Model 9110T NOx Analyzer

 

Principles of Operation

 

 

 

 

 

 

 

 

reaction cell.

 

 

 

 

O3 supply inlet of reaction cell

Controls rate of flow of ozone gas into the

0.004” (0.10 mm)

80 cm³/min

 

reaction cell.

 

 

 

 

 

 

Dry air return of Perma Pure® dryer

Controls flow rate of dry air return / purge

0.004” (0.10 mm)

80 cm³/min

 

 

air of the dryer.

 

 

 

 

Vacuum manifold, Auto Zero port.

Controls rate of sample gas flow when

0.010” (0.25 mm)

500 cm³/min

 

bypassing the reaction cell during the Auto

 

 

Zero cycle.

 

 

 

 

Vacuum manifold, Internal span gas

Controls rate of flow of zero purge gas

0.003” (0.10 mm)

60 cm³/min

 

through the optional Internal span gas

 

generator exhaust port

 

generator when it is installed.

 

 

 

 

 

 

 

 

The necessary 2:1 ratios across the critical flow orifices is largely exceeded by the pumps supplied with the analyzer which are designed to accommodate a wide range of possible variability in atmospheric pressure and age related degradation of the pump itself. Once the pump does degrade the ratio between sample and vacuum pressures may fall to less than 2:1. At this point, the instrument will display an invalid sample flow rate measurement (XXXX).

Note

The diameter of a critical flow orifice may change with temperature

 

because of expansion of the orifice material and, hence, the most crucial

 

critical flow orifices in the 9110T (those controlling the sample gas and O3

 

flow into the cell itself) are located in the reaction cell where they can be

 

maintained at a constant temperature.

13.2.3. OZONE GAS GENERATION AND AIR FLOW

The excess ozone needed for reaction with NO in the reaction cell is generated inside the analyzer because of the instability and toxicity of ozone. Besides the ozone generator itself, this requires a dry air supply and filtering of the gas before it is introduced into the reaction cell.

Due to its toxicity and aggressive chemical behavior, O3 must also be removed from the gas stream before it can be vented through the exhaust outlet.

CAUTION

GENERAL SAFETY HAZARD

Ozone (O3) is a toxic gas.

Obtain a Material Safety Data Sheet (MSDS) for this gas. Read and

rigorously follow the safety guidelines described there.

Always ensure that the plumbing of the O3 generation and supply system

is maintained and leak-free.

13.2.3.1. The O3 Generator

The 9110T uses a dual-dielectric, Corona Discharge (CD) tube for creating its O3, which is capable of producing high concentrations of ozone efficiently and with low excess heat (see Figure 13-10). The primary component of the generator is a glass tube with hollow walls of which the outermost and innermost surfaces are coated with electrically conductive material.

Air flows through the glass tube, between the two conductive coatings, in effect creating a capacitor with the air and glass acting as the dielectric. The layers of glass also separate the conductive surfaces from

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Teledyne 9110T instruction manual Ozone GAS Generation and AIR Flow, O3 Generator, Maintained at a constant temperature