Method for controlling bubble formation in polymerization reactors

Patent metadata

Field	Value
Publication number	US-9296833-B2
Application number	US-201013702845-A
Country	US
Kind code	B2
Filing date	Jul 16, 2010
Priority date	Jul 8, 2010
Publication date	Mar 29, 2016
Grant date	Mar 29, 2016

Abstract

Disclosed herein are methods for controlling bubble formation in a polymerization reactor. The method includes: (a) determining a concentration of at least one component at a location in the reactor using a mathematical model; (b) determining a vapor pressure of the composition based at least in part upon the concentration of the component; (c) determining an operating pressure of the reactor at the location; (d) determining a pressure difference as ΔP=P X −P V , wherein P X is the operating pressure and P V is the vapor pressure; (e) comparing the ΔP to a threshold value; and (f) implementing an effect when the ΔP is less than the threshold value.

First claim

The invention claimed is:

1. A method for controlling bubble formation in a polymerization reactor, the reactor containing a composition comprising at least one component, the method comprising:
(a) determining a concentration of the at least one component in the composition at a location in the reactor using a mathematical model;
(b) determining a vapor pressure of the composition based at least in part upon the concentration of the at least one component;
(c) determining an operating pressure of the reactor at the location;
(d) determining a pressure difference as ΔP=P X −P V , wherein P X is the operating pressure and P V is the vapor pressure;
(e) comparing the ΔP to a threshold value, wherein the threshold value reflects a desired difference between the vapor pressure and operating pressure, and wherein a ΔP that is greater than the threshold value produces an acceptable amount of bubble formation; and
(f) implementing an effect when the ΔP is equal or less than the threshold value.

2. The method of claim 1 , wherein one or more of (a) through (f) are conducted on a real-time basis.

3. The method of claim 1 , wherein the method is conducted during change of a reactant supplied to the reactor during a grade transition.

4. The method of claim 1 , wherein steps (a) through (f) are conducted at more than one location within the reactor.

5. The method of claim 1 , wherein the at least one component includes one or more of polyolefin, olefin, hydrogen and catalyst.

6. The method of claim 1 , wherein the mathematical model estimates the concentration as a function of at least one of reactor temperature, reactor inlet flow and consumption rate of one or more components of the composition.

7. The method of claim 6 , wherein the mathematical model determines the concentration as a function of the material balances in the reactor.

8. The method of claim 1 , wherein the operating pressure is determined through one of: (i) direct measurement at the location; (ii) estimation at the location based upon measurement of an operating pressure at a different location; or (iii) estimations of static and dynamic pressure losses throughout the reactor.

9. The method of claim 1 , wherein the threshold value is set at a value that substantially prevents the formation of vapor bubbles.

10. The method of claim 1 , wherein the reactor comprises a pump having a pump inlet, and wherein the location is immediately upstream of the pump inlet, and the threshold value is 0.

11. The method of claim 10 , wherein the reactor is a slurry loop reactor.

12. The method of claim 1 , wherein the threshold value is set to limit the amplitude of the pump power oscillations located at points of interest.

13. The method of claim 1 , wherein the threshold value is set to limit the cavitation of the pump located at points of interest.

14. The method of claim 1 , wherein the effect comprises increasing the operating pressure.

15. The method of claim 1 , wherein the effect comprises altering reactor temperature or component concentration.

16. The method of claim 1 , wherein the composition comprises hydrogen as a component and the effect comprises altering hydrogen concentration.

17. The method of claim 1 , wherein the effect reduces the reactor temperature.

18. The method of claim 1 , wherein the effect provides a reaction inhibitor directly or indirectly into the reactor.

19. The method of claim 18 , wherein the reaction inhibitor includes carbon monoxide.

20. The method of claim 1 , wherein the effect reduces or stops the addition of a catalyst to the reactor.

21. The method of claim 1 , wherein an effect is continuously implemented to maintain control of the ΔP at a setpoint, and wherein control is maintained by at least one of open loop feedback control, manual feedback control, automatic feedback control, and automatic feed forward control.

22. A method for controlling bubble formation in a slurry loop polypropylene polymerization reactor, the reactor containing a composition comprising at least one component, the method comprising:
(a) determining a concentration of at least one component in the reactor composition at a location in the reactor using a mathematical model;
(b) determining a vapor pressure of the composition based at least in part upon the concentration of the component;
(c) determining an operating pressure of the reactor at the location;
(d) determining a pressure difference as ΔP=P X −P V , where P X =the operating pressure and P V =the vapor pressure;
(e) comparing the ΔP to a threshold value, wherein the threshold value reflects a desired difference between the vapor pressure and operating pressure, and wherein a ΔP that is greater than the threshold value produces an acceptable amount of bubble formation; and
(f) implementing an effect when the ΔP is equal or less than the threshold value, wherein the effect comprises altering at least one process parameter.

Assignees

• Lawson Kevin W
• Hedengren John D
• Smith Lawrence C
• Exxonmobil Chem Patents Inc

Inventors

• Lawson Kevin W
• Hedengren John D
• Smith Lawrence C

Classifications

• C08F10/06

  Propene · CPC title

• C08F2/14

  Organic medium · CPC title

• C08F2/01 Primary

  characterised by special features of the polymerisation apparatus used · CPC title

• C08F210/06

  Propene · CPC title

• C08F2/00

  Processes of polymerisation · CPC title