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Active Contributor

Join Date: Apr 2018
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# MON/Methane Number

06/12/2018 12:55 AM

HI,

406.14 + 508.04*(H/C)-173.55*(H/C)^2+20.17*(H/C)^3

can any one tell me what is in above formula 406.14, and 508.04 , and 173.55 and 20.17

please need guide line to further learning .

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Guru

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#1

### Re: MON/Methane Number

06/12/2018 1:01 AM
Active Contributor

Join Date: Apr 2018
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#2

### Re: MON/Methane Number

06/12/2018 1:28 AM

Guru

Join Date: Oct 2008
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#3

### Re: MON/Methane Number

06/12/2018 4:53 AM

It wasn't intended to "give" you the answer.

It was intended to give you a guideline to further learning.

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#4

### Re: MON/Methane Number

06/12/2018 5:56 AM

Without contextual information, the chances are quite slim.

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Guru

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#5

### Re: MON/Methane Number

06/12/2018 9:34 AM

MON = "Motor Octane Number"

(H/C) is hydrogen to carbon ratio

It's a formula for determining the equivalent octane of natural gas.

I'm pretty sure the numbers were determined by curve fitting to actual data.

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#6

### Re: MON/Methane Number

06/12/2018 9:43 AM

..." the number of hydrogen atoms divided by the number of carbon atoms in the hydrocarbon components of the fuel."...

https://www.arb.ca.gov/regact/cng-lpg/appd.PDF

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Guru

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#7

### Re: MON/Methane Number

06/12/2018 11:02 AM

For what it's worth, here's a log-log plot of F(x) vs x, where x is H/C, and F(x) is the given formula.

A log-log plot seemed like the most useful graph; linear-linear and log-linear had funky axes for the info.

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Guru

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#8

### Re: MON/Methane Number

06/12/2018 8:28 PM

If the x-axis is H/C ratio and the y-axis is Octane rating, only the lower left corner of the graph is realistic. H/C for methane is 4 and it goes downhill from there. The formula is only valid for H/C = 2.5 to 4.

The OP has a sign error. MON should be

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

Here is a plot:

https://www.scribd.com/document/241241715/Carbon-Hydrogen-Ratio-of-Natural-Gas

Guru

Join Date: Apr 2010
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#9

### Re: MON/Methane Number

06/12/2018 8:57 PM

Here is a reference for the last post.

Appendix D - Methane Number and Fuel Composition

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