May 2003 ISSUE TONGBAI Page 4/5 COMPACT HYDRO in ...

(corresponding to 55.6% net
efficiency).
The reference conditions are:
• Barometric pressure 926.5 mbara
• Ambient temperature 11.8°C
• Relative humidity 60%
The power plant is designed for a
lifetime of at least 25 years and will
be built to recognised international
standards and will also meet the local
Turkish standards identified in
the grid code (APK359) and other
relevant local legislation.
Combined Cycle (CC) is the technology
of choice for new and
replacement power plants. CC is
forecast to account for over 30% of
Europe's installed capacity by
2020.
Reasons include:
• Low capital costs
• High levels of generating efficiency
(up to 56%)
• Low emission levels
• Short periods for erection and
commissioning
• Availability of low cost natural gas
• Development of combined cycle
systems suited to baseload
applications
What is “Combined Cycle” ?
The basic principle of a combined
cycle power plant is the following:
Burning gas in a gas turbine (GT)
produces not only power - which can
be converted to electric power by a
coupled generator - but also fairly
hot exhaust gases. Routing these
gases through a boiler produces
steam, which can be turned into
electric power with a coupled steam
turbine and generator.
This set-up of gas turbine, wasteheat
recovery boiler, steam turbine
and generator(s) is called a
combined cycle.
Gas Turbine (GT)
All gas turbines operate on the principle
of the Brayton cycle:
Compressed air is mixed with fuel
and burned under constant pressure
conditions. The resulting hot
gases are allowed to expand
through a turbine to produce electricity
with a coupled generator.
Both gas turbines for Ankara CCPP
are of the PG 9351 (FA++) type supplied
by General Electric.
At base load and ISO-conditions an
air flow of 2,170 t/h is cleaned in a
pulse type filter and compressed at
a pressure ratio of 15 in an axial flow
compressor (18 stages).
Natural gas as fuel is added to the
compressed air in the combustor
and raises temperature to approx.
1,290 C in a continuous combustion
process. NOx-emissions are minimized
by a Dry Low NOx combustor
(DLN 2+).
In the turbine work is extracted from
the hot combustion gases as they
expand to almost atmospheric pressure.
This allows to drive a generator
of 235 MW electrical output.
The expanded gases are lead to the
Heat Recovery Steam Generator
(HRSG) at a temperature of approx.
590°C.
HRSG
The waste heat available from the
GT exhaust gases is utilized in two
heat recovery steam generators
(HRSG) of the drum type.
For optimized efficiency steam is
generated at three pressure levels:
• High pressure (HP):
120 bar / 565 °C, 320 t/h (each)
• Intermediate pressure (IP):
25 bar / 565 °C, 360 t/h (each)
(with reheat)
• Low pressure (LP):
4.7 bar / 288 °C, 13 t/h (each)
A supplementary firing system is installed
to maximize the electrical
output of the plant on demand. The
temperature of the GT exhaust gases
is further increased by means of
gas-fired duct burners (52.5 MW).
Steam Turbine
The steam turbine is of the 4 casing
(2 LP casings, 4 floods) type with reheat
supplied by Alstom Power
(Mannheim). In full condensing
mode (condenser pressure 0.035
bar abs) the generator produces an
electrical output of 328 MW.
The nominal live steam conditions
are 120 bars, 565°C.
Generators
Gas turbine generator
• 2 x 276 MVA
• 15.75 kV
• cos phi = 0.85
Steam turbine generator
• 1 x 386 MVA
• 18 kV
• cos phi = 0.85
Cooling Towers
Cooling water for the condenser is
cooled by a mechanical draft cell
cooling tower with 16 cells by partial
evaporation. The wooden cooling
tower is constructed in 2 rows, each
150 m long. The circulating cooling
water system is equipped with 3
times 50% cooling water pumps.
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