Natural
gas flows from a well at 1425 psia and 60 F at a flowrate of 27 MMSCFD.
The gas is to be heated to 110 F before being directed to a transfer pipeline.
Calculate the duty of the heater and the dew point temperature of the gas.
| Component |
Composition
(mol %) |
Component |
Composition
(mol %) |
| Methane |
76.5588 |
n-Hexane |
0.0774 |
| Ethane |
6.4501 |
n-Heptane |
0.0253 |
| Propane |
4.2073 |
n-Octane |
0.0155 |
| i-Butane |
1.0702 |
n-Nonane |
0.0051 |
| n-Butane |
1.1903 |
CO2 |
4.3475 |
| i-Pentane |
0.3688 |
N2 |
2.2670 |
| n-Pentane |
0.2429 |
H2S |
3.1739 |
|
|
Total: |
100.0000 |
(Note:
EngVert can easily convert
mol/mass percentages and fractions of streams.)
NOTE: To ease data entry, this flash calculation file is stored in the directory where MixProps is installed...
Step
1: On the Mixprops "Settings"
tab, perform a temperature-pressure flash at T = 60 F and P = 1425 psia.
Select the PR-78 EOS model.
Step
2: On the Mixprops "Composition"
tab, enter the above natural gas analysis.
Step
3: Click on the "Interaction
Coefficients"tab. Since the T/P conditions are well above
the Tc/Pc conditions of typical natural gases, accurate BIPs will need
to be entered to model the system. Click on the Table
button and drag/drop or copy/paste BIPs from the table to the MixProps
interaction coefficients table.
Step
3: Click on the MixProps "Properties"
tab. Mixprops performs the T-P Flash calculation and computes all
the thermodynamic and transport properties of the natural gas. Note
the following:
T =
60 F ..... Vapor Enthalpy = -39,607.8 Btu/lbmol
Step
4: Click on the MixProps "Settings"
tab. Perform another T-P but this time at T = 110 F and P = 1425
psia.
Step
5: Click on the MixProps "Properties"
tab again. Note the following:
T =
110 F ..... Vapor Enthalpy = -38,833.6 Btu/lbmol
Step
6: Compute the heater duty:
Duty
= m * delH
(27
x 10^6 scf/d) ( 1/24 d/hr) ( 1/379.5 lbmol/scf) = 2,964.4 lbmol/hr
Duty
= ( 2,964.4 lbmol/hr) [ -38,833.6 - ( - 39,607.8 ) Btu/lbmol] = 2.3
MMBtu/hr
Step
5: Click on the MixProps "Settings"
tab again. Select a "Dew Point Temperature" calculation. Click
on the "Properties" tab.
Wait for the calculation to complete and then click on the "Summary"
tab:
Dew
Point Temperature = -9.62 F
