AO2000
CONTINUOUS GAS ANALYZERS | OI/AO2000-EN REV. B
237
Caldos25, Caldos27: Substitute gas calibration
Example
Substitute gas calibration in the Caldos25 and Caldos27 is described using
the example of "CO
2
measurement in flue gas".
CO
2
measurement in flue gas
The composition of the various combustion products in the sample gas is
known
2
measurements of flue gas from single-component firings. The flue
gas out of the cooler primarily contains CO
2
, O
2
, N
2
and Ar. CO
2
cannot be
measured in mixed-firing flue gases.
Test gases
The following table shows test gases for the calibration of the 0 to 20 vol.%
of CO
2
measurement range:
Fuel
Test gas composition in vol.% for
Zero
Middle concentration
Span
CO
2
O
2
N
2
Ar CO
2
O
2
N
2
Ar
Gas Air
10
3 86
1 20
– 79
1
Oil Air
10
8
81
1 20
–
79
1
Coal Air
10 10 79 1
20 – 79 1
Calibration with substitute gas
Since the test gases in this table are not available everywhere, the analyzer
module can be factory-set for calibration with a substitute gas. In this case
an additional measurement range is calibrated for 0 to 20 vol.% of CO
2
in N
2
(N
2
and CO
2
/N
2
mixtures are available practically everywhere).
Measurement ranges
Component 1 CO
2
in flue gas
Meas. range 1
0 to 10 vol.%
Meas. range 2
0 to 20 vol.%
Component 2 CO
2
in N
2
(substitute gas) Meas. range 1
0 to 20 vol.%
Calibration data
Calibration method
Substitute gas calibration
Zero component
Component 1
Meas. range 1 or
Component 2
Meas. range 1
Span component
Component 2
Meas. range 1
Calibration
•
Calibrate zero with air (component 1) or N
2
(component 2).
•
Calibrate span with test gas 18 vol.% CO
2
in N
2
.
Other measurement tasks
For other measurement tasks select the test gases and measurement ranges
in a similar manner according to the sample gas composition.
