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T201 Ammonia Analyzer Teledyne API Model T201 NH
3
Analyzer Operator Manual
10 07271B DCN6646
1.1 THEORY OF OPERATION
The Teledyne-API Model T201 analyzer measures ammonia by oxidizing
it to nitric oxide by the following reaction:
4NH
3
+ 5O
2
4NO + 6H
2
O
The resulting nitric oxide is then measured by the chemiluminescent
reaction with ozone. Consult Section 10.1 in the T200 manual (provided
with this instrument) for more details on the nitric oxide measurement.
The analyzer uses two converters to oxidize the different sample gases. A
high temperature catalytic converter, the M501 NH
3
, converts NH
3
and
NOx into NO creating the TN
x
channel. A second converter, housed inside
the T201 analyzer and consisting of heated molybdenum, converts all of
the NO
x
in the sample to NO producing the NO
x
channel. The nitric oxide
channel is measured while bypassing both the M501 NH
3
and
molybdenum converter. A Nafion® drier operated in reflux mode, is
installed prior to the molybdenum converter and the AutoZero valve. The
drier removes ammonia and water from the switched stream. The
ammonia would have otherwise been converted by the molybdenum and
registered as NO
x
. This location provides the drier with continuous flow,
thereby allowing it to stabilize faster.
Note
Due to the Nafion® drier, the analyzer has a maximum ammonia range of
2.0 PPM.
The calculated gas concentrations, ammonia and nitrogen dioxide, are
computed from the differences between the measured channels, as
outlined in the following equations:
NO (Nitric Oxide) Concentration = Measured
TN
x
(Total Nitrogen) Concentration = Measured (NH
3
+ NO
2
+ NO)
NO
x
(Total Nitrogen – Ammonia) Concentration = Measured
(NO
2
+ NO)
NH
3
(Ammonia) Concentration = Calculated as follows:
[(TNx - NOx) / (NH
3
_CE_FACTOR1)]
NO
2
(Nitrogen Dioxide) Concentration = Calculated as follows:
[(NOx – NO) / (NO
2
_CE_FACTOR1)]
Note
The
nitrogen dioxide efficiency factor (NO
2
_CE_FACTOR1) must be
calculated by conducting a GPT (gas phase titration) as described in Section
8.3.3 of the T200 manual and Section 6.0 of this manual. This value gives a
good indica
tion of how well the molybdenum is converting nitrogen dioxide
into nitric oxide. In a properly functioning analyzer the value should be close
to 1.0. It is recommended that the molybdenum efficiency be checked every
three months.