Separation of carbon dioxide from a synthesis gas

摘要

A method of separating a carbon-dioxide-rich liquid stream from a synthesis gas including carbon dioxide and hydrogen, includes carrying out a first cooling step to cool a synthesis gas feed stream using at least one heat exchanger such that a first two-phase mixture is formed. The first two-phase mixture is passed at a first pressure and a first temperature to a first separator and a first separation is carried out to separate the first mixture into a first CCVrich liquid stream and a H2-Hcli gas stream. The H2-rich gas stream is pressurised and a second cooling step is carried out to cool the H2-rich gas stream using at least one heat exchanger such that a second two-phase mixture is formed. The second mixture is passed at a second pressure and a second temperature to a second separator, the second pressure being higher than the first pressure and a second separation is carried out to separate the second mixture into a second CO2-rich liquid stream and a further H2-rich gas stream. Preferred examples further include the step of expanding at least one of the separated H2-rich vapour streams to recover mechanical work and/or to cool the H2-rich stream and subsequently using the expanded H2-rich stream as a coolant in the separation system.