This past June, researchers at the National Renewable Energy Laboratory (NREL), in partnership with Particulate Solids Research, Inc. and Springs Fabrication, installed a recirculating regenerating riser reactor (R-Cubed) in the pilot-scale Thermochemical Process Development Unit (TCPDU). Funded by the DOE Bioenergy Technologies Office (BETO), this unique unit represents the next generation of thermochemical biomass conversion technology and adds additional capabilities to NREL’s state-of-the-art Thermochemical Users Facility.
The R-Cubed system will now allow for catalytic upgrading of biomass pyrolysis vapors—a process that can significantly improve the efficiency and reduce the costs associated with upgrading bio-oil to a finished fuel product—at an industrially-relevant pilot scale.
During pyrolysis, biomass is heated rapidly at high temperatures (500 °C to 700 °C) in an oxygen-free environment. The heat breaks down biomass into pyrolysis vapor, gas, and char. Once the char is removed, the vapors are cooled and condensed into a liquid “bio-crude” oil.
This bio-oil intermediate must then undergo additional processing in order to produce upgraded hydrocarbon fuel blendstocks. However, these downstream upgrading steps are currently quite challenging, as bio-oil contains a variety of reactive oxygenated organic compounds.
Some of these challenges could be alleviated by improving the quality of the bio-oil intermediate through catalytic upgrading of the vapors, prior to condensation. This is the role of the R-Cubed reactor.
Pyrolysis vapors are fed to the unit where they are exposed to a catalyst that reduces oxygen content and improves chemical stability. The result is an upgraded bio-oil that could more easily be integrated into traditional petroleum refineries for further processing.
In addition to improving the quality of the end product, the R-Cubed system is also designed to extend the life of the upgrading catalyst. Catalytic upgrading of bio-oils can often suffer from what is known as fouling.
This occurs when unwanted material forms a layer on the surface of a catalyst, rendering it less effective. The new unit configuration is designed to prevent catalytic fouling by reducing catalytic contact time and fully regenerating the catalyst by essentially removing unwanted deposits off the catalyst and returning it back to the riser to be used again. This process can significantly improve the efficiency and reduce costs associated with this biomass-to-fuels process.
The new capabilities of the recently outfitted Thermochemical Process Development Unit (TPDU) demonstrate promising pathways for hydrocarbon biofuel production and will be used in the coming years to produce hundreds of gallons of upgraded pyrolysis oil. The facility is also available to industry partners to test their materials and processes without the added expense of building their own pilot facility.