Exhaust gas treatment apparatus

Abstract

To provide an exhaust gas treatment apparatus capable of enhancing the efficiency of removing nitrogen oxides contained in exhaust gas.SOLUTION: A heating device 1 is provided with: an exhaust gas introduction part 6 for introducing exhaust gas in a manner of swirlingly flowing into the heating device; and a nozzle 7 for spraying, in a mixed state of gas and liquid, the exhaust gas having been introduced into the exhaust gas introduction part 6.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an exhaust gas treatment device, and more particularly to an exhaust gas treatment device capable of enhancing the detoxification efficiency of nitrogen oxides contained in exhaust gas.

Background Art

[0002] PFC (perfluoro-compound) gas is a general term for CF4, C2F6, C3F8, SF6, NF3, etc. PFC gas is used in gases for semiconductor etching, cleaning gases for CVD devices for semiconductors, insulating gases, and the like. Since this PFC gas is a greenhouse gas and is subject to regulations on atmospheric emissions, various decomposition methods have been studied. For example, a treatment method and a treatment device in which the gas is heat-decomposed by a heater and then washed with water have been proposed.

[0003] By the way, when treating PFC gas by thermal decomposition, corrosive gases such as F2 are generated. Therefore, in the case of heater-type thermal decomposition, corrosion of pipes such as the core tube of the heater becomes a major problem. Conventionally, it has been necessary to use metals or high-purity ceramics rich in corrosion resistance for pipes such as the core tube, resulting in a problem that the treatment device becomes expensive.

[0004] In order to address this problem, the applicant of the present application previously proposed a treatment device for exhaust gas containing a fluorine compound, which includes a heating device for introducing and heat-decomposing exhaust gas containing a fluorine compound, an exhaust gas introduction section for introducing the exhaust gas into the heating device as a swirling flow, and a water vapor generation mechanism provided at the central position of the swirling flow (see Patent Document 1).

[0005] The exhaust gas treatment device containing a fluorine compound disclosed in Patent Document 1 weakens the corrosiveness of the exhaust gas containing the fluorine compound and protects the pipe through which the exhaust gas flows with an oxide film generated by heated steam, thereby significantly suppressing the corrosion of the pipe through which the exhaust gas flows, and can solve the problems of the conventional exhaust gas treatment method and treatment device containing a fluorine compound such as PFC gas.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, this type of exhaust gas may contain N2O (nitrogen oxide), but there is a problem that the detoxification efficiency of nitrogen oxide is low depending on the exhaust gas treatment device containing the fluorine compound disclosed in Patent Document 1.

[0008] In view of the problems of the above-mentioned conventional exhaust gas treatment device containing a fluorine compound, while weakening the corrosiveness of the exhaust gas containing a fluorine compound and protecting the pipe through which the exhaust gas flows with an oxide film generated by heated steam, the present invention aims to provide an exhaust gas treatment device that can enjoy the advantages of the exhaust gas treatment device containing a fluorine compound disclosed in Patent Document 1, which can significantly suppress the corrosion of the pipe through which the exhaust gas flows, and can increase the detoxification efficiency of nitrogen oxide contained in the exhaust gas.

Means for Solving the Problems

[0009] To achieve the above object, the exhaust gas treatment device of the present invention introduces exhaust gas and performs pyrolysis treatment In an exhaust gas treatment apparatus equipped with a heating device for treatment, an exhaust gas introduction section for introducing exhaust gas into the heating device as a swirling flow is provided, and a nozzle for spraying the exhaust gas introduced into the exhaust gas introduction section in a state where gas and liquid are mixed is provided.

[0010] In this case, the gas can be selected from one or more of nitrogen gas, air, CDA, argon gas, ammonia, and methane.

[0011] Also, the liquid can be selected from one or more of water, brine, ink, urea water, alkaline liquid, acidic liquid, and alcohol.

[0012] Also, the spraying can be performed from above the swirling flow, along the flow direction of the swirling flow, or against the flow direction of the swirling flow.

[0013] Also, the liquid preheated by heat exchange with the exhaust gas can be supplied to the nozzle.

Advantages of the Invention

[0014] According to the exhaust gas treatment apparatus of the present invention, the corrosiveness of the exhaust gas can be weakened, the pipe through which the exhaust gas flows can be protected, and thus, in addition to significantly suppressing the corrosion of the pipe through which the exhaust gas flows, the removal efficiency of nitrogen oxides contained in the exhaust gas can be increased.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments of the exhaust gas treatment apparatus of the present invention will be described with reference to the drawings.

[0017] Figs. 1 to 3 show an embodiment of the exhaust gas treatment apparatus of the present invention. This exhaust gas treatment apparatus is similar to the exhaust gas treatment apparatus containing a fluorine compound disclosed in Patent Document 1, and is for subjecting exhaust gas containing a fluorine compound or the like to pyrolysis treatment and then to washing treatment, and the pyrolysis treatment is carried out in the presence of water vapor.

[0018] Specifically, this exhaust gas treatment apparatus includes a heating device 1 for introducing exhaust gas containing a fluorine compound or the like and subjecting it to pyrolysis treatment, a washing device 2 for introducing the exhaust gas pyrolyzed by the heating device 1 and subjecting it to washing treatment, and an exhaust gas introduction section 6 for introducing the exhaust gas into the heating device 1 as a swirling flow, and a nozzle 7 for spraying the exhaust gas introduced into the exhaust gas introduction section 6 in a state where gas and liquid are mixed.

[0019] As shown in Fig. 2, the heating device 1 includes a cylindrical hearth tube 11 into which exhaust gas is introduced and a heater 12 surrounding the hearth tube 11.

[0020] The exhaust gas introduction section 6 is, for example, a multi-chamber forming an exhaust gas inlet 61 capable of introducing the exhaust gas as a swirling flow from a plurality of tangential directions (in this embodiment, four directions), and when the exhaust gas concentration is too high, the exhaust gas can be diluted by the N2 gas introduced from the N2 gas introduction section 4. Further, the heating device 1 is enabled to control the internal temperature, and an air introduction section 5 for introducing air as required is connected. to the heating device 1.

[0021] The cleaning device 2 includes a tank 21 for introducing the exhaust gas treated by the heating device 1 and a spray nozzle (not shown) for spraying water onto the exhaust gas introduced into the tank 21, and can remove water-soluble components such as HF and NO2 contained in the exhaust gas by absorbing them in water. After cleaning, the gas is discharged into the atmosphere, and the wastewater that has absorbed HF, NO2, etc. in the cleaning device 2 is discharged to the outside.

[0022] The liquid supply mechanism 3 for supplying liquid to the nozzle 7 includes a tank 31 for storing the liquid and a pump 32 for sending the liquid stored in the tank 31 to the nozzle 7, and the liquid sent through the pipe 33 is supplied to the nozzle 7. This liquid can be selected from one or more of water, brine, ink, urea water, alkaline liquid, acidic liquid, and alcohol, and thereby, the exhaust gas can be decomposed into substances with weak corrosivity. In particular, by applying an alkaline liquid, specifically, ammonia water, NaOH water, Ca(OH)2 water, KOH water, LiOH water, etc., the corrosive power of the exhaust gas can be further weakened by a neutralization reaction. As the acidic liquid, hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, acetic acid, HBr water, etc. can be used, and as the alcohol, methanol, ethanol, 1-propanol, 2-propanol, butanol, 2-aminoethanol, triethanolamine, diethanolamine, etc. can be used.

[0023] Gas is supplied to the nozzle 7 from a gas supply source 81 such as a gas cylinder or a compressor of the gas supply mechanism 8 through a pipe 82 in order to spray these liquids. This gas can be selected from one or more of nitrogen gas, air, CDA, argon gas, ammonia, and methane.

[0024] The nozzle 7 can spray in a state where the gas and the liquid supplied to the nozzle 7 are mixed, and a two-fluid nozzle or a three-fluid nozzle that can make the particle diameter of the mist finer can be preferably used. Thereby, the vaporization of the sprayed liquid can be promoted.

[0025] As the form of the spray from the nozzle 7, depending on the properties of the exhaust gas to be treated, etc., it is possible to select a form in which the spray is performed from above the swirling flow of the exhaust gas introduced into the exhaust gas introduction section 6 (Fig. 3(a)), the spray is performed along the flow direction of the swirling flow (Fig. 3(b)), or the spray is performed opposite to the flow direction of the swirling flow (Fig. 3(c)).

[0026] Here, as shown in Fig. 2, the liquid sent through the pipe 33 can be preheated by heat exchange with the exhaust gas and then supplied to the nozzle 7. The heat exchange between the liquid and the exhaust gas can be achieved by providing, as a heat exchange section above the exhaust gas introduction section 6, a tank 34 for temporarily storing the liquid (in this case, a partition such as a spiral through which the liquid circulates can be provided inside the tank), or by providing a flow path through which the liquid circulates in a spiral shape, a zigzag shape, etc. (not shown). Moreover, a switching valve 35 can be provided in the pipe 33 so that the flow path through which the liquid circulates can be switched between with preheating and without preheating. Thereby, by raising the temperature of the liquid (for example, to 50 to 80°C), the vaporization of the sprayed liquid can be promoted. In addition, the liquid sent through the pipe 33 can also be heated (or cooled) by a heating unit (or cooling unit) (not shown) provided in the pipe 33.

[0027] By this exhaust gas treatment apparatus, for example, in the decomposition of exhaust gas using water in the liquid, when NF3 is detoxified with water, HF is generated by the following reaction. At high temperatures, HF has a weaker corrosive power than F2. Also, in combination with this, the pipes including the core pipe 11 can be protected by the oxide film generated by the heated steam, so the corrosion of the pipes including the core pipe 11 can be suppressed. 2NF3 + 3H2O → NO + NO2 + 6HF

[0028] By the way, this type of exhaust gas may contain N2O (nitrogen oxide). This exhaust gas treatment device is provided with an exhaust gas introduction section 6 that introduces exhaust gas into the heating device 1 as a swirling flow, and a nozzle 7 that sprays the exhaust gas introduced into the exhaust gas introduction section 6 in a state where gas and liquid are mixed. Therefore, the detoxification efficiency of nitrogen oxides contained in the exhaust gas can be increased.

[0029] [Nitrogen Oxide Detoxification Test] Under the conditions shown in Table 1 (gas (CDA (clean dry air)): 20 slm, liquid (clean water): 10 cc / min, no preheating of the liquid), this exhaust gas treatment device (Example in which gas (CDA (clean dry air)) and liquid (clean water) are sprayed in a mixed state from nozzle 7) and an exhaust gas treatment device containing a fluorine compound disclosed in Patent Document 1 (Comparative Example in which gas (CDA (clean dry air)) and liquid (clean water) are separately introduced (the liquid (clean water) is dropped)) were used to conduct a nitrogen oxide detoxification test.

[0030]

Table 1

[0031] From the results shown in Table 1, it was confirmed that by changing the method of introducing the liquid (clean water) to be sprayed in a mist form (Example), the detoxification efficiency of N2O can be increased by about 5 to 10% and the power consumption of the heater can be reduced by about 10% compared to the comparative example in which the liquid (clean water) is dropped.

[0032] This exhaust gas treatment device can weaken the corrosiveness of the exhaust gas and protect the pipes through which the exhaust gas flows. As a result, in addition to being able to significantly suppress the corrosion of pipes such as the core pipe 11 through which the exhaust gas flows, the detoxification efficiency of nitrogen oxides contained in the exhaust gas can be increased.

[0033] As described above, the exhaust gas treatment device of the present invention has been described based on an example in the case of subjecting exhaust gas to heat decomposition treatment and then washing treatment. However, the present invention is not limited to the configuration described in the above example. Rather, for example, it can be appropriately configured within the scope not departing from the gist thereof, such as being applied to the thermal decomposition treatment of exhaust gas containing monosilane (SiH4) or the like.

Industrial Applicability

[0034] The exhaust gas treatment apparatus of the present invention can weaken the corrosiveness of exhaust gas and protect the pipes through which the exhaust gas flows. As a result, in addition to being able to significantly suppress the corrosion of the pipes through which the exhaust gas flows, it has the characteristic of being able to increase the removal efficiency of nitrogen oxides contained in the exhaust gas. Therefore, it can be suitably used for the treatment of exhaust gas generated in the semiconductor manufacturing process, and can also be widely used for the treatment of other exhaust gases.

Explanation of Signs

[0035] 1 Heating device 11 Core tube 12 Heater 2 Cleaning device 21 Tank 3 Liquid supply mechanism 31 Tank 32 Pump 33 Pipe 34 Tank 35 Switching valve 4 N2 gas introduction part 5 Air introduction part 6 Exhaust gas introduction part 61 Exhaust gas inlet 7 Nozzle 8 Gas supply mechanism 81 Gas supply source 82 Pipe

Claims

**Claim 1** In an exhaust gas treatment apparatus comprising a heating device for introducing exhaust gas and performing pyrolysis treatment, the heating device is provided with an exhaust gas introduction section for introducing exhaust gas as a swirling flow, and a nozzle for spraying the exhaust gas introduced into the exhaust gas introduction section in a state where gas and liquid are mixed. An exhaust gas treatment apparatus characterized by the above. **Claim 2** The exhaust gas treatment apparatus according to claim 1, wherein the gas is composed of one or more of nitrogen gas, air, CDA, argon gas, ammonia, and methane. **Claim 3** The exhaust gas treatment apparatus according to claim 1, wherein the liquid is composed of one or more of water, brine, ink, urea water, alkaline liquid, acidic liquid, and alcohol. **Claim 4** The exhaust gas treatment apparatus according to claim 1, 2, or 3, wherein the spraying is performed from above the swirling flow. **Claim 5** The exhaust gas treatment apparatus according to claim 1, 2, or 3, wherein the spraying is performed along the flow direction of the swirling flow. **Claim 6** The exhaust gas treatment apparatus according to claim 1, 2, or 3, wherein the spraying is performed in a direction opposite to the flow direction of the swirling flow. **Claim 7** The exhaust gas treatment apparatus according to claim 1, 2, or 3, wherein the liquid preheated by exchanging heat with the exhaust gas is supplied to the nozzle.

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