unit operations lectures 12 & 13

Unit OperationsLectures 12 & 13

1

12 Oct 2012

Overview

2

• AspenPlus:o Shortcut methods: DSTWUo Rigorous method: RADFRAC

• Efficiencies• Introduction to multicomponent distillation

AspenPlus: DSTWU

3

Tray Operation

4

a) Sprayb) Froth *c) Emulsiond) Bubblee) Cellular foam

Types of Trays

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a) Sieveb) Valvec) Bubble cap

Operation

6

Typically columns operated at 50% - 85% of flooding.

Seader et.al., 2012Figure 6.21 Limits of stable operation in a trayed tower. [Reproduced by permission from H.Z. Kister, Distillation Design, McGraw-Hill, New York (1992).]

Operation

7

Video:FRI (Fractionation Research, Inc.) non-profit research consortium“Design and Performance of Fractionating Devices”

http://www.fri.org/

Operation

8

Typically columns operated at 50% - 85% of flooding.

Seader et.al., 2012Figure 6.21 Limits of stable operation in a trayed tower. [Reproduced by permission from H.Z. Kister, Distillation Design, McGraw-Hill, New York (1992).]

Efficiencies

9

Assumed equilibrium stages, but may not reach equilibrium on a stage;

why?

Flooding!

Efficiencies

10

Overall column efficiency:actual

equilO N

NE

Murphree efficiency:..

.* equilatchangeconcvapor

changeconcvaporactualyyyyE

inout

inoutMV

)417(1

*1

eqnyyyyE

nn

nnMV

OGNMV eE 1

Efficiencies

11

Efficiencies

12

Seader & Henley, 2006

Efficiencies

13

MVE

P.C. Wankat, 2nd., 2007

Overview

14

• Questions on homework??• McCabe-Thiele graphical technique (binary systems)

• Condensers• Reboilers

• Binary Shortcut Methods• AspenPlus:o Shortcut methods: DSTWUo Rigorous method: RADFRAC

• Efficiencies• Introduction to multicomponent distillation (read Ch 5 & 7 in

Wankat)

Questions?

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