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Evidently a temperature rise of 70C would not be a safe design because the equilibrium line nearly touches the operating line near the bottom of the tower, creating a pinch. A temperature rise of 60C appears to give an operable design, and for this case LM = 349 kmol per 100 kmol of feed gas.

The design diagram for this case is shown in Fig. 14-10, in which the equilibrium curve is drawn so that the slope at the origin m2 is equal to 2.09 and passes through the point x1 = 0.02/3.49 = 0.00573 at y° = 0.00573 x 2.79 = 0.0160.

The number of transfer units can be calculated from the adiabatic design equation, Eq. (14-46):

Evidently a temperature rise of 70C would not be a safe design because the equilibrium line nearly touches the operating line near the bottom of the tower, creating a pinch. A temperature rise of 60C appears to give an operable design, and for this case LM = 349 kmol per 100 kmol of feed gas.

The design diagram for this case is shown in Fig. 14-10, in which the equilibrium curve is drawn so that the slope at the origin m2 is equal to 2.09 and passes through the point x1 = 0.02/3.49 = 0.00573 at y° = 0.00573 x 2.79 = 0.0160.

The number of transfer units can be calculated from the adiabatic design equation, Eq. (14-46):

The estimated height of tower packing by assuming HOG = 0.70 m and a design safety factor of 1.5 is hT = (14.4X0.7X1.5) = 15.1 m (49.6 ft)

For this tower, one should consider the use of two or more shorter packed sections instead of one long section.

Another point to be noted is that this calculation would be done more easily today by using a process simulator. However, the details are presented here to help the reader gain familiarity with the key assumptions and results.