Distillation columns Murphree vapor efficiency

A small distillation column separating benzene and toluene gives a Murphree vapor efficiency of 0.65 in the rectifying section where 17V = 0.8 and x z = The tray is perfectly mixed and has a liquid... 

Mols of distillate or overhead product, lb mols/hr or batch distillation, mols Mols component, i, in distillate Vaporization efficiency of steam distillation Overall column efficiency Overall tray efficiency Eqg = Murphree point efficiency, fraction Murphree plate/tray efficiency, = E ... 

Example 8 Calculation of Rate-Based Distillation The separation of 655 Ib mol/h of a bubble-point mixture of 16 mol % toluene, 9.5 mol % methanol, 53.3 mol % styrene, and 21.2 mol % ethylbenzene is to be carried out in a 9.84-ft diameter sieve-tray column having 40 sieve trays with 2-inch high weirs and on 24-inch tray spacing. The column is equipped with a total condenser and a partial reboiler. The feed will enter the column on the 21st tray from the top, where the column pressure will be 93 kPa, The bottom-tray pressure is 101 kPa and the top-tray pressure is 86 kPa. The distillate rate will be set at 167 Ib moPh in an attempt to obtain a sharp separation between toluene-methanol, which will tend to accumulate in the distillate, and styrene and ethylbenzene. A reflux ratio of 4.8 will be used. Plug flow of vapor and complete mixing of liquid will be assumed on each tray. K values will be computed from the UNIFAC activity-coefficient method and the Chan-Fair correlation will be used to estimate mass-transfer coefficients. Predict, with a rate-based model, the separation that will be achieved and back-calculate from the computed tray compositions, the component vapor-phase Murphree-tray efficiencies. 

It is standard practice in the modeling of distillation columns to assume that the liquid is incompressible and perfectly mixed on the trays, and that the vapor and liquid have the same temperature on the tray (thermal equilibrium), whereas the phases could be considered nonequilibrium and some vapor-phase efficiency is sometimes adopted in such cases (e.g., Murphree efficiency). Beyond these possible variants, the basic distillation column model can be reduced to total... 

You plan to produce a bottoms product containing 90 mol% ethanol using another old six-plate column (plus reboiler and a total condenser) which has a Murphree efficiency of 75% you plan to use a very high reflux. The feed, containing 50 mol% acetone, is 36 mol% vapor, (a) What will the distillate concentration be (b) How much bottoms product will be produced per mole of feed ... 

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