JPS6279843A - Gas dispersion plate for fluidized layer synthesizing apparatus - Google Patents

Abstract

PURPOSE:To prevent the formation of the immobile part of powder and to accelerate reaction by expanding the gas ejection port of a gas diffusion plate of a fluidized layer type apparatus for producing silicon nitride powder by silica reduction method to a funnel shape in the upper part on the synthesizing chamber side. CONSTITUTION:The gas diffusion plate 6 having the gas ejection ports 9 is provided in the lower part of the synthesizing chamber 8. Many pieces of the ports 9 are spaced from each other and are disposed over the entire part of the plate 6 and the upper parts 13 thereof expand like a funnel. The top edges 14 thereof are contiguous to each other and the upper parts 13 expand linearly. The angle theta of inclination thereof has an angle above the angle of repose of the powder 12. The powder (e.g.: silica granules, etc.) is put into the chamber 8 constituted in such a manner and gas (e.g.: gaseous N2, etc.) is blown through the ports 9 from below, then the powder 12 is fluidized by the gas and reacts at the same instant. There are substantially no surface parts where the powder 12 forms the immobile part atop 11 the plate 6 and therefore, the powder 12 and the gas contact satisfactorily with each other and make the reaction uniform.

Description

[Detailed description of the invention] Industrial 1! This invention relates to improvements in gas distribution plates for fluidized bed synthesis equipment.

A fluidized bed synthesis apparatus is used to synthesize, for example, Si 3 N 4 powder using N 2 gas at high temperatures. As shown in FIG. 11, this type of apparatus is equipped with a gas dispersion plate 2 for blowing gas into the synthesis chamber 1 below the synthesis chamber 1 into which raw materials are introduced.

The gas distribution plate 2 is made of carbon material so that it can withstand high temperatures and N2 gas or CO2 gas cloud surroundings. For this reason, it cannot be made into a complicated shape, and a certain level of strength must be maintained.

For this reason, the conventional gas distribution plate 2 has a shape in which vertical round holes 3 are bored at a certain distance in a carbon flat plate.

A bite )! try to do it. 1. However, when the gas dispersion plate 2 having this structure is used, the gas ejected into the synthesis chamber 1 does not spread much, and only blows up almost directly from the ejection port 4. Therefore, the raw material powder is not fluidized between the spout ports 4 and the stationary portion 5
These may remain as unreacted particles or may have poor contact with N2 gas, resulting in a synthetic powder with poor analytical values.

1 This invention was made to solve the above-mentioned problems. It eliminates the immobile part of the powder, obtains a uniform synthetic powder, and improves the synthesis reaction by uniformly dispersing N2 gas. It is an object of the present invention to provide a gas distribution plate for a fluidized bed synthesis apparatus that can efficiently perform reactions and promote reactions.

11 Therefore, the present invention provides a gas dispersion plate for blowing gas into powder in a synthesis chamber in a fluidized bed manufacturing apparatus for producing silicon nitride powder using a silica reduction method.
The gist of this paper is a gas distribution plate of a fluidized bed synthesis apparatus whose upper part on the side of the synthesis chamber is expanded into a funnel shape.

The gas dispersion plate 6 for blowing gas into the powder 12 in the synthesis chamber 8 has a large number of gas ejection ports 9, and the upper part on the synthesis chamber 8 side is leak-proof. It is spread out in a St-shape.

Specifically, the upper edges 14 of adjacent gas jet ports 9 are adjacent to each other.

Alternatively, adjacent gas outlets 9 are connected to each other at the upper edge 1
4 are overlapping.

LJL There is no part on the upper surface of the gas distribution plate 6 that forms a powder stationary portion, and no powder stationary portion is formed on the top surface of the gas distribution plate 6.

Support 11 FIGS. 1 to 4 show a first embodiment of the present invention. The gas distribution plate 6 is provided at the bottom of the cylindrical side wall 7. Inside this side wall 7 is a synthesis chamber 8 in which raw material powder 12 is charged and synthesized.

The gas distribution plate 6 has a large number of gas ejection ports 9 arranged therein. This gas outlet 9 penetrates from the lower surface 10 side of the gas distribution plate 6 to the upper surface 11 side. This gas distribution plate 6 is provided to blow, for example, N2 gas into the powder 12 in the synthesis chamber 8.

The gas jet ports 9 are arranged over the entire gas distribution plate 6 at predetermined intervals. As shown in FIGS. 1 and 2, the upper portion 13 of the gas outlet 9 on the side of the synthesis chamber 8 is widened into a funnel shape.

In this embodiment, the upper edges 14 of adjacent gas outlets 9 are adjacent to each other. The upper part 13 is
As shown in FIG. 1, it spreads out in a straight line, and its inclination angle θ is greater than the angle of repose of the powder 12, for example 70''.

The medium-heat portion 15 of the gas outlet 9 has a small inner diameter as shown in FIGS. 1 and 3. Further, the lower part 16 of the gas outlet 9 is connected to the central part 15 as shown in FIGS. 1 and 4.
It has the same inner diameter.

The gas distribution plate 6 having this structure is made of carbon.

In use, granules of silica, carbon, or silicon nitride, for example, are placed in the synthesis chamber 8 as the powder 12. Then, for example, N2 gas is blown into the powder 12 from below the gas distribution plate 6 through the gas outlet 9.

At this time, the powder 12 and the N2 gas are each heated to a predetermined temperature by a heat source (not shown).

By doing so, the powder 12 is fluidized by the N2 gas and undergoes a nitriding reaction.

By the way, the gas dispersion plate 6 has almost no surface portion on the upper surface 11 side where the immovable portion of the powder 12 is formed. Therefore, there is no possibility that an immobile part of the powder 12 will be formed on the gas distribution plate 6 during the reaction of the powder 12.

For this reason, the powder 12 and the N2 gas are in good contact, and the N2 gas is uniformly distributed, resulting in a uniform synthetic powder. Since the N2 gas is uniformly dispersed, the synthesis reaction can be carried out efficiently and the effect of promoting the reaction is increased.

Here, when α-8i3 N4 powder is synthesized, the reaction time and the total oxygen content and total carbon content in the produced powder are shown in the table (
(See below).

The conventional example and the embodiment of the present invention in the table (however, the inclination angle θ=7
The conditions for synthesizing the powder (0°) are as follows.

Raw material powder mixture ratio...1Si 02-0.50-
0. ISi 3 N4 (Weight) Weight of raw material powder......8kgN2 gas flow rate...100-0! Q/Bunai Kai Taki
Temperature: 1480°C In this case, the reaction time in the example of this invention is shorter by 1 hour. Further, both the total oxygen amount and the total carbon amount are smaller in the embodiment of the present invention.

1 sad circle 11 FIG. 5 shows a second embodiment of the invention.

The gas distribution plate 6 of this embodiment is different from the embodiment 1 shown in FIG. 1 in the shape of one gas outlet. That is, the upper part 20 of one gas outlet is funnel-shaped, but spreads out in a curved shape. Then, the central part 21 and the lower part 22
has a narrower inner diameter. The other side walls 7 and the like have the same structure as in the first embodiment shown in FIG.

FIG. 6 shows a third embodiment of the invention.

In Example 1.2 shown in FIGS. 1 and 5, the upper part of the gas outlet was circular, whereas in FIG. 6 it was a regular hexagon. The upper part 30 of the gas outlet 29 is a regular hexagon, and the upper edges 31 of two adjacent gas outlets overlap and are common. With such a structure, the upper surface 11 of the gas distribution plate 6 has no surface portion that would be formed by an immovable part of the powder.

Such a regular hexagonal upper shape can also be adopted in Embodiment 1.2 shown in FIGS. 1 and 5.

7 to 10 show Examples 4 to 7 of the present invention. The gas distribution plate 6 in FIG.
0 is funnel-shaped and straight, and the lower part 41 has a narrower inner diameter than the upper part. In FIG. 8, the gas distribution plate 6 is not a flat plate with a uniform thickness, but has a smaller thickness at both ends. The shape of the gas outlet 39 is similar to that shown in FIG.

In FIG. 9, the upper part 50 of the gas outlet 49 is river-like and curved. The lower part 51 has a narrow inner diameter.

In FIG. 10, the gas distribution plate 6 has a smaller thickness around it. The shape of the gas outlet 49 is similar to that shown in FIG.

However, the present invention is not limited to the embodiments described above. For example, the upper part is not limited to a regular hexagon or a circle, but may have other shapes.

As explained above, according to the present invention, there is no part on the upper surface of the gas distribution plate where a stationary part of the powder is formed.
Since no stationary part of the powder is formed, gas is uniformly distributed within the synthesis chamber, and uniform synthetic powder can be obtained. By uniformly dispersing the N2 gas, the synthesis reaction can be carried out efficiently and the reaction can be promoted.

[Brief explanation of drawings]

FIG. 1 shows Example 1 of the gas distribution plate of the fluidized bed synthesis apparatus of the present invention. fI side view, Figure 2 is a diagram showing a part of the upper surface of the gas distribution plate, Figure 3 is a sectional view showing a part of the middle part of the gas distribution plate, and Figure 4 is a part of the lower surface of the gas distribution plate. FIG. 5 is a sectional view showing a second embodiment of the invention, FIG. 6 is a partial view of the upper surface of a gas distribution plate according to a third embodiment of the invention, and FIGS. 7 to 10 are the fourth to fourth embodiments of this invention.
7 and 7E11 are cross-sectional views for explaining the disadvantages of the conventional gas distribution plate. 6... Gas distribution plate 8... Synthesis chamber 9... Gas outlet 13... Upper part 15... Center part 16... Lower part Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Figure 7 Figure 8 Figure 11

Claims (5)

[Claims] (1) Silica reduction method In the gas dispersion plate that blows gas into the powder in the synthesis chamber in a fluidized bed manufacturing device for silicon nitride powder, the upper part of the numerous gas outlets on the synthesis chamber side is shaped like a funnel. Gas distribution plate of a fluidized bed synthesis equipment being expanded. (2) The gas distribution plate of the fluidized bed synthesis apparatus according to claim 1, wherein the upper edges of the adjacent gas jet ports are adjacent to each other. (3) A gas dispersion plate for a fluidized bed synthesis apparatus according to claim 1, wherein the upper edges of adjacent gas outlets overlap each other. (4) The gas dispersion plate of the fluidized bed synthesis apparatus according to claim 1, wherein the gas jet ports extend linearly. (5) The gas dispersion plate of the fluidized bed synthesis apparatus according to claim 1, wherein the gas ejection ports are spread out in a curved shape.