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Ramping time of boiler decreased by 66% |
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Following identification, savings of $240,000/year from a repair to the air heater |
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$950,000 fuel cost savings from minimum loading within 8 months |
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Improvement in excess oxygen control following identification of faulty instrumentation |
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Benchmark generated for heat rate |
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Challenge
The Little Gypsy plant is part of Entergy's five core utility
businesses that produce and distribute electricity to 2.6 million
customers. At this steam-electric fossil-fired plant a boiler was
experiencing large temperature excursions outside the permitted
range when load conditions changed rapidly. This caused a response
to load changes to be slower than desired. Entergy required a tool
to help determine the cause and measure future load changes.In
addition, knowing the effect of minimizing the loading of each steam
boiler by making operational changes, to reap savings in fuel costs,
was required. Reducing the minimum load would decrease the losses of
production during non-profitable operating periods.
Solution
AMS Performance Monitor was selected and has
provided many benefits to Entergy including both operational cost
savings and help with determining the effects of performance changes
in operation, and improved maintenance strategies.AMS Performance
Monitor was able to highlight that the excess oxygen analysis and
air flow metering were in need of examination. It was found that the
temperature excursions were related to periods during which there
were airflow measurement discrepancies. After the measurement
problems were corrected and instruments recalibrated, it was
possible to improve the ramp rate by 66%. In addition, Entergy were
able to achieve more accurate control of the air-to-fuel ratio
bringing the excess oxygen levels down from 12% to approximately
8.5%.
The effect of operating at lower minimum loads in automatic control
was benchmarked against previous operation. With the changes Emerson
made in their field devices, primarily valves and regulators,
Entergy were able to decrease the minimum loads by 35-45% on Unit 1
& 2. AMS Performance Monitor documented this improvement,
identifying savings of $950,000 for both units over an eight month
period.
AMS Performance Monitor was used to determine that the air heater on
Unit 1 was in need of maintenance. Personnel were able to pinpoint
that the heat transfer from the stack gas into the air feed was
lower than expected. The increased fuel usage was a result of less
heat being recovered from the whole process. Subsequently, AMS
Performance Monitor was also able to gauge the effect of the air
heater repair. This resulted in an increase in the heat recovery by
35°F, calculated to save $240,000/year in fuel costs.
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