JP2002060402A - Flooded polymerization reactor and process for withdrawing polymerized slurry from flooded polymerization reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flooded polymerization reactor with which polymerization slurry can be withdrawn smoothly without clogging a withdrawing valve because the polymer does not stop at the withdrawing valve, to provide a process for withdrawing polymerization slurry from the flooded polymerization reactor, and to provide a preparation process of a polyolefin using this withdrawing process. SOLUTION: This flooded polymerization reactor has an accumulator, which is fixed on the flooded polymerization reactor which has at least a polymerization monomer-supplying apparatus, a catalyst-supplying apparatus, and a polymerization-slurry-withdrawing apparatus. In a process for withdrawing polymerization-slurry, the polymerization-slurry is continuously withdrawn from the flooded polymerization reactor by fully opening the withdrawing valve for the polymerization-slurry, which is normally slightly opened, for a short period of time periodically with a certain interval. In another process for withdrawing polymerization-slurry, the polymerization-slurry is withdrawn from the flooded polymerization reactor in a batch process by fully opening the withdrawing valve for the polymerization-slurry, which is normally fully closed. A polyolefin is prepared using either one of these processes for withdrawing polymerization-slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a full polymerization reactor,
Discharging the polymerization slurry from the flooded polymerization reactor,
And a method for producing a polyolefin using the discharge method. More specifically, since the polymer does not stay in the discharge valve portion, the discharge valve can be smoothly discharged without closing the discharge valve, and the polymerization slurry is discharged from the full polymerization reactor. The present invention relates to a method for discharging and a method for producing polyolefin using the discharging method.

[0002]

2. Description of the Related Art Known methods for producing polyethylene, polypropylene and the like include a solvent method, a bulk method, and a gas phase method. Among them, the solvent method and the bulk method can be classified into a liquid filling method and a method having a liquid phase portion and a gas phase portion.

As a method of discharging a polymerization slurry in the flooding method, a method is known in which a discharge device is installed in a polymerization reactor and the polymerization slurry is discharged from the polymerization reactor using the discharge device. . As a method of discharging the polymerization slurry using the discharge device, a discharge valve of the discharge device is opened so as to keep the polymerization pressure constant, a method of continuously discharging while automatically adjusting the opening degree, and a method of completely closing the discharge valve. A method is known in which the discharge valve is fully opened to discharge in batches while maintaining the polymerization pressure.

However, in the former method, when a polymer having a large particle size exists in the polymerization slurry or when the plant scale is small and the discharge flow rate of the polymerization slurry must be reduced, the polymer stays in the discharge valve. In some cases, the discharge valve may be closed, making smooth discharge difficult.In the latter method, it is necessary to limit the discharge flow per discharge in order to maintain polymerization pressure. It may become large and long-term stable operation may become difficult.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a full polymerization reactor capable of smoothly discharging a polymerization slurry without blocking the discharge valve because the polymer does not stay at the discharge valve. A method for discharging a polymerization slurry from the flooded polymerization reactor, and a method for producing a polyolefin using the discharge method.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above situation, and as a result, have found that a full polymerization reactor having at least a monomer supply device for polymerization, a catalyst supply device, and a device for discharging a polymerization slurry. , A full polymerization reactor equipped with an accumulator in the reactor, while discharging the polymerization slurry by slightly opening the discharge valve of the polymerization slurry,
At a certain interval, the discharge valve is fully opened for a short time,
The method for discharging the polymerization slurry, which continuously discharges the polymerization slurry from the full polymerization reactor, or the fully closed polymerization slurry discharge valve is fully opened, and the polymerization slurry is discharged from the full polymerization reactor. The inventors have found that the above problem can be solved by a method of discharging a polymerization slurry discharged in a batch, and have completed the present invention.

That is, the present invention relates to a flooded polymerization reactor having at least a polymerization monomer supply device, a catalyst supply device and a polymerization slurry discharge device, wherein the reactor is provided with an accumulator. It is related. Also, the present invention, while discharging the polymerization slurry by slightly opening the discharge valve of the polymerization slurry, at a certain interval, the discharge valve is fully opened for a short time, and the polymerization slurry is continuously discharged from the full polymerization reactor. The method relates to a method for discharging a polymerization slurry to be discharged, or a method for discharging a polymerization slurry in which the polymerization slurry is discharged in batches from the full polymerization reactor by fully opening a discharge valve of a polymerization slurry that is completely closed. is there. Further, the present invention relates to a method for producing a polyolefin using any one of the above-mentioned methods for discharging a polymerization slurry. Hereinafter, the present invention will be described in detail.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION (1) A flooded polymerization reactor having at least a monomer feeder for polymerization, a catalyst feeder, and a discharge device for a polymerization slurry, in which an accumulator is installed in the reactor. The polymerization monomer supply device used in the present invention is not particularly limited, and is a device capable of supplying the polymerization monomer to the polymerization reactor, for example, a device capable of supplying the polymerization monomer alone, a polymerization monomer And an apparatus capable of supplying a solution obtained by diluting the compound with a solvent. Examples of the monomer for polymerization include ethylene and propylene, and examples of the solvent include butane and hexane.

The catalyst supply device used in the present invention is not particularly limited, and is a device capable of supplying a polymerization catalyst to a polymerization reactor. For example, a catalyst slurry obtained by converting a polymerization catalyst into a slurry with a polymerization monomer or a solvent is used. And a device capable of simultaneously supplying a polymerization catalyst and a co-catalyst. Examples of the polymerization catalyst include a Ziegler-Natta type catalyst, and examples of the co-catalyst include organoaluminum. Examples of the polymerization monomer and the solvent include those described above.

The discharge device for the polymerization slurry used in the present invention comprises a transfer pipe from the full polymerization reactor to the next step and a discharge valve provided in the middle thereof.
In order to prevent the stagnation of the polymer, the discharge valve is preferably of an angle type. Further, in order to smoothly discharge the polymer having a large particle diameter, it is preferable to design the valve body of the discharge valve so that the flow path area when the discharge valve is fully opened is large.

The accumulator used in the present invention generally has a structure having a balloon-shaped rubber pladder inside a metal main body container, and plays a role of suppressing a large pressure drop of a full polymerization reactor. Have The large pressure drop of the full polymerization reactor is a sudden drop in pressure of the full polymerization reactor caused by discharging a large amount of polymerization slurry at a time when the opening of the discharge valve is increased. The pressure drop causes problems such as boiling of the polymerization slurry solvent and fluctuation of the rate of supplying the monomer to the polymerization vessel. An accumulator is installed to suppress this large pressure drop and prevent the above problems.

The size of the accumulator is determined by reducing the amount of the polymerization slurry by setting the type of the polymerization slurry and fully opening the discharge valve for a short time (hereinafter, this operation is referred to as bumping).
It can be appropriately determined according to the volume of the polymerization vessel, polymerization conditions (temperature and pressure), the allowable range of the fluctuation of the polymerization pressure, and the like.

The size of the accumulator is determined based on, for example, the following idea. When a part of the polymer slurry in a full state is discharged by bumping, the volume of the polymer slurry decreases and the pressure drops, and the liquid of the polymer slurry expands and the volume of the liquid increases. The target value of the pressure drop is set, and the volume obtained by subtracting the expansion amount of the liquid when the pressure drops from the reduction amount of the polymerization slurry due to the bumping to the set target value is equal to the set pressure drop. What is necessary is just to determine the size of the accumulator.

The suppression of the pressure drop by the accumulator is called an accumulator effect, and the suppression of the pressure drop by the liquid expansion is called a liquid expansion effect. The liquid expansion effect, that is, the amount of increase in the volume of the liquid due to the pressure drop, is determined by
-It can be estimated by the Thomson method, and the accumulator effect can be estimated from the performance of the accumulator.

The larger the size of the accumulator, the greater the ability to suppress the pressure drop, that is, the smaller the fluctuation in polymerization pressure. However, the larger the accumulator, the higher the equipment cost. Therefore, preferably, the fluctuation of the polymerization pressure is 0.1 to 0.1.
It is a size that can be suppressed to 5 MPa.

The accumulator is preferably installed in a monomer supply pipe at the same pressure as the polymerization reactor from the viewpoint of preventing the polymerized polymer from entering the accumulator and agglomerating.

The full polymerization reactor used in the present invention includes:
A reactor capable of performing polymerization in a liquid-filled state, and a liquid-filled state is a state in which the inside of the reactor is filled with a liquid or a polymerization slurry and has no gas phase. .
The reactor is not particularly limited, and includes a vessel-type reactor,
A tubular reactor, a loop reactor and the like can be mentioned.
Moreover, you may install a stirrer as needed.

(2) While discharging the polymerization slurry by slightly opening the discharge valve for the polymerization slurry, at a certain interval, the discharge valve is fully opened for a short time to continuously discharge the polymerization slurry from the above-mentioned full polymerization reactor. The method of discharging the polymer slurry to be discharged. While discharging the polymerization slurry by slightly opening the discharge valve of the polymerization slurry of the present invention, at a certain interval, the discharge valve is fully opened for a short time, and the polymerization slurry is continuously discharged from the above-mentioned full polymerization reactor. The method of discharging the polymerization slurry is to continuously produce polyolefin in a full polymerization reactor, and to continuously discharge the polymerization slurry by slightly opening the discharge valve of the polymerization slurry discharge device installed in the full polymerization reactor. In this state, at a certain interval, the discharge valve is fully opened (bumping) for a short time to discharge the polymerization slurry.

In the method for continuously discharging the polymerization slurry of the present invention, the discharge of the polymerization slurry, which is performed by slightly opening the discharge valve of the discharge device for the polymerization slurry, is performed by discharging the obtained polyolefin and a full polymerization reactor. Is the control of the polymerization pressure. The opening degree of the discharge valve at this time is usually 1 to 5
0%.

In the method for continuously discharging the polymerization slurry of the present invention, an operation (bumping) of fully opening the discharge valve for a short period of time is performed at a certain interval, and the certain interval is defined as a certain time interval. This is the time interval from when bumping is performed until the next bumping is performed. It is desirable that the interval be as small as possible to remove stagnant polymer and prevent clumping.
Considering the life of the discharge valve in addition to removing the retained polymer and preventing agglomeration, it is preferably 30 seconds to 2 minutes.

In the bumping operation, it is desired that the discharge valve be fully opened in order to minimize the fluctuation of the polymerization pressure as much as possible. Preferably, the fluctuation in polymerization pressure during bumping is small,
The time is such that the retained polymer can be effectively discharged. More preferably, the time is such that the fluctuation of polymerization pressure during bumping can be suppressed to 0.1 to 0.5 MPa.

(3) A method for discharging the polymerization slurry in which the polymerization slurry is discharged from the above-mentioned full polymerization reactor in batches by fully opening the discharge valve of the polymerization slurry which is completely closed. The method of discharging a polymerization slurry of the present invention, in which the discharge valve of the polymerization slurry that is completely closed is fully opened and the polymerization slurry is discharged in batches from the full polymerization reactor, is installed in a full polymerization reactor. With the discharge valve of the discharged polymerization slurry discharge device closed, polyolefin is produced in the full polymerization reactor, and when the polymerization pressure of the full polymerization reactor reaches the set pressure, the discharge valve is fully opened for a short time. Then, the polymerization slurry is discharged from the full polymerization reactor, and the polymerization slurry is discharged intermittently and batchwise.

In the method of discharging the polymerization slurry batchwise according to the present invention, the time for fully opening the discharge valve is not particularly limited, and the frequency of fully opening the discharge valve is not particularly limited. The time and frequency at which the discharge valve is fully opened are appropriately determined from the viewpoint of suppressing fluctuations in polymerization pressure and the life of the discharge valve. Preferably, the time and the frequency are such that the fluctuation of the polymerization pressure can be suppressed to 0.1 to 0.5 MPa. Also, in order to reduce the frequency of fully opening one discharge valve, a plurality of discharge lines may be installed.

The method for producing a polyolefin of the present invention comprises:
In a full polymerization reactor having at least a polymerization monomer supply device, a catalyst supply device and a polymerization slurry discharge device of the present invention, using a full polymerization reactor in which an accumulator is installed in the reactor, a polymerization slurry is formed. While discharging the polymerization slurry by slightly opening the discharge valve, at a certain interval, the discharge valve is fully opened for a short time, and a method of continuously discharging the polymerization slurry from the full polymerization reactor to produce a polyolefin, Alternatively, using the full polymerization reactor of the present invention, the discharge valve of the polymerization slurry that is completely closed is fully opened, and the polymerization slurry is discharged in batches from the full polymerization reactor to produce polyolefin. The method is not particularly limited, and a known apparatus, a polymerization method, or the like can be used. Also, the polyolefin is not particularly limited,
For example, polyethylene, polypropylene, synthetic rubber and the like can be mentioned.

Next, the details of the present invention will be described with reference to the drawings. FIG. 1 shows that, at a certain interval, the discharge valve is fully opened for a short period of time while the polymerization slurry is discharged by slightly opening the discharge valve for the polymerization slurry, and the polymerization slurry is continuously discharged from the full polymerization reactor. FIG. 1 shows an example of the overall flow of a full polymerization reactor equipped with a polymerization slurry discharge device and an accumulator used in such a case, and a method of discharging a polymerization slurry using the full polymerization reactor.

The monomer and catalyst are continuously and quantitatively supplied to the full polymerization tank. A heat exchanger is installed in the full polymerization tank. An accumulator is installed in the monomer supply pipe. The polymerization slurry discharge valve is slightly opened to keep the pressure in the polymerization tank constant, and its opening is automatically controlled.However, in order to prevent long-term retention of polymer near the discharge valve, a set interval is set. Periodically switches the control of the opening of the discharge valve from automatic control to manual control, makes the opening of the discharge valve 100%, and keeps the state where the opening of the discharge valve is 100% for a very short time ( (Bumping), return to the original opening, and return the control of the opening of the discharge valve to automatic control again.
The sequence is set in CS.

A large flow path is secured instantaneously by the above-described bumping operation, and a large amount of the polymerization slurry is discharged with the retained polymer. The pressure in the polymerization reactor decreases instantaneously with this bumping operation, but the fluctuation of the pressure in the polymerization reactor falls within a specified range due to the provision of the accumulator. Then, the pressure of the polymerization reactor, which once decreased, gradually increases to the set pressure of the polymerization reactor by automatic control of the opening of the discharge valve. Then, after the set interval, if the specified pressure has been reached, the bumping operation will be repeated again.

FIG. 2 shows a polymerization slurry discharge device and an accumulator used when the polymerization slurry discharge valve which is fully closed is fully opened and the polymerization slurry is discharged in batches from the full polymerization reactor. 1 shows an example of an overall flow of a full polymerization reactor equipped with a simulator and a method of discharging a polymerization slurry using the full polymerization reactor.

The monomer and the catalyst are continuously and quantitatively supplied to the full polymerization tank. A heat exchanger is installed in the full polymerization tank. An accumulator is installed in the monomer supply pipe. The pressure adjustment of the polymerization tank
It is performed by fully opening the discharge valve of the polymerization slurry which is fully closed and the batch. That is, when the pressure in the polymerization reactor reaches a specified pressure, one of the exhaust valves or the exhaust valves which are fully closed is fully opened for a short time and then fully closed. Thereafter, when the polymerization pressure reaches the prescribed pressure again, the other fully closed discharge valve is fully opened to discharge the polymerization slurry. Thus, the discharge valve alternately repeats the full-open and full-close operations to discharge the polymerization slurry.

[0030]

Next, the present invention will be described in detail with reference to examples. Example 1 A full polymerization reactor (loop reactor) having a capacity of 0.36 m ^3.
The propylene monomer was continuously charged at 300 kg / h to polymerize at a set temperature of 60 ° C. and a set pressure of 3.30 MPaG to produce polypropylene. As the catalyst, using the adjusted titanium catalyst component and the organoaluminum catalyst component,
An electron donating compound was added. The capacity of this filled polymerization vessel is 1
A 00 L accumulator was installed, and the time to open the discharge valve during bumping was set to 0.6 seconds. The average opening of the discharge valve except when bumping was about 20%.
When the bumping interval was set to 45 seconds, there was no blockage of the polymer near the discharge valve, and the polymerization could be continued stably. The change in polymerization pressure due to bumping at this time was in the range of 3.30 to 3.10 MPaG (change width: 0.20 MPaG).

Example 2 As in Example 1, 280 kg of propylene monomer was fed into a full-filled polymerization reactor (loop reactor) having a capacity of 0.36 m ^3.
h, the catalyst was not charged, and the set temperature was 6
At 0 ° C., discharge was performed batchwise using two discharge lines. An accumulator having a capacity of 100 L was installed in the full polymerization reactor, and the time for opening the discharge valve during bumping was set to 0.4 seconds. When the set pressure for starting the bumping is set to 3.30 MPa, the interval of the bumping is about 15 seconds (the interval of the bumping of each discharge valve is 30 seconds), and the fluctuation of the polymerization pressure due to the bumping at this time is as follows. The range was 3.30 to 3.18 MPaG (fluctuation range: 0.12 MPaG).

Comparative Example 1 Example 2 was repeated except that the main valve of the accumulator was closed.
When the polymerization was carried out under the same conditions as described above, the fluctuation of the polymerization pressure due to bumping was in the range of 3.30 to 2.75 MPaG (variation width: 0.55 MPaG).

[0033]

As described above, according to the present invention, the polymer is discharged without clogging at the discharge valve portion, and the discharge causes the pressure in the polymerization vessel to drop sharply, causing the boiling of the slurry solvent and the polymerization to the polymerization vessel. The polymerization can be stably continued without causing a fluctuation in the monomer feed rate.

[Brief description of the drawings]

FIG. 1 is a full polymerization reactor used for continuously discharging a polymerization slurry.

[Explanation of symbols] Full polymerization tank, heat exchanger, accumulator,
Polymerization slurry discharge valve, DCS

FIG. 2 Full-filled polymerization reactor used to discharge polymerization slurry in batches

[Explanation of symbols] Full polymerization tank, heat exchanger, accumulator,
Polymerization slurry discharge valve, Polymerization slurry discharge valve, DCS

Continuation of front page (72) Inventor Kojiro Matsui 5-1 Anesaki Beach, Ichihara-shi, Chiba F-term in Sumitomo Chemical Co., Ltd. 4J011 DB30

Claims (5)

[Claims] 1. A full polymerization reactor having at least a polymerization monomer supply device, a catalyst supply device and a polymerization slurry discharge device, wherein an accumulator is installed in the reactor. . 2. The full-fill polymerization reactor according to claim 1, wherein the accumulator is provided in a supply pipe of the monomer. 3. The polymerization slurry is discharged from the flooded polymerization reactor according to claim 1 or 2, by fully opening the discharge valve for a short time at a certain interval while discharging the polymerization slurry by slightly opening the discharge valve for the polymerization slurry. And discharging the polymerization slurry continuously. 4. A discharge of the polymerization slurry, wherein the polymerization slurry is discharged in batches from the full polymerization reactor according to claim 1 or 2, by fully opening the discharge valve of the polymerization slurry which is completely closed. Method. 5. A method for producing a polyolefin, comprising using the method for discharging a polymerization slurry according to claim 3 or 4.