Post-combustion CO2 capture -- the known alternatives and a new one

Let's briefly consider the proposals for post-combustion CO2 capture and acknowledge their fundamental limitations before wasting what little research money is available now.

Chemical capture by amine scrubbing drops plant efficiency 9% and doubles plant water consumption.  Heat-stable salts and corrosion in the sorbent regenerator remain unsolved problems.  Hot and dirty flue gas needs to be cooled down and cleaned before the chemicals get mixed in, and then the presence of the nitrogen ballast frustrates mixing the CO2 with the sorbent.  The additional footprint required by the scrubbing system rules out retrofit to existing plants. 

Fine fly ash, mercury vapor, and other aerosols in flue gas make post-combustion membrane capture impractical, especially at utility scale.  These aerosols gum up chemical capture too.  Dead-end filtration has the fundamental limitation that the retained particles blind the filter, so even if you get 95% separation efficiency from your particulate scrubbing, your membranes will need frequent replacement. 

Cryogenic distillation of CO2 is frustrated by the 75% nitrogen ballast and the enthalpy of the flue gas. 

Oxyfuel combustion, where the nitrogen ballast is stripped out prior to combustion by an air separation unit, has the same energy cost as post-combustion capture.

Nevertheless, CO2 capture funding has been exclusively along these familiar, though futile, paths, like the proverbial drunk looking for his keys under the streetlight because the light is better there.  But now that the optimism about CO2 capture has turned to gloom, and projects are being cancelled, maybe finally it is time to consider the possibility that maybe CO2 capture is not a chemistry problem after all. 

So what else is there?  Centrifugal capture by radial counterflow gas separation is a new alternative.  The conventional gas centrifuge (a rapidly rotating narrow cylinder) is, of course, not practical for flue gas, and vortex tubes and cyclones have too short a residence time for effective separation.  But a radial counterflow reactor provides a long residence time churning between counter-rotating centrifugal impellers, so the intrinsic momentum differences between the flue gas molecules at thermal equilibrium will sort them by organized flow in open von Karman geometry, and a fractal vascular network, like the root system of trees, provides a pathway for stripping out the nitrogen ballast in a continuous process.  When you have stripped out the nitrogen ballast, you've basically done carbon capture.  Along with CO2, mercury, NOx, SOx and <2.5 micron fly ash are continuously separated from the nitrogen ballast in a simple and scalable mechanical device that does not rely on chemicals or membranes, which has a small footprint, and which can be retrofitted to pulverized coal plants all over the world.