Fischer-Tropsch process for producing hydrocarbons from biogas

摘要

A Fischer-Tropsch process for producing hydrocarbons from synthesis gas which originates e.g. from biomass gasification, using membrane separators. In the process, an input stream which comprises hydrogen, carbon monoxide as well as further gases and/or vapours is initially fed to a first membrane stage which comprises a steam-selective and carbon dioxide-selective membrane and through which at least some of the steam present in the input stream and some of the carbon dioxide present in the input stream are separated from the input stream to form a permeate stream of the first membrane stage comprising steam and carbon dioxide and a retentate stream of the first membrane stage containing hydrogen and carbon monoxide.

主权项

1. A process for producing hydrocarbons from biomass in which an input stream (1) from biomass gasification or from another synthesis gas production process which comprises hydrogen, carbon monoxide as well as further gases and/or vapours is initially fed to a first membrane stage (GP1) which comprises a steam-selective and carbon dioxide-selective membrane and through which at least some of the steam present in the input stream and some of the carbon dioxide present in the input stream are separated from the input stream to form a permeate stream (3) of the first membrane stage comprising steam and carbon dioxide and a retentate stream (2) of the first membrane stage containing hydrogen and carbon monoxide,
the retentate stream (2) of the first membrane stage is fed to a Fischer-Tropsch reactor (R1) in which a product stream (5) is produced which comprises hydrogen, steam, hydrocarbons as well as optionally further gases and/or vapours, the product stream (5) from the Fischer-Tropsch reactor (R1) is fed to a second membrane stage (GP2) which comprises a hydrogen-selective and steam-selective membrane and through which at least some of the hydrogen and steam present in the product stream (5) of the Fischer-Tropsch reactor (R1) are separated to form a permeate stream (7) of the second membrane stage (GP2) containing hydrogen and steam and a retentate stream (6) of the second membrane stage containing hydrocarbons, the permeate stream (7) of the second membrane stage (GP2) is mixed with the retentate stream (2) of the first membrane stage (GP1) and fed back to the reactor (R1), the retentate stream (6) of the second membrane stage is fed to a first separator stage (S1) in which the retentate stream (6) of the second membrane stage is separated at least into a gas phase (10) and a liquid fraction of two phase stream (11), as well as optionally into further fractions, the gas phase (10) of the first separator stage (S1) is fed to a third membrane stage (GP3) which comprises a hydrogen-selective and steam-selective membrane and in which at least some of the hydrogen present in the gas phase (10) of the first separator stage (S1) is separated from light gases to form a permeate stream (13) of the third membrane stage (GP3) containing hydrogen and steam and a retentate stream (12) of the third membrane stage (GP3) containing light gases, and the permeate stream (13) of the third membrane stage (GP3) containing hydrogen is mixed with the retentate stream (2) of the first membrane stage (GP1) and the permeate stream (7) of the second membrane stage (GP2) for recirculation into the Fischer-Tropsch reactor (R1).