4. Measurement technology and measuring point
In the analysis mode, the gases are measured in a continuous flow every second and the
calculations of the gas composition are updated. The measured values can be displayed on site and
forwarded to a control room, for example.
4.1. Description of the measuring method
The used correlative measuring principle is based on the determination of infrared absorption and
the thermal conductivity of the gas being analyzed. Instead of the gas values such as superior
calorific value, density at base conditions and CO
2
content, the measuring method uses values
which are physically related to the target values and are easier to measure. GasLab Q2 therefore
analyzes the following gas properties:
• Infrared (IR) absorption of the CH gas
• Infrared (IR) absorption of the CO
2
gas
• Thermal conductivity of the full gas mixture
• Pressure and gas temperature
All the partial measurements are subjected to a correlative evaluation process which is based on the
physical background, the typical composition of natural gas. The nitrogen, as well as the superior
calorific value, density at base conditions and CO
2
content can be calculated using an appropriate
equation system.
The Wobbe index can be calculated using the superior calorific value and density at base conditions.
These values are enough to determine the other properties of the natural gas. This means that all
the main gas components can be identified directly or indirectly and are available for further
processing. The figure shows a schematic overview of the measuring principle (without pressure
and temperature).
Figure 4.1: Measuring method
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