System for injecting a pressurized liquid containing dissolved gas into a vessel for bringing same into contact with a fluid to be treated, and associated facility and method

Abstract

The invention relates to an injection system comprising: - a source of pressurized liquid containing dissolved gas, which is intended to be positioned outside the vessel (12); - an injection manifold (62) for injecting pressurized liquid containing dissolved gas into the vessel, the injection manifold (62) being connected to the source, the injection manifold (62) being configured so as to be positioned facing a bottom (42) of the vessel (12). The injection manifold (62) defines a plurality of injection openings (84A, 84B, 84C, 84D) for injecting pressurized liquid containing dissolved gas, each injection opening (84A, 84B, 84C, 84D) defining an injection axis (C) for injecting pressurized liquid containing dissolved gas received from the source into the vessel (12). All of the injection axes (C) of all of the injection openings (84A, 84B, 84C, 84D) are contained in a minimum number of distinct planes that is strictly greater than two, in particular greater than or equal to four.

Description

[0001] TITLE: System for injecting a pressurized liquid containing dissolved gas into a vessel for contact with a fluid to be treated, installation and associated process

[0002] The present invention relates to a system for injecting a pressurized liquid containing dissolved gas, in particular pressurized water containing dissolved gas, into a vessel for contacting the pressurized liquid containing dissolved gas with a fluid to be treated, the injection system comprising:

[0003] - a pressurized liquid source containing dissolved gas intended to be positioned outside the contacting capacity;

[0004] - a pressurized liquid injection manifold containing dissolved gas in the contacting vessel, connected to the pressurized liquid source containing dissolved gas, the injection manifold being configured to be positioned opposite the bottom of the contacting vessel,

[0005] the injection ramp defining a plurality of pressurized liquid injection openings containing dissolved gas, each injection opening defining an injection axis of pressurized liquid containing dissolved gas received from the source into the contacting capacity.

[0006] The pressurized liquid containing dissolved gas is prone to expand when injected into the fluid to be treated contained in the vessel, generating gas bubbles, in particular microbubbles.

[0007] The fluid to be treated is, for example, wastewater, sludge, seawater intended for desalination, or water intended to be made potable.

[0008] The contacting capacity is for example located within a water treatment installation, in particular by flocculation and flotation, being located for example between a flocculation zone and a flotation zone of a dissolved air flotation device.

[0009] In a known installation, flocs, preferably light and fragile, are formed in the water to be treated circulating in the flocculation zone.

[0010] The water to be treated, laden with flocs, then enters the contacting chamber, where it is brought into contact with pressurized, depressurized water injected via the manifold to form a fluid laden with microbubbles. A "bubble bed," consisting of a mattress with decreasing concentration from top to bottom, is formed in the contacting zone. Within this bubble bed, flocculation occurs, and the air bubbles bind to the floc. The bubble bed is then carried into the calmer flotation zone, where upward flows of bubble-floc aggregates occur through coalescence and / or agglomeration.

[0011] The flocs accumulate on the surface to form a floc accumulation layer, while clarified water is produced at the bottom of the flotation zone.

[0012] The accumulation layer is removed at the end of the flotation zone opposite the contacting capacity, for example by a scraper bridge moving back and forth to skim the portion of the basin where the accumulation layer thickens, without disturbing the expansion zone above the contacting capacity.

[0013] To inject pressurized water containing gas dissolved in the water to be treated, it is known to use at least one manifold having a linear distributor and injection nozzles equipped with injection openings aligned along a first and second parallel lines.

[0014] The injection openings on the first line open horizontally in the opposite direction to the injection openings on the second line. Alternatively, the injection openings on each line all open vertically towards the bottom or the top of the tank.

[0015] Such a manifold produces an injection of pressurized water containing dissolved gas along the linear distributor. This theoretically ensures intimate contact between the gas bubbles resulting from the injection of pressurized water containing dissolved gas and the water to be treated throughout the contact volume located above the manifold.

[0016] In practice, such a ramp does not give complete satisfaction, because part of the water to be treated above the ramp is not brought into intimate contact with the gas bubbles, resulting in less effective treatment of the water to be treated in the flotation zone.

[0017] One aim of the invention is therefore to provide a pressurized liquid injection system containing dissolved gas in a fluid to be treated within a fluid treatment installation, which increases the efficiency of the treatment of the fluid to be treated downstream of the contact with the pressurized liquid containing dissolved gas.

[0018] To this end, the invention relates to an injection system of the aforementioned type, characterized in that all the injection axes of all the injection openings of the injection rail are contained in a minimum number of distinct planes strictly greater than two, in particular greater than or equal to four.

[0019] The injection system according to the invention may include one or more of the following features, taken individually or in any technically possible combination: the minimum number of distinct straight lines containing all the injection openings of the injection rail is strictly greater than two, in particular greater than or equal to four;

[0020] the injection manifold includes at least one distributor extending linearly along a distributor axis and a connecting pipe from the distributor to the source, protruding from the distributor, all injection axes of all injection openings connected to the same distributor being contained in a minimum number of distinct planes strictly greater than two, in particular strictly greater than four;

[0021] the minimum number of distinct straight lines containing all the injection openings connected to the same distributor is strictly greater than two, in particular greater than or equal to four;

[0022] at least two injection openings connected to or defined by the distributor are angularly offset from the distributor axis by an angle between 5° and 170°, in particular by an angle between 20° and 160°; at least two injection openings connected to or defined by the distributor, angularly offset from the distributor axis, are located at an equal radial distance from the distributor axis and / or are located axially in the same position in projection along the distributor axis

[0023] the injection rail comprises a plurality of injection nozzles protruding from the distributor, each injection nozzle defining at least one injection opening, advantageously at most one injection opening;

[0024] at least two injection openings connected to the distributor or defined by the distributor are axially offset along the distributor axis;

[0025] the distributor axis is configured to extend horizontally in the contacting capacity, with the connecting pipe protruding vertically from the distributor;

[0026] the pressurized liquid source containing dissolved gas includes a pressurized liquid containing dissolved gas pressurization chamber comprising a liquid inlet and a pressurized gas injection port into the liquid supplied by the liquid inlet to form the pressurized liquid containing dissolved gas;

[0027] All injection axes of all injection openings of the injection rail, and / or of each distributor of the injection rail, are incapable of lying in at most two distinct, intersecting or parallel planes. All injection openings of the injection rail, and / or of each distributor of the injection rail, are incapable of lying in at most two distinct, intersecting or parallel straight lines.

[0028] The invention also relates to a treatment installation for a fluid to be treated, comprising a capacity for bringing the fluid to be treated into contact with a pressurized liquid containing dissolved gas, the contact capacity having a bottom, the treatment installation comprising an injection system as defined above, the injection ramp being disposed in the contact capacity, opposite the bottom.

[0029] The installation according to the invention may comprise one or more of the following features, taken individually or in any technically possible combination:

[0030] the contacting capacity is configured to mix the fluid to be treated with the pressurized liquid containing dissolved gas to form a microbubble-laden fluid, the treatment installation comprising a downstream structure, in particular a flotation zone, and a downstream separation bulkhead between the contacting capacity and the downstream structure, the downstream separation bulkhead defining an upper passage of microbubble-laden fluid from the contacting capacity to the downstream structure, the injection ramp being arranged below the upper passage;

[0031] the downstream separation partition has at least one region inclined from bottom to top towards the downstream structure, adjacent to the overpass.

[0032] The invention also relates to a method for injecting a pressurized liquid containing dissolved gas into a fluid to be treated, comprising the following steps:

[0033] bringing a fluid to be treated into a contacting capacity of a treatment installation as defined above;

[0034] circulation of pressurized liquid containing dissolved gas from the source to the injection rail of the injection system;

[0035] injection of pressurized liquid containing dissolved gas into the contacting capability via the plurality of pressurized liquid containing dissolved gas injection openings, each injection of pressurized liquid containing dissolved gas through an injection opening being carried out along the injection axis defined by the injection opening, all injection axes being contained in a minimum number of distinct planes strictly greater than two, in particular greater than or equal to four.

[0036] The method according to the invention may include the following features:

[0037] the pressurized liquid containing dissolved gas contains dissolved gas under pressure, the injection of the pressurized liquid containing dissolved gas through each injection opening causes the pressurized liquid containing dissolved gas to expand and gas bubbles to appear in the pressurized liquid containing dissolved gas and in the fluid to be treated.

[0038] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the attached drawings in which:

[0039] - [Fig. 1] Figure 1 is a schematic view of a first fluid treatment installation, comprising a flocculation zone, a pressurized liquid injection system containing dissolved gas according to the invention, disposed downstream of the flocculation zone, and a flotation zone, disposed downstream of the pressurized liquid injection system containing dissolved gas;

[0040] - [Fig. 2] Figure 2 is a partial perspective view of the bottom of the tank and a relevant part of the pressurized liquid injection ramp containing dissolved gas of the injection system according to the invention, comprising non-aligned injection nozzles along two lines;

[0041] - [Fig. 3] Figure 3 is a view analogous to Figure 2, illustrating a variant of the injection ramp;

[0042] - [Fig. 4] Figure 4 is a view analogous to Figure 2, illustrating another variant of the injection ramp;

[0043] - [Fig. 5] Figure 5 is a top view of the bottom of the tank, on which are marked the vertical projections on the bottom of the injection openings of the injection rail of Figure 4;

[0044] - [Fig. 6] Figure 6 is a schematic view along a vertical plane of the streamlines of the flows generated by the injection of pressurized water containing dissolved gas into the contacting capacity and into the flotation zone, via a state-of-the-art injection system having nozzles with injection openings aligned along two parallel horizontal lines;

[0045] - [Fig. 7] Figure 7 is a view analogous to Figure 6, for an injection system according to the invention.

[0046] Throughout this document, the terms "upstream" and "downstream" are generally understood in relation to the normal direction of fluid flow in the treatment plant.

[0047] A first injection system 10 according to the invention, intended for injecting a pressurized liquid containing dissolved gas, in particular pressurized water containing dissolved gas, into a contacting vessel 12 of an installation 14 containing a fluid to be treated 16, is illustrated in particular in Figures 1 and 2. The pressurized liquid containing dissolved gas is generally saturated with dissolved gas. It is prone to expand upon injection into the fluid to be treated 16 contained in the contacting vessel 12, generating gas bubbles, in particular microbubbles.

[0048] The dissolved gas content in the pressurized liquid containing dissolved gas is generally greater than 50 mg / l, and for example between 50 mg / l and 150 mg / l for an overpressure between 3 bar and 5 bar.

[0049] Pressurized liquid containing dissolved gas is generally generated and conveyed at a pressure higher than atmospheric pressure, for example, between 300% and 600% of atmospheric pressure. This pressurized liquid is usually transparent or translucent.

[0050] The gas contained in the pressurized liquid is preferably air or alternatively, a gas or mixture of gases contained in air, such as nitrogen.

[0051] A microbubble is generally a bubble with a maximum dimension of less than 0.1 millimeter, for example between 40 microns and 50 microns.

[0052] The fluid to be treated 16 is advantageously a liquid, for example wastewater, sludge, seawater intended for desalination, or water intended for potable treatment. The fluid to be treated 16, when it comes into contact with the injection system 10, generally contains flocs.

[0053] A floc is, in particular, an aggregate of particles formed during a coagulation and flocculation process. This process facilitates the removal of suspended solids (SS) and / or colloids by gathering them into flocs, which are then separated by sedimentation, flotation and / or filtration systems.

[0054] In the example shown in Figure 1, the treatment installation 14 includes, upstream of the contacting capacity 12, an upstream structure 20, here a flocculation zone, configured to receive the fluid to be treated 16, in order to form flocs within this fluid to be treated 16.

[0055] In this same example, the treatment installation 14 includes, downstream of the contacting capacity 12, a downstream structure 22, here a bubble bed flotation zone, configured to receive the microbubble-laden fluid 24 formed by mixing the fluid to be treated 16 with the pressurized liquid containing dissolved gas injected by the injection system 10 and expanded, to allow separation between a floc accumulation layer 26 on the surface and a clarified fluid 28 below the floc accumulation layer 26.

[0056] The upstream structure 20, the contacting chamber 12, and the downstream structure 22 extend linearly along a longitudinal axis A-A'. The upstream structure 20 comprises a plurality of upstream chambers 30A, 30B, 30C connected in series, each equipped with a respective agitator 32A, 32B, 32C to successively receive the fluid to be treated 16, and form flocs in successive upstream chambers 30A, 30B, 30C. Alternatively, only the upstream chamber 30A is equipped with an agitator 32A, the chambers 30B, 30C being simple baffles without agitators.

[0057] The treatment installation 14 includes, between the upstream capacity 30C and the contacting capacity 12, an upstream transverse separation partition 34. The upstream transverse separation partition 34 defines, in a lower region, at least one lower passage 36 for supplying the contacting capacity 12 with the fluid to be treated 16.

[0058] In the case where an agitator 32A to 32C is present in each capacitance 30A to 30C, the contacting capacity 12 advantageously has a volume less than that of the or each upstream capacity 30A, 30B, 30C.

[0059] The contact capacity 12 is delimited upstream by the upstream transverse separation partition 34, laterally by lateral partitions 38 and downstream by a downstream transverse separation partition 40 with the downstream structure 22. It is delimited downwards by a bottom 42.

[0060] The downstream transverse partition 40 projects from the bottom 42, opposite the upstream transverse partition 34. Here it comprises a lower vertical region 44 extending from the bottom 42 and an upper region 46 inclined from bottom to top downstream, from the contacting capacity 12 towards the downstream structure 22. The upper region 46 defines from its upper edge 48, an upper passage 50 for supplying the downstream structure 22 with fluid charged with microbubbles 24.

[0061] With reference to Figure 1, the injection system 10 comprises a pressurized liquid source 60 containing dissolved gas, advantageously located outside the contacting capacity 12, and at least one injection manifold 62 of pressurized liquid containing dissolved gas in the fluid to be treated 16, disposed in the contacting capacity 12 by being connected to the pressurized liquid source containing dissolved gas 60.

[0062] In the example visible in Figure 1, the pressurized liquid source containing dissolved gas 60 comprises a pressurization chamber 64, having a liquid inlet 66, a pressurized gas injection port 68 in the liquid received from the inlet 66 and a pressurized liquid outlet 70 containing the produced dissolved gas, connected to the injection manifold or manifold 62.

[0063] With reference to figures 1 and 2, the or each ramp 62 includes a tubular distributor 80, extending along a distributor axis B-B', and a connecting line 82 from the tubular distributor 80 to the pressurized liquid source containing dissolved gas 60, tapped on the distributor 80.

[0064] The ramp or each ramp 60 further comprises a plurality of pressurized liquid injection openings 84 containing gas dissolved in the contacting capacity 12, which are here located at the free end of a plurality of injection nozzles 86 projecting from the tubular distributor 80.

[0065] The distributor 80 extends horizontally here in relation to the bottom 42 of the contacting capacity 12 between the upstream transverse partition 34 and the downstream transverse partition 40. Advantageously, the distributor 80 is positioned above the one or each lower supply passage 36 so that the fluid to be treated 16 flows at least partially vertically in front of the distributor 80.

[0066] The B-B' distribution axis extends transversely, preferably parallel to the downstream transverse partition 40 and / or perpendicular to the A-A' axis. Here it extends horizontally.

[0067] The axial extent of the distributor 80, taken along the axis of the distributor B-B', is generally greater than 50%, in particular greater than 70%, preferably greater than 90% or even 95% of the width of the contacting capacity 12, taken at the level of the distributor 80. This ensures a distribution of pressurized liquid containing dissolved gas over a significant width of the contacting capacity 12.

[0068] Advantageously, the axial extent of the distributor 80 is generally substantially equal to the width of the contacting capacity 12. In other words, the distributor 80 advantageously extends over the entire width of the contacting capacity 12.

[0069] The connecting pipe 82 extends vertically from the distributor 80 through the contacting capacity 12 to the outside of it, to be connected to the source 60. It is advantageously tapped into a middle part of the distributor 80 along the distributor axis B-B'.

[0070] Each injection nozzle 86 protrudes from the distributor 80, defining a pressurized liquid ejection channel 88 containing dissolved gas from the distributor 80 (one of which is shown as a dashed line in Figure 2). The ejection channel 88 opens through an injection port 84.

[0071] Each injection opening 84 extends here to the free end of an injection nozzle 86. It defines an injection axis C of pressurized liquid containing dissolved gas received from the source 60 into the contacting capacity 12. This axis C generally corresponds to the geometric central axis of the injection opening 84. The number of injection openings 84 originating from each distributor 80, or more generally from the injection manifold 62, is preferably greater than four, in particular greater than eight.

[0072] The injection nozzles 86 are distributed regularly or not regularly along the axis of the distributor B-B'. Thus, at least two injection openings 84, preferably at least ten injection openings 84 are axially offset from each other along the axis of the distributor B-B'.

[0073] Furthermore, at least two injection nozzles 86A, 86B and therefore at least two injection openings 84A, 84B are angularly offset relative to the distributor axis B-B' by an angle between 5° and 170°, in particular by an angle between 20° and 160°.

[0074] In the example in Figure 2, the at least two injection nozzles 86A, 86B and the at least two injection openings 84A, 84B, which are angularly offset, are for example angularly adjacent and are located axially in the same position in projection along the distributor axis B-B'.

[0075] Their angular offset relative to the B-B' distribution axis is, for example, an angle between 5° and 170°, specifically an angle between 20° and 160°

[0076] Furthermore, at least two injection nozzles 86A, 86C and at least two injection openings 84A, 84C spaced axially along the distributor axis B-B' are axially adjacent while also being angularly offset with respect to the distributor axis B-B'.

[0077] Their angular offset relative to the distributor axis B-B' is for example also an angle between 5° and 175°, in particular an angle between 20° and 160° In the example of figure 2, at least two injection nozzles 86A, 86B and their injection openings 84A, 84B are located at the same axial position P1 while being angularly offset by an angle a from one another.

[0078] At least two injection nozzles 86C, 86D and their injection openings 84C, 84D are located at an axial position P2 axially adjacent to the axial position P1, being angularly offset by the same angle to each other.

[0079] Each injection nozzle 86A, 86B and its injection opening 84A, 84B located at the first position P1 is angularly offset from each injection nozzle 86C, 86D and its injection opening 84C, 84D located at the second position P2, for example by an angle different from angle a.

[0080] The pattern thus obtained is advantageously repeated along the distributor axis B-B'. In the variant shown in Figure 3, the two injection nozzles 86C, 86D and their injection openings 84C, 84D located at an axial position P2 axially adjacent to the axial position P1, are angularly offset by an angle p different from the angle a, less than the angle a, from each other.

[0081] In this example, the angle a between the two injection nozzles 86A, 86B and between their injection openings 84A, 84B at position P1 is greater than 170°, in particular equal to 180°, but the angle p between the two injection nozzles 86C, 86D and between their injection openings 84C, 84D located at axial position P2 is between 5° and 170°, in particular between 20° and 160°.

[0082] In the examples in Figures 2 and 3, the injection nozzles 86A, 86B, 86C, 86D all extend linearly and radially with respect to the distributor axis B-B'.

[0083] At least two injection openings 84A, 84B, 84C, 84D, angularly offset from the distributor axis B-B', are located at equal radial distances from the distributor axis B-B', in particular the injection openings 84A, 84B or 84C, 84D located axially at the same respective position P1, P2, in projection along the distributor axis B-B'.

[0084] In the variant shown in Figure 4, the injection nozzles 86E, 86F, 86G, 86H, which protrude from either side of the distributor 80, are curved. Advantageously, they have a free end that points downwards towards the bottom 42. The injection openings 84E, 84F, 84G, 84H open towards the bottom 42, for example along vertical injection axes C.

[0085] In this variant, the distances to the distributor axis B-B' of at least two injection openings 84E 84F, 84G, 84G offset axially along the distributor axis B-B' are different.

[0086] In the examples just described above, all the injection axes C of all the injection openings 84 of the rail 62, and of each distributor 80 of the rail 62, are contained in a minimum number of distinct, intersecting or parallel planes, strictly greater than two, in particular greater than or equal to four.

[0087] Unlike a distributor with two lines of nozzles, the nozzles of each line all injecting along parallel injection axes C, it is impossible to fit all the injection axes C of all injection openings 84 of the rail 62, and of each distributor 80 of the rail 62, in at most two distinct planes, intersecting or parallel.

[0088] Advantageously, but not necessarily, the minimum number of distinct, parallel or intersecting lines containing all the injection openings 84 of the rail 62 and of each distributor 80 of the rail 62 is strictly greater than two, in particular greater than or equal to four. Unlike a distributor having two lines of nozzles, the nozzles of each line all injecting along parallel injection axes C, it is impossible to fit all the injection openings 84 of the rail 62, and of each distributor 80 of the rail 62, into at most two distinct, intersecting or parallel lines.

[0089] With reference to figure 5, the vertical projections 90 of the injection openings 84 on the bottom 42 are distributed over the entire extent of the bottom 42.

[0090] Advantageously but not necessarily, the minimum number of distinct, parallel or intersecting straight lines containing all the vertical projections 90 of the injection openings 84 of the ramp 62 and of each distributor 80 of the ramp 62 onto the bottom 42 is strictly greater than two, in particular greater than or equal to four.

[0091] Unlike a distributor with two lines of nozzles, the nozzles of each line all injecting along parallel injection axes C, it is impossible to fit all the vertical projections 90 of the injection openings 84 of the rail 62 and of each distributor 80 of the rail 62 on the bottom 42 into at most two distinct, intersecting or parallel straight lines.

[0092] As will be described below, such a distributed and possibly random arrangement of the injection axes C of pressurized liquid containing dissolved gas and the corresponding injection openings 84, by misaligning them, limits the possibilities of cooperative grouping of the different jets of pressurized liquid containing dissolved gas emitted into the contacting capacity 12 from the ramp 62, through the injection openings 84, facilitating the efficient contact between the pressurized liquid containing dissolved gas and the fluid to be treated 16 in the contact zone above the ramp 62.

[0093] This leads to increased formation of fluid charged with microbubbles 24, minimizing the volume of fluid to be treated 16 not brought into contact with the pressurized liquid containing dissolved gas and consequently, to improved treatment of the fluid introduced into the downstream structure 22.

[0094] Thus, the contact between the microbubbles and the flocs is maximized and a low-speed upward flow is obtained.

[0095] With reference to Figure 1, the downstream structure 22 comprises a downstream capacity 92 separated from the contacting capacity 12 by the downstream transverse partition 40, to allow the separation of the microbubble-laden fluid 24 into the accumulation layer 26 and the clarified fluid 28. It further advantageously comprises a drainage system 94 for the clarified fluid 28 in a lower part of the downstream capacity 92 and advantageously, an upper scraper 96 on the surface of the downstream capacity 92.

[0096] The drainage system 94 includes, for example, at least one baffle and at least one pump. A process for treating the fluid to be treated 16 in a treatment plant 14 by implementing a pressurized liquid injection system containing dissolved gas 10 according to the invention will now be described.

[0097] Initially, the fluid to be treated 16, for example wastewater, sludge, seawater intended to be desalinated, or water intended to be made potable, is introduced into the upstream structure 20.

[0098] The fluid to be treated 16 advantageously undergoes pretreatment. In the example shown in Figure 1 where the upstream structure 20 is a flocculation zone, the fluid to be treated 16 passes successively through each upstream capacity 30A, 30B, 30C allowing the formation of flocs, being agitated where necessary by each agitator 32A, 32B, 32C.

[0099] Then, the fluid to be treated 16 passes into the contacting capacity 12 through the lower passage 36. It rises vertically between the upstream transverse partition 34 and the downstream transverse partition 40.

[0100] Simultaneously, pressurized liquid containing dissolved gas is continuously formed in the source 60, by pressurizing the liquid introduced through the supply inlet 66 and dissolving the gas injected via the injection nozzle 68.

[0101] The pressurized liquid containing dissolved gas is conveyed to the injection manifold 62. It enters the connecting pipe 82 and is distributed transversely along the distributor 80 to the injection nozzles 86. The pressurized liquid containing dissolved gas is then injected through the injection openings 84 in the form of jets into the fluid to be treated 16 circulating in the contact cavity 12.

[0102] During injection, a depressurization of the pressurized liquid containing dissolved gas occurs in the nozzles 86 at the injection openings 84, causing the formation of microbubbles of gas.

[0103] In the contact zone located above ramp 62, contact occurs between the microbubbles and the fluid to be treated 16 advantageously containing suspended solids, for example in the form of flocs.

[0104] Thanks to the injection system 10 according to the invention, the jets of pressurized liquid containing dissolved gas are injected in a distributed manner in the contact area, limiting their interactions, which promotes contact with the fluid to be treated 16 by minimizing dead zones in which the fluid to be treated 16 is not mixed with the pressurized liquid containing dissolved gas.

[0105] Then, the microbubbled fluid 24 thus obtained passes into the downstream structure 22 through the overpass 50 and is distributed in the downstream capacity 92. The microbubbled fluid then forms a "bubble bed", with a decreasing concentration from top to bottom, in which flocculation continues, with improved adhesion between the air bubbles and the floc.

[0106] A separation occurs in the downstream capacity 92 between an upper accumulation layer 26 of flocs and a clarified fluid 28 below the upper layer 26. The clarified fluid 28 is continuously discharged via the drain system 94 and the upper layer 26 is scraped by the scraper 96 to be extracted from the downstream structure 22.

[0107] An example illustrating the effect of the injection system 10 according to the invention on bringing the pressurized liquid containing dissolved gas into contact with the fluid to be treated 16 is illustrated by figures 6 and 7.

[0108] These figures were obtained by computational fluid dynamics (CFD) numerical simulation using Simcenter STAR-CCM+ software.

[0109] The fluid to be treated 16 considered for carrying out the simulations is water with a dynamic viscosity of 1.138 mPa.s. The pressurized liquid containing dissolved gas injected into the fluid to be treated 16 is pressurized water containing dissolved air under a pressure of 5 bars in the nozzles 86 upstream of the injection openings 84.

[0110] In Figure 6, the injection rail of the prior art injection system comprises a distributor with two opposing lines of nozzles, the nozzles in each line all injecting along parallel injection axes C. All injection axes C of all injection openings in the rail are contained within a minimum number of distinct planes, less than or equal to two.

[0111] The injection of pressurized water containing dissolved gas through such a ramp leads to strong cooperation between the jets from the different nozzles which drive each other at high speed along the upstream and downstream transverse partitions 34, 40, generating a very large zone 100 of no contact between the pressurized water containing dissolved gas and the water to be treated at the center of the contacting capacity 12.

[0112] In Figure 7, the injection system 10 according to the invention is implemented. The ramp 62 is for example that visible in Figure 2, in which all the injection axes C of all the injection openings 84A, 84B, 84C, 84D of each distributor 80 are contained in a minimum number of distinct planes strictly greater than two, in particular greater than or equal to four.

[0113] The injection of pressurized water containing dissolved gas through such a ramp 62 leads to weak cooperation between the jets from the different nozzles 86A, 86B, 86C, 86D, which are distributed in the center of the contacting chamber 12, generating a very thin zone of no contact between the pressurized water containing dissolved gas and the water to be treated, or the absence of such a zone. The effect is also beneficial in the downstream structure 22, where the microbubble-laden fluid 24 is distributed more extensively in the internal volume of the downstream chamber 92, ensuring a wider distribution of microbubbles in the microbubble-laden fluid 24 and therefore better separation and more efficient treatment of the water to be treated.

[0114] In one variant, the distributor 80 is devoid of protruding nozzles 86, the injection openings 84 being defined through an external surface of the distributor 80.

[0115] According to the very definition of the term "capacity", for example taken from the Petit Larousse dictionary, the contacting capacity 12 is generally an enclosure delimiting a determined volume, in which a process takes place, here a contacting of the pressurized liquid containing dissolved gas with a fluid to be treated.

Claims

DEMANDS 1. Injection system (10) for a pressurized liquid containing dissolved gas, in particular pressurized water containing dissolved gas, into a contacting vessel (12) of the pressurized liquid containing dissolved gas with a fluid to be treated (16), the injection system (10) comprising: - a source (60) of pressurized liquid containing dissolved gas intended to be positioned outside the contacting capacity (12); - an injection ramp (62) of pressurized liquid containing dissolved gas in the contacting capacity (12), connected to the source (60) of pressurized liquid containing dissolved gas, the injection ramp (62) being configured to be positioned opposite a bottom (42) of the contacting capacity (12), the injection ramp (62) defining a plurality of injection openings (84) of pressurized liquid containing dissolved gas, each injection opening (84) defining an injection axis (C) of pressurized liquid containing dissolved gas received from the source (60) into the contacting capacity (12); characterized in that all the injection axes (C) of all the injection openings (84) of the injection rail (62) are contained in a minimum number of distinct planes strictly greater than two, in particular greater than or equal to four.

2. Injection system (10) according to claim 1, wherein the minimum number of distinct straights containing all the injection openings (84) of the injection rail (62) is strictly greater than two, in particular greater than or equal to four.

3. Injection system (10) according to claim 1 or 2, wherein the injection ramp (62) comprises at least one distributor (80) extending linearly along a distributor axis (B-B') and a connecting pipe (82) from the distributor (80) to the source (60), projecting from the distributor (80), all injection axes (C) of all injection openings (84) connected to the same distributor (80) being contained in a minimum number of distinct planes strictly greater than two, in particular strictly greater than four.

4. Injection system (10) according to claim 3, wherein the minimum number of distinct straight lines containing all the injection openings (84) connected to the same distributor (80) is strictly greater than two, in particular greater than or equal to four.

5. Injection system (10) according to any one of claims 3 to 4, wherein at least two injection openings (84) connected to the distributor (80) or defined by the distributor (80) are angularly offset with respect to the distributor axis (B-B') by an angle between 5° and 170°, in particular by an angle between 20° and 160°.

6. Injection system (10) according to claim 5, wherein at least two injection openings (84) connected to the distributor (80) or defined by the distributor (80), angularly offset with respect to the distributor axis (B-B') are located at equal distance radially from the distributor axis (B-B') and / or are located axially in the same position in projection along the distributor axis (B-B').

7. Injection system (10) according to any one of claims 3 to 6, wherein the injection rail (62) comprises a plurality of injection nozzles (86) projecting from the distributor (80), each injection nozzle (86) defining at least one injection opening (84), advantageously at most one injection opening (84).

8. Injection system (10) according to any one of claims 3 to 7, wherein at least two injection openings (84) connected to the distributor (80) or defined by the distributor (80) are axially offset along the distributor axis (B-B').

9. Injection system (10) according to any one of claims 3 to 8, wherein the distributor axis (B-B') is configured to extend horizontally in the contacting capacity (12), the connecting pipe (82) projecting vertically from the distributor (80).

10. Injection system (10) according to any one of the preceding claims, wherein the pressurized liquid source (60) containing dissolved gas comprises a pressurized liquid pressurization chamber (64) containing dissolved gas comprising a liquid inlet (66) and a pressurized gas injection port (68) into the liquid supplied by the liquid inlet (66) to form the pressurized liquid containing dissolved gas.

11. Installation (14) for treating a fluid to be treated (16), comprising a contacting capacity (12) of the fluid to be treated (16) with a pressurized liquid containing dissolved gas, the contacting capacity (12) having a bottom (42), the installation 17 treatment (14) comprising an injection system (10) according to any one of the preceding claims, the injection ramp (62) being disposed in the contacting capacity (12), opposite the bottom (42).

12. Processing installation (14) according to claim 11, wherein the contacting capacity (12) is configured to mix the fluid to be treated (16) with the pressurized liquid containing dissolved gas to form a microbubble-laden fluid (24), the processing installation (14) comprising a downstream structure (22), in particular a flotation zone, and a downstream separation partition (40) between the contacting capacity (12) and the downstream structure (22), the downstream separation partition (40) defining an upper passage (50) of microbubble-laden fluid (24) from the contacting capacity (12) to the downstream structure (22), the injection ramp (62) being disposed below the upper passage (50).

13. Processing installation (14) according to claim 12, wherein the downstream separation partition (40) has at least one region inclined (46) from bottom to top towards the downstream structure (22), adjacent to the overpass (50).

14. A method for injecting a pressurized liquid containing dissolved gas into a fluid to be treated (16) comprising the following steps: - bringing a fluid to be treated (16) into a contacting capacity (12) of a treatment installation (14) according to any one of claims 11 to 13; - circulation of pressurized liquid containing dissolved gas from the source (60) to the injection rail (62) of the injection system (10); - injection of pressurized liquid containing dissolved gas into the contacting capacity (12) via the plurality of injection openings (84) of pressurized liquid containing dissolved gas, each injection of pressurized liquid containing dissolved gas through an injection opening (84) being carried out along the injection axis (C) defined by the injection opening (84), all the injection axes (C) being contained in a minimum number of distinct planes strictly greater than two, in particular greater than or equal to four.

15. Injection method according to claim 14, wherein the pressurized liquid containing dissolved gas contains dissolved gas under pressure, the injection of the pressurized liquid containing dissolved gas through each injection opening (84) causing the pressurized liquid containing dissolved gas to expand and gas bubbles to appear in the pressurized liquid containing dissolved gas and in the fluid to be treated (16).

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