Pressure Driven CO2 Separation
The primary separation for the process is performed by a pressure
difference driven separation unit (membrane or PSA) that pre-purifies at
high recovery the flue gas to a CO2 rich stream (
>65% CO2 Purity, >92%
CO2 recovery) that is then recovered at vacuum pressures
(membrane permeate or PSA vacuum product) to be sent to liquefaction.
The minimum recovery of the primary separator was selected such that
overall system recovery with the liquefaction step and recycle 90%
overall system recovery consistently, as required by US DOE standards.
This requirement for process recovery was enforced through all analysis
discussed herein. The CO2-rich product from the
separator is sent to the liquefaction process, which further purifies it
to pipeline specification purities. The N2-rich product,
remaining at the high-pressure condition (as the retentate of a membrane
process or the high-pressure products of PSA) is sent to the heat and
energy recovery system described previously.