Conversion of unsaturated hydrocarbon containing off-gases for more efficient hydrocarbon production plant

A system for producing a product stream, said system comprising:

• a first feed comprising carbon dioxide;
• a second feed comprising hydrogen;
• optionally, an external dilution feed;
• a syngas stage arranged to receive at least a first portion of said first feed, at least a first portion of said second feed, and at least a portion of a pre-converted off-gas stream, and to provide a first synthesis gas stream;
• a synthesis stage arranged to receive said first synthesis gas stream, and to provide one or more product stream(s) and an off-gas stream comprising unsaturated hydrocarbons;
• mixing means arranged to combine at least a portion of the off-gas stream with a dilution feed and provide a combined feed;
• an off-gas conversion stage arranged to receive at least a portion of the combined feed and provide a pre-converted off-gas stream to the syngas stage;
• wherein the off-gas conversion stage comprises at least one hydrogenation unit arranged to convert unsaturated hydrocarbons in said combined feed to saturated hydrocarbons in said pre-converted off-gas stream;
• and wherein the dilution feed is one or more feeds selected from:
• a second portion of said first feed of carbon dioxide,
• a second portion of said second feed of hydrogen, and
• the external dilution feed, comprising a carbon dioxide-rich feed, a steam feed, a saturated hydrocarbon feed, a hydrogen-rich feed, or a combination thereof.