Reduction Gas Detection; Operating System - Ametek ta7000R User Manual

Reduction Gas Detection

Operating system

12 | Model ta7000R Gas Purity Monitor
Species eluting from the RGD column set pass immediately into the
heated bed of mercuric oxide (HgO) and the photometric detector. Within
the HgO bed, the general reaction occurs:
X + HgO (solid) => XO + Hg (vapor)
where X is any appropriate reducing gas. The resulting mercury vapor
is quantified by means of an ultraviolet photometer located immediately
downstream of the mercuric oxide bed. The relative ease of measuring
mercury vapor at low concentrations lends the technique its inherent
sensitivity.
For carbon monoxide and hydrogen, the equilibrium reactions are as fol-
lows:
CO + HgO (solid) => CO2 + Hg (vapor)
H2 + HgO (solid) => H2O + Hg (vapor)
The hydrogen reaction undergoes approximately 20% conversion to mer-
cury vapor in relation to carbon monoxide. Under continuous operation,
the effective life of the mercuric oxide bed is approximately two years.
Contamination of carrier gases with reactive compounds such as sulfides,
chlorides, and aromatics will irreversibly impair reactivity and will neces-
sitate bed replacement. Care should be taken to bypass the instrument if
these compounds are present in the sample gas stream.
High concentrations of hydrogen and carbon monoxide will use up the
active sites in the reaction bed faster than lower level concentrations.
A six-button keypad enters commands to the microprocessor, which moni-
tors detector operation, controls heated zones, and operates all internal
valve functions. External signal outputs for a data collection system or
host computer are located at the rear panel.
The microprocessor control system allows complete unattended operation
of the ta7000R. This onboard system performs necessary operational and
analytical functions such as:
• · Analyzer Status Control
• · Contaminant identification
• · Concentration Calculations
• · Calibration