Determination of packing layer height at a counterflow movement of phases in an ideal displacement mode

Abstract

Mass exchange in an absorption packing column at a gas and liquid phases countercurrent movement in the mode of ideal displacement is analyzed. The main goal of the study is to solve the inverse problem – calculation of the apparatus height necessary to achieve concentration of a target product in a liquid phase at the device exit of desirable value .

 The basic mass exchange equations for this case are: , ,  where ,  - concentrations of the target component (TC) in gas and liquid, respectively; ,  - fictitious (constant) velocities of gas and liquid in a porous layer;    - specific surface area of ​​the packing particles;  - coefficient of packing wetness;  - coefficient in the taken linear relationship of the equilibrium dependence  and, accordingly,  (_* - the sign of the equilibrium law); ,  - mass transfer coefficients;  - a linear coordinate along the packing layer. 

 Dimensionless similarity criteria convenient for the problem analysis are introduced. From the initial equations, the dependence of apparatus dimensionless length  on dimensionless parameters (similarity criteria)  and  is obtained:

, where ; ; ; ;  - dimensional height of the device. The boundary conditions correspond to the set goal:  - concentration of the TC in a gas phase in an inlet section of the apparatus ();  - concentration of the TC in a liquid phase in an outlet section of the apparatus   ().

Borders in the field of criteria and, separating rational and undesirable organization of the process, are identified. The obtained dependence allows to calculate the height of the column in which it is possible to realize a noted requirement – achievement of required (for technical reasons) concentration of TC in a liquid phase (). These calculations are convenient in production practice.