JPH04140695A - Fluidized bed - Google Patents

Abstract

PURPOSE:To homoginize the mixing of particles and material gas and form homogenious coating layer by controlling gas linear velocity and direction of carrier gas jetting into a reaction chamber. CONSTITUTION:In a reaction chamber 4, particles to be coated are contained in advance. And the staff gas is vertically blown up in the reaction chamber 4 through a staff gas supply hole 2 provided at the bottom of the reaction chamber 4. Next, carrier gas is introduced through a carrier gas supply hole 3 into the reaction chamber 4. Since the supply hole 3 is provided apart from the center axis of the supply hole 2 to form a center axis slanting upward, the carrier gas is jetted from the center to outside slanting upward at the bottom surface 5 of the reaction chamber. That is to say, carrier gas is supplied in the vicinity of the bottom inner surface 5 of the reaction chamber 4, resultantly, particles are mixed well without stagnating in a good flow pattern, contact of the material gas and particles can be promoted and homogeneous coating layer is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to fluidized beds, and more specifically, for example,
The present invention relates to a fluidized bed that can be used to produce coated particles.

[Prior Art and Invention Section B] For example, a fluidized bed is used as an apparatus for producing coated particles, which are fuel for HTR.

1 (TR fuel particles have a fuel core with a carbon layer, S
These are coated fuel particles coated with an iC layer and a ZrC layer.

The method for producing coated fuel particles is to thermally decompose the decomposable gas in the raw material gas and chemically deposit the decomposed material on the surface of the fuel kernels while flowing the fuel kernels using a carrier cassette in a reaction chamber. In this method, a coating layer is formed on the surface.

A conventional fluidized bed used for producing coated fuel particles has a heat-resistant reaction chamber having an inner wall surface formed in an inverted conical shape on the circumferential side near the bottom, and a bottom portion provided with a gas jet port.

In this fluidized bed, a decomposable gas is introduced into the reaction chamber from the gas outlet, and the fuel kernels accommodated in the reaction chamber are maintained in a fluidized state by the carrier gas, and the decomposable gas is applied to the surface of the fuel kernels. Coated fuel particles are produced by coating the decomposed material produced from the decomposable gas.

However, in this fluidized bed, it is difficult to form a uniform mixture of fuel kernels and decomposable residue, especially when coating particles in industrial batch quantities, and therefore it is difficult to apply a homogeneous coating layer. There is a drawback that there is no such thing.

For example, in a fluidized bed in which the single hole at the bottom of the reaction chamber is formed into a double tube, and the decomposable gas is injected into the reaction chamber from the inner tube and the carrier gas is injected from the outer tube, the carrier gas simply flows into the reaction chamber. It is a tower that blows vertically upward through the center of the sky. Therefore, the flow state of the decomposable gas or carrier gas is poor, and the fuel kernels may remain near the inner wall surface of the reaction chamber, making it impossible to uniformly cover the fuel kernels, resulting in a stable jet flow. I can't get the floor.

Furthermore, since the carrier gas only blows vertically upward through the center of the reaction chamber, the cooling efficiency of the carrier gas is poor, and the vicinity of the inner wall surface at the bottom of the reaction chamber cannot be sufficiently cooled. As a result, the decomposable gas or the carrier gas is chemically deposited around the outlet, resulting in a reduction in the gas flow to be introduced and an adverse effect on the coating layer of the deposited volume.

The present invention has been made based on the above circumstances.

The purpose of the present invention is to uniformly mix particles and raw material gas to form a homogeneous coating layer, and also to prevent chemical vapor deposition of raw material gas at the gas introduction part at the bottom of the reaction chamber, and to create a stable jet flow. The object of the present invention is to provide a fluidized bed that can be used even in industrial-scale hatch-scale reactions.

[Means for Solving the Aforesaid Problems] The structure of the present invention for achieving the above object includes a material gas supply hole provided at the bottom of the reaction chamber for vertically blowing the material gas into one reaction chamber; A carrier dregs supply hole is provided around the gas supply hole and has a center axis that extends obliquely upward toward the reaction chamber away from the center axis of the raw material gas supply hole. It is a fluidized bed.

[Operation] When using the fluidized bed of the present invention, particles to be coated are stored in advance in the reaction chamber forming the fluidized bed.

The source gas is introduced into the reaction chamber from a source gas supply hole provided at the bottom of the reaction chamber.

The source gas is blown up vertically into the reaction chamber from the source gas supply hole.

The carrier gas is introduced into the reaction chamber from a carrier gas supply hole provided around the outer periphery of the raw material gas supply hole.

The carrier gas supply hole is provided so as to form a center axis that extends diagonally upward and away from the center axis of the raw material gas supply hole toward the reaction chamber, so that the carrier gas At the bottom of the reaction chamber,
It erupts diagonally from the center outward.

That is, the carrier gas is also supplied near the inner wall surface at the bottom of the reaction chamber.

As a result, the particles in the vicinity are well stirred, so that a good fluidity state can be obtained in which the particles do not stagnate, and the raw material gas and the particles come into uniform contact. It becomes possible.

Further, in the vicinity of the above, the concentration of the raw material gas is low because the cooled carrier gas is sufficiently supplied, and moreover, the carrier gas flows through the supply hole to increase the gas introduction member. It's cooling down. Therefore, the raw material gas is not deposited by chemical vapor deposition on the bottom surface of the reaction chamber and in the vicinity of the inner wall surface of the bottom portion.

[Example J] Hereinafter, a fluidized bed of the present invention will be described in detail with reference to FIGS. 1 and 2.

As shown in FIG. 1, in the fluidized bed of the present invention, a gas introduction member 1 is installed at the bottom of a reaction chamber 4, and a raw material gas and a carrier gas are supplied to the lower part or inside of the gas introduction member 1. Gas supply pipe 9 and carrier gas supply pipe IO
and.

The reaction chamber 4 has a circular bottom and a circumferential side surface having an inverted conical inner surface near the bottom.

The reaction chamber 4 is made of a material such as graphite and has heat resistance.

The gas introduction member 1 is attached to the bottom of the reaction chamber 4, for example, by screwing, and is further attached to the top 1 of the raw material gas supply pipe 9 and the carrier gas supply pipe IO.
It is installed at the top of 2.

The gas introduction member 1 includes a raw material gas supply hole 2 for supplying the raw material gas from the raw material gas supply pipe 9 to the reaction chamber 4, and a raw material gas supply hole 2 for supplying the raw material gas from the carrier gas supply pipe 10 to the reaction chamber 4.
and a carrier gas supply hole 3 for supplying the carrier gas.

The shape of the upper surface of the gas introduction member l is circular, as shown in FIG.

The gas introduction member has a raw material gas supply hole 2 on the central axis,
A carrier gas supply hole 3 is arranged around the raw material gas supply hole 2 and has a central axis that extends obliquely upward and away from the central axis of the raw material gas supply hole 2 toward the inside of the reaction chamber 4. have

The raw material gas supply hole 2 is a through hole provided substantially perpendicularly to the center of the gas introduction member 1, and the raw material gas supply pipe 9 is inserted into this through hole. The size of the raw material gas supply hole 2 is slightly larger than the size of the raw material waste supply pipe 9 so that the raw material gas supply pipe 9 can be inserted therein. Usually, the preferred diameter of the raw material gas supply pipe 9 is 3 to 10 mm. Therefore, the diameter of the raw material gas supply hole 2 is preferably set larger than the diameter of the raw material gas supply pipe 9 by about 0.1 to 0.51.

However, the diameter of the raw material gas supply hole 2 may be large enough to fit the raw material gas supply pipe 9 into the raw material gas supply hole 2.

The carrier gas can also be introduced into a small gap 8 between the raw material gas supply hole 2 and the raw material gas supply pipe 9, as shown in FIG.

The carrier gas supply hole 3 in the gas introduction member 1
As shown in FIG. 2, is a small through hole provided around the source gas supply hole 2, and communicates with the top portion 12 of the carrier gas supply pipe IO at its lower end.

Further, the center axis of the carrier gas supply hole 3 is formed to be diagonally upward and away from the center axis of the raw material gas supply hole 2.

As shown in FIG. 2, the jet lowers of the carrier gas supply hole 3 are provided in 4 to 16 at equal intervals on the same circle from the center of the jet port 6 of the raw material gas supply hole 2.

The diameter of the carrier gas supply hole 3 is usually 1 to 3 mm.

Further, the inclination of the carrier gas supply hole 3 is set such that the distance from the raw material gas outlet 6 to the carrier gas outlet lower in the reaction chamber bottom part 5 is 3 to 20 mm. The preferable material for the gas introduction member 1 is, for example, a heat-resistant material such as graphite or molybdenum.

The shape of the gas introduction member 1 is a cylinder with a diameter of 5 to 30 mm and a thickness of 10 to 50 mm.

The raw material gas supply pipe 9 and the carrier gas supply pipe 1
0 forms a double pipe provided with the carrier gas supply pipe IO around the raw material gas supply pipe 9.

As shown in FIG. 1, the raw material gas supply pipe 9 protrudes above the carrier gas supply pipe 10, and the protruding portion is connected to the raw material gas supply hole 2 of the gas introduction member 1 as described above. It has been inserted.

A cooling fluid introduction cylinder 11 is provided around the double pipe.

Below, for example, the case where coated fuel particles are produced using the fluidized bed of the present invention as shown in FIGS. 1 and 2 will be described in detail, and the operation of the fluidized bed of the present invention will be explained in detail. .

The coated fuel particles are fuel particles used as fuel for HTR, and have a fuel core containing, for example, a carbon layer, SiCMZ
They are particles coated with a coating layer such as an rC layer.

The method for producing the coated fuel particles is a method in which a raw material gas, which is a raw material for the coating layer, is decomposed and the resulting decomposed substance is chemically vapor deposited on the surface of the fuel core to form a coating layer.

The production of the coated fuel particles is carried out in the reaction chamber of the fluidized bed of the present invention.

The fuel kernels are supplied into the reaction chamber in advance.

The raw material gas and the carrier gas are supplied to the raw material gas supply pipe and the carrier waste supply pipe.

Examples of the raw material gas include decomposable gases such as acetylene, propylene, and methyltrichlorosilane gas.

Examples of the carrier gas include inert gases such as hydrogen gas, argon gas, and nitrogen gas.

Cooling fluid is supplied to the cooling fluid introduction tube.

The cooling fluid is preferably a gas or a liquid, such as argon gas, nitrogen gas, or water.

The cooling fluid sufficiently cools the raw material gas and the carrier gas in the raw material gas supply hole and the carrier gas supply hole, and prevents thermal decomposition of the raw material gas.

The raw material gas and the carrier gas move upward through the raw material gas supply pipe and the carrier gas supply pipe, respectively, and are introduced into the raw material gas supply hole and the carrier gas supply hole in the gas introduction member.

Since the raw material gas supply pipe is inserted into the raw material gas supply hole, the raw material gas moves upward through the raw material gas supply pipe as it is.

The carrier gas moves upward through the carrier gas supply hole provided in the gas introduction member from the top of the carrier gas supply pipe.

As the cooled carrier gas is introduced into the gas introduction member, the entire gas introduction member is cooled.

Therefore, it is possible to prevent the raw material waste from causing chemical vapor deposition or depositing decomposed substances before being supplied to the reaction chamber.

Furthermore, it is preferable that the carrier gas is also introduced into the gap existing between the raw material gas supply hole and the raw material gas supply pipe.

The raw material gas that has moved upward in the raw material gas supply hole is ejected into the reaction chamber from the upper surface of the gas introduction member, that is, from the bottom surface of the reaction chamber.

Since the source gas is inserted substantially perpendicularly into the center of the source gas supply pipe or the gas introduction member, it is ejected upward into the reaction chamber.

The ejected raw material gas undergoes thermal decomposition within the reaction chamber to produce decomposed substances.

The generated decomposed substances are chemically deposited on the surface of the fuel kernels that have been supplied into the reaction chamber in advance to form the coating layer.

The carrier gas that has moved within the carrier gas supply hole is ejected into the reaction chamber from the upper surface of the gas introduction member, that is, the bottom surface of the reaction chamber.

The carrier gas supply hole in the gas introduction member is
As shown in FIGS. 1 and 2, this is a through hole formed diagonally upward toward the reaction chamber and away from the source gas supply hole.

Therefore, at the bottom of the reaction chamber, the carrier gas is radially dispersed and ejected diagonally upward and outward, as shown in FIG.

Therefore, in the reaction chamber, the carrier gas is sufficiently supplied even near the inner wall surface where the fuel nuclei tend to accumulate.

Therefore, the fluidity of the fuel kernels is improved in the reaction chamber, and the fuel kernels and the source gas are better mixed, so that the fuel kernels can evenly contact the source gas. become.

As a result, the surface of the fuel kernel can be coated with a homogeneous coating layer.

Further, as described above, when the carrier gas is introduced into the gap between the raw material waste supply pipe and the raw material gas supply hole, the raw material gas supply hole is sufficiently cooled by the surrounding carrier gas. Moreover, the concentration of the source gas at the bottom of the reaction chamber is low.

Therefore, near the spout and at the bottom of the inner wall,
The raw material gas ejected into the reaction chamber can be chemically vapor-deposited to prevent decomposed substances from accumulating.

Furthermore, in the fluidized bed of the present invention, the center upward gas linear velocity of the raw material gas jetted out from the raw material gas supply hole is increased, and the gas linear velocity of the carrier gas jetted out from the carrier gas supply hole is decreased. As a result, a velocity distribution is generated within the reaction chamber, and a stable spouted bed can be formed within the reaction chamber.

The gas linear velocity of the raw material gas can be expressed as the flow rate of the raw material gas per unit time, and the preferred flow rate of the raw material gas is 10 to 1 sO4u/min.

The gas linear velocity of the carrier gas can be expressed by the flow rate of the carrier gas per unit time, and the preferable flow rate of the carrier gas is 10 to 100 deg/min.

Further fine adjustment of the gas linear velocity of the raw material gas can be easily performed by changing the diameter of the raw material gas supply pipe.

The gas linear velocity of the carrier gas can be easily adjusted by changing the diameter 8 and the slope of the carrier gas supply hole.

The diameter of the carrier gas in the gas introduction member is
It is preferable that it is 1 to 3 ■.

If the diameter of the carrier gas is 1 mm or less, it is not possible to obtain a sufficient flow rate of the carrier gas,
Furthermore, since the gas linear velocity becomes too high, the flow of the fuel kernels at the bottom of the reaction chamber is unstable, making it difficult to form a spouted bed.

When the diameter of the carrier gas is 3-1 or more, the carrier gas bubbles (a bubble refers to a lump of gas) generated from the carrier gas supply hole become too large, so that the center upward direction This will disturb the flow of the raw material gas.

Further, it is preferable that the inclination of the carrier gas supply hole is set such that the distance from the raw material gas outlet to the carrier gas outlet is 3 to 20+u+ at the bottom of the reaction chamber.

Regarding the size of the gas introduction member, the diameter is 5 to 30 mm.
■ Otori is preferred.

If the diameter of the gas introduction member is smaller than 51, bubbles of the raw material gas and the carrier gas in the center direction mix and coalesce, making it impossible to obtain the desired gas linear velocity distribution.

In addition, when the diameter of the gas introduction member is larger than 30 layers, especially the outer FI eaves of the gas introduction member;
B. The circulation of the fuel kernels existing in the νE reaction chamber is poor, causing problems such as stagnation.

The material of the gas introducing member is preferably a heat-resistant material such as graphite or molybdenum.

The fluidized bed of the present invention is not limited to the fluidized bed as described above, and various modifications may be made as long as the object of the present invention is not impaired.

For example, the shape of the reaction chamber, the overall shape of the gas introduction member, the shape of the carrier gas supply hole, the method of installing the gas introduction member, etc. may be appropriately modified without departing from the gist of the present invention. Something comes up. Regarding the overall shape of the gas introduction member, if the upper surface has a shape that follows the shape of the bottom of the reaction chamber, and the shape allows the provision of the raw material gas supply hole and the carrier gas supply hole, There are no particular restrictions.

The carrier gas supply hole in the gas introduction member should be designed to form a stable jet bed with appropriate inclination, shape, etc. You can change it. For example, the third
As shown in the figure, the carrier gas supply hole is provided in the shape of the jet port of the gas 5 gas, or in the shape of a piece when a ring surrounding the source gas supply hole is divided into several pieces. You can also do that.

That is, as the carrier gas supply hole, in addition to the cylindrical tube shown in the embodiment, a prismatic, round, or through hole whose stepped surface strength becomes larger toward the bottom of the reaction chamber may be used. I can list many things.

In addition, as shown in FIG. 4, as for the positions of the jet ports of the carrier gas supply holes, in addition to positioning all the jet ports on the same circular center, half of the jet ports are placed in the same circle with different radii like a staggered pattern. They can also be placed alternately on the mind.

Furthermore, as shown in FIG. 5, the carrier gas supply hole may be provided in a spiral shape rotated from the bottom to the top of the gas introduction member about the central axis of the gas introduction member.

Furthermore, there are various ways of attaching the gas introduction member, as shown in FIG. 6.

FIG. 6(A) shows a method of screwing the gas introduction member into the bottom of the reaction chamber.

FIG. 6(B) shows a method of providing a threaded projection on the lower part of the gas introduction member and screwing it into the top of the cooling fluid introduction pipe of FIG.

FIG. 6(c) shows a method of closing the gap between the source gas supply pipe and the source gas supply hole in FIG. 1 and directly welding and fixing them to the bottom of the reaction chamber.

FIG. 6(d) shows a method for introducing the gas introduction member into the carrier gas supply pipe.

[Effects of the Invention] According to the present invention, by adjusting the gas linear velocity and ejection direction of the carrier gas ejected into the reaction chamber, it is possible to improve the flow state within the reaction chamber and form a stable spouted bed. In addition, it is possible to prevent the raw material gas from chemical vapor deposition at the gas inlet at the bottom of the reaction chamber, and for example, a fluidized bed can be used to produce a homogeneous coating layer even in industrial-scale hatch quantities. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a fluidized bed according to the present invention. FIG. 2 is an explanatory diagram showing an example of the gas introducing member in the present invention. FIG. 3 is an explanatory diagram showing a modification of the carrier gas supply hole in the gas introduction member. FIG. 4 is an explanatory diagram showing an example of the formation of carrier gas jet ports. FIG. 5 is an explanatory diagram showing a modification of the gas introduction member. FIGS. 6(a), (b), (c), and (d) are explanatory views showing how to attach the gas introduction member. 1. Gas introduction member, 2. Raw material gas supply hole, 3.
...Carrier gas supply hole, 4...Reaction chamber, 5...Bottom part of reaction chamber, 6...Material gas outlet, 7...Carrier gas outlet, 8...Gap, 9... - Raw material gas supply pipe, 10... Carrier gas supply pipe, II... Cooling fluid introduction tube, 12... Top part of carrier gas supply pipe, 13.
... Circumferential side of the reaction chamber, 14... Gas introduction member is attached with screws, 15... Gas introduction member is attached with welded parts. Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] A raw material gas supply hole that blows raw material gas vertically into the reaction chamber at the bottom of the reaction chamber, and a raw material gas supply hole arranged around the raw material gas supply hole and away from the central axis of the raw material gas supply hole toward the reaction chamber. What is claimed is: 1. A fluidized bed comprising: a carrier gas supply hole having a central axis directed obliquely upward;