ELTRA CS-2000, Руководство пользователя

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Function description
79
7.3 Gas flow system
The oxygen supply is connected to the inlet of the gas flow system. Pure oxygen is available in
steel bottles. A 99.5% purity is fully sufficient. Any CO2 or H2O which may be contained in the
oxygen is retained in the CO2 and H2O trap. The upper half of the trap is filled with CO2
absorber and the lower half with H2O absorber.
Magnesium perchlorate (anhydrone) acts as H2O absorber. Sodium hydroxide acts as CO2
absorber, preferably with an indicator, so that the degree of saturation can be seen from the
coloration.
The oxygen inlet pressure should be 2 to 4 bar (30 to 60 psi), which is then regulated inside the
analyzer to 1.5 bar (22 psi), and shown on the pressure gauge. Any pressure fluctuation of the
external oxygen supply has no influence on the accuracy of the measurements.
The oxygen then enters the furnace after passing thru the oxygen valve. A pressure switch
reports whether there is sufficient pressure in the furnace and whether the furnace is closed, in
order to start the analysis cycle
The combustion gases from the furnace, flow first thru a dust trap and then through a H2O
absorber. Via the bypass valve, they reach the electronic controlled flow regulating valve V6,
which is the adjusting element of the electronic flow regulation.
Then, the gases pass through the SO2-selective cells. Any CO, that may be present, is oxidized
to CO2 in the catalyst furnace, which is filled with copper oxide. Unwanted SO3, which results
thereby from SO2, is retained in the SO3 trap which is filled with cotton wool.
A flow meter displays the gas flow. The flow rate is set internally to 180 l/h. The exact level of
the flow is not important, since the calibration of the analyzer takes this into account.
Very important is that the flow rate is constant. An electronic board ensures this. A slight
deviation from the set value or a conflict, as with mechanical regulators, cannot arise. The
regulation either functions precisely, in which case the flow rate is correct or, in the event of a
defect, the flow rate is completely blocked or extremely high.