POWER December 2013 - 33

TOP PLANTS
steam generator, auxiliary equipment, and
biomass yard, as well as carrying out civil
works, erection, and commissioning of the
boiler island.
Polish regulations require a minimum of
20% agro biomass, which includes a variety
of materials, such as straw, sunflower
pellets, dried fruit (marc), and palm kernel
shells. A major concern in the design
process was the high-alkali content of this
agricultural biomass. Pilot testing was conducted
to determine if the advanced agro
CFB concept would perform adequately
under these conditions. The design passed
with flying colors.
The Polaniec boiler has solids separators
built from steam-cooled panels integrated
with the combustion chamber, which avoided
heavy refractory linings in the separator. The
final superheating and reheating stages are
located in special enclosures at the bottom of
the furnace, adjacent to the main combustion
chamber (Figure 1). Because they are located
outside the main combustion area, they are
protected from the fouling and corrosive environment
of the boiler's hot flue gas, thus
resulting in higher steam temperatures. The
design also provides good load-following capabilities
and turndown ratios.
The ABC technology uses moderate fluidizing
velocity in the furnace and features
a full-step grid design in order to transfer
heavy unfluidized particles effectively into
the bottom ash removal system.
" The unit is indeed unique, as it is one of
the largest in its sector, " said GDF SUEZ
Chairman and CEO Gérard Mestrallet.
Table 1. Design performance data are for O2 6% in dry gases, emissions guarantees 50%
boiler maximum continuous rating, 24-hour average. Source: Foster Wheeler
Description
Flue gas exit temperature
Boiler efficiency
NOx
SO2
CO
Particulate matter (dry)
" It's a very original, ultra-modern unit. It
features fluidized bed combustion, which
is really at the cutting edge of combustion
technology. "
Other Major Contracts
The plant utilizes the Ovation distributed
control system, supplied by Emerson Process
Management. The system can handle 6,000
I/O points and includes the AMS Suite predictive
maintenance software.
A complete chipping line, which included
a drum chipper and corresponding handling
equipment, was supplied to the plant
by BRUKS Klöckner GmbH together with
Polimex Mostostal Warszawa.
Alstom was awarded a contract to retrofit
the existing steam turbine to optimally match
the new biomass configuration. In mid-2012,
Alstom parlayed that work into a contract
worth approximately €65 million ($89.6 million)
for modernization of Units 2 through 7.
Alstom also has an option to retrofit Unit 1,
but the decision on whether to move forward
1. Side view of Polaniec boiler. Source: Foster Wheeler
1 - Step grid
2 - Final SH and RH
3 - Conservative flue gas velocity and
effective temperature control
4 - Steam cooled solid separator and
return leg
5 - Optimal convective heat transfer
surfaces and correct flue gas temperature
4
148C (298.4F)
91.0%
<150 mg/Nm3
<150 mg/Nm3
<50 mg/Nm3
<20 mg/Nm3
with that upgrade is not expected until 2014.
The upgraded steam turbines will increase
efficiency and allow for capacity ratings of
over 240 MW per unit, which will also significantly
reduce CO2 emissions from the
rest of the facility.
Emissions Control
While GDF SUEZ is the largest independent
power producer in the world, with over 117
GW of installed capacity and 7.2 GW more
under construction, the company has developed
a management approach designed to
limit its environmental impact. It has embraced
a strategy that targets 20% of electric
generation capacity from renewables and
has also optimized the energy efficiency of
its production facilities in an effort to fight
climate change.
The Polaniec Green Unit is a flagship
plant that demonstrates the company's
commitment to this strategy. The boiler utilizes
a low and uniform temperature profile
in the furnace and staged combustion to
help control emissions. Additionally, it is
equipped with an ammonia injection system
and catalyst-selective noncatalytic
reduction plus selective catalytic reduction-for
controlling the nitrogen oxide
emissions. An electrostatic precipitator is
used for controlling particulate emissions.
With these measures, the Green Unit can
adequately meet the required emission limits
noted in Table 1.
Replacing the original coal-fired boiler
5
in Unit 8 with the Green Unit enabled the
project to meet its goal of saving almost 1.2
million tons of CO2 annually. As the world's
largest biomass-fired CFB boiler, the Polaniec
Green Unit is a well-qualified POWER
Top Plant.
The unit began commercial operation on
3
Nov. 15, 2012, six weeks ahead of schedule.
" It's a beautiful showcase, " said Jean-Fran2
1
çois
Cirelli, vice chairman of GDF SUEZ,
" All the ingredients are there for it to be a
success. " ■
-Aaron Larson is a POWER associate
editor (@AaronL_Power,
@POWERmagazine).
December 2013 | POWER
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