Galvanic Applied Sciences 943-TGXeNA, Руководство по эксплуатации

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Revision 5 58 August 2021
The
absorbance spectrum
is calculated by subtracting the current transmission spectrum
from the transmission spectrum that was obtained the last time the analyzer carried out a zero
calibration cycle OR when the New Reference button was pressed on the Spectrum panel,
whichever was most recent. The y-axis of this spectrum is absorbance units (AU). When the
analyzer is in back purge mode, the absorbance spectrum should be a horizontal line at an
absorbance of 0 AU. If it is not, and the analyzer is NOT in a fault condition, first confirm that
the current transmission spectrum in back purge is largely similar to the factory reference
spectrum, then immediately carry out a new zero calibration cycle OR use the New Reference
function on the Spectrum panel. After the zero calibration cycle is complete, confirm that the
absorbance spectrum does become a horizontal line at 0 AU.
The shape of the absorbance spectrum when sampling depends primarily on the concentrations
of H
2
S and SO
2
in the sample. Other components are generally not present in high enough
concentrations to be visibly recognizable on the absorbance spectrum. Figures 36 and 37 show
the typical appearance of absorbance spectra for H
2
S only and SO
2
only.
Figure 36: Absorbance Spectrum for H
2
S
Figure 37: Absorbance Spectrum for SO
2
In most typical operating conditions, the tail gas stream will not contain only H
2
S or only SO
2
,
so typically the displayed absorbance spectrum will appear as a combination of the H
2
S
spectrum and the SO
2
spectrum, as shown in the spectrum in Figure 35. The exact magnitude
of the absorbance for a given species will depend on the concentration of that species as well
as the measurement cell length. For a given analyzer, however, the higher the concentration of
the measured species is, the higher the absorbance (i.e. peak height) will be for that species.