Electrowinning Cell

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Contents 1 General Description 1.1 Diagram 2 Inputs and Outputs 3 Model Theory 4 Flowchart 5 Data Sections 5.1 Requirements 5.2 Results 6 Adding this Model to a Project

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

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

Label	Input / Output	No. of Connections		Description
		Min	Max
Feed	In	1	20	The feed to the Electrowinning Cell
Anolyte	Out	1	1	The Liquid outlet from the unit
Cathodes	Out	1	1	Solids, or cathode, outlet from the unit
Vent	Out	0	1	Vent Stream (Vapour Only)

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:

1. 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.
2. The Heat of Reaction is specified in the reaction file. This method is often used when the heats of formation are not known.

Flowchart

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

Data Sections

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

1. The first tab has the same name as the model tag and contains general information relating to the unit.
2. Optional tab RB, or Reaction Block, fully described in Reaction Block (RB).
3. The Info section, contains general settings for the unit and allows the user to include documentation about the unit and create Hyperlinks to external documents. This is fully described in Common Data Sections.
4. Links tab, only visible in SysCAD 9.2, contains a summary table for all the input and output streams.
5. Audit tab - contains summary information required for Mass and Energy balance. See Model Examples for enthalpy calculation Examples.

Class: ECell - The first tab page in the access window will have this name.

Tag / Symbol	Input / Calc	Description/Calculated Variables / Options
Common First Data Section
Requirements
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.
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 must configure the reaction block, if the Electrowinning cell is to do any work.
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.
		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.
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).
ShowQFeed	Tick Box	QFeed and associated tab pages (eg. Qm) will become visible, showing the properties of the combined feed stream. See Material Flow Section. This will be prior to any reactions occurring.
Results
ElecEnergyTotal	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.
ElecEnergyReact	Calc	The calculated energy requirements of the cell based on the heat of reaction. This represents the energy required for a 100% efficient cell.
ElecEnergyHeat	Calc	The calculated amount of energy that is converted to heat. This is based on the cell efficiency.
Feed.T	Calc	The feed temperature.
Prod.T	Calc	The final temperature of the cell after the required energy is added (calculated above).

Adding this Model to a Project

Insert into Configuration file

Sort either by DLL or Group.

	DLL:	Separ1.dll	→	Units/Links	→	Separation: Electrowinning Cell
OR	Group:	Mass Separation	→	Units/Links	→	Separation: Electrowinning Cell

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

Insert into Project

Insert Unit

→

Separation

→

Electrowinning Cell

See Insert Unit for general information on inserting units.