Process for preparing polyolefins in suspension

A continuous, suspension process for preparing polyolefin polymers having a bimodal or multimodal molar mass distribution from a monomer and at least one comonomer in the presence of a suspension medium in a first reactor and at least one downstream reactor which are connected in series and operated under different reaction conditions within each of the reactors, wherein an after-reactor is avoided and a total yield of more than 98% is obtained, the process comprises:

• collecting all offgases leaving the first reactor and the at least one downstream reactor;
• compressing the collected offgases to a pressure ranging from 0.5 to 2.5 MPa in a compression stage to produce compressed offgases;
• cooling the compressed offgases to produce a cooled offgas material comprising a gaseous fraction comprising an inert gas, hydrogen, and the monomer and a liquid fraction comprising the comonomer and the suspension medium;
• separating the cooled offgas material into the gaseous fraction and the liquid fraction;
• recirculating the gaseous fraction into the first reactor;
• and recirculating the liquid fraction into at least one of the downstream reactors,
• wherein the compressed offgases are cooled in a gas scrubber by contacting with at least a portion of the liquid phase fraction.