A volume of natural gas can be converted to its liquefiable hydrocarbon components (ethane, propane, etc) by using Mol% or GPM from the compositional analysis of the stream of natural gas.
Formula Definitions:
Cf/Mol = number of cubic feet in a Mol (see Note below)
Gal/#Mol = gallons per pound Mol
Note: The number of cubic feet in a Mol is pressure base sensitive. The standard per the Gas Processors Association is 379.49 cubic feet at a pressure base of 14.696. The formula to convert the standard to a different pressure base is as follows:
379.49 times (14.696 divided by PT)
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Table 7 – the number of cubic feet per Mol at different pressure bases.
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Pressure Base
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Cf/Mol Factor
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14.65
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380.68157
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14.696
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379.49000
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14.73
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378.61406
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15.025
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371.18037
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Table 8 – the number of gallons per pound Mol by component.
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Component
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Gal/#Mol
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N2
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Nitrogen
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4.1513
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CO2
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Carbon Dioxide
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6.4532
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H2S
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Hydrogen Sulfide
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5.1005
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C1
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Methane
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6.4142
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C2
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Ethane
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10.1259
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C3
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Propane
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10.4327
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IC4
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Isobutane
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12.3859
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NC4
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Normal Butane
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11.9371
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IC5
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Isopentane
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13.8595
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NC5
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Normal Pentane
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13.7130
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C6+
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Hexane+
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16.3920
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Formulas:
Mcf times GPM for the component = Gallons
Mcf times [(Mol% divided by 100) divided by Cf/Mol] times 1000 times Gal/#Mol = Gallons
Calculation Examples:
1,000 Mcf @ 14.73 times 3.0088 GPM C2 = 3,009 Gallons of C2 (Ethane)
1000 Mcf @ 14.73 times [(11.25 Mol% C2 divided by 100) divided by 378.61406] times 1000 times 10.1259=3,009 Gallons of C2 (Ethane)