Abby L. Harvey
GHG Monitor
2/13/2015
Carbon can be efficiently captured from flue gas using microcapsules consisting of a sodium carbonate solution encased in a highly permeable polymer shell, researchers from Lawrence Livermore National Lab, Harvard University and the University of Illinois at Urbana-Champaign announced in a new report published late last week in the journal Nature Communications. “We have demonstrated a new class of hybrid liquid/solid materials that are highly permeable, mechanically robust, chemically stable and environmentally benign,” the report says. “Our encapsulation scheme enables the use of liquid sorbents with more favourable thermodynamics and lower environmental impact than MEA by improving mass transfer rates, containing precipitates, and isolating degradation products. A system based on concentrated sodium carbonate slurry can be run with less parasitic heating and evaporation of water than conventional amine systems and will not release toxic volatile organic compounds. Hence, microencapsulated carbon sorbents offer a promising approach for large-scale carbon capture from power plants that is both safer and more energy efficient than current alternatives.”
The new process has various advantages over conventional methods such as amine based capture, including increased absorption, the researchers said. “It’s all about surface area,” said Roger Aines, one of the Lawrence Livermore team members in a Lawrence Livermore press release. “The capsules force the baking soda to stay in little tiny droplets (an order of magnitude smaller than a drop of amines would take on), and little drops react faster because they contact more of the CO2.”
Further, the microcapsules are easier on equipment, Aines said. “Our method is a huge improvement in terms of environmental impacts because we are able to use simple baking soda — present in every kitchen — as the active chemical. … Corrosiveness also is improved because the chemical is more benign and always is encapsulated. Putting the carbonate solution inside of the capsules allows it to be used for CO2 capture without making direct contact with the surface of equipment in the power plant, as well as being able to move it between absorption and release towers easily, even when it absorbs so much CO2 that it solidifies.”