Membranes - Introduction to Carbon Capture and Sequestration - page 347

also has the benefi t of being more sustainable in the sense that water use
and environmental impact (via emissions) are considerably less than for
absorption. For adsorption to become a dominant player in CCS, how-
ever, considerable research must be done to imagine, synthesize, and
deploy crafted nanoporous materials for CCS.
Membrane separation is also a mature chemical technology, most
often associated with water desalination. The engineering design of
membrane separation processes has similarities to absorption processes
in the sense that the device is operated in a countercurrent arrangement
so as to maximize the driving forces for transfer of CO 2 from the feed
stream to the exhaust stream. A detailed analysis of these operations,
though, reveals that both the absorption of CO 2 into the membrane mate-
rial, as well as the diffusion of CO 2 through the membrane, must be
crafted in order to address the scale of CCS. There is considerable
research activity throughout the world in the design of new types of
membranes that overcome limitations on diffusion solubility mecha-
nisms. These new designs employ a sophisticated molecular-level under-
standing of the kinetics and thermodynamics of small molecules in solid
materials. No less exciting are the emerging process schemes that
greatly minimize the compression and/or vacuum requirements of mem-
branes for CO 2 separations. The synergism of the molecular view of
membrane absorption and diffusion with the (macroscopic) process
analysis is thrilling.
The deployment of carbon capture awaits the political will to make it
happen. In the meantime, power plants and their operating companies
have several different technologies that may be employed for CCS, and
the ultimate choice for which technology is used will likely depend on
local constraints or opportunities. In the meantime, fundamental, pro-
cess, and demonstration scale research is needed to make these tech-
nologies the most cost effective and sustainable.