Polymerisation process
Process for the polymerization of monomer in a polymerization system having at least one component attached thereto which is flushed with a flush medium which enters the polymerization system. Initially, the component is flushed with a first flush medium, and subsequently the component is flushed with a second flush medium which differs in composition from the first flush medium. A flush gas containing monomer is used as the flush medium when the polymer production rate is above 10 Te/h.
1. A process for the polymerisation of monomer in a polymerisation system having at least one component attached thereto which is flushed with a flush medium which enters the polymerisation system, wherein initially said component is flushed with a first flush medium, and subsequently said component is flushed with a second flush medium which second flush medium differs in composition from the first flush medium, and wherein a flush gas comprising monomer is used as the flush medium when the polymer production rate is above 10 Te/h.
2. A process according to claim 1 wherein the at least one component is selected from seals, pressure relief valves, withdrawal lines, inlet lines, and instrument tappings.
3. A process according to claim 1 wherein there are multiple components attached to the polymerisation system and which are flushed with a flush medium which enters the polymerisation system.
4. A process according to claim 1 wherein the at least one component is attached on a polymerisation reactor and is selected from pressure relief valves, withdrawal lines, inlet lines, and instrument tappings.
5. A process according to claim 1 wherein one of the first and second flush mediums comprises an inert medium, and the other comprises one or more non-inert components.
6. A process according to claim 1 wherein the polymerisation system is a gas phase polymerisation system.
7. A process according to claim 1 wherein the first and second flush mediums are first and second flush gases.
8. A process according to claim 7 wherein one of the first and second flush gases comprises an inert gas or gases and the other comprises one or more non-inert gases.
9. A process according to claim 8 wherein the one or more non-inert gases include monomer, comonomers and hydrogen.
10. A process according to claim 7 wherein the first flush gas comprises an inert gas.
11. A process according to claim 10 wherein the second flush gas comprises the monomer being polymerised.
12. A process according to claim 7 wherein the first flush gas comprises a monomer and the second flush gas comprises an inert gas.
13. A process according to claim 11 wherein the second flush gas comprises relatively pure monomer, by which is meant at least 90 wt % monomer.
14. A process according to claim 11 wherein the second flush gas is a process stream comprising monomer, comonomer and nitrogen.
15. A process according to claim 12 wherein the first flush gas comprises relatively pure monomer, by which is meant at least 90 wt % monomer.
16. A process according to claim 12 wherein the first flush gas is a process stream comprising monomer, comonomer and nitrogen.
17. A process according to claim 10 wherein the first flush gas comprises at least 90 wt % nitrogen.
18. A process according to claim 12 wherein the second flush gas comprises at least 90 wt % nitrogen.
19. A process according to claim 6 wherein the polymerisation system is a fluidised bed gas phase polymerisation system.
20. A process according to claim 10 wherein the first flush gas comprises nitrogen.
21. A process according to claim 1 wherein the process starts-up with a first flush medium comprising an inert medium and switches to the flush gas comprising monomer as production rate increases.
22. A process according to claim 1 wherein a flush gas comprising inert gas is used as the flush medium when the polymer production rate is below 5 Te/h.
23. A process according to claim 22 wherein the flush gas comprising an inert gas comprises at least 90 wt % nitrogen.