PHREEQC Evaporator

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Navigation: Models -> TPS Models -> PHREEQC Models -> PHREEQC Evaporator

PHREEQC
Overview
PHREEQC
Model Configuration
PHREEQC
Direct Calc Model
PHREEQC
Side Calc Model
PHREEQC
Reactor
PHREEQC
Evaporator
PHREEQC
Flash Tank
PHREEQC
Reverse Osmosis

See Also PHREEQC SysCAD Project Workflow


New for Build 139. Currently in BETA - contact SysCAD for demonstrations or further information.

Related Links: Potash Evaporator, Evaporator


General Description

The Evaporator is used to 'flash' a feed stream to produce a liquid and vapour product at a set pressure or temperature. The unit may also have connections to an Embedded or External Heat Exchanger.

There are two operational modes for the Evaporator:

  1. as a stand-alone unit; or
  2. as part of a Flash Train.

The user sets the operational mode of the Evaporator. However, if the user sets the mode as Flash Train and the Evaporator is NOT connected to another Evaporator (Embedded Shell), Barometric Condenser, Heat Exchangers of any Flash Train aware destination unit, the model will go to an error state.

Crystallization

The Evaporator model may be used as a Crystallizer, as it behaves in the same way. Vapour is flashed off and the remaining solution is then supersaturated with the required species. This species then precipitates out as the crystal product.

If the PHREEQC model being used by the PHREEQC Evaporator has solubility data for the species, then the amount of species that precipitates will be automatically calculated. The solution properties will be calculated by PHREEQC and by the selected SysCAD species model.

Heat Exchange Options

The user may select any of the following 3 options for heat exchange:

  1. None - no Heat Exchange is required.
  2. Embedded - The Embedded Heat Exchange model uses a Shell and Tube style heat exchanger. The user connects the Steam (or other cooling or heating medium) to the Embedded HX Shell connection and the Condensate (or return heat exchange medium) to the Embedded HX Shell. The recycle flow to the heat exchanger must to be specified, but this is handled internally within the unit.
  3. External - External Heat Exchange models the use of external heat exchangers taking a recycle stream from the Evaporator contents and heating, or cooling, this recycle stream. The user must connect the Recycle stream from the Evaporator to an external heat exchanger. This recycle stream is either heated or cooled then returned to the Evaporator via the Recycle stream. The recycle flow to the heat exchanger must to be specified, and this is sent to the Recycle connection.

NOTES:

  1. The difference between the two heat exchange methods:
    • With Embedded heat exchange, the steam and condensate streams (or other heat exchange medium) are connected directly to Evaporator via the Embedded HX Shell connections. The Recycle stream to the heat exchanger is handled internally within the unit.
    • With external heat exchange, the recycle stream is sent to an external heat exchanger via the Recycle output connection and returned to the Evaporator via the Recycle input connection.
  2. For both Embedded and external heat exchange the user must set the recycle flow to the heat exchanger.

Diagram

Evaporator3.png

  • The diagram shows default drawings of the Evaporator with connecting streams, with heat exchanger connections.
  • The Heat Exchanger connections are optional.
  • The user does not have to connect a stream to the 'Overflow' connection, as the Evaporator will operate without this connection.
  • The physical location of the streams connecting to the Evaporator is unimportant. The user may connect the streams to any position on the unit.
  • When inserting an Evaporator into a flowsheet, the user may choose a different symbol from the menu.

Inputs and Outputs

Label Required
Optional
Input
Output
Number of Connections Description
Min Max.
Feed 1 Required In 1 20 Feed to the Evaporator.
Embedded HX Shell Optional In 0 10 Inlet stream to the Shell side of internal Shell and Tube Heat Exchanger (often the steam inlet).
Recycle Optional In 0 1 Recycle stream from an external Shell and Tube Heat Exchanger to the Evaporator.
Product Required Out 1 1 Product Slurry outlet - this stream normally contains the majority of the solids.
Vent Required Out 1 1 Vent outlet containing all Vapours from the unit.
Overflow Optional Out 0 1 Overflow liquor outlet.
Embedded HX Shell Optional Out 0 1 Outlet stream from the Shell side of internal Shell and Tube Heat Exchanger (often the condensate).
Recycle Optional Out 0 1 Recycle stream from the Evaporator to an external Shell and Tube Heat Exchanger.

Behaviour when Model is OFF

If the user disables the unit, by un-ticking the On tick box, then the following actions occur:

  • All material in streams connected to the 'Feed' and 'Recycle' inlets will flow straight out of the 'Product' outlet, with no change in phase or energy exchange with material flowing through the internal heat exchanger;
  • All material in streams connected to the 'Embedded HX Shell' connections will have no change in phase or energy exchange with material flowing through the Evaporator;
  • No sub-models will be called.

So basically, the unit will be 'bypassed' without the user having to change any connections.


Model Theory

Vapour Liquid Equilibrium

The unit is configured to achieve vapour : liquid equilibrium at a required pressure (or temperature) using the user defined VLE method. Any solids that may be in the stream entering the unit are ignored in the flash calculations. However the enthalpy balance does include the solids. For further information on the theory for the VLE calculations see Vapour Liquid Equilibrium (VLE).

Pressure used for Evaluation Block Calculations

For an Evaporator in the Stand Alone mode the calculations, including the PHREEQC Calculations may be performed at either:

  • The Feed pressure; or
  • The final pressure; or
  • The pressure into the Body of the Evaporator if the user has chosen Final Temperature as the mode.

The user enables the 'UseFeedP' tickbox on the first tab of the Evaporator to use the Feed pressure.

Using the Feed or other pressure may produce small differences in the final results from the Evaporator.

Flow Chart

TPS Evaporator 139.png

PHREEQC

The PHREEQC Evaporator uses the PHREEQC algorithms and data to determine the status of the solution. Mapping of SysCAD to PHREEQC streams is done as illustrated below.

PHREEQC MapCombined.png

The streams are mixed using the SysCAD enthalpy context prior to being loaded into PHREEQC.

The PHREEQC Evaporator can be incorporated into a SysCAD flowsheet, it can be connected with SysCAD inlet and outlet streams.

  1. User connects the PHREEQC Evaporator with SysCAD input streams,
  2. The SysCAD feed stream(s) using SysCAD species is converted into PHREEQC "Input" using PHREEQC Species. The species mapping is defined in the corresponding PHREEQC Model Configuration unit model.
  3. The PHREEQC Evaporator calls the PHREEQC algorithms to determine the status of the mixture using the converted PHREEQC "input" data.
  4. The PHREEQC results are displayed in the "output" tab using PHREEQC species.
    • If the PHREEQC reactor is in side calc mode, the results are NOT converted into SysCAD species. (SysCAD stream outlet = sum of SysCAD inlet streams, no change will occur)
    • If the PHREEQC reactor is in Evaporator mode, then the results are converted back into SysCAD species. Please see Species Mapping for more information.

NOTES:

  • The Input, Output and Diff tab pages are displayed using PHREEQC species, as defined in the PHREEQC database file (.dat) specified in the corresponding PHREEQC Model Configuration unit model.
  • The species used in the SysCAD project are shown on the optional Sp pages, shown as part of the QFeed, QBypass, QUnmapped, QRxnProdBypass and QProd pages.


Data Sections

The default access window consists of several sections:

  1. Evaporator - The first tab contains general information relating to the unit and allows the user to set the Heat Exchange type and flows.
  2. Results - This tab contains the results fields for the Evaporator.
  3. HX - Optional tab, only visible if an Internal Heat Exchanger is selected. (In this case the Internal HX connections should be connected).
  4. Separ - Only visible if the Overflow stream is connected. The tab allows the user to specify the split between the Product and Overflow streams.
  5. VLE - Always visible.
  6. QFeed - Optional tab, only visible if ShowQFeed is enabled. This page shows the properties of the mixed stream as the feed to the Evaporator.
    • This is before any Evaluation Block models are evaluated.
  7. QProd - This page shows the properties of the Evaporator discharge as a single stream.
    • This is AFTER the flash calculations, but before the split to slurry, overflow and vapour streams.
  8. Info tab - contains general settings for the unit and allows the user to include documentation about the unit and create Hyperlinks to external documents.
  9. Links tab, contains a summary table for all the input and output streams.
  10. Audit tab - contains summary information required for Mass and Energy balance. See Model Examples for enthalpy calculation Examples.

Evaporator Page

Unit Type: Evaporator - The first tab page in the access window will have this name.

Vapour Entrainment

Tag (Long/Short) Input / Calc Description/Calculated Variables / Options
Tag Display This name tag may be modified with the change tag option.
Condition Display OK if no errors/warnings, otherwise lists errors/warnings.
ConditionCount Display The current number of errors/warnings. If condition is OK, returns 0.
GeneralDescription / GenDesc Display This is an automatically generated description for the unit. If the user has entered text in the 'EqpDesc' field on the Info tab (see below), this will be displayed here. If this field is blank, then:
  • For pipes, SysCAD will use the text in the 'ConnectDesc' field - this displays the Source and Destination tags of the pipe;
  • For Feeders/Cross Page Connectors, SysCAD will display the state of the unit, i.e. if it is a Feeder or a Sink, etc.;
  • For other units SysCAD will display the unit class ID.

Requirements:

On Tickbox This variable in used to turn the unit ON or OFF. If this not ticked, the material will flow out of the Product outlet with no change in state, i.e. the unit acts as a pipe.
Mode Stand Alone (Manual) The Evaporator will act as a 'Stand Alone' unit and the user may set the required operating Pressure or Temperature.
Flash Train The Evaporator will act as part of a Flash Train. In this mode the Evaporator vent must be connected to a steam consumer, such as a Barometric Condenser, Shell and Tube Heat Exchanger, Shell and Tube Heat Exchanger 2 or a Direct Contact Heater. The steam requirements of the steam consumer will drive the operating pressure of the Evaporator, therefore the user may NOT set the operating temperature or pressure.
OperatingP

The user may only set the operating pressure or temperature of the Evaporator if it is NOT part of a Flash Train.

Method Atmospheric All flash calculations will be done at Atmospheric Pressure. The atmospheric pressure is calculated by SysCAD based on the user defined elevation (default elevation is at sea level = 101.325 kPa). The elevation can be changed on the Environment Tab page of the Plant Model.
RequiredP All flash calculations will be done at the user specified pressure.
RequiredT All flash calculations will be done at the user specified temperature.
PressureReqd / P_Reqd Input The Required Flash Pressure - This is only visible if the RequiredP Method is selected.
TemperatureReqd / T_Reqd Input The Required Flash Temperature - This is only visible if the RequiredT Method is selected.
Result Display This field displays the operating pressure of the Evaporator.
MinFlashP Input The minimum Pressure at which the Evaporator may operate. This is visible if the Evaporator is configured as part of a Flash Train, as it will not allow the unit to drop to an unrealistic pressure.
UseFeedP Tickbox This is only visible if the mode = Stand Alone. If this field is enabled then all of the Evaluation Block calculations will be performed at the Feed pressure. Otherwise, if it is not enabled, the calculations will be performed at the final pressure. See also Model Theory.

Body PHREEQC Block

This program contains PHREEQC Copyright U.S. Geological Survey (USGS)

AllowUnmappedDuringSolve / Slv.AllowUnmapped Tickbox If enabled, unmapped species will be ignored while the model is solving and no warnings will be given. If at the end of the solution there are still unmapped species, a warning will be given.
Chemistry Model
ChemModel...
UnitTag List The tag of the relevant PHREEQC Model Configuration unit model- this may be chosen from the drop down list of all PHREEQC Model Configuration unit models available in the project.
ChemModel.Selected Display The tag of the relevant PHREEQC Model Configuration unit model.
Check Check Tag.png If the user clicks on this button, SysCAD will check that the UnitTag is a valid PHREEQC Model Configuration unit model.
ConnOK Tickbox If SysCAD finds a valid PHREEQC Model Configuration unit model, then this field will be enabled.
Status OK The specified chemistry model (PHREEQC Model Configuration) has been initialised correctly and the database file has been found and loaded correctly.
ChemModel Tag not Specified No tag has been specified for the Chemistry Model. Specify the desired Chemistry Model (PHREEQC Model Configuration) in the UnitTag field.
Valid ChemModel Tag Required The tag specified for the Chemistry Model in the UnitTag field is invalid and needs to be corrected.
Init Required The specified Chemistry Model (PHREEQC Model Configuration) needs to be initialised.
ChemModel Load Required The database of the specified Chemistry Model ((PHREEQC Model Configuration) needs to be loaded.
DLL or Version Error There is a problem with the PHREEQC DLL or version.
Init Failed Initialisation of the specified Chemistry Model ((PHREEQC Model Configuration) has been attempted but failed.
UseSysCADVLE / VLE.On Tickbox This can be used to switch on the SysCAD Vapour Liquid Equilibrium (VLE) calculator. If this is 'On' then the associated page, VLE becomes visible and may be configured.
UseCFE Tickbox If this is ticked, then the CFE (Constrained Free Energy) tab page will appear.
  • If CFE is not available, this ticked box will be greyed out.
  • This option allows a portion of a species to be locked up and not allowed to react.
  • Applying CFE can have a significant effect on the final composition, use of this feature requires detailed knowledge of the process chemistry.
WithBypass Tickbox If this is ticked, then the Bypass tab page will appear.
ShowQUnmapped Tickbox Allows the user to view the QUnmapped and associated tab pages. See Material Flow Section. This is the SysCAD species flows which are not mapped to PHREEQC species, and therefore are not taken into account in the PHREEQC calculation.
ShowQBypass Tickbox Only visible when WithBypass is ticked. Allows the user to view the QBypass and associated tab pages. See Material Flow Section. This is the SysCAD species flows which bypass the PHREEQC calculation.
ShowQRxnBypass Tickbox Only visible when WithBypass is ticked. Allows the user to view the QRxnBypass and associated tab pages. See Material Flow Section.
ShowRxnDiff Tickbox Allows the user to view the Diff tab page. This shows the difference between the mapped input stream seen by PHREEQC and the PHREEQC calculation results.
ShowPlotter Tickbox Allows the user to perform a parameter sweep using the product stream of the reactor. If this is ticked, then the ParamSweep tab page will appear.
ShowSpIonRebuildRxns Tickbox When checked, the SpIonRxns Tab appears which shows how ions from the PHREEQC product stream were assembled into SysCAD species.
PhaseElemDeportment Tickbox Allows the user to view the Phase element deportment tab page. This shows how the elements move between phases due to the PHREEQC calculation results.
IPhaseElemDeportment Tickbox Allows the user to view the IPhase element deportment tab page. This shows how the elements move between individual phases due to the PHREEQC calculation results.
Environmental Heat Transfer
HeatLossMethod None No heat transfer between the unit and the environment.
Fixed HeatFlow The user specifies a fixed heat loss between the unit and the environment.
Ambient SysCAD calculates the overall heat loss based on user specified HTC and Area and the temperature difference between the Feed and environmental temperatures. The environmental temperature is assumed to remain constant.
EHX.HeatLossReqd Input Visible when the HeatLossMethod = Fixed HeatFlow. The required heat loss.
EHX.HTC Input Visible when the HeatLossMethod = Ambient. The Overall Heat Transfer coefficient.
EHX.Area Input Visible when the HeatLossMethod = Ambient. The Heat Transfer area.
EHX.AmbientT Display Visible when the HeatLossMethod = Ambient. The ambient temperature. The ambient temperature is specified in the Plant Model - Environment_Tab
EHX.HeatLoss Calc Visible when the HeatLossMethod = Ambient. The calculated heat flowrate.
FlashVapToLiquid Input This field allows the user to set a proportion of the flash vapour bypassing to the liquid stream. The default is 0%.
OtherGasToLiquid Input This field allows the user to set a proportion of any non-condensable gas bypassing to the liquid stream. The default is 0%.

Evaporator Heat Exchanger Options

HXType None The unit is not connected to a Heat Exchanger. No other fields are visible for the Heat Exchanger if this option is chosen.
External The Evaporator is connected to an External Heat Exchanger unit. This external unit may be any type of SysCAD model.
Embedded Heater The Evaporator contains an Embedded Heater. If this option is chosen, an additional page HX becomes visible and the user configures the Heat Exchanger within the Evaporator.
Embedded Cooler The Evaporator contains an Embedded Cooler. If this option is chosen, an additional page HX becomes visible and the user configures the Heat Exchanger within the Evaporator.
HXOut.SplitMethod Off No flow is sent to the Heat Exchanger.
Ratio to Feed MassFlow The flow to the Heat Exchanger (either Embedded or External) is a Ratio of the Feed mass. The composition and temperature of the stream to the Heat Exchanger is the same as the Combined Feed to the Evaluation Block.
Ratio to Prod MassFlow The flow to the Heat Exchanger (either Embedded or External) is a Ratio of the Product mass. The composition and temperature of the stream to the Heat Exchanger is the same as the Product from the Evaluation Block.
Note: The Product mass includes both the Overflow and the Product streams.
MassFlow The flow to the Heat Exchanger (either Embedded or External) is a fixed mass flow. The composition and temperature of the stream to the Heat Exchanger is the same as the Product from the Evaluation Block.
Note: The Product mass includes both the Overflow and the Product streams.
VolumeFlow The flow to the Heat Exchanger (either Embedded or External) is a fixed volumetric flow. The composition and temperature of the stream to the Heat Exchanger is the same as the Product from the Evaluation Block.
Note: The Product mass includes both the Overflow and the Product streams.
MassFlow Per Heater This option can be used for the Embedded Heater option, where user can define the number heaters used. The flow to each Embedded Heater is mass based. The composition and temperature of the stream to the Heat Exchanger is the same as the Product from the Evaluation Block.
Note: The Product mass includes both the Overflow and the Product streams.
VolumeFlow Per Heater This option can be used for the Embedded Heater option, where user can define the number heaters used. The flow to each Embedded Heater is volume based. The composition and temperature of the stream to the Heat Exchanger is the same as the Product from the Evaluation Block.
Note: The Product mass includes both the Overflow and the Product streams.
HXOut.RatioToFeedQm Input The flow to the Heat Exchanger (either Embedded or External) is Feed Flow times by Ratio.
HXOut.RatioToProdQm Input The flow to the Heat Exchanger (either Embedded or External) is Product Flow times by Ratio.
Note: The Product mass includes both the Overflow and the Product streams.
HXOut.MassFlowRqd Input The required Product mass flow to the Heat Exchanger (either Embedded or External).
HXOut.VolumeFlowRqd Input The required Product volumetric flow to the Heat Exchanger (either Embedded or External).
HXOut.EachHeaterQmRqd Input The required Product mass flow to the each Heater (Embedded Heater method only).
HXOut.EachHeaterQvRqd Input The required Product volumetric flow to the each Heater (Embedded Heater method only).

Options

VapStandardSpModel Tickbox This forces the vent stream to revert to the Standard species model. If this is NOT ticked, then the species model in the vent will be the same as the species model used in the Evaporator.
Normally this is left ticked, as the vent contains steam and the Standard species model will calculate all of the properties of steam correctly.
ShowQFeed Tick Box QFeed and associated tab pages (e.g. Qm) will become visible if this is enabled. These tabs will show the properties of the combined feed stream to the Unit. These values are BEFORE the Evaluation Block is processed.
ShowQBodyFeed Tick Box QBodyFeed and associated tab pages (e.g. Qm) will become visible if this is enabled. These tabs will show the properties of the feed to the Evaporator Body.
ShowQRecycle Tickbox This is only visible if an Embedded Heat Exchanger is used. If this option is ticked then the recycle stream to the Heat Exchanger is displayed as 'QRecycle' and the user may access properties of the stream feeding the Heat Exchanger.
ShowQProd Tick Box QProd and associated tab pages (eg Qm) will become visible if this is enabled. These tabs will show the properties of the product stream from the Unit, AFTER the Evaluation Block is processed, but BEFORE the stream is split to overflow and product.

Results Page

The page contains the results and the user may enable the Heat Exchanger function and set the type of Heat Exchanger (Internal or External) and the flow to the Heat Exchanger.

Tag (Long/Short) Input / Calc Description
Operating Conditions
TemperatureIn / Ti Calc The temperature of the combined Feed stream to the Evaporator.
PressureIn / Pi Calc The pressure of the combined Feed stream to the Evaporator.
VapFlashed.MassFlow / VapFlashed.Qm Calc The quantity of flashed vapour.
BPE Calc The Boiling Point Elevation used in the Flash calculations in the Evaporator.
FlashT Calc The final temperature (the Flash Temperature) in the Evaporator.
FlashP Calc The final pressure (the Flash Pressure) in the Evaporator.
Flash Train Macro Model
These extra fields are only visible if the unit is part of a Flash Train.
VapourMassFlow / VQm Calc The quantity of flashed vapour.
PressureReqd / P_Reqd Calc The required flash pressure calculated by the Flash Train.
FlashTrain Display A unique tag assigned to the Flash Train by SysCAD. Each unit in the Flash Train will have the same tag in this block.
FlashTearBlock Display Displays the name of the tear block that is part of the Flash Train.
FlashTrainEqp List This contains a list of all of the equipment tags in this Flash Train. For example, the list might be as follows:

Heat_Exchanger_2

Evaporator_1

PAdvBase Input Additional damping or acceleration for calculated pressure change (DP) for the iteration. DP = DP * PAdvBase when PAdvExtra=0.
PAdvExtra Input Additional damping or acceleration for calculated pressure change (DP) for the iteration. DP = DP * (PAdvBase + PAdvExtra*(VQmReqd-VQm)/Max(VQmReqd,VQm)).


Summary of input and output streams
Tag Feed Vapour OF Prod
Temperature / T Feed Temperature Vapour Temperature Overflow Temperature Product Temperature
MassFlow / Qm Feed Mass Flow Vapour Mass Flow Overflow Mass Flow Product Mass Flow
SolidMassFlow / SQm Feed Solids Mass Flow Vapour Solids Mass Flow Overflow Solids Mass Flow Product Solids Mass Flow
SolidFrac / Sf Feed Solids Fraction Vapour Solids Fraction Overflow Solids Fraction Product Solids Fraction


Results
BFeed.Temperature / BFeed.T Calc The temperature of the Feed to the Evaporator evaluation block.
BFeed.Pressure / BFeed.P Calc The Pressure used in the calculations in the Evaporator evaluation block. If the user has ticked the 'UseFeedP' then this will be the feed pressure to the Evaporator.
BFeed.MassFlow / BFeed.Qm Calc The mass flow of Feed to the Evaporator evaluation block.
BFeed.SolidMassFlow /BFeed.SQm Calc The mass flow of solids to the Evaporator evaluation block.
Body.SolidsYield Calc The mass flow of solids in the Product - mass flow of solids in the Feed.
SolidsYield Calc The mass flow of solids in the Product - mass flow of solids in the Feed.
Evaporator to Embedded or External Heater / Cooler
HXOut.MassFlow / HXOut.Qm Calc The mass flow to the specified Heat Exchanger.
HXOut.EachHeaterQm Calc The mass flow to the specified Heat Exchanger (per heater if more than one is used).
HXOut.VolFlow / HXOut.Qv Calc The volume flow to the specified Heat Exchanger.
HXOut.EachHeaterQv Calc The volume flow to the specified Heat Exchanger (per heater if more than one is used).
HXOut.Temperature / HXOut.T Calc The temperature of the stream to the specified Heat Exchanger.
Embedded Heater Recycle Loop convergence
RecycleConvergeMethod FullStream User can select to solve the recycle loop using Full stream data (loop has to solve and converge all mass and energy terms.)
Stream Mass Only User can select to solve the recycle loop using mass only. Loop will be solved when mass is converged, ignoring energy.
Duty User can select to solve the recycle loop using energy only. Duty from "shell" side of heat exchanger is added directly to the feed (recycle mass flow is not actually added). Loop will be solved when duty is matched, ignoring mass balance.
MaxIter(Global) Input The maximum number of iteration allowed within the recycle solver loop. Only shown for Stream Recycle Converge Methods.
IterSteps Calc The number of iteration used in the current step to solve the recycle loop. Only shown for Stream Recycle Converge Methods.
IterLastStep Calc The number of iteration used in the last step to solve the recycle loop. Only shown for Stream Recycle Converge Methods.
IterMaxInAStep Calc The maximum number of iterations (in a step) used to solve the recycle loop. Only shown for Stream Recycle Converge Methods.
IterTotal Calc The total number of iterations used to solve the recycle loop. Only shown for Stream Recycle Converge Methods.
FeedMaxDuty Calc The maximum amount of Duty that can be added to feed before temperature exceeds water critical temperature. Only shown for Duty Recycle Converge Method.
IterDuty Calc The number of iterations to apply duty and flash. When this is greater then 1 then the Duty from the condensing steam is applied in iterations, the values displayed on the VLE page reflect this. Only shown for Duty Recycle Converge Method.

HX Page

HX - Optional tab, only visible if an Internal Heat Exchanger is selected. (In this case the Internal HX connections should be connected).

Separ Page

The page allows the user to specify the split between the Underflow and Overflow streams.

Tag (Long/Short) Input / Calc Description/Calculated Variables / Options
Requirements
Split Method Mass Fraction The users may specify the mass fraction split between the Underflow and Overflow streams.
Mass Flow The user may specify the mass flow to either the Underflow or Overflow stream - either as total flow or on a phase basis.
Volume Fraction The users may specify the volumetric fraction split between the Underflow and Overflow streams.
Volume Flow The user may specify the Volume flow to either the Underflow or Overflow stream - either as total flow or on a phase basis.
Solid Separation The user may specify the solid split between the Underflow and Overflow streams.
Each of the above Split Methods will be described separately below:

Mass Fraction

With this method the user can specify the mass fraction to either the Underflow or the Overflow on a total or by phase basis.

SplitTo Underflow The user specifies the mass fraction split to the Underflow stream.
Overflow The user specifies the mass fraction split to the Overflow stream.
SplitBy Total The user specifies the total mass fraction split to the defined stream.
Phase The user specifies the solid and liquid mass fraction splits to the defined stream.
FracToUF or FracToOF Input This is visible if SplitBy = Total. The user sets the total mass fraction split to the defined stream.
SolidsToUF or SolidsToOF Input This is visible if SplitBy = Phase. The user sets the solid mass fraction split to the defined stream.
LiquidsToUF or LiquidsToOF Input This is visible if SplitBy = Phase. The user sets the liquid mass fraction split to the defined stream.

Mass Flow

With this method the user can specify the mass flow to either the Underflow or the Overflow on a total or by phase basis.

SplitTo Underflow The user specifies the mass flow to the Underflow stream.
Overflow The user specifies the mass flow to the Overflow stream.
SplitBy Total The user specifies the total mass flow to the defined stream.
Phase The user specifies the solid mass flow and the liquid mass flow to the defined stream.
UF or OF.MassFlowReqd /
UF or OF.QmReqd
Input This is visible if SplitBy = Total. The user sets the total mass flow to the defined stream.
UF or OF.SolidMassFlowReqd /
UF or OF.SolidQmReqd
Input This is visible if SplitBy = Phase. The user sets the solid mass flow to the defined stream.
UF or OF.LiquidMassFlowReqd /
UF or OF.LiquidQmReqd
Input This is visible if SplitBy = Phase. The user sets the liquid mass flow to the defined stream.

Volume Fraction

With this method the user can specify the volume fraction to either the Underflow or the Overflow on a total or by phase basis.

SplitTo Underflow The user specifies the volume fraction split to the Underflow stream.
Overflow The user specifies the volume fraction split to the Overflow stream.
SplitBy Total The user specifies the total volume fraction split to the defined stream.
Phase The user specifies the solid and liquid volume fraction splits to the defined stream.
FracToUF or FracToOF Input This is visible if SplitBy = Total. The user sets the total volume fraction split to the defined stream.
SolidsToUF or SolidsToOF Input This is visible if SplitBy = Phase. The user sets the solid volume fraction split to the defined stream.
LiquidsToUF or LiquidsToOF Input This is visible if SplitBy = Phase. The user sets the liquid volume fraction split to the defined stream.

Volume Flow

With this method the user can specify the volume flow to either the Underflow or the Overflow on a total or by phase basis.

SplitTo Underflow The user specifies the volume flow to the Underflow stream.
Overflow The user specifies the volume flow to the Overflow stream.
SplitBy Total The user specifies the total volume flow to the defined stream.
Phase The user specifies the solid Volume flow and the liquid volume flow to the defined stream.
UF or OF.VolFlowReqd /
UF or OF .QvReqd
Input This is visible if SplitBy = Total. The user sets the total volume flow to the defined stream.
UF or OF.SolVolFlowReqd /
UF or OF.SolidQvReqd
Input This is visible if SplitBy = Phase. The user sets the solid volume flow to the defined stream.
UF or OF.LiqVolFlowReqd /
UF or OF.LiquidQvReqd
Input This is visible if SplitBy = Phase. The user sets the liquid volume flow to the defined stream.

Solid Separation

With this method the user can choose between setting the solids composition of the Overflow stream or defining the Underflow flowrate and then specifying the solids composition of the Underflow.

SolidsSeparMethod OF Solids Fraction The user specifies the solids mass fraction in the Overflow stream.
OF Solids Conc The user specifies the solids concentration in the Overflow stream.
OF Solids Conc25 The user specifies the solids concentration at 25°C in the Overflow stream.
Recovery to UF The user specifies the solids recovery to the Underflow stream, i.e. how much of the solids in the unit reports to the Underflow stream.
UF MassFlow The user specifies the total mass flow of the Underflow stream.
UF VolumeFlow The user specifies the total volume flow of the Underflow stream.
Solids Density Each solid species is split between the Overflow and Underflow streams based on the user specified SolidsCutDensity.
Solids PSD The user then specifies one of the Solid Methods for defining a partition curve which then separates the solids based on PSD data in the feed.
OFSolidFracReqd Input This is visible if SolidsSeparMethod = OF Solids Fraction. The user sets the solids mass fraction in the Overflow stream.
OFSolidConcReqd Input This is visible if SolidsSeparMethod = OF Solids Conc. The user sets the solids concentration in the Overflow stream.
OFSolidConc25Reqd Input This is visible if SolidsSeparMethod = OF Solids Conc25. The user sets the solids concentration at 25°C in the Overflow stream.
SolidsToUFReqd Input This is visible if SolidsSeparMethod = Recovery to UF. The user sets the mass fraction of solids in the unit that must report to the Underflow stream.
UFQmReqd Input This is visible if SolidsSeparMethod = UF MassFlow. The user sets the total mass flow of the Underflow stream.
UFQvReqd Input This is visible if SolidsSeparMethod = UF VolumeFlow. The user sets the total volume flow of the Underflow stream.
CutDensityMethod This is visible if SolidsSeparMethod = Solids Density.
Simple If the density of a solid species is greater than the SolidsCutDensity then it is all sent to the Underflow stream, otherwise it is all sent to the Overflow stream.
Erf An error function is used to determine the split of each solid species between the Overflow and Underflow streams based on the species density, SolidsCutDensity and alpha.
Logistic This method is based on a Logisitic type of function. It is used to determine the split of each solid species between the Overflow and Underflow streams based on the species density, SolidsCutDensity and alpha.
SolidsCutDensity Input This is visible if SolidsSeparMethod = Solids Density. The user sets the solids cut density which is used to determine how much of each solid species to send to the Overflow and Underflow streams.
ErfAlpha Input This is visible if SolidsSeparMethod = Solids Density and CutDensityMethod = Erf. User specified efficiency parameter, alpha. See Erf Cut Density Method for more information.
LogisticAlpha Input This is visible if SolidsSeparMethod = Solids Density and CutDensityMethod = Logistic. User specified efficiency parameter, alpha. See Logistic Cut Density Method for more information.
SolidsBypassToUF Input This is visible if SolidsSeparMethod = Solids Density. The fraction of solids which bypasses the separation by density calculations and passes straight to the underflow.
The following Solids Method (with Solids PSD) assumes the Solid-Liquid separator is used to emulate the screen.
Solid Separation Requirements.
SolidMethod Simple (no PSD) The feed does not need size distribution for this method and the unit acts as a simple mass splitter. If the user chooses this mode then they must define the solids and liquids split from the unit. (This option is visible for the Screen 2 model only)
Partition Curve The user inputs a Partition curve (fraction of feed solids per size interval reporting to the oversize) on the PartCrv(deck number) tab. The screen will use this curve, so the size distribution in the feed to the screen has no effect on products.
Note: A single partition curve is used for all the size distributions.
Whiten The screen model will calculate the solids split using the Whiten method. The user must specify the d50 and alpha, a measure of the sharpness of separation.
Karra The screen model will calculate the solids split using the Karra method. The user may specify either the d50 or the Screen area and Cut aperture.
Rosin-Rammler This method is based on a Rosin-Rammler type of function with the efficiency curve expression derived by Reid and Plitt. User must specify d50, sharpness of separation, maximum size allowed to undersize and minimum percent of solids reporting to oversize.
Lynch This method is based on a Lynch type of function. User must specify d50, sharpness of separation (m), maximum size allowed to undersize and minimum percent of solids reporting to oversize.
DelVillar-Finch This method is similar to Rosin-Rammler, but includes a term for the "fish hook" effect for entrainment.

Solid Method - Whiten

Whiten.CalcMethod d50 The user specifies the d50 of the screen.
d50 with Beta The user specifies the d50 of the screen and uses the Beta method to adjust for uncertainties in the finer fractions.
Aperture, Eff The user specifies the Screen Aperture and Efficiency. The unit then calculates the d50 of the Screen deck.
Aperture, Eff with Beta The user specifies the Screen Aperture and Efficiency and uses the Beta method to adjust for uncertainties in the finer fractions. The unit then calculates the d50 of the Screen deck.
Whiten.Aperture Input Only visible if one of the two Aperture CalcMethods are chosen. The Screen Aperture, used to calculate the d50.
Whiten.Efficiency / Eff Input The Whiten Efficiency of the Screen.
  • If the user selects one of the 'Aperture' methods, then this is used to calculate the d50.
  • If the user selects one of the 'd50' methods, then this value is used to calculate the Screen aperture (see Theoretical Nominal Screen Aperture).
Whiten.d50 Input/Calc If either of the d50 methods are chosen, this is entered by the user. If the Aperture method is chosen, this is a calculated value. This is the particle size with a 50% probability of reporting to the over or under size.
Whiten.Alpha Input The Efficiency parameter, alpha. An alpha value of between 8 and 15 is normal for screening. However, this does depend on the screening conditions and hence experience and/or test or plant data is required for accurate results.
Whiten.Beta Input Only visible if the d50 with Beta or Aperture,Eff with Beta CalcMethods are chosen. The Beta Efficiency parameter. This value takes into account uncertainties in the finer size fractions.
Whiten.Beta* Calc Only visible if the d50 with Beta or Aperture,Eff with Beta CalcMethods are chosen. Efficiency parameter.
Whiten.MaxSizeToUS Input The model will ensure that all particles LARGER than this size all report to the Screen deck oversize product. This value is often = Screen Deck Aperture. (See Model Theory).
Whiten.MinToOS Input The model will ensure that a minimum fraction of solids in each size distribution reports to the oversize product. For example, if the user specifies a minimum of 5%, then at least 5% of each size distribution will report to oversize. (See Model Theory).
Whiten.Rf Input The proportion of feed liquid reporting to the over size product to be used in the fines calculation.
Note: This value is only used to adjust the solids fine fraction to the screen oversize and NOT to set the fraction of liquid reporting to the oversize stream.

If the user has selected SolidMethod=Whiten and Whiten.CalcMethod = d50 or d50 with Beta, the following fields will be visible:

Theoretical Nominal Screen Aperture

Whiten.Efficiency / Eff Input The Whiten Efficiency of the Screen. Used to calculate the Screen aperture.
Whiten.TheorAperture Calc The calculated screen aperture, based on the specified d50, alpha and efficiency. Refer to equation 2 in Whiten Method.

Solid Method - Karra

Karra.CalcMethod d50 The user specifies the d50 of the screen.
Area The user specifies the Area and Cut aperture of the screen and the model calculates the d50 of the screen.
Karra.d50 Input Only visible if CalcMethod=d50. The user specified d50 of the screen.
Karra.TotalArea Input Only visible if CalcMethod=Area. The deck area.
Karra.Aperture Input Only visible if CalcMethod=Area. The deck cut aperture.
Karra.Wet Tick Box Only visible if CalcMethod=Area. This must be ticked if this is a wet screening application.
Karra.Factor Input Only visible if CalcMethod=Area. This is a tuning factor that may be used to adjust the calculated d50 of the screen deck. The default value is 1.
Karra.MaxSizeToUS Input The model will ensure that all particles LARGER than this size all report to the Screen deck oversize product. This value is often = Screen Deck Aperture. (See Model Theory).
Karra.MinToOS Input The model will ensure that a minimum fraction of solids in each size distribution reports to the oversize product. For example, if the user specifies a minimum of 5%, then at least 5% of each size distribution will report to oversize. This accounts for fines adhering to coarse particles or fines in the liquid.
Karra.Calc_d50 Calc Only visible if CalcMethod=Area. The calculated d50 of the deck, using the Karra equations.
Karra.d50 Calc Only visible if CalcMethod=Area. The d50 that is used to determine the screen partition curve. This is normally equal to the field above. But, if the calculated d50 > screen deck aperture, then the model will use the screen deck aperture.
Karra.FeedOversize Calc Only visible if CalcMethod=Area. The fraction of oversize material (Q) in the Feed to the deck.
Karra.FeedHalfsize Calc Only visible if CalcMethod=Area. The fraction of half size material (R) in the Feed to the deck.
Karra.FeedNearsize Calc Only visible if CalcMethod=Area. The fraction of near size material (Xn) in the Feed to the deck.
Karra.SolQmPerArea Calc Only visible if CalcMethod=Area. The calculated solids flow rate divided by the screen area.

Solid Method - Rosin-Rammler

RR.d50 Input The user specifies the d50 of the screen, the size which divides equally between oversize and undersize.
RR.Sharpness Input The user specifies the sharpness factor for separation, high values for sharper separation
RR.MaxSizeToUS Input The maximum size allowed to report to undersize.
RR.MinToOS Input The minimum percent solids (from feed) to report to oversize.

Solid Method - Lynch

Lynch.d50 Input The user specifies the d50 of the screen, the size which divides equally between oversize and undersize.
Lynch.Sharpness (m) Input The user specifies the sharpness factor for separation, high values for sharper separation.
Lynch.Alpha Calc Calculated from the Sharpness (m), refer to Lynch Method for more information.
Lynch.MaxSizeToUS Input The maximum size allowed to report to undersize.
Lynch.MinToOS Input The minimum percent solids (from feed) to report to oversize.

Solid Method - DelVillar-Finch

Finch.d50 Input The user specifies the d50 of the screen, the size which divides equally between oversize and undersize.
Finch.Sharpness Input The user specifies the sharpness factor (m) for separation, high values of m for sharper separation
Finch.d0 Input The largest particle size affected by the fish-hook for entrainment function.
Finch.MaxSizeToUS Input The maximum size allowed to report to undersize.
Finch.MinToOS Input The minimum percent solids (from feed) to report to oversize.
Finch.Rf Input Proportion of feed liquid reporting to the over size product.
UFSolidsMethod UF Solids Fraction The user specifies the solids mass fraction in the Underflow stream.
UF Solids Conc The user specifies the Solids concentration in the Underflow stream.
UF Solids Conc25 The user specifies the Solids concentration in the Underflow stream at 25°C.
UF Density The user specifies the density of the Underflow stream.
UFSolidFracReqd Input This is visible if UFSolidsMethod = UF Solids Fraction. The user sets the solids mass fraction in the Underflow stream.
UFSolidConcReqd Input This is visible if UFSolidsMethod = UF Solids Conc. The user sets the solids concentration in the Underflow stream.
UFSolidConc25Reqd Input This is visible if UFSolidsMethod = UF Solids Conc25. The user sets the solids concentration at 25°C in the Underflow stream.
UFRhoReqd Input This is visible if UFSolidsMethod = UF Density. The user sets the density of the Underflow stream.
 
VapourToUF Input The user may set the fraction of vapour entrainment to the Underflow stream. This will only be relevant IF the user has set the vapour entrainment values on the first tab to a value greater than zero.

Selected Solid Species Calculation Method

With this method the user may specify fractions of any number of solid species to bypass to either the Underflow or Overflow streams, or the user may specify the bypass to both Over and Under flow streams. Please see the examples in Model Theory.

BypassSpecies.png
Method None There is no overriding of solid species to the Underflow or Overflow streams.
Bypass to Underflow The user may specify the fractions of one or more Solid species that bypass to the Underflow stream.
Bypass to Overflow The user may specify the fractions of one or more Solid species that bypass to the Overflow stream.
Bypass to Both The user may specify the fractions of one or more Solid species that bypass the Solid-Liquid calculation block and is then split between the Over and Under flow streams.
BypassSeparCalcs Tick Box If this is enabled then the unit will NOT include the bypassed species fraction in the solid/liquid separation calculations. If it is not ticked, then the unit will include the fraction of bypassed species in the solid/liquid separation calculations. Please see the examples in Model Theory for clarification.
ShowByPassSolids Tick Box If this is enabled then the Count and Speciesx fields will be shown, otherwise they will be hidden.
Count Input Only visible if ShowByPassSolids is enabled. The number of solid species for which the user wishes to configure bypasses. This may be up to 10 species.
Solids Species Overall Bypass to Underflow, Overflow or Both
Speciesx Species List Only visible if ShowByPassSolids is enabled. The user may select a species from a drop down list of all of the Solid species in the project.
BypassFracx Input The user sets that fraction of species x that must bypass to the Underflow or Overflow streams OR that must bypass Both.
Example 1: The user chooses Bypass to Overflow, with Count = 1, Species1 = B(s) and BypassFrac1 = 10%, then 10% of B(s) will bypass the solids separation step and will report to the Overflow stream. 90% of B(s) will be involved in the solid-liquid calculation.
Example 2: The user chooses Bypass to Both, with Count = 1, Species1 = B(s), BypassFrac1 = 100% and FracToOF1 = 10%. ALL of B(s) will bypass the solids separation step, 10% of B(s) and will report to the Overflow stream and the remaining 90% will report to the Underflow stream.
FracToOFx Input This field is only visible if the user selects Bypass to Both. The user sets that fraction of species x that must bypass to the Overflow streams.
For example: The user chooses Bypass to Both, with Count = 1, Species1 = C(s), FracToOf1 = 100% and FracToOF1 = 50%. ALL of the C(s) will bypass the solids separation step, 50% of C(s) and will report to the Overflow stream and 50% will report to the Underflow stream.

Results

Temperature / T Display The temperature of mixture in the solid liquid separator.
MassFlow / Qm Display The total mass flow to the Underflow and Overflow streams.
VapourMassFlow / VQm Display The total flow of vapour to the Underflow and Overflow streams. (This does NOT include the vapour to the Vent)
UF.BypassMassFlow / UF.BypassQm Display The mass flow of the material that bypasses the underflow.
OF.BypassMassFlow / OF.BypassQm Display The mass flow of the material that bypasses the overflow.
BypassMassFlow / BypassQm Display The mass flow of the solids in the unit that bypasses the separation section.
UF.SolidsTakeoffQm Display Only visible for Classifying Precipitator. The solids mass flow takeoff from the underflow for recycle.
UF.SolidsTakeoffFrac Display Only visible for Classifying Precipitator. The mass fraction of solids in the underflow that reports to takeoff for recycle.
UF.FinalSf Display Only visible for Classifying Precipitator. The final underflow solids mass fraction after removal of solids takeoff.

Slurry Separation Results (Excluding Bypass)

UFSolidsRecovery Display The fraction of feed solids sent to the underflow.
UFLiquidRecovery Display The fraction of feed liquid sent to the underflow.
The following table displays the flows and compositions of the Underflow and Overflow streams. Note: These are for slurry only, vapours are excluded.
MassFlow / Qm Display The total mass flow in each of the Underflow and Overflow streams.
VolFlow / Qv Display The total volume flow in each of the Underflow and Overflow streams.
SolidMassFlow / SQm Display The solids mass flow in each of the Underflow and Overflow streams.
LiquidMassFlow / LQm Display The liquid mass flow in each of the Underflow and Overflow streams.
SolidFrac / Sf Display The solid fraction in each of the Underflow and Overflow streams.
Density / Rho Display The total density of each of the Underflow and Overflow streams.
SolidConc Display The solid concentration (mass of solids/density of slurry) in each of the Underflow and Overflow streams.
SolidConc25 Display The solid concentration at 25°C (mass of solids/density of slurry at 25°C) in each of the Underflow and Overflow streams.

Adding this Model to a Project

Insert into Configuration file

Sort either by DLL or Group.

 

DLL:

ScdPHREEQC.dll

Units/Links

PHREEQC: Evaporator

or

Group:

Energy Transfer

Units/Links

PHREEQC: Evaporator

See Project Configuration for more information on adding models to the configuration file.


Insert into Project

 

Insert Unit

Heat Transfer

PHREEQC Evaporator

See Insert Unit for general information on inserting units.

Hints and Comments

  1. The information in the VLE Section must be correct for the Evaporator to operate as required. If the VLE configuration requires information that is not available, then the flashing will not occur.
  2. PHREEQC uses the SysCAD VLE submodel to perform flashing. Vapour-Liquid Equilibrium is not directly calculated by PHREEQC.

Example Project