In the second paper, they report that they’ve found a way to greatly extend the lifetime of the particles that enable the chemical reaction to transform coal or other fuels to electricity and useful products over a length of time that is useful for commercial operation.

Finally, the same team has discovered and patented a way with the potential to lower the capital costs in producing synthesis gas by about 50% over the traditional technology.

The technology, known as chemical looping, uses metal oxide particles in high-pressure reactors to “burn” fossil fuels and biomass without the presence of oxygen in the air. The metal oxide provides the oxygen for the reaction.

Chemical looping is capable of acting as a stopgap technology that can provide clean electricity until renewable energies such as solar and wind become both widely available and affordable, the engineers said.

Renewables are the future. 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, while wind and solar power become the prevailing technologies.

—Liang-Shih Fan, Distinguished University Professor in Chemical and Biomolecular Engineering, who leads the effort

Five years ago, Fan and his research team demonstrated a technology called coal-direct chemical looping (CDCL) combustion, in which they were able to release energy from coal while capturing more than 99% of the resulting carbon dioxide, preventing its emission to the environment. The key advance of CDCL came in the form of iron oxide particles which supply the oxygen for chemical combustion in a moving bed reactor. After combustion, the particles take back the oxygen from air, and the cycle begins again.

The challenge then, as now, was how to keep the particles from wearing out, said Andrew Tong, research assistant professor of chemical and biomolecular engineering at Ohio State.

While five years ago the particles for CDCL lasted through 100 cycles for more than eight days of continuous operation, the engineers have since developed a new formulation that lasts for more than 3,000 cycles, or more than eight months of continuous use in laboratory tests. A similar formulation has also been tested at sub-pilot and pilot plants.

The particle itself is a vessel, and it’s carrying the oxygen back and forth in this process, and it eventually falls apart. Like a truck transporting goods on a highway, eventually it’s going to undergo some wear and tear. And we’re saying we devised a particle that can make the trip 3,000 times in the lab and still maintain its integrity.

—Andrew Tong

This is the longest lifetime ever reported for the oxygen carrier, he added. The next step is to test the carrier in an integrated coal-fired chemical looping process.

Another advancement involves the engineers’ development of chemical looping for production of syngas, which in turn provides the building blocks for a host of other useful products including ammonia, plastics or even carbon fibers.

Taken together, Fan said, these advancements bring Ohio State’s chemical looping technology many steps closer to commercialization.

The university would like to partner with industry to further develop the technology.

The Linde Group, a provider of hydrogen and synthesis gas supply and plants, has already begun collaborating with the team. Andreas Rupieper, the head of Linde Group R&D at Technology & Innovation said that the ability to capture carbon dioxide in hydrogen production plants and use it downstream to make products at a competitive cost “could bridge the transition towards a decarbonized hydrogen production future.” He added that “Linde considers Ohio State’s chemical looping platform technology for hydrogen production to be a potential alternative technology for its new-built plants.”

The Babcock & Wilcox Company (B&W) has been collaborating with Ohio State for the past 10 years on the development of the CDCL technology—an advanced oxy-combustion technology for electricity production from coal with nearly zero carbon emissions. David Kraft, Technical Fellow at B&W, stated “The CDCL process is the most advanced and cost-effective approach to carbon capture we have reviewed to date and are committed to supporting its commercial viability through large-scale pilot plant design and feasibility studies. With the continued success of collaborative development program with Ohio State, B&W believes CDCL has potential to transform the power and petrochemical industries.”

Resources

• Mandar Kathe, Abbey Empfield, Peter Sandvik, Charles Fryer, Yitao Zhang, Elena Blair and Liang-Shih Fan (2017) “Utilization of CO₂ as a partial substitute for methane feedstock in chemical looping methane–steam redox processes for syngas production” Energy & Environmental Science doi: 10.1039/C6EE03701A

• Cheng Chung, Lang Qin, Vedant Shah and Liang-Shih Fan (2017) “Chemically and physically robust, commercially-viable iron-based composite oxygen carriers sustainable over 3000 redox cycles at high temperatures for chemical looping applications” Energy & Environmental Science doi: 0.1039/C7EE02657A