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Monitoring Ambient Air
(Sulphur Dioxide)
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SO2
highly reactivegasses
Source fossil fuel combustion at power plants
other industrial facilities fertiliser manufacturing, aluminium smelting and steel making
coal and oil (for example, coal being burnt in a home fireplace for heating and diesel-powered vehicles).
Natural sources - geothermal activity
One of thecriteriapollutants
as theindicatorgaseous sulfuroxides (SOx).
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Effects
5minutes
- 24
hours
adverserespiratory
high concentrations ofSO2formation of other SOx
SOx can reactwith other
compounds
penetratedeeply into
sensitive parts
of the lungsand can causeor worsenrespiratory
disease, suchas
ecosystems
acid rain affect
vegetationaroundindustrial
dischargesand in cities
visibility
Hazereduce
visibility.
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MAIN COMPONENTS OF UVANALYZER
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Pneumaticsystem
sample inletline
particulate filter
hydrocarbon
scrubber/kicker dryer (if
needed)
sample cell
reactionchamber
flowmeter
pump
Analyticalsystem
UV source withthe associatedsource filters,lenses, and
optics light baffles
detector(photomultipliertube)
bandpassfilters.
Electronichardware
consists of theelectroniccomponentsthat control the
analyzer andprocess thesignals.
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UV SAMPLER COMPONENTS
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Instrumentshelter
Calibrationsystem
Data
acquisitionsystem(DAS)
Wiring,
tubing &fittings
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OPERATING PRINCIPLE
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Measures emitted fluorescence of SO2produced by theabsorption of uv light
Narrow band-pass filter mirror allows only light wavelengthsof 190 to 230 nm to pass into the fluorescent chamber
The SO2molecules absorbed are excited by UV light andemit a characteristic decay radiation
A second filter allows only this decay radiation to contact aphotomultiplier tube (PMT). Electronic signal processingtransfers the light energy impinging on the PMT into a voltage
which is directly analyzed
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SO2 +h1 SO2 *SO2 +h2 where:
Where h1 = incidence light,
h2 = fluoresced light
SO2* = SO2 in its excited state
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METHODS FOR UV SAMPLER
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In sample mode, the sample isdrawn into the analyzer through the
sample bulkhead.
The sample flows through a
hydrocarbon kicker (scrubber) whichallows only hydrocarbon moleculesto pass through the tube wall.
The sample flows into thefluorescence chamber, wherepulsating UV light excites the SO2molecules.
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The band pass filter allows only thewavelengths emitted by the excitedSO2 molecules to reach the PMT. The
PMT detects the UV light emissionfrom the decaying SO2 molecules
The sample then flows through a flowsensor
Outputs the SO2concentration to thefront panel display and the analog ordigital outputs.