Figure 1. The experimental setup (a) a diagrammatic sketch and
(b) in the inner structure of the PDDC.
All experiments were carried out in a laboratory-scale PDDC made of
stainless steel. Figure 1 shows the diagrammatic sketch of the
experimental set-up. In order to perform a precisely optical
measurement, the cross section of PDDC is designed to be square and two
glass windows are set on opposite sides of the column. The height of the
column is 1000 mm and the dimension of the cross section is 100 mm × 100
mm. Ten pairs of disc and the doughnut plates are arranged alternately
in the column. All the plates are made of Teflon with a thickness of 2
mm. The distance between the disc and the doughnut plates is 30 mm. The
size of the disc is 87.7 mm × 87.7 mm and the size of the hole in the
middle of the doughnut is 48 mm × 48 mm, thus the free area of these two
kinds of plates are both 23%. There are seven sampling points arranged
equidistantly with an interval of 65 mm along one side of the column. A
high-speed camera (Olympus i-Speed TR) connected with a microscope
(Olympus SZ61) is used to capture the droplet breakage in the column.
The frame rate is 1000 frames per second. The high-speed camera is
located at 265 mm, 330 mm, 395 mm and 590 mm from the top of the column
respectively, as shown in Figure 1 (a). Figure 1(b) shows the inner
structure of the PDDC as well as the focal plane of the microscope
connected to the high speed camera. To promote the breakage of droplets
in the column, a pulsation generator is connected to the bottom of the
column. The pulsation generator induces reciprocal up and down movements
of the fluids by a piston, thus a sinusoidal pulsation of the liquid
system is produced. The pulsation frequency is 1 Hz and the amplitude
is10.5 mm. The aqueous phase entrance and organic phase exit are set at
the top of the pulsed column while the aqueous phase exit and organic
phase entrance are at the bottom. All exits and entrances are controlled
by a supply and collection system respectively. In the process of
operation, the aqueous phase is dispersed into droplets in the organic
phase by pulsation and the droplets coalesce at the bottom of the
column.
Materials
The experiments consist of two parts conclude mass transfer experiments
and blank experiments. In mass transfer experiments, 5% (v/v) tributyl
phosphate (TBP) in kerosene and 15% (v/v) acetic acid (AC) solution
were used as the continuous and dispersed phase separately. The AC, TBP,
and kerosene were purchased from
Aladdin
Reagent Co. Ltd., J&K Scientific Ltd., and Jinzhou Refinery Factory,
respectively. In the blank experiments, 5% (v/v) TBP in kerosene and
deionized water were used as the two-phase materials. The physical
properties of two-phase materials are shown in Table 1. Continuous phase
is pumped into the lower part of the pulsed column by a peristaltic pump
(Longer Pump WT600-2J) at the flow rate of 443 mL/min. The dispersed
phase is pumped into the upper part of the pulsed column through another
peristaltic pump (Longer Pump BT100-2J) at the speed of 21 mL/min. The
purpose of choosing a low flow rate of dispersed phase is to reduce the
holdup of dispersed phase, so that the behavior of droplets can be
optically measured. All experiments were conducted at a temperature of
20\(\pm\)1°C.
Table 1. Physical properties of the two-phase materials used in
experiments at 20 °C