Wed-Air Methods & Monitoring- Applications & Technology ... - NEMC

SO3 Emission Monitoring Method Overview and Update

David Ostaszewski, PE

© 2013 O’Brien & Gere

SO3 Emissions Issues   The formation of sulfur trioxide (SO3) and sulfuric acid mist (H2SO4) in

;lue gas streams has long been a major concern for coal-‐;ired combustion units   The presence of SO3 and acid mists in the ;lue gas results in several process operational issues such as: Ø  Visible plume problems and PM-‐2.5 precusor Ø  Ductwork corrosion Ø  Plugging of equipment including turning vanes, economizers, air heaters and baghouse units due to ammonium bisulfate formation Ø  Combustion device ef;iciency reductions due to higher back-‐end temperatures required to limit acid gas formation and condensation Ø  SCR catalyst degradation

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SO3 Acid Gas Measurement Challenges   SO3 and H2SO4 measurement is one of the more dif;icult source

emission testing challenges Ø  SO3 typically present in low concentrations Ø  Very hygroscopic, tends to condense very quickly Ø  SO3 tends to absorb onto surfaces and ;lyash Ø  Can exist in several states or phases simultaneously – SO3 vapor, H2SO4 vapor, H2SO4 aerosol, droplets. Ø  Equilibrium between phases varies with temperature, concentration, and ;lue gas moisture Ø  Many sources of interference and bias in traditional test methods. Ø  High levels of SO2 present in coal-‐;ired sources cause bias

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Traditional SO3 Test Methods   There are several sampling methods and analytical techniques for SO3

measurement Ø  ASTM D-‐3226-‐73T – The “Granddaddy” of SO3 measurement methods   Original controlled condensation method developed in the 1960s   Glass wool plug in probe tip used for particulate removal   Probe temperature maintained at >500 Deg. F   Condenser temperature maintained at 140 Deg. F Ø  USEPA Reference Method 8   Isokinetic method using USEPA Method 5 type probe   No controlled condensation, SO3 is absorbed into isopropyl alcohol (IPA) solution. Barium perchlorate titration or IC analysis   Not suitable for measurements from coal ;ired boilers due to high SO2 levels – portion of the SO2 is adsorbed in the IPA biasing the sample.

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Manual SO3 Sample Train Schematic

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© 2013 O’Brien & Gere File Loca7on


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Traditional SO3 Test Methods (Cont.) Ø 

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USEPA Reference Method 8A (Conditional Test Method 13)   Commonly used SO3 test method promulgated by USEPA in 1996   Attempts to address sulfate and particulate matter interference issues associated with Method 8   Non-‐isokinetic, single point sample method   Heated sample probe and quartz ;ilter upstream of condenser maintained at >500 Deg. F   Controlled condensation using modi;ied Graham condenser maintained between 167 to 185 Deg. F   SO3 sample recovered from condenser using water or IPA (recommended) rinse. Barium perchlorate titration or IC analysis on rinsate



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Traditional SO3 Test Methods (Cont.) Ø 

USEPA Modi;ied Reference Method 8   Isokinetic method using Method 5 type probe   No controlled condensation   Cyclone separator used on the end of the sample probe to knock out water droplets

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USEPA Conditional Test Methods 13A and B   Developed by USEPA as an alternative to Method 8   Method 13A is a non-‐isokinetic method that uses a ;ilter (heated to > 500 Deg. F ) upstream of impinger train   Method 13B is similar to 13A, only isokinetic for sampling sources equipped with wet scrubbers that may have water droplets present in exhaust stream   No controlled condensation, SO3 is absorbed into IPA impinger

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SO3 Test Method Enhancements ■ 

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There are several modi;ications that can be made to manual SO3 measurement methods to improve method performance Ø  Use alternate means to remove particulate matter to reduce SO3 sample loss in high PM locations(due to SO3 absorption onto ;lyash or SO2 oxidation)   inertial separation probes (coated)   electrostatic precipitation   cyclonic separation Ø  Dynamic sample train spiking Ø  Oxygen measurements taken at probe tip and from sample train Ø  Change location -‐ Sample downstream of particulate or acid gas control device and at multiple points whenever possible © 2013 O’Brien & Gere

SO3 Test Method Enhancements (Cont.) Ø  Ø  Ø 

Ø  Ø 

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Use ;ilter in backend of condensation coil to collect acid aerosols Be sure to condition PM ;ilter or thimble prior to sampling Use a sample probe of at least 5 feet in length when sampling downstream of FGD to ensure acid droplets are vaporized. Maintain probe temperature at ≥600 Deg. F if possible (can lower temperature if longer sample probe is used) Verify on-‐site titration results with ion chromatography (IC) Adjust condenser coil temperature as stack gas moisture levels increase


Condenser Coil Temperature Adjustment Condenser Coiler Operating Temperature versus Moisture

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Percent Moisture

Condenser Coil Temperature Increase (oF)

≤ 16

Baseline

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+2

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+4

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+6

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+8


Continuous SO3 Monitoring Methods   Acid deposition probes (Breen, EES, Land)

Ø  In-‐situ measurement, acid dew point measurement procedure Ø  Uses temperature controlled plate inserted into the ;lue gas stream to repeatedly condense and evaporate acid material Ø  H2SO4 concentrations are evaluated using the formation and evaporation temperatures of the acid material.   Can also potentially quantify other sulfate compounds Ø  ammonium bisulfate Ø  ammonium sulfate Ø  sodium bisulfate

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Continuous SO3 Monitoring Methods (Cont.)   FTIR -‐

Ø  Under development, in-‐situ cross duct measurement, therefore no issues with sample loss or bias Ø  Issues to resolve include -‐ long term reliability, probe design, detection limit, interferences   Continuous wet-‐chemical approach – EES/Pentol Ø  Semi-‐extractive sample system using heated probe Ø  Sample diluted in IPA and water in the probe head Ø  Sample transported to instrument where analysis occurs, typically a reaction with bariumchloranilate measured with a photometer or equivalent.

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Continuous SO3 Monitoring Methods (Cont.)   Tunable Diode Laser   Differential Optical Absorption Spectroscopy -‐ (DOAS)   Quantum Cascade Laser Spectroscopy – Thermo Scienti;ic Arke SO3

Ø  Dilution-‐extractive sample system Ø  Particulate removal via inertial particulate removal technique Ø  SO3 generation at the probe location   Cavity Enhanced Absorption Spectroscopy – Cemtek

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SO3 Measurement Developments -‐ Stay Tuned for:   There is signi;icant activity in both manual and instrumental SO3

method development   SO3 instrumental method is currently under development by ASTM (WK34495) Ø  Quantum cascade (QC) based Ø  Will include dynamic SO3 spiking/generation requirement   New SO3 manual test method also under development – ASTM WK36509 Ø  Final validation testing conducted in 2013, early 2014, ;inal ASTM method expected mid to late 2014 Ø  May be released in late 2013 as an USEPA “Other Test Method” (OTM) in current form Ø  Controlled condensation method expected to include many of the method enhancements discussed earlier © 2013 O’Brien & Gere 16 File Loca7on

Expected ASTM SO3 Manual Sampling Method Details   Acceptable for use at “clean” test location only(0.07 gr/dscf)   Can be used downstream of wet FGD units as H2SO4 droplet particle size

is relatively small so isokinetic sampling is not needed   Sample train conditioning run required to be conducted prior to testing   Sample probe and ;ilter temperature varies with probe length   Speci;ied condenser coil dimension speci;ications   Condenser coil temperature varies with ;lue gas moisture   Sulfuric acid mist ;ilter required (same temperature as coil)   Required conditioned ;ield blank train   Condenser coil blanks required after each run   IC analysis/con;irmation

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