Device, plant and method for the flow treatment of liquid substances

Abstract

Device (l 0), plant (100) an d method for the flow treatment of liquid substances. The device comprises a containing body (11), delimiting and defining inside it a reaction chamber (12) interposed between a feed unit (13) and an outlet unit (29); 5 a first nozzle stage (14) between said feed unit (13) and an adjacent two-phase flow formation segment (19) of said reaction chamber (12); three electrodes (18, 22, 25); and a diffuser (28) preceding said outlet unit (29).

Description

[0001] “DEVICE, PLANT AND METHOD FOR THE FLOW TREATMENT OF LIQUID SUBSTANCES”

[0002] FIELD OF THE INVENTION The present invention concerns a device, a plant and a related method for the flow treatment of liquid substances such as water and aqueous solutions, aimed at improving the quality of the treated water until it corresponds to hygienic-sanitary standards.

[0003] BACKGROUND OF THE INVENTION Liquid substances, such as water and aqueous solutions from surface sources, such as water from the river, or from a different source, for example technical water and wastewater, need treatments, typically of disinfection, before they can be used, or alternatively released into the environment, in compliance with hygienic- sanitary standards. Various methods for disinfecting water are known, such as treatments with chlorine or chlorine compounds, treatments with ozone, treatments with ultraviolet (UV) radiations and others.

[0004] The known methods all have advantages and disadvantages and it is therefore good practice to use more than one of them. However, the use of more treatments, generally sequentially one after the other, entails a low efficiency of the overall disinfection process and / or high energy expenditure and / or a high complexity of the devices used.

[0005] Patent RU 2 637 026 discloses a device for the flow treatment of aqueous substances that combines more treatment methods into a single step, subjecting a flow of liquid to be treated, inside a reaction chamber and essentially simultaneously, to the action of cavitation, plasma, ultraviolet rays, ultrasound and thermobaric effect. However, this device does not act uniformly on the entire volume of the liquid to be treated, in particular the layers of liquid adjacent to the walls of the reaction chamber are not affected, or are only marginally affected, by the treatment, so that the liquid is not completely disinfected.

[0006] JP 2009 119347 discloses a device for the flow treatment of water, which applies a high voltage to a cavitation bubble and performs a processing of industrial water and wastewater. This device discloses the use of two electrodes, one high-voltage side electrode (4) and one ground-side electrode (5), and no further electrodes are installed aside or in-between the high-voltage and ground electrodes.

[0007] This document does not disclose a vortex formation portion configured as a widening of a first plasma segment, because the device disclosed therein has no an intermediate electrode. Moreover, the two electrodes in JP’347 are positioned approximately at the same level along the axis line of the device, and there is no any visible expanded, in terms of diameter, portion before the electrode.

[0008] There is therefore a need to perfect a device and a relative plant for the flow treatment of liquid substances that can overcome at least one of the disadvantages of the state of the art.

[0009] To do this, it is necessary to solve the technical problem of efficiently subjecting the entire volume of a liquid substance to a treatment that guarantees the improvement of its quality until it falls within the hygienic-sanitary standards. In particular, one purpose of the present invention is to realize a device and a plant, and to develop a method, for the flow treatment of liquid substances capable of treating the volume of the liquid substances in its entirety.

[0010] Another purpose of the present invention is to realize a device and a plant, and to develop a method, for the flow treatment of liquid substances that allows an efficient treatment both from the point of view of the treated flow rate of liquid substances, and from the point of view of energy expenditure.

[0011] The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages. SUMMARY OF THE INVENTION

[0012] The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

[0013] In accordance with the above purposes, and to resolve the technical problem disclosed above in a new and original way, also achieving considerable advantages compared to the state of the prior art, a device according to the present invention for the flow treatment of liquid substances comprises: a containing body, delimiting and defining inside it a reaction chamber interposed between a feed unit and an outlet unit; a first nozzle stage, configured to cause a sudden pressure drop between the feed unit and an adjacent two-phase flow formation segment of the aforesaid reaction chamber, so as to allow the formation of a supersonic two-phase flow within said two-phase flow formation segment; three electrodes, configured to trigger, maintain, modulate and / or stabilize a plasma discharge in the supersonic two-phase flow inside suitable first and second consecutive plasma segments of the aforesaid reaction chamber; and a diffuser, configured to slow down the supersonic two-phase flow before it reaches the outlet unit by means of a sudden pressure increase. It should be noted that by "two-phase flow" is meant a flow comprising a liquid phase and an aeriform phase (vapour phase). In addition, by “sudden drop” in pressure is meant a pressure drop such as to cause the at least partial boiling of the liquid substance to be treated and the separation of the aeriform phase from the liquid, so as to form the aforementioned two-phase flow. By “sudden increase” in pressure is meant a pressure increase such as to trigger the condensation of the aeriform phase of the two-phase flow. In accordance with an aspect of the present invention, the reaction chamber comprises, in correspondence with a terminal end of the first plasma segment, a vortex formation portion, essentially configured as a widening of the first plasma segment to allow the formation of a toroidal vortex in the aforementioned supersonic two-phase flow.

[0014] In doing so, at least the advantage of being able to use the device in order to subject the entire volume of the substance being treated to a treatment is obtained, since the toroidal vortex allows the layers of fluid that flow adhering to the walls of the reaction chamber to be homogeneously mixed in the main flow of the device.

[0015] In accordance with another aspect of the present invention, the aforementioned three electrodes comprises at least one rod electrode, which extends from the first nozzle stage at least in an initial portion of the two-phase flow formation segment, and at least one ring-shaped trigger electrode in correspondence with a terminal end of the second plasma segment opposite to the rod electrode, which are configured to trigger between them, inside the aforementioned plasma segments, a longitudinal plasma discharge.

[0016] The provision of a rod-type electrode provides for a much higher electric strength as compared to conventional circle electrodes.

[0017] This rod-type shape has a specific effect on plasma generated in the first plasma segment causing the device to more effectively affect the liquid substance under treatment.

[0018] In accordance with another aspect of the present invention, the device further comprises a ring-shaped guide electrode, interposed between the plasma segments and configured to modulate and stabilize the plasma discharge.

[0019] In accordance with another aspect of the present invention, the reaction chamber further comprises a stabilization segment, interposed between the second plasma segment and the diffuser, configured to obtain a stabilization of the aforementioned supersonic two-phase flow.

[0020] In accordance with another aspect of the present invention, the aforementioned electrodes are made of a metallic electro-conductive material selected from a group which contains molybdenum, niobium, zirconium, silver, copper or an alloy of at least two of these metals.

[0021] In accordance with another aspect of the present invention, the aforementioned electrodes are made of an electro-conductive material selected from stainless steel, porous ceramic with electrical conductivity capacity, graphite or graphite superficially treated with silicon.

[0022] In accordance with another aspect of the present invention, a length of the aforesaid reaction chamber is equal to approximately 10 - 30 times the value of its diameter.

[0023] The present invention also concerns a plant for the flow treatment of liquid substances. This plant comprises: a device as described above; a fluidic circuit, configured to feed the liquid substance to be treated to the device and to convey the treated liquid substance and any waste gaseous substances toward suitable user devices or outlets; and an electric circuit, configured to supply adequate electrical power to the device.

[0024] In accordance with another aspect of the present invention, the aforementioned electric circuit comprises an alternating current generator connected to a nozzle electric contact of the aforementioned rod electrode and to a trigger electric contact of the aforementioned trigger electrode and a direct current generator connected to a guide electric contact of the aforementioned guide electrode. In accordance with another aspect of the present invention, the aforementioned fluidic circuit comprises, downstream of the device, a deaerator adapted to separate a liquid substance treated by said device from gases possibly dissolved or suspended inside it and suitable liquid outlet and gas outlet regulating valves for regulating the outflows.

[0025] In accordance with another aspect of the present invention, the aforementioned fluidic circuit comprises, downstream of the device, a recirculation line configured to recirculate in said device at least part of the liquid substance already treated and comprising a recirculation regulating valve configured to determine the quantity of liquid substance to be recirculated.

[0026] The present invention also concerns a method for the flow treatment of liquid substances with a device according to the present invention and comprising: a two- phase flow formation step, in which the liquid substance being treated passes through the at least one nozzle hole and enters in the two-phase flow formation segment, where a supersonic two-phase flow is formed by pressure drop; a plasma treatment step, which provides at least to trigger a longitudinal plasma discharge inside the aforementioned plasma segments, where broad spectrum electromagnetic radiations are thus emitted and a synthesis of at least ozone occurs; and a diffusion step, in which said two-phase flow is slowed down in correspondence with the diffuser by means of a pressure increase, causing an avalanche condensation of the aeriform phase of the aforementioned two-phase flow, which involves a generation of ultrasounds and electromagnetic radiations and local heating.

[0027] In accordance with another aspect of the present invention, the aforesaid plasma treatment step further provides the formation of a toroidal vortex within the two- phase flow in correspondence with the vortex formation portion.

[0028] In accordance with another aspect of the present invention, the plasma treatment step further provides to modulate and stabilize the plasma discharge by means of an electric current delivered by the direct current generator to the guide electrode.

[0029] In accordance with another aspect of the present invention, the method provides, after the plasma treatment step, to stabilize the aforesaid supersonic two-phase flow in correspondence with a stabilization segment in a flow stabilization step.

[0030] In accordance with another aspect of the present invention, the method provides, after the exit of the treated liquid substance from the device, to make at least a part of the treated liquid substance recirculate once again at least in said device.

[0031] In accordance with another aspect of the present invention, the aforementioned longitudinal plasma discharge is triggered by an alternating electric current of about 100 mA - 500 mA, with a voltage of about 1,000 V - 4,000 V and a frequency of about 100 kHz - 500 kHz, and is modulated and stabilized by a direct electric current of about 50 mA - 200 mA, with a voltage of about 3,000 V - 7,000 V.

[0032] In accordance with a further aspect of the present invention, the liquid substance to be treated enters in the reaction chamber at a pressure of about 0.4 MPa - 6 MPa and the pressure in the reaction chamber has a value of about 1 kPa - 10 kPa.

[0033] DESCRIPTION OF THE DRAWINGS

[0034] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

[0035] - fig. 1 is a schematic representation of a plant for the flow treatment of liquid substances according to the present invention;

[0036] - fig. 2 is a schematic representation of a device for the flow treatment of liquid substances of the plant of fig. 1 ; - fig. 2a is an enlarged detail of fig. 2.

[0037] We must clarify that in the present description the phraseology and terminology used, as well as the figures in the attached drawings also as described, have the sole function of better illustrating and explaining the present invention, their function being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims.

[0038] To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications. DESCRIPTION OF EMBODIMENTS

[0039] With reference to fig. 1, a plant 100 for the flow treatment of liquid substances according to the present invention comprises a device 10 for the flow treatment of liquid substances inserted in a suitable fluidic circuit 126 and in a suitable electric circuit 127.

[0040] The fluidic circuit 126 is configured to feed a liquid substance to be treated, for example water or an aqueous solution, to the device 10 and to convey the treated liquid substance and any waste gaseous substances toward suitable user devices or outlets.

[0041] The electric circuit 127 is configured to supply adequate electrical power to the device 10, as better explained below.

[0042] The fluidic circuit 126 may also comprise an inlet piping 101, configured to allow the entry of the liquid substance to be treated inside the fluidic circuit 126.

[0043] Said fluidic circuit 126 may comprise a feed pump 105, configured to feed the liquid substance to be treated to the device 10 by pumping. In embodiments, the feed pump 105 is hydraulically connected to the inlet piping 101 by a feed piping 104, and to the device 10 through a flow rate conduit 107.

[0044] A feed shut-off valve 102 and a filter 103, which is adapted to perform a preliminary filtering treatment on the incoming liquid substance, can be provided in a known manner along the feed piping 104.

[0045] In embodiments, the fluidic circuit 126 comprises, downstream of the device 10, a deaerator or degasser 113, adapted to separate the treated liquid substance from gases possibly dissolved or suspended inside it. The device 10 may be fluidically connected to the deaerator 113 by an outlet conduit 112.

[0046] According to possible embodiments, the fluidic circuit 126 may comprise, at the exit from the deaerator 113, a gas outlet line 115 and a liquid outlet line 119.

[0047] The liquid outlet line 119 may comprise a liquid outlet regulating valve 117, for regulating the outflow of liquid, and a liquid outlet shut-off valve 120 upstream of a liquid outlet piping 122.

[0048] The gas outlet line 115 may comprise a vacuum pump 114, configured to direct the gases exiting from the deaerator 113 toward a suitable gas outlet piping 123, a gas outlet regulating valve 118, for regulating the exiting gas flow, downstream of the vacuum pump 114 and a gas outlet shut-off valve 121 interposed between the gas outlet regulating valve 118 and the gas outlet piping 123.

[0049] In embodiments, the fluidic circuit 126 may further comprise a recirculation line 128, configured to recirculate at least in the device 10 at least part of the liquid substance already treated exiting from the deaerator 113. For example, the recirculation line 128 may hydraulically connect the deaerator 113 with the feed pump 105.

[0050] Along the recirculation line 128 a recirculation regulating valve 116 can be provided and configured to determine the quantity of treated liquid substance to be recirculated, possibly in cooperation with the liquid outlet regulating valve 117.

[0051] According to possible embodiments, the fluidic circuit 126 may further comprise one or more sensors for physical properties of the fluids circulating inside it. By way of non-limiting example, in the embodiments illustrated in fig. 1, the fluidic circuit 126 comprises a flow meter 106 downstream of the feed pump 105 and upstream of the device 10, a first pressure sensor 108 and a temperature sensor 109 downstream of the flow meter 106 and upstream of the device 10, a vacuum gauge sensor 110 and a second pressure sensor 111 downstream of the device 10.

[0052] According to possible embodiments, the electric circuit 127 comprises an alternating current generator 124 and a direct current generator 125, suitably connected to respective electrodes of the device 10.

[0053] With reference to fig. 2, the device 10 comprises a containing body 11, delimiting and defining a reaction chamber 12 inside it. The containing body 11 may for example have an essentially tubular shape and be made of dielectric material. The device 10 may preferably extend along a longitudinal axis X corresponding to a flowing direction of the liquid substance to be treated. For example, the device 10 may have an essentially cylindrical shape, with a longitudinal axis of the cylinder corresponding to the longitudinal axis X.

[0054] In embodiments, the device 10 comprises, in correspondence with one end thereof, a feed unit 13, configured to allow feeding the liquid substance to be treated, for example coming from the flow rate conduit 107, to the device 10. The device 10 may further comprise in correspondence with an opposite end thereof an outlet unit 29, configured to emit the treated liquid substance, for example by introducing it into the outlet conduit 112. The reaction chamber 12 may be interposed between the feed unit 13 and the outlet unit 29.

[0055] According to possible embodiments, the reaction chamber 12 may comprise a plurality of segments. For example, the reaction chamber 12 may comprise, in the order, a two-phase flow formation segment 19; a first plasma segment 20; a second plasma segment 24; and a stabilization segment 27.

[0056] Furthermore, the device 10 may comprise three electrodes 18, 22, 25 configured to trigger, maintain, modulate and / or stabilize a plasma discharge within the reaction chamber 12. The three electrodes 118, 22 and 25 are disposed in sequence along the path of the liquid substance and substantially along the longitudinal axis X.

[0057] The two-phase flow formation segment 19 can be adjacent to the feed unit 13 and be configured to allow the formation, starting from the flow of liquid substance entering in the device 10, of a two-phase flow, i.e. comprising a liquid phase and an aeriform phase (gaseous and / or vapour one).

[0058] The feed unit 13 and the two-phase flow formation segment 19 may be connected by a first nozzle stage 14 interposed between them. According to possible embodiments, the first nozzle stage 14 can be configured essentially as an electrode. The first nozzle stage 14 may for example be disc-shaped centred on the longitudinal axis X.

[0059] The first nozzle stage 14 is provided with at least one nozzle hole 16, adapted to put the feed unit 13 in hydraulic communication with the two-phase flow formation segment 19. The at least one nozzle hole 16 is preferably in the form of a cylinder parallel to the longitudinal axis X. According to possible embodiments, the first nozzle stage 14 comprises a plurality of nozzle holes 16.

[0060] Furthermore, the first nozzle stage 14 is preferably configured to form, in combination with the reaction chamber 12, a nozzle, intended as a means for transforming into kinetic energy much of the energy of a fluid outflowing therefrom. This effect can be achieved, for example, by realizing the plurality of nozzle holes 16 so that the overall area of their transverse surfaces is less than the area of the transverse surface of the two-phase flow formation segment 19.

[0061] In other words, the first nozzle stage 14 is configured to cause a sudden pressure drop between the feed unit 13 and the two-phase flow formation segment 19, so as to allow the formation of the two-phase flow within the two-phase flow formation segment 19. For example, the pressure may change from about 0.4 MPa - 6 MPa to about 1 kPa - 10 kPa.

[0062] The first nozzle stage 14 is preferably provided with a nozzle electric contact 17.

[0063] One of the three electrodes may be a rod electrode 18, which extends at least in an initial portion of the two-phase flow formation segment 19 from the first nozzle stage 14. For example, the rod electrode 18 can be placed in correspondence with the centre of the two-phase flow formation segment 19, with a larger dimension extended along the longitudinal axis X.

[0064] The rod electrode 18 provides for a much higher electric strength as compared to conventional circle electrodes.

[0065] The rod electrode 18 has a specific effect on plasma generated in the first plasma segment causing the device to more effectively affect the liquid substance under treatment.

[0066] In embodiments, the rod electrode 18 is partially inserted in the centre of the first nozzle stage 14 and the nozzle holes 16 are arranged around the rod electrode 18 in a centrally symmetrical manner.

[0067] The rod electrode 18 is preferably in electric contact with the nozzle electric contact 17, possibly indirectly by contact with the first nozzle stage 14, such that an electrical potential of the rod electrode 18 can be imposed by the nozzle electric contact 17.

[0068] According to possible embodiments, the two-phase flow formation segment 19 is followed by the first plasma segment 20.

[0069] The first plasma segment 20 may be followed by the second plasma segment 24. Between the first plasma segment 20 and the second plasma segment 24 a guide electrode 22 can be interposed, preferably ring-shaped, i.e. provided with a central gap to allow the passage of the fluid substance being treated. The guide electrode 22 may be provided with a guide electric contact 23.

[0070] The first and second plasma segment 20, 24 are configured to allow inside them the trigger and guided maintenance of a longitudinal plasma discharge, as explained in more detail below.

[0071] According to possible embodiments, the first plasma segment 20 may comprise, at a terminal end thereof adjacent to the guide electrode 22, a vortex formation portion 21.

[0072] The vortex formation portion 21 is configured to allow the formation of a toroidal vortex in the flow of the substance being treated. For example, the vortex formation portion 21 may be configured essentially as a widening of the first plasma segment 20 in a direction perpendicular to the longitudinal axis X, i.e. that a diameter of the vortex formation portion D21 is greater than a diameter of the first plasma segment 20. The second plasma segment 24 may be followed by the stabilization segment 27, which is configured to obtain a stabilization, or tempering, of the two-phase flow being treated.

[0073] A trigger electrode 25, preferably ring-shaped, may be provided between the second plasma segment 24 and the stabilization segment 27. The trigger electrode 25 may be provided with a trigger electric contact 26.

[0074] Preferably, the rod electrode 18, the guide electrode 22, the trigger electrode 25 and possibly also the first nozzle stage 14 can be made of electro-conductive material, such as for example a metal, or a metalloid, or other electric current conductor, or even a porous dielectric material with electro-conductive filling. For example, such an electro-conductive material may be a metallic material selected from a group which contains molybdenum, niobium, zirconium, silver, copper or even an alloy of at least two of these metals.

[0075] Alternatively, such electro-conductive material can be selected for example from stainless steel, porous ceramic with electrical conductivity capacity, graphite or graphite superficially treated with silicon.

[0076] In embodiments, the nozzle electric contact 17 and the trigger electric contact 26 are configured to be connected to suitable outlets of a current generator, preferably alternating current, such as for example the alternating current generator 124. The alternating current generator 124 may be configured to supply an electric current adapted to trigger and maintain a preferably longitudinal plasma discharge within the first and second plasma segment 20, 24. The rod electrode 18 and the trigger electrode 25 are thus configured to trigger between them, preferably within the first 20 and the second 24 plasma segment, such plasma discharge.

[0077] Furthermore, the electric guide contact 23 can be configured to be connected to a suitable outlet of a power generator, preferably direct current, such as for example the direct current generator 125. The direct current generator 125 may be configured to supply an electric current adapted so as to “guide” or “manoeuvre”, i.e. modulate and stabilize, the plasma discharge triggered within the first and second plasma segment 20, 24. Thus, the guide electrode 22 is configured to modulate and stabilize such plasma discharge.

[0078] According to possible embodiments, the stabilization segment 27 can be followed by a diffuser 28, which connects it with the outlet unit 29. The diffuser 28 is configured to slow down the flow of the liquid substance flowing inside it.

[0079] Preferred, but non-limiting, embodiments provide the following dimensions for the device 10.

[0080] An inner diameter of the feed unit D13 and an inner diameter of the outlet unit D29 may advantageously be selected in such a way that the flow speed in the device 10 is equal to no more than about 1.0 m / s - 1.5 m / s.

[0081] A diameter of the nozzle hole DI 6 may be selected in such a way that the pressure at the outlet of the at least one nozzle hole 16 does not exceed the saturation pressure of water at the temperature inside the two-phase flow formation segment 19. A length of the nozzle hole LI 6, essentially equal to a length of the first nozzle stage 14, may be equal to approximately 3 - 15 times the value of the diameter of the nozzle hole DI 6.

[0082] Further, the number of nozzle holes 16 may be selected to be as large as possible compatibly with the extension of the surface of the first nozzle stage 14 facing the two-phase flow formation segment 19. Preferably, the two-phase flow formation segment 19, the first plasma segment 20, the second plasma segment 24 and the stabilization segment 27 may all have a same diameter, hereinafter also referred to as the diameter of the reaction chamber D12.

[0083] The diameters of the gaps of the guide electrode 22 and of the trigger electrode 25 may also be equal to the diameter of the reaction chamber DI 2.

[0084] The diameter of the reaction chamber D12 may be selected in such a way that the local speed of the sound in the fluid substance within the reaction chamber 12 is in the order of about 10 m / s - 20 m / s. For example, the diameter of the reaction chamber D12 may be equal to about 1.5 - 2.5 times the sum of the diameters of nozzle hole DI 6 of all the nozzle holes 16 (or, equivalently, the diameter of nozzle hole DI 6 multiplied by the number of nozzle holes 16).

[0085] A length of the reaction chamber L12 may be selected in such a way as to be equal to about 10 - 30 times the value of the diameter of the reaction chamber D 12. The Applicants have found that, in this way, during the operation of the device 10, described in detail below, it is possible to use a voltage at the electrodes in the range 1,000 V - 5,000 V. This is advantageous from the point of view of energy saving.

[0086] A diameter of the rod electrode DI 8 may be selected in such a way as to be equal to about 1.5 - 4 times the diameter of the nozzle hole DI 6, while a length of the rod electrode LI 8 may be selected in such a way as to be equal to about 5 - 15 times the diameter of the reaction chamber DI 2.

[0087] A length of the two-phase flow formation segment LI 9 may be selected in such a way as to be equal to about 2 - 7 times the diameter of the reaction chamber DI 2.

[0088] A length of the first plasma segment L20 may be equal to a length of the second plasma segment L24 and such lengths L20, L24 may be selected in such a way as to be equal to about 5 - 10 times the diameter of the reaction chamber DI 2.

[0089] A length of the guide electrode L22 may be equal to a length of the trigger electrode L25 and such lengths L22, L25 may be selected in such a way as to be equal to about 0.5 - 1.5 times the diameter of the reaction chamber 12.

[0090] The diameter of the vortex formation portion D21 may be selected in such a way as to be equal to about 1.5 - 2.5 times the diameter of the reaction chamber DI 2. A length of the vortex formation portion L21 may be selected in such a way as to be equal to about 0.4 - 1.5 times the diameter of the vortex formation portion D21.

[0091] A length of the stabilization segment L27 may be selected in such a way as to be equal to about 8.0 - 15.0 times the diameter of the reaction chamber DI 2.

[0092] Furthermore, the diffuser 28 can be shaped so that its diameter grows from an initial value equal to the diameter of the reaction chamber D12 to a final greater value equal to the inner diameter of the outlet unit D29. For example, but not in a limiting manner, the growth of the diameter of the diffuser 28 from the initial value to the final value may be a linear growth, or in other words the diffuser 28 may have the shape of a truncated cone or the like. In such a case, the shape of the diffuser 28 can be described by an opening angle AD, preferably equal to about 6° - 30°.

[0093] The operation of the plant 100 and of the device 10 described so far, which corresponds to the method according to the present invention comprises the following steps. In a step of entry in the plant 100, the liquid substance to be treated enters in the plant 100 from the inlet piping 101.

[0094] In embodiments, a subsequent filtering step may be provided, in which the filter 103 filters the liquid substance to be treated. Subsequently, in step of entry in the device 10, the liquid substance to be treated enters in the device 10 through the feed unit 13.

[0095] According to possible embodiments, the method then comprises a two-phase flow formation step, in which the liquid substance being treated passes through the at least one nozzle hole 16 and enters in the two-phase flow formation segment 19. The crossing of the at least one nozzle hole 16 can advantageously occur under pressure, for example thanks to the feed pump 105. For example, such crossing may occur at a pressure of about 0.4 MPa - 6 MPa.

[0096] Because of a sudden pressure drop due to the passage from channels with a small cross-section (the nozzle holes 16) to a channel with a larger cross-section (the two-phase flow formation segment 19), the liquid substance may at least partially undergo a boiling. In this way, the liquid substance emits gases dissolved inside it and vapours, so that the entering flow becomes a two-phase flow, in particular comprising a liquid phase and an aeriform phase.

[0097] Advantageously, the two-phase flow is supersonic: in fact, even if the flow speed itself remains continuous, the speed of the sound in such a homogeneous two-phase flow decreases (see for example V. V. Fisenko, Energoatomizdat, 1987). The device 10 is configured to ensure that the speed of the sound in the two- phase flow inside it is lower than the speed of the flow itself.

[0098] Subsequently, a plasma treatment step provides to at least trigger a plasma discharge within the plasma segments 20, 24, to treat with it the supersonic two- phase flow. The plasma discharge is preferably longitudinal. According to possible embodiments, the plasma discharge is triggered by an electric current delivered by the alternating current generator 124 between the rod electrode 18 and the trigger electrode 25. Preferably, the alternating current generator 124 delivers an alternating electric current of about 100 mA - 500 mA, with a voltage of about 1,000 V - 4,000 V and a frequency of about 100 kHz - 500 kHz.

[0099] In alternative embodiments, the plasma discharge is triggered by a direct electric current, with a voltage of about 1 ,000 V - 4,000 V.

[0100] It should be noted that the wear of the electrodes under these conditions is irrelevant compared to the wear of electrodes in use in devices of the prior art.

[0101] For plasma discharge formation, it is preferable for the pressure in the reaction chamber 12 to be lower than atmospheric pressure.

[0102] Advantageously, a suitable pressure lowering can be obtained thanks to the nozzle formed by the first nozzle stage 14 with the reaction chamber 12. For example, such pressure may have a value of about 1 kPa - 10 kPa.

[0103] Advantageously, the plasma discharge entails an emission of broad spectrum electromagnetic radiation within the plasma segments 20, 24, comprising ultraviolet, visible spectrum, infrared and radio frequency spectrum radiations.

[0104] Furthermore, advantageously, the plasma discharge causes at least one ozone synthesis starting from the oxygen separated from the liquid phase during the previous the two-phase flow formation step. The plasma discharge may also cause further synthesis and / or decompositions, or dissociations, of gases emanated from the liquid substance in the two-phase flow formation step or of other gases introduced into the reaction chamber 12.

[0105] In embodiments, the plasma treatment step further provides to maintain the effect of plasma discharge in the two-phase flow for a suitable period of time, preferably of about 10’4s - 10’2s, for example of about 0.003 s - 0.008 s.

[0106] The plasma treatment step may further provide for the formation of a vortex, preferably a ring-shaped toroidal vortex, within the two-phase flow, e.g. in correspondence with the vortex formation portion 21. The Applicants have found that this toroidal vortex guarantees the treatment of the entire volume of the fluid being treated, allowing to treat also the layers of fluid adjacent to the walls of the reaction chamber 12, which the devices according to the known technique are not able to treat. In fact, the toroidal vortex allows the layers of fluid flowing adhering to the walls of the reaction chamber 12 to be homogeneously mixed in the main flow of the device 10.

[0107] According to possible embodiments, the plasma treatment step may also provide to modulate and stabilize the plasma discharge by means of an electric current delivered by the direct current generator 125 to the guide electrode 22. Preferably, the direct current generator 125 delivers a direct electric current of about 50 mA - 200 mA, with a voltage of about 3,000 V - 7,000 V.

[0108] In embodiments, a subsequent flow stabilization step provides to stabilize the supersonic two-phase flow in correspondence with the stabilization segment 27.

[0109] In a subsequent diffusion step, the two-phase flow being treated is slowed down in correspondence with the diffuser 28, for example by means of a pressure increase. In embodiments, this pressure increase can be caused by the shape of the diffuser 28, or by a back pressure outside the outlet of the device 10, for example generated by means of the recirculation regulating 116, liquid outlet 117 and gas outlet 121 valves, or by a combination of these factors and / or by further factors. During the diffusion step, the pressure increase causes an avalanche condensation of the aeriform phase of the two-phase flow, which involves the generation of ultrasounds and electromagnetic radiations that contribute to the implosion of the aeriform bubbles, which, by in turn imploding, generate new oscillations. A powerful ultrasonic field is therefore created, with a consequent local heating of the liquid that also results in a heat treatment of the liquid substance inside the diffuser 28. At the end of the diffusion step, the two-phase flow thus becomes single-phase (liquid).

[0110] The presence of the stabilization segment 27 and of the relative flow stabilization step is necessary to end all physical, chemical and biochemical processes in correspondence with the pressure increase of the diffusion step.

[0111] Subsequently, in a step of exit from the device 10, the treated liquid substance exits from the device 10 via the outlet unit 29.

[0112] In embodiments, the step of exit from the device 10 may be followed by a deaeration or degassing step, in which, in correspondence with the deaerator 113, gases dissolved or trapped in the treated liquid substance are extracted by the latter, for example by means of the vacuum pump 114. Such extracted gases may exit from the plant, for example to be conveyed to suitable user devices or to be suitably disposed of and / or released, through the gas outlet line 115, the gas outlet regulating valve 118 and the gas outlet shut-off valve 121, thus reaching the gas outlet piping 123.

[0113] The degassed liquid substance can in turn exit from the plant in a step of exit from the plant. In this step, the degassed liquid substance may flow in the liquid outlet line 119, passing through the liquid outlet regulating valve 117 and the liquid outlet shut-off valve 120 to reach the liquid outlet piping 122, from which it may be directed to one or more user devices.

[0114] According to possible embodiments, at least a part of the degassed liquid substance can be recirculated in the plant 100, at least, but not exclusively, in the device 10. For example, but not in a limiting manner, a part of the degassed liquid substance may be reintroduced into circulation again downstream of the filter 103 and upstream of the feed pump 105 by means of the recirculation line 128. The quantity of degassed liquid substance that is recirculated can be regulated by the recirculation regulating valve 116, possibly in cooperation with the liquid outlet regulating valve 117. For example, about 3% - 30% of the total flow rate of liquid substance in the plant can be recirculated.

[0115] The method described above therefore provides that all the treatment processes of the liquid substance take place in a continuous flow in the reaction chamber 12. Advantageously, these processes comprise: a hydrodynamic action on the liquid substance of the flow, due to the sudden pressure lowering that causes the boiling of the liquid and the formation of the two-phase flow; an ignition of the plasma with emission of broad spectrum electromagnetic radiation; an action of the ultrasounds that are created in the substance due to the sudden pressure increase in the diffuser 28; a synthesis and / or decomposition (dissociation) of the gas emanated from the liquid substance or of the gas introduced into the reaction chamber 12; and a partial recirculation of the liquid to be treated.

[0116] Possible embodiments may also provide for the introduction of different metal ions into the liquid substance, by selecting a corresponding material to make the electrodes 18, 22 and / or 25. It is clear that modifications and / or additions of parts can be made to the device 10, to the plant 100 and to the method as described heretofore, without departing from the field and scope of the present invention, as defined by the claims.

[0117] It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve other equivalent forms of device, plant and method for the flow treatment of liquid substances having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0118] In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.

Claims

CLAIMS1. Device (10) for the flow treatment of liquid substances, comprising:- a containing body (11), defining inside it a reaction chamber (12) interposed between a feed unit (13) and an outlet unit (29);- a first nozzle stage (14), configured to cause a pressure drop between said feed unit (13) and an adjacent two-phase flow formation segment (19) of said reaction chamber (12), in which a supersonic two-phase flow can thus be formed;- three electrodes (18, 22, 25), configured to trigger, maintain, modulate and / or stabilize a plasma discharge in said supersonic two-phase flow inside suitable consecutive first (20) and second (24) plasma segments of said reaction chamber (12); and- a diffuser (28), configured to slow down said supersonic two-phase flow before it reaches said outlet unit (29) by means of a pressure increase; wherein said reaction chamber (12) comprises, in correspondence with a terminal end of said first plasma segment (20), a vortex formation portion (21) configured as a widening of said first plasma segment (20) to allow the formation of a toroidal vortex in said supersonic two-phase flow.

2. Device (10) as in claim 1, characterized in that said three electrodes (18, 22, 25) comprises at least one rod electrode (18), which extends from said first nozzle stage (14) at least in an initial portion of said two-phase flow formation segment (19).

3. Device as in claim 2, characterized in that said three electrodes comprises at least one ring-shaped trigger electrode (25) in correspondence with a terminal end of said second plasma segment (24) opposite to said rod electrode (18), which are configured to trigger between them, inside said plasma segments (20, 24), a longitudinal plasma discharge.

4. Device (10) as in any claim hereinbefore, characterized in that said three electrodes (18, 22, 25) further comprise a ring-shaped guide electrode (22), interposed between said plasma segments (20, 24) and configured to modulate and stabilize said plasma discharge.

5. Device (10) as in any claim hereinbefore, characterized in that said electrodes (18, 22, 25) are made of a metallic electro-conductive material selected from a group which contains molybdenum, niobium, zirconium, silver, copper or an alloyof at least two of these metals.

6. Device (10) as in any claim from 1 to 4, characterized in that said electrodes (18, 22, 25) are made of an electro-conductive material selected from stainless steel, porous ceramic with electrical conductivity capacity, graphite or graphite superficially treated with silicon.

7. Device (10) as in any claim hereinbefore, characterized in that a length (LI 2) of said reaction chamber (12) is equal to approximately 10 - 30 times the value of its diameter (DI 2).

8. Plant (100) for the flow treatment of liquid substances, characterized in that it comprises: a device (10) as in any claim hereinbefore; a fluidic circuit (126) configured to feed the liquid substance to be treated to said device (10) and to convey the treated liquid substance and any waste gaseous substances toward suitable user devices or outlets; and an electric circuit (127) configured to supply adequate electrical power to said device (10).

9. Plant (100) as in claim 8 when depending from claim 2, characterized in that it comprises a device (10) as in claim 3, said electric circuit (127) comprising an alternating current generator (124) connected to a nozzle electric contact (17) of said rod electrode (18) and to a trigger electric contact (26) of said trigger electrode (25), and a direct current generator (125) connected to a guide electric contact (23) of said guide electrode (22).

10. Plant (100) as in claim 9, characterized in that said fluidic circuit (126) comprises, downstream of said device (10), a recirculation line (128) configured to recirculate at least in said device (10) at least part of the liquid substance already treated and comprising a recirculation regulating valve (116) configured to determine the quantity of said liquid substance to be recirculated.

11. Method for the flow treatment of liquid substances with a device (10) as in any claim from 1 to 7 and comprising: a two-phase flow formation step, in which the liquid substance being treated passes through said at least one nozzle hole (16) and enters said two-phase flow formation segment (19), where a supersonic two-phase flow is formed by pressure drop; a plasma treatment step, which provides at least to trigger a longitudinal plasma discharge inside said plasma segments (20, 24), where broad spectrum electromagnetic radiations are thus emitted and a synthesis of at least ozone occurs; and a diffusion step, in which said two-phase flow isslowed down in correspondence with said diffuser (28) by means of a pressure increase, causing an avalanche condensation of the aeriform phase of said two- phase flow, which involves a generation of ultrasounds and electromagnetic radiations and a local heating, characterized in that said plasma treatment step also provides the formation of a toroidal vortex within said two-phase flow in correspondence with said vortex formation portion (21).

12. Method as in claim 11, characterized in that said plasma treatment step also provides to modulate and stabilize said plasma discharge by means of an electric current delivered by a direct current generator (125) to a guide electrode (22) of said three electrodes.

13. Method as in claim 11 or 12, characterized in that it provides, after the exit of the treated liquid substance from said device (10), to make a part of said treated liquid substance recirculate once again at least in said device (10).

14. Method as in any claim from 11 to 13, characterized in that said longitudinal plasma discharge is triggered by an alternating electric current of about 100 mA - 500 mA, with a voltage of about 1,000 V - 4,000 V and a frequency of about 100 kHz - 500 kHz, and is modulated and stabilized by a direct electric current of about 50 mA - 200 mA, with a voltage of about 3,000 V - 7,000 V.

15. Method as in any claim from 11 to 14, characterized in that said plasma treatment step provides to maintain the effect of said plasma discharge in said supersonic two-phase flow for about 0.003 s - 0.008 s.

16. Method as in any claim from 11 to 15, characterized in that said liquid substance to be treated enters in said reaction chamber (12) at a pressure of about 0.4 MPa - 6 MPa and that the pressure in said reaction chamber (12) has a value of about 1 kPa - 10 kPa.

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