POWER October 2020 - 23

TOP PLANT
proven, having been deployed on six GE
GT models-the 7HA.01, 7HA.02, 7EA,
9E, 7F, and 9HA.02. These fleets have
amassed more than 300,000 fired hours
and 6,000 fired starts.
IBH acts to increase air flow through
1. GE's 9E heavy-duty gas turbine provides essential
power and performs in a vast number of
duty cycles. Applications include combined heat
and power schemes in desert climates, the tropics,
and arctic cold regions. Courtesy: GE Power
minimizing the use of hardwired signal
cables, which was critical for the distances
between RaM and TEM substations.
Contextually, the specific ABB software
(PCM600) enables remote diagnostics
and configuration control of IEC
61850 subnet, and several features related
to the Industry 4.0 and IoT framework.
Finally, with the support and cooperation
of ABB and GE, important national grid
integrated local frequency requirements
were implemented and checked, according
to TSO code testing.
Gas Turbine Upgrades
In order to expand TEM's flexibility and
effectively match its output with RaM's
electrical energy demand for both power
and steam production, the project team
wanted to reduce the GT's minimum
turndown as much as possible while
preserving baseload performance. GE's
Axial Fuel Staging (AFS) technology upgrade
was installed on the existing GT.
In detail, the following modifications
and upgrades were implemented by GE
on the 9E GT:
■ Axial Fuel Staging (AFS) was employed,
which consists of an additional
fuel injection beyond the premix flame
in order to comply with NOx and CO
emissions requirements at lower load.
■ Inlet Bleed Heating (IBH) was added,
which recirculates air from the final
section to the compressor intake in order
to maintain a higher temperature
in the combustion system. (This was a
precondition for the AFS upgrade.)
■ Migration of Mark VIe control including
modification for partial load-shedding
logic.
Axially staging combustion to two
zones allows for increased firing temperature
at baseload (while maintaining
the same NOx
level) by operating the
later/second stage hotter than the first/
primary stage. AFS technology is wellOctober
2020 | POWER
the compressor while decreasing air flow
through the GT. The primary use of IBH
is compressor surge and icing protection.
When closing the inlet guide vanes to reduce
load, the risk of compressor icing increases,
thus, the addition of IBH enables
operation at lower loads. During low-load
operation, as the GT firing temperature
is reduced, percentage fuel split in the
staged fuel system can either be reduced
significantly or turned off, thereby keeping
the overall combustion system in compliance
with emissions limits over a wider
range of firing temperatures.
By performing this upgrade, the TEM
GT is now able to have a turndown less
than 40% of GT ISO nominal power, corresponding
at about 55% of whole combined
cycle performance. This greatly improved
upon the previous 80% turndown level.
Consequently, it has also achieved an important
decrease in emissions at turndown
due to a reduction in GT exhaust total
mass flow of about 20% (about 200,000
kilograms/hr). Furthermore, a significant
improvement of GT part-load efficiency
was ensured by a reduction in fuel burn.
Solving Metallurgy and Control
Issues
Decreasing the minimum turndown had
other impacts on the plant, however. For
example, there were important metallurgy
temperature limitations in the heat recovery
steam generator (HRSG) superheater
and in the high-pressure steam turbine.
With third-party support, RaM carefully investigated
and evaluated the total thermal
stress to avoid short- and long-term issues
on HRSG and steam turbine components.
According to CE rules (Conformitè
Europëenne, which is a European Union
quality standard), the HRSG had to be officially
rechecked from a design point of
view. This study highlighted the need for
a metal upgrade of some exposed HRSG
components (mainly on the medium- and
high-pressure superheater) and the need
to install a water desuperheater to control
the temperature of the high-pressure
admission section of the steam turbine.
During commissioning of AFS injection
technology, GE accurately tuned combustion
parameters to adjust related isotherm
factors in order to mitigate the GT
exhaust impacts on the HRSG, matching
its constraints.
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POWER POINTS
Winning Attributes
✔ The project included a complex
integration, connecting power plant
assets with a refinery to match
the facility's needs and improve
flexibility.
✔ Upgrades enhanced gas turbine
capabilities to allow a wider range
of emissions-compliant operation,
achieving a turndown to less than
40% ISO nominal output.
✔ New operating schemes support
refinery operation in a more
reliable manner, while providing
the ability to capture energy market
opportunities.
Integration of the TEM CCGT unit with
the refinery plant presented some challenges
from an automation and control
perspective. But with challenges come
opportunities for collaboration. Specifically,
contractors, cogeneration plant staff, and
the refinery plant team all worked together
to ensure the electrical and automation integration
was completed successfully.
During the design phase, several issues
related with the fast dynamics of
electrical response, refinery stability constraints,
and the need to have an efficient
and safe main general control capable of
seizing energy market opportunities were
solved. All of the related tasks planned in
the integrated automation system were
implemented on a unique DCS architecture
based on the recent AC 800M (800xA
and INFI90) ABB family of products.
The duration of the project, from its preliminary
phase to completion, was about
three years. It involved more than 100,000
man-hours for engineering and site work.
The main GT modifications were assembled
and installed during a GT major overhaul,
which began in late 2018 and finished
in early 2019. After the first startup, operational
commissioning and tuning required
several months due to necessary project
optimization, finalized in the TSO official
code test, which was completed successfully
in September 2019.
The teamwork demonstrated by the
owner and various contractors make the
project a remarkable success. The editors
of POWER would like to congratulate
RaM, GE, Terna, ABB, and all others involved
in the project on a job well done. ■
-Aaron Larson is POWER's
executive editor.
23
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POWER October 2020

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