Hydrocarbon Processing - October 2021 - 31

Special Focus Plant Safety and Environment
A. R. DİNÇER, E. ÖZSAĞIROĞLU, F. ISERI, G. DOGAN,
G. D. YAVUZ, G. S. ANDAŞ, O. AKA and S. MUTLU,
TÜPRAŞ İzmir Refinery, Izmir, Turkey
CO2
emissions reduction via a pinch study
in a vacuum distillation unit
The project detailed here was carried
out on a vacuum distillation unit (VDU)
in the TÜPRAŞ İzmir refinery. Decreasing
the carbon footprint of the facilities
and being eco-friendly are some of the
main strategies for TÜPRAŞ. Because the
process is one of the largest units in the refinery,
any energy improvement in the unit
significantly affects the refinery's efficiency
and carbon footprint. To determine the
optimum energy efficient application, a
pinch analysis of the unit was executed.
The refinery staff performed pinch
studies with five different cases and also
changed a number of shells for new heat
exchangers in end of run (EOR) and start
of run (SOR). Within a VDU, SOR and
EOR mean the clean stage and dirty stage
of heat exchangers in a turnaround cycle,
respectively. The reasons for comparing
two different cases in the project are
that the VDU processes heavy products;
therefore, fouling occurs in the heat exchangers
between turnaround periods
and the heat efficiency of the pre-heat
train changes dramatically. Finally, 38 different
scenarios were achieved for heat
integration of the unit.
During the pinch study for each scenario,
new operating conditions were determined
and compliance with the temperature/pressure
design criteria of the
existing equipment were evaluated. In addition
to the above evaluations, the most
suitable scenario was selected by considering
equipment costs and fuel consumption
in all alternatives.
With the selected case, the project cost
was reduced marginally because no new/
additional heat exchangers were required.
The fired heater duty was decreased approximately
4.6% for EOR and 2.4% for
SOR conditions. This improvement is
equivalent to ~1,700 tpy reduction of carbon
dioxide (CO2
) emissions, which requires
approximately 4,150 trees to offset.
The re-arrangement of the preheat
train (or pinch study, in general) of process
units via simulation tools promises
huge potential. Such holistic solutions
have been proven to decrease fuel consumption,
EII index and CO2
for energy intensive industries.
emissions
Importance of the VDU. VDUs are
among the largest units in refineries. The
VDU separates atmospheric residue (AR)
and contains valuable products that cannot
be obtained in crude distillation units
(CDUs) without high temperatures. Atmospheric
columns may cause uncontrolled
cracking after a certain temperature,
which limits the maximum temperature.
Uncontrolled cracking of hydrocarbons
in distillation columns is undesirable, as
this operation must occur only in well-designed
reactors. Vacuum conditions lower
the boiling point of hydrocarbons so valuable
products in the atmospheric residue
can be obtained by distillation without
cracking. VDU products can be produced
Feed-LT distillate
heat exchanger
Feed
Feed-VR
Feed-PA
heat exchangers
(4 Shells)
Feed-HV distillate-1
heat exchanger
Lube oil feed
heat exchangers
(4 Shells)
Lube oil
HEX
VR to tanks
FIG. 1. Base model of the pre-heat train in a VDU and the heat integration between the
VDU and the lube oil plant.
Hydrocarbon Processing | OCTOBER 2021 31
Lube oil
process
Lube oil unit
fired heater
by diesel hydroprocessing (DHP) units,
hydrocrackers, fluid catalytic cracking
units (FCCUs) and a lube oil plant.
The VDU products mainly used in the
lube oil plant (LOP) are spindle distillate,
light distillate and heavy distillate. Additionally,
the unit produces light vacuum
gasoil (LVGO) and vacuum residue (VR).
LVGO is sent to the diesel hydroprocessing
unit and VR is sent to the propane
deasphalting unit. Spindle distillate, light
distillate and heavy distillate products are
processed in the lube oil plant to produce
spindle oil, light oil and heavy oil products.
The need for this study. Energy efficiency
is always a hot topic in petrochemical
plants and refineries-high-capacity
production necessitates the search for
energy reduction, so new technologies are
implemented and potential improvements
are always evaluated.
VDU energy consumption is immense,
as is the unit's impact on a refinery's
total energy requirements. Energy
reduction projects are high priority, and
it was considered that potential might exist
to improve the authors' refinery's preVR
Feed-HV
distillate-2
heat exchanger
Fired heater
Vacuum
distillation
column
Hydrocarbon Processing - October 2021

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