MP309b

SCR Performance Issues: Coal----Natural Gas

L. J. MuzioFossil Energy Research Corp.

Laguna Hills, CA

CEMTek Environmental 2018 Emissions Monitoring Seminar and Training

September 12, 2018Santa Ana, CA

2 MP309b

Key Points

• Gas Turbine SCR Units• How important is AIG tuning?• Tune at modest levels of NOx reduction, or use an

FTIR?• Need a permanent probe grid at the SCR outlet• AIG design affects tuning

• Coal SCR Units• AIG Design Affects Tuning• Impacts at Low Load operation (becoming a major

issue)

3 MP309b

AIG Tuning: Why is it important?

Coal-fired SCR (NOxin=300 ppm) Gas Turbine SCR (NOxin=25 ppm)

0

2

4

6

8

10

80 85 90 95 100

dNOx, %

NH

3-sl

ip, p

pm

2%

5%

7%

10%

11%

RMS

0

5

10

15

80 85 90 95 100dNOx, %

NH

3-sl

ip, p

pm

3%

6%

9%

11%

14%

RMS

• Performance improvement (can be as important as the catalyst quantity)

• Becoming more important as emission limits decrease

• Catalyst Guarantees are usually based on a given NH3/NOx uniformity (RMS); need to quantify the RMS

Chart1

808079.987181136379.97703516179.880863074680

8584.919531581184.819617930584.696463823384.4950176412100

89.754482804789.582042743489.260276921688.956134226288.4298596095

91.918085428391.664573897291.296181421590.706478145590.1030111008

9493.545906556792.948406181692.276648055291.6421504587

95.641593644795.157378358194.316270669593.620463652492.9837975242

98.597.991072945197.422502149696.657175320696.1478381993

RMS

0.022969332

0.051643434

0.074507144

0.097120444

0.114782368

y

dNOx, %

NH3-slip, ppm

0

0

0.0281886813

0.050499681

0.2619820989

2

0

0.1769500531

0.3966601708

0.6674760525

1.1104562071

2

0.5398923124

0.9190880074

1.6266510495

2.2954608365

3.4527387186

1.2796301432

1.837102

2.647197054

3.9439545581

5.2709785894

2.199

3.1975514818

4.5114548066

5.9886509266

7.3839111413

4.0866355754

5.1514249906

7.0010207979

8.5311004285

9.9311292443

14.2935

15.4126305937

16.662917773

18.34587147

19.4659037998

Sheet1

Sheet1

808079.987181136379.97703516179.880863074680

8584.919531581184.819617930584.696463823384.4950176412100

89.754482804789.582042743489.260276921688.956134226288.4298596095

91.918085428391.664573897291.296181421590.706478145590.1030111008

9493.545906556792.948406181692.276648055291.6421504587

95.641593644795.157378358194.316270669593.620463652492.9837975242

98.597.991072945197.422502149696.657175320696.1478381993

RMS

0.022969332

0.051643434

0.074507144

0.097120444

0.114782368

y

dNOx, %

NH3-slip, ppm

0

0

0.0281886813

0.050499681

0.2619820989

2

0

0.1769500531

0.3966601708

0.6674760525

1.1104562071

2

0.5398923124

0.9190880074

1.6266510495

2.2954608365

3.4527387186

1.2796301432

1.837102

2.647197054

3.9439545581

5.2709785894

2.199

3.1975514818

4.5114548066

5.9886509266

7.3839111413

4.0866355754

5.1514249906

7.0010207979

8.5311004285

9.9311292443

14.2935

15.4126305937

16.662917773

18.34587147

19.4659037998

Sheet2

79.86157325179.865950404479.804901761579.768551353779.6097407819808080

84.786416782284.725227726984.531838454684.373519116284.0054851947100100100

89.448126934789.283490379488.765535556788.39642616187.7524824865

91.638421363991.324881376290.614456917590.063747737589.3698579526

93.484486584193.105624639692.208828829591.548535651390.7903927544

95.254810747294.536438106693.645688798892.905826020592.0410062446

97.991821914697.474998298296.727891650496.011786257295.0002651039

RMS

0.033152776

0.061170791

0.087961844

0.10933116

0.137728686

y

y

y

dNOx, %

NH3-slip, ppm

0.1730334363

0.1675619945

0.2438727981

0.2893108079

0.4878240227

10

5

5

0.2669790222

0.3434653414

0.5852019317

0.7831011047

1.2431435066

10

5

5

0.6898413317

0.8956370257

1.5430805541

2.0044672988

2.8093968918

1.0769732951

1.4688982797

2.3569288531

3.0453153281

3.9126775592

1.8943917699

2.3679692004

3.4889639631

4.3143304359

5.262009057

2.806486566

3.7044523667

4.8178890015

5.7427174744

6.8237421943

8.7602226067

9.4062521272

10.340135437

11.2352671786

12.4996686201

Sheet3

4 MP309b

AIG Tuning: How is it Done𝑵𝑵𝑵𝑵𝟑𝟑𝒊𝒊𝒊𝒊𝒊𝒊 = 𝑵𝑵𝑵𝑵𝒙𝒙𝒊𝒊𝒊𝒊𝒊𝒊 − 𝑵𝑵𝑵𝑵𝒙𝒙𝒐𝒐𝒐𝒐𝒐𝒐𝒊𝒊 + 𝑵𝑵𝑵𝑵𝟑𝟑𝒔𝒔𝒔𝒔𝒊𝒊𝒔𝒔𝒊𝒊

• Tune at reduced NH3 injection rate

• Local NH3 slip=0• Just need to measure NOx at the

exit

• For the NOx- in turn off NH3• For GT NOx-in is basically

uniform• Are there issues with this

approach?• Yes

𝑵𝑵𝑵𝑵𝟑𝟑𝑵𝑵𝑵𝑵𝒙𝒙 𝒊𝒊

=𝑵𝑵𝑵𝑵𝒙𝒙𝒊𝒊𝒊𝒊𝒊𝒊 − 𝑵𝑵𝑵𝑵𝒙𝒙𝒐𝒐𝒐𝒐𝒐𝒐𝒊𝒊

𝑵𝑵𝑵𝑵𝒙𝒙𝒊𝒊𝒊𝒊𝒊𝒊

• Use FTIR• Measure NOx-in, NOx-out,

NH3-in, NH3 –out• Are there issues with this

approach?• YES

5 MP309b

Tuning at Reduced NH3 Injection Rate• For a valid RMS local NH3 slip needs to be near zero• If NH3 slip is present it is not accounted for• RMS will be artificially low

0

2

4

6

8

10

0

2

4

6

8

10

12

14

16

18

20

22

24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

NH

3 Sl

ip, p

pm

Appa

rent

RM

S,%

NOx, ppm

RMS=5% RMS=10% RMS=15% RMS=25%

6 MP309b

FTIR Measurements: Site 1

0

5

10

15

20

25

30

35

40

45

0 1 2 3 4 5 6 7

Amm

onia

Slip

, ppm

vdc

Outlet NOX, ppmvdc

NH3 slip 10% RMS NH3 slip 20% RMS NH3 slip 30% RMS

7 MP309b

FTIR Measurements: Site 2

05

1015202530354045

0 10 20 30 40 50

NH3

-in:F

TIR

Calc

NO

x-in

-NO

x-ou

t+N

H3

slip

NH3 in: FTIR Measurement, ppm

B C D E F Y

8 MP309b

Permanent Sample Probes Should Be Installed

9 MP309b

Outside View of a Permanent Sample Grid on a Large Combined Cycle

Sample probe exit ports

Sample probe lines brought down to grade

10 MP309b

FERCo’s Multipoint Instrumentation

• Samples 48 points in 12-15minutes (4 groups of 12)

• NOx and O2

11 MP309b

GT:AIG Design Affects Tuning

• No Adjustments: Some systems have no adjustmentvalves- Bad Idea ! ! ! Best RMS~ 17%

• 1-D: Commonly used design

• Multi Zone: Better Direct Injection:

Two Horizontal Horizontal and Three Horizontal

Zones Vertical ZonesReagent

Struggle to get RMS~10%

RMS ~5%

RMS ~3%

12 MP309b

Coal:AIG Design Affects Tuning

0

2

4

6

8

10

Delta Wing Static Mixer A Static Mixer B Multi Zone Cross Grids

AIG Design

RMS

NH3/

NOx,

%

Flow Into Page

Flow

mixer mixer

Flow

mixer mixer

Flow

Flow

Sheet1

Flow

Flow Into Page

mixermixer

Flow

Flow Into Page

mixermixer

Flow

Sheet2

Sheet3

Sheet1

Flow

Flow Into Page

mixermixer

Flow

Flow Into Page

mixermixer

Flow

Sheet2

Sheet3

Sheet1

Flow

Flow Into Page

mixermixer

Flow

Flow Into Page

mixermixer

Flow

Sheet2

Sheet3

Sheet1

Flow

Flow Into Page

mixermixer

Flow

Flow Into Page

mixermixer

Flow

Sheet2

Sheet3

Sheet1

Flow

Flow Into Page

mixermixer

Flow

Flow Into Page

mixermixer

FlowFlow

Sheet2

Sheet3

13 MP309b

Changes in Coal Boiler Operations

14 MP309b

Changes in Coal Boiler Operations

15 MP309b

More Cycling-More Time at Low load

0 5 10 15 20 25 30 35Wall Closest to Boiler (ft) Flow Toward Page

0

5

10

15

20

25

30

35

40

Nor

th W

all (

ft)

0.80.820.840.860.880.90.920.940.960.9811.021.041.061.081.11.121.141.161.181.2

Full Load (RMS=3.2%)

0 5 10 15 20 25 30 35Wall Closest to Boiler (ft) Flow Toward Page

0

5

10

15

20

25

30

35

40

Nor

th W

all (

ft)

0.10.20.30.40.50.60.70.80.911.11.21.31.41.51.61.71.81.9

Low Load (RMS=51.2%)

• Historically Tuning was done at Full Load• Now Tuning should at least be checked at Low loads

16 MP309b

Low Load : ABS Formation/Catalyst Deactivation (Two ABS Formation Mechanisms)

Bulk Dewpoint (like fog forming)

NH3+SO3+H2O NH4HSO4

NH3+H2SO4 NH4HSO4XNH3 (ppm) * XSO3 (ppm) = 2.97 * 1025 * exp (-54,950/RT)

17 MP309b

Operation Below Bulk Dew Point

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 20 40 60 80 100 120 140Hours

K/K 0

1st Layer 2nd Layer

525°F

600°F650°F

700°F

18 MP309b

Low Load : ABS Formation/Catalyst Deactivation

Progressing Formation of ABS in Catalyst Pores

Flue Gas Flow

ABS

Catalyst Surface

ln (P/Peq) = 2.33 * 10-4 / γ T (cm-1 K-1)

Thomson’s Eq.

ABS Surface Tension

Capillary Condensation

19 MP309b

Operation With Capillary Condensation

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 5 10 15 20 25 30 35 40 45 50 55 60

Rela

tive

Cata

lyst

Act

ivity

(K/K

0)

Time (Hours)

Plate SCR Catalyst Extruded Ceramic Honeycomb SCR Catalyst

• Depending on T,NH3,SO3 will only fill up certain pores sizes with ABS

• Deactivation will level off

20 MP309b

ABS Deactivation is Recoverable

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 20 40 60 80 100 120 140Hours

K/K 0

1st Layer 2nd Layer

525°F

600°F650°F

700°F

21 MP309b

Summary

• AIG Tuning (Nat. Gas)• How well is your AIG tuned?• Do you need an accurate RMS value (catalyst

guarantees)?• AIG Tuning Approach

• NOx Measurements at the SCR exit• Permanent probe grid• Variance to allow SCR operation at lower dNOx• Yields accurate RMS

• FTIR• permanent probe grid • Make sure data follows SCR fundamentals

• Coal Units (Load Cycling)• Check AIG tuning at low loads• Change low load combustion for better NOx

distribution• Modify AIG to accommodate both full and low load• Assess ABS catalyst issues-Tools Exist!

22 MP309b

www.ferco.comlmuzio@ferco.com

Questions?

mailto:lmuzio@ferco.com

SCR Performance Issues: Coal----Natural GasKey PointsAIG Tuning: Why is it important?AIG Tuning: How is it DoneTuning at Reduced NH3 Injection RateFTIR Measurements: Site 1FTIR Measurements: Site 2Permanent Sample Probes Should Be InstalledOutside View of a Permanent Sample Grid on a Large Combined CycleFERCo’s Multipoint InstrumentationGT:AIG Design Affects TuningCoal:AIG Design Affects TuningChanges in Coal Boiler OperationsChanges in Coal Boiler OperationsMore Cycling-More Time at Low loadLow Load : ABS Formation/Catalyst Deactivation (Two ABS Formation Mechanisms)Operation Below Bulk Dew PointLow Load : ABS Formation/Catalyst DeactivationOperation With Capillary CondensationABS Deactivation is RecoverableSummarywww.ferco.com�lmuzio@ferco.com�