A charge gas compression train for ethylene, comprising on the same shaft line a steam turbine and a first compressor comprising a first group of compression stages, a second group of compression stages and a third group of compression stages, a. the first group of compression stages comprising an outlet configured to be connected to a first intercooler inlet, b. the second group of compression stages comprising a second compressor inlet configured to be connected to a first intercooler outlet, the second group of compression stages comprising a second compressor outlet configured to be connected to a second intercooler inlet, c. the third group of compression stages comprising a third compressor inlet configured to be connected to a second intercooler outlet, the first, the second and the third group of compression stages being integrated in a first common casing and operating at the same rotation speed of the steam turbine; wherein the first group of compression stages, the second group of compression stages and the third group of compression stages are mounted on the same compressor shaft, the steam turbine being directly coupled with the compressor shaft, wherein the compressor shaft is formed in a single piece, or in different parts torsionally coupled to each other, characterized by the first group of compression stages comprising a plurality of unshrouded and shrouded impellers, wherein at least an unshrouded impeller is positioned upstream to at least a shrouded impeller and the unshrouded impellers have a larger diameter than the shrouded impellers, and wherein the compression train is configured to operate at a rotating speed up to 22000 rpm, preferably in a speed range comprised between 5000 and 12000 rpm. a. the first group of compression stages comprising an outlet configured to be connected to a first intercooler inlet, b. the second group of compression stages comprising a second compressor inlet configured to be connected to a first intercooler outlet, the second group of compression stages comprising a second compressor outlet configured to be connected to a second intercooler inlet, c. the third group of compression stages comprising a third compressor inlet configured to be connected to a second intercooler outlet, the first, the second and the third group of compression stages being integrated in a first common casing and operating at the same rotation speed of the steam turbine; wherein the first group of compression stages, the second group of compression stages and the third group of compression stages are mounted on the same compressor shaft, the steam turbine being directly coupled with the compressor shaft, wherein the compressor shaft is formed in a single piece, or in different parts torsionally coupled to each other, characterized by the first group of compression stages comprising a plurality of unshrouded and shrouded impellers, wherein at least an unshrouded impeller is positioned upstream to at least a shrouded impeller and the unshrouded impellers have a larger diameter than the shrouded impellers, and wherein the compression train is configured to operate at a rotating speed up to 22000 rpm, preferably in a speed range comprised between 5000 and 12000 rpm.