March 2016

Ship Emissions Monitoring with Laser-based Cantilever-enhanced Photoacoustic Detection

Dr. Jaakko Lehtinen, Client Partner, Gasera Ltd.Pittcon 2016, 8.3.2016, 10:45 am

Gasera Ltd. Tykistökatu 4, 20520 Turku, Finland

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Why to monitor ship emissions?

Ships using marine fuel oil release SO2 emissionsShips using marine diesel oil release NO2 emissionsBiogas ships release unburnt CH4Both SO2 and NO2 are air pollutantsCH4 is a greenhouse gasNIOSH Relative Exposure Limits: SO2 2ppm, NO2 1 ppmUS National Ambient Air Quality Standards limits: SO2 only 75 ppb, NOx only 53 ppb!

SO2 and NO2 emission control areas

ECA (emission control area)Sulphur emission control areas (SECA) include the Baltic Sea, the North Sea, the North American ECA, including most of US and Canadian coast and the US Caribbean ECAAllowed SO2 emissions from ships are notably lower in SECAsSimilarly NECA for nitrogen emissions

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https://www.bbc-chartering.com/informations/news/archive/2014.html

Timeline for tighter regulation fuels

The new regulation for sulphur content in fuel in ECAs is a relatively new topic

From January 2015 the maximum allowed Sulphur content in fuel in ECAs has been 0.1%

The regulations are becoming global in near future

Global limit for sulphur content in fuel will decrease from 3.50% to 0.50% from 1 January 2020, subject to a feasibility review to be completed no later than 2018

Also, new tighter regulations for nitrogen dioxide emission have been effective since the beginning of 2016

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http://www.aecm aritime.com/eca

Motivation for emissions monitoring

Shipping companies can save around $10000 per day per ship by using illegal higher sulfur level fuel New regulations cost around $45 billion per year to the shipping industryThe emissions of an individual ship are not directly monitoredThe SO2 content in fuel is mainly determined by taking samples straight from the fuel tank of the ship and sending them to analysisThe inspections can be random occasional checks or based on suspicionThe inspections are performed by authoritiesThe ships often have two different tanks for operation in different areas

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Emissions monitoring is required to reliably ensure that the regulations are being obeyed!

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Problems with current technologies

Different gases are detected with different technologies

SO2, UV-fluorescenceCO2, InfraredNO2, ChemiluminescenceCH4, Infrared

Different analyzer is required for every gas compoundAir monitoring station with multiple expensive analyzers and costly maintenance -> therefore the number of stations is limitedAlready single analyzers are expensiveDifferent technologies have different sources for uncertainty

https://www.portoflosangeles.org/environment/air_quality.asp

Air monitoring stations in the Port of Los Angeles

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Solution

Multi-gas analyzer with high sensitivity is requiredHigh selectivity is required because of the ambient air backgroundSub-ppb detection limit is required for SO2Proposed solution is based on cantilever enhanced photoacoustic laser spectroscopyEnough sensitivity to use Mid-infrared (MIR) region instead of UV for SO2Pressure can be lowered for sufficient selectivityHigh resolution laser spectroscopy is needed as the SO2 absorption lines are normally buried under stronger absorption lines of water

Optical cantilever microphoneCantilever sensor

Over 100 times greater physical movement can be achieved compared to conventional microphone membrane – cantilever has very low string constant 1 N/mHighly linear response

Optical readout systemContactless optical measurement based on laser interferometryMeasures cantilever displacements smaller than picometer (10-12 m)Extremely wide dynamic measurement range

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Concept for SO2 and CO2

A combination of quantum cascade laser (QCL) and diode laser is used in conjunction with the photoacoustic cellA narrow linewidth QCL is used to measure SO2 absorption lines in MIR regionCO2 is measured in the NIR region with a tunable diode laser

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Simulations for SO2

A QCL operating between 1340-1350 cm-1 was chosen based on the simulationsPossible absorption lines for detection are in 1343-1344 cm-1 and 1345-1346 cm-1 regions

The strongest absorption features of SO2 in infrared region are between 1300 and 1400 cm-1

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Simulations for CO2

For CO2, a standard diode laser was used

CO2 lines are well separated and 2nd harmonic simulations are not necessary

Selectivity is easily achieved as the concentrations are typically above 400 ppm

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Realization

Prototype analyzer pictured under the hood

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Measured spectra

Higher concentration CH4 sample was used to confirm the range of the laser sourceCH4 has a simple absorption pattern in this rangeCoarse tuning of the wavelength is done by altering temperatureFine tuning is done by altering currentWavelength modulation is done with currentOptimal temperature for maximal power output in the desired range was determined

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Measured spectra

SO2 sample was measured when the optimal temperature of the laser was determinedSpectrum of SO2 has more features in this region than CH4Based on the spectrum, the optimal spectral line was chosen

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Achieved performance

Application requirement is sub-ppb level detection limitAchieved detection limit with photoacoustic setup was 0.5 ppbTypical concentration in the application is below 100 ppbHigher sensitivity enables the placing of the monitoring stations further away from the seawaysThe analyzer will be further tested against the SO2 reference method (UV-fluorescence) by Finnish Meteorological Institute FMIResponse time, linearity, repeatability, drift, pressure, temperature

Gas compound Integration time Detection limit

SO2 1 s 3.2 ppb60 s 0.5 ppb

Achieved detection limits:

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Concept for implementing all the necessary gas compounds

Simulated concept for all required gas componentsTwo GASERA ONE analyzers working in slave/master configurationSimulations are based on the measurements made with SO2Also ammonia (greenhouse gas) from Denox scrubbers can be included in two analyzer configuration

Gas compound Integration time Detection limit

NO2 10 s 0.2 ppb

CH4 10 s 0.5 ppb

HyperGlobal

Part of a HyperGlobal consortiumGASERAFinnish Meteorological InstituteVTT- Technical research centre of FinlandUniversity of OuluRikola OyAeromon OyMosaic Mill OyAvartek

Idea is to provide a solution for reliable emissions monitoringUAV and fixed measurement stationsConsortium is funded by Tekes – the Finnish Funding Agency for Innovation

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Booth #1657

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