Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a process for treating an
aqueous liquid, in which this liquid is subjected to the effects
of an electrical field as it flows between two electrodes that
are located opposite each other and are separated from the
liquid by an insulating material, in particular for removing
boiler scale and corrosion in the vessels or pipe systems
through which the treated liquid flows, or to prevent the
formation of such scale and corrosion. In addition, the present
invention also relates to an apparatus Por carrying out this
process, said apparatus comprising a treatment chamber that has
an inlet and an outlet and two electrodes arranged opposite each
other on the two sides of the processing chamber and being
electrically insulated from the processing chamber, and an
source for high-voltage electricity that is connected to said
electrodes.
Because of substances of various kinds that are contained
in water, in particular lime that may be dissolved in water,
boiler scale and corrosion are caused in vessels and pipes
within which water is subjected to physical effects such as, for
example, intensive heating in hot-water boilers and steam
boilers. It is known that c~unter-measures can be adopted
against the unwanted precipitates from substances contained in
water, which result in boiler scale, and against the formation
oP corrosive characteristics of water in that, prior to being
Ped into vessels or pipes within which it is exposed to
~s extraordinary conditions, the water can be exposed to the effect
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of an electrical field. By this means it is possible to reduce,
to a greater or lesser extent, the tendency for substances
dissolved in the water to precipitate and for the water to
develop corrosive characteristics, and it is also possible to
further reduce the degree to which boiler scale and corrosion
occur in vessels and pipes because they are supplied with
untreated water, by supplying such vessels or pipes ~ith water
treated as discussed above; the degree of effectiveness of the
treatment of water or aqueous liquids with electrical fields
depends to a significant degree on the physical conditions
acting on the water or the aqueous solution after such
preliminary treatment; thus, for example, the effect that can be
achieved with techniques that have become known up to know falls
the more, the higher the thermal load to which the pretreated
water is subjected. Various known devices have only a slight
effect, and very often these apparatuses are of a relatively
costly construction and require constant and costly maintenance,
and for these reasons alone are scarcely suitable for general
use. Many of these apparatuses require that a special pre-
filter be installed ahead of them, and this results inaddit.ional procurement and maintenance costs.
It is the task of the present invention to create a process
and an apparatus of the type described in the introduction
hereto, with which it is possible to achieve a better effect
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than is possible with known technologies of the type discussed
herein, and which can be realised in a simple manner at lower
cost.
The process according to the present invention, of the type
discussed in the introduction hereto, is characterized in that
the liquid that is to be treated is subjected to the electrical
field effect generated by a high-voltage dc potential with one
pole on the two named opposing electrodes that are insulated
from the liquid, and with the other pole connected electrically
to the liquid. The objectives set out above can be achieved
very well using this process. It can be assumed that the
advantageous properties of the process according to the present
invention stem from the fact that the water, or aqueous liquid,
undergoes changes in the area of the boundary layer that flows
along the insulation of the electrodes or the electrodes, and
that this change or these changes acts or act very stronly
against the precipitation of content substances from the liquid
and the creation of corrosive properties in the liquid. In this
connection, it can be stated that aqueous liquids respond to the
field effect described herein because water molecules are
themselves dipoles and the content substances contained in the
water (either dissolved or not) are present in the form of
positive or negative ions and can thus be oriented in accordance
with the polarity. Thus, during the preparation of boiling
water with rod-type heating elements, in practical tests the
deposits that result when water with a high lime content is
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heated could be reduced by pretreatment of the water at a
quantity determined for the preparation of boiling water to one-
quarter compared to the use of water that was untreated; in
addition to this, when water pretreated by the process according
to the present invention was used, this brought the added effect
that the ~uantity of deposits that occured on the rod-type
heater elements during the preparation of boiling water did not
exceed a specific limiting value even after a longer period of
operation. It was also possible to establish the fact that
deposits or boiler scale that had formed previously when
untreated water was used for the preparation of boiling water
were clearly diminished during the subsequent use of water that
had previously been treated with the process according to the
present invention. It seemed that, for the achievable effect,
it is not so much the absolute value of the high-voltage d.c.
potential that is used as much as the electrical field strengths
on the electrodes or in the insulation of these compared to the
liquid, which also forms an electrode and, in connection with
this, the charge densities that occur in the fluid and the
electrode area that are influential. The distance between the
electrodes that are opposite each other is also important.
It is also an advantage for the objectives to be achieved,
namely, the most extensive possible deferment of the
precipitation of substances contained in the liquid, if the
liquid in the area of the electrodes is held at a negative
potential relative to the electrodes. However, one can also
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keep the liquid in the area of the electrodes at a positive
potential and thus counter a migration of liquid particles or
substances contained in the liquid into the insulation that
covers the electrodes. It is preferred that the liquid be
maintained at ground potential.
In connection with the above cited measures, foreseen in
the process according to the present invention, with regard to
the field effect that results from this, it is also advantageous
if the liquid is also subjected to the field effect between two
essentially flat, conductively connected electrodes and the
liquid flowing between these. In this way, it is possible to
optimize the distance between the two electrodes that are
opposite each other in a simple way.
The effect of the treatment of liquid by the process
according to the present invention can also be improved
significantly if the liquid in the area of the electrodes is
subjected to a change in direction of approximately 180 degrees.
The process according to the present invention, of the type
described in the introduction hereto, is characterized in that
the two opposing electrodes are connected electrically to each
other and!one connection of the electrical high-voltage source
is connected to both electrodes, and the other connection for
the electrical high-voltage source is connected with a connector
electrode that produces an electrically conductive connection to
the liquid, and in that the high-voltage source is a d.c. high-
voltage source. This apparatus makes it possible to achieve a
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very good processing effect with a very simple construction and
a relatively low high voltage. In this connection, it is also
favourable if the positive connection of the high-voltage source
is connected with the electrodes that are electrically insulated
from the liquid, and the negative connection of the high-voltage
source is connected to the connector electrode that constitutes
the electrically conductive connection to the liquid.
A favourable form for the surface of the liquid that flows
along the electrodes can be achieved in a simple manner if one
provides for the fact that one of the two electrodes that are
connected electrically to each other is arranged on a flat side
of a treatment chamber that is configured in the shape of a flat
can. The processing effect achieved with the apparatus can be
further improved, in a simple manner, if one foresees that a U-
shaped cross-flow path is formed in the treatment chamber by
means of a cross-piece and the openings for the ingress and the
egress of the liquid are adjacent, each being on one side of the
cross piece.
The treatment of aqueous liquids with the process according
to the present invention and with the apparatus according to the
present invention is not only significant with regard to
avoiding the precipitation of substances contained in the water
and deferring the appearance of corrosion phenomena in the
vessels or in the pipe systems through which the liquid flows,
and for the subsequent reduction of boiler scale and corrosion
damage that has already occured; the changes in the properties
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themselves that occur can be used in various other areas. As an
example, the treatment according to the present invention makes
it possible to condition the water in swimming pools by using a
smaller quantity and number of chemical additives than has been
the case up to now; thus, it is possible to achieve a specific
disinfection effect with a smaller quantity of added chlorine
than is possible with untreated water, and one can correct the
pH value of the water in a swimming pool by the addition of a
smaller ~uantity of pH- or p~+ additives.
It is stated most emphatically that during the process
according to the present invention there is practically no
electrical current between the liquid that is connected
electrically to a high-voltage potential relative to the
insulated electrodes and the electrically insulated electrodes;
there may possibly be a negligible leakage current that is
extemely small through the finite insulation resistance to the
insulating material that covers the electrodes.
In the process according to the present invention, the
treatment effect is influenced essentially by the field strength
and by the charge density on the surface layer of the liquid to
be treated that is proximate to the insulated electrodes.
The present invention is descrihed in greater detail below
on the basis of examples that are shown in the illustration
appended hereto. These drawings show the following:
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Figure 1: A first embodiment of an apparatus according to
the present invention, this being in plan view;
Figure 2: This embodiment in cross-section on the line
II-II in figure l;
Figure 3: This embodiment in cross-section on the line
III-III in figure l;
~igure 4: The circuit of a high-voltage source provided for
the present invention;
Figure 5 and figure 6 show a further embodiment in two
cross sections, with figure 5 being a cross-
section on tha line V-V in figure 6, and figure 6
being a cross-section on the line VI-VI in figure
5.
The embodiment of an apparatus according to the present
invention that is shown in figures 1 to 3 has a treatment
chamber 1 through which the liquid to be treated flows. Inlet
and outlet openings 2, 3 are provided for the liquid to be
treated. The direction of flow can be in either direction. On
each side of the treatment chamber 1 there are two electrodes 4,
5, and these are electrically insulated from the treatment
chamber 1. The electrodes are connected to each other
electrically by the line 6. One connection 7 of an electrical
high-voltage source 8 is connected to the electrodes 4, 5. The
high-voltage source 8 is supplied with electrical energy, for
example, from the electrical supply network, through its
terminals ~. The other high-voltage connection 10 of the high-
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voltage source 8 is connected to a connector electrode 11 that
forms an electrical connection to the aqueous liquid within the
treatment chamber 1. As is shown in the case illustrated in
figures 1 to 3, the connector electrode can be a single
electrode that is arranged in the treatment chamber l; however,
this connector electrode can also be formed by other metallic
conductive components that are in contact with the liquid
flowing through the treatment chamber 1, for example, by metal
tubes that lead to the outlet or inlet openings of the
apparatus.
The high-voltage source 8 can be in the form of a
condensor-rectifier-cascade circuit, as is shown in figure 4.
However, other configurations of the high-voltage sources can be
considered, such as the so-called combination circuits with a
high-voltage output, and if so desired, one can also provide the
high-voltage source with an isolating transformer for galvanic
separation of the power supply.
The treatment chamber is in the form of a flat can that is
configure~ from two plastic halves 14, 15. The electrodes are
imbedded in the flat wall sides 16, 17 of the two halves 14, 15.
The half sections 14, 15 are arranged between two clamping
plates 1~, 20 that are held together by means of clamping bolts
21. The clamping plates 18, 20 press the two half sections 14,
15 together, and a gasket 22 is interposed between the edges of
the half sections 14, 15 that face each other.
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It is expedient that these clamping plates 18, 20 be
connected electrically to ground potential. These clamping
plates 18, 20 are in contact, either directly or indirectly
through pipes that lead to the inlet and outlet for the liquid,
with the liquid and so these clamping plates can also act as
electrodes that produce the electrically conductive connection
to the liquid.
Within the treatment chamber 1 there is a cross-piece 23
that is formed by ribs that are molded onto the two half
sections 14, 15, and this cross-piece forms a U-shaped flow
through the treatment chamber 1, as is indicated by the arrow 24
in figure 1, this path leading from the inlet opening to the
outlet opening. These openings 2, 3 are adjacent to each other,
one on each side of the cross-piece 23.
In practical versions of the apparatuses that were provided
for the treatment of water by way of preventing the formation of
boiler scale or by the elimination of boiler scale,
respectively, a high-tension voltage of between 3.5 and 6 kV,
preferably of 5 kV, was used. The partitions 16, 17 that
separates the electrodes 4, 5 from the water in the treatment
chamber l were thus 3 mm thick.
In view of the fact that there is practically no flow of
current--or at most an extremely small one-- between the
electrically insulated electrodes and the liquid, when a high-
tension source that is galvanically connected to the current
supply is used the electrode that is in contact with the liquid
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need only be connected to ground potential and only the
connection of the high-tension source that leads the high
tension relative to ground need be connected to the insulated
electrodes 4, 5. This provides a potential connection from the
high-tension source through the constantly available ground
connection of the power supply to the electrode that is at
ground potential, which creates an electrically conductive
connection to the liquid. Thus, for example, in the high-
tension source 8 as shown in figure 4 the connection lOa can be
eliminated since the high-tension connection 10 is at ground
potential and a potential connection to the connector lO is
provided through the ground connection of a power supply network
that is connected to the terminal 9.
In the embodiment of an apparatus according to the present
invention shown in figures 5 and 6, the treatment chamber 1 is
elongated and is in the form of a chamber within a plastic
vessel 26, within the walls 27, 28 of which the electrodes 4, 5
are imbedded. In the same way as in the embodiment shown in
figures 1 to 3, the electrodes 4, 5 are connected to each other
electrically by the conductor 6, and are connected to one high-
tension connectlon 7 of a high-tension source 8; the other high-
tension connector 10 of the high-tension source 8 is connected
to a metal inlet pipe 29 through which passes liquid that is
flowing into the treatment chamber 1. In this case., too, the
high-tension source 8 can be configured in various forms, as has
; been discussed above.
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