Ametek TRACE ANALYTICAL ta7000F Series, Руководство пользователя

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12 | Model ta7000F Gas Purity Monitor
Flame Ionization Detection
Species eluting from the FID column set pass immediately into the heated
bed of ruthenium oxide (Ru
3
O
4
)) and the flame detector. Within the ru-
thenium oxide bed, the general reaction occurs:
CO
x
+ (2+X)H
2
=> CH
4
+XH
2
O (vapor)
Where CO
x
is an appropriate carbon-oxygen compound gas. For carbon
dioxide the equilibrium reaction is:
CO
x
+ 4H
2
=> CH
4
+2H
2
O (vapor)
The resulting methane is quantitatively determined by means of flame
ionization immediately downstream of the ruthenium oxide bed. Meth-
ane and other simple hydrocarbons pass through the methanizer unaf-
fected.Within the flame ionization region hydrocarbons are reduced via a
series of reaction steps to CH
+
ions and electrons prior to complete com-
bustion into H
2
O and CO
2
. The resultant electrons are collected to gener-
ate a current signal. Higher hydrocarbons, those containing more than a
single carbon group, generate additional CH
+
Ions in proportion to the
carbon number. As a result the theoretical sensitivity of the flame ioniza-
tion detector to non-methane hydrocarbons is at least two times higher
than methane.
Contamination of carrier gases with reactive compounds such as sulfides,
chlorides, and aromatics will irreversibly impair reactivity and will neces-
sitate methanizer replacement. Care should be taken to bypass the instru-
ment if these compounds are present in the sample gas stream.
Operating System
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 ta7000F. This onboard system performs necessary operational and
analytical functions such as:
• Analyzer Status Control
• Contaminant identification
• Concentration Calculations
• Calibration
• Sampling Frequency
• Data Output
• Alarm Output