Heavy Hydrocarbon Dropout
Heavy Hydrocarbon Dropout
(OP)
I have a standard pipeline quality natural gas steam which is composed primarily of methane, but some heavy hydrocarbons are present such as pentane, propane, and butane. My question is, for this given gas stream, how can I calculate the amount of NGL (nat gas liquid) available in the form of pentane, propane, and butane in metric tons/(unit time). The heavies will have to be condensed out, but I am not sure how to make the calculation on the volume of the NGL that will be available. Gas composition makeup on volume basis (mol %) is as follows:
CO2: 1.49
N2: 0.13
C1: 89.24
C2: 1.94
C3: 2.24
iC4: 1.46
C4: 1.46
iC5: 0.87
C5: 0.17
H2O: 1.0
MW: 18.854
Gross Heating Value: 42.160 MJ/m^3
Flow: 220 mmscfd @ 65 bar, 80F.
Thanks in advance for your assistance.
CO2: 1.49
N2: 0.13
C1: 89.24
C2: 1.94
C3: 2.24
iC4: 1.46
C4: 1.46
iC5: 0.87
C5: 0.17
H2O: 1.0
MW: 18.854
Gross Heating Value: 42.160 MJ/m^3
Flow: 220 mmscfd @ 65 bar, 80F.
Thanks in advance for your assistance.





RE: Heavy Hydrocarbon Dropout
RE: Heavy Hydrocarbon Dropout
I see an elec engr getting an answer from a mech engr on a chem engr forum, so I am going to give you a chemical engineering answer. I think you just want to calculate how much is available to be recovered on a mass basis. If you want to know what temperatures and seperations schemes are needed to actually do the recovery, then it is more complicated, but to only figure the amount available is easy.
best wishes,
Sean Shepherd
1) Figure out the total mass of the stream by converting the molar flow to mass flow using your avg MW. By normal convention, 220 mmscfd is a molar flow- it is an ideal gas evaluation done at standard conditions. The actual flowing temperature, pressure, density, and compressibility are irrelevant to the molar to mass conversion.
2) Convert the mol fractions of each gas to weight fractions in excel by assuming a 100 mole basis (column A). Convert each mole flow into a mass flow by ratio of the molecular weights (column B). Convert your mass flows to mass fractions by dividing by the sum of all mass flows (column C)
3) To find the mass flow of the components of interest: choose the components of interest, sum their mass fractions, and then multiply by the total mass flow calc from 220mmscfd which was calculated in step#1.
RE: Heavy Hydrocarbon Dropout
Now you will have to calculate the K values using any EOS available. Don't have one? At this point, you need to hire a ChemE.
I'll give you a clue to what they will ask. How much do you want condensed out? I can get from 0.0 to 100,000 pounds per hour.