A bubble curtain model applied in chlorate electrolysis

Chapter 4.
Two-phase flow in an electrode gap
4.1 Chlorate electrolyte
Before going deeper into detail in the chlorate process, some values of parameters that will be used, are
written here. For some of them also a brief explanation is added to see how they are calculated.
The typical composition of the chlorate electrolyte and its physical properties are tabulated below. Unless
differently mentioned, these values will be used in further calculations. The mass percentages of 8% and
43% of chloride and chlorate are numbers representative under industrial conditions. Same line of
reasoning accounts for the temperature of 70°C, the inter-electrode distance of 3 mm and an electrode
length of 0,5 m.
mass percentage NaCl 8%
mass percentage NaClO 3 43%
density electrolyte [19] 1419 kg/m 3
density hydrogen bubble 1 kg/m 3
bubble diameter [1] 0,0001 m
temperature 70°C
conductivity [23] 37,8 S/m
vapor pressure of water [19] 180 mmHg
hydrogen solubility [20]: 0,3 10 −5 mole fraction
surface tension [44] 0,0644 N/m
electrode gap 0,003 m
terminal velocity bubble 0,0068 m/s
liquid velocity [25] 0,5 m/s
viscosity continue phase [1] 0,001 kg/(m. s)
thickness bubble layer [1] 0,0005 m
wall voidage 0,5
diffusivity[17] 6,73 ∙ 10 −9 m 2 /s
electrode length
0,5 m
In later calculations all bubbles are considered to have a diameter of 0,1 mm since this is a common size
of hydrogen bubbles in the electrode gap in the chlorate process when no coalescence occurs [1]. A
typical composition of the electrolyte under industrial conditions is 8% NaCl and 43% NaClO 3 . The
electrolyte also contains 3-7 g/L Na 2 Cr 2 O 7 . The density of this mixture is 1419 kg/m 3 at 70°C.[19] Liquid
velocity is chosen as 0,5 m/s [25]. The terminal velocity of a single 1 mm bubble is calculated in
chapter 4.6.
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