Evaporative Dryer

From SysCAD Documentation

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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 Evaporative Dryer is used to remove the water from the solids in the feed stream. The model will use the user defined moisture remaining in the cake to calculate the amount of water to be evaporated off. Any liquid impurities will remain in the cake moisture. The unit also allows for some solids loss with the evaporated moisture.

The model assumes that the cake has a minimum of at least 0.1% moisture.

Diagram

The diagram shows the default drawing of the Evaporative Dryer, with all of the streams that are required for operation of the unit.

The physical location of the streams connecting to the dryer 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 Evaporative Dryer
Moisture	Out	1	1	The evaporated moisture outlet from the unit
Cake	Out	1	1	The Solids outlet from the unit

Model Theory

The Evaporative Dryer is based on the user-defined variables of cake moisture content and solids loss. Any impurities within the liquid feed to the unit will remain in the cake moisture, i.e. only the water will be evaporated from the cake.

Assumptions

Only water is evaporated from the feed stream. All other liquid impurities remain in the cake moisture.

The final dryer cake contains between 0.1 and 99% moisture, i.e. not all of the liquid is evaporated.

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 several sections,

1. The first tab has the same name as the model tag, contains general information relating to the unit.
2. Optional tab RB, or Reaction Block, is 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: Dryer 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
On	Tick Box	This allows the user to switch the model on or off. All feed reports to cake.
ReqdTemp	Input	The required temperature of the dryer. Both the dryer cake and the moisture streams will exit the unit at this temperature.
RqdSolidsLoss	Input	The fraction of feed solids that will be lost with the evaporated moisture.
RqdCakeMoist	Input	The required moisture content of the final dryer cake.
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.
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).
Results
CakeMoist	Calc	The calculated fraction of liquids in the final dryer cake.
WaterEvaporated	Calc	The amount of water evaporated.
EnergyRqd	Calc	The energy required to evaporate the water and heat both product streams to the final dryer temperature.

Adding this Model to a Project

Insert into Configuration file

Sort either by DLL or Group.

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

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

Insert into Project

Insert Unit

→

Separation

→

Dryer

See Insert Unit for general information on inserting units.