• How does hydrotreated Vacuum gas oil product specification with respect to Sulphur content/Nitrogen content/ Aromatics/ product distillation ( D5 %) impacts the FCC unit operations and its product yields?



  • Marcio Wagner da Silva, Petrobras, marciows@petrobras.com.br

    These parameters can be translated as the quality of feedstock to the FCC unit.

    The sulfur content normally cant be reduced in the FCC unit, so the sulfur content in the FCC product streams will be proportional to the feed content, this is specially critical with current regulations of gasoline (Tier 3) which can limit the use of cracked naphtha in gasoline pool or demands higher hydrotreating capacity/severity from the refiner.

    The Nitrogen content is a key parameter to FCC feedstock once can be a severe poison to the FCC catalyst leading to the deactivation of acid function of the catalyst (basic nitrogen), furthermore will produce deleterious impact over the quality of FCC products.

    Regarding the aromatics content in the FCC feed, aromatics compounds tends to be refractories to the catalytic cracking process, by this reason the crackability of the FCC feedstock tends to be lower for feeds with high aromatics concentration which will led to high bottom yield (normally with lower added value) in the FCC units. For the same reason, higher distillation temperatures of the feed tends to reduce the crackability of the FCC feedstock, leading to higher yields of bottom streams and high catalyst consumption considering the fact that the contaminants like sulfur, nitrogen and metals tends to concentrate in the heavier fractions of the crude oil.