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5K-MNL-BIOGAS5000
8.7 Cross gas effects on chemical cells
Cross-gas effects on methane, carbon dioxide and oxygen
Methane is measured using dual beam infrared absorption. Analyzers are calibrated using
certified methane mixtures and will give correct readings provided there are no other
hydrocarbon gases present within the sample (e.g. ethane, propane, butane, etc). If there
are other hydrocarbons present, the methane reading will be elevated (never lower) than
the actual methane concentration being monitored.
The extent to which the methane reading is affected depends upon the concentration of the
methane in the sample and the concentration of the other hydrocarbons. The effect is
totally non-linear and difficult to predict.
Carbon dioxide is measured by infrared absorption at a wavelength specific to carbon
dioxide. Therefore, the carbon dioxide reading will not be affected by any other gases
usually found on landfill sites.
The oxygen sensor is a galvanic cell type and suffers virtually no influence from CO
H
S, NO
, SO
or H
2
2
2
The infrared sensors will not be 'poisoned' by other hydrocarbons and will revert to normal
operation as soon as the gas sample has been 'purged'.
H
S Measurement:
2
H
S measurement could be affected by other gases. The main cross gas effects are:
2
SO
: 20% effect
2
NO
: 20% effect
2
Other cross sensitivities are possible. If you suspect a cross sensitivity problem please
contact your supplier for additional information.
:
Note
Other gases could cause cross-gas effects. If you suspect a cross sensitivity
problem please contact the Technical Support Team at QED at+1
(734) 995-2547.
Page 42
, unlike many other types of oxygen cell.
2
BIOGAS 5000 gas analyzer
Copyright LANDTEC North America
, CO,
2
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