Determine the number of equilibrium stages needed for separation of light hydrocarbons in a stripping column by stepping off stages and doing a dew- or bubble-point calculation at each stage. The \(100.0 \mathrm{kmol} / \mathrm{h}\) of saturated liquid feed at \(7.0 \mathrm{bar}\) is \(35.0 \mathrm{~mol} \% \mathrm{n}\)-butane, \(45.0 \mathrm{~mol} \% \mathrm{n}\)-pentane, and \(20.0 \mathrm{~mol} \%\) n-hexane. The column is at 7.0 bar, has a partial reboiler, and CMO can be used. The bottoms product is \(98.2 \mathrm{~mol} \% \mathrm{n}\)-hexane and \(\approx / \mathrm{B}=19.0\). Make an appropriate assumption about distribution of the components, solve the mass balances, and determine \(\mathrm{B}, \mathrm{D}\), and mole fractions of distillate and bottoms products. Use either DePriester charts or Eq. (2-28) to step off stages. Report the temperature of each stage and the vapor and liquid mole fractions leaving each stage. Use of Table 2-5 constants in a spreadsheet to do dew- or bubblepoint calculations will probably save you time.

Equation 2-28

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TABLE 2-5. Constants for fit to K values using Eq. (2-28) Compound a1 12 ap1 ap2 ap3 Mean Error Methane -292,860 0 8.2445 -0.8951 59.8465 0 1.66 Ethylene -600,076.875 0 Ethane -687,248.25 0 Propylene -923,484.6875 0 Propane -970,688.5625 0 7.90595 -0.84677 42.94594 0 7.90694 -0.88600 49.02654 0 7.71725 -0.87871 47.67624 0 2.65 1.95 1.90 7.15059 -0.76984 0 6.90224 2.35 Isobutane-1,166,846 0 7.72668 -0.92213 0 0 2.52 n-Butane -1,280,557 Isopentane -1,481,583 0 7.94986 -0.96455 0 0 3.61 0 7.58071 -0.93159 0 0 4.56 n-Pentane -1,524,891 0 7.33129 -0.89143 0 0 4.30 n-Hexane -1,778,901 0 6.96783 -0.84634 0 0 4.90 n-Heptane -2,013,803 0 6.52914 -0.79543 0 0 6.34 n-Octane 0 -7646.81641 12.48457 -0.731520 0 7.58 n-Heptane -2,013,803 0 6.52914 -0.79543 0 0 6.34 n-Octane 0 -7646.81641 12.48457 -0.731520 0 7.58 n-Nonane -2,551,040 0 5.69313 -0.678180 0 9.40 n-Decane 0 -9760.45703 13.80354 -0.714700 0 5.69