JP2722969B2 - Gas dispersion plate for fluidized bed reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas dispersion plate of a fluidized bed reactor suitable for gas phase polymerization of olefins such as ethylene and propylene. Further, the gas dispersion plate of the present invention can be used in a fluidized bed reactor equipped with a stirrer.

[0002] The terms "polymerization" and "polymer" used in the present specification include "homopolymerization", "copolymerization", "homopolymer" and "copolymer", respectively. .

[0003]

2. Description of the Related Art In recent years,
Improvements in transition metal catalysts for olefin polymerization have dramatically improved the production capacity of olefin polymers per unit transition metal, and as a result, the operation of removing the catalyst after polymerization has been omitted. When using such a highly active catalyst,
In general, a method in which olefin is polymerized in a gas phase is employed because the operation after polymerization is the simplest. In such a gas-phase polymerization, a fluidized bed reactor is usually used frequently in order to smoothly carry out the polymerization, and the olefin or olefin-containing gas introduced from the lower portion of the reactor through an introduction pipe is uniformly dispersed by a gas dispersion plate and raised. The polymerization is carried out while flowing the catalyst particles comprising the olefin polymer and the solid particles in the fluidized bed.

In this type of fluidized bed type reactor, a porous plate has been widely used as a gas dispersion plate, but polymer particles may adhere to pores and cause blockage. Long-term operation continuation becomes impossible. The use of a material having a large pore diameter solves the above-mentioned problem of clogging to some extent, but the polymer particles fall through the pores and adhere to the wall under the gas dispersion plate, or the distance between the pores. That is, the pitch becomes longer, and a portion having poor flow may be formed between the holes. In this case, the removal of the heat of polymerization becomes insufficient, and troubles such as agglomeration of the polymer occur, and there is a high possibility that the operation will be stopped. In order to improve such a problem, there has been proposed a gas dispersion plate in which various caps are mounted on a hole of the gas dispersion plate. For example, JP-A-57-079543 discloses a roof-type cap, JP-A-58-154702 discloses a triangular pyramid-shaped cap, and JP-A-58-196205 discloses a cap using a partition wall.
JP-A-58-201802 discloses a bubble cap and JP-A-61-201802.
In Japanese Patent Application Laid-Open No. -106608, angle caps are respectively proposed.

On the other hand, irrespective of the size of the hole diameter, the flow immediately above the gas dispersion plate is liable to cause poor flow. Also in this case, troubles such as agglomeration of the polymer occur, and there is a high possibility that the operation is stopped or the product quality is deteriorated. To solve this problem,
A method was considered in which the gas blowing from the gas distribution plate was given a directivity to generate a swirling gas flow on the gas distribution plate (Tetsuo, "Reaction Engineering of Fluidized Bed", page 85, October 1983) Published by Tsuki Baifukan). In addition, JP-A-01-284509
In Japanese Unexamined Patent Publication No. 2003-157405, an integrated structure in which one or more plates in which a horizontal unidirectional blowout hole is perforated in a staggered arrangement is combined or more is disclosed. Using a gas dispersion plate having
Proposals have been made to generate a swirling flow. However, these gas dispersion plates cannot sufficiently prevent troubles such as adhesion of polymer particles and generation of lumps, and are not satisfactory for maintaining a good fluid state.

In general, in a large-scale reactor on a commercial operation scale, the gas dispersion plate must support the weight of tens of tons of polymer particles, and a supporting structure is required under the gas dispersion plate. In the gas dispersion plate described above, the holes are irregularly arranged, and therefore, in a simple structure, for example, a lattice-shaped support structure, any one of the holes is closed by the structure. Therefore, there is a disadvantage that a complicated structure, for example, a concentric support structure must be used.

[0007]

In view of such circumstances, the present inventors have intensively studied a gas dispersion plate for preventing troubles such as adhesion of polymer particles and generation of lumps and maintaining a good fluidized state. As a result, the present inventors have found a gas distribution plate that solves the problem by setting the holes in a specific arrangement and setting the direction of the cap disposed on the holes to a specific direction, and completing the present invention by further various studies. I let it.

That is, according to the present invention, there is provided a gas dispersion plate for a fluidized bed reactor, wherein a large number of holes are arranged in a square array, and the gas is blown out in a horizontal direction along the dispersion plate. Is disposed above the hole, and the direction is substantially the swirling direction of the fluidized bed, and the holes (10, 2,
0, 30 and 40), the direction is approximately the midpoint between the hole (30) on the diagonal of the hole (10) in which the cap is located and the other hole (20 or 40). In the direction of (X or Y), the smaller angle between the tangent of the circumference and the concentric circle with the cross section of the reactor is selected, and the outermost hole is near the inner wall of the reactor. A fluidized bed reactor characterized in that it is on a circle concentric with the cross section, and a cap similar to that described above is arranged on the circumference so that the gas blows out from the tangential direction of the circumference. A gas distribution plate is provided.

Hereinafter, the present invention will be described specifically. In the gas dispersion plate of the present invention, a large number of holes are arranged in a square array except for a portion near the inner wall of the reactor. In this case, the distance between the holes, that is, the pitch, is the opening ratio of the dispersion plate, that is, the total area of the opening of the hole to the total area of the reactor or the opening of the cap.
The ratio of the total area to the smaller area and the opening of the hole
Face with the smaller area of the part or the area of the opening of the cap
Determined by the product . The opening ratio is preferably designed so that the required pressure loss of the dispersion plate is about 40% of the total pressure loss in order to maintain uniform fluidization in the layer radial direction. If the pore size is less than 5 times the average particle size of the polymer particles, the gas dispersion plate may be clogged. Therefore, the pore size is preferably designed to be 5 times or more the average particle size of the polymer particles. On the other hand, if the pitch is too long, a poor flow portion is formed between the holes, so it is desirable to make the pitch as short as possible. Therefore, the aperture ratio is usually 0.5 to 10
%, The hole diameter is 5 to 30 mm, and the hole pitch is 15 to
The range is 400 mm.

FIGS. 1 to 3 each show a specific example of a cap used in the present invention, wherein a is a plan view of the cap, b is a side view thereof, and c is an elevation view thereof.
In FIG. 1, a cap 2 mounted on the hole 1 is a streamlined cap as shown in FIG. 1 a or b so as not to hinder the swirling flow of the gas and not to generate a stagnation portion upstream of the cap. Opening 3 as shown in FIG.
Has, for example, a semicircular shape, and has a structure in which gas is blown out from one horizontal direction. In this case, the outline of the opening may be a flat triangle or square. As shown in FIGS. 2 and 3, the cap may be streamlined, such as the so-called front half of a boat turned upside down. The cap having a streamlined outer shape is not limited to those shown in FIGS. With a hole having a cap having such a structure, there is no problem of polymer particles falling to the lower part of the gas dispersion plate as compared with a conventional perforated plate. By arranging the cap in a specific direction in the circumferential direction on the dispersion plate, for example, a gas flow in the circumferential direction on the gas dispersion plate, that is, a swirling flow, can be generated during fluidization. Due to this swirling flow, the flow / mixing of the entire fluidized bed, particularly at the bottom of the fluidized bed, becomes good. Even if some lump is generated, the lump can be quickly moved and swirled to the outer peripheral portion of the gas dispersion plate by the centrifugal force, and can be discharged out of the system before the lump grows large.

This cap is one side of the smallest square composed of the diagonal hole to which the gas blown out from the hole comes closest and the above-mentioned hole, and one side having the diagonal hole as an end. It is disposed so as to pass substantially through the middle portion. That is, the arrangement of the cap indicates one of the arrangements shown in FIG. FIG. 4 is a plan view of caps arranged in holes arranged in the smallest square at preferred angles in two directions shown in a and b. That is, in FIG. 4, the direction of the opening 3 of the cap 2 provided above the hole 10, that is, the gas blowing direction is substantially the midpoint (X) between the hole 30 and the hole 20 or the substantially midpoint between the hole 30 and the hole 40. (Y). The angle θ at which the cap is disposed is 10 to 30 with respect to a diagonal line connecting the hole 10 and the hole 30.
゜, preferably 15 to 25 。. Here, the angle θ is 1
In the case of 0 to 30 °, the gas blown out from the hole 10 is
It passes through a hole 30 and a hole 20 located downstream or a substantially intermediate point (X or Y) between the holes 30 and 40. However, in the gas dispersion plate of the present invention, in order to generate a swirling flow, the gas blowing direction of the cap further passes through the holes 10 arranged in the smallest square as shown in FIG. The smaller the angle θ ′ formed between the tangent of the circumference 4 to be formed and the opening 3 of the cap 2, that is, the direction in which the gas is blown out, may be selected. FIG. 5 is a plan view of the cap in which the smaller angle θ ′ between the tangent of the circumference passing through the hole and the blowing direction of the cap in FIG. 4 is selected. Then, the gas flowing from each hole is substantially blown out in the swirling direction of the fluidized bed, for example, the right turning direction or the left turning direction, and as a result,
A swirling flow is generated as a whole.

The attachment of the cap to the dispersion plate is not particularly limited as long as the method does not hinder the swirling flow generated on the dispersion plate. For example, welding and screwing can be used. Welding is preferred.

In the gas dispersion plate of the present invention, a hole is newly arranged on the outer periphery of the gas dispersion plate close to the inner wall of the reactor, and the gas is blown outward from the circumferential tangential direction. The same cap as that described above is provided. As a result, the gas can wash away particles adhering to the inner wall surface and promote flow and mixing near the inner wall surface at the bottom of the layer. The diameter of the hole, the interval between the holes, and the distance between the hole and the inner wall surface are not particularly limited as long as the above-described effects can be obtained. For example, the diameter of the holes, the distance between the holes and the distance between the holes and the inner wall surface are approximately the same as the diameters and pitches of the holes in the square array, for example, the diameter of the holes is 5 to 30 mm, the distance between the holes and the distance between the holes and the inner wall surface. Is 15 to 400 mm. Also, preferably, the cap blowing direction (angle θ ″, FIG. 6 a) is directed in the same swirling direction so as to follow the swirling flow of the gas blown out from the square array of holes, and outwardly with respect to the circumferential tangential direction.
What is necessary is just to have an angle of 0-70 degrees.

In the case where the inner diameter of the reactor is large, if the gas dispersion plate is integrated, the plate thickness is required to be about several tens of mm due to the strength of the plate, which is extremely uneconomical and difficult to manufacture. In addition, the thickness and the width of the plate are naturally limited. FIG. 6a is a plan view showing an example of the gas dispersion plate of the present invention, in which holes are arranged in a square array, and the outermost holes are near the inner wall of the reactor;
The holes are arranged at the same pitch on the same circumference which forms a concentric circle with the cross section of the reactor, and the cap 2 has a specific arrangement such that a swirling flow is generated as described above. In FIG. 6a, the cap is shown only on a part of the dispersion plate, and other parts are omitted, but the other parts are also arranged on the entire surface in the same pattern. The gas dispersion plate of the present invention can be composed of a single plate. However, as shown in FIG. 6B, two or more plates 7 constituting the dispersion plate are combined to form an integrated gas dispersion plate 5.
It can also be. In this case, the blowing direction of each cap is determined within the above angle range so as to generate a swirling flow of gas on the gas distribution plate. For installation method,
The plates are arranged without gaps, and their contact portions are connected by, for example, welding or screws, and the dispersing plate support structure 6 is installed below the gas dispersing plate and fixed thereon by welding or screws. Can be done by The gas dispersion plate of the present invention, except for its outer peripheral portion, the holes are arranged in a square array, so that the holes are not closed by the supporting structure only by appropriately adjusting the pitch of the holes provided on the outer peripheral portion of the gas dispersion plate, For example, a lattice-shaped support structure having a simpler structure than the conventional structure as shown in FIG. 6A can be used.

[0015]

As described in detail above, the use of the gas dispersion plate of the present invention allows the polymer particles to adhere and stay
The flow / mixing state near the inner wall of the reactor which is likely to agglomerate or on the gas dispersion plate is improved, and stable long-term continuous operation is achieved. Further, the gas dispersion plate of the present invention is easier to manufacture and to reinforce with a support structure than the conventional gas dispersion plate.

[0016]

【Example】

Example 1 Using a fluidized bed experimental apparatus with an inner diameter of 1000 mm, the presence or absence of a flow failure portion immediately above a gas dispersion plate was measured. The gas dispersion plate used in the fluidized bed experimental apparatus is of the same type as in FIG. 6a. In this gas dispersion plate, the diameter of the holes arranged in a square array was 16 mm, and the pitch of the holes was 66 mm. In addition, the diameter of the hole at the outer peripheral portion of the gas dispersion plate near the inner wall of the reactor is 16 m.
m, and the pitch of the holes was 66 mm. Furthermore, the blowing direction of the cap on the hole at the outer peripheral portion of the gas dispersion plate close to the inner wall of the reactor is directed in the same direction so as to follow the swirling flow of the gas blown out from the square array of holes, and with respect to the circumferential tangential direction. Angle of 30 °. The cap was of the same type as that shown in FIG. 1, and a cap having a semicircular opening was used. Colored polyethylene particles (average particle size of 920 μm) were spread over the surface until the cap was buried, and uncolored polyethylene particles were filled to a height of 1.5 m. In this state, nitrogen gas at normal pressure was fed at a flow rate of 1400 m ³ / hr and fluidized for 5 minutes. Thereafter, the polymer particles were withdrawn little by little from above, and the position of the colored polyethylene particles remaining on the gas dispersion plate was observed.As a result, it was colored over the entire gas dispersion plate, including between the holes and near the inner wall of the reactor. Almost no polyethylene particles were observed.

Comparative Example 1 In the gas dispersion plate of Example 1, a cap disposed on the circumference near the inner wall of the reactor was plugged and the same method as in Example 1 was performed. As a result, the inner wall was partially colored near the inner wall. Polyethylene particles remained without being dispersed.

[Brief description of the drawings]

FIG. 1 is a drawing showing a specific example of a cap used in the present invention, wherein a is a plan view of a cap mounted on a hole, b
Shows a side view thereof, and c shows an elevation view thereof.

FIG. 2 is a view showing a specific example of a cap used in the present invention, wherein a is a plan view of a cap mounted on a hole, b
Shows a side view thereof, and c shows an elevation view thereof.

FIG. 3 is a drawing showing a specific example of a cap used in the present invention, wherein a is a plan view of the cap mounted on a hole, b
Shows a side view thereof, and c shows an elevation view thereof.

FIG. 4 is a plan view of a cap arranged at two preferred angles in two smallest directions in a hole arranged in the smallest square.

FIG. 5 is a plan view of a cap arrangement in a case where a smaller angle θ ′ between a tangent of a circumference passing through a hole and a blowing direction of the cap in FIG. 2 is selected.

FIG. 6 is a plan view showing a specific example of the gas dispersion plate of the present invention, wherein a is a plan view of the gas dispersion plate in which a cap is shown as a part of the dispersion plate, and b is a constitution of the dispersion plate. It is the top view which took out a part of board.

[Explanation of symbols]

1, 10, 20, 30, and 40 holes, 2 caps, 3 cap openings, 4 concentric circles with the reactor cross section through the holes, 5 dispersion Plate, 6 ...
Dispersion plate support structure, 7... Plate constituting dispersion plate

Claims (10)

(57) [Claims] In a gas dispersion plate of a fluidized bed reactor, a large number of holes are arranged in a square array, and a cap having a streamlined outer shape in which gas is blown out along the dispersion plate in a horizontal direction is provided. Disposed above, wherein the direction is substantially the swirling direction of the fluidized bed, and in the smallest square formed by the holes (10, 20, 30, and 40), the direction is such that the cap is disposed. Approximately the midpoint (X or Y) of hole (30) on the diagonal of hole (10) and other holes (20 or 40)
And the smaller angle between the tangent of the circumference and the concentric circle with the reactor cross section is selected.The outermost hole is near the inner wall of the reactor and forms a concentric circle with the reactor cross section. A gas dispersion plate for a fluidized bed reactor, wherein the gas dispersion plate is provided on a circumference, and a cap similar to the above is disposed on the circumference so that gas is blown outward from a tangential direction of the circumference. 2. The gas dispersion plate according to claim 1, wherein the cap has a semicircular outer shape at the opening. 3. The gas dispersion plate according to claim 1, wherein the cap is a cap having an opening having a triangular outline. 4. The gas dispersion plate according to claim 1, wherein the cap is a cap having a square outline of the opening. 5. The diameter of the holes arranged in a square array is 5 to 3.
0 mm and the pitch of the holes is 15 to 400 mm.
The gas dispersion plate as described in the above. 6. The gas dispersion plate according to claim 1, wherein the diameters of the holes arranged on the same circumference in the vicinity of the inner wall of the reactor are 5 to 30 mm, and the distance between the holes and the distance between the holes and the inner wall are 15 to 400 mm. . 7. A cap at the upper part of the outermost hole is provided outwardly with respect to a tangential direction of a circle concentric with the cross section of the reactor.
The gas distribution plate according to claim 1, wherein the gas distribution plate is disposed at an angle of 0 to 70 °. 8. A plate (7) wherein the gas dispersion plate constitutes a dispersion plate.
2. The gas dispersion plate according to claim 1, wherein the gas dispersion plate is formed by combining at least two sheets of the gas dispersion plate. 9. The gas dispersion plate according to claim 1, wherein the gas dispersion plate has a stirrer in the fluidized bed. 10. The gas dispersion plate according to claim 1, wherein the gas dispersion plate is a gas dispersion plate provided with a support structure (6) provided on a lower surface of the plate and reinforced.