CN1134454C - Improved method for determining stable operating region of gas-phase fluidized-bed polymerizing reactor operating in condensation mode - Google Patents
Improved method for determining stable operating region of gas-phase fluidized-bed polymerizing reactor operating in condensation mode Download PDFInfo
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- CN1134454C CN1134454C CNB991181875A CN99118187A CN1134454C CN 1134454 C CN1134454 C CN 1134454C CN B991181875 A CNB991181875 A CN B991181875A CN 99118187 A CN99118187 A CN 99118187A CN 1134454 C CN1134454 C CN 1134454C
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- bed
- fluidized
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- recycle stream
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Abstract
The present invention relates to an improved method for determining a stable operating area of a gas phase fluidized bed polymerizing reactor. The method comprises the following steps that the variation of the temperature indication values of the layers of a fluidized bed relative to the variation of fluidizing medium components in the reactor is observed, and the fluidizing medium components are changed to enhance the cooling capacity of the circulating material flow without exceeding the temperature indication values of the fluidized bed and becoming an irreversible level.
Description
The present invention relates to carry out in fluidized-bed reactor the improvement of gas phase olefin polymerization process, the stable operation district that relates more specifically to gas-phase fluidized-bed polymerizing reactor determines the improvement of method.
Being produced by 'alpha '-olefin monomers in the gas fluidized-bed process of polymkeric substance, for the temperature maintenance with air-flow in the reactor is being lower than polymkeric substance and the temperature below the catalyst degradation temperature, it is very important removing the heat that is produced by reaction.In addition, it also is very important preventing to take place as the polymkeric substance that product takes out to assemble or form polymer lumps.Normally by in the reactor outside air-flow being cooled off and heat being taken out from circulating current.Think that in the past the recycle stream temperature can not reduce to below the dew point.The dew point of cycling stream is the temperature that begins to form liquid condensate in air-flow.It is believed that to insert the liquid into the obstruction that must cause pipeline, interchanger and gas distribution grid in the fluidised bed polymerisation process and disturb fluid mapper process that the result makes the fluidized-bed collapse, polymer bonding becomes block, makes reactor shutdowns when serious.Hold opposite view be Jenkins etc. at US 4,543,399 and 4,588, open in 790: cycling stream can be cooled to below the dew point of fluidised bed polymerisation process, and the result makes a part of cycling stream generation condensation, and the air-flow that contains entrained liquids that will obtain then is back in this reactor.The operation of this being referred to as " condensation mode " can't cause above-mentioned gathering and latch up phenomenon, also can not change product performance, but can increase the space-time yield of polymkeric substance greatly.In circulating current, add inertia condensing agent (as iso-pentane) to improve dew point, can from reaction system, remove more heat, thereby further improve space-time yield.The content of phlegma should not surpass 20wt% in suggestion such as the Jenkins circulating current, preferred 2-12wt%.Jenkins etc. just refer to overall control and attempt to extend the stable operation district so that optimized difficulty of space-time yield and complicacy in the fluidized-bed reactor, but do not have to discuss the upper limit how to determine condensable liquid hold-up and solve what use is made of " condensation mode " operation to make space-time yield reach optimized problem.
Usually, the fluidized-bed polymerization reactor care should be used to is controlled to prevent to cause polymkeric substance to become piece or conditioned disjunction in blocks more seriously because fluidized-bed collapse or polymer beads fusing and must stopped reaction and allow the reaction parking.Controllable fluidized-bed reactor is in demand, and it can provide stable operational zone, obtains the density polymer of desired molten exponential sum optimum yield.The Chinese patent application 93105791 of exxon chemical company proposes a kind of method of steady operation conditions of definite fluidized-bed polymerization reactor, with the optimum design that helps factory with determine desirable method condition in given plant design.Wherein the method for definite steady operation conditions comprises: (a) form the variation that changes relevant fluidized-bed loose density or its indication parameter with fluidizing medium in the observing response device and improve the recycle stream cooling power with (b) changing by composition, composition changes to be no more than makes fluidisation loose density or the reduction of its indication parameter become irreversible level.The fluidisation loose density is called for short FBD, and FBD makes progress in the reactor through the mensuration pressure drop of center fixation part and the ratio of this section height, and the deposition loose density is called for short SBD.In general, the ratio of FBD and SBD drops to and just has the danger that fluidized-bed collapses below 0.59, should be avoided.Find, along with the condensable components concentration in the gaseous stream of the bed of flowing through raises, can reach a discernible point, just might make technology cause the danger of ruining and losing efficacy if concentration continue to raise and surpass this, the feature of this point is that condensable fluid concentrations improves and will make fluid density that irreversible variation takes place in the gas.In addition, the document also provides a kind of phase fluid bed polymerizing method that can obtain maximum reactor productivity.Wherein under reaction conditions, allow and comprise that monomeric gas stream makes polymerisate and comprise the logistics of unreacted monomer by the fluidized-bed reactor that has catalyzer, to mix with the charging composition after this logistics compression and the cooling and gas phase and liquid phase loopback be gone into reactor, its improvement comprises that this logistics of cooling makes liquid phase reach the 15wt% of loopback logistics gross weight, preferred 20wt% is above and allow the logistics composition that FBD and the ratio of SBD are reached above 17.8-30.2, preferred 18.1-30.2.
For the fluidized-bed polymerization reactor of operating under condensation mode, prior art is the stability that monitors reactor with the variation of observation fluidisation loose density FBD or other associated arguments.But the measurement of this parameter is not directly to get, and will draw by the pressure reduction of mensuration fluidized-bed layer and the ratio of this section bed height.Since the obstruction of the error of pressure measuring instruments, instrument pressure guiding pipe and condensing agent impulse in-tube condensation etc. all multifactor often make measure inaccurate, thereby cause the error of fluid bedreactors judgement of stability, even cause the Serious Accident of fluidized-bed bed collapse.In addition, the prior art document is pointed out: the condensable liquid concentration, FBD also depends on other variable, comprising in cycling stream: superficial velocity, the height of bed, product SBD, temperature of reactor and pressure.The variation of these variablees also can cause the skew of FBD value.
The inventor makes us finding uncannily through the practice of long term stabilization operation: select for use the temperature of bed different positions more direct and desirable as the parameter of fluidized-bed stability monitoring.
Therefore, a kind of fluidised bed polymerisation method that provides is provided, contain the gas phase recycle stream that monomeric gaseous stream generates polymerisate by the fluidized-bed reactor that catalyzer is housed and contains unreacted monomer comprising under reaction conditions, making, mixture flow with this logistics compression and cooling back generation gas phase and liquid phase, restock charging composition, send reactor then back to, it is characterized in that the method for determining steady operation conditions comprises:
A. in the observing response device with fluidizing medium form to change relevant fluidized-bed bed temperature indicator value variation and
B. improving the cooling power of recycle stream but be no more than by the composition that changes fluidizing medium makes the bed temperature indicator value become irreversible level.
Fig. 1 is a fluidized bed reaction system process flow diagram of the present invention.
Among the figure:
A-recycle stream compressor
B-recycle stream water cooler
The c-fluidized-bed reactor
D-polymerization product drawing mechanism
E-catalyzer feeder
The f-reactant feed lines
The g-condensing agent injects pipeline
H-polymerization product and contained reaction monomers and condensing agent are at the downstream processing pipeline
I-recycle stream Returning reactor pipeline
The present invention utilizes the temperature of fluid bed bed diverse location as the parameter of fluid bed stability monitoring, can adopt particularly following two kinds of method for optimizing to be implemented. Two kinds of methods can independently be used, and also can consult and use mutually. Preferably mutually with reference to relatively using.
1. utilize the stability of reactor fluidisation bed axial-temperature gradient threshold Tz monitoring fluid bed under condensing mode operation. Whether what and fluid bed fluidisation of the distribution of axial temperature and variation sign liquid phase component content be good. The available following formula of Tz value (1) expression:
In the formula:
T
24-fluidized-bed middle and upper part bed temperature (℃)
T
40-fluidized-bed middle and lower part bed temperature (℃)
T
44-fluidized-bed bed bottom temp (℃)
By evidence, there is a certain threshold value A of Tz value.When Tz was less than or equal to this threshold value A, fluidized bed process was highly stable.As Tz during greater than this threshold value A, fluidized bed process stability descends gradually and is irreversible.
For example, when producing ldpe resin The time Tz threshold value A=0.8.
2. the T that calculates with following experimental formula (2)
44Threshold value B monitor the stability that fluidized-bed is operated under condensation mode.
B＝A
0+A
1lnC
x+A
2ln(P
92+W
33/S×100) (2)
In the formula: A
0-system constants
A
1-condensing agent concentration factor
A
2-pressure factor
C
xCondensation concentration (Vol%) in-recycle stream
P
92-reactor reaction pressure (kPa)
W
33-resin bed heavy (kg)
The S-reactor cross section is amassed (cm
2)
Work as T
44During greater than the threshold value B that calculates, the bed stable operation is worked as T
44Be equal to or less than bed stability decreases when calculating threshold value B, even irreversible accident takes place.
The derivation principle and the method for formula (2):
Facts have proved that to dew point 3 ℃ the time, it is the hazardous area that causes the unstable trend of bed " collapse " that powder and liquid phase form " mud " to the toner in the fluidized-bed at the dew point of recycle stream.According to this experience, control fluidized-bed bed bottom temp T
44Under this state below the dew point 3 ℃ be very crucial.Test is proof again, and the cryogen amount of fluidized-bed toner absorption is relevant with density, the bed bottom temp of resin.Therefore prevent the cryogen amount of toner absorption, not enough so that it becomes the minimum temperature of " snowball " state under operational stage, should be that dew-point temperature is more than 8 ℃ under the operational stage, this temperature is called T
44Threshold value B.
The concrete derivation method of formula (2):
Make cryogen concentration and T under the level pressure
44The functional relation of threshold value B be
B＝A
1lnC
x+A
0’-(a)
Under operational stage, the C under test " snowball " condition
xReach two groups of B values, in the substitution formula (a), obtain A
1And A
0'.
System's stagnation pressure and the T under the cryogen concentration decided in order
44The functional relation of threshold value B be
B＝A
2lnP
c+A
0”-(b)
P under operational stage under test " snowball " condition
cReach two groups of B values, in the substitution formula (b), try to achieve A
2And A
0".
With (a) formula and (b) formula addition, and make A
0=A
0'+A
0", P
c=P
92+ W
33/ S * 100; Promptly get experimental formula (2).
For example, when production DGM-1820 polyethylene product, the LLDPE powder base resin that it forms for a kind of direct polymerization, melt flow rate (MFR) is 2.1g/10min, density is 0.921g/cm
3, when condensing agent is selected hexanaphthene for use, A
0=58.363, A
1=14.1165, and A
2=-1.3115
Can be according to following parameters be regulated in the requirement of the rosin products trade mark, state of the art and production yield, thus control Tz value, T
44Value, make them satisfy above-mentioned (1), the determined stabilization scope of (2) formula, these parameters comprise: catalizer variety, catalyzer add-on, olefin partial pressures, condensing agent concentration, reaction total pressure, temperature of reaction, recycle stream flow, hydrogen component concentration and terminator C.
The used catalyzer of the present invention comprises: coordination anion catalyzer, cationic catalyst and transition metal component or metallocene catalyst, bimodal polyethylene catalyzer.
The used condensing agent of the present invention comprises volatile liquid stable hydrocarbon.As iso-pentane and normal hexane.But optimization cyclopentane, this be own together with the application, the main inventive point of common unsettled another application 99118185.9.At this this application is incorporated herein by reference in full.
The inventive method is not limited to produce polyolefine, also can be used for the enforcement of any thermopositive reaction of carrying out in the gas fluidized bed, the enforcement of the polymerization exotherm of especially operating under condensation mode reaction.
The recycle stream of the inventive method enters the inlet device of reactor bottom, preferably adopts director, and it is made up of a concentric annular plate and conical plate, and it can provide three passages that make air-flow feed reactor at least.This director be own together with the application, the main inventive point of common unsettled another application 99118186.7.At this this application is incorporated herein by reference in full.
The present invention can improve cooling power by the ratio that strengthens the condensing agent that can improve dew point.Polymerization product of the present invention can be the film-grade material, molding graae material or high density material.
Embodiment
Use the Unipol fluidized-bed polyethylene production equipment of the U.S. combinating carbide company that introduces to carry out condensing mode operation.Adopt pentamethylene as the inertia condensing agent.The service data of noon 12 up to 12 o'clock midnights of processing parameter, logistics composition and space-time yield etc. sees Table 1.
Table 1
DGM-1820 service data table
| Time | 12：00 | 14：00 | 16：00 | 18：00 | 20：00 | 22：00 | 24：00 |
| Recycle stream is formed | |||||||
| Ethene % | 46.0 | 46.2 | 45.7 | 45.5 | 44.9 | 45.2 | 46.1 |
| Butene-1 % | 18.4 | 18.48 | 18.28 | 18.2 | 17.96 | 18.08 | 18.44 |
| Hydrogen % | 9.2 | 9.24 | 9.14 | 9.15 | 8.98 | 9.04 | 9.22 |
| Pentamethylene % | 4.0 | 5.4 | 4.4 | 4.2 | 3.8 | 3.7 | 4.0 |
| Nitrogen % | 20.6 | 18.88 | 20.78 | 22.23 | 22.76 | 22.48 | 20.72 |
| Ethane % | 1.8 | 1.8 | 1.7 | 1.72 | 1.6 | 1.5 | 1.57 |
| Circulation gas dew point ℃ | 59.7 | 66.0 | 61.5 | 60.46 | 58.24 | 57.88 | 59.75 |
| Reactor inlet temperature ℃ | 52.3 | 49.5 | 46.2 | 45.7 | 48.5 | 48.8 | 47.6 |
| Liquid WT% in the circulation gas | 6.1 | 14.3 | 12.8 | 12.3 | 7.9 | 7.4 | 10.2 |
| Temperature of reactor ℃ | 88.1 | 87.5 | 87.7 | 88.1 | 87.9 | 87.6 | 88.2 |
| Reactor pressure KpaG | 2400.5 | 2410.7 | 2400.3 | 2360.8 | 2369.8 | 2361.5 | 2355.3 |
| Reactor gas speed M/S | 0.76 | 0.77 | 0.74 | 0.73 | 0.73 | 0.72 | 0.71 |
| Reactor beds layer height M | 12.8 | 13.0 | 12.7 | 12.6 | 12.7 | 12.9 | 13.1 |
| The Tz value | 0.333 | 0.562 | 0.580 | 0.570 | 0.421 | 0.411 | 0.490 |
| T 44The B value | 67.33 | 74.00 | 69.2 | 68.1 | 66.24 | 65.88 | 67.75 |
| Space-time yield KG/HR M 3 | 155.8 | 207.5 | 209.1 | 207.8 | 175.2 | 171.8 | 190.9 |
| Circulating current enthalpy change CAL/G | 22.1 | 29.4 | 29.6 | 29.45 | 24.8 | 24.35 | 27.1 |
| Reactor size | |||||||
| Diameter M | 3.05 | 3.05 | 3.05 | 3.05 | 3.05 | 3.05 | 3.05 |
| Direct tube section height M | 12.0 | 12.0 | 12.0 | 12.0 | 12.0 | 12.0 | 12.0 |
| Director | Modified version | Modified version | Modified version | Modified version | Modified version | Modified version | Modified version |
| The product physical index | |||||||
| MI g/10min | 1.98 | 2.01 | 2.02 | 2.10 | 2.09 | 1.99 | 1.98 |
| DEg/cc | 0.919 | 0.920 | 0.920 | 0.919 | 0.918 | 0.918 | 0.919 |
| Material consumption t/t | 1.022 | 1.021 | 1.022 | 1.020 | 1.020 | 1.019 | 1.021 |
The present invention selects the parameter of the temperature of bed different positions as gas-phase fluidized bed stability monitoring for use., steady running continuous at device is found after 18 months to monitor the stability of fluidized-bed under condensation mode than that habitually practised, more direct, more accurate, more reliable with the method for fluid density monitoring in the past with the Tz value.Avoided occurring easily when monitoring mishandle because of pressure guiding pipe stops up or other fault causes with fluid density.
Claims (7)
1. fluidised bed polymerisation method, this method is included in to make under the reaction conditions and contains the gas phase recycle stream that monomeric gaseous stream generates polymerisate by the fluidized-bed reactor that catalyzer is housed and contains unreacted monomer, in recycle stream, introduce the saturated hydrocarbons inert condensable agent that is used to improve its dew point, mixture flow with recycle stream compression and cooling back generation gas phase and liquid phase, restock charging composition, send reactor then back to, it is characterized in that the method for determining steady operation conditions comprises:
A. observe in the reactor and form the variation that changes relevant fluidized-bed bed temperature indicator value with fluidizing medium; With
B. improve the cooling power of recycle stream but be no more than by the composition that changes fluidizing medium and make the bed temperature indicator value become irreversible level,
Wherein said temperature indicator value is reactor axial-temperature gradient threshold Tz
In the formula, T
24-fluidized-bed middle and upper part bed temperature, ℃
T
40-fluidized-bed middle and lower part bed temperature, ℃
T
44-fluidized-bed bed bottom temp, ℃
T
z≤ threshold value A, fluidized-bed is in the stable operation district;
Perhaps
Wherein said temperature indicator value is the temperature T of fluidized-bed bed bottom
44, its threshold value B is calculated by following experimental formula:
B＝A
0+A
1lnC
x+A
2ln(P
92+W
33/S×100) (2)
In the formula: A
0-system constants
A
1-condensing agent concentration factor
A
2-pressure factor
C
xCondensing agent concentration in the-recycle stream, Vol%
P
92-reactor reaction pressure, kPa
W
33-resin bed is heavy, kg
The S-reactor cross section is long-pending, cm
2
T
44＞threshold value B fluidized-bed is in the stable operation district.
2. according to the process of claim 1 wherein that the saturated hydrocarbons condensing agent of introducing is a pentamethylene.
3. improve cooling power according to the ratio that the process of claim 1 wherein by strengthening the condensing agent that can improve dew point.
4. according to the process of claim 1 wherein that recycle stream introduces through a director from the reactor lower part inlet device, this director is made up of a concentric annular plate and conical plate, and it can provide three passages that make air-flow feed reactor at least.
5. according to the process of claim 1 wherein that polymerization product can be the film-grade material, molding graae material or high density material.
6. according to the process of claim 1 wherein the threshold value A=0.8 of when producing ldpe resin Tz.
7. produce the DGM-1820 polyethylene product according to the process of claim 1 wherein to work as, the LLDPE powder base resin that it forms for a kind of direct polymerization, melt flow rate (MFR) is 2.1g/10min, density is 0.921g/cm
3, when condensing agent is selected pentamethylene for use, A
0=58.363, A
1=14.1165, and A
2=-1.3115.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB991181875A CN1134454C (en) | 1999-08-30 | 1999-08-30 | Improved method for determining stable operating region of gas-phase fluidized-bed polymerizing reactor operating in condensation mode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB991181875A CN1134454C (en) | 1999-08-30 | 1999-08-30 | Improved method for determining stable operating region of gas-phase fluidized-bed polymerizing reactor operating in condensation mode |
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| Publication Number | Publication Date |
|---|---|
| CN1286269A CN1286269A (en) | 2001-03-07 |
| CN1134454C true CN1134454C (en) | 2004-01-14 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB991181875A Expired - Lifetime CN1134454C (en) | 1999-08-30 | 1999-08-30 | Improved method for determining stable operating region of gas-phase fluidized-bed polymerizing reactor operating in condensation mode |
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| CN103183753B (en) * | 2011-12-29 | 2015-07-01 | 中国石油化工股份有限公司 | Method for preparing polymer |
| PL3044238T3 (en) * | 2013-09-12 | 2018-07-31 | W.R. Grace & Co. - Conn. | Gas-phase polymerization process with wet zone |
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1999
- 1999-08-30 CN CNB991181875A patent/CN1134454C/en not_active Expired - Lifetime
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