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07303C DCN6646 17
4.0 THE T200U-NOY EXTERNAL CONVERTER
4.1 Principle of Operation
The T-API Model T200U-NOy is designed to measure the concentration of NO,
NO
2
, and other compounds that are too unstable to be measured when taken in
through the normal ambient air sample inlet system. Please refer to the T200U
manual supplied with this system for a general discussion of the operation of a
NOx analyzer. The suite of compounds known collectively as NOy is composed
of roughly 30 compounds. The NOy measurement is generally done in
conjunction with a standard NOx measurement, with the difference between the
two being the concentration of the unstable compounds, sometimes referred to as
NOz.
The analyzer measures two independent gas streams. One bypasses the external
Converter and measures NO in the sample. The other pulls the sample through
the external Converter and is displayed as NOy
.
Under normal calibration
conditions the NOy measurement
is equivalent to the delivered NOx calibration
gases.
The system is composed of four modules:
The T200U-NOy analyzer, without a Moly converter
A 501Y Bypass Pump containing:
bypass pump
flow control
sample filtration
moly temperature control
pneumatic provisions for calibration
Externally mounted molybdenum converter (external Converter)
External Pump
The T200U-NOy system allows the point of sampling to be located in close
proximity to the Converter. This configuration provides minimal time delay
between the sample inlet and the remotely mounted (~10 meters above ground)
external Converter. Minimizing the transit time between the sample inlet and
Converter enables the conversion of labile components of NOy. The equation for
the conversion is:
315
o
C
3 NO
Y
+ Mo ---> 3 NO + MoO
3