JP2003117381A - Gas diffusion tube of fluidized bed reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas diffusion column for a fluidized bed reactor in which reaction efficiency is improved compared to the conventional reactor. SOLUTION: The gas diffusion column is provided with: a cylindrical body provided on a partition plate in the fluidized bed reactor in which solid particles are fluidized by the gas; and an orifice attached to the lower end of the cylindrical body and introducing the gas into the fluidized bed. A swirling means for swirling the gas passing through the orifice and ascending is provided inside the cylindrical body. It is preferable that the swirling means is a spiral member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas diffusion cylinder of a fluidized bed reactor, and in particular, it is an effective technique for promoting the reaction between solid particles such as a catalyst to be fluidized and a fluidizing gas.

[0002]

2. Description of the Related Art A fluidized bed reactor is an effective device for promoting a chemical reaction in a solid-gas reaction system. As shown in FIG. 4, solid particles (catalyst particles) 1 are made to flow by a gas 2. It is layered to increase the contact area between the gas and solid particles. Therefore, even in the field of the chemical industry, oxidization reaction at a uniform temperature and with large heat generation, for example, when benzene or butane is air-oxidized to produce oleic acid, or naphthalene is air-oxidized to produce phthalic anhydride. Is used for.

In a fluidized bed reactor 3 for producing these substances, air (gas) 2 as a raw material is charged into the fluidized bed reactor in order to fill the solid particles 1 as catalyst particles and maintain the fluidized state. Blow from the bottom of 3. Usually, this gas 2 has a gas diffusion cylinder (also called a diffuser) 4 having a narrow gas inlet side and a wide gas outlet side so as to spread as uniformly as possible over the entire fluidized bed.
(The reactor has a structure in which an upper space 6 for forming a fluidized bed 11 and a lower space 7 are divided) and is vertically provided, and is blown through it. Although there are various shapes of the gas diffusion cylinder 4, it is possible to prevent the solid particles (catalyst particles) 1 from dropping into the lower space 7 of the fluidized bed reactor 3 when the blowing of gas is stopped and to perform maintenance. A cylindrical shape as shown in FIGS. 2A and 2B is widely used because it is easy. That is, the partition plate 5 in the reactor
A cylindrical body having a circular cross section (hereinafter referred to as a cylindrical body 8), which is joined by welding, is basically used, and the lower end of the cylindrical body 8 is covered with a cap 9 having a through hole in a part of the end face. Has become. A plate having a small diameter through-hole (referred to as an orifice 10) is inserted between the cap 9 and the lower end of the cylindrical body 8 to form a gas introduction port to the fluidized bed existing above. There is. The cap 9 is of a screw type so that it can be easily replaced with a new one when the orifice 10 is worn. Also, the orifice 1
0 is usually the linear velocity of the passing gas is 50 to 100 m /
It is designed to be s. Further, the cylindrical body 8
Has a flat cross-sectional area several tens of times larger than that of the orifice 10, and the linear velocity of the gas is greatly increased above the orifice 10 so that the flowing solid particles 1 do not easily collide with the gas and are not easily ground or worn. It is becoming lower.

[0004]

By the way, in the inside of such a conventional gas diffusion tube (hereinafter, simply referred to as diffusion tube 4), the inner wall surface is smooth, as shown in FIG. 2 (b). The gas 2 flowing into the diffusion cylinder 4 through the orifice 10 rises linearly. When the gas 2 reaches the upper fluidized bed in this state, the gas rises as bubbles in the fluidized bed as it is. Generally, in a fluidized bed, a chemical reaction proceeds at the contact portion between the bubbles and the solid particles which are catalysts, and therefore the reaction rate is greatly affected by the contact area between the bubbles and the solid particles.

Therefore, in order to increase the reaction rate, the contact area between the bubbles and the flowing solid particles should be increased. This is nothing but reducing the diameter of the bubbles, that is, the diameter of the bubbles, and many attempts have been made to reduce the diameter of the bubbles as compared with the related art. For example, it is generally known that a dispersion plate is installed horizontally in the fluidized bed, or the inner diameter of the diffusion tube is reduced. However, the method of horizontally installing the dispersion plate in the fluidized bed can surely achieve the redispersion of the bubbles, but since the upward and downward movement of the solid particles forming the fluidized bed is hindered, the dispersion plate above the dispersion plate is prevented. Or, a phenomenon disadvantageous to the reaction such as a difference in ambient temperature appears below. That is, as described above, a chemical reaction employing a fluidized bed reactor is often accompanied by a large reaction heat such as a partial oxidation reaction. However, in the partial oxidation reaction, controlling the atmospheric temperature affects the reaction yield. The installation of the dispersion plate is not preferable because the runaway of the reaction due to the temperature difference may occur. On the other hand, when the inner diameter of the diffusion tube is reduced, the aperture ratio is decreased, the pressure difference between the upper end and the lower end of the diffusion tube is increased, and the power consumption of the blower that blows the gas is increased. To prevent this problem, it is easy to increase the number of diffusion tubes installed. However, if the inner diameter of the diffusion tube is halved, the number of installations will be four times, and not only the construction cost but also the problem of additional welding work and the like will occur.

In view of such circumstances, an object of the present invention is to provide a gas diffusion tube of a fluidized bed reactor capable of further enhancing the reaction efficiency by one step.

[0007]

The diffusion cylinder is not limited to the cylindrical shape, and as its name implies, the diffusion cylinder spreads the gas flow for fluidizing the solid particles by self-diffusion so that the gas can spread over the entire area of the fluidized bed. It is for wide and even distribution. Therefore, in the partition plate of one fluidized bed reactor,
A large number of diffusion tubes are installed.

In order to achieve the above object, the inventor first examined the gas flow in such a diffusion cylinder and found that the gas passing through the orifice simply rises linearly. Then, paying attention to this knowledge, it was thought that it would suffice if the bubbles could be dispersed in the fluidized bed more than before without increasing the number of diffusion cylinders simply by changing the direction of the gas flow, and the research was continued. As a result, they have found that the bubble diameter can be effectively reduced by making the gas rising in the diffusion tube into a swirl flow, and completed the present invention.

That is, according to the present invention, a cylinder provided on a partition plate in a fluidized bed reactor for fluidizing solid particles with a gas, and an orifice attached to the lower end of the cylinder for guiding the gas into the fluidized bed. In a gas diffusion tube equipped with
A gas diffusion tube of a fluidized bed reactor, characterized in that swirling means for swirling gas rising through the orifice is provided inside the cylindrical body. In this case, it is preferable that the turning means is a spiral member.

According to the present invention, the rising gas in the diffusion cylinder swirls smoothly and stably, and the diameter of the bubbles introduced into the fluidized bed becomes smaller than before. As a result, the contact area between the solid particles and the gas in the fluidized bed is further increased, the chemical reaction is promoted, and the yield and productivity of the reaction product are improved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, considering the background of the invention,
An embodiment of the present invention will be described.

Generally, in the flow reactor 3, 50 μm to
The solid particles 1 having an average particle diameter of several mm are fluidized by the gas 2, and so-called "fluidized reaction bed (hereinafter, simply fluidized bed 11
That) ”is formed. This fluidized bed is in a state almost similar to a liquid. That is, when gas is blown into the liquid in a vertical direction from below, bubbles are generated in the liquid and the bubbles rise due to the difference in density between the liquid and the bubbles, but also in the solid-gas fluidized bed, It is thought that it will be exactly the same as this.

On the other hand, when gas is blown into the liquid in an oblique direction from the lower side, since the vector of the ascending force of the gas and the inertial force due to the difference in density are different, the bubbles are split by the viscosity of the water and the gas is blown from the vertical direction. The diameter of the bubbles is smaller than that in the case of blowing. Considering the similarity between the liquid and the solid-gas fluidized bed, this phenomenon may occur in the same manner in the solid-gas fluidized bed.

Therefore, the inventor conducted a flow experiment using glass beads as the solid particles and air as the gas in order to confirm that this phenomenon occurs in the solid-gas fluidized bed. At that time, it is possible to install the diffusion cylinder by inclining it from the vertical, but considering the application to the actual installation,
It is difficult to put it into practical use because it needs to be extensively modified. Therefore, as shown in FIG. 1, a means 14 (helix-shaped member) for swirling the passing gas 2 is provided inside the cylindrical diffusion tube 4 provided vertically on the partition plate 5 of the fluidized bed reactor. I chose This is because, even if the diffusion cylinder 4 is not installed obliquely, the swirled gas 2 is discharged as bubbles into the fluidized bed from the upper end (exit) of the diffusion cylinder 4 in an oblique direction. The result of the experiment is
As in the case of the liquid, it was observed that the diameter of the bubble 12 becomes smaller because the vector of the ascending force of the bubble and the vector of the inertial force of the swirling gas due to the difference in density between the solid particles forming the fluidized bed and the bubble are different. . Therefore, the diffusion cylinder 4 to which the swivel means 14 is attached is defined as the present invention.

Various types of turning means 14 are conceivable, so the present invention is not limited thereto.
It is preferably a helical member. As the helical member, a twisted ribbon-shaped member as shown in FIGS. 4A and 4B can be exemplified. The twisted ribbon shape has a high porosity, and therefore is preferable because the pressure loss when passing gas is reduced. Further, the twist angle 15 for swirling the gas is not particularly limited in the present invention. However, twist angle 1
If 5 is small, the effect of the present invention is enhanced, but the pressure loss tends to be large. On the other hand, if the twist angle 15 is large, the pressure loss is small, but the effect of the present invention is small. According to the research conducted by the inventor, the twist angle of the swiveling means 14 varies from 45 ° to 135, though it depends on the situation of use.
It is recommended to use °.

[0016]

EXAMPLE A gas diffusion tube (inner diameter 35 mm, length 250 mm, 35 in each partition plate) installed in a fluidized bed reactor for producing phthalic anhydride having two partition plates as shown in FIG.
Phthalic anhydride was produced depending on whether a twisted ribbon-shaped member (twist angle 90 °) as shown in FIG. The average particle size of the catalyst particles is 100 μm, and the fluidizing gas (air)
Was introduced from the lower part of the reactor, and naphthalene gas was introduced from the supply port provided on the side wall of the fluidized bed. The reaction conditions were the same regardless of the presence or absence of the twisted ribbon-shaped member. Since it is difficult to directly measure the diameter of the bubbles generated in the fluidized bed, measure the density of the fluidized bed with and without the twisted ribbon-shaped member, and evaluate the fluctuation range. I chose Here, the fluidized bed density is such that a pressure gauge is installed at a certain distance in the height direction of the fluidized bed reactor,
It is a value obtained by measuring the differential pressure and dividing the measured value by the distance. Further, the smaller the fluctuation range, the smaller the bubble diameter.

When a twisted ribbon-shaped member is charged (example of the present invention), the fluctuation range of the fluidized bed density is 10 g / m ^3.
However, when the member is not charged (conventional example),
The fluctuation range of the fluidized bed density was 25 g / m ³ , and the bubble diameter was reduced by charging the twisted lyobon-shaped member. Also, by loading a twisted ribbon-shaped member, the yield of phthalic anhydride is about 10% higher than before.
Improved.

[0018]

As described above, according to the present invention, the bubble diameter of the gas introduced into the fluidized bed is reduced and the reaction efficiency is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a gas diffusion cylinder of a fluidized bed reactor according to the present invention.

2A and 2B are views showing a gas diffusion cylinder of a conventional fluidized bed reactor, FIG. 2A is a perspective view of the appearance, and FIG. 2B is a sectional view.

3A and 3B are views showing a gas swirling means, FIG. 3A is a cross section of a twisted ribbon-shaped member, and FIG. 3B is a plane.

FIG. 4 is a cross-sectional view showing an example of a fluidized bed reactor.

[Explanation of symbols]

1 Solid particles (catalyst particles) 2 gas 3 fluidized bed reactor 4 gas diffusion tubes 5 partition boards 6 Upper space 7 lower space 8 cylindrical body 9 cap 10 Orihuis 14 Gas turning means 15 helix angle

Claims (2)

[Claims] 1. A cylinder provided on a partition plate in a fluidized bed reactor for fluidizing solid particles with a gas, and an orifice attached to the lower end of the cylinder to guide the gas into the fluidized bed. The gas diffusion tube of a fluidized bed reactor, wherein a swirling means for swirling a gas rising through the orifice is provided inside the cylindrical body. 2. The gas diffusion cylinder of the fluidized bed reactor according to claim 1, wherein the swirling means is a spiral member.