MP2581

Tools for Maintaining and Optimizing SCR System Performance

L. J. Muzio, T. D. MartzFossil Energy Research Corp.

Laguna Hills, CA

EPA FCC Technical Team Meeting #17November 10, 2009

Baltimore, MD

MP2582

FERCo SCR Background and Experience

MP2583

FERCo SCR Background and Experience

NOx control experts; serving the electric utility industry since 1984 (SCR, SNCR, Burner Tuning, Low NOx Burners)

Involved with SCR design and testing for 15+ years– Pilot Studies– Cold Flow Modeling– Catalyst Testing (Laboratory & In Situ Activity)– AIG Tuning– System Performance Diagnostics

Since 2002, performed numerous SCR flow model studies and AIG tuning programs for refinery SCR systems:

MP2584

Refinery SCR ExperienceOrganization Cold Flow AIG AIG

Model Study Design TuningBP

Whiting XConocoPhillips

Alliance Crude Heater X XSweeny FCC X

Wood River FCC X XExxonMobil

Baytown FCC XBeaumont FCC X X

Billings FCC X XJoliet FCC X

SunocoPhiladelphia Heaters X X

Philadelphia FCC XToledo FCC X X

ValeroDelaware City Crude Heater X

Benicia FCC X X

MP2585

Tools for Maintaining and OptimizingSCR System Performance

Utilizing Physical Cold Flow & CFD Modeling for SCR Design

Measuring and Tuning Catalyst NH3/NOx Distribution

Catalyst Management

Measuring Catalyst Activity

Continuous NH3 Slip Monitoring

Measuring SO2/SO3 Conversion

Measuring Catalyst Velocity Distribution

Identifying Gas Sneakage

Topics

Note:Most of the topics we will discuss involve NOx measurements at the catalyst exit. Include a permanent sampling grid at the exit during construction to facilitate these measurements.

MP2586

SCR

NH3 Injection:(Uniform NH3/NOx Critical)

Catalyst Layer(s)

Turning Vanes to give uniform Velocity across the Catalyst

NO + NH3 + ¼ O2 → N2 + 1.5H2O (1)6NO2 + 8NH3 → 7N2 + 6H2O (2)2NO2 + 4NH3 + O2 → 3N2 + 6H2O (3)

Flue gas (650-750°F)

SCR Performance:• NOx Reduction• Ammonia Slip

MP2587

Physical Cold Flow and CFD Modelingfor SCR Design

MP2588

SCR Flow Model Study

Specific Model Performance Goals

Catalyst Inlet Velocity Profile RMS < 15%

RMS < 5%

System Pressure Loss Minimize

Catalyst Inlet NH3 Profile

Catalyst Inlet Temperature Profile +/- 20°F

Measurement Criteria

Profiles Measured atCatalyst Inlet

AIG Design(Evaluation / Optimization)

Turning Vane Design

Flow Distribution Devices(Perforated Plates / Resistance Bars)

MP2589

Technical Approach – Physical Model

Geometric Similarity– Scale Linear Dimensions– Scale Factor 1/8 to 1/20– Clear Acrylic Walls

Dynamic Similarity– Keep Flow Fully Turbulent (Re > 20,000)– Match Full-Scale Velocity Head, (ρV2)/2

• Implication: Vm ~ 0.7 * Vfs– Match Pressure Coefficient (PC = DP / (ρV2)/2)– Match Catalyst Pressure Drop, DPcat

– Match AIG Momentum Ratio (ρV2)jet / (ρV2)bulk

MP25810

Physical Flow Model and Full Scale Results Comparison

Predicted Ammonia Distribution, Flow Model(Normalized)

Actual Ammonia Distribution, Full Scale System(Normalized)

FCC Catalyst Inlet (AIG Valves Wide Open)

0 5 10 15 20East Wall (ft)

0

5

10

15

20

Sou

th W

all (

ft)

RMS = 3.6%

0 5 10 15 20

East Wall (Inches)

0

5

10

15

20

Sou

th W

all (

Inch

es)

RMS: 3.6%

MP25811

Physical vs. CFD Flow Modeling

- Can simulate all primary forces- Can simulate particle size distributions- Can simulate where particles hit surfaces-Can identify potential deposition areas-Cannot predict deposition rates- Not able to simulate particle re-entrainment

- Not possible to simulate drag, gravity and centrifugal forces simultaneously- Not recommended

Particulate Distribution and Deposition

- Good agreement with full scale- Easy to determine ”true” catalyst inlet profile (with enough cell resolution)- Easy to determine flow angles

- Match dynamic pressure- Good agreement with full scale- Difficult to measure ”true” catalyst inlet profile- Difficult to measure flow angles

Catalyst Inlet Velocity Distribution and System Pressure Loss

- Turbulence models are not perfect- Will under-predict mixing unless “tuned” using physical model results- Can lead to over-design (i.e., unnecessary static mixers)

- Keep Re in fully turbulent range - Bulk flow turbulence is simulated- Good agreement with full-scale

Catalyst Inlet Ammonia Distribution(Gas Mixing)

CFD ModelPhysical ModelParameter

MP25812

Measuring and TuningCatalyst NH3/NOx Distribution

MP25813

NH3/NOx Distribution and AIG Tuning

0

2

4

6

8

10

80 90 100

NOx Reduction, %

NH

3 sl

ip, p

pm

RMS=2.5% RMS=5% RMS=7.5% RMS=10% RMS=15%

MP25814

AIG Design Influences Tuning

Flow Into PageFlow Into Page

Flow

mixer mixer

Flow

mixer mixer

Flow Flow

Cross Grids Two Zones Multi-Zones

Mixer with 1-D Adj. Mixer with Multi Zone Grid Bluff Body Mixer

MP25815

Tuning Methods

Measure and Adjust the NH3/NOx RatioMost preciseRequires turning off the NH3 for a short timeIs done by just measuring NOX

Adjust to a Uniform Outlet NOx DistributionEasierDoes not require that the NH3 be turned offHowever, there is not a unique relationship between outlet NOx profile and NH3/NOx uniformity

MP25816

Measure and Adjust the NH3/NOx

Basis (SCR operated with no local NH3 slip)

Procedure1. Turn off NH3, obtain NOx outlet profile (or measure an inlet profile

above the first layer)2. Turn NH3 on to produce 50-70% ΔNOx, obtain NOx outlet profile3. Use 1 and 2 to calculate local NH3/ NOx ratios4. Make contour plot of NH3/ NOx distribution5. Adjust AIG and repeat 2-4

islipioutiiniinNHNONONH xx 33 )( +−=

−−

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛−=⎟⎟

⎠

⎞⎜⎜⎝

⎛

iin

iout

x

x

ix NO

NO

NONH 13

MP25817

Adjust to a Uniform Outlet NOx Distribution

Performed Without Turning Off the Ammonia

The Relationship Between The Outlet NOx Profile and NH3/NOx Distribution Depends On Operating Conditions

MP25818

Outlet NOx Distribution vs. NH3/NOx Distribution

0

2

4

6

8

10

12

14

0 20 40 60 80 100 120RMS- outlet NOx, %

RMS

-NH3

/NO

x, %

93% dNOx90% dNOx80% dNOx70% dNOx

MP25819

Multipoint Instrumentation: FERCo'S MCDA

Traditional Point-by-Point96 points x 2-3 minutes/point ⇒ 4-5

hours

MCDA96 points x 5 min/12 pts ⇒ 40

minutes

MP25820

AIG Tuning, FCC SCR System

NH3/NOx RMS = 6.0%

0 5 10 15 20 25 300

5

10

15

20

25

NH3/NOx RMS = 1.0%

0 5 10 15 20 25 300

5

10

15

20

25

As Found RMS = 6.0% Tuned RMS = 1.0%

Normalized NH3/NOx Distribution

MP25821

14 MW Gas Turbine SCR

As-found (RMS = 14.7%) Optimized (RMS = 6.5%)

0 5 10 15 20 25 300

5

10

15

20

Sout

h

Nor

th

0 5 10 15 20 25 300

5

10

15

20

Sout

h

Nor

th

Flow Into Page

AIG

MP25822

Annual Tuning?

0

1

2

3

4

5

6

7

8

A B C D EUnit

RM

S-N

H3/

NO

x, %

Year 1As Found Year 2Tuned Year 2

MP25823

Catalyst Management

MP25824

Catalyst Management

What is Catalyst management?– Keeping track of catalyst activity to ensure continued environmental

compliance

How is Catalyst Management Done?– Periodically determining the activity of the catalyst in the reactor– Laboratory analysis (if a sample can be obtained)– In situ analysis (later discussion topic)– Utilize catalyst management software for planning

Why is it Done?– Forecast when catalyst additions or replacements are necessary– Is the addition of a spare layer adequate, or is replacement necessary?– Provide sufficient lead time to procure catalyst (6-9 months)

MP25825

Catalyst Degrades With Time(Utility Coal Example)

0

2

4

6

8

0 10000 20000 30000 40000 50000 60000 70000

Operating Hours

Reac

tor

Pot

entia

l, or

NH

3 sl

ip

RPNH3slip

Cat

alys

t Act

ivity

(K) o

r Am

mon

ia S

lip

K

MP25826

Catalyst Degrades With Time

00.10.20.30.40.50.60.70.80.9

1

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5Time, yrs

K/K

o

Design Add additional layer Won't make planned Outage

Minimum Activity

MP25827

Deactivation Rates Key to Catalyst Management

Catalyst Management depends on accurately measuring catalyst deactivation for each layer

K/Ko

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

0 5000 10000 15000 20000 25000Operating Hours

K/K

oLayer 1 Layer 2 Layer 3 Layer 4 Layer 5

MP25828

Comprehensive Catalyst Management Tools

Activity Decay Model

SCR Process Simulation Model

Activity Catalyst Geometry

DeactivationData

Unit Operating, Cost Factors

Reactor Design

NH3/NO Ratio

Informed Catalyst ManagementDecisions

Planned Outages

MP25829

Example: EPRI’s CatReact

Case 1

Layer 1 Layer 2 Layer 3 Layer 4 Layer 5

Startup 1 1 1Event 1 1Event 2 1Event 3 1Event 4 1Event 5 1Event 6 1Event 7 1Event 8 1Event 9 1Event 10 1Event 11 1Event 12 1Event 13 1Event 14 1Event 15 1Event 16 1Event 17 1Event 18 1Event 19 1Event 20 1

Note: Numbers signify Catalyst Type

Calculation Scenario

Initiate Calculaton

CATREACT

UnitData

SCRData

CatalystData

Time Factors

EconomicFactors

Planned Outages

CapacityFactors

Input Buttons

Calculate

OutputData

1 1+1

2 2+1

3 3+1

4

1+2

2+2

3+2

4+1

Reset All Forms

Catalyst Deactivation

Check for Changes

MP25830

Catalyst Activity Measurement

MP25831

In Situ Catalyst Activity Measurement*

- Traditional catalyst activity measurement requires plantoutage to extract sample

- FERCo’s new KnoxCheckTM

system measures catalystactivity in situ

- No outage required- Provides more data forcatalyst management

Activity K

* Patent Pending

Activity K

MP25832

In Situ Catalyst Activity Measurement*

Laboratory:

Test Conditions:AVd = Design Area VelocityNH3/NOx = 1

Measure:ΔNOx

Calculate:K = -AVd ln(1-ΔNOx)

In Situ:

Test Conditions:AV,FS = Full-Scale Area VelocityNH3/NOx > 1(NH3 added only in test sections)

Measure:ΔNOx

Calculate:K = -AV,FS ln(1-ΔNOx)

* Patent Pending

MP25833

In Situ Catalyst Activity Measurements

MP25834

KnoxCheckTM In Situ Test Modules*

* Patent Pending

Basically turn a small section of the catalyst bed into a laboratory

MP25835

In Situ vs Laboratory Activity Measurements

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Insitu Vendor 3rd Party

K/K

vend

or

MP25836

Typical KNOxCheckTM Test Results

dNO maximum = 77.3% dNO maximum = 86.6% dNO maximum = 91.3%

Catalyst Layer 3Catalyst Layer 2Catalyst Layer 1

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0

AIG NH3/NO

dNO

(%)

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0

AIG NH3/NO

dNO

(%)

0

10

20

30

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0

AIG NH3/NO

dNO

(%)

MP25837

In Situ KnoxCheckTM Measurements: Individual Layers

4-years of operation beginning in 2005

700 MW unit

E. bituminous coal

SCR on-line May 2002

Seasonal operation

Two reactors

3 + 1 configuration

Initial load: 3 layers honeycomb catalyst

Layer 1 replaced with plate catalyst prior to 2006 ozone season

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 5000 10000 15000 20000 25000

Operating Hours

Rel

ativ

e R

eact

or P

oten

tial (

RP/

RPo

)

Layer 1Layer 2Layer 3 2005 2006 2007 2008

MP25838

In Situ KnoxCheckTM Measurements: 700 MW SCR

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 5000 10000 15000 20000 25000

Operating Hours

Lab

ora

tory

Rel

ativ

e A

ctiv

ity (K

/Ko

)

Layer 2Layer 3

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 5000 10000 15000 20000 25000

Operating Hours

Rel

ativ

e R

eact

or P

ote

ntia

l (R

P/R

Po)

Layer 2

Layer 3

(a) Annual Laboratory Analysis(b) On-Demand KnoxCheckTM

Measurements

In S

itu R

elat

ive

Act

ivity

(K/K

0)

MP25839

Continuous Ammonia Slip Monitoring

MP25840

Continuous Gas Phase NH3 Instrumentation

Measurement Method• In situ• Tunable IR Laser Spectroscopy• WM,TTFM or Fast Scan Techniques

Manufacturers- Analyzers• Unisearch Associates• NEO (Norsk Elektro Optikk)( Servomex)• Siemens AG Automation• LTG Lasertech ( not yet commercial)• Sick-Maihak• OPSIS• Boreal Laser

Manufacturers- Auto Align System• Bergman’s Mechatronics LLC

MP25841

In-Situ NH3 Analyzer Issues

Path Length/Laser Power/ Dust LoadingNumber of lines of siteLocation (representative sample)Port Installation and AlignmentLaser AlignmentData Presentation– Short term process information– Long term tracking of catalyst

Cost

MP25842

In-Situ NH3 Monitors

Purge Air Purge Air

Electronics

Optical Fiber Coupled or Laser Located at Duct

Single Path or Dual Path

(Detector or Retro Reflector)

Shields May Be Needed To Restrict

Optical Path

MP25843

NH3 Monitor Characteristics

(a) TTFM: Two Tone Frequency Modulation (2nd Derivative Spectroscopy)(b) Wavelength Modulation (2nd Derivative Spectroscopy)

Manufacturer Fiber Optic Coupled

Maximum Lines

of Sight

Beam Split/ Multiplexed

Measurement Technique

Cost

Unisearch Yes 2

32

Beam Split Multiplexed

Fast Scan 42 K$ (2-Lines of Sight)

65 K$

(4-Lines of Sight)

Siemens Yes 3 Beam Split (3 paths)

TTFM (a) 30 K$ (1-Line of Sight

60 K$

(3-Lines of Sight)

NEO No 1 NA WM (b) 38 K$

)

MP25844

Measuring SO2/SO3 Conversion

MP25845

SO3 Issues

Why Measure SO3?– Verify SO2 to SO3 conversion across catalyst– Determine the absolute level of SO3 at the catalyst outlet

Catalyst Oxidizes SO2 to SO3– Measure at full scale?– Measure in a laboratory?

Measurement Methods– EPA Method 8 (Not applicable due to SO2 interference)– Most use Controlled Condensation– Measure H2SO4 Dew Point, infer SO3

SO3 Consequences– Reacts with ammonia slip forming ammonium bisulfate (ABS)– ABS is a sticky liquid that can foul downstream equipment– ABS forms a fine aerosol that can cause opacity problems

MP25846

NH3 Impacts on SO2 Conversion

T=716 F, 1000 ppm SO2, 500 ppm NOx

SO2

Con

vers

ion

(%) Fresh Catalyst

NH3/NOx

MP25847

SO3 Measurement: Controlled Condensation

Controlled Condensation System (CCS) Sampling Train

MP25848

SO3 Measurement: Controlled Condensation

Sample Flow

MP25849

Industry Need for Continuous SO3 Measurement Method

0.010.1

110

1001000

10000100000

200 400 600 800 1000Temperature, F

H2S

O4/

SO3SO3 and H2SO4 are

gas phase species

Approach Advantages Disadvantages

FTIR-Extractive >Can potentially measure both >ExpensiveSO3 and H2SO4 >Complex Instrument

>Need to maintain sample at high Temperature

FTIR- Insitu >Can potentially measure both >ExpensiveSO3 and H2SO4 >Complex Instrument>Sample heating unnecessary >High Power IR source required?

DOAS-Extractive >Relatively inexpensive >Only measures SO3

DOAS-Insitu >Relatively inexpensive >Only measures SO3>High Power UV sources available

Breen ABS/H2SO4 >Relatively inexpensive >Measures Dewpoint- need Dewpoint >Simple measurement correlation to extract H2SO4

Severen Science >Relatively inexpensive >Skilled operator required> Automated Wet Chemical Meas. >Little data available

MP25850

Measuring Catalyst Velocity Distribution

MP25851

Catalyst Velocity Distribution

Velocity uniformity typically in the specification

Velocity uniformity established during the SCR Design (Cold Flow and/or CFD)

Can it be measured at full scale?– Difficult; large reactors, long probes, low velocities(~15 ft/sec)– Pitot Probes, Thermal Anemometers– Pitot Probe dPs ~0.02 in H2O– Velocity profile re-aligns very close to the surface

Velocity distribution can be inferred using NOx measurements

MP25852

Local Outlet NOx VS. NH3 Injection Rate

0

20

40

60

0 50 100 150 200

Ammonia Injection Rate, lb/hr

Loca

l Out

let N

Ox,

ppm

raw

pt-1pt-2pt-3pt-4pt-5pt-6pt-7pt-8pt-9pt-10pt-11pt-12pt-13pt-14pt-15pt-16pt-17pt-18pt-19pt-20

NOx variations due to velocity maldistribution NOx variations due

primarily to NH3/NOx maldistribution

0

1

2

3

4

5

6

7

8

9

10

150 160 170 180 190 200

Am m onia Injection Rat e, lb/hr

Loca

l Out

let N

Ox,

ppm

raw

dNOx=1-e-K/Av

MP25853

Velocity Profile for a Coal-Fired SCR

Cold Flow Model (RMS = 5.8%)

0 5 10 15 20 25 30 35 400

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 25 30 35 400

5

10

15

20

25

30

35

40

45

50

Full Scale (RMS = 3.6%)

MP25854

Identifying Gas Sneakage

MP25855

Gas Sneakage

Improper perimeter sealsImproper seals between catalyst modulesDifficult to diagnose just looking at overall performance

MP25856

Gas Sneakage

0

20

40

60

0 0.5 1 1.5

NH3/NOx, scaled by ammonia injection

NOx

, ppm

pt-1pt-2pt-3pt-4pt-5pt-6pt-7pt-8pt-9pt-10pt-11pt-12pt-13pt-14pt-15pt-16pt-17pt-18pt-19pt-20

Plot Local NH3/NOx rather than ammonia injection rate

Data should fall on a single line defined by the catalyst activity

MP25857

Gas Sneakage

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

NH3/NOx

NO

-out

, ppm

As-Found

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

NH3/NOx

NO

-out

, ppm

Repaired

MP25858

Summary

Cold Flow/CFD– Cold flow recommended (better simulation of mixing)– CFD does a better job with particulate

AIG Tuning– Important activity– Easy to do– How often for FCC SCRs?

Catalyst Management/Catalyst Activity– New activity for FCC units– Requires knowledge of Activity vs Time– KNOxCheck® allows online determination of activity

Continuous NH3 Monitors– Recommended (TDL analyzers)

SO3 Measurements– Why? ( SO2/SO3 conversion, outlet SO3?)– Controlled Condensation

Other– Velocity Profiles and Sneakage– Can be determined with NOx measurements

MP25859

Questions?