View source for Electrowinning Cell

[[Category:Models]]
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== General Description ==

The electrowinning cell converts metal in solution into solid elemental metal.  The user specifies the reaction in the normal way using the [[Reaction Block (RB)]].  In the dynamic mode, the solids are removed separately in a batch process, to emulate the removal of cathodes on a plant.  The energy required by the cell is calculated from the heats of reaction and the efficiency of the cell.  The excess energy is used to heat the contents of the unit.

=== Diagram ===

[[Image:Electrowinning Cell.jpg]]

The diagram shows the default drawing of the Electrowinning Cell, with all of the streams that are available for operation of the unit.

The physical location of the streams connecting to the Electrowinning Cell is unimportant.  The user may connect the streams to any position on the unit.

== Inputs and Outputs ==

{| border="1" cellpadding="5" cellspacing="0"  
|- 
| valign="top" rowspan="2" | '''Label''' || valign="top" rowspan="2" | '''Required<br>Optional''' || valign="top" rowspan="2" | '''Input<br>Output ''' ||  colspan="2"   | '''Number of Connections''' || valign="top" rowspan="2" | '''Description'''
|- 
|  '''Min''' || '''Max''' 
|-
| Feed      || 1 Required   || In           || 1   || 20                       || The feed to the Electrowinning Cell
|-
| Anolyte   || Required     || Out           || 1   || 1                        || The Liquid outlet from the unit
|-
| Cathodes  || Required     || Out           || 1   || 1                        || Solids, or cathode, outlet from the unit
|-
| Vent      || Optional     || Out           ||  0   || 1                        || Vent Stream (Vapour Only)
|}

== Behaviour when Model is OFF ==

If the user disables the unit, by un-ticking the ''On'' tick box, then the following actions occur:
* The field ''MassFracToCath'' becomes visible and the user may set the fraction of the feed stream that reports to the 'Cathode' outlet.  The default is 100%.
* All streams connected to the unit will flow out of the 'Cathode' outlet, unless the user has changed the above field from 100%.  In which case the user defined fraction of the feed streams will report to the Anolyte stream;
* No reactions or heating will occur.

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

== Model Theory ==

The Electrowinning Cell is modelled as a tank that contains an electrolytic reaction, where a metal is plated out onto a cathode from an aqueous solution.  The reactions occurring in electrowinning require energy to proceed and the amount of energy is calculated as follows:

At 100% efficiency the energy value calculated by the model is the amount of energy required to maintain the material in the cell at the temperature of the cell feed.

If the cell is less than 100% efficient, then the extra energy increases the temperature of the products from the cell.

The energy required by the electrowinning cell is governed by the enthalpy of the electrolytic reaction occurring the unit.  This  enthalpy of the reaction is calculated in one of two ways:

# Enthalpy of Reaction = Sum of Heats of formation of the products - Sum of Heats of formation of reactants.  (This is the default method of calculating the heat of reaction.)  The heats of formation of the species are defined in the species database.
# The Heat of Reaction is specified in the reaction file.  This method is often used when the heats of formation are not known.

Note that the above calculations ignore the effect of using the [[Reaction_Block_-_HOR_%26_Energy#Override_Product_Temperature_Option|OverrideProductT]] or [[Reaction_Block_-_Other#Reaction_Heat_Exchange|Heat Exchange]] options in the Reaction Block. In Build 139 or later, the [[Reaction_Block_-_HOR_%26_Energy#Override_Product_Temperature_Option|OverrideProductT]] and most [[Reaction_Block_-_Other#Reaction_Heat_Exchange|Heat Exchange]] methods are not allowed. Only the [[Reaction_Block_-_Other#Power|RHX-Power]] option is allowed.

== Flowchart ==

The following shows the sequence of events if sub model options are switched on.  See next heading for more information.

[[Image:Electrowinning Cell Sequence of Events.gif]]

== Data Sections ==

The default access window consists of a number of sections, depending on user specifications.  The tabs that may be visible are: 

# '''[[#Electrowinning Cell Page|ECell]]''' tab - Contains general information relating to the unit.
# '''[[RB]]''' - Optional tab, only visible if the Reactions are enabled in the Evaluation Block.
#{{ShowQout|Feed|combined feed|139only=no}}
# '''[[Common Data Sections#Common Data on Info Tab Page|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 Table|Links]]''' tab, 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.

===Electrowinning Cell Page===
'''Unit Type: ECell''' - The first tab page in the access window will have this name.

{|   border="1" cellpadding="5" cellspacing="0" align="center"
|  Width=160  |'''Tag (Long/Short)'''||'''Input / Calc'''||'''Description/Calculated Variables / Options'''
{{Common Data on First Tab Page}}
|-
|  colspan="3" font style="background: #ebebeb"    |

=== Requirements ===
|-
| On || Tick box || Switch the model on or off. If the unit is 'Off' then by default all Feed reports to the Cathodes outlet.  If the user specifies a value (less than 100%) in the MassFracToCath field, then some feed may report to the Anolyte stream.
|-
| MassFracToCath_WhenOff / MassFracToCath || Input || This field becomes visible when the unit is switched off.  The user may set the fraction of the feed stream that reports to the Cathodes outlet. The default is 100%.
|-
|| CellEfficiency / CellEff || Input || The required energy efficiency of the cell.  This is used to calculate the energy required by the cell, and the temperature rise in the cell.
|-
| valign="top" | Reactions|| valign="top" | 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 '''must''' configure the reaction block, if the Electrowinning cell is to do any work.
{{OperatingP}}
|-
|colspan="3" font style="background: #ebebeb"|'''''Options'''''  
{{ShowQout DataSection|Feed|combined feed|139only=no}}
|-
|  colspan="3" font style="background: #ebebeb"    |

=== Results ===
|-
| Feed.MassFlow / Feed.Qm ||font style="background: #ebebeb"| Calc || Only available in Build 139 or later. The total mass flow of the combined feeds.
|-
| Feed.Temperature / Feed.T ||font style="background: #ebebeb"| Calc || The feed temperature.
|-
| Prod.Temperature / Prod.T ||font style="background: #ebebeb"| Calc || The final temperature of the cell after the required energy is added.
|-
| ElecEnergyTotal ||font style="background: #ebebeb"| Calc || The calculated electrical energy requirements of the cell.  This is based on the heat of reaction and the efficiency of the cell. This is the sum of ElecEnergyReact and ElecEnergyHeat or ElecEnergyReact/CellEfficiency, where CellEfficiency is expressed as a fraction.
|-
| ElecEnergyReact ||font style="background: #ebebeb"| Calc || The calculated energy requirements of the cell. This represents the energy required to maintain the material in the cell at the temperature of the cell feed. <br>'''Note:''' This calculation ignores the effect of using the [[Reaction_Block_-_HOR_%26_Energy#Override_Product_Temperature_Option|OverrideProductT]] or [[Reaction_Block_-_Other#Reaction_Heat_Exchange|Heat Exchange]] options in the Reaction Block.
|-
| ElecEnergyHeat ||font style="background: #ebebeb"| Calc || The calculated amount of energy that is converted to heat. This is based on the cell efficiency and ElecEnergyReact. For a 100% efficient cell, ElecEnergyHeat = 0. For <100% efficiency, ElecEnergyHeat  = ElecEnergyReact*(1-CellEfficiency)/CellEfficiency, where CellEfficiency is expressed as a fraction.
|-
| RHX.HeatFlow||font style="background: #ebebeb"| Calc || Only available in Build 139 or later. The amount of energy that is added by the [[Reaction_Block_-_Other#Reaction_Heat_Exchange|Reaction Block Heat Exchange]]. '''Note:''' Only the ''Power'' method is able to be used.
|-
|}

== Adding this Model to a Project ==

{{Adding Model to a Project | DllName=HeatExchange| DllSubGroup=Heat Transfer| UnitOp=Electrowinning Cell | Group=Energy Transfer |}}

== Example Project ==

Please see [[Example_-_03UnitModels_Projects_2#Solvent_Extraction_Project|Solvent Extraction Project]] OR [[Nickel Copper Project]]