AWMA 17 March 2016 - Sulfuric Acid Measurement - Geosyntec

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, Ph.D.980.333.2954badair@geosyntec.com

Curt Laush, Ph.D.512.497.1571claush@geosyntec.com