Exhaust gas treatment furnace and exhaust gas treatment apparatus using the same
The compact exhaust gas treatment furnace with a ceramic inner cylinder and reversing gas flow, along with reducing gas and oxygen, addresses the inefficiencies of conventional furnaces by improving energy use and reducing thermal NOx, achieving efficient pollutant detoxification.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- KANKEN TECHNO
- Filing Date
- 2025-03-11
- Publication Date
- 2026-07-03
AI Technical Summary
Conventional exhaust gas treatment furnaces for semiconductor manufacturing exhaust gases are large due to heat diffusion, inefficient in energy use, and produce significant thermal NOx as a by-product.
A compact exhaust gas treatment furnace design with a ceramic inner cylinder member to insulate heat and a reversing gas flow path, combined with reducing gas and oxygen addition for enhanced thermal decomposition, reduces heat loss and thermal NOx production.
The furnace achieves efficient detoxification of pollutants like CF4 and N2O with reduced energy consumption and minimal thermal NOx production, enhancing the overall treatment efficiency.
Smart Images
Figure 2026111465000001_ABST
Abstract
Description
Technical Field
[0001] The present invention mainly relates to an exhaust gas treatment furnace suitable for detoxifying exhaust gas containing hardly decomposable CF4 and the like, and an exhaust gas treatment apparatus using the exhaust gas treatment furnace.
Background Art
[0002] In the manufacturing processes of semiconductor devices and liquid crystal displays, various types of fluorine compound gases are used as cleaning gases, etching gases, etc. Such fluorine compounds are referred to as "PFCs", and typical examples include perfluorocarbons such as CF4, C2F6, C3F8, C4F8, C5F8, hydrofluorocarbons such as CHF3, and inorganic fluorine-containing compounds such as SF6 and NF3. In addition, in the manufacturing process of semiconductor devices and the like, N2O (nitrous oxide) etc. are used as material gases in the production of nitride films. And various types of PFCs, N2O, etc. used in the manufacturing processes of semiconductor devices and liquid crystal displays are discharged as exhaust gas together with N2, Ar, etc. used as carrier gases, purge gases, etc. In this specification, this exhaust gas is referred to as "semiconductor manufacturing exhaust gas" or simply "exhaust gas" throughout. Also, the manufacturing processes of semiconductor devices and liquid crystal displays are collectively referred to as "semiconductor manufacturing processes".
[0003] Here, the proportion of PFCs, N2O, etc. in the entire exhaust gas is small compared to other gases such as N2 and Ar, but these PFCs, N2O, etc. have a very large global warming potential (GWP) hundreds to tens of thousands of times that of CO2 and a very long atmospheric lifetime compared to CO2. Therefore, even when a small amount is discharged into the atmosphere, the impact is enormous. Furthermore, perfluorocarbons represented by CF4 and C2F6 are known to be difficult to decompose because the C-F bond is stable (the bond energy is as large as 130 kcal / mol). For this reason, various technologies for detoxifying used PFCs, N2O, etc. from exhaust gas have been developed.
[0004] As a technology for detoxifying exhaust gases containing such persistent PFCs and N2O, for example, Patent Document 1 (Japanese Patent Publication No. 2002-188810) discloses an exhaust gas treatment device in which dust and other particles contained in the harmful exhaust gas are removed by an inlet scrubber, the exhaust gas is then heated and decomposed in an exhaust gas treatment furnace equipped with an electric heater, and the decomposed gas is detoxified by gas-liquid contact in a wet outlet scrubber. [Prior art documents] [Patent Documents]
[0005] [Patent Document 1] Japanese Patent Publication No. 2002-188810 [Overview of the Initiative] [Problems that the invention aims to solve]
[0006] However, the above-mentioned conventional technology had the following problems. Specifically, when the PFCs in the exhaust gas mainly consist of the persistent CF4, the electric heater must be used at a very high temperature of 1500°C or higher. When an electric heater is used in such a temperature range, heat tends to diffuse easily to the surrounding area through the furnace wall of the exhaust gas treatment furnace. Therefore, in order to prevent such heat diffusion, the insulation material attached to the outer perimeter of the furnace wall must be made thicker, which leads to the problem of the exhaust gas treatment furnace becoming larger. Furthermore, the "2030 Agenda for Sustainable Development" was adopted at the UN Summit in September 2015, and since then, various discussions and considerations have been held regarding the efficient use of energy in the future. Under these circumstances, there is an increasing need for higher efficiency and the resulting energy savings in exhaust gas treatment systems equipped with the aforementioned conventional electric heaters, which consume a relatively large amount of electricity as energy during heating. Furthermore, as mentioned above, semiconductor manufacturing exhaust gases contain a large amount of nitrogen components derived from N2O and N2, which also presents the problem that a large amount of thermal NOx (nitrogen oxides) is produced as a by-product during thermal decomposition of these exhaust gases.
[0007] Therefore, the primary objective of the present invention is to provide an exhaust gas treatment furnace that is more compact than conventional ones, enables more efficient use of electrical energy, and can significantly improve the efficiency of exhaust gas treatment for various types of pollutants, such as semiconductor manufacturing exhaust gas, and an exhaust gas treatment apparatus using the same. A secondary objective of the present invention is to reduce the by-production of thermal NOx associated with the thermal decomposition of exhaust gas. [Means for solving the problem]
[0008] To achieve the above objectives, the present invention provides, for example, a flue gas treatment furnace that thermally decomposes flue gas E mainly discharged from semiconductor manufacturing processes, as shown in Figure 1, as follows. Specifically, the furnace body 12 is a sealed, vertically cylindrical furnace body 12 with a gas processing space 12a formed inside and a gas outlet 12b drilled in the center of its bottom wall; a long electric heater 14 is suspended from the center of the ceiling of the furnace body 12 to heat the gas processing space 12a; and a ceramic inner cylinder member 16 is attached to the inner bottom surface of the furnace body 12 so that its base end surrounds the periphery of the gas outlet 12b, and its tip opens at a position close to the ceiling of the furnace body 12 to surround the outer circumference of the electric heater 14. A gas inlet 12c is drilled in either the ceiling wall or the bottom wall of the furnace body 12 so that the flow of exhaust gas E in the gas processing space 12a flows along its axial direction on the outer surface of the ceramic inner cylinder member 16, then reverses direction and flows along its axial direction on the inner surface of the ceramic inner cylinder member 16.
[0009] The present invention provides, for example, the following effects: When the electric heater 14 is activated within the furnace body 12 to begin heating, the inside (internal space) of the ceramic inner cylinder member 16 is heated first, and this heat is then propagated to the outside via the ceramic inner cylinder member 16. In the exhaust gas treatment furnace of the present invention, the flow of exhaust gas E within the gas treatment space 12a flows along the axial direction of the outer circumferential surface of the ceramic inner cylinder member 16, and then (with the flow direction reversed) flows along the axial direction of the inner circumferential surface of the ceramic inner cylinder member 16. Therefore, the exhaust gas E flowing along the outer circumferential surface of the ceramic inner cylinder member 16 is preheated before it flows into the inner circumferential surface of the ceramic inner cylinder member 16 (= the internal space which is the site of actual thermal decomposition of the exhaust gas E). Furthermore, the layer of exhaust gas E flowing along the axial direction of the outer circumferential surface of the ceramic inner cylinder member 16 functions as an insulating layer, thus reducing the release of heat from within the gas treatment space 12a to the outside of the furnace through the furnace wall of the furnace body 12.
[0010] In the present invention, it is preferable to further include, for example as shown in Figure 2, a reducing gas supply means 40 that supplies a reducing gas G to the exhaust gas E supplied into the furnace body 12, and an oxygen supply means 42 that supplies oxygen to the exhaust gas E supplied into the furnace body 12. In this case, by adding reducing gas G and oxygen when thermally decomposing the exhaust gas E in the furnace body 12, it is possible to improve the thermal decomposition efficiency of the exhaust gas E and reduce the amount of thermal NOx produced as a by-product.
[0011] Furthermore, in the present invention, for example, as shown in Figure 3, one or more ceramic outer cylinder members 18 are arranged concentrically in a plan view around the ceramic inner cylinder member 16 within the gas processing space 12a. Of these ceramic outer cylinder members 18, odd-numbered members counting from the ceramic inner cylinder member 16 side are suspended from the ceiling surface of the furnace body 12, and even-numbered members counting from the ceramic inner cylinder member 16 side are erected from the bottom surface of the furnace body 12. Furthermore, it is preferable that the gas inlet 12c be drilled in either the ceiling wall or the bottom wall of the furnace body 12 such that the flow of exhaust gas E in the gas processing space 12a flows along the axial direction of the outermost ceramic outer cylinder member 18, then reverses direction and flows along the axial direction of the inner circumferential surface of the outermost ceramic outer cylinder member 18, and also flows along the axial direction of the outer circumferential surface of the ceramic inner cylinder member 16, then reverses direction and flows along the axial direction of the inner circumferential surface of the ceramic inner cylinder member 16. In this case, the heat propagated to the outside via the ceramic inner cylinder member 16 can be recovered more effectively by the exhaust gas E, and the release of heat from the gas processing space 12a to the outside of the furnace via the furnace wall of the furnace body 12 can be further reduced.
[0012] The second invention in the present invention is an exhaust gas treatment apparatus using the above-described exhaust gas treatment furnace, characterized in that it comprises any of the above-described exhaust gas treatment furnaces and at least one of an inlet scrubber 20 for pre-washing the exhaust gas E to be treated before being introduced into the exhaust gas treatment furnace, or an outlet scrubber 22 for cooling and washing the exhaust gas E that has been thermally decomposed in the exhaust gas treatment furnace. [Effects of the Invention]
[0013] According to the present invention, in addition to being more compact than conventional devices, it is possible to further improve the efficient use of electrical energy and provide an exhaust gas treatment furnace that can significantly improve the detoxification efficiency of semiconductor manufacturing exhaust gases consisting of various types of substances to be detoxified, such as CF4 and N2O, and an exhaust gas treatment apparatus using the same. Furthermore, it is possible to significantly reduce the amount of thermal NOx produced as a by-product during the thermal decomposition of exhaust gas. [Brief explanation of the drawing]
[0014] [Figure 1] This is an explanatory diagram showing an example of an exhaust gas treatment device using an exhaust gas treatment furnace according to one embodiment (first embodiment) of the present invention. [Figure 2] This is an explanatory diagram showing an example of an exhaust gas treatment device using an exhaust gas treatment furnace according to another embodiment of the present invention (a modification of the first embodiment). [Figure 3] Figure 3A shows an exhaust gas treatment furnace of another embodiment (second embodiment) of the present invention, with Figure 3A being a partial vertical cross-sectional view in a front view and Figure 3B being a cross-sectional view taken along line A-A' in Figure 3A. [Modes for carrying out the invention]
[0015] The following describes embodiments of the exhaust gas treatment furnace and exhaust gas treatment apparatus using the present invention, which are primarily suitable for removing harmful substances from exhaust gases discharged from semiconductor manufacturing processes, with reference to the drawings. Figure 1 is an explanatory diagram showing an example of an exhaust gas treatment device X using an exhaust gas treatment furnace 10 according to one embodiment (first embodiment) of the present invention. This exhaust gas treatment device X is a device that detoxifies exhaust gas E containing PFCs, N2O, etc., emitted from an emission source (mainly semiconductor manufacturing process) not shown, by thermal decomposition, and is generally composed of an exhaust gas treatment furnace 10, an inlet scrubber 20, and an outlet scrubber 22.
[0016] The exhaust gas treatment furnace 10 is a device that thermally decomposes PFCs, N2O, etc. in the exhaust gas E using an electric heater 14, and is generally composed of a furnace body 12, an electric heater 14, and a ceramic inner cylinder member 16.
[0017] The furnace body 12 is a sealed cylindrical (sealed circular cylindrical in the illustrated embodiment) container body in which at least its inner surface is made of a refractory material such as castable, and a gas treatment space 12a is formed inside. As shown in FIG. 1, this furnace body 12 is erected so that the flat part (of the furnace body 12) faces up and down during use, and a gas discharge port 12b is formed in the central part of the bottom wall surface. Further, in the present embodiment, a ceramic inner cylinder member 16 is attached so as to surround the gas discharge port 12b, and a gas inlet 12c for introducing the exhaust gas E to be treated into the gas treatment space 12a inside the furnace body 12 is formed at a position separated from the gas discharge port 12b on the bottom wall surface of the furnace body 12. For this reason, the exhaust gas E introduced into the gas treatment space 12a of the furnace body 12 flows along the outer peripheral surface side of the ceramic inner cylinder member 16 in its axial direction and then reverses, and flows along the inner peripheral surface side of the ceramic inner cylinder member 16 in its axial direction. Furthermore, a heater insertion port 12d for inserting the electric heater 14 is formed in the ceiling part of the furnace body 12, and a heat insulating material 12e is attached to the outer peripheral surface of the furnace body 12 and the outer wall side of the ceiling part.
[0018] In addition, in the present embodiment, the case where the furnace body 12 is formed in a sealed circular cylindrical shape is shown, but the shape of this furnace body 12 may be any shape as long as it is a cylindrical shape with both ends sealed, for example, a sealed rectangular cylindrical shape or the like.
[0019] The electric heater 14 serves as a heat source for heating the gas treatment space 12a within the furnace body 12 and has a long, rod-shaped heating element 14a. The heating element 14a can be appropriately selected from known ones according to the thermal decomposition temperature of the exhaust gas E to be treated and the types of thermal decomposition products. For example, when the exhaust gas E contains PFCs as the component to be treated, a heating element 14a is used that has corrosion resistance against HF (hydrogen fluoride) by-produced by the thermal decomposition of the PFCs and can generate heat at high temperatures. Specifically, it includes those made of ceramics such as silicon carbide (SiC), molybdenum disilicide (MoSi2), and lanthanum chromite (LaCrO3), or those in which a heating resistance metal wire such as a nichrome wire or a kanthal (registered trademark of Sandvik AB) wire is spirally wound inside a protective tube made of ceramics such as alumina or metal such as Hastelloy (registered trademark). Among these, it is particularly preferable to use a heating element 14a made of ceramics.
[0020] This electric heater 14 is detachably attached by inserting the heating element 14a into the internal space of the furnace body 12 through a heater insertion port 12d provided at the center of the ceiling wall of the furnace body 12. For this reason, this electric heater 14 comes to be vertically installed from the ceiling portion of the furnace body 12, and the outer periphery of the long heating element 14a is surrounded by the ceramic inner cylinder member 16 with a gap. In the illustrated embodiment, a case where one electric heater 14 is vertically installed is shown, but the number of electric heaters 14 installed in the furnace body 12 is not limited to this, and for example, two or more may be used. Also, when installing a plurality of electric heaters 14, the electric heaters 14 may be arranged on the outer peripheral surface side of the ceramic inner cylinder member 16.
[0021] The ceramic inner cylinder member 16 is for controlling the flow of exhaust gas E in the gas processing space 12a, and is made of ceramics such as alumina (Al2O3), zirconia (ZrO2), silicon carbide (SiC), silicon nitride (Si3N4), molybdenum disilicide (MoSi2), and lanthanum chromite (LaCrO3), and is a cylindrical member with both longitudinal ends open. One longitudinal end of this ceramic inner cylinder member 16 is attached to the inner bottom wall surface of the furnace body 12 so as to surround the gas outlet 12b. The ceramic inner cylinder member 16 extends across the gas processing space 12a of the furnace body 12, and its other longitudinal end is positioned close to the ceiling surface of the furnace body 12.
[0022] In this embodiment, the ceramic inner cylinder member 16 is shown to be formed in a cylindrical shape, but the shape of the ceramic inner cylinder member 16 can be any shape as long as it is a cylinder with both ends open, for example, it may be a rectangular cylinder.
[0023] The exhaust gas treatment furnace 10, configured as described above, is equipped with temperature measuring means, such as a thermocouple for detecting the temperature of the gas treatment space 12a (not shown), and the temperature data (temperature signal) detected by this temperature measuring means is provided via a signal line to a control means consisting of a CPU (Central Processing Unit), memory, input device, and display device. A power supply unit (not shown) is also connected to this control means, and these various devices are controlled by this control means.
[0024] Furthermore, the exhaust gas treatment furnace 10 configured as described above is installed on a storage tank 24 in which a chemical solution such as water is stored. The upper end of an introduction pipe 26, which has approximately the same inner diameter as the gas inlet 12c, is connected to the gas inlet 12c, and the lower end of the introduction pipe 26 is connected to communicate with the flow region of the exhaust gas E (before thermal decomposition) after it has passed through the inlet scrubber 20, which will be described later, within the storage tank 24. On the other hand, the upper end of an exhaust pipe 28, which has approximately the same inner diameter as the gas outlet 12b, is also connected to the gas outlet 12b, and the lower end of the exhaust pipe 28 is connected to a region different from the flow region of the exhaust gas E (before thermal decomposition) after it has passed through the inlet scrubber 20 within the storage tank 24.
[0025] The inlet scrubber 20 is a wet scrubber that removes dust and water-soluble components contained in the exhaust gas E introduced into the exhaust gas treatment furnace 10. It consists of a straight-tube scrubber body 20a, a spray nozzle 20b installed near the top of the inside of the scrubber body 20a for spraying a chemical solution such as water, and a packing material 20c for promoting gas-liquid contact between the chemical solution sprayed from the spray nozzle 20b and the exhaust gas E. The packing material 20c is installed as needed. This inlet scrubber 20 is connected to an exhaust gas source (not shown), such as semiconductor manufacturing equipment, via an exhaust gas duct 30.
[0026] Furthermore, the inlet scrubber 20 is erected on top of the storage tank 24 (see Figure 1), or (not shown) it is installed separately from the storage tank 24 and connected to it by piping so that the drained liquid is sent to the storage tank 24. A circulation pump 32 is installed between the spray nozzle 20b and the storage tank 24 to lift the stored chemical solution in the storage tank 24 to the spray nozzle 20b.
[0027] In this embodiment shown in Figure 1, not only the wastewater from the inlet scrubber 20 but also the exhaust gas E after washing is sent to the storage tank 24, and the space between the liquid surface and the ceiling of the storage tank 24 (upper space) is used as an exhaust gas passage. Here, the symbol 24a in Figure 1 is a "partition" that separates the exhaust gas E washed in the inlet scrubber 20 so that it does not flow into the outlet scrubber 22 without passing through the exhaust gas treatment furnace 10.
[0028] The outlet scrubber 22 is a wet scrubber that cools the exhaust gas E after thermal decomposition that has passed through the exhaust gas treatment furnace 10, and ultimately removes dust, water-soluble components, etc., produced as by-products by thermal decomposition from the exhaust gas E. In this embodiment, it consists of a straight-tube scrubber body 22a, a downward-facing spray nozzle 22b installed near the top of the inside of the scrubber body 22a that sprays a chemical solution such as water from above, opposite to the direction of flow of the exhaust gas E, and a packing material 22c to promote gas-liquid contact between the chemical solution sprayed from the spray nozzle 22b and the exhaust gas E. The packing material 22c is installed as needed. This outlet scrubber 22 is erected in a region different from the flow area of the exhaust gas E (before thermal decomposition) after it has passed through the inlet scrubber 20 on the storage tank 24. From the opening at the bottom, the exhaust gas E after thermal decomposition (discharged into the storage tank 24 via the discharge pipe 28) is introduced, and the chemical solution that has been supplied by the spray nozzle 22b and then turned into wastewater is sent into the storage tank 24.
[0029] Furthermore, similar to the inlet scrubber 20 described above, in the illustrated embodiment, a circulation pump 32 is installed between the spray nozzle 22b and the storage tank 24 to lift the stored chemical solution in the storage tank 24 to the spray nozzle 22b. However, instead of the stored chemical solution in the storage tank 24, a new chemical solution such as fresh water may be supplied to the spray nozzle 22b.
[0030] Then, an exhaust fan 36 is connected to the atmospheric discharge piping system 34 near the top outlet of the outlet scrubber 22 to discharge the treated exhaust gas E into the atmosphere.
[0031] In addition, in the exhaust gas treatment apparatus X of this embodiment, parts other than the exhaust gas treatment furnace 10 are coated with corrosion-resistant linings or coatings made of polyvinyl chloride, polyethylene, unsaturated polyester resin, and fluororesin to protect each part from corrosion caused by corrosive components such as hydrofluoric acid contained in the exhaust gas E or produced by the decomposition of the exhaust gas E. Furthermore, the reference numeral 38 in Figure 1 is a heat exchanger for exchanging heat between the exhaust gas E flowing through the introduction pipe 26 and the exhaust gas E flowing through the discharge pipe 28, and is installed as needed.
[0032] Next, when performing exhaust gas E decontamination treatment using the exhaust gas treatment device X configured as described above, first, the operating switch (not shown) of the exhaust gas treatment device X is turned on to activate the electric heater 14 of the exhaust gas treatment furnace 10 and start heating inside the exhaust gas treatment furnace 10. Then, when the temperature in the gas processing space 12a reaches a predetermined temperature corresponding to the type of exhaust gas E to be processed, the exhaust fan 36 is activated and the introduction of exhaust gas E into the exhaust gas treatment device X begins. The exhaust gas E then passes through the inlet scrubber 20, the exhaust gas treatment furnace 10, and the outlet scrubber 22 in that order, and the components to be removed from the exhaust gas E (e.g., PFCs and N2O) are removed. Furthermore, a control means (not shown) controls the amount of electricity supplied to the electric heater 14 of the exhaust gas treatment furnace 10 so that the temperature in the gas processing space 12a is maintained at a predetermined temperature.
[0033] In the exhaust gas treatment device X of this embodiment, when the electric heater 14 is activated in the furnace body 12 to start heating, the inside (internal space) of the ceramic inner cylinder member 16 is heated first, and that heat is propagated to the outside via the ceramic inner cylinder member 16. Here, in the exhaust gas treatment furnace 10 of this embodiment, the flow of exhaust gas E in the gas treatment space 12a flows along the axial direction on the outer circumferential surface side of the ceramic inner cylinder member 16, and then (the flow direction reverses) flows along the axial direction on the inner circumferential surface side of the ceramic inner cylinder member 16. Therefore, the exhaust gas E flowing along the outer circumferential surface side of the ceramic inner cylinder member 16 is preheated before it flows into the inner circumferential surface side of the ceramic inner cylinder member 16 (= the internal space which is the site of actual thermal decomposition of the exhaust gas E). Furthermore, the layer of exhaust gas E flowing along the axial direction on the outer circumferential surface side of the ceramic inner cylinder member 16 functions as an insulating layer, which reduces the release of heat from the gas treatment space 12a to the outside of the furnace through the furnace wall of the furnace body 12.
[0034] In the above embodiment, the exhaust gas treatment device X is shown to be equipped with both an inlet scrubber 20 and an outlet scrubber 22. However, since the inlet scrubber 20 and the outlet scrubber 22 are provided as needed, it is also possible to provide only one of them.
[0035] Furthermore, the above-described embodiment can be modified as shown in Figure 2. Specifically, it comprises a reducing gas supply means 40 that supplies a reducing gas G to the exhaust gas E supplied into the furnace body 12, and an oxygen supply means 42 that supplies oxygen to the exhaust gas E supplied into the furnace body 12. Here, the reducing gas G supplied to the exhaust gas E by the reducing gas supply means 40 can be hydrogen, carbon monoxide, ammonia, hydrocarbons, etc. Also, in the embodiment of Figure 2, the reducing gas supply means 40 is connected near the gas inlet 12c and the oxygen supply means 42 is connected to the upper part of the furnace body 12, but the connection positions of the reducing gas supply means 40 and the oxygen supply means 42 are not limited to these, and any position is acceptable as long as the exhaust gas E, reducing gas G and oxygen can be sufficiently mixed in the gas processing space 12a of the furnace body 12.
[0036] In the exhaust gas treatment device X shown in Figure 2, configured as described above, for example, if a device with a power consumption of 7.0 kW, a treatment gas flow rate of N2 (carrier gas) = 180 L / min, CF4 = 1.25 L / min, and a set temperature of the electric heater 14 of 1320°C is used, adding 3.5 to 5.0 L / min of natural gas (13A) mainly composed of methane as the reducing gas G, and 8.0 to 11.5 L / min of oxygen, the CF4 decontamination efficiency can be increased to 90% or more, and the amount of NOx produced as a by-product can be reduced to 10 ppm or less.
[0037] Next, the exhaust gas treatment furnace 10 of the second embodiment shown in Figures 3A and 3B will be described. The difference from the exhaust gas treatment furnace 10 of the first embodiment described above is that it has a ceramic outer cylinder member 18. Note that the other parts are the same as those of the first embodiment described above, so the description of the first embodiment will be used to describe this embodiment.
[0038] The ceramic outer cylinder member 18, like the ceramic inner cylinder member 16 described above, is for controlling the flow of exhaust gas E in the gas treatment space 12a. It is made of ceramics such as alumina (Al2O3), zirconia (ZrO2), silicon carbide (SiC), silicon nitride (Si3N4), molybdenum disilicide (MoSi2), and lanthanum chromite (LaCrO3), and is a cylindrical member with both longitudinal ends open. One or more of these ceramic outer cylinder members 18 are provided so as to surround the outside of the ceramic inner cylinder member 16, and in a plan view, the ceramic outer cylinder member 18 and the ceramic inner cylinder member 16 are arranged concentrically (see Figure 2B). In the embodiment shown in Figure 2, two of these ceramic outer cylinder members 18 are installed.
[0039] Furthermore, of the ceramic outer cylinder members 18, odd-numbered members counting from the ceramic inner cylinder member 16 side are suspended from the ceiling surface of the furnace body 12, and even-numbered members counting from the ceramic inner cylinder member 16 side are erected from the bottom surface of the furnace body 12 (see Figure 2A). Then, a gas inlet 12c is drilled in either the ceiling wall or the bottom wall surface of the furnace body 12 so that the flow of exhaust gas E in the gas processing space 12a flows along the outer peripheral surface of the outermost ceramic outer cylinder member 18 in its axial direction, then reverses direction, flows along the inner peripheral surface of the outermost ceramic outer cylinder member 18 in its axial direction, and also flows along the outer peripheral surface of the ceramic inner cylinder member 16 in its axial direction, and then flows along the inner peripheral surface of the ceramic inner cylinder member 16 in its axial direction. In the embodiment shown in Figure 3, the outermost ceramic outer cylinder member 18 is the even-numbered member (second one) counting from the ceramic inner cylinder member 16 side, and is therefore erected from the bottom surface of the furnace body 12. Therefore, in order for the exhaust gas E to flow along the axial direction on the outer peripheral surface side of the outermost ceramic outer cylinder member 18, then reverse direction and flow along the axial direction on the inner peripheral surface side of the outermost ceramic outer cylinder member 18, a gas inlet 12c is drilled in the bottom wall surface of the furnace body 12, which is surrounded by the inner wall of the furnace body 12 and the outermost ceramic outer cylinder member 18.
[0040] According to the exhaust gas treatment furnace 10 of this embodiment, the heat from the electric heater 14 that is propagated to the outside via the ceramic inner cylinder member 16 can be recovered more effectively with the exhaust gas E, and the amount of heat released from the gas treatment space 12a to the outside of the furnace via the furnace wall of the furnace body 12 can be further reduced.
[0041] In the exhaust gas treatment furnace 10 of the second embodiment described above, the ceramic outer cylinder member 18 is shown to be formed in a cylindrical shape. However, the shape of this ceramic outer cylinder member 18 can be any shape as long as it is a cylindrical shape with both ends open, for example, it may be a rectangular cylinder. When the ceramic outer cylinder member 18 and the ceramic inner cylinder member 16 are formed in a rectangular cylinder shape or the like, they are arranged so that their circumscribed circles or inscribed circles are concentric in a plan view.
[0042] Furthermore, while the exhaust gas treatment furnace 10 of the first and second embodiments described above shows a case where one gas inlet 12c is drilled in the furnace body 12, for example, multiple gas inlet 12c may be provided and introduction piping 26 connected to each of them in order to uniformly pass exhaust gas E throughout the entire circumferential direction within the gas treatment space 12a. Of course, various modifications can be made within the scope that a person skilled in the art could foresee. [Explanation of Symbols]
[0043] 10: Exhaust gas treatment furnace, 12: Furnace body, 12a: Gas treatment space, 12b: Gas outlet, 12c: Gas inlet, 14: Electric heater, 16: Ceramic inner cylinder member, 18: Ceramic outer cylinder member, 20: Inlet scrubber, 22: Outlet scrubber, 40: Reducing gas supply means, 42: Oxygen supply means, E: Exhaust gas, X: Exhaust gas treatment device.
Claims
1. An exhaust gas treatment furnace that thermally decomposes exhaust gas (E), A sealed, vertically cylindrical furnace body (12) has a gas processing space (12a) formed inside and a gas outlet (12b) drilled in the center of the bottom wall, A long electric heater (14) is suspended from the center of the ceiling surface of the furnace body (12) to heat the gas processing space (12a), The furnace body (12) is attached to the inner bottom surface of the furnace body (12) such that its base end surrounds the periphery of the gas outlet (12b), and the ceramic inner cylinder member (16) has a tip that opens at a position close to the ceiling surface of the furnace body (12) and surrounds the outer circumference of the electric heater (14). An exhaust gas treatment furnace characterized in that a gas inlet (12c) is drilled in either the ceiling wall or the bottom wall of the furnace body (12) such that the flow of exhaust gas (E) in the gas treatment space (12a) flows along the outer circumferential surface of the ceramic inner cylindrical member (16), then reverses direction, and flows along the inner circumferential surface of the ceramic inner cylindrical member (16) along its axial direction.
2. In the exhaust gas treatment furnace according to claim 1, An exhaust gas treatment furnace further comprising: a reducing gas supply means (40) for supplying a reducing gas (G) to the exhaust gas (E) supplied into the furnace body (12); and an oxygen supply means (42) for supplying oxygen to the exhaust gas (E) supplied into the furnace body (12).
3. In the exhaust gas treatment furnace according to claim 1, Outside the ceramic inner cylindrical member (16) within the gas processing space (12a), one or more ceramic outer cylindrical members (18) are arranged concentrically in a plan view, surrounding the ceramic inner cylindrical member (16). Of the ceramic outer cylinder members (18) described above, odd-numbered members counting from the ceramic inner cylinder member (16) side are suspended from the ceiling surface of the furnace body (12), and even-numbered members counting from the ceramic inner cylinder member (16) side are erected from the bottom surface of the furnace body (12). An exhaust gas treatment furnace characterized in that a gas inlet (12c) is drilled in either the ceiling wall or the bottom wall of the furnace body (12) such that the flow of exhaust gas (E) in the gas treatment space (12a) flows along the axial direction of the outermost ceramic outer cylinder member (18), then reverses direction and flows along the axial direction of the inner circumferential surface of the outermost ceramic outer cylinder member (18), and also flows along the axial direction of the outer circumferential surface of the ceramic inner cylinder member (16), then reverses direction and flows along the axial direction of the inner circumferential surface of the ceramic inner cylinder member (16).
4. An exhaust gas treatment furnace according to any one of claims 1 to 3, An exhaust gas treatment apparatus characterized by comprising at least one of the following: an inlet scrubber (20) for pre-washing the exhaust gas (E) to be treated before introducing it into the exhaust gas treatment furnace, or an outlet scrubber (22) for cooling and washing the exhaust gas (E) that has been thermally decomposed in the exhaust gas treatment furnace.