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The separation parameter is calculated using Eq. (3.3).

The separation parameter is calculated using Eq. (3.3).

To estimate the relative volatility, one can use the volatility between the key components. This may provide a good approximation when the fraction of nonkeys is small, but a less satisfactory approximation when the fraction of nonkeys is large. In this case, this approximation will give an N of 44 stages, which compares unfavorably with previous calculations (Example 3.4).

An alternative approach is to use a pseudo relative volatility, which can be obtained if the number of theoretical stages is known. This number of stages can be computed using a rigorous simulation of the column. A pseudo relative volatility is then calculated using Eq. (3.40), and can be applied for control purposes. A rigorous computer simulation gave 20 theoretical stages for this calculation (Example 3.4). The pseudo relative volatility is therefore back-calculated from i /, 1.5 + 0.34

Solving give apseud0 = 2.572

A material balance for the new conditions gives

Component

Feed

Distillate

Bottoms

Distillate

Bottoms

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