FR3133190A1 - Water treatment installation and process using a hydrocyclone - Google Patents

Abstract

Installation (1) for treating water, comprising a device (7) for injecting a source of calcium and/or magnesium ions into the water, a contact space configured to allow dissolution of the calcium and /or magnesium in water so as to constitute a remineralized water composition and a hydrocyclone (8) configured to separate the remineralized water composition from solid residues. Figure for abstract: Fig. 1

Description

Water treatment installation and process using a hydrocyclone

The invention relates to the field of water treatment.

The invention is of particular interest in the field of desalination, in particular for the remineralization of water having undergone prior purification treatment such as reverse osmosis.

The invention can also be implemented for restoring the calcium-carbonic balance of water, typically fresh water.

State of the prior art

Several known techniques make it possible to remineralize water, typically fresh water.

A first technique consists of dissolving limestone in water, generally in the form of grains. The limestone grains are brought into contact with water and a reagent such as carbon dioxide within a gravity or pressure filter reactor.

This technique is generally implemented within an installation of the limestone filter type which must be sufficiently voluminous to ensure the contact time necessary for the dissolution of the grains, this contact time being linked to the size of the grains and the dose of CO2. In addition, an increase in the flow speed through the filter leads to an increase in the quantity of fines passing through the filter and in the turbidity at the filter outlet, which implies a limitation of the flow speed.

A second remineralization technique consists of bringing lime water and carbon dioxide into contact.

This second technique requires facilities to prepare lime water while limiting leaks of residues or impurities, and the CO2 dosage is stoichiometrically doubled compared to the previous solution. Operating costs are therefore very high.

The invention aims in particular to overcome the disadvantages of water remineralization techniques known in the prior art, particularly in terms of installation size and/or yield and/or water quality.

A particular aim of the invention is to provide a solution capable of providing satisfactory results with different types of sources of calcium and/or magnesium ions.

To this end, the subject of the invention is a water treatment installation, comprising an injection device capable of injecting a source of calcium and/or magnesium ions into the water, a contact space configured to allow dissolving the ions in water so as to constitute a remineralized water composition and a separation device configured to separate the remineralized water composition from solid residues.

According to the invention, the separation device comprises a hydrocyclone.

In a manner known per se, a hydrocyclone is a device comprising a chamber having at least one inlet and two outlets, and being configured to allow water-particle separation under the action of a centrifugal force.

In the context of the present invention, the hydrocyclone is configured so that the composition of remineralized water enters the chamber via said inlet, that at least part of the solid residues it contains are entrained towards one of said outlets and that the water composition thus separated from these solid residues is evacuated from the chamber through the other of said outlets.

Among other advantages, the use of a hydrocyclone to separate solid residues from the remineralized water composition makes it possible to:
– reduce the contact time required, possibly by recirculating part of the composition leaving the hydrocyclone, which makes it possible to increase the compactness of the installation and reduce its footprint,
– reduce or at least control the turbidity of treated water, particularly in the context of drinking water production,
– improve the dissolution efficiency of calcium and/or magnesium ions,
while making the installation compatible with the use of various sources of calcium and/or magnesium ions.

The source of calcium and/or magnesium ions is typically a solid grain or powder compound.

The source of calcium and/or magnesium ions preferably comprises calcium and/or magnesium salts.

More preferably, the calcium salts are chosen from calcium hydroxides and calcium carbonates.

Alternatively or additionally, the magnesium salts can be chosen from magnesium hydroxides and magnesium carbonates.

As an example of calcium and/or magnesium salts, the source used may include limestones – not limited to the formula CaCO ₃ , in particular calcite – or limes – not limited to the formula Ca(OH) ₂ .

The source of calcium and/or magnesium ions may comprise another type of reagent and/or a combination of different reagents chosen from a list including, in a non-limiting manner, the aforementioned calcium and/or magnesium salts.

In one embodiment, the source of calcium and/or magnesium ions has a particle size of between 30 µm and 4.0 mm, preferably between 50 µm and 1.5 mm.

Sources of calcium and/or magnesium ions, in particular calcium carbonates, having such a particle size are abundant, which makes it possible to reduce the operating cost.

The invention can nevertheless be implemented with a source of calcium and/or magnesium ions having a different particle size, in particular less than 30 µm, for example between 0.1 µm and 30 µm.

In one embodiment, the separation device comprises, preferably downstream of the hydrocyclone, a polishing device which may include a disk filter and/or another contact space and/or another hydrocyclone.

The use of a polishing device, in addition to the hydrocyclone, makes it possible to improve the quality of the treated water if the turbidity recommendations for the treated water are very restrictive.

In one embodiment, the hydrocyclone comprises an inlet fluidly connected to the contact space and an outlet fluidly connected to a conduit, this conduit being configured to reintroduce into the contact space a portion of the composition with at least one part of the solid residues leaving the hydrocyclone through this outlet.

Such a conduit makes it possible to recirculate in the contact space parts of the source of undissolved calcium and/or magnesium ions, thus reducing the quantity of ion source necessary for treatment and improving the efficiency of the installation.

Concerning the contact space, this can be formed by a conduit and/or by a tank of the installation.

Thus, the invention covers a first alternative embodiment in which the contact space is formed by a conduit and a second alternative embodiment in which it is formed by a tank.

These variants can be combined so that, for example, the conduit forms a first part of the contact space and the tank forms a second part of the contact space.

Thus, more generally, the installation may include a conduit forming at least part of the contact space and/or a tank forming at least part of the contact space.

In one embodiment, the installation comprises a mixing and/or stirring device configured to mix and/or agitate the source of calcium and/or magnesium ions and the water within the contact space.

This device may include a static mixer.

In one embodiment, said separation device is a second separation device, the installation comprising a first separation device and a recirculation branch configured to convey part of the remineralized water composition leaving the second separation device in upstream of the first separation device.

The first separation device may comprise a hydrocyclone as defined above and, more generally, may have characteristics identical or similar to said second separation device.

In a manner known per se, the installation may include a CO2 injection and/or dosing device. This device is preferably configured to inject CO2 in at least stoichiometric quantity.

In one embodiment, the installation comprises a device configured to take CO2, preferably from the composition of remineralized water, and to reinject the CO2 thus taken into the installation, preferably upstream of, or in, the contact space.

The invention also relates to a process for treating water using an installation as defined above.

This process preferably comprises the following steps:
– injection of a source of calcium and/or magnesium ions into the water,
– dissolution of ions in water so as to constitute a composition of remineralized water,
– separation of solid residues from the remineralized water composition.

In a manner known per se, the dissolution step can be carried out by using a reagent such as carbon dioxide or sulfuric acid.

The dissolution step is preferably carried out by bringing the source of calcium and/or magnesium ions into contact with water for a period of between 1 minute and 15 minutes, more preferably between 2 minutes and 10 minutes.

Of course, the duration of contact depends in particular on the source of calcium and/or magnesium ions used and the characteristics of the installation and can be determined experimentally depending on the quality of the desired water, using well-established techniques. known to those skilled in the art.

The process may include a step of prior treatment of the water by reverse osmosis.

Furthermore, the process may include, after the separation step, a step of mixing the remineralized water composition with another water in order to remineralize it or neutralize its acidity.

The invention can thus be implemented for the treatment of drinking water.

The invention is, however, not limited to such an application and can, for example, be used to produce water not intended for human consumption.

Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows.

The detailed description which follows refers to the appended drawings in which:

is a schematic view of an installation according to a first embodiment of the invention;

is a schematic view of a hydrocyclone, illustrating a cyclonic flow making it possible to achieve water-solid residue separation;

is a schematic view of an installation according to a second embodiment of the invention;

is a schematic view of an installation according to a third embodiment of the invention;

is a schematic view of an installation according to a fourth embodiment of the invention;

is a schematic view of an installation according to a fifth embodiment of the invention.

Detailed description of embodiments

There illustrates in a schematic and simplified manner an installation 1 according to the invention.

The installation 1 comprises a primary water flow conduit 2 and a system 3 configured to take a fraction of the water flowing in this conduit 2 so as to treat this fraction of water and to reinject at least part of the fraction of water thus treated in the primary conduit 2.

The treatment system 3 comprises a flow network 4, a reservoir 6 for storing a source of calcium and/or magnesium ions, an injection device 7, a separation device 8 and an extraction member 9 of residues.

In this embodiment, the separation device 8 is a hydrocyclone.

In this example, network 4 comprises a conduit 4A, a conduit 4B and a conduit 4C.

The conduit 4A is fluidly connected on the one hand to a sampling point 11 of the primary conduit 2 and on the other hand to an inlet 12 of the hydrocyclone 8.

The conduit 4B is fluidly connected on the one hand to a first outlet 13 of the hydrocyclone 8 and on the other hand to a reinjection point 5 of the conduit 4A.

The conduit 4C is fluidly connected on the one hand to a second outlet 14 of the hydrocyclone 8 and on the other hand to a reinjection point 16 of the primary conduit 2.

Relative to a direction of flow of water in the primary conduit 2, going in this example from the left to the right of the , the reinjection point 16 is located downstream of the sampling point 11.

In this example, the water arriving in the primary conduit 2 has undergone prior treatment by reverse osmosis and the installation 1 is configured to remineralize this water in the manner described below.

The installation 1 is here configured to continuously take from the primary conduit 2 between 10% and 50% of the water flowing there and to reinject the fraction of water treated within the system 3 into the primary conduit 2 so as to mix the fraction of treated water with the fraction of untreated water which circulates in the primary conduit 2.

In this example, the source of calcium and/or magnesium ions comprises calcium carbonate in the form of grains having an average size of approximately 150 µm.

The injection device 7 is configured to inject grains of calcium carbonate stored in the tank 6 into the water circulating in the conduit 4A.

In this example, the device 7 is also configured to inject carbon dioxide into the water circulating in the conduit 4A.

The part of the conduit 4A extending between the injection device 7 and the inlet 12 of the hydrocyclone 8 forms a contact space dimensioned to allow the dissolution of the calcium and/or magnesium ions in the water, which in this example results in a manner known per se from a reaction between water, calcium carbonate and carbon dioxide.

The dissolution of calcium and/or magnesium ions in water constitutes a remineralized water composition, in which at least part of the calcium and/or magnesium ions are solubilized in water. This composition also comprises solid residues such as insolubles, impurities and/or grains or parts of grains of undissolved calcium carbonate and/or magnesium.

In reference to the , the hydrocyclone 8 comprises a wall 21 extending around an axis A1 so as to delimit a chamber which extends along this axis A1.

In operation, the hydrocyclone 8 is arranged so that the axis A1 is vertical, or substantially vertical, so that the inlet 12 and the outlet 14 are located vertically towards the top of the chamber and the outlet 13 is located vertically at the bottom of the room.

More precisely, the inlet 12 opens laterally at an upper end of the chamber in order to introduce the remineralized water composition tangentially. The outlet 13 opens at a vertically lower axial end of the chamber. The outlet 14 opens at a vertically upper axial end of the chamber, opposite the outlet 13.

The chamber has a section that decreases vertically from top to bottom. In this case, the section of the chamber, through a plane perpendicular to the axis A1, is circular so that the chamber has a generally frustoconical geometry.

In a manner known per se, when a flow of water containing unsolubilized residues of relatively high density compared to the water is injected into the chamber via the inlet 12, a descending vortex 23 develops, radially at the level of the wall 21. Taking into account the narrowing of the chamber vertically downwards, it is formed concomitantly, radially inside the descending vortex 23, an ascending vortex 24 which develops against the current of the descending vortex 23 and which drives the water vertically upwards towards the outlet 14. Due to the pressure differential induced by such cyclonic flow, said residues fall vertically downwards, that is to say towards the outlet 13.

The hydrocyclone 8 thus makes it possible to separate unsolubilized or undissolved residues from water under the action of centrifugal force.

In installation 1 of the , the hydrocyclone 8 thus makes it possible to separate at least part of the solid residues it contains from the remineralized water composition.

More precisely, a first part of the composition entering the hydrocyclone 8 leaves via the outlet 13, this first part comprising the solid residues carried towards this outlet 13 in the manner described above. A second part of the composition, devoid of solid residues leaving the hydrocyclone 8 via outlet 13, leaves via outlet 14.

Conduit 4B of installation 1 of the forms a conduit configured to recirculate in conduit 4A and in the contact space at least part of the composition leaving the hydrocyclone 8 via outlet 13.

Such recirculation makes it possible to dissolve calcium and/or magnesium ions not dissolved in the part of the composition leaving the hydrocyclone 8 via outlet 13.

Such recirculation is optional. Thus, in a variant embodiment, the conduit 4B can be fluidly connected on the one hand to the outlet 13 of the hydrocyclone 8 and on the other hand to a tank (not shown) for recovering solid residues.

In the example of the , the member 9 is configured to retain at least part of the solid residues contained in the composition leaving the hydrocyclone 8 via the outlet 13 and to reintroduce the rest of the composition into the conduit 4A via the reinjection point 5.

In an alternative embodiment, the member 9 may comprise an element such as a valve (not shown) controlled so as to reintroduce for a first duration the composition leaving the hydrocyclone 8 via the outlet 13 into the conduit 4A via the point reinjection 5 and to convey this composition for a second period to a tank (not shown) in order to extract the solid residues from the network 4. For example, out of a total duration of ten minutes, the first duration can be nine minutes and 45 seconds and the second duration 15 seconds.

More generally, such an organ 9 makes it possible to extract solid residues from the network 4 continuously or intermittently.

Installation 1 of the thus makes it possible to convey to the primary conduit 2, via conduit 4C, the composition leaving the hydrocyclone 8 via outlet 14, this composition comprising remineralized water with solubilized calcium and/or magnesium ions and being devoid in all or part of solid residues of the insoluble type, impurities and grains of undissolved calcium and/or magnesium carbonate.

Many variations can be made to installation 1 described above with reference to the without departing from the scope of the invention. For example, the installation 1 may comprise a separation device comprising, in addition to the hydrocyclone 8, an additional separation member such as a disk filter (not shown) which can be mounted downstream of the outlet 14 of the hydrocyclone 8. Alternatively or complementary, the hydrocyclone 8 can constitute part of a separation member such as a hydrocyclonic disk filter (not shown), combining filtration and hydrocyclonic effect and/or belong to a device separation comprising a polishing device downstream of the hydrocyclone, the polishing device possibly comprising a member forming one or more additional contact spaces and/or one or more secondary hydrocyclones and/or one or more disc filters.

In an embodiment not shown, the installation comprises a contact tank forming said contact space, or forming an additional contact space.

Particularly when the installation includes such a contact tank, the installation can include a stirring device (not shown) in order to agitate the water and the source of calcium and/or magnesium ions within this tank. contact.

The dissolution of calcium and/or magnesium ions and, where appropriate, carbonate ions can also be improved by equipping the installation with a static mixer (not shown on the figure). ), particularly upstream of the hydrocyclone.

He is represented on the an embodiment in which the installation 1 comprises two hydrocyclones 8A and 8B. This embodiment is described below only according to its differences compared to that of the , the preceding description applying by analogy.

The conduit 4A is fluidly connected on the one hand to the sampling point 11 of the primary conduit 2 and on the other hand to an inlet 12A of the hydrocyclone 8A.

The conduit 4B is fluidly connected on the one hand to a first outlet 13A of the hydrocyclone 8A and on the other hand to a reinjection point 30 of a conduit 4E of the network 4.

The flow network 4 comprises a conduit 4D which is fluidly connected on the one hand to a second outlet 14A of the hydrocyclone 8A and on the other hand to an inlet 12B of the hydrocyclone 8B.

The conduit 4C is fluidly connected on the one hand to a second outlet 14B of the hydrocyclone 8B and on the other hand to the reinjection point 16 of the primary conduit 2.

The conduit 4E is connected on the one hand to a first outlet 13B of the hydrocyclone 8B and on the other hand to a reinjection point 31 of the conduit 4A, that is to say upstream of the hydrocyclone 8A.

Installation 1 of the also comprises a device 32 for injecting a reagent, in this example an acid stored in a reservoir 33, configured to inject this reagent upstream of the reinjection point 31.

The part of the conduit 4D extending between the injection device 7 of the source of calcium and/or magnesium ions and the inlet 12B of the hydrocyclone 8B forms a contact space dimensioned to allow the dissolution of the calcium and /or magnesium in water, which in this case results from a reaction between water, calcium carbonate and acid.

In installation 1 of the , the conduits 4B and 4E make it possible to recirculate in the hydrocyclone 8A, and where appropriate in the contact space upstream of the hydrocyclone 8B, a fraction of the remineralized water composition with solid residues that it comprises leaving hydrocyclones 8A and 8B via outlets 13A and 13B respectively, thus constituting two separation stages and promoting the dissolution of calcium and/or magnesium ions.

In alternative embodiments not shown, the installation may comprise more than two stages and/or one or more stages of the installation may comprise a separation device different from a hydrocyclone and/or a hydrocyclone different from that shown in the figure. and/or one or more stages of the installation may include a recirculation duct while one or more other stages may be without a recirculation duct.

Another example of embodiment is shown on the , which is described below only according to its differences from that of the . The preceding description applies by analogy.

In this example, the conduit 4B is fluidly connected on the one hand to the first outlet 13A of the hydrocyclone 8A and on the other hand to a reinjection point 36 of the conduit 4A, that is to say upstream of the hydrocyclone 8A. The reinjection point 36 is located downstream of the injection device 32.

The conduit 4E is connected on the one hand to the first outlet 13B of the hydrocyclone 8B and on the other hand to a reinjection point 37 of the conduit 4B.

Installation 1 of the also includes a storage tank 41.

The conduit 4C is fluidly connected on the one hand to the second outlet 14B of the hydrocyclone 8B and on the other hand to an inlet 42 of the tank 41.

The flow network 4 of the installation of the comprises a conduit 4F which is fluidly connected on the one hand to an outlet 43 of the tank 41 and on the other hand to the reinjection point 16 of the primary conduit 2.

The tank 41 makes it possible to store the remineralized water before reinjection into the primary conduit 2, allowing shutdowns of the installation 1 and control of the dosage of the remineralized water to be injected into the primary conduit 2.

Installation 1 of the also includes two static mixers 46 and 47.

The mixer 46 is mounted downstream of the reinjection point 36 and upstream of the hydrocyclone 8A, while the mixer 47 is mounted downstream of the injection device 7 and upstream of the hydrocyclone 8B.

In a variation of the , installation 1 includes a disk filter (not shown) mounted on conduit 4C downstream of outlet 14B of hydrocyclone 8B and upstream of tank 41.

He is represented on the a measuring device 51 configured to measure one or more parameters of the composition leaving the hydrocyclones 8A and 8B, respectively via the outlets 14A and 14B.

By way of example, these parameters can be representative of the turbidity and/or conductivity of the composition, making it possible to respectively evaluate the quantity of calcium and/or magnesium ion source injected and/or the dissolution of calcium ions. and/or magnesium.

In the different embodiments which have just been described and in their variants, the installation 1 can comprise such a measuring device and a control device (not shown) configured for example to control the injection device(s). source of calcium and/or magnesium ions and/or reagent(s) and/or the sampling rate and/or circulation in the flow network depending on the measurements carried out.

In the embodiments described above, the source of calcium and/or magnesium ions may comprise grains of calcium and/or magnesium carbonate having an average size different from 150 µm, for example a size between 50 µm and 1.5 mm, and/or another type of source of calcium and/or magnesium ions, for example lime. Furthermore, the carbon dioxide or the acid or more generally the reagent can be injected into the water before introducing it into the primary conduit 2.

For another example, the water arriving in the primary conduit 2 may have undergone a prior purification treatment other than reverse osmosis or another type of treatment. Of course, the water treated by installation 1 can also undergo further treatment depending on its destination.

Installation 1 can also include a CO2 recovery device 61 as shown in Figures 5 and 6.

Figures 5 and 6 show installations 1 similar to those of Figures 1 and 3, respectively, and are described only according to their differences from the latter. The preceding description applies by analogy to the embodiments of Figures 5 and 6.

In reference to the , the installation 1 comprises a CO2 injection device 62 which is in this example configured to inject CO2 into the conduit 4A, upstream of the injection device 7.

In this example, the device 61 is configured to take CO2 in gaseous form from the composition circulating in the conduit 4C and to convey the CO2 thus sampled via a conduit 63 so as to reinject it into the conduit 4A via the injection device 62.

Installation 1 of the includes a CO2 recovery device 61 similar to that of the .

Such a CO2 recovery device, which makes it possible to reduce the total quantity of CO2 injected into the installation 1, can be implemented so as to take and/or reinject CO2 at different points of the installation 1 and/or or on installations different from those of Figures 5 and 6, for example an installation such as that illustrated in the .

Claims (10)

Installation (1) for treating water, comprising an injection device (7) capable of injecting a source of calcium and/or magnesium ions into the water, a contact space configured to allow dissolution of the ions in water so as to constitute a remineralized water composition and a separation device configured to separate the remineralized water composition from solid residues, characterized in that the separation device comprises a hydrocyclone (8). Installation (1) according to claim 1, in which the source of calcium and/or magnesium ions:
– comprises calcium and/or magnesium salts, preferably chosen from limestones and limes, and/or
– has a particle size of between 30 µm and 4.0 mm, preferably between 50 µm and 1.5 mm. Installation (1) according to claim 1 or 2, in which the hydrocyclone (8) comprises an inlet (12) fluidly connected to the contact space and an outlet (13) fluidly connected to a conduit (4B), this conduit (4B) being configured to reintroduce into the contact space a part of the composition with at least part of the solid residues leaving the hydrocyclone (8) via this outlet (13). Installation (1) according to any one of claims 1 to 3, comprising a conduit forming at least part of the contact space. Installation (1) according to any one of claims 1 to 4, comprising a tank forming at least part of the contact space. Installation (1) according to any one of claims 1 to 5, in which said separation device is a second separation device (8B), the installation (1) comprising a first separation device (8A) and a branch of recirculation (4E) configured to convey part of the remineralized water composition leaving the second separation device (8B) upstream of the first separation device (8A). Installation (1) according to any one of claims 1 to 6, comprising a device (62, 63) configured to take CO2 from the remineralized water composition and to reinject the CO2 thus taken upstream of, or into, the contact space. Process for treating water using an installation (1) according to any one of claims 1 to 7, comprising the following steps:
– injection of a source of calcium and/or magnesium ions into the water,
– dissolution of ions in water so as to constitute a composition of remineralized water,
– separation of solid residues from the remineralized water composition. Method according to claim 8, comprising a step of prior treatment of the water by reverse osmosis. Process according to claim 8 or 9, comprising, after the separation step, a step of mixing the remineralized water composition with another water in order to remineralize it or neutralize its acidity.