JPH05163303A - Device for supporting operation of polymerization reaction for producing polyolefin - Google Patents

Abstract

PURPOSE:To produce a polyolefin having a predetermined density by polymerizing an olefin with a comonomer in a polymerization zone in the presence of a catalyst and hydrogen. CONSTITUTION:The density of a polyolefin obtained by polymerization is measured. The found value and operating condition data K1 to K10 which govern the reaction conditions are inputted into a computer 30, which arithmetically processes all these data to estimate the state of the reaction. Based on the estimate, a change in the density of the polyolefin to be produced in the polymerization vessel is estimated. The amounts in which the operating conditions should be changed are calculated based on a comparison between the estimated density and the desired one, and the operating conditions are changed according to the calculation results (S1 to S5) to thereby produce a polyolefin having a predetermined density. Thus, a polyolefin having a desired density according to a molding method or application therefore can be stably produced without fail.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymerization reaction operation support device in the production of polyolefin. Specifically, in the presence of hydrogen using a Ziegler-based catalyst, Phillips-based catalyst, etc., when polymerizing the olefin in the polymerization zone, the physical properties of the polyolefin obtained by the polymerization reaction, particularly the density value was measured, and the measured value and The operating data of the reaction conditions are loaded into the computer, the reaction state is estimated by arithmetic processing, the transition of the density value of the polyolefin produced in the reactor in the future is predicted based on the estimated value, and the predicted value and the target value are calculated. The present invention relates to a driving support device for manufacturing a polyolefin having a predetermined density value by calculating the change amount of the operating condition by comparing the above and changing the operating condition based on the calculated amount.

[0002]

2. Description of the Related Art Conventionally, polyolefin has been molded by various molding methods and used for various purposes. Depending on these molding methods and uses, polyolefins having various physical properties, particularly melt florate (melt flow index; referred to as “MFR” in this specification) and density are desired. Generally, to control these physical properties,
A method is known in which the type, composition, amount, etc. of the catalyst are changed and the polymerization conditions are changed.

By the way, in order to produce polyolefin on an industrial scale, a predetermined amount of catalyst and cocatalyst, a predetermined amount of olefin, and a predetermined amount of hydrogen, and further a solvent are placed in a polymerization zone kept at a predetermined temperature. As supplied, the operation is carried out under conditions such that a polyolefin having a specified standard, that is, a specified MFR and density, is continuously produced.

However, it is difficult to keep the state in the polymerization zone constant even if the continuous polymerization is carried out under the condition that the respective supply amounts are constant as described above. For this reason, it is almost impossible to manufacture a polyolefin having a predetermined physical property standard with a constant production amount. That is, the olefin concentration in the polymerization zone changes due to minute changes in the catalyst due to uncertain disturbances, changes in activity, and the like. For example, when the activity of the catalyst is reduced, the concentration of olefin in the zone is increased, the ratio of the concentrations of hydrogen, which is a molecular weight regulator, and olefin is reduced, and the density of the produced polyolefin is reduced. .. Such fine disturbances for which the reason is not clear frequently occur, which changes the olefin concentration in the polymerization zone, resulting in physical properties of the produced polyolefin, especially MFR.
And density will change.

Conventionally, various methods for improving such problems have been proposed, for example, the following methods (1) to (3) are available. A method of actually measuring the olefin concentration and the hydrogen gas concentration in the liquid phase portion of the polymerization reactor (USP 3,835,106).
issue). A method of monitoring the polymerization reaction system and measuring the pressure to homogenize the composition of the final ethylene copolymer (U
SP 3,691,142). A method of monitoring the ethylene and hydrogen concentrations in the gas phase or liquid phase of a polymerization reactor and incorporating them into a computerized control system to control the ethylene and / or hydrogen supply (USP 4,469,853, JP 62-25
No. 0010).

[0006]

Of the above-mentioned conventional methods,
The method (1) has a problem that the polymerization reaction proceeds until the sample is taken from the reactor and the state in the reaction system cannot be accurately grasped.

Further, the method (1) has the desired physical properties, especially MF.
It is not a suitable technique for producing polyethylene having R and / or density.

In the method (1), the reaction state changes when there is a minute disturbance in the polymerization zone. Therefore, it is necessary to control the ethylene and hydrogen concentrations in the gas phase or the liquid phase to predetermined amounts. It is difficult to obtain MFR or density of polyolefin.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a polymerization reaction operation support device for producing a polyolefin capable of stably and reliably obtaining a polyolefin having a predetermined density value. ..

[0010]

A polymerization reaction operation support apparatus for producing a polyolefin of the present invention is a polymerization reaction operation apparatus for producing a polyolefin having a predetermined density by polymerizing an olefin and a comonomer in a polymerization zone in the presence of a catalyst and hydrogen. A polymerization reaction operation support device for carrying out, a process state detecting means for detecting a process state quantity representing a process state in a polymerization zone, a density measuring means for measuring a density of a polyolefin product flowing out from the polymerization zone, A data storage means for taking in the process state quantity and the density measurement value from the process state detection means and the density measurement means and accumulating the data in time series, and a designated time from the designated time to the past in response to the start instruction. At the sampling cycle, the process state quantity and the density measurement value are extracted from the data storage means and the time series data is extracted. Below using the data (1) and (6)
Γ value calculation calculation means for dynamically estimating the density of the polyolefin instantaneously generated in the polymerization zone by the calculation processing by the formula, and calculating the γ value in the formula (6) below from the estimated value, and the γ value calculation A density prediction calculation means for predicting a future density value transition by calculation processing according to the following equations (1) and (6) using the γ value calculated by the calculation means and the current process state amount or process state change amount A process state target value calculation means for calculating a target value of the process state quantity in the polymerization zone by comparing the transition of the density value predicted by the density prediction calculation means with the target value of the density, and the process state target value calculation The set value of the process state quantity is changed based on the process state target value calculated by the means.

[0011]

[Equation 2]

That is, the inventors of the present invention have solved the above-mentioned problems of the prior art, quickly grasp the reaction state even when there is a disturbance or the like and change the reaction state, and set a predetermined value in accordance with the state quantity. As a result of extensive studies to provide a method for producing a polyolefin capable of changing the reaction conditions to obtain a polyolefin having physical properties, the operation data in the polymerization zone and the measured value of the density of the polyolefin obtained in the polymerization zone are taken into a computer and arithmetic processing is performed. Then, the density of the polyolefin instantaneously generated in the polymerization zone is dynamically and sequentially estimated, and the transition of the density in the future is predicted based on the estimated value, and the predicted value of the density and the target value corresponding to the predetermined density are obtained. By contrast with
The inventors have found that the above problems can be solved by calculating the target value of the reaction conditions and changing the reaction conditions of the polymerization zone based on the calculated target value, and have completed the present invention.

The present invention will be described in detail below.

Examples of the catalyst used for producing the polyolefin according to the present invention include Ziegler type catalysts and Phillips type catalysts. An organoaluminum compound is used as the cocatalyst. If desired, a third component such as an electron donating compound may be used.

As the solvent, there may be used an aliphatic hydrocarbon such as hexane and heptane, an aromatic hydrocarbon such as benzene, toluene and xylene, and an inert hydrocarbon solvent such as an alicyclic hydrocarbon such as cyclohexane and methylcyclohexane.

Examples of olefins include α-olefins such as ethylene, propylene, butene-1, hexene-1, 4-methylpentene-1.

The comonomer means a small proportion of other olefins copolymerized with these olefins. For example, when ethylene is used as the olefin, propylene, butene-1 or the like is used as the comonomer. The amount of the comonomer used is 30 mol% or less, preferably 10 mol% or less, based on the olefin.

In the olefin polymerization reaction, olefin, comonomer, hydrogen, catalyst and co-catalyst, if desired a solvent and a third component are supplied in a predetermined amount to the polymerization zone, and usually 50 to 150.
It is carried out under reaction conditions of a temperature of C, a pressure of 0.1 to 100 kg / cm ² G and a hydrogen / olefin molar ratio in the gas phase of 0.01 to 1000. Of course, the reaction conditions are appropriately selected within the above range depending on the desired physical properties of the polyolefin.

Embodiments of the driving support system of the present invention will be described below in more detail with reference to the drawings. FIG. 1 is a block diagram of a polyolefin manufacturing process to which the driving support device of the present invention is applied.

In FIG. 1, a hydrogen supply line 2, an olefin supply line 3, a comonomer supply line 20, a solvent supply line 4, a catalyst supply line 5, a cocatalyst and a third component supply line 5'are connected to the polymerization reactor 1. The hydrogen, olefin, comonomer, solvent, catalyst, co-catalyst, third component and the like are continuously supplied in a predetermined amount according to the density of the polyolefin to be produced.

Inside the polymerization reactor 1, a liquid phase portion 1a and a gas phase portion 1b are formed by the above-mentioned feed, and the olefin is polymerized while being stirred by the stirrer 1c.

The produced polyolefin is continuously withdrawn from the polyolefin extraction line 6 and supplied to a degassing tank or gas separator 12 to separate unreacted gas from a pipe 12A, and then through a feed line 6A. The solvent is supplied to the solvent separator 13 and the solvent is separated from the pipe 13A. Next, it is supplied to the dryer (dryer) 14 through the feeding line 6B to be a dried polyolefin solid. This is supplied to the extruder 15 by a feeding line 6C to be pelletized,
Extract from the polyolefin pellet extraction line 16.

In the present invention, the polyolefin withdrawn from the polymerization reactor 1, preferably the polyolefin pellets withdrawn from the withdrawal line 16, is sampled from the sampling lines 16A and 16B at predetermined time intervals, and the MFR measuring device 17 and The MFR and the density of the produced polyolefin are measured by introducing the density measuring instrument 18. A signal based on this measured value (actual measured value) is input to the data storage unit 31 of the computer 30 (signal K ₁ ).

Further, the above-mentioned hydrogen supply line 2, olefin supply line 3, comonomer supply line 20, and solvent supply line 4 are provided with supply valves 2a, which adjust the respective supply amounts.
3a, 20a, 4a and flow rate detectors 2b, 3b, 20b, 4b for detecting respective supply amounts are respectively provided, and detection signals (corresponding to flow rates from the flow rate detectors 2b, 3b, 20b, 4b ( K ₂ , K ₃ , K ₄ , K ₅ ) are input to the data storage unit 31 of the computer 30. On the other hand, the stroke of the catalyst supply pump 5a for changing the olefin concentration, the comonomer concentration and the hydrogen concentration so as to produce a polyolefin having a predetermined density by control signals S _{1 to} S ₅ from a control unit 36 of the computer 30 described later,
The stroke of the co-catalyst supply pump 5'a, the opening degree of the olefin supply valve 3a, the comonomer supply valve 20a, and the hydrogen supply valve 2a are controlled.

Further, a sampling line 7 is provided in the gas phase portion 1b of the polymerization reactor 1, and the gas in the gas phase portion 1b is introduced into an analyzer 8, for example, gas chromatography, through an on-off valve 7a. The analyzer 8 measures the hydrogen concentration, olefin concentration and comonomer concentration in the gas. The signal (K ₆ ) based on the hydrogen concentration, olefin concentration and comonomer concentration measured by the analyzer 8 is also input to the data storage unit 31 of the computer 30.

Numerals 9 and 10 denote detectors for the pressure and temperature of the gas phase portion of the polymerization reactor 1. The pressure detector 9 and the temperature detector 10 detect signals (K) that correlate with the pressure and temperature. ₇ , K ₈ ) is also the data storage unit 31 of the computer 30.
Entered in.

Reference numeral 11 is a supply line for supplying cooling water to the polymerization reactor 1, which is provided with a supply valve 11a for adjusting the supply amount and a flow rate detector 11b for detecting the supply amount. The detection signal (K ₉ ) correlated with the flow rate from 11b is input to the data storage unit 31 of the computer 30. The opening degree of the cooling water supply valve 11a is also controlled by the control signal S ₆ from the control unit 36 of the computer 30 described later so as to change the polymerization temperature so as to generate polyolefin having a predetermined density. ..

Further, a solvent supply line 18 is connected to the degassing tank 12 for adjusting the slurry concentration, and a supply valve 18a for adjusting the supply amount and a flow rate detector 18b for detecting the supply amount are provided. The detection signal (K ₁₀ ) correlated with the flow rate from the flow rate detector 18b is sent to the computer 3
0 is input to the data storage unit 31.

The pipe 19A is a line for returning the hot water to the cooling tower, and the pipe 19B is a line for circulating the hot water.

As described above, in the present embodiment, the process state amount representing the process state in the polymerization reactor 1, that is, the supply amounts of olefin, comonomer, hydrogen, solvent, catalyst and cocatalyst, olefin, comonomer and hydrogen in the gas phase part. concentration, reaction pressure, the polyolefin is withdrawn from the signal K ₂ ~K ₉ and a polymerization reactor 1 operating data of the reaction conditions detected in each process state detecting means such as reaction temperature and surface level of the liquid phase portion generated The actual density value of the product (in the present invention, as shown in FIG. 1, the polyolefin pellets obtained through the degassing tank 12, the solvent separator 13, the dryer 14 and the extruder 15 are used as the MFR measuring device 17 and the density measuring device 18). It is desirable to adopt the MFR and the density actual measurement value measured in _1. ) into the computer 30, and store the data in the data storage unit 31. Store as series data.

The computer 30 includes a data storage unit 31,
a γ value calculation calculation unit 32, a density prediction calculation unit 33, a process state target value calculation unit 34, and a display 35,
It has a printer 37 and a reaction condition setting value changing unit 38.

As described above, the driving support system of this embodiment is
Process state detecting means for transmitting the detection signals K _{2 to} K ₁₀ ,
An MFR and a density measuring means (MF) for transmitting a detection signal K _1.
R measuring device 17 and density measuring device 18), data storage means (data storage part 31), γ value calculation calculation means (γ value calculation calculation part 32), density prediction calculation means (density prediction calculation part 3)
3), process state target value calculation means (process state target value calculation unit 34) is provided. The operation of the driving support device will be described. By inputting a start instruction from the outside (for example, input by the display 35), a sampling cycle designated from the designated time to the past, for example, data of the past 24 hours. Is extracted from the above-mentioned data storage unit 31 every time period as data of the process state quantity, MFR, and density measurement value (detection signals K _{1 to} K ₉ ) as time series data, and using this data, the γ value calculation operation unit In 32, the density of the polyolefin instantaneously generated in the polymerization zone is dynamically estimated by the arithmetic processing according to the above equations (1) and (6), and the γ value in the equation (6) is calculated from the estimated value.

Using the γ value and the current process state quantity or its change amount, the density prediction calculation unit 33 performs calculation processing according to the equations (1) and (6) to calculate the future (future) density value. The transition is predicted, and the transition of the density value is displayed as a table or a graph on the printout or CRT screen.

The process state target value calculation unit 34 compares the two with the density value transition and the density target value, and changes the process state quantity until the transition of the predicted density value matches the target value. Then, the prediction of the transition of the density value is repeated by a trial-and-error method by the calculation processing by the following equations (1) and (6) to calculate the target value of the process state quantity.

Based on the process state target value calculated by the process state target value calculation unit 34, for example, the comonomer / olefin molar ratio in the gas phase, the process state amount of the polymerization reactor 1, for example, olefin, hydrogen, comonomer, Control signal S ₁ to change the set value of the supply amount of the catalyst or cocatalyst
~ S ₆ is output to produce a polyolefin having a predetermined density value.

Hereinafter, the density of the polyolefin instantaneously produced in the polymerization reactor is calculated by the calculation process based on the prediction model using the actual measurement value of the density of the polyolefin produced in the polymerization reactor 1 and the operation data of the polymerization reaction conditions. The estimation method will be described in detail.

The symbols indicate the following. G _L1 : Liquid phase capacity of polymerization reactor 1 G _L2 : Liquid phase capacity of degassing tank 12 G _L3 : Liquid phase capacity of solvent separator 13 C _P1 : Polymer concentration of polymerization reactor 1 C _P2 : Degassing tank 12 Polymer concentration C _P3 : Polymer concentration in the solvent separator 13 F _P1 : Instantaneous reaction amount in the polymerization reactor 1 F _Ol1 : Olefin supply amount in the polymerization reactor 1 F _S1 : Solvent supply amount in the polymerization reactor 1 F _S2 : Desorption Amount of solvent supplied to gas tank 12 F _S3 : Amount of solvent supplied to solvent separator 13 S _Ol1 : Amount of olefin dissolved in solvent of polymerization reactor 1 ρ ₁ : Instantaneous production density of polymerization reactor 1 ρ ₂ : Polymerization reactor 1 density of outlet ρ ₃ : density of outlet of degassing tank 12 ρ ₄ : density of outlet of solvent separator 13 ρ ₅ : density of outlet of dryer 14 ρ ₆ : density of outlet of extruder 15 L: delay time k: powder Drop-off coefficient k = f (additive type and concentration, extruder specific energy, etc.) First, the polymerization reactor 1, the degassing tank 12, the solvent separator 13,
The mass balance of the dynamic characteristics of the density of the polyolefin in the dryer 14 and the extruder 15 is represented by the following prediction model formula.

(1) Polymerization reactor 1 During unsteady operation (when the polymerization reaction is started or stopped, when disturbance is generated, or when the polymerization reaction conditions are changed)

[0039]

[Equation 3]

During steady operation (C _L1 , C _P1 , F _P1 , S
_(Ol1 is constant)

[0041]

[Equation 4]

(2) Degassing tank 12 during unsteady operation

[0043]

[Equation 5]

During steady operation (G _L2 and C _P2 are constant)

[0045]

[Equation 6]

(3) Solvent Separator 13 During unsteady operation

[0047]

[Equation 7]

During steady operation

[0049]

[Equation 8]

(4) Dryer 14

[0051]

[Equation 9]

(5) Extruder 15

[0053]

[Equation 10]

Here, for example, the polyolefin pellets (granular bodies) extracted from the extruder 15 are sampled every predetermined time, the density of the polyolefin is measured by the density measuring device 18, and the measured value ρ ₆ is used. Formula (5) →
The density of the polyolefin instantaneously generated in the polymerization reactor 1 can be estimated by sequentially performing the arithmetic processing based on the formula (4) → the formula (3) → the formula (2) → the formula (1). The γ value is calculated from this density estimated value ρ ₁ and the following equation (6).
(Each symbol in the equation (6) is as described above.) Log ρ (t) = B
₁ log (H ₂ / Ol) _G + B ₂ log (Co / Ol) _G + B ₃ MFR _l + γ ...
(6) Next, the γ value and the process state amount of the polymerization reactor 1,
That is, the transition of the density value of the polyolefin produced in the polymerization reactor 1 in the future (future) is predicted by the calculation process of the formula (6) → the formula (1) using the operation data of the reaction conditions or the changed amount thereof. To do.

The predicted value of the transition of the density is compared with the target value of the density, and the process state quantity in the expression (6) is changed until the predicted value matches the target value, and the expression (6) and the expression ( By predicting the transition of the density value by the trial and error method by the calculation process according to 1), the process state amount in the formula (6), that is, the target value of the reaction condition, particularly the target value of the comonomer / olefin molar ratio in the gas phase part, is calculated. calculate.

Based on this target value, the reaction condition set value changing section 38 and the control section 36 output control signals S _{1 to} S ₅ to supply olefin, comonomer, hydrogen, catalyst or cocatalyst in the polymerization reactor 1. By changing the set value such as the amount, a polyolefin having a predetermined density value can be produced.

The MFR ₁ (instantaneous MFR) in the above equation (6) is calculated from the measured MFR value of the MFR measuring device 17,
It can be calculated from the following equation (7).

[0058]

[Equation 11]

MFR ₁ : Instantaneous production MFR MFR ₂ : Reactor outlet MFR Y: Exponent

[0060]

As described above, in the driving support system of the present invention, the above signals input to the computer are processed in accordance with a preset program in the computer, and the hydrogen content in the gas phase portion (1b in FIG. 1) is calculated. Calculated values such as pressure, olefin partial pressure, comonomer partial pressure, hydrogen / olefin molar ratio, comonomer / olefin molar ratio, polyolefin polymerization amount in polymerization reactor, polymer concentration, co-catalyst concentration, catalyst activity, etc. The deviation is obtained by comparing and calculating each calculated value with each target value set in advance to manufacture a polyolefin having a predetermined density, and a control signal based on the deviation is used to, for example, a hydrogen supply valve (Fig. 2a) of 1 to adjust the hydrogen concentration of the gas phase part (1b), or the olefin supply valve (3a), como The hydrogen / olefin molar ratio of the gas phase part by adjusting the olefin concentration or comonomer concentration of the gas phase part (1b) by operating the stroke of the polymer supply valve (20a) or the catalyst supply pump (5a). Alternatively, the hydrogen concentration, the olefin concentration, and the comonomer concentration are controlled so as to produce a polyolefin having a predetermined density by adjusting the comonomer / olefin molar ratio to a predetermined value.

The predetermined density can also be obtained by operating the stroke of the co-catalyst supply pump (5'a) as necessary to adjust the co-catalyst concentration and further change the setting of the polymerization temperature. A polyolefin having can be produced.

The method of changing the reaction conditions depends on the type of brand of the polyolefin product, but it is effective as a density control means for which the above-mentioned comonomer / olefin molar ratio control is generally carried out.

[0063]

The present invention will be described in more detail with reference to specific control examples.

Example 1 Using the apparatus shown in FIG. 1, a polyolefin was produced according to the control method described above.

FIG. 2 shows the actual measured value of the density when the process assisting apparatus of the present invention shown in FIG. (A) and its estimated value (b)
It is a graph which shows the change of.

As is apparent from FIG. 2, the estimated value of the density and the actually measured value are in good agreement, and the operation assisting device of the present invention can favorably adjust the process state quantity.

[0067]

As described in detail above, according to the polymerization reaction operation support device for producing the polyolefin of the present invention,
An olefin and a comonomer can be polymerized in a polymerization zone in the presence of a catalyst and hydrogen to reliably, stably and efficiently produce a polyolefin having a predetermined density.

[Brief description of drawings]

FIG. 1 is a block diagram of a polyolefin manufacturing process using a driving support device according to an embodiment of the present invention.

FIG. 2 is a graph showing a transition of an actually measured value (a) and an estimated value (b) of the density when the process state quantity is adjusted by the driving support device shown in FIG.

[Explanation of symbols]

 1 Polymerization Reactor 2 Hydrogen Supply Line 3 Olefin Supply Line 4 Solvent Supply Line 5 Catalyst Supply Line 6 Polyolefin Extraction Line 7 Sampling Line 8 Analyzer 12 Degassing Tank 13 Solvent Separator 14 Dryer 15 Extruder 17 MFR Meter 18 Density meter 20 Comonomer supply line 30 Computer 31 Data storage unit 32 γ value calculation calculation unit 33 Density prediction calculation unit 34 Process state target value calculation unit 36 Control unit 38 Reaction condition set value change unit

Claims (1)

[Claims] 1. A polymerization reaction operation support device for producing a polyolefin having a predetermined density by polymerizing an olefin and a comonomer in a polymerization zone in the presence of a catalyst and hydrogen, the process representing a process state in the polymerization zone. A process state detecting means for detecting the state quantity, a density measuring means for measuring the density of the polyolefin product flowing out from the polymerization zone, and a process state quantity and a density measurement value from the process state detecting means and the density measuring means, A data storage means for accumulating the data in time series, and a process state quantity and a density measurement value are extracted from the data storage means at a specified sampling cycle with respect to the past from a time specified upon receiving a start instruction, The time series data is used to perform an arithmetic process according to the following formulas (1) and (6) to instantaneously The density of the polyolefin to be produced is dynamically estimated, and the γ value calculation calculation means for calculating the γ value in the following formula (6) from the estimated value, and the γ value calculated by the γ value calculation calculation means and the current value Using the process state quantity or process state change quantity, the following (1)
Density prediction calculation means for predicting future changes in the density value by calculation processing according to equation (6) and the process in the overlapping zone by comparing the change in density value predicted by the density prediction calculation means with the target value of the density A process state target value calculating means for calculating a target value of the state amount, and changing the set value of the process state amount based on the process state target value calculated by the process state target value calculating means. A polymerization reaction operation support device for producing a polyolefin. [Equation 1]