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Chemical looping: a clean energy milestone 30 years in the making

In a chemical-looping system, a metal oxide provides the oxygen for combustion

“This is my life’s work,” Liang-Shih Fan, PhD, has said about the groundbreaking clean energy technology he’s spent the past 30 years developing.

Fan’s work reached an important milestone recently when Akron-based Babcock & Wilcox licensed a chemical looping process and oxygen carrier particle used for decarbonization and the production of hydrogen, steam and/or syngas. The technology chemically harnesses the energy in feedstocks such as natural gas, biogas from biomass, or coal among other carbonaceous feedstocks and efficiently isolates the carbon dioxide produced before it can be released into the atmosphere. Fan is a Distinguished University Professor and the C. John Easton Professor in Engineering in the Department of Chemical and Biomolecular Engineering.

In a chemical-looping system, a metal oxide, such as iron oxide, provides the oxygen for combustion. The metal oxide reacts with the fuel in the reducer, donating its oxygen to produce a highly concentrated stream of carbon dioxide. The reduced metal cycles to an oxidation chamber, the combustor, where the metal oxide is regenerated by contact with air. The metal oxide is then reintroduced into the reducer, thus completing the loop.

“In the simplest sense, combustion is a chemical reaction that consumes oxygen and produces heat,” Fan said. “Unfortunately, it also produces carbon dioxide, which is difficult to capture and bad for the environment. So, we use a method for releasing the heat without combustion. We carefully control the chemical reaction so that the feedstock never burns—it is consumed chemically, and the carbon dioxide is entirely contained inside the reactor.”  

The key to the technology is the use of tiny metal oxide beads as the oxygen carrier for the fuel to spur the chemical reaction. In this instance, the fuel is natural gas, biogas from biomass, or pulverized coal to name a few, and the metal oxide beads are made of iron oxide composites. The result of this process is an economical way to convert fossil fuels and biomass into useful products including hydrogen or electricity without emitting carbon dioxide to the atmosphere.

This technology can capture at least 95% of the CO2 emitted from coal combustion power plants if it is fully implemented.

Fan’s team first proved the technology could work in 2013 and published two papers in the journal Energy & Environmental Science in 2018 proving the technology could do so efficiently.

“Ohio State’s mission guides us to address society’s biggest and most complex challenges and reducing the environmental impact of energy production is one of those critical issues,” said Grace Wang, executive vice president for research, innovation and knowledge at Ohio State. “We’re proud of the work Dr. Fan has led over his career to develop this chemical looping solution, and we’re excited to see how his transformative work can impact society.”

The concept of chemical looping has been around for a long time, as early as the end of the 19th century, according to Fan, but bringing it to the point of commercialization has proven difficult. Previously, “the complexity of chemical looping technology and its daunting technical challenges has rendered its commercialization elusive despite a number of attempts,” he said. “However, the dedicated and long enduring effort and commitment of our team at Ohio State has overcome these challenges through our multiscale-based fundamental, multifaceted approaches.”

Chemical looping will be an effective stopgap technology to provide clean electricity until renewable energies, such as solar and wind, become both widely available and affordable, according to Fan.

“Renewables are the future,” he said. “We need a bridge that allows us to create clean energy until we get there—something affordable we can use for the next 30 years or more, until wind, biomass, solar, green hydrogen and other renewable energy become the prevailing technologies.”

Fan takes great pride in not only the technology’s potential impact on society, but also in the people that have been instrumental in its development. More than 40 students have completed their Ph.D. dissertations through their work on chemical looping in Fan’s lab.

“The rigor, viability and success of our technologies have been confirmed through the successful testing protocol conducted by these team members over the years, particularly with respect to the development of oxygen carriers and the moving bed reduction platform and applying them for converting such carbonaceous feedstocks as coal, natural gas, biogas and biomass to useful products,” said Fan. This commercialization journey has also provided my team with the opportunities to engage with many of our undergraduates at Ohio State, at HBCU (historically black colleges and universities), and with K-12 students.”

Both public and private partnerships have pushed the technology forward. “Such a major undertaking could not have been conducted without the support of many entities who have believed in and funded this program throughout its long history,” said Fan.

Considerable financial support has been provided by the State of Ohio’s Ohio Coal Development Program, the Ohio Third Frontier Program, the U.S. Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E), the National Energy Technology Laboratory (NETL) and the National Renewable Energy Laboratory (NREL). Babcock & Wilcox has provided support for nearly 15 years on the technology’s development including as a strong partner on two large pilot-scale demonstrations: the operation of reforming at the U.S. National Carbon Capture Center for hydrogen generation, and combustion at the Babcock & Wilcox Research Center for heat generation.

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