standard gas condition

[sixfacecha]

I have a sour gas mixture of 140mmscfd operating conditions are 75K and 1050psi.Does it means that at this condition the volume is 140mmscfd or at standard conditions. If in standard condition what is the temp and pressure. If I have to find the density of a particular gas say H2S what is the procedure.

I am egarly waiting for your response

 

[zdas04]

You see, when someone writes mmscfd it is understood that the volume flow rate is stated as though it was at some "standard" conditions. Standard conditions are set by contract and/or by regulation so no one can answer your "what pressure and temperature is that?" question. The standart temperature (in the U.S) is ususally 60F, but sometimes I see 68F. Pressure can be one of a dozen values mostly ranging around 14.7 psia, but 15.025 comes up pretty often.

The way you get density is to calculate it. The equation I use (which is by no means the only one) is

[ρ]= (P*SG)/(R(air)*T*Z)

Pressure and temperature are in absolute units. You didn't ask, but I'm sure you need to know that you cannot calculate a meaningfule velocity at an imaginary (i.e., standard) set of conditions, so:

q_acutal=q_standard*[ρ]_standard/[ρ]_actual

David

 

[sixfacecha]

My doubt is then why we are saying that the gas is 130mmscfd at 80F and 1050psi. Its clear from the volumetric flow itself that the pressure is 1 atm and 6oF

 

[katmar]

Have a look at thread378-309578 which discusses the same question. You will see why some of us prefer to think of a flow expressed in scfm as a mass or molar flow, and not as a volumetric flow at all.

This leads to your second question. Yes, you do need to get the density of the gas at the flowing condition. In order to calculate the density you need to know the actual pressure, temperature and compressibility factor so that you can solve the gas equation PV = ZnRT.

As a first approximation you can take Z=1, but for good accuracy you should include Z as well. Finding Z is a whole new question. gogoogleit


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