From mmScfd to m3/h

[sincere1983]

Can someone help me with converting million STANDARD cubic feet per day to m3/h.

i Have a max gasflow of 190 mmscfd.
Max pressure = 40 Bar(g)
Max temperature = 35 degrees
Max Molecular weight = 19,82 (natural gas with 85% CH4).

Can someone give me a formula so i can convert the mmScfd to m3/h..

Note: Important is that there will be taken notice of the high pressure and the higher temperature.

So just using the conversion-factor from the API-document (converting SI-units) doesn't work.

Please help me out..

 

[katmar]

As a chemical engineer I am sure you are aware of the
PV = ZnRT relationship for gases, so your problem boils down to 2 questions.

A. What are the conditions for your definition of "standard" in scfm.

B. What is Z for the gas at 40 Bar(g) and 35 degrees (presumably degrees C). To estimate Z you must know the composition of the gas. Then any handbook on physical property prediction will enable you to predict Z.

Once you have these two answers, and you can safely assume Z=1 under standard conditions, then you have your problem solved.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[sincere1983]

So if I calculate the density with:

rho = ((P*M)/R*T))/Z

and after that I calculate the mass flowrate:

n = vol. flowrate (mmscfd)/(1/3600*rho)

this will give the correct answer?

I got a flowrate of 190 mmscfd given.
The gas is 85% methane, 5% ethane, and 3% propane (and for the rest a little H2O, butane, pentane etc).

Z is (don't have a book by hand) 0,75 (a estimation).
I already gave pressure and temperature

 

[25362]

To convert standard CFD to standard m[sup]3[/sup]/h, whatever standard means to you, the only thing you have to do is multiply by 0.028316 m[sup]3[/sup]/CF and divide by 24 h/d.

 

[speco]

Sincere1983,

In the US, a standard cubic foot of gas is is normally defined as being at 60 deg F and 14.696 PSIA (GPSA definition).

However, sometimes there are slight temperature and pressure variations for the "normal" cubic meter. That's probably why the straight volume conversion doesn't work. You need to know how the cubic meter is being defined.

Regards,

Speco (

http://www.stoneprocess.com)

 

[katmar]

Yes, you are the right track. If you take your standard conditions to be 60 deg F and 14.7 psia then the density of a gas with a MW of 19.82 and Z=1 is 0.8369 kg/m[sup]3[/sup], giving a flowrate of 52.11 kg/s.

I would estimate the compressibility of the mixture to be closer to 0.88 than your value of 0.75, but you should check that as any error in Z will result in an equivalent error in the flowrate. This gives a flow of 5203 actual m[sup]3[/sup]/h.

There is a calculator aimed at this sort of calculation built into my Uconeer units converter program. You can download a free copy from my web page. See address in my signature below.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[25362]

Of course I assumed absolutely "equal" standards for cubic foot and cubic meter, since sincere1983 didn't define the standard P,T conditions for scf. This item has been discussed many times in past threads.

 

[mechtimeng]

If you need to convert between normal cubic meters and standard cubic feet use the following conversion.

1 Nm3 @ 0 deg C & 1 atm => 37.326 standard ft3 @ 60 deg F & 1 atm

 

[Ifakiz]

In Okwori FPSO,we convert from mscfd to m3/h like this though we deal with oil but try it out

{(mscfd value)*1000}/(35314676*24)

 

[mrspcs]

I agree with 25362, if there is no change in conditions (whatever they may be) and what you want is expres volume flow rate in different units, all that is needed is the conversion factors having to do with vol. (m3 and ft3) and time (day and hr). No need to get into PVT calcs.

A different story is if there was a change in conditions (temp. for instance) or the vol. flow rate for different mass flow rates etc etc.

However, this does sound like a Custody Transfer related question where instruments in different units are used.
Although not related to gas, the following is just to illustrate how this type of situation can lead to errors where one least expects it (copied from an answer to a question in another thread dealing with crude oil):

"A word of WARNING about conversion of LEVEL to BARRELS.
We were measuring Tank Level with RADAR gauges in metric units (callibrated in -milimeters- )
The Tank Callibration Tables however where in Imperial units (inches) with an appreciation of 1/16".
The application calculating tank volumes (for the inventory and mass balances of the tank farm) was taking the tank level readings direct from the radar readings (mm), it would then ROUND THE FIGURE to the nearest 1/16" to be able to use the tank callibration tables and calculate the volume (bbls).
This rounding process over time would accumulate sufficient error to get the operation of the tank farm off-spec. (accuracy limits for inventory / custody transfer mass balances etc.)".


MS

http://www.3rps.com