Council of Gas Detection and Environmental Monitoring

CoGDEM (UK) is the Council of Gas Detection and Environmental Monitoring, a trade association with a membership of over fifty companies involved in the gas detection industry. We are pleased to have ILM/ETP (the publishers of this IET magazine) as an Associate Member, so we will place a regular column of news from the gas detection industry in IET magazine.

A current topic of interest to gas analysis instrument designers is the requirement to measure the variations of piped natural gas coming from all global sources. For example, it is expected that the fuel gas’s Wobbe Index (the amount of combustion energy from a unit volume) that the UK controls tightly will be allowed to slip to wider tolerances as a result of European standardisation, and this could have combustion safety implications.

CoGDEM attended a Natural Gas Quality Sensors Workshop organised by Marcogaz/GERG in Brussels on 27th February 2014, concentrating on the ability of current gas sensing techniques to measure the component parts of natural gas. The full proceedings, attendance lists and presentations can be downloaded from the organiser’s website at: http://www.marcogaz.org/index.php/gas-sensors-workshop-2014

A spokesman from the European Commission opened proceedings, stating that the harmonisation standard for natural gas composition across Europe would undoubtedly be a compromise, but he hoped it would be a standard that “everyone can buy into”.

GIE then set the scene on behalf of gas transporters, stating that gas sources are changing now, with GB and NL North Sea output declining, but Norwegian and Russian output increasing, particularly with new Arctic production.  Also, shipped LNG ‘quality’ varies tremendously, and the landscape for piped gas will further change as we see more injection of biomethane (with H2S) and hydrogen (from ‘power-to-gas’ projects).

The ‘Wobbe Index’ represents the amount of combustion energy achievable from a standard volume of fuel gas, and the WI varies widely according to the components within the gas supply.  For reference, the current range of WI in the UK is 13.1 – 14.3 kWh/Nm3 but the EU proposal is to set the acceptable range across Europe to 13.5 – 15.8 kWh/Nm3 with the present EASEE-Gas limits defined as 13.8 – 15.7 kWh/Nm3

Denmark gave a real-world example of how the change in Wobbe Index has affected them since 2010 as their sources of gas have changed.  Their national variation had been 15.0 – 15.5 kWh/Nm3, but when changing to German sources of gas in 2010 they had to accept gas within the range 13.8 – 15.7 kWh/Nm3. The Danish authorities feel that appliance installers need a portable instrument to measure the Wobbe Index at time of installation so that they can adjust the appliance burners to take into account deviations from whatever gas is being supplied on that day.  In any one hour, the WI has been seen to change by as much as 1.0 kWh/Nm3. There are concerns that CO and NOx emissions increase if the burner is not adjusted to suit the fuel gas.

The gas-fired appliance manufacturers were represented by their trade body EHI (European Heating Industry), of which the UK’s HHIC is a member. Current EU regulations only permit a small range of emissions from combustion appliances, but the emissions are very much affected by the Wobbe Index of the fuel gas.  Since 2000 some self-adjusting condensing boilers have been available which monitor either: Ionisation current within a flame probe, CO in the flue, or excess air.

However, such self-adjusting appliances only represent 0.4% of the appliance population in use today.  To cope with the legacy of millions of appliances, EHI will lobby for all gas appliances across Europe to be regularly serviced.  In Germany, a requirement to service appliances every 2 years is now relaxed for self-adjusting appliances to every 5 years.