Led by the University of Pittsburgh and Lawrence Livermore National Laboratory (LLNL) the advance hopes to mitigate the USA’s CO2 output from coal and natural gas, which amounted to 1,713 million metric tons of CO2, or 98 per cent of all CO2 emissions from the electric power sector in 2017.
"Our approach is very different than the traditional method of capturing carbon dioxide at a power plant," said Katherine Hornbostel, assistant professor of mechanical engineering at Pitt's Swanson School of Engineering. "Instead of flowing a chemical solvent down a tower, we are putting the solvent into tiny microcapsules."
Hornbostel added that in the proposed carbon capture reactor design, microcapsules would be packed into a container and power plant exhaust gas would be flown through them.
"The heat required for conventional reactors is high, which translates to higher plant operating costs,” said Hornbostel. “Our design will be a smaller structure and require less electricity to operate, thereby lowering costs."
Conventional designs also use an amine solvent that is expensive and can be dangerous to the environment. The microcapsule design created by Hornbostel and her collaborators at LLNL uses a solution that is made from a common household item.
"We're using baking soda dissolved in water as our solvent," said Hornbostel. "It's cheaper, better for the environment, and more abundant than conventional solvents. Cost and abundance are critical factors when you're talking about 20 or more-metre-wide reactors installed at hundreds of power plants."
Hornbostel explained that the small size of the microcapsule gives the solvent a large surface area for a given volume. This high surface area makes the solvent absorb carbon dioxide faster, which means that slower absorbing solvents can be used.
"This is good news because it gives cheaper solvents like baking soda solution a fighting chance to compete with more expensive and corrosive solvents," said Hornbostel.
"Our proposed microcapsule technology and design are promising for post-combustion carbon capture because they help make slow-reacting solvents more efficient," said Hornbostel. "We believe that the decreased solvent cost combined with a smaller structure and lower operating cost may help coal and natural gas power plants maintain profits long-term without harming the environment."
Hornbostel has detailed her model in Applied Energy, "Packed and fluidized bed absorber modeling for carbon capture with micro-encapsulated sodium carbonate solution"
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