LHV, Wobbe Number and Methane Number Calculation

[Gary Martin]

Hi,

I use CoolProp to evaluate LNG and NG properties (density, GHV, etc.). I was wondering what is the formula or equation to determine the following:

1. Wobbe Index of a given gas mixture
2. LHV of a given gas mixture
3. Methane number of a given gas mixture

Thank you.

Best Regards,

Gary Martin

[Ian Bell]

I have no idea.   What are those things you mention? I think they are included in GPA standard? 

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[Gary Martin]

Hi,

LHV = Lower Heating/Calorific Value.

Wobbe Index = GHV (Gross Heating/Calorific Value)/sqrt(Specific Gravity)

Methane Number = Resistance to Knock (can be found using AVL, MWM methods)

These terms are included in the GPA, SGMF, AGA, etc. standards related to oil and gas. 

[Ian Bell]

Are you really using CoolProp for LHV calculations?  There are issues with reference states for the enthalpy and Gibbs energy, so you need to be quite careful about how you do heat of combustion calculations. There are a number of postings on this mailing list about this general problem.  The point is that the reference state should be set to yield the right enthalpy and entropy of formation, but nobody has done this work thus far (that I know of).

On Thu, Oct 21, 2021 at 2:59 AM Gary Martin <garyc...@gmail.com> wrote:

Hi,

LHV = Lower Heating/Calorific Value.

Wobbe Index = GHV (Gross Heating/Calorific Value)/sqrt(Specific Gravity)

Methane Number = Resistance to Knock (can be found using AVL, MWM methods)

These terms are included in the GPA, SGMF, AGA, etc. standards related to oil and gas. 

On Thursday, October 21, 2021 at 5:20:59 AM UTC+2 ian.h...@gmail.com wrote:

I have no idea.   What are those things you mention? I think they are included in GPA standard? 

On Wed, Oct 20, 2021, 7:59 AM Gary Martin <garyc...@gmail.com> wrote:

Hi,

I use CoolProp to evaluate LNG and NG properties (density, GHV, etc.). I was wondering what is the formula or equation to determine the following:

1. Wobbe Index of a given gas mixture
2. LHV of a given gas mixture
3. Methane number of a given gas mixture

Thank you.

Best Regards,

Gary Martin

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