C h e m i c a l P r o c e s s a n d P r o d u c t D e s i g n
Aspen HYSY HYSYS S: Steady states and Dynamic Simulator (EG Plant Exercise) S e o u l N a t i o n a l U n i v e r s i t y
Spring Semester, 2014
TA : Ikhyun Ikhyun Kim (
[email protected])
Instruc Ins tructor tor : En Sup Su p Yoon
Basic Steps for HYSYS • Select the the components components • Choose a property package (Thermodynamic model) Basic Environment
• Define Define Reactions Reactions
• Create Create a unit unit set • Create and Specify the streams streams Simulation Environment
• Install and Define the unit operation and column
• DOF & Specifica Specification tion Analysis
• Analyzing the Result (Case Study, 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
? Chemical Process and Product Design
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Adding the Ethylene Glycol Tower Press the Run Button
In stead of Specifying the Distillate Rate, Specify the reboiler Temperature Chemical Process and Product Design
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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 ! Chemical Process and Product Design
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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 Chemical Process and Product Design
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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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