Gas Calculation 2

[jegan84]

Hello,
I was tasked today on how much it would cost for us to fill 19 miles of 12" schedule 80 pipe with pipeline grade methane at 150 psi.Any help in calculations I should use to figure out roughly how many Dekatherms would be greatly appreciated.

 

[EmmanuelTop]

12" SCH 80 has 0.7058 ft³ per 1ft of length.

http://www.engineeringtoolbox.com/ansi-steel-pipes-d_306.html

19 miles long line contains 70,806 ft³

Now you start with p*V*M = z*m*R*T and since you know all the terms except mass, it is easy to calculate the quantity (kg or lb) of Methane. Compressibility factor should be around 0.985 at 150 psi(g).

Methane heating value (LHV) is 21,433 BTU/lb. Mass times LHV and there you are.

Dejan IVANOVIC
Process Engineer, MSChE

 

[zdas04]

I find this kind of problem to be more intuitive in standard volume than in mass, probably my upstream bias instead of Dejan's plant bias.

ρ_std=(P_std*SG)/(R_air*T_std*Z_std)=0.046 lbm/ft³
ρ_actual=(P_actual*SG)/(R_air*T_actual*Z_actual)=0.479 lbm/ft³ (assuming that the gas is at 60F)

So:
q_std=Vol*ρ_actual/ρ_std=739 MSCF

Since methane contains a LHV of 909 BTU/SCF and a dekatherm is 1 MMBTU, it is 672 dekatherms


David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[BigInch]

Neglecting compressibility factor (which you can normally do at that relatively low pressure).

 

[bimr]

At 150 psi and 60 Deg F, the density of methane = 7.056 kg/m3. Natural gas = 7.401 kg/m3.

http://www.peacesoftware.de/einigewerte/methan_e.html

70,806 ft3 * 0.441 lb/ft3 * 21,433 (net heating value) = 669 dekatherms

 

[BigInch]

What if the pipeline grade methane is actually NATURAL GAS, which in the USA had an average BTU content of 1025 BTU/SCF in 2014.

672 Deks / 909 * 1025 = 757 Deks

 

[jegan84]

Thanks everyone for the help. Greatly appreciated!