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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