Fit the test run data and review the results

When data has been correctly entered for each product, pressing Fit will fit the entered data to provide the best-fit set of parameters consistent with the measured distillation and yield data, according to the separation model you have chosen. See Select a separation model.

After fitting the test run data, you may review:

• The numerical quality of the fit.

• The generated parameters for the fit.

• The graphical quality of the fit.

The numerical quality of the fit may be reviewed by checking the values in the grid cells, to review how closely the yields and distillation profiles were matched during the fitting process. The top right value of each cell shows the fitted value, for comparison against the measured value you entered. Small differences are to be expected, while large boiling point or yield discrepancies should lead to a review of the input data. For more information on grid cells and their contents. See Standard and advanced grid.

To review the generated parameters for the fit, examine the grid at the bottom of the window. Here you can see the cut points and fractionation indices which have been fitted to the test-run data. It is unusual to have fractionation indices less than 0.5 or higher than about 6, and such indices may suggest erroneous data. Similarly, cut points should sensibly map to the products you have entered.

Several buttons are available for working with distillation unit fitting data and results:

• Fit: calculate the system fractionation parameters based on the entered test run data.

• Clear: delete any distillation present in the Distillation Grid but does not affect any entered values for ECP or FI.

• Import: import distillation unit fitting data from an external .tfd file.

• Export: export distillation unit fitting data to a .tfd file.

• View: choose between the standard and advanced grid.

• Show/Hide Graph: show or hide the distillation graph.

Distillation Unit fitting data can be exported to an external .tfd file, and these files can be imported to the Distillation Unit Fitting dialog. Such data can only be imported to the Distillation Fitting Unit dialog if the flowsheet has the same number of flowsheet streams. Distillation unit fitting data is saved in a flowsheet file and will be exported if the flowsheet is exported.