Analysis of the measuring behavior of gas measuring devices when hydrogen is added to the natural gas network

Examination of sensor properties and their application in different applications - Part 1 Building

Hydrogen (H2) has long been used in industry and business as a versatile energy source. In order to increase the share of renewable energy and reduce CO2 emissions, hydrogen can also help drive climate change in the supply of households. For this purpose, hydrogen can be mixed with natural gas in different concentrations and fed into the supply networks.

So how does the measurement behavior of a gas measuring instrument change with increasing hydrogen content in natural gas? And what effects does this have on the sensors?

In gas measuring devices used in the field of gas supply, a wide variety of sensors are used. In order to make it easier for the user to select the measuring range /sensor correctly, the German Association of Gas and Water Engineers (DVGW) defines use cases. Here the intended activity can be found directly in the name.

The EX-TEC PM 580 includes three of these applications:

Use case Activities Sensors
Warnings Monitoring of working areas; Warning of toxic gas concentrations; Lack of oxygen/oxygen excess; Explosive gas concentrations Infrared sensor electrochemical measuring cell  
Measurements Proof gas purity or gas-freeness in gas lines Infrared sensor electrochemical measuring cell  
Building Measurement of smallest gas concentrations in buildings; localization of gas origin; warning of toxic CO concentrations; explosive gas concentrations Gas sensitive semiconductor sensor infrared sensor electrochemical measuring cell  

Due to the complexity, we will only cover the “Warning” use case in this first part. The “Warning” and “Building” scenarios will follow in subsequent parts.

Use case “Building inspection”

The gas-sensitive semiconductor sensors used in the building test react to all combustible gases due to their function.

The following test gases were used to demonstrate the different admixtures of H2 in the natural gas network:

Hydrogen admixture in natural gas Corresponds to test gas mixture Sum of combustible gases  
5 vol% H2 950 ppm CH4 & 50 ppm H2 1000 ppm
10 vol.% H2 900 ppm CH4 & 100 ppm H2 1000 ppm  
20 vol% H2 800 ppm CH4 & 200 ppm H2 1000 ppm  


The EX-TEC® PM 580 is set to the gas type methane.


Results:

Sensor 5% H2 10% H2 20% H2
CH4 + 5% + 7% + 14%
CO 18 ppm 36 ppm 75 ppm

Conclusion:

As the hydrogen content increases the measured value display, no adjustments need to be made to the device during leak detection. Leaks are still reliably detected with a methane setting. In terms of operating instructions, it can be discussed whether the detection limits should be increased in line with the hydrogen content.

The use of a CO sensor should be avoided due to the high cross-sensitivity. In the next part, another application case follows.