Uj

Figure 3.13 Renamed flowsheet.

column C1. Some logical scheme for renaming units and streams is essential in a large plantwide simulation with many units and many streams.

The structure of the flowsheet is now completely specified. Next we must define the chemical components involved in the separation and specify what physical property package is to be used. Chapter 1 discussed many aspects of choosing a physical property relationship to ensure that an accurate representation of reality is used.

A simple binary separation of propane from isobutane is used in the numerical example considered in this chapter. The VLE relationships for most hydrocarbon systems are well handled by the Chao-Seader correlation, so we select that package.

To start specifying chemical components, go to the toolbar at the top of the window and click the fourth item from the left Data. Select the top item Setup. This opens the Data Browser window shown in Figure 3.14. This is the window that is used to look at all aspects of the simulation. It is used to define components, set physical properties, specify the parameters of the equipment (e.g., the number of stages in the column and the pressure), and specify properties of various streams (e.g., flowrate, composition, temperature and pressure).

A couple of preliminary items should be done first. In the middle of the window there are two boxes in which we can specify the units to be used in the simulation. Figure 3.15 shows the standard three alternatives: ENG (English engineering), MET (metric) and SI (Systeme International). We will use SI units in most of the examples in this book because of their increasing importance in our global economy. However, we will make one departure from regular SI units. In the SI system, pressures are expressed in pascals

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