Cylindrical heating part of exhaust gas treatment device

Abstract

A cylindrical heating part 14 of an exhaust gas treatment device 1 is configured from a cylindrical body 20 in which an exhaust gas E to be treated flows and which opens into an exhaust gas reaction processing space S within a reactor 10, an insulator 30 provided to the cylindrical body 20 over a plurality of stages in the vertical direction, an electric heater 80 suspended from the insulator 30, and a power supply member 85 connected to the electric heater 80. The electric heater 80 is configured as one electric resistor by alternately connecting upper-end portions 82 and lower-end portions 83 of a plurality of adjacent rod-form portions 81, the electric heater 80 being suspended from the insulator 30 at an upper-end portion 82. The power supply member 85 is configured from a guide cylinder 86 that is inserted and fixed to a bottom plate 11 of the reactor 10, and an electroconductive rod material 87 that is thinner than the inside diameter of the guide cylinder 86 and is connected to the lower-end portion 83a of the rod-form portion 81a positioned at the end of the electric heater 80.

Description

Cylindrical heating section of exhaust gas treatment equipment

[0001] The present invention relates to an improvement in a cylindrical heating section of an exhaust gas treatment device that thermally decomposes gases harmful to humans and ozone-depleting gases emitted from industrial processes and the like.

[0002] Various types of gases are used in industrial processes for manufacturing and treating products. As a result, the types of gases emitted from industrial processes (hereinafter referred to as "exhaust gases to be treated") are extremely diverse, and various types of exhaust gas treatment methods and systems are used depending on the type of exhaust gas to be treated.

[0003] For example, in the semiconductor manufacturing process, monosilane (SiH ４ Various types of gases are used, including chlorine gas, PFCs (perfluorocompounds), and other gases. Because these gases have adverse effects on the human body and the global environment, they must be decomposed or removed by some means, and various treatment methods have been put into practical use. Representative examples include adsorption, wet, electrothermal oxidation decomposition, and flame combustion, each of which has its own advantages and disadvantages.

[0004] Of these, the flame combustion type has a wide range of application areas for the exhaust gases to be treated (i.e., it can decompose and treat a large number of types of exhaust gases) and is capable of treating large volumes of gas, but there are concerns about safety when it comes to operation.This is because the flame combustion type basically uses a burner for combustion, and introduces exhaust gas into the combustion atmosphere for thermal decomposition, so if the flame goes out (misfire) for some reason, it can lead to an unsafe situation.

[0005] On the other hand, the electrothermal oxidative decomposition method using an electric heater is currently the most widely used decomposition method for exhaust gas treatment in semiconductor manufacturing processes, and it is easy to control the treatment process when decomposing the exhaust gas to be treated, and it can safely decompose the exhaust gas to be treated. An example of an exhaust gas treatment system using an electric heater is a system such as that described in Patent Document 1.

[0006] Patent No. 7140440 Publication 1

[0007] The exhaust gas treatment system 100 described in Patent Document 1 includes a cylindrical heating section 114 for thermally decomposing the target gas 100E introduced into the exhaust gas treatment space 100S in the reactor 110 (FIG. 8). The cylindrical heating section 114 includes an electric heater 180 installed between the walls of a double-walled pipe formed by a metal inner pipe 121 and an outer pipe 122. A three-phase alternating current is applied to the electric heater 180, and power supply members 185 are installed at multiple locations (six locations for three-phase AC). Heat-resistant external electric wires 190 connected to an external power source are connected to the power supply members 185.

[0008] Insulators 130 are installed in multiple vertical stages on the outer periphery of the inner tube 121 of the cylindrical heating section 114. Heater holding holes 132h are drilled in the flange portions 132 of the insulators 130. The electric heater 180 is composed of multiple heating resistors 181, which are rod-shaped electrical resistors bent into an inverted U shape, and a heater bridge plate 184. The rod-shaped portions of the inverted U-shaped heating resistors 181 are thinner than the inner diameter of the heater holding holes 132h of the insulators 130 and are movably inserted therethrough, with the upper end portions 182 of the inverted U-shape engaging with the top-most insulator 130 and hanging down. The electric heater 180 is divided equally into three phases, U, V, and W. The rod-shaped portions at both ends of the inverted U-shaped heating resistor 181 (these rod-shaped portions are called rod-shaped portions to which the power supply member 185 is attached or rod-shaped portions on the power supply side and are indicated by 181a) are provided with power supply members 185 at their lower ends, and the other inner rod-shaped portions (these rod-shaped portions are called rod-shaped portions to which the power supply member 185 is not attached or rod-shaped portions on the jumper plate side and are indicated by 181b) are connected at their lower ends by heater jumper plates 184, with the adjacent jumper plate-side rod-shaped portions 181b being connected.

[0009] The conventional power supply member 185 is composed of an insulating tube 186 and a rod-shaped conductive rod 187. The insulating tube 186 is a cylindrical ceramic member with a bottom, and a through-hole 186h having a diameter smaller than the inner diameter is opened in the bottom 186a. The insulating tube 186 is inserted into and fixed to the bottom plate 111 of the reactor 110.

[0010] Conductive rod 187 is made of a heat-resistant conductor (metal rod), and a thin connecting portion 188 protrudes from its lower end surface. Conductive rod 187 is housed in insulating tube 186, and its upper end protrudes upward from the upper opening of insulating tube 186 and is connected to rod-shaped portion 181a on the power supply side. Rod-shaped connecting portion 188 protrudes from the lower end surface of conductive rod 187 and protrudes downward from through-hole 186h in bottom portion 186a of insulating tube 186. Heat-resistant electric wire 190, connected to an external power source, is connected to connecting portion 188. To prevent electric shock, connecting portion 188 is covered with an insulating coating on heat-resistant electric wire 190 so that it is not exposed to the outside. Because conventional power supply member 185 is configured as described above, conductive rod 187 is prevented from moving downward by bottom portion 186a of insulating tube 186.

[0011] This cylindrical heating section 114 is erected in the center of the interior of the reactor 110, and when the treatment target exhaust gas 100E is treated, an electric heater 180 is energized to maintain the interior of the reactor 110 at a high temperature (ambient temperature of 800 to 1150°C). The treatment target exhaust gas 100E is introduced through an exhaust gas inlet 115 provided at the bottom of the cylindrical heating section 114, passes through the high-temperature internal space of this cylindrical heating section 114, and is released from its upper end opening into a high-temperature exhaust gas treatment space 100S formed near the ceiling of the reactor 110. The treatment target exhaust gas 100E is thermally decomposed by the ambient high temperature while passing through the interior of the cylindrical heating section 114 and further while passing through the exhaust gas treatment space 100S.

[0012] Here, each heating resistor 181 of the electric heater 180 is energized and heated to a high temperature in order to maintain a high ambient temperature. This high-temperature heating causes the rod-shaped portions 181a and 181b of each heating resistor 181 to thermally expand and stretch significantly in the longitudinal direction. This stretch is indicated by ΔL (delta L) ( FIG. 6 ). Each heating resistor 181 of the electric heater 180 is suspended from the top insulator 130, but the rod-shaped portion 181a on the power supply side of the heating resistor 181 stretches upward because it is restrained by the power supply member 185. The rod-shaped portion 181b on the jumper plate side, not connected to the power supply member 185, is connected by the heater jumper plate 184. Therefore, the rod-shaped portion 181b on the jumper plate side moves within the heater holding hole 132h and is lifted in accordance with the stretch of the rod-shaped portion 181a on the power supply side connected to the power supply member 185. The entire load of the rod-shaped portion 181b on the crossover plate side is applied to the upper end portion 182 of the inverted U-shape of the rod-shaped portion 181a on the power supply side or its vicinity.

[0013] The electric heater 180 is repeatedly turned on and off in accordance with operation, and each time it is heated and released, large strains are repeatedly generated, particularly in the upper end portion 182. Moreover, when heated to a high temperature, the mechanical strength of the electric heater 180 decreases, and the upper end portion 182 or its vicinity may fracture in a short period of time (see the circled portion in Figure 8). In addition, because the electric heater 180 is suspended by being inserted into the heater holding hole 132h of the insulator 130, if dirt accumulates in the heater holding hole 132h due to aging, it becomes difficult to slide, and as a result, the above-mentioned strain becomes even greater when the entire electric heater 180 is lifted by the rod-shaped portion 181a on the power supply side.

[0014] The present invention has been made in consideration of the problems of the conventional example, and the object of the present invention is to provide a cylindrical heating section of an exhaust gas treatment device that can eliminate distortion that occurs in an electric heater and extend its lifespan.

[0015] The invention described in claim 1 (FIG. 3) is a cylindrical heating section 14 of an exhaust gas treatment device 1 installed in a reactor 10 for decomposing exhaust gas E to be treated, wherein the cylindrical heating section 14 is composed of a cylindrical body 20 erected on a bottom plate 11 of the reactor 10, through which the exhaust gas E to be treated flows and which opens into an exhaust gas reaction treatment space S in the reactor 10, insulators 30 provided in multiple stages in the vertical direction on the cylindrical body 20, an electric heater 80 suspended from the insulators 30, and a power supply member 85 connected to the electric heater 80, wherein the electric heater 80 is configured as a single electric resistor in which upper end portions 82 and lower end portions 83 of a plurality of adjacent rod-shaped portions 81 are alternately connected, and the electric heater 80 is suspended from the insulator 30 at the upper end portion 82, The power supply member 85 is characterized by comprising a guide tube 86 inserted and fixed to the bottom plate 11 of the reactor 10, and a conductive rod 87 that is thinner than the inner diameter of the guide tube 86, inserted movably into the guide tube 86, and connected to a lower end portion 83 a of a rod-shaped portion 81 a located at an end of the electric heater 80.

[0016] The invention described in claim 2 (Figure 3) is characterized in that, in the cylindrical heating section 14 of the exhaust gas treatment device 1 described in claim 1, the distance L1 between the lower end 86d of the guide tube 86 and the lower end 87d of the conductive rod 87 is configured to be greater than the elongation allowance L2 of the rod-shaped portion 81a connected to the conductive rod 87 when heated.

[0017] The invention described in claim 3 (Figure 3) is characterized in that in the cylindrical heating section 14 of the exhaust gas treatment device 1 described in claim 2, the connection end 90a of the external electric wire 90 connected to the external power source and connected to the lower end 87d of the conductive rod material 87 is formed smaller than the inner diameter of the guide tube 86.

[0018] Since the cylindrical heating section 14 of the present invention is configured as described above, when the rod-shaped portion 81a connected to the conductive rod 87 is stretched by heating, the conductive rod 87 connected to the lower end portion 83a of the rod-shaped portion 81a moves downward within the guide tube 86, and the stretch L2 can be released downward. As a result, no stress is generated in the upper end portion 82 of the rod-shaped portion 81a, and damage to the upper end portion 82 can be avoided, thereby significantly extending the life of the heater.

[0019] Furthermore, the distance L1 between the lower end 86d of the guide tube 86 and the lower end 87d of the conductive rod 87 is set to be greater than the extension allowance L2 of the rod-shaped portion 81a connected to the conductive rod 87 when heated, so that the conductive rod 87, which is a live wire, is not exposed to the outside from the lower end 86d of the guide tube 86 when heated, thereby preventing electric shock accidents.

[0020] In addition, since the connection end 90 a of the external electric wire 90 is formed to be smaller than the inner diameter of the guide tube 86 , the conductive rod 87 can move smoothly through the guide tube 86 .

[0021] 1 is a schematic configuration diagram of an exhaust gas treatment system of the present invention. FIG. 2 is an enlarged cross-sectional view of a reactor of the exhaust gas treatment device of FIG. 1. FIG. 2 is a view of the right half of FIG. 2, where (a) is an enlarged cross-sectional view when not heated and (b) is an enlarged cross-sectional view when heated. FIG. 2 is a plan view taken along the arrows A-A' in FIG. 2 and an enlarged plan view of a rod-shaped member holding portion of an insulator. FIG. 2 is a perspective view of a first embodiment of a cylindrical heating section of FIG. 2, with the intermediate portion omitted, as seen obliquely from above. FIG. 2 is a perspective view of a second embodiment of a cylindrical heating section of FIG. 2, with the intermediate portion omitted, as seen obliquely from below. FIG. 2 is a perspective view of a third embodiment of a cylindrical heating section of FIG. 2, with the intermediate portion omitted, as seen obliquely from above. FIG. 3 is an enlarged cross-sectional view of a heater device when current is applied in a reactor of a conventional example, and a partially enlarged view of the heater when broken. EMBODIMENT OF THE INVENTION

[0022] The present invention will be described below with reference to illustrated embodiments. FIG. 1 is a schematic diagram showing one embodiment of an exhaust gas treatment system X using an exhaust gas treatment device 1 of the present invention, which is an apparatus for thermally decomposing exhaust gas E to be treated that is emitted from an industrial process. The exhaust gas treatment system X of this embodiment is generally composed of an exhaust gas treatment device 1, an inlet scrubber 2, an outlet scrubber 5, and associated equipment. The exhaust gas treatment device 1 includes an electrothermal oxidative decomposition method, a flame combustion method, and a combined method that combines electrothermal oxidative decomposition and flame combustion methods. The present invention is an exhaust gas treatment device 1 that uses an electrothermal oxidative decomposition method. The exhaust gas treatment device 1 that uses an electrothermal oxidative decomposition method is generally composed of a reactor 10, a cylindrical heating section 14, and a chemical tank 18.

[0023] The inlet scrubber 2 is used to remove (liquid wash) dust and water-soluble components contained in the exhaust gas E to be treated that is introduced into the exhaust gas treatment device 1, and is composed of a straight-tube inlet scrubber main body 2a and a spray nozzle 4 that is installed near the top inside the inlet scrubber main body 2a and sprays a spray of water or other chemical solution Y. The top of this inlet scrubber main body 2a is connected via an exhaust gas duct 92 to a source of exhaust gas to be treated (not shown), such as a semiconductor manufacturing device.

[0024] The inlet scrubber body 2a is erected on a chemical tank 18, and its lower end is immersed in the chemical Y stored in the chemical tank 18. A circulation pump 19 is installed between the spray nozzle 4 and the chemical tank 18, so as to pump the chemical Y stored in the chemical tank 18 to the spray nozzle 4. The lower end of the inlet scrubber 2 is connected to the exhaust gas inlet 15 of the cylindrical heating section 14 via an exhaust gas feed pipe 3.

[0025] The exhaust gas treatment device 1 is a device that thermally decomposes the exhaust gas E to be treated, which is discharged from an industrial process and has passed through the inlet scrubber 2, using an electrothermal oxidative decomposition method, and is roughly composed of a cylindrical heating section 14, a reactor 10 incorporating the cylindrical heating section 14, and a chemical tank 18.

[0026] At least the inner surface of the reactor 10 is made of a refractory material such as castable, and an exhaust gas treatment space S is formed inside. As shown in Fig. 1 , the reactor 10 is installed upright on a chemical tank 18 with the flat surface facing upright. The reactor 10 is a cylindrical container, and an opening is provided in its bottom plate 11 to which a cylindrical heating unit 14 is attached. The cylindrical heating unit 14 attached to the opening extends upright from the bottom plate 11 toward the ceiling of the reactor 10. A cracked exhaust gas outlet 12 is provided in the bottom plate 11 of the reactor 10 adjacent to the cylindrical heating unit 14 (Figs. 2 and 3). A cracked exhaust gas exhaust pipe 13 extending from the cracked exhaust gas outlet 12 is connected to the top surface of the chemical tank 18 and is connected to the outlet scrubber 5 via the upper space within the chemical tank 18.

[0027] A heat exchanger 50 is installed between the exhaust gas supply pipe 3 and the decomposition exhaust gas discharge pipe 13 so as to straddle them, and heat is exchanged between the low-temperature exhaust gas E to be treated which is introduced into the cylindrical heating section 14 and the high-temperature exhaust gas G which has been thermally decomposed in the reactor 10 and treated.

[0028] The cylindrical heating section 14 is a heat source that heats the internal space of the cylindrical heating section 14 and the exhaust gas treatment space S inside the reactor 10. Although this embodiment shows a case where the cylindrical heating section 14 is formed into a cylindrical shape, the cylindrical heating section 14 may have any shape as long as it is a cylindrical shape with both ends open, and may be, for example, a rectangular cylindrical shape.

[0029] As already described, the cylindrical heating section 14 is inserted into the reactor 10 through the opening provided in the bottom plate 11 of the reactor 10, and is erected in the center of the exhaust gas treatment space S of the reactor 10. The upper end opening (heated exhaust gas outlet 16) of the cylindrical heating section 14 is located close to the ceiling surface of the reactor 10, in the area that becomes the highest temperature. The cylindrical heating section 14 is configured with a double-structured cylindrical body 20 composed of a metallic inner cylinder 21, an outer cylinder 22, and a ceiling plate 24 and a bottom plate 23 provided between them, a plurality of insulators 30 surrounding the inner cylinder 21 and provided in multiple vertical stages in a heater installation space P between the inner cylinder 21 and the outer cylinder 22 at intervals in the vertical direction, an electric heater 80 attached to the insulator 30, a power supply member 85 attached to the electric heater 80, and a holding member 40 attached to at least one of the inner cylinder 21 and the outer cylinder 22 and holding the insulator 30 in the heater installation space P. The bottom plate 23 of the cylindrical body 20 is connected to the bottom plate 11 of the reactor 10 after assembly, and therefore forms a part of the bottom plate 11 of the reactor 10.

[0030] In the embodiment shown in Figure 2, the inner cylinder 21 of the double-structured cylinder 20 can be inserted and removed from the bottom opening of the outer cylinder 22 with the electric heater 80 mounted on the insulator 30, the circulation pipe 25 described below, and the temperature sensor 70 attached to the bottom plate 23. This is referred to as a removable cylinder 20. (The cylinder 20 may not be removable, and the inner cylinder 21, outer cylinder 22, ceiling plate 24, and bottom plate 23 may be integrated by welding their joints. This is referred to as an integrated cylinder 20.) With the inner cylinder 21 attached to the outer cylinder 22, the heater installation space P is sealed, and atmospheric gas Q is supplied and exhausted through the circulation pipe 25 to circulate within the heater installation space P. In this state, the bottom plate 23 of the cylinder 20 is connected to the bottom plate 11 of the reactor 10 as described above, and is therefore included in the bottom plate 11 of the reactor 10. The inner cylinder 21, outer cylinder 22, ceiling plate 24, and bottom plate 23 of the cylindrical body 20 are formed of a highly heat-resistant and highly corrosion-resistant alloy (e.g., Hastelloy, Incoloy, or Inconel (all registered trademarks)). A steel type containing aluminum as an additive is preferred for reasons described below.

[0031] As described above, the top opening of the cylindrical body 20 opens toward the ceiling of the reactor 10, and this top opening that opens into the exhaust gas treatment space S is the heated exhaust gas outlet 16. The exhaust gas supply pipe 3 that is led out from the outlet of the inlet scrubber 2 is connected to the bottom end, and the connection opening of this exhaust gas supply pipe 3 is the exhaust gas inlet 15.

[0032] As already mentioned, the space between the inner tube 21 and the outer tube 22 of the double-structured tube body 20 is the heater installation space P, in which a plurality of insulators 30 are installed vertically at regular intervals. The insulators 30 hold the electric heater 80 in the installation space P while maintaining electrical insulation.

[0033] The insulator 30 shown in Figures 4 and 5 is one example of such an insulator, and is made of a disk-shaped ceramic member, i.e., a flat ring-shaped member in a plan view. A central hole 33, through which the inner tube 21 is inserted, is formed in the center of the insulator 30, and the area surrounding the central hole 33 is raised by one step. The raised portion is a cylindrical step 31, and the surrounding disk-shaped portion, which is one step lower, is a flange portion 32. The periphery of the flange portion 32 is chamfered in an arc shape, giving it a rounded shape all around. The flange portion 32 is also provided with an even number of heater holding holes 32h that are evenly distributed on a concentric circle centered on the central hole 33 and that penetrate the flange portion 32 from top to bottom.

[0034] The outer diameter of the insulator 30 is smaller than the inner diameter of the outer tube 22, and the inner diameter is larger than the inner tube 21, so that the two do not come into contact with each other when the electric heater 80 is in a high-temperature state. A gap K is provided between the inner peripheral surface of the insulator 30 (i.e., the central hole 33) and the outer peripheral surface of the inner tube 21 (FIG. 4).

[0035] The electric heater 80 of the first embodiment shown in Figures 2 and 4 is formed with three phases, U, V, and W. Each phase of the electric heater 80 is composed of multiple long, rod-shaped heating resistors formed in an inverted U shape (each of the two parallel, straight rod-shaped portions of the heating resistor is referred to as a rod portion 81). A heater bridge plate 84 connects the lower end portions 83 of adjacent inner rod portions 81 in series. The rod portions 81 connected by the inner heater bridge plate 84 (these portions are referred to as the bridge plate-side rod portions) are designated by the symbol 81b. The outer rod portions 81 connected to the power supply member 85 (these portions are referred to as the power supply-side rod portions) are designated by the symbol 81a. The upper end portions of the inverted U-shaped rod portions 81 are designated by the symbol 82. If the heating resistor of the electric heater 80 is, for example, an Fe / Cr / Al-based metal heater, alumina that inhibits oxidation of the electric heater 80 is formed on the heater surface, so an inert gas (nitrogen) to which oxygen is added periodically or irregularly is selected as the atmospheric gas Q. If the electric heater 80 is, for example, a SiC-based heater, if the atmospheric gas Q is mainly nitrogen, a SiN protective coating is formed on the surface, so an atmospheric gas Q that does not contain oxygen is selected. If oxygen is contained in the atmospheric gas Q, Si will gradually oxidize to SiO ２ and the power will no longer flow.

[0036] In a second embodiment of the electric heater 80 (FIG. 6), the heating resistor is used in the opposite manner to that of the first embodiment, with the U-shaped portion positioned below and a heater bridge plate 84 welded to the upper end portion 82 of the adjacent rod-shaped portion 81. The heater bridge plate 84 is engaged with the uppermost insulator 32 to suspend the U-shaped heating resistor. The U-shaped portion is positioned below the lowermost insulator 32. The heating resistor to which the power supply member 85 is connected is a straight rod-shaped member, and is connected at its upper end portion 82 to the rod-shaped portion 81 of the adjacent U-shaped heating resistor by the heater bridge plate 84.

[0037] A third embodiment of the electric heater 80 (FIG. 7) uses a straight rod-shaped heating resistor instead of an inverted U-shaped heating resistor. In this case, the upper end portions 82 and lower end portions 83 of adjacent heating resistors are alternately connected by a heater bridge plate 84. This specification will mainly describe the electric heater 80 (first embodiment) configured with an inverted U-shaped heating resistor. The heating resistor may be a metal wire such as nichrome wire or Kanthal wire (Kantal is a registered trademark of Sandvik), or a heating element such as SiC. By passing an electric current through these, the temperature rises to approximately 800°C to 1400°C depending on the type of material.

[0038] As shown in Fig. 3, the power supply member 85 is composed of a ceramic guide tube 86 and a heat-resistant metal conductive rod 87. The guide tube 86 is inserted vertically into a through-hole 23h formed in the bottom plate 23 of the inner tube 21 that constitutes part of the bottom plate 11 of the reactor 10, and is fixed to the bottom plate 23 with a heat-resistant fixing agent such as an inorganic adhesive. The conductive rod 87 is a heat-resistant metal rod that is thinner than the inner diameter of the guide tube 86 and is movably inserted into the guide tube 86. The upper ends of the conductive rods 87 are connected to the lower end portions 83a of the rod-shaped portions 81a at the ends of the electric heaters 80 of the U, V, and W phases, respectively.

[0039] The lower end 87d of the conductive rod 87 is connected to a heat-resistant external electric wire 90. The external electric wire 90 is connected to an external power source 75. In the embodiment shown in FIG. 3 , an attachment hole 87h is formed in the lower end 87d of the conductive rod 87. The conductive member 90a of the external electric wire 90 is attached to this attachment hole 87h, and the insulating portion 90b of the external electric wire 90 is attached to a position where it contacts the lower end 87d of the conductive rod 87. The attachment structure of the conductive rod 87 and the external electric wire 90 is not limited to the above example. A connecting member protruding from the lower end of the conductive rod may be inserted into and connected to the external heat-resistant electric wire 90, and this portion may be covered with an insulating portion (not shown). In either case, the insulating portion 90b of the external electric wire 90 is connected to the lower end 87d of the conductive rod 87. Since this insulating portion 90b is drawn into the guide tube 86, its outer diameter is narrower than the inner diameter of the guide tube 86. As a result, the external electric wire 90 does not interfere with the movement of the conductive rod 87 within the guide tube 86 .

[0040] The lower end 87d of the conductive rod 87 connected to the rod-shaped portion 81a on the power supply side is always housed within the guide tube 86, whether energized or not, so that the connection portion between the external electric wire 90 and the conductive rod 87 is always hidden from view. That is, when energized, the distance between the lower end 87d of the conductive rod 87 and the lower end 86d of the guide tube 86 is L1. When energized, the rod-shaped portion 81a on the power supply side extends, and the distance (extension) by which the lower end 87d of the conductive rod 87 moves downward within the guide tube 86 is L2. The distance L1 is greater than the distance (extension) L2 (distance L1 > distance (extension) L2). This prevents the lower end 87d of the conductive rod 87 from being exposed from the lower end 86d of the guide tube 86 when energized, thereby preventing electric shock hazards. The distance L1 minus the distance (extension) L2 is the allowance of the guide tube 86, which is indicated by the symbol L3.

[0041] The holding member 40 is, for example, a ring-shaped metal plate, and is attached by welding to either the inner tube 21 or the outer tube 22, or both (not shown), to support the insulator 30 and hold them in the heater installation space P. Welding to both the inner tube 21 and the outer tube 22 is not applicable to the removable tube body 20. In the case of Figure 4, the holding member 40 is welded to the outer peripheral surface of the inner tube 21, sandwiching the insulator 30 from above and below to secure it to the inner tube 21. Unlike the above case, the holding member 40 can be made of a material different from the materials of the inner tube 21 and the outer tube 22, such as a metal or ceramic having a higher electrical resistance than these. In this case, an inorganic adhesive is used instead of welding.

[0042] A plurality of circulation pipes 25 are installed on the bottom plate 23 of the cylindrical body 20, extending from the bottom plate 23 toward the ceiling. The circulation pipes 25 are installed in a variety of lengths, from long to short, and the long circulation pipes 25 supply or exhaust the atmospheric gas Q near the ceiling of the heater installation space P, while the short circulation pipes 25 supply or exhaust the atmospheric gas Q near the bottom plate 23. Of these, the circulation pipe 25 on the supply side is connected to a supply source of inert gas (nitrogen) or inert gas (nitrogen) to which oxygen has been periodically or irregularly added, depending on the type (material) of the electric heater 80. The atmospheric gas Q circulated within the heater installation space P is extracted from the circulation pipe 25 on the exhaust side, cooled, and then released to the outside.

[0043] In addition to a circulation pipe 25 extending from the bottom plate 23 toward the ceiling, a temperature sensor 70 such as a thermocouple is installed on the bottom plate 23 of the cylindrical body 20. This temperature sensor 70 measures the ambient temperature in the heater installation space P, and the amount of power supplied to the cylindrical heating section 14 is controlled based on the measured temperature data.

[0044] As described above, the chemical tank 18 stores the chemical Y to be supplied to the inlet scrubber 2 and collects the chemical Y discharged from the inlet scrubber 2 and the outlet scrubber 5. This chemical tank 18 is constantly supplied with new chemical Y sprayed by the spray nozzles 7 of the outlet scrubber 5, so that excess chemical Y is allowed to overflow and sent to a wastewater treatment device (not shown) so that more than a predetermined amount of chemical Y does not accumulate. There is a space between the ceiling surface of the chemical tank 18 and the stored chemical Y.

[0045] In addition, in the exhaust gas treatment system X of this embodiment, except for the exhaust gas treatment device 1 which becomes hot, other parts are provided with corrosion-resistant linings or coatings made of vinyl chloride, polyethylene, unsaturated polyester resin, fluororesin, etc. to protect each part from corrosion caused by corrosive components such as hydrofluoric acid contained in the exhaust gas E to be treated or generated by decomposition of the gas E.

[0046] The outlet scrubber 5 is used to finally remove (liquid wash) dust and water-soluble components in the exhaust gas G that are by-produced when the exhaust gas E to be treated is thermally decomposed in the exhaust gas treatment device 1, and to cool the exhaust gas G. It is composed of a straight-tube outlet scrubber main body 5a, multiple perforated plates 6 (four stages in this embodiment) installed at intervals in the vertical direction within the outlet scrubber main body 5a, and downward-facing spray nozzles 7 attached directly above the uppermost perforated plate 6 and spraying a chemical solution Y such as water from above in a direction opposite to the flow direction of the exhaust gas G.

[0047] The outlet scrubber 5 is erected on a chemical tank 18 that stores a chemical Y such as water, and its lower end opens to the top surface of the chemical tank 18, so that the chemical Y sprayed from the spray nozzles 7 is sent into the chemical tank 18. Note that the spray nozzles 7 are supplied with new chemical Y such as fresh water, rather than the circulating chemical Y in the chemical tank 18 as described above. The top outlet of the outlet scrubber 5 is connected to an exhaust fan 8 that releases the treated exhaust gas G into the atmosphere.

[0048] The operation of the exhaust gas treatment system X and exhaust gas treatment device 1 configured as described above will now be described. First, the operation switch (not shown) of the exhaust gas treatment device 1 is turned on to operate the cylindrical heating section 14 and start heating the inside of the reactor 10. Next, when the heat from the cylindrical heating section 14 causes the temperature of the internal space of the reactor 10 (in this embodiment, the temperature of the internal space of the cylindrical heating section 14 and the temperature of the exhaust gas treatment space S of the reactor 10) to reach or exceed the thermal decomposition temperature of the exhaust gas E to be treated, the exhaust fan 8 is operated to start introducing the exhaust gas E to the exhaust gas treatment system X. Then, the exhaust gas E to be treated is first introduced into the inlet scrubber 2, where it is washed with a chemical solution Y such as water to remove dust, water-soluble components, and the like.

[0049] The exhaust gas E to be treated that has been chemically washed in the inlet scrubber 2 is introduced into the internal space of the cylindrical heating section 14 through the exhaust gas inlet 15 from the exhaust gas delivery pipe 3 extending from the bottom of the inlet scrubber 2, and is heated by the electric heater 80. The exhaust gas E to be treated is then thermally decomposed in the high-temperature atmosphere in the internal space heated by the inner cylinder 21. The exhaust gas E to be treated then moves from the tip opening (heated exhaust gas outlet 16) of the cylindrical heating section 14 into the high-temperature region of the exhaust gas treatment space S located in the ceiling portion of the reactor 10. The moving gas flow, i.e., the high-temperature gas flow containing a portion of the undecomposed exhaust gas E to be treated, proceeds with the thermal decomposition of the undecomposed exhaust gas E to be treated remaining in this high-temperature region, wrapping around the outer periphery of the cylindrical heating section 14 and moving to the decomposed exhaust gas outlet 12, where the harmful components have been completely decomposed into exhaust gas G, which is then introduced into the outlet scrubber 5 through the decomposed exhaust gas outlet 13 and the internal space of the chemical tank 18.

[0050] The exhaust gas G introduced into the outlet scrubber 5 is washed with a chemical solution Y such as water to remove dust and water-soluble components, and is cooled, and then released outside the system (into the atmosphere) via an exhaust fan 8. During operation, atmospheric gas Q is supplied to and exhausted from the heater installation space P to protect the electric heater 80 and the inner wall of the cylindrical body 20.

[0051] During the thermal decomposition treatment of the exhaust gas E to be treated, the electric heater 80 is heated to a high temperature, and due to thermal expansion, the rod-shaped portion 81 constituting the electric heater 80 extends downward from the uppermost insulator 30 as a suspension point. When the rod-shaped portion 81a on the power supply side extends downward, the conductive rod 87 connected to it also moves downward within the guide tube 86. At the same time, the external electric wire 90 connected to the lower end 87d of the conductive rod 87 also moves downward. Because the outer diameter of the connection portion of the conductive rod 87 and the external electric wire 90 housed in the guide tube 86 is smaller than the inner diameter of the guide tube 86, the conductive rod 87 moves smoothly within the guide tube 86.

[0052] Furthermore, because the distance L1 between the lower end 87d of the conductive rod 87 and the lower end 86d of the guide tube 86 before current is applied is set to be greater than the elongation L2, even during heating, the conductive rod 87, and in turn the connection end 90a of the external electric wire 90 connected to the conductive rod 87, is maintained within the guide tube 86. Because this portion is an insulated portion of the external electric wire 90, the connection portion of the conductive rod 87 and the external electric wire 90 in a live state during heating is not exposed to the outside, and electric shock accidents can be reliably prevented.

[0053] Furthermore, as a result of aging, oxides accumulate on the insulator 30 and enter the heater holding hole 32h, but since there is a sufficient gap between the rod-shaped portion 81 of the electric heater 80 and the heater holding hole 32h, even if oxides enter this gap, the movement of the rod-shaped portion 81 is not hindered. In the above first embodiment, the electric heater 80 has been mainly described as using an inverted U-shaped heating resistor.

[0054] Second Embodiment Figure 6 shows a second embodiment of an electric heater 80, in which a U-shaped bent heating resistor is used with the U-shaped bent portion facing downward. In this case, a rod-shaped member is used as the heating resistor connected to a power supply member 85, rather than a U-shaped bent heating resistor. This is the power supply side rod-shaped member, designated by the symbol 81a. The rod-shaped portion of the U-shaped bent heating resistor is designated by 81b. The upper ends of the power supply side rod-shaped member 81a and the rod-shaped portion 81b of the U-shaped bent heating resistor are designated by 82a and 82b, respectively. The upper end portion 82a of the power supply side rod-shaped member 81 and the upper end portion 82b of the adjacent rod-shaped portion 81b, as well as the upper ends 82b of the adjacent rod-shaped portions 81b of the U-shaped bent heating resistors, are connected by a heater bridge plate 84. This heater transition plate 84 contacts the uppermost insulator 30 and suspends the electric heater 80 from the insulator 30.

[0055] 6 shows a third embodiment of an electric heater 80, which uses only a rod-shaped heating resistor. Instead of the U-shaped bent portion of the first embodiment, this portion is connected to a heater bridge plate 84 and suspended from the insulator 30. In either case, when power is applied, the entire electric heater 80 extends smoothly downward from the heater bridge plate 84 as a suspension point, as in the first embodiment, and does not cause stress on the heating resistor.

[0056] As a result, the present invention can avoid the problem of damage to the upper end portion or the portion nearby, which was a problem with conventional electric heaters, and can significantly extend the life of the heater. Stress applied to the upper end portion 82 during heating occurs mainly in the welded portion between the heater bridge plate 84 connecting the upper end portion 82 and the rod-shaped portion (or rod-shaped member) 81.

[0057] 1...exhaust gas treatment device, 2...inlet scrubber, 2a...inlet scrubber main body, 3...exhaust gas supply piping, 4...spray nozzle, 5...outlet scrubber, 5a...outlet scrubber main body, 6...perforated plate, 7...spray nozzle, 8...exhaust fan, 10...reactor, 11...bottom plate, 12...cracked exhaust gas discharge port, 13...cracked exhaust gas discharge piping, 14...cylindrical heating section, 15...exhaust gas inlet, 16...heated exhaust gas outlet, 18...chemical tank, 19...circulation pump, 20...cylindrical body, 21...inner cylinder, 22...outer cylinder, 23...bottom plate, 23h...through hole, 24...ceiling plate, 25...circulation pipe, 30...insulator, 31...cylindrical step portion, 32...flange portion, 32h...heater holding hole, 33...central hole, 40...holding member, 50...heat exchanger, 60... Sensor holding portion, 70... temperature sensor, 75... external power source, 80... electric heater, 81... rod-shaped portion, 81a... rod-shaped portion (on the power supply side) located at the end of the electric heater / rod-shaped member on the power supply side, 81b... rod-shaped portion (on the plate connection side) connected by the heater bridge plate, 82... upper end portion, 82a... upper end portion of the rod-shaped member on the power supply side, 82b... upper end portion of the rod-shaped portion adjacent to the rod-shaped member on the plate connection side or the power supply side, 83... lower end portion, 83a: lower end portion of the rod-shaped portion (on the power supply side) located at the end of the electric heater, 84... heater bridge plate, 85... power supply member, 86... guide tube, 86d... lower end, 87... conductive rod material, 87d... lower end, 87h... mounting hole, 90... external electric wire, 90a... connection end portion, 92... exhaust gas duct E...exhaust gas to be treated, G...exhaust gas, K...gap, L1...distance between the bottom end of the guide tube and the bottom end of the conductive rod, L2...elongation, L3...allowance of the guide tube obtained by subtracting the distance (elongation) L2 from the distance L1, P...heater installation space, Q...atmospheric gas, S...exhaust gas treatment space, U, V, W...phases, X...exhaust gas treatment system, Y...chemical solution, ΔL...elongation of the heating resistor100E...gas to be treated, 100S...exhaust gas treatment space, 110...reactor, 111...bottom plate, 114...cylindrical heating section, 115...exhaust gas inlet, 121...inner cylinder, 122...outer cylinder, 130...insulator, 132...flange section, 132h...heater holding hole, 180...electric heater, 181...heating resistor, 181a...rod-shaped sections at both ends (power supply side) of the inverted U-shaped heating resistor of the electric heater, 181b...rod-shaped section (transfer plate side) to which the power supply member is not attached, 182...upper end section, 183...lower end section, 184...heater transfer plate, 185...power supply member, 186...insulating cylinder, 186a...bottom section, 186h...through hole, 187...conductive rod material, 188...connection section, 190...external electric wire

Claims

1. In the cylindrical heating section 14 of the exhaust gas treatment apparatus 1 installed in the reactor 10 for decomposing the exhaust gas E to be treated, the cylindrical heating section 14 is erected on the bottom plate 11 of the reactor 10, and includes a cylindrical body 20 through which the exhaust gas E to be treated flows and opens into the exhaust gas reaction treatment space S in the reactor 10, insulators 30 provided in a plurality of stages in the vertical direction on the cylindrical body 20, an electric heater 80 suspended from the insulators 30, and a power supply member 85 connected to the electric heater 80. The electric heater 80 is configured as a single electric resistor by alternately connecting the upper end portions 82 and the lower end portions 83 of a plurality of adjacent rod-shaped portions 81, and is suspended from the insulator 30 at the upper end portion 82. The power supply member 85 includes a guide cylinder 86 inserted and fixed to the bottom plate 11 of the reactor 10, and a conductive rod 87 that is thinner than the inner diameter of the guide cylinder 86, is movably inserted into the guide cylinder 86, and is connected to the lower end portion 83a of the rod-shaped portion 81a located at the end of the electric heater 80. The cylindrical heating section of the exhaust gas treatment apparatus is characterized by the above.

2. The distance L1 between the lower end 86d of the guide cylinder 86 and the lower end 87d of the conductive rod 87 is configured to be larger than the elongation allowance L2 during heating of the rod-shaped portion 81a connected to the conductive rod 87. The cylindrical heating section of the exhaust gas treatment apparatus according to claim 1 is characterized by the above.

3. The connection end portion 90a of the external electric wire 90 connected to the external power supply to the lower end 87d of the conductive rod 87 is formed to be smaller than the inner diameter of the guide cylinder 86. The cylindrical heating section of the exhaust gas treatment apparatus according to claim 2 is characterized by the above.

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