Potash Evaporator

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Potash Species Model	Potash Solubility	Potash Properties Utility	Potash Evaporator

Related Links: Energy Transfer Models, Solid-Liquid Separator, Evaporator

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General Description

The Potash Evaporator is only available to users with the Potash add-on.

The unit may be operated at a user defined temperature or pressure, or it may be part of a Flash Train. SysCAD will attempt to run the unit at equilibrium at the required temperature or pressure. This may involve vapour to be flashed in the unit, with a subsequent increase in concentration of the remaining solution.

If the user enables Solubility and selects Potash solubility, if either KCl or NaCl are above their saturation values they will precipitate out as the crystal product. Alternatively, the user may use the Reaction Block (RB) to set the precipitation reaction and extent.

The unit has a 'Body' and a 'Leg'. The Body section receives the main unit feeds, recycles solution to the heat exchangers and the overflow and vent streams come from this section. The crystals drop into the Leg section and are usually washed with the solution in the 'Leg Feed'. The product is then discharged from the Evaporator leg.

Operational Modes

There are two operational modes for the Potash Evaporator:

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

The user sets the required operational mode of the Potash Evaporator. However, if the user sets the mode as Flash Train and the Potash 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.

Available Sub-Models

Sub-Models	Feed Block	Body Block	Leg Block	Description
Solubility	No	Yes	Yes	May be enabled in the Body and Leg. This is required to automatically calculate the KCl and NaCl solubility.
Makeup Blocks (one or more)	Yes	No	No	This allows the user to control the addition of streams such as reagents or brine to the Potash Evaporator, often without having to use a PID or General controller.
Reaction Block (RB)	Yes	No	Yes	Allows the user to configure any number of reactions in the Feed or Leg of the Evaporator.
Environmental Heat Exchanger Block	Yes	No	No	Allows the user to add or remove energy from the Evaporator using a number of different methods.
Vapour Liquid Equilibrium Block	No	Yes	No	ALWAYS enabled in an Evaporator. This will attempt to ensure that the water and steam will be in equilibrium in the unit.

Heat Exchange Options

The unit may also have connections to an Embedded or to an External Heat Exchanger.

Often Evaporators are operated by recycling the liquor through one or more heat exchangers. This model allows the user to embed these heat exchangers as part of the model. (This is often more efficient when carrying out the modelling calculations.)

The user sets the amount of flow to the heat exchanger, either as a fixed flowrate or as a fraction of the throughput. This flow will then be heated in either the embedded heat exchanger, or sent to an External heat exchanger via the Recycle outlet.

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 input port and the Condensate (or return heat exchange medium) to the Embedded HX Shell output port. The recycle flow to the heat exchanger must to be specified, but this is handled internally within the unit.
3. External - A recycle stream from the Potash Evaporator is heated, or cooled, in a separate Heat Exchanger unit. The user must connect the Recycle output port from the Potash Evaporator to an external heat exchanger. This recycle stream is then either heated or cooled and returned to the Potash Evaporator via the Recycle input port.

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 Potash 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 connection and returned to the Potash Evaporator via the Recycle connection.
2. For both internal and external heat exchange the user must set the recycle flow to the heat exchanger.

Diagram

• The above 2 diagrams show the Potash Evaporator with and without an embedded heat exchanger.
• The physical location of the streams connecting to and from the Potash Evaporator is unimportant. The user may connect the streams to any position on the unit.
• When inserting a Potash Evaporator into a flowsheet, the user may choose a different symbol from the menu.
• Many of the above connections are optional. Please see the Input/Outputs table below for further information.

Inputs and Outputs

Label	Required Optional	Input Output	Number of Connections		Description
			Min	Max
Feed	1 Required	In	1	20	Feed to the main body of the Potash Evaporator.
Leg Feed	Optional	In	0	10	Potash Evaporator Leg feed - this is often a wash stream for the crystals.
Embedded HX Shell	Optional	In	0	10	Inlet stream to the Shell side of Embedded Shell and Tube Heat Exchanger (often the steam inlet).
Recycle	Optional	In	0	10	Recycle stream from external Heat Exchanger(s).
Product	Required	Out	1	1	Product Slurry outlet - this stream flows from the evaporator leg and normally contains the crystals.
Vent	Required	Out	1	1	Vent outlet containing all Vapours from the unit.
Overflow	Optional	Out	0	1	Overflow liquor outlet - this stream flows from the body of the evaporator and normally contains very little solids.
Embedded HX Shell	Optional	Out	0	1	Outlet stream from the Shell side of Embedded Shell and Tube Heat Exchanger (often the condensate).
Recycle	Optional	Out	0	1	Recycle stream from the Potash Evaporator to external Shell and Tube Heat Exchanger(s).

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' inlet 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 Potash 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).

Solubility

If Potash Solubility is enabled in the Potash Evaporator then the solubility calculations will be performed simultaneously with the VLE calculations. Therefore, the product from the Potash Evaporator will contain liquid at, or below, the saturation value of KCl, NaCl and optionally CaSO4.

Flow Chart

Data Sections

The default access window consists of several sections:

1. PotashEvaporator - The first tab contains general information that can be set by the user.
2. Results - This tab contains the unit results.
3. HX - Optional tab, only visible if an Embedded Heat Exchanger is selected. (In this case the Embedded HX Shell connections should be connected).
4. RB - Optional tab, only visible if the Reactions are enabled in the Feed Evaluation Block.
5. EHX - Optional tab, only visible if the EnvironHX is enabled in the Feed Evaluation Block.
6. MU - Optional tab, or multiple tabs if more than 1 Makeup is selected. Only visible if one of more Makeup is enabled in the Feed Evaluation Block.
7. VLE - Always visible. This is calcualted in the Body of the Evaporator.
8. PC - Optional tab, only visible if the Solubility is enabled in the Body Evaluation Block.
9. LPC - Optional tab, only visible if the Solubility is enabled in the Leg Evaluation Block.
10. LRB - Optional tab, only visible if the Reactions are enabled in the Leg Evaluation Block.
11. QFeed - Optional tab, only visible if ShowQFeed is enabled. This page shows the properties as a mixed stream of all of the Feed streams to the Potash Evaporator. This EXCLUDES the recycle from the external heat exchanger, if there is one.
    • This is before any Evaluation Block models are evaluated.
12. QBodyFeed - Optional tab, only visible if ShowQBodyFeed is enabled. This page shows the properties of the mixed stream as the feed to the Body of the Potash Evaporator.
    • This is before any Evaluation Block models are evaluated.
13. QProd - This page shows the properties of the Potash Evaporator discharge as a single stream.
    • This is AFTER the flash calculations, but before the split to slurry, overflow and vapour streams.
14. Info tab - contains general settings for the unit and allows the user to include documentation about the unit and create Hyperlinks to external documents.
15. Links tab - contains a summary table for all the input and output streams.
16. Audit tab - contains summary information required for Mass and Energy balance. See Model Examples for enthalpy calculation Examples.

Potash Evaporator Page

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

Tag (Long/Short)	Input / Calc	Description
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 SysCAD will display the UnitType or SubClass.
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 Body 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. Note If the Evaporator does have an embedded Heat Exchanger, this can be set up separately as part of a Flash Train.
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 Plant Model - Environment tab.
	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 useful if the Evaporator is configured as part of a Flash Train, as it will not allow the unit to drop to an unrealistic pressure. This is only visible if the unit is operated as part of a Flash Train.
Feed Evaluation Block These sub-models operate on the combined Feed streams.
EvalSequence	Display	The sequence in which the sub models (which are part of the evaluation blocks) will be calculated. The sequence is determined by the priority selection for the individual sub-models. Note: If the user chooses On-AutoSequence then SysCAD will determine the sequence of the sub-models. The sequence followed will be MU1,MU2, etc., RB, EHX.
Makeups	Input	The number of makeup blocks required. Extra drop-down options Makeup1, Makeup2, etc. will be added to allow these to be switched on and off and prioritised in relation to the other sub-models.
MakeupX	List	This can be used to switch the Makeup Block (MU) on or off and prioritise it in relation to the other sub-models. If this is 'On' then the associated page, MUX becomes visible and may be configured. Note: This field is only visible if the entry for 'Makeups' is greater then 0. If there is one makeup then X=1. If there are two makeups, then X=1 and X=2, etc.
Reactions	List	This can be used to switch on the Reaction Block (RB). If this is 'On' then the associated page, RB becomes visible and may be configured. Note: The user does not have to configure a reaction file, even if this block is checked.
EnvironHX	List	This can be used to switch on the Environmental Heat Exchanger (EHX). If this is 'On' then the associated page, EHX may become visible and may be configured. Note: The user does not have to configure an environmental heat exchange, even if this block is checked.
Body Evaluation Block These sub-models operate on the streams to the Evaporator body.
Solubility.On	Tickbox	The user may enable the solubility in the body. This MUST be enabled if the Potash Evaporator is required to automatically calculate the precipitation of KCl and NaCl.
EvalSequence	Display	This will always only display VLE.
VLEquilibrium	Display	Vapour Liquid Equilibrium (VLE) is always ON in the Evaporator - the user may NOT turn it off.
Leg Evaluation Block These sub-models operate on the streams to the Evaporator leg.
Solubility.On	Tickbox	The user may enable the solubility in the leg. This MUST be enabled if the Potash Evaporator Leg is required to automatically calculate the precipitation of KCl and NaCl.
EvalSequence	Display	This will display either LRB, if the reactions are enabled, or nothing.
Reactions	List	This can be used to switch on the Reaction Block (RB) in the Leg. If this is 'On' then the associated page, LRB becomes visible and may be configured. Note: The user does not have to configure a reaction file, even if this block is checked.
Fraction of Leg Feed Liquid reporting to Evaporator Body
LegFeedToBody	Input	The Required fraction of the liquid in the leg feed that reports directly to the Evaporator body. The remainder flows to the leg section. Note that all solids in the Leg Feed stream will always report directly to the leg.
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.
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.MassFlowReqd	Input	The required Product mass flow to the Heat Exchanger (either Embedded or External).
HXOut.VolumeFlowReqd	Input	The required Product volumetric flow to the Heat Exchanger (either Embedded or External).
HXOut.EachHeaterQmReqd	Input	The required Product mass flow to the each Heater (Embedded Heater method only).
HXOut.EachHeaterQvReqd	Input	The required Product volumetric flow to the each Heater (Embedded Heater method only).
OverFlow and Product Split
CalcSplitMethod	Simple Estimate	The model will do a simple estimate to calculate the liquid split required from the body to the leg to give the desired solids fraction in the product.
	Iterative	The model will iteratively calculate the liquid split required from the body to the leg to give the desired solids fraction in the product.
OFSolSaltsReqd	Input	The required solid salts species fraction in the overflow stream. Salts species include KCl, NaCl and MgCl2.
GypsumSplitMethod Note: 'Gypsum' includes CaSO4.2H2O(s) and CaSO4(s)	Follow Solid Salts	The fraction of gypsum to the Overflow stream will be the same as the solid salts fraction to the Overflow stream.
	All to OF	All of the gypsum from the Evaporator body will report to the Overflow stream. Note - there may be some gypsum in the Leg that reports to the Product stream.
	None to OF	None of the gypsum in the Evaporator body will report to the overflow stream, i.e. it will all report to the Product stream.
	User Frac to OF	The user may define the fraction of gypsum in the Evaporator body that will report to the Overflow stream.
GypsumToOF	Input	The required fraction of gypsum in the Evaporator body that will report to the Overflow stream. This field is only visible if the user selects User Frac to OF.
OtherSolidSplitMethod 'Other Solids' are any solid species that are not gypsum or salts, i.e. NOT KCl, NaCl, MgCl2 or gypsum.	Follow Solid Salts	The fraction of other solids to the Overflow stream will be the same as the solid salts fraction to the Overflow stream.
	All to OF	All of the other solids from the Evaporator body will report to the Overflow stream. Note - there may be some other solids in the Leg that report to the Product stream.
	None to OF	None of the other solids in the Evaporator body will report to the overflow stream, i.e. they will all report to the Product stream.
	User Frac to OF	The user may define the fraction of other solids in the Evaporator body that will report to the Overflow stream.
OtherSolidToOF	Input	The required fraction of other solids in the Evaporator body that will report to the Overflow stream. This field is only visible if the user selects User Frac to OF.
ProductSolidFracReqd	Input	The required solids fraction in the Product Stream.
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 combined feed stream to the Evaporator Body.
ShowQRecycle	Tickbox	This is only visible if an Embedded Heater 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 (e.g. 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.
ShowResultsTable	Tick Box	This adds a section in the Results Page showing a summary of QFeed, QBodyFeed and QProd Results.

Results Page

The page contains the results fields.

Tag (Long/Short)	Input / Calc	Description
Operating Conditions
TemperatureIn / Ti	Calc	The temperature of the combined Feed stream to the Evaporator. (This is a normally hidden field)
PressureIn / Pi	Calc	The pressure of the combined Feed stream to the Evaporator. (This is a normally hidden field)
VapFlashed.MassFlow / VapFlashed.Qm	Calc	The quantity of flashed vapour.
LiqChange.MassFlow / LiqChange.Qm	Calc	The mass change of liquid in the evaporator.
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.
TotalPressChange/ TotaldP	Calc	The total pressure change.
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 QFeed, QBodyFeed and QProd Results
This Summary table is only visible when the ShowQResultsTable option has be ticked (located in the PotashEvaporator Tab). It shows the values of each of the following variables for QFeed QBodyFeed and QProd
Temperature / T	Calc	The Temperature in each stream.
MassFlow / Qm	Calc	The total mass flow in each stream.
SolidMassFlow / SQm	Calc	The mass flow of solids in each stream.
SolidFrac / Sf	Calc	The solids fraction in each stream - this includes all solids and gypsum.
SolSaltsQm	Calc	The mass flow of solid salts (KCl and NaCl) in each stream.
SolSaltsFrac	Calc	The mass frac of solid salts (KCl and NaCl) in each stream.
GypsumMassFlow / GypsumQm	Calc	The mass flow of Gypsum in each stream.
Summary of Input and Output Streams
This Summary table shows the values of each of the following variables for the Feed and Product streams that are connected to the Evaporator. The possible streams are: Feed - this will display the values for the total Feed stream = Sum of all feed streams connected to the unit. Leg Feed (LF)- this will display the values for the total Leg Feed stream = Sum of all leg feed streams connected to the unit. This will only be visible if there are any streams connected to the Leg Feed connection. Vapour - this will display the values for the Vent stream from the unit. Overflow (OF)- this will display the values for the Overflow stream from the unit, if it is connected. Product (Prod) - this will display the values for the Product stream from the unit.
Temperature / T	Calc	The Temperature in each stream.
MassFlow / Qm	Calc	The total mass flow in each stream.
SolidMassFlow / SQm	Calc	The mass flow of solids in each stream.
SolidFrac / Sf	Calc	The solids fraction in each stream - this includes all solids and gypsum.
SolSaltsQm	Calc	The mass flow of solid salts (KCl and NaCl) in each stream.
SolSaltsFrac	Calc	The mass frac of solid salts (KCl and NaCl) in each stream.
GypsumMassFlow / GypsumQm	Calc	The mass flow of Gypsum in each stream.
Results
LegBypass.MassFlow / LegBypass.Qm	Calc	The mass flow of material bypassed to the Leg.
BFeed.Temperature	Calc	The temperature of feed in the main body of the evaporator.
BFeed.Pressure	Calc	The pressure of feed in the main body of the evaporator.
Body.SolidsYield	Calc	The mass flow of solids in the Product - mass flow of solids in the Feed.
Leg.SolidsYield	Calc	The mass flow of solids in the Leg.
SolidsYield	Calc	The mass flow of solids in the Product - mass flow of solids in the Feed.
OF.AqSaltsFrac	Calc	Aqueous salts fraction in the Overflow.
Leg.SolidFrac / Leg.Sf	Calc	Solids fraction in the leg.
Leg.SolSaltsFrac	Calc	Solid Salts fraction in the leg.
Leg.AqSaltsFrac	Calc	Aqueous Salts fraction in the leg.
Internal Calculations
PrevLiqQmToUF	Calc	The amount of liquid mass flow to underflow in the previous iteration.
BodySolSaltsFracToLeg	Calc	Body solid salts fraction to leg.
BodyGypsumSolFracToLeg	Calc	Body solid gypsum fraction to leg.
BodyOtherFracToLeg	Calc	Body other solids (not including salts and gypsum) fraction to leg.
BodyLiqFracToLeg	Calc	Body Liquid fraction to leg.
CalcLegSplit.Iters	Calc	Number of iterations allow to calculate the split to leg.
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.
Iter_Steps	Calc	The number of iteration used in the current step to solve the recycle loop. Only shown for Stream Recycle Converge Methods.
Iter_LastStep	Calc	The number of iteration used in the last step to solve the recycle loop. Only shown for Stream Recycle Converge Methods.
Iter_MaxInAStep	Calc	The maximum number of iterations (in a step) used to solve the recycle loop. Only shown for Stream Recycle Converge Methods.
Iter_Total	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.
Iter_Duty	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.

Adding this Model to a Project

Add to Configuration File

Sort either by DLL or Group:

	DLL:	PotashUnits.dll	→	Units/Links	→	Heat Transfer: Evaporator - Potash OR PotashEvaporator (note1)
or	Group:	Energy Transfer	→	Units/Links	→	Heat Transfer: Evaporator - Potash

See Model Selection for more information on adding models to the configuration file.

Insert into Project Flowsheet

Insert Unit

→

Heat Transfer

→

Evaporator - Potash OR PotashEvaporator (note1)

See Insert Unit for general information on inserting units.

NOTE:

1. Name change in Build139 and later.

Hints and Comments

1. There may be mass entering or leaving the unit via the Reaction Block source or sink, so if the outgoing mass is not the same as the incoming mass, this may be a place to check first.
2. 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.

Example Project

• Four Stage Crystallisation Example Project
• Three Stage Evaporator Example Project