Duke Energy SeminarSeptember 3 – 5, 2008Concord, NC

Care and Feeding of SNCR Systems

Presented to2008 WPCA / Duke Energy Seminar

bySteve Johnson

Quinapoxet Solutions

4 September 2008

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Outline

Workshop Objectives

O&M Guidelines

Operational Issues

A Few Answers

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Workshop Objectives

What would Youlike to discuss in the next hour?

What SNCR issues do you face?

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SNCR Operating Strategies

Use with LNB/OFA

Select NOx Set Point

Typical NOx reduction is 20-40 percent

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SNCR Design

AKA: where do you put the injectors?

Design factors:– Temperature vs. Load– Time– Dispersion/coverage– CO

Operation: question becomes which injectors do you use?

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Other Design Factors

Urea vs. ammonia

Droplet size (atomizer selection)

Reagent concentration

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Fuel Tech Control

Injector level and flow rate indexed to load.

NOx emission set point selected

NOx CEM provides feedback for reagent flow

Reagent flow is trimmed to hold set point

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NOxOut Control

NOx Emissions for Boiler 1 on 24 JUly 2008

100.0

120.0

140.0

160.0

180.0

200.0

220.0

240.0

260.0

280.0

300.0

8:00 9:00 10:00 11:00 12:00

Time, Hours

Stea

m F

low

(Klb

/h),

NO

xEm

issi

on (p

pm)

0.0

5.0

10.0

15.0

20.0

25.0

Ure

a Fl

ow, G

PH

Steam Flow NOx Urea Flow

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Alternate Control Scheme

Constant reagent flow selected based on experience.

Over-control NOx early in the day

Calculate NOx reduction required for compliance

When NOx reduction is zero, turn off reagent

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Operating Issues

NOx reduction is limited by ammonia slip

Consequences of NH3– Ammonium bisulfate– Air heater fouling– Ash contamination– “blue plume”

Can also consume lots of reagent!

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N

S

EW

“El 45” “El 50”

Temperatures at Boiler #2 Urea Injector Locations

GasTemp 15-ft

45-ft

Platform el-54-ft Platform el-65-ft

2045 F

2136 F

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N

S

EW 45-ft.

15-ft.

Boiler # 3 Boiler # 2 Boiler # 1

Alternate Arrangement

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SpectraTemp

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Typical Temperature FluctuationsFurnace Tempeatures at the SNCR Injection Elevation on 23 July 2008

1700

1750

1800

1850

1900

1950

2000

2050

2100

2150

2200

9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:0

Time, Hours

Tem

pera

ture

, Deg

rees

F

Boiler 3 Boiler 2

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Ammonium Bisulfate Forms

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Ammonium Bisulfate Condenses

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AbSensor – AbS/SO3What is it? What does it do?

•• InIn--SituSitu, Continuous, Continuous measurementmeasurement•• Temp at which material condenses out from flue gasTemp at which material condenses out from flue gas

This material could be:This material could be:•• Moisture (HMoisture (H22O),O),•• Sulfuric Acid (HSulfuric Acid (H22SOSO44) (H) (H22O + SOO + SO33))•• Ammonium Bisulfate (NHAmmonium Bisulfate (NH33HSOHSO44) (NH) (NH33 + H+ H22O + SOO + SO33))

212 ° F 330 ° F

H2O H2SO4 NH3HSO4

212 ° F 330 ° F

H2O H2SO4 NH3HSO4

212 ° F 330 ° F

H2O H2SO4 NH3HSO4

The same device measures condensables across the spectrum!

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How does it work? - I

Cooling Air Inlet

Cooling Air Return

Cooling air flow to the probe tip is precisely controlled to indCooling air flow to the probe tip is precisely controlled to induce uce condensation on the probe surfacecondensation on the probe surface

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AbSensor – AbS/SO3System

•• 44”” 150 lb 8150 lb 8--bolt flanged portbolt flanged port•• 5050 psipsi service airservice air•• 1212 cfmcfm air consumptionair consumption•• 110 VAC power supply110 VAC power supply

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Terminology

•• Formation TemperatureFormation Temperature–– The temperature at which condensation is first The temperature at which condensation is first

detecteddetected

•• Evaporation TemperatureEvaporation Temperature–– The temperature at which condensed material on the The temperature at which condensed material on the

instrument tip evaporates below the threshold current instrument tip evaporates below the threshold current levellevel

•• Dew PointDew Point–– The temperature at which the current curve peaks. The temperature at which the current curve peaks.

This is the temperature where evaporation from the This is the temperature where evaporation from the probe is in equilibrium with the condensation onto the probe is in equilibrium with the condensation onto the probe.probe.

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Dewpoint to SO3 ppm

VerhoffVerhoffCurvesCurves

••SO3 ppm can be calculated SO3 ppm can be calculated using a relationship based using a relationship based on Flue Gas Moisture and on Flue Gas Moisture and Duct Pressure.Duct Pressure.

••This calculation is part of This calculation is part of the the AbSensorAbSensor algorithm.algorithm.

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Typical ABS Results Dew Points at Air Preheater Inlet

150

200

250

300

350

400

450

500

Time and Date

Tem

pera

ture

, Deg

rees

F

Evaporation Formation

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SOSO33 & ABS Control& ABS Control

SO3: need SO3: need Sorbent Sorbent Injection ControlInjection Control

ABS: need integrated ABS: need integrated NOx and Air Heater NOx and Air Heater

ControlControl

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Three Layer APH Model

100

200

300

400

500

600

700

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Distance From Cold End (ft)

Tem

pera

ture

(deg

F)

Min Metal TempMax Metal Temp

Air Heater FoulingBreen Model*

Evaporation Temperature

Soot BlowerCleanable

Depth

* Licensed from EPRI; developed by Lehigh* Licensed from EPRI; developed by Lehigh

Fouling

Reduce Ammonia FlowReduce Ammonia FlowIncrease Air Heater Increase Air Heater Outlet TemperatureOutlet Temperature

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Integrated Air Heater Temperature/Mitigation Controller

20 Deg F 20 Deg F reduction in reduction in

ACET ~ to 1% ACET ~ to 1% Efficiency Efficiency

improvementimprovement

•Hydrated Lime• Trona,• MgOH•Ammonia

Mitigation

ChemicalsAir

Air Heater

Flue Gas

Air bypass damper Steam Coils

AbSensor-SO3

Evaporation Temp

Temperature/MitigationController

AH Operating Data

AbSensor-SO3

ACET Control

* *Mitigation

ChemicalsAir

Air Heater

Flue Gas

Air bypass damper Steam Coils

AbSensor-SO3

Evaporation Temp

Temperature/MitigationController

AH Operating Data

AbSensor-SO3

ACET Control

*Mitigation

ChemicalsAir

Air Heater

Flue Gas

Air bypass damper Steam Coils

AbSensor-SO3

Evaporation Temp

Temperature/MitigationController

AH Operating Data

AbSensor-SO3

ACET Control

*** *

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Air Heater Sootblowing

•• The AH Controller The AH Controller allows control of the allows control of the NHNH33 reagent based on reagent based on effective cleanable effective cleanable depthdepth

•• If the cleanable depth If the cleanable depth were not a factor, more were not a factor, more reagent could be reagent could be employed and NOx employed and NOx could be loweredcould be lowered

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Air Heater Cleaning

Gas Side

Air Side

SootBlower

Variable Frequency

Drive

Soot BlowerControl

Gas Side

Air Side

SootBlower

Variable Frequency

Drive

Soot BlowerControl

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LSBB (Low Speed Bottom Blow)

Bottom soot blower operation only (reduces hot end element damage)Uses VSC operation (1.5 rpm – 0.33 rpm)Reduced ‘step’ (75mm to 60mm)Increased SB sequence from 1 hr – Over 4 hrsBut reduced number of daily SB operations (4 per day - one to two per day)

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Belews Creek – What was the Benefit?

Eliminated two scheduled outages per year

Reduced forced outage time – SAH cleaning not mandatory

Off-line cleaning is more efficient – 24 hrs vs. 48 hrs

Lowered CCE set point

Reduced NOx – Raised NH3 slip

Eliminated hot side element damage ($$)

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SNCR Tuning

Temperature

Injector location

Injector sprays

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Spare Parts

Jackson Machine

Advanced Combustion Technology (ACT)

ACT has a portable injection system that they use to show improved operation of their components

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Now Back to Your Concerns…

Comments?

Questions?

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