Hydrocarbon Processing - October 2021 - 10

Business Trends
of the incident and to mitigate unwanted
effects. This has been the mainstay of
process control since the days of pneuover
the run-length cycle of a plant. When
linked to the overall economic optimization
of a site, this enables the enforcement
The key to progressing performance is to look at cross-domain
linkages and ultimately render these as intelligent, resilient
and autonomous. Defined procedures that cut across domains
are key to achieving intelligent, resilient and autonomous
operations. The primary goal is deploying technology that
allows those humans to make better decisions.
matic control and wall-filled panels of
controllers and alarm lights.
The progression of technology means
that the scope of a single operator today
is easily three times what it was before
digital control systems. Combining multiple
event occurrences by the control
system into concluded conditions can
help operators achieve more intelligent
operations. Automated or semi-automated
operational procedures also help
guide operators, along with context-sensitive
documentation.
Advanced process control (APC) is
used to manage multiple interactions
and control complex processes to reduce
energy consumption while maximizing
product yields. Industry is now benefitting
from APC models that update themselves,
even in closed-loop ones, with no interruption.
This helps achieve the resilience
of advanced controls.
The oil and gas industry also understands
the importance of optimizing
multiple units-particularly in refineries
and petrochemical complexes where
there are multiple processing options for
different streams-to meet production
goals or maximize the output of highervalue
products.
Refineries and petrochemical complexes
typically have run lengths of
3 yr-4 yr between major shutdowns.
During that time, plant equipment (e.g.,
reactors or distillation towers) gradually
fouls and/or degrades over time. Catalyst
performance degrades, as well. This
means that reaction severity, as expressed
by temperature, must rise closer to metallurgy
or refractory limits. Presently, this
long-term cycle is managed manually,
with multiple decision points.
However, much of this can be supported
using simulation (e.g., using a digital
twin) to achieve better performance
10 OCTOBER 2021 | HydrocarbonProcessing.com
of run-length driven objectives, underscoring
intelligent and resilient operations.
There is also optimization across multiple
units in which the interaction is more
economic than process-driven. Technologies
to express this relationship of macrolevel
economics and micro-level stream
flow targets are part of the latest developments,
helping to make overall optimization
more autonomous. A site-wide or refinery
linear program model can be linked
to individual
controls
through clever
transformation of the decision space from
one level to another. Therefore, the governance
of plant economics can be made
more autonomous.
Similarly, models that run dynamically
can help instruct and train operators to
understand the state of their unit and what
actions may be required, enabling them to
react in the best possible way. Again, this
underscores resilient operations.
Lastly, for offsites operations, where
there is remarkable linkage between feed
logistics, process units, product blending
in refineries and finished product logistics,
more can be achieved by taking new approaches
to tank farm valve management
or the capture of measurements from the
field. The use of wireless communications
over a tank farm or marine loading dock
can help achieve more intelligent logistics
operations, enabling field devices to provide
additional information. An operator
may then be guided to the exact location
for a needed manual operation.
Alarms and process safety. Alarm
management and the analysis of alarm logs
can help operators and engineers understand
the nature of over-frequent events.
There are also events captured automatically
by safety instrumented systems.
Safety event logs have been the subject
of manual reviews, while alarm management
has progressed in scope and breadth
of supporting analytics. Enforcement of
mode-based alarms has also expanded
the scope of alarm management,
but these remain same-unit mode
indications. Cross-unit or transitional
alarm settings are not generally
implemented.
Process and functional safety
have-for several years-had
well-defined
rules
nance
principles,
and
goverfrom
hazard
and operability study (HAZOP)
and layers of protection analysis
(LOPA) to defined safety integrity
requirements. However, verification of
function remains largely described in
concept as part of standards such as IEC
61511. Achieving more closed-loop verification
and flagging the need for remediation
of safety elements, such as sensors,
valves or logic, are also part of achieving
more resilient operations. Whether the
scheduling of valve and sensor verification
or the notification of results, capturing
such information and linking with the
process control domain are part of an autonomous
approach. Lastly, autonomously
managing temporarily degraded safety
loops can benefit a plant by removing the
requirement for human intervention and
ensuring consistent, safe operation.
Process and equipment asset health
and performance. In recent times,
the health and performance of equipment
assets (e.g., pumps, heat exchangers,
compressors and filters) have been
undertaken using representation models
of structure and behavior. For example,
design and real-time performance data of
a pump, including its pump curve, along
with information on the motor driver
and its characteristics, are used to model
pump behavior. This has helped give rise
to a templated model to benefit all instances
of the same type of equipment.
While the health and performance of individual
equipment are better observed
and flagged automatically to engineers for
observation and maintenance (including
the link to a maintenance system), this is
still undertaken on single assets.
The industry has reached a point in
engineering oversight where the next step
is to benefit from cross-asset behavior
flags. Does the temperature of incoming
fluid from an upstream exchanger flag an
event to the pump? Does a deficiency in
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Hydrocarbon Processing - October 2021

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