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

• US 20030121330A1
• Filed: 11/18/2002
• Published: 07/03/2003
• Est. Priority Date: 12/17/2001
• Status: Active Grant

• Current Assignee: Univation Technologies LLC (Dow, Inc.)
• Original Assignee: Univation Technologies LLC (Dow, Inc.)
• Inventors: Muhle, Michael E., Daw, Stuart, Nguyen, Ke, Finney, Charles
• Granted Patent: US 7,226,789 B2
• Time in Patent Office: Days
• US Class Current: 73/600
• 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 at least one system variable of the reactor during a time period to generate data;

b. filtering said data set to demodulate a time series;

c. calculating a signal from said filtered data; and

d. determining the reactor continuity by comparing said signal for said reactor to a signal of a control reactor.

2. The method of claim 1, wherein said system variable comprises an acoustic emission, a differential pressure, a bed pressure drop, a fluidized bulk density, a static voltage and a reactor wall temperature.

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

4. The method of claim 1, wherein said data comprises high speed data.

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

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

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

8. The method of claim 1, wherein said signal comprises a mean deviation to indicate disturbance.

9. The method of claim 1, wherein said determining is selected from a group consisting of a precursor state of sheeting, a change in fluidization, and a fluidization transition state.

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

30. The method of claims 1, 11 or 18, wherein the determination is performed locally.

31. The method of claims 1, 11 or 18, wherein the determination is performed remotely.

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

a. applying an acoustic emission to a reactor wall;

b. measuring an acoustic transmission to generate data;

c. filtering said data to demodulate a time series;

d. calculating a first signal for said time series; and

e. determining the reactor continuity by comparing said first signal to a control signal of a control reactor wherein a decrease in signal for the control signal indicates the presence of sheeting.

12. The method of claim 11, wherein said applying comprises about 100 kHz to 400 kHz.

13. The method of claim 11, wherein said measuring comprises a passive acoustic emission detector.

14. The method of claim 11, wherein said filtering comprises a low pass filter.

15. The method of claim 11, wherein said filtering comprises a root mean squared filter.

16. The method of claim 11, wherein said signal is selected from the group consisting of an entropy, a cycle time, a mean deviation and the eigenvalues of an embedded time series.

17. The method of claim 11, wherein said determining is selected from a group consisting of a precursor state of sheeting, a change in fluidization, and a fluidization transition state.

18. A method of controlling reactor continuity in a gas-phase fluid bed reactor comprising the steps of:

a. measuring at least one system variable of the reactor during a time period to generate data;

b. filtering said data set to demodulate a time series;

c. calculating a signal from said filtered data; and

d. determining the reactor continuity by comparing said signal for said reactor to a signal of a control reactor; and

e. applying a counter measure to control reactor continuity.

19. The method of claim 18, wherein said system variable comprises an acoustic emission, a differential pressure, a bed total pressure drop, a fluidized bulk density, a static voltage and a reactor wall temperature.

20. The method of claim 19, wherein said acoustic emission is measured with a passive acoustic emission detector.

21. The method of claim 18, wherein said data set comprises high speed data.

22. The method of claim 18, wherein said high speed data is selected from the group consisting of a filtered fluidized bulk density, a bed total pressure drop, a static voltage, am acoustic emission and a skin thermocouple measurement.

23. The method of claim 18, wherein said signal is selected from the group consisting of a signal entropy, a cycle time, a mean deviation and the eigenvalues of an embedded time series.

24. The method of claim 18, wherein said counter measure comprises injecting poisons into said reactor.

25. The method of claim 18, wherein said counter measure comprises adding anti-static and pro-static agents.

26. The method of claim 18, wherein said counter measure comprises adjusting a temperature of said reactor.

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

28. The method of claim 18, wherein said counter measure comprises adding a reactor surface modifier.

29. The method of claim 18, wherein said counter measure comprises adding a gas pulse.

32. The method of claim 18, wherein the counter measure control is performed locally.

33. The method of claim 18, wherein the counter measure control is performed remotely.

34. The method of claim 18, wherein the determination is performed locally and the counter measure control is performed locally.

35. The method of claim 18, wherein the determination is performed locally and the counter measure control is performed remotely.

36. The method of claim 18, wherein the determination is performed remotely and the counter measure control is performed locally.

37. The method of claim 18, wherein the determination is performed remotely and the counter measure control is performed remotely.