JP2020110753A - Treatment equipment for and treatment method of gas including nitrogen oxide - Google Patents

Abstract

To provide treatment equipment capable of treating nitrogen oxide at comparatively low cost.SOLUTION: Treatment equipment 100 of the present invention comprises: a treatment tank 8 to be filled with synthetic zeolite; an inlet line 5 connected to an inlet of the treatment tank 8 and introducing gas including nitrogen oxide to the treatment tank 8; and an ozone generator 1 connected to the inlet line 5. The ozone generator 1 generates ozone of a sufficient quantity for oxidizing nitrogen monoxide included in the gas to nitrogen dioxide, and the synthetic zeolite decomposes excessive ozone unconsumed by oxidation reaction of the nitrogen monoxide, and physically adsorbs the nitrogen dioxide included in the gas.SELECTED DRAWING: Figure 2

Description

The present invention relates to a treatment apparatus and a treatment method for a gas containing nitrogen oxides such as nitric oxide and nitrogen dioxide, and particularly to a treatment apparatus for a gas discharged from an exhaust gas treatment apparatus installed on the downstream side of a semiconductor treatment apparatus. , And a processing method.

In a semiconductor manufacturing process for manufacturing a semiconductor device, a liquid crystal panel, an LED and the like, a process gas is introduced into a vacuum-exhausted process chamber to perform various kinds of processing such as etching and CVD. Further, the process chamber and the exhaust system equipment connected to the process chamber are regularly cleaned by flowing a cleaning gas. Exhaust gas such as process gas and cleaning gas contains silane-based gas, halogen gas, PFC gas, etc., and has an adverse effect on the human body and adversely affects the global environment such as causing global warming. It is not preferable to release it as it is.

Therefore, these exhaust gases are detoxified by an exhaust gas treatment apparatus installed on the downstream side of the semiconductor processing apparatus and then released to the atmosphere. Examples of such an exhaust gas treatment device include a combustion type exhaust gas treatment device, a heater type exhaust gas treatment device, a plasma type exhaust gas treatment device, and a catalytic type exhaust gas treatment device.

In these exhaust gas treatment devices, when trying to treat a hardly decomposable substance such as PFC with a high removal rate, nitrogen oxides (hereinafter simply referred to as "NOx") are used because the treatment is performed at a high temperature. However, there is a problem in that the amount of NOx emitted increases and the amount of NOx discharged as a by-product increases. For example, when an excessive amount of oxygen is supplied to a combustion-type exhaust gas treatment device to form a high-temperature flame, nitrogen in the air, which is originally difficult to react, and oxygen react with each other to generate nitrogen oxides (called “thermal NOx”). And nitrogen oxides (sometimes referred to as "fuel NOx") are produced from fuel-derived nitrogen compounds. In particular, when the gas introduced into the exhaust gas treatment device contains nitrogen-containing compounds such as nitrogen trifluoride (NF ₃ ), ammonia (NH ₃ ), and amine compounds, the gas discharged from the exhaust gas treatment device is The amount of NOx contained increases.

In recent years, from the viewpoint of environmental problems, regulations on the amount of NOx emitted from factories have become stricter. Therefore, it has become necessary to install a NOx treatment device downstream of the exhaust gas treatment device to significantly reduce the amount of NOx emitted from the factory.

Conventional NOx treatment devices are roughly classified into a dry treatment device that uses a catalyst, ammonia, and the like, and a wet treatment device that uses water, an alkaline agent, and the like. Examples of the wet treatment device are a device for contacting a large amount of water with NOx to absorb NOx in water, a device for absorbing NOx in water in which an alkaline agent such as sodium hydroxide (NaOH) is dissolved, and a peroxide. Examples include a device that oxidizes NOx by bringing hydrogen water (H ₂ O ₂ ) into contact with NOx.

Examples of a conventional dry processing apparatus include an apparatus that oxidizes and decomposes NOx by bringing NOx into contact with a processing agent containing a noble metal catalyst such as platinum (Pt) or palladium (Pd), and after adding ammonia as a reducing agent to the gas. Then, a selective catalytic reduction (SCR) denitration device that decomposes the gas with a catalyst, ozone gas (or ozone water) is added to the exhaust gas, and nitric oxide (NO) contained in NOx is converted into nitrogen dioxide (NO). ₂ ), and then adsorbing nitrogen dioxide to the adsorbent.

JP, 2003-284925, A JP, 2010-240620, A

Each of the above-mentioned wet treatment devices has a problem that the treatment efficiency of NOx is low. Further, when NOx is treated using the wet treatment device, a wastewater treatment device for treating a large amount of wastewater discharged from the wet treatment device is required. When the wet treatment device uses an alkaline agent or hydrogen peroxide solution, a chemical solution supply device for the alkaline agent or hydrogen peroxide solution is also required. Therefore, if the factory does not have an existing waste water treatment device and chemical liquid supply device, it is difficult to install the wet treatment device in the factory. Even if the factory has an existing wastewater treatment device and chemical liquid supply device, installing the wet treatment device increases the running costs of these wastewater treatment device and chemical liquid supply device.

Furthermore, in a factory where semiconductor processing equipment is arranged, there is a tendency to dislike equipment that uses a large amount of water and alkaline agents. As a result, semiconductor manufacturers are reluctant to employ wet process equipment to treat NOx.

The dry treatment apparatus has the advantages of high treatment efficiency and the advantage of not requiring water and alkaline agents. As a result, semiconductor manufacturers tend to prefer dry processing equipment to wet processing equipment. In addition, some relatively small-scale facilities (or factories) such as laboratories that do not have existing wastewater treatment equipment and chemical liquid supply equipment cannot use large amounts of water and alkaline agents. In this case, a dry processing device has to be adopted.

However, in a dry processing apparatus that uses a treating agent containing a noble metal catalyst, the treating agent deteriorates as it comes into contact with NOx, so it is necessary to periodically replace the treating agent. In particular, since the exhaust gas of the exhaust gas processing device installed on the downstream side of the semiconductor processing device contains a high concentration (for example, a concentration of 500 ppm or more) of NOx, the life of the processing agent becomes relatively short. The treating agent containing the noble metal catalyst is expensive, and if the treating agent is frequently replaced, the running cost will increase significantly.

In a dry treatment apparatus in which ammonia is added as a catalyst, ammonia itself is a toxic substance, and it is necessary to strictly prevent leakage of ammonia. Furthermore, since an ammonia supply device for supplying ammonia and a device for treating surplus ammonia discharged from the dry treatment device are required, the running cost also rises.

Devices that add ozone to the gas to oxidize nitric oxide to nitrogen dioxide can be operated at relatively low cost. However, since ozone itself has a very high oxidizing power, it is harmful to the human body and the environment, so that the residual ozone gas cannot be directly emitted to the atmosphere. Therefore, this device has a problem that a separate device for decomposing residual ozone gas is required. The residual ozone gas decomposing device is, for example, a device that has a processing tank filled with a processing agent containing manganese oxide and decomposes the residual ozone gas by bringing the residual ozone gas into contact with manganese oxide. However, since manganese oxide is a relatively expensive substance, the running cost is relatively high even in an apparatus that oxidizes nitric oxide into nitrogen dioxide.

Therefore, an object of the present invention is to provide a processing apparatus and a processing method capable of processing nitrogen oxides at a relatively low cost.

As a result of earnest research on the decomposition of residual ozone, the present inventors have obtained the following knowledge and completed the present invention. That is, they have found that ozone can be decomposed into oxygen simply by contacting inexpensive synthetic zeolite with ozone. This finding is new, and an apparatus and method for treating ozone with a simple substance of synthetic zeolite that has not been subjected to treatment such as chlorine treatment has not been reported yet.

FIG. 1 is a schematic diagram of an experimental machine used to obtain the knowledge that ozone can be decomposed into oxygen simply by bringing the synthetic zeolite into contact with ozone. The experimental machine shown in FIG. 1 includes an ozone generator 101 and a processing tank 108 filled with only synthetic zeolite. Nitrogen and oxygen can be introduced into the ozone generator 101 from the nitrogen gas cylinder 150 and the oxygen gas cylinder 151, respectively. An oxygen gas supply line 123 extending from the oxygen gas cylinder 151 is connected to the introduction gas line 122 extending from the nitrogen gas cylinder 150 to the ozone generator 101. When the ozone generator 101 is operated in a state where oxygen is supplied from the oxygen gas cylinder 151 to the ozone generator 101, the ozone generator 101 generates ozone.

The processing tank 108 is connected to the ozone generator 101 via a connection line 125 extending from the ozone generator 101. The connection line 125 is connected to a processing tank inlet provided at a lower portion of the processing tank 108, and nitrogen and oxygen that have passed through the ozone generator 101 and ozone generated from oxygen in the ozone generator 101 are connected to each other. It is introduced into the processing tank 108 via 125. The connection line 125 is provided with an inlet port 120. A sample of the gas flowing through the connecting line 125 can be taken via the inlet port 120. A discharge line 127 is connected to the processing tank outlet provided at the upper part of the processing tank 108, and the discharge line 127 is provided with an outlet port 128. A sample of the gas flowing through the exhaust line 127 can be taken via the outlet port 128. Table 1 shows the results of experiments conducted using the experimental machine shown in FIG.

In this experiment, first, nitrogen was supplied from the nitrogen gas cylinder 150 to the ozone generator 101 and the processing tank 108. In this case, the only gas flowing through the ozone generator 101 and the processing tank 108 is nitrogen. Since the ozone generator 101 is not in operation, the gas sample taken out through the inlet port 120 does not contain ozone.

Five minutes after the start of the supply of nitrogen (that is, the start of the experiment), oxygen was further supplied from the oxygen gas cylinder 151 to the ozone generator 101 and the treatment tank 108. In this case, the gas flowing through the ozone generator 101 and the processing tank 108 is nitrogen and oxygen. Since the ozone generator 101 is not in operation, the gas sample taken out through the inlet port 120 does not contain ozone. On the other hand, the gas sample withdrawn via the outlet port 128 contained oxygen with a concentration of 8.10-8.13%.

After 15 minutes had passed since the supply of oxygen was started (that is, 20 minutes had passed since the start of the experiment), the operation of the ozone generator 101 was started. When the ozone generator 101 is operated, ozone is generated from a part of the oxygen introduced into the ozone generator 101. Therefore, the gas sample taken through the inlet port 120 contained 224 to 228 g/Nm ³ of ozone (see “Ozone Concentration” in Table 1 in the Test Conditions column). On the other hand, the gas sample taken through the outlet port 128 did not contain ozone. Furthermore, the concentration of oxygen contained in the gas sample taken out through the outlet port 128 is almost the same as the concentration of oxygen before the operation of the ozone generator 101 was started. If the synthetic zeolite is not able to decompose ozone, the gas sample withdrawn via outlet port 128 should contain ozone. Furthermore, if the synthetic zeolite physically adsorbs ozone, the concentration of oxygen contained in the gas sample taken out through the outlet port 128 is higher than the concentration of oxygen before the start of the operation of the ozone generator 101. Should be low. Therefore, it was found from this experimental result that the synthetic zeolite decomposes ozone into oxygen.

Table 2 is a table showing experimental results for confirming whether or not ozone is decomposed by bringing ozone into contact with an inorganic adsorbent generally used in a conventional dry treatment apparatus.

In Table 2, the inorganic adsorbents A1 and A2 are hydrophobic zeolites having different properties, the inorganic adsorbents B1 to B3 are activated alumina having different properties, and the inorganic adsorbent C is silica gel. In the experiment, a predetermined amount of each adsorbent was packed in a quartz column, a gas containing ozone was caused to flow from the lower part of the column, and the concentration of ozone contained in the outlet gas discharged from the upper part of the column was measured. The concentration of ozone in the gas introduced into the column was set to 0.40%, and the flow rate of the gas containing ozone was set to 4.31 L/min. The column diameter was 29 mm and the length was 500 mm. Under the same conditions, a gas containing ozone was caused to flow through a column packed with synthetic zeolite, and the concentration of ozone contained in the outlet gas was also measured.

As shown in Table 2, in any of the inorganic adsorbents, the concentration of ozone contained in the outlet gas exceeded 1000 ppm 2 minutes after the experiment was started. On the other hand, the outlet gas discharged from the column packed with the synthetic zeolite did not contain ozone. Therefore, it was found that ozone cannot be decomposed into oxygen with an inorganic adsorbent other than synthetic zeolite.

In view of the above findings, one embodiment of the present invention is a treatment device for a gas containing nitrogen oxide, the treatment tank being filled with synthetic zeolite, and being connected to the inlet of the treatment tank, the gas is treated in the treatment tank. And an ozone generator connected to the inlet line, wherein the ozone generator produces sufficient amount of ozone to oxidize nitric oxide contained in the gas to nitrogen dioxide. The treatment device is characterized in that the synthetic zeolite decomposes excess ozone that has not been consumed in the oxidation reaction of nitric oxide and physically adsorbs nitrogen dioxide contained in the gas.

In one aspect, a heater further attached to the treatment tank is further provided, and the heater heats the synthetic zeolite to a predetermined temperature.
In one aspect, the heater further includes a heater attached to the inlet line, and the heater heats the gas flowing through the inlet line to a predetermined temperature.
In one aspect, a heat exchanger attached to the treatment tank is further provided, and the heat exchanger heats the synthetic zeolite to a predetermined temperature.
In one aspect, a heat exchanger attached to the inlet line is further provided, and the heat exchanger heats the gas flowing through the inlet line to a predetermined temperature.

Another aspect of the present invention is a method for treating a gas containing nitrogen oxides, wherein ozone is added to the gas in an amount sufficient to oxidize nitric oxide contained in the gas to nitrogen dioxide. Oxidizing the nitric oxide to the nitrogen dioxide, and decomposing excess ozone that has not been consumed in the oxidation reaction of the nitric oxide by contacting it with the synthetic zeolite filled in the treatment tank to remove the dioxide contained in the gas. The treatment method is characterized in that nitrogen is physically adsorbed on the synthetic zeolite.

In one aspect, the synthetic zeolite is heated to a predetermined temperature by a heater.
In one aspect, the gas flowing through an inlet line connected to the inlet of the processing tank is heated to a predetermined temperature by a heater.
In one aspect, the synthetic zeolite is heated to a predetermined temperature by a heat exchanger attached to the treatment tank.
In one aspect, the gas flowing through an inlet line connected to the inlet of the processing tank is heated to a predetermined temperature by a heat exchanger attached to the inlet line.
In one aspect, the heat exchanger is supplied with high-temperature cooling water discharged from an exhaust gas processing apparatus installed on the downstream side of the semiconductor processing apparatus.

According to the present invention, surplus ozone not consumed in the reaction of oxidizing nitric oxide to nitrogen dioxide is decomposed into oxygen by the synthetic zeolite, and nitrogen dioxide is physically adsorbed on the synthetic zeolite. Since synthetic zeolite is an inexpensive substance (for example, a substance cheaper than manganese oxide), nitrogen oxide can be treated at a relatively low cost.

FIG. 1 is a schematic diagram of an experimental machine used to obtain the knowledge that ozone can be decomposed into oxygen simply by bringing the synthetic zeolite into contact with ozone. FIG. 2 is a schematic diagram showing a processing device according to one embodiment. FIG. 3 is a schematic diagram showing an experimental machine imitating the processing apparatus shown in FIG. FIG. 4 shows an experimental machine for investigating the ozone decomposing ability of synthetic zeolite when a gas containing water is introduced into the treating tank while heating the synthetic zeolite filled in the treating tank by a heater to a predetermined temperature. It is a schematic diagram. FIG. 5 is a schematic diagram showing a processing device according to another embodiment.

Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding components will be assigned the same reference numerals and overlapping description will be omitted.
FIG. 2 is a schematic diagram showing a processing device according to one embodiment. The processing apparatus 100 shown in FIG. 2 is installed downstream of an exhaust gas processing apparatus 300 that processes exhaust gas discharged from a semiconductor processing apparatus 200 such as a CVD apparatus or an etching apparatus. The exhaust gas treatment device 300 is, for example, a combustion type exhaust gas treatment device, a heater type exhaust gas treatment device, a plasma type exhaust gas treatment device, or a catalytic type exhaust gas treatment device. As described above, the gas discharged from the exhaust gas treatment device 300 contains NOx such as nitric oxide and nitrogen dioxide at a high concentration. For example, the exhaust gas discharged from the exhaust gas treatment device 300 contains NOx having a concentration of 500 ppm or more.

As shown in FIG. 2, the treatment apparatus 100 is connected to the treatment tank 8 filled with synthetic zeolite, an inlet line 5 extending from the treatment tank 8 to the exhaust gas treatment apparatus 300, and the inlet line 5 via an ozone supply line 10. The ozone generator 1 and the discharge line 12 extending from the processing tank 8 are provided. In the present embodiment, the treatment tank 8 is filled with only synthetic zeolite that has not been subjected to any treatment such as chlorine treatment, acid treatment, hydrothermal treatment, and calcination treatment. Such synthetic zeolite is, for example, an X-type synthetic zeolite. X-type synthetic zeolite is widely used in various industries and is easily available on the market. The ozone supply line 10 is connected in the middle of the inlet line 5, and the ozone generated by the ozone generator 1 is introduced into the inlet line 5 via the ozone supply line 10.

One end of the inlet line 5 is connected to the exhaust gas treatment device 300, and the gas discharged from the exhaust gas treatment device 300 is introduced into the inlet line 5. The other end of the inlet line 5 is connected to a treatment tank inlet provided at the lower part of the treatment tank 8, and the gas introduced into the treatment tank 8 through the inlet line 5 is treated while contacting with the synthetic zeolite. It flows to the upper part of the tank 8. A treatment tank outlet to which a discharge line 12 is connected is provided in the upper portion of the treatment tank 8, and the gas passing through the treatment tank 8 is discharged to the atmosphere through the discharge line 12.

The ozone generator 1 is a device that generates ozone from a source gas such as dry air or oxygen. The raw material gas is supplied to the ozone generator 1 from a raw material gas supply source (not shown). The raw material gas supply source is, for example, a dry air supply source (for example, a dry air line installed in the factory) provided in the factory where the processing apparatus 100 is installed, or oxygen connected to the ozone generator 1. It is a gas cylinder.

The ozone supply line 10 is connected to the inlet line 5 at a connection point C. The ozone generated by the ozone generator 1 is introduced into the inlet line 5 through the ozone supply line 10 and mixed with the gas flowing through the inlet line 5. In one embodiment, a mixer (not shown) may be arranged in the inlet line 5 on the downstream side of the connection point C, and the ozone and the gas flowing through the inlet line 5 may be efficiently mixed by the mixer. ..

The ozone generator 1 produces enough ozone to oxidize nitric oxide contained in the gas flowing through the inlet line 5 into nitrogen dioxide. In other words, the ozone generator 1 generates an excessive amount of ozone with respect to the amount of nitric oxide contained in the gas flowing through the inlet line 5. The ozone generated by the ozone generator 1 is introduced into the inlet line 5, and in the inlet line 5, almost all the amount of nitric oxide contained in the gas is oxidized to nitrogen dioxide. Excess ozone that has not been consumed in the oxidation reaction of nitric oxide is introduced into the processing tank 8 through the inlet line 5.

Table 3 is a table showing the experimental results for confirming that nitric oxide is oxidized to nitrogen dioxide by bringing NOx containing nitric oxide into contact with ozone.

In an experiment whose results are shown in Table 3, a gas bag (specifically, a Tedlar bag) was filled with NOx containing nitric oxide, a predetermined amount of ozone was added to the gas bag, and then the NOx concentration was measured. .. In Experiment 1 shown in Table 3, nitrogen containing ozone at a concentration of 200 ppm was added to a gas containing nitric oxide having a concentration of 20 ppm and nitrogen dioxide having a concentration of 155 ppm. When the components of the gas in the gas bag after adding ozone were analyzed, it was found that the concentration of nitric oxide was reduced to 0.2 ppm or less. Similarly, in Experiment 2 shown in Table 3, nitrogen containing ozone at a concentration of 200 ppm was added to a gas containing 81 ppm of nitric oxide and 1.7 ppm of nitrogen dioxide. When the components of the gas in the gas bag after adding ozone were analyzed, it was found that the concentration of nitric oxide was reduced to 0.2 ppm or less. From these experiments 1 and 2, it was found that the nitric oxide contained in the gas was oxidized to nitrogen dioxide only by contacting with ozone.

Table 4 is a table showing experimental results obtained by injecting a predetermined amount of ozone into a gas bag (specifically, a Tedlar bag) filled with NOx containing nitrogen dioxide.

In the experiment whose results are shown in Table 4, the concentration of NOx contained in the gas in the gas bag was confirmed with a detector tube before injecting ozone into the gas bag filled with NOx. According to the measurement by the detector tube, the gas in the gas bag contained nitrogen dioxide having a concentration of 120 ppm and nitric oxide having a concentration of 12 ppm. Furthermore, the concentration of NOx contained in the gas in the gas bag was measured using a nitrogen oxide concentration meter (NOx meter). As measured by the NOx meter, the gas in the gas bag contained nitrogen dioxide having a concentration of 155 ppm and nitric oxide having a concentration of 20 ppm.

Ozone having a predetermined concentration (specifically, a concentration of 200 ppm) was injected into this gas bag. When the concentrations of nitric oxide and nitrogen dioxide in the gas bag after ozone injection were measured using a detector tube, nitric oxide and nitrogen dioxide were not detected. Furthermore, when the concentrations of nitric oxide and nitrogen dioxide in the gas bag after ozone injection were measured using a nitrogen oxide concentration meter (NOx meter), the concentration of nitric oxide was 0.2 ppm. Was 14.8 ppm. Also in the experiment whose results are shown in Table 4, it was found that the nitric oxide can be oxidized to nitric dioxide simply by contacting ozone with nitric oxide.

Further, in the experiment whose results are shown in Table 4, it was found that when ozone was injected into the gas bag filled with NOx, the concentration of nitrogen dioxide was also significantly reduced. This is because ozone has a very high oxidizing power. That is, ozone can oxidize nitric oxide into nitrogen dioxide by its oxidizing power, and further oxidize nitrogen dioxide to nitric acid state (NO ₃ ). However, the amount of nitrogen dioxide that is oxidized to the nitrate state by ozone changes depending on processing conditions such as the contact time between ozone and nitrogen dioxide and the mixing ratio of ozone and nitrogen dioxide. Therefore, when ozone is brought into contact with a gas containing NOx, nitric oxide is oxidized to nitrogen dioxide, but nitrogen dioxide may remain in the gas without being oxidized to nitric acid depending on the treatment conditions. ..

Therefore, in the processing apparatus 100 shown in FIG. 2, even if a sufficient amount of ozone to oxidize nitric oxide contained in the gas flowing through the inlet line 5 into nitrogen dioxide is introduced from the ozone generator 1 into the inlet line 5. The gas reaching the processing tank 8 may contain nitrogen dioxide. More specifically, the gas flowing through the inlet line 5 contains nitrogen dioxide originally contained in the gas discharged from the exhaust gas treatment device 300 and nitrogen dioxide oxidized from nitric oxide by ozone. A part of this nitrogen dioxide may remain in the gas flowing through the inlet line 5 and reach the processing tank 8 without being oxidized to a nitric acid state by contact with ozone. Further, as described above, the amount of nitrogen dioxide that is oxidized to the nitrate state by ozone changes depending on the processing conditions such as the contact time between ozone and nitrogen dioxide and the mixing ratio of ozone and nitrogen dioxide. Therefore, depending on the treatment conditions, almost all of the nitrogen dioxide originally contained in the gas discharged from the exhaust gas treatment device 300 and the nitrogen dioxide oxidized from nitric oxide by ozone may reach the treatment tank 8.

However, the nitrogen dioxide contained in the gas reaching the treatment tank 8 through the inlet line 5 is physically adsorbed by the synthetic zeolite packed in the treatment tank 8. Therefore, the gas discharged from the processing tank 8, that is, the gas flowing through the discharge line 12 does not contain nitrogen oxides such as nitric oxide and nitrogen dioxide. Furthermore, as is clear from the experimental results shown in Table 1, the synthetic zeolite filled in the treatment tank 8 can decompose excess ozone into oxygen. As a result, since the gas discharged from the processing tank 8 does not contain nitrogen oxides and ozone, it can be directly discharged to the atmosphere.

FIG. 3 is a schematic diagram showing an experimental machine imitating the processing apparatus 100 shown in FIG. The components corresponding to those of the processing device 100 shown in FIG. 2 are designated by the same reference numerals, and redundant description will be omitted.

The experiment whose results are shown in Table 1 confirmed that ozone could be decomposed into oxygen by the synthetic zeolite alone, and the experiments whose results were shown in Tables 3 and 4 oxidize nitric oxide in contact with ozone to nitrogen dioxide. It was confirmed that Therefore, by adding ozone to the pipe through which the gas containing nitric oxide and nitrogen dioxide flows using the experimental machine shown in FIG. 3, whether or not the nitric oxide contained in the gas is completely oxidized to nitrogen dioxide. Then, a verification experiment was conducted to confirm whether or not the synthetic zeolite decomposes ozone into oxygen and can completely physically adsorb nitrogen dioxide contained in the gas.

The experimental machine shown in FIG. 3 has a treatment tank 8 filled with synthetic zeolite, an ozone generator 1, an inlet line 5 connected to the inlet of the treatment tank 8, and an exhaust line connected to the outlet of the treatment tank 8. 12 and an ozone supply line 10 extending from the ozone generator 1 and connected in the middle of the inlet line 5. The tip of the inlet line 5 is branched into two branch pipes 5A and 5B. One branch pipe 5A is connected to a nitrogen gas cylinder 30, and the other branch pipe 5B is filled with nitric oxide and nitrogen dioxide. A gas cylinder 31 filled with NOx containing is connected. An oxygen supply line 35 extending from the oxygen cylinder 33 is connected to the ozone generator 1, and the oxygen used to generate ozone in the ozone generator 1 is ozone from the oxygen cylinder 33 via the oxygen supply line 35. It is supplied to the generator 1.

Flow rate regulators (for example, mass flow meters) 38 and 39 are arranged in the branch pipes 5A and 5B, respectively, and the concentration of NOx contained in the gas introduced into the treatment tank 8 is adjusted by the flow rate regulators 38 and 39. Is adjustable. As described above, it is assumed that the gas discharged from the exhaust gas treatment device 300 contains NOx at a high concentration of 500 ppm or more. Therefore, in this verification experiment, the flow rate adjusters 38 and 39 adjusted the flow rates of nitrogen and NOx so that the concentration of NOx contained in nitrogen was 1000 ppm or more.

A flow rate adjuster (for example, a mass flow meter) 40 is also arranged in the oxygen supply line 35, and the flow rate adjuster 40 can adjust the amount of oxygen introduced into the ozone generator 1. The amount of ozone generated by the ozone generator 1 changes according to the amount of oxygen introduced into the ozone generator 1. As described above, the ozone generator 1 has a sufficient amount of ozone to oxidize nitric oxide contained in the gas flowing through the inlet line 5 into nitrogen dioxide, that is, the monoxide contained in the gas flowing through the inlet line 5. An excessive amount of ozone is generated with respect to the amount of nitrogen. In this verification experiment, the amount of oxygen supplied to the ozone generator 1 was adjusted by the flow rate adjuster 40 so that the amount of ozone generated by the ozone generator 1 was 5500 ppm.

Further, the inlet line 5 is provided with two sample ports 43 and 45. One sample port 43 is provided on the upstream side of the connection point C between the inlet line 5 and the ozone supply line 10, and the other sample port 45 is provided on the downstream side of the connection point C. Therefore, the sample gas taken out through the sample port 43 is a gas before the ozone is added, and the sample gas taken out through the sample port 45 is a gas after the ozone is added. In Table 5 below, the sample port 43 is described as “inlet port 1”, and the sample port 45 is described as “inlet port 2”.

Further, the discharge line 12 is provided with an outlet port 48. The sample gas taken out through the outlet port 48 is the gas that has passed through the processing tank 8.

Table 5 is a table showing the results of verification experiments performed using the experimental machine shown in FIG.

In Experiments 1 to 5 shown in Table 5, the flow rates of nitrogen and NOx were adjusted using the flow rate adjusters 38 and 39 so that the NOx concentrations were 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, and 5000 ppm, respectively. .. In Experiments 1 to 5, the gas taken out through the sample port 43 contained nitric oxide at concentrations of 680 ppm, 1340 ppm, 2000 ppm, 2650 ppm, and 3350 ppm, respectively. Ozone generated by the ozone generator 1 was added to these gases at a concentration of 5500 ppm. The gas after the addition of ozone was taken out through the sample port 45. In Experiments 1 to 5, nitric oxide was not contained in any gas taken out through the sample port 45, and the concentration of nitrogen dioxide was increased. From these results, it was found that by adding an excessive amount of ozone to the gas flowing through the inlet line 5, the nitric oxide contained in the gas can be completely oxidized to nitrogen dioxide. It was found that even if an excessive amount of ozone was added to the inlet line 5, nitrogen dioxide remained in the gas flowing through the inlet line 5. This nitrogen dioxide is contained in the gas flowing through the inlet line 5 without being oxidized to the nitric acid state by the nitrogen dioxide and the nitrogen dioxide, which is originally contained in the gas supplied from the gas cylinder 31, and is oxidized by the ozone. It is the remaining nitrogen dioxide.

In Experiments 1 to 5, it was confirmed that none of the gases taken out through the outlet port 48 contained ozone, nitric oxide, and nitrogen dioxide. From these results, it was found that ozone was completely decomposed into oxygen by the synthetic zeolite filled in the treatment tank 8, and nitrogen dioxide was completely physically adsorbed by the synthetic zeolite. That is, it was found that the processing apparatus 100 shown in FIG. 2 can completely process a gas containing a high concentration of nitrogen oxides, which is discharged from the exhaust gas processing apparatus 300.

As described above, according to the processing apparatus 100 according to the present embodiment, it is possible to process the gas discharged from the exhaust gas processing apparatus 300 and containing nitrogen oxide at a high concentration. Specifically, by adding to the gas an amount of ozone in excess of the amount necessary to completely oxidize the nitric oxide contained in the gas discharged from the exhaust gas treatment device 300, the nitrogen monoxide is removed. Excess ozone that was oxidized to nitrogen dioxide and was not consumed in the oxidation reaction of nitric oxide was decomposed into oxygen by the synthetic zeolite filled in the treatment tank 8, and nitrogen dioxide contained in the gas that reached the treatment tank 8 was removed. Physical adsorption to synthetic zeolite. With such a configuration, a gas containing neither nitrogen oxides nor ozone can be discharged from the processing tank 8. Since nitrogen dioxide is physically adsorbed by the synthetic zeolite, it is necessary to periodically replace the synthetic zeolite filled in the processing tank 8, but the synthetic zeolite is an inexpensive substance. Therefore, the running cost of the processing device 100 can be greatly reduced as compared with the conventional NOx processing device.

As shown in FIG. 2, the heater 15 may be attached to the outer surface of the processing tank 8. The heater 15 is configured to heat the synthetic zeolite filled in the processing tank 8 to a predetermined temperature. By heating the synthetic zeolite with the heater 15, the decomposition reaction of ozone can be promoted. In one embodiment, the heater 15 may be arranged inside the synthetic zeolite filled in the treatment tank 8.

As described above, the treatment device 100 shown in FIG. 2 is a device that is installed on the downstream side of the exhaust gas treatment device 300 and that treats NOx contained in the exhaust gas of the exhaust gas treatment device 300. The exhaust gas treatment device 300 may be supplied with cooling water for cooling the gas heated to a high temperature in the exhaust gas treatment device 300. The cooling water comes into contact with the high-temperature gas treated in the exhaust gas treatment device 300 to cool the gas. Therefore, the gas discharged from the exhaust gas treatment device 300 may contain water.

As a result of intensive studies by the present inventors on the decomposition of ozone by synthetic zeolite, it was found that the ozone decomposition ability of the synthetic zeolite decreases when the gas introduced into the treatment tank 8 contains water. Further, it was also found that even if the gas introduced into the treatment tank 8 contains water, the ozone decomposing ability of the synthetic zeolite can be maintained by heating the synthetic zeolite to a predetermined temperature or higher.

FIG. 4 is a schematic diagram of an experimental machine used to obtain these findings. More specifically, FIG. 4 shows the ozone decomposing ability of synthetic zeolite when a gas containing water is introduced into the treatment tank while heating the synthetic zeolite filled in the treatment tank by a heater to a predetermined temperature. It is a schematic diagram which shows the experimental machine investigated. In the experimental machine shown in FIG. 4, the components corresponding to those of the experimental machine shown in FIG.

The experimental machine shown in FIG. 4 has a nitrogen supply line 201 extending from the nitrogen gas cylinder 30, and a tank 202 in which pure water is stored. Also in this experimental machine, the treatment tank 8 is filled with only synthetic zeolite, and the heater 15 is attached to the outer surface of the treatment tank 8. The heater 15 can heat the treatment tank 8 and the synthetic zeolite filled in the treatment tank 8 to a predetermined temperature.

A nitrogen supply line 201 extending from the nitrogen gas cylinder 30 is connected to a tank 202, and the tip of the nitrogen supply line 201 is opened below the liquid surface of pure water stored in the tank 202. Further, a flow rate adjuster (for example, a mass flow meter) 38 is arranged on the nitrogen supply line 201. The flow rate adjuster 38 adjusts the flow rate of nitrogen supplied to the tank 202. The inlet line 5 extending from the inlet of the processing tank 8 is also connected to the tank 202, but the tip of the inlet line 5 opens above the liquid level of the pure water stored in the tank 202. Therefore, the nitrogen supplied from the nitrogen supply line 201 to the tank 202 comes into contact with the pure water in the tank 202, and the nitrogen containing the pure water is introduced into the inlet line 5. Further, nitrogen containing pure water is supplied to the processing tank 8 through the inlet line 5.

Also in this experimental machine, the ozone generator 1 is connected to the inlet line 5 via the ozone supply line 10. An oxygen supply line 35 extending from the oxygen cylinder 33 is connected to the ozone generator 1, and the oxygen used to generate ozone in the ozone generator 1 is ozone from the oxygen cylinder 33 via the oxygen supply line 35. It is supplied to the generator 1. A flow rate regulator (for example, a mass flow meter) 40 is arranged on the oxygen supply line 35. The flow rate adjuster 40 adjusts the flow rate of oxygen supplied to the ozone generator 1, and the ozone generator 1 generates ozone according to the amount of oxygen supplied. Ozone generated by the ozone generator 1 is introduced into the inlet line 5 at the connection point C, and as a result, a mixed fluid of nitrogen and ozone containing pure water is introduced into the processing tank 8.

Table 6 is a table showing the results of the experiment performed using the experimental machine shown in FIG.

In the experiment whose results are shown in Table 6, Experiment 1 in which the temperature of the treatment tank 8 and the synthetic zeolite was maintained at room temperature without operating the heater 15, and the control temperature of the heater 15 was 100°C, 150°C, 200°C, and Experiments 2 to 5 were performed in which the temperature of the treatment bath 8 was set to 250° C. and the treatment bath 8 was heated to the control temperature (that is, the set temperature). In Experiments 1 to 5, the flow rate adjusters 38 and 40 adjusted the flow rates of nitrogen and ozone so that the concentration of ozone introduced into the processing tank 8 was 0.44 to 0.45%. Further, in Experiments 1 to 5, the amount of water contained in the gas introduced into the processing tank 8 was measured via the sample port 43. This amount of water is expressed as "amount of introduced water" in the column of test conditions in Table 6. Further, in Experiments 1 to 5, a thermometer 205 was placed in the discharge line 12, and the temperature of the gas flowing through the discharge line 12 (that is, the gas discharged from the processing tank 8) was measured using this thermometer 205. .. The temperature of this gas is expressed as "outlet gas temperature" in Table 6.

The “ozone treatment amount” shown in the test result column of Table 6 is an index value indicating the ozone decomposing ability of the synthetic zeolite. Specifically, the “ozone treatment amount” is a value indicating the amount (deposition) of ozone that can be decomposed by the synthetic zeolite per unit volume. In this experiment, this ozone treatment amount was calculated as follows.

First, while introducing ozone adjusted to have a predetermined concentration (specifically, a concentration of 0.44-0.45%) into the treatment tank 8 filled with synthetic zeolite, the discharge line 12 The concentration of ozone contained in the gas flowing through (i.e., the gas discharged from the processing tank 8) was measured. At this time, the elapsed time from the start of the introduction of ozone into the treatment tank 8 is also measured. This elapsed time is shown as "gas passage time" in the column of test results in Table 6. In addition, the numerical value described in the column of "gas passage time" in Table 6 is the elapsed time until the concentration of ozone at the outlet of the processing tank 8 exceeds the allowable value of 0.05 ppm. Next, this elapsed time was multiplied by the flow rate of ozone generated by the ozone generator 1 to calculate the integrated amount of ozone introduced into the processing tank 8. This integrated amount of ozone is expressed as "amount of ozone passing gas" in the column of test results in Table 6. Next, the ozone treatment amount was calculated by dividing the integrated amount of ozone by the volume of the synthetic zeolite filled in the treatment tank 8.

As shown in Table 6, in Experiment 1 in which the treatment tank 8 was at room temperature and Experiment 2 in which the control temperature of the heater 15 was set to 100° C., when the accumulated amount of ozone reached 5450 mL and 8237 mL, respectively. The concentration of ozone contained in the gas discharged from the processing tank 8 exceeded 0.05 ppm. The “ozone treatment amount” in Experiments 1 and 2 was 20.7 L/L and 20.8 L/L, respectively. In Experiment 1 and Experiment 2, the outlet gas temperatures were 30.9° C. and 55.0° C., respectively.

The results of Experiments 1 and 2 indicate that, when the gas introduced into the treatment tank 8 contains water, the ozone decomposing ability of the synthetic zeolite decreases when a certain amount of gas is introduced into the treatment tank 8. Showing.

In contrast, in Experiments 3 to 5 in which the control temperature of the heater 15 was set to 150° C., 200° C., and 250° C., respectively, even if the elapsed time exceeded 2000 minutes, the ozone concentration at the outlet of the processing tank 8 was 0. It did not exceed 0.05 ppm. Therefore, the “amount of ozone passing gas” in Table 6 is the cumulative amount of ozone from the start to the end of the experiment (that is, from the introduction of the gas into the treatment tank 8 to the stop). Described. The ozone treatment amounts of Experiments 3 to 5 in Table 6 are also values for convenience calculated based on the integrated amount of ozone. Specifically, the ozone treatment amount of Experiment 3 is described as "434 or more", the ozone treatment amount of Experiment 4 is described as "294 or more", and the ozone treatment amount of Experiment 5 is "317 or more". Described. In Experiments 3 to 5, the outlet gas temperatures were 75.5°C, 92.8°C, and 103.9°C, respectively.

From the results of Experiments 3 to 5, it was found that by setting the control temperature of the heater 15 for heating the synthetic zeolite via the treatment tank 8 to a predetermined temperature or higher, the ozone decomposing ability of the synthetic zeolite does not decrease. The predetermined temperature is, for example, a control temperature of the heater 15 at which the temperature of the gas discharged from the processing tank 8 becomes 75.5° C. or higher.

For the same reason (that is, promotion of ozone decomposition reaction by the synthetic zeolite and maintenance of ozone decomposing ability of the synthetic zeolite), it is preferable to increase the temperature of the gas introduced into the treatment tank 8. Therefore, the processing apparatus 100 may have the heater 17 (see FIG. 2) attached to the outer surface of the inlet line 5. The heater 17 can heat the gas flowing through the inlet line 5 and introduced into the processing tank 8 to a predetermined temperature.

The processing apparatus 100 shown in FIG. 2 has two heaters 15 and 17, but the present embodiment is not limited to this example. For example, the processing apparatus 100 may have only one of the heaters 15 and 17. Alternatively, the processing device 100 may not include the heaters 15 and 17.

FIG. 5 is a schematic diagram showing a processing device 100 according to another embodiment. The configuration of this embodiment that is not particularly described is the same as the configuration of the processing device 100 shown in FIG.

The treatment apparatus 100 shown in FIG. 4 has a heat exchanger 19 for exchanging heat with the synthetic zeolite filled in the treatment tank 8 instead of the heater 15 attached to the outer surface of the treatment tank 8. It is different from the processing device 100 shown in FIG.

As described above, if the temperature of the synthetic zeolite is raised, the decomposition reaction of ozone can be promoted. Furthermore, by raising the temperature of the synthetic zeolite, the ozone decomposing ability of the synthetic zeolite can be maintained even if the gas introduced into the treatment tank 8 contains water. Therefore, in the present embodiment, the heat exchanger 19 that uses the exhaust heat released from the exhaust gas treatment device 300 is provided. The heat exchanger 19 is attached to the outer surface of the processing tank 8.

As described above, cooling water is supplied to the exhaust gas treatment device 300 in order to cool the gas that has been heated to a high temperature in the exhaust gas treatment device 300. The cooling water exchanges heat with the gas processed in the exhaust gas processing device 300 and becomes high temperature. Therefore, the high-temperature cooling water discharged from the exhaust gas treatment device 300 is used as the heating liquid for the heat exchanger 19. The heating liquid supplied to the heat exchanger 19 can heat the synthetic zeolite to a predetermined temperature via the treatment tank 8.

In one embodiment, instead of the heater 17, a heat exchanger (not shown) may be attached to the outer surface of the inlet line 5. This heat exchanger exchanges heat with the gas flowing through the inlet line 5 and heats the temperature of the gas to a predetermined temperature. This heat exchanger can also use high-temperature cooling water discharged from the exhaust gas treatment device 300 as a heating liquid.

The above-described embodiments are described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above-described embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but should be the broadest scope according to the technical idea defined by the claims.

DESCRIPTION OF SYMBOLS 1 processing apparatus 5 inlet line 8 processing tank 10 ozone supply line 12 exhaust line 15,17 heater 19 heat exchanger 100 processing apparatus 200 semiconductor processing apparatus 300 exhaust gas processing apparatus

Claims (11)

A processing device for a gas containing nitrogen oxides, comprising:
A treatment tank filled with synthetic zeolite,
An inlet line connected to the inlet of the processing tank for introducing the gas into the processing tank;
An ozone generator connected to the inlet line,
The ozone generator generates ozone in an amount sufficient to oxidize nitric oxide contained in the gas into nitrogen dioxide,
The treatment apparatus characterized in that the synthetic zeolite decomposes excess ozone not consumed in the oxidation reaction of the nitric oxide and physically adsorbs nitrogen dioxide contained in the gas. Further comprising a heater attached to the processing tank,
The processing device according to claim 1, wherein the heater heats the synthetic zeolite to a predetermined temperature. Further comprising a heater attached to the inlet line,
The processing apparatus according to claim 1, wherein the heater heats the gas flowing through the inlet line to a predetermined temperature. Further comprising a heat exchanger attached to the processing tank,
The processing device according to claim 1, wherein the heat exchanger heats the synthetic zeolite to a predetermined temperature. Further comprising a heat exchanger attached to the inlet line,
The said heat exchanger heats the said gas which flows through the said inlet line to predetermined temperature, The processing apparatus of Claim 1 or 4 characterized by the above-mentioned. A method for treating a gas containing nitrogen oxides, comprising:
Ozone in an amount sufficient to oxidize the nitric oxide contained in the gas to nitrogen dioxide, is added to the gas to oxidize the nitric oxide to the nitrogen dioxide,
Excess ozone that was not consumed in the oxidation reaction of the nitric oxide, decomposed by contacting the synthetic zeolite filled in the treatment tank,
A treatment method comprising physically adsorbing nitrogen dioxide contained in the gas to the synthetic zeolite. The processing method according to claim 6, wherein the synthetic zeolite is heated to a predetermined temperature by a heater. The processing method according to claim 6 or 7, wherein the gas flowing through an inlet line connected to the inlet of the processing tank is heated to a predetermined temperature by a heater. The treatment method according to claim 6, wherein the synthetic zeolite is heated to a predetermined temperature by a heat exchanger attached to the treatment tank. 10. The processing method according to claim 6, wherein the gas flowing through an inlet line connected to the inlet of the processing tank is heated to a predetermined temperature by a heat exchanger attached to the inlet line. 11. The treatment method according to claim 9, wherein the heat exchanger is supplied with high-temperature cooling water discharged from an exhaust gas treatment device installed on the downstream side of the semiconductor treatment device.

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