POWER September 2012 - 32

TOP PLANTS
1. Successful second act. A recent repowering
of the 1970s-era Claus B unit in the
Netherlands increased the plant's capacity to
1,309 MW by adding three Alstom GT26 gas
turbines, three heat recovery steam generators,
and retrofitted steam turbines. Courtesy:
Alstom Power
features.) The single-shaft GT24/26 has a
high power density and a small footprint
that works particularly well in a combined
cycle configuration (Figure 1).
The GT24/GT26 combustion system has
the following advantages:
■ Superior part-load efficiencies and virtually
constant efficiency between 100%
and 80% load.
■ High operational flexibility from " daily
start and stop " to baseload operation.
■ Low emissions over a wide operating
range, from 100% down to below 40%
load.
■ Increased fuel flexibility (natural gas combustion
with fuel oil as back-up fuel).
Overall, Alstom's KA26 fleet has demonstrated
availability rates of 93%, above Fclass
average (data of 45 GT26 gas turbines,
certified by Strategic Power Systems Inc.).
Claus C complies with European environmental
restrictions with respect to emissions
and with local noise restrictions.
Alstom factories in Poland, France, Turkey,
Germany, and Switzerland supplied all
the main components: three GT26 gas turbines,
three horizontal HRSGs, the TOPAIR
turbogenerators, and the ALSPA distributed
control system. In addition, Alstom performed
the retrofit of Unit B's original steam
turbines and furnished the electrical equipment
and breakers. Alstom built the project
on a turnkey basis and used experienced subcontractors
in the fields of civil engineering
and mechanical and electrical erection.
Gross said that " the target setting for the
operations and maintenance crew-after
having passed the learning curve-is below
70 people. "
New Gas Turbines Ramp
up Efficiency
" The main technology differentiator of Alstom's
power plants is the gas turbines, "
Gross said. " The GT26 gas turbine and its
sister product for the 60 Hz market, the
GT24, use the sequential combustion principle
as a way of increasing efficiency and
operational flexibility. "
Gross explained that the GT24/GT26
combustion system is based on an Alstom
combustion concept using the dry lowNOx
EV
( " EnVironmental " ) burner in an
annular combustor followed by the SEV
( " Sequential EnVironmental " ) burner in
the second, annular combustion stage.
(See " Flexible Turbine Operation Is Vital
for a Robust Grid " in the September 2010
issue of POWER for a complete description
of the GT24/26 design and operational
32
■ Very short combined cycle startup times.
■ Overnight parking of combined cycle with
low load operation concept at approximately
20% CCPP load.
Successful Integration of
Old and New
Repowering projects need to be completely
project-specific and highly customized in
order to achieve the optimum solution. The
optimum solution depends on the size of the
equipment, its age and condition, and other
project-specific conditions.
" The advantage of Alstom's repowering
proposal for Claus C was the fact that the
plant was designed in a way that it was possible
to reuse the existing condenser and cooling
system, " Gross said. " The three GT26
gas turbines provided the flexibility that is
required in today's electricity market. "
Integrating items such as the existing hybrid
main cooling water system (including
the cooling water pumps), three condensers
(retubed with titanium), the gas-receiving station,
as well as the existing generator into the
new configuration " was quite a challenge, "
Gross said. Existing systems were integrated
with the new plant and are controlled by a
common ALSPA distributed control system.
Bringing the new steam header into the
existing steam turbine building, plus the integration
of steam piping coming from the
HRSG into the existing plant structure and
existing steam turbines, were also challenging
because fully preengineered steam piping
could not be used. " Engineering support
teams from both Alstom and Essent successfully
solved this problem, and in a smart
way, " Gross said.
Essent issued the Claus C project notice
to proceed to Alstom in December 2008. Despite
all the project obstacles, the PAC was
issued only 36 months later. Gross explained
that in order to achieve such remarkable
results, Alstom and Essent employed two
teams of highly skilled specialists-one from
www.powermag.com
Alstom and one from Essent-working in
close cooperation.
Project Design Highlights
" The complexity of the repowering project
was challenging given the high number of
interfaces (more than 4,000!) that needed
to be identified and tied in. The project also
included in-parallel retrofitting the existing
steam turbine as well as integrating parts
and machinery into existing civil structures, "
Gross said.
Gross noted that the Claus C project was
the first time Alstom has successfully provided
a 3 x 1 configuration for a KA26 CCPP.
This was done to increase the efficiency of
plant operations.
Another design accomplishment was Alstom's
successful reuse and refurbishment
of much of the existing infrastructure, such
as the steam turbine building and electrical
building and direct cooling facilities, including
the main cooling water pumps and cooling
tower.
In addition, Alstom carried out a complete
new design of the steam turbines to meet the
specific requirements for Claus C. The retrofit
included replacement of the high-pressure
and intermediate-pressure steam turbines.
The rotor and inner casings of the low-pressure
turbine were replaced as well, but bearings
and outer casings were reused.
Promoting Sustainable Energy
After its successful retrofit, the Claus C Power
Plant is now one of Europe's most efficient
and clean generators. As the leading energy
utility of the Netherlands and part of RWE,
Essent is working to modernize the power
supply in the Netherlands and Europe and advance
diverse energy sources. In addition to
the billions being invested in the generation
of renewable energy-including €10 billion
in onshore and offshore wind power alone-
RWE/Essent has invested almost €5 billion in
new, extremely efficient power plants in the
Netherlands: the Claus C plant, the Moerdijk
2 plant (430 MW, gas), and the Eemshaven
plant (1,600 MW, biomass/coal).
" The Claus Power Plant epitomizes the independent
combination of renewable energy
sources (wind and sun) and conventional
electric power plants, " Peter Terium, deputy
chairman of the executive board of RWE,
said on July 1. " This power plant is extremely
flexible and, at any point, can be started up
when there is a lack of wind and solar power,
and while there is, of course, still a demand
for electricity by consumers, businesses, and
industries. This includes when this happens
in our neighboring countries. " ■
-Angela Neville, JD, is POWER's
senior editor.
POWER | September 2012
http://www.powermag.com
POWER September 2012

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