Semester 1, Academic Year 1998/1999 Section C
Question 14
A liquid mixture of benzene-toluene is to be continuously separated in a distillation column operating at 101.3 kPa. The feed flow rate is 100 kg-mole/hr and enters the column at its bubble point. It contains 45 mole% benzene and 55 mole% toluene. A distillate containing 95 mole% benzene and a bottoms containing not more than 10 mole% benzene are to be obtained. The reflux ratio used is 2 times the minimum reflux ratio Rmin .
Determine:
(a) Distillate and bottoms flow rates in kg-mole/hr
( 6 marks )
(b) Minimum reflux ratio Rmin
( 7 marks )
(c) Number of theoretical trays needed
( 7 marks )
Equilibrium curve for benzene-toluene system at 101.3 kPa is given below:
Question 15
A counter-current gas absorption column is to be designed
to absorb SO2 from an air-SO2
mixture using pure water at 293 K. The column is to be operated at 293 K and
101.3 kPa.
Laboratory analysis showed that the gas entering the column contains 20 mole% SO2 and environmental regulations require that the gas leaving the column contains no more than 2 mole% SO2. The inert air (MW = 29) flow rate is 150 kg air/m2.hr, and the entering pure water (MW = 18) flow rate is 6000 kg water/m2.hr.
If the overall tray efficiency is 25%, determine the actual number of trays required for the separation.
( 20 marks )
Equilibrium data for SO2-water system at 101.3 kPa are given below:
