Generalized Variable Parameters

The generalized variable parameters are those which can be explicitly varied in order to satisfy the specifications set in unit operations such as controller, column and sidestripper. There is always a one-to-one relationship between the number of specifications and degrees of freedom (number of parameters that can be varied to achieve the desired result).

See Generalized Performance Specifications for more information on specifications.

Controller/Multivariable Controller

Controllers can be used to set a specification for any stream or unit operation by varying a generalized variable parameters. There is a one-to-one relationship between the specifications and degrees of freedom (variable parameters). For a list of parameters that can be varied using a controller for various unit operations, see the tables under Parameters Available for Cross-Referencing. For details on using a controller or multivariable controller within a simulation, see Controller Main Window or Multivariable Controller Main Window.

Flowsheet Optimizer

Optimizers can vary any number of flowsheet parameters in order to meet a specified objective function. For a list of parameters that can be varied using an optimizer, see the tables under Parameters Available for Cross-Referencing. For details on using an optimizer within a simulation, see Flowsheet Optimizer Main Window.

Column

Any number of specifications can be set from within a column using the Column Specification and Variable Window. However, for every column internal specification, PRO/II requires a corresponding parameter that can be varied. Inside-Out columns with sidestrippers balance the degrees of freedom across the entire system of columns. Each column or sidestripper may have an unequal number of specifications and variables, but the total sum of specifications and variables for the merged column system must be equal.

The parameters that can be varied from within the column are heater/cooler duties and feed and side draw rates. These parameters are listed under "Vary - Within unit operation" in Column Parameters Available for Cross-Referencing. Note that when these parameters are varied within the unit, they may not also be varied with a controller. See Column Internal Variable Parameters for more details.

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