Heavy Hydrocarbon Dropout 2

[doehl1]

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.

 

[PaoloPemi]

if I understand the question you wish to calculate the amount of condensate (easy to do with a simulator or some equivalent tool providing you know composition, temperature and pressure) the output will show the molar anounts of different components in condensate, you can get also additional properties as volume/density, enthalpy etc. etc. for both gas and condensate phases, it is not easy to do all this by hand so if you have not access to a simulator you may consider a tool as Properties (prode.com) or REFPROP (NIST).

 

[sshep]

Hey doehl1,

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.

 

[dcasto]

First off, there is not 1% water in the gas. You can use a the McKetta charts to find how much water there is or the equations I've posted here before for water content of natural gas.


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.