Jun 18, 2019 | Updated: 05:32 PM EDT

Oxalic acid from captured carbon dioxide: a new process

Feb 23, 2019 10:49 AM EST

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Oxalic acid
(Photo : Pixabay)

Michigan Technological University scientists discovered a method in capturing carbon dioxide and converting it to oxalic acid. 

S. Komar Kawatra, lead researcher and professor of chemical engineering at the said university, together with Ph.D. students Sriram Valluri and Victor Claremboux, and undergraduate Sam Root, designed a carbon dioxide scrubber. 

Industries use oxalic acid in leaching rare earth elements from bodies of ore. Some of the uses of these rare elements include in producing mobile phones. China is the main producer of rare earth metals in the world. The United States does not produce. With this innovation, rare earth metals can be extracted in the United States domestically. 

What happens during the process

The carbon dioxide scrubber was installed at the Michigan Tech steam plant where the real flue gas is tested. 

Flue gas produced by the steam plant contains eight percent carbon dioxide. The team's goal is to reduce emissions below two percent. The carbon dioxide scrubber was able to reduce it down to four percent. 

"Below two percent, we are happy," Kawatra said. "Below one percent, we will be very happy."

The team believes it is possible since they have brought the emission to zero percent in the laboratory. 

A sample stream of flue gas comes from the main exhaust line of the boiler which flows out of the burner at 300 to 350 degrees Fahrenheit. A filter compresses the sample and removes the particle. This sample cools down in the cooling unit before proceeding to the bottom of the scrubbing column. 

Carbon dioxide removal

A scrubbing column that is 11 feet high is pumped with a sodium carbonate solution. The column serves as the pathway of the flue gas. Soda ash or sodium carbonate removes carbon dioxide as the gas moves toward the top. The team constantly monitors the amount of carbon dioxide. 

"The biggest challenge is a fluctuating ratio of gases in the flue gas," Valluri said. Team member Root elaborates, "You need a cascade control system that measures the carbon dioxide and manipulates the amount of scrubbing solution accordingly."

"Our next challenges are, how much can we scale the scrubber up and what can we use the carbon dioxide for," Valluri says. This is related to the team's other research studies involving carbon dioxide conversion to useful by-products. 

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