NID Modular and Multi-Pollutant Control DFGD Technology

NID™ Modular and Multi-Pollutant Control
DFGD Technology
– Fundamentals and Operational Experience
Jürgen Dopatka, P.E.
Manager Process Engineering - DFGD
([email protected] ph. +1 865-694-5342)
ALSTOM Power - Steam
Environmental Control Systems
1409 Centerpoint Boulevard
Knoxville, TN 37932
USA
Jiangtian Zhang
Unit Technology Manager
([email protected] ph. +86 10 8460 9092)
ALSTOM Technical Service (Shanghai) Co.,Ltd.
Environmental Control Systems
3F, Qiankun Plaza, No.6 Sanlitun West 6 St. Chaoyang Dist.
Beijing 100027
CHINA
Presented at:
POWER-GEN Asia 2013
Bangkok, Thailand
October 2-4, 2013
Page 1 of 20
1. ABSTRACT
The NID™ Dry Scrubber System is an advanced dry scrubber process that was developed by
Alstom starting in the late 1980s, with commercial units in operation since 1996. The system
allows for SO2 removal rates up to 98% while operating with high-sulphur fuels that would be
beyond the capabilities of traditional SDA (Spray Dryer Absorber) dry scrubber systems.
Continuous innovation and improvement of this dry scrubbing system has allowed it to be
applied to the ever-tightening environmental emissions limits in many countries for pulverized
coal-fired boilers. Its modular configuration practically sets no limits to the boiler size and
allows for great turndown without the need for gas recirculation. Furthermore, the NID system
with its integrated fabric filter not only removes SO2, but is very effective in removing other acid
gases (SO3, HCl, HF), as well as mercury in the presence of activated carbon, and of course
particulate matter (PM). While the majority of the installed NID capacity is on power
applications with various fuels, its effective multi-pollutant removal makes it also a great choice
for WtE (waste-to-energy) and iron and steel applications.
This paper provides an overview of the NID system, highlights recent developments in the
technology, and introduces several NID reference units as well as a few new projects currently in
execution.
Page 2 of 20
2. INTRODUCTION
Alstom’s NID system is the integration of a semi-dry desulphurization and particulate removal
system into a design characterized by its simplicity and compactness. The development of this
system started in the late 1980s, with the first commercial units (2x120 MWe) going into
operation in 1996 [1]. Since then, additional key developments have taken place, and a large
number of units have been installed and are operating in broad applications including power,
waste-to-energy and iron & steel industry applications.
In power applications, units using coal, oil, oil-shale and pet coke have been built in excess of 12
GW. In the field of Waste-to-Energy, a variety of waste types are being fired in an installed base
totaling over 4 million Nm3/h treated flue gas capacity. Industrial applications such as Iron &
Steel have an installed base treating over 1 million Nm3/h of flue gas.
This widespread application is largely due to its flexibility and adaptability, and this large
experience base is available to further build on. One of the more recent developments is the
application of the modular system into multi-modular units that can serve plants with practically
no limits to boiler capacity (600-800 MWe and larger) while maintaining good turndown
characteristics without the need for flue gas recirculation.
Key evaluation criteria that are commonly applied for air pollution control equipment are shown
in Table 1. The NID system excels in several of these criteria.
Table 1. Evaluation Criteria for AQCS Equipment.
1. Environmental Compliance
a. Removal efficiency requirements
b. System reliability, availability, and maintainability
2. Cost and Schedule
a. Initial capital expense and recurring operating expense
b. Delivery and construction time
3. Footprint and General Layout
a. Greenfield and retrofit
b. Space requirements
c. Layout flexibility
Page 3 of 20
Key features and benefits of the NID system are summarized in Table 2.
Table 2. Key Features and Benefits of the NID Technology.
Multi-pollutant control: High efficiency removal
of SO2, SO3, PM, HCl, and HF
Lime-based semi-dry FGD technology
Simple, compact design
Modular design
o
SO2 removal: up to 98%; SO2 emissions 200
mg/Nm3 typical
o
SO3 emissions: < 1 ppm
o
PM (filterable): < 15 mg / Nm3
o
Patented, integrated hydrator/mixer – no slurry
handling
o
Zero liquid discharge – no waste
water/treatment
o
Low water consumption; ability to use low
quality water: CTB, WFGD purge
o
Small footprint offers retrofit advantage
o
Low capital cost
o
Low BOP/construction cost
o
Low O&M cost
o
High reliability
o
Good turndown
o
No scale-up issues
Fuel flexibility of up to 2.5% sulphur coal or higher
With the above mentioned key benefits of the NID, the most stringent regulations can be met
with minimized cost and smallest footprint, while enabling reliable operation and allowing high
fuel flexibility.
3. NID PROCESS AND PERFORMANCE
3.1 NID Process Chemistry
The chemical reactions underlying the NID process are the same as for any semi-dry FGD
process, such as, for example, in a traditional SDA. They are based on the absorption of SO2 by a
dry absorbent containing quicklime (CaO) or hydrated lime, Ca(OH)2. Either of these absorbents
may be used, or a fly ash containing an appropriate amount of alkali. The SO2 reacts to calcium
Page 4 of 20
sulfite/sulfate solids, and similarly for the other acid gas components. The underlying reactions
are shown below.
Reagent
•
•
Hydrated Lime - Ca(OH)2
Quick Lime - CaO
• CaO + H2O Æ Ca(OH)2 + Heat
•
SO2(g) + Ca(OH)2 Æ CaSO3 • ½ H2O(s) + ½ H2O(g)
• CaSO3 • ½ H2O(s) + ½ O2 + 1.5 H2O(g)Æ CaSO4 • 2 H2O(s)
SO3(g) + Ca(OH)2 + H2O Æ CaSO4 • 2 H2O(s)
2 HCl(g) + Ca(OH)2 Æ CaCl2 • 2 H2O(s)
2 HF(g) + Ca(OH)2 Æ CaF2 + 2 H2O(s)
Reactions
•
•
•
While the reactions make use of hydrated lime, the NID process through its patented, integrated
NID Hydrator is able to use the less costly quick lime, which gets converted to hydrated lime just
in time when it is demanded from the process.
3.2 Operating Principle of the NID Process
Fly ash from the boiler or other gas source
is filtered from the flue gas in a Dust
Collector, preferably a Fabric Filter (FF),
and the ash recycled back into the flue gas
duct upstream the FF through the NID
Mixer and NID Reactor (Figure 1). Quick
lime (CaO) and water is added to the NID
Hydrator that is attached to the NID
Mixer, and produces hydrated lime
(Ca(OH)2). The hydrated lime overflows
Figure 1. NID System.
into the NID Mixer, where recycle ash and water is continuously added. The moistened mix is
dispersed into the NID reactor and cools the NID inlet flue gas temperature by evaporating the
water added onto the dry ash particles.
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The key parameter to be controlled in any dry FGD (DFGD) process is the humidity of the flue
gas. In power applications, at a relative humidity of 40-50% the hydrated lime becomes highly
activated and can effectively absorb SO2 [2]. The relative humidity of the flue gas is increased
by the addition of water into the system. In a conventional spray dry absorption (SDA) process,
water and lime is supplied to the flue gas as a slurry (with or without recycle) with a solids
content of 35-50%. In the NID process, the same amount of water is added into the flue gas,
through distribution onto the surface of dust particles at a water content of only a few percent.
Thus, the amount of absorbent that is recycled is much greater than in an SDA process. This
means that the surface available for the evaporation is very large. Thereby, the time for drying of
the dust added to the flue gas is very short, which in turn makes it possible to use very small
reactor vessels compared to conventional spray dryer technology. In fact, the volume is an order
of magnitude smaller than the corresponding size for a spray drying system. The resulting
increase of the relative humidity of the flue gas is sufficient to activate the lime for absorption of
SO2 at typical DFGD operation temperatures of 15-25°C above saturation in power applications.
The cooled flue gas then flows to the dust collector, where the particles in the flue gas are
removed and recycled back through the NID process. Clean gases from the fabric filter are
transported to a stack by means of induced draft (ID) fan. This process provides the appropriate
conditions for the required SO2 removal efficiency. A FF hopper level controls the quantity of
end products delivered to the end product handling system.
The NID process is thus characterized by a very high recycle rate of dry solids, which in turn
means that the utilization of the reagent is maximized. The moistened ash is still practically dry,
and thus remains free flowing material even after humidification in the NID mixer. The amount
of absorbent, which is recycled, is much greater than in a conventional SDA process. Further, the
need for sophisticated special equipment is minimized in the NID process (e.g. no high speed
machinery or high pressure nozzles), and all equipment that needs operator attention is placed
near ground level. Finally, there is no slurry handling with requirements for special pumps etc.,
since water is added directly to the NID mixer. The high recycle rate also means that only dry
material is handled in the system. The system is thus free from build-ups in gas ducts etc., since
there is no wet slurry that can impinge on surfaces in the installation.
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The FF is of high ratio type, and filtration is from the outside of the filter bags, inwards through a
dust layer deposited on the surface of the bags and eventually through the felted fabric itself.
Bags are cleaned by sending a pulse of compressed air backwards through the bags, which makes
the dust fall off the bag into the hopper below. The bags are cleaned on-line to maintain the
differential pressure drop over the FF within operating range.
3.3 NID Features and Components
The key characteristics of the NID process, as shown in Table 3, make it a versatile and compact
DFGD technology.
Table 3. Key Characteristics of the NID Process.
•
Large gas flow range
•
Unitized compartment design
•
Compact footprint
•
Gas cooling by thin film evaporation
•
Very high solids recirculation
•
Fluid bed / dust recirculated continuously
•
No external hydrator
•
No external dust recycle
•
No slurry handling
•
Free flowing dry waste product
•
No intermediate hydrated lime storage
Each NID module size has a wide range of gas flows that it can handle. Putting multiple unitized
compartment modules together allows for a very compact footprint while covering a very large
range of plant capacity while keeping the system simple without complex pieces of equipment.
Page 7 of 20
Each NID module (Figure 2) is independently
isolatable, which allows for good turn-down and
load-following capabilities without the need for
flue gas recirculation. Modules are isolated by
dampers upstream of the reactor, and downstream
of each FF compartment. Each module, depending
on module size, has a nominal gas flow capacity
corresponding to 15 – 70 MWel. The system can
be designed to achieve emission guarantees at full
load with one module out of service. This allows
for online maintenance, such as for example
replacement of bags.
Figure 2. NID System Module.
Key components that define the NID system are:
•
NID Reactor
•
NID Hydrator
•
NID Mixer
•
Fluid Trough
•
Recycle Feeder
•
Fabric Filter
Page 8 of 20
NID Reactor
The NID reactor (Figure 3), in the
shape of a J, provides an excellent
interface between the flue gas and
the humidified recycle dust for SO2
collection, while providing good
turndown per module. Each reactor
has its dedicated mixer and
hydrator. Neither high pressure nor
high speed equipment are used.
Dust is being recycled
continuously by means of the
fluidized troughs and recycle
Figure 3. NID Reactor.
feeders, in order to provide the required flue gas humidity as well as lime reagent for effective
acid gas removal. The dust moistening is managed by a constant water-to-recycle ratio
controller. The recycle dust and the waste product (calcium sulfite/sulfate) are dry and thus easy
to handle.
NID Mixer and NID Hydrator
The mixer and hydrator are of Alstom’s
Rotary
Rotary
Feeder
Feeder
proprietary design. The mixer is designed to
work in concert with the NID reactor and is
bolted onto the reactor walls (Figure 4). Thus
wetted ash has a very short distance to be
transported before it is dispersed into the flue
FDA
NID
Reactor
Reactor
Lime
Hydrator
FDANIDMixe r
gas. The recycled ash flows into the mixer
through a recycle feeder of rotary valve type,
Lime
Distributo r
Lime
Hydrator
Figure 4. NID Equipment Arrangement.
placed above the mixer. The recycle feeder
has the same width as the mixer to achieve an even flow of recycle ash over the entire cross
section of the mixer and hence an even distribution into the reactor. Nozzles are used to spray
Page 9 of 20
water onto the recycle ash to moisten its surface. The mixer has two shafts with mixing elements
that are arranged parallel to the reactor
wall.
This arrangement, which is based on a
rectangular geometry of the reactor and
its mixer, is a key feature that allows for
easy scale up and standardization of the
equipment. Based on this concept a
series of standard size reactor, mixer and
hydrator modules have been developed
(Figure 5).
Figure 5. NID Mixer/Hydrator.
The cost of dry hydrated lime is higher than that for quick lime, when compared on a molar
basis. Moreover, the bulk density of the two reagents are very different; lime is typically 900 to
1200 kg/m3, whereas dry hydrated lime is only 450 to 640 kg/m3. These factors make quick lime
the preferred material from a transportation as well as silo storage capacity point of view.
To overcome the shortcomings of conventional lime hydrators, the NID Integrated Lime
Hydrator Mixer was developed. Lime and water are fed into the hydrator, which comprises two
stages; in the first stage water and lime are mixed together and the wetted lime overflows into the
second stage. There, the somewhat lumpy material from the first stage literally disintegrates into
a very fine powdery material: (dry) hydrated lime. The feed of lime is controlled on an “as
needed” basis; i. e. the feeds of lime and water into the hydrator are controlled to match the
quantity requested by the NID control system in order to maintain SO2 emissions.
Advantages:
•
No intermediate silo for hydrated lime
•
No separate silo air filter - venting through NID FF
•
No transport of hydrated lime - direct overflow into the NID Mixer
Page 10 of 20
Fluidizing Trough and Recycle Feeder
The fluidizing trough located below the FF hoppers and leading
immediately to the NID reactor and by-product removal is a very
simple but highly effective means to move the large amounts of
solids within the NID system in a reliable manner. The trough
(Figure 6) is furnished with a fluidizing cloth that is continuously
provided with the required amount of air in order to keep the solids
Figure 6. Internal View of
Fluidizing Trough.
fluidized and moving as required. The trough at the same time
acts as the intermediate storage for inventory control. Excess
amounts of solids that need to be removed due to the
continuous production of by-product and collection of fly ash
are removed through the by-product removal (Figure 7)
located upstream of the recycle feeder. All remaining
materials get recycled back into the NID reactor by means of
Figure 7. Byproduct Removal.
the Recycle Feeder.
High Ratio Fabric Filter (Pulse Jet FF)
The FF is associated with each reactor module into an
integrated NID module. Each FF compartment/module
(Figure 8) consists of several sequentially arranged bag
nests. The FF compartment is characterized by
•
High ratio (high air-to-cloth ratio)
•
Collects ash particles from the flue gas stream –
outside to inside filtration
•
Fabric and dust layers act as filter – on-line cleaning
by means of air pulse
•
< 10% Opacity
•
< 15 mg / Nm3 emissions
•
Bag diameter ~ 0.13m, bag length up to 10 m, bag
Page 11 of 20
Figure 8. Fabric Filter Compartments.
material: needle felt
•
Pressure Loss: 1–2 kPa (4–8 in.H2O)
•
Bag Life: 2–4 years depending on operating conditions
Additionally, the dust cake provides a means for second stage
reactions, removing additional acid gases (SO2, SO3, HCl, HF)
(Figure 9) as well as mercury (Hg) and other trace elements
while passing through the cake layer and filter, and removing fly
ash and activated carbon (if used) for recycle.
Figure 9. Second Stage SO2
Removal across Filter Cake.
4. ALSTOM NID BENEFITS
4.1 Technology Comparison and Evaluation
Traditionally, there have been two technology options for desulphurization: Wet FGD and Dry
FGD.
•
WFGD is using limestone as reagent that is being recycled in a spray tower. The
byproduct is gypsum which is sold or landfilled, based on market conditions.
•
DFGD (NID or SDA) is employing quick lime or hydrated lime as the reagent, with the
lime being injected into the flue gas stream. The byproduct is a mixture of calcium sulfite
and calcium sulfate, which can be used for mine or road fill or soil nutrition, and often is
being landfilled.
Page 12 of 20
Table 4. FGD Technology Evaluation Criteria.
WFGD
SDA/FF
NID/FF
Remedy existing PM emission issue
3
1
1
CO2 capture ready
1
3
2
Load following capability
1
1
1
Byproduct Flexibility
1
3
3
Footprint
2
2
1
Water Consumption
3
1
1
Fuel Flexibility
1
2
2
Reuse existing stack or No GGH
3
1
1
O&M staffing requirements
3
2
1
Project Lead Time
3
1
1
HAPS Capture
2
2
2
1 – Best Score: Product Most Suited
2 – Medium Score: Product Suited
3 – Worst Score: Product Least Suited
When evaluated against WFGD and SDA technology, NID technology ends up with the best
overall score (Table 4). The individual score for each plant site may vary, depending on the
relevance and importance of each criteria for a particular project. The DFGD technologies can
remedy existing particulate matter emission issues, while excelling with respect to water
consumption, reuse of existing stack, and project lead time. DFGD also doesn’t produce any
waste water that needs to be treated and discharged. The NID technology has by far the smallest
footprint, which makes it a particularly suitable candidate for retrofit situations where space is
very limited. Additionally, due to its simplicity, the NID technology has the lowest O&M
requirements.
Due to their simplicity and use of less costly materials, the capital investment required for DFGD
systems is lower than WFGD systems. In the past, SDA-based DFGD systems were limited to
1.0-1.5% sulphur fuels, thus making the more capital intensive WFGD the only choice for
medium and high sulphur fuels. With the introduction of NID, low cost DFGD systems can now
Page 13 of 20
be used for medium and high sulphur fuels as well. From an operating cost standpoint, WFGD
systems benefit from the use of low cost limestone reagent especially when high sulfur fuels are
used. When considering overall lifecycle cost (i.e. capital and operating cost), experience has
showed that NID can still be the best economic solution even in medium/high sulphur
applications due to the low capital cost. However, a detailed site-specific analysis must be
performed to confirm the optimal solution.
4.2 NID Modularization and Design Flexibility
The modular feature of the NID system allows for highly flexible arrangements that can suit the
restrictive conditions of almost any existing site. Figure 10 shows several examples of how the
modules can be arranged into a system.
Figure 10. NID Module Arrangement Flexibility.
Page 14 of 20
Individual design features as well as customer
preferences could result in further variations of
the design possibilities. Fabric filters can be
designed with top doors to access the bag nests, or
alternately with walk-in plenums. Figure 11
shows an arrangement using a top door design
with a total of six modules arranged in a
symmetrical configuration, all based on the same
single module design.
Figure 11. Symmetrical NID arrangement with six
NID modules.
Furthermore, the modularization allows
shop fabrication of a number of key
components at significantly lower cost
than field fabrication. A high degree of
shop fabrication (Figure 12) with
subsequent truck shipment is possible for
the
•
NID reactors
•
Inlet ducts
•
Day Silos for quick lime
•
Mixers/Hydrators
Figure 12. Shop-fabricated reactor section,
mixer/hydrator, and lime day silo.
If access to shipping by barge is available, further pre-assembly is possible for Fabric Filter
compartments as well as Inlet and Outlet plenums.
Page 15 of 20
4.3 Summary of NID Benefits
Compared to WFGD technology, NID has the following key advantages:
•
Lower capital expense and lower lifecycle costs for medium-sized, medium-sulphur
applications
•
Multi-pollutant control including PM, SO3 (as well as HCl, and HF)
•
No waste water requiring treatment
•
Smaller footprint, better constructability
•
Ability to reuse existing stack when retrofitting AQCS
•
Shorter project execution schedule (no items with long lead times, such as ball mill, new
stack, etc.)
5. ALSTOM NID EXPERIENCE AND PROJECT PROFILES
Alstom’s experience base in DFGD projects encompasses over 130 DFGD units (SDA+NID)
totaling over 28 GW, of which 19 units are larger than 450 MW totaling 12 GW. The NID
system has been in operation for over 15 years, with the first commercial units going into service
in 1996. While a large number of the earlier NID power installations are serving smaller to
medium size units (25 … 300 MWe), more recent units have been designed, constructed or
operated for boiler capacities ranging up to 400 – 700 MWe. The introduction of NID into higher
capacity ranges occurred for a number of reasons, including
•
Compact, low cost multi-pollutant control
•
Experience gained in reliably achieving high (up to 98%) SO2 removal efficiencies while
using lime stoichiometry that challenge WFGD economics, even when firing fuels with
medium/high sulphur contents.
•
Integration of inlet and outlet plenum as part of the overall NID structure for more
compact and lower cost construction.
•
Leveraging of modularized fabrication and construction.
Additionally, the large variety of applications where NID has been applied demonstrates the
adaptability of this technology:
Page 16 of 20
Fuels/Applications: bituminous, oil shale without lime injection, CFB boilers with limestone
injection (without lime addition in NID), heavy fuel oil, Orimulsion, waste fuel, waste-to-energy
plants, sintering plants in the iron & steel industry, ESP as dust collector, ESP casing retrofitted
to FF, and more.
The following is a selection of a few projects that reflect the recent more demanding applications
on larger power plants. The Indian River Unit 4 was the first 8-compartment NID system that
Alstom delivered [3].
Changes in load of the PC boiler require addition and subtraction of compartments/modules to
maintain performance. The resulting control logic challenges required automatic sequences for
adding a compartment and to remove a compartment from service. It also required the automatic
gas flow balancing of multiple parallel gas paths in order to avoid overload or underload
situations on any single module that is in service.
Due to an extremely tight site, the placement of the lime day silos had to be compromised. As a
result, the lime distribution systems consist of multiple screw conveyors. Most recent designs
consider a larger number of smaller lime silos closely located to their respective NID hydrators
for shortest conveying distance and quick response.
The design of the integrated Fabric Filter was
optimized by reviewing the gas and dust
distribution within compartments by means of
CFD and physical modeling.
A view of the Indian River Unit 4 NID
installation after completion with one of the two
lime silos serving four NID modules in the
Figure 13. Indian River Unit 4 NID System.
foreground is shown in Figure 13. Four of the
eight rectangular NID reactors are shown along the right side of the building, with the FF
compartment penthouse being the roof of the structure. Table 5 summarizes key design and
performance data of that installation.
Page 17 of 20
Table 5. Key Design & Performance Characteristics of Recent Large Power NID Systems.
NRG - Indian River
Unit 4, USA
End-User/Project:
Application
Unit Size. MWe
Fuel
Inlet SO2, mg/Nm3
Gas Flow, m3/h
Commercial
operation
Reagent
Byproduct
NID Modules
NTP to PAC
EMISSIONS
SO2 Removal
SO2 Emissions,
mg/Nm3
SO3/H2SO4, ppmv
HCl / HF, mg/Nm3
Hg, µg/Nm3
Particulates
(filterable), mg/Nm3
Opacity
PC Boiler
436 (net)
Bituminous coal
6800
3900000
Dominion Energy
Brayton Point
Unit 3, USA
PC Boiler
660
Bituminous coal
3800
4100000
EME - Homer City
Units 1 & 2, USA
Minnesota Power
Boswell Unit 4, USA
FW PC Boiler
670 (gross)
East. Bituminous coal
4950
4453600
PC Boiler
652 (gross)
Sub-Bituminous-PRB
1780
3947000
Dec. 2011
Q1 2013
Q4 2014
Q1 2016
Pebble Lime
Landfill
(7+1) x 4m
26 months
Actual
96% at design inlet
sulphur
Pebble Lime
Landfill
(7+1) x 4m
35 months
Actual
Crushed Lime
Landfill
(9+1) x 4m
34 months
Design/Guarantees
Crushed Lime
Landfill
(8+1) x 4m
42 months
Design/Guarantees
≥ 98%
≥ 98%
≥ 98.1%
≤ 170
<1
≤ 1.6 / ≤ 0.9
≤ 175
≤ 0.7
<< 1
no guarantee, but
well below current
standards
≤ 1.6
<< 15
<< 8%
≤ 4.5 / -
< 1 (dry)
≤ 2.2 / ≤ 1.1
≤ 2.2
≤ 1.3
<< 10
≤ 22
≤ 26
-
-
-
The Brayton Point Unit 3 NID system benefited
from lessons learned at Indian River. A 3D model
view of this 8-compartment NID system with four
NID modules on each side is shown in Figure 14,
and an aerial view near completion in Figure 15
[4]. The integrated inlet and outlet plenum
ductwork can be seen in the center bottom and top
of the front side. This design has the inlet and
outlet interfacing on the same side of the
structure, but a design with interfaces on opposing
sides is equally possible, depending on site
Page 18 of 20
Figure 14. Brayton Point Unit 3 NID System 3D
Model View.
requirements. The lime day silos are integrated between
individual reactor modules for close coupling. Flue gas
enters into individual modules perpendicular to the inlet
plenum underneath each FF compartment to the NID
reactor, from where is enters the FF module and then
back to the outlet plenum. Key design and performance
parameters are summarized in Table 5.
The Homer City Units 1&2 NID system (Figure 16)
consists of two units, each with a 10-module symmetrical
Figure 15. Brayton Point Unit 3 NID
System close to completion.
arrangement design. Its design approach follows
closely that of Brayton Point. Key design and
performance characteristics are summarized in
Table 5. The system is under construction, and is
scheduled to go into service in late 2014.
The NID system currently under design and
construction for Minnesota Power’s Boswell Unit
4 station is shown as 3D model view in Figure
17. It shows another unique feature of the NID
Figure 16. Homer City Units 1 & 2 NID Systems
3D Model Views.
design feasibilities – a 9-module in-line (as opposed
to symmetrical) design out of necessity of a very
tight site that only offered a narrow plot plan. Its
design and performance characteristics are
summarized in Table 5.
Figure 17. Boswell, Unit 4, NID System 3D
Model.
Page 19 of 20
6. REFERENCES
1. Åhman, S., C.B. Barranger, and P.G. Maurin, Alstom Power’s Flash Dry Absorber for Flue
Gas Desulfurization. Proceedings of IJPGC’02, Phoenix, AZ, 2002.
2. Åhman, S, J. Buschmann, NID – A New Flue Gas Desulfurization System. Proceedings
MEGA Symposium, Washington, DC, 1997.
3. Fiedler, M., G. Hopper, Start-Up and Operating Experience: NRG Indian River NID DFGD
System. Proceedings DSUA Conference, Providence, RI, 2012.
4. Reynolds, T., B.E. Teixeira, Start-up and Operating Experience with Alstom’s NID DFGD
Technology at Brayton Point. To be presented at DSUA Conference, Denver, CO, 2013.
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