8-C-4 Chapter 8: Gas Analyzer Calibration 42/24-10 EN Rev. 9
Caldos25 and 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
in the case of CO
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 0-20 Vol.-% 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 03 86 1 20 – 79 1
Oil Air 10 08 81 1 20 – 79 1
Coal Air 10 10 79 1 20 – 79 1
Calibration with
Substitute Gases
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 0–20 Vol.-% CO
2
in
N
2
(N
2
and CO
2
/N
2
mixtures are available practically everywhere).
Component 1 CO
2
in Flue Gas Meas. Range 1 0-10 Vol.-%
Meas. Range 2 0-20 Vol.-%
Measurement Ranges
Component 2 CO
2
in N
2
(Substitute Gas) Meas. Range 1 0-20 Vol.-%
Calibration Method Substitute Gas Calibration
Zero Component Component 1 Meas. Range 1 or
Component 2 Meas. Range 1
Calibration Parameters
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.
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