Galvanic Applied Sciences 943-TGX-CE, Operation Manual

Page: 60 / 151

Revision 4 60 April 2020
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 35 and 36 show
the typical appearance of absorbance spectra for H
2
S only and SO
2
only.
Figure 35: Absorbance Spectrum for H
2
S
Figure 36: 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 34. 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.
The concentrations shown below the absorbance spectrum are calculated by using a calibration
matrix specific to the analyzer’s spectrometer to mathematically convert the absorbance
spectrum into concentration values. For more information on the calibration matrix, refer to
Section 5.2.2.