Teledyne T200, Руководство по эксплуатации, Страница: 299 / 425

Teledyne API
– T200 NO/NO
2
/NO
X
Analyzer Operation Manual Principles of Operation
297
Figure 13-8: Ozone Generator Principle
13.2.3.2. OZONE GENERATOR DRY AIR SUPPLY
Ambient air usually contains enough water vapor to greatly diminishes the yield of
ozone produced by the ozone generator. Water also reacts with chemicals inside the O
3
Generator to produce caustic substances such as ammonium sulfate or highly corrosive
nitric acid that will damage the optical filter located between the reaction cell and the
PMT.
To prevent this, the air supply for the O
3
generator is dried using a special single tube
permeation dryer. The dryer consists of a single tube of Nafion
®
that is mounted within
an outer, flexible plastic tube. Nafion
®
is a co-polymer that absorbs water very well but
not most other chemicals. As gas flows through the inner Nafion
®
tube, water vapor is
absorbed into the membrane walls. The absorbed water is transported through the
membrane wall and evaporated into the dry purge gas flowing through the outer tube,
countercurrent to the gas in the inner tube.
Figure 13-9: Semi-Permeable Membrane Drying Process
The process by which the water vapor molecules are collected and transported through
Nafion
®
material is called per-evaporation and is driven by the humidity gradient
between the inner and outer tubes as well as the flow rates and pressure difference
between inner and outer tubing. Unlike micro-porous membrane permeation, which
06858E DCN7057