Patent ID: 8883918

Claim:
A process for recycling product streams separated from a hydrocarbon-containing feed stream comprising olefin monomer, one or more optional olefin co-monomer, hydrocarbon diluent and components selected from H 2 , N 2 , O 2 , CO, CO 2 , and formaldehyde, wherein said hydrocarbon-containing feed stream is separated by the steps of: a) introducing said hydrocarbon-containing feed stream into a first distillation column for subjecting said hydrocarbon-containing feed stream to distillation conditions adapted to remove: a1) a bottom stream comprising hydrocarbon diluent and one or more optional co-monomer, and a2) an overhead stream comprising hydrocarbon diluent, olefin monomer and components selected from H 2 , N 2 , O 2 , CO, CO 2 , and formaldehyde; b) condensing the overhead stream issued from the first distillation column in step a2) to form a first condensate and storing said first condensate in a first separator adapted to separate a first vapor stream and a first liquid stream; c) removing from said first separator said first vapor stream comprising olefin monomer, hydrocarbon diluent and components selected from formaldehyde, H 2 , N 2 , O 2 , CO, and CO 2 ; d) condensing the first vapor stream removed in step c) to form a second condensate and storing said second condensate in a second separator adapted to separate a second vapor stream and a second liquid stream; e) removing from said second separator said second liquid stream of step d); f) separating said second liquid stream into a first side stream comprising hydrocarbon diluent and olefin monomer; and a remainder stream; g) introducing said remainder stream in a second distillation column and subjecting said remainder stream to distillation conditions adapted to remove: g1) a bottom stream comprising substantially olefin-free hydrocarbon diluent, g2) a substantially hydrogen-free second side stream comprising hydrocarbon diluent and olefin monomer, and g3) an overhead vapor stream comprising olefin monomer, hydrocarbon diluent and components selected from formaldehyde, H 2 , N 2 , O 2 , CO, and CO 2 , wherein said first side stream and said substantially hydrogen-free second side stream are recycled in a polymerization process for preparing bimodal polyolefin comprising at least two different polyolefin fractions that have been obtained in two different polymerisation reactors connected to each other in series, and wherein one of said polyolefin fractions has a higher molecular weight than said other polyolefin fraction, and wherein said substantially hydrogen-free second side stream is re-used in the polymerization process wherein the polyolefin fraction having the higher molecular weight is prepared, and wherein said first side stream is re-used in the polymerization process wherein the other polyolefin fraction is prepared.