JP2005262122A - Exhaust gas treatment method in carbon fiber manufacturing process, and treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treatment method and a treatment apparatus therefor enabling long time continuous operation by catalytic treatment at a lower facility cost, running cost and thermal NOx discharge than a direct combustion system, even if gaseous catalyst poison like organic silicone is contained in an exhaust gas when the exhaust gas from a high temperature heat treatment furnace is treated in a carbon fiber manufacturing process. <P>SOLUTION: In the treatment method for exhaust gas discharged from the high temperature heat treatment furnace in a carbon fiber manufacturing process, after tar-like catalyst poison and gaseous catalyst poison in the exhaust gas are removed, remaining gas is subjected to catalytic treatment. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust gas treatment method and a treatment apparatus for treating exhaust gas containing decomposition products generated during firing of a fibrous material in a high-temperature heat treatment furnace in a carbon fiber production process.

  In the production of carbon fibers, a precursor (for example, acrylonitrile fiber) is fired to form flame resistant fibers, and the flame resistant fibers are fired and carbonized to form carbon fibers.

  In the production of carbon fibers, the exhaust gas from these high-temperature heat treatment furnaces to be fired contains decomposition products generated during firing of the fibrous material. This decomposition product contains gaseous substances such as hydrogen cyanide, ammonia, carbon monoxide and carbon dioxide, and tar-like substances mainly composed of organic components. In particular, hydrogen cyanide and ammonia in gaseous substances are Due to its strong toxicity and high environmental load, it is not possible to release the exhaust gas as it is. Therefore, these decomposition products must be decomposed before being released into the atmosphere. In the present specification, gaseous means a gas at 1 atm 50 ° C., and tar means a liquid or solid at 1 atm 50 ° C.

  As one method for decomposing a decomposition product, conventionally, a method in which exhaust gas is directly heated and directly combusted at 500 ° C. or higher has been proposed (see, for example, Patent Document 1). However, this method has problems such as a higher equipment cost, a higher running cost, and a larger-scale equipment than the catalyst treatment method described later. Moreover, since thermal NOx is generated depending on the processing temperature, the load on the environment is large.

  Further, as another method for decomposing a decomposition product, a catalyst processing method in which exhaust gas is heated to about 200 ° C. to 400 ° C. and brought into contact with a platinum-based or vanadium-based catalyst has been proposed (for example, Patent Documents 2 and 3). This method has the advantages of lower cost, lower running cost and more compactness than the direct combustion method, and low thermal NOx emissions due to low temperature operation. However, in the case of catalyst treatment, the tar-like substance in the exhaust gas physically coats the catalyst surface and becomes a catalyst poison that lowers the catalyst performance.

  Therefore, it is necessary to remove this tar-like substance in advance, and the removal methods of the tar-like substance in the exhaust gas so far include treatment by electric dust collection method, washing shower treatment, filtration treatment by filter, cooling condensation treatment, etc. It has been known. However, there is a problem that clogging of piping pipes and clogging occurs in the filtration process using the electrostatic dust collection method and the filter, and in the water washing shower process, there is a new treatment facility for treating the washing water containing tar-like substances. Necessary.

  In addition, as a catalyst treatment method for exhaust gas, there is also a report of performing a catalyst treatment after trapping a tar-like substance in the exhaust gas in a packed column of a magnetic Raschig ring and removing it (see, for example, Patent Document 3).

  On the other hand, in recent years, with the increase in strength and performance of carbon fibers, silicone oil is applied to the fibers during the production of acrylic fibers in order to prevent adhesion between single yarns and improve the convergence of non-twisted yarns. The organic silicone contained in the oil is contained not only in the tar form but also in the gaseous form by evaporation or thermal decomposition in the furnace. Organosilicones are tar-like and poisonous to the catalyst, but even in gaseous form, they are chemically poisoned to the catalyst surface and become catalyst poisons that lower the activity of the catalyst. Therefore, in the case of exhaust gas containing organosilicone, the catalyst treatment method that involves only the removal of the conventional tar-like substance does not remove the gaseous organosilicone. There is a problem that continuous processing cannot be performed.

For this reason, the direct combustion method is generally used for the treatment of exhaust gas containing organic silicone. However, the direct combustion method has a high equipment cost, a high running cost, and a large-scale equipment. Furthermore, when the exhaust gas treatment flow rate is large, temperature unevenness is likely to occur in the combustion furnace, and there is a risk that the decomposition rate of the gas that has passed through the low temperature portion will be reduced. Therefore, as the exhaust gas treatment flow rate is increased, the merit of the catalyst treatment method with respect to the direct combustion method becomes more remarkable in terms of cost, space, and decomposition rate. Therefore, even when a catalyst poison such as organic silicone is contained in the exhaust gas, it has been considered necessary to be able to operate continuously for a long time by the catalyst treatment method.
JP 2001-324119 A JP 49-30628 A JP-A-56-24022

  An object of the present invention is to solve the above-mentioned conventional problems, and in a high-temperature heat treatment furnace exhaust gas treatment in a carbon fiber production process, a gaseous catalyst poison such as organic silicone is contained in the exhaust gas. Even in such a case, an object is to provide an exhaust gas treatment method and a treatment apparatus capable of continuous operation for a long time by catalyst treatment which is lower in equipment cost, lower running cost, and lower thermal NOx emission than the direct combustion method.

The present invention adopts the following configuration in order to achieve the above-described problems. That is,
(1) In a method for treating exhaust gas discharged from a heat treatment furnace in a carbon fiber production process, after removing the tar-like catalyst poison and the gaseous catalyst poison in the exhaust gas, the exhaust gas treatment in which the remaining gas is treated with a catalyst Method.

  (2) The exhaust gas treatment method according to (1), wherein in the treatment of the exhaust gas, the exhaust gas is condensed through a temperature reducing chamber, and the exhaust gas is further brought into contact with a pretreatment agent.

  (3) The exhaust gas treatment method according to any one of (1) and (2), wherein the catalyst poison that deactivates the catalyst by the chemical action is organic silicone and / or organic phosphorus.

  (4) The exhaust gas treatment method according to any one of (2) and (3), wherein a cooling temperature of the temperature reducing chamber is 50 ° C. or lower and a residence time is 2 seconds or longer.

  (5) The exhaust gas treatment method according to any one of (2) to (4), wherein the pretreatment agent is alumina and / or ceramic.

  (6) The exhaust gas treatment method according to any one of (2) to (5), wherein the pretreatment agent is at least one selected from a honeycomb shape, a foam shape, and a granular shape.

  (7) The exhaust gas treatment method according to any one of (2) to (6), wherein exhaust gas is brought into contact with the pretreatment agent at a temperature of 200 ° C. or higher and 400 ° C. or lower.

  (8) The exhaust gas treatment method according to any one of (2) to (7), wherein a contact time of the exhaust gas with the pretreatment agent is 0.05 seconds or more.

  (9) The exhaust gas treatment method according to any one of (1) to (8), wherein the catalyst treatment is a decomposition treatment by catalytic oxidation with a catalyst.

  (10) The exhaust gas treatment method according to any one of (1) to (9), wherein the catalyst is at least one selected from a honeycomb shape, a foam shape, and a granular shape.

  (11) The exhaust gas treatment method according to any one of (1) to (10), wherein a gas is brought into contact with the catalyst at 200 ° C. or more and 400 ° C. or less.

  (12) The exhaust gas treatment method according to any one of (2) to (4), wherein a contact time of the exhaust gas with the catalyst is 0.05 seconds or more.

  (13) An apparatus for treating exhaust gas discharged from a heat treatment furnace for producing carbon fiber has means for removing tar-like catalyst poison and gaseous catalyst poison in the exhaust gas, and means for catalytic treatment of the remaining gas. Exhaust gas treatment equipment.

  The exhaust gas treatment method in carbon fiber production of the present invention can capture and decompose a gaseous catalyst poison with a pretreatment agent. For this reason, even when firing a precursor to which a silicon-based oil is applied for higher performance, it is lower than direct combustion treatment without being affected by gaseous catalyst poisons such as organic silicone contained in the exhaust gas. Continuous operation of long-time decomposition treatment by a catalyst treatment method with low running cost is possible. Further, since the processing temperature is low, hydrogen cyanide can be more effectively reduced to a low concentration without discharging thermal NOx.

  Hereinafter, the present invention will be described in more detail based on embodiments shown in the drawings.

  FIG. 1 is a schematic view showing an example of an entire exhaust gas treatment apparatus of a high-temperature heat treatment furnace for producing carbon fibers according to the present invention.

  The gas discharged from the high-temperature furnace for producing carbon fiber is drawn through the pipe 1 by the exhaust pump 2, stays in the temperature reducing chamber 3, and is cooled. The tar-like catalyst poison in the exhaust gas is condensed, trapped in the temperature reducing chamber 3 and removed from the exhaust gas. In addition, it is preferable to cover the piping with the heat insulating material 11 from the high-temperature heat treatment furnace exhaust gas port to the temperature-decreasing chamber 3 in order to prevent tar condensation in the pipe due to a temperature drop due to heat radiation. Thereafter, the gas exiting the temperature reducing chamber 3 is heat-exchanged with the gas at the outlet of the catalyst 7 by the heat exchanger 4 used for effective use of heat, and is heated. Thereafter, the catalyst is heated by the electric heater 5 and the pretreatment agent 6 captures and decomposes and removes gaseous catalyst poisons such as organic silicone and / or organic phosphorus that could not be removed in the temperature reducing chamber 3. The catalyst 7 decomposes harmful gaseous substances such as hydrogen cyanide, ammonia and carbon monoxide in the exhaust gas. Thereafter, the decomposed exhaust gas is reduced in temperature by the heat exchanger 4 and then released into the atmosphere.

  2A and 2B are schematic views showing an example of the temperature reducing chamber 3, wherein FIG. 2A is a top view and FIG. 2B is a cross-sectional view. The volume inside the temperature-decreasing chamber 3 is made sufficiently large from the gas flow rate so that the residence time of the exhaust gas can be secured sufficiently. Further, in the temperature reducing chamber 3, the cooling water pipe 4b is put in the chamber to increase the surface area of the cold water pipe 4b, thereby increasing the cooling efficiency. Further, by installing the partition plate 4a in the chamber, the exhaust gas flow path is narrowed down to the vicinity of the cooling water pipe as shown by the arrow in FIG. Further, a filter 4c is provided in front of the outlet so that the condensed tar content does not leak out.

  FIG. 3 is a detailed view of the pretreatment agent 6 and the catalyst 7. A metal mesh 6a is laid on the lower portion of the filling tank 10, and a platinum-based honeycomb catalyst 7 is filled thereon. A metal mesh 6b is placed on the upper surface of the catalyst 7 as a spacer, and a particulate pretreatment agent 6 is filled with alumina on the top of the catalyst 7, and the metal mesh 6c is placed on the catalyst 7 for stabilization. The tar-shaped catalyst poison is removed in the temperature reducing chamber 3, and the exhaust gas heated by the heat exchanger 4 and the electric heater 5 is introduced into the pretreatment agent 6 from the upper inlet 8 of the vertical tank, Gaseous catalyst poisons are captured and decomposed. Thereafter, the gaseous substance is decomposed by the catalyst 7 and discharged from the discharge port 9.

  As described above, in the treatment of exhaust gas discharged from a high-temperature heat treatment furnace in the carbon fiber production process, the present invention removes the tar-like catalyst poison and the gaseous catalyst poison with substances in the exhaust gas, and then remains The gas is subjected to catalytic treatment.

  For the exhaust gas to be treated, the hydrogen cyanide concentration in the exhaust gas at the heat treatment furnace entrance / exit seal part diluted with air or the like is measured according to the 4-pyridinecarboxylic acid-pyrazolone spectrophotometric method defined in the JIS K0109 method. The thing of 1500 ppm or less is preferable. If the hydrogen cyanide concentration in the exhaust gas of the heat treatment furnace body exceeds 1500 ppm in the above measurement, the decomposition treatment with the catalyst may be insufficient, and continuous operation may be difficult.

  As a method for decomposing the remaining gaseous substance, the catalyst treatment method is preferable because both the equipment cost and the running cost are low, and the amount of NOx generated is small. However, the exhaust gas contains a gaseous substance and a tar-like substance. If the tar-like substance is present, it accumulates in the pipe or becomes a catalyst poison that physically deactivates the catalyst surface to deactivate the catalyst. This hinders exhaust and decomposition processes. Therefore, it is important to remove the tar-like catalyst poison in advance before the catalyst treatment. In addition, the gaseous substance in the exhaust gas may contain a substance that becomes a catalyst poison that deactivates the catalyst due to a chemical action. It will fall. For this reason, it is important to remove this gaseous catalyst poison. Thereafter, when the remaining gas is subjected to catalyst treatment, the active state of the catalyst can be maintained for a long time, and high treatment efficiency can be maintained.

  Examples of the gaseous catalyst poison include organic silicones and organic phosphorus that are often imparted to the precursor, and these are imparted with the aim of improving the performance of the precursor. Not as long.

  As a method for removing the tar-like catalyst poison, it is preferable to first condense in the temperature reducing chamber 3. Further, the inside of the temperature reducing chamber 3 can be easily opened, and the sectional area in the temperature reducing chamber 3 is preferably 5 times or more than the sectional area in the pipe. By configuring as described above, the temperature reducing chamber 3 is easier to clean than the magnetic Raschig ring packed tower.

  The temperature reduction chamber 3 has a residence time of 2 seconds or more to sufficiently condense the tar-like catalyst poison in the temperature reduction chamber 3, and the temperature after the temperature reduction is 50 ° C. or less. It is preferable. If the temperature is higher than 50 ° C. or the residence time is less than 2 seconds, the tar-shaped catalyst poison is insufficiently condensed and passes through the temperature-reducing chamber 3 without being partially condensed. There is a possibility of accumulation in the pretreatment agent and the catalyst device. The upper limit of the residence time is not limited and may be determined in consideration of the equipment size. The temperature after the temperature reduction is preferably 5 ° C. or higher in consideration of the condensation effect and freezing prevention.

Here, the residence time indicates a time calculated by dividing the exhaust gas flow rate [m ³ / h] by the volume [m ³ ] of the temperature reducing chamber. Here, the temperature-decreasing chamber volume indicates the volume of the substantial part through which the exhaust gas passes, excluding the part such as the cold water pipe, among the volumes inside the temperature-decreasing chamber. In order to prevent condensation in the pipe, the length of the pipe from the furnace to the temperature reducing chamber is short, and it is preferable to keep the pipe warm with a heat insulating material or the like.

  As a method for removing the gaseous catalyst poison that cannot be completely removed by the temperature reducing chamber 3, it is preferable that the pretreatment agent 6 captures and decomposes it. This is because the trapping and decomposing method does not cause accumulation of catalyst poisons in the pretreatment agent 6 and is easy to handle without trouble such as new cleaning.

  The material of the pretreatment agent 6 is preferably alumina and / or ceramic because of its heat resistance and high decomposition efficiency. More preferably, alumina is preferable because of high decomposition efficiency.

  Further, the shape of the pretreatment agent 6 is preferably a honeycomb shape, a foamed shape or a granular shape because of its ease of handling and a large surface area per volume. The pretreatment agent 6 is brought into contact with the exhaust gas after the removal of the tar-like substance. However, since the remaining tar-like substance is slightly contained, clogging occurs in the pretreatment agent, thereby greatly increasing the pressure loss. There is a concern that a part where the exhaust gas does not reach in the pretreatment agent is generated. For this reason, the shape of the pretreatment agent 6 is particularly preferable among the above because the gas flow paths are formed at random, so that the above-mentioned influence due to clogging is difficult to be received and the processing efficiency is high.

  Furthermore, in order to sufficiently exhibit the effect of capturing and decomposing the pretreatment agent 6, it is preferable that the exhaust gas is brought into contact with the pretreatment agent 6 at 200 ° C. or more and 400 ° C. or less. When contacted at less than 200 ° C., the decomposition efficiency of the pretreatment agent is lowered, and the catalyst poison is not sufficiently removed. Moreover, even if it contacts at the temperature over 400 degreeC, decomposition | disassembly efficiency has reached the upper limit, and since it does not increase any more, conversely, since the required power of the heater increases, running cost increases.

Further, the contact time of the exhaust gas with the pretreatment agent 6 is preferably 0.05 seconds or more. This is because when the time is less than 0.05 seconds, the decomposition efficiency of the catalyst poison is lowered, the removal of the catalyst poison is insufficient, and the catalyst life is shortened. In consideration of the upper limit of the equipment size and decomposition efficiency, the contact time of the exhaust gas pretreatment agent is preferably 1 second or less. Here, the contact time is a value obtained by dividing the filling volume of the pretreatment agent, that is, the apparent volume [m ³ ] including the internal voids, by the exhaust gas flow rate [Nm ³ / sec].

  As the catalyst treatment, it is preferable to perform a decomposition treatment by bringing a gas into contact with the catalyst 7 and oxidizing a gaseous substance. The reason is that the catalyst treatment has high treatment efficiency, low fuel consumption, easy operation, and easy maintenance.

  Further, the shape of the catalyst 7 is preferably a honeycomb shape, a foam shape or a granular shape because of its ease of handling and a large surface area per volume. Furthermore, it is more preferable to have a honeycomb shape. This is because the tar-like substance in the gas is almost removed up to the pretreatment agent, so there is no concern about clogging, and the honeycomb-like substance has the smallest pressure loss and high processing efficiency.

  In order to sufficiently exhibit the effect of decomposition of the catalyst, it is preferable to bring the gas into contact with the catalyst at 200 ° C. or higher and 400 ° C. or lower. When contacting at 200 ° C. or lower, the decomposition efficiency of the catalyst is lowered. Moreover, even if it contacts at 400 degreeC or more, decomposition | disassembly efficiency has reached the upper limit, and since the required electric power of a heater increases conversely not increasing any more, running cost increases.

  The catalytically active substance may be a noble metal type or a nonmetal type. In general, however, noble metal systems are preferred because of their high catalytic activity, thermal stability against use temperature, and high toxicity resistance. Furthermore, since this property is more remarkable, it is particularly preferable to use a palladium-based or platinum-based alumina support.

Further, the contact time of the exhaust gas with the catalyst is preferably 0.05 seconds or more. This is because if it is less than 0.05 seconds, a gas that passes through unreacted is generated, and the decomposition efficiency of the gaseous substance in the exhaust gas decreases. In consideration of the equipment size and the upper limit of decomposition efficiency, the contact time of the exhaust gas with the catalyst is preferably 0.3 seconds or less. Here, the contact time “second” is a value obtained by dividing the packing volume of the catalyst, that is, the apparent volume [m ³ ] including the internal voids, by the exhaust gas flow rate [Nm ³ / sec].

  Exhaust gas treatment equipment for high-temperature heat treatment furnace for carbon fiber production In the treatment of exhaust gas discharged from high-temperature heat treatment furnace for carbon fiber production, the substances in the exhaust gas sufficiently remove tar-like catalyst poison and gaseous catalyst poison. Then, the apparatus is preferably characterized in that the remaining gas is subjected to catalyst treatment. Further, from the preferable method under each of the above conditions, the tar-like catalyst poison in the exhaust gas is removed by the temperature reducing chamber, and the gaseous catalyst poison such as organic silicone that cannot be completely removed by the temperature reducing chamber is removed before the alumina granular particles. More preferably, the exhaust gas treatment apparatus is configured to decompose the remaining gas components by bringing the treatment agent into contact with a platinum honeycomb catalyst after sufficiently removing the exhaust gas by contacting the treatment agent.

Example 1
Single fiber fineness with 2% by weight of silicone oil applied by spinning acrylonitrile polymer as acrylic fiber, drawing, washing with water and then immersing in methylsilicone oil with about 30% silicon element in the oil. Was 1.1 decitex, and the number of single yarns was 12,000.

Using this fiber yarn as a precursor, a flame resistant yarn was continuously prepared by heat treatment in an air atmosphere at 240 ° C. to 260 ° C. for 34 minutes in a high temperature heat treatment furnace. A total amount of gas of 4000 Nm ³ / h discharged from the seal portion of the high-temperature furnace for producing the flame resistant yarn was drawn by the pump 2 and cooled to 30 ° C. in the temperature reducing chamber 3 through the pipe 1 as shown in FIG. The internal volume excluding the piping of the temperature reducing chamber 3 was 5.0 m ³ . The residence time at this time is about 4 seconds. The gas taken out in the temperature-reducing chamber 3 is heated in the heat exchanger 4 and heated at 350 ° C. in the electric heater 5, and then pre-treatment agent 6 filled with granular pure alumina of φ2.5 to 4 mm. The active metal was processed through a platinum honeycomb catalyst 7. The filling volume of the pretreatment agent 6 was 0.2 m ³ , the filling volume of the catalyst 7 was 0.16 m ^3, and both temperatures were maintained at 350 ° C. The contact time at this time is 0.2 seconds for the pretreatment agent and 0.1 seconds for the catalyst. The treated exhaust gas was cooled by the heat exchanger 4 and released into the atmosphere. The gas containing decomposition products from the fibers taken out from the pipe 1 contained a gaseous substance at room temperature containing hydrogen cyanide 150 ppm, ammonia 110 ppm, other carbon monoxide and carbon dioxide, and a tar-like substance at room temperature. As a result of operating once a day for 10 days, the concentration of gas collected from the catalyst outlet was 5 ppm or less for hydrogen cyanide, no ammonia was detected, and the displacement was stable. After 10 days, about 10 kg of tar-like substance was deposited in the temperature reducing chamber.

  In addition, the measurement of the density | concentration of the hydrogen cyanide shown to the above-mentioned and the postscript Example and comparative example and ammonia was all performed with the following method. About hydrogen cyanide, the density | concentration was measured according to the 4-pyridinecarboxylic acid-pyrazolone absorption photometry method prescribed | regulated to JISK0109 method. Regarding ammonia, gas was collected in a bag by a pump, and the concentration of the gas was measured by a gas detection tube method according to JIS K0804.

Example 2
In Example 1, the filling volume of the pretreatment agent 6 was 0.02 m ³ , and the other conditions were the same. The contact time at this time is 0.02 seconds. As a result, the gas concentration collected from the catalyst outlet was detected to be 5 ppm or less for both hydrogen cyanide and ammonia immediately after the start of operation. Then, it rose, and after 2 days, both reached about 20 ppm, and the decomposition capacity of the catalyst was slightly reduced.

Example 3
As shown in FIG. 4, two filling tanks were used, the pretreatment agent 6 was filled in one filling tank 10a and the catalyst 7 was filled in the other filling tank 10b, and electric heaters 5a and 5b were installed between the filling tanks. In addition, the bypass pipe 12 and the dampers 13 and 14 for the heat exchanger are installed as shown in the figure, and the opening amount of the dampers 13 and 14 is adjusted so that the gas flowing out of the catalyst 7 flows to the heat exchanger and the bypass. The distribution with the flow rate can be adjusted. Under the above apparatus, the opening of the dampers 13 and 14 and the output of the electric heaters 5a and 5b are set so that the temperature of the pretreatment agent 6 is 150 ° C. and the temperature of the catalyst 7 is 350 ° C. It carried out on the conditions similar to an example. As a result, the concentration of gas collected from the catalyst outlet was detected to be 5 ppm or less for both hydrogen cyanide and ammonia immediately after the start of operation. After that, it rose to about 20 ppm after one day, and the decomposition capacity of the catalyst was slightly reduced.

Example 4
In Example 1, the temperature reduction chamber volume was 1.2 m ³ , and the other conditions were the same. The residence time at this time is 1 second. As a result, the gas concentration collected from the catalyst outlet was detected to be 5 ppm or less for both hydrogen cyanide and ammonia immediately after the start of operation. After that, it increased to 12 ppm after 12 hours, and the decomposition ability of the catalyst was slightly reduced. Further, a small amount of tar adhered to the pretreatment agent.

Example 5
In Example 1, the temperature of the temperature reducing chamber was 100 ° C., and the other conditions were the same. As a result, the gas concentration collected from the catalyst outlet was detected to be 5 ppm or less for both hydrogen cyanide and ammonia immediately after the start of operation. After that, it increased, and after 12 hours, both reached 20 ppm or more, and the decomposition ability of the catalyst was slightly decreased. Further, tar was deposited on the pipe between the temperature reducing chamber and the heat exchanger.

Example 6
In Example 1, the filling volume of the catalyst 6 was 0.02 m ³ , and the other conditions were the same. The contact time at this time is 0.02 seconds. As a result, the gas concentration collected from the catalyst outlet was detected to be 5 ppm or less for both hydrogen cyanide and ammonia immediately after the start of operation. After that, it increased, and after 2 days, both reached 20 ppm or more, and the decomposition ability of the catalyst was slightly decreased.

Comparative Example 1
In Example 1, the filling tank 10 was not filled with the pretreatment agent 6, and the others were carried out under the same conditions. As a result, the gas concentration collected from the catalyst outlet was observed to be about 20 ppm immediately after the start of operation, but gradually increased, and after 2 days, both hydrogen cyanide and ammonia were detected to be 100 ppm or more, and the decomposition capacity of the catalyst was exhibited. lost.

Comparative Example 2
In Example 1, the temperature reducing chamber 3 was not used, and the other conditions were the same. As a result, the concentration of gas collected from the catalyst outlet was detected to be 100 ppm or more for both hydrogen cyanide and ammonia immediately after the start of operation, and the decomposition treatment ability of the catalyst was not exhibited. Further, tar was deposited on the pipe between the temperature reducing chamber and the heat exchanger.

Comparative Example 3
In Example 1, two filling tanks were used, the pretreatment agent 6 was filled in one filling tank, the catalyst 7 was filled in the other filling tank, and a cooling unit capable of setting the cooling temperature was installed between the two filling tanks. Under the apparatus as described above, the temperature of the pretreatment agent 6 was set to 350 ° C., the temperature of the catalyst 7 was set to 150 ° C., and the other conditions were the same as in the example. As a result, the concentration of gas collected from the catalyst outlet was detected to be 100 ppm or more for both hydrogen cyanide and ammonia immediately after the start of operation, and the decomposition treatment ability of the catalyst was not exhibited.

Comparative Example 4
In Example 1, the filling tank 10 was not filled with the catalyst, and the others were carried out under the same conditions. As a result, the concentration of gas collected from the catalyst outlet was detected to be 100 ppm or more for both hydrogen cyanide and ammonia immediately after the start of operation, and the decomposition treatment ability of the catalyst was not exhibited.

It is the schematic which shows an example of the waste gas processing apparatus which concerns on this invention. FIG. 2 is an enlarged view of the temperature reducing chamber portion of FIG. 1, (A) is a top view, and (B) is a cross-sectional view. FIG. 2 is an enlarged cross-sectional view of a pretreatment agent 6 and a catalyst 7 in FIG. 1. It is the schematic which shows an example different from FIG. 1 of an exhaust gas processing apparatus.

Explanation of symbols

1: Piping 2: Exhaust pump 3: Temperature reduction chamber 4: Heat exchanger 4a: Partition plate 4b: Cold water piping 4c: Filter 5: Electric heater 5a: Electric heater 5b: Electric heater 6: Pretreatment agent 6a: Wire net 6b: Wire mesh 6c: Wire mesh 7: Catalyst 8: Inlet 9: Discharge port 10: Filling tank 10a: Filling tank 10b: Filling tank 11: Insulation material 12: Bypass piping 13: Damper 14: Damper

Claims (13)

  An exhaust gas treatment method for treating exhaust gas discharged from a heat treatment furnace in a carbon fiber manufacturing process, wherein after removing the tar-like catalyst poison and the gaseous catalyst poison in the exhaust gas, the remaining gas is subjected to catalyst treatment.   The exhaust gas treatment method according to claim 1, wherein in the treatment of the exhaust gas, the exhaust gas is condensed through a temperature reducing chamber, and the exhaust gas is further brought into contact with a pretreatment agent.   The exhaust gas treatment method according to claim 1, wherein the catalyst poison that deactivates the catalyst by the chemical action is organic silicone and / or organic phosphorus.   The exhaust gas treatment method according to any one of claims 2 and 3, wherein a cooling temperature of the temperature reducing chamber is 50 ° C or lower and a residence time is 2 seconds or longer.   The exhaust gas treatment method according to any one of claims 2 to 4, wherein the pretreatment agent is alumina and / or ceramic.   The exhaust gas treatment method according to any one of claims 2 to 5, wherein the pretreatment agent is at least one selected from a honeycomb form, a foam form, and a granular form.   The exhaust gas treatment method according to any one of claims 2 to 6, wherein the exhaust gas is brought into contact with the pretreatment agent at a temperature of 200 ° C or higher and 400 ° C or lower.   The exhaust gas treatment method according to any one of claims 2 to 7, wherein a contact time of the exhaust gas with the pretreatment agent is 0.05 seconds or more.   The exhaust gas treatment method according to any one of claims 1 to 8, wherein the catalyst treatment is a decomposition treatment by catalytic oxidation with a catalyst.   The exhaust gas treatment method according to any one of claims 1 to 9, wherein the catalyst is at least one selected from honeycomb, foam, and granule.   The exhaust gas treatment method according to claim 1, wherein a gas is brought into contact with the catalyst at 200 ° C. or more and 400 ° C. or less.   The exhaust gas treatment method according to any one of claims 1 to 11, wherein a contact time of the exhaust gas with the catalyst is 0.05 seconds or more.   In an apparatus for treating exhaust gas discharged from a heat treatment furnace for producing carbon fiber, an exhaust gas treatment apparatus having means for removing tar-like catalyst poison and gas-like catalyst poison in the exhaust gas and means for catalytically treating the remaining gas .

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