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Process for enhancing the separation of monomer components from light components other than monomer by providing a first stream containing monomer and light components other than monomer and passing the first stream to a first separator at a first pressure to separate a gaseous second stream contain

Process for enhancing the separation of monomer components from light components other than monomer by providing a first stream containing monomer and light components other than monomer and passing the first stream to a first separator at a first pressure to separate a gaseous second stream containing at least some of the light components other than monomer and provide a liquid third stream containing monomer. A portion of the third stream and a fourth stream containing monomer and light components other than monomer is passed to a second separator at a second pressure which is lower than the first pressure to separate a gaseous fifth stream containing at least some of the light components other than monomer from the fourth stream and provide a liquid sixth stream containing monomer.

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1. A process for enhancing the separation of monomer components from light components other than monomer, which process comprises: A) Providing a first stream comprising monomer and light components other than monomer,B) Passing the first stream to a first separator at a first pressure to separate a

1. A process for enhancing the separation of monomer components from light components other than monomer, which process comprises: A) Providing a first stream comprising monomer and light components other than monomer,B) Passing the first stream to a first separator at a first pressure to separate a gaseous second stream comprising at least some of the light components other than monomer and provide a liquid third stream comprising monomer,C) Passing a portion of the third stream and a fourth stream comprising monomer and light components other than monomer to a second separator at a second pressure which is lower than the first pressure to separate a gaseous fifth stream comprising at least some of the light components other than monomer from the fourth stream and provide a liquid sixth stream comprising monomer. 2. A process according to claim 1 wherein the first pressure is at least 0.5 MPa (5 bar). 3. A process according to claim 1 wherein the second pressure is less than 0.5 MPa (5 bar). 4. A process according to claim 1 wherein the pressure difference between the first and second pressures is at least 0.2 MPa (2 bar). 5. A process according to claim 1 wherein the second separator is at a pressure of less than 0.4 MPa (4 bar) and a temperature of less than 10° C. 6. A process according to claim 1 wherein the monomer is ethylene or propylene. 7. A process according to claim 1 wherein fresh diluent and/or fresh comonomer is passed to the second separator. 8. A process according to claim 1 which is applied to a polymerisation process operating in one or more reactors. 9. A process according to claim 8 wherein there are at least two reactors operating in series. 10. A process according to claim 8 which has a monomer efficiency in excess of 99.5%. 11. A process according to claim 8 wherein comonomer is fed to the polymerisation process and the process has a comonomer efficiency in excess of 95%. 12. A process according to claim 8 wherein the first separator is operated to provide a separation of hydrogen, nitrogen and methane from monomer and heavier components. 13. A process according to claim 8 wherein the second stream is cooled to less than −10° C. whilst maintaining pressure at 0.5 MPa (5 bar) and above. 14. A process according to claim 8 wherein the second separator is at a pressure of less than 0.4 MPa (4 bar) and at a temperature of less than −10° C. 15. A process according to claim 8 comprising: 1) Polymerising a monomer and a comonomer in a polymerisation reaction,2) Withdrawing an effluent stream comprising solid polymer and a mixture comprising unreacted monomer and unreacted comonomer, and passing the effluent to a high pressure recovery system comprisinga. a high pressure separation step for separating a first vapour stream comprising unreacted monomer and unreacted comonomer from said solids, andb. a high pressure recycle system for recycling a portion of the first vapour stream to the polymerisation reaction, said high pressure recycle system comprisingi. the first separator at a pressure greater than 0.5 MPa (5 bar) for separating the second stream comprising at least a portion of light components other than monomer in the first vapour stream and the third stream which is a liquid stream comprising condensed portions of the first vapour stream,3) Passing the solids from the high pressure recovery system to a low pressure recovery system comprisinga. a low pressure separation step for separating further unreacted monomer and unreacted comonomer from said solids, andb. a low pressure recycle system for recycling at least a portion of the further unreacted monomer and unreacted comonomer to the polymerisation reaction, said low pressure recycle system comprisingi. the second separator which operates at a pressure of less than 0.5 MPa (5 bar) and at a temperature of less than −10° C. 16. A process according to claim 15 wherein at least two reactors are operated in parallel and effluent stream from each is withdrawn, combined and passed to a common recovery system. 17. A process according to claim 15 wherein at least two reactors are operated in series, and an effluent stream is withdrawn from the last reactor in series for passage to the high pressure recovery system and then to the low pressure recovery system. 18. A process according to claim 15 wherein the portion of the third stream which is passed to the second separator comprises at least 1% by weight of the vapour separated in step 2(a). 19. A process according to claim 15 wherein the portion of the third stream which is passed to the second separator comprises between 20 and 40 wt % of the vapour separated in step 2(a). 20. A process according to claim 15 wherein a portion of the overhead stream from the separator in the low pressure recovery system is purged from the system. 21. A process according to claim 3 wherein the second pressure is less than 0.4 MPa (4 bar). 22. A process according to claim 4 wherein the pressure difference between the first and second pressures is at least 0.3 MPa (3 bar). 23. A process according to claim 6 wherein the monomer is ethylene. 24. A process according to claim 14 wherein the second separator is part of a low pressure recovery system. 25. A process according to claim 15 wherein the second separator operates at a pressure of less than 0.4 MPa (4 bar).