A process to separate propylene and propane to produce (99 mathrm{~mol} %) propylene and (95 mathrm{~mol} %)

Question:

A process to separate propylene and propane to produce \(99 \mathrm{~mol} \%\) propylene and \(95 \mathrm{~mol} \%\) propane is shown in Figure 21.16. Because of the high product purities and the low relative volatility, 200 stages may be required. Assuming 100\% tray efficiency and a tray spacing of 24 in., two towers are installed because a single tower would be too tall. The distillate is vapor at \(280 \mathrm{psia}\), and a pressure increase of \(0.1 \mathrm{psi}\) is assumed on each tray with a 0.2 -psi increase in the condenser. Note that the stage numbers and reflux ratio are for a nominal design. In this exercise, a suitable objective function is to be selected and the number of stages and reflux ratio are to be adjusted to find the optimum. Pay close attention to the determination of the proper feed stage to avoid pinch or near-pinch conditions.

Figure 21.16:-

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