awma 17 march 2016 - sulfuric acid measurement - geosyntec
TRANSCRIPT
FTIR Monitoring of Sulfuric Acid
in Coal-Fired Power Plant Flue
Gas
Brian Adair, Ph.D., Curt Laush, Ph.D.,
Constant Marks, Darwan Pursoo, P.E.
AWMA
17 March 2016
Why Measure Sulfuric Acid Concentration?
Sulfuric Acid Effects
PluggageOpacity Corrosion
NH3 + H2SO4 (NH4)HSO4
H2SO4 Aerosol
Surface Condensation
Sulfuric Acid Sources and Sinks
FGDSCR
Concentration
ESPBoiler APH Fan
Stack
SO2 + ½ O2 SO3
Mg(OH)2 + SO3 MgSO4 + H2O
NH3 + SO3 + H2O (NH4)HSO4
CaCO3 + H2SO4 CaSO4 + H2O + CO2
NH3
Mg(OH)2
CaCO3Lime, trona
Na2CO3 + H2SO4
Na2SO4 + H2O + CO2
Sulfuric Acid Sources and Sinks
FGDSCR
Concentration
ESPBoiler APH Fan
Stack
H2SO4 conc: 3-29 ppmv
Why Measure Sulfuric Acid ConcentrationContinuously?
SCR Conversion Changes with Flow Rate and NH3/NOx
SCR Conversion Changes Over Time As Catalyst Ages
SCR Conversion Changes with Flue Gas Composition
SO3 + H2O ↔ H2SO4
NH3 + H2SO4 (NH4)HSO4
1000/TDewPoint =1.784−0.027log(PH2O)
−0.103log(PSO3)+0.033log(PH2O)log10(PSO3)
Sulfuric Acid Chemistry
SO3 + H2O ↔ H2SO4Exists as H2SO4 at Scrubber
Mostly SO3 at
SCR Out
Perc
enta
ge a
s SO 3
or H
2SO 4
NH3 + H2SO4 (NH4)HSO4
ABS forms
No ABS
[NH
3] x
[H
2SO
4] (
ppm
2 )
Acid Dew Point
Sulfuric Acid Testing
Measurement Methods
David Ostaszewski, Recent Developments in SO3 Source Emission Testing Methods, National Environmental Monitoring Conf (2013)
Method 8AHeated probe & filter; controlled condensation; titration or ICMost commonly used; EPA promulgated in 1996
Acid dew point measurementIn situ; measure conductance affected by deposition of material; control temperature to cycle condensation/evaporation of material
Continuous wet-chemical analysisExtractive; continuous reaction with barium chloraniliate; anilate ions measured in continuous flow photometer
Quantum Cascade Laser SpectroscopyExtractive; commercial?
Cross-duct FTIRMeasure concentrations spectroscopically in native environment
16
Method 8A Example
FTIR for H2SO4 Measurement
Fourier Transform Infrared SpectroscopyMinimizes introduction of method artifacts
Multicomponent analysisSimultaneous quantification: SO3/H2SO4, SO2, NH3, NO, NO2, CO, CO2, HCl, HBr, H2O
Continuous (near) real-time operationData rate about 2-5 minutes at sufficient detection limits
Sub-ppmv detection limitsEspecially important for SO3/H2SO4, NH3, HCl, HBr
Mobile and field rugged in industrial environments
Monitor at almost any location
Unattended operationPermanent CEM; weeklong process optimization campaigns
Conventional FTIR
Upgrade materials in contact with the sample flue gas
Many metals will corrode; stainless steel catalyzes SO2 oxidationNickel-coated materials too porousGlass & silicon-coatings better for inertness but rigid and expensive
In extraction configuration, carefully control sampling and heating/cooling
Too hot: H2SO4 SO3 + H2OToo cold: Aerosols not dissociated and/or condense in system; H2SO4 aerosols cannot be directly observed by FTIR since absorption bands broad & continuousProbes/extraction lines should deliver aerosol content to cell
Quantitatively accurate spectral calibration setsNo documented sets for vaporous H2SO4 and SO3 available
Field validation proceduresSpike sample gases with known amounts of H2SO4
Extractive FTIR for SO3/H2SO4
Custom probe for mist/aerosol extraction
Shrouded aerosol tip for continuous monitoring; dimensions aerodynamically matched to typically flue gas exhaust flow rates Avoids isokinetic sampling errors at nonzero pitch or yaw angles
PTFE for probe, gas transfer system, sample cell In-line conditioning to convert aerosols to vaporsH2SO4 calibration reference set generated
Tailored to expected flue gas conditions
Spectrometer configured for low-level H2SO4
Monitoring system NEMA enclosed and ruggedized
Compact and lighter weight for lower cost, ease of installation and use
Aerosol/Gas Calibration Assembly
Sulfuric Acid Measurement #1
FGD
Concentration
ESP B/B
ESP B/A
Econ B APH B
FanESP A/B
ESP A/A
Stack
FTIR
SCR B
Test ConditionsParameter average unitsGross Load 569 MW
Stack Gas Flow Rate 85,300 SCFHAPH Gas Out Temp 268 °F
Fuel Flow 234 ton/hSCR Out NOx 41.7 ppmv
ESP #3 Opacity 4.77 %FGD Inlet CEM SO2 1567 ppmv
FTIR dataat ESP Out
SO2 1605 ppmvH2SO4 20.6 ppmv
NO 19.1 ppmvNO2 19.2 ppmvCO 85 ppmvHCl 101.5 ppmvH2O 6.78 %CO2 13.7 %
Real Time H2SO4 (ESP Out)
Data Quality – SO2
Trending Model Results
Sulfuric Acid Measurement #2
FGD
Concentration
ESP B/B
ESP B/A
Econ B APH B
FanESP A/B
ESP A/A
Stack
FTIR
SCR B
Real Time H2SO4 (Stack)
Summary
Real time FTIR-based portable process monitor for sulfuric acid demonstrated
Potential for compliance monitoringBrian Adair, [email protected]
Curt Laush, [email protected]