Hydrocarbon Processing - September 2021 - 43

Refining Technology
Performance improvement and sustainment.
To build the process digital
twin of a unit and for the overall site, it
is necessary to understand the operating
strategies before analyzing the data.
Marginal mechanisms and constraints are
identified during in-depth technical sessions
and are validated using the operating
data at a later stage. A brainstorming
session, including the process expertise
of all participants, is used to identify the
gaps and opportunities.
KPIs calculated by the process digital
twin often help identify additional areas
for improvement. This is especially true
for KPIs that are difficult to estimate and
that are rarely calculated in normal operation
(e.g., an approach toward equilibrium,
fractionation efficiencies and flooding
in distillation columns).
Process digital twins are validated on
a continuous basis to provide an accurate
representation of the asset over its
full range of operations. Before deployment,
additional insights regarding the
operating trends can be found in the last
few months of data. Variations of selected
KPIs during a day, week or season also
help identify areas that can improve performance
of the process unit.
All the opportunities identified
through the brainstorming session, the
preparation of the process digital twin,
data analysis and model assurance are
screened. The opportunities are ranked
based on the following criteria:
* Expected benefits from the
opportunity
* Investment required
* Ease of implementation.
Qualitative analysis, rather than quantitative
analysis, is performed to rank the opportunities.
Based on the qualitative ranking,
high-value opportunities are selected.
These opportunities are pursued further
for detailed techno-economic analysis,
using the process digital twin as the main
key evaluation tool. The opportunities
are implemented, and benefits are proved
through a controlled test run and demonstrated
with the change in the KPIs (FIG. 3).
To sustain benefits from the implemented
opportunities, selected margin
improvement indicators (MIIs) are also
configured in the process digital twin.
MIIs indicate the gain or loss of margin associated
with specific opportunities. The
impact of MIIs is calculated using the process
digital twin's ability to understand the
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complex-wide benefit calculation. Monitoring
of MIIs ensures that the process
engineers and operators continue to optimize
and benefit from the opportunity.
Deviations from the targets and associated
losses are reported on a continuous basis
and acted upon, thereby developing a culture
of profitability in the organization.
Process monitoring: Hydrocracker
unit pilot. Saudi Aramco and the co-author's
company collaborated to develop a
pilot of Saudi Aramco's first process digital
twin for the Ras Tanura refinery's (RTR's)
hydrocracker unit. The pilot project was a
result of a Memorandum of Understanding
between Saudi Aramco and the co-author's
company. The application is designed as
per the unit process specifications, with the
objective to monitor unit performance and
continuously recommend the operational
optimum. This project was a collaboration
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Hydrocarbon Processing - September 2021

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