and production of a lot of low value product (like fuel oil). This type of refinery is
usually not economically viable in low margin periods.
Hydroskimming Refinery
The next most complex and capable refinery is the hydroskimming facility, illustrated
in Fig. 4. In this configuration, the diesel and lighter products from the crude unit are
processed to meet final product specifications. There is still no cracking involved.
Products from a hydroskimming refinery could include light ends (C 1 –C 4 ),
finished gasoline, finished jet fuel, and ultralow sulfur diesel. The light ends may
also be upgraded to improve their value (e.g., isomerizing butanes).
This configuration gains some crude flexibility, but still wants a light crude. The
crude does not have to be sweet. It is still fairly inexpensive to build and easy to
operate. Hydrogen produced by naphtha reforming opens several doors to
upgrading.
The key disadvantages of hydroskimming are that you still are producing a lot of
fuel oil and you are limited to relatively light crudes.
Cracking Refinery
A cracking refinery begins to chew into the atmospheric resid to convert it to more
valuable products. Figure 5 shows two block flow configurations for cracking
refineries. Compared to hydroskimming, a cracking refinery adds a vacuum tower
and (a) a fluid catalytic cracking (FCC) unit plus an alkylation unit or (b) a
hydrocracker to convert the vacuum gas oil. Some refineries may have both.
Additional feed or product treating is needed to meet the most stringent specifications, such as US Tier III gasoline. The vacuum resid is still sold as fuel oil
(usually high sulfur) or made into asphalt. On-purpose hydrogen production may
be needed.
A cracking refinery with a high gasoline market will favor an FCC route. Some
resid conversion may also be accomplished by feeding resid to the FCC, with
Light Ends
To Fuel
Butanes
Surplus Butane
Lt SR Naphtha
Lt Naphtha
Finished Gasoline
SR Hvy Naph
Reformate
Crude
SR Kerosene
Jet Stock
Jet Fuel/ULSK
SR Diesel
ULSD Stock
ULSD
Atm Residuum To Fuel Oil or Asphalt
Atm
Crude
Unit
Distillate
Hydrotreater
Naphtha
Hydrotreater
Naphtha
Reformer
Gasoline
Blending
Distillate
Blending
Fig. 4 Simple hydroskimming refinery flow sheet
84
D.S.J. Jones and S.A. Treese
usually not economically viable in low margin periods.
Hydroskimming Refinery
The next most complex and capable refinery is the hydroskimming facility, illustrated
in Fig. 4. In this configuration, the diesel and lighter products from the crude unit are
processed to meet final product specifications. There is still no cracking involved.
Products from a hydroskimming refinery could include light ends (C 1 –C 4 ),
finished gasoline, finished jet fuel, and ultralow sulfur diesel. The light ends may
also be upgraded to improve their value (e.g., isomerizing butanes).
This configuration gains some crude flexibility, but still wants a light crude. The
crude does not have to be sweet. It is still fairly inexpensive to build and easy to
operate. Hydrogen produced by naphtha reforming opens several doors to
upgrading.
The key disadvantages of hydroskimming are that you still are producing a lot of
fuel oil and you are limited to relatively light crudes.
Cracking Refinery
A cracking refinery begins to chew into the atmospheric resid to convert it to more
valuable products. Figure 5 shows two block flow configurations for cracking
refineries. Compared to hydroskimming, a cracking refinery adds a vacuum tower
and (a) a fluid catalytic cracking (FCC) unit plus an alkylation unit or (b) a
hydrocracker to convert the vacuum gas oil. Some refineries may have both.
Additional feed or product treating is needed to meet the most stringent specifications, such as US Tier III gasoline. The vacuum resid is still sold as fuel oil
(usually high sulfur) or made into asphalt. On-purpose hydrogen production may
be needed.
A cracking refinery with a high gasoline market will favor an FCC route. Some
resid conversion may also be accomplished by feeding resid to the FCC, with
Light Ends
To Fuel
Butanes
Surplus Butane
Lt SR Naphtha
Lt Naphtha
Finished Gasoline
SR Hvy Naph
Reformate
Crude
SR Kerosene
Jet Stock
Jet Fuel/ULSK
SR Diesel
ULSD Stock
ULSD
Atm Residuum To Fuel Oil or Asphalt
Atm
Crude
Unit
Distillate
Hydrotreater
Naphtha
Hydrotreater
Naphtha
Reformer
Gasoline
Blending
Distillate
Blending
Fig. 4 Simple hydroskimming refinery flow sheet
84
D.S.J. Jones and S.A. Treese