Natural gas composition
Natural gas composition
(OP)
Is there any standard composition for natural gas (a certain percent methane, ethane,...) Or is natural gas an ambigious term tat covers a range of percent composition?
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Natural gas composition
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Natural gas compositionNatural gas composition(OP)
Is there any standard composition for natural gas (a certain percent methane, ethane,...) Or is natural gas an ambigious term tat covers a range of percent composition?
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RE: Natural gas composition
Best regards
Morten
RE: Natural gas composition
RE: Natural gas composition
Natural gas from the well is processed to remove more desirable - and less desirable components then sold according to a pipeline specification for heating value and moisture content.
Liquid hydrocarbon compounds from ethane and higher may be removed leaving sufficient ethane etc. for the heating value. Water is largely removed. Other components removed include hydrogen sulfide and other sulfur compounds, carbon dioxide, etc. Many different levels of processing exist. The simplest may only include dew point suppression and perhaps compression.
RE: Natural gas composition
Maximum amount of water in ppm or pounds/MMSCF (US)
Maximum amount of sulpher compounds in ppm
Maximum inerts N2 or CO2 in mole %
Maximum O2 in ppm or mole %
minimum or maximum heating value in BTU/cf or energy/volume
WOBBIE number = BTU/CF / (sqrt(sp gr))
Dew point temperature or the cricondenterm point
maximum amount C4 and larger in mole% or gallons/MSCF
Other contaminates such as; free liquids dirt, dust, gum
Pressure and temperature limits
RE: Natural gas composition
The other "Natural Gas" is what comes from the well. The gathering system constraints on this stuff are very much looser and the gas can be what it is. I've sold wellhead gas with 25% CO2, 5,000 lbm/MMCF water vapor, and a heating value below 850 BTU/SCF. This mess goes to a sweetening plant, the CO2 is removed, the gas is dehydrated, and sold as commodity "Natural Gas".
It is unfortunate that the two widely different things have the same name, but the world is what it is.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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RE: Natural gas composition
http://www.engineering-4e.com
RE: Natural gas composition
If you are interested in the processing of raw natural gas (including a shematic flow diagram), read this article in the Citizendium online encyclopedia:
Natural gas processing
Milton Beychok
(Visit me at www.air-dispersion.com)
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RE: Natural gas composition
CH4 - 85 Mol%
C2H6 - 10 Mol%
C3H8 - 5 Mol%
This gives estimated physical properties equivalent to 0.65 gravity (18.85 Mol. Wt.)gas.
RE: Natural gas composition
HEATING VALUE (GROSS) BTU/SCF 1161.38
WOBBE NUMBER BTU/SCF 1437.04
RE: Natural gas composition
Below are some common specs you will have to meet for natural gas:In US units
Hydrocarbon Dew Point at ceratain pressure (F)
HHV or LHV (Btu/ft3)
Water content (#/Mmscf)
CO2,H2S content.
So depending upon the specs provided by the customer you will have a certain Gas composion after processing of the raw gas from the wellhead or from other sources.
In common Fuel gas has a HHV value of 1000 to 1100 Btu/ft3 and has CH4 content more than 90%.
RE: Natural gas composition
2) The question is not specifically oriented towards pipelines - it may e.g. be for LNG production or e.g. with reference to feedstock for chemical processes
I tink your statment is too "square". The last two posts from srfish and dcasto shows that its not easy to throw a definition on the table - because its not just Europe og US that uses NG - and we dont have the same definitions!
Best regards
Morten
RE: Natural gas composition
It gets a little more complicated because as you separate the gas from the liquid and then send the oil to lower pressure separators, treaters or tanks, more hydrocarbons will flash out of the crude oil as it goes through the pressure drop. This gaseous hydrocarbon phase will be called "natural gas" too, but it will be a lot heavier (less methane, more ethane, propane, butanes, etc.) than the natural gas at the well head.
In many calculations, we don't need to know the composition. We just use typical values for specific gravity, specific heat ratio, etc. and go from there. That usually provides close enough results to design equipment that works. If we need more exact results, process simulation software works really well.
Andy
New Orleans, LA
Petronyx Consulting Engineers, LLC
http://www.petronyx.com
RE: Natural gas composition
And i dont agree with your definition of natural gas
Best regards
Morten