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

The renewable feeds available for co-processing in FCC units present some different properties and impurities compared to conventional feedstock that will have an impact on the operation, heat balance, catalyst activity and performances of the unit. This impact even will depend on the co-processing ratio. The main modifications in FCC units that can be required to include or increase the co-processing of renewable feedstock are:  

• Dedicated feed injection nozzle, specifically for injecting Fast Pyrolysis Bio-Oil into the FCC riser, to ensure refiners can co-process bio-oils while minimizing potential plugging or corrosion due to mixtures of fossil and renewable feeds that might result in blending issues. The latter are 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) 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, for instance in storage system.
• Evaluation of upgrading in the equipment materials of the reaction section and main fractionation overhead section due to corrosion risks associated to chloride-containing compounds. 

In general, Axens through its portfolio of technological solutions provides support in co-processing matter, offering feedstock characterization, pilot plant tests, catalyst evaluation, corrosion study and revamp study to deal with the co-processing challenges related to incorporation of renewable feedstock in commercial units.