Column Plot Options

This window is used to select several types of plots for column results, formatted for a line printer. To produce graphical plots, select Output\Generate Plot command.

Usage

Select the desired plot options and select the desired phase and component names from the drop-down list boxes.

Temperature and Flow Profiles

Selecting this option produces a plot which has the column temperatures and flowrates versus tray number.

Composition Profiles

This option produces a plot of selected component mole fractions for each phase on the tray. The Plot Basis drop-down list box may be used to select a linear or logarithmic basis for the composition axis.

Multiple groups of components or conglomerates of individual components for the plots are selected in the table provided. The drop down list boxes are used to select the phase, starting, and ending components. For a single component, the same starting and ending component should be selected. When a different ending component is provided, all

consecutive components from the starting component through the ending component are summed and included in the plot data.

Separation Factor Profiles

This option produces a plot first suggested by Hengstebeck, where the logarithm of the ratio of the light key mole fraction divided by the heavy key mole fraction is plotted versus tray number. A classic "S" shaped curve is produced, with the inflection point at the column feed tray for properly designed columns. The plot is useful for analysis of the column feed point and tray performance.

The drop-down list boxes are used to select the light and heavy key components, where a range of consecutive components may be designated as the light or heavy key by using an ending component different from the beginning component.

The light key is that component which is mostly (but not completely) recovered in the overhead product. The heavy key is that component which is mostly (but not completely) recovered in the bottom product. Sometimes there is a split key, i.e., a component or components which fall between the light and heavy keys in the column recovery table. Selection of the proper key components is essential when using the separation factor profile for column analysis.

Tip on Column Analysis

It is good practice to arrange the problem components in volatility order. This makes it easier to analyze the distributed components in the products and locate the separation keys. When the separation keys are used for performance specifications a unique column solution which matches the operation is assured. For example: specify the isopentane (heavy key) recovered in the bottoms and the normal butane (light key) recovered in the overhead for a debutanizer column.