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R-Cubed: Assessing Commercial Viability of Biofuel Technologies

July 20, 2016

Cleaner, domestic, renewable, and sustainable. The benefits of making fuels from plants seem obvious. The challenge is to do it more cost-effectively.

The National Bioenergy Center at NREL, with its extensive bioenergy research expertise and capabilities, is working to reduce costs and overcome technical barriers—an effort that will bring more bio-derived fuels and chemicals into the marketplace. A recent and significant step toward that goal is the retrofitting of a reactor system in NREL's Thermochemical Process Development Unit (TCPDU): the recirculating regenerating riser reactor or "R-Cubed."

Time-lapse video of the challenging R-Cubed installation “lift” of (in order of appearance) the catalytic riser, nitrogen and air stripper, steam riser, and transfer line.

With R-Cubed, the TCPDU system represents the next generation of upgrading technologies that convert lignocellulosic biomass (plant material not used for food or feed) to biofuels through a thermochemical process. It takes vapors produced from the biomass at the front end through a high-temperature pyrolysis process and exposes them to a catalyst that upgrades the resulting condensed bio-oil by reducing its acidity and oxygen content. The reactor can now lessen the catalyst contact time typically needed in the conversion process and fully regenerate the catalyst and return it to the riser. These two important steps will extend the overall life of the catalyst and eliminate regeneration down-time, which saves time and money.

The end product is an upgraded “bio-crude” oil that is more attractive to oil refineries than previous types of bio-derived feedstocks, because it requires less infrastructure retooling to process.

"The flexibility of the TCPDU lets us reconfigure unit operations to test different pilot-scale technologies," said Esther Wilcox, section supervisor for the Thermochemical Research and Development Evaluation section in the National Bioenergy Center. "The R-Cubed redesign adds the capability of pilot-scale vapor phase upgrading to NREL's biofuels research portfolio."

"NREL can now take bench-scale biofuels research and scale it up to a pilot-plant scale process that includes vapor-phase upgrading—and do it in a timely, cost-effective, and safe way," said Tom Foust, center director for the National Bioenergy Center. "That's something we weren't able to do before.

"The new pilot-plant reactor took more than two years of design and fabrication by vendors, and months of installation work by the engineers and researchers in the TCPDU. After conducting a large technology pathway demonstration project in 2017 for the Department of Energy's Bioenergy Technologies Office, NREL will invite industry partners to use the pilot plant for their own testing.

"The capacity to scale up and demonstrate promising pathways at NREL will reduce costs and risks to industry, leading to broader industrial deployment of biofuels technology." said Adam Bratis, associate laboratory director for Bioenergy Science and Technology and laboratory program manager for bioenergy. "This moves us closer to meeting the Bioenergy Technologies Office objective of developing and demonstrating commercially viable, high-performance biofuels and bio-products made from renewable, U.S. biomass resources."

—Kathy Cisar