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

  Feb-2025

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Answers

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• Hernando Salgado, BASF Refinery Catalysts, hernando.salgado@basf.com

  To increase the coprocessing of renewable feedstocks in FCC units and hydrotreaters, specific modifications are necessary to enhance compatibility, efficiency, and yield. Each modification must be tailored to the type of alternative feedstock being processed, such as vegetable oils, animal fats, or other bio-based materials. The following discussion focuses on suggested modifications, their relevance to various feedstocks, and recommended pretreatment changes.

  FCC modifications
  Catalyst selection
  Modification: Use catalysts specifically designed for renewable feedstocks, such as those that are more effective in cracking triglycerides found in vegetable oils.
  Relevance: Different feedstocks have varying molecular structures. For instance, vegetable oils require catalysts that promote the cracking of larger hydrocarbon chains into lighter fractions.

  Reactor design enhancements
  Modification: Implement dual riser reactors or modify existing risers to allow for better mixing and residence time for alternative feeds.
  Relevance: Lighter renewable feedstocks may require different flow dynamics compared to heavier petroleum feedstocks.

  Feed injection
  Modification: Install dedicated feed nozzles for renewable feedstocks.
  Relevance: Renewable feedstocks may not be stable at typical FCC feed conditions and may have to be handled differently (thermal stability, fouling, solution compatibility) to ensure reliable operation.

  Operating conditions adjustment
  Modification: Adjust temperature and pressure settings to optimise the processing of renewable feeds.
  Relevance: Each type of feedstock may have an optimal temperature and pressure range for effective cracking. For example, animal fats typically require slightly different conditions than vegetable oils.

  Downstream hardware modifications
  Modification: Increase sour water handling capacity.
  Relevance: Processing high concentrations of renewables (particularly bio-derived oils) can produce significant water, CO, and CO₂ yields in the riser.

  Hydrotreater modifications
  Hydrogen supply and management
  Modification: Upgrade hydrogen supply systems to ensure consistent and adequate hydrogen availability for the hydroprocessing of renewable feeds.
  Relevance: Many renewable feedstocks have higher oxygen content and thus require more hydrogen for effective hydrotreatment.

  Catalyst adaptation
  Modification: Utilise catalysts that are optimised for renewable feedstocks, particularly those that can effectively remove oxygen and sulphur.
  Relevance: Different feeds, like palm oil vs used cooking oil, may require unique catalyst properties to achieve desired saturation and hydrodesulphurisation outcomes.

  Reactor configuration
  Modification: Modify existing reactors to accommodate higher flow rates and pressures, which can enhance the processing of lighter biofeedstocks.
  Relevance: Different feedstocks can have varying viscosities; heavier oils might necessitate different reactor designs compared to lighter, more fluid alternatives.

  Pretreatment modifications
  De-oxygenation
  Modification: Implement de-oxygenation processes such as hydrotreatment or thermal treatment before feeding into the FCC, hydrotreater, or downstream equipment.
  Relevance: Reducing oxygen content can enhance yield and performance by minimising the formation of undesirable byproducts during processing.

  Filtration and degumming
  Modification: Install filtration systems to remove impurities and solids from feedstocks like vegetable oils.
  Relevance: Impurities can lead to catalyst poisoning and operational issues. For instance, the presence of phospholipids in crude vegetable oils can hinder catalytic activity.

  Heating and viscosity reduction
  Modification: Preheat feedstocks to reduce viscosity and improve flow characteristics.
  Relevance: Heavier feedstocks, like used cooking oils, may benefit from preheating to allow for better mixing and improved processing in the FCC or hydrotreater.

  Mixing and emulsification
  Modification: Use emulsification techniques to create a homogenous mixture for coprocessing.
  Relevance: Certain feedstocks may not blend well with conventional feeds without emulsification, leading to inconsistent processing and lower yields.

  These modifications are integral for optimising the coprocessing of renewable feedstocks in FCC and hydrotreaters. Each type of alternative feedstock may require specific adaptations in both equipment and processing conditions to maximise yield and performance. By implementing these changes, refineries can better integrate renewable feedstocks into their existing processes, thereby enhancing sustainability while maintaining economic viability.

   

  Jan-2025