DE102012101031B4 - Method for preventing lime scale - Google Patents

Abstract

A method for treating running water to prevent lime deposits, wherein the water is supplied to a container (10) in which the water is subjected to an ultrasonic field by means of one or more ultrasound sources (30) and after the treatment via a drain (12 ) drains off,
wherein the lime dissolved in the water is precipitated by means of a precipitation reaction on surfaces inside the container (10) and removed by means of the ultrasonic field from these surfaces and returned as solid lime in the form of suspended particles in the water,
and wherein the dissolved lime is electrolytically precipitated by means of direct current in a cathode chamber (13) at a cathode (40), wherein the surface of the cathode (40) is acted upon by the ultrasound field at least temporarily,
characterized,
that the water is first passed through the cathode space (13) and then through an anode space (14) with one or more anodes (50) or that the cathode space (13) and the anode space (14) are flowed through in parallel,
and that the dissolved lime precipitates on the surface of a mineral squeeze, a mineral fluid bed or a mineral bed.

Description

The invention relates to a method for treating running water to prevent lime, wherein the water is fed via an inlet to a container as part of a water treatment plant for preventing lime, in which the water is exposed to an ultrasonic field by means of one or more ultrasonic sources, and after the treatment drains off via a drain.

Economically speaking, the trend is towards increased heat recovery and efficient use of heat energy, especially for solar collectors and heat exchangers. With increased heat input u.a. on surfaces / heating and heat exchanger surfaces to increased lime discharge and deposits, which reduce the effect of efficiency measures. A classic method for preventing lime discharge is water softening by means of ion exchangers. The disadvantage of this process is that low-lime water often has a lower pH and can have a corrosive effect on copper and galvanized pipes. This is counteracted by the addition of phosphate. However, phosphate in drinking water is generally undesirable and ion exchange resins can release organic trace substances. In addition, the water is enriched by the ion exchanger with sodium. This can be prevented by a hardness stabilization as described below.

From many publications it is known that so-called seed crystals can serve to prevent lime precipitation on walls and heating elements. Tap water is i.d.R. a supersaturated lime solution. This is even true for rather soft waters, since drinking water is set by the waterworks so that it does not cause calcite dissolving, otherwise it might be due to the drinking water regulation. Concrete and marble attacks and prevents the formation of passivating layers on metals. The lime deposit is kinetically inhibited, which is why the lime remains in solution despite supersaturation. Surfaces favor lime precipitation. These include u.a. the walls of the pipes and heating rods. However, if seed crystals are present in suspension, the deposit is transferred to the seed crystals by this additional surface supply.

Also known are electrolytically assisted processes for lime deposition. In cathodic limescale, water is electrolyzed. Hydrogen is generated at the cathode. In contrast, hydroxide ions remain in the water, so that the solution becomes alkaline at the cathode. Lime and carbonic acid are subject to chemical equilibrium. In the alkaline environment, the equilibrium is on the side of calcium carbonate, which precipitates at the cathode and is deposited. This can be used to form seed crystals. The chemical solution equilibrium is determined by the reaction equation Ca ²⁺ + 2HCO ₃ ^- > CaCO ₃ + H ₂ O + CO ₂ (1) described. In an acidic environment, this equilibrium is shifted in favor of bicarbonate (dissolved lime), whereas in an alkaline environment it is in favor of the precipitated lime, producing CO ₂ and water. Since the environment around the cathode by the production of hydrogen and hydroxide ions is alkaline, there lime precipitation is favored. A corresponding electrolysis device for lime precipitation is for example from the EP 0 932 583 B1 known.

From the DE 41 07 708 C2 For example, there is known a method and apparatus for treating flowing water against limescale deposits by cavitation and an alternating electric field applied between at least two electrodes through which the cavitation-treated water passes. In this case, the following steps are provided: passing the water on the input side through an operating depending on the water flow injector from an axially movable sealing body, which forms an opening biased between an outer body in a Kavitationskammer depending on the water flow, and passing the pretreated water for electrolysis between Electrodes with irregular surface structure, so that the water flows through areas of smaller electrode spacing with a higher local current density and through regions of further electrode spacing. During cavitation, as a result of strong swirling, there are zones in which the pressure is significantly reduced, so that local outgassing of CO ₂ occurs in these zones. As a result, the solution equilibrium is disturbed such that lime can dissolve worse.

Another method of precipitating lime is lime precipitation on metals. With certain metallic surfaces (for example, iron and iron-containing alloys, copper), the lime connects firmly and is difficult to remove, especially if corrosion products come as an adhesion-promoting layer to it.

Ultrasound is used to clean surfaces. It exploits its ability to form cavitation bubbles, which cause high mechanical stress peaks when collapsed, which can be used to blow off the grown lime. The resulting effects are, inter alia, from the writing Heinrich Kuttruff: Physics and ultrasound technology, S. Hirzel Verlag Stuttgart known.

The size of the lime crystals formed during cleaning is influenced by several factors, such as the frequency, the amplitude and the duration of the ultrasound exposure. The higher the frequency, the smaller are the cleaved fragments. Likewise, increasing the amplitude leads to accelerated fragmentation of the lime. Due to a long exposure time of the ultrasound fragmentation continues.

Other techniques, such as shaking, scraping or electrolytic stripping, can also be used to limescale release, but have specific disadvantages. The shaking, which corresponds to an ultrasound application at very low frequency, has the disadvantage that arise too coarse particles. Mechanical scraping, for example with brushes, also leads to the formation of rather coarse particles with poorly controllable size spectrum. In addition, the process of scraping has the disadvantage that lime precipitated in the brush adds the brush over time, resulting in replacement of the brush.

In an electrolytic detachment, as they are from the DE 198 12 801 A1 is known, electrodes are alternately connected as cathodes and anodes. During its wiring as a cathode lime precipitates on the surface, which is replaced during the wiring as an anode again. In this case, an electrode material is required which is chemically stable both in the acidic and in the alkaline medium. This is made possible by graphite as electrode material; the electrode is preferably expanded by activated carbon. Graphite and activated carbon are not very stable mechanically and the deposition efficiency against lime is rather low due to the lack of polarity of the activated carbon. The graphite electrodes are supplied with inert metallic connections, for example made of titanium, which considerably increases the price, because graphite is too brittle and porous for sealing. Also from WO 98/17587 is an electrolytic deposition of lime known. In this case, a treatment space is separated by means of a diaphragm into an anode space and a cathode space.

In the EP 1 301 437 B1 a device for reducing stone formation in aqueous solutions is described. In this case, four electrodes are accommodated in electrode chambers. Two of the electrodes form anodes. The other two electrodes form cathodes. The electrodes are separated from each other and electrically isolated from each other by means of insulating bodies. The electrode chambers are each filled with a bed of electrically conductive material, which consists of a granulate.

From the EP 1 002 765 B1 Another device for the treatment of water is known. Here, a brush-shaped cathode is used, which is arranged in a water-flowing treatment chamber. When the cathode is energized, limescale may deposit on the bristles. Because the bristles are flexible, the lime can be removed from the bristles with a cleaned mechanical cleaning system.

However, it has also been shown in practice that pure ultrasonic treatment for limescale prevention does not have the desired effect under certain operating parameters, as is known from a test series of physical water treatment devices from Stiftung Warentest in 2006. Especially at elevated temperatures (60 ° C and more) no reduction of lime could be observed.

The object of the invention is to provide a method with which lime deposits in drinking water systems are avoided. Since drinking water should by no means be treated with chemical additives, only physical effects should be exploited in this process.

The object is achieved in that the lime dissolved in the water deposited by means of a precipitation reaction on surfaces inside the container and removed by means of the ultrasonic field at certain intervals from these surfaces and as solid lime in the form of suspended particles, which can also act as seed crystals , is returned to the water. With the method, an effective hardness stabilization can be achieved without the use of chemical aids, such as salts. It combines different physical effects that allow a high Impfkristallentstehungsrate to avoid lime, even under practical conditions. On the one hand, a high surface area on the released seed crystals, and the lowest possible visibility are desirable. Particles under a size of 30 to 100 microns are no longer perceptible as individual particles, but still fall as a cloud. However, such a heavy loading of the water with seed crystals is undesirable because a small amount of particles is already sufficient for the effectiveness. The lime deposit can happen in two ways.

In one case, the lime is deposited electrolytically on a cathode. The invention therefore provides that the dissolved lime is precipitated electrolytically by means of direct current in a cathode space at a cathode, wherein the surface of the cathode is acted upon by the ultrasonic field at least temporarily. You do it yourself mentioned above shift the solution equilibrium according to (1) to use. Due to the water flow, there is a mixing and removal of the electrolytically generated gases oxygen and hydrogen, thus there is no dangerous accumulation of a so-called "pop-gas mixture". In addition, it must be ensured that there is no acid-related corrosion of the cathode, triggered by the reaction at the anode. A separation of anode and cathode space is therefore advantageous. This can be achieved by a corresponding device such as a semipermeable membrane or other devices.

In a preferred variant of the method it is provided that the water is first passed through the cathode space and then through an anode space with one or more anodes or that the cathode space and the anode space are flowed through in parallel. In the case of a serial flow through the cathode space and the anode space, the cathode space has a relatively high pH in the first part of the device. Lime can be precipitated to a greater extent. If the lime crystals enter the anode space together with the water, it is very likely that the co-purged OH ^- ions from the cathode space and the H ₃ O ⁺ ions from the anode space will be neutralized. The calcium crystals are thus only slightly attacked.

It is also advantageous to increase the flow rate in the anode compartment, so that the residence time of the calcium crystals in the acidic anode compartment is shortened. A shorter residence time of the water in the anode space than in the cathode space can be achieved, for example, by a corresponding geometrical design, in which the flow area of the anode space is smaller than the flow area of the cathode space.

In order to increase the residence time of the seed crystals generated in the cathode space in the cathode space, so that further lime can deposit on these, it is provided in a process variant that at least a portion of the water circulates in the container, in particular in the cathode space, by means of a turbulent flow. This can be achieved by a corresponding geometric configuration of the cathode space. In this case, a lime-crystal incubator is obtained.

An alternative provides that a portion of the effluent via the drain water is returned to the container via a return. The seed crystals contained in the effluent water can thus be used for further lime enrichment.

A further preferred variant of the method provides that the dissolved lime is precipitated on the surface of a mineral press, a mineral fluid bed or a mineral bed, in particular quartz and / or quartz flour. Quartz sand has proven to be a suitable material for precipitating limescale on its surface and thus preventing calcification at other interfaces. Here, a sieving to certain, i. defined grain sizes guaranteed by the manufacturer.

In order to ensure a "shaking off" of the lime formed on the surface, it is provided that the mineral pressing, the mineral fluid bed or the mineral fill inside the container held by sieves in a certain volume range of the container and applied in this with the ultrasonic field becomes. The mineral pack can thus be optimally positioned in the resonator so that an efficient sonication can take place.

Various parameters are crucial for optimal operation. For lime precipitation by means of electrolysis, this is in particular the current and dependent thereon the voltage in relation to the flow rate. For calcination on quartz sand, these are the grain size and the filter volume. For the ultrasound, the frequency to be selected is critical, the minimum intensity for removing the lime from the precipitation surfaces and a suitable pulse rate or average intensity, in order to replace a suitable particle size in an appropriate amount. It is therefore provided that the voltage, and thus the current flow of the electrolysis between the cathode and anode, and / or the intensity and / or the duty cycle and / or the time intervals of the activation of the ultrasonic field depending on a flow rate of water through the Container controlled. A flow meter determines the amount of water that has flowed through. Based on the flow rate of the electrolysis current is adjusted accordingly to precipitate the required amount of calcium crystals. After a certain flow rate, the pulse-like detachment of the lime takes place by ultrasound. Alternatively, the ultrasound intensity can be adjusted in proportion to the flow rate. In the case of lime precipitation of quartz sand, the electrolysis is eliminated. The setting of the pulse rate or the intensity of the ultrasound is analog. The process can be initiated by a suitable controller that responds to the flow rate.

If, as is provided by a preferred variant of the method, the ultrasound field is excited in a chaotic resonator and / or if a plurality of ultrasound sources with different frequencies and / or a plurality of ultrasound sources excited in pulses is used, the effect of the so-called destructive interference or interference shadows can occur which leads to a neutralization of the sound field, be minimized as far as possible or completely avoided. The sound can thus be distributed evenly. Therefore, in one embodiment, ultrasound sources having different frequencies are used. The other possible embodiment consists in the use of a pulsed excited sound source, thereby a frequency mixture is generated. According to Heisenberg's uncertainty principle, the frequency uncertainty widens, the shorter the excitation time is - the frequency-sharpest excitation would be an infinite sound, ie continuous irradiation of the sound. The quartz sand or the sponge cathode fills the resonator, as both the lime is deposited on this material and also detached as microcrystals.

In order to prevent a congestion in the line in the event of a clogging of the container due to various reasons, such as a failure of the ultrasound in the event of a power failure, the water is bypassed between inlet and outlet, depending on a pressure in the container.

It can be provided that the bypass is designed as a self-closing pressure relief valve valve is opened when a predetermined or predetermined first limit value for the pressure of the bypass and automatically closed after a pressure drop below a predetermined or predetermined second limit for the pressure , Commercially available mechanical working pressure relief valves are particularly suitable for this purpose. These can also be provided with a mechanical display.

On the one hand, the cathode material must be conductive and, on the other hand, electrochemically stable as a cathode and robust with respect to the ultrasonic treatment, ie have a certain toughness or ductility. The material selection is therefore based on the electrochemical series of voltages. In addition, it must be prevented that parts of the alloy, such as chromium go into the drinking water. Corresponding limit values of the Drinking Water Ordinance must be observed. The largest possible surface is desirable in order to achieve the highest possible yield of seed crystals. The anode material must be chemically inert over a wide voltage range. In addition, electrode material transferred in suspension should be physiologically harmless. In a preferred variant of the method it is therefore provided that the cathode used is a spongy or tangle-like structure with a large surface, in particular made of stainless steel, and / or as an anode of graphite, in particular consisting of one or more graphite rods. At the cathode arise hydrogen and hydroxide ions (OH ^- ), which is due to the shift of the lime-carbonic acid equilibrium to the formation of calcium carbonate. The particularly large surface favors the precipitation of lime crystals. Stainless steel has correspondingly good properties with regard to the chemical requirements. Oxygen and hydronium ions (H ₃ O ⁺ ) are produced at the anode. The graphite rods of the anode are preferably arranged spatially separated from the ultrasonic source, so that there is no separation of graphite during the sonication. A special soundproofing wall can ensure a suitable shielding. In this case, for example, one or more graphite electrodes (anode) may be arranged spatially away from the cathode (for example a steel sponge), or a diffusion barrier such as, for example, a porous, water-permeable ceramic in order to avoid thorough mixing of the pH environments.

In order to be able to uniformly irradiate the entire cathode space or the space of the mineral pressing, the mineral fluidized bed or the mineral fill, it is provided that an ultrasound field is arranged in a plane, for example in the center plane, around a cylindrical resonator inside the container Ultrasonic sources is generated. In the case of, for example, three ultrasound sources, these can be arranged in an approximately equilateral triangle around the cathode space or the space with the quartz sand.

As for the particle size of the lime floating particles, there is a lower limit: below 4 nm, lime precipitation no longer occurs on the seed crystals. Instead, the solution kinetics forces the seed crystals back into the solution. Another limitation arises from the wipeability of the lime when drying on surfaces. Too small calcium crystals are difficult to wipe off and should therefore be avoided when used in households. The optimal size is 500 to 2000 nm. Larger particles sediment in drinking water systems, for example in boilers, while smaller particles tend to settle in rock spores and thus are not wipeable. It is therefore provided that the suspended particles, which are discharged via the outlet, have a size of ≥ 4 nm, in particular a size in the range between 500 and 2000 nm.

A preferred application of the method, as previously described in its variants, provides for use in domestic water treatment plants for hardness stabilization and in areas where food is produced or processed, in which the preservation of drinking water quality is of great importance and treatment drinking water with chemical additives is undesirable. In addition, the method according to the invention can advantageously be used in compact, space-saving operating units are implemented, which is particularly advantageous in domestic environments.

Other applications are, for example, mobile water treatment plants, if consumables for softening is not available or its use is not desired; also small and medium-sized (stationary) systems for water treatment in which lime should not be removed from the water, but limescale deposits are to be reduced as much as possible.

• 1 eine Wirkeinheit als Bestandteil einer Wasserbehandlungsanlage zur Härtestabilisierung mit serieller Durchströmung;
• 1b eine Abwandlung von 1 mit axialer Ultraschall-Einwirkung;
• 2 eine zu 1 alternative Ausführungsform mit paralleler Durchströmung;
• 3 eine weitere zu 1 alternative Ausführungsform mit einem Kalkkristall-Inkubator;
• 4 eine Wirkeinheit mit einer Bypass-Beschaltung; und
• 5 eine Wirkeinheit mit einer Mineralschüttung zur Kalkfällung.

The invention will be explained in more detail below with reference to an embodiment shown in the figure. Show it:

• 1 an active unit as part of a water treatment plant for hardness stabilization with serial flow;
• 1b a modification of 1 with axial ultrasonic action;
• 2 one too 1 alternative embodiment with parallel flow;
• 3 another one too 1 alternative embodiment with a lime-crystal incubator;
• 4 an active unit with a bypass circuit; and
• 5 an activity unit with a mineral fill for lime precipitation.

The 1 . 2 and 3 show device variants as an example of process variants with an electrolytic lime precipitation and a seed crystal release by means of ultrasound.

1 shows a schematic representation of an embodiment of an active unit of a water treatment plant 1 with a serial flow in the form of a cylindrical container 10 who has a feed 11 and a process 12 having. The water first flows through a cathode compartment 13 in which there is a cathode 40 which has a sponge-like structure with a large surface and is preferably made of stainless steel. Surrounded is this cathode compartment 13 with a partition 15 which gives extra sound insulation 16 having. The partition 15 is designed in the example shown as an inner container. The water then flows into an anode compartment 14 over, which is outside the inner container. In this anode compartment protrude several anodes 50 , which as graphite rods 51 can be executed. An arrangement of 6 graphite rods 51 around the inner container has proved to be advantageous. Subsequently, the water flows through the drain 12 from the container 10 ,

To the cathode compartment 13 are in the sound insulation 16 several sources of ultrasound 30 provided in the example shown near the center plane of the cylindrical cathode space 13 are arranged and a resonator 17 sonicated, whose volume is substantially that of the cathode compartment 13 equivalent.

The as stainless steel sponge 41 executed cathode 40 and as an anode 50 executed graphite rods 51 are electrically conductive with a control unit 90 connected. The ultrasound sources 30 are also from the control unit 90 driven.

The hardness stabilization proceeds in the steps described below. First, in the cathode compartment 13 alkalinize the water to make lime at the cathode 40 precipitate and put on the market with ultrasound as seed crystals. At the cathode 40 Hydrogen and hydroxide ions (OH ^- ) are formed, which leads to the formation of calcium carbonate due to the shift in lime-carbonic acid equilibrium. Subsequently, the water is flowing through the anode compartment 14 neutralized. Oxygen and hydronium ions (H ₃ O ⁺ ) are formed at the anode. In order to shorten the effect of the dissolution of the lime in an acidic environment, the anode space can 14 be narrowed so that it flows through faster. Due to the water flow, there is a mixing and removal of the electrolytically generated gases oxygen and hydrogen, thus there is no dangerous accumulation of a so-called "pop-gas mixture". It must also be ensured that there is no acid-related corrosion of the cathode 40 comes, triggered by the reaction at the anode 50 , The reaction spaces are therefore spatially separated from each other by a corresponding device such as a semi-permeable membrane or other devices. Im shown

Example, this is through the partition 15 reached. The arrangement of graphite rods 51 outside the inner container with its sound insulation 16 also ensures that the anode 50 from graphite is protected from excessive mechanical stress due to the ultrasonic field and there is no replacement of graphite.

The process is initiated by a suitable controller that responds to the flow rate. One in the inflow 11 attached flow meter 20 determines the amount of water that has flowed through. Based on a flow rate, the applied DC voltage at the cathode 40 and anode 50 and thus the electrolysis current adjusted accordingly to precipitate the required amount of calcium crystals. After a certain flow rate, the pulse-like separation of the Lime by ultrasound. Alternatively, the ultrasound intensity can be adjusted in proportion to the flow rate.

1b shows a variant of 1 , Here is an ultrasound source 30 axially attached to the resonator 17 To sonicate lengthwise, whose volume is essentially the cathode space 13 equivalent. This arrangement has the advantage of using only one ultrasonic source to sonicate the entire resonator cell; in return, the ultrasonic source must be made larger.

2 shows an alternative embodiment of the in 1 shown active unit. In this arrangement, the cathode and anode space 13 . 14 flows through in parallel, so that the neutralization of the alkaline cathode water takes place by mixing with the acidic anode water. Otherwise, the components used and their function correspond to those previously described in 1 have been described. In addition, there is a limitation of the cathode and anode space 13 . 14 one sieve each 18 ,

3 shows in part, without the in 1 and 2 shown control unit 90 , an electrolytically operating unit, whose cathode space 13 as lime-crystal incubator 70 is trained. Here is the cathode compartment 13 additionally with a swirling room 19 provided in which the water circulates many times, so that once formed lime crystals after detachment from the cathode 40 return to the cathode environment many times and continue to grow to become fragmented again. Another part is straightforward. As a result, an increased crystal yield can be achieved.

Alternatively, it may be provided that a part of the seed crystals produced at the end of the cathode space seen in the flow direction of the water 13 be diverted and the active unit at the inlet 11 be fed again. For this purpose, a small part of the water is circulated.

In order to prevent congestion or impermissible overpressure in the line in the event of a clogging of the active unit, for example due to a failure of the ultrasound in the event of a power failure, this is 4 schematically shows a bypass 80 between inlet and outlet 11 . 12 switched, whereby mechanically, at too high pressures, a valve 81 opened or a pressure sensor 82 , which on the inlet side of the container 10 is arranged, the valve 81 opens when an applicable limit for the pressure is exceeded and after a pressure drop below this limit or a deviating second limit the valve 81 closes again independently. The valve 81 can be designed as a self-shooting pressure relief valve and a mechanical display 83 Press when the valve 81 opens for the first time, which must be reset manually, so that a visual inspection is possible.

5 shows as an example a device variant in which a lime precipitation on a bed of mineral and the Impfkristallfreisetzung by means of ultrasound.

The container 10 the active unit has only one chamber, by means of a sound insulation 16 is shielded. The mineral fill in the form of quartz sand 60 is in each case by a sieve 18 in the area of the inlet 11 and the process 12 positioned. In the inflow 11 is the flowmeter 20 that with the control unit 90 is in active connection. The ultrasound sources are in a preferred arrangement around the cylindrically shaped resonator 17 arranged in or near the median plane and are controlled by the control unit 90 driven. In this case, the electrolysis is eliminated. the setting of the pulse rate or the intensity of the ultrasound is analog, ie, depending on the flow rate.

A grain size of 0.5 to 5 mm has proved to be advantageous for the mineral fill, with a small grain size giving a larger surface area and promoting limescale deposition, but thereby increasing the dynamic pressure in the system. In addition, the sieve can 18 enforce. On the other hand, a rather larger grain size promotes the leaching of the lime from the surface.

The lime precipitates on the grains of sand and is marketed by means of ultrasound as seed crystals. In a fluidized bed design, as in 5 shown, the sand is moved by the water flowing through and kept in suspension, leaving a fluidized bed 61 training and all sand grains can be irradiated and decalcified by the ultrasound. In a densely compressed version, the grains of sand are immovable. As a result, a higher density can be achieved. The ultrasound can be introduced there at several frequencies to avoid acoustic shadowing in wave nodes, where otherwise a lime separation would not take place.

The container 10 the active unit typically has a volume of 1.5 to 5 l for efficient hardness stabilization. An important size limitation in the environment of, for example, private households is the space available there. Preferably, the active unit fits into a small cabinet and is no larger than, for example, a large thermos flask of about 2 to 2.5 liters in volume, if space constraints exist and can be economically scaled up to larger designs, with upwardly open ones volume limits.

The process according to the invention can also be used, in particular, in plants or application environments, where the wipeability of the lime base on dried surfaces plays a role and softening is out of the question. Furthermore, in mobile systems, if consumables for softening is not available or its use is not desired; as well as small and medium-sized (stationary) systems for water treatment, where lime should not be removed from the water, but limescale deposits are to be reduced as much as possible.

Claims (15)

A method for treating running water to prevent lime deposits, wherein the water is supplied to a container (10) in which the water is subjected to an ultrasonic field by means of one or more ultrasound sources (30) and after the treatment via a drain (12 ), wherein the lime dissolved in the water by means of a precipitation reaction on surfaces inside the container (10) deposited and removed by means of the ultrasonic field from these surfaces and is returned as solid lime in the form of suspended particles in the water, and wherein the dissolved Lime electrolytically by means of direct current in a cathode chamber (13) at a cathode (40) is precipitated, wherein the surface of the cathode (40) is acted upon by the ultrasonic field at least temporarily, characterized in that the water first through the cathode chamber (13) and then passed through an anode compartment (14) with one or more anodes (50) or that Cathode space (13) and the anode space (14) are flowed through in parallel, and that the dissolved lime is precipitated on the surface of a mineral press, a mineral fluid bed or a mineral fill. Method according to Claim 1 , characterized in that the residence time of the water in the anode compartment (14) is shorter than the residence time in the cathode compartment (13). Method according to one of Claims 1 or 2 , characterized in that at least a part of the water in the container (10) circulates by means of a vortex flow. Method according to Claim 3 , characterized in that at least a part of the water in the cathode space (13) circulates by means of the turbulent flow. Method according to one of Claims 1 to 4 , characterized in that the mineral pressure, the mineral fluidized bed or the mineral fill in the interior of the container (10) by means of sieves (18) in a certain volume range of the container (10) and is acted upon in this with the ultrasonic field. Method according to one of Claims 1 to 5 , characterized in that the voltage, and thus the current flow of the electrolysis between the cathode (40) and anode (50), and / or the intensity and / or the duty cycle and / or the time intervals of the activation of the ultrasonic field depending on a Flow rate of the water through the container (10) are controlled. Method according to one of Claims 1 to 6 , characterized in that the ultrasonic field in a chaotic resonator (17) excited and / or a plurality of ultrasonic sources (30) having different frequencies and / or a plurality of pulse-excited ultrasonic sources (30) are used. Method according to one of Claims 1 to 7 , characterized in that the water between the inlet (11) and outlet (12), depending on a pressure in the container (10), via a bypass (80) is guided. Method according to Claim 8 , characterized in that the bypass (80) is associated with a self-closing pressure relief valve (81) is opened when a predetermined or predetermined first limit value for the pressure of the bypass (80) and after a pressure drop below a predetermined or predetermined second limit for printing is closed automatically. Method according to one of Claims 1 to 9 , characterized in that the cathode (40) a spongy or tangle-like structure with a large surface, in particular consisting of stainless steel, and / or as an anode (50) graphite, in particular consisting of one or more graphite rods (51) are used. Method according to one of Claims 1 to 10 , characterized in that a portion of the effluent via the drain (12) water is fed back to the container (10) via a return. Method according to one of Claims 1 to 11 , characterized in that an ultrasonic field is generated by means of in a plane around a cylindrical resonator and / or along the axis of the cylindrical resonator (17) in the interior of the container (10) arranged ultrasonic sources (30). Method according to one of Claims 1 to 12 , characterized in that the suspended particles, which are discharged via the outlet (12), have a size in the range between 500 and 2000 nm. Method according to one of Claims 1 to 13 , characterized in that the mineral pressing, the mineral fluidized bed or the mineral fill, in particular quartz and / or quartz flour. Application of the method according to one of Claims 1 to 14 for water hardness stabilization in domestic water treatment plants (1) or in industrial environments.

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