85 / 160
separator uses a similar principle to remove solids from
liquids. For over 30 years, electrostatic separation has
evolved to be a robust, proven, automatic process to remove
FCC catalyst fines from slurry oil or other hydrocarbon
streams. Unaffected by the presence of asphaltenes,
electrostatic separation can be used to remove solids not
only from resid FCC derived slurry oil but also from gas oil
crackers. Operating at 160°C – 220°C, electrostatic separators
use depolarised glass beads to departiculate fines from the
product stream. The fluidised glass bead allows for a low
pressure drop and is not susceptible to blockage from
asphaltenes or waxes. Even the presence of antimony does
not cause issues within the system.
7
Economics
Recently, a Middle Eastern refinery installed an electrostatic
separator to replace a failed mechanical filtration unit. The
refinery conducted an economic study to evaluate the impact
of the change in separation and filtration technologies. Several
advantages became evident once the electrostatic separator
unit was put on line, including the following:
The increased quality of clarified slurry oil and proper
fines removal provided a fast return on investment (ROI),
offering increased profit realisation within months.
The use of raw FCC/RFCC feed enabled the refinery to
realise all the LCO and heavy cycle oil (HCO) for
production. The mechanical filtration unit was depriving
Table 3.
Electrostatic separation vs mechanical filtration. Economics based on 49 tph - 8558 bpd slurry (design)
Middle Eastern Refinery RFCC
Electrostatic separation Mechanical
~ ES economic value Comments
HCO back flush medium
impact
0 bpd (raw feedback
flush)
8558 bpd (slurry) * 4% =
342 bpd
US$5 367 690/y
savings
342 bpd * 365 days *
US$43/bbl
RFCC overall production
yield impact
0 bpd displacement of
RFCC feed with HCO
(342 bpd ) 4% HCO
backflush will have
-2% impact on overall
production yield
US$6 865 650/y
savings
171 bpd * US$110/bbl,
conversion lost production
Market 'conversion'
impact
Increased sub-micron
removal: instantaneous
3 months off spec
product to develop cake
(initial commissioning
and every time the filter
has to be taken offline
for repair – average one
month per year)
US$4 621 320/y
increased revenue
from clarified slurry oil
(CSO) market (numbers
for first year and start
up only)
US$6/bbl * 8558 bpd
(slurry) * 90 days
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