Methane Number 1

[BiogasEngine]

What is the best method for calculating the methane number of a gas? Clarke Energy's website suggests that methane, having a high knock resistance is given a value of 100. Hydrogen given a value of 0. Also there are gases with a knock-resistance higher than 100. Does anyone know which gases would have these characteristics? I have historically worked in the biogas combined heat and power sector where methane number is not typically an issue due to the high methane number of biogases.

Thanks in anticipation of your assistance.

 

[Hoxton]

As far as I am aware, there is no international definition of the calculation of Methane Number. Each engine manufacturer has its own method of calculation, based on the gas composition. The engine manufacturer then assignes a power rating for an engine, based on the methane number. As you say, bio gases (landfill gas, digester gas, sewage gas) contain CO2, this suppresses combustion and increases the methane number.

L ong chain hydrocarbons (propane, butane etc) have very low methane number and can dramatically reduce the methane number of the gas mixture. Natural gas from the North Sea containers propane and butane and thus the methane number can be as low as 70.

Natural gas from Siberia is nearly 100% methane, and thus the methane number can be over 85.

Methane number does not depend on the arithmetic ration between the gases, so a calculation has to be performed

The engine makers do not seem to release their calculation program's, so you have to approach then each time.

 

[maddocks]

Actually check with Cat - we've used their methane number program for years. However, each engine mfr seems to define it a little differently so it's difficult to compare the differing reference methane numbers.

 

[BiogasEngine]

Thanks for the information. It's interesting to learn that different engine manufacturers have different guidelines on the calculation of methane number.

 

[dcasto]

If you try to use the methane number calc from one manufacturers program on another engine, the engine control system will be off and so will your emissions.