Comparison between co-, cross- and counter-current

1. Comparison between co-, cross- and counter-current Prof. Dr. Marco Mazzotti - Institut für Verfahrenstechnik

2. In order to compare the three cascade configuration, co-, cross- and counter-current, we use the fraction of absorption, a. The fraction of absorption is defined as: ... and represents the amount of solute absorbed divided by the maximum amount of solute that can be absorbed, which is given by the equilibrium. The fraction of absorption represents therefore the extension of the absorption process. The fraction of absorption increases when the number of stages increases. When an infinity number of stages is used the fraction of absorption is maximum. This value of a when the number of stages tends to infinity, will be used to compare the different configurations.

3. y1 y2 G, y0 y3 1 2 3 x1 x2 L, x0 x3 a n Co-current cascade

4. L, x0 1 2 3 L/3 L/3 L/3 y1 y2 G, y0 y3 x1 x2 x3 a n Cross-current cascade

5. y1 L, x0 1 2 3 y1 y2 x1 x3 a x2 G, y4 n Counter-current cascade

6. a n Comparison The graphical representation gives the picture of the maximum absorption factor for each case. The absorption factor is always bigger for the counter-current case. Counter-current Cross-current Co-current