JP7656333B2 - Thermal detoxification device and thermal detoxification method using said device - Google Patents

Description

The present invention relates to a thermal detoxification device and a thermal detoxification method for safely discharging gases used in the manufacturing process of electronic products such as semiconductors.

Conventionally, there are various methods for abating gases emitted from electronics manufacturing plants. For example, thermal abatement is performed on gases that can remove harmful or hazardous substances through thermal decomposition, such as TMA (trimethylaluminum) used in thin-film formation technologies such as ALD (atomic layer deposition).

The mainstream thermal abatement equipment is a combustion type that uses a gas burner. While this type of thermal abatement equipment has the advantage of being able to efficiently heat the gas to be treated to the temperature required for abatement, it has the disadvantage of requiring relatively large amounts of extra utilities such as gas cylinders and combustion chambers, as well as safety concerns.

Therefore, in order to perform detoxification safely and to make the device itself compact, thermal detoxification devices have been developed that can thermally decompose the gas to be treated by heating it with an electric heater. For example, the thermal detoxification device shown in Patent Document 1 below is known.

However, in the thermal detoxification device of Patent Document 1 below, it is difficult to create the desired high-temperature atmosphere by heating using an electric heater alone, so as shown in Patent Document 2 below, a thermal detoxification device has been developed that creates the desired high-temperature atmosphere by igniting fuel gas with an electric heater (paragraph 0009 of Patent Document 2).

Patent No. 3016690 Patent No. 3866412

As mentioned above, the reality with thermal detoxification equipment is that even if an electric heater is used to solve the concerns about the size and safety of combustion-type equipment, the electric heater alone cannot provide the heating required for thermal detoxification, so in the end heating by combustion is used.

Therefore, there is a strong demand for a device that can effectively perform detoxification treatment using only heating by an electric heater without involving combustion, i.e. a thermal detoxification device that can be made compact and does not require consideration of the dangers of combustion.

The present invention provides a thermal detoxification device that realizes effective detoxification treatment using an electric heater alone, by utilizing a heater structure characterized by the arrangement of the electric heater and the gas flow path, and a thermal detoxification method using the device.

In brief, the thermal detoxification device according to the present invention is a thermal detoxification device that includes a cylindrical chamber and a heater section that fits into the inner circumferential surface of the chamber, and that heats and detoxifies the gas to be treated by passing it directly through the heater section in an upward vertical direction. The heater section is made by forming a planar or linear electric heater into a spiral shape in a planar view, and has a gas passage that is spiral in a planar view consisting of the spacing between adjacent electric heaters, and is provided with a flow straightening section that covers the upper part of the heater section. The flow straightening section fits into the inner circumferential surface of the chamber, and has a discharge hole in the center that allows the treated gas to pass through.

Therefore, the gas to be treated can be effectively heated to the temperature required for pyrolysis and detoxified by the electric heaters arranged in close proximity in a direction perpendicular to the gas flow direction (up and down), eliminating the need for any heating means other than the electric heater. In addition, the powder produced as a by-product of pyrolysis can be trapped in the gas flow path, eliminating the need for cleaning equipment such as a scrubber.

Preferably, the planar electric heater has a large number of gas passage holes penetrating the surface, which allows for more efficient heating and trapping of by-product powder.

In addition, by providing a pressure sensor upstream of the heater section, it is possible to monitor whether the heater section is clogged with powder or other by-products produced by pyrolysis.

Preferably, a preheater section is provided upstream of the start point of the gas flow passage in the heater section, and the preheater section is made of a truncated inverted cone-shaped reflector that covers the lower end of the heater section, thereby making it possible to effectively utilize the thermal energy of the heater section for preheating, and effectively preventing thermal decomposition and the generation of powder by-products.

More preferably, a net made of a metal that functions as a catalyst in the decontamination process can be placed at the lower end opening of the reflector to promote even more efficient decontamination.

The thermal detoxification method according to the present invention is a thermal detoxification method using the thermal detoxification device according to the present invention described above, and by directly passing the gas to be treated upward through the gas flow passage of the heater section and heating it, the gas to be treated is thermally decomposed and the powder produced as a by-product by the thermal decomposition can be trapped, enabling a safe and clean detoxification process.

The thermal detoxification device of the present invention has an arrangement structure in which electric heaters are closely spaced in a direction perpendicular to the gas flow direction, allowing the gas to be treated to be efficiently heated while also providing a gas flow path structure that can trap by-product powder, making it possible to perform thermal detoxification using only the electric heaters while also contributing to the miniaturization and safety of the device.

In addition, the thermal detoxification method of the present invention can perform pyrolysis treatment using only a heater unit consisting of an electric heater without combustion, making it possible to perform safe detoxification treatment. In addition, clean detoxification treatment is possible without using cleaning equipment such as a scrubber.

FIG. 1 is a schematic diagram of a thermal detoxification device using a planar electric heater according to the present invention. 1A is a diagram illustrating a heater section configured with a planar electric heater, (A) being a plan view of the heater section, (B) being a side view of the heater section, and (C) being a perspective view of the heater section. FIG. FIG. 1 is a schematic diagram of a thermal detoxification device using a linear electric heater according to the present invention. 1A is a plan view of the heater part configured with a linear electric heater, FIG. 1B is a side view of the heater part, and FIG. 1C is a perspective view of the heater part. FIG. 2 is a side view showing an example of a heater unit in which a plurality of linear electric heaters are combined.

The optimal embodiment of the thermal detoxification device and the thermal detoxification method using the device according to the present invention will be described with reference to Figures 1 to 5. Note that in each figure, the power sources and electric wires related to the electric heaters 4 and 5 are omitted.

<Basic configuration of thermal detoxification device>
As shown in Figures 1 and 3, the thermal detoxification device 1 of the present invention has a basic structure including a cylindrical chamber 2 and a cylindrical or conical heater section 3 that fits into the inner surface 2a of the chamber 2, and the gas to be treated can be passed directly upward through the heater section 3 to be heated and detoxified.

Therefore, a gas inlet 2b is provided at the lower end of the chamber 2, a gas outlet 2c is provided at the upper end of the chamber 2, and the heater section 3 is fitted to the inner peripheral surface 2a of the cylindrical chamber 2, so that the target gas introduced into the chamber 2 through the gas inlet 2b is not discharged from the gas outlet 2c without passing through the heater section 3.

The chamber 2 is made of metals that do not affect the thermal decontamination process, such as stainless steel (SUS: Steel Use Stainless), heat-resistant steel (SUH: Steel Use Heat Resisting), Inconel (registered trademark), and Hastelloy (registered trademark), and not only can its internal volume be adjusted as appropriate, but the volume of the heater section 3 relative to the internal volume of the chamber 2 can also be adjusted as appropriate. As described below, it is preferable to use an electric heater that uses a resistance heating method for the heater section 3, and it is desirable to place an insulating sheet between the inner surface 2a of the chamber 2 and the outer surface 3a of the heater section 3 to prevent problems such as short circuits and leakage current.

In addition, P in Figures 1 and 3 is a pipe for transporting the gas to be treated and the treated gas for removal treatment, and C is a cooler for cooling the treated gas. The gas to be treated transported from a semiconductor factory or the like to the thermal detoxification device 1 through the pipe P is detoxified by the thermal detoxification device 1 to become treated gas, which is then cooled in the cooler before being transported through the pipe P and released into the atmosphere or the like.

<Heater section configuration>
The heater section 3 is formed by winding a planar electric heater 4 into a spiral shape in plan view and forming it into a cylindrical shape as shown in Figures 1 and 2, or by forming a linear electric heater 5 into a spiral shape in plan view as shown in Figures 3 and 4. As the electric heater, a known electric heater can be used, but in order to form a high-temperature atmosphere required for thermal decomposition of a target gas at, for example, 600°C or higher, or even 1000°C or higher, and in addition to forming it into a spiral shape in plan view, it is preferable to use an electric heater of a resistance heating type, and in particular, it is preferable to use an electric heater that uses a metal such as nichrome or Kanthal (registered trademark) as a heating resistor.

When using a planar electric heater 4, as shown in Figures 1 and 2, it is formed so that it is spirally shaped in plan view and has a cylindrical overall shape, and the spacing between adjacent planar electric heaters 4, i.e., the spacing between adjacent spirals in plan view, is made as narrow as possible, and this spacing is used as a gas flow path 6. Therefore, the heater section 3 is formed by winding the planar electric heaters 4 in a spiral shape while bringing them as close together as possible, and a gas flow path 6 that is as narrow as possible is formed.

In this way, by arranging the planar electric heaters 4 closely together in a direction perpendicular to the gas flow direction (upward in the vertical direction), the gas flow passage 6 is structured to efficiently heat the gas to be treated and trap by-product powder. Note that in the present invention, as long as the gas flow passage 6 can be provided, cases in which the planar electric heaters 4 are in partial contact with each other are not excluded.

In addition, although not specifically shown, it is desirable for the planar electric heater 4 to have a large number of gas passage holes penetrating it. This is because it allows for more efficient heating and makes it possible to trap the powder by-product of pyrolysis. In addition, it is optional to roughen the surface of the planar electric heater 4 to make it easier to collect the by-product powder, depending on the implementation.

Or, when a linear heater 5 is used, it is formed so that it is spiral-shaped in plan view and has a conical overall shape, as shown in Figures 3 and 4, and the adjacent spacing between the linear electric heaters 5, i.e., the adjacent spacing between the spirals in plan view, is made as narrow as possible, and the adjacent spacing is used as a gas flow path 6.

Therefore, when using the linear electric heater 5, as in the case of the planar electric heater 4, the linear electric heaters 5 are arranged closely together in a direction perpendicular to the gas flow direction, so that the gas flow passage 6 can efficiently heat the gas to be treated and trap by-product powder. In addition, in the present invention, as long as the gas flow passage 6 can be provided, cases in which the linear heaters 5 are partially in contact with each other are not excluded. In addition, it is optional to roughen the surface of the linear heater 5 to make it easier to collect the by-product powder depending on the implementation.

When using a linear electric heater 5, as shown in FIG. 5, multiple linear electric heaters 5 formed into a spiral shape in plan view can be stacked to form the heater section 3, thereby realizing more efficient heating and trapping of by-product powder. Note that, although the overall shape of the linear electric heater 5 formed into a spiral shape in plan view is shown as a cone in this embodiment, in the present invention, it is also possible to make it a truncated cone, an inverted cone, or a truncated inverted cone, depending on the implementation.

In the present invention, the gas flow passage 6 in the heater section 3, whether configured as a planar electric heater 4 or a linear electric heater 5, has a lower end portion 6a as a starting point and an upper end portion 6b as a terminal point. As described above, this is because the gas to be treated is brought in through the gas inlet 2b at the lower end of the chamber 2 and comes into contact with the heater section 3 from below. Also, this is because the gas to be treated is heated and expands, moving from the bottom to the top inside the gas flow passage 6.

In addition, in the present invention, as described above, the planar electric heaters 4 or the linear electric heaters 5 are arranged closely together in the direction perpendicular to the gas flow direction, thereby making the gas flow passage 6 of the heater section 3 as narrow as possible, thereby achieving both highly efficient heating and trapping of by-product powder.

Therefore, there is a risk that the trapped by-product powder will clog the gas flow passage 6, but in the present invention, a pressure sensor is provided upstream of the heater section 3 to monitor whether the heater section 3 is clogged. Although not specifically shown, the pressure sensor can be located anywhere upstream of the heater section 3, and may be located inside or outside the chamber 2.

It goes without saying that the heater section 3 is equipped with a circuit to detect problems such as short circuits and leakage currents that may occur when the planar electric heaters 4 or the linear electric heaters 5 are placed in close proximity to each other.

<Configuration of rectifier>
1 and 3, the present invention is configured to provide a rectifier 7 so as to cover the upper part of the heater part 3. The rectifier 7, like the chamber 2, is made of a metal that does not affect the thermal detoxification treatment, such as stainless steel, heat-resistant steel, Inconnel (registered trademark), or Hastelloy (registered trademark).

The flow straightening section 7 has an exhaust hole 7a in the center that allows the treated gas to pass through, and is arranged to encourage the gas to pass through the center (the part along the central axis) of the heater section 3, where the loss of thermal energy is the least, i.e., where the temperature is the highest.

As shown in Figures 1 and 3, the gas to be treated flowing through the gas flow passage 6 of the heater section 3 is guided to the center of the heater section 3 by the flow straightener section 7 as shown by the arrow in the figure, and after the thermal decomposition process, the treated gas is discharged from the exhaust hole 7a. Therefore, the electric heaters 4 and 5 alone can effectively heat the gas to the temperature required for thermal decomposition and perform the detoxification process.

The flow straightening section 7 is preferably shaped to match the shape of the upper part of the heater section 3. As shown in FIG. 1, when the heater section 3 is cylindrical, the flow straightening section 7 is disk-shaped. As shown in FIG. 3, when the heater section 3 is conical, the flow straightening section 7 is conically shaped to match the shape of the heater section 3. This effectively covers the upper part of the heater section 3 and promotes efficient passage of the gas to be treated to the heater section 3.

<Preheater section configuration>
In the present invention, as shown in Figures 1 and 3, a preheater section 8 is preferably provided upstream of the starting point 6a of the gas flow passage 6 in the heater section 3. The preheater section 8 makes it possible to effectively utilize the thermal energy leaked from the heater section 3 for preheating, thereby enabling effective thermal decomposition and suppression of powder by-production.

The preheater section 8 is made of a reflector 9 in the shape of a truncated inverted cone that covers the lower end of the heater section 3. By covering the lower end of the heater section 3 with the upper opening 9b of the reflector 9, the heat energy leaking from the heater section 3 can be reflected and collected for effective use. The reflector 9 is made of a metal such as stainless steel that has good heat reflectivity and does not affect the thermal detoxification process.

More preferably, a net 10 made of a metal that functions as a catalyst in the abatement process can be placed at the lower end opening 9a of the deflector 9 to promote even more efficient abatement. Examples of metals that function as catalysts include platinum for hydrocarbon gases and nickel for ammonia gas.

<Thermal detoxification method>
The thermal abatement method according to the present invention is a thermal abatement method using the thermal abatement device 1 according to the present invention described above, and has the following characteristics.

That is, the gas to be treated is heated by passing it directly upward through the gas flow passage 6, which is made up of closely spaced electric heaters 4 and 5 arranged in a direction perpendicular to the gas flow direction, thereby pyrolyzing the gas to be treated and trapping the powder produced as a by-product of the pyrolysis.

Therefore, the pyrolysis process can be performed without combustion using only the heater section 3 consisting of the planar electric heater 4 or the linear electric heater 5, enabling safe detoxification. In addition, clean detoxification can be performed without using cleaning equipment such as a scrubber.

1...thermal abatement device, 2...chamber, 2a...inner surface, 2b...gas inlet, 2c...gas outlet, 3...heater section, 3a...outer surface, 4...planar electric heater, 5...linear electric heater, 6...gas flow path, 6a...starting point, 6b...ending point, 7...rectifying section, 7a...exhaust hole, 8...preheater section, 9...reflector, 9a...lower end opening, 9b...upper end opening, 10...net, C...cooler, P...pipe.

Claims (6)

A thermal detoxification device that includes a cylindrical chamber and a heater section that fits into the inner circumferential surface of the chamber, and that heats and detoxifies the gas to be treated by passing it directly through the heater section in an upward vertical direction, the heater section being formed into a spiral shape in a plan view, with a gas passageway that is spiral in a plan view consisting of the spacing between adjacent electric heaters, and a straightening section that covers the upper part of the heater section, the straightening section being fitted into the inner circumferential surface of the chamber, and having a discharge hole in the center that allows the treated gas to pass through. The thermal detoxification device according to claim 1, characterized in that the planar electric heater has a large number of gas passage holes passing through it. The thermal detoxification device according to claim 1 or 2, characterized in that a pressure sensor is provided upstream of the heater section. The thermal detoxification device according to any one of claims 1 to 3, characterized in that a preheater section is provided upstream of the start point of the gas flow passage in the heater section, and the preheater section is made of a truncated inverted cone-shaped reflector that covers the lower end of the heater section. The thermal detoxification device according to claim 4, characterized in that a net made of a metal that functions as a catalyst in the detoxification process is placed at the lower end opening of the reflector. A thermal detoxification method using the thermal detoxification device according to any one of claims 1 to 5, characterized in that the gas to be treated is directly passed upward through the gas flow passage of the heater section to heat the gas, thereby pyrolyzing the gas to be treated and trapping the powder produced as a by-product of the pyrolysis.

Images