Comparison of CO2 separation options for geo-sequestration: are membranes competitive?

The sequestration of CO2 as a greenhouse mitigation option is becoming an increasingly important priority for industry. Theoretically membrane based CO2 removal systems have the potential to provide a cost effective, low maintenance approach for removing CO2 from gas streams. This study examines the effect of membrane characteristics, operating parameters and system design on sequestration costs for any source-sink combination. The total sequestration cost per tonne of CO2 avoided for separation, transport and storage are compared for the separation of CO2 from a black coalfired power plant in Australia. The results show that the membranes currently available have a total sequestration cost of US$55-61/tonne CO2 avoided. Lower costs for CO2 avoided can be achieved using an MEA amine based absorption separation system. Gas separation membranes would require significant improvements in CO2 permeability and selectivity, together with reductions in the cost of membranes and changes to the process configurations and operating pressures to be competitive against MEA systems for the purposes of geo-sequestration.

In this study, currently available gas separation membranes have been shown to be more costly for the recovery of CO2 from flue gas than MEA absorption systems. The capture cost is dominated by the costs of flue gas and post-capture compression. Costs of capture using gas separation membranes system can be reduced by increasing the membrane permeability and selectivity, coupled with reductions in the feed pressure. Improvements in these could make membrane capture systems competitive with MEA capture systems. Acknowledgments The authors of this paper would like to acknowledge the Australian Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) for their financial support.