Carbon Capturing Can Make Power Plants More Efficient

Process helps reduce emissions and energy costs

By Megan Cowie, SPARK writer (Students Promoting Awareness of Research Knowledge)

From left, John Carroll, Yohann Coulier, Peter Tremaine, Lucas Applegarth and Hugues Arcis. Photo by Martin Schwalbe

From left, John Carroll, Yohann Coulier, Peter Tremaine, Lucas Applegarth and Hugues Arcis. Photo by Martin Schwalbe

Carbon dioxide, a greenhouse gas, is projected to cause serious environmental problems over the next century. Although technologies exist to capture carbon dioxide produced by coal- and oil-burning power stations — a main source of carbon dioxide worldwide — they are not widely used because current carbon-capture techniques have huge energy and economic costs.

A typical coal-fired power station, for example, requires about a third of the power it generates to capture carbon dioxide and pump it underground. This means that the power station needs to burn about one-third more coal and generate the difference.

That’s why chemistry professor Peter Tremaine is working towards more efficient carbon-capture techniques. He is collaborating with John Carroll, director of geostorage process engineering at Gas Liquids Engineering Ltd., and researchers in France.

“Greenhouse gas emissions are a huge problem, and we need to do everything we can to keep them under control,” says Tremaine, adding that the group is working on a process that could cut energy costs by one-quarter.

Canada produces about 600 million tonnes of carbon dioxide every year. On a global scale, that represents billions of tonnes of carbon dioxide every year.

Coal-fired power plants capture carbon dioxide by bubbling combustion gases through an aqueous solution at a low temperature. The process captures carbon dioxide when it binds to molecules in the solution, called amines. The solution is then heated to about 100 C, and the carbon dioxide is released so that the solution can be reused.

Heating the solution to such a high temperature requires huge amounts of energy, which makes the process inefficient, but Tremaine’s research team recently developed a much more efficient carbon-capture process.

In the new process, amines in a solution capture carbon dioxide, just like in the current process, but when the temperature is raised, the solution separates into two phases, much like the way oil and vinegar separate in salad dressing. One phase contains the amines, and the other contains water and carbon dioxide.

That means less energy is required to recover the solution, because the phase separation does some of the work.

The researchers are studying amine solutions that have this separation property to determine which molecules are optimal for the new carbon-capture process. They are looking at how the carbon dioxide gas solubility depends on its pressure and the amine solution’s chemical composition.

Once the researchers put the chemistry’s fundamental understanding in place, chemical engineers will be able to design the new carbon-capture process.

“The goal is to develop a process that is economic, effective and able to handle the huge amounts of carbon dioxide that exist,” says Tremaine.

The members of the French team are Ballerat-Busseroles and Vladimir Majer, Centre National de la Recherche Scientifique, France; and Jean-Yves Coxam, Université Blaise-Pascal, France.

Canadian funding for this research is provided by NSERC’s International Strategic Grant. French funding is provided by the Agence Nationale de la Recherche and IFP Energies Nouvelles.