Note: Descriptions are shown in the official language in which they were submitted.
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Bac~ground of invention
(1) Field to which invention relates
The invention relates to an electrolytic cell for the
treatment of water, more particularly for the purification and
sterilization of water; it relates in particular to a multipole
electrolytic cell, which can be used in the most varied fashions
for the treatment, and more particularly for the purification
and sterilization of water, and comprises a closed container with
a lower inlet opening and an upper outlet opening for the water
and at least two electrodes within the container, which are
adapted to be connected with the positive and negative pole of
a DC source.
(2) The prior art
The most varied types of electrolytic cells for the
treatment, and more particularly for the purification and sterili-
zation of water, have been proposed. With these known cells it
is yossible to remove the dissolved and suspended contaminating
materials contained in the water to be treated electrolytically
by using either consumable or non-consumable electrodes such as
of iron, aluminum, copper, silver, platinum, and carbon. However
during the operation of such electrolytic cells many problems
are encountered which are due to different causes.
Normally during electrolysis of water, especially of
hard water, the cathode is rapidly covered by a skin of calcium
carbonate which inhibits the flow of current; anodes of silver,
copper, iron, aluminum etc. during the electrolysis are covered
with oxide films. In case of aluminum anodes the formed aluminum
oxide prevents the flow of current. In the case of silver, iron
and copper anodes the formed oxide film is highly conductive, so
that the dissolution of the metal is prevented and oxygen is
produced at the electrodes.
Another problem encountered in electrolytic water puri-
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fication systems is that the water normally encountered has only
a very small number of ions and that, although platinum anodes
can provide oxidation, the oxidation-reduction potential of the
water remains very low. e.g., if chlorine is to be produced, the
chloride concentration in the water must be very high and this
concentration is normally not encountered in fresh water, particu-
larly drinking water.
The standard electrolytic technique for the chlorina~
tion of water in swimming-pools is to provide a separate cell
containing a high concentration of common salt which upon elec-
trolysis gives sodium hypochlorite or chlorine which is fed into
the swimming-pool. Theoretically, it is possible to add suffi-
cient common salt to the swimming-pool water and to electrolyze
it directly. However, this technique has the disadvantage that
the water tastes salty to the bathers and that the calcium con-
tained in the water deposits onto the cathodes to such an extent
that the flow of the current stops. Changing of polarity to
remove the calcium deposits on the cathodes has been found in
practice only to lead to corrosion of the cathode and aggravates
the problem.
Summary of invention
It is one object of the present invention to prevent
the formation of deposits on the electrodes which stop the flow
of current and the dissolution of metal electrodes required for
water purification.
It is another object of this invention to keep clean
electrodes within the electrolytic cell by means of a fluidized
(agitated) bed of particles whose movements and impacts contin-
uously scratch off any deposits formed on the surfaces of the
electrodes.
It is a further object of the invention to effect the
concentration of ions contained in the water by electrodialysis
so that these ions can be electrolyzed to produce effective
oxidizing agents.
It is another object OL the invention to dispose the
electrodes within the cell in such way that they are corroded
evenly and radially.
It is another object of the invention to effect
electrodialysis by using an electrodialysis diaphragm surround-
ing the anode, forming a closed anode compartment, wherein water
flows at a very low flow rate compared with the main flow or not
at all and wherein the negative ions are concentrated.
It is another object of the invention to use the same
current for ion concentration as well as for achieving the
electrolytical oxidation of concentrated ions.
The above and other objects are realized in accordance
with the present invention by providing a new and improved
electrolytic cell, having particular utility in water treatment
systems, especially in water purification and sterilization
systems, used in various installations requiring clear, soft,
sterile water, e.g. swin~ing-pools, water works, sewage plants,
etc.
Detailed description of invention
The above mentioned and other objects according to
the present invention are achieved by an electrolytic cell for
the treatment more particularly for the purification and steri
lization of water, which comprises a closed container with a
lower inlet opening and an upper outlet opening for the water
and at least two electrodes which are adapted to be connected
with the positive and with the negative poles of a DC source,
characterized in that in the interior of the container (electro-
lytic cell) free movable particles are located whose density ishigher than that of the water to be treated as well as means
for retaining the particles within the container (electrolytic
cell).
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Description of preferred embodiments
According to one preferred embodiment o~ the invention
the electrolytic cell comprises a cylindrical container with a
lower inlet opening and an upper outlet opening for the water
flow and radially disposed cathodes and a centrally located
anode, surrounded by a porous electrodialysis diaphragm completely
surrounding it forming a closed anode compartment having a small
upper aperture for the escape of produced gases and of liquids
that have permeated throu~h the porous diaphragm.
Near the inlet and near the outlet grids are located
whose function is to prevent particles placed within the cell
from escaping through the inlet or outlet of the cell. These
particles, due to the velocity of the water flow, are fluidized
or agitated thus forming an agitated or fluidized bed of particles
surrounding the cathodes, and by their movement continuously
clean the electrodes in a mechanical way. Due to the electrical
potential difference between the electrodes a concentration
gradient is established which serves through the electrodialysis
to concentrate the anions within the anode compartment. E.g.,
if water containing 3 ppm chloride ions is electrolyzed without
using an electrodialysis diaphragm no chlorine is produced, but
only oxygen is produced at the anode. Once the diaphragm is used
the chloride concentration increases within the anode compartment
up to a level that causes the formation of free chlorine. If
chloride ions are absent, other ions like carbonate ions or sul-
phate ions contained in the water, concentrate within the anode
compartment forming through electrolysis percarbonate or persul-
phate which are also excellent oxidizing agents. In the same way
any organic acid will be oxidized.
Another preferred embodimentofthe invention is realized
with an electrolytic cell comprising an optionally transparent
cylinder as container having a lower inlet opening and an upper
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outlet opening, each provided with grids. In the interior of the
cylinder there are radially disposed electrodes whose length in
the axial direction of the cylinder is about 1/2 to 2/3 of the
length of the cylinder, and in the centre of the cylinder there
is disposed a concentrical cylindrical anode ring compartment
defined by an outer cylindrical diaphragm and an inner concentri-
- cal cylindrical pipe with the anode therebetween. The anode ring
compartment is closed at both ends and has at least one upper
small opening to permit the escape of products formed within the
anode compartment. The axial length of anode, anode compartment
and inner pipe is about the same as that of the cathodes outside
the anode compartment. Within the cylinder (the outer wall of
the cell) and outside the anode compartment there is placed a
sufficient number of particles whose size is greater than that of
the openinys of the grids. These particles by the flowing water
within the cell are agitated and rise up to surround the cathodes
~in the cathode compartment), thereby cleaning them mechanically
through impacts and scratches. The upper free space in the
interior of the cell serves as a disengaging space for the par-
ticles so that, in case the water-flow rate is too high, the
particles do not become entrained and held at the upper grid.
The purpose of the central pipe (inner boundary of the anode
ring compartment) is to permit a recirculation of the particles
flowing upwardly in the cathode compartment and downwardly
through the inner pipe, especially when the lower grid under
the lower end of the central pipe is blocked at its centre,
i.e. has no apertures.
Further objects, advantages and preferred embodiments
of the invention are obvious from the following illustrating
description of the invention in connection with the accompanying
drawings and claims. It is to be noted that in the accompanying
drawings like parts are deno~ed by like reference numerals.
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The Drawings
Fig. 1 illustrates a preferred embodiment of the
electrolytic cell of the invention.
Fig. 2 illustrates arother preferred embodiment of
the electrolytic cell of the invention.
Fig. 3 illustrates a further preferred embodiment of
the electrolytic cell of the invention.
Fig. 4 illustrates a particularly preferred embodi-
ment of the elec-trolytic cell of the invention.
Fig. 1 shows a preferred embodiment of the electrolytic
cell of the invention in a schematic manner consisting of a
cylindrical container 1 with a lower inlet 2 and an upper outlet
3 for the water-flow and radially disposed cathodes 4 as well as
a centrally, axially located anode 5 surrounded by a porous
electrodialysis diaphragm 6 completely surrounding it, forming
a closed anode compartment 7 having a small upper aperture 8
for the escape of produced gases and of liquids that have permeated
through the porous diaphragm 6. Located below, near the inlet 2
and above, near the outlet 3 there are grids 9 and 10, respectively
~hose function is to prevent that particles 11 placed within the
cell escape through the inlet 2 or outlet 3 of the cell.
Fig. 2 shows another preferred embodiment of electro-
lytic cell of the invention cornprising a cylinder 1 having a
lower inlet 2 and an upper outlet 3 provided with grids 9 and
10, respectively. In the interior of the cylinder ~ there are
radially disposed electrodes (cathodes) 4 whose length in the
axial direction of the cylinder 1 is shorter than the total
length of the cylinder ~cell) 1. The axial length of anode 5,
anode compartment 7 and inner pipe 12 is about the same as that
of the cathodes 4~ Within the cylinder 1 are placed sufficient
particles 11 whose size is greater than that of the openings of
grids 9, 10. The upper free space in the interior of
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cell 1 serves as disengaging space 13 for the particles. The
central part 9' of lower grid 9 has no apertures. The upper
grid 10 has apertures both in the horizontal portions and in the
vertical cylindrical portions 10' to provide a greater area.
Fig. 3 shows a further preferred embodiment of the
electrolytic cell of the invention comprising a cylinder 1 having
a lower inlet 2 and an upper outlet 3 provided with grids 9 and
10 respectively. In the interior of the cylinder 1 there are
radially disposed alternating cathodes 4 and anodes 5'. The
center of the cell 1 is provided with a pipe 12 open at both ends
which serves to lead the particles 11 downwardly. Below pipe
12 there is positioned a grid 9 whose central part 9' is closed
to the flow of water, and above electrodes 4 and 5' and pipe 12
there is provided a disengaging space 13.
Fig. 4 shows a particularly preferred embodiment of the
invention wherein in cell 1 the inlet 2 and the outlet 3 are con-
nected to by-pass conduit 15 outside cell 1. In by-pass conduit
15 there is interposed pump 14 which serves to recirculate the
water through cell 1 to provide sufficient flow rate in order to
agitate and entrain the particles within cell 1. It is also pro-
vided with an inlet 16 for the raw water and an outlet 17 for the
treated water.
With reference to fig. 2 a further preferred embodiment
is obtained by omitting the electrodialysis diaphragm 6 and by
using corrodable metals for anode 5.
It is also possible to dispose an energized turbine or
propeller (not shown) within pipe 12 of fig. 2 to 4 to provide
additional reflux and to ensure enough contact time between
particles 11 and electrodes 4, 5'.
With reference to fig. 1 to 4 it is also possible and
beneficial to provide an additional outer pipe (not shown)
between the radially disposed electrodes 4 or 4,5' and the outer
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cylinder 1. The distance between this pipe and the outer cylinder
1 must be large enough to allow the free downward flow of particles
11. The holes in the lower grid 9 can be closed along the peri-
phery of grid 9 at least to an extent corresponding to the dis-
tance between the outer pipe and cylinder 1.
The materials for constructing the electrolytic cell
of the invention, e.g. as illustrated in fig. 1 and 2, are as
follows:
The anodes preferably consist of platinized titanium
or niobium in mesh form, although they also can be of any other
metal of the platinum family that resist corrosion or they can
consist of graphite or carbon or metal oxides. The anodes can
be solid or have the form of a grid.
The corrodable anodes of fig. 3 and 4 preferably are
chosen from the metals commonly used in the water treatment,
like aluminum, iron or copper for the provision of flocking
materials in water treatment processes or metals like silver
and copper to provide obligodynamic desinfecting ions to the
water being treated.
As material for the cathodes any conductive material
can be used, preferably metals like stainless steel, copper etc.
Usable materials for the construction of the cylinder,
inlet, outlet, grids, pipes and supports are e.g. plastics,
porcelain, glass, hard rubber and concrete or metal, wherein
the metal can act as cathode.
Materials for the electrodialysis diaphragms are e.g.
porous porcelain, microporous plastics like polyolefines and
polyvinylchloride, cellulosenitrate, and ion exchange resins.
In case the porous diaphragms are mechanically sensitive to the
impacts of the particles they can be shielded with a protective
grid of a non-conductive material like plastic.
The particles within the cell can be spheres of
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porcelain, hard plastics, stone, glass, alumina and any other
hard materials whose density must be greater than that of the
water to be treated. Of course, the size of this particles must
be larger than that of the openings of the grids which are to
retain them within the cell.
The invention has been explained above with reference
to preferred embodimentsO It is however quite obvious to a man
skilled in the art that it is in no way limited to such embodi-
ments and that it can be modified and changed in many respects
without leaving the scope of the invention defined in the claims.
For example, the cell need not be cylindrical, but can
be elliptical, hexagonal and the like, in section. Also the
closed grid area can have many other shapes depending on the
flow pattern required within the cell. It is also possible, for
example, to combine the central anode with additional radially
disposed anodes of the same or any other metal with or without
centrally or outwardly located downflow pipes or any other com-
bination thereof.
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