distillation column presentation problem.pptx

distillation

1. Distillation design – problem Acetone is to be recovered from an aqueous waste stream by continuous distillation. The feed will contain 10 per cent w/w acetone. Acetone of at least 98 per cent purity is wanted, and the aqueous effluent must not contain more than 50 ppm acetone. The feed will be at 20 o C. Take the minimum feed rate as 13,000 kg/h. Use sieve plates.

2. Solution Molecular weights Acetone 58, Water 18 Mole fractions

3. Solution From McCabe Thiele Diagram : total stages Rectification = 7 total stages Stripping = 9 Feed Location = 8 th Tray Summary Number of stages = 16 Slope of the bottom operating line = 5.0 Slope of top operating line = 0.57 Top composition = 94 per cent mol. = 98 per cent w/w. Bottom composition essentially water. Reflux ratio = 1.35

4. Solution Assume 60% tray efficiency, Actual No. of trays = (16 – 1)/0.6 = 25 stages Initial Estimate of column pressure:

5. Physical properties Top, 98% w/w acetone, top temperature 57 o C

6. Estimation of column diameter Flow Parameter:

7. K1 values Take tray spacing = 0.5 m From the graph, Correction for surface tensions :

8. Flooding velocity

9. Maximum volumetric flow rate

10. Calculation of column c/s area

11. Column diameter

12. Provisional plate design Active area Aa = Ac - 2 A d = 0.50 - 0.12 = 0.38 m 2 Hole area A h take 10 per cent A a = 0.038 m 2 A d / A c = 0.12 , From figure, Lw /dc = 0.76 Weir length = 0.76 x 0.79 = 0.60 m Take weir height = 50 mm Hole diameter = 5 mm Plate thickness = 5 mm

13. Check weeping

14. Plate pressure drop Dry plate drop:

15. Check Entrainment

16. THANK YOU