Method of recovering olefins in a solution polymerisation process
The present invention relates to a process for removing hydrocarbons comprising the steps of: (A) passing a stream of a solution into a separator wherein a liquid phase comprising polymer and a vapour phase coexist; (B) withdrawing a vapour stream and a concentrated solution stream from the separator; (C) passing at least a part of the vapour stream into a first fractionator; (D) withdrawing a first overhead stream and a first bottom stream from the first fractionator; (E) passing the first overhead stream to a second fractionator; (F) withdrawing a second overhead stream and a second bottom stream from the second fractionator; (G) passing the second overhead stream to a third fractionator; (H) withdrawing a third overhead stream and a third bottom stream from the third fractionator; characterised in that at least a part of the third bottom stream is withdrawn as a purge stream.
1. A process for removing hydrocarbons comprising the steps of:
(A) passing a stream of a solution into a separator wherein a liquid phase comprising polymer and a vapour phase coexist;
(B) withdrawing a vapour stream and a concentrated solution stream from the separator;
(C) passing at least a part of the vapour stream into a first fractionator;
(D) withdrawing a first overhead stream and a first bottom stream from the first fractionator;
(E) passing the first overhead stream to a second fractionator;
(F) withdrawing a second overhead stream and a second bottom stream from the second fractionator;
(G) passing the second overhead stream to a third fractionator;
(H) withdrawing a third overhead stream and a third bottom stream from the third fractionator;
wherein at least a part of the third bottom stream is withdrawn as a purge stream.
2. The process according to claim 1 wherein the stream of the solution comprises 1-hexene and n-octane and a mixture of isomers of 1-hexene and n-hexane.
3. The process according to claim 2 comprising the step of purging isomers of 1-hexene and n-hexane with the purge stream.
4. The process according to claim 1 , comprising the additional step of:
(I) passing the first bottom stream to a fourth fractionator;
(J) withdrawing a fourth overhead stream and a fourth bottom stream from the fourth fractionator;
(K) passing optionally at least a part of the fourth overhead stream to a polymerisation reactor.
5. The process according to claim 1 , comprising the additional step of:
(L) passing at least a part of the third overhead stream to a polymerisation reactor.
6. The process according to claim 1 , comprising the additional step of:
(M) passing at least a part of the third bottom stream to a polymerisation reactor.
7. The process according to claim 1 , comprising the additional steps of:
(N) passing at least a part of any of the third bottom stream, or third overhead stream to a feed vessel;
(O) withdrawing a feed stream from the feed vessel;
(P) passing the feed stream via a cooling step to a polymerisation reactor.
8. The process according to claim 1 , wherein the stream of the solution comprises ethylene.
9. The process according to claim 1 , wherein any of the first, second, or third fractionators are distillation columns, stripping columns, multi-phase separators, extractors, or liquid-liquid separators.
10. The process according to claim 1 , wherein at least a part of the purge stream is used as a gasoline additive or as a fuel additive.
11. The process according to claim 1 , wherein at least a part of the purge stream sent to a hydrogenation step.
12. The process according to claim 1 , wherein at least a part of the purge stream is sent to an isomerisation step.
13. The process according to claim 4 , comprising the additional steps of:
(N) passing at least a part of any of the fourth overhead stream to a feed vessel;
(O) withdrawing a feed stream from the feed vessel;
(P) passing the feed stream via a cooling step to a polymerisation reactor.
14. The process according to claim 4 , wherein the fourth fractionator is a distillation column, stripping column, multi-phase separator, extractor, or liquid-liquid separator.