The Ohio State University is leading a joint development effort to scale up chemical looping technology at the U.S. Department of Energy’s National Carbon Capture Center, operated by Southern Company in Wilsonville, Ala. Ohio State and Southern Company have a collaborative testing agreement to demonstrate the high pressure syngas-to-hydrogen chemical looping process.
Chemical looping is a novel process for effectively converting carbon-based fuels to electricity, hydrogen and/or liquid fuels with near-zero carbon emissions. This process could achieve one of the lowest cost and most efficient technologies yet developed for CO2-free energy from coal. Liang-Shih Fan, Ohio State professor of chemical and biomolecular engineering and principal investigator on the project, is committed to advancing and industrializing such clean coal technology.
Typical coal-fired power plants burn coal to heat water to make steam, which turns the turbines that produce electricity. In chemical looping, the coal isn't burned with fire, but instead chemically combusted in a sealed chamber so that it doesn't pollute the air.
"In the simplest sense, combustion is a chemical reaction that consumes oxygen and produces heat," Fan says. "Unfortunately, it also produces carbon dioxide, which is difficult to capture and bad for the environment. So we found a way to release the heat without burning."
According to Fan, the breakthrough was the production of pure hydrogen and carbon dioxide during the long-term, continuous sub-pilot demonstration. The production of pure hydrogen and carbon dioxide was achieved by a combination of the moving bed concept and the iron looping chemistry. By successfully demonstrating the moving bed idea, the iron looping process can achieve one of the lowest cost and most efficient technologies to produce affordable, pure hydrogen while attaining nearly 100 percent CO2 control and complying with all environmental regulations.
The Ohio State syngas iron looping process circulates various iron oxide forms through different reaction zones. Carbon-based fuel is first oxidized to CO2, captured and sequestered, and simultaneously iron oxide is reduced to its elemental form. After the reducer, the elemental iron is oxidized by steam, producing hydrogen and an intermediate iron oxide form. The intermediate iron oxide is then burned in air to produce a more reactive iron oxide, which is circulated back to the reducer.
The patented Ohio State syngas chemical looping process uses countercurrent moving bed reducer and oxidizer and iron-based composite oxygen carriers under reduction-oxidation conditions. In particular, the unit converts coal syngas, a mixture of carbon monoxide and hydrogen, to carbon-free energy carriers. The system is unique, as it can allow both electricity and hydrogen co-production as compared to other chemical looping technologies.
"Ohio State's chemical looping technology has the potential to secure coal and biomass as fuels for reliable, low-carbon domestic energy," said Eric Toone, the U.S. Department of Energy’s ARPA-E Deputy Director for Technology. "The collaboration between project participants at the National Carbon Capture Center holds great promise to accelerate the technology from demonstration into the marketplace."
Ohio State’s demonstration project will be the largest scale-up of the chemical looping gasification technology for hydrogen generation from coal. The project is co-funded by the U.S. Department of Energy/Advanced Research Projects Agency-Energy (ARPA-E) and the Ohio Department of Development’s Office of Energy through the Ohio Coal Development Office, as well as industrial partners Babcock & Wilcox, CONSOL Energy Inc. and Clear Skies Consulting.
For further details on The Ohio State University’s research efforts on chemical looping coal combustion technologies, see the following:
Power Engineering, “Chemical Looping for Nearly Zero-Pollution Coal Power,” Liang-Shih Fan and Elena Chung, pp. 12-19, July 2013.
This article was excerpted from publically available information, and was authored by Rick Wilson, Acacia Environmental Group LLC. Any opinions expressed in this article are those solely of the author, and are not intended as legal or professional guidance to any specific readers. For more information on the author see here.