View source for Flash Tank 2

[[Category:Models]]
{{Navigation|[[Models]]|[[Models#Energy Transfer Models|Energy Transfer Models]]}}
{{Flash Cond HX header table|currentpage=1}}
Related Links:[[Flash Tank 2 in Dynamic Mode|Flash Tank 2 in Dynamic Mode]] 
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== General Description ==

The Flash Tank 2 is used to 'flash' a feed stream to produce a liquid and vapour product at a set pressure. The liquids and vapours leave the unit separately. 

:<u>'''Flash Tank 2 in Steady State Mode'''</u>
:*There are two operational modes for the flash tank 2 model, a) as a stand-alone unit or b) as part of a [[Flash Train]]. The operational mode is chosen by the user, but in order for the Flash Train method to work, the Flash Tank needs to be connected to other flash train aware units such as other flash tanks, Barometric Condensers and/or heat exchangers.
:*If the Flash Tank 2 is inserted as part of a Flash Train, see [[Flash Train]] for a description of the theory and variables. This documentation will only discuss the variables for a 'stand alone' Flash Tank 2.

:<u>'''Flash Tank 2 in Dynamic Mode'''</u>
:*In Dynamic Mode, the flash tank will only operate in the Stand Alone mode, user will need to set/adjust the pressure of the flash tank either manually or via a controller.  The [[Flash Train Control]] is recommended if the flash tank is to be part of a flash train (flash train units needs to be specified by the user, as the flash train will not be formed automatically in dynamic mode).
:*In Dynamic mode, user is allowed to define volume and shape for the flash tank.
:*See [[Flash Tank 2 in Dynamic Mode]] for more information.

The Vapour Liquid Equilibrium section allows the user to configure which species to flash and / or the flashing method, fully described in [[Vapour Liquid Equilibrium (VLE)]].

The VLE sub-model is always enabled and would usually be the last sub-model evaluated. Other sub-models allowed as part of the Evaluation Block (EB) are [[Makeup Block (MU)]], [[Reaction Block (RB)]] and [[Environmental Heat Exchanger (EHX)]].

=== Diagram ===

[[Image:Models-Flash-Tank2-image001.gif]]

The diagram shows the default drawing of the flash tank, with the required connecting streams. When the user inserts a flash tank into a flowsheet, he may choose a different drawing from a pull down menu.

== 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''' 
|-
| Feeds  || 1 Required  ||  In || 1 || 20 || Flash tank feed
|-  
| Liquor || Required    || Out || 1 || 1  || Liquor outlet
|-  
| Vapour || Required    ||  In || 1 || 1  || Vapour outlet
|}

== 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;
* No material will flow out of the 'Vapour' outlet;
* The pressure of the outlet streams will be the pressure of the input stream, or the minimum pressure of all input streams if more than one inlet;
* No Flashing or sub-models such as reactions will occur.

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

== Model Theory ==

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)]]'''.

== Flowchart ==

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

 

[[Image:Models-Flash-Tank2-image008.gif]]

== Data Sections ==

The default access window consists of several sections: 
# '''[[#Flash Tank2 Page|FlashTank2]]''' tab. This first tab contains general information relating to the unit.
# '''[[Flash Tank 2 in Dynamic Mode]]''' tab. This section contains the variables that will only be visible in dynamic mode.
# '''[[RB]]''' - Optional tab, only visible if the Reactions are enabled.
# '''[[EHX]]''' - Optional tab, only visible if the EnvironHX is enabled in the Evaluation Block.
# '''[[VLE]]''' - Only visible if the VLEquilibrium is enabled (If it is NOT enabled, then the Flash Tank will operate as a pipe)
# '''[[MU]]''' - Optional tab, or multiple tabs if more than 1 Makeup is selected.  Only visible if one of more Makeup is enabled in the Evaluation Block.
# '''[[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 tank.
#* This is before any Evaluation Block models are evaluated.
# '''[[Material Flow Section|QProd]]''' - This page shows the properties of the Flash Tank discharge as a single stream.
#* This is AFTER the flash calculations, but before the split to liquid and vapour streams.
# '''[[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.

===Flash Tank2 Page===
'''Unit Type: FlashTank2''' - The first tab page in the access window will have this name.

{|   border="1" cellpadding="5" cellspacing="0" 
|-
|width=200|'''Tag (Long/Short)'''||'''Input / Calc'''||'''Description/Calculated Variables / Options'''
{{Common Data on First Tab Page}}
|-
|  colspan="3" font style="background: #ebebeb"    |

=== Requirements ===
|-
| Width=150|On || Width=150|Tickbox || This variable in used to enable flashing in the unit. If this not selected, the material will flow out of the liquor outlet with no change in state, i.e. the unit acts as a pipe.
|- 
| valign="top" rowspan="2" | Mode|| Stand Alone (Manual)|| The flash tank will not form part of a flash train.
|-
| | Flash Train || The flash tank will form part of a [[Flash Train]] if appropriate units are connected to it. The ''OperatingP - Method'' will be set to '''Saturated'''.

{{OperatingP FlashTank | UnitOp=Flash Tank}}
|-
| font style="background: #ebebeb" colspan="3"  |
=== EB (Evaluation Block)... ===
{{EB Evaluation Data Section | Makeups = Yes | Reactions = Yes | EnvironHX = Yes }}
|-
| VLEquilibrium || font style="background: #ebebeb"|Display|| This shows that the [[Vapour Liquid Equilibrium (VLE)]] is always on for the Flash Tank2 model. The associated page, VLE may be configured. <br> '''Note''': This option may automatically adjust the species make-up.
|-
| font style="background: #ebebeb" colspan="3"  |

=== Options ===
|- 
|  VapStandardSpModel ||  Tick Box ||If ticked then the Standard (default) species model will be used in the vapour exit stream. This selection has no effect on the model operation.
|- 
|ShowQFeed||  Tick Box ||[[Material Flow Section|QFeed]] and associated tab pages (e.g. Sp) 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 any flashing calculations or other sub-models occur.
|- 
|ShowQProd||  Tick Box ||[[Material Flow Section|QProd]] and associated tab pages (e.g. Sp) will become visible if this is enabled.  These tabs will show the properties of the combined product streams from the Unit.  These values are after any flashing calculations or other sub-models occur but before the final phase split is made.
|- 
| font style="background: #ebebeb" colspan="3"  |

=== Vapour Entrainment ===
|- 
| FlashVapToLiquid || Input || This field allows the user to set a proportion of the flash vapour bypassing to the liquid stream.  The default is 0%. 
|- 
| OtherGasToLiquid || Input || This field allows the user to set a proportion of any non-condensable gas bypassing to the liquid stream.  The default is 0%. 
|- 
|  colspan="3" font style="background: #ebebeb"    |

=== Results ===
{{Flash Tank Results Data Section}}
|-
|  colspan="3" font style="background: #ebebeb"    | '''''Flash Train Macro Model''''' 
These extra fields are only visible if the unit is part of a [[Flash Train]].
{{Flash Train Macro Data Table Section| Cond = No | Evap = Yes | Name1=FT_001   | Name2=ST2_001  }}
|}

== Adding this Model to a Project ==

{{Adding Model to a Project | DllName=HeatExchange | DllSubGroup=Heat Transfer | UnitOp=Flash Tank(2) | Group=Energy Transfer}}

== Hints and Comments ==

# There may be mass entering or leaving the unit via the [[Reaction Block (RB)|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.
# The information in the [[Vapour Liquid Equilibrium (VLE)|VLE Section]] must be correct for the Flash Tank to operate as required. If the VLE configuration requires information that is not available, then the flashing will not occur.