Methane Number Calculation 2

[msonnet]

Hi everybody,

I preiouly posted this question in another forum. Can anybody help?

I am trying to figure out how to calculate the Methane Number (MN) for a given gas composition. I tried to find some information in the literature but was not successful.

I only found the following formulas:

MON = -406.14 + 508.04*(H/C) – 173.55*(H/C)^2 + 20.17*(H/C)^3
MN = 1.624*MON – 119.1

with H/C being the hydrogen/carbon ration. (MON = motor octane number).

Having tried it on several gas compositions, I am always off by some 10% of the real MN number. Even if I take 100% CH4,I get a MN=108 which is obviously wrong.

Would it be possible to calculate the MN of the gas composition based on the MN of the various constituents multiplied by the Mol %, such as done to calculate the Molecular Weight of the gas? If yes, where can I find the MN numbers for the various elements?

Thanks in advance.

 

[radomir]

msonnet

A qick search led me to the same equations you specified for MON and MN (probably we visited the same internet site:

http://www.arb.ca.gov/regact/cng-lpg/appe.doc)

But there are more sites talking about MN, for example: uk.dgc.dk/publications/algotitme.htm - 4k ,

http://speonline.spe.org/events/urls/2002gts/SPE75509.pdf

, etc.

Since you posted your question almost two months ago maybe there is no need for this reply?!?

 

[ElwoodGreen]

I hope I am not to late to this discussion, but I think a Caterpillar rep gave me the program they use for performing methane number calculations. I suggest you contact your local rep. If you don't succeed, then I might be able to find it and see if it is transmittable. I do not know the calculation method. Please re-post if you want me to look for the program.