Date post: | 21-Feb-2017 |
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Environment |
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Molecular laser analytics for combustion power plants
(WP4.3.2)
Kim Patokoski, Jan Viljanen, Antti Aalto, Victor Contreras, Tapio Sorvajärvi, and Juha Toivonen
Tampere University of Technology, Tampere, Finland
In collaboration with Valmet Technologies Oy
MMEA final seminar, Nov 26, 2015
Supercontinuum spectroscopy• Supercontinuum sources
– ”White light laser”– Applications: spectroscopy,
microscopy, OCT, LIDAR, etc.
• Broadband Cavity Enhanced Absorption Spectrocopy (Fiedler, 2003)– Multiple species– Specificity Visible supercontinuum
at TUT Optics Lab
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Measurement principle
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CO2
CH4C2H2
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Tailored supercontinuum source
Keopsys Kult laser at TUT Optics Lab
• Pulsed fiber laser: 700 ps pulses, 800 mW average power @ 1.5 µm wavelength
• Nonlinear fiber: 3 meters of SMF(OFS UltraWave SLA)
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Matched light source
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Excellent accuracy
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A. Aalto, G. Genty, T. Laurila, and J. Toivonen, Optics Express 23, 25225-25234 (2015).
A. Aalto, CLEO Europe (2013).
Expansion to mid-IR
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C. Amiot, CLEO Europe (2015). C. Amiot, Frontiers in Optics (2015).
Lead in combustion of waste and demolition wood
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• PbCl2 accelerates the corrosion of low-alloy and stainless steels – online monitoring would help to control the process.
• Vibrational transitions at wavelengths ~ 30 μm – no laser sources available.
• Electronic transitions at UV – wide spectral shapes overlap with other molecules. Absorption not strong enough for ppm-level measurements.
PbCl2 + hv266 -->
PbCl* + Cl
PbCl2 + hv355 -->
PbCl + Cl
Absorption spectrum of PbCl2
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Photofragmentation
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355 nm
PbCl2
PbCl + Cl
PbCl* + Cl
266 nm
PbCl
Pb + Cl
Pb 6p23P0
3P1
3P2
3P1
405.8 nm
283 nm
3P0
Pb 7s1
Cl ClPb Cl Cl
Pb Cl Cl
Pb
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Experimental arrangement
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PbCl2
405 nm
355 nm266 nm
PD
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Furnace
Quartz tubeat 480 °C
Pb atomic absorption
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Probe laser wavelength (nm)
Concentration of PbCl2
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Concentration of PbCl2:
I0k
Ik
• PbCl2 concentration is calculated from the intensity drop of the probe laser transmission at t=0
Calibration curve for PbCl2
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Saturated PbCl2 concentration (ppm)
Pump energies:E1 = 4 mJE2 = 0.1 mJ
Interaction length: 0.5 m
First full-scale PbCl2 detection
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• Delfzijl, Netherlands (2015)
Measurement data from power plant
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CPFAAS signal from Feb 4th CPFAAS signal from Feb 3rd
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• First in-situ detectection of PbCl2• Method developed to exclude strong laser beam extinction
Conclusions• Spectroscopy with customized supercontinuum sources for
acetylene, methane, and carbon dioxide
• In-situ optical technique for PbCl2 detection having:• Good sensitivity• Good dynamic range (scalable)• Molecule specific• Allows in-situ measurements of fluctuating sample
• The PbCl2 measurement demonstrated for the first time at full-scale power plan environment
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