JP2012106877A - Gas discharge apparatus of reaction chamber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas discharge apparatus capable of suppressing generation of a chemical synthetic composition containing a harmful substance such as a tar-like material in an exhaust part at low cost.SOLUTION: A gas discharge apparatus discharges a gas in a heating chamber 13 for forming a carbon nanotube by a vacuum pump 36. A cylindrical body 31 having a decompression chamber which is decompressed at a lower pressure than the heating chamber 13 is disposed in an exhaust gas route between the heating chamber 13 and the vacuum pump 36. At the same time, a cooler 34 is disposed at its downstream side.

Description

  The present invention relates to a gas discharge device for a reaction chamber.

  Exhaust gas is released in devices that use chemical reactions of high-temperature gases such as CVD equipment, waste incinerators, and internal combustion engines. During the exhaust process, chemically synthesized substances containing harmful substances such as tar, dioxin, and nitrogen oxides appear.

  For example, as a method for removing harmful substances in exhaust gas, a method for decomposing harmful substances with a catalyst, a method for removing harmful substances with a filter, or a temperature at which harmful substances are produced by spraying water on the exhaust gas and quenching it. There is a method of passing through an area in a short time.

  As a method of passing through the temperature region in a short time, specifically, when producing carbon nanostructures such as carbon nanotubes, the production temperature region of the tar-like substance (300 to 600 ° C.) is not entered. A technology is disclosed in which a raw material gas (acetylene) preheated to 300 ° C. or lower is sent all at once to a reaction chamber of 600 ° C. or higher (see, for example, Patent Document 1).

Japanese Patent No. 3962773

  By the way, when using a catalyst, there is a problem that the catalyst is a precious metal and expensive and has limited resources, and when using a filter, it is necessary to reprocess harmful substances adhering to the filter and clean it. There is a problem that replacement work is required.

Furthermore, Patent Document 1 described above discloses a method for suppressing the generation of tar-like substances in the reaction chamber, but there is no mention of suppressing the generation of tar-like substances in the exhaust part.
Therefore, if it is attempted to suppress the generation of tar-like substances in the exhaust part, it is necessary to control the temperature in the exhaust part, which causes a problem that the cost of the apparatus is high.

  Accordingly, an object of the present invention is to provide a gas discharge device that can suppress the production of a chemically synthesized substance containing a harmful substance such as a tar-like substance at a low cost in an exhaust part.

In order to solve the above problems, a gas discharge device for a reaction chamber according to the present invention is a device for discharging gas in a reaction chamber with a vacuum pump,
In the exhaust gas path between the reaction chamber and the vacuum pump, a decompression section that is lower than the pressure in the reaction chamber is disposed,
In the gas discharge device, the pressure in the decompression part is lowered by providing an orifice in the gas discharge part of the reaction chamber,
Alternatively, in the gas discharge device, a decompression chamber is provided in the decompression unit, and the volume of the decompression chamber is set to be twice or more the volume of the reaction chamber.

  Furthermore, in the gas exhaust apparatus, the reaction chamber is a heating chamber for thermal chemical vapor deposition in a carbon nanotube formation facility.

  According to the above configuration, since the pressure reducing unit that is lower in pressure than the pressure in the reaction chamber is disposed in the exhaust gas path between the reaction chamber and the vacuum pump, the discharged gas is discharged from the reaction chamber in a leaner pressure reducing unit. Therefore, collision between molecules floating in the gas is reduced, and polymerization is suppressed. For example, when a hydrocarbon gas is contained in the gas, carbon molecules are prevented from being polymerized, and thus the formation of tar-like substances is suppressed. That is, it is possible to suppress the production of a chemically synthesized substance containing a harmful substance such as a tar-like substance in the exhaust part with an inexpensive configuration.

It is a typical perspective view which shows schematic structure of the thermal CVD apparatus which concerns on Example 1 of this invention. It is a typical perspective view which shows the principal part of the thermal CVD apparatus which concerns on the same Example 1. FIG. It is a typical perspective view which shows the principal part of the thermal CVD apparatus which concerns on Example 2 of this invention.

Hereinafter, a gas discharge device for a reaction chamber according to an embodiment of the present invention will be described.
The gas exhaust apparatus is schematically described as an apparatus for exhausting a gas in a reaction chamber with a vacuum pump, which is lower than a pressure in the reaction chamber in an exhaust gas path between the reaction chamber and the vacuum pump. The pressure reducing part is arranged, and the pressure in the pressure reducing part is lowered by providing an orifice in the gas discharge part of the reaction chamber, or the pressure reducing part is provided with a pressure reducing chamber. The chamber volume is at least twice that of the reaction chamber. Further, the reaction chamber is a heating chamber (also referred to as a carbon reaction chamber) in which a thermal CVD method is performed in a carbon nanotube formation facility.

  Hereinafter, Embodiment 1 and Embodiment 2 of the gas discharge device will be described with reference to the drawings.

The reaction chamber gas discharging apparatus according to the first embodiment is provided in a carbon nanotube forming facility, that is, a thermal CVD apparatus for forming carbon nanotubes.
Here, as a substrate for forming carbon nanotubes, a stainless steel sheet, that is, a stainless steel sheet (an example of a thin sheet material, for example, a foil material having a thickness of about 20 to 300 μm is used, which is referred to as a stainless steel foil. In the case of a plate material, a thickness of about 300 μm to several mm is used, and the stainless steel plate has a predetermined width, that is, a belt shape. A case of using the above will be described. Therefore, this stainless steel plate is wound around a roll, and when forming carbon nanotubes, the carbon nanotubes are continuously formed by being pulled out from this roll. It is intended to be wound on a roll. That is, a stainless steel plate is pulled out from one unwinding roll, carbon nanotubes are formed on the surface of the pulled stainless steel plate, and then the stainless steel plate on which the carbon nanotubes are formed is wound on the other winding roll. ing.

Hereinafter, a thermal CVD apparatus for forming carbon nanotubes on the surface of the above-described strip-shaped stainless steel plate (hereinafter, mainly referred to as a substrate) will be described.
As shown in FIG. 1, the thermal CVD apparatus includes a heating furnace 1 in which an elongated processing space for forming carbon nanotubes is provided in a furnace body 2. The processing space provided in is partitioned (divided) into a plurality of, for example, five rooms by partition walls 3 arranged at predetermined intervals.

  That is, in the furnace body 2, a stainless steel plate, that is, a substrate supply chamber 11 in which an unwinding roll 16 on which the substrate K is wound is disposed, and the substrate K drawn from the unwinding roll 16 is guided to the surface thereof. A pretreatment chamber 12 for performing pretreatment, and a heating chamber (corresponding to the reaction chamber in the reaction vessel) for introducing the substrate K pretreated in the pretreatment chamber 12 and forming carbon nanotubes on the surface thereof. ) 13 and a post-processing chamber 14 for guiding the substrate K on which the carbon nanotubes are formed in the heating chamber 13 and performing post-processing, and for winding the substrate K post-processed in the post-processing chamber 14 A substrate recovery chamber (also referred to as a product recovery chamber) 15 in which a winding roll 17 is disposed is provided. The rotational axes of the rolls 16 and 17 are horizontal, so that the substrate K drawn (guided) into the heating chamber 13 moves in a horizontal plane, and carbon nanotubes are placed on the surface of the substrate K. To be formed.

  In the pretreatment chamber 12, the surface of the substrate K, particularly the surface that forms the carbon nanotubes (the carbon nanotube generation surface, which will be described later, here is the bottom surface), the passivation film coating, and the carbon nanotube generation The catalyst fine particles, specifically, iron fine particles (metal fine particles) are applied. For cleaning, alkali cleaning or UV ozone cleaning is used. In addition, as a method for applying the passive film, a roll coater or LPD is used. As a method for applying the catalyst fine particles, sputtering, vacuum deposition, roll coater or the like is used.

In the post-processing chamber 14, the cooling of the substrate K and the inspection of the carbon nanotubes formed on the surface, that is, the lower surface of the substrate K are performed.
In the substrate recovery chamber 15, a protective film is attached to the upper surface (back surface) of the substrate K, and the substrate K, which is a stainless steel plate to which the protective film is attached, is taken up by the take-up roll 17. The reason why the protective film is attached to the upper surface of the substrate K is to protect the carbon nanotubes formed on the substrate K wound around the outer side when the substrate K is wound up.

  As described above, five chambers are formed in the furnace body 2 by the partition walls 3. Naturally, each partition wall 3 has a communication opening (also referred to as a slit) through which the substrate K can pass. 3a is formed.

  Incidentally, in the heating chamber 13, carbon nanotubes are formed (generated) by a thermal CVD method (thermal chemical vapor deposition method). Of course, the inside is given a predetermined degree of vacuum by a gas exhaust device (described later). (Negative pressure state) is maintained, and a carbon nanotube production gas, that is, a raw material gas (for example, a lower hydrocarbon gas such as acetylene, methane, or butane is used) G is supplied. Is considered not to leak into the adjacent room. For example, in the heating chamber 13, the raw material gas G is supplied from the lower side together with the inert gas N such as helium gas and discharged (extracted) from the upper side. In addition to the heating chamber 13, that is, the substrate supply chamber 11, the pretreatment chamber 12, the posttreatment chamber 14 and the product recovery chamber 15, an inert gas N such as helium gas is supplied from below and discharged from above. Thus, unnecessary gas is prevented from entering. Note that the front and rear walls of the heating chamber 13 are a pair of upper and lower surfaces in which a stainless steel plate as a substrate is sandwiched from above and below in order to hermetically cut off the heating chamber 13 and the pretreatment chamber 12 and the heating chamber 13 and the posttreatment chamber 14. Gate valves 18 and 19 each comprising a knife-type plate body are provided.

Here, the configuration of the heating chamber 13 will be described in detail together with the heating device and the gas discharge device.
As shown in FIGS. 1 and 2, a gas supply port 5 for supplying a raw material gas G containing carbon is formed at the center position of the bottom wall portion 2 a of the heating chamber 13. A heating device 21 including a plurality of columnar (or rod-like) heating elements 22 for heating the inside of the heating chamber 13 is provided above the intermediate portion (above the substrate), and further, the upper wall portion 2b. Is connected to a gas discharge device 23 for making the inside of the heating chamber 13 have a predetermined degree of vacuum.

  Further, between the bottom wall portion 2a of the heating chamber 13 and the substrate K, there is provided a gas guiding duct body 24 having a hopper shape (reverse trapezoidal shape) as a side view for guiding the source gas G to the substrate K. Yes. Although not shown, a baffle plate for diffusing the raw material gas may be disposed in the gas guiding duct body 24, and the raw material gas is rectified at the upper end opening of the gas guiding duct body 24. A current plate such as a punching metal may be arranged.

As the heating element 22, a non-metallic resistance heating element is used. Specifically, silicon carbide, molybdenum silicide, lanthanum chromite, zirconia, graphite, or the like is used.
The gas discharge device 23 is inserted into the upper wall portion 2b in the vertical direction, and the lower end wall 31a is formed with an orifice 32 and has a pressure reducing chamber (an example of a pressure reducing portion, which can also be called a pressure reducing container). 31 and a cooler having a cooling chamber (for example, in the cooling chamber) connected to the upper end wall 31b of the cylindrical body 31 through the communication pipe 33 and cooling the gas derived from the cylindrical body 31, that is, the exhaust gas. (With a radiator for heat exchange) 34, a vacuum pump 36 for discharging (suctioning) the exhaust gas cooled by the cooler 34 through a discharge pipe 35, and bypassing the cylindrical body 31 A bypass pipe 37 that is a bypass path for directly guiding the gas in the heating chamber 13 to the discharge pipe 35, and a switching valve (for example, three-way switching) that is provided in the middle of the discharge pipe 35 and switches to the bypass pipe 37 side. And a is) 38. which employed. Since the bypass pipe 37 is used when evacuating the heating chamber 13 in a short time, the diameter of the bypass pipe 37 is larger than the hole diameter of the orifice 32.

The diameter of the orifice 32, and the flow rate Q of the exhaust gas, the pressure P ₁ in the heating chamber 13, the pressure P ₂ of the cylindrical body _31, i.e. the pressure in the vacuum chamber, on the basis of the following formula (1) It is determined.

Q = C (P ₁ −P ₂ ) (1)
However, in the equation (1), C is the conductance of the orifice and includes a parameter relating to the shape, that is, a hole diameter. Therefore, the hole diameter of the orifice can be obtained from (1). Although the orifice has been described as a circular shape, it may be anything as long as a predetermined pressure difference can be obtained. For example, it may be an elongated rectangular hole, a gap, or a filter made of a porous material.

  Further, the outer portion of the heating chamber 13 of the cylindrical body 31 is covered with a heat insulating material 39 to keep warm, and of course, the inner wall surface of the furnace body 2 forming the heating chamber 13 has a predetermined thickness. The heat insulating material 4 is affixed.

Here, the process in the pretreatment chamber 12 will be described.
In the pretreatment chamber 12, after the substrate K is washed, a passive film such as silica or alumina is applied, and further, for example, catalyst fine particles of metal such as iron (Fe) are applied on the upper surface of the passive film. . Of course, although not shown, in the pretreatment chamber 12, there are provided cleaning means for the substrate K, means for applying a passive film, and means for applying catalyst fine particles of metal such as iron (Fe).

  By the way, as described above, a thin stainless steel plate (also a stainless steel foil) rolled into a coil shape and wound into a coil shape is used as the substrate K, and such a substrate K is used. Since there is a tensile residual stress in the coil winding direction, the substrate K warps due to the release of the residual stress during atomization of the catalyst and thermal CVD. In order to prevent such warpage, a mechanism for applying tension in the coil winding direction, specifically, tension is generated between the unwinding roll and the winding roll (for example, rotation of both rolls). The tension is generated by making the torque different, specifically, the one motor may be pulled and the other motor may exhibit the brake function.) The substrate K may be pulled. Further, a weight may be provided on the winding roll side and pulled.

When the thermal CVD method is performed in the heating furnace 1, the inside of the heating chamber 13 is set to a predetermined pressure.
This pressure value is maintained in the range of several thousand Pa to atmospheric pressure. For example, it is maintained at 5000 Pa to 20000 Pa. In this apparatus, since the exhaust is performed under a reduced pressure, the generation of tar in the exhaust part is suppressed, so that the CVD can be performed with a high pressure in the heating chamber 13 (furnace body). Moreover, the inside of the heating chamber 13 in the heating furnace 1 is kept at a high temperature, and no substances that adversely affect CVD other than soot are attached. In addition, firewood is periodically baked and cleaned.

  Although the processing chambers other than the heating chamber 13, that is, the substrate supply chamber 11, the preprocessing chamber 12, the postprocessing chamber 14, and the product recovery chamber 15 have not been described in detail, these chambers 11, 12, 14 are not described. , 15 are also in a state in which the pressure is controlled, and in order to prevent gas such as air that adversely affects the formation of carbon nanotubes from flowing into the heating chamber 13, as shown in FIG. The wall 2a is provided with a gas supply port 5 'for supplying an inert gas such as helium gas, and the upper wall 2b is provided with a gas discharge port 6 so as to discharge the inert gas. Yes. The pressure in these other processing chambers is controlled so that the pressure is the same as that in the heating chamber 13 by an automatic pressure control valve (not shown) arranged between the vacuum pumps. Note that an orifice 32 provided in the cylindrical body 31 corresponds to the gas discharge port in the heating chamber 13. That is, the orifice 32 is disposed on the start end side of the exhaust gas path. Moreover, the position of the orifice 32 should just be a high temperature part from the production | generation temperature of tar.

The communication pipe 33 and the discharge pipe 35 are for discharging gas and constitute a so-called exhaust gas path.
FIG. 1 shows a schematic configuration of a thermal CVD apparatus, and the side wall portion on the near side and the heat insulating material 4 are omitted so that the inside thereof can be understood.

Next, a method for forming carbon nanotubes using the thermal CVD apparatus will be described.
First, the substrate K is pulled out from the unwinding roll 16, and the communication openings 3 a of the partition walls 3 in the pretreatment chamber 12, the heating chamber 13, and the posttreatment chamber 14 are inserted, and the leading ends thereof are wound around the winding roll 17. Make it. At this time, a tension is applied to the substrate K so as to form a straight horizontal plane.

  Then, after the substrate K is cleaned in the pretreatment chamber 12, a passive film is applied over the entire upper and lower surfaces, and iron fine particles are applied (attached) to the surface of the passive film. The catalyst fine particles are applied to the carbon nanotube formation surface (generation surface).

  After this pretreatment, the substrate K is taken up by the take-up roll 17 by a predetermined length, that is, by a length for forming the carbon nanotube. Therefore, the portion where the pretreatment is performed in the pretreatment chamber 12 is sequentially moved above the gas guiding duct body 24 in the heating chamber 13.

  Then, the temperature of the substrate K is heated to a predetermined temperature, for example, 700 to 800 ° C. by the heating device 21, that is, the heating element 22, and the outer wall temperature of the heating chamber 13 is 80 ° C. or less (preferably 50 ° C.) by the heat insulating material. And so on.

When the above temperature is reached, acetylene gas (C ₂ H ₂ ) is supplied as a source gas from the gas supply port 5 to cause a predetermined reaction to generate (grow) carbon nanotubes on the lower surface of the substrate K.

  Then, when a predetermined time passes and a carbon nanotube having a predetermined height is obtained, the substrate K is similarly moved by a predetermined length, and the substrate K on which the carbon nanotube is formed is moved into the post-processing chamber 14.

In the post-processing chamber 14, the substrate K is cooled and inspected.
When this post-processing is completed, the substrate K is moved into the product recovery chamber 15, and a protective film is attached to the upper surface of the substrate K, and the substrate K is wound around the winding roll 17. That is, the substrate K on which the carbon nanotubes are formed is collected as a product. When all the substrates K on which the carbon nanotubes are formed are taken up by the take-up roll 17, they are taken out to the outside.

Here, the operation of the gas discharge device 23 will be described in detail.
The gas in the heating chamber 13 is discharged to the outside through the cylindrical body 31 and the cooler 34 by the operation of the vacuum pump 36, and the inside of the heating chamber 13 is maintained at a predetermined degree of vacuum.

  Incidentally, the lower end wall 31a of the cylindrical body 31 is provided with an orifice 32, and the discharged gas (exhaust gas) is drawn into the cylindrical body 31 through the orifice 32. The degree of vacuum is lower than the degree of vacuum in the heating chamber 13 (for example, 1000 Pa or less). That is, the inside of the cylindrical body 31 is more dilute than the inside of the heating chamber 13, and passes through the orifice 32 and enters the dilute space, so that the foreign substance, that is, hydrocarbon molecules floating in the gas. The collision between each other is reduced, and the polymerization or polymerization reaction of hydrocarbon molecules is suppressed, and thus the generation of tar is suppressed. Thereafter, the gas enters the cooler 34 where it is cooled and discharged to the outside. Since the inside of the cooler 34 is also in a reduced pressure state, it passes through a temperature region where tar is generated in the cooling process. However, like the inside of the cylindrical body 31, the number of collisions between reacting molecules is very small. Is not formed and is exhausted in a relatively low molecular state. Depending on the amount of tar that can be tolerated, the decompression chamber and the cooling chamber may not be separated, and the decompressed gas may be applied to the pipe for natural cooling.

  As described above, when the gas in the heating chamber 13 is discharged by the vacuum pump 36, the gas is introduced into the cylindrical body 31 in a more dilute state through the orifice 32. It is suppressed, that is, the production of tar-like substances in the exhaust part can be suppressed with an inexpensive configuration.

  In other words, even when the thermal CVD reaction is performed at a high pressure, that is, when a large amount of raw material gas is supplied, the generation of tar is suppressed, and therefore, the supply of a large amount of raw material gas (high productivity) and the suppression of tar generation Can be made compatible.

Furthermore, since tar generation is suppressed, the lifetime and maintenance period of the vacuum pump can be extended, and a filter and the like can be omitted.
In addition, the cylindrical body 31 which is a decompression chamber is arranged to penetrate the upper wall portion 2b of the heating chamber 13, that is, to penetrate the high temperature portion and the low temperature portion, and heat is transmitted on the high temperature portion side. The structure is easy, and the low temperature part side is covered with a heat insulating material 39 so that the exhaust gas inside the cylindrical body 31 is warmed. That is, even at the boundary where the exhaust gas is depressurized, the temperature is higher than the temperature at which tar is generated.

  In addition, when the exhaust gas falls to the tar generation temperature at the decompression boundary, the tar is thermally decomposed by adopting a structure in which the orifice 32 of the cylindrical body 31 that is the decompression chamber can be sufficiently heated by the heater. May be.

  Furthermore, there is no problem of tar generation in the heating chamber 13 and a large gas flow rate is required. However, when work cannot be efficiently performed by the orifice 32, the switching valve 38 is switched to the bypass pipe 37 side, and the gas is flowed at a large flow rate. The heating chamber 13 can be evacuated in a short time.

In short, high-pressure CVD is possible without generating tar or the like by the orifice, and the quality and productivity of the product are improved.
By the way, in this Example 1, although the cooling chamber was arrange | positioned in the downstream of a decompression chamber, if gas is cooled in the pressure reduction state by piping itself, tar can be suppressed. That is, the piping itself can be used as a cooling chamber.

Next, a gas discharge device for a reaction chamber according to Embodiment 2 of the present invention will be described with reference to FIG.
As a decompression chamber in the gas discharge apparatus in the first embodiment described above, a cylindrical body (decompression section) is provided through the upper wall of the heating chamber. In this second embodiment, the exhaust connected to the heating chamber is provided. It is provided in the middle of the pipe. In other words, a decompression container (decompression unit) as a decompression chamber is provided separately from the heating chamber. In addition, a decompression chamber is provided in the decompression section, and the volume of the decompression chamber is at least twice that of the heating chamber (reaction chamber).

  In the second embodiment, the parts other than the gas discharge device have the same configuration as in the first embodiment. Therefore, the same components as those in the first embodiment are denoted by the same member numbers, and the description thereof is omitted. Omitted.

  That is, as shown in FIG. 3, the gas discharge device 41 according to the second embodiment is connected to the upper wall portion 2b of the heating chamber 13 through the communication pipe 43 and has a decompression container 42 having a decompression chamber, A discharge pipe 45 having one end connected to the decompression container 42 and a vacuum pump 44 provided on the other end, and a cooling chamber arranged in order from the decompression container 42 in the middle of the discharge pipe 45. A cooler 46 (for example, a heat exchange radiator disposed in the cooling chamber) 46 and an automatic pressure control valve 47. Further, the volume of the decompression chamber of the decompression container 42 is set to be twice or more than the volume of the heating chamber 13. The communication pipe 43 is connected to a bypass pipe 48 provided with a hydrogen lead-out member 49 having a hydrogen permeable membrane in the middle. The communication pipe 43 and the bypass pipe 48 are respectively provided with a first exhaust valve (open / close valve) 51 and a second exhaust valve (open / close valve) 52 for selectively guiding the gas discharged from the heating chamber 13. It has been. Note that the first exhaust valve 51 and the hydrogen outlet member 49 are covered with a heat insulating material 50. Similarly to the first embodiment, the communication pipe 43 and the exhaust pipe 45 are for exhausting gas, and constitute a so-called exhaust gas path.

Therefore, in the above configuration, when the gas in the heating chamber 13 is discharged, the first exhaust valve 51 may be opened while the vacuum pump 44 is driven.
Then, the gas in the heating chamber 13 enters the decompression vessel 42 through the communication pipe 43, where the gas, that is, the exhaust gas is diluted to become a decompressed state, and the generation of tar is suppressed. The exhaust gas entering the decompression vessel 42 is cooled by the cooler 46 and then discharged to the outside through the discharge pipe 45.

Other operations are the same as those described in the first embodiment, but the thermal CVD process will be briefly described.
The gas supply port 5 is provided with a first supply valve (open / close valve) 66 and a raw material gas supply pipe 61 for supplying a raw material gas such as hydrocarbon and a second supply valve (open / close valve) 67. A hydrogen gas supply pipe 62 for supplying hydrogen gas (H2) and a third supply valve (open / close valve) 68 are provided, and an inert gas supply pipe 63 for supplying an inert gas such as helium (He) is connected. .

  That is, when performing thermal CVD, the first exhaust valve 51 is opened, the second supply valve 67 and the third supply valve 68 are opened, and hydrogen gas and helium gas are supplied for a predetermined time to adhere to the surface of the substrate K. Make iron fine particles.

  Next, the 2nd supply valve 67 and the 3rd supply valve 68 are closed, and supply of hydrogen gas and helium gas is stopped. Note that the first exhaust valve 51 remains open, and the gas in the heating chamber 13 is exhausted to a high vacuum. Of course, the gate valves 18 and 19 are closed before and after the heating chamber 13 to maintain the degree of vacuum.

Next, the first exhaust valve 51 is closed and the first supply valve 66 is opened to supply a necessary amount of hydrocarbon gas, specifically acetylene gas, as a raw material gas.
Next, the supply of the source gas is stopped by closing the first supply valve 66, and thermal chemical vapor deposition is performed for a predetermined time at a pressure determined by the amount of the source gas. At this time, the second exhaust valve 52 is opened, the exhaust gas is guided to the hydrogen outlet member 49, and only the hydrogen gas generated by vapor deposition is discharged. Thereby, the fall of the decomposition efficiency of acetylene gas by the increase in hydrogen is prevented.

  Finally, after the second exhaust valve 52 is closed, the first exhaust valve 51 is opened, and the gas remaining in the heating chamber 13 is discharged. When the first exhaust valve 51 is opened, the decompression container 42 is connected, so the side closer to the outlet than the first exhaust valve 51 is the decompression container 42, that is, the volume of the decompression chamber, the exhaust amount of the vacuum pump 44, and The low pressure determined by the pressure loss due to the first exhaust valve 51 is maintained. By maintaining this low pressure, that is, the gas is depressurized and the generation of tar is suppressed. Of course, the volume of the decompression vessel (decompression chamber) 42 is designed so that the pressure on the exhaust side is lower than the pressure at which tar is generated by recombining the raw material gas decomposed.

The decompressed exhaust gas is cooled by a cooler 46 as necessary, and is discharged by a vacuum pump 44 via an automatic pressure control valve 47.
The reason why the first exhaust valve 51 and the hydrogen outlet member 49 are covered with the heat insulating material 50 is to prevent tar and the like from adhering to the furnace body side of these devices by keeping warm. .

As described above, the effect of being able to suppress the generation of tar-like substances in the exhaust part with an inexpensive configuration is the same as that of the first embodiment.
Further, since the decompression container 42 is disposed, the vacuum pump 44 having a relatively low exhaust capacity can be used. That is, since the volume of the decompression container (decompression chamber) 42 is twice the volume of the heating chamber 13, the exhaust side pressure is 1/3 or less of the CVD pressure in a steady state.

  By the way, in each of the embodiments described above, the case where the present invention is applied to a thermal CVD apparatus as a reaction furnace in a carbon nanotube production facility has been described. The present invention can also be applied to the exhaust device of the high temperature gas generator.

  For example, when applied to a garbage incinerator, it can prevent the generation of dioxins and the like, and when applied to a chemical reaction furnace such as a plant, it can suppress the generation of polymer, When applied to the exhaust system of an engine, it is possible to reduce harmful substances in the exhaust gas and omit the catalyst filter.

DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Furnace main body 13 Heating chamber 21 Heating apparatus 23 Gas discharge apparatus 31 Cylindrical body 32 Orifice 33 Communication pipe 34 Cooler 35 Discharge pipe 36 Vacuum pump 37 Bypass pipe 41 Gas discharge apparatus 42 Decompression container 43 Communication pipe 44 Vacuum Pump 45 Drain pipe 46 Cooler 48 Bypass pipe

Claims (4)

An apparatus for discharging the gas in the reaction chamber with a vacuum pump,
A gas discharge device for a reaction chamber, characterized in that a pressure reducing unit having a pressure lower than the pressure in the reaction chamber is disposed in an exhaust gas path between the reaction chamber and a vacuum pump.   The reaction chamber gas discharge device according to claim 1, wherein the pressure in the decompression section is lowered by providing an orifice in the gas discharge section of the reaction chamber.   2. The gas discharge device for a reaction chamber according to claim 1, wherein a decompression chamber is provided in the decompression section, and the volume of the decompression chamber is set to be twice or more the volume of the reaction chamber.   The reaction chamber gas discharge device according to any one of claims 1 to 3, wherein the reaction chamber is a heating chamber for thermal chemical vapor deposition in a carbon nanotube formation facility.

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