JPH0352616A - Method for device for treating poisonous waste gas - Google Patents

Abstract

PURPOSE:To make the poisonous waste gas completely harmless even when trouble is caused in the device by stopping the supply of the poisonous waste gas to a combustion device when abnormality is caused in the combustion device and supplying the poisonous waste gas to an adsorption device. CONSTITUTION:Switching valves 67 and 68 are set in a poisonous waste gas pipeline 66, one of the valves is connected to the adsorption device 62, and the other valve is connected to the combustion device 63 through a flashback arrester 64. The valve 67 connected to the adsorption device 62 is closed in the normal operation, the valve 68 connected to the combustion device 63 is opened, and the waste gas is burnt. Meanwhile, when an abnormal increase in pressure is caused at least in the line of the combustion device 63, a flame in the furnace of the combustion device is extinguished, or a combustion gas is detected in the waste combustion gas discharged from the device 63, the valve 68 is closed, and the valve 67 is opened to adsorb the poisonous waste gas.

Description

Detailed Description of the Invention (Technical Field) The present invention provides arsine (AsH, ), phosphine (PH,
), diborane (Bzos)-monosilane (SiH4), etc., and related to a treatment device for rendering toxic gases harmless. (Prior Art and its Problems) A semiconductor manufacturing process generates toxic exhaust gas containing the above-mentioned gaseous toxic substances. Since such toxic exhaust gases are extremely toxic to the human body, it is necessary to completely remove the toxic substances contained in them before releasing them into the atmosphere. Combustion method is known as one of the effective methods for removing toxic substances contained in exhaust gas (Japanese Patent Laid-Open No. 62-134414, Japanese Patent Laid-Open No. 62-15).
No. 2517). This method removes toxic substances in exhaust gas by oxidizing and decomposing them under combustion conditions, converting them into solid substances such as elemental elements and oxides. Since this solid substance is also toxic, it must be completely removed from the combustion gas, but the solid substance produced is a submicron-sized fine powder because it is generated in the gas phase, so it is different from normal Compared to fine powder of several microns in size, it is extremely difficult to completely remove this solid fine powder from the combustion gas. In order to efficiently remove such fine solid powder, the present inventors first developed a series of toxic exhaust gases in which a film of water was flowed down the inner wall of a combustion furnace, and the fine solid powder was captured and absorbed by this water film. We are proposing a combustion treatment method and device (Japanese Patent Application No. 1983-218389,
3-284930). By the way, in the combustion treatment of toxic exhaust gases as described above, if a problem occurs with the equipment or an abnormality occurs in the combustion conditions of the toxic exhaust gases, the toxic exhaust gases may be released into the atmosphere untreated. This causes major pollution problems. Therefore, the combustion treatment equipment for toxic exhaust gases must be able to cope with such problems. With conventional equipment, if a problem occurs, the only measure taken is to dilute the toxic exhaust gas with a large amount of air and release it into the atmosphere, but it is still far from perfect.

(Problem of the Invention) An object of the present invention is to provide a method and apparatus for treating toxic exhaust gas that can safely detoxify toxic exhaust gas even when equipment trouble occurs. (Means for Solving the Problems) The present inventors have completed the present invention as a result of intensive research to solve the above problems. That is, according to the present invention, two switching valves are installed in the toxic exhaust gas pipe, one of which is connected to the adsorption treatment device, and the other one is connected to the combustion treatment device via the flashback prevention device. A method for treating toxic exhaust gas using a toxic exhaust gas treatment device, in which the switching valve connected to the adsorption treatment device is normally closed, and the switching valve connected to the combustion treatment device is opened to perform combustion treatment of the toxic exhaust gas. , on the other hand, at least when an abnormal rise in pressure occurs in the combustion processing equipment system, when the flame in the combustion furnace of the combustion equipment is extinguished, or when flammable gas is detected in the combustion exhaust gas discharged from the combustion processing equipment. A method for treating toxic exhaust gas is provided, which comprises closing a switching valve connected to the device and opening a switching valve connected to an adsorption treatment device to adsorb and treat toxic exhaust gas. Further, according to the present invention, there is provided a toxic exhaust gas piping, a toxic exhaust gas adsorption treatment device connected between the piping and the combustion treatment device via a switching valve, and a switching valve and a flashback prevention device connected to the piping. A toxic exhaust gas combustion treatment device connected through the combustion treatment device, a dust removal filter connected to the combustion treatment device, and an abnormal increase in pressure in the piping attached to the piping between the piping and the combustion treatment device are detected. a pressure sensor, a flame detection sensor attached to the combustion furnace of the combustion treatment device to detect the disappearance of the flame in the furnace, and a combustible gas sensor attached to the piping between the combustion treatment device and the dust removal filter; , a control device for closing a switching valve connected to the combustion processing device and opening a switching valve connected to the adsorption processing device based on abnormal signals detected by each of the sensors. is provided. The toxic exhaust gases to be treated in the present invention include toxic gases that produce solid fine powder through combustion treatment. Typical examples of such toxic gases include arsine, phosphine, diborane, hydrogen selenide, monosilane, chlorosilane, trimethylgallium, trimethylindium, trimethylaluminum, etc.
Compounds of group elements that exhibit a gaseous state at room temperature. These toxic gases are contained in exhaust gases generated from reaction processes such as semiconductor manufacturing processes, new material manufacturing processes, and optical fiber manufacturing processes. In such exhaust gas, the toxic gas content is 0.01 at a volume of 2.
~50%, and the remainder consists of gases such as hydrogen gas, nitrogen, and argon, depending on the type of exhaust gas.

In addition, when there are few combustible components in the toxic exhaust gas and flame formation is insufficient, combustible gases such as hydrogen and methane can be mixed with the exhaust gas. When exhaust gas containing the above-mentioned toxic gases is combusted, fine solid powder is produced. For example, when arsine is combusted, arsenic (As), arsenic oxide (A8203), and phosphine are combusted.
Phosphorus (P), phosphorous oxide (pzos). When silane is burned, silicon (SL), silicon oxide (Sin, Sin2
) and other fine solid powders are produced respectively. In the combustion treatment device used in the present invention, combustion treatment of toxic exhaust gas,
This combustion treatment simultaneously achieves the removal of the solid fine powder produced.

Next, one example of the combustion processing apparatus used in the present invention will be explained with reference to drawings. Figure 1 shows an explanatory cross-sectional view of the toxic exhaust gas combustion treatment equipment. This device consists of a combustion furnace and a gas-liquid separator directly connected to the bottom of the combustion furnace, and the entire device is shaped like a single cylinder.

In this case, the combustion furnace and the gas-liquid separator can be arranged vertically, thereby minimizing the installation space and making it industrially practical. In FIG. 1, the cylindrical body part A forms the combustion furnace A, and the cylindrical body part B forms the gas-liquid separator B. The combustion furnace ^ consists of a cylindrical body l having a ceiling part 2;
A diffusion type burner 3 is provided at the top of the burner, a water spray nozzle 4 is provided at the upper end of the burner (see FIG. 2), and a water spray nozzle 5 is provided at the bottom of the burner. 16 indicates a line that supplies combustion supporting gas (oxygen or air) to the diffusion burner. Furthermore, if necessary, a part of the furnace wall at the upper part of the furnace interior is formed into a concave wall 6 projecting outward, and a pilot burner 7 is disposed therein, and an opening is formed in the furnace wall opposite the pilot burner. This opening is sealed with a shield glass 8, and an ultraviolet detection device is attached to the rear of the glass to confirm the presence of flame.6 This ultraviolet detection device consists of an ultraviolet detection tube 9 and a support tube that supports it. It is constructed from lO. As shown in Fig. 2, the water injection nozzle 4 disposed at the upper end of the furnace has its injection direction directed in the circumferential direction (tangential direction) of the cylinder 1, and the injection water becomes a swirling flow and flows into the furnace. Supplied to the inner wall surface. By supplying such jet water. A water film l1 is formed on the inner wall of the furnace, flowing down from the top to the bottom.
Injection water can be formed, for example, by injecting compressed water from a nozzle using a pump, or preferably by mixing water with compressed gas and injecting this mixture tangentially to the inner wall surface of the upper end of the furnace. This can be done by doing. Air is usually used as the compressed gas. As described above, when the water is introduced into the upper end of the furnace by swirling it in the direction of the inner circumference of the furnace, a water film can be easily formed on the inner surface of the furnace wall without being greatly affected by the inclination of the furnace. Also, when mixing compressed gas to increase the flow velocity and inject,
Not only does the amount of water required for injection water be small, but it also has the advantage of forming a water film on the ceiling and also on the outer peripheral surface of the burner through the ceiling. In addition, by forming a water film on the outer surface of the burner, it is possible to capture and remove solid fine powder that adheres to the burner outer surface and the burner tip, thereby preventing corrosion and blockage of the burner due to solid fine powder. Furthermore, in this case, a water cooling jacket is formed on the outer circumference of the burner to lower the burner temperature and prevent the water film on the outer surface of the burner from evaporating, thereby forming a water film on the outer circumferential surface of the burner with a smaller amount of water. Can be done. As the combustion burner used in the combustion device, it is preferable to use a diffusion type burner. In the diffusion type PANA, toxic exhaust gas and combustion-supporting gas are mixed at the tip of the burner inside the combustion furnace. In a premix burner that mixes toxic exhaust gas and combustion-supporting gas before entering the combustion furnace, if the toxic gas is highly reactive, the toxic gas and combustion-supporting gas may react in the nozzle. However, this is not desirable because it generates solid content, which causes the problem of nozzle clogging. The basic structure of this diffusion-type burner is to have a toxic gas flow path and a combustion-supporting gas flow path independently, and to have a combustible gas flow path or an inert gas flow path as necessary. It has a water cooling jacket on the outer periphery. Air or oxygen is used as the combustion supporting gas. Hydrogen, methane, propane, etc. are used as flammable gases. Nitrogen etc. are used as the inert gas.
When interposing a flammable gas flow path between the toxic gas flow path and the combustion-supporting gas flow path, it is possible to prevent the diffusion and mixing of the toxic gas and the combustion-supporting gas immediately after the burner outlet, so that solid fine powder Prevents adhesion to the burner tip. Moreover, in this case, the combustion-supporting gas is completely consumed by the reaction with the combustible gas at the tip of the burner and does not diffuse into the toxic gas, so the reaction between the toxic gas and oxygen at the tip of the burner can be reliably prevented. By using an inert gas such as nitrogen gas instead of the flammable gas,
Diffusion mixing of toxic gas and combustion-supporting gas at the tip of the burner can be prevented, but in this case, the reaction between the toxic gas and oxygen at the tip of the burner cannot be completely prevented. When toxic gases are at high temperatures or during long-term combustion processes, it is not possible to sufficiently prevent solid fine powder from adhering to the tip of the burner, and furthermore, combustion efficiency decreases. There's a problem. Figure 3 shows an explanatory cross-sectional view of the diffusion type burner. Figure 3 (
a) is an explanatory diagram of a burner having a quadruple tube structure.

The first conduit 41 located in the center forms a toxic gas nozzle, the second conduit 42 located outside it forms a primary combustion supporting gas nozzle, and the third conduit 43 located outside it forms a toxic gas nozzle.
A secondary combustion supporting gas nozzle is formed, and the fourth conduit 44 on the outside thereof is sealed at its tip to form a cooling jacket. Figure 3(b) is an explanatory cross-sectional view of a burner with triple tube structure. The first conduit 4l located in the center forms a toxic gas nozzle, the second conduit 42 located on the outside forms a combustion-supporting gas nozzle, and the third conduit 43 located on the outside has its tip sealed. to form a cooling jacket. FIG. 3(c) is an explanatory cross-sectional view of another burner having a quadruple tube structure. The first conduit 4l located in the center forms a toxic gas nozzle, the second conduit 42' located on the outside forms a flammable gas nozzle, and the third conduit 43 located on the outside forms a combustible gas nozzle. The fourth conduit 44 located on the outside thereof is sealed at its tip to form a cooling jacket. In the combustion furnace A of the apparatus shown in FIG. 1, a spray nozzle 5 arranged on the lower wall of the furnace injects water droplets into the furnace,
By colliding with the combustion gas, the combustion gas is rapidly cooled, and
This was installed to remove solid fine powder from the combustion gas together with the water film on the furnace inner wall. In other words, by rapidly cooling the combustion gas, the water vapor in the gas condenses with the solid fine powder as the nucleus and becomes water droplets, and the solid fine powder is taken into the water droplets and removed. As a result of the collision, solid fine powder is captured in the water droplets and removed. This water droplet jet together with the water film on the inner wall of the furnace efficiently removes the fine solid powder inside the furnace.

In addition, as shown in FIG.
A spark plug l2 is arranged together with the pilot burner 7. The outer circumferential surface of the spark plug l2 is made of an insulator, and the distance a between the insulator surface and the wall surface of the recess and the distance b between the insulator surface and the outer surface of the pilot burner are at least several times the length of the insulator. It is held in It is preferable that the tip discharge portion of the spark plug is hook-shaped as shown in FIG. When arranging the piston burner and the spark plug in this manner, it is possible to prevent the tip of the piston burner and the tip of the spark plug from becoming linked by a water film,
This prevents short circuits between the spark plug and pilot burner and sparks from occurring at locations other than the spark plug. In addition, water droplets fall from the furnace wall surface on which a water film is formed above the pilot burner and spark plug, wetting the surfaces of the pilot burner and spark plug, and causing water droplets to fall onto the pilot burner and spark plug surfaces. Adhesion of solid fine powder is prevented. If solid fine powder adheres to the tip of the pilot burner or the tip of the spark plug, it will cause problems such as difficulty in igniting the pipe burner, but by arranging the pilot burner as described above, this problem can be avoided. This prevents any inconvenience from occurring and ensures reliable ignition. Further, the insulator portion of the spark plug 12 may be dried by introducing a gas such as air into the insulator portion. Hydrogen gas is preferably used as the flammable gas for the pilot burner. Compared to the use of flammable gases such as methane and propane, the use of hydrogen gas has a wider combustion range (mixture ratio, linear velocity), allows the pilot burner to be smaller, and even at higher linear velocity, the flame does not ignite. This has the advantage that blow-off does not occur. The ultraviolet light detection device installed on the upper wall of the furnace through the shield glass 8 detects the presence or absence of flames in the pilot burner and main burner. In the case of this combustion treatment device, the shield glass is cleaned with a water film to prevent solid fine powder from adhering to it, allowing for reliable flame detection. In FIG. 1, a gas-liquid separator B directly connected to the bottom of the combustion furnace A includes a cylindrical body 21, a combustion gas exhaust pipe 22 disposed at the top thereof, and a liquid reservoir 26 at the bottom thereof. The drain pipe 23 is provided with a drain pipe 23, and a filling layer 24 is further provided inside the pipe. Basically, the gas-liquid separator B may have any structure as long as it can separate the water that has captured and absorbed the solid fine powder produced in the combustion furnace A and the combustion gas, and the arrangement of the packed bed 24 may be sufficient. is not necessarily required. However, when the packed bed 24 is provided, sufficient gas-liquid contact between the combustion gas and water is achieved in this packed bed, so if the combustion gas from the combustion furnace A contains residual solid fine powder, This makes it possible to easily remove toxic solid fine powders that are captured and absorbed by the water that comes into contact with them, and that remain in the combustion gas discharged from the combustion furnace. Therefore, in this case, it is not necessary to completely remove the solid fine powder contained in the combustion gas in the combustion furnace. The amount of water used in the combustion furnace is reduced, and the operating conditions of the combustion furnace are significantly relaxed.
The combustion furnace itself can also be downsized. The structure of the packed bed 24 is arbitrary, as long as it can bring the combustion gas from the combustion furnace A into gas-liquid contact with water. For example, a filled layer may be provided at the top of the cylindrical body 21, a space may be provided below the filled layer, and a liquid reservoir section 26 may be further provided below the filled layer. In this case, the drain pipe 23 has a liquid reservoir at its bottom.
and an exhaust pipe 22 are arranged in the space between them. The packed bed suitable for use in the combustion apparatus has a shape, as shown in FIG. 1, in which the upper part of the packed bed can merge and mix the water film flowing down the inner surface of the furnace wall and the falling water droplets formed by the spray nozzle. For example, it has a structure in which it has a downward conical shape, the lower part is in the shape of a column extending downward to the upper part of the liquid reservoir 26, and the space 25 is disposed outside of the column. When a packed bed having such a structure is used, the gas-liquid multiphase flow collides with the water surface of the liquid reservoir 26 from the lower end of the columnar packed bed, so that gas-liquid separation can be performed efficiently. In addition, fine bubbles generated by the gas-liquid multiphase flow flowing from the top to the bottom of the packed bed blow out from the bottom end of the packed bed, forming a bubble layer on the water surface. Efficient contact between the air bubbles and the water film surrounding the gas phase is obtained, resulting in
The solid fine powder contained in the gas is efficiently captured and absorbed into the water.

In this case, all or part of the space 25 outside the packed bed 24 may be made into a packed bed separately from the filling N24, and water may be supplied to the top of this packed bed to perform gas-liquid contact again. This further increases the capture rate of solid fine powder. As the filler used to form the packed layer, general fillers used for gas-liquid contact (e.g., Larschig rings, balls, etc.) can be used, but in the case of the present invention,
It is preferable to use a packing that can efficiently bring about gas-liquid contact, such as a small piece of 10 to 100 mesh wire gauze (size = about 5 to 301+I1), which is used in a normal rectification column. It is preferable to use the small piece of wire mesh in a cylindrical, saddle-shaped, etc. shape. When a gas-liquid multiphase flow is passed from the top to the bottom of the wire mesh packed bed, the liquid is uniformly dispersed on the wire mesh surface to form a liquid film, and the combustion gas passes through this liquid film, resulting in good air flow. Liquid contact occurs and at the same time a large number of fine bubbles are generated. In this bubble, the gas moves violently due to the kinetic energy of the gas within the bubble, so that efficient contact with the surrounding liquid film can be obtained. In this way, the pressure loss can be reduced and solid fine powder in the combustion gas can be efficiently transferred to the aqueous phase and removed. Moreover, in order to perform gas-liquid separation in the cylinder body 21,
The water and combustion gas from the combustion furnace A are collected by a funnel-shaped collection tube, and after being bubbled into the water in the liquid reservoir 26 to cause gas-liquid contact, the combustion gas is separated from the water. , this can also be exhausted out of the system. Next, we will explain a specific example of combustion treatment of toxic exhaust gas using the apparatus shown in Figure 1. First, the liquid reservoir 26 is filled with water, and this water is passed from the upper end of the combustion furnace A through the drain pipe 23, the pump 32, the conduit 36, and the conduit 38, and is injected into the furnace together with pressurized air from the conduit 39 by the water injection nozzle 4. The water is sprayed in the inner circumferential direction, and is also passed through the conduit 37 and sprayed from the spray nozzle 5 into the furnace. Water is injected from the top of the furnace, creating a falling water film on the inside walls of the furnace. In this case, by slightly tilting the water jet direction upward, a water film can be formed on the ceiling of the furnace, and a water film can also be formed on the outer peripheral surface of the burner 3 through this water film on the ceiling. can do.

Next, the hydrogen gas is combusted with air in seven pipe holes to form a hydrogen flame, and the ends of the burner 3 (see the quadruple tube structure diffusion burner shown in Fig. 3(a)) are sealed. 4th stop
Water is sent to the conduit 44 to form a water cooling jacket, and the third
Secondary oxygen is supplied to the conduit 43, primary oxygen is supplied to the second conduit 42, and the first
Toxic gases are introduced into the conduit 4l, and these gases are ejected from the tip of the burner, ignited by the hydrogen flame of the pipe burner, and combusted. By burning the toxic exhaust gas in this way, fine solid powder is generated. It is also captured and absorbed by water droplets. Then, the water and combustion gas that have captured and absorbed the solid fine powder are sent to the gas-liquid separator B directly connected to it.
After the solid fine powder remaining in the combustion gas is further captured in the packed bed, it is separated into gas and liquid.

That is, water flowing down as a water film on the inner surface of the furnace wall, water falling as water droplets formed by injection from a spray nozzle, and combustion gas are mixed together at the upper part of the filling M24,
It passes through the packed bed as a gas-liquid mixed flow, and is ejected from the lower end of the packed bed onto the water surface of the liquid reservoir 26 as a gas-liquid mixed phase flow containing bubbles, where it is separated into gas and liquid. The separated combustion gas is discharged from the space 25 to the outside of the system through the exhaust pipe 22.

The water in the liquid reservoir 26 passes through the drain pipe 23 and is circulated by the pump 32 to the water injection nozzle 4 and the spray nozzle 5 of the combustion furnace. is cooled to

The water level in the liquid reservoir 26 is maintained at a constant level by a water level gauge 35 and a water level control valve 33 attached to a conduit 31' connected to the drain tank 31. That is, in the combustion treatment of toxic gases, water is produced as a by-product, and this by-product water forms surplus water in the system. This surplus water is stored in the tank 31 through the line 31' by the water level gauge 35 and the water level regulating valve 33. By matching the amount of liquid extracted by the drain pipe 23 and discharged to the outside of the system through the conduit 31' with the amount of water generated when toxic exhaust gas is burned in a burner, the amount of liquid drained is minimized. system can be obtained.

When the toxic exhaust gas is burnt as described above, the toxic exhaust gas to be supplied to the combustion burner is heated to 70V, or the combustible gas component that produces water by combustion of methane, hydrogen, etc.
It is preferable to set it to oQ% or more.

When the combustible components in the toxic exhaust gas are adjusted to 70 voQ% or more, flame formation in the burner is easy and a high combustion decomposition rate of the toxic gas can be obtained. On the other hand, if the toxic exhaust gas contains less combustible components and more inert components such as nitrogen and helium, AsH,... Ptl3,S i t{ 4
The combustion decomposition rate of toxic gases such as

Further, the combustion treatment device used in the present invention is not limited to the structure described above, and conventionally known devices can also be used.

The toxic exhaust gas adsorption treatment device used in the present invention consists of a packed column containing an adsorbent that exhibits adsorption reactivity to toxic gases. As the adsorbent, there are various conventionally known adsorbents, such as:
Adsorbents containing heavy metal oxides such as copper, iron, nickel, and zinc (JP-A-60-68034, JP-A-61-9072)
No. 6, JP-A-61-129026, JP-A-61-20
No. 9030, JP-A-62-1439, JP-A-62-i
No. 52515) is used.

As the flashback prevention device used in the present invention, conventionally known devices such as those with a water seal structure and those using wire mesh or porous materials can also be used, but more preferably, the flashback prevention device developed by the present inventors It is advantageous to use a structure filled with non-flammable oil developed by This flashback prevention device is shown in FIG. Fifth
The figure shows a cross-sectional view of a flashback prevention device preferably used in the present invention, and the overall structure includes a container-shaped main body 51 with closed upper and lower surfaces, an exhaust gas inlet pipe 52, and an exhaust gas outlet pipe 53 near the upper end. A nonflammable oil 54 is sealed in the container-shaped main body 51 so that the lower end of the exhaust gas inlet pipe 52 is immersed therein. As the nonflammable oil 54, trifluorochloroethylene low polymer ((c, cnF, )n) is preferably used, as well as hydrogen-free carbon halides having a boiling point of 100° C. or higher, such as CCQ2CCQ2F,
CCQ2C(,!, etc. are used.

With this configuration, under normal conditions, exhaust gas enters through the exhaust gas infiltration pipe 52, bubbles in the nonflammable oil 54, is discharged from the exhaust gas outlet pipe 53, is processed by the combustion processing device in the subsequent stage, and is reversed by the combustion burner. Even if a fire occurs, the flame propagation is blocked by the non-flammable oil 54 surface, so it will not reach the exhaust gas inlet pipe 52. However, if the pressure in the exhaust gas outlet pipe 53 increases due to backfire, the cylindrical container-shaped main body 1
As the internal pressure increases, the liquid level of the non-flammable oil 54 in the exhaust gas inlet pipe 52 rises, and the exhaust gas inlet pipe 52 is filled with a sufficient amount of non-flammable oil 54, and the exhaust gas passage is blocked and the reverse occurs. Fire is prevented.

Next, FIG. 6 shows a modification of FIG. 5, in which a pubbling hole 55 is provided around the lower end edge of the exhaust gas inlet pipe 52. Other parts are shown with the same symbols as in Figure 5. In this configuration, since the bubbles during bubbling can be made smaller, the generation of mist and pressure fluctuations due to bubbling can be reduced, and the small pressure fluctuations caused by this bubbling can stabilize the flame of the burner. can.

The dust removal filter used in the present invention may be any filter as long as it can capture particulates contained in combustion exhaust gas.
Conventionally known materials can be used.

FIG. 7 shows a system diagram of the apparatus of the present invention.

In FIG. 7, 61 indicates a toxic exhaust gas generation source such as a semiconductor device. 62 is an adsorption treatment device, 63 is a combustion treatment device, 64 is a flashback prevention device, and 65 is a dust removal filter. Toxic exhaust gas supply line from the toxic exhaust gas source (
Piping) is connected to a line 69 which continues to the adsorption treatment device 62 through its two switching valves 67 and 68, and a flashback prevention device! ! 6
4 into a line 70 which continues to a combustion treatment device 63. In a steady state, the valve 67 following the adsorption treatment device is closed, and the valve 68 following the flashback prevention device is opened. Toxic exhaust gas (hereinafter also simply referred to as exhaust gas) from the toxic exhaust gas source 6l is released. , line 66, valve 6B and line 70, and then passes through the flashback prevention device 64, passes through the line 7l, passes through the parner 72, and is injected into the combustion treatment device 63, where it is combusted. Combustion exhaust gas is line 73
The air is extracted through the dust removal filter 65 and the exhaust pump 74 and discharged to the atmosphere. In the combustion treatment device 63, the fine powder generated by the combustion treatment of toxic exhaust gas flows down from the upper end of the combustion treatment device to the bottom, passes through a line 75, a liquid circulation pump 76, a cooler 77, and a line 78, and is combusted again. It is captured by the circulating water circulating to the upper end of the furnace, and a portion of the circulating water passes through line 79 and is stored in waste liquid drum 80 .

Combustible gas is introduced into the line between the toxic exhaust gas source and the flashback prevention device through line 81 as necessary, and oxygen or air as a combustion supporting gas is introduced into the combustion burner 72 through line 82. introduced through.

A nitrogen gas line 83 is connected to the exhaust gas supply line 71 to the combustion burner via a valve 85 and a line 87, and a water supply line 84 is connected to the exhaust gas supply line 71 via a valve 85 and a line 87.
7 so that, if necessary, a mixture of nitrogen gas and water flows through the exhaust gas supply line 87 into the combustion burner nozzle. The burner nozzle can be cleaned by flowing a mixture of water and nitrogen gas through the burner nozzle. The exhaust gas contains fine particles such as As and Ga produced by decomposition, which may clog the burner, but in that case, a mixture of nitrogen gas and water should be introduced into the exhaust gas line as described above. By introducing the burner and allowing it to flow through the burner, the blockage can be removed without removing the burner. Even if nitrogen gas and water are used alone, it is almost impossible to remove blockages, so it is necessary to use a mixture of the two. Further, an air conduit 99' having a control valve 99 can be connected to the combustion exhaust gas line 73 between the combustion treatment device and the dust removal filter. This air conduit 9
By mixing gas such as air into the combustion exhaust gas from 9' and diluting the combustion exhaust gas, clogging of the dust removal filter can be avoided. Combustion exhaust gas contains fine liquid droplets (mist) and fine particles containing moisture, but if this is directly sent to the dust removal filter, the moisture will cause the fine particles captured by the dust removal filter to solidify together and remove the dust. This may cause the filter to become clogged. When gas is mixed into the combustion exhaust gas as described above, the moisture is diluted to below the dew point by the gas and vaporized at the same time, so the problem of clogging of the filter can be avoided.

In this case, the amount of gas mixed in is 0.
The ratio is between 5 and 1012. Further, the gas used has a relative humidity of 30% or less, preferably 5% or less.

In the present invention, the above-mentioned toxic exhaust gas treatment device is equipped with various sensors so as to ensure safe detoxification of the toxic exhaust gas even if an inconvenience such as trouble with the device occurs. And each sensor! A control device 90 is provided which switches and operates valves 67 and 68 attached to a pipe 66 connected to a toxic exhaust gas generation source based on a signal from the sensor. A pressure sensor 91 attached to the pipe 71 that detects an abnormal increase in pressure within the pipe is used as the sensor in the present invention.
．． It includes at least a flame detection sensor 92 attached to the combustion furnace of the combustion treatment device that detects the disappearance of the flame in the furnace, and a combustible gas sensor 94 attached to the piping 73 between the combustion treatment device and the dust removal filter. Furthermore, if necessary, a temperature sensor 93 for detecting an abnormal rise in the temperature inside the furnace can be provided. In addition, the flammable gas sensor is
This is to detect combustible gas remaining when incomplete combustion occurs when exhaust gas is burned in a burner, and to confirm whether the inside of the furnace has been completely purged when starting up the combustion treatment equipment. Each of these sensors is electrically connected to the control device W90, and when each sensor detects an abnormal state, the control device 90 closes the valve 68 following the combustion processing device 63 based on the abnormal signal from each sensor. , a valve 67 following the adsorption treatment device 62
The toxic exhaust gas is rendered harmless by the adsorption treatment device 62.

As a combustion treatment device, a structure equipped with a gas-liquid separator at the bottom and treated water stored at the bottom as shown in Figure 1 is used, or a gas-liquid separator independent of the combustion treatment device is used. When using a water treatment system, it is preferable to control the liquid level of the treated water within a predetermined range and to install a liquid level sensor that detects an abnormal rise or fall in the liquid level.

A liquid level sensor 95 is attached to the lower part of the combustion treatment device R63 shown in FIG. 7, and this liquid level sensor is connected to a liquid level controller 97 that operates a valve 96 attached to a drain line 79. , the liquid level of the treated water at the bottom of the combustion treatment device is maintained within a predetermined range. Also, the liquid level sensor 9
5 is also connected to the control device 90, and when an abnormal rise or fall in the liquid level occurs, it sends the abnormal signal to the control device 90, closes the valve 68 connected to the toxic exhaust gas pipe 66, and closes the valve 67. Open. Further, a pressure sensor 98 is installed inside the combustion furnace of the combustion processing device 63, and this pressure sensor is connected to a pressure controller 100 that operates a control valve 99 of an air conduit 99' attached to the combustion exhaust gas line 73. ,
By controlling the amount of air sucked in by air conduit 99', the pressure within the combustion furnace can be maintained within a predetermined range.

Furthermore, the valve 67, the valve 68, and the pipe 69 are connected to the eighth
As shown in the figure, instead of connecting to the pipe 66, it may be connected to the pipe 7l. (Effects of the Invention) The method and apparatus for treating toxic exhaust gas of the present invention are constructed as described above. Toxic exhaust gases from toxic exhaust gas sources are effectively rendered harmless by combustion treatment equipment under normal conditions. However, when an abnormal condition occurs in the combustion treatment equipment, the appropriate place is set to detect the abnormal condition. The supply of toxic exhaust gas to the combustion treatment equipment is stopped by the operation of the sensor attached to the sensor and the control device connected to it, and the toxic exhaust gas is supplied to the adsorption treatment equipment, which is easy to operate and extremely safe. and adsorption treatment. Therefore, in the present invention, even if an abnormality occurs in the combustion treatment equipment, the treatment of toxic exhaust gases can be continued by the adsorption treatment equipment without stopping the treatment. It has no effect on the exhaust gas generation source.

Furthermore, by connecting a sensor that detects an abnormal environment such as an earthquake or flame to the control device, it is possible to stop the combustion process and start the adsorption process when such an abnormal environment occurs.

[Brief explanation of drawings]

Fig. 1 is an explanatory sectional view of the combustion processing device, and Fig. 2 is an explanatory view of the arrangement of injection nozzles arranged at the upper end of the furnace. Figures 3(.)-(e) are explanatory cross-sectional views of the tip of the combustion burner. Figure 4 is an enlarged view of the recessed furnace wall where the pilot burner is installed. Fig. 5 is a longitudinal sectional view of the flashback prevention device, and Fig. 6 is a longitudinal sectional view showing a modification thereof. FIG. 7 shows a system diagram of the device of the invention. Figure 8 shows an example of piping connections. l... Combustion furnace cylindrical body part, 2... Furnace ceiling part, 3...
Combustion burner, 4... Water injection nozzle, 5... Water spray nozzle, 6... Recessed furnace wall, 7... Pilot burner, 8... Shield glass, 9... Ultraviolet detection tube,
DESCRIPTION OF SYMBOLS 11...Water film, 21...Cylinder part for gas-liquid separation, 22.
...Exhaust pipe, 23...Drain pipe, 24...Filled bed, 2
5... Space part, 26... Liquid storage part, 31... Water storage tank, 32... Pump, 34... Cooler, 35...
・Water level gauge, 36...Water level control valve, 5l...Cylindrical container-shaped main body, 52...Exhaust gas inlet piping, 53...Exhaust gas outlet piping, 54...Nonflammable oil, 55...Pubbling Hole, 61... Source of toxic exhaust gas, 62...
・Adsorption treatment device, 64...Flashback prevention device, 67, 68
...Toxic exhaust gas switching valve, 90...Control device,
91...Pressure sensor, 92...Flame detection sensor, 93...Temperature sensor, 94...Flammable gas sensor, 95...Liquid level sensor

Claims (9)

[Claims] (1) A toxic exhaust gas treatment system in which two switching valves are installed in the toxic exhaust gas piping, one of which is connected to an adsorption treatment device, and the other connected to a combustion treatment device via a flashback prevention device. A method for treating toxic exhaust gases, in which the switching valve connected to the adsorption treatment device is normally closed and the switching valve connected to the combustion treatment device is opened to perform combustion treatment of the toxic exhaust gas. Connect to the combustion treatment equipment when there is an abnormal rise in the pressure of the treatment equipment system, when the flame in the combustion furnace of the combustion equipment disappears, or when flammable gas is detected in the combustion exhaust gas discharged from the combustion treatment equipment. A method for treating toxic exhaust gas, characterized in that a switching valve is closed, and a switching valve connected to an adsorption treatment device is opened to perform adsorption treatment on toxic exhaust gas. (2) The combustion processing equipment consists of a vertical combustion furnace and a gas-liquid separator that is directly connected to the bottom of the combustion furnace. The gas-liquid separator has a structure including a combustion gas exhaust pipe at the top and a drain pipe at the bottom. The separated water is extracted from the drain pipe, a part of the water extracted from the drain pipe is circulated to the water injection nozzle and the water spray nozzle, and the remainder of the extracted water is discharged as waste liquid to the outside of the system. 2. The method of claim 1. (3) The method according to claim 3, wherein the amount of waste water is an amount corresponding to water generated by combustion treatment of toxic exhaust gas, and the combustion treatment apparatus is not substantially supplied with water from the outside. (4) The method according to any one of claims 2 to 4, wherein the combustion gas extracted from the combustion gas exhaust pipe is mixed with a gas having a relative humidity of 30% or less, and then discharged to the outside of the system through a dust removal filter. (5) Toxic exhaust gas piping, a toxic exhaust gas adsorption treatment device connected to the piping and the combustion treatment device via a switching valve, and a device connected to the piping via the switching valve and flashback prevention device. A toxic exhaust gas combustion treatment device, a dust removal filter connected to the combustion treatment device, a pressure sensor attached to the piping between the piping and the combustion treatment device for detecting an abnormal increase in pressure within the piping, and A flame detection sensor attached to the combustion furnace of the combustion treatment device to detect the disappearance of the flame in the furnace, a combustible gas sensor attached to the piping between the combustion treatment device and the dust removal filter, and each of the above-mentioned sensors. A toxic exhaust gas processing device comprising a control device that closes a switching valve communicating with the combustion processing device and opens a switching valve communicating with the adsorption processing device based on a detected abnormal signal. (6) The combustion processing device consists of a vertical combustion furnace and a gas-liquid separator that is directly connected to the bottom of the combustion furnace, and the combustion furnace has a diffusion burner on the ceiling and a peripheral burner on the upper end. 7. The apparatus of claim 6, further comprising a directional water injection nozzle and a water spray nozzle at the bottom thereof, and the gas-liquid separator has a structure including a combustion gas exhaust pipe at the top and a drain pipe at the bottom. (7) The flashback prevention device has a cylindrical container-shaped main body whose upper and lower surfaces are closed, and has an exhaust gas inlet pipe and an exhaust gas outlet pipe near the upper end, and the lower end of the exhaust gas inlet pipe is immersed in the interior of the pipe to provide non-flammable oil. 8. The device according to claim 6, wherein the device has a structure in which the device is encapsulated. (8) The device according to any one of claims 6 to 8, wherein an air introduction pipe is attached to the combustion exhaust gas piping of the combustion processing device and the dust removal filter via a valve. (9) The apparatus according to any one of claims 6 to 9, wherein the combustion burner disposed in the combustion processing apparatus is provided with a nitrogen gas introduction pipe and a water introduction pipe via valves.