9_primary denox measures in large pulverized coal and lignite units practical solutions for existing...
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International CAFENOx Symposium
June 23 & 24th, 2005
FP5 CAFENOx project - NNE5-2001-830
2003 – mid 2005
International Symposium
June 23rd – 24th, 2005
Primary DeNOx Measures in Large Pulverized Coal and Lignite Units
Practical Solutions for Existing Units
Jacques BLONDINTel : +33 3 21 72 8432 – Fax : +33 3 21 72 8351 – jacques.blondin@snet-electricite.fr
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International CAFENOx Symposium
June 23 & 24th, 2005
INTRODUCTION
• Main objectives of the CERCHAR study• Large SNET coal fired units
– NOx emission reduction strategy– Financial impact of 900650500 mg/Nm3
primary NOx emission reduction
• Primary DeNOx measure experiments– 3MW CERCHAR furnace– 2 x 600 MWe pulverized coal fired SNET units
• Practical approach for existing units
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International CAFENOx Symposium
June 23 & 24th, 2005
Main objectives of the CERCHAR study
From semi-industrial tests (3 MWth furnace pilot facility) and industrial tests (1500 MWth commercial units) :
• A wide range of simple and cheap primary DeNOx measures were carried out with a collection of continuous data (up to 200 measurements/analysis – 5 min refreshment – Implog software Excel files) during long periods of time in different configurations
• Combustion and NOx models were developed thanks to accurate and various data collection
• Economical measures were selected for reducing NOx emission in 2 x 600 MWe units having their own specificities clearly identified, confirmed and explained to the operators
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International CAFENOx Symposium
June 23 & 24th, 2005
Large SNET coal fired unitsNOx emission reduction strategy
2 x 600 MWe coal fired F units – once through Alstom boiler
Provence unit 5 at Meyreuil E. Huchet unit 6 at Carling (Lorraine)
Concerned by Directive 2001/80 as far as these 2 units will be operated after 2015 and don’t yet fulfill NOx emission limit values DeNOx technique implementation became compulsory
2 x Alstom-Lurgi CFBC units : 125 MWe SODELIF unit 4 at Carling 250 MWe SOPROLIF unit 4 at Meyreuil
(EDF main shareholder)
Concerned by Directive 2001/80 but already fulfill NOx emission limit values Nothing to be done regarding NOx emission in flue gas
1 x 343 MWe coal + gas combined cycle at Carling
E. Huchet unit 5 2 x 250 MWe coal fired units
Hornaing unit 3 at Hornaing (North) Lucy unit 3 at Montceau les Mines
Decision taken on June 30th 2004 to stop these units 20000 h after January 1st 2008 Nothing to be done regarding NOx emission in flue gas
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International CAFENOx Symposium
June 23 & 24th, 2005
Financial impact of primary NOx emission reduction for SNET 600MWe units
Based on that analysis, SNET decided at the end of 2001 to invest (2 x 25-30 M€) in SCR equipments for its 2 x 600 MWe units
900 650 mg/Nm3 NOx at 6% O2
900 500 mg/Nm3 NOx at 6% O2
Taxes and penalties linear to NOx emitted
0.20 – 0.27 M€/yr 0.15 – 0.21 M€/yr
Primary DeNOx technique implementation implies :
pay off in 7 years a long period of shunt down for
modifications no clear interest as far as SCR is
compulsory after 2015 technical risks for the boiler
about 0.7 – 0.9 M€/yr
about 1.1 – 1.3 M€/yr
Temporary measures (< 200 h/yr)
linear to effective application (the shorter, the cheaper)
clearly correlated to coal selection
0.1 M€/yr to 1 M€/yr
maximum for max 200 h/yr but the costs may be
dissuasive for a continuous application (3000 h/yr)
impossible without primary
DeNOx technique implementation
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International CAFENOx Symposium
June 23 & 24th, 2005
Primary DeNOx measure experiments3MW CERCHAR furnace
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International CAFENOx Symposium
June 23 & 24th, 2005
3MW CERCHAR flame furnace ATC coal – Low NOx combustion test
low NOx = 500 ppm ATC coal char 1 char 2 char 3 char 4 fly ashC 72.62 72.95 72.21 56.1 34.08 7.42N 1.63 1.45 1.34 0.39 0.4 0.41VM 25.7 12.3 3.02 5.61 4.89 5.3ash 13.4 21.35 24.88 42.09 64.9 91.98distance from the burner 0 100 300 500 1000 > 7000
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International CAFENOx Symposium
June 23 & 24th, 2005
3MW CERCHAR flame furnaceATC coal – High NOx combustion test
High NOx = 1000 ppm ATC coal char 1 char 2 char 3 char 4 fly ashC 72.62 55.9 54.62 62.36 18.12 5.96N 1.63 0.63 0.48 0.54 0.22 0.15VM 25.7 5.89 3.75 2.72 3.55ash 13.4 42.51 44.02 45.03 78.66 92.19distance from the burner 0 100 300 500 1000 > 7000
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International CAFENOx Symposium
June 23 & 24th, 2005
3MW CERCHAR flame furnace N combustion in ATC coal
C & N - coal combustion
0
10
20
30
40
50
60
70
80
90
100
- 20 40 60 80 100
C coal burn out (%)
resi
du
al N
in
ch
ar (
%)
% residual N low NOx
% residual N high NOx
ignition in
reducing conditions
at 1380°C
ignition in
oxidiz ing conditions
at 1570°C
end of volatile matters combustion
Char 1 at 1380°C
Low NOx
Char 1 at 1570°C
High NOx
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International CAFENOx Symposium
June 23 & 24th, 2005
3MW CERCHAR flame furnace N combustion in ATC coal
N behaviour along ATC coal combustion process
1300
1350
1400
1450
1500
1550
1600
30 40 50 60 70 80 90 100
percent of burnt N from coal
T°C
of
the
flam
e
T°C - low NOx
T°C - high NOx
final 500 ppm NOin flue gas
final 1000 ppm NOin flue gas
reducing ignition zoneCO = 55000 ppmO2 = 0.5 %
oxidizing ignition zoneCO = 900 ppmO2 = 7.5 %
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International CAFENOx Symposium
June 23 & 24th, 2005
Synthesis of 3 MW CERCHAR combustion tests
• Char, temperatures and gas composition measurements possible along a 5 m in length flame having different NOx emission configurations available for other experiments (e.g. O2 enriched flame)
• Selection/classification of « low NOx » coals and fuel blends, when no information available at industrial scale
• Data collection available for modeling• Training of thermal plant operators and probe/analyser
testing
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International CAFENOx Symposium
June 23 & 24th, 2005
2 SNET 600 MWe pulverized units
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International CAFENOx Symposium
June 23 & 24th, 2005
Comparison of the 2 SNET 600 MWe units
Provence 5 designed for Gardanne lignite – 7 mills
A to G furnace section 19.9 x 19.9 m2 now fed with imported coal 4/3 mills in use for PC max/mid OFA possibilities by switching off the
upper burners SCR to be implemented between ECO and Air Reheater (too « cold » zone) SCR designed for 1000 mg/Nm3 at 6% O2 NOx inlet
CEH 6 designed for Freyming hard coal –
6 mills ‘61’ to ‘66’ furnace section16.6 x 16.6 m2 now fed with a mixture of imported
coal + ashy colliery residues 5/4 mills in use for PC max/mid lack of flexibility for OFA
SCR to be implemented between ECO2 and ECO1 (too « hot » zone) SCR designed for 800 mg/Nm3 at 6% O2 NOx inlet
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International CAFENOx Symposium
June 23 & 24th, 2005
Design of tangential burners
Air II-2
Air II-1
coal burner + air I
oil fuel burner
Provence unit 5ABCE configuration
Huchet unit 662-63-64-65 configuration
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International CAFENOx Symposium
June 23 & 24th, 2005
Critical limits – Provence unit 5
Provence 5 - NOx versus reheated steam temperatures as a function of fuel ratio of differents coals
400
500
600
700
800
900
1000
480 490 500 510 520 530 540 550
T°C reheated steam
NO
x m
g/N
m3
- 6
% O
2
1.47
2.27
1.5
2.1
1.8
1.46
1.42
threshold
possible compromise
T°C must be > 525°C at MP turbine inlet
"Low NOx" coal selected
OFA through BOOS induced a dramatic decrease of reheated steam
temperatures and a subsequent reduction of global efficiency
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International CAFENOx Symposium
June 23 & 24th, 2005
Critical limits – Huchet unit 6
CEH 6 - Low NOx possibilities
500550600650700750800850900
1.6 1.8 2 2.2 2.4
Fuel ratio
NO
x m
g/N
m3
- 6%
O2
1.82
2.16
goalbut 4 mills+ OFA
goal for optimizing
SCR
OFA through BOOS was only possible with 4 mills in service when pure imported
coal was burnt instead of cheaper blends of coals with old ashy colliery residues
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International CAFENOx Symposium
June 23 & 24th, 2005
Synthesis of combustion tests carried out on the 2 SNET 600 MWe PF units
• Primary DeNOx measures based on OFA through BOOS allowed an emission reduction from about 800-1100 to an absolute minimum 600 mg/Nm3 NOx at 6% O2 without any investments, but with determinal impact on operating costs
• NOx emission reduction possible at full load, but very poor at middle load
• Selection of « low NOx » coals would rather be made through industrial scale tests carried out on the concerned units than based on index such « fuel ratio » or « N content »
• Temporary reduction methods of NOx emission were defined for both units : they are available for local Authority requirements before SCR commissioning date in 2007-2008
• At Huchet unit 6, SCR will have to be completed with moderate but continuous primary DeNOx measures (target : 700 – 800 mg/Nm3 at 6% O2)
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International CAFENOx Symposium
June 23 & 24th, 2005
Practical approach for existing units
• Return of experience
• Fractional conversion of char-N into NO and N2O at total char burnout (de Soete)
normal NOx emission with primary low NOx measures
with SCR
hard coals 800 - 1200 500 - 700 < 200 lignites 400 - 600 250 - 350 < 200
Char from FNO (range) FN2O (range)
Low and high volatiles bituminous coals
0.35 – 0.67 0.013 - 0.057
Lignite 0.084 0.006 – 0.012
SCR more or less compulsory after 2015
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International CAFENOx Symposium
June 23 & 24th, 2005
Mechanisms of SCR catalyst deterioration
• Thermal reaction : rapid and irreversible deterioration when temperatures > 450°C, even locally and on a quite short period of operating time
• Mechanical plugging up : by ultra-fine and coarse particles > 1/3 honeycomb pitch (6.4 – 9.2 mm for coal from Cormetech)
• Chemical plugging up including :– Ammonia-sulfur compounds, especially when temperatures
< 320°C– Alkaline metals from fuel (e.g. As)– Non metals, such Ca, P
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International CAFENOx Symposium
June 23 & 24th, 2005
Data collection of measurements in a view of SCR equipment implementation
Measurements and analysis in various configurations having an impact on … Coal, fuel oil and secondary fuels characteristics, including trace-elements
Duration life of SCR catalyst (poisons)
Limestone or lime injection when primary DeSO2 is implemented
Duration life of SCR catalyst (poisons)
Flue gas characteristics (average and extreme values) at the location point of SCR implementation – Detailed mapping:
flow rate (dry and wet), local velocity temperatures NOx, SO2, O2, CO2, CO
SCR catalyst design, dimension and implementation
Probes, instrumentation, control regulation
Geometric design of the unit SCR casing implementation including a possible hopper to trap coarse particles
By-pass of SCR Maintenance of NH3 injection
Fly ash at the point of SCR implementation : flow rate, including peaks during soot blowing size dimension distribution – popcorn chemistry and mineralogy – slagging detection
Dimension of catalyst channel section
Risk of catalyst channels or cells plugging up
Additional hopper to trap coarse particles
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International CAFENOx Symposium
June 23 & 24th, 2005
Consequences of SCR equipment implementation
Modification induced by SCR implementation
having an incidence on …
Pressure drop : normal accidental (plugging up)
Pressure profile of downstream flue gas pass-by Mechanical strength resistance of flue gas duct, ESP Fan design and dimension Safety equipments – Reinforcement of structures Decrease of global efficiency due to the rise of auxiliary
consumption Leakage of NH3 in fly ash Fly ash quality, market, smelliness
Additional cost of disposal SO3 in flue gas Risk of acidic corrosion of metallic components
Atmospheric SO3 release in flue gas Acidic attack of concrete chimney (in case of DeSO2 wet
scrubber without final flue gas reheater) Weight and dimension Whole installation stability
Maintenance design especially when SCR catalyst modules should be changed
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International CAFENOx Symposium
June 23 & 24th, 2005
Practical approach for existing units
200
NOx mg/Nm3 6% O2
500
date of SCR commissioning
2015 end of life
scenario 2 – 2nd step – option 3 SCR alone with low NH3 flow rate
if allowed by local Authorities
scenario 2 – 2nd step – option 2 SCR alone with normal NH3 flow rate
Longer SCR catalyst life duration thanks to primary DeNOx measures added to SCR equipment
primary DeNOX benefit
higher NOx
at SCR inlet
normal design
lower NOx
at SCR inlet
NOx at SCR inlet
(mg/Nm3 at 6% O2) 1 000 800 600 initial
percent of SCR
abatement 90 90 90
SCR operating
hours NH3 slip
ppm
Catalyst potential
K/Ko initial NOx
at SCR outlet
(mg/Nm3 at 6% O2) - - 1.00 100 80 60
5 000 0.29 0.95 105 84 63 10 000 0.57 0.90 111 89 67 15 000 0.86 0.85 118 94 71 20 000 1.14 0.80 125 100 75 25 000 1.43 0.75 133 107 80 30 000 1.71 0.70 143 114 86
reinvestment of a catalyst
module 35 000 2.00 0.65 154 123 92
Primary DeNOx measures may reduce SCR costs by postponing SCR catalyst module replacements
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International CAFENOx Symposium
June 23 & 24th, 2005
Primary DENOx measure application possibilities
• Small PF units (50 < P < 500 MWth) may fulfill 600 mg/Nm3 at 6% O2 without any problems and at moderate costs thanks to existing primary DeNOx techniques
• Large pulverized lignite fired units (P > 500 MWth) should fulfill 200 mg/Nm3 at 6% O2 in due time (before 2015) thanks to further technical enhancements of primary DeNOx measures – Think about NOx emission expression (mg/Nm3 at 6% O2 mg/MWh at 6% O2)
• Large pulverized coal fired units (P > 500 MWth) should need SCR, but SCR operating costs may be reduced – Think about end of life of unit without any SCR catalyst module replacement thanks to primary DeNOx measures
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International CAFENOx Symposium
June 23 & 24th, 2005
Thanks for your attention
The final report of the CAFENOx project will be available before the end of 2005after its approval by the Commission
CENTRE D'ETUDES ET DE RECHERCHES DE LA COMBUSTION – LA SNET – ENDESA Group
FUNDACION CIRCE Centre of Research for Energy Resources and Consumption
NATIONAL TECHNICAL UNIVERSITY OF ATHENS Laboratory of Steam Boilers and Thermal Plants
PUBLIC POWER CORPORATION OF GREECE (PPC)
IFRF INTERNATIONAL FLAME RESEARCH FOUNDATION
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