Aspen Plus. Unit Operation Models. Version STEADY STATE SIMULATION. AspenTech

Transcription

1 Aspen Plus STEADY STATE SIMULATION Version 10 Unit Operation Models AspenTech REFERENCE MANUAL

2 COPYRIGHT Aspen Technology, Inc. ALL RIGHTS RESERVED The flowsheet graphics and plot components of ASPEN PLUS were developed by MY-Tech, Inc. ADVENT, Aspen Custom Modeler, Aspen Dynamics, ASPEN PLUS, AspenTech, BioProcess Simulator (BPS), DynaPLUS, ModelManager, Plantelligence, the Plantelligence logo, POLYMERS PLUS, PROPERTIES PLUS, SPEEDUP, and the aspen leaf logo are either registered trademarks, or trademarks of Aspen Technology, Inc., in the United States and/or other countries. BATCHFRAC and RATEFRAC are trademarks of Koch Engineering Company, Inc. Activator is a trademark of Software Security, Inc. Rainbow SentinelSuperPro is a trademark of Rainbow Technologies, Inc. Élan License Manager is a trademark of Élan Computer Group, Inc., Mountain View, California, USA. Microsoft Windows, Windows NT, and Windows 95 are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. All other brand and product names are trademarks or registered trademarks of their respective companies. The License Manager portion of this product is based on: Élan License Manager Élan Computer Group, Inc. All rights reserved Use of ASPEN PLUS and This Manual This manual is intended as a guide to using ASPEN PLUS process modeling software. This documentation contains AspenTech proprietary and confidential information and may not be disclosed, used, or copied without the prior consent of AspenTech or as set forth in the applicable license agreement. Users are solely responsible for the proper use of ASPEN PLUS and the application of the results obtained. Although AspenTech has tested the software and reviewed the documentation, the sole warranty for ASPEN PLUS may be found in the applicable license agreement between AspenTech and the user. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESS OR IMPLIED, WITH RESPECT TO THIS DOCUMENTATION, ITS QUALITY, PERFORMANCE, MERCHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE.

3 Contents About the Unit Operation Models Reference Manual For More Information...x Technical Support...xi 1 Mixers and Splitters Mixer Flowsheet Connectivity for Mixer Specifying Mixer FSplit Flowsheet Connectivity for FSplit Specifying FSplit SSplit Flowsheet Connectivity for SSplit Specifying SSplit Separators Flash Flowsheet Connectivity for Flash Specifying Flash Flash Flowsheet Connectivity for Flash Specifying Flash Decanter Flowsheet Connectivity for Decanter Specifying Decanter Sep Flowsheet Connectivity for Sep Specifying Sep Sep Flowsheet Connectivity for Sep Specifying Sep Heat Exchangers Heater Flowsheet Connectivity for Heater Specifying Heater HeatX Flowsheet Connectivity for HeatX Specifying HeatX References Unit Operation Models iii

4 MHeatX Flowsheet Connectivity for MHeatX Specifying MHeatX Hetran Flowsheet Connectivity for Hetran Specifying Hetran Aerotran Flowsheet Connectivity for Aerotran Specifying Aerotran Columns DSTWU Flowsheet Connectivity for DSTWU Specifying DSTWU Distl Flowsheet Connectivity for Distl Specifying Distl SCFrac Flowsheet Connectivity for SCFrac Specifying SCFrac RadFrac Flowsheet Connectivity for RadFrac Specifying RadFrac Free-Water and Rigorous Three-Phase Calculations Efficiencies Algorithms Rating Mode Design Mode Reactive Distillation Solution Strategies Physical Properties Solids Handling MultiFrac Flowsheet Connectivity for MultiFrac Specifying MultiFrac Efficiencies Algorithms Rating Mode Design Mode Column Convergence Physical Properties Free Water Handling Solids Handling Sizing and Rating of Trays and Packings PetroFrac Flowsheet Connectivity for PetroFrac Specifying PetroFrac Efficiencies iv Unit Operation Models

5 Convergence Rating Mode Design Mode Physical Properties Free Water Handling Solids Handling Sizing and Rating of Trays and Packings RateFrac Flowsheet Connectivity for RateFrac The Rate-Based Modeling Concept Specifying RateFrac Mass and Heat Transfer Correlations References Extract Flowsheet Connectivity for Extract Specifying Extract Reactors RStoic Flowsheet Connectivity for RStoic Specifying RStoic RYield Flowsheet Connectivity for RYield Specifying RYield REquil Flowsheet Connectivity for REquil Specifying REquil RGibbs Flowsheet Connectivity for RGibbs Specifying RGibbs References RCSTR Flowsheet Connectivity for RCSTR Specifying RCSTR RPlug Flowsheet Connectivity for RPlug Specifying RPlug RBatch Flowsheet Connectivity for RBatch Specifying RBatch Pressure Changers Pump Flowsheet Connectivity for Pump Specifying Pump Compr Flowsheet Connectivity for Compr Specifying Compr Unit Operation Models v

6 MCompr Flowsheet Connectivity for MCompr Specifying MCompr References Valve Flowsheet Connectivity for Valve Specifying Valve References Pipe Flowsheet Connectivity for Pipe Specifying Pipe Two-Phase Correlations Closed-Form Methods References Pipeline Flowsheet Connectivity for Pipeline Specifying Pipeline Two-Phase Correlations Closed-Form Methods References Manipulators Mult Flowsheet Connectivity for Mult Specifying Mult Dupl Flowsheet Connectivity for Dupl Specifying Dupl ClChng Flowsheet Connectivity for ClChng Specifying ClChng Solids Crystallizer Flowsheet Connectivity for Crystallizer Specifying Crystallizer References Crusher Flowsheet Connectivity for Crusher Specifying Crusher References Screen Flowsheet Connectivity for Screen Specifying Screen References FabFl Flowsheet Connectivity for FabFl Specifying FabFl vi Unit Operation Models

7 References Cyclone Flowsheet Connectivity for Cyclone Specifying Cyclone References VScrub Flowsheet Connectivity for VScrub Specifying VScrub References ESP Flowsheet Connectivity for ESP Specifying ESP References HyCyc Flowsheet Connectivity for HyCyc Specifying HyCyc References CFuge Flowsheet Connectivity for CFuge Specifying CFuge References Filter Flowsheet Configuration for Filter Specifying Filter References SWash Flowsheet Connectivity for SWash Specifying SWash CCD Flowsheet Connectivity for CCD Specifying CCD User Models User Flowsheet Connectivity for User Specifying User User Flowsheet Connectivity for User Specifying User Pressure Relief Pres-Relief Specifying Pres-Relief Scenarios Compliance with Codes Stream and Vessel Compositions and Conditions Rules to Size the Relief Valve Piping Reactions Unit Operation Models vii

8 Relief System Data Tables for Pipes and Relief Devices Valve Cycling Vessel Types Disengagement Models Stop Criteria Solution Procedure for Dynamic Scenarios Flow Equations Calculation and Convergence Methods Vessel Insulation Credit Factor References A Sizing and Rating for Trays and Packings Single-Pass and Multi-Pass Trays...A-2 Modes of Operation for Trays...A-8 Flooding Calculations for Trays...A-8 Bubble Cap Tray Layout...A-9 Pressure Drop Calculations for Trays...A-10 Foaming Calculations for Trays...A-11 Packed Columns...A-12 Packing Types and Packing Factors...A-12 Modes of Operation for Packing...A-12 Maximum Capacity Calculations for Packing...A-13 Pressure Drop Calculations for Packing...A-15 Liquid Holdup Calculations for Packing...A-16 Pressure Profile Update...A-17 Physical Property Data Requirements...A-17 References...A-18 Index viii Unit Operation Models

9 About the Unit Operation Models Reference Manual Volume 1 of the ASPEN PLUS Reference Manuals, Unit Operation Models, includes detailed technical reference information for all ASPEN PLUS unit operation models and the Pres-Relief model. The information in this manual is also available in online help and prompts. Models are grouped in chapters according to unit operation type. The reference information for each model includes a description of the model and its typical usage, a diagram of its flowsheet connectivity, a discussion of the specifications you must provide for the model, important equations and correlations, and other relevant information. An overview of all ASPEN PLUS unit operation models, and general information about the steps and procedures in using them is in the ASPEN PLUS User Guide as well as in the online help and prompts in ASPEN PLUS. Unit Operation Models ix

10 For More Information Online Help ASPEN PLUS has a complete system of online help and context-sensitive prompts. The help system contains both context-sensitive help and reference information. For more information about using ASPEN PLUS help, see the ASPEN PLUS User Guide, Chapter 3. ASPEN PLUS Getting Started Building and Running a Process Model This tutorial includes several hands-on sessions to familiarize you with ASPEN PLUS. The guide takes you step-by-step to learn the full power and scope of ASPEN PLUS. ASPEN PLUS User Guide The three-volume ASPEN PLUS User Guide provides step-by-step procedures for developing and using an ASPEN PLUS process simulation model. The guide is task-oriented to help you accomplish the engineering work you need to do, using the powerful capabilities of ASPEN PLUS. ASPEN PLUS reference manual series ASPEN PLUS reference manuals provide detailed technical reference information. These manuals include background information about the unit operation models and the physical properties methods and models available in ASPEN PLUS, tables of ASPEN PLUS databank parameters, group contribution method functional groups, and a wide range of other reference information. The set comprises: Unit Operation Models Physical Property Methods and Models Physical Property Data User Models System Management Summary File Toolkit ASPEN PLUS application examples A suite of sample online ASPEN PLUS simulations illustrating specific processes is delivered with ASPEN PLUS. ASPEN PLUS Installation Guides These guides provide instructions on platform and network installation of ASPEN PLUS. The set comprises: ASPEN PLUS Installation Guide for Windows ASPEN PLUS Installation Guide for OpenVMS ASPEN PLUS Installation Guide for UNIX The ASPEN PLUS manuals are delivered in Adobe portable document format (PDF) on the ASPEN PLUS Documentation CD. You can also order printed manuals from AspenTech. x Unit Operation Models

11 Technical Support World Wide Web For additional information about AspenTech products and services, check the AspenTech World Wide Web home page on the Internet at: Technical resources To obtain in-depth technical support information on the Internet, visit the Technical Support homepage. Register at: Approximately three days after registering, you will receive a confirmation and you will then be able to access this information. The most current Hotline contact information is listed. Other information includes: Frequently asked questions Product training courses Technical tips AspenTech Hotline If you need help from an AspenTech Customer Support engineer, contact our Hotline for any of the following locations: If you are located in: Phone Number Fax Number Address North America & the Caribbean / / (toll free) / support@aspentech.com South America (Argentina office) +54-1/ / tecnoba@aspentech.com (Brazil office) / / tecnosp@aspentech.com Europe, Gulf Region, & Africa (Brussels office) +32-2/ / atesupport@aspentech.com (UK office) / / atuksupport@aspentech.com Japan +81-3/ / atjsupport@aspentech.com Asia & Australia +85-2/ / atasupport@aspentech.com Unit Operation Models xi

12 xii Unit Operation Models

13 Chapter 1 1 Mixers and Splitters This chapter describes the unit operation models for mixing and splitting streams. The models are: Model Description Purpose Use For Mixer Stream mixer Combines multiple streams into one stream FSplit Stream splitter Divides feed based on splits specified for outlet streams SSplit Substream splitter Divides feed based on splits specified for each substream Mixing tees. Stream mixing operations. Adding heat streams. Adding work streams Stream splitters. Bleed valves Stream splitters. Perfect fluid-solid separators Unit Operation Models 1-1

14 Mixers and Splitters Mixer Stream Mixer Use Mixer to combine streams into one stream. Mixer models mixing tees or other types of mixing operations. Mixer combines material streams (or heat streams or work streams) into one stream. Select the Heat (Q) and Work (W) Mixer icons from the Model Library for heat and work streams respectively. A single Mixer block cannot mix streams of different types (material, heat, work). Flowsheet Connectivity for Mixer Material (2 or more) Material Water (optional) Flowsheet for Mixing Material Streams Material Streams Inlet At least two material streams Outlet One material stream One water decant stream (optional) 1-2 Unit Operation Models

15 Chapter 1 Heat (2 or more) Heat Flowsheet for Adding Heat Streams Heat Streams Inlet At least two heat streams Outlet One heat stream Work (2 or more) Work Flowsheet for Adding Work Streams Work Streams Inlet At least two work streams Outlet One work stream Specifying Mixer Use the Mixer Input Flash Options sheet to specify operating conditions. When mixing heat or work streams, Mixer does not require any specifications. Unit Operation Models 1-3

16 Mixers and Splitters When mixing material streams, you can specify either the outlet pressure or pressure drop. If you specify pressure drop, Mixer determines the minimum of the inlet stream pressures, and applies the pressure drop to the minimum inlet stream pressure to compute the outlet pressure. If you do not specify the outlet pressure or pressure drop, Mixer uses the minimum pressure from the inlet streams for the outlet pressure. You can select the following valid phases: Valid Phase Solids? Number of phases? Free Water? Phase? Vapor-Only Yes or no 1 No V Liquid-Only Yes or no 1 No L Vapor-Liquid Yes or no 2 No Vapor-Liquid-Liquid Yes or no 3 No Liquid Free-Water Yes or no 1 Yes Vapor-Liquid Free-Water Yes or no 2 Yes Solid-Only Yes 1 No S Check Use Free Water Calculations checkbox on the Setup Specifications Global sheet. An optional water decant stream can be used when free-water calculations are performed. Mixer performs an adiabatic calculation on the product to determine the outlet temperature, unless Mass Balance Only Calculations is specified on the Mixer BlockOptions SimulationOptions sheet or the Setup SimulationOptions Calculations sheet. Use the following forms to enter specifications and view results for Mixer: Use this form Input BlockOptions Results Dynamic To do this Enter operating conditions and flash convergence parameters Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block View Mixer simulation results Specify parameters for dynamic simulations 1-4 Unit Operation Models

17 Chapter 1 FSplit Stream Splitter FSplit combines streams of the same type (material, heat, or work streams) and divides the resulting stream into two or more streams of the same type. All outlet streams have the same composition and conditions as the mixed inlet. Select the Heat (Q) and Work (W) FSplit icons from the Model Library for heat and work streams respectively. Use FSplit to model flow splitters, such as bleed valves. FSplit cannot split a stream into different types. For example, FSplit cannot split a material stream into a heat stream and a material stream. To model a splitter where the amount of each substream sent to each outlet can differ, use an SSplit block. To model a splitter where the composition and properties of the output streams can differ, use a Sep block or a Sep2 block. Flowsheet Connectivity for FSplit Material (any number) Material (2 or more) Flowsheet for Splitting Material Streams Material Streams Inlet At least one material stream Outlet At least two material streams Unit Operation Models 1-5

18 Mixers and Splitters Heat (any number) Heat (2 or more) Flowsheet for Splitting Heat Streams Heat Streams Inlet At least one heat stream Outlet At least two heat streams Work (any number) Work (2 or more) Flowsheet for Splitting Work Streams Work Streams Inlet At least one work stream Outlet At least two work streams Specifying FSplit To split material streams Give one of the following specifications for each outlet stream except one: Fraction of the combined inlet flow Mole flow rate Mass flow rate Standard liquid volume flow rate Actual volume flow rate Fraction of the residue remaining after all other specifications are satisfied FSplit puts any remaining flow in the unspecified outlet stream to satisfy material balance. You can specify mole, mass, or standard liquid volume flow rate for one of the following: The entire stream A subset of key components in the stream 1-6 Unit Operation Models

19 Chapter 1 To specify the flow rate of a component or group of components in an outlet stream, specify a group of key components and the total flow rate for the group (the sum of the component flow rates) on the Input Specifications sheet, and define the key components in the group on the Input KeyComponents sheet. Outlet streams have the same composition as the mixed inlet stream. For this reason, when you specify the flow rate of a key component, the total flow rate of the outlet stream is greater than the flow rate you specify. When FSplit has more than one inlet, you can do one of the following: Enter the outlet pressure on the FSplit Input FlashOptions sheet Let the outlet pressure default to the minimum pressure of the inlet streams To split heat streams or work streams Specify the fraction of the combined inlet heat or work for each outlet stream except one. FSplit puts any remaining heat or work in the unspecified outlet stream to satisfy energy balance. Use the following forms to enter specifications and view results for FSplit: Use this form Input BlockOptions Results To do this Enter split specifications, flash conditions and calculation options, and key components associated with split specifications Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block View split fractions for outlet streams, and material and energy balance results Unit Operation Models 1-7

20 Mixers and Splitters SSplit Substream Splitter SSplit combines material streams and divides the resulting stream into two or more streams. Use SSplit to model a splitter where the split of each substream among the outlet streams can differ. Substreams in the outlet streams have the same composition, temperature, and pressure as the corresponding substreams in the mixed inlet stream. Only the substream flow rates differ. To model a splitter in which the composition and properties of the substreams in the output streams can differ, use a Sep block or a Sep2 block. Flowsheet Connectivity for SSplit Material (any number) Material (2 or more) Material Streams Inlet At least one material stream Outlet At least two material streams Specifying SSplit For each substream, specify one of the following for all but one outlet stream: Fraction of the inlet substream Mole flow rate Mass flow rate Standard liquid volume flow rate SSplit puts any remaining flow for each substream in the unspecified stream. You cannot specify standard liquid volume flow rate when the substream is of type CISOLID, and mole and standard liquid volume flow rates when the substream is of type NC. 1-8 Unit Operation Models

21 Chapter 1 You can specify mole or mass flow rate for one of the following: The entire substream A subset of components in the substream You can specify the flow rate of a component in a substream of an outlet stream. To do this, define a key component and specify the flow rate for the key component. Similarly, you can specify the flow rate for a group of components in a substream of an outlet stream. To do this, define a key group of components and specify the total flow rate for the group (the sum of the component flow rates). Substreams in outlet streams have the same composition as the corresponding substream in the mixed inlet stream. For this reason, when you specify the flow rate of a key, the total flow rate of the substream in the outlet stream is greater than the flow rate you specify. When SSplit has more than one inlet, you can do one of the following: Enter the outlet pressure on the Input FlashOptions sheet. Let the outlet pressure default to the minimum pressure of the inlet streams. The composition, temperature, pressure, and other substream variables for all outlet streams have the same values as the mixed inlet. Only the substream flow rates differ. Use the following forms to enter specifications and view results for SSplit: Use this form Input BlockOptions Results To do this Enter split specifications, flash conditions, calculation options, and key components associated with split specifications Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block View split fractions of each substream in each outlet stream, and material and energy balance results Unit Operation Models 1-9

22 Mixers and Splitters 1-10 Unit Operation Models

23 Chapter 2 2 Separators This chapter describes the unit operation models for component separators, flash drums, and liquid-liquid separators. The models are: Model Description Purpose Use For Flash2 Two-outlet flash Separates feed into two outlet streams, using rigorous vaporliquid or vapor-liquid-liquid equilibrium Flash3 Three-outlet flash Separates feed into three outlet streams, using rigorous vapor-liquid-liquid equilibrium Decanter Liquid-liquid decanter Separates feed into two liquid outlet streams Sep Component separator Separates inlet stream components into multiple outlet streams, based on specified flows or split frractions Flash drums, evaporators, knock-out drums, single stage separators Decanters, single-stage separators with two liquid phases Decanters, single-stage separators with two liquid phases and no vapor phase Component separation operations, such as distillation and absorption, when the details of the separation are unknown or unimportant Sep2 Two-outlet component separator Separates inlet stream components into two outlet streams, based on specified flows, split fractions, or purities Component separation operations, such as distillation and absorption, when the details of the separation are unknown or unimportant You can generate heating or cooling curve tables for Flash2, Flash3, and Decanter models. Unit Operation Models 2-1

24 Separators Flash2 Two-Outlet Flash Use Flash2 to model flashes, evaporators, knock-out drums, and other singlestage separators. Flash2 performs vapor-liquid or vapor-liquid-liquid equilibrium calculations. When you specify the outlet conditions, Flash2 determines the thermal and phase conditions of a mixture of one or more inlet streams. Flowsheet Connectivity for Flash2 Vapor Heat (optional) Material (any number) Heat (optional) Water (optional) Liquid Material Streams Inlet At least one material stream Outlet One material stream for the vapor phase One material stream for the liquid phase. (If three phases exist, the liquid outlet contains both liquid phases.) One water decant stream (optional) You can specify liquid and/or solid entrainment in the vapor stream. 2-2 Unit Operation Models

25 Chapter 2 Heat Streams Inlet Any number of heat streams (optional) Outlet One heat stream (optional) If you give only one specification (temperature or pressure) on the Input Specifications Sheet, Flash2 uses the sum of the inlet heat streams as a duty specification. Otherwise, Flash2 uses the inlet heat stream only to calculate the net heat duty. The net heat duty is the sum of the inlet heat streams minus the actual (calculated) heat duty. You can use an optional outlet heat stream for the net heat duty. Specifying Flash2 Use the Input Specifications sheet for all required specifications and valid phases. For valid phases you can choose the following options: You can choose the following options Solids? Number of phases? Free Water? Vapor-Liquid Yes or no 2 No Vapor-Liquid-Liquid Yes or no 3 No Vapor-Liquid-FreeWater Yes or no 2 Yes Use the Input FlashOptions sheet to specify temperature and pressure estimates and flash convergence parameters. Use the Input Entrainment sheet to specify liquid and solid entrainment in the vapor phase. Use the Hcurves form to specify optional heating or cooling curves. Use the following forms to enter specifications and view results for Flash2: Use this form Input Hcurves Block Options Results Dynamic To do this Enter flash specifications, flash convergence parameters, and entrainment specifications Specify heating or cooling curve tables and view tabular results Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block View Flash2 simulation results Specify parameters for dynamic simulations Unit Operation Models 2-3

26 Separators Solids All phases are in thermal equilibrium. Solids leave at the same temperature as the fluid phases. Flash2 can simulate fluid phases with solids when the stream contains solid substreams or when you request electrolytes chemistry calculations. Solid Substreams Materials in solid substreams do not participate in phase equilibrium calculations. Electrolyte Chemistry Calculations You can request these on the Properties Specifications Global sheet or the BlockOptions Properties sheet. Solid salts participate in liquid-solid phase equilibrium and thermal equilibrium calculations. The salts are in the MIXED substream. 2-4 Unit Operation Models

27 Chapter 2 Flash3 Three-Outlet Flash Use Flash3 to model flashes, evaporators, knock-out drums, decanters, and other single-stage separators in which two liquid outlet streams are produced. Flash3 performs vapor-liquid-liquid equilibrium calculations. When you specify outlet conditions, Flash3 determines the thermal and phase conditions of a mixture of one or more inlet streams. Flowsheet Connectivity for Flash3 Vapor Heat (optional) Material (any number) Heat (optional) 1st Liquid 2nd Liquid Material Streams Inlet At least one material stream Outlet One material stream for the vapor phase One material stream for the first liquid phase One material stream for the second liquid phase You can specify liquid entrainment of each liquid phase in the vapor stream. You can also specify entrainment for each solid substream in the vapor and first liquid phase. Unit Operation Models 2-5

28 Separators Heat Streams Inlet Any number of heat streams (optional) Outlet One heat stream (optional) If you give only one specification on the Input Specifications Sheet (temperature or pressure), Flash3 uses the sum of the inlet heat streams as a duty specification. Otherwise, Flash3 uses the inlet heat stream only to calculate the net heat duty. The net heat duty is the sum of the inlet heat streams minus the actual (calculated) heat duty. You can use an optional outlet heat stream for the net heat duty. Specifying Flash3 Use the Input Specifications sheet for all required specifications. Use the Input Entrainment sheet to specify solid entrainment. To specify optional heating or cooling curves, use the Hcurves form. Use the following forms to enter specifications and view results for Flash3: Use this form Input Hcurves Block Options Results Dynamic To do this Enter flash specifications, key components, flash convergence parameters, and entrainment specifications Specify heating or cooling curve tables and view tabular results Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block View Flash3 simulation results Specify parameters for dynamic simulations Solids All phases are in thermal equilibrium. Solids leave at the same temperature as the fluid phases. Flash3 can simulate fluid phases with solids when the stream contains solid substreams, or when you request electrolyte chemistry calculations. Solid Substreams Materials in solid substreams do not participate in phase equilibrium calculations. 2-6 Unit Operation Models

29 Chapter 2 Electrolyte Chemistry Calculations You can request these on the Properties Specifications Global sheet or on the Input BlockOptions Properties sheet. Solid salts do participate in liquid-solid phase equilibrium and thermal equilibrium calculations. You can only specify apparent component calculations (Select Simulation Approach=Apparent Components on the BlockOptions Properties sheet). The salts will not appear in the MIXED substream. Unit Operation Models 2-7

30 Separators Decanter Liquid-Liquid Decanter Decanter simulates decanters and other single stage separators without a vapor phase. Decanter can perform: Liquid-liquid equilibrium calculations Liquid-free-water calculations Use Decanter to model knock-out drums, decanters, and other single-stage separators without a vapor phase. When you specify outlet conditions, Decanter determines the thermal and phase conditions of a mixture of one or more inlet streams. Decanter can calculate liquid-liquid distribution coefficients using: An activity coefficient model An equation of state capable of representing two liquid phases A user-specified Fortran subroutine A built-in correlation with user-specified coefficients You can enter component separation efficiencies, assuming equilibrium stage is present. Use Flash3 if you suspect any vapor phase formation. Flowsheet Connectivity for Decanter Material (any number) Heat (optional) 1st Liquid 2nd Liquid Heat (optional) Material Streams Inlet At least one material stream Outlet One material stream for the first liquid phase One material stream for the second liquid phase You can specify entrainment for each solid substream in the first liquid phase. 2-8 Unit Operation Models

31 Chapter 2 Heat Streams Inlet Any number of heat streams (optional) Outlet One heat stream (optional) If you specify only pressure on the Input Specifications sheet, Decanter uses the sum of the inlet heat streams as a duty specification. Otherwise, Decanter uses the inlet heat stream only to calculate the net heat duty. The net heat duty is the sum of the inlet heat streams minus the actual (calculated) heat duty. You can use an optional outlet heat stream for the net heat duty. Specifying Decanter You can operate Decanter in one of the following ways: Adiabatically With specified duty At a specified temperature Use the Input Specifications sheet to enter: Pressure Temperature or duty Use the following forms to enter specifications and view results for Decanter: Use this form Input Properties Hcurves Block Options Results Dynamic To do this Specify operating conditions, key components, calculation options, valid phases, efficiency, and entrainment Specify and/or override property methods, KLL equation parameters, and/or user subroutine for phase split calculations Specify heating or cooling curve tables and view tabular results Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block Display simulation results Specify parameters for dynamic simulations Unit Operation Models 2-9

32 Separators Defining the Second Liquid Phase If two liquid phases are present at the decanter operating condition, Decanter treats the phase with higher density as the second phase, by default. When only one liquid phase exists and you want to avoid ambiguities, you can override the default by: Specifying key components for identifying the second liquid phase on the Input Specifications sheet Optionally specifying the threshold key component mole fraction on the Input Specifications sheet When Two liquid phases are present One liquid phase is present Decanter treats the Phase with the higher mole fraction of key components as the second liquid phase Liquid phase as the first liquid phase, unless the mole fraction of key components exceeds the threshold value Methods for Calculating the Liquid-Liquid Distribution Coefficients (KLL) When calculating liquid-liquid distribution coefficients (KLL), by default Decanter uses the physical property method specified for the block on the Properties PhaseProperty sheet or BlockOptions Properties sheet. On the Input CalculationOptions sheet, you can override the default by doing one of the following: Specify separate property methods for the two liquid phases using the Properties PhaseProperty sheet Use a built-in KLL correlation. Enter correlation coefficients on the Properties KLLCorrelation sheet. Use a Fortran subroutine that you specify on the Properties KLLSubroutine sheet See ASPEN PLUS User Models for more information about writing Fortran subroutines. Phase Splitting Decanter has two methods for solving liquid-liquid phase split calculations: Equating fugacities of two liquid phases Minimizing Gibbs free energy of the system You can select a method on the Input CalculationOptions sheet Unit Operation Models

33 Chapter 2 If you select Minimizing Gibbs free energy of the system, the following must be thermodynamically consistent: Physical property models Block property method You cannot use the Minimizing Gibbs free energy of the system method when: You specify Separate property methods for the two liquid phases The built-in correlation for liquid-liquid distribution coefficient ( KLL) calculations A user subroutine for liquid-liquid distribution coefficient (KLL) calculations On this sheet Properties PhaseProperty Input CalculationOptions Input Calculation Options Equating fugacities of two liquid phases is not restricted by physical property specifications. However, Decanter can calculate solutions that do not minimize Gibbs free energy. Efficiency Decanter outlet streams are normally at equilibrium. However, you can specify separation efficiencies on the Input Efficiency sheet to account for departure from equilibrium. If you select Liquid-FreeWater for Valid Phases on the Input CalculationOptions sheet, you cannot specify separation efficiencies. Solids Entrainment If solids substreams are present, they do not participate in phase equilibrium calculations, but they do participate in enthalpy balance. You can use the Input Entrainment sheet to specify solids entrainment in the first liquid outlet stream. Decanter places any remaining solids in the second liquid outlet stream. Unit Operation Models 2-11

34 Separators Sep Component Separator Sep combines streams and separates the result into two or more streams according to splits specified for each component. When the details of the separation are unknown or unimportant, but the splits for each component are known, you can use Sep in place of a rigorous separation model to save computation time. If the composition and conditions of all outlet streams of the block you are modeling are identical, you can use an FSplit block instead of Sep. Flowsheet Connectivity for Sep Material (any number) Material (2 or more) Heat (optional) Material Streams Inlet At least one material stream Outlet At least two material streams Heat Streams Inlet No inlet heat streams Outlet One stream for the enthalpy difference between inlet and outlet material streams (optional) 2-12 Unit Operation Models

35 Chapter 2 Specifying Sep For each substream of each outlet stream except one, use the Sep Input Specifications sheet to specify one of the following for each component present: Fraction of the component in the corresponding inlet substream Mole flow rate of the component Mass flow rate of the component Standard liquid volume flow rate of the component Sep puts any remaining flow in the corresponding substream of the unspecified outlet stream. Use the following forms to enter specifications and view results for Sep: Use this form Input BlockOptions Results To do this Enter split specifications, flash specifications, and convergence parameters for the mixed inlet and each outlet stream Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block View Sep simulation results Inlet Pressure Use the Sep Input Feed Flash sheet to specify either the pressure drop or the pressure at the inlet. This is useful when Sep has more than one inlet stream. The inlet pressure defaults to the minimum inlet stream pressure. Outlet Stream Conditions Use the Sep Input Outlet Flash sheet to specify the conditions of the outlet streams. If you do not specify the conditions for a stream, Sep uses the inlet temperature and pressure. Unit Operation Models 2-13

36 Separators Sep2 Two-Outlet Component Separator Sep2 separates inlet stream components into two outlet streams. Sep2 is similar to Sep, but offers a wider variety of specifications. Sep2 allows purity (mole-fraction) specifications for components. You can use Sep2 in place of a rigorous separation model, such as distillation or absorption. Sep2 saves computation time when details of the separation are unknown or unimportant. If the composition and conditions of all outlet streams of the block you are modeling are identical, you can use FSplit instead of Sep2. Flowsheet Connectivity for Sep2 Material Material (any number) Material Heat (optional) Material Streams Inlet At least one material stream Outlet Two material streams Heat Streams Inlet No inlet heat streams Outlet One stream for the enthalpy difference between inlet and outlet material streams (optional) 2-14 Unit Operation Models

37 Chapter 2 Specifying Sep2 Use the Input Specifications sheet to specify stream and/or component fractions and flows. The number of specifications for each substream must equal the number of components in that substream. You can enter these stream specifications: Fraction of the total inlet stream going to either outlet stream Total mass flow rate of an outlet stream Total molar flow rate of an outlet stream (for substreams of type MIXED or CISOLID) Total standard liquid volume flow rate of an outlet stream (for substreams of type MIXED) You can enter these component specifications: Fraction of a component in the feed going to either outlet stream Mass flow rate of a component in an outlet stream Molar flow rate of a component in an outlet stream (for substreams of type MIXED or CISOLID) Standard liquid volume flow rate of a component in an outlet stream (for substreams of type MIXED) Mass fraction of a component in an outlet stream Mole fraction of a component in an outlet stream (for substreams of type MIXED or CISOLID) Sep2 treats each substream separately. Do not: Specify the total flow of both outlet streams Enter more than one flow or frac specification for each component Enter both a mole-frac and a mass-frac specification for a component in a stream Use the following forms to enter specifications and view results for Sep2: Use this form Input Block Options Results To do this Enter split specifications, flash specifications, and convergence parameters for the mixed inlet and each outlet stream Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block View Sep2 simulation results Unit Operation Models 2-15

38 Separators Inlet Pressure Use the Input Feed Flash sheet to specify either the pressure drop or pressure at the inlet. This information is useful when Sep2 has more than one inlet stream. The inlet pressure defaults to the minimum of the inlet stream pressures. Outlet Stream Conditions Use the Input Outlet Flash sheet to specify the conditions of the outlet streams. If you do not specify the conditions for a stream, Sep2 uses the inlet temperature and pressure Unit Operation Models

39 Chapter 3 3 Heat Exchangers This chapter describes the unit operation models for heat exchangers and heaters (and coolers), and for interfacing to the B-JAC heat exchanger programs. The models are: Model Description Purpose Use For Heater Heater or cooler Determines thermal and phase conditions of outlet stream HeatX Two-stream heat exchanger Exchanges heat between two streams MHeatX Multistream heat exchanger Exchanges heat between any number of streams Heaters, coolers, condensers, and so on Two-stream heat exchangers. Rating shell and tube heat exchangers when geometry is known. Multiple hot and cold stream heat exchangers. Two-stream heat exchangers. LNG exchangers. Hetran Shell and tube heat exchanger Provides interface to the B-JAC Hetran shell and tube heat exchanger program Shell and tube heat exchangers, including kettle reboilers Aerotran Air-cooled heat exchanger Provides interface to the B-JAC Aerotran air-cooled heat exchanger program Crossflow heat exchangers, including air coolers Unit Operation Models 3-1

40 Heat Exchangers Heater Heater/Cooler You can use Heater to represent: Heaters Coolers Valves Pumps (whenever work-related results are not needed) Compressors (whenever work-related results are not needed) You also can use Heater to set the thermodynamic condition of a stream. When you specify the outlet conditions, Heater determines the thermal and phase conditions of a mixture with one or more inlet streams. Flowsheet Connectivity for Heater Heat (optional) Material (any number) Material Heat (optional) Water (optional) Material Streams Inlet At least one material stream Outlet One material stream One water decant stream (optional) Heat Streams Inlet Any number of heat streams (optional) Outlet One heat stream (optional) 3-2 Unit Operation Models

41 Chapter 3 If you give only one specification (temperature or pressure) on the Specifications sheet, Heater uses the sum of the inlet heat streams as a duty specification. Otherwise, Heater uses the inlet heat stream only to calculate the net heat duty. The net heat duty is the sum of the inlet heat streams minus the actual (calculated) heat duty. You can use an optional outlet heat stream for the net heat duty. Specifying Heater Use the Heater Input Specifications sheet for all required specifications and valid phases. Dew point calculations are two- or three-phase flashes with a vapor fraction of unity. Bubble point calculations are two- or three-phase flashes with a vapor fraction of zero. Use the Heater Input FlashOptions sheet to specify temperature and pressure estimates and flash convergence parameters. Use the Hcurves form to specify optional heating or cooling curves. This model has no dynamic features. The pressure drop is fixed at the steady state value. The outlet flow is determined by the mass balance. Use the following forms to enter specifications and view results for Heater. Use this form Input Hcurves Block Options Results To do this Enter operating conditions and flash convergence parameters Specify heating or cooling curve tables and view tabular results Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block View Heater results Unit Operation Models 3-3

42 Heat Exchangers Solids Heater can simulate fluid phases with solids when the stream contains solid substreams or when you request electrolyte chemistry calculations. All phases are in thermal equilibrium. Solids leave at the same temperature as fluid phases. Solid Substreams Materials in solid substreams do not participate in phase equilibrium calculations. Electrolyte Chemistry Calculations You can request these on the Properties Specifications Global sheet or the Heater BlockOptions Properties sheet. Solid salts participate in liquid-solid phase equilibrium and thermal equilibrium calculations. The salts are in the MIXED substream. 3-4 Unit Operation Models

43 Chapter 3 HeatX Two-Stream Heat Exchanger HeatX can model a wide variety of shell and tube heat exchanger types including: Countercurrent and cocurrent Segmental baffle TEMA E, F, G, H, J, and X shells Rod baffle TEMA E and F shells Bare and low-finned tubes HeatX can perform a full zone analysis with heat transfer coefficient and pressure drop estimation for single- and two-phase streams. For rigorous heat transfer and pressure drop calculations, you must supply the exchanger geometry. If exchanger geometry is unknown or unimportant, HeatX can perform simplified shortcut rating calculations. For example, you may want to perform only heat and material balance calculations. HeatX has correlations to estimate sensible heat, nucleate boiling, and condensation film coefficients. HeatX cannot: Perform design calculations Perform mechanical vibration analysis Estimate fouling factors Flowsheet Connectivity for HeatX Water (optional) Cold Outlet Hot Inlet Hot Outlet Water (optional) Cold Inlet Unit Operation Models 3-5

44 Heat Exchangers Material Streams Inlet One hot inlet One cold inlet Outlet One hot outlet One cold outlet One water decant stream on the hot side (optional) One water decant stream on the cold side (optional) Specifying HeatX Consider these questions when specifying HeatX: Should rating calculations be simple (shortcut) or rigorous? What specification should the block have? How should the log-mean temperature difference correction factor be calculated? How should the heat transfer coefficient be calculated? How should the pressure drops be calculated? What equipment specifications and geometry information are available? The answers to these questions determine the amount of information required to complete the block input. You must provide one of the following specifications: Heat exchanger area or geometry Exchanger heat duty Outlet temperature of the hot or cold stream Temperature approach at either end of the exchanger Degrees of superheating/subcooling for the hot or cold stream Vapor fraction of the hot or cold stream Temperature change of the hot or cold stream Use the following forms to enter specifications and view results for HeatX: Use this form Setup Options Geometry UserSubroutines Hot-Hcurves To do this Specify shortcut or detailed calculations, flow direction, exchanger pressure drops, heat transfer coefficient calculation methods, and film coefficients Specify different flash convergence parameters and valid phases for the hot and cold sides, HeatX convergence parameters, and block-specific report option Specify the shell and tube configuration and indicate any tube fins, baffles, or nozzles Specify parameters for user-defined Fortran subroutines to calculate overall heat transfer coefficient, LMTD correction factor, tube-side liquid holdup, or tube-side pressure drop Specify hot stream heating or cooling curve tables and view tabular results continued 3-6 Unit Operation Models

45 Chapter 3 Use this form Cold-Hcurves BlockOptions Results Detailed Results Dynamic To do this Specify cold stream heating or cooling curve tables and view tabular results Override global values for physical properties, simulation options, diagnostic message levels, and report options for this block View a summary of results, mass and energy balances, pressure drops, velocities, and zone analysis View detailed shell and tube results, and information about tube fins, baffles, and nozzles Specify parameters for dynamic simulations Shortcut Versus Rigorous Rating Calculations HeatX has two rating modes: shortcut and rigorous. Use the Calculation Type field on the Setup Specifications sheet to specify shortcut or rigorous rating calculations. In shortcut rating mode you can simulate a heat exchanger block with the minimum amount of required input. The shortcut calculation does not require exchanger configuration or geometry data. For rigorous rating mode, you can use exchanger geometry to estimate: Film coefficients Pressure drops Log-mean temperature difference correction factor Rigorous rating mode provides more specification options for HeatX, but it also requires more input. Rigorous rating mode provides defaults for many options. You can change the defaults to gain complete control over the calculations. The following table lists these options with valid values. The values are described in the following sections. Unit Operation Models 3-7

46 Heat Exchangers Variable Calculation Method Available in Shortcut Mode Available in Rigorous Mode LMTD Correction Factor Constant Geometry User subroutine Default No No Yes Default Yes Heat Transfer Coefficient Constant value Phase-specific values Power law expression Film coefficients Exchanger geometry User subroutine Yes Default Yes No No No Yes Yes Yes Yes Default Yes Film Coefficient Constant value Phase-specific values Power law expression Calculate from geometry No No No No Yes Yes Yes Default Pressure Drop Outlet pressure Calculate from geometry Default No Yes Default Calculating the Log-Mean Temperature Difference Correction Factor The standard equation for a heat exchanger is: Q = U A LMTD where LMTD is the log-mean temperature difference. This equation applies for exchangers with pure countercurrent flow. The more general equation is: Q = U A F LMTD where the LMTD correction factor, F, accounts for deviation from countercurrent flow. Use the LMTD Correction Factor field on the Setup Specifications sheet to enter the LMTD correction factor. 3-8 Unit Operation Models