Countercurrent mass transfer

Fig. 17. Effect of axial dispersion in both phases on solute distribution through countercurrent mass transfer equipment. A, piston or plug flow B, axial...

The concept of a transfer unit for a countercurrent mass transfer process, introduced in Volume 1, is developed further for distillation in packed columns in Section 11.11. The number of transfer units is defined as the integrated value of the ratio of the change in composition to the driving force. Thus, considering the vapour phase, the number of overall gas transfer, units Nog is given by ... 

Consider a countercurrent mass-transfer device for which the equilibrium-distribution relation consists of a set of discrete values XiD,YiD instead of a continuous model such as Henry s law. An analysis to determine minimum flow rates similar to that presented in Problem 3.14 is still possible using the cubic spline interpolation capabilities of Mathcad. Cubic spline interpolation passes a smooth curve through a set of points in such a way that the first and second derivatives are continuous across each point. Once the cubic spline describing a data set is assembled, it can be used as if it were a continuous model relating the two variables to predict accurately interpolated... 

Osmotic dehydration is a complex process of countercurrent mass transfer between the plant tissue and hypertonic solution. This leads to dehydration of the material and changes in its chemical composition as well. Hence, it must be expected that the properties of the material dehydrated... 

The solid trickle phase column A column is filled with Raschig rings, or a similar packing, and a good fluidizable powder is introduced continuously at the top. Gas passes upward through the column. The powder flows downward over the packing surface. A very effective countercurrent mass transfer can be obtained in this manner (Roes, 1979). 

A crystal in such a column has a certain amount of molten liquid adhering to it (Figure 8.1.42(b)). The impurities in the crystal and the "adhering liquid have to be transferred to the free liquid flowing in the column (Albertins et al., 1967). The countercurrent mass transfer of the impurity from the crystal phase... 

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