Solvent Extraction Unit
The Solvent Extraction unit is designed for use as a solvent extraction model, which can also be configured to do organic stripping. The model ensures that mainly aqueous phases leave via the aqueous stream and organic phases leave through the organic stream.
The user is responsible for setting up a suite of species which accurately portrays the application that is being evaluated e.g. H2O, H2SO4, Cu, Fe, CuSO4, FeSO4, Fe2[SO4]3, Kerosene, RH, R2Cu, R2Fe, R3Fe. This suite of species is typically set up for chelating type of organic solvents such as the LIX hydroxy oxime copper extractants available from the Henkel Corporation i.e. LIX 64N, 65N, 860, 864, 865, and 622.
The model is capable of the following:
- The unit will separate the phases based on either Individual Phase or density:
- The user may specify an Individual phase to report to the Organic outlet. All solids and other liquid phases will report to the Aqueous outlet; or
- The user may specify the density of separation. The aqueous species are denser than the user defined density of separation and the organic species less dense. e.g. with a separating density of 950 kg/m3, water and all dissolved aqueous species will report to the aqueous phase and the organic species, normally with densities less than approximately 850 kg/m3, will report to the organic phase.
- The user would select a primary metallic element of interest that is to be extracted, e.g. Primary Metal 'Cu'
- The user should supply a reaction which utilises the specified Primary Metal, for example:
- Or, in the case of stripping:
- The model may be configured to use Isotherms (McCabe-Thiele diagrams) to determine the extent of the reaction, or the user may specify the reaction extent directly.
- If the Isotherm method is chosen, the model uses the concentration of the primary metal in the streams entering the unit and the extraction (or stripping) isotherm, provided by the user, to determine the required primary metal concentration within the aqueous and organic phases. The model then calculates the extent to which the defined reaction should proceed to give the desired concentrations.
- The ratio of the organic phase volume flow to the aqueous phase volume flow within the unit also fulfils a crucial role in the equilibrium extraction calculation. It provides the slope of the McCabe-Thiele operating line (a straight line). The Y-intercept is calculated by SysCAD using the data provided by the user. It is called MinOrgConc in the case of extraction, and MinAqsConc in the case of stripping.
- The model is not currently sensitive to pH and assumes that the pH is correct for a particular equilibrium isotherm.
The diagram shows the default drawing of the Solvent Extraction unit, with all of the streams that have to be connected for the unit to operate.
The physical location of the streams connecting to the Solvent Extraction unit is unimportant. The user may connect the streams to any position on the unit.
Inputs and Outputs
|Number of Connections||Description|
|Aqueous Inlet||1 Required||In||1||20||Aqueous feed to Solvent Extraction unit.|
|Organic Inlet||1 Required||In||1||20||Organic feed to Solvent Extraction unit.|
|Aqueous Outlet||Required||Out||1||1||Aqueous outlet from Solvent Extraction unit.|
|Organic Outlet||Required||Out||1||1||Organic outlet from Solvent Extraction unit.|
Behaviour when Model is OFF
If the user disables the unit, by un-ticking the On tick box, then the following actions occur:
- All streams connected to the 'Aqueous' inlet will flow straight out of the 'Aqueous' outlet;
- All streams connected to the 'Organic' inlet will flow straight out of the 'Organic' outlet;
- No reactions will occur.
So basically, the unit will be 'bypassed' without the user having to change any connections.
The Isotherm Method of modelling a Solvent extraction unit is based on the McCabe-Thiele method. This assumes that the operating line on the xy diagram, representing a single solvent extraction stage, is linear. The diagram below illustrates the graphical representation of the unit:
The operating line is the ratio of the incoming organic stream to the incoming aqueous stream.
The Equilibrium line is determined from experimental test data.
(This is the Isotherm that the user is required to input to the model. For extraction, the x axis is the concentration of the primary metal in the aqueous phase and the y axis is the concentration of the primary metal in the organic phase. For stripping, the x axis is the concentration of the primary metal in the organic phase and the y axis is the concentration of the primary metal in the aqueous phase.)
If the Metal (in this case Copper) concentration in the incoming Aqueous stream is 1.7 g/l, then, move vertically up the red line to the operating line, then horizontally to the Equilibrium line to find the equilibrium values of the Copper concentrations in the exiting Aqueous and Organic streams.
In this case the Organic Stream will contain 5g/l Cu and the Aqueous 0.4g/l Cu at equilibrium.
The values will be adjusted to take into account the stage efficiency, as the two phases are not usually in contact long enough to achieve perfect equilibrium.
In this example, the user will insert the Equilibrium curve into the model, and then the Reaction file should contain a reaction with the following form:
Where (aq) denotes the aqueous phase and (o) the organic phase.
The model will adjust the extent of the reaction to produce the required aqueous and organic Copper concentrations.
The default access window consists of several sections:
- SolvExtr-1 tab - Contains general information relating to the unit.
- RB - Optional tab, only visible if the Reactions are enabled in the Evaluation Block.
- Isotherm tab - The user can set up and view the isotherm.
- Info tab - Contains general settings for the unit and allows the user to include documentation about the unit and create Hyperlinks to external documents.
- Links tab, only visible in SysCAD 9.2, contains a summary table for all the input and output streams.
- Audit tab - Contains summary information required for Mass and Energy balance. See Model Examples for enthalpy calculation Examples.
Solvent Extraction Page
Class: SolvExtr-1 The first tab page in the access window will have this name.
Symbol / Tag
Input / Calc
Description/Calculated Variables / Options
|On||Tick box||If this is enabled then the unit will be in full operational mode. If this is disabled, then unit will be 'inoperative', as described in Inoperative Mode. Only available in SysCAD 9.2 Build 133 and later.|
| SeparationMethod / SeparMethod
(Only available in SysCAD 9.2 Build 133 and later)
|Density||The user selects the Density of Separation. All species that have a density LESS than this density will report to the organic outlet. All species with a density GREATER than this density will report to the Aqueous outlet.|
|IndPhase to Organic||The user selects the Individual liquid Phase(s) (usually (o)) that reports to the organic outlet. All solids and other liquid phases will report to the Aqueous outlet.|
|SeparDensity / SeparRho||Input|| Visible if SeparMethod = 'Density'. The required liquid separation density. |
This must be a value between the density of the aqueous and organic streams.
Note: The density of water is a function of temperature, and is often less than 1000 kg/m3; therefore it is safer to specify a separation density below 950 kg/m3.
|List of Liquid Individual Phases||Tick Boxes|| Visible if SeparMethod = 'IndPhase to Organic'. The user must select one or more Individual liquid phases that will report to the Organic outlet. Normally, the user will select the 'o', or 'org' phase. All other liquid phases will report to the Aqueous outlet.|
(The user defines the Individual phase for each species in the Species Database. Normally organic species are defined to have an individual phase of 'o', or 'org'. Please see Individual Phase Label for information on how to change the Individual Phase of a species)
|Aqueous_Losses / AqLoss||Input||The mass fraction of Aqueous liquid in the unit lost to the Organic product stream.|
|Organic_Losses / OgLoss||Input||The mass fraction of Organic liquid in the unit lost to the Aqueous product stream.|
|ExtractionMethod / Method||None|| The model does not use Isotherms to determine the extent of the extraction or stripping reaction. |
The user sets the extent/s of the reaction/s manually.
|Isotherm|| The model uses Isotherms to determine the extent of the extraction or stripping reaction. |
Reactions will be switched on by SysCAD if the isotherm method is chosen.
The user must still specify the reaction file and the reaction/s, but the model will set the extent of the extraction or stripping reaction/s manually.
Notes The model will set the extent of the First reaction in the file.
The reaction file may contain more than one reaction.
The user must set the required extents of the other reactions.
|The following fields will be visible if the Isotherm Method is chosen.|
|AllowOveride||Tickbox||This allows the user to override the reaction extent calculated by the isotherm and manually set the reaction extent on the RB tab page.|
|Mode||Extraction||This mode is selected if the unit is used to extract the metal from the aqueous into the organic phase.|
|Stripping||This mode is selected if the unit is used to strip the metal from the organic into the aqueous phase.|
|StageEfficiency / StageEff||Input||The efficiency of the solvent extraction stage.|
|ExtentSpecies / ExtentSp||Input||The liquid containing the primary metal, e.g. for Extraction it may be CuSO4, and for Stripping R2Cu.|
|Primary Metal||List||The user must select the metal of interest from the list of available elements in the project. A valid element must be selected if the "Isotherm" method is selected. It is optional for the method "None", however it is useful to set this so that the feed and product concentrations can be shown.|
|Reactions||List||The user may turn the reactions 'On' or 'Off'. If this is 'On' then the RB tab page will become visible. Reactions will be switched 'On' by SysCAD if the isotherm method is chosen.|
|OperatingP... (available in SysCAD 9.2 or later)|
|Method||List||Atmospheric -- outlet streams will be 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 Species tab page of the Plant Model.|
|AutoDetect -- This option is only available in SysCAD 9.2 Build 133 or later. If there are any liquids AND no vapours present in the feed, outlet streams will take the highest pressure of the feeds. Else (eg. some vapours present) outlet streams will take the lowest pressure of the feeds.|
|LowestFeed -- outlet streams will take the lowest pressure of the feeds.|
|HighestFeed -- outlet streams will take the highest pressure of the feeds.|
|RequiredP -- outlet streams will be at the user specified pressure.|
|IgnoreLowQm||Tick Box||This option is only visible if the AutoDetect, LowestFeed or HighestFeed methods are chosen. When calculating the outlet pressure and temperature of the tank, SysCAD will ignore the low flow feed streams should this option be selected. The low flow limit is set in the field below.|
|LowQmFrac||Input||This field is only visible if the IgnoreLowQm option is selected. This is the amount any stream contributes to the total flow. For example, if the total feed to the tank is 10 kg/s, and this field is set to 1%. Then any feed streams with less than 0.1 kg/s will be ignored in the pressure calculations.|
|Pressure_Rqd / Reqd||Input||This field is only visible if the RequiredP method is chosen. This is user specified pressure.|
|Result||Display||The actual pressure used for the sum of the feeds which will also be the outlet pressure (unless further model options change the pressure).|
|MinOrgConc OR MinAqsConc||Output|| This field is only visible if the Isotherm Method has been chosen. The Y-intercept of the McCabe-Thiele operating line, MinOrgConc in the case of extraction, and MinAqsConc in the case of stripping. |
NOTE this is defined by the feed streams entering the unit operation.
|ReactExtent||Feedback|| This field is only visible if the Isotherm Method has been chosen. This is the reaction extent required as appears in the RB tab page. |
Displayed here for easy access.
|ActReactExtent||Feedback|| This field is only visible if the Isotherm Method has been chosen. This is the actual reaction extent achieved as appears in the RB tab page. |
Displayed here for easy access.
|MaxLoadedConc||Output|| If the Isotherm Method has been chosen, this field will only be visible if Extraction Mode is chosen. Displays the maximum concentration based on 100% extraction and calculated by mass balance. |
This will serve as a warning for incorrectly supplied data if the results differ to those expected.
|MaxStripConc||Output|| If the Isotherm Method has been chosen, this field will only be visible if Stripping Mode is chosen. Displays the maximum concentration based on 100% strip efficiency and calculated by mass balance. |
This will serve as a warning for incorrectly supplied data if the results differ to those expected.
|AqueousConcIn / AqsConcIn||Calc||The concentration of the Primary metal in the incoming Aqueous stream.|
|OrganicConcIn / OrgConcIn||Calc||The concentration of the Primary metal in the incoming Organic stream.|
|Calc||The calculated volumetric ratio of Organic to Aqueous liquid entering the unit.|
|Calc||The calculated volumetric ratio of Aqueous to Organic liquid entering the unit.|
|AqueousConcOut / AqsConcOut||Calc||The concentration of the Primary metal in the outgoing Aqueous stream.|
|OrganicConcOut / OrgConcOut||Calc||The concentration of the Primary metal in the outgoing Organic stream.|
The user types in the Isotherm describing the Solvent Extraction process, either in the space required, or as a csv file.
Examples of full tags of the fields on the Isotherm page:
|Tag / Symbol||Options||Description|
The black rectangle is for display purposes only.
|Equation||+ / -||This is NOT used.|
|Information||+ / -||The user clicks on the + to obtain the following buttons, these allow the user to configure the display.|
|Lin > Log X||Button||Toggles between normal and log on the x scale|
|Lin > Log Y||Button||Toggles between normal and log on the Y scale|
|Auto>Manual Scale Display||Button||Toggles between automatic and manual display parameters. If the display is in auto mode, then the model sets the minimum and maximum display parameters. Changing to manual allows the user to set these parameters.|
|Graph : Width & Height||Inputs||These numbers determine the size of the graph on this page.|
|Display Min||Display||The minimum display point on the graph|
|Display Max||Display||The maximum display point on the graph|
|Lower Boundary||Inputs||The lower boundary of the actual data points, i.e. the lowest point to which the data may be extrapolated.|
|Upper Boundary||Inputs||The upper boundary of the actual data points, i.e. the highest point to which the data may be extrapolated.|
|Data Points||+ / -|| The user clicks here to enter the data points.|
The data may be entered in a csv file, or in the two columns on this page. For example, for extraction, x represents the mass fraction of solute in raffinate, and y represents the mass fraction of solute in extract.
The model interpolates linearly between the points and beyond the first and last points.
|Load Points||Button||This will load the points from a CSV file.|
|Save Points||Button||This will save the points to a CSV file.|
|File||Input||The user may type in the file and path if the points are stored in a csv file.|
|Length||Input||The number of data points. If the user wishes to type the data points directly into the model, then this value needs to be filled in. Once a number has been typed in, the X and Y columns will be visible with the required number of lines.|
|Sort||Button||This will sort the data points into ascending x values.|
|X and Y Columns||Inputs||The X and Y values for the Isotherm.|
Adding this Model to a Project
Insert into Configuration file
Sort either by DLL or Group.
Separation : Mixer/Settler
See Project Configuration for more information on adding models to the configuration file.
Insert into Project
See Insert Unit for general information on inserting units.
Hints and Comments
- Check that the Separation Density specified in the model is a value between the aqueous and organic densities.
- Isotherm data plot X and Y axes are in concentrations (g/L). For extraction, the x axis is the concentration of the primary metal in the aqueous phase and the y axis is the concentration of the primary metal in the organic phase. For stripping, the x axis is the concentration of the primary metal in the organic phase and the y axis is the concentration of the primary metal in the aqueous phase.
- If the isotherm is required to be used outside the range of the data points entered, then SysCAD will linearly extrapolate from the nearest set of 2 points.