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experiment, it is more expedient to use methods giving the possibility to obtain
the necessary value only by one experiment.
2.1.2.4.1. Mass transfer coefficient for the piston flow model

2.1.2.4.1.1. Liquid-side controlled mass transfer coefficient
As systems for obtaining the liquid-side partial mass transfer
coefficient, all processes of absorption or desorption of poorly soluble gases in
pure liquid can be used. So for example at the beginning of the investigations in
this area, to examine the influence of the diffusivity on the volumetric mass
transfer coefficient, Sherwood and Holloway [67] used 02, CO2, Ar and He.
From point of view of convenience and accuracy of the experiment, CO2
desorption from water is the best of these systems. For determination of the
liquid-side mass transfer coefficient, the experimental installation (Fig, 2) can
be used. The liquid from the bottom of the column (7) enters the pump (22) and
thought pipe (23) enters in the upper part of the head tank (25). In the vertical
part of the pipe (23) the liquid is saturated in CO2 entering from the bottles (27).
(The respective pipe is not shown in the figure). In (25) the liquid is separated
from the gaseous CO2 and through the pipe (24) and rotameters (18) enters the
liquid phase distributor (8) of the column (7). The superfluous liquid overflows
trough pipe (13) in the bottom of the column.
The gas (air) from the ventilator (1) measured by the diaphragm (2) and
its differential manometer (4) enters the column (7), As well known, under the
loading point the gas velocity does not influence the liquid-side controlled
processes. A proper velocity value is about 0.5 m/s
Samples for analysis are taken at A u and Au- The analysis can be
made by means of modem analysers, or by transforming CO2 into NaHCOj, and
applying the well known analytical methods of Winkler [68], to obtain the
initial CO2 concentration. Using this method samples with volume about 200 ml
are taken in flasks full right up. In a sample about 2 ml 0,2 N NaOH is added by
a pipette on the bottom of the flask. The sample is mixed. According to the ratio
of NaOH to CO2, only the first or both of the following reactions take place.

(26)
CO 2 +NaOH= NaHCO 3

NaHCO 3+NaOH = Na 2CO 3+H 2O (27)

According to the classical method of Winkler [68], the sample is titrated
with a strong acid, for example solution of salt acid with concentration 0.1 N.