GB2593256A

GB2593256A - Method and apparatus for water processing

Info

Publication number: GB2593256A
Application number: GB2018405.7A
Authority: GB
Inventors: Vozyakov Igor; Scheblanov Alexander
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-03-16
Filing date: 2020-11-23
Publication date: 2021-09-22
Also published as: GB2593241A; CH717232A1; GB2593242A; GB202013079D0; GB202016345D0; WO2021186155A1; GB2593955B; GB202013075D0; WO2021186159A1; GB2593241B; GB2593243A; GB202018405D0; GB202013078D0; GB2593242B; WO2021186157A3; GB2593243B; WO2021186168A1; WO2021186157A2; GB2593955A

Abstract

A method of precipitating salt out of an aqueous solution comprises the step of forming a flow with toroidal vortices in the aqueous solution such that the aqueous solution is exposed to alternating flow velocities and alternating pressures, thereby initiating precipitation of salts from the solution. The flow may comprise high-frequency alternating flow velocities and/or high-frequency alternating pressures, preferably wherein the high frequency is at least 500 Hz. An apparatus for precipitating salt out of an aqueous solution is also claimed, which comprises a flow generator adapted to perform the method. Suitably, the flow generator comprises a notched rotor 108 rotatable in cooperation with a notched stator 114 to block and open cyclically a plurality of passages for a fluid to form the flow. A method of forming salt particles, e.g. nanocrystalline particles, and a method of dissolving a water-insoluble substance in water are also claimed. In a further aspect, a method of reacting a substrate in water is also claimed, wherein the reaction may be hydrolysis, hydration, creation and break-down of carbon-to-carbon bonds, and/or hydrogenation of the substrate.

Description

Method and Apparatus for Water Processing The present invention relates to the field of water processing, and in particular to desalination of water.

Summary

Aspects of the invention are set out in the independent claims and preferred features are set out in the dependent claims.

According to a first aspect there is provided a method of precipitating salt out of an aqueous solution, comprising steps of: providing an aqueous solution of one or more salts; and forming a flow with toroidal vortices in the aqueous solution, such that the aqueous solution is exposed to alternating flow velocities and alternating pressures, thereby initiating precipitation of salts from the solution.

According to another aspect there is provided a method of forming salt particles, comprising steps of: providing an aqueous solution of one or more salts; forming a flow with toroidal vortices in the aqueous solution, such that the aqueous solution is exposed to alternating flow velocities and alternating pressures, thereby initiating precipitation of salts from the solution; and separating salt particles from an aqueous suspension formed by precipitation of salts from the aqueous solution. The flow may be as aforementioned.

According to another aspect there is provided a method of dissolving a water-insoluble substance in water, comprising steps of: providing an aqueous suspension of a water-insoluble substance; forming a flow with toroidal vortices in the aqueous suspension, such that the aqueous suspension is exposed to alternating flow velocities and alternating pressures, thereby initiating dissolution of the water-insoluble substance. The flow may be as aforementioned.

According to another aspect there is provided a method of precipitating a solute out of a solvent, comprising steps of: providing an solution of one or more solutes in a solvent; and forming a flow with toroidal vortices in the solution, such that the solution is exposed to alternating flow velocities and alternating pressures, thereby initiating precipitation of solute from the solution. The flow may be as aforementioned.

According to another aspect there is provided a method of dissolving an insoluble substance in a solvent, comprising steps of: providing a mixture of one or more insoluble substance in a solvent; and forming a flow with toroidal vortices in the mixture, such that the solution is exposed to alternating flow velocities and alternating pressures, thereby initiating dissolution of the insoluble substance. The flow may be as aforementioned.

According to another aspect there is provided a method of reacting a substrate in water, comprising steps of: providing an aqueous suspension or solution of a substrate; forming 113 a flow with toroidal vortices in the aqueous suspension or solution, such that the aqueous suspension or solution is exposed to alternating flow velocities and alternating pressures, thereby initiating reaction of the substrate. The flow may be as aforementioned.

According to another aspect there is provided a method of producing hydrogen from water, comprising steps of: forming a flow with toroidal vortices in water, such that the water is exposed to alternating flow velocities and alternating pressures; and exposing the water to an electrical potential below 1.23 V, thereby initiating electrolysis of the water. The flow may be as aforementioned. The electrical potential may be below 1.2 V, or below 1.1 V, or below 1 V, or below 0.75 V, or below 0.5 V. According to another aspect there is provided apparatus for precipitating salt out of an aqueous solution, comprising a flow generator adapted to form a flow with toroidal vortices in an aqueous solution such that the aqueous solution is exposed to alternating flow velocities and alternating pressures for initiating salt precipitation.

According to another aspect there is provided apparatus for dissolving a water-insoluble substance in water, comprising a flow generator adapted to form a flow with toroidal vortices in an aqueous suspension of a water-insoluble substance such that the aqueous suspension is exposed to alternating flow velocities and alternating pressures for initiating dissolution of the water-insoluble substance. The flow generator may comprise a notched rotor rotatable in cooperation with a notched stator to block and open cyclically a plurality of passages for a fluid to form the flow. Apparatus may be adapted to perform a method as aforementioned.

According to another aspect there is provided apparatus for precipitating a solute out of a solvent, comprising a flow generator adapted to form a flow with toroidal vortices in an solution such that the solution is exposed to alternating flow velocities and alternating pressures for initiating solute precipitation.

According to another aspect there is provided apparatus for dissolving an insoluble substance in a solvent, comprising a flow generator adapted to form a flow with toroidal vortices in a mixture of an insoluble substance and a solvent such that the mixture is exposed to alternating flow velocities and alternating pressures for initiating dissolution of the insoluble substance. The flow generator may comprise a notched rotor rotatable in cooperation with a notched stator to block and open cyclically a plurality of passages for a fluid to form the flow. Apparatus may be adapted to perform a method as aforementioned.

According to another aspect there is provided apparatus for reacting a substrate in water, comprising a flow generator adapted to form a flow with toroidal vortices in an aqueous suspension or solution of a substrate such that the aqueous suspension or solution is exposed to alternating flow velocities and alternating pressures for initiating a reaction with the substrate. The flow generator may comprise a notched rotor rotatable in cooperation with a notched stator to block and open cyclically a plurality of passages for a fluid to form the flow. Apparatus may be adapted to perform a method as aforementioned.

According to another aspect there is provided apparatus for producing hydrogen from water, comprising a flow generator adapted to form a flow with toroidal vortices in water such that the water is exposed to alternating flow velocities and alternating pressures; and, downstream of the flow generator, electrodes for exposing the water to an electrical potential for initiating electrolysis of the water. The flow generator may comprise a notched rotor rotatable in cooperation with a notched stator to block and open cyclically a plurality of passages for a fluid to form the flow. The flow generator may comprise electrodes downstream of the rotor. Apparatus may be adapted to perform a method as aforementioned.

According to further aspects there is provided a method for hydrodynamic precipitation, wherein flow conditions are created in an aqueous salt solution with linear flow portions with flow speed of 2-4 meters per second, and toroidal vortices with peripheral flow speed of 200-400 meters per second. Such flow conditions can disrupt aqueous solvation of ions, for example by creating a field of centrifugal force, resulting in ion association and precipitation.

Brief Description of the Drawings

Example embodiments are illustrated in the accompanying figures in which: Figure 1 shows a schematic flow diagram of a system for precipitating salts from an aqueous solution; Figure 2 shows a cross sectional view of a generator; Figure 3 illustrates a perspective view of a rotor disc of a generator; Figure 4 illustrates a perspective view of a stator disc of a generator; Figures 5 illustrates a perspective view of a permanent flow generated by conditions in a generator; Figure 6 illustrates a perspective view of a periodical flow generated by conditions in a generator; Figures 7a, 7b and 7c show graphs of local flow velocity, acceleration and absolute pressure in flow in a generator during different phases of operation; and Figure 8 shows a graph comparing diameter of toroidal vortices against efficiency of salt precipitation.

In the drawings, like reference numerals are used to indicate like elements.

Detailed Description

Figure 1 shows a schematic flow diagram of a system for precipitation of salts from an aqueous solution. An aqueous solution 4 of one or more salts is pumped by a pump 6 to a tank 8 with liquid level 10. The solution is provided to a generator 2 where flow conditions are generated that result in precipitation of salts from the aqueous solution. The generator 2 and the flow conditions generated at the generator 2 are described in more detail below. An aqueous suspension of salt particles is formed. The suspension is flowed to a filter unit 12. The filter unit 12 separates the salt particles from the fluid. The filtered fluid 20 is with its salt content reduced. The filtered salt particles 18 can be collected.

In the generator 2 flow conditions are generated that result in precipitation of salts from the aqueous solution. In more detail, the generator 2 generates toroidal vortices in the flow. The toroidal vortices can for example have peripheral flow speeds of 200-400 meters per second, whereas the bulk fluid flow speed is for example 2-4 meters per second. The toroidal vortices can for example be 20-40 pm diameter. The flow conditions generated in the generator 2 are described in more detail below. Under the influence of these toroidal vortices the supra-molecular structure of water is affected, and the solvation of salt ions is affected.

Normally, molecular attraction forces prevail in water (Van der Waals' forces or hydrogen bonds). Water has a comparatively high relative permittivity (also referred to as a dielectric constant) of 78.7 at 298K (25 °C), a relative measure of its chemical polarity; in aqueous solutions many ions are fully solvated. For example NaCI does not form ion pairs to an appreciable extent except when the solution is very concentrated, but instead fully solvated ion-pairs are present. Even a minor change of temperature or pressure can alter physical and chemical properties of water, and in particular solubility of salts can change significantly. The generator creates flow conditions that alter pressure, fluid shear, centrifugal fields, and other forces that can affect the structure of water, and hence its performance as a solvent. Previously fully solvated ions can become associated with one another in the altered solvent environment, resulting ions of opposite electrical charge coming together and precipitate out as particles.

It is thought that the flow conditions created at the generator can disrupt hydrogen bonds in water, affecting the molecular structure of water, including in the region of an ion. It is thought that, at the toroidal vortices the structure of water can be disrupted, and a border can be formed. Instead of quasi-endless water clusters, an ion may become exposed to finite-size water clusters with a large deficit of hydrogen bonds and borders instead of continuum. Under these conditions, water can behave differently than a liquid and assume different properties. Nor does water under such conditions behave like a gas (where most of the molecules can freely rotate), as configurations typical of liquid state persist to a degree. Water is instead in a transient state. In the transient state characteristics such as relative permittivity (dielectric constant), electrical conductivity, hydrogen bond structure are different from water under ordinary conditions (i.e. in the absence of toroidal vortices).

Water in the described transient state (also referred to as 'activated' water) may no longer sufficiently solvate ions, and exposed ions may associate with one another and come together and precipitate. Even a minor local change of temperature or pressure in activated water can alter its physical and chemical properties, and in particular its solvation properties. Minute fluctuations of pressure and temperature in activated water in the flow with toroidal vortices can cause ions to precipitate out virtually completely to form inorganic salts and oxides for example. The flow is pressurised by the generator to an average fluid pressure of for example 8-12 atm, and this pressure can assist in precipitation of salt as well.

As mentioned above, water ordinarily has a comparatively high relative permittivity (dielectric constant) of 78.7 at 25 °C, a relative measure of its chemical polarity. Water molecules have a certain asymmetry of intramolecular forces. The "gravity centre" of a molecule's positive and negative charges do not coincide with one another and molecules constitute a "hard" dipole, even in the absence of an external electric field.

Thermal motion of molecules causes their dipole moments to be chaotically oriented in space. In the presence of an external electric field, dipole moments become oriented towards the field. Processing inside the generator disrupts such orientation; inside the generator chaotic motion of water molecules obstructs dipole orientation and increases spatial disorientation of water's dipole moments, observable in a drop in relative permittivity. Processing by the generator not only disrupts the quasi-spatial structure of water molecules but, by that token, influences the degree of orientation of its dipole moments.

A similar spatial disorientation occurs in water around the critical point, at 3740 at 22.054 M Pa. It is known that around the critical point, water assumes different properties than otherwise (e.g. water becomes compressible) and in particular assumes a lower relative permittivity, and becomes a poor solvent for electrolytes, and becomes a better solvent for nonpolar substances. A similar phenomenon initiates precipitation of calcium carbonate from tap water from 60-650.

The conditions created in the generator affect water in two ways: 1. Spatial disorientation of water's dipole moments.

2. Disruption of spatial quasi-structure of water owing to which transition of precipitated residue back to the solution slows down.

Following dielectric constants are observed (at ambient temperature and pressure) in distilled water and in a salt solution similar to seawater (30g NaCI, 1.6g MgC12, 4.1g MgSO4, 1.1g CaSO4 and 0.2g CaCl2 per 1000g distilled water): * distilled water, prior to treatment in generator: dielectric constant of 80-82 * salt solution similar to seawater, prior to treatment in generator: dielectric constant of 75-78 * distilled water, following treatment in generator: dielectric constant of 25-30 * salt solution similar to seawater, following treatment in generator: dielectric constant of 25-30 In the conditions created by the operation of the generator, treatment of both seawater and pure water causes the relative permittivity to drop from around 80 to 25-30, which is similar to the relative permittivity of acetone or ethanol. The time during which said value of relative permittivity persists is rather short and does not exceed 20-30 minutes, subsequent to which the relative permittivity reverses to its original level. In case precipitated salt particles are removed from the salt solution similar to seawater following treatment in the generator, the relative permittivity reverses to 79-81 consistent with the content of residual ions in the desalinated water.

In the activated solution, relative permittivity is around 25-30, similar to the relative permittivity of acetone or ethanol. The maximum solubility of NaCI in acetone and ethanol is 0.00042 g NaCI per 1 kg of acetone; or 0.65 g NaCI per 1 kg of ethanol. In the aqueous solution with relative permittivity around 25-30 the observed drop of solubility of NaCI is consistent with the expected solubility based on comparison to substance with similar relative permittivity.

The treatment can be applied to other solvent-solute systems to achieve precipitation of a solute that is ordinarily well soluble, for example for precipitating urea (polar) from dimethyl sulfoxide (polar).

The described process can be operated without high temperatures (e.g. unlike approaches involving water evaporation), for example at ambient temperature. The described process can be operated without requiring high pressures (e.g. unlike some approaches involving membrane desalination). Pre-set productivity and operating stability can be achieved. The process is suitable in small scale or decentralised processing, or for large scale processing. The process can be implemented in batches or in continuous operation. By virtue of the precipitation and separation of the precipitated particles (e.g. by filtration), water can be demineralized.

The filtration process should take place immediately after the aqueous salt solution is treated in the reaction zone, without any interruption in the flow, within 30 minutes. The flow is pressurised by the generator to an average fluid pressure of for example 8-12 atm, and this pressure can assist in filtration through a filter. Other suitable techniques may be used to separate particles from the liquid, for example centrifugation at ambient pressure and sedimentation.

The precipitation of salts from an aqueous solution can provide potable water from sea water, and can also be used in various other branches of chemical industry. For example, the described process may be used: * To produce potable fresh water; * To produce non-potable fresh water; * For purification of sea, ocean, and brackish water sources * To treat water in the thermal power sector; * To treat water in food processing; * To treat nuclear energy effluents that combines production of concentrated * radioactive isotopes and non-potable fresh water; * To treat industrial and household effluents to remove dissolved inorganic salts and obtain treated water plus dry inorganic salts; * To remove water-soluble mineral admixtures from sea and ocean waters; and * To convert inorganic salts that may be dissolved in water into a non-soluble state.

Instead of or in addition to desalination of water, the process described above can be used to harvest salt particles with desired properties such as average size and size distribution. Particle size may vary depending on the flow conditions, the salt concentration in the solution, and how soon after water activation the particles are separated from the water. The salt particles may for example be nanocrystalline particles. Particle composition can be varied by suitable selection of ions in the solution.

Activated water can cause ion association and precipitation, but it can have other effects on other chemical species. For example the chemical polarity of activated water can change, and affect solubility of substances. Substances that are otherwise not readily soluble in water, such as some organic substances, can become dissolved in activated water. Activated water can safely and efficiently dissolve substances that are otherwise only poorly soluble in water.

A general theory of solubility of substances in water does not exist, but generally polar substances (with a comparatively high relative permittivity) are well soluble in water, and substances with low polarity (and a comparatively low relative permittivity) are not well soluble in water. In other words, generally there exists a link between a substance's relative permittivity and its solubility in water. However, this linkage is highly individual and each liquid possesses certain specifics characterizing said dependence.

As discussed above, under the conditions generated in the generator the structure of water is affected and the relative permittivity decreases, and solvent behaviour changes. Substances that are not soluble in water prior to treatment typically become more soluble (e.g. oils, benzene, non-polar organic solvents). This holds true for both solid and liquid substances; to avoid damaging the generator solids can be provided dissolved in a suitable solvent (e.g. a nonpolar solvent). Alternatively, solids can be added immediately after treatment of the solvent in the generator. The treatment can be applied to other solvent-solute systems to achieve dissolution in a solvent not otherwise able to dissolve a substance, for example for dissolving urea (polar) in benzene (nonpolar).

Activated water can also enable reactions due to the altered hydrogen bond structure of the medium. If a suitable substrate is present in the activated water, reactions of hydrolysis, hydration, creation and break-down of carbon-to-carbon bonds, and hydrogenation may occur. For example, chemical warfare agents may be destroyed by exposure to activated water.

Activated water can also enable electrolysis of water to produce hydrogen. The decomposition of water into hydrogen and oxygen at standard temperature and pressure requires an electrical potential of at least 1.23 V. Activated water is in a higher energetic -10 -state and an electrical potential below 1.23 V can suffice for the decomposition of water. In an example hydrogen is produced from activated water by electrolysis with an electrical potential of 0.5 V, 0.75 V, 1 V, 1.1 V or 1.2 V. A suitable electrical potential can depend on factors such as the conditions in the generator and the operational settings of the generator, the time elapsed following processing in the generator, and the presence of other species in the water (e.g. ions). In an example a suitable cathode and anode for electrolysis are provided downstream of the generator, or incorporated in an outlet portion of the generator, to enable electrolysis of activated water following activation. Following activation the water can be brought to ambient pressure for the electrolysis, as the activation of the water persists for some time following activation as discussed above. To promote electrolysis suitable additives such as electrolytes may be added to the water, before or after activation of the water, depending on whether or not the electrolyte is likely to undergo reactions in the generator (e.g. hydrolysis, hydration, creation or break-down of carbon-to-carbon bonds, or hydrogenation). To accelerate electrolysis it may be desired to apply an electrical potential that is higher than the minimum necessary. In any case the electrical power input for electrolysis of activated water is lower than it would be to achieve the same effect in water prior to treatment in the generator.

An example of the performance of the system illustrated in Figure 1 is now provided, in which precipitation of salts from water is achieved.

Table 1. Performance results for sea water treatment.

Mass, Refraction Density at pH Dry residue, mg/1 grams 20°C, kg/m3 Source fresh water 1000 1.33410 998.6 7.4 498 Substances added to water NaCI 30.00 MgC12 1.6 MgSO4 4.1 CaSO4 1.1 CaCl2 0.2 Total 37.0 Water following introduction of additives 1036.9 1.33986 1026.5 8.2 37251 Water, 10-30 minutes after 1.32217 946.8 processing and filtration Water, 60 minutes after 1.33486 998.8 6.8 826 processing and filtration Filtrate residue after drying 36.70 Losses 0.36 g (1%) Table 1: measurement of properties and masses at various process stages.

The data in Table 1 reflects an example where known quantities of a number of salts are added to source fresh water and then precipitation of salts from an aqueous solution is performed by providing the solution to a generator. In the generator flow conditions are generated that result in precipitation of salts from the aqueous solution. Subsequently filtration is performed to separate the aqueous suspension of salt particles. The weight of the salts added to source fresh water is 37.0g, compared to 36.7g of salts that are recovered as filtrate residue after drying. The index of refraction, density, pH and dry residue weight per volume is determined for the source fresh water, the source fresh water with salts added, and the solution at various time points after -12 -precipitation and filtration of salt particles. It is calculated that around 99% of the salts added to the water are precipitated and filtered out.

Generator The following description of the generator 36 used for precipitating salt will be discussed below with reference to Figures 2 to 8.

Figure 2 illustrates a cross sectional view of a generator 36 for generating toroid and spatial vortices in a liquid 102. As used herein, the term 'spatial vortex' is used to distinguish non-toroid vortices from toroid vortices, and includes vortices where the axis of rotation does not form a closed loop (e.g. tubular vortices, cone-shaped vortices). The generator 36 comprises: a substantially rotationally symmetrical stator housing 103, symmetrical about axis 107; an axial inlet opening 104, an eccentric outlet opening 105 directed in a plane 106 that is normal to axis 107, and a rotor 108 rotatable around axis 107 in the stator housing 103, the rotor 108 comprising radially outwardly extending channels 109 in constant fluid connection to the inlet opening 104. In an example, the rotor 108 has an outer diameter of about 30 cm ± 20%.

The generator further comprises a rotor disc 110 and a stator disc 114 rotatable about axis 107. Figures 3 and 4 illustrate a perspective view of a rotor disc 110 and a stator disc 114 of a generator 36 respectively. Inner notches 112 are arranged periodically about the rotor disc 110, and notches 116 are arranged periodically about the stator disc 114.

The rotor disc 110, shown in Figure 3, is attached to the rotor 108 in a rotationally fixed manner radially outside the rotor 108. The rotor disc 110 comprises a side surface 111 normal to axis 107 with inner notches 112, spaced apart from one another and equidistant from the axis 107 for channelling a liquid 102. The rotor disc 110 may additionally comprise outer notches 113 on the same surface 111 as the inner notches 112. These outer notches 113 can also be spaced apart from one another and equidistant from the axis 107.

The rotor disc 110 also includes outer notches 113. By virtue of the outer notches 113 the building of toroid vortices within the periodical liquid flow 119 is further increased before the liquid 102 exits the rotor disc 110.

-13 -The stator disc 114, shown in Figure 4, is attached with torque proof connection to the stator housing 103. The stator disc 114 comprises a side surface 115 configured to face the side surface 111 of the rotor disc 110 as well as stator notches 116 spaced apart from one another and spaced equidistantly around axis 107.

The number of each kind of notch 112, 113, 116 determines the throughput of liquid and is preferably between 16 and 42, although it will be appreciated that any number of notches can be used. It is not necessary for the notches 112, 113, 116 to be arranged equidistant from one another on the discs 110, 114, but it is preferred. The number of the inner notches 112 may equal the number of the outer notches 113 and/or the number 113 of the stator notches 116. This is the case illustrated in Figures 3 and 4.

The generator 36 may further comprise a guide vane 121 inside the stator housing 103 radially outside the stator disc 114 and rotor disc 110 for guiding a total liquid flow 120 to the eccentric outlet opening 105. Passages radially outside of the stator disc 114 to the outlet opening 105 are provided by the guide vane 121.

Figures 5 and 6 illustrate perspective views of a permanent flow 118 and a periodic flow 119 generated by conditions in a generator 36 respectively. In particular, Figures Sand 6 illustrate how the conditions change as the rotor disc 110 and the stator disc 114 move relative to one another. A permanent flow 118 flows in a direction illustrated by arrows in Figure Sand flows perpendicular to a periodic flow 119 illustrated by an arrow in Figure 6. Manipulation of these flows helps to create toroid vortices in the liquid 102.

A permanent liquid flow 118 between the discs 110, 114 flows between the flat parallel side surface 111, 115 of rotor disc 110 and stator disc 114 and moves in a constant radial direction, independent of the positioning of the notches 112, 116. The rotor disc 110 and the stator disc 114 are spaced apart by a gap 117. This gap 117 allows a liquid flow, defined as the permanent flow 118, through from the inner notches 112 to the outlet opening 105. The gap 117 provides for spatial vortices to be generated in the liquid flow, in use, due to the velocity difference between the opposing side surfaces 111, 115, which define the gap 117, and due to periodical disruptions by the portioned liquid 102 passing through the gap 117 in an axial direction from the centre of the discs outward as illustrated by arrows 118 in Figure 5. This permanent liquid flow 118 contributes between 5% and 30% of the total liquid flow 120 through the generator 36 depending on the size of the gap 117. In some examples the gap 117 between the rotor disc 110 and -14 -stator disc 114 is preferably between 0.8 mm and 1.2 mm wide. This permanent liquid flow 118 is independent of the actual position of the rotor 108.

Inner and outer notches 112, 113 of the rotor disc 110 and stator notches 116 of the stator disc 114 provide volumes in which to form a periodic liquid flow 119 of liquid 102.

The periodic liquid flow 119 flows between the inner notches 112 and the stator notches 116 as illustrated, for example, in Figure 6. When the inner notches 112 and stator notches 116 are aligned, the liquid 102 flows from the inner notches 112 to the stator notches 116, forming the periodic flow 119. Portions of liquid 102 pass back and forth from the inner notches 112 to the stator notches 116 caused by a change in volume as 113 the rotor 108 rotates and the notches 112, 113, 116 successively align and misalign with each other. The periodic flow 119 helps to generate toroid vortices in the portioned liquid 102 by shear stress.

Liquid 102 leaves the rotor 108 to enter the inner notches 112 of rotor disc 110 when it is opposite the stator notch 116 of stator disc 114; it has roughly the same linear peripheral speed until the rotor disc 110 rotates to a position opposite the enclosed space between the notches 112, 113, 116. At that point, the passage for liquid 102 to exit the chamber of the rotor disc notch 112 closes off. This produces a pressure spike in liquid in the inner notch 112 of rotor disc 110 until an exit for the liquid 102 via a notch 116 in the stator ring 114 opens again, due to rotation, and the liquid 102 is able to flow into the stator notch 116.

Figure 5 illustrates the case after the closure point of the flow from an inner notch 112 to a stator notch 116. The periodical flow becomes further accelerated; a portion of the flow turns 180° and begins to move in the opposite direction to the principal flow within the inner notches 112, taking the shape of a twisted flow and forming a stable vortex braid 122 along the full length of the inner notches 112, which partially enters the stator notch 116.

Further rotation of the rotor disc 110 partially opens the flow passage from the inner notches 112 into the stator notches 116. Given that the opening is still very narrow, the space for the vortex braid flow 122 becomes tight, and the braid begins to break up into toroid vortex pieces. The toroid vortices so generated enter the stator notches 116, where the shape of the notches shapes the vortices into separate toroid vortices.

-15 -As the flow passage from the inner notches 112 to the stator notches 116 then gradually widens, each stator notch 116 is filled with a screw-like vortex braid that, once the total flow of liquid reverses its direction 1800, breaks up into portions, generating similar toroid vortices.

The time period when the stator notches 116 are fully aligned with the inner notches 112 is very brief, as the rotor disc 110 rotates at around 3000 revolutions per minute (50 Hz). The frequency of rotation can be adjusted to achieve variations in pressure experienced by the liquid 102. The rotor's continued rotation tightens the spaces for the vortex braid, as the inner notches 112 gradually close. This promotes continued breakup of the vortex braid into toroid vortices.

As the rotor disc 110 rotates and the stator notches 116 are closed off from the inner notches 112 again, the entire process repeats, submitting the liquid 102 to high frequency alternating flow velocities and pressures. Rotation of the rotor ring creates a suction effect and draws fluid in.

The generator 36 can be used for generating toroid and spatial vortices in a liquid 102, by: guiding the liquid 102 to the inlet opening 104 and rotating the rotor 108 with the attached rotor disc 110 to produce a permanent liquid flow 118 and a periodical liquid flow 119 between the stator disc 114 and the rotor disc 110 as described above.

Toroid vortices are generated in the portioned liquid 102 of the periodic liquid flow 119 by shear stress as the portions of liquid 102 pass from the inner notches 112 to the stator notches 116 and move back and forth therebetween. Further, spatial vortices are generated in the permanent liquid flow 118 in the gap 117 between the side surfaces 111, 115 due to the velocity difference of the side surfaces 111, 115 and due to periodical disruptions by the portioned liquid 102 passing the gap 117 in the axial direction.

Figures 7a, 7b and 7c show graphs of local flow velocity, acceleration and absolute pressure in flow in an exemplary generator during different phases of operation. The graphs show flow conditions immediately downstream from the rotor ring / stator ring passage, from t=0 just before a rotor ring inner notch 112 starts to line up with a stator notch 116, continuing until the rotor ring notch fully opens (i.e. is in alignment with a stator notch) and further until the rotor ring notch closes.

-16 -As the notch 112 starts to open up, over a duration of 0.000092 seconds (0.092 milliseconds), flow velocity increase from 10 to 160-200 meters per second (m/sec). As the rotor ring notch then comes into full alignment, over a duration of 0.00023 seconds, flow velocity drops to 30 m/sec. Subsequent movements of the rotor ring result in continued progressive closure of the notch, boosting the flow velocity to 160-200 m/sec.

With further rotation of the rotor ring, the notch closes (i.e. it no longer is located at a stator notch), and the flow velocity (from flow through the gap 117) drops to 10 m/sec. As the rotor ring continues to rotate, the notch 112 is in its closed configuration (with only flow through the gap 117) for 0.00064 second. The notch 112 remains in its open configuration (fully or partially lined up with a stator notch) for 0.00046 second.

Such rapid changes in flow velocity occasioned by rotor ring rotation within the same time period produce significant alternating accelerations of the flow that change from +16,000,000 to -16,000,000 m/sec2. Such accelerations affect the liquid within the rotor ring notch and the slot-like gap between the rotor and stator rings.

The forces that develop in the process produce pressure in a portion of liquid flow, which varies from 500 bar (50 Megapascal MPa or 510 atmosphere atm) overpressure to 0.1 bar (0.01 MPa) vacuum over a period of 0.00046 seconds. In a 0.000092 second timespan the pressure drops from 500 bar (50 MPa) overpressure to 0.7 bar (0.07 MPa) vacuum. Such rapid pressure changes, from overpressure to vacuum and back, can be very effective at initiating precipitation.

In some examples, depending on the generator design, the maximum local pressure in a toroid vortex may reach 200-400 kg/cm2 (around 20-40 MPa) and flow velocity change per unit of time (acceleration) is 50,000 G (around 490,000 m/sec2) The permanent liquid flow 118 is disturbed by vortex flows that pass from the inner notches 112 to the stator notches 116 perpendicular to the permanent liquid flow 118.

In this context, the permanent liquid flow 118 is affected by shear stresses the rotor disc 110 generates as it moves in relation to the freely attached stator disc 114 that is blocked to prevent its rotation. The notches 112, 113 in the rotor disc's side surface 111 continuously disrupt the linear nature of inter-disc flow along the permanent liquid flow 118 and generate spatial vortices therein.

-17 -A conical funnel-shaped spatial vortex forms in at a rotor ring notch as the stator ring blocks the flow exit from the rotor ring. As the rotor ring exit is closed off, the outside portion of the vortex braid produces a maximum diameter funnel and unfolds towards the rotor ring entrance.

As those spatial vortices come into contact with toroid vortices, first from the inner notches 112 and then from the stator notches 116, they morph into yet smaller and more intense toroid vortices and, along with toroid vortices from the stator disc notches 112, are dispersed in total flow 120 and carried out into a discharge system. Alternating flow velocities may be produced using this technique at a frequency of at least 500 Hz, for example. Alternating pressures may also be produced using this technique at a frequency of at least 500 Hz, for example.

Contact between spatial vortices in the permanent liquid flow 118 and the spatial vortex braid for the periodical flow 119 exiting the stator notches 116 as they fully open help to cause the toroid vortices to stabilise. As the two flows 118, 119 mix, they generate a total liquid flow 120 featuring an internal volume comprising a plurality of toroid vortices.

Peripheral liquid flow velocity in a toroid vortex is greater than that of the fluid outside the toroid vortex. For example, peripheral flow velocity in a toroid vertex may be between 5 and 10 times that of the flow velocity outside the toroid vertex. Peripheral flow velocities of liquid flow in a toroid vortex may be at least 100 m/s, for example, 200 m/s to 400 m/s.

Pressure of a toroid vortex may also be greater than the pressure in the fluid outside the toroid vortex. Local pressures of at least 500 kPa may be achieved.

At 3000 revolutions of the rotor ring per minute, and from 12 to 48 notches on the rotor ring, the vortex braid generation process is near enough continuous to be effectively continuous. The spatial vortexes formed in the chamber comprised by rotor ring notches and stator ring notches may be deemed stable, and their number deemed consistent with the number of notches, i.e., 12 to 48; in their turn, the spatial vortexes produce a large number of smaller toroid vortexes with a typical torus diameter of 20-40 micrometres. The vortex braid breaks down into toroid vortexes typically ranging from 20 to 40 micrometres in diameter. Larger and smaller toroid vortexes are present as well, but in lower numbers. As the toroid vortexes travel in the flow they gradually dissipate and shrink. In an example at a distance of 3 meters from the outlet port of the generator 20-40 micrometre vortexes are still found in the pipeline. At that point smaller -18 -vortexes may have dissipated and may not be observed, whereas larger vortexes may have split into smaller ones and coincide in the 20-40 micrometre size.

In an example the rotor ring rotates at 40-60 Hz and has 16-42 notches to generate toroid vortices at 640 to 2520Hz. In this example 256-1764 vortices are produced per revolution. In addition to such primary vortexes formed at a primary frequency, secondary vortexes are formed with an integral multiple frequency (integer N = 2, 4, 6, 8), but the efficiency of those secondary vortexes is significantly less compared to efficiency of the primary vortexes. In an example where the generator throughput is about 160-240 m3/hour, a density of around 190-3000 primary vortices may be generated per litre of fluid.

As described above, under such conditions, in particular due to the liquid in the permanent liquid flow 118 and the sudden change of direction in the periodical liquid flow 119 On a direction perpendicular to the permanent liquid flow 118), a vortex is built and the liquid 102 forms toroid currents therein. The liquid 102 is subjected to resulting high frequency alternating pressures and flow velocities. Conditions experienced by the aqueous salt solution in the liquid 102 initiate precipitation.

The generator's productivity does not fall due to the emergence of a water slickness effect. Disruption of the quasi-spatial structure of water also results in localised reduction of viscosity of the fluid, which makes up for apparent loss of productivity in the generator.

Figure 8 shows a graph comparing diameter of toroidal vortices against efficiency of salt precipitation. Efficiencies over 90% (i.e. causing over 90% by mass of salts to precipitate from the solution) are achieved when the average diameter of toroidal vortices is in the region of around 25-40 micrometres. At significantly lower or higher average diameters the efficiency of salt precipitation decreases.

Alternatives It will be appreciated from the above description that many features of the different examples are interchangeable and combinable. The disclosure extends to further examples comprising features from different examples combined together in ways not specifically mentioned. Indeed, there are many features presented in the above examples and it will be apparent that these may be advantageously combined with one another.

Claims

-19 -Claims 1. A method of precipitating salt out of an aqueous solution, comprising steps of: providing an aqueous solution of one or more salts and forming a flow with toroidal vortices in the aqueous solution, such that the aqueous solution is exposed to alternating flow velocities and alternating pressures, thereby initiating precipitation of salts from the solution.
2. A method according to claim 1, further comprising filtering precipitated salt particles from an aqueous suspension formed by precipitation of salts from the aqueous solution.
3. A method according to claim 2, wherein filtering is within 30 minutes of formation of toroidal vortices, preferably within 10 minutes, further preferably within 1 minute.
4. A method according to claim 2 or 3, further comprising maintaining the flow following formation of toroidal vortices until filtering.
A method according to any preceding claim, wherein the method is continuous.
6. A method according to any preceding claim, wherein the aqueous solution is provided at ambient temperature.
7. A method according to any preceding claim, wherein the flow comprises local velocities of at least 100 meters per second, preferably at least 200 meters per second, further preferably up to 400 meters per second.
8. A method according to any preceding claim, wherein the flow comprises local velocities of up to 10 meters per second, preferably up to 4 meters per second, further preferably up to 2 meters per second.
9. A method according to any preceding claim, wherein the flow with toroidal vortices has an average velocity of at least 10 meters per second, preferably at least 20 meters per second, further preferably up to 60 meters per second.
10. A method according to any preceding claim wherein the peripheral flow velocity in a toroidal vortex is greater than the flow velocity in the fluid outside the toroidal vortex -20 -by a factor of at least 3, preferably by a factor of at least 6, further preferably by a factor of at least 10.
11. A method according to any preceding claim, wherein the flow comprises local pressures of at least 10 MPa, preferably at least 25 MPa, further preferably at least 50 MPa
12. A method according to any preceding claim, wherein the flow comprises local pressures of up to 1 mPa, preferably up to 0.1 mPa, further preferably up to 0.01 mPa.
13. A method according to any preceding claim, wherein the flow with toroidal vortices has an average pressure of at least 600 kPa, preferably at least 800 kPa, further preferably up to 1.2 MPa.
14. A method according to any preceding claim, wherein the flow comprises high-frequency alternating flow velocities and/or high-frequency alternating pressures, preferably wherein high frequency is at least 500 Hz, preferably at least 1000 Hz, further preferably at least 2000 Hz.
15. A method according to any preceding claim, wherein the toroidal vortices have a typical diameter of at least 10 pm, preferably at least 20 pm, further preferably at least 40 pm;
16. A method according to any preceding claim, wherein the flow includes at least 150, preferably at least 200, further preferably at least 500 toroidal vortices per litre of aqueous solution.
17. A method according to any preceding claim, wherein the flow is formed by a notched rotor rotating in cooperation with a notched stator to block and open cyclically a plurality of passages for a fluid.
18. A method of forming salt particles, comprising steps of: providing an aqueous solution of one or more salts; forming a flow with toroidal vortices in the aqueous solution, such that the aqueous solution is exposed to alternating flow velocities and alternating pressures, thereby initiating precipitation of salts from the solution; and -21 -separating salt particles from an aqueous suspension formed by precipitation of salts from the aqueous solution.
19. A method according to claim 18, wherein the separation is by filtration and/or wherein the salt particles are nanocrystalline particles.
20. A method according to claim 18 or 19, comprising precipitating salt out of an aqueous solution according to any of claims 1 to 17.
21. A method of dissolving a water-insoluble substance in water, comprising steps of providing an aqueous suspension of a water-insoluble substance; and forming a flow with toroidal vortices in the aqueous suspension, such that the aqueous suspension is exposed to alternating flow velocities and alternating pressures, thereby initiating dissolution of the water-insoluble substance.
22. A method of reacting a substrate in water, comprising steps of: providing an aqueous suspension or solution of a substrate; and forming a flow with toroidal vortices in the aqueous suspension or solution, such that the aqueous suspension or solution is exposed to alternating flow velocities and alternating pressures, thereby initiating a reaction with the substrate.
23. A method according to claim 21, wherein the reaction is hydrolysis, hydration, creation and break-down of carbon-to-carbon bonds, and/or hydrogenation of the substrate.
24. Apparatus for precipitating salt out of an aqueous solution, comprising a flow generator adapted to form a flow with toroidal vortices in an aqueous solution such that the aqueous solution is exposed to alternating flow velocities and alternating pressures for initiating salt precipitation.
25. Apparatus according to claim 24, wherein the flow generator comprises a notched rotor rotatable in cooperation with a notched stator to block and open cyclically a plurality of passages for a fluid to form the flow.-22 -
26. Apparatus according to claim 24 or 25, adapted to perform the method of any of claims 1 to 20.