optical feedback cavity enhanced spectroscopy
TRANSCRIPT
AP2E
FRANCE
Direct SO3 measurement with the
ProCEAS Cavity Enhanced Spectrometer
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OFCEAS
(Hyper-reflective gas cell mirrors reflectivity`99.999%)
MEASUREMENT ADVANTAGES
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(Same energy emission becomes concentrated in narrower band- Governed by Lavoisier’s Law of Energy Conservation)
No FeedbackBandwidth 1 MHzIntensity 1X
FeedbackBandwidth 10 kHzIntensity 10X
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MEASUREMENT ADVANTAGES
200 pt high resolution spectrum(1500 nm source used as example)
Direct measurement actual optical resolution
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MEASUREMENT ADVANTAGES
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MEASUREMENT ADVANTAGES
Actual 11 day accuracy and drift tests results comparing w/ GC for sample gas CH4 shown
Results show 20ppb or 1% drift over 11 days compared w/ reference GC recalibrated every 30 mins
(References: Romanani et al. report to Atmospheric Stations Instrumentation Workshop 2008; Chappellaz report at NEEM Gas Consortium Meeting Copenhagen 2009)
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UNIQUE SAMPLING METHOD
Reduced pressure sampling probe w/ sonic velocity nozzle
Supports accelerated sample transport times; typical – 5 seconds for every 3 meters (@ 0.2 scfm flow rate)
Low flow (typically 0.11-0.33 scfh) allows for low cost precision vacuum pump. Sample line only ~ 4mm ID
SO3
UNIQUE SAMPLING METHOD
100 meter sample line on post combustion SCR outlet has been demonstrated with conditions of sample pt. temp ~200 deg C, 15% H2O by Vol and using UNHEATED line
Thermodynamic sampling conditions at the actual sampling point are effectively moved to more advantageous conditions for sampling.
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UNIQUE SAMPLING METHOD
The diagram shows how absorption peak selectivity can clearly be manipulated with sample line vacuum pressure
Diagram reference: as reported by authors Lonigro & Lanher at IFPAC 2010 Baltimore
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DIRECT SO3 MEASUREMENT
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H2O
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H2O effects selectively removed
PUTTING IT ALL TOGETHER
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TDLAS – Tunable Diode Laser Absorption Spectroscopy; CRDS – Cavity Ring Down Spectroscopy
SO3
Direct SO3 measurement with the
ProCEAS Cavity Enhanced
Spectrometer