ELTRA CS-580A, Manual

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1 Carrier gas inlet 15 Dust filter cartridge
2 Pressure regulator 16 Pressure regulator
3 Oxygen stop valve (power switch
control) 17 Flow adjustment restrictor
4 Pressure switch and pressure gauge 18 Gas flow meter
5 Oxygen stop valve (software
controlled) 19 Infrared cell
6 Flow adjustment restrictor 20 Gas flow meter
7 Carrier gas flow meter 21 Attenuator before the pump
8 Gas pre-cleaning unit 22 Gas flow pump
9 Oxygen diverting valve 23 Attenuator after the pump
10 Flow adjustment restrictor 24 Microcontroller
11 Gas flow meter 25 Computer
12 Upper furnace closure assembly 26 Monitor
13 Flow adjustment restrictor 27
Printer
14 Moisture trap 28
Balance
The analyzer is operated with pure oxygen. A purity of 99.5% is sufficient. It is normally
available in steel bottles. CO2 and H2O impurities in the oxygen are trapped in the trap (8). The
upper half of the trap is filled with CO2 absorber and the lower half with moisture absorber.
Magnesium perchlorate (anhydrone) acts as a 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, which is then regulated inside the analyzer to
1.5bar, as shown on the pressure gauge (4). Any pressure fluctuation of the external oxygen
supply has no influence on the accuracy of the measurements.
A pressure switch (4) becomes conductive at around 1 bar (15 psi). This information is passed
to the software which energizes the valve (5) and starts the gas pump (22) as long as the
pressure is higher than 1 bar. This ensures that the pump runs only when sufficient pressure of
oxygen is available, so that no air enters the gas flow system, if there is no input oxygen
pressure.
With the help of the adjustable restrictor (6) the inlet flow is set at a level of at least
200 l/h. The flow rate is shown on the lower flow meter (7) on the front panel. This flow rate
enters the furnace. During analysis when the furnace is closed, the inlet flow rate is split. One
part enters the furnace top to exit the lance over the crucible. This flow is shown on the middle
flow meter (11). The rest of the oxygen flow enters the furnace at the low end. The ratio of the
two flows can be adjusted with the restrictors (10) and (13).See chapter
”Adjusting gas flow”
.
The flow at the outlet of the furnace is created by a pump (22) at the end of the gas flow system,
which sucks a flow of 180L/h out of the furnace.
A tube connects the furnace outlet with the moisture trap (14). The gases that come out of the
furnace normally contain some moisture. This particularly happens when analyzing coal
samples. The dried gases pass thru the dust filter (15) and then enter the Infrared cells which
are accommodated in the cell module (19), where the measurements of CO2 and SO2 take
place.