JPH10218612A - Production of silicon nitride powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing silicon nitride powder by a direct nitrification method using a nitrification oven equipped with a gas-charging pipe and a gas-discharging pipe and used for producing the silicon nitride, enabling to prevent the gas-discharging pipe from clogging by the deposition and adhesion of silicon monoxide to the inside of the gas- discharging pipe, and enabling to constantly stably and continuously operate also a nitrification oven for continuously producing the silicon nitride over a long time, even when the continuous nitrification oven is used, thereby enabling to efficiency and profitably produce the silicon nitride powder. SOLUTION: This method for producing silicon nitride powder comprises directly nitrifying metal silicon with a non-oxidizing gas containing nitrogen gas or ammonia gas in a temperature range of 1,150-1,500 deg.C by the use of a nitrifying over equipped with a gas-charging pipe and a gas-discharging pipe and used for producing the silicon nitride. Therein, the linear rate for discharging the gas after the nitrification reaction is 3 to 50m/s in a temperature range of 1,000-1,200 deg.C in the gas-discharging pipe. In the method for producing the silicon nitride powder, a nitrification over for continuously producing the silicon nitride is used as the nitrification oven for producing the silicon nitride, and a nitrification produce/discharged gas ratio after the nitrification reaction is 0.03-0.3kg/m<3> in a temperature range of 1,000-1,200 deg.C in the gas-discharging pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing silicon nitride powder directly from metallic silicon by a nitriding method using a nitriding furnace for producing silicon nitride provided with a gas introduction pipe and an exhaust gas exhaust pipe. The present invention relates to a method for producing a silicon nitride powder capable of preventing clogging of an exhaust pipe due to precipitation and adhesion of silicon monoxide, and continuously producing silicon nitride powder by operating a nitriding furnace in a stable and stable manner for a long time.

[0002]

2. Description of the Related Art
Metal silicon is directly nitrided with a non-oxidizing gas containing nitrogen gas or ammonia gas, and when producing silicon nitride powder, comprises a gas introducing pipe for introducing the non-oxidizing gas and an exhaust pipe for discharging exhaust gas. Silicon nitride production nitriding furnace is used, in this silicon nitride production nitriding furnace,
A silicon monoxide gas is generated from the natural oxide film on the metal silicon surface as shown by the following reaction formula. This silicon monoxide gas is entrained in the exhaust gas and precipitates and adheres to the inner wall of the discharge pipe.
Since the exhaust pipe is easily narrowed, the furnace pressure rises, making steady and stable operation difficult, or in the worst case, the exhaust pipe becomes blocked,
There was a problem that the operation of the furnace itself had to be interrupted.

[0003] Si + SiO ₂ → 2SiO SiO ₂ → SiO + 1 / 2O ₂ SiO ₂ + H ₂ → SiO + H ₂ O

In this case, since the silicon monoxide deposit adheres very strongly to the inner wall of the exhaust pipe, it is difficult to remove it during high-temperature operation. There was a way to clean and replace the garbage.

However, such a method is effective when the operation is completed in a short time, but is applicable when the operation is performed for a long time and nitriding is performed by continuously supplying new metal silicon and performing nitriding continuously. It was difficult. In particular, a continuous metal silicon nitriding furnace, such as a fluidized bed reactor, a rotary furnace, a moving bed reactor,
This tendency is remarkable when using a tunnel furnace or the like, especially when using a fluidized bed reactor, a rotary furnace, or a moving bed reactor having high contact efficiency between metal silicon and a nitriding gas. A measure to prevent the deposition and adhesion of silicon monoxide gas deposits on the surface has been an issue.

The present invention has been made in view of the above circumstances, and is directed to a method of producing silicon nitride powder directly from metallic silicon using a nitriding furnace for producing silicon nitride having a gas introduction pipe and an exhaust gas exhaust pipe. In the method for producing silicon nitride powder, it is possible to prevent the deposition and adhesion of silicon monoxide deposits on the inner wall of the exhaust pipe, and to continuously and stably operate the nitriding furnace for a long time to produce silicon nitride powder. The purpose is to provide.

[0007]

Means for Solving the Problems and Embodiments of the Invention The present inventor has conducted intensive studies to achieve the above object, and as a result, has found that a nitriding furnace for producing silicon nitride equipped with a gas inlet pipe and an exhaust gas exhaust pipe. 1,150 to 1,500 ° C. using a non-oxidizing gas containing nitrogen gas or ammonia gas
When nitriding directly in the temperature range of to produce silicon nitride powder,
By setting the exhaust gas linear velocity in the temperature range of 1,000 to 1,200 ° C. in the exhaust pipe to a range of 3 to 50 m / s, it is possible to prevent the deposition and adhesion of silicon monoxide deposits on the inner wall of the exhaust pipe. It has been found that silicon nitride powder can be produced by continuously and stably operating a nitriding furnace for a long time.

That is, the present inventor has found that in direct nitridation using a nitriding furnace for producing silicon nitride, the deposition of silicon monoxide on the inner wall of the exhaust pipe occurs in a specific temperature range of 1,000 to 1,200 ° C. In that case, a correlation is found between the gas linear velocity in the exhaust pipe and the amount of silicon monoxide deposited, and the larger the exhaust gas linear velocity, the smaller the amount of silicon monoxide deposited,
By adjusting the linear velocity of the exhaust gas containing silicon monoxide after the nitriding reaction in the above temperature range to a range of 3 to 50 m / s and flowing the exhaust gas at a high speed, the silicon monoxide is deposited on the inner wall of the exhaust pipe. That adhesion can be prevented and the above problems can be solved, and furthermore, the generation of silicon monoxide gas is relatively large,
In the case of a continuous reaction system such as a fluidized bed reactor, a rotary furnace, or a moving bed reactor in which silicon monoxide is likely to precipitate and adhere to the inner wall of the exhaust pipe, nitriding products including silicon nitride nitrided in the reactor are continuously discharged. When the exhaust gas is discharged together with the exhaust gas, the nitrided product containing silicon nitride nitrided in the reactor is accompanied by the high-speed exhaust gas having the specific linear velocity, and the ratio of the nitrided product / the exhaust gas is 0.03 to 0.03. It is effective to set the range to 0.3 kg / m ³ , and it is possible to efficiently remove silicon monoxide deposited and adhered to the inner wall of the discharge pipe, and it is necessary to interrupt the operation of the reactor on the way. It has been found that silicon nitride powder can be produced by operating stably for a long time even in a continuous reaction system to produce silicon nitride powder, and the present invention has been accomplished.

Accordingly, the present invention provides a method for manufacturing a silicon nitride by using a nitriding furnace having a gas introduction pipe for introducing a non-oxidizing gas containing nitrogen gas or ammonia gas and an exhaust gas exhaust pipe for discharging exhaust gas. In a method for producing silicon nitride powder by directly nitriding silicon in a temperature range of 1,150 to 1,500 ° C. with the non-oxidizing gas, a method of producing a silicon nitride powder in a temperature range of 1,000 to 1,200 ° C. in the exhaust pipe. Provided is a method for producing silicon nitride powder, characterized in that the linear velocity of exhaust gas is in the range of 3 to 50 m / s.

Further, according to the present invention, in the above-mentioned method, while continuously supplying metallic silicon to a nitriding furnace, continuously introducing a non-oxidizing gas from a gas introducing pipe, and further comprising a nitriding method containing the produced silicon nitride. When the product is continuously discharged from the exhaust gas exhaust pipe together with the exhaust gas to continuously produce silicon nitride powder, the nitriding product / exhaust gas ratio in the temperature range of 1,000 to 1,200 ° C. of the exhaust pipe is set to 0.1. 03-0.3kg / m
^{3. A} method for continuously producing silicon nitride powder, which is characterized in that:

Hereinafter, the present invention will be described in more detail. The method for producing a silicon nitride powder according to the present invention uses a nitriding furnace for producing silicon nitride provided with a gas introduction pipe for introducing a non-oxidizing gas containing nitrogen gas or ammonia gas, and an exhaust pipe for discharging exhaust gas. Silicon is directly nitrided with a non-oxidizing gas containing nitrogen gas or ammonia gas in a temperature range of 1,150 to 1,500 ° C.

In this case, the nitriding furnace for producing silicon nitride may be a discontinuous nitriding furnace for producing silicon nitride such as a batch furnace, or a continuous furnace such as a fluidized bed reactor, a rotary furnace, a moving bed reactor, or a tunnel furnace. Although a metal silicon nitriding furnace can be used, a continuous metal silicon nitriding furnace, especially a fluidized bed reactor is preferably used.

The exhaust gas exhaust pipe provided in the nitriding furnace is
The material is not particularly limited as long as it can withstand a high temperature of 1,000 to 1,200 ° C. For example, alumina, mullite,
Ceramics such as zirconia, silicon carbide, and silicon nitride, and those obtained by subjecting their surfaces to CVD and CVR treatments,
Alternatively, a heat-resistant metal such as molybdenum or tungsten is preferably used.

Here, the metal silicon powder used as a raw material is not particularly limited, but it is preferable to use a 150 mesh pass, particularly a 325 mesh pass metal silicon powder in order to complete nitriding in a short time.

When the continuous reaction is carried out using a continuous metal silicon nitriding furnace such as a fluidized bed reactor, a rotary furnace, a moving bed reactor, etc., the metal silicon powder is used to improve the fluidity of the metal silicon powder. A binder such as polyvinyl alcohol is added to the mixture, and the average particle size is 100 μm to 10 mm, particularly 300 μm.
It is more preferable to use those granulated to μm to 1 mm.

The non-oxidizing gas used for nitriding the metal silicon powder contains one or both of a nitrogen gas and an ammonia gas, and further incorporates a hydrogen gas if necessary, or is diluted with a rare gas such as argon or helium. A normal nitriding gas can be used, and the introduced amount may be a normal introduced amount.

The nitriding reaction temperature is 1,150 to 1,5.
00 ° C, preferably 1,200 to 1,400 ° C.

According to the present invention, in the method for producing silicon nitride powder by the direct nitriding method as described above, the exhaust gas containing silicon monoxide gas generated during nitriding is caused to flow at a high speed in an exhaust pipe to thereby form a mono-oxide. Prevents the deposition and adhesion of silicon gas. In particular, since the deposition of silicon monoxide gas occurs in the temperature range of 1,000 to 1,200 ° C. in the exhaust pipe, the gas linear velocity in the temperature range is specified. It is important to have a range.

In this case, the gas linear velocity in the exhaust pipe is obtained by subtracting the amount of the nitrogen gas and the amount of the ammonia gas used for nitriding from the amount of the non-oxidizing gas introduced into the nitriding furnace as the amount of the exhaust gas. This exhaust gas amount can be calculated as a value obtained by dividing the exhaust gas amount by the cross-sectional area of the exhaust pipe.
The gas linear velocity of the exhaust gas in the exhaust pipe in the temperature range of 000 to 1,200 ° C. is 3 to 50 m / s, preferably 5 to 3 m / s.
0 m / s, more preferably in the range of 7 to 20 m / s. If the gas linear velocity is less than 3 m / s, the effect is small,
When the silicon monoxide gas is deposited and adheres to the exhaust pipe and the gas linear velocity is higher than 50 m / s, not only the effect is not particularly improved, but also the exhaust pipe is worn or the non-oxidizing gas ( Since a large amount of nitriding gas is required, the cost may increase.

In order to control the gas linear velocity within the above range, a method of controlling the amount of non-oxidizing gas (amount of nitriding gas) and a method of controlling the diameter of the exhaust pipe are selected according to the operating conditions and conditions of the nitriding furnace. Can be.

When continuous operation is performed using a fluidized-bed reactor, a rotary furnace, or a moving-bed reactor, new metal silicon powder is always supplied, so that the amount of silicon monoxide gas is increased and the exhaust gas is exhausted. Precipitation and adhesion of silicon monoxide to silicon may increase. In this case, it is effective to entrain the nitrided product containing the silicon nitride powder with the high-speed exhaust gas having the gas linear velocity in the above-described specific range and scrape off the silicon monoxide deposited and adhered to the exhaust pipe inner wall, For this purpose, the nitriding product / exhaust gas ratio in the temperature range of 1,000 to 1,200 ° C. of the discharge pipe is set to 0.03 to 0.3 kg / m ³ , particularly 0.05 to 0.2 kg / m ³ . Is preferred. If the nitriding product / exhaust gas ratio is less than 0.03 kg / m ³ , the scraping effect may be reduced, and conversely, 0.3 kg / m ^3.
If it is more than m ^{3, the} inner wall of the exhaust pipe will be worn and present as impurities in the product, which may lower the quality.

The silicon nitride powder obtained by the nitriding reaction as described above is discharged together with the exhaust gas and can be recovered.

[0023]

According to the method for producing silicon nitride powder of the present invention, when producing silicon nitride powder by a direct nitriding method using a nitriding furnace for producing silicon nitride provided with a gas introduction pipe and an exhaust gas exhaust pipe, It is possible to prevent clogging of the exhaust pipe due to deposition and adhesion of silicon monoxide in the exhaust pipe, and it is possible to operate continuously and stably for a long time even with a nitriding furnace for continuous silicon nitride production. It can be produced efficiently and industrially advantageously.

[0024]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1 1 kg of 325 # metal silicon powder was placed in a silicon nitride tray, and 20 trays, 20 kg in total, were placed in a batch furnace. Thereafter, nitrogen 6 m ³ / Hr, the temperature was raised at a heating rate of hydrogen 2m ³ / Hr 100 ℃ / Hr while flowing a mixed gas of, 1,40
Nitriding was performed at 0 ° C. for 5 hours. In this case, the exhaust pipe used was an alumina pipe having an inner diameter of 40 mm. In this case, assuming that the nitriding rate is 100%, the nitrogen consumption by nitriding is 2.1 m ³ / Hr on average, so the gas linear velocity in the exhaust pipe at 1,100 to 1,200 ° C. is smaller than the remaining gas amount. It can be estimated from 6.1 to 6.6 m / s.

The obtained silicon nitride powder has a nitriding ratio of 100%.
Met. Further, the furnace was dismantled, and observation in the exhaust pipe and measurement of silicon monoxide deposition amount revealed that the amount of silicon monoxide deposited in the exhaust pipe was about 4 g, and it was confirmed that almost no narrowing had occurred. .

Comparative Example 1 For comparison, nitriding was performed under the same conditions as in Example 1 except that a mixed gas of ³ m ³ / Hr of nitrogen and 1 m ³ / Hr of hydrogen was introduced as a nitriding gas. In this case, assuming that the nitriding rate is 100%, the nitrogen consumption is 2.1 m ³ / Hr as in Example 1, so that the gas in the exhaust pipe at 1,100 to 1,200 ° C. is smaller than the remaining gas amount. The linear velocity can be estimated to be 2.0 to 2.1 m / s.

The obtained silicon nitride powder has a nitriding ratio of 100
%Met. When the furnace was dismantled and the inside of the exhaust pipe was observed and the amount of silicon monoxide deposited was measured, the amount of silicon monoxide deposited in the exhaust pipe was about 53 g, and the exhaust pipe cross-sectional area was 7%.
0% was blocked and needed immediate replacement.

Examples 2 and 3 and Comparative Examples 2 and 3 Silicon nitride powder was produced using the continuous fluidized bed reactor shown in FIG. The nitriding raw material was obtained by granulating 325 # under metal silicon powder to an average particle diameter of 0.6 mm, and the granulated particles were charged from the hopper 1 into the screw feeder 2. On the other hand, 25 kg of silicon nitride powder was previously placed on a gas dispersion plate 4 in a processing apparatus main body (reactor) 3 having an inner diameter of 250 mm.
The mixed gas of nitrogen gas / hydrogen gas at the flow rate shown in Table 1 mixed in the gas blender 5 was allowed to flow from the gas introduction pipe 6 through the gas dispersion chamber 7 into the reaction zone 1a through the vent hole of the gas dispersion plate 4, After forming the fluidized bed 8, the heating device 9 was heated to raise the temperature to 1,300 ° C.

Next, the screw feeder 2 is operated,
The granulated raw material was continuously supplied at a rate shown in Table 1 through a metal silicon supply pipe 10, and a continuous operation was performed for one month.
The nitrided product powder nitrided in the fluidized bed 8 was discharged from the alumina exhaust pipe 11 having the inner diameter shown in Table 1 with the exhaust gas, and was recovered by the recovery device 12. In addition, pressure gauge 13
This makes it possible to measure the furnace pressure and predict the narrowing of the exhaust pipe.

Table 1 also shows the silicon nitride reaction rate, nitrogen consumption, exhaust pipe gas linear velocity, and silicon nitride / exhaust gas ratio under each condition.

After completion of each experiment, the apparatus was disassembled, and the weight of the amount of silicon monoxide deposited in the exhaust pipe and the aluminum content in the nitrided product were measured. Table 2 shows the results.

From the results shown in Table 2, it was confirmed that according to the production method of the present invention, silicon nitride powder can be produced in a stable and continuous operation by preventing silicon monoxide from adhering to the exhaust pipe.

[0034]

[Table 1]

[0035]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a schematic view of a continuous fluidized bed reactor used in Examples of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hopper 2 Screw feeder 3 Processing apparatus main body 4 Gas dispersion plate 5 Gas blender 6 Gas introduction pipe 7 Gas dispersion chamber 8 Fluidized bed 9 Heating device 10 Metal silicon supply pipe 11 Exhaust pipe 12 Recoverer 13 Pressure gauge

Claims (3)

[Claims] 1. A method according to claim 1, further comprising: using a nitriding furnace for producing silicon nitride, comprising: a gas introducing pipe for introducing a non-oxidizing gas containing nitrogen gas or ammonia gas; and an exhaust gas exhaust pipe for discharging exhaust gas. 1,150- depending on oxidizing gas
In a method for producing silicon nitride powder by directly nitriding in a temperature range of 1,500 ° C.,
The linear velocity of the exhaust gas in the temperature range of 1,200 ° C is 3 to 50
m / s, a method for producing silicon nitride powder. 2. The method according to claim 1, wherein metal silicon is continuously supplied to the nitriding furnace, a non-oxidizing gas is continuously introduced from a gas introduction pipe, and the nitriding includes the generated silicon nitride. When the silicon nitride powder is continuously produced by continuously discharging the product together with the exhaust gas from the exhaust gas exhaust pipe, the nitriding product / exhaust gas ratio in the temperature range of 1,000 to 1,200 ° C. of the exhaust pipe is set to 0. 0.03 to 0.3 kg / m
^3. A continuous method for producing silicon nitride powder, wherein 3. The method for producing silicon nitride powder according to claim 1, wherein the nitriding furnace for producing silicon nitride is a fluidized bed reactor.