Hydrocarbon Processing - October 2021 - GP-24

GREEN TECHNOLOGIES
Ju`aymah NGL fractionation
energy optimization initiatives
P. GARG and N. M. MENAIKHRR, Saudi Aramco, Ras Tanura, Saudi Arabia
Wasting energy reduces plant profitability and its sustainability
footprint. With increasing energy costs and environmental
impact, energy efficiency is becoming more important than
ever. To be aligned with these requirements, an energy optimization
program launched in 2017 as well as several in-house
initiatives were implemented to optimize the processes for the
reduction of energy consumption.
Three major initiatives implemented at an NGL fractionation
plant are outlined here, including steam reserve optimization,
Adip propane trim heaters shutdown and an automating LPG dehydration
regeneration cycle. Implementing these energy saving
initiatives successfully reduced approximately 296 MMBtu/hr
of energy, lowered operating cost, improved plant energy intensity
key performance indicators (KPIs) (EII) by approximately
8.5%, and increased equipment life and reliability.
The energy intensity index (EII) is an index of energy
intensity that compares the consumption of primary energy
1,200
1,000
800
600
400
200
2015
2016
FIG. 1. Steam reserve trend.
40
30
20
10
2015
2016
FIG. 2. Fuel gas index trend.
24 SEPTEMBER/OCTOBER 2021 | GasProcessingNews.com
2017
2018
2019
2020
2017
2018
2019
2020
sources at a plant with benchmarks of a similar complex, measuring
energy performance. It is worth highlighting that all of
the initiatives were implemented without major process modification
or capital expenditures.
Process background. There are four identical fractionation
modules (trains): each module consists of de-ethanizer
(De-C2
), depropanizer (De-C3
uct received from De-C3
and C4
) and debutanizer (De-C4
S) and carbonyl sulfide (COS) from C3
) colprodumns;
an amine treating facility (Adip unit) to remove hydrogen
sulfide (H2
products, followed by the C3
overhead; and mercaptan oxidation
and C4
(merox) processing units for mercaptan sulfur removal from
C3
dehydration
system for moisture removal from the final product. A common
utility area supplies plant chemicals, boiler feed water and
steam. The plant's steam demand is met by three cogeneration
units and several high-pressure (HP) boilers. The following
sections detail all three energy optimization initiatives.
Steam reserve optimization. The plant's steam demand is
met by three cogeneration units and several HP boilers. The
total steam demand fluctuates heavily due to significant changes
in the feed rate. To meet the steam demand and avoid any
adverse operational impact during sudden cogeneration unit
or boiler trip, more than the net required number of boilers
were always operated. The availability of additional steam production
capacity by maintaining the extra number of boilers in
operation is defined as steam reserve. Historically, more than
1.1 MMlb/hr (million pounds per hour) of steam reserve was
maintained; to maintain a greater steam reserve than net steam
demand, additional boilers were forced to operate at a minimum
maximum continuous rating (MCR), which is close to
30%. Operating boilers at a minimum MCR is inefficient and
results in significant energy wastage.
The objective of this study was to re-evaluate and optimize
the steam reserve strategy to improve plant EII and reduce operating
costs.
Historically, the steam reserve supported plant operations
during cogeneration unit or boiler trips and maintained plant
processing capacity. Due to feed fluctuations, cogeneration
plant and boilers reliability, associated risks and potential financial
losses with no steam reserve, it was concluded that
maintaining zero steam reserve is impractical for operation.
During any trip of steam-producing facilities, the available
steam reserve from the boilers helped maintain plant processFuel
gas index, sft3/bbl
Steam reserve, thousands lb/hr
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Hydrocarbon Processing - October 2021

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