Basic Steps for HYSYS

Seoul National University
Chemical Process and Product Design
Aspen HYSYS :
Steady states and Dynamic Simulator
(EG Plant Exercise)
Spring Semester, 2014
TA : Ikhyun Kim
([email protected])
Instructor : En Sup Yoon
Basic Steps for HYSYS
• Select the components
• Choose a property package (Thermodynamic model)
Basic
Environment
• Define Reactions
• Create a unit set
Simulation
Environment
• Create and Specify the streams
• Install and Define the unit operation and column
• DOF & Specification
Analysis
• Analyzing the Result (Case Study, Verification, Optimization, etc.)
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Example – Ethylene Glycol Plant
Ethylene glycol has many industrial uses: a feed stock for polyester resins,
a hydrate inhibitor in natural gas pipelines, an all-weather antifreeze and
coolant, or an industrial solvent. Ethylene oxide and water are fed to a
reactor to produce ethylene glycol. The product stream is fed to a
distillation column where the excess water and ethylene oxide are stripped
off the top and the ethylene glycol is the bottom product.
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Defining the Simulation Basis
Fluid Package : NRTL Activity Model.
Components : Ethylene Oxide (C2H4O), Water (H2O)
and Ethylene Glycol (C2H6O2).
On the Binary Coeffs tab,
Select UNIFAC VLE as the Coeff. Estimation method to estimate the missing
binary coefficients and press Unknowns Only.
On the Rxns tab,
Add the following reaction (Kinetic) to the Fluid Package :
C2H4O + H2O
C2H6O2
Basis and
Parameters pages,
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Defining the Simulation Basis
No reverse reaction is defined in this example.
Return to the Simulation Basis Manager by closing the Kinetic Reaction window.
Return to the Rxns tab of the Fluid Package. Press the Add Set button to add the
Global Rxn Set to the Current Reaction Sets group. Close the Fluid Package
view.
Press the Enter Simulation Environment button.
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Adding the Feed Stream
(Mole Fraction)
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Adding the CSTR Reactor
On the Reactions tab, select the Global Rxn Set and Rxn-1 as the Reaction.
Specify the temperature of stream Rx Liquid to be 65°C (150°F).
From the Reaction results, what is the % Conversion of Ethylene Oxide?
_______99.70
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Ethylene Glycol Tower - Overview
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Adding the Ethylene Glycol Tower
No. of Trays
?
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Adding the Ethylene Glycol Tower
Press the Run Button
In stead of Specifying the Distillate Rate, Specify the reboiler Temperature
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Adding the Ethylene Glycol Tower
In stead of Specifying the Distillate Rate,
Specify the reboiler temperature !!
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Adding the Ethylene Glycol Tower
On the Performance tab, analyze the column result !
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Installing the Recycle
The stream Distillate contains mostly unreacted water. This water can be recycle
d to the reactor in order to reduce the feed water requirements
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Installing the Recycle
A Recycle operation is a mathematical unit operation and is installed as
any other. It has an inlet (calculated) stream and an outlet (assumed)
stream. The operation is called/calculated whenever changes to the
inlet stream fall outside of the converged tolerance.
•
•
•
HYSYS uses the conditions of the assumed stream (outlet)
and solves the flowsheet up to the calculated stream (inlet).
HYSYS then compares the values of the calculated stream to
those in the assumed stream.
Based on the difference between the values, HYSYS modifies
the values in the calculated stream and passes the modified
values to the assumed stream.
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Installing the Recycle
• Attach the Stream
• Delete the specified molar flow rate of the Water Feed stream. This value will
be back-calculated from the outlet of the mixer.
• Specify the molar flow of the mixer outlet stream, Water to Reactor, as 150
kgmole/h (330 lbmole/hr). Once the flow rate in this stream is set, HYSYS will
automatically calculate the flowrate of the Water Feed stream.
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Installing the Recycle
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Recycles
What is a Recycle operation?
– mathematical / logical unit operation
Assumed
Calculated
R
When to use a Recycle operation?
– Required when downstream material stream(s) mix with
upstream material stream(s) and when there is mass I/O across
the flowsheet
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Adding Recycle Operations (1)
Procedure 1
1.
Solve flowsheet without recycled stream
2.
Add Recycle, and only attach the calculated stream
(calculated = estimated)
3.
Connect assumed stream to flowsheet
2
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Adding Recycle Operations (2)
Procedure 2
1.
Guess (estimate) assumed stream
2.
Solve flowsheet up to calculated stream
3.
Add and connect recycle operation
1
2
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Tear Locations
To minimize the number of tear locations, add recycles
– Downstream of gathering points (mixer)
– Upstream of distribution points (column, tee, separator)
To minimize the number of recycle variables (T, P, etc.)
– Choose a tear location that maximizes number of fixed variables
– Add recycle operations at separator inlets
– Compressor after cooler outlets
Choose a stable tear location
– To minimize effect of fluctuations
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