Solvents and Sorbents
In order to divert CO2 from large, point sources in industry and electricity generation to storage in a geologic sink, it must be isolated from other gases. Effluent from these sources typically contains CO2 in dilute concentrations (3-15% mol). It is likely to be impractical to store effluent with all its constituents because of costs associated with transportation and compression in addition to storage space considerations. An efficient method of capturing CO2 as a pure stream would greatly enhance the potential for carbon storage to make an impact on global CO2 emissions.
Separation of CO2 is commonly practiced, although it is currently done at a relatively small scale compared to that required for significant impact on global CO2 emissions. Pure CO2 streams are produced from combustion gases for products such as beverages, urea, and soda ash. During natural gas processing, CO2 is removed to increase the energy density of the fuel and to decrease corrosion and catalyst poisoning in processes that use natural gas as a feedstock.
A good CO2 Capture agent should have the following desirable properties:
1) Low energy requirement for capture and release of CO2 that decreases the energy penalty of applying carbon capture to the power plant or point source.
2) High CO2 capture capacity of solvent i.e. the amount of CO2 captured per gram or solvent or sorbent.
3) Low cost and easy availability in large quantities - It should be naturally available in nature or it should have a simple and cost effective way of synthesis.
4) High cyclic ability -The solvent should not lose its solubility even after many cycles.
5) The solvent/sorbent should be non-toxic and non-polluting.
6) The solvent/sorbent should have high CO2 selectivity- It should not capture inert gases like Nitrogen.
7) Not only should the solvent have high capacity, it should also release the captured CO2 with minimum energy input.