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  • What FCC and hydrotreater modifications are needed to increase refinery coprocessing of renewable feedstocks?

    Feb-2025

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  • Francy Barrios, Axens, Francy.Barrios@axensgroup.com

    Renewable feeds available for co-processing in FCC units present different properties and impurities compared to conventional feedstock, impacting operation, heat balance, catalyst activity, and unit performance. This impact will even depend on the co-processing ratio. The main modifications that can be required in FCC units to increase the co-processing of renewable feedstock are dedicated feed injection nozzles, bio-oil storage and feed lines, and equipment materials upgrading.

    Dedicated feed injection nozzles, specifically for injecting fast pyrolysis bio-oil into the FCC riser, ensure refiners can co-process bio-oils while minimising potential plugging or corrosion due to mixtures of fossil and renewable feeds that might result in blending issues. The latter is due to the presence of many oxygen-containing molecules that result in a polar phase immiscible with fossil feedstock.

    Bio-oil storage and feed lines should be built with material resistant to corrosion over long-duration exposure to bio-oils feeds. For renewable feedstock, organic acid (RCOOH, which is measured by total acid number [TAN]) and chlorides are the main impurities that could cause corrosion issues. The long-chain organic acids usually present in these feedstock are weak acids that slightly acidify free water in contact with the feedstock, such as in storage systems.

    Equipment materials upgrading of the reaction section and main fractionation overhead section should be evaluated due to corrosion risks associated with chloride-containing compounds. Against this backdrop, the Axens technological solutions provide support in co-processing matters, offering feedstock characterisation, pilot plant tests, catalyst evaluation, and corrosion and revamp studies to deal with the co-processing challenges related to the incorporation of renewable feedstock in commercial units.

     

    Jan-2025


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