The worldwide demand for gasoline, diesel and petrochemicals is shifting towards a greater emphasis on diesel and propylene. Flexibility to meet changing demands will be vital for refinery profitability. Axens has developed the new FlexEneTM technology to expand the capabilities of the FCC process which is the main refinery conversion unit traditionally oriented to maximize gasoline and at times propylene production.
FlexEne relies on the integration of an FCC unit and an Oligomerization unit, called Polynaphtha, to process light FCC olefins and recycle valuable feed back to the FCC. By adjusting the catalyst formulation and operating conditions, the FCC process is able to operate in different modes: Maxi Distillate, Maxi Gasoline and High Propylene. This provides the product flexibility required by the market.
The flexibility offered by FlexEne can be illustrated by the following modes of operation:
- Maximum gasoline mode: light olefins (C3-C4) are transformed into gasoline range product via the Polynaphtha oligomerization unit operating in maximum gasoline mode. A small distillate range by-product is recycled and cracked in the FCC unit to produce more gasoline and olefins.
- Maximum distillate mode: selected olefins in the (C3-C9) range are converted into distillate range product in the Polynaphtha unit which is operated in maximum distillate mode. The olefinic gasoline by-product is recycled to crack in the FCC to produce more feed for the Polynaphtha unit and make more distillate. If LPG olefins are valued, the C5-C9 cut alone can be oligomerized to reduce the Gasoline/Diesel product ratio, and reduce the gasoline pool olefin content and vapor pressure (RVP).
- Maximum propylene mode: propylene is recovered and (C4-C9) olefins are oligomerized in the Polynaphtha unit at high conversion. All of the olefinic oligomer products are recycled and selectively cracked in the FCC unit towards propylene.
In each case, the C6+ oligomers recycled to the FCC may be cracked with the main feedstock under normal FCC conditions. Selection of the appropriate light olefins to oligomerize, and product cut to recycle allows the refiner to control the production of gasoline, distillate, and propylene. Thus the addition of FlexEne is simple and low cost with little impact on the FCC, while providing product flexibility to help the refiner respond to the market and maximize returns.
The FlexEne concept can be easily implemented to grassroots or existing FCC units. Since its introduction in 2008, seven FlexEne units are in project or construction phases.
Axens Flexene ARTC 2012 CD
Gasoline and Diesel Imbalances - Part 1
Gasoline and Diesel Imbalances - Part 2