8 replies to this topic

[Boualem]

Hello every one.

I calculated the flow rate of a liquid CO2 (Supercritical) through a pipeline, the result I found was in MMACFD (Actual cubic feet), I am wondering if there is a formula to convert this volume (flow rate) into standard conditions of pressure and temperature.

What are the conditions to take into account while sizing pipelines and equipment dealing with Liquid CO2.


Thank you

[Absolute Zero]

Use General gas equation for convert MMACFD to MMSCFD,

[paulhorth]

Boualem,

• Find the density of the liquid CO2 at the operating temperature.
• Convert your volume flow to mass flow
• Convert the mass flow to molar flow by dividing by 44
• From molar flow you can work out the equivalent gas volume at standard gas conditions in MMSCFD. One lbmol = 379.3 SCF. One kgmol = 23.63 Sm3

Design piping for liquid CO2 as you would for any other liquid, using mass flow and density.

Paul

[Boualem]

Thank you for your reply,

I tried the method mentioned by Paul, i think I didn't work for the folloowing conditions: P = 2200 Psig and T = 100 F (Fluid is: Liquid CO2 at supercritical conditions).

I am wondering if we can use this relations: Q(St) = Q(Act)*(Pact/Pst)*(Tst/Tact)

Thank you

[paulhorth]

Boualem,
The equation you give is p1.V1/T1 =p2.V2/T2 which is the ideal gas law.
You do not have an ideal gas. You do not have even a non-ideal gas. You have a LIQUID. Therefore this relation is not applicable.

To calculate the equivalent standard gas volume flowrate from your liquid volume flowrate, you have to calculate mass flow and molar flow, like I said.
Now, what is the density of the liquid CO2?

Paul

[Boualem]

Paul

At these conditions, P = 2200 Psig and T = 80 F is (based on an online program) 778 Kg/m3.

The product is a supercritical (P over or equal to 72 bar and T over or equal to 31 C).

Thank you

[kkala]

Referred CO2 seems to have pressure 2200 psig and temperature 80 - 100 oF. As the diagram of http://en.wikipedia...._carbon_dioxide indicates, at 80 oC it is liquid, at 100 oC supercritical fluid. Critical temperature of CO2 is 31.1 oC = 88 oF. Difference may not be significant, apart from the fact that supercritical fluid will not develop two phases, as long as it remains in the supercritical region.
Density at 2200 psig is calculated through the compressibility factor method, offered by breizh (critical pressure=73.9 bara, see http://www.cheresour...n-control-valve), post No 5. Result is ρ=706 kg/m3 at 100 oF and 767 kg/m3 at 80 oF, according to this method.
Probably it would be better to express rate of CO2 as mass flow, multiplying volumetric flow rate at known temperature and pressure by the resulting density. Standard conditions refer to 1 Atm a (=1.01325 Bara) and 15 oC (*). Gas molar volume at standard conditions is 22.414* (273+15)/273=23.65 m3/mol, and corresponding density of CO2 44/23.65=1.86 kg/m3. This assumes ideal gas at standard conditions, method as above would give ρ=1.87 kg/m3, which is more precise. So flow at standard conditions can be found from mass flow divided by density at standard conditions.
Example: 1000 MMACFD at 2200 psig and 80 oF is equivalent to 1000*767/1.87 = 410160 MMSCFD of CO2 gas.

* see http://www.cheresour...and-actual-m3hr.

Edited by kkala, 30 December 2011 - 04:11 PM.

[paulhorth]

Boualem,

OK, so the liquid density is 778 kg/m3 at your operating conditions. This equals 778 x 0.0624 = 48.5 lb/cu.ft.
You said

I calculated the flow rate of a liquid CO2 (Supercritical) through a pipeline, the result I found was in MMACFD (Actual cubic feet)

Suppose your volume flowrate is V expressed in million actual cubic feet per day of this liquid.

We convert to mass flow: m = V x 48.5 million lb/day
to molar flow; M = m/44 = Vx 48.5/44 million lbmol/day

This quantity of CO2 when converted to gas at standard conditions has a volume of
Q (gas) = M x 379.3 mmSCFD (this conversion is valid for any gas)
Q (gas) = V x 48.5/44 x 379.3 mmSCFD

There is your answer, I leave the arithmetic to you.

Paul

[Boualem]

Thank you so much for your reply Paul, KKala and Zak, I really appreciated it.