JP7356298B2 - 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 (also called setters) containing raw materials stacked in multiple stages inside a furnace surrounded by heat insulating material. Batch type furnaces are known in which a heater is arranged around a reaction vessel (see, for example, Patent Documents 1 to 3).
Such a batch-type nitriding 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. Furthermore, compared to continuous type nitriding reactors, batch type nitriding reactors have a great advantage over continuous type nitriding reactors in that the operating conditions can be adjusted for each production batch, and a wide variety of products can be produced.

By the way, in the batch type nitriding reactor having the above structure, nitrogen gas to be reacted with the raw material is supplied from the periphery of the box-shaped container, or a nitrogen gas supply pipe is passed through the center of the box-shaped container, and the nitrogen gas is supplied from the periphery of the box-shaped container. Although methods such as supplying nitrogen gas from the center of the nitriding process 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 nitriding 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 and insulation materials is significant.

Japanese Unexamined Patent Publication No. 61-282790 Japanese Unexamined Patent Publication 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 a heat insulating casing,
A reaction chamber surrounded by a shield wall and a heater disposed outside the reaction chamber are disposed within the heat insulating casing,
In the reaction chamber, trays containing reaction raw materials to be subjected to the nitriding reaction are stacked in multiple stages, and each tray has a cylinder in the center for passing through an exhaust pipe and a notch in the side wall to serve as a gas flow path. and an exhaust pipe extends from the bottom of the reaction chamber through the shield wall and through the exhaust pipe penetration pipe of each loaded tray,
Nitrogen gas is supplied to the gap formed between the peripheral edge of each stacked tray and the shield wall, and the nitrogen gas is supplied from the gap through the notch of each tray to the reactor contained in each tray. A nitriding reaction is performed by contacting the raw material, and unreacted nitrogen gas and byproduct gas are discharged from the exhaust pipe extending through the exhaust pipe penetration tube of each tray. A nitriding reactor 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 to the gap formed between the peripheral edge of the tray and the shield wall. Things.
(2) A mixed powder containing oxygen-containing aluminum compound 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 in 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 periphery to 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 tray. It has a structure in which it is discharged from an exhaust pipe that extends through an exhaust pipe penetration cylinder formed at the center of the exhaust pipe. 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. In other words, the nitrogen gas supplied to the reaction chamber is supplied from the periphery of each tray into the interior without contacting the heater or the heat insulating casing, making it possible to effectively prevent nitrogen gas contamination. Become.
In addition, in the furnace structure of the present invention, the gas flow is from the periphery of the tray to the center, so volatiles of metal oxides and oxidizing gases such as carbon monoxide generated by the reduction-nitridation reaction can flow inside the furnace. The risk of contact with the heater or insulating casing on the outer periphery is extremely low, making it ideal for extending equipment life.

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, for example, by stacking carbon blocks. . 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, the heaters 3 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 an internal space of a box-shaped shield wall 13 placed on a heat-insulating pedestal 11 provided at the bottom of the heat-insulating casing 1 . Therefore, the heater 3 described above is arranged outside the reaction chamber 5 (shield wall 13), and the inner surface of the heat insulating casing 1 is completely separated from the reaction chamber 5.

The above-mentioned pedestal 11 is made of a heat insulating material such as graphite carbon, like the heat insulating casing 1, and an exhaust pipe 17 passes through its center. It penetrates the shield wall 13 and extends into the reaction chamber 5 . That is, the structure is such that the gas supplied from the exhaust pipe 17 into the reaction chamber 5 is exhausted by evacuation or the like through the exhaust pipe 17.
I can do it.

In the present invention, in the reaction chamber 5 surrounded by the shield wall 13 described above, trays 19 containing reaction 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, this tray 19 consists of a bottom wall 19a and a side wall 19b rising from the periphery of the bottom wall 19a. (Four in the figure) notches 19c are formed point-symmetrically. Further, an exhaust pipe penetrating cylinder 19d is formed upright in the center of the bottom wall 19a. That is, the exhaust pipe 17 penetrates the trays 19 stacked in multiple stages through the exhaust pipe penetration cylinder 19d and extends from the lowest stage to the highest stage tray 19. This exhaust pipe 17 is closed at its upper end, and has a large number of small holes 17a (omitted in FIG. 1) in its wall so as to face the inside of each of the stacked trays 19. (see FIG. 5), so that the nitrogen gas supplied into the trays 19 is exhausted from the center of each tray 19. 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.

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 exhaust pipe penetration tube 19d.

Referring to FIG. 5, with the above structure, the gas flow Z of nitrogen gas introduced into the gap S between the outer surface of the tray 19 and the inner surface of the shield wall 13 is directed toward the side wall of the tray 19. It flows into each tray 19 through the notch 19c formed in the notch 19b, and is discharged to the outside of the tray 19 (outside of the heat insulating casing 1) through the exhaust pipe 17 penetrating the center thereof.

As understood from such a gas flow Z of nitrogen gas, nitrogen gas flows into each tray 19 from the gap S at the peripheral edge of each tray 19, and at this time, the nitrogen gas contained in each tray 19 A nitriding reaction takes place in contact with the reaction raw materials. The gas produced by this reaction is quickly discharged from the exhaust pipe 17 passing through the center of the tray 19 together with the unreacted nitrogen gas. That is, the gas produced by the nitriding reaction is immediately discharged without remaining in the tray 19, so that the reaction between the reaction raw material and nitrogen proceeds without being inhibited by the by-product gas, and the reaction from the reaction raw material is The nitride generation time can be significantly shortened, and the gas passing through the tray 19 is quickly discharged without stagnation, so that the reaction raw materials contained in the tray 19 can be uniformly nitrided. I can do it. 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 13 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 exhaust pipe penetration pipe 19d formed at the center of the tray 19 and the height _h1 of the notch 19c are such that the reaction raw material accommodated in the above amount is inside the exhaust pipe penetration pipe 19d. The height is set to such an extent that it does not intrude into the body and does not fall out 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 flowing into the tray 19 from the gap S outside the tray 19 becomes uniform in the circumferential direction. , the plurality of notches 19 are arranged point-symmetrically. Further, although the number of notches 19 is four in FIGS. 2 and 3, it may be two, three, or five or more.

Further, 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 gas suction from the gap S by the exhaust pipe 17 and smooth gas flow. This is suitable for ensuring 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 passes through the casing 1 and is connected to the upper part of the preheating chamber 23, and on the other hand, the lower peripheral edge of the preheating chamber 23 and the upper wall of the shield wall 13 are provided with the above-mentioned space S. A hole serving as a gas flow path is formed so that nitrogen gas is supplied. In FIG. 1, the hole formed in the peripheral portion of the upper wall of the shield wall 13 is indicated by 13a.

That is, nitrogen gas flows into the preheating chamber 23 from the nitrogen gas introduction pipe 25, is introduced from the preheating chamber 23 into the space S outside the tray 19, and is sucked into the space S by the exhaust pipe 17 passing through the center of the tray 19. Nitrogen gas is supplied into the tray 19 from inside. However, since the reaction for nitriding the reaction raw material used in the tray 19 (for example, direct nitriding or reductive nitriding) is performed at extremely high temperatures, the interior 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 tray 19 is passed through the preheating chamber 23, which is heated to the same temperature as the inside of the reaction chamber 5, to be heated in advance. 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. It has a structure in which a preheating plate 29 having a gas flow permeation port is stacked inside a box-shaped frame 27 made of material.

The above-mentioned preheating plate 29 is formed of a highly thermally conductive boron nitride sintered body, etc., but in order to increase the residence time, plates with different gas flow permeation opening positions are made and these are overlapped. It is preferred to use

For example, in FIG. 6(a), a large number of small holes 31 serving as gas permeation ports are distributed on the peripheral edge, and a peripheral small hole preheating plate 29a is shown. This peripheral small hole 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.
Further, FIG. 6(b) shows a center opening preheating plate 29b in which an opening 34 serving as a gas flow permeation port is provided in the center.

The preheating chamber 23 is formed by alternately stacking the peripheral small hole preheating plates 29a and the center opening preheating plates 29b in the frame 27 as described above. In this case, a peripheral small hole preheating plate 29a is located at the lowermost position, and this small hole 31 communicates with an opening 13a formed in the peripheral edge of the upper wall of the shield wall 13. That is, the nitrogen gas introduced into the preheating chamber 23 from the nitrogen introduction pipe 25 passes through the center opening 34 of the center opening preheating plate 29b, flows onto the peripheral small hole preheating plate 29a, and flows downward from the small holes 31 on the peripheral edge. In this way, the nitrogen gas flow is caused to flow in a zigzag pattern from center to periphery to center to periphery, increasing the residence time of the nitrogen gas, and directing the nitrogen gas heated to a sufficiently high temperature into the gap S around the tray 19. High temperature nitrogen gas can be supplied onto the tray 19 from this gap S.

In this way, nitride can be obtained on the tray 19 by supplying sufficiently heated nitrogen gas onto the tray 19 in the reaction chamber 5 maintained at a predetermined reaction temperature and performing a nitriding reaction. I can do it.

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 volatile matter of metal oxides and oxidizing gases such as carbon dioxide, but these oxidizing gases are prevented from coming into contact with the heat insulating casing 1 and the heater 3 due to the shield wall 13. Therefore, 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 produced the above-mentioned h-BN 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, resulting in areas with low whiteness. However, in the present invention, since reductive nitriding progresses uniformly and deep inside, the whiteness also increases overall. It is high throughout.
Further, when the number of stacked trays ₁₉ with an inner diameter D1 of 60 mm is set to 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 mold release layer made of boron nitride molded body or powder is spread over the bottom wall 19a of the tray 19 to prevent 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: cradle 13: Shield wall 17: Exhaust pipe 19: Tray 19c: Notch 19d: Exhaust pipe penetration pipe 23: Preheating chamber 25: Nitrogen gas introduction pipe S: void

Claims (7)

In a nitriding reactor for carrying out a nitriding reaction,
The nitriding reactor has an adiabatic casing,
A reaction chamber surrounded by a shield wall and a heater disposed outside the reaction chamber are disposed within the heat insulating casing,
In the reaction chamber, trays containing reaction raw materials to be subjected to the nitriding reaction are stacked in multiple stages, and each tray has a cylinder in the center for passing through an exhaust pipe and a notch in the side wall to serve as a gas flow path. and an exhaust pipe extends from the bottom of the reaction chamber through the shield wall and through the exhaust pipe penetration pipe of each loaded tray,
Nitrogen gas is supplied to the gap formed between the peripheral edge of each stacked tray and the shield wall, and the nitrogen gas is supplied from the gap through the notch of each tray to the reactor contained in each tray. A nitriding reaction is performed by contacting the raw material, and unreacted nitrogen gas and byproduct gas are discharged from the exhaust pipe extending through the exhaust pipe penetration tube of each tray. A nitriding reactor featuring: A preheating chamber is provided in the upper part of the reaction chamber, and nitrogen gas heated in the preheating chamber is supplied to a gap formed between the peripheral edge of the tray and the shield wall . 1. The nitriding reactor according to 1. The nitriding reactor according to claim 1 or 2, wherein a mixed powder containing oxygen-containing aluminum compound 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. The nitriding method according to claim 3 or 4, wherein a mold release layer made of a nitride plate-shaped molded body or powder is laid in the tray, and the reaction raw material is arranged in a layer on the mold release layer. Reactor. The nitriding reactor according to any one of claims 1 to 5 , wherein heating is performed by the heater so that the temperature inside 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.