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Modeling & Simulation Lab Report

Mixers/Splitters

Name Figure Purpose, Basic Principle & Applications

Mixer

As the name specifies it is used for the mixing of streams. Mixer combines material streams (or heat streams or work streams) into one stream. A single Mixer block cannot mix streams of different types (material, heat, work).

FSplit

Use FSplit to model a splitter to combine streams of same type and divide the resulting stream into two or more streams of the same type 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

SSplit

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.


Separators

Name Figure Purpose, Basic Principle & Applications Flash2

Use Flash2 to model flashes, evaporators, knock-out drums, and other single-stage 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.

Flash3

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.

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.


Sep

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.

Sep2

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.


Heat Exchangers

Name Figure Purpose, Basic Principle & Applications Heater

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.

HeatX

HeatX can model a wide variety of shell and tube heat exchanger types including:

• Countercurrent and co-current • 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.

HeatX can

• Perform design calculations • Perform mechanical vibration analysis • Estimate fouling factors


MHeatX

Use MHeatX to represent heat transfer between multiple hot and cold streams, such as in an LNG exchanger. You can also use MHeatX for two-stream heat exchangers. Free water can be decanted from any outlet stream. MHeatX ensures an overall energy balance but does not account for the exchanger geometry.

MHeatX can perform a detailed, rigorous internal zone analysis to determine the internal pinch points and heating and cooling curves for all streams in the heat exchanger. MHeatX can also calculate the overall UA for the exchanger and model heat leak to or from an exchanger.

HXFlux

HxFlux is used to perform heat transfer calculations between a heat sink and a heat source, using convective heat transfer. The driving force for the convective heat transfer is calculated as a function of log-mean temperature difference (LMTD).

Specify variables among inlet and outlet stream temperatures, duty, heat transfer coefficient, and heat transfer area. HxFlux calculates the unknown variable and determines the log-mean temperature difference, using either the rigorous or the approximate method.

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Column

Name Figure Purpose, Basic Principle & Applications DSTW

DSTWU performs shortcut design calculations for single-feed, two-product distillation columns with a partial or total condenser.

DSTWU assumes constant molal overflow and constant relative volatilities. For the specified recovery of light and heavy key components, DSTWU estimates:

• Minimum reflux ratio • Minimum number of theoretical stages

DSTWU also estimates the optimum feed stage location and the condenser and reboiler duties. DSTWU can produce tables and plots of reflux ratio versus number of stages.

Distl

RadFrac

Distl simulates multistage multicomponent columns with a feed stream and two product streams.

Distl performs shortcut distillation rating calculations for a single-feed, two-product distillation column. The column can have either a partial or total condenser. Distl calculates product composition using the Edmister approach. Distl assumes constant mole overflow and constant relative volatilities..


Extract

Extract is a rigorous model for simulating liquid-liquid extractors. It can have multiple feeds, heater/coolers, and side streams. Extract can calculate distribution coefficients using:

• An activity coefficient model or equation of state capable of representing two liquid phases

• A built-in temperature-dependent correlation (KLL Correlation sheet)

• A Fortran subroutine (KLL Subroutine sheet)

Although equilibrium stages are assumed, you can specify component or stage separation efficiencies. Extract can be used only for rating calculations.

MultiFrac

MultiFrac is a rigorous model for simulating general systems of interlinked multistage fractionation units. MultiFrac models can handle a complex configuration consisting of:

• Any number of columns, each with any number of stages

• Any number of connections between columns or within each column

• Arbitrary flow splitting and mixing of connecting streams

MultiFrac can handle operations with:

• Side strippers • Pumparounds • External heat exchangers • Single-stage flashes • Feed furnace

Typical MultiFrac applications include:

• Heat-interstaged columns, such as Petlyuk towers • Air separation column systems • Absorber/stripper combinations • Ethylene plant primary fractionator/quench tower

combinations


SCFrac

Use SCFrac to simulate complex distillation columns with a single feed, optional stripping steam, and any number of products. SCFrac also estimates the number of theoretical stages and the heating/cooling duty for each section.

SCFrac can model complex columns, such as crude units and vacuum towers. SCFrac performs shortcut distillation calculations for columns with a single feed, one optional stripping steam stream, and any number of products. SCFrac divides a column with n products into n – 1 sections. These sections are numbered from the top down. SCFrac assumes:

• Relative volatilities are constant for each section • The flow of liquid from section to section is

negligible

PetroFrac

PetroFrac is a rigorous model designed for simulating all types of complex vapor-liquid fractionation operations in the petroleum refining industry. Typical operations include:

• Preflash tower • Atmospheric crude unit • Vacuum unit • Catalytic cracker main fractionator • Delayed coker main fractionator • Vacuum lube fractionator

You also can use PetroFrac to model the primary fractionator/quench tower combination in the quench section of an ethylene plant. PetroFrac can detect a free-water phase in the condenser or anywhere in the column. It can decant the free-water phase on any stage.


Reactors

Name Figure Purpose, Basic Principle & Application RStoic

Use RStoic to model a reactor when:

• Reaction kinetics are unknown or unimportant and • Stoichiometry and the molar extent or conversion is known for

each reaction

RStoic can model reactions occurring simultaneously or sequentially. In addition, RStoic can perform product selectivity and heat of reaction calculations.

RYield

Use RYield to model a reactor when:

• Reaction stoichiometry is unknown or unimportant • Reaction kinetics are unknown or unimportant • Yield distribution is known

You must specify the yields (per mass of total feed, excluding any inert components) for the products or calculate them in a user-supplied Fortran subroutine. RYield normalizes the yields to maintain a mass balance. RYield can model one-, two-, and three-phase reactors.

REquil

Use REquil to model a reactor when:

• Reaction stoichiometry is known and • Some or all reactions reach chemical equilibrium

REquil calculates simultaneous phase and chemical equilibrium. REquil allows restricted chemical equilibrium specifications for reactions that do not reach equilibrium. REquil can model one- and two-phase reactors.


RGibbs

RGibbs uses Gibbs free energy minimization with phase splitting to calculate equilibrium. RGibbs does not require that you specify the reaction stoichiometry. Use RGibbs to model reactors with:

• Single phase (vapor or liquid) chemical equilibrium • Phase equilibrium (an optional vapor and any number of liquid

phases) with no chemical reactions • Phase and/or chemical equilibrium with solid solution phases • Simultaneous phase and chemical equilibrium

RGibbs can also calculate the chemical equilibria between any number of conventional solid components and the fluid phases. RGibbs also allows restricted equilibrium specifications for systems that do not reach complete equilibrium.

RCSTR

RCSTR:

RCSTR rigorously models continuous stirred tank reactors. RCSTR can model one-, two-, or three-phase reactors. RCSTR assumes perfect mixing in the reactor, that is, the reactor contents have the same properties and composition as the outlet stream.

RCSTR handles kinetic and equilibrium reactions as well as reactions involving solids.

RPlug

RPlug is a rigorous model for plug flow reactors. RPlug assumes that perfect mixing occurs in the radial direction and that no mixing occurs in the axial direction. RPlug can model one-, two-, or three-phase reactors. You can also use RPlug to model reactors with coolant streams (co-current or counter-current).

RPlug handles kinetic reactions, including reactions involving solids. You must know the reaction kinetics when you use RPlug to model a reactor. You can provide the reaction kinetics through the built-in Reactions models or through a user-defined Fortran subroutine.

RBatch

RBatch is a rigorous model for batch or semi-batch reactors. Use RBatch when you know the kinetics of the reactions taking place. You can specify any number of continuous feed streams. A continuous vent is optional. The reaction runs until it reaches a stop criterion that you specify.


Batch operations are unsteady-state processes. RBatch uses holding tanks and your specified cycle times to provide an interface between the discrete operations of the batch reactor and the continuous streams used by other models.

RBatch can model one-, two-, or three-phase reactors.


Pressure Changers

Name Figure Purpose, Basic Principle & Application

Pump

Use Pump to model a pump or a hydraulic turbine.

Pump is designed to handle a single liquid phase. For special cases, you can specify two- or three-phase calculations to determine the outlet stream conditions and to compute the fluid density used in the pump equations. The accuracy of the results depends on a number of factors, such as the relative amounts of the phases present, the compressibility of the fluid, and the efficiency specified.

Use Pump to change pressure when the power requirement is needed or known. For pressure change only, you can use other models such as Heater.

Pump can model pumps and hydraulic turbines.

Compressor

Use Compr to model a compressor or turbine. For a compressor, the following types are available:

• A polytropic centrifugal compressor • A polytropic positive displacement compressor • An isentropic compressor

For a turbine, only the isentropic type is allowed.

Use Compr to change stream pressure when energy-related information, such as power requirement, is needed or known.

Compr can handle single-phase as well as two- and three-phase calculations.


Multi Stage Compressor

Use MCompr to model:

• A multi-stage polytropic compressor • A multi-stage polytropic positive displacement compressor • A multi-stage isentropic compressor • A multi-stage isentropic turbine

For polytropic compressors, MCompr can handle a single, compressible phase. For special cases you can specify two- or three-phase calculations. These calculations determine the outlet stream conditions and the properties used in the compressor equations. The accuracy of results depends primarily on the relative amounts of the phases present and the efficiency specified. The rigorous polytropic compressor uses real fluid properties calculated from the property method you specify.

Valve

Valve models control valves and pressure changers. Valve relates the pressure drop across a valve to the valve flow coefficient. Valve assumes the flow is adiabatic, and determines the thermal and phase condition of the stream at the valve outlet. Valve can perform one-, two-, or three-phase calculations.

Pipe

Pipe calculates the pressure drop and heat transfer in a single segment pipe. You can also use Pipe to model the pressure drop due to fittings.

Pipe handles a single inlet and outlet material stream. Pipe assumes the flow is one-dimensional, steady-state, and fully developed (that is, no entrance effects are modeled). Pipe can perform one-, two-, or three-phase calculations. Flow direction and elevation angle are arbitrary.

To model multiple pipe segments of different diameters or elevations, use Pipeline instead of Pipe.

Pipeline

Use Pipeline to calculate the pressure drop in a straight pipe or annular space. Pipeline can:

• Simulate a piping network with successive blocks, including wellbores and flowlines

• Contain any number of segments within each block to describe pipe geometry

• Calculate inlet or discharge conditions • Calculate pressure drops for one-, two-, or three-phase vapor and

liquid flows. Pipeline treats multiple liquid phases (for example, oil and water) as a single homogeneous liquid phase for pressure-


drop and holdup calculations. If vapor-liquid flow exists, Pipeline calculates liquid holdup and flow regime (pattern).

You may specify a flowing fluid temperature profile, or Pipeline can calculate it from heat transfer calculations. Flow is assumed to be one-dimensional, steady-state, and fully developed (no entrance effects are modeled). Flow direction and elevation angle are arbitrary. To model a single pipe segment with constant diameter and elevation, you can also use Pipe.


Manipulators

Name Figure Purpose, Basic Principle & Applications

Stream Multiplier

Mult multiplies the component flow rates and the total flow rate of a material stream by a factor you supply on the Mult Input Specifications sheet. For heat or work streams, Mult multiplies the heat or work flow. Select the Heat (Q) and Work (W) Mult icons from the Model Library for heat and work streams respectively.

Mult is useful when other conditions during the simulation determine the flow rate of the stream. Mult does not maintain heat or material balances. For material streams, the outlet stream has the same composition and intensive properties as the inlet stream.

Use the Mult form to specify the stream multiplication factor and diagnostics message levels.

Stream Duplicator

Dupl copies an inlet stream (material, heat, or work) to any number of duplicate outlet streams. It is useful for simultaneously processing a stream in different types of units. Select the Heat (Q) and Work (W) Dupl icons from the Model Library for heat and work streams respectively. Dupl does not maintain heat or material balances.

Use the Dupl form to specify diagnostics message levels.

ClChng

ClChng changes the stream class between blocks and flowsheet sections. You can use ClChng to add or delete empty solid substreams between flowsheet sections. ClChng does not represent a real unit operation.

Use the ClChng Input Form to specify diagnostics message levels.

Stream Analyzer

The Analyzer block is a mole flow based model that allows you to calculate values of material stream component fractions and stream properties for use in the equation-oriented (EO) simulation and optimization phases of a flowsheet. You can specify one inlet and one outlet material stream, or specify a stream to analyze on the Input form.

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Analyzer performs selected analyses on a connected or referenced stream.You refer an existing stream in the flowsheet or specify the connectivity by identifying an inlet and an outlet stream.

FEEDBL

Use Feedbl to maintain compatibility with Feedbl blocks in RT-OPT version 10.0 projects. If you are creating a new simulation in Aspen Plus, do not use Feedbl. Aspen Plus automatically creates the necessary feed specifications.

Selector

The Selector block is a switch between different inlet streams. Any number of streams may enter the block, and one designated stream from among these is copied to the outlet stream. The Selector block can be used with material, heat, or work streams.

Use the Selector Input Form to specify which stream is copied to the outlet stream.

QTVEC

Qtvec is a load stream manipulator which can be used to combine multiple heat streams into a single load stream or to add an additional temperature and duty point to an existing load stream.

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Solids

Name Figure Purpose, Basic Principle & Application

Crystallizer

Crystallizer models a mixed suspension, mixed product removal (MSMPR) crystallizer. It performs mass and energy balance calculations and optionally determines the crystal size distribution.

Crystallizer assumes that the product magma leaves the crystallizer in equilibrium, so the mother liquor in the product magma is saturated.

The feed to Crystallizer mixes with recirculated magma and passes through a heat exchanger before it enters the crystallizer.

The product stream from Crystallizer contains liquids and solids. You can pass this stream through a hydrocyclone, filter, or other fluid-solid separator to separate the phases. Crystallizer can have an outlet vapor stream.

Crusher

Use Crusher to simulate the breaking of solid particles.

Crusher can model the wet or dry continuous operation of:

• Gyratory/jaw crushers • Single-roll crushers • Multiple-roll crushers • Cage mill impact breakers

Crusher assumes the feed is homogeneous. The breaking process creates fragments with the same composition as the feed. Crusher calculates the power required for crushing, and the particle size distribution of the outlet solids stream.

Screen

Screen simulates the separation by screens of a mixture containing various sizes of solid particles into particles that have more uniform sizes than the original mixture. You can use Screen to model wet or dry operations and upper or lower level screens.


Screen calculates the separation efficiency of the screen from the size of screen openings you specify.

Cyclone

Cyclone separates an inlet gas stream containing solids into a solids stream and a gas stream carrying the residual solids.

Use Cyclone to simulate cyclone separators in which solid particles are removed by the centrifugal force of a gas vortex. You can use Cyclone to size or rate cyclone separators. In simulation mode, Cyclone calculates the separation efficiency and pressure drop from a user-specified cyclone diameter.

In design mode, the cyclone geometry is calculated to meet the user-specified separation efficiencies and maximum pressure drop. In both calculation modes, the particle size distributions of the outlet solids streams are determined.

VScrub

Use VScrub to simulate venturi scrubbers.

Venturi scrubbers remove solid particles from a gas stream by direct contact with an atomized liquid stream.

You can use VScrub to rate or size venturi scrubbers.

CFuge

Use CFuge to simulate centrifuge filters. The centrifuge filters separate liquids and solids by the centrifugal force of a rotating basket.

Use CFuge to rate or size centrifuge filters.

CFuge assumes that the separation efficiency of the solids equals 1, so that the outlet filtrate stream contains no residual solids.

Filter

Use Filter to simulate continuous rotary vacuum filters. You can use Filter to rate or size rotary vacuum filters.

Filter assumes the separation efficiency of the solids equals 1, so that the outlet filtrate stream contains no residual solids.

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CCD

CCD simulates a counter-current decanter or a multistage washer. CCD calculates the outlet flow rates and compositions from:

• Mixing efficiency • Liquid-to-solid mass ratio of each stage

CCD can calculate:

• The heat duty profile from a specified temperature profile • The temperature profile from a specified heat duty profile

Dryer

Use the sheets on the Dryer | Input form to enter the specifications for the Dryer model.

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