NGL Fractionation
NGL Fractionation
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
NGL Fractionation
Workshop
Recovery of natural-gas liquids (NGL) from natural gas is quite common
in natural gas processing. Recovery is usually done to:
- Produce transportable gas (free from heavier hydrocarbons which
may condense in the pipeline).
- Meet a sales gas specification.
- Maximize liquid recovery (when liquid products are more valuable
than gas).
Aspen HYSYS can model a wide range of different column configurations.
In this simulation, an NGL Plant will be constructed, consisting of three
columns:
De-Methanizer (operated and modeled as a Reboiled Absorber column)
De-Ethanizer (Distillation column)
De-Propanizer (Distillation column)
Learning Objectives
Once you have completed this section, you will be able to:
Add columns using the Input Experts.
Add extra specifications to columns.
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
NGL Fractionation
NGL Fractionation Train
It's required to process a crude natural gas to remove the heavier hydrocarbons from it
thus the composition of it would be suitable for transportation by passing the crude
gas which comes from two different wells to three towers: De-Methanizer, DeEthanizer and De-Propanizer.
The first well at (-140 oF, 330 psia and flow rate of 3575 lbmol/hr) have the following
conditions and compositions: (Fluid Package: Peng Robinson)
Component Mol frac Component Mol frac
N2
0.0025
n-C4
0.0085
CO2
0.0048
i-C5
0.0036
C1
0.7041
n-C5
0.002
C2
0.1921
n-C6
0.0003
C3
0.0706
n-C7
0.0002
i-C4
0.0112
n-C8
0.0001
o
The second one at (-120 F, 332 psia and flow rate of 475 lbmol/hr) have the
following conditions and composition
Component Mol frac Component Mol frac
N2
n-C4
0.0057
0.0197
CO2
i-C5
0.0029
0.0147
C1
n-C5
0.7227
0.0102
C2
n-C6
0.1176
0.0037
C3
n-C7
0.075
0.0047
i-C4
n-C8
0.0204
0.0027
There's also an energy supplied to the De-Methanizer of (2e6 BTU/hr) which is used
to improve the efficiency of the separation.
The De-Methanizer (reboiled absorber) has the following specifications:
- Feed 1 Material Stream enters the column from the top stage inlet
- Feed 2 Material stream enters from the 2nd stage
- Ex-duty Energy Stream enters from the 4th stage
- Number of stages = 10
- Top Stage pressure = 330 psia & Reboiler pressure = 335 psia
- Top Stage temperature = -125oF & Reboiler temperature = 80 oF
- Ovhd Prod Rate = 2950 lbmole/hr (1338 Kg/hr)
After running the column with the above specifications, the design is
then modified to ensure that the overhead molar fraction of the
methane is 0.96
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
NGL Fractionation
Most of methane is removed from the top of the tower and the bottom
stream is pumped to 2790 kpa then it enters to the De-Ethanizer
(distillation Column) where most of the ethane in the crude is taken as an
overhead product then it is processed to use in different applications.
The de-ethanizer has the following specifications:
After running the column with the above specifications, the design is
modified to ensure that the bottom stream has ratio between C2/C3 =
0.01
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
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NGL Fractionation
Then the bottom product is sent to a valve where the pressure of it
decrease to 1690 kpa, the outlet flow from the valve is sent to a depropanizer (distillation Column) where most of propane is removed from
the top and the heavier hydrocarbons is removed from the bottom
The specifications of the de-propanizer are:
After running the column with the above specifications, the design is
modified to ensure that the overhead molar fraction of the i-C4 & nC4 =0.15 AND propane bottom product molar fraction = 0.02
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
NGL Fractionation
To start the program, From Start Menu, Select All Programs >>
Aspen Tech >> Process Modeling V8.x >>>> Aspen HYSYS >> Aspen
HYSYS
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
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NGL Fractionation
1- First, Start a new case
2- Add the Components
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NGL Fractionation
3- Choose the system components from the databank:
After adding the pure components (N2, CO2, C1, C2, C3, n-C4, i-C4, nC5, i-C5, n-C6, C7, C8)
Now, select the suitable fluid package
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NGL Fractionation
In this case, select Peng-Robinson
Now you can start drawing the flow sheet for the process by clicking the
Simulation button:
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NGL Fractionation
Now add a material stream to define the composition and the conditions
of the feed stream
From the palette:
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NGL Fractionation
After adding the compositions and the conditions for the first stream, add
another stream for feed 2:
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NGL Fractionation
Part 1: De- Methanizer Column
The De-Methanizer is modeled as a reboiled absorber operation, with two feed
streams and an energy stream feed, which represents a side heater on the column.
-
Add an Energy stream with the duty = 2.1 e6 kJ/hr
Double-click on the Reboiled Absorber icon on the Object Palette.
De-Methanizer Specs:
- Feed 1 Material Stream enters the column from the top stage inlet
- Feed 2 Material stream enters from the 2nd stage
- Ex-duty Energy Stream enters from the 4th stage
- Number of stages = 10
- Top Stage pressure = 330 psia
- Reboiler pressure = 335 psia
- Top Stage temperature = -125oF
- Reboiler temperature = 80 oF
- Ovhd Prod Rate = 2950 lbmole/hr (1338 Kg/hr)
- C1 fraction in the Ovhd stream = 0.96
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
Although the column is converged, it is not always practical to
have flow rate specifications. These specifications can result in
columns which cannot be converged or that produce product
streams with undesirable properties if the column feed conditions
change.
An alternative approach is to specify either component fractions
or component recoveries for the column product streams.
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
Run the column:
After running the column, add a pump to transfer the bottom liquid to the
De-ethanizer:
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
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NGL Fractionation
The pump outlet pressure is 2790 kPa (from Worksheet)
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
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NGL Fractionation
Part 2: De- Ethanizer Column
The outlet from the pump is then fed to the de-ethanizer:
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
Add the Column component ratio from the monitor page as follows:
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
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NGL Fractionation
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
Add a valve on the bottom liquid stream:
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
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NGL Fractionation
Outlet pressure from the valve = 1690 kPa (from the Worksheet tab)
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
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NGL Fractionation
Part 3: De- Propanizer Column
Add a distillation column (De-propanizer):
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
Now, let's add a new 2 specifications instead of the current:
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NGL Fractionation
After running the column, you can view the results from the Performance
page (for any column)
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
Save Your Case!
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
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NGL Fractionation
By: Eng. Ahmed Deyab Fares - http://www.adeyab.com
Mobile: 002-01227549943
- Email: eng.a.deab@gmail.com
30
