An aqueous solution of 10 mol% isopropanol at its bubble point is fed to the top of a stripping column, operated at 1 atm, to produce a vapor of 40 mol% isopropanol. Two schemes, both involving the same heat expenditure, with V / F (moles of vapor/mole of feed) = 0.246, are under consideration. Scheme 1 uses a partial reboiler at the bottom of a stripping column, with steam condensing inside a closed coil. In Scheme 2, live steam is injected directly below the bottom plate. Determine the number of stages required in each case. Equilibrium data are given in Exercise 7.33.

Data From Exercise 7.33

A 10 mol% isopropanol-in-water mixture at its bubble point is to be distilled at 1 atm to produce a distillate containing 67.5 mol% isopropanol, with 98% recovery. At a reflux ratio L=D of 1.5 times the minimum, how many theoretical stages will be required: 

(a) if a partial reboiler is used? 

(b) if no reboiler is used and saturated steam at 101 kPa is introduced below the bottom plate? 

(c) How many stages are required at total reflux?
Vapor–liquid data in mole-fraction isopropanol at 101 kPa are:

Transcribed Image Text:

T,°C 93.00 y 84.02 82.12 81.25 80.62 80.16 80.28 81.51 0.2195 0.4620 0.5242 0.5686 0.5926 0.6821 0.7421 0.9160 0.0118 0.0841 0.1978 0.3496 0.4525 0.6794 0.7693 0.9442 X