Hydrocarbon Processing - August 2022 - 21

Refining Technology
sure drop caused by liquid hold-up in the random packings.
Most column revamps necessitate the evaluation and
modification of ancillary equipment. However, associated
equipment such as condensers, receivers, pumps, valves and
instrumentation may remain as they are. With the latest generation
structured packinga
with enhanced geometric structure,
the pressure drop across the packing is much lower and
the maximum capacity can be extended up to 20% compared
to conventional structure packing in a simulation study. The
new packing has a smooth curved shape at the junction of two
packing layers, lowering the accumulation of liquid/solid at
this point and resulting in high packing capacity. The corrugation
angle in relation to the vertical is gradually reduced to
zero at both ends of each sheet, as seen in FIG. 3.
This design modification of the corrugation angle causes
smooth and steady changes of flow direction, as opposed to
abrupt direction changes found in conventional structure
packing. The result is a reduction in pressure drop and reduced
shear force between the gas and liquid phase, and a reduction
of gas velocity.
Hydraulics calculations of a packed bed based on plant
match conditions showed that the proprietary structured
packinga
operated at 62.7% of its capacity compared to 79.4%
of the existing packing (providing an 16.7% additional capacity).
This indicates better column performance with the new
packing if the " exponential increase in pressure drop of the
existing packing " could be resolved. TABLE 1 shows capacity
and pressure drop values for the existing packing and the new
structured packinga
from hydraulic calculations.
Replacement of existing liquid distributor. Precise liquid
distribution is crucial for the performance of packed beds, and
distributor selection is vital to achieve maximum packing performance-even
the best packing will never provide its full
performance if the related internals are not designed appropriately.
In a simulation study, the authors' company noticed that
the existing liquid distributor drip point density was limited
for distribution. The existing liquid distributor was replaced
with a high-performance liquid distributorb
(with a drip point
density of 116 holes/m2) to improve liquid distribution. In
turn, this provided better performance in product recovery
and delayed plugging problems.
MAKE YOUR FLOW PATH INERT
Revamp results. The replacement of the entire packed bed
internals and distributor was conducted without any hot
work. On startup, the pressure drop across the packing was
reduced. The column has been in operation for 8 mos without
any operational problems compared to the cleaning/washing
cycle required every 3 mos before the revamp.
The project shows how proper cooperation between the
authors' companies resulted in successful troubleshooting of a
long-prevailing problem. The revamp of the column provided
energy savings and increased product yield. MAN recovery
has been improved compared to the old packing (FIG. 4).
This successful revamp illustrates how unexpected downtime
for packing washing-a costly operation for any plant
operation in the oil and gas industries-can be avoided. The
project achieved numerous benefits with a lucrative payback
period of 0.5 mos.
HC Feb 2022.indd 1
Hydrocarbon Processing | AUGUST 2022 21
1/10/2022 3:20:00 PM
*
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OPTIMIZE PROCESSING PERFORMANCE WITH
NOTES
a Sulzer's MellapakPlus™
b Sulzer's MellaTech™
c AspenTech's Aspen Plus
ACKNOLEDGEMENTS
The case study presented here was performed by Sahara International
Petrochemical Company (Sipchem) Saudi Arabia. Sulzer extends its thanks to Ali
S. Al-Wadie (Process Engineer and Control System Manager) for his encouragement
and engineering approval for this project, and Mohammad M. Al-Zahrani
(Operation Manager) for his professionalism, approval and coordination provided
within the team during project execution.
LITERATURE CITED
1
Gmehling, J., et al., " Chemical thermodynamics for process simulation, " 2nd Ed.,
Wiley-VCH, Germany, June 2019.
VIJAY SHIRPURKAR is a Staff Process Engineer at Sipchem. He has 19 yr
of experience in technical services and plant operation in the refining and
petrochemicals industries, and has published multiple papers in various
international publications. Mr. Shirpurkar holds a BS degree in chemical
engineering from Dr. Babasaheb Ambedkar Technological University Lonere,
Maharashtra, India.
AJAY ARORA is Head of Application and Process Technology at Sulzer
Chemtech, Bahrain. He has 17 yr of experience in process simulation,
internals design and distillation column troubleshooting in the refining and
petrochemicals industries. Mr. Arora holds an MS degree from IIT, Delhi, India.
VINIT KALE is Head of sales for the downstream business at Sulzer Chemtech,
Bahrain, with 18 yr of experience in refining, petrochemicals and specialty
chemicals processing. Mr. Kale holds a BS degree in chemical engineering from
MIT Pune India.
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