In all the experiments, the concentrations of AC in both phases were
measured by titration method (Metrohm 809 Titrando automatic titrator).
The densities were measured by a densitometer (Density Meter DM-340.1,
LEMIS Baltic). The viscosities were determined by a viscometer
(DV3TLVTJ0, Ametek Brookfield).
Operation
proc edure
The operation process of mass transfer and blank experiments is
basically the same. Firstly, the continuous phase is filled in the
pulsed column. The steady flow of continuous phase can be obtained
through continuous phase feed pump. Then, the pulsation generator is
turned on at the time that the dispersed phase is added. After a
periodical steady state is achieved (the AC concentration does not
change for both the discharged continuous and dispersed phases), the
high-speed camera is turned on to record the droplet behavior at
different heights of the column. At each location, the high-speed camera
records totally 97.88 seconds (97,880 images). The droplet diameter is
measured by GetData software and the droplet number density is counted
at the same time. Droplet breakage is counted manually. During the
experiment, the measurement errors caused by different refractive index
can be eliminated by calibrating a standard length of pixel size.
Method
The measurement of DIFT in the PDDC is divided into three steps.
Firstly, the number density functions of droplets at different heights
are measured. Then the DBFF is determined based on the obtained number
density function after the droplet breakup events are counted. Finally,
the obtained DBFF is submitted into the correlation between the
interfacial tension and DBFF for regression, in order to determine the
value of DIFT. The detailed description for the three steps is as
follows.
The droplet number density function is denoted as . is defined as the
number of droplets within the infinitesimal size interval of dDabout size D per unit volume. Thus has a unit of
(m-4). In order to measure , the differential
dD is replaced by difference , and can be calculated by Eq. 1.