View source for Reverse Osmosis (RO) Unit

[[Category:Models]]
{{Navigation|[[Models]]|[[Models#Mass Separation Models|Mass Separation Models]]}}

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{{TOC}}
== General Description ==

This model is designed to simulate a reverse osmosis membrane process, often used in water treatment, especially for desalination of sea water.

The user may specify the yield and efficiency of the process, as well as the outlet pressure requirements.

The unit expects the feed to be free of solids.  If solids are fed to the unit, the user will receive a warning and any solids will be sent to the Brine stream.

If a vent stream is connected, then all gases will exit via the Vent.  If gases are present and there is no vent connection then the user will receive a warning and all gases will be sent to the Brine stream.

=== Diagram ===

[[Image:RO Unit.png]]

* The diagram shows default drawing of the Reverse Osmosis unit with connecting streams.
* The physical location of the streams connecting to the unit is unimportant. The user may connect the streams to any position on the unit.
* When inserting a Reverse Osmosis unit into a flowsheet, the user may choose a different symbol from the menu.

=== Demand ===

In Build 139 or later, [[Demand]] logic will now be passed through the Reverse Osmosis unit. The Demand can only be passed from the Product stream to the Feed streams. Any demand from Brine or Vent streams is ignored. This allows a user to set the desalinated water requirement using demand logic, and this can be passed through the reverse osmosis unit to the raw water source (usually a feeder), to determined the required raw water to satisfy the desalinated water demand. An example of this is shown in the [[Example_-_02Feature_Projects#Water_Treatment_.28Demand.29_Project|Water Treatment (Demand) Example Project]].

== 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 || '''Required''' || In || 1 || 20 || Inlet liquid feed stream to the unit, usually water with dissolved salts.
|- 
| FeedProdSide || '''Optional''' || In || 1 || 20 || Inlet liquid feed stream to the product side of the membrane.  This is useful for modelling numerous technologies including forward osmosis, diffusion dialysis, etc.
|- 
| Product || '''Required''' || Out || 1 || 1 || Outlet product stream of the unit, usually purified water.
|- 
| Brine || '''Required''' || Out || 1 || 1 || Outlet brine or waste stream of the unit.
|- 
| Vent || '''Optional''' || Out || 0 || 1 || Optional gas outlet from the unit.
|}

== Behaviour when Model is OFF ==

If the user disables the unit, by un-ticking the ''On'' tick box, then the following actions occur:
* In Build 139 or later, the feed material will be split between the Brine and Product outlets based on the user specified ''MassFracToBrine'' parameter;
* In Build 138 or earlier, all feed material will flow straight out of the Brine outlet and no material will flow out of the Product outlet.
* No material will flow out of the Vent outlet;
* No sub-models will be called.

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

== Data Sections ==

The default access window consists of several sections: 

# '''[[#ReverseOsmosis|ReverseOsmosis]]''' - The first tab contains general information relating to the unit and allows the user to configure the unit 
# '''[[Phase Change (PC)|PC]]''' - Optional tab, only visible if EB.Solubility.On and/or EB.PhaseChange@T.On is enabled in the Evaluation Block.
# '''[[RB]]''' - Optional tab, only visible if Reactions are enabled in the Evaluation Block.
# '''[[EHX]]''' - Optional tab, only visible if EnvironHX is enabled in the Evaluation Block.
# '''[[Evap]]''' - Optional tab, only visible if Evaporator is enabled in the Evaluation Block.
# '''[[MU]]''' - Optional tab, or multiple tabs if more than 1 Makeup is selected.  Only visible if one of more Makeups are enabled in the Evaluation Block.
# '''[[DB]]''' - Optional tab, or multiple tabs if more than 1 Discard Block is selected.  Only visible if one of more Discard Blocks are enabled in the Evaluation Block. Only available in Build 138 or later.
# '''[[Material Flow Section|QFeed]]''' - Optional tab, only visible if ''ShowQFeed'' is enabled. This page shows the properties of the mixed stream as the feed to the unit.  If user has specified a required pressure in the unit, the mixed feed will be set to this pressure. This may cause the temperature of the mixture to change if the delta P is significantly different. 
#* This is before any [[Evaluation Blocks|Evaluation Block]] sub-models are evaluated.
#{{ShowQout|Prod|Product}}
#{{ShowQout|Brine}}
# '''[[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.

=== ReverseOsmosis ===

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

{|   border="1" cellpadding="5" cellspacing="0" 
|-
|width=250|'''Tag (Long/Short)'''||width=110|'''Input / Calc'''||'''Description/Calculated Variables / Options'''
|-
{{Common Data on First Tab Page}}
|-
|  colspan="3" font style="background: #ebebeb"    | '''''Requirements'''''
|-
| On || Tickbox || This variable in used to turn the unit ON or OFF. If the unit is OFF:<br>* In Build 139 or later, the feed will be split between the two outlets based on the value of ''MassFracToBrine'' (see below).<br>* In Build 138 or earlier, all feed will exit via the Brine outlet.
|- 
| MassFracToBrine_WhenOff / MassFracToBrine || Input || Only available in Build 139 or later. Only visible if Model is Off ('On' is unticked). This variable allows the user to set the fraction of the feed to send to the Brine outlet. The remainder will be sent to the Product outlet.
|- 
| valign="top" rowspan="2" | Model|| Simple || User only needs to specify Yield and Overall efficiency.  No setting of pressures.  No sub-models can be used.
|-
| General || User can choose from several efficiency methods and specify the outlet pressures. Sub-models can be used.
|-
| YieldReqd || Input || Required fraction of pure water in the feed which is recovered to the product stream.
|-
| valign="top" rowspan="3" | EffMethod <br>(Only visible if ''Model=General'')|| Overall  || User can specify a single efficiency of removal for all non-water liquid species.
|-
| Individual Phase || User can specify an efficiency of removal for each individual liquid phase.
|-
| Impurity Frac || User can specify the fraction of impurities in the product stream.
|-
| EfficiencyReqd || Input || Only available if Model is set to '''Simple''', or with '''General''' Model, EffMethod is set to '''Overall'''. Required fraction of liquid species other than water that are recovered to the brine stream.
|- 
| EfficiencyReqd.x || Input || Only available if EffMethod is set to '''Individual Phase'''. Required fraction of species in individual phase '''x''' (other than water) that are recovered to the brine stream.
|- 
| ImpurityFracReqd / ImpFracReqd || Input || Only available if EffMethod is set to '''Impurity Frac'''. Required fraction of liquid species other than water in the product stream.
|- 
|  colspan="3" font style="background: #ebebeb"    | '''''Pressure Requirements''''' (Only visible if '''Model''' selected is '''General''')
|-
| Prod.PressureReqd / Prod.P_Reqd || Input || Required pressure of the product stream.
|-
| Brine.PressDropReqd / Brine.PDropReqd || Input || Required pressure drop from the feed pressure to the brine stream.
{{OperatingP}}
|-
| font style="background: #ebebeb" colspan="3"  | '''EB...''' (Flow Evaluation Block)  (Only visible if '''Model''' selected is '''General''')
{{EB Evaluation Data Section | Makeups = Yes | Reactions = Yes | EnvironHX = Yes | Evaporation = Yes | Discard = Yes}}
|-
| font style="background: #ebebeb" colspan="3"  | '''''Residence Time'''''
{{Residence Time Data Section}}
|-
| font style="background: #ebebeb" colspan="3"  | '''''Options'''''
|-
| ShowQFeed || Tick Box || QFeed and associated tab pages (e.g. Sp) will become visible, showing the properties of the combined feed stream. See [[Material Flow Section]]. This will be prior to any sub-model (e.g. reactions) actions.
{{ShowQout DataSection|Prod|Product}}
{{ShowQout DataSection|Brine}}
|-
| TrackStatus || Tick Box || If this box is checked, the unit will flag warnings if gases are present but no vent connected, or if solids are present.
|-
| font style="background: #ebebeb" colspan="3"  | '''''Separation Results'''''
|-
| Yield ||font style="background: #ebebeb"| Calc || Fraction of pure water in the feed which is recovered to the product stream.
|-
| Efficiency ||font style="background: #ebebeb"| Calc || Fraction of liquid species other than water that are recovered to the brine stream.
|-
| Brine.PressDrop / Brine.PDrop ||font style="background: #ebebeb"| Calc || Pressure drop from the feed pressure to the brine stream.
|-
| font style="background: #ebebeb" colspan="3"  | ''Product''
{{RO Unit Results Data Table| Tag=Prod | Name=product }}
|-
| font style="background: #ebebeb" colspan="3"  | ''Brine''
{{RO Unit Results Data Table| Tag=Brine| Name=brine}}
|-
| GridDisplay || Tickbox || Toggles between showing the product and brine stream results in a grid (table) format or in a list. This is a global selection that will affect the display of results in other access windows.
|}

== Adding this Model to a Project ==

{{Adding Model to a Project | DllName=Separation | DllSubGroup=Separation | UnitOp=Reverse Osmosis | Group=Mass Separation}}

== Example Project ==
*[[Example_-_02Feature_Projects#Water_Treatment_.28Demand.29_Project|Water Treatment (Demand) Project]]
*[[Example_90_Water#Desalination_Example|Desalination Example]]
*[[Nickel Copper Project]]