Hydrocarbon Processing - February 2022 - 38

Process Optimization
vent recovery column) was undisturbed
by this modification.
LITERATURE CITED
1
Buffalo Brewing Blog, " Columns, " March 2021,
online: https://www.buffalobrewingstl.com/practical-distillation/columns.html
2
Deshmukh,
B., R. K. Malik and S. Bandyopadhyay,
" Feed preheat targeting to minimize energy consumption
in distillation, " International Symposium
on Process Systems Engineering and Control, 2003.
FIG. 5. The impact of feed pre-vaporization on aromatics in raffinate and non-aromatics in extract.
TABLE 1. The eff ect of feed pre-vaporization on product specifi cations
Cases
Feed
pre-vaporization, %
Percent increase
in feed throughput
Base/Case 1 Case 2
0.6
0.2
Column parameters Base/Case 1 Case 2
Feed fl ow, kg/hr
Pressure drop, kg/cm2
Aromatics content
in raffi nate, wt%
Non-aromatics
in extract, wt%
X
y
a
b
Case 3
3.6
0.9
Case 3
(1.002*x)
y
(1.001*a)
(1.01*b)
Aromatics slippage in raffinate increases
due to increased pre-vaporization of the
feed. Similarly, the slippage of non-aromatics
also increases. However, it should
be confirmed that the loss is well within
desired product specifications.
Scope to increase feed throughput.
In the studies and feed conditions, the
authors found that increasing feed prevaporization
can help to reduce the pressure
drop across the extractive distillation
column. This provided the authors
with a scope to increase feed throughput
by the same fraction as pressure drop decreases,
thus maintaining base pressure
drop without significantly affecting separation
efficiency. For example, at 7.6%
feed vaporization, the pressure drop decreases
by 2.2% (FIG. 4). Therefore, the
feed throughput can be increased by
2.2%, thus debottlenecking the column.
The same principle can be applied to
other pre-vaporization cases by retaining
base pressure drop. The process constraints
and product specifications must
be monitored for any such alteration.
38 FEBRUARY 2022 | HydrocarbonProcessing.com
(1.009*x)
y
(1.008*a)
(1.03*b)
Case 4
5.6
1.5
Case 4
(1.015*x)
y
(1.013*a)
(1.05*b)
Case 5
7.6
2.2
Case 5
(1.022*x)
y
(1.02*a)
(1.09*b)
Case 6
18.6
4.5
Case 6
(1.045*x)
y
(1.05*a)
(1.2*b)
TABLE 1 considers a base case depicting
some column parameters using alphabetical
variables. The effect of increasing
feed throughput for each pre-vaporization
case on column parameters is also
represented. It should be noted that the
operation of the SRU was undisturbed,
and it did not hit any operation or quality
constraints due to increased pre-vaporization
of the feed.
Takeaway. For this case study, with an
increase in feed pre-vaporization, the
pressure drop across the extractive distillation
column and reboiler duty was
found to decrease. The degree of prevaporization
will depend on the competence
of the extractive distillation heat
exchanger circuit and desired product
specifications.
This case study provides a cost-effective
and accessible solution that can
be further extended for similar plant
challenges where extractive distillation
columns are bounded by high pressure
drops. It should be noted that the operation
of the downstream unit (i.e., the solRAHUL
PATIL is the Lead Research
Scientist in the refining R&D division
of Reliance Industries Ltd. He has 14
yr of experience in debottlenecking,
computational fluid dynamics and
process modeling, as well as in the
optimization of various petroleum
refinery and petrochemical units. Mr. Patil earned a Bch
degree in chemical engineering from the Institute of
Chemical Technology, in Mumbai, India, along with an
MTech degree in chemical engineering from IIT-Kanpur.
AJAY GUPTA is the Principal
Researcher in the R&D division of
Reliance industries Ltd. He has 35 yr
of experience in the petroleum and
petrochemical industries. His areas
of interest include modeling
simulations, advanced process
control, reactor hydrodynamics, and the scale-up of
equipment. Dr. Gupta earned BTech and MTech
degrees, as well as his PhD, from IIT-Delhi.
MADHUKAR GARG is the President
of Refining and Petrochemicals R&D
at Reliance Industries Ltd. He was
previously Director of the Indian
Institute of Petroleum-Dehradun.
Dr. Garg has 45 yr of experience in
the petroleum and petrochemical
industries. His areas of specialization include solvent
extraction, process integration, advanced control,
simulation and modeling. He is an elected Fellow of
the Indian National Academy of Engineering. Dr. Garg
earned a BTech degree from LIT in Nagpur, India; an
MTech degree from IIT-Kanpur; and his PhD from the
University of Melbourne.
MADHURA REWATKAR is a
Research Scientist in the refining
research and development (R&D)
division of Reliance Industries Ltd.
She has 3 yr of experience in the
modeling and simulation of
separation, aromatics and solvent
recovery processes. Ms. Rewatkar earned a BTech
degree in chemical engineering from the Laxminarayan
Institute of Technology (LIT) in Nagpur, India, along
with an MTech degree from the Visvesvaraya National
Institute of Technology in Nagpur, India. She has also
worked as a Research Fellow at the Indian Institute
of Technology (IIT)-Kharagpur.
PRAFULL PATIDAR is a Senior
Manager in the R&D division of
Reliance Industries Ltd. He has
9 yr of industrial experience in
separation processes, and in the
process modeling and simulation
of petrochemical and refinery
units. Dr. Patidar earned a PhD in reactive distillation
from IIT-Bombay.

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