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M201E Ammonia Analyzer Teledyne API Model M201E NH
3
Analyzer Operator Manual
12 05206H DCN5910
signal. This process improves zero baseline stability by minimizing the effect of
PMT sensor drift.
1.1.2 Purging the Reaction Cell
As with many chemical reactions the conversion of ammonia in the presence of
other oxides of nitrogen is complicated. It is important to note that the valve
DWELL time for an AZERO measurement has a default setting of 8 seconds.
Shortening this value may not allow enough time to properly purge the reaction cell
of excess nitric oxide from the previous measurements.
In the molybdenum converter operating at 315
o
C the following significant reactions
are taking place:
Mo + NO
2
MoO
3
+ NO ~100% Efficiency
The M501 NH
3
,
ammonia converter operates at 825
o
C. At this high temperature,
several reactions occur:
NO NO Loss = ~ 3%
NO
2
NO Efficiency = ~97%
NH
3
NO Efficiency = ~97%
NH
3
NO
2
Efficiency = ~5%
As can be seen from the above reactions, the calculation of the ammonia
concentration and overall calibration of the instrument must be done carefully, if
accurate ammonia concentrations are to be measured.
1.2 SPECIAL CONSIDERATIONS FOR AMMONIA MEASUREMENT
Ammonia is a difficult gas to measure due to its chemical characteristics. The
gas tends to adsorb onto surfaces and diffuse into many materials. The following
precautions should be observed when designing ammonia sampling systems and
connecting them to the M201E analyzer:
Do NOT use copper tubing or fittings designed for household plumbing.
Use ONLY Chromatography grade (cleaned, passivated) stainless steel
tubing.
Use ONLY Glass tubing for sample inlet manifold.
ALWAYS keep the tubing from the M702SS calibrator to the analyzer as
short as possible. USE stainless steel tubing throughout, especially from the
ammonia calibration bottle to the calibrator.
If possible HEAT the sample line and DRY the sample gas.
Sample filters Will cause response delays on both the rise and fall of the
sample signal.