WO2005075890A1

WO2005075890A1 - Apparatus for treating exhaust gas in apparatus for producing carbon fiber by gas phase method

Info

Publication number: WO2005075890A1
Application number: PCT/JP2005/001692
Authority: WO
Inventors: Fuminori Munekane; Hirosuke Kawaguchi
Original assignee: Bussan Nanotech Research Institute, Inc.
Priority date: 2004-02-05
Filing date: 2005-02-04
Publication date: 2005-08-18
Also published as: JP2005221150A

Abstract

An exhaust gas treatment apparatus (10) for discharging a gas to be discharged to the outside thereof, which constitutes a gas phase carbon fiber production apparatus for producing a carbon fiber in a reaction furnace (33) by a gas phase method from a carbon source using a combination of a transition metal or a transition metal compound and sulfur or a sulfur compound as a catalyst, wherein it has a combustion oxidation means (11) for oxidizing by combustion, under prescribed conditions, a gaseous component having flame retardency contained in the gas having been generated in a reaction furnace (33) for conducting a heat treatment of a raw material gas in the presence of a catalyst to produce a carbon fiber and being to be discharged, a wet absorption means (12) and a circulation tank (13), and wherein an absorbing fluid comprising water or an alkali solution is fed to the wet absorption means (12), to absorb prescribed harmful components from a combustion-oxidized gas, and a part of an absorbing fluid having harmful components absorbed therein is removed in the circulation tank. The above exhaust gas treatment apparatus can be suitably used for converting hydrocarbons and sulfur compounds in an exhaust gas generated in the production of carbon fiber by a gas phase method to harmless materials, desirably further reducing a carbon dioxide content of the exhaust gas, and then discharging the resulting gas into the atmosphere.

Description

Specification

Exhaust gas treatment equipment for vapor-phase carbon fiber production equipment

Technical field

The present invention relates to a vapor-grown carbon fiber that pyrolyzes a hydrocarbon as a raw material gas to form a carbon fiber in the presence of a catalyst composed of a transition metal or a compound of a transition metal and sulfur or a sulfur compound. (VGCF), carbon nanotubes, carbon nanohorns, carbon nanocoils, ribbon-shaped carbon fibers, etc. The present invention relates to an exhaust gas treatment device for a gas-phase carbon fiber production device for producing fine fibrous carbon fibers.

Background art

[0002] The production of carbon fibers by a gas phase method is performed by using an organic solvent such as benzene or toluene as a carbon source, a transition metal or a compound of a transition metal such as iron as a catalyst, and a sulfur or a compound of sulfur as a catalyst. Is supplied together with hydrogen into a reactor controlled at a temperature of 800-1500 ° C., where the carbon source is thermally decomposed, and the decomposed carbon is grown with a transition metal as a nucleus. Manufactures carbon nanotubes (CNTs).

[0003] When carbon fibers are vapor-phase grown by pyrolyzing a raw material gas, apart from carbon fibers as a main product, by-products such as hydrogen, chain hydrocarbons, aromatic hydrocarbons, and hydrogen sulfide are produced. Things are created. Of these by-products, most of the high-boiling components in aromatic hydrocarbons are recovered together with the main product, carbon fiber, but not high-boiling aromatic hydrocarbons, hydrogen, and chain hydrocarbons that are not recovered. In addition, low-boiling aromatic hydrocarbons and hydrogen sulfide need to be discharged out of the system together with carrier gas as exhaust gas due to material balance.

[0004] Conventionally, these exhaust gases have been incinerated with the power to emit them as they are to the atmosphere. However, since high-boiling aromatic hydrocarbons are incombustible, they cannot be incinerated. Or, the result was that it was directly emitted to the atmosphere together with the sulfur acid sword.

[0005] On the other hand, the carbon fiber produced in the reaction furnace is subjected to a heat treatment at 800 ° C-3000 ° C in order to satisfy the quality required by the product user. The transition metal used as a catalyst contains most of the high-boiling components among the hydrogen hydrides, and the transition metal used as a catalyst is present as a sulfide (carbon fiber in this state is called crude carbon fiber). Upon treatment, part of the high-boiling aromatic hydrocarbon is volatilized as it is, and a low-boiling hydrocarbon and sulfur-hydrogen are generated by a thermal decomposition reaction. This heat-treated exhaust gas was also emitted to the atmosphere as it was or incinerated and emitted to the atmosphere, but the sulfur compound or sulfur oxide was emitted to the atmosphere as it was.

[0006] In other words, the production of carbon fiber by the gas phase method is currently carried out on a small scale, so that by-products and exhaust gas are released to the atmosphere as they are without any particular regulations! / This is the current situation.

[0007] However, even in the case of small-scale production, in consideration of the environment, it is preferable to reduce harmful substances by burning by-products and heat-treated exhaust gas. Burning is a good thing, and it's actually.

[0008] In order to solve such a problem, a vapor-grown carbon fiber production method in which a transition metal is used as a catalyst to thermally decompose an organic compound in a reaction furnace to obtain a carbon fiber uses a vertical incinerator and a propane. A combustible gas such as gas and city gas is constantly burned by a pilot burner, and the reaction exhaust gas and the heat treatment exhaust gas are supplied to it through a main burner and ignited by the flame of the pilot burner for incineration. ! Puru (for example, see Patent Document 1).

[0009] As described above, in the production of carbon fiber by the gas phase method, even high-boiling aromatic hydrocarbons, which are flame-retardant, are not completely decomposed even after incineration and are emitted to the atmosphere as they are. It is inevitable that carbon dioxide will be produced from chain hydrocarbons, low-boiling hydrocarbons and high-boiling hydrocarbons decomposed by incineration, and sulfur oxides will be produced from hydrogen sulfide. At present, since the amount of vapor-grown carbon fiber produced is small, the amount of carbon dioxide, sulfur sulfide, or sulfur sulfide that is released to the atmosphere is also relatively small, and the production equipment Is located in a part of a large-scale dangling plant, so it fully satisfies the regulation value of total sulfur oxides stipulated in the Air Pollution Control Law!

[0010] However, when the scale of the production equipment is increased to increase the production amount of the vapor grown carbon fiber, the emission of carbon dioxide, sulfur compound, or sulfur acid compound which is released to the atmosphere is reduced. It is also conceivable that the production volume will be large and that the production facility will be located at a single location, which may make it impossible to satisfy the total sulfur oxide regulation value stipulated by the Air Pollution Control Law. Furthermore, global warming It is desirable to minimize the carbon dioxide generated by the combustion of exhaust gas as much as possible when considering production facilities that take prevention into account.

[0011] In Patent Document 1, there is no way to deal with the substance that is not treated even by the combustion treatment.

Patent Document 1: Patent No. 3397155

Disclosure of the invention

Problems to be solved by the invention

[0012] The present invention detoxifies hydrocarbons and sulfur compounds in exhaust gas generated during the production of vapor-grown carbon fiber, and desirably removes carbon dioxide generated as a result of the detoxification. It is an object of the present invention to provide an exhaust gas treatment device that emits the reduced exhaust gas to the atmosphere.

Means for solving the problem

[0013] In order to solve the above problems, the present invention introduces exhaust gas from a reaction furnace in a process of producing vapor grown carbon fiber into a combustion furnace and performs incineration treatment. The exhaust gas from the reactor furnace contains hydrogen gas as a carrier and hydrogen generated by the decomposition reaction of hydrocarbons, which are raw materials for producing carbon fibers, in combination with flame-retardant high-boiling aromatic hydrocarbons and sulfur-containing hydrogen. Exists. In the present invention, in order to completely oxidize these flame-retardant high-boiling aromatic hydrocarbons and hydrogen sulfides, the temperature of the combustion furnace exhaust gas is set to 400 to 600 ° C using an auxiliary burner using city gas or the like as a fuel. Adjust and burn oxidation. The gas subjected to the combustion oxidation treatment is introduced into wet absorption means provided at the latter stage of the combustion furnace, and is absorbed and removed by contact with water as an absorbing solution, preferably an alkaline aqueous solution. The gas detoxified through these combustion oxidation treatment and absorption removal treatment is released to the atmosphere.

That is, the present invention provides a vapor-grown carbon fiber production method in which a transition metal or a compound of a transition metal and sulfur or a compound of sulfur are used as catalysts to produce carbon fibers from a carbon source by a vapor phase method in a reaction furnace. An exhaust gas treatment device that constitutes the device and discharges the gas to be emitted from the reaction furnace to the outside of the system is generated in a reaction furnace that performs heat treatment on the raw material gas in the presence of a catalyst to produce carbon fibers. Combustion oxidizing means for burning and oxidizing a flame-retardant gas among the gases to be discharged under predetermined combustion conditions; And a harmful component removing device for removing a predetermined harmful component from the gas force.

Further, according to the present invention, in the above-mentioned exhaust gas treatment apparatus, the harmful component removing apparatus has a wet absorption means and a circulation tank, and supplies water or an absorbing solution having an alkaline solution power to the wet absorption means. Combustion oxidizing gas power A predetermined harmful component is absorbed, and a part of the absorbing liquid that has absorbed the harmful component in the circulation tank is eliminated.

Further, the present invention provides a method for producing a carbon fiber produced by a gas phase method in a reactor from a carbon source using a transition metal or a compound of a transition metal and sulfur or a compound of sulfur as a catalyst. In an exhaust gas treatment device that discharges a gas to be discharged generated in a heat treatment furnace that heat-treats at a temperature of ° C outside the system, the hydrogen sulfide gas that is generated and discharged in the heat treatment is burned and oxidized under predetermined combustion conditions. Combustion oxidizing means, wet oxidizing means for absorbing predetermined harmful components from exhaust gas oxidized by the combustion oxidizing means into water or an alkaline solution, and a part of the absorbing solution. A circulation tank is provided for removal outside the system. Further, the present invention provides the exhaust gas treatment device described above, further comprising a dispersing unit for dispersing the gas from which the harmful components have been removed by the wet absorbing unit to the atmosphere.

[0017] The present invention provides a process for producing carbon fibers from a carbon source by a gas phase method in a reactor using a transition metal or a compound of a transition metal and sulfur or a compound of sulfur as a catalyst. Exhaust gas that discharges at least one of the target gas and the target gas generated when the carbon fiber manufactured in the above manufacturing process is heat-treated in a heat treatment furnace at a temperature of 800 to 3000 ° C. The processing apparatus further includes a harmful component removing device that removes a predetermined harmful component from the gas to be discharged. In addition, the harmful component removing device has a wet absorbing means and a circulation tank, and supplies water or an alkaline absorbing solution to the wet absorbing means to absorb harmful substances of a gas to be discharged. And a part of the absorbing solution that absorbed the harmful substances was removed from the system by the circulation tank. Further, the gas to be discharged includes a hydrocarbon gas or a hydrogen gas.

The invention's effect

[0018] The present invention provides an exhaust gas treatment method for burning and oxidizing exhaust gas generated by vapor-phase carbon fiber production under appropriate combustion conditions, and wet-absorbing the combustion oxidized gas. Hydrocarbon and sulfur compound concentrations can be reduced to less than 100 ppm.

Brief Description of Drawings

FIG. 1 is a diagram illustrating an outline of a configuration of a vapor-grown carbon fiber production apparatus using an exhaust gas treatment apparatus according to the present invention.

FIG. 2 is a diagram illustrating the configuration of an exhaust gas treatment device used in the vapor-grown carbon fiber production device shown in FIG.

Explanation of symbols

[0020] 10: Exhaust gas treatment unit

11: Combustion acid tower

111: Nylon Nonna

112: burner 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: Discharge blower

17: Heat exchanger

30: CNT production department

31: Reactor

311: Raw material supply pipe

312: Hydrogen gas supply pipe

313: Gas exhaust pipe

32: Piping

50: CNT purification section 51: 1st heat treatment furnace

511: Furnace section

512: Exhaust gas exhaust pipe

52: Second heat treatment furnace

521: Furnace section

522: Exhaust gas exhaust pipe

53: Piping

70: Separation section

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. Figure

FIG. 1 is a diagram schematically illustrating the configuration of a vapor-grown carbon fiber production apparatus provided with an exhaust gas treatment apparatus according to the present invention. The vapor-grown carbon fiber production apparatus includes a CNT production section 30, a CNT purification section 50, and an exhaust gas treatment section 10.

[0022] The exhaust gas treatment section 10 includes a combustion oxidation tower 11 serving as combustion oxidation means, a wet absorption tower 12 serving as wet absorption means, a circulation tank 13, a circulation pump 15, and a discharge blower 16, These devices (means) are connected and connected as shown in the figure using pipes 141-145.

[0023] The combustion oxidation tower 11 has an exhaust gas supply nozzle 113 that supplies exhaust gas sent from the CNT production unit 30 via the pipe 141 into the tower, and supplies air to the exhaust gas at an appropriate air ratio. An air supply nozzle 114, a pilot burner 111 that ignites a mixed gas of exhaust gas and air, and a city gas for completely oxidizing flame-retardant high-boiling aromatic hydrocarbons and sulfide hydrogen And an auxiliary burner 112 using the same as fuel. The gas that has been oxidized by combustion in the combustion oxidation tower 11 (hereinafter referred to as “combustion oxidation gas”) is supplied to the wet absorption tower 12 via the pipe 142.

[0024] In the wet absorption tower 12, water, preferably having an alkaline solution power, is sprayed 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 via the pipes 14-13. The treated exhaust gas, from which harmful components have been removed and rendered harmless, is supplied to piping 145 散 Emitted to the atmosphere via 16.

[0025] In the circulation tank 13, a part of the absorbing solution that has absorbed the combustion and oxidation gas is discharged, and the absorbing solution that has been poured by the discharged amount is sent to the wet absorption tower 12 by the circulating pump 15 and the piping 14 Feed through 4.

The CNT manufacturing unit 30 includes a reaction furnace 31.

[0027] The reaction furnace 31 is a furnace for thermally decomposing a hydrocarbon as a raw material under a catalyst composed of a transition metal or a compound of a transition metal and sulfur or a sulfur compound to produce carbon nanotubes. A supply pipe 311 for containing raw material solution, a supply pipe 312 for hydrogen gas, and a discharge pipe 313 for vaporized gas are provided. In the reaction furnace 31, a transition metal or a compound of a transition metal such as iron (Fe) serving as a catalyst (for example, hydrogen chloride) and an organic compound containing sulfur (S) or a sulfur sulfide (for example, thiophene) are used. ) And a raw material liquid (for example, toluene) are heated together with hydrogen gas.

[0028] In the reaction furnace 31, the generated unreacted raw materials and the residue of the unused catalyst ゃ the carbon fibers containing non-fibrous carbides and tar components (hereinafter referred to as “crude carbon fibers”) are piped 32,53— It is supplied to the CNT refining section 50 via 1.

[0029] The CNT refining section 50 is a section for refining crude carbon fiber into carbon fiber (carbon nanotube) as a final product, and has a first heat treatment furnace 51 and a second heat treatment furnace 52. Be composed.

[0030] The first heat treatment furnace 51 is a heat treatment means for removing volatile components of the crude carbon fibers and volatile components sent from the reaction furnace 31, and includes a furnace section 511 and a gas discharge pipe 512. It is configured to have. The volatile components of the crude carbon fibers and volatile components sent from the reaction furnace 31 are vaporized in a furnace section 511 maintained at, for example, 800 to 1500 ° C., and then removed from a gas discharge pipe 512. The volatile components discharged from the gas discharge pipe 512 are burned and oxidized by the combustion oxidizing and recovering means similar to the exhaust gas processing unit 10, and then the harmful substances are recovered, and only the detoxified gas is released to the atmosphere. . The crude carbon fiber from which the volatile components have been removed is sent out to the second heat treatment furnace 52 via the pipe 53-2.

[0031] The second heat treatment furnace 52 is means for performing a heat treatment for graphitizing the crude carbon fiber from which volatile components have been removed, and includes a furnace part 521 and a gas discharge pipe 522. Is done. Arrangement The crude carbon fiber supplied from the first heat treatment furnace 51 to the furnace part 521 via the pipe 52-2 is subjected to a graphite treatment in the furnace part 521 by being maintained at, for example, 1300-3000 ° C. The exhaust gas generated by this process is exhausted from the gas exhaust pipe 522. The exhaust gas discharged from the gas discharge pipe 522 is burned and oxidized by the combustion oxidizing and recovering means similar to the exhaust gas processing unit 10, and then the harmful substances are recovered, and only the detoxified gas is released to the atmosphere. In this embodiment, the carbon fiber (CNT) commercialized from the composition carbon fiber is obtained through two-stage heat treatment (heat treatment), but the present invention is not limited to this. At least one stage of heat treatment at 800 to 3000 ° C. may be performed depending on the desired carbon fiber (CNT).

[0032] The inside of the reactor 31 for producing the vapor grown carbon fiber is in a hydrogen atmosphere, and the pressure in the system is controlled to 0.1 to 5 kPa in order to prevent accidents due to intrusion of air. Even in the furnace sections 511 and 512 where heat treatment is performed, the pressure in the system is controlled to 0.1-5 kPa to prevent accidents due to air intrusion.

Example

With reference to FIG. 2, a detailed configuration of the exhaust gas treatment unit 10 that performs a wet absorption treatment after combusting and oxidizing exhaust gas containing hydrocarbons and hydrogen sulfate will be described.

[0034] Exhaust gas accompanying the reaction treatment and the heat treatment is extruded out of the system at the above-mentioned system pressure, and is sent to an 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 144, respectively. The pipe 142 is provided with a heat exchanger 17, the pipe 144 is provided with a circulation pump 15, and the pipes 14-5 are provided with a discharge blower 16.

The combustion oxidation tower 11 is provided with a pilot burner 111, an auxiliary burner 112, an exhaust gas nozzle 113, and an air nozzle 114. The pilot burner 111 and the auxiliary burner 112 burn the fuel such as city gas and propane gas, and the exhaust gas from the reactor 31 introduced into the combustion oxidation tower 11 through the exhaust gas nozzle 113 having a burner structure. In the following, combustion-oxidized exhaust gas) is burned and oxidized to produce water and carbon dioxide from hydrocarbons and sulfur oxides from hydrogen sulfide. The combustion state of the combustion oxidation target exhaust gas is appropriately controlled by maintaining the temperature of the combustion oxidation target exhaust gas within a required range. Is controlled. Specifically, the amount of air introduced is adjusted so that the temperature of the exhaust gas to be subjected to combustion oxidation becomes 400 to 600 ° C. Combustion state control may be performed by the ratio of the amount of exhaust gas to be oxidized for combustion and the amount of air separately introduced.In this case, the ratio is 1.2 to 1.6 times the theoretical combustion air amount. What is necessary is to control. Alternatively, control may be performed by the residual oxygen concentration in the exhaust gas to be oxidized.In this case, the control may be performed so that the residual oxygen concentration becomes 4% to 8%.

[0036] Exhaust gas that has been burnt and oxidized in the combustion oxidation tower 11 and has been treated (hereinafter, treated exhaust gas! /！) Is sent to the wet absorption tower 12 after its volume has been reduced by heat exchange. In this embodiment, a caustic soda aqueous solution is used as an absorbing solution of the wet absorption tower 12, and its concentration is ρΗ4-6. The treated exhaust gas is introduced from the bottom of the tower in a direction perpendicular to the tower wall. The above absorbing solution 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.

[0037] The absorbent that has absorbed the carbon dioxide and sulfur oxide in the treated exhaust gas is drawn out from the bottom of the tower and stored in the circulation tank 13 via the pipe 143. Since sodium sulfate and sodium carbonate are dissolved in this absorption solution and these compounds are concentrated and precipitated when used in circulation, 110% of the circulated amount is purged out of the system and drained. The amount of circulation is determined by the structure of the wet absorption tower 12, the concentration of the exclusion substance in the exhaust gas, and the concentration of the exclusion substance in the processing gas to be obtained. Since the basicity of the absorbing solution increases due to absorption of carbon dioxide and sulfur oxides, an aqueous caustic soda solution is appropriately replenished so as to be within the above-mentioned control basicity. The absorbent adjusted for basicity is drawn by the pump 15 and sent to the wet absorption tower 12 again.

[0038] The gas detoxified by absorbing and removing carbon dioxide and hydrogen sulfide in the wet absorption tower 12 is drawn from the top of the tower by a blower 16 and released to the atmosphere. The higher the temperature of the treated exhaust gas from the combustion oxidation tower 11 to the wet absorption tower 12, the lower the absorption rate of the diacid carbon and sulfur oxide in the treated exhaust gas into the absorbent is. Therefore, if the heat exchange is provided as described above, it is possible to suppress the decrease in the absorption rate as much as possible, which is preferable.

Claims

The scope of the claims

[1] A reaction furnace comprising a vapor-phase carbon fiber production device that produces a carbon fiber from a carbon source by a vapor phase method in a reaction furnace using a transition metal or a transition metal compound and sulfur or a sulfur compound as a catalyst. In an exhaust gas treatment device that discharges the gas to be discharged generated in

Among the gases to be discharged in a reactor for producing carbon fibers by subjecting a raw material gas to heat treatment in the presence of a catalyst, a nonflammable gas is burned and oxidized under predetermined combustion conditions. Burning oxidation means;

A harmful component removing device for removing a predetermined harmful component from the gas oxidized by combustion by the combustion oxidizing means;

An exhaust gas treatment device comprising:

[2] The harmful component removing device has a wet absorbing means and a circulating tank, and supplies water or an absorbing solution such as an alkaline solution to the wet absorbing means to cause a predetermined harmful effect such as burning and oxidizing gas. 2. The exhaust gas treatment device according to claim 1, wherein a part of the absorbing solution that absorbs the components and absorbs the harmful components into the circulation tank is removed.

[3] Heat treatment of carbon fiber produced by a gas phase method in a reactor using a transition metal or a compound of a transition metal and sulfur or a compound of sulfur as a catalyst at a temperature of 800 to 3000 ° C. In an exhaust gas treatment device that discharges the gas that is generated in the furnace and is targeted for emission,

Combustion oxidizing means for burning and oxidizing sulfur gas to be discharged in the heat treatment furnace under predetermined combustion conditions;

Wet absorption means for absorbing a predetermined harmful component in the exhaust gas burned and oxidized by the combustion oxidizing means into an absorbing solution comprising water or an alkaline solution;

A circulation tank that removes part of the absorbing solution out of the system

An exhaust gas treatment device comprising:

4. The exhaust gas treatment device according to claim 2, further comprising a dispersing unit that disperses the gas from which the harmful components have been removed by the wet absorbing unit to the atmosphere.

[5] using a transition metal or a compound of a transition metal and sulfur or a compound of sulfur as a catalyst, Carbon source power The gas to be discharged generated in the production process of producing carbon fiber by the gas phase method in the reactor, and the carbon fiber produced in the production process are heat-treated in the heat treatment furnace at a temperature of 800 to 3000 ° C. In an exhaust gas treatment device that discharges at least one of the gases to be discharged generated during

An exhaust gas treatment apparatus comprising a harmful component removing device for removing a predetermined harmful component of the gas to be discharged.

[6] The harmful component removing device has a wet absorbing means and a circulation tank, and supplies the wet absorbing means with water or an absorbing solution composed of an alkaline solution to absorb harmful substances of a gas to be discharged. 6. The exhaust gas treatment apparatus according to claim 5, wherein a part of the absorption liquid that has been absorbed into the liquid and has absorbed the harmful substance is removed outside the system by a circulation tank.

7. The exhaust gas treatment device according to claim 5, wherein the gas to be discharged includes a hydrocarbon gas.

[8] The exhaust gas treatment apparatus according to any one of claims 1 to 7, wherein the gas to be discharged includes hydrogen sulfide gas.