1. Stripping process design Prof. Dr. Marco Mazzotti - Institut für Verfahrenstechnik

2. 1. The Column Material balance: Simplifications T,P constant value Raoults law m=distribution coefficient xn xn Specification T, p Lx0Lx0 Given Data y n+1 L G Unknown G y1y1 n

3. 2. Diagram xnxn x0x0 y n+1 The known data is plotted in a x,y Diagram x * n+1 Equilibrium line The equilibrium line is plotted Operating line The operating line is plotted for n  The slope of the operating line =

4. 3. Dimensioning of the Column 3.1 Calculating the necessary gas amount Good values of a are between 1.2 and 2 In the practice, the slope for the operating line is taken as 1 to 2 times the minimum slope:

5. 3.2. Number of stages by graphical Construction y n+1 xnxn x0x0 The known data is ploted in a x,y Diagram Equilibrium line The Equilibrium line is plotted The Operating line is plotted Goal (here 3 Stages) n n-1 n-2 The number of stages n are constructed using the proceedure seen in the counter- current stage configurationcounter current

6. 3.3. Number of stages by Kremser Equation Solving this equation for n gives the number of stages Kremser Equation (as shown in Counter current cascade)Counter current cascade Stripping Factor: Fractional stripping:

7. 4. Final Procedure As it is not possible to build decimal stages the number resulting from the Kremser equation has to be round up to the next integer. From this the exact stripping fraction  and the concentration x 0 can be calculated xn:xn: y1:y1: The gas concentration y 1 can be calculated by using the total mass balance

8. Unknown: Gas flow rate G Number of stages n Temperature T Pressure P Gas composition at outlet y 1 Goal: Liquid stream purification using a gas to a certain specification x n Given data: Liquid flow rate L Liquid composition, x 0 Composition of gas stream y n+1