JP3907879B2 - Vapor phase polymerization method and vapor phase polymerization apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention supplies a solid catalyst for polymerization into a fluidized bed reactor and blows gaseous monomers from the bottom of the fluidized bed reactor through a dispersion plate into the fluidized bed reactor by a blower. The present invention relates to a gas phase polymerization method and a gas phase polymerization apparatus in which a fluidized bed is formed in a reactor and a polymer is produced by a gas phase polymerization reaction in the fluidized bed.
[0002]
[Prior art]
Conventionally, when a polyolefin such as polyethylene is obtained, for example, a gas phase polymerization method in which an olefin monomer such as ethylene is vapor-phase polymerized in the presence of a titanium-based solid catalyst has been used.
[0003]
In such a gas phase polymerization method, for example, as shown in FIG. 4, the solid catalyst A is supplied into the fluidized bed reactor 110 via the supply line 112, and the fluidized bed reactor via the supply line 113. While maintaining the fluidized bed (reaction system) 114 in a fluidized state by blowing gaseous olefin from the bottom of 110 through a gas dispersion plate 111 comprising a perforated plate disposed near the bottom of the fluidized bed reactor 110. The polymerization reaction is performed in the fluidized bed 114. The polymer particles generated by the polymerization reaction in the fluidized bed 114 are continuously extracted from the fluidized bed reactor 110 via the line 115. Further, the unreacted gaseous olefin or the like that has passed through the fluidized bed reactor 110 in the fluidized bed reactor 110 is reduced in flow velocity in the deceleration region 116 provided in the upper part of the fluidized bed reactor 110, and fluidized bed reaction. It is discharged out of the fluidized bed reactor 110 through a gas outlet 110A provided at the top of the vessel 110. On the other hand, the unreacted gaseous olefin discharged from the fluidized bed reactor 110 is again blown into the fluidized bed 114 in the fluidized bed reactor 110 via the circulation line 117. The gaseous olefin is cooled through a heat exchanger (cooling device) 119 disposed on the circulation line 117 and supplied to the blower 118 via a supply line 120 that joins the circulation line 117. 118 is continuously supplied to the fluidized bed reactor 110.
[0004]
[Problems to be solved by the invention]
By the way, if a portion where the state of the catalyst, the polymer, the gaseous monomer and the like is not uniform exists in the fluidized bed 114, a polymer lump is formed. This mass inhibits the uniform polymerization reaction in the fluidized bed 114. Furthermore, the presence of the lump may cause a vicious circle in which the non-uniform portion expands and promotes lump formation.
[0005]
Therefore, it is necessary to detect whether or not such lumps are formed, and to maintain a constant state in the fluidized bed 114 when the lumps are detected.
As a lump formation detection method, as disclosed in, for example, Japanese Patent Laid-Open No. 4-361150, the fluidized bed reactor 110 detects a change in capacitance between a detection location and a wall surface in the vicinity thereof. There is a method in which a capacitance detecting means is arranged to detect a change in the capacitance and confirm that a lump is formed in the fluidized bed.
[0006]
However, this method is expensive to install the capacitance detection means, and has safety problems such as leakage of high-pressure gas and necessity of explosion-proof measures. Furthermore, the sensitivity of lump detection differs depending on the location of the detection means, and the capacitance fluctuates due to factors other than lump formation, such as impurities such as hydrogen, carbon monoxide and carbohydrates mixed in the raw material gas. For example, it was difficult to objectively evaluate the obtained data.
[0007]
As another example of the method for detecting the formation of lumps, an infrared sensor is provided in the fluidized bed reactor, and the density of the powdered polymer is monitored using this infrared sensor, and the sensitivity observed in a dense state. There is a method of confirming that a lump has been formed.
[0008]
However, this method has a problem in that it uses an infrared sensor and is expensive. Furthermore, since it is only possible to determine whether the powder obtained using an infrared sensor is dense or sparse, it is difficult to distinguish whether a lump is formed or whether the powder is only dense. Was difficult to evaluate objectively.
[0009]
The present invention has been made in view of the above circumstances, and accurately detects the formation of polymer lumps formed in the fluidized bed and controls the operation of the fluidized bed reactor according to the detection result. An object of the present invention is to provide a gas phase polymerization method and a gas phase polymerization apparatus.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problem, the gas phase polymerization method according to the present invention supplies a solid catalyst for polymerization into a fluidized bed reactor, and at a predetermined density from the bottom of the fluidized bed reactor by a blower through a dispersion plate. In the production of a polymer by a gas phase polymerization reaction in the fluidized bed reactor, the gaseous monomer is blown into the fluidized bed reactor to form a fluidized bed in the fluidized bed reactor,
A monitoring step of monitoring the state of lump formation in the fluidized bed reactor by detecting the lump contained in the powdered polymer extracted from the fluidized bed reactor;
And a control step of controlling the reaction conditions of the fluidized bed reactor in a direction to suppress the formation of lumps based on this result.
[0011]
Moreover, it is preferable that the monitoring step is a step of detecting whether or not a load greater than a predetermined size is applied by detecting a load applied to the rotary valve through which the extracted powdery polymer is passed.
[0012]
According to the gas phase polymerization method, in the monitoring step, it is determined using an appropriate determination means whether or not a lump is contained in the powdered polymer produced and extracted in the fluidized bed reactor. Depending on the determination result, the state of mass formation in the fluidized bed reactor is indirectly monitored. In the control step, when formation of lumps is confirmed based on the determination result obtained in the monitoring step, the reaction conditions of the fluidized bed reactor are set in the direction to suppress the formation of lumps, for example, the amount of circulating gas (empty tower Direction to improve the flow state by increasing the speed), to reduce the partial pressure of olefin, to lower the polymerization temperature, to reduce the catalyst supply amount, etc. To control.
[0013]
Further, for example, when a rotary valve is used as the appropriate discrimination means, a lump is detected as follows. That is, since the rotary valve operates to pass a certain amount of the powdered polymer per unit time, when a polymer lump is caught in the rotary valve, a load is applied to the motor of the rotary valve to maintain this operation. Take it. This load is detected as an electric signal such as electric power or current supplied to the motor. Therefore, when this electric signal changes and becomes a predetermined magnitude, it is determined that the polymer mass has passed through the rotary valve. In this way, it can be confirmed that polymer agglomeration has occurred in the fluidized bed reactor.
[0014]
The gas phase polymerization apparatus according to the present invention supplies a solid catalyst for polymerization into a fluidized bed reactor, and a gaseous monomer having a predetermined density from the bottom of the fluidized bed reactor by a blower through a dispersion plate. In a fluidized bed reactor, forming a fluidized bed in the fluidized bed reactor, and obtaining a polymer by a gas phase polymerization reaction in the fluidized bed reactor,
Detection means for detecting a lump contained in the powdered polymer extracted from the fluidized bed reactor;
And a control means for controlling the reaction conditions of the fluidized bed reactor in a direction to suppress the formation of lumps based on the result detected by the detection means.
[0015]
The detecting means includes a rotary valve for passing the extracted powdered polymer,
It is preferable to have a discriminating means for detecting a load applied to the rotary valve and discriminating whether or not a load of a predetermined magnitude or more is applied.
[0016]
According to the gas phase polymerization apparatus, the detection means detects whether or not a lump is contained in the powdered polymer produced and extracted in the fluidized bed reactor, and flows according to the detection result. Monitor the status of mass detection in the bed reactor indirectly. When the mass formation is confirmed based on the detection result obtained by the detection means, the control means sets the reaction conditions of the fluidized bed reactor in the direction to suppress the formation of the mass, for example, the amount of circulating gas (empty tower Direction to improve the flow state by increasing the speed), to reduce the partial pressure of olefin, to lower the polymerization temperature, to reduce the catalyst supply amount, etc. To control.
[0017]
Further, for example, when a rotary valve and appropriate discriminating means are used as the detecting means, a lump is detected as follows. That is, the rotary valve operates so as to pass a certain amount of the powdered polymer per unit time. Therefore, when a polymer lump is caught in the rotary valve, a load is applied to the motor of the rotary valve in order to maintain this operation. Take it. The discriminating means detects this load as an electric signal such as electric power and current supplied to the motor, and discriminates whether or not the electric signal has a predetermined magnitude. Therefore, when the electric signal changes and becomes a predetermined magnitude, it can be determined that the polymer mass has passed through the rotary valve. In this way, it is possible to confirm that polymer formation has occurred in the fluidized bed reactor by using the rotary valve and appropriate discriminating means.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a gas phase polymerization method according to the present invention and a gas phase polymerization apparatus to which the method is applied will be described in detail with reference to the drawings.
[0019]
In the present invention, the term “polymerization” may be used in the meaning including not only homopolymerization but also copolymerization, and the term “polymer” refers not only to homopolymers but also to copolymers. It may be used in the meaning including. Moreover, the gaseous monomer in the case of performing copolymerization refers to a mixture of a plurality of gas monomers.
[0020]
FIG. 1 is a schematic view of a gas phase polymerization apparatus to which a gas phase polymerization method according to the present invention is applied. As shown in FIG. 1, the gas phase polymerization apparatus supplies a solid catalyst A for polymerization into the fluidized bed reactor 1, and is in a gaseous state from the bottom of the fluidized bed reactor 1 through a gas dispersion plate 11 by a blower 8. A monomer is blown into the fluidized bed reactor 1 to form a fluidized bed 4 in the fluidized bed reactor 1, and a polymer or copolymer is obtained by a gas phase polymerization reaction in the fluidized bed 4. It is configured. Here, the gaseous monomer is one or more monomers (monomer, comonomer) that are polymerized by the action of a solid catalyst for polymerization, and a molecular weight control agent such as hydrogen, nitrogen or hydrocarbons to the polymerization system. It may be supplied together with an inert gas such as
[0021]
In the gas phase polymerization apparatus, the solid catalyst A is supplied into the fluidized bed reactor 1 through the supply line 2, while the monomer such as gaseous olefin is supplied into the fluidized bed through the supply line 3. The fluidized bed (reaction system) 4 is maintained in a fluidized state by blowing from the bottom of the reactor 1 through a gas dispersion plate 11 made of a porous plate or the like disposed near the bottom of the fluidized bed reactor 1. The polymerization reaction is carried out within 4. The gaseous monomer prepared in the raw material preparation unit 21 is continuously supplied via a supply line 20 that joins the circulation line 7.
[0022]
The powdery polymer (polymer powder) produced by the progress of the polymerization reaction in the fluidized bed 4 is continuously extracted from the fluidized bed reactor 1 via the line 5.
[0023]
On the other hand, the unreacted gaseous monomer that has passed through the fluidized bed 4 is provided in the upper part of the fluidized bed reactor 1 by reducing the flow velocity in the deceleration region 6 provided in the upper part of the fluidized bed reactor 1. The gas is discharged out of the fluidized bed reactor 1 through the gas outlet 10A.
[0024]
By the way, since the unreacted monomer discharged from the fluidized bed reactor 1 needs to remove its polymerization reaction heat before being blown into the fluidized bed 4 in the fluidized bed reactor 1 again, the circulation line 7 It is introduced into a heat exchanger (cooling device) 9 connected to the upstream side of the air and cooled.
[0025]
The monomer gas cooled by the heat exchanger 9 is subsequently passed from the bottom of the fluidized bed reactor 1 through the blower 8 and the supply line 3 disposed on the downstream side of the circulation line 7. And is again blown into the fluidized bed 4 in the fluidized bed reactor 1.
[0026]
Here, when a polymer lump is formed in the fluidized bed reactor 1, the polymerization reaction performed in the fluidized bed 4 may not be performed efficiently. In accordance with the detection result, the operation of the fluidized bed reactor 1 is controlled in a direction to suppress the formation of lumps as will be described later.
[0027]
The polymer powder taken out from the line 5 is solid-gas separated in the purge bottles 31 and 32 and then taken out by the rotary valve 13. Note that the solid-gas separation is performed by providing two stages of purge bins in order to effectively perform the solid-gas separation, and the solid-gas separation may be performed by connecting one or three or more purge bins in series. Needless to say, the purge bin may be omitted, and in any case, the effects of the present invention can be obtained.
[0028]
In this way, the lump contained in the polymer powder extracted from the fluidized bed reactor 1 is detected by a detection means comprising a rotary valve and a discrimination section as a suitable discrimination means.
[0029]
The rotary valve feeds the polymer powder after solid-gas separation. The discriminating unit detects the load applied to the motor for driving the rotary valve when delivering the polymer powder as the power or current supplied to the motor, and the detected power or current is a threshold power or current having a predetermined magnitude. By determining whether or not the load is larger than the predetermined value, it is determined whether or not a load of a predetermined size or more is applied, and the formation of a lump is detected according to the determination result.
[0030]
Specifically, in FIG. 1, a rotary valve 13 is disposed at the outlet of the purge bin 32 on the downstream side, and the rotary valve 13 operates to send out a certain amount of powdered polymer (polymer powder) per unit time. Let Further, the determination unit (sequencer) 14 detects the power or current supplied to the rotary valve 13, and the result of performing a predetermined determination according to the detected power or current is a monitoring and control unit (DCS) 15 to be described later. It is connected so that it can output.
[0031]
Note that the power or current supplied to the rotary valve 13 is monitored to detect the polymer mass in order to maintain a constant operation of the rotary valve 13 when the formed mass bites into the rotary valve 13. As a result, a load is applied to the motor for driving the rotary valve 13 and, as a result, much electric power or current is required. Therefore, the lump can be detected by monitoring this power or current and following this change.
[0032]
The monitoring and control unit 15 controls the operation of each member of the gas phase polymerization apparatus such as the catalyst supply line 2, the blower 8, the raw material preparation unit 21, and the valve 33 and the peripheral equipment.
[0033]
The raw material preparation unit 21 prepares a gaseous monomer as a raw material. Further, when the gaseous monomer is a mixture of a plurality of gases, the gaseous monomer having a constant composition is prepared by adjusting the output of each gas supply source.
[0034]
In FIG. 2, the flowchart for demonstrating the principal part of the monitoring process (step S3-S5) and control process (step S6) in the gas phase polymerization method of this invention is shown.
The monitoring process is a process performed by the detection means, and the control process is a process performed by the monitoring and control unit 15.
[0035]
In step S1, gas phase polymerization proceeds in the fluidized bed reactor 1 to form a polymer powder, and the process proceeds to step S2. In step S2, the polymer powder is extracted from the line 5, solid-gas separation is performed in the purge bins 31 and 32, and the process proceeds to step S3.
[0036]
Step S <b> 3 is a detection process for detecting the power supplied to the rotary valve 13. Here, electric power is detected using appropriate detection means such as a power meter, and the process proceeds to step S4. The information detected here includes, in addition to electric power, the current applied to the motor as described above.
[0037]
Step S4 is a determination step in which the determination unit 14 determines whether or not the detected power obtained in the detection step is larger than a predetermined threshold value. Here, it is determined whether or not the detected power obtained in step S3 is larger than a predetermined amount of power, that is, threshold power.
[0038]
FIG. 3 shows the change over time of the detected power. The vertical axis represents power, and the horizontal axis represents time. In this determination step, detection and monitoring of power is started at time t _0, and since the detected power is below the threshold power P _t until time t ₁ , a NO determination result is output. That is, it is determined that the detected power is smaller than the predetermined power, and the process returns to step S1 in FIG. The threshold power is a preset value, but can be changed each time depending on the progress of the reaction.
[0039]
Since the detected power exceeds the threshold power P _t from time t ₁ to time t ₂ , a determination result of YES is output. That is, it is determined that the detected power is larger than the predetermined power, and the process proceeds to step S5 in FIG.
[0040]
After the time t ₂ , the detected power falls below the threshold power P _t , so a NO determination result is output. That is, it is determined that the detected power is smaller than the predetermined power, and the process returns to step S1 in FIG.
[0041]
In step S5, it is detected that a polymer lump has been formed when a YES determination result is output in the determination step.
In step S4, the magnitude of the supplied power depends on the magnitude of the load applied to the rotary valve 13. That is, there is a close relationship with the size of the mass detected in step S5. When the detected power is large, the mass detected is large, and when the detected power is small, the mass detected is small. Further, the time during which the detected power exceeds the threshold power has a relationship that becomes longer when the frequency of occurrence of a lump of a predetermined size becomes higher and becomes shorter when the frequency becomes lower.
[0042]
In any of the conventional methods, it is difficult to obtain data that correlates both.
Subsequently, in step S6, when it is determined in step S4 that the detected power is larger than a predetermined amount of power, and when lump formation is detected in step S5, based on the operation of the monitoring and control unit 15, The conditions for the polymerization reaction in the fluidized bed reactor 1 are to suppress the formation of lumps, for example, to improve the flow state by increasing the amount of circulating gas (superficial velocity) and reducing the powder level, Control is made to make the polymerization reaction mild, such as reducing the pressure, lowering the polymerization temperature, and reducing the catalyst supply amount.
[0043]
For example, when reducing the partial pressure of olefin, the monitoring and control unit 15 controls the raw material preparation unit 21 to reduce the gas partial pressure of a predetermined monomer gas such as ethylene or propylene in the gaseous monomer. Send data. This control data is data indicating that the predetermined partial pressure of the monomer gas is to be continuously decreased until no lump is detected even if there is data indicating that the partial pressure of the predetermined monomer gas should be decreased to a predetermined value. There may be. The raw material preparation unit 21 reduces the partial pressure of the predetermined monomer gas according to the control data.
[0044]
For example, when improving the flow state by increasing the amount of circulating gas (superficial velocity) and reducing the powder level, the monitoring and control unit 15 instructs the blower 8, for example, to change the rotational speed of the impeller. Send control data. Further, when a suction vane is disposed on the suction side of the blower 8, the suction vane may be controlled to adjust the opening degree. Moreover, you may adjust the opening degree of the valve 33 inserted and connected between the two purge bins 31 and 32 as needed.
[0045]
In step S7, it is determined whether or not to continue the production of the polymer. Furthermore, when continuing the polymer production, the process returns to step S1, and when not continuing, the operation of the gas phase polymerization apparatus is stopped and finished.
[0046]
According to FIG. 2, polymer powder generation is continued unless it is determined in step S4 that the detected power is greater than a predetermined threshold power. Further, when it is detected that a lump having a predetermined size or more is mixed in the polymer powder (step S5), the operation of the fluidized bed reactor 1 is controlled so as to suppress lump formation.
[0047]
In FIG. 2, the continuation of the polymer production is asked only when the formation of lumps is detected, and the flow of stopping the operation of the fluidized bed reactor 1 is completed. Needless to say, the operation of the fluidized bed reactor 1 may be arbitrarily stopped even when the detection of the above is not performed.
[0048]
Also, these controls may be performed automatically or manually.
As described above, according to the gas phase polymerization method and the gas phase polymerization apparatus according to the present invention, the state in the fluidized bed reactor is not directly monitored, but the produced polymer powder is taken out to perform mass detection. Therefore, since it is not necessary to arrange a special member in the fluidized bed reactor, the cost is not increased, and the lump detection can be performed only by adding a simple member outside the current fluidized bed reactor. .
[0049]
Furthermore, since the presence or absence of a lump mixed in the polymer powder is directly detected, lump formation can be reliably detected. In addition, since directly monitoring the state of the produced polymer powder indirectly monitors the state in the fluidized bed reactor, the state in the fluidized bed can be detected by detecting the formation of lumps in the polymer powder. It is possible to detect the lump formation accurately reflected. Therefore, it is possible to accurately detect the formation of polymer lumps formed in the fluidized bed, and it is possible to control the operation of the fluidized bed reactor in accordance with such accurate information.
[0050]
Further, by using a rotary valve and an appropriate discriminating unit as a detection means for detecting a lump of polymer powder, the lump detection can be performed only by adding a simple configuration.
The preferred embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications can be made without departing from the object of the present invention.
[0051]
【The invention's effect】
According to the gas phase polymerization method and the gas phase polymerization apparatus according to the present invention, it is not necessary to dispose a special member in a normally used fluidized bed reactor. The lump detection can be performed only by adding a member. In addition, because it can accurately detect the state in the fluidized bed, it can accurately grasp the state in the fluidized bed and control the operation of the fluidized bed reactor based on accurate information. Is possible.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a main part of a gas phase polymerization apparatus according to the present invention.
FIG. 2 is a flowchart for explaining a gas phase polymerization method according to the present invention.
FIG. 3 is an explanatory diagram for explaining the gas phase polymerization method.
FIG. 4 is a schematic view showing a main part of a conventional gas phase polymerization apparatus.
[Explanation of symbols]
1 Fluidized bed reactor 4 Fluidized bed (reaction system)
8 Blower 11 Gas Dispersion Plate 13 Rotary Valve 14 Discrimination Unit (Sequencer)
15 Monitoring and Control Unit 21 Raw Material Preparation Unit

Claims (4)

A solid catalyst for polymerization is supplied into the fluidized bed reactor, and a gaseous monomer having a predetermined density is blown into the fluidized bed reactor from the bottom of the fluidized bed reactor through a dispersion plate by a blower. When a fluidized bed is formed in the reactor and a polymer is produced by a gas phase polymerization reaction in the fluidized bed,
A monitoring step of monitoring the state of lump formation in the fluidized bed reactor by detecting the lump contained in the powdered polymer extracted from the fluidized bed reactor;
And a control step of controlling the reaction conditions of the fluidized bed reactor in a direction to suppress mass formation based on the result. 2. The monitoring step according to claim 1, wherein a load applied to the rotary valve that passes the extracted powdery polymer is detected, and it is determined whether or not a load of a predetermined magnitude or more is applied. Gas phase polymerization method. A solid catalyst for polymerization is supplied into the fluidized bed reactor, and a gaseous monomer having a predetermined density is blown into the fluidized bed reactor from the bottom of the fluidized bed reactor through a dispersion plate by a blower. In a gas phase polymerization apparatus configured to form a fluidized bed in a reactor and obtain a polymer by a gas phase polymerization reaction in the fluidized bed,
Detection means for detecting a lump contained in the powdered polymer extracted from the fluidized bed reactor;
A gas phase polymerization apparatus comprising: control means for controlling reaction conditions of the fluidized bed reactor in a direction to suppress lump formation based on a result detected by the detection means. The detection means includes a rotary valve for passing the extracted powdered polymer,
4. The gas phase polymerization apparatus according to claim 3, further comprising: a determination unit that detects a load applied to the rotary valve and determines whether or not a load greater than a predetermined amount is applied.

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