Modern Pumping Today November 2024 - 20

MOTOR SOLUTIONS
PLANT OPTIMIZATION FOR COLD STARTS:
MORE EFFICIENCY, LESS TIME TO
LOADING CONDITIONS
The ability to start-up a CCPP's turbine block much
faster from longer shutdowns can make a difference in
dispatch in competitive markets. During extended offline
periods of several days or longer, the steam cycle will
cool down, especially its high and intermediate pressure
steam turbines.
Implementing a steam turbine hot standby method,
such as using electrical heating blankets, to either prevent
or limit this cooling can shorten start-up times during a
shutdown phase of up to two weeks. If the plant was built
without a gas-fired auxiliary steam boiler, an electrical
auxiliary steam generator can be retrofitted. The electrical
auxiliary steam generator's objective is to provide enough
steam to seal the steam turbine and create a vacuum in
the condenser before the gas turbine starts.
This helps allow early steam condenser bypass
operation and helps avoid long low load operation
times with the HRSG venting valves. Keeping the steam
turbine sealed and under vacuum also helps prevent
air ingress, improve the feedwater quality, and minimize
water-chemistry related hold times during the start. This
concept is intended to help (1) increase responsiveness to
transmission ISO / RTO demand signals, (2) shorten startup
time, in some cases up to 50 percent, and (3) boost
efficiency in the start-up process.
In addition, the degassed conductivity concept may
shorten the start-up time of a combined cycle power
plant-especially for cold starts as the waiting time for
steam purity may be significantly reduced. This method
controls the steam purity and distinguishes between the
corrosive contaminants and less harmful carbon by reboiling
the sample downstream from the cation column to
remove carbon.
FAST PLANT SHUTDOWN OPTIMIZATION:
SAVING FUEL, LOWERING CARBON OUTPUT
CCPP shutdowns can require considerable time and fuel
for conducting the necessary unloading processes. In
competitive markets, the ability to shut down a plant faster
can help reduce time spent in transient conditions with
non-optimal efficiencies and enhance responsiveness.
The fast plant shutdown concept was developed to
significantly shorten a CCPP's shutdown time, in some
cases to less than thirty minutes. As shown in figure 10,
the concept leads to less fuel consumption and potential
improvements to both operating costs and profitability.
SUMMARY: FLEXIBILITY WITH SPEED
AND RELIABILITY
In the past decade, the operating profiles of CCPPs have
significantly shifted due to the growth in renewables
in producers' energy resource mix as well as volatile
fuel prices and governmental legislation. The impact of
these trends on the current and future operations and
profitability of typical CCPPs necessitate a shift from
outdated base load to cyclical operation.
CCPP flexibility and responsiveness to market signals
are critical to sustainable margins and profits. To help
achieve these capabilities and prepare their CCPPs for
current and upcoming market conditions, operators can
implement fast start-up concepts across hot, warm, and
cold turbine conditions along with fast shutdowns and
load gradient improvements to potentially improve their
competitiveness, asset utilization, and profitability.
Figure 10: The fast plant shut down concept can shorten the time to less
than thirty minutes in some cases, saving fuel costs while potentially
improving profitability.
Located in ninety countries, Siemens Energy operates
across the whole energy landscape-from conventional
to renewable power, from grid technology to storage
to electrifying complex industrial processes. For more
than 150 years our engineers have been spearheading
the electrification of the world. Today, we are a team of
99.000 sharing the same passion, vision, and values. Our
diversity makes us strong and helps us to find answers
together with our partners. For more information, visit
www.siemens-energy.com.
20 | NOVEMBER 2024
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Modern Pumping Today November 2024

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