JPH06136013A - Gas diffusion plate of fluidized bed type reactor - Google Patents

Abstract

PURPOSE:To obtain a gas diffusion plate for a fluidized bed type reactor, improved in a flowing and mixing state of polymeric particles, capable of attaining stabilized continuous operation for a long period and suitable for the vapor polymerization of olefins. CONSTITUTION:This gas diffusion plate for a fluidized bed type reactor has many holes 10, 20, 30 and 40 arranged in a square array and caps 2 of a streamlined outer shape having an opening 3 for blowing a gas in the horizontal direction along the gas diffusion plate are arranged on the holes. This blowing direction is substantially the turning direction of the fluidized bed and further the direction of nearly the intermediate point (X or Y) of the hole 30 on the diagonal line of the hole 10 where each cap 20 is arranged and the other hole 20 or 40 in the minimum square formed from the holes 10, 20, 30 and 40 and a smaller angle of the direction from the tangent line to the circumference forming a concentric circle with the reactor cross section is simultaneously selected. The holes on the outermost circumference are located near the inner wall of the reactor and on the circumference forming a concentric circle with the cross section of the reactor. The similar caps are arranged thereon so as to blow the gas from the tangent line to the circumference to the outside.

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. The gas dispersion plate of the present invention can also be used in a fluidized bed reactor equipped with a stirrer.

The terms "polymerization" and "polymer" used in the present specification are meant to include "homopolymerization" and "copolymerization" and "homopolymer" and "copolymer", respectively. .

[0003]

2. Description of the Related Art In recent years,
Due to the improvement of the transition metal catalyst for olefin polymerization, the production capacity of the olefin polymer per unit transition metal has been dramatically improved, and as a result, the catalyst removal operation after the polymerization has been omitted. When using such a highly active catalyst,
Since the operation after the polymerization is the simplest, the method of carrying out the polymerization of the olefin in the gas phase is generally adopted. In such gas phase polymerization, a fluidized bed reactor is often used to smoothly proceed the polymerization, and the olefin or the olefin-containing gas introduced from the lower part of the reactor through the introduction pipe is uniformly dispersed by the gas dispersion plate and raised. Then, polymerization is carried out while flowing the catalyst particles composed of the olefin polymer and solid particles in the fluidized bed.

In this type of fluidized bed reactor, a porous plate has been widely used as a gas dispersion plate, but polymer particles may adhere to the pores to cause clogging. It becomes impossible to continue long-term operation. If a large pore size is used here, the problem of clogging is solved to some extent, but polymer particles fall through the holes and adhere to the wall under the gas dispersion plate, or the distance between the holes is small. That is, the pitch becomes long, and a poor flow portion may occur in the portion between the holes. In this case, the heat of polymerization is insufficiently removed, and troubles such as agglomeration of the polymer occur and it is highly possible that the operation is stopped. In order to improve such problems, it has been proposed that various caps are attached on the holes of the gas dispersion plate. For example, in JP-A-57-079543, a roof-shaped cap, in JP-A-58-154702, a triangular pyramid-shaped cap, and in JP-A-58-196205, a cap using a partition wall,
In JP-A-58-201802, a bubble cap is used,
-106608 publication proposes angle caps respectively.

On the other hand, irrespective of the size of the hole diameter, flow failure is likely to occur immediately above the gas dispersion plate. In this case also, there is a high possibility that troubles such as agglomeration of the polymer will occur, resulting in operation stop and product quality deterioration. As a way to solve this problem,
A method has been considered in which gas is blown out from a gas dispersion plate so as to have directivity, and a swirling gas flow is generated on the gas dispersion plate (Hippan, "Reaction Engineering of Fluidized Bed", p. 85, 1983, 10). Published by Geifufukan). In addition, Japanese Patent Laid-Open No. 01-284509
In the publication, horizontal one-way blowing caps are arranged on concentric circles, and in JP-A-03-157405, one or more plates having holes for horizontal one-way blowing are combined in a zigzag arrangement to form an integrated structure. Using a gas dispersion plate having
Proposals have been made to generate swirl flow. However, these gas dispersion plates cannot sufficiently prevent troubles such as adhesion and lump formation of polymer particles, and are not satisfactory for maintaining a good fluid state.

[0006] Generally, in a large-scale reactor on a commercial operation scale, the gas dispersion plate must support the weight of several tens of tons of polymer particles, and a support structure is required under the gas dispersion plate. Since the holes are irregularly arranged in the gas dispersion plate of (1), any hole is blocked by the structure in a simple structure, for example, a lattice-like support structure. Therefore, there is an inconvenience that it is unavoidable to use a complicated structure, for example, a concentric support structure.

[0007]

In view of the above circumstances, the present inventors have diligently studied a gas dispersion plate for preventing troubles such as adhesion and agglomeration of polymer particles and maintaining a good flow state. As a result, the inventors have found a gas dispersion plate that solves the problem by arranging the holes in a specific arrangement and by making the direction of the cap disposed on the holes in a specific direction, and further completed various studies to complete the present invention. Let

That is, according to the present invention, in a gas dispersion plate of a fluidized bed reactor, a large number of holes are arranged in a square array, and the gas is blown out horizontally along the dispersion plate. Is disposed above the holes, 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). (X or Y) orientation and a smaller angle between the cross section of the reactor and the tangent of the concentric circle is selected, and the outermost hole is located near the inner wall of the reactor. A fluidized bed reactor characterized in that it is on a circumference forming a concentric circle with a cross section, and that a cap similar to the above is arranged so that gas is blown to the outside of the tangential direction of the circumference. A gas dispersion plate is provided.

The present invention will be specifically described below. In the gas dispersion plate of the present invention, a large number of holes are arranged in a square array except for the vicinity of the inner wall of the reactor. In this case, the distance between the holes, that is, the pitch is determined by the opening ratio of the dispersion plate, that is, the ratio of the total area of the openings of the gas distribution plate to the total cross-sectional area of the reactor, and the hole diameter. 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 radial direction of the bed.
If the pore size is less than 5 times the average particle size of the polymer particles, the gas dispersion plate may be clogged, so it 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, flow-defective portions are formed between the holes, so it is desirable to make it as short as possible. Therefore, the aperture ratio is usually 0.5 to 10%, the diameter of the holes is 5 to 30 mm, and the pitch of the holes is 15 to 400 mm.

1 to 3 are drawings showing a specific example of a cap used in the present invention, in which 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. 1a or b so as not to impede the swirling flow of gas and to not generate a retention part upstream of the cap. Opening 3 as shown in FIG. 1c
Has a structure in which a gas is blown out from one horizontal direction. In this case, the outline of the opening may be a flat triangle or a quadrangle. As shown in FIGS. 2 and 3, the cap may have a streamlined shape in which a so-called front half of a boat is turned over. The streamlined cap is not limited to the one shown in FIGS. With the holes having the cap having such a structure, there is no problem of the polymer particles falling to the lower portion of the gas dispersion plate as compared with the conventional porous plate. By arranging this cap, for example, in a specific circumferential direction on the dispersion plate, a circumferential gas flow, that is, a swirl flow, can be generated on the gas dispersion plate during fluidization. This swirling flow improves the flow and mixing in the entire fluidized bed, especially in the bottom of the bed. Even if some lumps are formed, the lumps 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 lumps grow large.

This cap is one side of the smallest square composed of the hole and the hole on the diagonal line to which the gas blown from the hole is closest, and the side of which the end is the hole on the diagonal line. It is arranged so as to pass through the substantially middle portion. That is, the arrangement of the caps means any one of the arrangements shown in FIG. FIG. 4 is a plan view of the caps arranged in the smallest square holes at the preferred angles in the two directions shown in a and b. That is, in FIG. 4, the direction of the opening 3 of the cap 2 provided on the upper part of the hole 10, that is, the gas blowing direction, is approximately the midpoint (X) between the holes 30 and 20, or the approximately midpoint between the holes 30 and 40. (Y) is mentioned. The angle θ for disposing the cap is 10 to 30 with respect to the diagonal line connecting the holes 10 and 30.
Is preferably 15 to 25 °. Where the angle θ is 1
When the angle is 0 to 30 °, the gas blown from the hole 10 is
It passes through the hole 30 and the hole 20 or the hole 30 and 40 located at the downstream side at a substantially midpoint (X or Y). However, in order to generate a swirling flow, the gas dispersion plate of the present invention has a gas blowing direction of the cap that passes through the holes 10 arranged in the smallest square and is concentric with the reactor cross section, as shown in FIG. The angle θ ′ formed by the tangent to the circumference 4 and the opening 3 of the cap 2, that is, the gas blowing direction may be selected to be smaller. FIG. 5 is a plan view of the cap in which the smaller angle θ ′ between the tangent to 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, in the right swirling direction or the left swirling direction, and as a result,
A swirl flow is generated as a whole.

The attachment of the cap to the dispersion plate is not particularly limited as long as it is a method that does not interfere with the swirling flow generated on the dispersion plate. For example, welding or screws can be used. Welding is preferred.

Further, in the gas dispersion plate of the present invention, holes are newly arranged on the outer circumference of the gas distribution plate close to the inner wall of the reactor, and the gas is blown outward from the circumferential tangential direction. A cap similar to is provided. As a result, the gas can wash away particles adhering to the inner wall surface, and promote the flow and mixing near the inner wall surface of the bed bottom. The diameter of the holes, the distance between the holes, and the distance between the holes and the inner wall surface are not particularly limited as long as the above 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 the same as the diameter and the pitch 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 inner wall surface and the hole. Is 15 to 400 mm. In addition, preferably, the blowing direction of the cap (angle θ ″, FIG. 6a) is directed in the same swirling direction along the swirling flow due to the gas blown out from the holes of the square arrangement, and is 2 outwards with respect to the circumferential tangential direction.
It may have an angle of 0 to 70 °.

When the inner diameter of the reactor is large, if the gas dispersion plate is integrated, the plate thickness is required to be several tens of millimeters because of the strength of the plate, which is very uneconomical and difficult to manufacture. In addition, there is a natural limitation on the thickness and width of the plate. FIG. 6a is a plan view showing an example of the gas distribution plate of the present invention, in which the holes are arranged in a square array, and the outermost holes are near the inner wall of the reactor,
The holes are arranged at equal pitches on the same circumference forming a concentric circle with the reactor cross section, and the cap 2 has a specific arrangement so 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 may be composed of a single plate, but as shown in FIG. 6b, two or more plates 7 constituting the dispersion plate are combined to form an integrated gas distribution plate 5.
Can also be In this case, the blowing direction of each cap is determined within the above angle range so that a swirling flow of gas is generated on the gas dispersion plate. As an installation method,
Arranging the plates without gaps, connecting the contact parts with each other, for example, by welding or screws, or by installing the dispersion plate support structure 6 under the gas dispersion plate and fixing it with welding or screws or the like. Can be done by Since the gas dispersion plate of the present invention has a square array of holes other than the outer peripheral portion thereof, the holes are not blocked by the support structure simply by appropriately adjusting the pitch of the holes provided in the outer peripheral portion of the gas dispersion plate, For example, a lattice-like support structure having a simpler structure than the conventional one as shown in FIG. 6a can be used.

[0015]

As described above in detail, the use of the gas dispersion plate of the present invention allows the polymer particles to be adhered and retained due to the retention of the polymer particles.
The fluidized / mixed state near the inner wall of the reactor, which tends to agglomerate, or on the gas dispersion plate is improved, and stable long-term continuous operation is achieved. In addition, the gas dispersion plate of the present invention is easier to manufacture and reinforce with the support structure than the conventional gas dispersion plate.

[0016]

【Example】

Example 1 Using a fluidized bed experimental apparatus having an inner diameter of 1000 mm, the presence or absence of a poor flow portion immediately above the gas dispersion plate was measured. The gas distribution plate used in the fluidized bed experimental apparatus is of the same type as in FIG. 6a. In this gas dispersion plate, the holes arranged in a square array had a diameter of 16 mm and a hole pitch of 66 mm. Also, the diameter of the holes on the outer periphery 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. Further, the blowing direction of the cap on the holes on the outer periphery of the gas distribution plate near the inner wall of the reactor is directed in the same direction along the swirling flow due to the gas blown from the holes of the square array, 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 920 μm) were laid on the entire surface until the cap was embedded, and the same 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 to fluidize for 5 minutes. After that, the polymer particles were extracted little by little from above, and the positions of the colored polyethylene particles remaining on the gas dispersion plate were observed.As a result, the entire gas dispersion plate was colored, including the spaces between the holes and the vicinity of the inner wall of the reactor. Little polyethylene particles were observed.

Comparative Example 1 In the gas dispersion plate of Example 1, the cap placed on the circumference of the inner wall of the reactor was capped and the same procedure as in Example 1 was carried out. As a result, the inner wall was partially colored. The polyethylene particles thus formed remained without being dispersed.

[Brief description of drawings]

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

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

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

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

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

FIG. 6 is a plan view showing a specific example of the gas dispersion plate of the present invention, a is a plan view of the gas dispersion plate in which a cap is shown in a part of the dispersion plate, and b is a 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 ... Circumferences that pass through the holes and form concentric circles with the reactor cross section, 5 ... Dispersion Board, 6 ...
Dispersion plate support structure, 7 ... Plates constituting the dispersion plate

[Procedure amendment]

[Submission date] October 13, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

The present invention will be specifically described below. In the gas dispersion plate of the present invention, a large number of holes are arranged in a square array except for the vicinity of 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 openings of the holes or the opening of the cap with respect to the total area of the reactor.
Of the total area of the above and the smaller area , and the opening of the above holes
Area with smaller area or opening area of cap
It is 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 radial direction of the bed. If the pore size is less than 5 times the average particle size of the polymer particles, the gas dispersion plate may be clogged, so it 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, flow-defective portions are formed between the holes, so it is desirable to make it as short as possible. Therefore, the aperture ratio is usually 0.5 to 10
%, The diameter of the holes is 5 to 30 mm, and the pitch of the holes is 15 to
It is in the range of 400 mm.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuyuki Takagi 5-1 Anezaki Kaigan, Ichihara City, Chiba Sumitomo Chemical Co., Ltd.

Claims (10)

[Claims] 1. A gas dispersion plate of a fluidized bed reactor, wherein a large number of holes are arranged in a square array, and a cap having a streamlined outer shape is provided so that gas is blown out horizontally along the dispersion plate. In the smallest square above which the direction is substantially the swirl direction of the fluidized bed and which is formed by the holes (10, 20, 30 and 40), which direction the cap is located. Near the midpoint (X or Y) between the hole (30) on the diagonal of the hole (10) and the other holes (20 or 40)
And the smaller angle between the reactor cross section and the tangent to the concentric circle, 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, which is on a circumference and is provided with a cap similar to the above so that the gas blows out from the tangential direction of the circumference. 2. The gas dispersion plate according to claim 1, wherein the cap has a semicircular outline of the opening. 3. The gas dispersion plate according to claim 1, wherein the cap is a cap whose opening has a triangular outline. 4. The gas dispersion plate according to claim 1, wherein the cap has a quadrangular outline of its 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 described. 6. The gas dispersion plate according to claim 1, wherein the diameter of the holes arranged on the same circumference in the vicinity of the inner wall of the reactor is 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 on the outer side with respect to the tangential direction of the circumference of a circle concentric with the reactor cross section.
The gas dispersion plate according to claim 1, wherein the gas dispersion plate is arranged at an angle of 0 to 70 °. 8. A plate (7), wherein the gas dispersion plate constitutes the dispersion plate.
The gas dispersion plate according to claim 1, which is a gas dispersion plate formed by combining at least two of them as an integrated structure. 9. The gas dispersion plate according to claim 1, wherein the gas dispersion plate has a stirrer in a fluidized bed. 10. The gas dispersion plate according to claim 1, wherein the gas distribution plate is a gas dispersion plate formed by reinforcing a support structure (6) on the lower surface of the plate.