Scavenger injection
Process for the polymerization of olefins in a polymerization reactor system including (i) a gas phase reactor having a gas outlet and one or more withdrawal lines for withdrawal of a polymer-containing stream, (ii) a recycle loop for recycling gas exiting the reactor through the gas outlet back to the reactor, (iii) a polymer separation system for separating reactants from the polymer product in the withdrawn polymer-containing stream, and (iv) a recycle system for recycling reactants removed from the reactor in the withdrawn polymer-containing stream back to the reactor. A scavenger is introduced directly into one or more of the recycle loop, the polymer separation system and the recycle system.
1. A process for the polymerisation of olefins in a polymerisation reactor system, the polymerisation reactor system comprising:
(i) a gas phase reactor having a gas outlet and one or more withdrawal lines for withdrawal of a polymer-containing stream,
(ii) a recycle loop for recycling gas exiting the reactor through the gas outlet back to the reactor,
(iii) a polymer separation system for separating reactants from the polymer product in the withdrawn polymer-containing stream, and
(iv) a recycle system for recycling reactants removed from the reactor in the withdrawn polymer-containing stream back to the reactor,
the process comprising introducing a scavenger directly into one or more of the recycle loop, the polymer separation system and the recycle system and into or upstream of a vessel or other equipment which is in the recycle loop, in the polymer separation system or in the recycle system and in which liquid may accumulate during polymerisation.
2. A process according to claim 1 wherein the recycle loop comprises at least one step where, during polymerisation, the gas which has exited the reactor is cooled sufficiently to form condensed liquid.
3. A process as claimed in claim 2 wherein the recycle loop in the reaction system comprises at least one step where, during polymerisation, the gas which has exited the reactor is cooled sufficiently to form a mixture of gas and condensed liquid and a subsequent separator wherein at least part of the condensed liquid is separated from the mixture.
4. A process as claimed in claim 3 wherein scavenger is introduced into a line upstream of the separator.
5. A process as claimed in claim 4 wherein scavenger is introduced in the line between the condenser and the separator.
6. A process as claimed in claim 3 wherein a fresh feed is passed to the process via a feed line to the separator and scavenger is introduced to the separator in the same line.
7. A process as claimed in claim 3 wherein scavenger is introduced directly to the separator.
8. A process as claimed in claim 7 wherein scavenger is introduced directly into the liquid phase in the separator.
9. A process as claimed in claim 1 wherein scavenger is introduced directly in one or more olefin recovery steps in the recycle system where the olefin is condensed, and/or in lines or equipment in the recycle system by which the condensed olefin is recycled to the reactor.
10. A process as claimed in claim 1 wherein scavenger is introduced directly in one of more steps by which olefins are recovered by condensation from a process vent.
11. A process as claimed in claim 1 wherein scavenger is introduced in a recycle stream to a catalyst injection nozzle.
12. A process as claimed in claim 1 wherein scavenger is introduced to said one or more of the recycle loop, the polymer separation system and the recycle system prior to commencement of catalyst injection.
13. A process as claimed in claim 4 wherein scavenger is introduced prior to commencement of catalyst injection.
14. A process as claimed in claim 6 wherein scavenger is introduced prior to commencement of catalyst injection.
15. A process as claimed in claim 7 wherein scavenger is introduced prior to commencement of catalyst injection.
16. A process as claimed in claim 6 wherein a fresh feed is fresh comonomer.