Method of applying non-linear dynamics to control a gas-phase polyethylene reactor operability

• US 7,226,789 B2
• Filed: 11/18/2002
• Issued: 06/05/2007
• Est. Priority Date: 12/17/2001
• Status: Active Grant

• Current Assignee: Univation Technologies LLC (Dow, Inc.)
• Original Assignee: Univation Technologies LLC (Dow, Inc.)
• Inventors: Daw, Stuart C., Muhle, Michael E., Nguyen, Ke, Finney, Charles E.A.
• Primary Examiner(s): Soderquist; Arlen
• Application Number:
  US10/298,311
• Publication Number:
  US 20030121330A1
• Time in Patent Office: 1,660 Days
• Field of Search: 422/62, 422/105, 422108-112, 436/37, 436/50, 436/55
• US Class Current: 436/55
• CPC Class Codes: C08F 10/00 Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
• CPC Class Codes: C08F 10/02 Ethene
• CPC Class Codes: C08F 2/00 Processes of polymerisation
• CPC Class Codes: C08F 2/34 Polymerisation in gaseous state
• CPC Class Codes: C08F 2400/02 Control or adjustment of polymerization parameters
• CPC Class Codes: G01N 2291/02491 Materials with nonlinear acoustic properties
• CPC Class Codes: G01N 2291/02872 Pressure
• CPC Class Codes: G01N 2291/02881 Temperature
• CPC Class Codes: Y10T 436/115831 Condition or time responsive
• CPC Class Codes: Y10T 436/12 Condition responsive control

Abstract

The present invention describes a method for determining reactor continuity of a polymerization reactor by non-linear dynamics. Specifically, the invention relates to a method of analyzing system variables to indicate gas phase reactor continuity in real-time and controlling the reactor continuity to maintain operability.

Claims

1. A method of determining a reactor continuity comprising the steps of:

a. measuring system variables of the reactor during a time period to generate data, said variables comprising an acoustic emission, a differential pressure, a bed total pressure drop, a fluidized bulk density, a static voltage and a skin thermocouple measurement;

b. filtering said data;

c. calculating a signal from said filtered data employing chaotic non-linear dynamics wherein said signal comprises entropy, cycle time or mean deviation (MD); and

d. comparing said calculated signal for said reactor to a calculated signal of a control reactor to detect reactor continuity comprising, detecting fluidization changes in the reactor, detecting sheeting or identifying sheeting precursors;

wherein said reactor is an ethylene gas-phase polymerization reactor.

2. The method of claim 1, wherein said acoustic emission is measured with a passive acoustic emission detector.

3. The method of claim 1, wherein said data comprises high speed data obtained at a collection rate greater than 1 Hz, recorded at least at 10 data points per second for a duration of 1–

60 minutes.

4. The method of claim 3, wherein said high speed data set is selected from the group consisting of a fluidized bulk density, a bed total pressure drop, a static voltage, an acoustic emission and a skin thermocouple measurement.

5. The method of claim 1, wherein said signal comprises entropy.

6. The method of claim 1, wherein said signal comprises said cycle time.

7. The method of claim 1, wherein said signal comprises said mean deviation.

8. The method of claim 1, wherein said filtering comprises a root mean square filter.

9. The method of claim 1, wherein said filtering comprises a low pass filter.

10. The method of claim 1, wherein said acoustic emission is measured at about 100 kHz to 400 kHz.

11. The method of claim 1, wherein the determination is performed locally.

12. The method of claim 1, wherein the determination is performed remotely.

13. The method of claim 1 further comprising:

applying a counter measure to control reactor continuity when a difference between the signal for the control reactor and the signal for the reactor being controlled is one of mean deviation decrease, entropy decrease, or cycle time increase.

14. The method of claim 13, wherein said signal comprises eigenvalues of an embedded time series.

15. The method of claim 13, wherein said counter measure comprises injecting poisons into said reactor.

16. The method of claim 13, wherein said counter measure comprises adding anti-static and pro-static agents into said reactor.

17. The method of claim 13, wherein said counter measure comprises adjusting a temperature of said reactor.

18. The method of claim 13, wherein said counter measure comprises adjusting a velocity of a medium in said reactor.

19. The method of claim 13, wherein said counter measure comprises adding a reactor surface modifier to said reactor.

20. The method of claim 13, wherein said counter measure comprises adding a gas pulse to said reactor.

21. The method of claim 13, wherein the counter measure control is performed locally.

22. The method of claim 13, wherein the counter measure control is performed remotely.

23. The method of claim 13, wherein the determination is performed locally and the counter measure control is performed locally.

24. The method of claim 13, wherein the determination is performed locally and the counter measure control is performed remotely.

25. The method of claim 13, wherein the determination is performed remotely and the counter measure control is performed locally.

26. The method of claim 13, wherein the determination is performed remotely and the counter measure control is performed remotely.

27. A method of determining a reactor continuity comprising the steps of:

a. measuring system variables of the reactor during a time period to generate data, said variables consisting essentially of an acoustic emission, a differential pressure, a bed total pressure drop, a fluidized bulk density, a static voltage and a skin thermocouple measurement;

b. filtering said data;

c. calculating a signal from said filtered data employing chaotic non-linear dynamics wherein said signal comprises entropy, cycle time or mean deviation (MD); and

d. comparing said calculated signal for said reactor to a calculated signal of a control reactor to detect reactor continuity comprising, detecting fluidization changes in the reactor, detecting sheeting or identifying sheeting precursors;

wherein said reactor is an ethylene gas-phase polymerization reactor.