JP7356297B2 - Nitriding reactor - Google Patents

Description

The present invention relates to a nitriding reactor that is applied to nitriding reactions at high temperatures.

Various nitrides, such as aluminum nitride (AlN) and boron nitride (BN), which have excellent heat resistance and properties such as thermal conductivity and electrical insulation, are produced by adding nitrogen to the raw material powder of various metals or metal compounds. It is produced by contacting and reacting at high temperatures. In addition, silicon nitride (Si ₃ N ₄ ), which has excellent mechanical properties such as hardness, and gallium nitride (GaN) and indium nitride (InN), which have semiconducting properties, are similarly produced by nitriding reactions at high temperatures. .

A high-temperature reactor that can be applied to the high-temperature nitriding reaction described above consists of box-shaped containers containing raw materials (hereinafter also referred to as setters) stacked in multiple stages inside a furnace surrounded by heat insulating material. Batch type furnaces are known in which a heater is arranged around the reaction vessel (for example, see Patent Documents 1 to 3).
Such a batch-type high-temperature reactor has the advantage that a large amount of raw material can be subjected to a nitriding reaction at one time because box-shaped containers containing raw materials are loaded in multiple stages. Moreover, compared to continuous type high-temperature reactors, batch-type high-temperature reactors have a great advantage over continuous-type high-temperature reactors in that the operating conditions can be adjusted for each production batch, and they can produce a wide variety of products.

By the way, in the batch-type high-temperature reactor having the above structure, the gas to be reacted with the raw materials and the atmospheric gas are supplied from the periphery of the box-shaped container, or a gas supply pipe is passed through the center of the box-shaped container. Although means such as supplying gas from the center of the container have been adopted, there are problems such as it takes a long time to complete the reaction or it is difficult to carry out the reaction uniformly. Another problem is that the heater placed in the furnace and the surrounding heat insulating material deteriorate in a short period of time due to gases produced as by-products during the reaction. In particular, when performing a reductive nitriding reaction using a metal oxide as a raw material using a reducing agent such as carbon powder, volatile matter of the metal oxide and oxidizing gases such as carbon dioxide are produced as by-products. Deterioration of heaters, insulation materials, etc. is noticeable.

Japanese Unexamined Patent Publication No. 61-282790 Japanese Patent Application Laid-Open No. 61-282785 Japanese Patent Application Publication No. 4-273988

Therefore, an object of the present invention is to provide a batch-type nitriding reactor that can complete the nitriding reaction uniformly in a short time and that can effectively suppress deterioration of the heater and the heat insulating material due to by-product gas. It is in.

According to the present invention, in a nitriding reactor for performing a nitriding reaction,
The nitriding reactor has an adiabatic casing,
The insulating casing includes a reaction chamber surrounded by a shield wall held by a bottom plate with an exhaust port, and a heater disposed outside the reaction chamber.
In the reaction chamber, trays are stacked on the bottom plate in multiple stages, each having an opening in the center, containing a reaction material to be subjected to a nitriding reaction, and having a notch formed in a side wall. and a nitrogen gas supply pipe extending through the opening of the tray;
A nitriding reaction is performed by bringing the nitrogen gas supplied from the nitrogen gas supply pipe into contact with the reaction raw material contained in the tray, and unreacted nitrogen gas and by-product gas are formed on the side wall of the tray. The nitriding reaction has a structure in which the nitriding reaction is discharged through the notch in the tray, through the gap formed between the peripheral edge of the tray and the shield wall, and from the exhaust port in the bottom plate. A furnace is provided.

In the nitriding reactor of the present invention, the following aspects are suitably applied.
(1) A preheating chamber is provided in the upper part of the reaction chamber, and nitrogen gas heated in the preheating chamber is supplied through the nitrogen gas supply pipe into a tray disposed within the reaction chamber.
(2) A mixed powder containing oxygen-containing aluminum powder and carbon powder is used as the reaction raw material.
(3) A mixed powder containing boron oxide powder, carbon powder, and an auxiliary agent is used as the reaction raw material.
(4) A mold release layer made of a plate-shaped molded nitride or powder is laid inside the tray, and the reaction raw material is arranged in a layer on the mold release layer.
(5) Heating is performed by the heater so that the temperature inside the reaction chamber is in the range of 1200 to 2200°C.
(6) The tray has a circular planar shape.

In the nitriding reactor of the present invention, nitrogen gas is supplied from the center of each tray containing reaction materials to be reacted with nitrogen, and unreacted nitrogen gas and by-product gas are removed from the cutters formed in the trays. The structure is such that the liquid is discharged to the outside of the tray (the gap formed between the peripheral edge of the tray and the shield wall) through the notch. That is, the gas produced as a by-product during the nitriding reaction is quickly released to the outside without remaining on the reaction raw material contained in the tray. Therefore, the nitriding reaction is not inhibited by the by-produced gas, and the nitrogen gas can be quickly brought into contact with every corner of the reaction raw materials contained in the tray. As a result, the nitriding reaction can proceed sufficiently in a short time, and moreover, the nitriding reaction can proceed uniformly.

Further, in the present invention, the reaction chamber is separated from the heater and the heat insulating casing by a shield wall. That is, the structure is such that by-produced gas and the like do not come into contact with the heater and the heat insulating casing, so deterioration of the heater and the heat insulating casing is effectively suppressed, and the life of the device is extremely long.
In particular, in the furnace structure of the present invention, since the gas flow is from the center of the tray to the periphery, it is possible to supply nitrogen gas with extremely few impurities to the raw material layer, making the nitriding reaction smoother. It is ideal in that it can be carried out by

FIG. 1 is a schematic side sectional view of the nitriding reactor of the present invention. 2 is a cross-sectional view taken along line AA in the nitriding reactor shown in FIG. 1. FIG. 2 is a schematic perspective view showing the form of a tray in which reaction raw materials are accommodated in the nitriding reactor of FIG. 1. FIG. FIG. 3 is a diagram showing the state of reaction raw materials accommodated in a tray. 2 is a schematic diagram showing a flow path of nitrogen gas in the nitriding reactor of FIG. 1. FIG. FIG. 2 is a plan view showing the form of a preheating plate arranged in a preheating chamber in the nitriding reactor of FIG. 1; FIG. 2 is a schematic side sectional view showing a preferred example of a configuration in which reactive raw materials are accommodated on a tray when boron nitride is manufactured using the nitriding reactor of the present invention.

Referring to FIGS. 1 and 2, the nitriding reactor of the present invention has a basic structure in which a heater 3 and a reaction chamber 5 are provided inside an adiabatic casing 1.

The heat insulating casing 1 is formed into a cylindrical shape using a highly heat insulating material, but is usually made of carbon because it has excellent heat resistance, and is formed by stacking carbon fiber blocks, for example. Ru. The carbon material used for the heat insulating casing is preferably a molded body of fibrous carbon in order to improve the heat insulating performance. Further, for the purpose of improving durability, it is also possible to affix a C/C composite material sheet or the like to the inner surface of the furnace.
The fibrous carbon molded body is manufactured by laminating carbon fibers or impregnating them with resin. Molding is done by carbonizing and graphitizing resin that is easily carbonized and impregnated with resin.

The heater 3 is of a type that heats by resistance heating, and in the nitriding reaction, it is necessary to heat the reaction chamber 5 to a high temperature, so a heater made of carbon, preferably graphite, is used. Ru. For example, as shown in FIG. 2, they are symmetrically arranged at four locations in the casing 1 so as to surround the reaction chamber 5.

As shown in FIG. 1, this heater 3 is held in a holder 9 attached to the tip of a support rod 7 extending through the heat insulating casing 1, and is attached to the reaction chamber 5. The length should be such that it extends around the entire height of the area. Therefore, when the height of the reaction chamber 5 is large, the heater 3 may be divided into upper and lower parts. That is, it is also possible to divide the arrangement into two parts: one arranged around the upper part of the reaction chamber 5 and the other arranged around the lower part of the reaction chamber 5.

Furthermore, although not shown, the output of the heater 3 is controlled based on temperature data from a thermocouple, radiation thermometer, etc. provided in the heat insulating casing, so that the temperature can be controlled. There is.
Note that the inner diameter d of the heat insulating casing 1 may be normally set to a size such that the temperature inside the reaction chamber 5 is heated by the heater 3 to a temperature suitable for the nitriding reaction.
Further, although not shown, a frame made of stainless steel or the like may be provided on the outer surface of the heat insulating casing 1 in order to stably hold the casing 1.

In the present invention, the reaction chamber 5 is formed from a bottom plate 11 and a cylindrical shield wall 13 provided so as to cover the bottom plate 11. That is, the internal space surrounded by the bottom plate 11 and the shield wall 13 is the reaction chamber 5, and the above-mentioned heater 3 is arranged outside the reaction chamber 5, and the heat insulating casing 1 The inner surface of the chamber is completely separated from the reaction chamber 5.

The bottom plate 11 is placed on a pedestal 15 provided at the bottom of the heat insulating casing 1. An exhaust port 17 is formed in the center of the bottom plate 11, and the reaction chamber 5 is opened from the exhaust port 17 by evacuation through an exhaust pipe 19 communicating with a hole 15a formed in the pedestal 15. The structure is such that exhaust is exhausted from the inside.
Further, the shield wall 13 is attached to the pedestal 15 so that the bottom plate 11 is completely covered by the shield wall 13. Thereby, leakage of gas from between the pedestal 15 and the shield wall 13 can be prevented.
The bottom plate 11 and the shield wall 13 are made of a material with high heat resistance, such as carbon, preferably graphite.

In the present invention, in the reaction chamber 5 surrounded by the bottom plate 11 and the shield wall 13, trays 19 containing reaction raw materials to be subjected to a nitriding reaction are stacked in multiple stages. A gap S serving as a gas flow path is formed between the outer surface of the trays 19 stacked in multiple stages and the inner surface of the shield wall 13.

Referring to FIG. 3(a), this tray 19 consists of a bottom wall 19a and a side wall 19b rising from the periphery of the bottom wall 19a. A plurality of (four in the figure) notches 19c are formed point-symmetrically. Further, a hollow cylinder 19d is formed upright at the center of the bottom wall 19a. That is, the nitrogen gas supply pipe 21 penetrates the trays 19 stacked in multiple stages through the hollow cylinder 19d and extends to the lowest tray 19x. This nitrogen gas supply pipe 21 is closed at its lower end, and has a large number of small holes 21a (omitted in FIG. 1) in the pipe wall, which are located inside each of the stacked trays 19. (See FIG. 4), and nitrogen gas is supplied to the inside of each tray 15. The tray 19 has an outer diameter smaller than the inner diameter of the cylindrical shield wall 13, thereby creating an appropriately sized gap between the outer surface of the tray 19 and the inner surface of the shield wall 13. S is formed.

Incidentally, among the stacked trays 19, the tray 19x located at the lowest stage has a plurality of legs 19e formed thereon, as shown in FIG. 3(b). S is configured to communicate with a space Y formed between the lower surface of the tray 19x and the bottom plate 11.
Incidentally, instead of forming the legs 19e as described above on the lower surface of the tray 19, an appropriate stand is provided on the peripheral edge of the bottom plate 11, and the tray 19x is placed on this stand to communicate with the gap S. It is also possible to form a space Y.

On the bottom wall 19a of the tray 19, as shown in FIG. 4, reaction raw material powder is laid down. The thickness t of the reaction raw material is naturally set to a size that prevents the reaction raw material from spilling out from the notch 19c or the central hollow cylinder 19d.

With reference to FIG. 5, with the above structure, the gas flow Z of nitrogen gas introduced into the nitrogen gas supply pipe 21 is released from the small hole 21a formed in the supply pipe 21, A gas flow Z passes through the tray 19 from the center of each tray 19, flows into the gap S between the outer surface of the tray 19 and the inner surface of the shield wall 13, and flows into the gap S via the above-mentioned notch 19c. flows into the space Y between the bottom surface of the lowermost tray 19x and the bottom plate 11, and is discharged to the outside from the exhaust port 17 formed in the bottom plate 11.

As understood from the gas flow Z of nitrogen gas, the nitrogen gas flows from the center of each tray 19 to the gap S formed by the peripheral edge of each tray 19 and the shield wall 13, and at this time, , a nitriding reaction is carried out in contact with the reaction raw materials contained in each tray 19, but the gas by-produced by this reaction quickly exists outside the tray 19 together with unreacted nitrogen gas. The air is discharged into the space S, which passes through the space Y, and is then discharged from the exhaust port 17. That is, the gas produced by the nitriding reaction does not remain in the tray 19 and is immediately discharged, so that the reaction between the reaction raw material and nitrogen proceeds without being inhibited by the by-product gas. The time required to form nitrides can be significantly shortened. Moreover, since the gas passing through the tray 19 is quickly discharged without stagnation, the reaction raw materials contained in the tray 19 can be uniformly nitrided. For example, the reaction raw materials located at the periphery of the tray 19 will also be nitrided in the same way as the reaction materials located at the center.

In the present invention, from the viewpoint of allowing the nitrogen gas mentioned above to flow smoothly in a laminar flow state without disturbance, the shield wall 13 is preferably formed into a cylindrical shape as shown in FIG. Furthermore, it is preferable that the tray 19 has a circular planar shape. That is, if there are corners in the shield wall 19 or the tray 19, nitrogen gas (unreacted nitrogen gas and by-product gas) is likely to be disturbed when it hits the corners, causing gas flow to stagnate, especially near the corners. This is because the nitriding reaction of the reaction raw material located therein may become unstable and the nitriding reaction may become non-uniform.

In addition, the inner diameter _D1 of the tray 19 as described above is not particularly limited, but is usually 200 mm or less, especially 10 to The range is preferably about 80 mm. Further, the height h of the tray 19 is not particularly limited, but the height h of the tray 19 is set so that the height t of the reaction raw material (in powder form) accommodated in the tray 19 is about 10 to 80 mm. It is preferable to set it according to the inner diameter _D1 of. If this height h is too small, the amount of processing per tray 19 will decrease, and in order to industrially mass-produce nitrides, the number of stacked trays 19 must be increased more than necessary. The shield wall 13 and the casing 1 become excessively large, and the work of stacking the trays 19 containing the reaction raw materials, the work of assembling the shield wall 13, and furthermore the work of taking out the trays 19 after the reaction is completed are large-scale work. It becomes a thing. Furthermore, if the height h is too large, it may be difficult to nitride the reaction raw material deep into the reactor.
Therefore, the height of the hollow cylinder 19d formed at the center of the tray 19 and the height _h1 of the notch 19c are set such that the reaction raw materials accommodated in the above amount do not enter the inside of the hollow cylinder 19, and The height is set to such an extent that it does not fall from the notch 19c.

Further, the width and number of the plurality of notches 19c formed in the tray 19 may be set so that the gas flow Z from the center of the tray 19 to the external gap S becomes uniform in the circumferential direction. The notches 19 are arranged point-symmetrically. Further, although the number of notches 19 is four in FIG. 3, it may be two, three, or five or more.

Furthermore, the outer diameter D ₂ of the tray 19 described above is set to about 50 to 95% of the inner diameter D ₃ of the shield wall 13 to ensure efficient and smooth suction from the exhaust pipe 19 through the exhaust port 17. This is suitable for ensuring a good gas flow.

In the present invention, the tray 19 having the above configuration is formed of a heat-resistant material used for various nitriding reactions, reduction nitriding of oxides, etc., and carbon, particularly graphite, is preferably used, for example. In addition to this, the tray 19 may be formed of a sintered body of ceramic powder such as alumina, silicon carbide, boron nitride, or the like. It is also a preferred embodiment to prevent deterioration of the carbon tray by placing a plate made of a sintered or molded ceramic powder such as alumina, silicon carbide, or boron nitride on the carbon tray.

The number of stacking stages of the tray 19 described above is set so that an industrially sufficient amount of nitride can be obtained in one batch depending on the size of the tray, etc., and is usually set to 5 to 40 stages.

In the nitriding reactor of the present invention described above, a preheating chamber 23 is preferably formed in the upper part of the reaction chamber 5 partitioned by the shield wall 13. That is, the nitrogen introduction pipe 25 penetrates the casing 1 and is connected to the upper part of the preheating chamber 23, while the upper end of the nitrogen gas supply pipe 21 mentioned above is connected to the lower part of the preheating chamber 23. That is, nitrogen gas flows into the preheating chamber 23 from the introduction pipe 25, and is introduced from the preheating chamber 23 into the nitrogen gas supply pipe 21, and as described above, nitrogen gas is supplied from this supply pipe 21 into the tray 19. That is, since the reaction for nitriding the reaction raw material used in the tray 19 (for example, direct nitriding or reductive nitriding) is performed at an extremely high temperature, the inside of the reaction chamber 15 is heated to a predetermined reaction temperature by the heater 3. Even so, if the temperature of the nitrogen gas supplied into the tray 19 is low, the nitriding reaction may become unstable. For this reason, a preheating chamber 23 is provided in the upper part of the reaction chamber 5, and the nitrogen gas introduced into the nitrogen supply pipe 21 is passed through the preheating chamber 23, which is heated to the same temperature as the inside of the reaction chamber 5, and is heated in advance. This is desirable.

Such a preheating chamber 23 heats the nitrogen gas introduced from the nitrogen introduction pipe 25 to as high a temperature as possible by increasing the residence time of the nitrogen gas as much as possible. A preheating plate 29 having a gas flow permeation port is stacked inside a box-shaped frame 27 made of a material.

The preheating plate 29 described above is made of highly thermally conductive carbon, preferably a sintered body of graphite or boron nitride, etc., but in order to increase the residence time, the preheating plate 29 is made with different gas flow permeation opening positions. , it is preferable to use these in combination.

For example, in FIG. 6(a), an opening 31 serving as a gas permeation port is formed in the center, and a center opening preheating plate 29a is shown. The center opening preheating plate 29a is provided with airflow regulating protrusions 33 arranged in a ring shape at regular intervals in the circumferential direction so as to surround the center opening 31.
Further, FIG. 6(b) shows a peripheral small hole preheating plate 29b in which a large number of small holes 34 serving as gas flow permeation ports are distributed on the peripheral edge.

By forming the preheating chamber 23 by stacking the center opening preheating plate 29a and the peripheral small hole preheating plate 29b alternately within the frame 27, the residence time of nitrogen gas in the preheating chamber 23 can be extended. can do. That is, the nitrogen gas introduced into the preheating chamber 23 from the nitrogen introduction pipe 25 flows onto the center opening preheating plate 29a through the small holes 34 formed on the periphery of the peripheral small hole preheating plate 29b. The nitrogen gas that has flowed onto the center opening preheating plate 29a passes between the airflow regulating protrusions 33 and flows from the center opening 31 onto the peripheral small hole preheating plate 29b. By making the flow of the nitrogen gas zigzag from the periphery to the center to the periphery to the center in this way, the residence time can be increased and the nitrogen gas can be heated to a sufficiently high temperature.

In this way, sufficiently heated nitrogen gas is introduced from the nitrogen gas supply pipe 21 into the reaction chamber 5, which is maintained at a predetermined reaction temperature, and a nitriding reaction is carried out, thereby depositing nitrides on the tray 19. Obtainable.
After the reaction is completed, the heat insulating casing 1 is opened, the preheating chamber 23 is taken out, the shield wall 13 is pulled out, the tray 19 is taken out, and the reaction product (nitride) on the tray 19 is recovered.
The recovered nitride is appropriately purified through operations such as oxidation, pickling, washing with water, etc., and drying, and subjected to processes such as classification, and then used as a product.

The above-mentioned nitriding furnace of the present invention performs the nitriding reaction in a batch manner, but since it is structured so that the by-product gas does not come into contact with the inner surface of the heat-insulating casing 1 or the heater 3, it is particularly It is suitable for carrying out a reductive nitriding reaction, and is extremely suitable, for example, for producing aluminum nitride (AlN) and hexagonal boron nitride (h-BN), which are stable at room temperature and normal pressure, by a reductive nitriding method.

Production of aluminum nitride (AlN) by the reduction nitridation method is carried out as follows. That is, an oxygen-containing aluminum compound such as aluminum oxide (Al ₂ O ₃ ) is used as an aluminum source, and a mixed powder of this oxygen-containing boron compound powder and carbon powder is spread on a tray 19 as a reaction raw material. 19 is loaded in the reaction chamber 5 of the nitriding furnace described above, nitrogen is supplied from the nitrogen gas supply pipe 21, and AlN is obtained on the tray 19 by reducing and nitriding the oxygen-containing aluminum compound.
The above reaction is represented by the following formula.
Al ₂ O ₃ +3C+N ₂ → 2AlN+3CO
The above reaction is generally carried out with the reaction chamber 5 set at a temperature of 1200 to 2000°C, preferably 1400 to 1800°C. If this temperature is too low, the reduction nitridation will not proceed sufficiently, and if the temperature inside the reaction chamber 5 is higher than necessary, there is a risk that the generated AlN will volatilize and be discharged.

Further, hexagonal boron nitride (h-BN) is produced by the reductive nitriding method as follows. That is, an oxygen-containing boron compound such as boron oxide (B ₂ O ₃ ) is used as a boron source, and a mixed powder of this oxygen-containing boron compound powder, carbon powder, and an auxiliary agent is spread on a tray 19 as a reaction raw material. The tray 19 is loaded in the reaction chamber 5 of the nitriding furnace described above, nitrogen is supplied from the nitrogen gas supply pipe 21, and h-BN is obtained on the tray 19 by reducing and nitriding the oxygen-containing boron compound.
The above reaction is represented by the following formula.
B ₂ O ₃ +3C+N ₂ → 2BN+3CO

The above reaction is generally carried out with the inside of the reaction chamber 5 set at a temperature of 1200 to 2200°C, preferably 1800 to 2100°C. If this temperature is too low, the reduction nitridation will not proceed sufficiently, and if the temperature inside the reaction chamber 5 is higher than necessary, there is a risk that the generated h-BN will volatilize and be discharged.

In addition, the above reaction produces by-products of metal oxide volatiles and oxidizing gases such as carbon dioxide, but this CO gas is prevented from coming into contact with the heat insulating casing 1 and the heater 3 due to the shield wall 13. Thereby, deterioration of the heat insulating casing 1 and the heater 3 can be effectively suppressed, and the life of the device can be maintained for a long time.

Furthermore, the auxiliary agent in the reaction raw material is used to uniformly advance the above-mentioned reductive nitriding reaction to the inside of the raw material. For example, an oxygen-containing alkaline earth metal compound, particularly calcium carbonate or calcium oxide, is suitable. used for. That is, when the reduction-nitriding reaction is carried out at a high temperature as described above, such an auxiliary agent is decomposed and gas (for example, carbon dioxide gas) is generated during the process of raising the temperature inside the reaction chamber 5 to a high temperature. As a result, voids are generated inside the reaction raw material at the stage of supplying nitrogen gas, and the nitrogen gas penetrates deep into the reaction raw material, allowing the reductive nitriding reaction to proceed quickly and uniformly. For example, when the present inventors manufactured h-BN as described above using the nitriding furnace shown in the above-mentioned figure, the entire tray 19 was covered with h-BN powder having high whiteness (for example, It has been confirmed that a product with a W of 90 or more was manufactured. For example, when reductive nitriding progresses unevenly, carbon remains and parts with low whiteness are formed. However, in the present invention, because reductive nitriding progresses uniformly and deep inside, the whiteness also decreases overall. It is high throughout.
In addition, when the number of stacked trays ₁₉ with an inner diameter D1 of 60 mm is 20 and the discharge speed (linear velocity) of nitrogen gas from the nitrogen gas supply pipe 21 is set to be 0.5 Ncm/s or more, 15 hours It has also been confirmed that the reduction-nitridation reaction was completed within the same period.

The mixing for preparing the mixed powder, which is the reaction raw material, is not particularly limited as long as each component is mixed uniformly, and may be performed using a mixing device such as a vibration mill, a ball mill, a drum mixer, or a vibration stirrer. .

In addition, the quantitative ratio of the boron source and carbon powder in the reaction raw materials is set so that the elemental ratio (B/C) is in the range of 0.60 to 0.85, particularly 0.65 to 0.80. . If this elemental ratio (B/C) is smaller than the above range, there will be a large amount of unreacted carbon in the reaction product, which may make it difficult to obtain the desired h-BN. Moreover, if it is larger than the above range, the amount of boron compounds that volatilize without being reduced increases, which not only reduces the yield but also causes inconveniences such as clogging of the exhaust line due to reductive nitridation in the exhaust line. may also occur.
Further, the quantitative ratio of the boron-containing compound to the auxiliary agent is such that, for example, the molar ratio of boron to calcium (B ₂ O ₃ /CaO) in terms of oxide is 4.0 to 6.0, particularly 4.5 to 5. A range of 5 is preferable. If this molar ratio is smaller than the range, a large amount of impurities derived from calcium will be present on the tray 19, resulting in a decrease in yield. Furthermore, if the molar ratio is larger than the above range, the amount of boron compound that is volatilized without being reduced will increase, which may not only lower the yield but also cause blockage of the exhaust line.

In addition, in the present invention, when producing h-BN using the above-mentioned reaction raw materials, as shown in FIG. It is preferable to spread the mold layer on the bottom wall 19a of the tray 19, and spread the reaction raw materials on top of this.
That is, when producing h-BN by reductive nitriding on the tray 19, there is a risk that the produced h-BN powder will adhere to the bottom wall 19a of the tray 19, making it difficult to take it out from the tray 19. be. This tendency is particularly strong when the tray 19 made of graphite carbon is used. In order to prevent such inconvenience, a molded body or powder of boron nitride is spread over the bottom wall 19a of the tray 19 to form a release layer, thereby preventing direct contact between the generated boron nitride powder and the bottom wall 19a of the tray 19. By avoiding this, the above-mentioned inconveniences can be effectively prevented.

The hexagonal boron nitride (h-BN) powder generated on the tray 19 as described above is recovered from the tray 19, and unreacted boron oxide and Ca or Ca compounds derived from the auxiliary agent are removed by pickling. The particles are then washed with water, classified to a predetermined particle size using a vibrating sieve, etc., collected in packaging bags, and sold.

As described above, according to the nitriding reactor of the present invention, a large amount of nitride can be produced at once even though it is a batch type, and the nitriding reaction can also proceed quickly and uniformly. Deterioration of the heat insulating casing 1 and heater 3 can also be effectively avoided, the life of the device is long, and nitrides can be produced efficiently, which is extremely useful industrially.

1: Heat insulating casing 3: Heater 5: Reaction chamber 11: Bottom plate 13: Shield wall 17: Exhaust port 19: Tray 19c: Notch 21: Nitrogen gas supply pipe 23: Preheating chamber S: Gap

Claims (7)

In a nitriding reactor for carrying out a nitriding reaction,
The nitriding reactor has an adiabatic casing,
The insulating casing includes a reaction chamber surrounded by a shield wall held by a bottom plate with an exhaust port, and a heater disposed outside the reaction chamber.
In the reaction chamber, trays are stacked on the bottom plate in multiple stages, each having an opening in the center, containing a reaction material to be subjected to a nitriding reaction, and having a notch formed in a side wall. and a nitrogen gas supply pipe extending through the opening of the tray;
A nitriding reaction is performed by bringing the nitrogen gas supplied from the nitrogen gas supply pipe into contact with the reaction raw material contained in the tray, and unreacted nitrogen gas and by-product gas are formed on the side wall of the tray. The nitriding reaction has a structure in which the nitriding reaction is discharged through the notch in the tray, through the gap formed between the peripheral edge of the tray and the shield wall, and from the exhaust port in the bottom plate. Furnace. 2. A preheating chamber is provided in an upper part of the reaction chamber, and nitrogen gas heated in the preheating chamber is supplied through the nitrogen gas supply pipe into a tray disposed within the reaction chamber. nitriding reactor. The nitriding reactor according to claim 1 or 2, wherein a mixed powder containing oxygen-containing aluminum powder and carbon powder is used as the reaction raw material. The nitriding reactor according to claim 1 or 2, wherein a mixed powder containing boron oxide powder, carbon powder, and an auxiliary agent is used as the reaction raw material. 5. A mold release layer made of a plate-shaped molded nitride or powder is laid inside the tray, and the reaction raw material is arranged in a layer on the mold release layer. nitriding reactor. The nitriding reactor according to any one of claims 1 to 5, wherein heating is performed by the heater so that the temperature within the reaction chamber is in the range of 1200 to 2200°C. The nitriding reactor according to any one of claims 1 to 6, wherein the tray has a circular planar shape.