Stage calculations optimum reflux

Follow the calculation procedure outlined in Table 6.28 using Equations listed in Table 6.27. The light key (LK) is ethane and the heavy key (HK) is propylene. First, calculate the composition of the top and bottom products. Then, determine the optimum reflux ratio. Next, calculate the number of equilibrium stages. Finally, calculate the location of the feed tray. 

It is required to separate the benzene-toluene mixture of Example 6.1 into a benzene-rich distillate with 0.80 mole fraction benzene and a toluene-rich bottoms with 0.05 mole fraction benzene. The separation is to be made using a distillation column with 15 theoretical stages that include a partial condenser and a partial reboiler. Calculate the reflux ratio required to achieve the specified separation and determine the optimum feed location. What effect would lowering the number of stages to ten have on the reflux ratio and the optimum feed location ... 

The analysis of the minimum reflux mode is used at the stage of sequence selection, as well as at the stage of determination of optimum reflux ratios and the quantity of column trays. The geometric theory of distillation makes it possible to develop the general methods of calculation of minimum and more reflux mode. 

However, the total number of equilibrium stages N, N/N,n, or the external-reflux ratio can be substituted for one of these three specifications. It should be noted that the feed location is automatically specified as the optimum one this is assumed in the Underwood equations. The assumption of saturated reflux is also inherent in the Fenske and Underwood equations. An important limitation on the Underwood equations is the assumption of constant molar overflow. As discussed by Henley and Seader (op. cit.), this assumption can lead to a prediction of the minimum reflux that is considerably lower than the actual value. No such assumption is inherent in the Fenske equation. An exact calculational technique for minimum reflux is given by Tavana and Hansen [Jnd. E/ig. Chem. Process Des. Dev., 18, 154 (1979)]. A computer program for the FUG method is given by Chang [Hydrocarbon Process., 60(8), 79 (1980)]. The method is best applied to mixtures that form ideal or nearly ideal solutions. 

A distillation column is separating 100 mol/s of a 30 mol% acetone, 70 mol% methanol mixture at atmospheric pressure. The feed enters as a saturated liquid. The column has a total condenser and a partial reboiler. We desire a distillate with an acetone content of 72 mol%, and a bottoms product with 99.9 mol% methanol. A reflux ratio of 1.25 the minimum will be used. Calculate the number of ideal stages required and the optimum feed location. VLE for this system is described by the modified Raoult s law, with the NRTL equation for calculation of liquid-phase activity coefficients, and the Antoine equation for estimation of the vapor pressures. 

One hundred kilogram/moles per hour of a saturated liquid mixture of 12mole% ethyl alcohol in water is distilled continuously by direct steam at I atm. Steam is introduced directly to the bottom plate. The distillate required is 85 mole% alcohol, representing 90% recovery of the alcohol in the feed. The reflux is saturated liquid with L/D = 3. Feed is on the optimum stage. Vapor-liquid equilibrium data are given in Problem 8.30. Calculate ... 

An equimolal mixture of carbon tetrachloride and toluene is to be fractionated so as to produce an overhead containing 4 mole% toluene and a bottoms containing 4 mole% carbon tetrachloride. Calculate by the Ponchon method the theoretical minimum reflux ratio, the theoretical minimum number of stages, and the number of theoretical stages when LID = 2.5. The thermal condition of the feed is saturated liquid, which is sent to the optimum stage. 

G3. Write a computer, spreadsheet, or calculator program to find the number of equilibrium stages and the optimum feed plate location for a binary distillation with a constant relative volatility. System will have CMO, saturated liquid reflux, total condenser, and a partial reboiler. The given variables will be F, Zp, q Xg, Xp, a, and Lq/D. Test your program by solving the following... 

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