Specify a dynamic controller by defining a temperature or purity specification on any stage. This specification will be satisfied by varying the reflux ratio. Only one dynamic controller is allowed in any policy segment.
Usage
Controlled Variable
Select the type of specification required as either Temperature or Purity. The Purity may be molar or weight fraction.
Stage Selection
For a Temperature or Purity specification, the number of the specification stage must be entered at Column Stage.
Component Selection
Push this button to display the BATCHFRAC - Component Selection window. Then, select the first and last component in the range of the Purity specification.
Manipulated Variable
The Distillate Specification of the current Distill action is varied to meet the specification for the Controlled Variable. Though a Manipulated Variable from any of FIVE variables (Reflux Ratio, Distillate Rate, Boilup Rate, Condenser Duty or Reboiler Duty), it should be one of the distillate spec variables should be chosen as manipulated variable. Then enter the limiting minimum and maximum values.
Minimum/Maximum Values
These define the range over which the Manipulated Variable may be changed. Entries are required (there are no defaults). Manipulated Variable Lag Time constant (default =0.0) can be given if present.
Control Parameters
Dynamic Controller Gain: The controller gain represents a proportional controller action. Controller gain. Gain units are manipulated variable units divided by set point units. (All must be in SI units.) The default controller gain is 1.0, which represents a 1:1 control ratio (i.e., no scaling).
Integral time constant: Integral time constant (reset time). (Default=1x106 seconds for no integral action)
Derivative time: Derivative Time Constant can also be given for adjust the manipulated variables. (Default=zero for no derivative action)
Measured Time Lag constant: Measurement lag time constant (Default=0) if present can be given which the program take to adjust the controller variable.
To change dimensional units displayed for entries shown on the screen, open the Unit of Measure Selection Window by pressing the UOM button.
How to get to this window
The BATCHFRAC - Control Specification window is accessed by selecting Control in the Action/Condition table in the BATCHFRAC - Policy Segment window and then clicking on the linked text under Description.
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Related Topics
BATCHFRAC - Component Selection