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CO2 scrubber supplies raw material for oxalic acid production

By Scott Jenkins |

A novel carbon-capture project at Michigan Technical University (MTU; Houghton, Mich.; www.mtu.edu) couples the collection of carbon dioxide from power-plant fluegas with a system to use the captured CO2 as a raw material to make oxalic acid, which can be used in the mining industry to leach rare earth elements from ore.

“Coal-fired power plants can be acceptable economically and environmentally if you can use the CO2 for a productive purpose, rather than allowing it into the atmosphere, where it is harmful, or sequestering it underground, where it is wasted,” says MTU professor and project leader Komar Kawatra.

In the first phase of the project, a sodium carbonate solution is pumped to the top of a scrubbing column, where CO2-rich exhaust gas from the MTU power plant is bubbled through the solution. “The scrubber is able to reduce the CO2 content in the exhaust gas from 8% to less than 1%,” says MTU researcher and doctoral student Sriram Valluri.

Waste heat from the power plant is used to regenerate CO2 from the sodium carbonate after it is captured. The sodium carbonate scrubber is less expensive than conventional carbon-capture systems based on amines, and the chemicals are much less toxic than amines, the team says.

In the second stage of the project, the CO2 that has been captured from the exhaust gas is reacted in an electrolytic cell to convert it to the two-carbon dicarboxylic acid known as oxalic acid. Locally produced oxalic acid could boost the production of rare-earth elements in the U.S., says Kawatra.

Currently, the CO2 scrubber is operating at pilot scale on the MTU power plant, while the oxalic acid production system is operating at bench scale, doctoral student Victor Claremboux says. The next step in the project is to scale up the oxalic acid system.

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