Distillation Design and Control Using Aspen Simulation

511 Pages·2013·59.127 MB·English

by  William L. Luyben

DISTILLATION DESIGN
AND CONTROL USING
TM
ASPEN SIMULATION

DISTILLATION DESIGN
AND CONTROL USING
TM
ASPEN SIMULATION
Second Edition
WILLIAM L. LUYBEN
Lehigh University
Bethlehem, Pennsylvania
Cover design: John Wiley & Sons, Inc.
Cover image: # William L. Luyben
Copyright # 2013 by John Wiley & Sons, Inc. All rights reserved.
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LibraryofCongressCataloging-in-PublicationData
Luyben,WilliamL.
DistillationdesignandcontrolusingAspensimulation/WilliamLLuyben.–2nded.
p.cm.
“AIChE.”
Includesindex.
ISBN978-1-118-41143-8(cloth)
1. Distillationapparatus–Designandconstruction. 2. Chemicalprocesscontrol–Simulationmethods.
3. Petroleum–Refining. I. AmericanInstituteofChemicalEngineers. II. Title.
TP159.D5L892013
0
660.28425–dc23
2012030047
PrintedintheUnitedStatesofAmerica
10 9 8 7 6 5 4 3 2 1
Thisbookisdedicatedtofarmersallovertheworld.
NoFarmers,NoFood!

CONTENTS
PREFACETOTHESECONDEDITION xv
PREFACETOTHEFIRSTEDITION xvii
1 FUNDAMENTALSOFVAPOR–LIQUID–EQUILIBRIUM(VLE) 1
1.1 VaporPressure / 1
1.2 BinaryVLEPhaseDiagrams / 3
1.3 PhysicalPropertyMethods / 7
1.4 RelativeVolatility / 7
1.5 BubblePointCalculations / 8
1.6 TernaryDiagrams / 9
1.7 VLENonideality / 11
1.8 ResidueCurvesforTernarySystems / 15
1.9 DistillationBoundaries / 22
1.10 Conclusions / 25
Reference / 27
2 ANALYSISOFDISTILLATIONCOLUMNS 29
2.1 DesignDegreesofFreedom / 29
2.2 BinaryMcCabe–ThieleMethod / 30
2.2.1 Operating Lines / 32
2.2.2 q-Line / 33
2.2.3 Stepping Off Trays / 35
2.2.4 Effect of Parameters / 35
2.2.5 Limiting Conditions / 36
vii
viii
CONTENTS
2.3 ApproximateMulticomponentMethods / 36
2.3.1 Fenske Equation for Minimum Number of Trays / 37
2.3.2 Underwood Equations for Minimum Reflux Ratio / 37
2.4 Conclusions / 38
3 SETTINGUPASTEADY-STATESIMULATION 39
3.1 ConfiguringaNewSimulation / 39
3.2 SpecifyingChemicalComponentsandPhysicalProperties / 46
3.3 SpecifyingStreamProperties / 51
3.4 SpecifyingParametersofEquipment / 52
3.4.1 Column C1 / 52
3.4.2 Valves and Pumps / 55
3.5 RunningtheSimulation / 57
3.6 UsingDesignSpec/VaryFunction / 58
3.7 FindingtheOptimumFeedTrayandMinimumConditions / 70
3.7.1 Optimum Feed Tray / 70
3.7.2 Minimum Reflux Ratio / 71
3.7.3 Minimum Number of Trays / 71
3.8 ColumnSizing / 72
3.8.1 Length / 72
3.8.2 Diameter / 72
3.9 ConceptualDesign / 74
3.10 Conclusions / 80
4 DISTILLATIONECONOMICOPTIMIZATION 81
4.1 HeuristicOptimization / 81
4.1.1 Set Total Trays to Twice Minimum Number of Trays / 81
4.1.2 Set Reflux Ratio to 1.2 Times Minimum Reflux
Ratio / 83
4.2 EconomicBasis / 83
4.3 Results / 85
4.4 OperatingOptimization / 87
4.5 OptimumPressureforVacuumColumns / 92
4.6 Conclusions / 94
5 MORECOMPLEXDISTILLATIONSYSTEMS 95
5.1 ExtractiveDistillation / 95
5.1.1 Design / 99
5.1.2 Simulation Issues / 101
5.2 EthanolDehydration / 105
5.2.1 VLLE Behavior / 106
ix
CONTENTS
5.2.2 Process Flowsheet Simulation / 109
5.2.3 Converging the Flowsheet / 112
5.3 Pressure-SwingAzeotropicDistillation / 115
5.4 Heat-IntegratedColumns / 121
5.4.1 Flowsheet / 121
5.4.2 Converging for Neat Operation / 122
5.5 Conclusions / 126
6 STEADY-STATECALCULATIONSFORCONTROL
STRUCTURESELECTION 127
6.1 ControlStructureAlternatives / 127
6.1.1 Dual-Composition Control / 127
6.1.2 Single-End Control / 128
6.2 FeedCompositionSensitivityAnalysis(ZSA) / 128
6.3 TemperatureControlTraySelection / 129
6.3.1 Summary of Methods / 130
6.3.2 Binary Propane/Isobutane System / 131
6.3.3 Ternary BTX System / 135
6.3.4 Ternary Azeotropic System / 139
6.4 Conclusions / 144
Reference / 144
7 CONVERTINGFROMSTEADY-STATETODYNAMIC
SIMULATION 145
7.1 EquipmentSizing / 146
7.2 ExportingtoAspenDynamics / 148
7.3 OpeningtheDynamicSimulationinAspenDynamics / 150
7.4 InstallingBasicControllers / 152
7.4.1 Reflux / 156
7.4.2 Issues / 157
7.5 InstallingTemperatureandCompositionControllers / 161
7.5.1 Tray Temperature Control / 162
7.5.2 Composition Control / 170
7.5.3 Composition/Temperature Cascade Control / 170
7.6 PerformanceEvaluation / 172
7.6.1 Installing a Plot / 172
7.6.2 Importing Dynamic Results into Matlab / 174
7.6.3 Reboiler Heat Input to Feed Ratio / 176
7.6.4 Comparison of Temperature Control with Cascade
CC/TC / 181
7.7 Conclusions / 184