is provided with a discharge blower 16.

  The combustion oxidation tower 11 is provided with a pilot burner 111, an auxiliary combustion burner 112, an exhaust gas nozzle 113, and an air nozzle 114. The pilot burner 111 and the auxiliary combustion burner 112 are exhaust gas from the reaction furnace 31 (hereinafter referred to as combustion) introduced into the combustion oxidation tower 11 through the exhaust gas nozzle 113 having a burner structure by combustion of fuel such as city gas or propane gas. Combusted and oxidized (referred to as oxidation target exhaust gas), water and carbon dioxide are generated from hydrocarbons, and sulfur oxides are generated from hydrogen sulfide. The combustion state of the exhaust gas subject to combustion oxidation is appropriately controlled by maintaining the temperature of the exhaust gas subject to combustion oxidation within a required range. Specifically, the amount of air to be introduced is adjusted so that the temperature of the combustion oxidation target exhaust gas becomes 400 to 600 ° C. Combustion state control may be performed by the ratio of the amount of exhaust gas subject to combustion oxidation and the amount of air introduced separately, in this case, the ratio is 1.2 to 1.6 times the theoretical amount of combustion air. Control is sufficient. Alternatively, the residual oxygen concentration in the combustion oxidation target exhaust gas may be controlled. In this case, the residual oxygen concentration may be controlled to be 4% to 8%.

  The exhaust gas that has been burned and oxidized in the combustion oxidation tower 11 and has been treated (hereinafter referred to as treated exhaust gas) is reduced in volume by the heat exchanger 17 and then sent to the wet absorption tower 12. In this embodiment, an aqueous caustic soda solution is used as the absorbent of the wet absorption tower 12, and its concentration is pH 4-6. The treated exhaust gas is introduced in a direction perpendicular to the tower wall from the tower bottom. The absorption liquid is sprayed from the top of the tower and brought into countercurrent contact with the treated exhaust gas to absorb carbon dioxide and sulfur oxide in the exhaust gas.

  The absorption liquid that has absorbed carbon dioxide and sulfur oxide in the treated exhaust gas is extracted from the bottom of the tower and stored in the circulation tank 13 via the pipe 14-3. In this absorption solution, sodium sulfate and sodium carbonate are dissolved, and these compounds are concentrated and precipitated when used in circulation. Therefore, 1 to 10% of the circulation amount is purged out of the system and drained. The amount of circulation is determined by the structure of the wet absorption tower 12 and the concentration of excluded substances in the exhaust gas and the concentration of excluded substances in the processing gas to be obtained. In addition, since the basicity of the absorption liquid increases due to absorption of carbon dioxide and sulfur oxides, an aqueous caustic soda solution is appropriately replenished so as to be within the control basicity. The absorption liquid whose basicity is adjusted is drawn by the pump 15 and sent to the wet absorption tower 12 again.

  The gas obtained by absorbing and removing carbon dioxide and hydrogen sulfide in the wet absorption tower 12 is drawn by the blower 16 from the top of the tower and is released to the atmosphere. As the temperature of the treated exhaust gas from the combustion oxidation tower 11 to the wet absorption tower 12 is higher, the absorption rate of the carbon dioxide and sulfur oxide in the treated exhaust gas into the absorbent is decreased. If the heat exchanger 17 is provided, this decrease in absorption rate can be suppressed as much as possible, which is preferable.

The figure explaining the outline | summary of a structure of the vapor-grown carbon fiber manufacturing apparatus using the waste gas processing apparatus concerning this invention. The figure explaining the structure of the waste gas processing apparatus used for the vapor-grown carbon fiber manufacturing apparatus shown in FIG.

Explanation of symbols

10: exhaust gas treatment unit 11: combustion oxidation tower 111: pilot burner 112: auxiliary combustion burner 113: exhaust gas supply nozzle 114: air supply nozzle 12: wet absorption tower 121: shower nozzle 13: circulation tank 14: piping 15: circulation pump 16: Exhaust blower 17: Heat exchanger 30: CNT production part 31: Reactor 311: Raw material solution supply pipe 312: Hydrogen gas supply pipe 313: Gas exhaust pipe 32: Pipe 50: CNT purification part 51: First heat treatment furnace 511: Furnace part 512: Exhaust gas discharge pipe 52: Second heat treatment furnace 521: Furnace part 522: Exhaust gas discharge pipe 53: Pipe 70: Separation part

Claims (8)

Occurred in a reaction furnace that constitutes a vapor-phase carbon fiber production apparatus that produces carbon fiber from a carbon source by a vapor phase method in a reaction furnace using a transition metal or a compound of a transition metal and sulfur or a sulfur compound as a catalyst. In exhaust gas treatment equipment that discharges gas to be discharged out of the system,
Combustion oxidation means for burning and oxidizing a flame-retardant gas generated in a reactor for producing carbon fiber by heat-treating the raw material gas in the presence of a catalyst under a predetermined combustion condition ,
An exhaust gas treatment apparatus comprising: a harmful component removal device that removes a predetermined harmful component from the gas that is burnt and oxidized by the combustion oxidizing means.   The harmful component removal apparatus has a wet absorption means and a circulation tank, and supplies the wet absorption means with an absorption liquid made of water or an alkaline solution to absorb a predetermined harmful component from the combustion oxidizing gas. The exhaust gas treatment apparatus according to claim 1, wherein a part of the absorbing liquid that has absorbed harmful components is excluded. It was produced in a heat treatment furnace using a transition metal or a transition metal compound and sulfur or a sulfur compound as a catalyst, and carbon fiber produced by a gas phase method in a reaction furnace from a carbon source at a temperature of 800 to 3000 ° C. In exhaust gas treatment equipment that discharges gas to be discharged out of the system,
Combustion oxidation means for burning and oxidizing the hydrogen sulfide gas generated in the heat treatment furnace to be discharged under a predetermined combustion condition;
Wet absorption means for absorbing a predetermined harmful component from the exhaust gas combustion-oxidized by the combustion oxidation means into an absorption liquid consisting of water or an alkaline solution;
An exhaust gas treatment apparatus comprising: a circulation tank that excludes a part of the absorption liquid from the system.   The exhaust gas treatment apparatus according to claim 2 or 3, further comprising a diffusion unit that diffuses the gas from which harmful components have been removed by the wet absorption unit to the atmosphere. A transition metal or a transition metal compound and sulfur or a sulfur compound as a catalyst, a gas to be discharged in a production process for producing carbon fiber from a carbon source by a gas phase method in a reaction furnace, and the production process In the exhaust gas treatment apparatus for discharging at least one of the gases to be discharged generated when the produced carbon fiber is heat-treated in a heat treatment furnace at a temperature of 800 to 3000 ° C.,
An exhaust gas treatment apparatus comprising a harmful component removal device for removing predetermined harmful components from the gas to be discharged.   The harmful component removal apparatus has a wet absorption means and a circulation tank, supplies an absorption liquid composed of water or an alkaline solution to the wet absorption means, and absorbs harmful substances of gas to be discharged into the absorption liquid, 6. The exhaust gas treatment apparatus according to claim 5, wherein a part of the absorbing liquid that has absorbed the harmful substance is excluded from the system by a circulation tank.   The exhaust gas treatment apparatus according to claim 5 or 6, wherein the gas to be discharged contains a hydrocarbon gas. The exhaust gas treatment apparatus according to any one of claims 1 to 7, wherein the gas to be discharged contains hydrogen sulfide gas.

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