JP5232407B2 - Exhaust gas purification equipment - Google Patents

Description

The present invention relates to a purification apparatus that thermally decomposes and purifies harmful components contained in exhaust gas discharged from a semiconductor manufacturing process using a flame. More specifically, even CF ₄ , which is generally known as a harmful component that is difficult to be thermally decomposed, can be thermally decomposed to a low concentration, and further, thermal NOx (NO, NO ₂ ) The present invention relates to an exhaust gas purifying apparatus capable of suppressing generation and further generation of CO ₂ .

  With the development of the semiconductor industry in recent years, a great variety of gases have been used in the semiconductor manufacturing process. However, many of these gases are harmful to the human body and the environment, and it is essential to purify them before they are discharged outside the factory. Combustion-type purification methods that decompose these gases by burning them are convenient methods that can be applied regardless of the composition and physical properties of the exhaust gas. It is more efficient than the purification method.

  Exhaust gas treated by the combustion purification method can be made harmless oxide or easily harmless by mixing and burning fuel gas such as propane, LPG, LNG, etc., air or oxygen, and inert gas if necessary in the combustion chamber Processed as a substance. Conventional combustion purification devices that have been used in the past introduce an oxygen-containing gas such as a combustion chamber for thermally decomposing harmful components contained in exhaust gas, exhaust gas to be treated, fuel gas, and air into the combustion chamber. Each of the pipes (nozzles) for combustion, and a discharge port for discharging the gas after combustion from the combustion chamber.

JP 10-54534 A JP-A-10-110926 JP 2000-342931 A JP 2005-522660 Gazette JP 2006-122790 A

In the combustion purification method, when the temperature is high enough for the thermal decomposition of CF ₄ , these react with each other in the presence of oxygen and nitrogen to generate thermal knox (NO, NO ₂ ). NO and NO ₂ are pollutants that cause acid rain, and it is desirable that the NO and NO ₂ concentrations in the gas purified by the combustion purification method be low. Furthermore, it is preferable to suppress the generation of CO ₂ by efficiently using the fuel gas.
Therefore, the problem to be solved by the present invention is that even CF ₄ that is generally known as a harmful component that is difficult to be thermally decomposed can be thermally decomposed to a low concentration, and NO, An object of the present invention is to provide an exhaust gas purifying device capable of suppressing the generation of NO ₂ and further the generation of CO ₂ .

As a result of intensive investigations to solve these problems, the present inventors have conducted thermal decomposition of harmful components in a purification apparatus that thermally decomposes and purifies harmful components contained in the exhaust gas discharged from the semiconductor manufacturing process. In addition to the combustion chamber, (1) a nozzle for injecting a gas containing fuel gas and air into the combustion chamber, (2) a nozzle for injecting a gas containing exhaust gas and fuel gas into the combustion chamber, and further its outer periphery (3) A nozzle for injecting a gas containing oxygen into the combustion chamber is disposed on the side, and the ratio of the cross-sectional areas at the gas outlets of the three types of nozzles is set to a specific range ratio, so that the fuel gas and the air are By configuring the gas outlet containing gas and the gas outlet containing oxygen to protrude from the gas outlet containing the exhaust gas and the fuel gas into the combustion chamber , the fuel gas is efficiently consumed, and CF _{4 is used.} Even low concentration It has been found that it can be thermally decomposed until it reaches the limit, and generation of thermal knox (NO, NO ₂ ) and further generation of CO ₂ can be suppressed, and the exhaust gas purification apparatus of the present invention has been reached.

That is, the present invention is a purification device that thermally decomposes and purifies harmful components contained in exhaust gas discharged from a semiconductor manufacturing process by a flame, and includes a combustion chamber that thermally decomposes harmful components, a gas containing fuel gas and air. A nozzle for injecting gas containing exhaust gas and fuel gas into the combustion chamber on the outer peripheral side, and a nozzle for injecting gas containing oxygen into the combustion chamber on the outer peripheral side. The ratio of the cross-sectional area at the gas outlet of the nozzle is 1: 1.5 to 15: 0.2 to 2 in the above order, and the gas outlet including the fuel gas and air and the gas including oxygen The jet port is a device for purifying exhaust gas, characterized in that the jet port projects from the gas jet port containing the exhaust gas and fuel gas into the combustion chamber .

The exhaust gas purifying apparatus of the present invention disperses a part of the fuel gas that is the raw material of the flame, and ejects it from the nozzle adjacent to the nozzle that ejects the flame into the combustion chamber together with the exhaust gas. Since the cross-sectional area at is set to a ratio in a specific range, fuel gas is efficiently consumed. As a result, during pyrolysis treatment, harmful components such as CF ₄ can be efficiently pyrolyzed without raising the temperature of the gas more than necessary, and thermal knox (NOx) is present even in the presence of oxygen and nitrogen. , NO ₂ ) can be suppressed. Further, the generation of CO ₂ can be suppressed. In the exhaust gas purification apparatus of the present invention, CF ₄ contained in the exhaust gas discharged from the semiconductor manufacturing process has a decomposition rate of 99% or more depending on conditions, and generation of thermal knox (NO, NO ₂ ) is 300 ppm or less. It is also possible to perform the thermal decomposition treatment while suppressing the heat treatment.

The present invention is applied to a purification apparatus that thermally decomposes and purifies harmful components contained in exhaust gas discharged from a semiconductor manufacturing process using a flame.
As harmful components contained in the exhaust gas that can be treated by the purification apparatus of the present invention, arsenic, phosphine, silane, disilane, dichlorosilane, diborane, hydrogen selenide, germanium hydride gas, boron trifluoride, boron trichloride, Acid gases such as silicon tetrafluoride, silicon tetrachloride, titanium tetrachloride, aluminum chloride, germanium tetrafluoride, tungsten hexafluoride, basic gases such as ammonia, monomethylamine, dimethylamine, trimethylamine, hydrazine, perfluorocarbon, Illustrative are halogenated carbons such as hydrofluorocarbons.
Moreover, propane gas, natural gas, etc. can be used as fuel gas. These gases are used together with an inert gas such as nitrogen as necessary.

Hereinafter, although the purification apparatus of the waste gas of this invention is demonstrated in detail based on FIG.1 and FIG.2, this invention is not limited by these.
FIG. 1 is a vertical sectional view showing an example of the exhaust gas purifying apparatus of the present invention. FIG. 2 is a horizontal cross-sectional view (horizontal cross-sectional view at the gas outlet including the exhaust gas and the fuel gas) showing an arrangement example of each nozzle in the exhaust gas purifying apparatus of the present invention.

  As shown in FIG. 1, the exhaust gas purifying apparatus of the present invention includes a combustion chamber 4 for thermally decomposing harmful components, a nozzle for injecting a gas containing fuel gas and air into the combustion chamber (burning the fuel gas and injecting a flame. 1), a nozzle 2 for injecting gas containing exhaust gas and fuel gas into the combustion chamber on the outer peripheral side thereof, and a nozzle 3 for injecting gas containing oxygen into the combustion chamber on the outer peripheral side thereof. The ratio of the cross-sectional area at the gas outlet of the nozzle (the cross-sectional area of the portion through which the gas passes) is 1: 1.5 to 15: 0.2 to 2 in the ratio of nozzle 1: nozzle 2: nozzle 3 It is.

  In the exhaust gas purifying apparatus of the present invention, the side wall 5 of the combustion chamber 4 is usually a cylinder, a rectangular cylinder, a polygonal cylinder, or a cylindrical shape similar to these. A nozzle 1 for injecting gas containing fuel gas and air into the combustion chamber, a nozzle 2 for injecting gas containing exhaust gas and fuel gas into the combustion chamber, and a nozzle 3 for injecting gas containing oxygen into the combustion chamber are usually combusted. Located on the upper wall of the chamber. The arrangement positions of these nozzles are not particularly limited except that the nozzle 2 is arranged on the outer circumferential side of the nozzle 1 and the nozzle 3 is arranged on the outer circumferential side thereof. For example, an arrangement example as shown in FIG. Can be mentioned. The nozzle 2 and the nozzle 3 can usually be divided and provided in the range of about 1 to 10, respectively. In such a case, the sectional area of each nozzle is the total sectional area of each nozzle. Calculated.

The ratio of the cross-sectional area (the cross-sectional area of the part through which the gas passes) of these nozzles is 1: 1.5 to 15: 0.2 to 2 in the ratio of nozzle 1: nozzle 2: nozzle 3. If each nozzle is set to be out of the above range, the decomposition rate decreases when thermally decomposing CF ₄ which is difficult to thermally decompose, and the generation of thermal knox (NO, NO ₂ ) is suppressed. become unable. In this respect, the decomposition rate and thermal knock are also affected by the hollow cylinder velocity of the gas ejected from each nozzle, but adjustment is difficult when the ratio deviates from the above-mentioned cross-sectional area ratio range.

  Moreover, the jet outlet of the nozzle 1 which jets the gas containing fuel gas and air to a combustion chamber, and the jet outlet of the nozzle 3 which jets the gas containing oxygen to a combustion chamber are the gas containing exhaust gas and fuel gas to a combustion chamber. From the jet nozzle of the nozzle 2 which ejects, it is normally arrange | positioned so that it may protrude into the combustion chamber 4 1-20 mm, Preferably 2-10 mm. If the protrusion of the nozzle 1 outlet is smaller than 1 mm compared to the nozzle 2 outlet, a flame may enter the nozzle 2, and if it exceeds 20 mm, the decomposition rate of harmful components decreases. . Further, when the protrusion of the nozzle 3 that ejects the gas containing oxygen into the combustion chamber is smaller than 1 mm as compared with the nozzle 2 outlet and larger than 20 mm, the combustion in the combustion chamber may become unstable.

  Furthermore, it is preferable that the nozzle 2 that ejects the gas containing the exhaust gas and the fuel gas into the combustion chamber has a gas reservoir immediately before the ejection port, as shown in FIG. By setting it as such a structure, the gas containing exhaust gas and fuel gas is heated just before ejection, and a thermal decomposition of a harmful component is performed efficiently. When the gas reservoir is provided, the jet outlet is preferably provided close to the nozzle 1 for jetting a gas containing fuel gas and air into the combustion chamber.

  As shown in FIGS. 2 (a) and 2 (b), a nozzle 1 for injecting a gas containing fuel gas and air into the combustion chamber and a nozzle 2 for injecting a gas containing exhaust gas and fuel gas into the combustion chamber, respectively, It can also be set as the structure which consists of a flow path inside a double tube, and a flow path outside. When the nozzle 2 for injecting a gas containing exhaust gas and fuel gas into the combustion chamber or the nozzle 3 for injecting a gas containing oxygen into the combustion chamber is divided into a plurality of parts, FIGS. As shown in d), the nozzles are usually provided at equal intervals on the circumference of a circle centered on the center point, with the gas injection nozzle 1 containing fuel gas and air as the center point. In the case of such a configuration, it is possible to simultaneously eject exhaust gases containing different types of harmful components from the nozzle 2 into the combustion chamber.

  In addition, in the exhaust gas purifying apparatus of the present invention, the side wall 5 of the combustion chamber 4 can be a non-breathable side wall having heat insulation, or a side wall having air permeability and heat insulation. When the harmful component is thermally decomposed, a powdered product is generated depending on the type of the harmful component. However, in the case of a side wall having air permeability and heat insulation, oxygen is included in the direction shown by the arrow in FIG. By flowing gas, it can suppress that a pulverized material accumulates on the side wall of a combustion chamber. The material of the side wall 5 is not particularly limited as long as it has corrosion resistance against harmful components, heat resistance that can withstand the thermal decomposition temperature, and heat insulation, but a preferable material is ceramic. Can do. Among ceramics, alumina, silica, titania and the like are preferable in terms of heat resistance and heat insulation.

  In the case of the above configuration, the oxygen-containing gas flow path 6 is usually provided over the entire outer periphery of the side wall 5. The width of the oxygen-containing gas channel 6 is usually 5 to 200 mm, preferably 10 to 100 mm. When the exhaust gas is treated, the temperature of the combustion chamber becomes a high temperature of 500 to 1200 ° C. With such a configuration, it is possible to prevent the heat of the combustion chamber from diffusing outside. Further, if necessary, a water channel (not shown) can be provided on the outer periphery of the oxygen-containing gas flow channel 6 for the same purpose as described above.

  In the exhaust gas purifying apparatus of the present invention, the fuel gas and the gas containing air are mixed and burned immediately before the combustion chamber. During the combustion of fuel, the flame tip may or may not enter the combustion chamber. The temperature of the combustion gas when jetted into the combustion chamber is usually about 600 to 1500 ° C. Further, the gas pressure in the combustion chamber is not particularly limited and is usually normal pressure, but is processed under a reduced pressure such as 10 KPa (absolute pressure) or a pressurized pressure such as 0.5 MPa (absolute pressure). It is also possible.

The pyrolyzed gas is released into the atmosphere or sent to the next processing step. In the case of being sent to the next processing step, the exhaust gas purifying apparatus of the present invention does It is also possible to equip equipment for carrying out various processing steps.
The facility of the water tank 12 and the scrubber in FIG. 1 removes the pulverized material contained in the treated gas, and newly generated harmful components (components that can be easily detoxified) for the exhaust gas treated by the exhaust gas purification apparatus of the present invention. ) And is not an essential facility in the present invention, but it is preferable to provide these facilities. That is, an exhaust gas purification device in which a powdery substance removal unit and / or an acid gas removal unit is provided on the discharge side of the combustion chamber is preferable.

For example, when hydrides such as arsine, phosphine, silane, and diborane are treated with the exhaust gas purifying apparatus of the present invention, solid particulate oxides such as arsenic, phosphorus, silicon, and boron are generated by combustion. In addition, when a halide such as boron trifluoride, boron trichloride, silicon tetrafluoride, silicon tetrachloride, or C ₂ F ₆ is treated, a new acidic gas such as hydrogen chloride or hydrogen fluoride (which is easily harmless) Component that can be converted into In the purification apparatus of FIG. 1, the powdered material can be removed mainly by watering from the spray nozzle 9 and trapping in the perforated plate 14. Moreover, it is preferable that the piping between the exhaust gas purifying apparatus of the present invention and the scrubber equipment is inclined toward the scrubber equipment so that the pulverized material can be easily washed out to the water tank 12.

  When the purification apparatus as shown in FIG. 1 in which the water tank 12 and the scrubber equipment are combined is used for the exhaust gas purification apparatus of the present invention, acidic gases such as hydrogen chloride and hydrogen fluoride are mainly removed by the filler 15. Is possible. Further, the demister 16 can also remove moisture. In FIG. 1, 8 is a cooling pipe, 10 is a flow meter, 11 is a pump, 13 is a drain pipe, and 17 is a discharge port for discharging the pyrolyzed gas to the outside.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited by these.

(Production of purification equipment)
As shown in FIG. 1, a purification device having an outer wall made of stainless steel (SUS316) and having a height of 2000 mm was manufactured. The configuration of the horizontal cross section of each nozzle provided on the upper wall of the combustion chamber is as shown in FIG. 2 (b), a nozzle 1 (outer diameter 60 mm) for jetting a gas containing fuel gas and air to the combustion chamber, and The four nozzles 2 (outlet diameter 145 mm) for jetting gas containing exhaust gas and fuel gas into the combustion chamber have a double tube structure. Further, the diameters of the four nozzles 3 for ejecting the gas containing oxygen on the outer peripheral side to the combustion chamber were 19 mm, and they were provided at equal intervals on the circumference of a circle centering on the ejection nozzle 1. (The ratio of the cross-sectional area at the gas outlet of each nozzle is 1: 4.7: 0.4 in the ratio of nozzle 1: nozzle 2: nozzle 3) Also, the outlet of nozzle 1 and the outlet of nozzle 3 are It arrange | positioned so that it may protrude from a jet nozzle of the nozzle 2 to a 5 mm combustion chamber.

As a side wall of the combustion chamber, a silica-alumina cylinder having fine porosity was used. The side wall had a diameter of 200 mm, a length of 600 mm, a thickness of 25 mm, and had micropores corresponding to a diameter of 10 to 100 μm. Further, a stainless steel cylinder having an inner diameter of 300 mm and a thickness of 3 mm was used for the outer wall on the outside.
The oxygen-containing gas channel is an annular channel formed by a side wall and an outer wall, and is divided into two in the vertical direction. As shown in FIG. 2, a total of four oxygen-containing gas inlets were set so that two oxygen-containing gas inlets were introduced from the tangential direction of the annular flow path.
A water tank having a length of 400 mm, a width of 400 mm, and a height of 500 mm was installed in the lower right part of the purification device, and a scrubber having a porous plate, a filler mainly composed of polypropylene resin, and a demister was installed in the upper part of the water tank. . In addition, the purification device and the water tank were connected by an inclined pipe, and a spray nozzle, a flow meter, a pump, etc. were connected to complete the device.

(Pyrolysis test of purification equipment)
After water was poured into the water tank until the depth reached 350 mm, the pump was operated to eject water from the spray nozzle. Also, propane gas (flow rate 12 L / min) and air (flow rate 285 L / min) are introduced from the nozzle 1 into the combustion chamber to burn the propane gas, and oxygen (flow rate 15 L / min (1 piece) from the four nozzles 3. Were introduced into the combustion chamber. Oxygen (flow rate 21 L / min) and nitrogen (flow rate 79 L / min) were also introduced into the thermal decomposition chamber from the side wall of the combustion chamber.

Next, CF ₄ (flow rate 0.5 L / min (one nozzle)), propane gas (flow rate 3 L / min (one nozzle)), and nitrogen (flow rate 50 L / min (1) from the four nozzles 2. A number of nozzles)) were introduced into the combustion chamber, and CF ₄ which is a harmful component was thermally decomposed.
The thermal decomposition treatment of CF ₄ is performed for 100 hours. During this period, in order to measure the thermal decomposition rate of CF ₄ and the generation state of thermal knox (NO, NO ₂ ), a part of the gas discharged from the outlet at intervals of about 30 minutes Were sampled and their concentrations were measured. As a result, the thermal decomposition rate of CF ₄ was 99.1 to 99.3%, and the concentration of thermal knock (NO, NO ₂ ) was 270 to 280 ppm.

In the production of the purification device of Example 1, the purification device was produced in the same manner as in Example 1 except that the outer diameter of the nozzle 2 outlet was changed to 105 mm. (The ratio of the cross-sectional area at the gas outlet of each nozzle is the ratio of nozzle 1: nozzle 2: nozzle 3 1: 2.0: 0.4)
A thermal decomposition test was performed in the same manner as in Example 1 except that this purification device was used. As a result, the thermal decomposition rate of CF ₄ was 96.3 to 97.0%, and the concentration of thermal knock (NO, NO ₂ ) was 450 to 500 ppm.

In the production of the purification device of Example 1, the purification device was produced in the same manner as in Example 1 except that the outer diameter of the nozzle 2 outlet was changed to 175 mm. (The ratio of the cross-sectional area at the gas outlet of each nozzle is the ratio of nozzle 1: nozzle 2: nozzle 3 1: 7.4: 0.4)
A thermal decomposition test was performed in the same manner as in Example 1 except that this purification device was used. As a result, the thermal decomposition rate of CF ₄ was 98.5 to 98.8%, and the concentration of thermal knock (NO, NO ₂ ) was 360 to 400 ppm.

In the production of the purification apparatus of Example 1, the purification apparatus was produced in the same manner as in Example 1 except that the outer diameter of the nozzle 3 outlet was changed to 36 mm. (The ratio of the cross-sectional area at the gas outlet of each nozzle is the ratio of nozzle 1: nozzle 2: nozzle 3 1: 4.7: 1.4)
A thermal decomposition test was performed in the same manner as in Example 1 except that this purification device was used. As a result, the thermal decomposition rate of CF ₄ was 97.3 to 97.8%, and the concentration of thermal knock (NO, NO ₂ ) was 480 to 550 ppm.

[Comparative Example 1]
In the production of the purification device of Example 1, the purification device was produced in the same manner as in Example 1 except that the outer diameter of the nozzle 2 outlet was changed to 90 mm. (The ratio of the cross-sectional area at the gas outlet of each nozzle is a ratio of nozzle 1: nozzle 2: nozzle 3 of 1: 1.2: 0.4)
A thermal decomposition test was performed in the same manner as in Example 1 except that this purification device was used. As a result, the thermal decomposition rate of CF ₄ was 92.2 to 94.5%, and the concentration of thermal knock (NO, NO ₂ ) was 600 to 700 ppm.

[Comparative Example 2]
Example 1 except that propane gas introduced from the nozzle 2 into the combustion chamber was added to the nozzle 1 using the same purification device as in Example 1, and CF ₄ and nitrogen were introduced from the nozzle 2 into the combustion chamber. The same pyrolysis test was conducted.
As a result, the thermal decomposition rate of CF ₄ was 80 to 85%, and the concentration of thermal knox (NO, NO ₂ ) was 4000 to 4500 ppm.

From the above results, the exhaust gas purifying apparatus of the present invention is capable of pyrolyzing even to CF ₄ which is generally known as a harmful component that is difficult to be pyrolyzed, until it has a low concentration. It was confirmed that generation of thermal knock (NO, NO ₂ ) can be suppressed.

Vertical sectional view showing an example of the exhaust gas purifying apparatus of the present invention Horizontal sectional view showing an arrangement example of each nozzle in the exhaust gas purifying apparatus of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nozzle which ejects gas containing fuel gas and air to combustion chamber 2 Nozzle which ejects gas containing exhaust gas and fuel gas to combustion chamber 3 Nozzle which ejects gas containing oxygen to combustion chamber 4 Combustion chamber 5 Side wall 6 Oxygen Contained gas flow path 7 Oxygen-containing gas inlet 8 Cooling pipe 9 Spray nozzle 10 Flow meter 11 Pump 12 Water tank 13 Drain pipe 14 Perforated plate 15 Filler 16 Demister 17 Exhaust port for discharging the pyrolyzed gas to the outside

Claims (10)

It is a purification device that thermally decomposes and purifies harmful components contained in the exhaust gas discharged from the semiconductor manufacturing process with a flame, and injects gas containing fuel gas and air into the combustion chamber. A nozzle for injecting a gas containing exhaust gas and fuel gas into the combustion chamber on the outer peripheral side thereof, and a nozzle for injecting a gas containing oxygen into the combustion chamber on the outer peripheral side thereof. The ratio of the cross-sectional area at the outlet is from 1: 1.5 to 15: 0.2 to 2 in the above order, and the gas outlet containing fuel gas and air and the gas outlet containing oxygen are exhaust gas. And an exhaust gas purifying device characterized by projecting into a combustion chamber from a gas outlet containing a fuel gas .   The exhaust gas purifying apparatus according to claim 1, wherein the nozzle that ejects the gas containing the exhaust gas and the fuel gas into the combustion chamber has a gas reservoir immediately before the ejection port.   The nozzle for injecting a gas containing fuel gas and air into the combustion chamber and the nozzle for injecting a gas containing exhaust gas and fuel gas into the combustion chamber are each composed of a channel inside and outside a double tube. The exhaust gas purifying device according to claim 1.   There are a plurality of nozzles for injecting gas containing exhaust gas and fuel gas into the combustion chamber, and nozzles for injecting gas containing oxygen into the combustion chamber. The exhaust gas purifying device according to claim 1, which is provided at equal intervals on a circumference of a circle centered on the center point. The exhaust gas purifying apparatus according to claim 4 , wherein the plurality of nozzles for ejecting gas containing exhaust gas and fuel gas to the combustion chamber are nozzles for ejecting exhaust gas containing different types of harmful components to the combustion chamber.   The exhaust gas purifying device according to claim 1, wherein the side wall of the combustion chamber has a cylindrical shape, a rectangular tube, a polygonal tube, or a cylindrical shape similar thereto.   The exhaust gas purifying apparatus according to claim 1, wherein the side wall of the combustion chamber is a side wall having air permeability and heat insulation, and a gas flow path containing oxygen is provided on an outer periphery of the side wall.   The harmful gas purification device according to claim 1, wherein a dust removal unit and / or an acid gas removal unit is provided on a discharge side of the combustion chamber.   The exhaust gas purification apparatus according to claim 1, wherein the harmful component is halogenated carbon. Harmful components are CF ₄ gas purifying apparatus of an exhaust gas according to claim 1.

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