3 replies to this topic

[Sherif Morsi]

Hi all,

I am currently working on the design of a new fuel gas conditioning skid. The client is using the Methane Number (MN) of gas as a reference for the outlet gas specifications for the skid. Inlet MN: 15 and required outlet MN is 45.

I found the following two equations:

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

I couldn't find anything else to use for this. Are these equations credible?
Also, how could I calculate H/C ratio for a gas mixture?

Regards,
Sherif

[Art Montemayor]

Sherif:

I googled and found the attached information for your review and use as needed.

Your equations are supported by one of the web sources. However, there are no references given in this source. If you need documented backup and credible references, I would rely on something more authoritative - such as the Danish Gas Technology Centre source. If you are working on a project, 400 Euros is not a large amount of cash to pay for this type of resource that can be further used in the future. I would recommend you obtain such a tool for calculating the Methane Number for your Client. I would, of course, research the capabilities of this source before committing to a purchase.

You of course calculate the H/C ratio by dividing the hydrogen atoms by the carbon atoms. However, that is easily enough said. Your fuel may have other significant "goodies" - such as heavy hydrocarbons, sulfur, CO, etc., etc. That is why I would look into the Danish product and see if it resolves all these issues.

Good luck on your project.

Attached Files

•  How to Calculate Methane Number.doc   37KB   125 downloads

[sheiko]

Hi,

Question n°2:
I would proceed as follow:

1/ Get the composition of the gas.

2/ Calculate the amount of hydrogen in the Kgs of Hydrocarbon using Hydrogen Number and find out the moles of the Hydrogen.

3/ Calculate the amount of Carbon in the Kgs of Hydrocarbon using Carbon Number and find out the moles of the Carbon.

4/ Divide the moles of Hydrogen by the moles of Carbon to get Hydrogen to Carbon ratio.

Edited by sheiko, 03 July 2012 - 06:03 PM.

[kkala]

An elementary assessment of reported equation's precision can be found in http://www.eng-tips....d.cfm?qid=29668 '> http://www.eng-tips....d.cfm?qid=29668 , as well as other data probably useful. The estimating formula can be also seen at http://www.arb.ca.go...ng-lpg/appd.PDF '> http://www.arb.ca.go...ng-lpg/appd.PDF , where references are reported.
However I would search for more evidence (look at post No 2), especially if the exit MN=45 is going to be a guaranteed value. Also specify the apparatus / method to be used for the measurement of MN.