JP3189339B2 - Polymerization reaction operation support equipment for polyolefin production - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for supporting a polymerization reaction in the production of polyolefin. Specifically, in the presence of hydrogen using a Ziegler-based catalyst, a Phillips-based catalyst, and the like, when polymerizing an olefin in a polymerization zone, physical properties of a polyolefin obtained by a polymerization reaction, particularly, a density value are measured, and the measured values and The operation data of the reaction condition is taken into a computer, the processing is performed to estimate the reaction state, and based on the estimated value, the transition of the density value of the polyolefin produced in the reactor in the future is predicted, and the predicted value and the target value are calculated. The present invention relates to a driving support apparatus that calculates an amount of change in operating conditions based on a comparison of the above, and changes the operating conditions based on the calculated amount to produce a polyolefin having a predetermined density value.

[0002]

2. Description of the Related Art Hitherto, polyolefins have been molded by various molding methods and used for various purposes. Depending on these molding methods and applications, it is desired that the polyolefin has various physical properties, particularly a melt flow rate (melt flow index; referred to as “MFR” in this specification) and a density. Generally, to adjust these properties,
There are known methods for changing the type, composition, amount, etc. of the catalyst and changing the polymerization conditions.

In order to produce a polyolefin on an industrial scale, a predetermined amount of a catalyst and a cocatalyst, a predetermined amount of an olefin, a predetermined amount of hydrogen, and a solvent are placed in a polymerization zone maintained at a predetermined temperature. The feed is run under conditions such that a polyolefin having a predetermined specification, ie, a predetermined MFR and density, is continuously produced.

[0004] However, even if continuous polymerization is carried out under the conditions where the feed rates are kept constant as described above, it is difficult to keep the state in the polymerization zone constant. For this reason, it is almost impossible to produce a polyolefin having a predetermined physical property specification at a constant production amount. That is, the olefin concentration in the polymerization zone changes due to a minute change in the catalyst or a change in the activity due to the uncertain disturbance. For example, when the activity of the catalyst decreases, the olefin concentration in the zone increases, the ratio of the concentration of hydrogen and the olefin, which are molecular weight regulators, decreases, and the density of the generated polyolefin decreases. . Frequent minute disturbances for which the reason is not clear often occur, which changes the olefin concentration in the polymerization zone and the physical properties of the resulting polyolefin, especially the MFR
And the density and the like will fluctuate.

Conventionally, various methods for improving such a problem have been proposed. For example, there are the following methods. A method for measuring the olefin concentration and the hydrogen gas concentration in the liquid phase portion of a polymerization reactor (US Pat. No. 3,835,106)
issue). A method for monitoring the polymerization reaction system and measuring the pressure to homogenize the composition of the ethylene copolymer as the final product (U
SP 3, 691, 142). A method for monitoring the ethylene and hydrogen concentrations in the gas phase or liquid phase of a polymerization reactor, incorporating this into a control system using a computer, and controlling the ethylene and / or hydrogen supply amounts (US Pat. No. 4,469,853, 1962-25
0010).

[0006]

SUMMARY OF THE INVENTION Among the above conventional methods,
However, the method (1) has a problem that the polymerization reaction progresses until the sample is collected from the reactor and the state in the reaction system cannot be accurately grasped.

Further, the method of the present invention is characterized in that desired physical properties, particularly MF
It is not a suitable technique for producing polyethylene having R and / or density.

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

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 obtaining a polyolefin having a predetermined density value stably and reliably. .

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a polymerization reaction operation support apparatus for producing a polyolefin, which comprises polymerizing an olefin and a comonomer in a polymerization zone in the presence of a catalyst and hydrogen to produce a polyolefin having a predetermined density. A process state detecting means for detecting a process state quantity representing a process state in the polymerization zone, a density measuring means for measuring the density of a polyolefin product flowing out of the polymerization zone, Data storage means for taking in process state quantities and density measurement values from the process state detection means and density measurement means and accumulating the data in a time series, At the sampling period, 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 calculating means for dynamically estimating the density of the polyolefin instantaneously generated in the polymerization zone by the arithmetic processing according to the equation, and calculating the γ value in the following equation (6) from the estimated value; A density prediction calculating means for predicting a future density value transition by a calculation process using the following formulas (1) and (6) using the γ value calculated by the calculating means and the current process state amount or the process state change amount; A process state target value calculating means for calculating a target value of a process state quantity in a polymerization zone by comparing a transition of a density value predicted by the density prediction calculating means with a target value of the density; The setting value of the process state quantity is changed based on the process state target value calculated by the means.

[0011]

(Equation 2)

In the present invention, the process state quantity is
Supply of fins, comonomers, hydrogen, solvents, catalysts and cocatalysts
Supply, gas phase olefin, comonomer and hydrogen concentration,
Reaction pressure, reaction temperature of liquid phase and reaction conditions of liquid level
Related operation data. That is, the present inventors have solved the problems of the prior art, and quickly grasp the reaction state even when the reaction state changes due to disturbance or the like, and polyolefin having predetermined physical properties corresponding to the state quantity. As a result of intensive studies to provide a method for producing a polyolefin that can be changed to the reaction conditions to obtain the following, operation data in the polymerization zone and actual measured values of the density of the polyolefin obtained in the polymerization zone are loaded into a computer and subjected to arithmetic processing. Dynamically and sequentially estimates the density of polyolefins produced instantaneously in the polymerization zone, predicts future changes in density based on the estimated values, and compares the predicted density with a target value corresponding to a given density. Thus, the present inventors have found that the above problem can be solved by calculating a target value of the reaction condition and changing the reaction condition of the polymerization zone based on the calculated target value. It has been completed.

Hereinafter, the present invention will be described in detail.

The catalyst used for producing the polyolefin according to the present invention includes a Ziegler catalyst, a Phillips catalyst and the like. An organic aluminum compound is used as a promoter. If desired, a third component such as an electron donating compound may be used.

As the solvent, inert hydrocarbon solvents such as aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as benzene, toluene and xylene, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane are used.

Examples of the olefin include α-olefins such as ethylene, propylene, butene-1, hexene-1, and 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 and the like are used as the comonomer. The use amount of the comonomer is 30 mol% or less, preferably 10 mol% or less based on the olefin.

The olefin polymerization reaction is carried out by supplying a predetermined amount of an olefin, a comonomer, hydrogen, a catalyst and a cocatalyst, a solvent and a third component, if desired, to a polymerization zone.
The reaction is carried out at 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 according to the desired properties of the polyolefin.

Hereinafter, embodiments of the driving support device of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a block diagram of a polyolefin production 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 promoter and a third component supply line 5 'are connected to a polymerization reactor 1. A predetermined amount of hydrogen, olefin, comonomer, solvent, catalyst, co-catalyst, third component, and the like are continuously supplied according to the density of the polyolefin to be produced.

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

The produced polyolefin is continuously extracted from the polyolefin extraction line 6, supplied to a degassing tank or a gas separator 12, and after separating unreacted gas from a pipe 12A, passes through a supply 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 via the feed line 6B, and is made into a dried polyolefin solid. This is supplied to the extruder 15 through the feed line 6C and pelletized,
Withdraw from polyolefin pellet extraction line 16.

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

The above-mentioned hydrogen supply line 2, olefin supply line 3, comonomer supply line 20, and solvent supply line 4 have supply valves 2a,
3a, 20a, and 4a, and flow detectors 2b, 3b, 20b, and 4b that detect the supply amounts of the respective detectors are provided. K ₂ , K ₃ , K ₄ , K ₅ ) are input to the data storage unit 31 of the computer 30. On the other hand, according to control signals S _{1 to} S ₅ from the control unit 36 of the computer 30 described later, the stroke of the catalyst supply pump 5a is changed to change the olefin concentration, the comonomer concentration and the hydrogen concentration so as to generate a polyolefin having a predetermined density.
The stroke of the co-catalyst supply pump 5'a and the opening 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 guided to an analyzer 8 such as gas chromatography via an on-off valve 7a. The analyzer 8 measures the hydrogen concentration, olefin concentration and comonomer concentration in the gas. A signal (K ₆ ) based on the hydrogen concentration, the olefin concentration, and the comonomer concentration measured by the analyzer 8 is also input to the data storage unit 31 of the computer 30.

Reference numerals 9 and 10 denote detectors for detecting the pressure in the gas phase and the temperature in the gas phase of the polymerization reactor 1, and the detection signals (K ₇ , K ₈ ) is also the data storage unit 31 of the computer 30.
Is input to

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

Further, a solvent supply line 18 is connected to the degassing tank 12 for adjusting the slurry concentration. A supply valve 18a for adjusting the supply amount and a flow 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
0 is input to the data storage unit 31.

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

As described above, in this embodiment, the process state quantity 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 Of the reaction conditions, such as the concentration, reaction pressure, reaction temperature of the liquid phase and liquid level, detected by the respective process state detecting means, K _{2 to} K _9, and the production of polyolefin extracted from the polymerization reactor 1 The measured density of the product (in the present invention, as shown in FIG. 1, a polyolefin pellet obtained through a degassing tank 12, a solvent separator 13, a dryer 14 and an extruder 15 is converted into an MFR measuring instrument 17 and a density measuring instrument 18 It is desirable to use the MFR and the density actually measured values measured in the above.) The signal K ₁ is input to the computer 30 and the data is stored in the data storage unit 31. Store as sequence data.

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

As described above, the driving support apparatus according to the present embodiment
Process state detecting means for transmitting detection signals K _{2 to} K ₁₀ ,
An MFR for transmitting the detection signal K ₁ and a density measuring means (MFF)
R measuring device 17 and density measuring device 18), data storage means (data storage section 31), γ value calculation operation means (γ value calculation operation section 32), density prediction operation means (density prediction operation section 3)
3) a process state target value calculating means (process state target value calculating unit 34); The operation of the driving support device will be described. When a start instruction is input from the outside (for example, input from the display 35), data of a sampling cycle specified from the specified time to the past, for example, data of the past 24 hours is obtained. Is extracted as time series data from the data storage unit 31 for each time period, and data (detection signals K _{1 to} K ₉ ) of the process state quantity, the MFR, and the density, and the γ value calculation calculation unit is used by using this data. At 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 amount or its change amount, the density prediction operation unit 33 performs an arithmetic operation based on the above-described equations (1) and (6) to calculate the future (future) density value. The transition is predicted, and the predicted value is displayed as a table or a graph, and the transition of the density value is printed out or displayed on a CRT screen.

Using the transition of the density value and the target value of the density, the process state target value calculation unit 34 compares the two, 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 arithmetic processing according to 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 calculating section 34, for example, the molar ratio of comonomer / olefin in the gas phase, the process state quantity of the polymerization reactor 1, for example, olefin, hydrogen, comonomer, The control signal S ₁ changes the set value of the supply amount of the catalyst or the promoter.
And outputs to S _6, to manufacture polyolefins having a predetermined density value.

Hereinafter, the density of the polyolefin instantaneously generated in the polymerization reactor by an arithmetic processing based on the prediction model is calculated using the actual measured value of the density of the polyolefin generated in the polymerization reactor 1 and the operation data of the polymerization reaction conditions. The estimation method will be described in detail.

Each symbol indicates the following. G _L1 : Liquid phase capacity of polymerization reactor 1 G _L2 : Liquid phase capacity of degassing tank 12 _GL3 : Liquid phase capacity of solvent separator 13 C _P1 : Polymer concentration of polymerization reactor 1 C _P2 : Degassing tank 12 C _P3 : Polymer concentration of solvent separator 13 F _P1 : Instantaneous reaction amount of polymerization reactor 1 F _Ol1 : Olefin supply amount of polymerization reactor 1 F _S1 : Solvent supply amount of 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 density of polymerization reactor 1 ρ ₂ : Polymerization reactor Density at 1 outlet ρ ₃ : density at outlet of degassing tank 12 ρ ₄ : density at outlet of solvent separator 13 ρ ₅ : density at outlet of dryer 14 ρ ₆ : density at outlet of extruder 15 L: delay time k: powder Drop-off coefficient k = f (additive type and concentration, extruder specific energy, etc.) First, a polymerization reactor 1, a degassing tank 12, a solvent separator 13,
The material balance of the dynamic characteristics of the density of 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 starting or stopping polymerization reaction, when disturbance occurs, or when changing polymerization reaction conditions, etc.)

[0039]

(Equation 3)

During normal 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 ( _GL2 and _CP2 are constant)

[0045]

(Equation 6)

(3) Solvent separator 13 During unsteady operation

[0047]

(Equation 7)

During normal operation

[0049]

(Equation 8)

(4) Dryer 14

[0051]

(Equation 9)

(5) Extruder 15

[0053]

(Equation 10)

[0054] Here, for example, by density measuring instrument 18 the polyolefin pellets withdrawn from the extruder 15 (granules) was sampled every predetermined time and measuring the density of the polyolefin, using the measured value [rho _6, Equation (5) →
The density of the polyolefin instantaneously generated in the polymerization reactor 1 can be estimated by performing the sequential processing based on the formula (4) → the formula (3) → the formula (2) → the formula (1). A γ value is calculated from the estimated density value ρ ₁ and the following equation (6).
(Each sign in 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, this γ value and the process state quantity of the polymerization reactor 1
That is, by using the operation data of the reaction conditions or the amount of change thereof, the transition of the density value of the polyolefin generated in the polymerization reactor 1 in the future (future) is predicted by the arithmetic processing of the equation (6) → the equation (1). I do.

The predicted value of the density change is compared with the target value of the density, and the process state quantity in the equation (6) is changed until the predicted value matches the target value. The prediction of the transition of the density value is repeated by a trial-and-error method by the arithmetic processing according to 1). calculate.

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

The MFR ₁ (instantaneously generated 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 : MFR generated instantaneously MFR ₂ : MFR at reactor outlet Y: Power number

[0060]

As described above, in the driving support apparatus of the present invention, the above-mentioned signals input to the computer are subjected to arithmetic processing in the computer in accordance with a preset program, and the hydrogen content in the gas phase (1b in FIG. 1). Pressure, olefin partial pressure, comonomer partial pressure, hydrogen / olefin molar ratio, comonomer / olefin molar ratio, polyolefin polymerization amount in the polymerization reactor, polymer concentration, cocatalyst concentration, catalytic activity, etc., are calculated. By comparing and calculating each calculated value and each target value set in advance to produce a polyolefin having a predetermined density, a deviation is obtained, and a control signal based on the deviation is used to determine, for example, a hydrogen supply valve (FIG. 1-2a) to adjust the hydrogen concentration in the gas phase (1b), or to control the olefin supply valve (3a) By controlling the olefin concentration or comonomer concentration of the gas phase part (1b) by operating the stroke of the mer supply valve (20a) or the catalyst supply pump (5a), the molar ratio of hydrogen / olefin in the gas phase part is adjusted. 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 molar ratio of comonomer / olefin to a predetermined value.

The predetermined density can also be obtained by operating the stroke of the co-catalyst supply pump (5'a) as needed to adjust the co-catalyst concentration or changing the setting of the polymerization temperature. Can be produced.

The manner of changing the reaction conditions varies depending on the brand of the polyolefin product, but is effective as a density control means for generally controlling the molar ratio of the comonomer / olefin described above.

[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.

[0065] Figure 2 is a driving support apparatus of the present invention shown in FIG. 1, a given process state quantity adopts arithmetic processing using the process state quantity and density measured value at the present time
It is a graph which shows transition of the actual measurement value (a) of the density when the density is adjusted to 0.949, and the estimated value (b).

As is apparent from FIG. 2, the estimated value of the density and the actually measured value are in good agreement, and the driving support 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 are polymerized in a polymerization zone in the presence of a catalyst and hydrogen, whereby a polyolefin having a predetermined density can be reliably, stably and efficiently produced.

[Brief description of the drawings]

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

FIG. 2 is a graph showing transitions of measured values (a) and estimated values (b) of densities when a process state quantity is adjusted by the driving support device shown in FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 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 measuring device 18 Density measuring device 20 Comonomer supply line 30 Computer 31 Data storage unit 32 γ value calculation unit 33 Density prediction calculation unit 34 Process state target value calculation unit 36 Control unit 38 Reaction condition setting value change unit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08F 2 / 00,2 / 01

Claims (1)

(57) [Claims] An apparatus for supporting a polymerization reaction 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 a state quantity; a density measuring means for measuring a density of a polyolefin product flowing out of a polymerization zone; and a process state quantity and a density measurement value from the process state detecting means and the density measuring means. Data storage means for accumulating the data in chronological order; extracting a process state quantity and a density measurement value from the data storage means at a designated sampling period with respect to the past from a designated time in response to a start instruction; Using this time-series data, an instantaneous change in the overlap zone is performed by the arithmetic processing according to the following equations (1) and (6) Γ-value calculating means for dynamically estimating the density of the polyolefin to be generated and calculating the γ value in the following equation (6) from the estimated value; γ-value calculated by the γ-value calculating means and the current Using the process state amount or the process state change amount, the following (1)
Density prediction calculating means for predicting the future transition of the density value by the arithmetic processing according to the equations (6) and (6); and a process in the overlapping zone by comparing the density value transition predicted by the density prediction calculating means with the target density value. A process state target value calculating means for calculating a target value of the state quantity, wherein the set value of the process state quantity is changed based on the process state target value calculated by the process state target value calculating means. A polymerization reaction operation support device for producing polyolefin. (Equation 1)