Fast Cycling Upgrades for Combined Cycle
Power Plants – Hot-start on the Fly
for Highest Operational Flexibility
Our solution
For SCC5-4000F single shaft combined
cycle power plants (see Fig. 1) Siemens
developed an innovative upgrade package
designed to significantly reduce the plant’s
hot-start times from currently 65 or more
minutes down to approx 40 minutes.
The significant improvement is based on
a parallel start-up of the gas turbine and
the steam turbine – the so- called hotstart on the fly.
The main elements of this start-up
procedure are summarized below
(see also Fig. 2):
■ Gas turbine start-up and loading
without load hold to wait for the
steam turbine start-up
■ Early steam turbine roll off with first
steam production (“cold steam“) at
low pressure
■ Steam turbine run-up to synchronized
speed, synchronization and loading
during continuous pressure increase
■ Lower steam production because of
higher pressure ramp rates, to minimize
start-up losses by reduced steam dump
to the condenser
Performance Enhancement – Combined Cycle Power Plants
Answers for energy.
■
Early closing of high pressure/intermediate pressure
bypass valves, possibly before the gas turbine is at
base load or at gas turbine part load (e.g. for plant
warm start).
Fig. 1: View of a SCC5-4000F single shaft combined
cycle power plant.
Plant Load
High operational flexibility – the ability
of a power plant for fast start-up and to
adjust load output fast and predictable
to changing market requirements – is an
essential element of economic success in
a deregulated market. Many combined
cycle power plants which were originally
built as base load plants are now – due
to changing market conditions and fuel
prices – reportedly operated as peak load
plants or as cycling plants with daily
start-up. Hot-starts after an overnight
shutdown may need to be performed
fast, predictable and reliable to ensure
a high dispatch ability and in-market
availability.
Gas turbine
start-up
& parallel steam
turbine start-up
Steam turbine
& gas turbine loading
Gas turbine hold time
Gas turbine start-up
Time
Fig. 2: New plant start-up concept with steam
turbine hot-start on the fly.
Our concept includes:
■ Modified high pressure/hot reheat
steam temperature control and
modified unit controls
■ New high pressure and hot reheat
bypass control philosophy
■ Modifications in the steam turbine
controller and new balance of plant
system signals
■ Improved gas turbine control promoting
usage of maximal possible load ramps
over a wide operating range
■ Implementation of logic changes into
the plant’s digital control system
■ Stress and fatigue monitoring systems
for the steam turbine and the heat
recovery steam generator
■ Re-commissioning, testing and
verification
■ Operator training and documentation.
Fig. 3: Automated optimized start-up process.
Published by and copyright © 2009:
Siemens AG
Energy Sector
Freyeslebenstrasse 1
91058 Erlangen, Germany
Siemens Energy, Inc.
4400 Alafaya Trail
Orlando, FL 32826-2399, USA
www.siemens.com/energy
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1)
Scope of supply
Siemens supplies an integral solution –
tailored to the specific situation and
configuration of the power plant.
2)
%
~ 25-40 min.
faster start-up
with steam
turbine
hot-start
on the fly.
&'(
)*+
&,*+
1) Typical expirience - may vary.
2) Illustration only - results may vary.
Fig. 4: Benefits of new plant start-up concept.
Customer benefits
With this solution for a hot-restart after an
overnight shutdown a total unit start-up
time below 40 minutes can be achieved –
from gas turbine ignition to full plant load.
In comparison: a hot-restart after an
overnight shutdown for a SCC5-4000F
combined cycle power plant may take
about 65 or more minutes depending on
the current plant configuration and the
age of the plant (see Fig. 4).
For more information please contact
your local Siemens sales representative.
Our automated start-up procedure can
help you to save fuel and gain a higher
efficiency during start-up which can result
in saving. In addition, the capability to
provide full MW loading in as little as
40 minutes opens up new revenue opportunities like utilizing hourly and seasonal
market arbitrage or peak shaving in a
deregulated market environment, which
need to be quantified plant-specifically.
For more information, please contact
our Customer Support Center.
Phone: +49 180 524 70 00
Fax:
+49 180 524 24 71
(Charges depending on provider)
E-mail: support.energy@siemens.com
Energy Service Division
Order No. E50001-G520-A204-V1-4A00
Printed in Germany
Dispo 34805, c4bs No. 7816
TH 258-090760 460326 DB 09092.0
Printed on elementary chlorine-free
bleached paper.
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Trademarks mentioned in this document
are the property of Siemens AG, its affiliates,
or their respective owners.
Subject to change without prior notice.
The information in this document contains
general descriptions of the technical options
available, which may not apply in all cases.
The required technical options should therefore
be specified in the contract.