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Presentation of the MKS Instruments, MultiGas 2030 FTIR for use in Stack Testing and CEM applications.
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Recent Developments in FTIR for Stack Emissions
and CEM Monitoringin the Power Generation
Industry
Recent Developments in FTIR for Stack Emissions
and CEM Monitoringin the Power Generation
Industry
Sylvie Bosch-CharpenayMKS Instruments
On-Line Product Group
2
New Regulations
New Standards for Combustion Engines– Standards of Performance for Stationary Spark Ignition
Internal Combustion Engines : 40 CFR Part 60 subpart JJJJ. Gases to be measured: NOx, CO, THC
– National Emission Standards for Hazardous Air Pollutants (NESHAP) for Reciprocating Internal Combustion Engines (RICE): 40 CFR Part 63 subpart ZZZZ. Gases to be measured: NOx, CO, THC, formaldehyde
Hazardous Air Pollutants – Formaldehyde (year 2013, test on annual basis)– Future speciation of individual HCs (NMHC=non-methane
HC’s, methane, ethane)– Methanol, etc…
3
Emission Monitoring
Standard methods– NOx : Chemiluminescence (CLD) – lower accuracy in high NO2
– CO, CO2 : Non-Dispersive Infrared (NDIR) – separate analyzer for each gas
– THC : Field Ionization Detectors (FID) – provides a single number (no speciation)
– Electrochemical sensors – separate analyzer for each gas
FTIR provides measurements of many gases simultaneously– CO, CO2, NO, NO2, N2O, NH3, CH4, HCl, HF, ethane, ethylene,
propylene, formaldehyde, H2O, etc…
4
FTIR Advantages
FTIR is cost-effective if more than 4 gases need to be measuredFTIR requires minimum calibration and so reduces costsCan be easily (and inexpensively) shipped on-site, instead of deploying an entire vehicleFTIR is best method to measure formaldehyde
5
Infrared (IR) SpectroscopyBased on IR light absorption– Energy (IR radiation) heats molecule - vibrations and rotations– The pattern and intensity of the spectrum provides all the
information about gas (type and concentration)
H2O Spectrum
6
FTIR Provides Real-Time Analysisof Multiple Species
Averaging 15 sec to 1 minute per point
7
Measurements Requirements
<2% of cal span<3% of cal spanDrift
Typically less than 200 sec_System Response Time
<4% of cal span. Tested annually.
<2.5% of cal span. Tested once.
Interferences(=cross-sensitivity)
<2% of cal span<2% of cal spanAccuracy (= calibration error)
<2% of cal span<2% of cal spanSensitivity (=short term repeatability)
DIN EN 15277-3EPA Methods 3A, 4, 7E, 10
cal span = calibration span = upper limit of calibration range
8
How Can FTIR Meet the Measurement Requirements?
Sensitivity usually not an issue (long acquisition times OK)Accurate FTIR instrument neededOptimization of Analysis Method (minimal effect of interferences)Drift usually not an issue (background in N2 taken prior to testing)Optimization of Sampling System (response time, effective transport of “sticky” species)
9
Instrument Spectral Accuracy Requirements
Instrument Accuracy Optimization– Spectra linearity
Accurate absorbance in the whole range of absorbance level– Resolution
Instrument has same resolution (i.e., line width) as the calibration spectra
– Line position Instrument spectra are “lining up” exactly with the calibration spectra
Validation– Standard historical approach is to run cal cylinder and
create instrument-specific calibration
– New, better approach is to use transferrable calibrations (possible because of excellent instrument to instrument matching) and verify cal cylinder
10
Comparison of calibration (yellow) to sample (white) for CO
=> Excellent overlap of calibration and sample spectra
Accuracy Validation: Correct Resolution, Line Position and Absorbance Level
11
Accurate Multi-Point Calibrations
Multiple frequencies and calibration levels
12
Tuning of Analysis Method to Minimize Interferences
For minimal interferences, optimized analysis range and masking (“picket fencing”) Correction factors included to compensate for matrix effects (NO, CO) for best accuracyCustom water calibration may be needed (but only for very low calibration spans)“Canned methods” should be made available by manufacturerAdditional components can be easily added
13
Ability to Measure NO between Water Peaks
Sample = 150 ppm NO in 35% H2O
Top: sample (white) and water spectrum (red)
Bottom: sample minus water (white) and NO calibration (green). Grey areas are “picket-fenced” regions which are not used in the analysis
14
No Interference of WaterHigh Sensitivity
No artificial bias even in very high water (up to 40%)
Low detection
limits
Note: The HCl and HF sharp decaying peaks are real and represent small amounts accumulated in transfer lines. Other sharp positive and negative peaks are short duration artifacts due to fast water levels changes
H2O steps up to 40%
15
Typical Achievable Measurement Ranges
Ranges in mg/m3Species
0-15, 0-50
0-40%
0-25%
0-75, 0-300, 0-2000
0-15, 0-90, 0-200
0-5, 0-10
0-75, 0-150, 0-1500
0-10, 0-75
0-50, 0-100, 0-500
0-50, 0-100, 0-1000
0-30, 0-200, 0-400, 0-1500
SO2
CO2
H2O
CH4
HCl
HF
CO
NH3
N2O
NO2
NO
16
Optimization of FTIR Sampling System
Heated probe with filtering– Metal or Glass– Stainless steel filter required for “sticky compounds” HF, HCl,
NO2, NH3– <0.1 um recommended (must keep particulate low)
Heated sampling line– SS (not Teflon) recommended for most applications– As short a length as possible– Maintain temp – 191 C (very important, no cold spot!)– Maintain pressure – 1.0 Atm (+/- 5% recommended)
Sampling pump before or after FTIR Gas Analyzer– Before: Be careful about contamination or sample loss
Additional Filtering Possible– After: Be careful not to let pressure go too low
17
Mechanical & EquilibrationResponse Times
“Sticky” compounds are the same when H2O is present
18
Formaldehyde Easy to Measure
sample
Formaldehyde
H2O
Sample with 5 ppm formaldehyde and 5% water (broad peaks on right correspond to diesel, also measured)
19
Formaldehyde Testing In Stationary Combustion Turbines
DL = 200-300 ppb under typical conditionsDL as low as 30 ppb under optimized conditions
20
InformationASTM Method 6348 -03 Standard Test Method for
Determination of Gaseous Compounds by Extractive Direct Interface Fourier Transform Infrared Spectroscopy
http://www.epa.gov/ttn/atw/rice/fr05mr09.pdf
Q & A