JPH06129627A - Exhaust gas combustion method and apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] An exhaust gas combustion method and device capable of efficiently combusting low-concentration combustible harmful components in exhaust gas while preventing adhesion of combustion products to the furnace wall in the combustion device. provide. [Structure] The upper part of the combustion furnace 1, the exhaust gas flow path 2 inside
a, a gas inlet 3 composed of a double pipe 2 having a flow path 2b for combustion-supporting gas with a swirler 6 provided outside, and a discharge port 4a for combustion gas at the bottom, respectively, and the combustion furnace body 1a is enlarged. The large diameter barrel portion 1a is connected to the gas introduction port 3 by a conical surface 1b, and a pilot burner 5 is provided on the conical surface 1b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for burning exhaust gas, and more particularly to a method and a device for burning a harmful combustible component contained in the exhaust gas to render it harmless.

[0002]

2. Description of the Related Art For example, since exhaust gas discharged from a semiconductor manufacturing process contains silane and arsine which are semiconductor material gases and other combustible and harmful components, this exhaust gas is conventionally used in a combustion apparatus. It is introduced to burn it to make it harmless (Japanese Patent Laid-Open No. 62-134414).
(See Japanese Patent Publication).

The above-mentioned conventional combustion apparatus can satisfactorily perform the combustion treatment when the combustible and harmful components have a high concentration, but in recent years, exhaust gas from the semiconductor manufacturing apparatus is, for example, in a pipe from the semiconductor manufacturing apparatus to the combustion apparatus. For safety reasons such as preventing the combustion of the above, the semiconductor material gas is diluted with an inert gas such as nitrogen until the concentration of the contained semiconductor material gas becomes a low concentration below the combustion range.

Therefore, in the case where a large amount of air or an inert gas is flowed or water is sprinkled like the conventional combustion device, the temperature in the combustion device does not rise sufficiently, resulting in insufficient combustion. Therefore, there is an inconvenience that only a low decomposition rate can be obtained.

[0005]

However, if the amount of air, inert gas, or water supplied to the combustion device is reduced in order to raise the combustion temperature, combustion products will be generated on the tip of the burner or on the inner wall of the combustion device. Adheres to the surface, making continuous operation impossible.
For this reason, it has been practiced to further dilute the exhaust gas after incomplete combustion with air to make the harmful components below the permissible concentration and exhaust the exhaust gas.

Therefore, the present invention aims to provide an exhaust gas combustion method and device capable of efficiently combusting burnable and harmful components in exhaust gas while preventing adhesion of combustion products to the inner wall of the combustion device. I am trying.

[0007]

In order to achieve the above-mentioned object, an exhaust gas combustion method of the present invention is an exhaust gas in which an exhaust gas containing a combustible harmful component is mixed with a combustion-supporting gas and burned to remove harmful substances. In the above combustion method, the exhaust gas is caused to flow down into the combustion-supporting gas that forms a swirling flow and is mixed and burned.

Further, the exhaust gas combustion apparatus of the present invention comprises a double tube having an exhaust gas passage inside and a combustion supporting gas passage outside in the upper part of the combustion furnace. At the outlet of the flow path, a swirler that gives a swirling force to the combustion-supporting gas or a gas inlet provided with a swirling flow generating means such as a gas inlet for introducing the combustion-supporting gas in the tangential direction is provided at the bottom of the combustion gas. Discharge ports are respectively provided, the combustion furnace body is formed to have a large diameter, and the large diameter body and the gas introduction port are connected by a conical surface,
It is characterized in that a pilot burner is provided on the conical surface or the large-diameter body portion, and further, three or more pilot burners are provided with the flame ejection direction decentered from the central axis of the combustion furnace. I am trying.

Air may be usually used as the combustion-supporting gas, but when sufficient combustion is difficult due to a low concentration of combustible harmful components in the exhaust gas, oxygen, ozone, etc. It is possible to use air (gas) to which is added the combustion accelerator.

[0010]

[Operation] According to the combustion device having the above structure, the combustion-supporting gas introduced into the combustion furnace becomes a swirl flow due to the swirler provided at the gas introduction port or the combustion-supporting gas introduced from the tangential direction, It flows down along the conical surface of the furnace wall by centrifugal force.
On the other hand, the exhaust gas containing the combustible and harmful components flows down from the central portion of the gas introduction port to the central portion of the combustion-supporting gas forming a swirling flow. Therefore, the exhaust gas reaches the flame tip of the pilot burner in the center of the furnace with almost no mixing with the combustion-supporting gas in the initial stage, where flammable harmful components in the exhaust gas come into contact with the combustion-supporting gas. To burn.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail based on an embodiment shown in the drawings.

In the combustion furnace 1 shown in this embodiment, the body portion 1a has a large diameter, and the upper and lower portions 1b. A double tube 2 having a conical surface 1c and an exhaust gas passage 2a on the inside and a combustion-supporting gas, for example, air passage 2b on the outside in the upper portion.
Is provided with a gas inlet 3 and an exhaust pipe 4 is provided at the bottom.
Is provided with a combustion gas discharge port 4a.

Further, three pilot burners 5, 5 are attached to the conical surface 1b with the flame ejection direction facing downward and in a state of being eccentric from the central axis c of the combustion furnace. At the lower end of the gas passage 2b, the passage 2
A swirler 6 is provided for introducing the combustion-supporting gas introduced from b into the furnace as a swirling flow.

In the combustion furnace 1 having the above-mentioned structure, the spread angle of the conical surface of the furnace upper portion 1b is appropriately in the range of 40 to 100 degrees, and when the angle is less than 40 degrees, the combustion supporting property is increased. Combustion efficiency (decomposition rate) because the gas does not spread sufficiently and the exhaust gas from the flow path 2a is entrained in the combustion-supporting gas from the flow path 2b and diluted, resulting in a lower concentration of combustible and harmful components. On the contrary, when the temperature exceeds 100 degrees, the combustion-supporting gas spreads too much and the swirling force decreases, and a swirling flow that descends along the furnace wall portion becomes difficult to occur, and the exhaust gas flowing down from the flow path 2a becomes less likely to flow. The combustion-supporting gas flows in the same direction to similarly dilute the exhaust gas, resulting in a decrease in the decomposition rate.

The angle of the vane plate 6a of the swirler 6 is appropriately in the range of 30 to 75 degrees with respect to the axis. If this angle is less than 30 degrees, the exhaust gas is diluted with the combustion-supporting gas in a short time. As a result, the decomposition rate is reduced, and the amount of the combustion-supporting gas flowing through the furnace wall is reduced, so that the combustion products adhere to the furnace wall. If it exceeds 75 degrees, the exhaust gas is entrained in the furnace wall by the combustion-supporting gas, and the decomposition rate is reduced as described above.

The pilot burner 5 burns a fuel gas such as propane with a combustion-supporting gas such as air to eject a flame into the furnace. The downward angle of the pilot burner 5 is preferably 10 to 50 degrees. , When the downward angle is small and is close to horizontal, the vertical spread of the flame is small, so the high temperature area in the furnace is narrowed, and when the downward angle is too large and it is close to vertical, the pilot burner 5 Since the flame is dispersed, the temperature of the central part does not rise sufficiently, and in either case, the decomposition rate decreases.

Further, the pilot burner 5 has a flame ejection direction of 1 at the center of the furnace with respect to the center axis of the combustion furnace.
It is preferable to decenter about 5 to 20 mm. When the amount of eccentricity is small, the flame concentrates at one point, and the swirl flow promotion by the flame formed in the furnace cannot be fully exerted, and the high temperature region becomes narrow.When the amount of eccentricity is too large, the flame is dispersed. The decomposition rate decreases because the temperature of the central part does not rise sufficiently.

Here, when the pilot burners 5 are eccentric as described above, the number of pilot burners 5 is 3 or more, the eccentric direction is the same as the swirling direction of the combustion-supporting gas, and each pilot burner 5 is eccentric. It is desirable that the eccentricity amounts of the above are substantially the same and that they are provided at substantially equal intervals. As means for eccentricizing the flame ejection direction with respect to the central axis of the combustion furnace, as shown in FIG. 2, a straight tubular pilot burner may be offset or inclined with respect to the line r in the radial direction of the combustion furnace. Alternatively, the tip of the burner may be bent.

With the above-mentioned structure, the exhaust gas containing the combustible and toxic components can flow through the flow passage 2a at the center of the gas inlet.
From the above, the swirler 6 acts as a swirl flow into the combustion-supporting gas flowing down, and reaches the high temperature region H in the center of the furnace with almost no mixing with the combustion-supporting gas. Combustible and harmful components burn in contact with supporting gas.

That is, according to the present invention, the exhaust gas can be introduced into the high temperature region H in the center of the furnace without being diluted with the combustion-supporting gas, and in the high temperature region H, the combustible harmful components in the exhaust gas are
The high-temperature region H becomes slightly lower in pressure than the surroundings due to the swirling flow of the combustion-supporting gas, and the combustion-supporting gas that rises due to convection due to combustion in the furnace can be brought into contact with and burned. With this, it is possible to sufficiently burn even a low concentration of combustible and harmful components, and the product generated by combustion due to the flow of the combustion-supporting gas that swirls the inner circumference of the furnace wall does not adhere to the furnace wall, Since the combustion is performed at a position away from the gas introduction port 3, the combustion products do not adhere to the gas introduction port 3.

The constitution of each part of the combustion furnace is not limited to the above-mentioned embodiment, but can be appropriately set according to the treatment amount of exhaust gas and the kind and concentration of combustible and harmful components contained therein. The pilot burner may be provided in the large-diameter body portion depending on the extent of the conical surface, the length of the large-diameter body portion, and the like, and the number of pilot burners can be changed. Further, in the combustion furnace of the above-described embodiment, the portion from the large-diameter body portion to the discharge port is narrowed in an inverted conical shape, but the large-diameter body portion may be directly connected to the exhaust pipe.

Next, the results of a silane combustion experiment using the above-configured combustion apparatus will be described. Experimental Example 1 Silane in nitrogen gas as exhaust gas was 1.0, 0.5,
Three kinds of gas containing 0.2% by volume were used. Air was used as the combustion-supporting gas, and a mixed gas of propane and air was supplied to the pilot burner 5. The flow rate of each gas was as follows.

Silane + Nitrogen 6 Nm ³ / h Combustion supporting gas (air) 3 Nm ³ / h Propane 0.1 Nm ³ / h Propane air 2.38 Nm ³ / h (theoretical air ratio = 1)

The combustion furnace 1 has a height of 400 mm and a maximum diameter of 165.2 mm, and the inner tube of the double tube 2 of the gas inlet 3 has a diameter of 34.0 mm and the outer tube has a diameter of 48. 6m
m, the diameter of the discharge port 4a is 101.6 mm, the spread angle of the conical surface of the furnace upper part 1b is 60 degrees, the angle of the swirler 6 is 70 degrees with respect to the axis, and the downward angle of the pilot burner 5 is 3 degrees.
It was set at 0 degree and offset by 15 mm with respect to the radial line of the combustion furnace.

As a result, the silane concentration in the combustion exhaust gas is
With respect to the silane concentration in the exhaust gas, 1.0%, 0.5, and 0.2% by volume, respectively, 0.27, 1.10, and 0.95 ppm were obtained, respectively, and sufficient removal below the allowable silane concentration of 5 ppm was performed. It was recognized that it had a harmful ability.

Experimental Example 2 An experiment was conducted under the same conditions as in Experimental Example 1, except that the angle of divergence of the conical surface of the furnace upper portion 1b was 150 degrees. As a result, the silane concentration in the combustion exhaust gas was 6.45, 5.55, and 11.4 ppm for the silane concentration in the exhaust gas, 1.0, 0.5, and 0.2% by volume, respectively. became.

Comparative Example Exhaust gas containing 0.2% by volume of silane in nitrogen was treated using a combustion furnace having the structure described in JP-A-62-134414, but most of the silane was burnt. Instead, it remained in the combustion exhaust gas.

[0028]

As described above, in the exhaust gas combustion method and apparatus of the present invention, the exhaust gas containing combustible and harmful components is introduced into the swirl flow formed in the furnace and combusted. Toxic components can be burned sufficiently to make them harmless, and it is possible to prevent the swirling combustion-supporting gas from flowing through the furnace wall and to prevent combustion products from adhering to the furnace wall. Inflammable harmful components such as silane, arsine, phosphine, germane, and diborane can be removed efficiently.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a combustion apparatus showing an embodiment of the present invention.

FIG. 2 is a cross sectional view of the same.

FIG. 3 is a cutaway front view of the same main portion.

[Explanation of symbols]

1 ... Combustion furnace, 2 ... Double pipe, 3 ... Gas inlet, 4 ... Exhaust pipe, 5 ... Pilot burner, 6 ... Swirler

Claims (4)

[Claims] 1. In a combustion method of an exhaust gas in which an exhaust gas containing a combustible harmful component is mixed with a combustion-supporting gas and burned to remove harmful substances, a swirling flow is formed in the combustion-supporting gas to flow down.
An exhaust gas combustion method, characterized in that the exhaust gas is allowed to flow down to perform mixed combustion. 2. An exhaust gas combustion apparatus in which an exhaust gas containing a combustible harmful component and a combustion-supporting gas are introduced and mixed in a combustion furnace and burned, wherein an upper portion of the combustion furnace, an inner passage of the exhaust gas, and an outer portion thereof. It consists of a double tube with a flow path for combustion-supporting gas,
A gas inlet provided with a swirler that gives a swirling force to the combustion-supporting gas is provided at the exit of the flow path of the combustion-supporting gas, and a discharge port for the combustion gas is provided at the bottom to form the combustion furnace body with a large diameter. Then, the large-diameter body portion and the gas introduction port are connected by a conical surface, and a pilot burner is provided on the conical surface or the large-diameter body portion. 3. A swirling gas generating port for introducing at least a part of the combustion-supporting gas in a tangential direction is provided at the outlet of the flow path of the combustion-supporting gas instead of the swirler. The exhaust gas combustion apparatus according to claim 1, which is characterized in that. 4. The exhaust gas combustion apparatus according to claim 1, wherein three or more pilot burners are provided such that the flame ejection direction is eccentric from the central axis of the combustion furnace.