JP2006026614A - Waste gas treating method and waste gas treating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste gas treating method capable of appropriately performing the thermal decomposition treatment of a desired waste gas such as PFC (perfluoro carbon) gas while prolonging the using life of a member for heating and reducing the loads of apparatus manufacture costs and maintenance costs, or the like. <P>SOLUTION: The waste gas treating method is provided with a waste gas thermal decomposition treatment process of introducing the waste gas into a chamber 1 and heating it by using the members 3A and 3B for heating. As the members 3a and 3B for heating, the ones for which an oxidation protective layer whose heat resistance is higher than the base of the members 3A and 3B for heating is formed on the surfaces are used. The method has a protective layer reproduction process of oxidizing the surface of the members 3A and 3B for heating by introducing oxygen or a gas containing the oxygen into the chamber 1 instead of the waste gas and heating the members 3A and 3B for heating and reproducing the oxidation protective layer degraded at the time of the thermal decomposition process when the thermal decomposition process is stopped. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas treatment method and an exhaust gas treatment apparatus capable of suitably performing a thermal decomposition treatment of various exhaust gases discharged along with semiconductor production, liquid crystal production, and the like.

For example, PFC gas (Per Fluoro Carbon) in a narrow sense such as CF ₄ , C ₂ F ₆ , C ₃ F ₆ , NF ₃ , SF ₆ , CHF _3, etc. is used for etching processing in semiconductor manufacturing processes and cleaning in CVD equipment. It is used for processing and is discharged as exhaust gas. However, since these gases have a large amount of infrared absorption and cause global warming, their release into the atmosphere is regulated.

  As a means for performing the exhaust gas detoxification treatment as described above, a heating member using an electric heater is provided in the exhaust gas introduction chamber, and the exhaust gas introduced into the chamber is used for the heating. There is a means for heating and pyrolyzing with a member (for example, see Patent Document 1). According to such a thermal decomposition method, compared with a so-called combustion decomposition method in which exhaust gas is burned and decomposed into carbon dioxide gas, water, and halides, the equipment cost, running cost, and maintenance cost can be kept considerably low. Is possible.

The above-mentioned PFC gas, NF _{3 and the} like are chemically stable, and the conditions for thermally decomposing them are preferably as high as possible, for example, about 800 to 1100 ° C. or higher than 1300 to 1400. It is necessary to heat to a high temperature of about ° C. In order to perform such heating, the surface temperature of the heating member provided in the chamber must also be as high as described above. On the other hand, when such high temperature heating is performed, if the electric heater is exposed to the atmosphere of the exhaust gas in a so-called naked state, the heater is greatly damaged, and disconnection or the like occurs in a short time. For this reason, for example, in Patent Document 1, a heating member having a structure in which a heater body is inserted into a ceramic pipe is used. However, according to such means, in order to set the surface of the ceramic pipe to a predetermined temperature, the heat generation temperature of the heater body needs to be heated to a higher temperature than that. Since the heat generation temperature of the main body is high, the service life of the heater main body is shortened. More specifically, there is a possibility that an unexpected disconnection may occur in the heater body. Furthermore, although the ceramic has a relatively high strength against high temperatures, the surface portion thereof is still damaged if it is used by being directly exposed to exhaust gas in a temperature range exceeding 1100 ° C., for example. Therefore, it is necessary to replace parts as appropriate, and there is a problem that the maintenance cost of the apparatus becomes expensive.

  The present applicant has previously proposed a method of thermally decomposing exhaust gas using an electromagnetic induction type heat generating action instead of an electric heater (see, for example, FIG. 3 of Patent Document 2). In this method, an electromagnetic induction coil is provided outside the exhaust gas introduction chamber, a metal heating member is provided inside the chamber, and the heating member is heated by electromagnetic induction. The exhaust gas is pyrolyzed.

  According to such a method, since the electromagnetic induction coil is located outside the chamber, the coil is not damaged due to the atmosphere in the chamber. Further, the heat generation by the electromagnetic induction method has higher heat generation efficiency than the case where the above-described electric heater is used. Furthermore, the electromagnetic induction effect provides a characteristic that the surface of the heating member generates heat intensively, and is therefore suitable for increasing the surface temperature of the heating member.

  However, even in the method using the electromagnetic induction method described above, it is necessary to use a member having excellent strength (heat resistance, corrosion resistance) at a high temperature as the heating member. However, in reality, it is difficult to find a metal that has excellent strength in a high temperature atmosphere of around 1100 ° C. or higher, and that satisfies the condition that the cost is relatively low and easy to obtain. Specific examples of metals that are relatively excellent in strength at high temperatures and relatively easily available include, for example, an Fe—Cr—Al alloy (Cr: 22%, Al: 4-6%), or Co added thereto. Mention may be made of Fe—Cr—Co—Al alloys. However, even if a heating member is formed using such an alloy as it is, it cannot be said that it can sufficiently withstand long-term use under the high temperature conditions described above, and heat damage is caused. Parts replacement must be done relatively frequently.

JP 11-188231 A JP 2002-153726 A

  The present invention has been conceived under such circumstances, such as extending the service life of the heating member, reducing the burden of manufacturing cost and maintenance cost of the apparatus, It is an object of the present invention to provide an exhaust gas treatment method and an exhaust gas treatment apparatus capable of appropriately performing desired pyrolysis treatment of exhaust gas.

  In order to solve the above problems, the present invention takes the following technical means.

  The exhaust gas treatment method provided by the first aspect of the present invention is a method for introducing an exhaust gas into an exhaust gas treatment chamber and using the heating member provided in the chamber or capable of generating heat to form the chamber. An exhaust gas treatment method having a thermal decomposition step for heating exhaust gas, wherein the heating member is formed with an oxidation protection layer having a higher heat resistance than the substrate of the heating member on the surface. In use, when the thermal decomposition step is stopped, instead of the exhaust gas, oxygen or a gas containing oxygen is introduced into the chamber and the heating member is caused to generate heat. It has a protective layer regeneration step of oxidizing the surface and regenerating the oxidation protective layer deteriorated during the thermal decomposition step.

  In the above configuration, the “gas containing oxygen” is a concept including “air”. “Heat generation” is not limited to so-called self-heating. For example, when a specific member is heated by another member capable of self-heating, heat is generated so that the specific member can heat exhaust gas. It is a concept that includes the case of diverging.

  According to the present invention, as the heating member, a member having an oxidation protective layer formed on the surface thereof and having improved heat resistance is used, so that the heating member is not formed with such an oxidation protective layer. Compared with the case where a member is used, the heat resistance of the heating member can be increased and thermal damage can be made difficult to occur. On the other hand, when the thermal decomposition step is performed, the oxidation protective layer deteriorates due to exposure to exhaust gas under high temperature conditions, but the oxidation protective layer can be regenerated when the thermal decomposition step is stopped. The heating member can be used for a long time thereafter. As a result, the service life of the heating member is extended and the heating member need not be frequently replaced.

  Furthermore, as an important effect, according to the present invention, the step of regenerating the oxidation protection layer is performed without removing the heating member to the outside. Further, since the heating for regenerating the oxidation protection layer is performed by the heat generated by the heating member, it is not necessary to separately provide a heating means dedicated to the regeneration of the oxidation protection layer. Therefore, the regeneration of the oxidation protection layer can be rationally performed easily and quickly and without using any special apparatus / equipment.

  In a preferred embodiment of the present invention, as the heating member, a member provided with an alloy part containing aluminum is used. In the protective layer regeneration step, alumina is used as an oxidation protective layer of the heating member. Form. Specific examples of the aluminum-containing alloy include the aforementioned Fe—Cr—Al alloy and Fe—Cr—Co—Al alloy. When the heating member is made of such an alloy, it is possible to form an alumina layer on the surface of the heating member by oxidizing the surface. As can be understood from this specific example, according to the above configuration, an alumina layer having excellent heat resistance and corrosion resistance can be obtained while using a relatively inexpensive and easily available alloy material as a material for the heating member. It can be formed and is excellent in practicality.

  In a preferred embodiment of the present invention, the electrical resistance of the surface portion of the heating member, the amount of pyrolysis treatment of the exhaust gas, or the time or frequency of the pyrolysis treatment of the exhaust gas is measured, and based on this measured value It further has the process of judging the deterioration degree of the said oxidation protective layer. According to such a configuration, the regeneration process of the oxidation protection layer can be performed at an appropriate timing. For example, the regeneration process of the oxidation protection layer is wasted although the oxidation protection layer is hardly deteriorated. In practice, or conversely, it is adequately avoided that the oxidation protection layer is left to stand in spite of the considerable deterioration of the oxidation protection layer.

  The exhaust gas treatment apparatus provided by the second aspect of the present invention includes a chamber for introducing exhaust gas to be treated, and is provided in or forms the chamber. And a heating member capable of generating heat for heating and pyrolyzing the introduced exhaust gas, wherein the exhaust gas is replaced with the exhaust gas when the thermal decomposition process is stopped. And an introduction gas switching means capable of introducing oxygen or a gas containing oxygen into the chamber, and the heating member generates heat in a state where oxygen or a gas containing oxygen is introduced into the chamber. Thus, an oxidation protective layer having higher heat resistance than the substrate of the heating member can be formed on the surface of the heating member.

  According to such a configuration, the exhaust gas is thermally decomposed by introducing the exhaust gas into the chamber and heated, and the surface of the heating member is oxidized and protected by introducing and heating oxygen or a gas containing oxygen in the chamber. The regeneration process of the oxidation protective layer forming the layer can be selectively performed, and the exhaust gas treatment method provided by the first aspect of the present invention can be appropriately performed. Therefore, the same effect as described for the exhaust gas treatment method provided by the first aspect of the present invention can be obtained.

  In a preferred embodiment of the present invention, the chamber is connected to an exhaust gas supply pipe for supplying the exhaust gas toward the chamber, and the introduction gas switching means is provided from the outside to the inside of the chamber. An air inlet for introducing air; and at least one valve capable of switching between air introduction from the air inlet into the chamber and exhaust gas introduction from the exhaust gas supply pipe into the chamber. . According to such a configuration, it is possible to appropriately switch between introduction of exhaust gas into the chamber and introduction of air as a gas containing oxygen.

  In a preferred embodiment of the present invention, there is further provided a measuring instrument for measuring the electrical resistance of the surface portion of the heating member, the amount of pyrolysis treatment of the exhaust gas, or the time or number of times of the pyrolysis treatment of the exhaust gas. . According to such a configuration, it is possible to appropriately determine the deterioration degree of the oxidation protection layer on the surface of the heating member by measurement using the measuring instrument, and to execute the regeneration process of the oxidation protection layer at an appropriate timing. It becomes possible.

  In a preferred embodiment of the present invention, an electromagnetic induction coil provided outside the chamber is provided, and at least a part of the heating member generates electromagnetic induction heat by energization of the coil. Has been. If such a heat generation method using electromagnetic induction is employed, the heat generation efficiency is high, and the surface of the heating member can be efficiently heated to a desired high temperature. The heating member may be made entirely of metal, for example, and the structure of the heating member itself can be simplified, so that the manufacturing cost of the apparatus can be further reduced. Of course, since the coil is provided outside the chamber and does not come into direct contact with the exhaust gas in a high temperature atmosphere, the coil is not easily damaged. However, as will be described later, in the present invention, for example, an electric heater type can be used as the heating member instead of the electromagnetic induction type.

  In a preferred embodiment of the present invention, the heating member includes a cylindrical first heating member and a cylindrical second heating member disposed inward of the first heating member. The exhaust gas introduced into the chamber passes through the gap between the first and second heating members in the axial direction thereof, and then enters the inner side of the second heating member. And is configured to pass through the second heating member in the axial direction. According to such a configuration, when the exhaust gas passes through the gap between the first and second heating members, the exhaust gas is efficiently heated, and the thermal decomposition treatment is suitably performed.

  In a preferred embodiment of the present invention, a spiral member is disposed in the gap, and at least a part of the exhaust gas advances spirally in the gap along the spiral member. It is configured as follows. According to such a configuration, the travel distance of the exhaust gas becomes longer when the exhaust gas passes through the gap in a spiral manner than when the exhaust gas passes linearly. It is suitable for enhancing the thermal decomposition treatment capacity.

  In a preferred embodiment of the present invention, the second heating member is provided with a member that inhibits the exhaust gas from going straight in the axial direction of the second heating member. Yes. According to such a configuration, it is possible to take a longer heating time when the exhaust gas passes through the second heating member, and it is more preferable to increase the thermal decomposition processing capability.

  In a preferred embodiment of the present invention, both end openings are provided with a tube body having an exhaust gas inlet and an exhaust port, and the inside of the tube body is the chamber, while the tube body is The heating member is formed by at least partly being capable of generating heat. According to such a configuration, since the exhaust gas is introduced into the inside of the tubular body as the heating member and heated, highly efficient heating of the exhaust gas becomes possible while the entire structure is extremely simplified. If a spiral part or a zigzag meandering part is formed in the tube body, the time for exhaust gas to pass through the tube body is lengthened and the heating efficiency is further increased while suppressing the overall enlargement. It is possible.

In a preferred embodiment of the present invention, a cylindrical wall portion surrounding the chamber and capable of generating heat is provided, and the exhaust gas swirls along the inner periphery of the cylindrical wall portion in the chamber. It is set as the structure introduce | transduced into the said chamber so that it may become a flow. According to such a configuration, the degree of contact between the exhaust gas and the inner peripheral surface of the cylindrical wall portion is increased, which is suitable for increasing the heating efficiency. Some exhaust gases are solidified by thermal oxidative decomposition and become powder (for example, SiF ₄ ). However, the powder is separated from the inner peripheral surface of the cylindrical wall portion by the action of the swirling flow of the exhaust gas. In addition, it can be expected to prevent deposits from adhering.

  Other features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  1 and 2 show an embodiment of an exhaust gas treatment apparatus according to the present invention. As clearly shown in FIG. 1, the exhaust gas treatment apparatus A of this embodiment includes a chamber 1 into which exhaust gas is introduced, an electromagnetic induction coil 2 disposed outside the chamber 1, and an exhaust gas introduction device. A pair of pipes 5 and first and second heating members 3A and 3B disposed in the chamber 1 are provided.

  The chamber 1 is formed as a space portion surrounded by a peripheral wall portion 10 made of a ceramic cylinder, and an upper member 11A and a lower member 11B partially fitted to the upper and lower portions of the peripheral wall portion 10. The material of the upper member 11A and the lower member 11B will be described later. A base tube body 12 is connected to the lower part of the lower member 11B, so that the exhaust gas thermally decomposed in the chamber 1 passes through the lower opening 12a of the base tube body 12 and is discharged below it. It has become. Although not shown in the drawing, a water reservoir is provided below the lower opening 12a, and the exhaust gas is cooled by being passed through the water in the water reservoir, and depending on the components, To be caught. The upper member 11A is detachably held by the ring bodies 11C and 11D. When the upper member 11A is removed from the ring bodies 11C and 11D, the upper portion of the chamber 1 is opened, and the first and second heating members 3A, 3B, etc. can be taken out and attached from the outside. As will be described later, the upper member 11A has, for example, an opening 16a for allowing the measuring instrument 4 for measuring the electrical resistance of the surface of the first heating member 3A to enter and leave, and for closing the opening 16a. The lid member 16b is provided. The ring bodies 11C and 11D and the upper flange 12b of the base tube body 12 are connected via a plurality of shaft bodies 13, thereby ensuring the assembly of a plurality of members forming the chamber 1. Yes.

The pair of pipes 5 is for introducing exhaust gas such as PFC gas and NF ₃ into the chamber 1 from, for example, a semiconductor manufacturing facility (not shown). Although not shown in the drawings, the pair of pipes 5 is a part obtained by branching one pipe connected to the exhaust port of the semiconductor manufacturing facility into two parts. It is connected to a pair of opening holes 14 provided in the lower member 11B. The exhaust gas passes through the pair of opening holes 14 and is supplied into the chamber 1. Thus, if the exhaust gas is introduced into the chamber 1 from a plurality of locations, it is possible to avoid the exhaust gas being introduced to a part of the chamber 1 in an uneven manner. Of course, the introduction of the exhaust gas into the chamber 1 may be performed through only one pipe 5 unlike the present embodiment, or may be performed through more than two pipes 5. You may be made to do.

  Each pipe 5 is provided with an on-off valve V1 capable of introducing exhaust gas into the chamber 1 and switching its stop. A pipe portion 51 having an air introduction port 50 is branched and connected to a portion closer to the chamber 1 than the on-off valve V1, and the on-off valve V2 is provided in the pipe portion 51. Therefore, when the on-off valve V1 is closed and the on-off valve V2 is opened, air can be introduced into the chamber 1 instead of the exhaust gas. A blower intake pipe (not shown) is connected to the lower opening 12 a of the base tube body 12. When the air is introduced into the chamber 1, negative pressure is generated in the chamber 1 by driving the blower. This is done by the action that occurs.

  The coil 2 is for heating the first and second heating members 3 </ b> A and 3 </ b> B, and is provided so as to surround the outer periphery of the peripheral wall portion 10 of the chamber 1. The first heating member 3A generates heat due to electromagnetic induction when the coil 2 is energized, while the second heating member 3B is located inside the first heating member 3A. Therefore, it is heated mainly by radiant heat from the first heating member 3A. The coil 2 is formed of, for example, a metal pipe made of copper or the like having a spiral portion, and the cooling water circulates inside the coil 2 and serves as a cooler. Therefore, the coil 2 also exhibits a function of suppressing the ambient temperature from increasing due to the heat in the chamber 1 being radiated to the outside. As means for further enhancing such a function, a heat insulating material (not shown) may be provided between the coil 2 and the peripheral wall portion 10. The coil 2 is connected to a high frequency power supply 20 by wiring. Preferably, the output and frequency of the high frequency power supply 20 are variable.

  The coil 2 is supported by a plurality of stays 21. Each stay 21 has a bar shape extending in the vertical direction, and an upper portion thereof is attached to the ring body 11D. As shown in FIG. 5, a plurality of recesses 21 a are formed on one side surface of the stay 21. As shown in FIG. 4, a plurality of loop portions of a spiral portion of the coil 2 are fitted in the plurality of recesses 21a. By this fitting operation, each loop portion of the spiral portion of the coil 2 can be fixed at a desired position. Unlike the present embodiment, for example, if the upper part of the coil 2 is gripped and simply supported by being suspended, the coil 2 extends downward due to its own weight, and a plurality of loop portions of the spiral portion have an inappropriate pitch. However, according to the present embodiment, such a fear can be solved.

The first and second heating members 3A and 3B are members for heating the exhaust gas, for example, made of Fe—Cr—Al alloy (Cr is 5 to 25%, Al is 2 to 8%), or this It is made of an Fe—Cr—Co—Al alloy with Co added to. However, as shown in FIG. 3, an alumina (Al ₂ O ₃ ) layer 30 as an oxidation protection layer is formed on the entire surface of the first and second heating members 3A and 3B. The alumina layer 30 is formed by oxidizing the surfaces of the first and second heating members 3A and 3B, and details thereof will be described later.

  The first heating member 3A has a cylindrical shape having an upper wall portion 31, and is supported by the lower member 11B in an upright posture. Between the peripheral wall portion of the first heating member 3 </ b> A and the peripheral wall portion 10 of the chamber 1, a ceramic auxiliary cylinder 39 having an opening 39 a at the top is provided. The exhaust gas introduced into the chamber 1 flows upward through the gap 19a between the auxiliary cylinder 39 and the peripheral wall portion 10 and then passes through the opening 39a so as to pass through the peripheral wall of the auxiliary cylinder 39 and the first heating member 3A. It flows through the gap 19b.

  The second heating member 3B has a cylindrical shape with both upper and lower ends opened, and is supported in an upright posture by the lower member 11B in the same manner as the first heating member 3A. However, the second heating member 3B is located inward of the first heating member 3A, and a gap 32 is formed between them. One or more openings 33 are formed in the vicinity of the lower end of the first heating member 3A. The exhaust gas that has traveled to the lower portion of the gap 19b passes through the opening 33 and flows into the gap 32, and then travels upward through the gap 32 and then passes through the upper opening of the second heating member 3B. Into the heating member 3B, and then proceeds downward, passes through the opening 17 of the lower member 11B, and reaches the lower opening 12a of the base tubular body 12.

  Spiral coils 40 and 41 are arranged inside the gap 32 and the second heating member 3B. The spiral coils 40 and 41 are made of the same material as the first and second heating members 3A and 3B, for example. An alumina layer (not shown) similar to the alumina layer 31 shown in FIG. 3 is formed over substantially the entire surface of the helical coils 40 and 41. Further, the upper member 11A and the lower member 11B constituting the chamber 1 are preferably made of the same material as that of the helical coils 40 and 41 and the first and second heating members 3A and 3B. An alumina layer (not shown) is formed on the facing portion.

  The outer periphery and the inner periphery of the spiral coil 40 are arranged so that no large gap is generated between the inner surface of the peripheral wall portion of the first heating member 3A and the outer surface of the peripheral wall portion of the second heating member 3B. . According to such a configuration, as shown in FIG. 6, the exhaust gas flowing into the lower portion of the gap 32 spirals around the peripheral wall portion of the second heating member 3 </ b> B along the spiral coil 40. It will progress upward. Therefore, the heating time of the exhaust gas is lengthened, which helps to increase the heating efficiency. In addition, if the spiral coil 40 is provided so as to be in contact with each of the first and second heating members 3A and 3B, when the first heating member 3A generates heat due to electromagnetic induction, Since it is transmitted to the second heating member 3B, it is more preferable that the second heating part 3B generates heat to a high temperature. Unlike the spiral coil 40, the spiral coil 41 does not exhibit the action of causing the exhaust gas to advance in a spiral shape, but as described later, it also helps increase the heating efficiency of the exhaust gas.

  Next, an example of an exhaust gas treatment method using the above-described exhaust gas treatment apparatus A will be described.

  First, in order to thermally decompose the exhaust gas, the exhaust gas is introduced into the chamber 1 from the pair of pipes 5 and a high-frequency current is passed through the coil 2 to cause the first heating member 3A to generate heat by electromagnetic induction. Then, due to the radiant heat and the like, the second heating member 3B and the helical coils 40 and 41 are also heated to a high temperature. The heat generation temperature on the surface of the first heating member 3A is, for example, 800 to 1100 ° C, but may be about 1300 to 1400 ° C depending on the type of exhaust gas. When the surface of the first heating member 3A generates heat to 1400 ° C., for example, the temperature of the surface of the second heating member 3B is slightly lower, for example, about 1300 ° C.

  As described above, the exhaust gas introduced into the chamber 1 passes through the gap 19a and the opening 39a and flows downward through the gap 19b. At that time, the exhaust gas is heated by contacting the outward surface of the first heating member 3A, and is also heated by radiant heat. Since the surface of the first heating member 3A is the portion that generates heat at the highest temperature, according to the configuration of the present embodiment in which the exhaust gas is circulated along the gap 19b on the outer periphery of the surface, the heating of the exhaust gas is performed. High efficiency. If a member similar to the spiral coil 40 is inserted into the gap 19b so that the exhaust gas advances in a spiral shape, the heating efficiency of the exhaust gas can be further increased. It may be adopted.

The exhaust gas that has traveled to the lower end of the gap 19b then passes through the opening 39a, travels through the clearance 32 between the first and second heating members 3A, 3B, and travels inside the second heating member 3B. To do. When the exhaust gas advances through the gap 32, as described with reference to FIG. 6, the exhaust gas advances spirally along the spiral coil 40, so that the heating time can be increased. Further, since the helical coil 40 is also at a high temperature, the heating efficiency of the exhaust gas is further improved. On the other hand, since the spiral coil 41 has a high temperature in the second heating member 3B, the spiral coil 41 is also useful for increasing the heating efficiency of the exhaust gas. The exhaust gas is thermally decomposed by heating in the course of the progression of the exhaust gas. For example, when the exhaust gas is C ₂ F ₆ , 2C ₂ F ₆ + 3O ₂ + 6H ₂ O → 4CO ₂ + 12HF.

  In the above-described pyrolysis process of exhaust gas, the first and second heating members 3A and 3B are at a high temperature in a state where they are exposed to the exhaust gas atmosphere. In contrast, an alumina layer 30 is formed on the surfaces of the first and second heating members 3A and 3B, and the alumina layer 30 is formed of the first and second heating members 3A and 3B. Since it has better heat resistance and corrosion resistance than the base portion, it will not be damaged significantly in a short time. Further, the presence of the alumina layer 30 protects the base portion. However, if the alumina layer 30 continues to be exposed to the exhaust gas atmosphere at a high temperature of 1000 to 1400 ° C. during the above-described thermal decomposition step, it is gradually damaged and deteriorated. The same applies to the alumina layers of the helical coils 40 and 41.

  Next, when the alumina layer 30 deteriorates as described above, a process for regenerating the alumina layer 30 is executed. In order to execute this process, first, the introduction of exhaust gas into the chamber 1 is stopped, and air is introduced into the chamber 1 from the air inlet 50. Further, along with this, the coil 2 is energized to cause the first heating member 3A to generate heat by electromagnetic induction at, for example, about 1000 to 1200 ° C. The second heating member 3B is heated using radiant heat from the first heating member 3A. Then, the surfaces of the first and second heating members 3A and 3B are oxidized, and the alumina layer 30 is regenerated (heating time is, for example, about 10 hours). Specifically, the alumina layer 30 is formed by combining aluminum in the alloy components of the first and second heating members 3A and 3B with oxygen in the air. If the alumina layer 30 is regenerated in this manner, the heat resistance and corrosion resistance of the surfaces of the first and second heating members 3A and 3B are enhanced, which makes it suitable for the thermal decomposition treatment of the exhaust gas thereafter. It is possible to prevent the bases of the first and second heating members 3A and 3B from receiving great damage. As a result, the service life of the first and second heating members 3A and 3B can be extended. The portions of the spiral coils 40 and 41 and the upper member 11A and the lower member 11B facing the chamber 1 can also be regenerated with an alumina layer on the surfaces thereof as described above.

  The regeneration process of the alumina layer 30 described above is performed after the introduction switching between the exhaust gas and the air is performed without taking out the first and second heating members 3A and 3B to the outside of the chamber 1, and then the first heating member. Since the operation is performed by heating 3A, the operation is very simple and the workability is good. Further, the heating for regenerating the alumina layer 30 is performed by energizing the coil 2 in the same manner as in the pyrolysis process of the exhaust gas, and a dedicated heating device for regenerating the alumina layer 30 is separately provided. I don't need it.

  The exhaust gas supply from the semiconductor manufacturing facility to the exhaust gas processing apparatus A is stopped, for example, at the time of maintenance of the semiconductor manufacturing facility or the introduction or removal of a product to be manufactured. The above-described regeneration treatment of the alumina layer 30 may be performed at an appropriate time when such exhaust gas supply is stopped.

  The timing for performing the regeneration treatment of the alumina layer 30 can be determined by measuring the electrical resistance of the surface of the first heating member 3A, for example, as described below. That is, in the state where the supply of exhaust gas into the chamber 1 is stopped, first, as shown in FIG. 7, the lid member 16b at the top of the chamber 1 is removed, and the opening 16a is opened. Next, the electrical resistance measuring instrument 4 is caused to enter the chamber 1 through the opening 16a. The measuring instrument 4 is provided with, for example, a pair or a plurality of pairs of energizing probes 40 at its tip, and these probes 40 are brought into contact with the surface of the first heating member 3A so that the contact points are not contacted. Measure the electrical resistance. The alumina layer 30 is non-conductive, whereas the base Fe—Cr—Al alloy or Fe—Cr—Co—Al alloy has conductivity. Therefore, it is possible to easily determine whether the alumina layer 30 remains on the surface of the first heating member 3A based on the measured value of the electrical resistance or the presence / absence of conduction. As a result of the above measurement, if the contact position between the probes 40 on the surface of the first heating member 3A is in a conductive state, it can be determined that the alumina layer 30 is severely deteriorated. May be started.

  Preferably, the exhaust gas treatment apparatus A includes the above-described measuring instrument 4 for electric resistance, and this measuring instrument 4 is located outside the chamber 1 so as not to receive thermal damage in normal times. . And the drive device (not shown), such as a motor and a cylinder, drives as needed, and the measuring instrument 4 enters the chamber 1 and measures the electrical resistance of the surface of the first heating member 3A. It is said that. According to such a configuration, there is no need to manually measure the electrical resistance, which is convenient.

  However, in the present invention, the means for determining the deterioration of the alumina layer 30 is not limited to the measurement of the electric resistance, and a means different from the above can be adopted as described below.

  That is, the alumina layer 30 is deteriorated as the treatment of exhaust gas is continuously performed and the amount of treatment increases. Therefore, for example, as shown by the phantom line in FIG. 1, a flow meter 4A is attached to a piping path for introducing exhaust gas into the chamber 1, and the flow rate (exhaust gas treatment amount) measured by the flow meter 4A is previously set. When the set value is reached, it may be determined that the alumina layer 30 is in a certain deterioration state at that time. The above value can be determined, for example, by performing a test operation of the exhaust gas treatment apparatus A and examining in advance the relationship between the flow rate of the exhaust gas and the degree of deterioration of the alumina layer 30. Further, instead of the above-described exhaust gas flow rate, the time or number of times of pyrolysis treatment of exhaust gas is measured, and when this measured value becomes a preset value, the alumina layer 30 is in a certain deterioration state at that time. It doesn't matter if you decide that it is something. As the exhaust gas treatment time becomes longer or the number of times of a certain exhaust gas treatment increases, the deterioration of the alumina layer 30 progresses. Therefore, even if the exhaust gas treatment time and the number of times are based, the degree of deterioration of the alumina layer 30 Can be determined appropriately.

  In the above-described embodiment, the first and second heating members 3A and 3B are formed with the alumina layer 30 formed from the beginning. May be used. More specifically, as the first and second heating members 3A and 3B, those that do not have the alumina layer 30 are initially used, and before the exhaust gas treatment is actually started, the first and second members 3A and 3B are used. The alumina layer 30 may be formed by raising the temperature of the heating members 3A and 3B to a high temperature. According to such means, it is not necessary to carry out the forming process of the alumina layer 30 before the first and second heating members 3A and 3B are incorporated in the chamber 1, thereby reducing the manufacturing cost. Preferred.

  FIG. 8 shows another embodiment of the exhaust gas treatment apparatus according to the present invention. In the figure, the same or similar elements as those of the above embodiment are denoted by the same reference numerals as those of the above embodiment.

  The exhaust gas treatment apparatus Aa shown in FIG. 8 is configured to be able to perform a detoxification process without mixing two types of exhaust gases with each other. In the chamber 1, a cylinder that generates heat by the electromagnetic induction action of the coil 2. The first to third heating members 3C to 3E are provided. These first to third heating members 3C to 3E are similar to the first and second heating members 3A and 3B of the above embodiment, for example, an Fe—Cr—Al alloy having an alumina layer formed on the surface thereof. Or it is a product made from a Fe-Cr-Co-Al alloy. Since the first heating member 3C is located on the outermost side near the coil 2, the first heating member 3C can generate heat at a high temperature by energizing the coil 2, whereas the second and third heating members 3D and 3E Heated by the first heating member 3C.

  The first exhaust gas introduced into the chamber 1 from the pipe 5 flows through the gap between the peripheral wall portion 10 of the chamber 1 and the first heating member 3C as indicated by an arrow Na, and then the first and first The gap between the two heating members 3 </ b> C and 3 </ b> D flows downward and is discharged below the chamber 1. On the other hand, the second exhaust gas is supplied from the pipe 70 to the upper part in the third heating member 3E, and flows downward from the upper part of the third heating member 3E as indicated by an arrow Nb. And it is discharged | emitted below the chamber 1 from the lower end opening part. Air is supplied from the pipe 71 to the gap between the second and third heating members 3D and 3E, and this air is supplied to the plurality of peripheral walls of the third heating member 3E. It passes through the air circulation hole 39 and circulates inside the third heating member 3E.

The exhaust gas treatment apparatus Aa of the present embodiment is used, for example, to thermally decompose exhaust gas discharged from a single wafer type CVD apparatus, and cleaning exhaust gas such as PFC gas and NF ₃ supplied from the CVD apparatus is The first exhaust gas is introduced into the chamber 1 from the pipe 5. This cleaning exhaust gas is heated and thermally decomposed by the first and second heating members 3C and 3D when flowing along the path indicated by the arrow Na described above. On the other hand, deposit exhaust gas such as SiF ₄ supplied from the CVD apparatus is introduced into the third heating member 3E from the pipe 70 as the second exhaust gas, and is heated by the third heating member 3E. It is oxidatively decomposed. When the deposit exhaust gas is, for example, SiF ₄ , SiO ₂ powder is generated by the oxidative decomposition. This powder easily adheres and accumulates on the inner peripheral wall surface of the third heating member 3E, but in the present embodiment, air blows out from the plurality of air circulation holes 39 into the third heating member 3E, and SiO ₂ It is designed to drop the powder. Therefore, there is also an advantage that the above-described deposition deposition of SiO ₂ powder is suitably prevented. In general, the oxidative decomposition temperature of the deposit exhaust gas is lower than the thermal decomposition temperature of the cleaning exhaust gas. In this exhaust gas treatment apparatus Aa, the temperature of the third heating member 3E is the first and Since the temperature is lower than that of the second heating members 3C and 3D, it is convenient in terms of setting these heating temperatures. Of course, in this exhaust gas treatment apparatus Aa, when the alumina layers on the surfaces of the first to third heating members 3C to 3E deteriorate due to the thermal decomposition treatment of the exhaust gas, After the introduction is stopped, the alumina layer can be re-formed by introducing air into the chamber 1 and raising the temperature of the first to third heating members 3C to 3E to a high temperature.

  As understood from the present embodiment, the exhaust gas treatment apparatus according to the present invention can be configured as an apparatus capable of thermally decomposing not only one type but also a plurality of types of exhaust gas. The exhaust gas treatment apparatus according to the present invention is suitable for the thermal decomposition of various exhaust gases generated in the semiconductor manufacturing process and the liquid crystal manufacturing process, but is also used for the pyrolysis of gases discharged in a different field. Of course, this is possible.

  The present invention is not limited to the contents of the above-described embodiment. The specific contents of each step of the exhaust gas treatment method according to the present invention can be variously changed. Similarly, the specific configuration of each part of the exhaust gas treatment apparatus according to the present invention can be varied in design in various ways.

  For example, instead of the helical coil 41 of the exhaust gas treatment apparatus A shown in FIG. 1, a configuration using a plurality of conical helical coils 42 as shown in FIG. According to such a configuration, since the diameter of each part of the conical spiral coil 42 is not constant, the contact area with the exhaust gas flowing through the second heating member 3B is increased, and the diameter shown in FIG. It is possible to further increase the heating efficiency of the exhaust gas than in the case of the spiral coil 41 having a constant. In addition, when using the helical coils 40-42, although it is preferable to make it from the material which can reproduce | regenerate an oxidation protective layer on the surface, this invention is not limited to this.

  10 and 11 schematically show another example of the exhaust gas treatment apparatus according to the present invention.

  The exhaust gas treatment apparatus Ab shown in FIG. 10 has a configuration in which a tubular body 8 having a spiral portion is provided inside the coil 2A for electromagnetic induction. The inside of the pipe body 8 corresponds to a chamber 1A for introducing exhaust gas. The upper end opening of the pipe body 8 is an exhaust gas inlet 80a, and the lower end opening is an exhaust gas outlet 80b. . The tube body 8 is made of, for example, a Fe—Cr—Al alloy or a Fe—Cr—Co—Al alloy, like the first and second heating elements 3A and 3B of the previous embodiment, and its surface (inner surface portion). An alumina layer (not shown) is formed in the entire region including Although not shown in the drawing, a pipe provided with a valve capable of switching between introduction of exhaust gas and introduction of air into the chamber 1A in the pipe body 8 is connected to the introduction port 80a.

  According to the configuration of the exhaust gas treatment apparatus Ab, when the exhaust gas is introduced into the chamber 1A and the coil 8A is energized to cause the tube 8 to generate heat by electromagnetic induction, the exhaust gas is efficiently contained in the tube 8. Heated and pyrolyzed. If exhaust gas is directly introduced into the tube 8 that has generated heat in this way, the configuration of the entire apparatus can be greatly simplified. Further, since the tubular body 8 is formed with a spiral portion, it is possible to sufficiently heat the exhaust gas by taking a long heating time of the exhaust gas while suppressing the entire apparatus from becoming large and bulky. In FIG. 10, a gap is formed between the spiral portions of the tube body 8. However, if the pitch of the spiral portions is reduced so that this gap is not formed, the overall size is reduced and the heating time is increased. It is possible to further promote time. When the alumina layer on the inner surface of the tubular body 8 is deteriorated, the regeneration of the alumina layer can be appropriately performed by introducing air into the tubular body 8 to generate heat. .

  As understood from the above embodiment, in the present invention, a tubular body is used, and the inside of the tubular body may be used as it is as a chamber for exhaust gas treatment. Further, the heating member referred to in the present invention may not be provided inside the chamber, and the member forming the chamber itself may be the heating member. When a tubular body is used, for example, even when the whole or a part of the tubular body is meandered in a zigzag shape, the enlargement of the entire body is suppressed in the same manner as when a helical portion is formed in the tubular body. However, it is possible to increase the heating time of the exhaust gas. However, in the present invention, instead of such a configuration, the tube forming the chamber may be a straight tube.

  The exhaust gas treatment apparatus Ac shown in FIG. 11 has a cylindrical wall portion 75 surrounding the periphery of the exhaust gas introduction chamber 1B inside the electromagnetic induction coil 2A (not shown in FIG. 11B). Is provided. The cylindrical wall 75 has a portion whose inner peripheral surface is inclined so that the inner diameter becomes smaller toward the lower end, and the upper opening is closed by a lid member 76. An upper part of the cylindrical wall part 75 is provided with an introduction port 77 for introducing exhaust gas into the chamber 1B, and the bottom opening of the cylindrical wall part 75 serves as an exhaust gas exhaust port 75a. ing. The cylindrical wall portion 75 and the lid member 76 are made of, for example, a Fe—Cr—Al alloy or a Fe—Cr—Co—Al alloy, and an alumina layer (not shown) is formed on the surface thereof. The pipe body 78 connected to the introduction port 77 extends in the tangential direction of the cylindrical wall portion 75 or a direction close thereto, and the exhaust gas is introduced into the chamber 1B from the introduction port 77 through the pipe body 78. Then, the exhaust gas is configured to be a swirling flow along the inner peripheral wall surface of the cylindrical wall portion 75.

In the exhaust gas treatment apparatus Ac configured as described above, the exhaust gas introduced into the chamber 1B gradually descends while turning along the inner peripheral wall surface of the cylindrical wall portion 75, and is discharged from the discharge port 75a. In this process, the exhaust gas contacts the inner peripheral surface of the cylindrical wall portion 75 with a large degree, and is efficiently heated and thermally decomposed. In addition, when the exhaust gas is, for example, SiF ₄ , as described above, SiO ₂ powder is generated by oxidative decomposition, but the swirling flow also exerts an action of dropping this powder downward. Therefore, the possibility that SiO ₂ powder adheres and accumulates on the cylindrical wall portion 75 can be eliminated. The regeneration process when the alumina layer of the cylindrical wall portion 75 and the lid member 76 is deteriorated is to introduce air into the chamber 1B and cause the cylindrical wall portion 75 to generate electromagnetic induction heat, as in the embodiment described above. It is possible to carry out appropriately.

  In the present invention, from the viewpoint of heat generation efficiency and ease of maintenance, it is preferable to heat the heating member by an electromagnetic induction method, but the present invention is not limited to this. The heating member in the present invention may be configured as a so-called electric heater type. More specifically, as the heating member in the present invention, for example, an electrothermal heater main body is accommodated in a case made of Fe—Cr—Al alloy or Fe—Cr—Co—Al alloy, and the surface of this case It can be configured such that an alumina layer is formed on the surface. In this heating member, the alumina layer on the surface of the case is excellent in heat resistance, and when the alumina layer deteriorates, it can be used for a long time by regenerating it.

  In the present invention, as shown in FIG. 12, an electric heater 79 is provided outside the cylindrical wall portion 75, and the cylindrical wall portion 75 is heated by the electric heater 79. It can also be configured such that the wall 75 can dissipate heat and heat the exhaust gas in the chamber 1B. According to such a configuration, since the electrothermal heater 79 is provided outside the chamber 1B and does not directly contact the exhaust gas, the service life can be made relatively long.

  The material of the heating member is not limited to the above-described Fe—Cr—Al alloy or Fe—Cr—Co—Al alloy, and various materials can be used as long as the material can achieve the intended effect of the present invention. It is possible. For example, Fe-Cr-Al alloy (Al is 2 to 10%), Ni-Al alloy (Ni and Al are more preferably 50% heavy), Ni-Cr-Al alloy (Al is 2 to 50%) Even if it is a Co—Al alloy (Al is 2 to 50%) or a Ni—Co—Al alloy (Al is 2 to 50%), it can be heated and oxidized to make the surface heat resistant such as an alumina layer. An excellent oxidation protective layer can be formed. Of course, the oxidation protective layer referred to in the present invention is not limited to the alumina layer.

  When the above-described oxidation protection layer is formed, air may be introduced into the chamber, but it goes without saying that oxygen may be introduced instead of air. The coil for electromagnetic induction does not have to be of the water cooling type as in the above-described embodiment.

  The introduction gas switching means referred to in the present invention is not limited to the configuration using two on-off valves V1 and V2 as shown in FIG. 1, for example, and is introduced into the chamber by one valve (for example, a three-way valve). It can also be set as the structure which made gas changeable. Further, such switching of the introduced gas may be performed by either remote operation or manual operation.

It is sectional drawing which shows an example of the waste gas processing apparatus which concerns on this invention. It is II-II sectional drawing of FIG. FIG. 2 is a cross-sectional view schematically showing alumina layers on the surfaces of first and second heating members provided in the exhaust gas treatment apparatus shown in FIG. FIG. 2 is a cross-sectional view of a main part of an electromagnetic induction coil provided in the exhaust gas treatment apparatus shown in FIG. FIG. 5 is a perspective view of a main part of a stay that supports the electromagnetic induction coil shown in FIG. 4; FIG. 3 is a main part explanatory view showing a state in which exhaust gas travels around a second heating member of the exhaust gas treatment apparatus shown in FIG. 1. FIG. 2 is a main part cross-sectional view showing a state in which the electrical resistance of the surface of the first heating member of the exhaust gas treatment apparatus shown in FIG. It is a schematic sectional drawing which shows the other example of the waste gas processing apparatus which concerns on this invention. It is principal part sectional drawing which shows the other example of the helical coil for assisting a heating. It is sectional drawing which shows typically the other example of the waste gas processing apparatus which concerns on this invention. (A) is sectional drawing which shows typically the other example of the waste gas processing apparatus which concerns on this invention, (b) is principal part plane sectional drawing of (a). It is principal part sectional drawing which shows the other example of the waste gas processing apparatus which concerns on this invention.

Explanation of symbols

A, Aa to Ac Exhaust gas treatment device V1, V2 On-off valve 1 Chamber 2 Electromagnetic induction coil 3A First heating member 3B Second heating member 4 Measuring instrument 5 Piping 30 Alumina layer (oxidation protection layer)
40, 41 Spiral coil 50 Air inlet 51 Piping section

Claims (10)

An exhaust gas treatment method comprising a pyrolysis step of introducing exhaust gas into a chamber for exhaust gas treatment, and heating the exhaust gas using a heating member that is provided in the chamber or capable of generating heat to form the chamber Because
As the heating member, a member having an oxidation protective layer having a higher heat resistance than the substrate of the heating member is used.
When the thermal decomposition step is stopped, oxygen or a gas containing oxygen is introduced into the chamber instead of the exhaust gas, and the heating member is heated to oxidize the surface of the heating member. And a protective layer regeneration step for regenerating the oxidation protective layer deteriorated during the thermal decomposition step. As the heating member, use a member having an alloy part containing aluminum,
The exhaust gas treatment method according to claim 1, wherein in the protective layer regeneration step, alumina is formed as an oxidation protective layer of the heating member.   The electrical resistance of the surface portion of the heating member, the amount of pyrolysis treatment of the exhaust gas, or the time or number of times of the pyrolysis treatment of the exhaust gas is measured, and the degree of deterioration of the oxidation protective layer is judged based on this measured value. The exhaust gas treatment method according to claim 1, further comprising a step. A chamber for introducing exhaust gas to be treated;
A heating member capable of generating heat for heating and thermally decomposing the exhaust gas provided in or forming the chamber and introduced into the chamber;
An exhaust gas treatment apparatus comprising:
When the thermal decomposition process is stopped, instead of the exhaust gas, oxygen or a gas containing oxygen can be introduced into the chamber, and an introduction gas switching means is provided.
When the heating member generates heat in a state where oxygen or a gas containing oxygen is introduced into the chamber, an oxidation protective layer having higher heat resistance than the base of the heating member is formed on the surface of the heating member. An exhaust gas treatment apparatus characterized in that it can be formed.   The chamber is connected to an exhaust gas supply pipe for supplying the exhaust gas toward the chamber, and the introduction gas switching means includes an air introduction port for introducing air from the outside to the inside of the chamber. 5. An exhaust gas treatment apparatus according to claim 4, further comprising at least one valve capable of switching between air introduction from the air introduction port into the chamber and exhaust gas introduction from the exhaust gas supply pipe into the chamber. .   The exhaust gas according to claim 4 or 5, further comprising a measuring instrument for measuring the electrical resistance of the surface portion of the heating member, the amount of pyrolysis treatment of the exhaust gas, or the time or number of times of the pyrolysis treatment of the exhaust gas. Processing equipment.   The electromagnetic induction coil provided outside the chamber is provided, and at least a part of the heating member is configured to generate electromagnetic induction heat by energizing the coil. The exhaust gas treatment apparatus according to any one of the above.   The heating member includes a cylindrical first heating member and a cylindrical second heating member disposed inside the first heating member, and is introduced into the chamber. The exhausted gas that has passed through the gap between the first and second heating members in the axial direction thereof, enters the second heating member, and enters the second heating member. The exhaust gas treatment apparatus according to claim 7, wherein the exhaust gas treatment apparatus is configured to pass in a longitudinal direction thereof. Both ends are equipped with pipes with exhaust gas inlets and outlets,
The exhaust gas according to any one of claims 4 to 7, wherein the inside of the tubular body is the chamber, and the tubular body serves as the heating member because at least a part of the tubular body can generate heat. Processing equipment. A cylindrical wall surrounding the chamber and capable of generating heat;
The exhaust gas treatment according to any one of claims 4 to 7, wherein the exhaust gas is introduced into the chamber so as to form a swirl flow along an inner periphery of the cylindrical wall portion in the chamber. apparatus.

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