Hydrocarbon Processing - July 2022 - 54

Process Optimization
The main issue is diesel yield loss vs.
the costs of CFPP additive injection.
Increasing the dewaxing abilities of the
catalyst to -20°C or -22°C results in
substantial diesel yield loss, as diesel is
converted to naphtha (slops) and offgas,
as well as a reduced cycle length for the
stringent CFPP -22°C case. For the dewaxing
cases, a significant economic loss
is incurred. Therefore, the costs for the
revamp compound the financial losses;
it is financially beneficial to achieve the
required CFPP specification of -20°C or
-22°C by using additives. The original
design of the MAA units was promising,
so a partial product upgrade by dewaxing
and by CFPP additives was adopted.
A pilot plant was initiated with a licensor
and a division of KNPC. However,
due to the unavailability of a location
and some other disputes, the Kuwait Institute
of Scientific Research (KISR) was
engaged to address some of the concerns.
Unfortunately, due to confidentiality issues
between KISR and the licensor, the
pilot plant remained on hold and was subUltra-low
sulfur diesel
Lubricity
injection
WAFI
injection
sequently canceled. After discussions with
Kuwait Petroleum Corporation and obtaining
required details/approvals for the
additives considered, the MAA refinery
decided to perform its own analysis and
studies on producing winter-grade ULSD.
The process began by communicating
with various vendors, performing initial
unit trials, conducting analytical testing
in both the vendors' and the MAA refinery's
laboratory facilities to pinpoint the
requirements based on reports from the
vendors, procuring sample additives from
selected vendors, and performing the
field trial. The field trial is the final hurdle
for the MAA refinery to confirm its capabilities
to produce winter-grade ULSD in
the actual plant environment.
Unit configuration. KNPC has two
refineries-MAB and MAA-that can
CDU/
eocene
CDU/eocene
Lt. diesel
Feed
surge
drum
Reactor
charge
heater
HDS
reactor
Posttreatment
reactor
Recycle
gas
compressor
Make-up hydrogen
Amine
system
FIG. 2. Simplified block flow diagram of the MAA refinery's gasoil desulfurization plant.
Ultra-low sulfur diesel
CDU/
eocene
ARD - 1
ARD - 2/
DCU
CDU/
eocene Lt.
diesel
ARD dist.
Feed
ARD dist. /
coker
diesel
Make-up hydrogen
Recycle gas
compressor
Amine
system
Vacuum
drier
Product
stripper
Separator
collection
vessel
Feed
surge
vessel
Reactor
charge
heater
DHT
reactor
Lubricity
injection
WAFI
injection
Vacuum
drier
Product
stripper
Separator
produce clean-burning fuels conforming
to Euro 5 standards. It has a major share
in boosting Kuwait's global position in
the oil refining industry. In the MAA refinery,
three processing units can produce
ULSD: the revamped gasoil desulfurization
unit, the CFP DHT unit and the hydrocracking
(HCR) unit.
As per design, KNPC will produce
Euro 5 diesels for the local market and export
requirements from all units. The gasoil
desulfurization unit will consume the
diesel stream from the CDU and eocene
(EOC) unit as its primary feed, while the
feed streams going to the DHT unit are a
combination of multiple diesel/distillate
streams from the CDU, the EOC unit,
the ARD unit, the delayed coker unit
(DCU) and the fluidized catalytic cracking
unit (FCCU). Therefore, feed blending
is one of the critical considerations
for DHT operation in the MAA refinery.
Meanwhile, HCR consumed vacuum
gasoil and produced 10 ppm sulfur diesel
as one of its products. FIG. 1 details
the diesel configuration at the MAA refinery.
No additive injection facilities are
available at the HCR unit. This is compensated
by higher injection at the gasoil
desulfurization unit or offsite facilities
(finished product site) in case of any offspecification
situation. Simplified block
flow diagrams of the MAA refinery's gasoil
desulfurization and DHT plants are
shown in FIGS. 2 and 3, respectively.
FIG. 3. Simplified block flow diagram of the MAA refinery's DHT plant.
54 JULY 2022 | HydrocarbonProcessing.com
Lab-scale analysis. Understanding
diesel characteristics is essential in deter
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