Integrated low-temperature CO2 capture from IGCC power plant by partial
condensation and separation of syngas
D. Berstada, R. Anantharamana, P. Neksåa
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SINTEF Energy Research, Sem Sælandsvei 11, NO-7465, Trondheim, Norway
CO2 capture by pre-combustion decarbonisation of syngas has potential of high energy efficiency,
compact process units and highly competitive capture cost. In post-combustion processes CO2 is
captured from flue gas at low concentration, atmospheric pressure and thus very low partial pressure.
As a consequence, chemical solvents with high regeneration energy and large absorbers are required.
On the other hand, coal gasifiers can generate synthesis gas with high CO2 concentration at high
pressure, implying very favourable CO2 capture conditions.
Since physical solvents such as Selexol and Rectisol are commercially proven technologies for CO2
removal from syngas, these are considered to be baseline technologies for pre-combustion capture. As
an alternative technology to physical solvents, the present work presents a low-temperature/cryogenic
CO2 removal unit for IGCC applications.
Shifted syngas is first dehydrated before being cooled in a heat exchanger network against other
process streams and auxiliary refrigeration cycles. When the final separation temperature is reached,
typically between -56°C and -50°C, the partially condensed gas is separated into a hydrogen-rich
gaseous phase and a CO2-rich liquid phase. In order to ensure high energy efficiency, the process
design requires effective heat integration of hot and cold process streams as well as recovery of shaft
power from expanders.
The design of the low-temperature capture unit is made up of several process units common in
cryogenic applications such as LNG, air separation and other liquefaction processes: compressors,
cryo-expanders, cryo-pumps, multi-stream heat exchangers, separation vessels and refrigeration
cycles. The fact that the capture unit is made up of standard process units is an inherent advantage with
respect to realisation potential. Furthermore, the high operating pressure reduces the volume and
footprint.
Process flow diagrams and an evaluation of energy efficiency, capture rate and a consistent
benchmarking with physical solvents will be presented in the paper.