Galvanic Applied Sciences 962-AGX, Operation Manual

Page: 12 / 100

Revision 1 12 9/10/2019
Section 1 Model 962-AGX Acid Gas Analyzer
Spectrophotometer Overview
The use of an Acid Gas Analyzer to provide a continuous measurement of the H
2
S
concentration in the Acid Gas feed stream in Claus sulfur recovery plants is a standard
procedure in industry. If a single sulfur plant vents into an incinerator stack equipped with an
SO
2
CEM system or if the sulfur plant is equipped with a Tail Gas analyzer system that can
provide an accurate total sulfur number, it is possible to achieve a sulfur balance by knowing
the total sulfur into the plant via an Acid Gas analyzer. The acid gas stream is analyzed using
ultraviolet spectroscopy and a corresponding output signal is determined.
1.1 Analytical Method
The Model 962-AGX analyzer system measures the broadband absorption of H
2
S in the
ultraviolet (UV) region of the electromagnetic spectrum. The UV radiation is supplied from a
highly stable deuterium broadband source and is transmitted to and from the measurement
cell via UV fibre optic cables. The measurement cell has a specific optical path length through
which a sample of the acid gas flows. Light from the source is transmitted to the
measurement cell via a fibre optic cable. After passing through the gas space in the
measurement cell, it is transmitted to the spectrometer by a second fibre optic cable. The
CCD array converts the light into electrical signals which represent the intensity of the
spectral distribution within the band of interest. The spectral data is acquired from the
spectrometer by the system controller which calculates the concentration of the H
2
S.
The system includes a spectrometer with the grating efficiency optimized in the spectral
region where the species of interest absorb (200-400nm). A detection system is coupled to
the grating which is well suited for the desired analysis in terms of sensitivity and resolution
while minimizing dark current and stray light noise. To achieve this, a 2048 element CCD
detector is employed.
This system design provides for high analytical accuracy beyond that of a conventional
photometer (using narrow band optical filters measuring only a few discrete wavelengths) and
spectrometers having lower resolution and fewer elements in the detector.
1.2 Analyzer Design
The 962-AGX analyzer system consists of a sample handling panel and a control cabinet
mounted to a supporting framework. The oven cabinet, pressure transmitter and all the
necessary plumbing, fittings and valving associated with transporting the sample and
calibration (zeroing) of the analyzer are mounted to the sample handling panel.
The oven cabinet contains the measurement cell. The interior of the oven cabinet maintains
the area classification of the installed location, which is generally Class I, Division 2, Groups
C & D.