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 – [email protected]

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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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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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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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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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June 23 & 24th, 2005

Primary DeNOx measure experiments3MW CERCHAR furnace

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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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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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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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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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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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June 23 & 24th, 2005

2 SNET 600 MWe pulverized units

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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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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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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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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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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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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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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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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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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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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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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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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

9_primary denox measures in large pulverized coal and lignite units practical solutions for existing...

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