Scrubbing CO2 and sulfur from power plant emissions

The Department of Energy’s Pacific Northwest National Laboratory has developed a reusable organic liquid that can remove harmful acid gases from emissions generated by power plants. The process could easily replace current industrial practices to help clean the environment in a way that is energy efficient, cost effective and saves on water.

“Reversible Acid Gas Capture” utilises organic liquids that, unlike current methods, require no water to bind with harmful acid gases such as carbon dioxide and sulphur dioxide.

Resembling an oily compound, the liquid is made up of water and monoethanolamine, a basic organic molecule that grabs these acid gases at approximately room temperature. In addition to being reusable, the liquid can trap and hold two times more harmful gases by weight than the liquid absorbents currently being used in power plants. Scientists then heat the liquid to recover and safely dispose of these gases.

The project’s lead research scientist, David Heldebrant, explains that “current methods used to capture and release carbon dioxide emissions from power plants use a lot of energy because they pump and heat an excess of water during the process.” In PNNL’s process the acid-gas binding organic molecules require less heat, compared to water, to release the captured gases.

Previous work conducted by Heldebrant includes a carbon dioxide-binding organic liquid called CO2BOL which, when mixed with carbon dioxide emissions, demonstrated a chemical bond with the CO2 to form a liquid salt solution. Reheating the salt solution safely extracts the toxic compounds, returning the CO2BOL solution to its original state ready for reuse.

Heldebrant's research continues with the removal of other toxic elements from industrial emissions such as sulphur dioxide. The work is supported by Pacific Northwest National Laboratory's Energy Conversion Initiative.