aspen+hysys+reactive+distillation
TRANSCRIPT
Reactive Distillation 1
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Reactive Distillation
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2 Reactive Distillation
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WorkshopWith the continuous removal of reaction products, reactive distillation has found acceptance as a means of improving the technical and economic operation of processes where it is applicable. Advantages of this process include higher yields, energy savings and reduced capital costs.
In this example, you will study the manufacture of Methyl Acetate, an important oil resin used in the manufacture of artificial leathers. You will simulate the synthesis of Methyl Acetate from Methanol and Acetic Acid in a catalytic distillation column.
Learning ObjectivesOnce you have completed this section, you will be able to:
• Model reactive distillation columns
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Process Overview
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Column Overview
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Reactive Distillation 5
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Building the Simulation
Defining the Simulation Basis1. Start a new case using the Wilson Activity Model. The
components are: Methanol, Acetic Acid, M-Acetate and Water.
Enter the Simulation Environment.
Add the Feed Stream
Add the feed stream with the following values:
In the HYSYS component database, M-Acetate is the SimName and Methyl-Acetate is the FullName.
In This Cell... Enter...
Conditions
Stream Name Feed
Temperature 75°C (165°F)
Pressure 101.3 kPa (14.7 psia)
Molar Flow 45 kgmole/h (100 lbmole/hr)
Composition - Mole Fractions
Methanol 0.4
Acetic Acid 0.4
M-Acetate 0.1
Water 0.1
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Add the Distillation ColumnAdd a Distillation Column with the following connections:
Go to the Monitor page of the Design tab and run the column. Complete the following table with information from the simulation:
In This Cell... Enter...
Connections
Column Name Reactive Distil
No. of Stages 15
Feed Feed, Stage 10
Condenser Type Total
Ovhd Liquid Distillate
Bottoms Liquid Bottoms
Condenser Energy Cond Q
Reboiler Energy Reb Q
Pressure
Delta P, Condenser 0 kPa (0 psi)
Condenser 90 kPa (13 psia)
Reboiler 97 kPa (14 psia)
Specs
Reflux Ratio 5
Distillate Rate 20 kgmole/h (44 lbmole/hr)
ComponentDistillate - Mole Fraction
Bottoms - Mole Fraction
Methanol
Acetic Acid
Methyl Acetate
Water
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Reactive Distillation 7
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Adding the Reaction
Another way to add reactions in HYSYS is through the Simulation Environment.
The reaction occurring in this simulation is a Kinetic reaction,
CH3OH + CH3COOH = CH3CH3COO + H2O
1. From the Flowsheet menu, select Reaction Package.
2. From the Available Reactions group, press the Add Rxn button.
3. Select Kinetic from the list of reactions and press the Add Reaction button.
4. Enter the stoichiometric coefficients on the Stoichiometry tab. Remember that reactants are negative and products are positive.
5. Go to the Basis tab. The Base Component is methanol and the RxnPhase is Liquid. Leave the Basis and Rate Units at their default values.
6. On the Parameters tab, for the Forward Reaction enter the Arrenhius Parameter as A=1.0e5, and for the Energy Parameter E=2.3e4 kJ/kgmole (1.0e4 Btu/lbmole). The reaction status should now be Ready. Close the view.
7. Add the Global Rxn Set to the Current Reaction Sets group by pressing the Add Set button.
Open the case OptReact.hsc
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8 Reactive Distillation
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Adding the Reaction to the Column
In this case, the reaction occurs on stages 5 - 10 of the column. Reaction Sets in HYSYS can be attached to any of the stages in the column, including the Condenser, Reboiler and Side operations.
1. On the Reactions tab, press the New button. Enter the following data:
2. Check the Active box on the ColumnReaction view. The default column solver in HYSYS "HYSIM Inside-Out" is not capable of handling reactions in the column. Therefore, HYSYS will change the solver to Newton-Raphson Inside-Out.
3. However, for this column, we need to use the Sparse Continuation Solver. Select this solver on the Solver page of the Parameters page.
4. Run the column. (The column may run automatically after the solver is changed.)
5. Due to the substantial changes that were introduced as part of adding the reaction to the column. The column may not solve. On the Profiles page of the Parameters tab, enter a condenser temperature estimate of 50 oC (122 oF), an estimate of 55 oC (130 oF) for the 15th tray, and 100 oC (212 oF) for the Reboiler.
6. Rerun the column by pressing the Run button. The column should now solve.
7. You can view the results on the Performance tab, and the reaction results on the Reactions tab, Results page.
The Sparse Continuation Solver can be used for highly non-ideal, unusual profiles, or otherwise difficult to converge towers. It is good for Chemical Systems when Inside-Out is not successful and for 3-Phase distillation.
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Reactive Distillation 9
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8. Complete the following table with information from the simulation.
ComponentDistillate - Mole Fraction
Bottoms - Mole Fraction
Methanol
Acetic Acid
Methyl Acetate
Water
Does the reaction inside the column have any effect on the compositions of the product streams? __________
Save your case!
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10 Reactive Distillation
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