Teledyne T200, Руководство по эксплуатации, Страница: 64 / 425

Getting Started Teledyne API
– T200 NO/NO
2
/NO
X
Analyzer Operation Manual
62
N
ITRIC
A
CID AND THE
C
HEMISTRY OF
NO
2
P
ERMEATION
T
UBES
H
2
O reacts with NO
2
to form HNO
3
(nitric acid). The T200 mitigates this reaction by
passing the air supply for the span gas generator through a special dryer; however, the
permeable membrane of the NO
2
tube will still allow H
2
O from the ambient
environment to slowly collect in the tube at increasingly higher concentrations. Over
time this results in the presence of HNO
3
in the permeation tube which is exuded into
the T200‟s pneumatics along with NO
2
.
HNO
3
is a liquid at room temperature, so once the HNO
3
is released by the permeation
tube, it condenses and collects along the T200‟s wetted surfaces. While liquid HNO
3
does not directly affect the quality of NO
x
measurements of the T200, it does give off
small amounts of gaseous HNO
3
which is converted into NO by the T200‟s NO
x

NO
converter, resulting in an artificially high NO
2
concentration by 8% to 12%. This is
particularly bothersome when the T200 is attempting to measure a zero point, such as
during calibration, since the NO
2
concentration will only reach a true zero point once the
majority of the HNO
3
coating the wetted surfaces has reverted to NO
2
and this can take a
very long time.
To resolve this, the T200 includes a special HNO
3
desorber, which eliminates any HNO
3
given off by the permeation tube before it can be converted into NO by the analyzer‟s
converter.
P
NEUMATIC
L
AYOUT FOR
Z
ERO
S
CRUBBER AND
IZS (OPT 50G)
SAMPLE
PRESSURE
SENSOR
VACUUM
PRESSURE
SENSOR
O
3
FLOW
SENSOR
FLOW PRESSURE
SENSOR PCA
INSTRUMENT CHASSIS
PMT
OZONE DRYER
EXH
AU
ST
M
AN
IF
O
L
D
NO/NO
X
VALVE
AUTOZERO
VALVE
O
3
Destruct
O
3
GENERATOR
O
3
Cleanser
Filter
NO
2
Converter
SAMPLE
GAS
INLET
ZERO GAS
INLET
SAMPLE/ CAL
VALVE
ZERO/SPAN
VALVE
2
-S
ta
ge
NO
X
S
cr
ub
be
r
Exhaust
Outlet
DRY AIR
OUTLET
IZS Permeation
Source
DESORBER
NO
NC
NO
NC
NO
NC
NO
NC
IZS OPTION w/
DESORBER
PUMP
NO
X
Ex
h
a
u
s
t
Sc
ru
b
b
e
r
Orifice Dia.
0.004"
Orifice Dia.
0.010"
Orifice Dia.
0.010"
Orifice Dia.
0.004"
Orifice Dia.
0.003"
COM
COM
COM
COM
Figure 3-27: Pneumatics with the Internal Span Gas Generator (OPT 50G)
06858E DCN7057