Executing the Simulation

If you are new to PRO/II, or are looking for an overview on how to set up a simulation, see Process Simulation Using PRO/II's GUI.

The simulation cannot be run until all flowsheet topology has been correctly defined, all required unit operation and stream input have been supplied, and the component data and thermodynamic methods have been defined. Completeness of these data is indicated visually by the absence of red push buttons on the toolbar and red stream or unit labels. Pressing the button or the Run button when the data is incomplete brings up a message to indicate the required data.

To execute the flowsheet, push the button on the Run toolbar or click the <F9> key. This option first performs the Check Data cross checks on the simulation data; and if no errors are found, the flowsheet calculations begin. If errors are found, they are viewed by pressing the Status button on the Run Toolbar or by selecting the Status option on the View menu. When the errors have been corrected, push the button again to cross check and execute the flowsheet.

You may wish to interact with the flowsheet calculations. You may do this by stepping through the calculations one unit at a time with the Step button on the Run Toolbar or you may set calculation "breakpoints" in the flowsheet. Calculations are halted at the "breakpoints" until you restart them by pushing the Run or Step buttons. Thus, you can halt the calculations, inspect the results, change unit and/or stream data, and then resume the calculations.

To set breakpoints, push the Set Breakpoints button on the Run Toolbar to enter Breakpoint mode. The Breakpoints Window will be displayed giving a list of the units in the flowsheet. To set a breakpoint at a unit, position the cursor on the unit icon and press the left mouse button. The selected unit is highlighted in the list box in the Breakpoints Window and the icon fill color is changed to purple, indicating a breakpoint. To delete a breakpoint, select the unit and click the left mouse button again.

You may add new units and/or streams to the flowsheet and then push the Run button to run the revised flowsheet. Note that if you restart the calculations by pushing the Run button, they are started from the beginning of the flowsheet by default.

You may wish to restart the calculations at a particular unit operation after you have made changes to the unit and/or stream data or to the flowsheet topology. To mark a unit operation as the first unit to recalculate, select the unit and then click the Goto button on the Run Toolbar. Click Run to restart the flowsheet calculations at the marked unit, or the Step button to calculate the marked unit only.

Calculations may also be halted by pushing the button on the toolbar or by clicking the Pause/Break key. PRO/II stops the calculations at an appropriate juncture and marks the current unit as the beginning of calculation when calculations are restarted. However, if you make changes to the flowsheet topology or input data, the calculations are restarted at the beginning of the flowsheet unless the Goto feature is used as described above to mark a desired starting unit for the calculations.

The calculation status of each unit operation is indicated by using the following color code:

Green : Unit is being calculated.

Blue : Unit calculations were performed successfully.

Yellow : Unit calculations were performed successfully with warnings.

Red : Unit calculations failed.

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