Gas processing with propane Refrigeration loop
Refrigerated Gas Plant
A gas stream is to be processed using a propane refrigeration loop. The purpose
is to find the LTS (low temperature separator) temperature at which the
hydrocarbon dewpoint target is met. The Sales Gas hydrocarbon dewpoint
should not exceed –15 oC at 7000 kPa. The incoming gas is cooled in two stages
– first by exchange with product Gas Sales in a gas-gas exchanger, and then in a
chiller which use the propane as a refrigerant.
- Gas stream has the following composition:
Component
N2
H2S
CO2
C1
C2
C3
i-C4
Pressure: 6500 kPa
-
-
-
Mole Fraction
0.0066
0.0003
0.0003
0.7575
0.1709
0.0413
0.0068
Component
n-C4
i-C5
n-C5
C6
Mole Fraction
0.0101
0.0028
0.0027
0.0006
C7+
0.0001
C7+ has a boiling point of 110 oC.
Temperature: 15 oC
Flow Rate: 1500 kgmole/hr
For the Gas-Gas exchanger:
Shell Side Inlet: LTS Vap
Tube Side Inlet: Inlet Sep Vap
Shell Side Outlet: Sales Gas
Tube Side Outlet: Gas to Chiller
Shell side Delta P: 5 kPa
Tube side Delta P: 30 kPa
Min Approach = 5 oC
For the Chiller:
Feed Stream: Gas to Chiller
Product Stream: Gas to LTS
Pressure drop: 40 kPa
Existing Propane refrigeration loop:
Condenser pressure drop: 30 KPa
Condenser outlet: Saturated liquid @ 45 oC
Evaporator pressure drop: 5 KPa
Evaporator heat duty: 1.5e+6 KJ/hr
Evaporator outlet: at its dew point @ -15 oC
Process Simulation Using aspen HYSYS
Eng.\ Ahmad M. Mokhtar
2020
1
Gas processing with propane Refrigeration loop
Process Simulation Using aspen HYSYS
Eng.\ Ahmad M. Mokhtar
2020
2
Depropanizer Column
Depropanizer Column
The Liquids from Inlet separator and LTS in the refrigerated gas plant combined
together and are fed to a depropanizer to get a liquid product with 2% propane
mole fraction.
-
The Depropanizer Column has the following specification:
o Condenser Pressure:
1379 KPa.
o Reboiler Pressure:
1413 KPa.
o Condenser Temperature:
4.5 OC.
o Reboiler Temperature:
93 OC.
o Reflux Ratio:
1.
Process Simulation Using aspen HYSYS
Eng.\ Ahmad M. Mokhtar
2020
3
Crude Oil Refining
Crude Oil Refining
A pre-heated crude needs to be fractionate to produce the following product:
1. Naphtha: produced from top 3-phase condenser.
20,000 bbl/day
2. Kerosene: produced from reboiler side stripper.
13,000 bbl/day
3. Diesel fuel: produced from steam side stripper.
17,000 bbl/day
4. Gas oil: produced from steam side stripper.
5,000 bbl/day
5. Residue: produced from the bottom.
The feed conditions are:
▪ Temp. = 450 Of
▪ Press. = 5.171 bar
▪ Liq. Vol. flow rate = 100,000 bbl/day
The oil will be heated in the furnace to 650 of with 3.5% over flash, and then
feed to the tower that have (29 tray + partial condenser).
The feed enter the tower at stage 28, and a steam stream enters at the bottom.
The oil has the following laboratory assay data:
TBP Distillation Assay
Temperature. of
Liquid Volume Percent Distilled
Molecular weight
0.0
80.0
68.0
10.0
255.0
119.0
20.0
349.0
150.0
30.0
430.0
182.0
40.0
527.0
225.0
50.0
635.0
282.0
60.0
751.0
350.0
70.0
915.0
456.0
80.0
1095.0
585.0
90.0
1277.0
713.0
98.0
1410.0
838.0
Process Simulation Using aspen HYSYS
Eng.\ Ahmad M. Mokhtar
2020
4
Crude Oil Refining
Light Ends Liquid Volume Percent
i-Butane
0.19
n-Butane
0.11
i-Pentane
0.37
n-Pentane
0.46
Liq. Vol. % distilled
API Gravity
13.0
63.28
33.0
54.86
57.0
45.91
74.0
38.21
91.0
26.01
Viscosity Assay
Bulk Crude Properties
MW
300.00
API Gravity
48.75
Liq. Vol. %
Distilled
Viscosity (cP)
100 OF
Viscosity (cP)
210 OF
10.0
0.20
0.10
30.0
0.75
0.30
50.0
4.20
0.80
70.0
39.00
7.50
90.0
600.00
122.30
And the other operation conditions are listed below:
Steam Streams Information
o
Pressure (psia)
Mass flow (lb/hr)
Bottom steam
Temp. ( f)
375
150
7500
Diesel steam
300
50
3000
AGO steam
300
50
2500
Kerosene Reboiler Duty: 7.5 x 106 BTU/hr
Initial estimated values
o
Pressure (psia)
Condenser
Temperature ( f)
100
Condenser press. drop
-
9
Top stage
250
-
Bottom stage
700
32.7
Process Simulation Using aspen HYSYS
19.7
Eng.\ Ahmad M. Mokhtar
2020
5
Crude Oil Refining
Pump around specifications
Pump
around
Drawn
stage
Return
stage
Circulation
rate(bbl/day)
Duty
(BTU/hr)
PA_1
2
1
50,000
- 55e6
PA_2
17
16
30,000
-3.5e7
PA_3
22
21
30,000
-3.5e7
Strippers Specifications
stripper
Type
Draw stage
Return stage
Kerosene
Reboiled
9
8
Diesel
Steam
17
16
AGO
steam
22
21
Process Simulation Using aspen HYSYS
Eng.\ Ahmad M. Mokhtar
2020
6
Chemical Reaction – Toluene Production
Chemical Reaction
Toluene is produced from n-heptane by Dehydrogenation over a Cr2O3 catalyst:
CH3CH2CH2CH2CH2CH2CH3
C6H5CH3 + 4H2
The toluene production process is started by heating n-heptane (100 lb mol/hr)
from 65oF to 800oF in a heater.
It is fed to a catalytic reactor, which operates isothermally and converts 15% of
the n-heptane to toluene.
Its effluent is cooled to 65oF and fed to a separator (flash).
Assuming that all of the units operates at atmospheric pressure, Determine the
species flow rates in every stream?
Process Simulation Using aspen HYSYS
Eng.\ Ahmad M. Mokhtar
2020
7
Chemical Reaction – Toluene Production
Chemical Reaction
Propylene glycol is being produced from propylene oxide, the reaction takes
place in a CSTR reactor operate in atmospheric pressure.
H2O + C3H6O
C3H8O2
Feed streams:
1.Propylene oxide:
Temp. = 75of
Press. = 1.1 atm.
Molar flow rate. = 150 lbmole/hr
Press. = 16.17 psia.
Mass flow rate. = 11000 lb/hr
2.Water:
Temp. = 75of
The Arrhenius parameters for Kinetic reaction:
A = 1.7 x 1013
,
E = 32400 BTU/lbmole
The CSTR reactor:
Vol. = 280 ft3
,
85% full
The outlet temp. = 140 of
The distillation column:
Condenser press. = 15 psia. Condenser press. Drop = 0
Reboiler press. = 17 psia.
Reflux ratio = 1
Bottom product (glycol) specification is 0.005 mole fraction of water.
Process Simulation Using aspen HYSYS
Eng.\ Ahmad M. Mokhtar
2020
8
Gas Gathering
Gas Gathering
In this example, a gas gathering system located on varied terrain is simulated
using the steady state capabilities of HYSYS. The following figure shows the
physical configuration of this system superimposed on a topographic map. The
system consists of four wells distributed over an area of approximately 2.0
square km, connected to a gas plant via a network of pipelines.
Pipe Diameters for each of the branches are:
Pipe Branch
Diameter
Branch 1
Branch 2
Branch 3
Branch 4
Branch 5
Branch 6
Branch 7
76.2 mm (3")
76.2 mm (3")
76.2 mm (3")
101.6 mm (4")
76.2 mm (3")
152 mm (6")
203.2 mm (8")
Schedule 40 steel pipe is used throughout and all branches are buried at a depth
of 1m (3 feet). All pipes are uninsulated.
Process Simulation Using aspen HYSYS
Eng.\ Ahmad M. Mokhtar
2020
9
Gas Gathering
Elevation data for each of the branches are provided in the following table: Branch
Segment
Branch 1
GasWell A
Branch 2
Length
meter
639
1
150
645
6
2
125
636.5
-8.5
3
100
637
0.5
GasWell B
614
1
Branch 3
Branch 4
200
Branch 6
23
635.5
1
160
648
12.5
2
100
634
-14
3
205
633
-1
Branch 1 & 2
637
355
633
-4
GasWell D
632.5
1
180
625
-7.5
2
165
617
-8
Branch 3 & 4
1
Branch 7
637
GasWell C
1
Branch 5
Elevation Change
meter
Elevation
meter
633
300
617
-16
Branch 5 & 6
1
617
340
604
-13
- All wells streams have the same following composition: Component
N2
H2S
CO2
C1
C2
C3
Mole Fraction
Component
Mole Fraction
i-C4
0.0002
0.0405
n-C4
0.0151
i-C5
0.7250
n-C5
0.0815
C6
0.0455
C7+
C7+ has normal boiling point = 110 of
Process Simulation Using aspen HYSYS
0.0150
0.0180
0.0120
0.0130
0.0090
0.0252
Eng.\ Ahmad M. Mokhtar
2020
10
Gas Gathering
- The four streams should have the following values:
GasWell A
GasWell B
GasWell C
GasWell D
Temperature
°C
40
45
43
35
Pressure
kPa
4135
3450
Flow
kgmole/h
425
375
575
545
- Ambient Temperature = 5°C.
- For all pipes in this simulation, use Overall and the Heat Transfer
Coefficient Estimation method.
Process Simulation Using aspen HYSYS
Eng.\ Ahmad M. Mokhtar
2020
11
Gas Gathering
Process Simulation Using aspen HYSYS
Eng.\ Ahmad M. Mokhtar
2020
12