1070-4272/01/7401-0044$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 1, 2001, pp. 44 ! 47. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 1,
2001, pp. 44!47.
Original Russian Text Copyright C 2001 by Zenin, Sazonov.
AND CORROSION PROTECTION OF METALS
Modeling of Gaseous Chlorine Production
in a Static Electrolyzer
G. S. Zenin and A. M. Sazonov
St. Petersburg Northwest Polytechnic Institute, St. Petersburg, Russia
Received March 20, 2000
Abstract-Transfer of hydroxide and hydroxonium ions in bulk of sodium chloride solution in the course of
gaseous chlorine production in a static electrolyzer was considered and a relationship was derived to deter-
mine the characteristics of a chlorinator. Principles of selecting electrolyzer currents to obtain gaseous chlorine
in a static chlorinator were recommended.
Sodium hypochlorite produced by electrolysis of
sodium chloride solutions is used in water treatment
. Since the resulting solutions also contain sodi-
um chloride, it is fed into water being treated together
with the hypochlorite solution, which results in in-
creased consumption of the salt and excessive minera-
lization of water.
There are some data [4, 5] on the electrochemical
production of gaseous chlorine for water decontamina-
tion in reactors similar in design to those used in the
chlorine industry . However, the implementation of
this process in water-treatment stations requires com-
plicated process schemes.
In the early stage of development of the chlorine
industry, gaseous chlorine was produced in static elec-
trolyzers, for which a qualitative theory of the elec-
trolysis process was developed , and semiem-
pirical relationships concerning interelectrode transfer
of hydroxide and hydroxonium ions were obtained.
These ions, generated in the course of electrolysis,
determine the current efficiency with respect to gase-
ous chlorine . The publications on the production
of gaseous chlorine in static electrolyzers practically
do not consider the effects of design characteristics of
reactors on the current efficiency with respect to
gaseous chlorine and on the electrolyte service life as
a function of the electrolysis current.
To determine the ratio between the volumes of
anodic and cathodic zones and to substantiate the
optimum electrolysis conditions, we simulated in this
work the operation of a chlorinator.
The relationships in gaseous chlorine formation in
static electrolyzers are determined, along with the
electrode current density, by the anolyte acidity, which
depends on the conditions of the transfer of hydroxide
ions generated on the cathode and of hydroxonium
ions generated on the anode at simultaneous formation
of oxygen and chlorine, and also on secondary reac-
tions in solution involving dissolved chlorine .
During the electrolysis, simultaneously with the trans-
fer of sodium ions and chlorine, hydroxide ions are
transferred to the anode and hydroxonium ions, to the
cathode. The ions form in the interelectrode space
a neutral boundary whose width and position depend
on the migration and diffusion flows in the bulk of
, and j
are the flows of the negative
and positive ions driving under the action of migration
and diffusion, respectively.
As the current efficiency with respect to gaseous
chlorine at a constant current density is determined
by the anolyte pH , we will consider a model of
transfer of hydroxonium and hydroxide ions at a con-
stant sodium chloride concentration (Fig. 1). Taking
into consideration the condition of solution electro-
Fig. 1. Directions of ion flows in the electrolysis in a
chlorinator with an immobile solution: (n
) rates of the
motion of hydroxide and hydroxonium ions from the cath-
ode and anode, respectively; (L) chlorinator length; (x,
x +dx) unit thickness of a solution layer.