Ve = V(1.0 -



2.3.4 Hengstebeck diagrams: construction

End points. These can be calculated from the overhead and bottom compositions using Eqs. (2.46) and (2.47).

Slopes of component balance lines. These can be calculated from Eqs. (2.54c), (2.54d), (2.55c), and (2.55d).

Example Calculate the end points and the slope of the operating line for Example 2.4.

1. End points: Using the data in Table 2.7, the end points are calculated using Eqs. (2.46) and (2.47)

yo.Cj 0 41

2. Vapor and liquid flow rates are set in a manner similar to the binary calculation (Sec. 2.2.4), that is,

3. Find the limiting compositions: The limiting nonkey composition is relatively a weak function of the nonkey A'-value ratios. Because of this, the K-ratios (i.e., volatilities) used in the limiting nonkey composition calculation can be approximate. Hengstebeck (14) recommends the use of if-ratios at an intermediate temperature. Inspection of Fig. 2.17 shows that the feed temperature of 205°F is close enough to being an intermediate temperature. Therefore, the if-values shown in Table 2.8 are satisfactory for limiting composition calculation.

0.274(40.1/123.9) _ *C5.lim = L0 _ (0.38/1.55) "

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