Algorithm for methane number determination for natural gasses

Paw Andersen, June 1999, R9907

So far, DGC has calculated the methane number for the Danish natural gas quality using an algorithm developed by DGC. Since the introduction of gas from the Harald field and the ensuing changes to the Danish natural gas composition, the sphere of application of the algorithm has been exceeded.

This report describes a new algorithm for determination of the methane number for natural gasses.

On the basis of the new algorithm a program has been developed to calculate the methane number. The program together with a user manual can be requested from Danish Gas Technology Centre.

In the AVL work a test engine of the same type as the engines used for octane number determination was used to determine the gasses’ relative tendency for knocking. As for petrol’s octane number the scale for the gasses is relative. The definitions are that pure methane has a methane number of 100 and pure hydrogen has a methane number of 0.

The AVL study includes the components CH₄, C₂H₄, C₂H₆, C₃H₆, C₃H₈, n-C₄H₁₀, H₂, CO₂, N₂ and H₂S in binary and ternary component mixtures. In addition, some measurements have been made for a limited number of natural gasses. Primarily all the AVL data are available as ternary diagrams, as shown in the Figures below. For further information on the AVL studies see: "Forschungsberichte Verbrennungskraftmaschinen Heft 120, 1971, ’Erweiterung der Energieerzeugung durch Kraftgase, Teil 3".