Method for polymerization reaction monitoring with determination of entropy of monitored data

• US 20070244271A1
• Filed: 03/30/2007
• Published: 10/18/2007
• Est. Priority Date: 12/17/2001
• Status: Active Grant

• Current Assignee: Univation Technologies LLC (Dow, Inc.)
• Original Assignee: Univation Technologies LLC (Dow, Inc.)
• Inventors: Nguyen, Ke, Muhle, Michael, Finney, Charles, Daw, C.
• Granted Patent: US 7,846,736 B2
• Time in Patent Office: Days
• US Class Current: 526/60
• 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
• CPC Class Codes: Y10T 436/25875 Gaseous sample or with change of physical state

Abstract

In some embodiments, a method of monitoring a resin-producing polymerization reaction in a fluid bed reactor system to generate reaction parameter data in on-line fashion, determining an indicator of at least one of entropy and complexity (for example, Kolmogorov or Shannon entropy) of each of at least two subsets of the reaction parameter data, and optionally also determining from at least one value of the indicator (for example, from a time series of Kolmogorov or Shannon entropy values) an indication of at least one of degree of resin stickiness, an approach to or imminence of resin stickiness, and an approach to or imminence of an unsafe or undesired reactor operating condition (e.g., that can result in sheeting or chunking). Optionally also, the reaction is controlled in response to at least one value of the indicator, for example, in an effort to prevent the occurrence of sheeting or another discontinuity event or to maintain the reactor in a stable, non-sticking condition.

Claims

1. A method for monitoring a resin-producing polymerization reaction in a fluidized bed reactor system, including the steps of:

(a) monitoring at least one reaction parameter of the reaction to generate in on-line fashion time-domain reaction parameter data; and

(b) determining mathematical entropy of each of at least two subsets of the reaction parameter data, each of said subsets of the reaction parameter data including data values in a different one of a sequence of different time intervals.

2. The method of claim 1, wherein the mathematical entropy is Kolmogorov entropy.

3. The method of claim 2, also including the step of:

determining from entropy values generated in step (b) at least one indication of at least one of degree of resin stickiness, approach to or imminence of resin stickiness, likelihood of imminent resin stickiness, and an approach to or imminence of an unsafe or undesired reactor operating condition that can result in at least one of sheeting and chunking.

4. The method of claim 1, wherein the mathematical entropy is Shannon entropy.

5. The method of claim 4, also including the step of:

determining from entropy values generated in step (b) at least one indication of at least one of degree of resin stickiness, approach to or imminence of resin stickiness, likelihood of imminent resin stickiness, and an approach to or imminence of an unsafe or undesired reactor operating condition that can result in at least one of sheeting and chunking.

6. The method of claim 1, wherein the reactor system includes a fluidized bed reactor and a product discharge vessel into which polymer product is discharged from the fluidized bed reactor, and step (a) includes the step of:

measuring product chamber static data indicative of static charge transferred from the polymer product to the product discharge vessel during each of a sequence of intervals.

7. The method of claim 6, wherein the product chamber static data are indicative of static charge transferred to the product discharge vessel during each of a sequence of intervals while said product discharge vessel is filled.

8. The method of claim 6, wherein the product chamber static data comprise data values, each indicative of static charge transferred to the product discharge vessel since said vessel was last emptied.

9. The method of claim 6, wherein the product discharge vessel functions as a Faraday cup during measurement of the product chamber static data.

10. The method of claim 6, also including the step of determining from entropy values generated in step (b) at least one indication of imminent wall sheeting.

11. The method of claim 1, wherein the reaction parameter data generated in step (a) are static data.

12. The method of claim 11, wherein the reaction parameter data generated in step (a) are carryover static data.

13. The method of claim 11, wherein the reaction parameter data generated in step (a) are entrainment static data.

14. The method of claim 1, wherein the reaction parameter data generated in step (a) are acoustic emission data.

15. The method of claim 1, wherein the reaction parameter data generated in step (a) are differential pressure data.

16. The method of claim 1, wherein the reaction parameter data generated in step (a) are high speed reaction parameter data.

17. The method of claim 16, wherein the high speed reaction parameter data are bed temperature data.

18. The method of claim 16, wherein the high speed reaction parameter data are skin temperature data.

19. The method of claim 1, also including the step of:

(c) determining from entropy values generated in step (b) at least one indication of at least one of degree of resin stickiness, approach to or imminence of resin stickiness, likelihood of imminent resin stickiness, and an approach to or imminence of an unsafe or undesired reactor operating condition that can result in at least one of sheeting and chunking.

20. The method of claim 19, wherein step (c) includes the step of generating a signal indicative of at least one of degree of resin stickiness, approach to or imminence of resin stickiness, likelihood of imminent resin stickiness, and an approach to or imminence of an unsafe or undesired reactor operating condition that can result in at least one of sheeting and chunking.

21. The method of claim 19, wherein step (c) includes the step of generating a display indicative of at least one of degree of resin stickiness, approach to or imminence of resin stickiness, likelihood of imminent resin stickiness, and an approach to or imminence of an unsafe or undesired reactor operating condition that can result in at least one of sheeting and chunking.

22. The method of claim 19, also including the step of:

(d) controlling the reaction in response to the at least one indication determined in step (c).

23. The method of claim 22, wherein step (d) includes the step of adjusting reaction temperature.

24. The method of claim 22, wherein step (d) includes the step of controlling a feed rate of a continuity additive.

25. The method of claim 22, wherein step (d) includes the step of controlling a feed rate of an induced condensing agent.

26. The method of claim 1, also including the step of controlling the reaction in response to at least one mathematical entropy value determined in step (b) in an effort to prevent occurrence of a discontinuity event.

27. The method of claim 1, wherein the reaction polymerizes ethylene and at least one comonomer in the presence of a catalyst selected from a group consisting of Ziegler-Natta, chromium, chromium oxide, AlCl₃, cobalt, iron, palladium, and metallocene catalyst.

28. The method of claim 1, wherein the reaction produces polyethylene.

29. The method of claim 1, wherein the reaction produces a polyolefin.

30. A method for monitoring a resin-producing polymerization reaction in a fluidized bed reactor system, including the steps of:

(a) monitoring at least one reaction parameter of the reaction to generate in on-line fashion time-domain reaction parameter data;

(b) determining an indicator of at least one of entropy and complexity of each of at least two subsets of the reaction parameter data, each of said subsets of the reaction parameter data including data values in a different one of a sequence of different time intervals; and

(c) determining, from values of the indicator determined in step (b), at least one indication of at least one of degree of resin stickiness, approach to or imminence of resin stickiness, likelihood of imminent resin stickiness, and an approach to or imminence of an unsafe or undesired reactor operating condition that can result in at least one of sheeting and chunking.

31. The method of claim 30, wherein the indicator is Kolmogorov entropy.

32. The method of claim 30, wherein the indicator is Shannon entropy.

33. The method of claim 30, wherein the indicator is a Lyapunov exponent.

34. The method of claim 30, wherein the reactor system includes a fluidized bed reactor and a product discharge vessel into which polymer product is discharged from the fluidized bed reactor, and step (a) includes the step of:

measuring product chamber static data indicative of static charge transferred from the polymer product to the product discharge vessel during each of a sequence of intervals.

35. The method of claim 34, wherein the product chamber static data are indicative of static charge transferred to the product discharge vessel during each of a sequence of intervals while said product discharge vessel is filled.

36. The method of claim 34, wherein the product chamber static data comprise data values, each indicative of static charge transferred to the product discharge vessel since said vessel was last emptied.

37. The method of claim 34, wherein the product discharge vessel functions as a Faraday cup during measurement of the product chamber static data.

38. The method of claim 34, wherein step (c) includes the step of determining from the values of said indicator at least one indication of imminent wall sheeting.

39. The method of claim 30, wherein the reaction parameter data generated in step (a) are static data.

40. The method of claim 39, wherein the reaction parameter data generated in step (a) are carryover static data.

41. The method of claim 39, wherein the reaction parameter data generated in step (a) are entrainment static data.

42. The method of claim 30, wherein the reaction parameter data generated in step (a) are acoustic emission data.

43. The method of claim 30, wherein the reaction parameter data generated in step (a) are differential pressure data.

44. The method of claim 30, wherein the reaction parameter data generated in step (a) are high speed reaction parameter data.

45. The method of claim 44, wherein the high speed reaction parameter data are skin temperature data.

46. The method of claim 30, wherein step (c) includes the step of generating a signal indicative of at least one of degree of resin stickiness, approach to or imminence of resin stickiness, likelihood of imminent resin stickiness, and an approach to or imminence of an unsafe or undesired reactor operating condition that can result in at least one of sheeting and chunking.

47. The method of claim 30, wherein step (c) includes the step of generating a display indicative of at least one of degree of resin stickiness, approach to or imminence of resin stickiness, likelihood of imminent resin stickiness, and an approach to or imminence of an unsafe or undesired reactor operating condition that can result in at least one of sheeting and chunking.

48. The method of claim 30, also including the step of:

(d) controlling the reaction in response to the at least one indication determined in step (c).

49. The method of claim 48, wherein step (d) includes the step of adjusting reaction temperature.

50. The method of claim 48, wherein step (d) includes the step of controlling a feed rate of a continuity additive.

51. The method of claim 48, wherein step (d) includes the step of controlling a feed rate of an induced condensing agent.

52. The method of claim 30, also including the step of controlling the reaction in response to at least one value of the indicator determined in step (b) in an effort to prevent occurrence of a discontinuity event.

53. The method of claim 30, wherein the reaction polymerizes ethylene and at least one comonomer in the presence of a catalyst selected from a group consisting of Ziegler-Natta, chromium, chromium oxide, AlCl₃, cobalt, iron, palladium, and metallocene catalyst.

54. The method of claim 30, wherein the reaction produces polyethylene.

55. The method of claim 30, wherein the reaction produces a polyolefin.