FR3106826A1 - SAFE ELECTROCATALYTIC WATER TREATMENT DEVICE AND PROCESS - Google Patents

Abstract

TITLE: SAFE ELECTROCATALYTIC WATER TREATMENT DEVICE AND METHOD (115) immersed in a tank containing electrolytic liquid, at least one electrical voltage source configured to supply an electrical voltage between the cathode and the anode and to generate hydroxyl radicals on the anode surface by electrocatalytic oxidation of water and at least one accumulator and/or one capacitor electrically connected to the anode, with a view to preventing the appearance of explosive gases at the cathode, in particular with a view to preventing the generation of dihydrogen. The invention also relates to a safe electrocatalytic method for treating water. Figure for the abstract: figure 2

Description

SAFE DEVICE AND PROCESS FOR ELECTROCATALYTIC WATER TREATMENT

The present invention relates to a secure device for the electrocatalytic treatment of water. The present invention falls within the field of apparatus and methods for water treatment, sanitation and depollution.

Advanced oxidation processes (usually abbreviated as “AOP” for advanced oxidation process ) are oxidation methods that use highly reactive derivatives for the destruction of pollutants contained in water to be treated. Such a derivative is in particular the hydroxyl radical (OH), capable of oxidizing the majority of organic compounds until total mineralization in the form of carbon dioxide and water. The hydroxyl radical is particularly effective, due to its oxidation potential which is much higher than that of ozone or hydrogen peroxide.

Thus, the release of hydroxyl radicals in water to be treated is an effective method for purifying water and particularly effective for the treatment of wastewater containing persistent or toxic organic pollutants.

One way to generate hydroxyl radicals is through anodic oxidation also called electro-oxidation, electrocatalysis or electrocatalytic treatment. This method makes it possible to generate the hydroxyl radicals in situ . However, electro-oxidation consumes a lot of electrical energy. Another disadvantage is that this electrolytic process is accompanied by the formation of highly explosive gas comprising dihydrogen. This requires the implementation of a ventilation system or a suction system to prevent the accumulation of explosive gas in the electro-oxidation device. A failure or malfunction of these safety systems is liable to endanger the electro-oxidation device and the safety of the operators.

The present invention aims to remedy all or part of these drawbacks.

To this end, according to a first aspect, the present invention relates to a secure electrocatalytic water treatment device, which comprises:
- at least one electrocatalytic cell comprising at least one anode and one cathode immersed in a tank containing electrolytic liquid,
- at least one electric voltage source configured to supply an electric voltage between the cathode and the anode and to generate hydroxyl radicals on the anode surface by electrocatalytic oxidation of water and
- at least one capacitor and/or an accumulator electrically connected to the anode, in order to prevent the appearance of explosive gases at the cathode, in particular in order to prevent the generation of dihydrogen.

Within the meaning of the invention, the electrocatalytic process is carried out by the formation of hydroxyl radicals on the anode surface, in the tank containing the electrolytic liquid, in particular according to the following simplified reaction:

The hydroxyl radicals formed have a very high oxidizing capacity. Hydroxyl radicals allow the mineralization of pollutants of different natures present in solution.

This reaction of formation of hydroxyl radicals is accompanied by a parasitic reaction of formation of dihydrogen on the surface of the cathode. This last reaction is as follows:

The electrocatalytic device, object of the invention, makes it possible to generate hydroxyl radicals by anodic oxidation while considerably reducing the formation of gaseous dihydrogen, which is highly explosive. The charges essential to the parasitic reaction mentioned above are captured by the electric capacitor or by the electric accumulator, so as to prevent the formation of dihydrogen.

These provisions secure the polluted water treatment installations housing the electrocatalytic device that is the subject of the invention and make it possible to avoid the implementation of means of renewal and circulation of the air essential for securing the installations of the prior art. .

It is specified that “anodic oxidation”, also called “electro-oxidation”, designates the ability of positively polarized electrodes (anodes) to behave as oxidizing walls. The more general term “electrocatalysis” can also be used.

In the context of the present application, the term "anodic oxidation" denotes the reaction which takes place in an aqueous medium in two consecutive stages:

The first step of anodic oxidation is a step of generation of hydroxyl radicals from adsorbed hydroxyl anions. This reaction applies in particular to the oxidative treatment of polluted waters, it promotes the partial catalytic oxidation of the hydroxyl anions on the surface sites which are designated for the anode surfaces composed of oxides under the name of basic centers of Lewis.

The second stage of anodic oxidation is a stage of electrolysis of water which itself takes place by total oxidation of the adsorbed hydroxyl anions to oxygen gas (abbreviated from OER meaning Oxygen Evolution Reaction ).

In some embodiments, the electrocatalytic device comprises an electric accumulator which acts as the main consumer of the additional charges generated at the anode, resulting from the electrocatalytic formation of hydroxyl radicals or from the direct oxidation of soluble organic compounds, and a capacitor electric configured to recover the charges not accumulated by the electric accumulator.

Thanks to these provisions, the electric accumulator recovers the charges resulting from the anodic oxidation reactions described above and the capacitor makes it possible to trap at least part of the electric charges which are not captured by the accumulator. The capacitor can capture charges generated during the charging period of the accumulator and/or when the accumulator is no longer able to accept all of the excess charges generated at the anode.

In other words, the electrocatalytic device comprises, in addition to the accumulator which acts as the main electrical consumer, a capacitor positioned in parallel with the main circuit and which can be connected to a secondary electrical consumer.

Thanks to these provisions, the excess electrical charges (not picked up by the main consumer) are accumulated at the terminals of the electrical capacitor.

In embodiments, a secondary electrical consumer is connected across the capacitor.

Thanks to these provisions, the excess electrical charges (not picked up by the main consumer) accumulated at the terminals of the electrical capacitor are dissipated or recovered by the secondary electrical consumer. The secondary electrical consumer is for example an accumulator (rechargeable battery) or an electrical resistor (dissipation by Joule effect).

Advantageously, the discharge of the capacitor is carried out at regular time intervals or when a predetermined charge is reached at the terminals of the capacitor.

The electrical charges recovered can in particular be additional charges generated by the oxidation reactions which take place on the surfaces of the anodes.

In particular, these electric charges can be generated during the reaction for the formation of hydroxyl radicals, represented below in a generalized and simplified manner.

In particular, these electric charges can be generated during the electrolysis of water itself by total oxidation of the adsorbed hydroxyl anions up to gaseous oxygen, below represented generalized and simplified.

It is emphasized that other well-known hydrolysis reactions can generate additional charges. These reactions are not detailed here.

In embodiments, the electric capacitor and/or the electric accumulator are electrically connected directly to the anode.

Within the meaning of the invention, a direct electrical connection between the anode and the electrical capacitor means that these two components are directly connected by an electrical wire, with no component placed between them, other than one or more electrical resistors.

Thanks to these provisions, the electrical charges generated at the anode are picked up more easily by the electrical capacitor or by the electrical accumulator.

In some embodiments, the electrocatalytic device comprises a sensor for measuring a physical value representative of the electric current flowing in the electrocatalytic device or in one of its components and an actuator controlling the opening or closing of a switch, positioned on the shunt electrical circuit across the terminals of the electrical capacitor, depending on the physical value measured.

In some embodiments, the physical value representative of the electrical current flowing in the measured electrocatalytic device is a charge rate of the capacitor.

In some embodiments, the physical value representative of the electrical current flowing in the measured electrocatalytic device is an electrical voltage value. Preferably, the electrical voltage value is measured by a voltmeter positioned across the terminals of the capacitor.

In embodiments, the anode and the cathode are inert with respect to the electrolyte liquid.

Thanks to these provisions, the electrodes do not deteriorate in contact with the electrolytic liquid and during the reactions.

In embodiments, the anode is a conductive oxide anode and the cathode is a metal cathode or a conductive oxide cathode resistant to medium conditions.

According to a second aspect, the invention relates to a secure process for the electrocatalytic treatment of water, by means of a secure device for the electrocatalytic treatment of water, which comprises the following steps:
- application of an electric voltage between an anode and a cathode immersed in an electrolytic liquid,
- electrocatalytic generation of hydroxyl radicals and electrical charges on the anode surface,
- Storage of electric charges by an electric accumulator and/or an electric capacitor electrically connected to the anode, in order to prevent the appearance of explosive gases at the cathode, in particular in order to prevent the appearance of dihydrogen.

In some embodiments, the method includes a step of dissipating or recovering the electrical charges stored by the electrical capacitor by means of a secondary electrical consumer electrically connected to the terminals of the electrical capacitor.

The step of dissipating or recovering the electrical charges stored by the electrical capacitor by means of a secondary electrical consumer aims to recover the excess charges, that is to say the charges not accumulated by the accumulator which acts as the main consumer. .

In some embodiments, the method comprises a step of measuring a physical value representative of the current flowing in the capacitor or in the electric circuit electrically connected to the electric capacitor and in which the step of dissipating the electric charges is initiated as a function of the measured physical value.

In some embodiments, the electrical charge dissipation step is initiated as a function of the charge rate of the capacitor.

In some embodiments, the method comprises a step of storing electrical charges resulting from the electrocatalytic formation of hydroxyl radicals or from the direct oxidation of soluble organic compounds, by means of a rechargeable electric battery.

The aims, advantages and particular characteristics of the method which is the subject of the present invention being similar to those of the device which is the subject of the present invention, they are not repeated here.

Other advantages, aims and particular characteristics of the invention will emerge from the non-limiting description which follows of at least one particular embodiment of the device and of the method which are the subject of the present invention, with reference to the appended drawings, in which:

represents, schematically, a first particular embodiment of a secure electrocatalytic water treatment device, object of the present invention,

represents, schematically, a second particular embodiment of a secure electrocatalytic water treatment device, object of the present invention, and

represents, schematically and in the form of a flowchart, a particular succession of steps of the secure electrocatalytic process for treating water which is the subject of the present invention.

This description is given on a non-limiting basis, each characteristic of an embodiment being able to be combined with any other characteristic of any other embodiment in an advantageous manner.

Note that the figures are not to scale.

We observe, in FIG. 1, which is not to scale, a schematic view of an embodiment of the secure device 100 for the electrocatalytic treatment of water, which is the subject of the present invention.

The device 100 comprises an electrical voltage source 130, for example it is a connection to the electrical network or a current generator. Preferably, the electrical energy source used is a renewable energy source, for example the electrical voltage source 130 is a solar panel. Preferably, the electric voltage source 130 is a direct current source.

The electric voltage source 130 is electrically connected via electric cables to the electrodes of an electrocatalytic cell. The electrocatalytic cell comprises a reservoir 110 containing an electrolytic liquid 105. The electrocatalytic cell comprises two electrodes, respectively an anode 120 and a cathode 115.

The voltage applied between the anode 120 and the cathode 115 makes it possible to generate hydroxyl radicals by electrocatalytic oxidation of water. The hydroxyl radicals formed on the anode surface make it possible to mineralize the pollutants present in solution in the tank 110.

In embodiments, anode 120 and cathode 115 are inert to electrolytic liquid. In embodiments, the material forming the anode 120 comprises a conductive oxide. In embodiments, the cathode 115 is made of metal, for example golden copper.

The device 100 comprises a means 101 configured to capture electric charges so as to make these electric charges unavailable for the parasitic reaction of formation of dihydrogen. In embodiments, the means 101 comprises an electric capacitor. In embodiments, the means 101 comprises an electric accumulator. Preferably, the means 101 is positioned on a bypass circuit which further comprises a resistor 136.

Preferably, an electrical resistor 135 is also present as a shunt to the resistor 136. It is sized to force the additional charges generated from the operation of the electrocatalytic cell to be accumulated at the terminals of or captured by the means 101 configured to capture electrical charges. .

We observe, in FIG. 2, which is not to scale, a schematic view of an embodiment of the secure device 200 for the electrocatalytic treatment of water, which is the subject of the present invention.

The elements of device 100 already described in FIG. 1 are also present on device 200 with the exception of means 101. These elements are not described again here.

Device 200 includes an electrical capacitor 125 electrically connected to the electrocatalytic cell. Preferably, the electric capacitor 125 is electrically connected directly to the anode 120.

The device 200 comprises an electric accumulator 140 electrically connected to the electrocatalytic cell. Preferably, the electric accumulator 140 is electrically connected directly to the anode 120.

Within the meaning of the invention, a direct electrical connection between the anode 120 and the electrical capacitor 125 and/or the electrical accumulator 140 means that these components are connected to the anode directly by an electrical wire, with no component other than an electrical resistor placed between them.

The electric capacitor 125 is an electronic component consisting of two conductive armatures separated by a polarizable insulator. A capacitor has the property of being able to store opposite electric charges on its plates.

The electrical accumulator 140 is a component configured to store electrical energy. In embodiments, the electric accumulator 140 is a battery, for example a lithium-ion battery.

During operation of the electrocatalytic cell, electrical charges are released on the anode surface 120 and, without special preventive measures, can reach the cathode surface, thus causing a hydrogen formation reaction.

The function of the electric capacitor 125 and the accumulator 140 is to capture at least a part of these electric charges and thus to slow down the hydrogen formation reaction.

In embodiments, the device 200 comprises only an electrical capacitor 125 or an accumulator 140.

Preferably, the device 200 comprises an electric capacitor 125 and an accumulator 140.

Preferably, the device 200 is configured so that the accumulator 140 recovers the additional electrical charges generated by reactions at the anode surface 120. Preferably, the capacitor 125 is configured to trap at least some of the electrical charges not captured by the accumulator 140. In other words, capacitor 125 picks up charges when accumulator 140 is no longer able to accept all of the excess charges generated at anode 120. Capacitor 125 then makes it possible to recover the charges not accumulated by element 140.

In embodiments, the electrical voltage source 130 and the electrocatalytic cell are electrically connected in series with a resistor 135. Preferably, the resistor 135 is a variable resistor configured so that the additional charges resulting from the reactions at the anode can be directed to the accumulator 140 and/or to the capacitor 125. In some embodiments, the resistor 135 is configured to keep the intensity of the current flowing through it constant. In some embodiments, the resistance value expressed in ohms of the resistor 135 is controlled by a control means 161 according to the intensity value measured by an ammeter 150. The ammeter 150, the electrical voltage source 130 and the electrocatalytic cell are connected in series.

In embodiments, resistor 135 is a potentiometer.

In embodiments, resistor 135 is a varistor.

In embodiments, the device 200 includes a resistor 136 positioned on the electrical connection between the anode 120 and the electrical accumulator 140 and/or between the anode 120 and the electrical capacitor 125. The inventors have found that if the resistance 135 is too high a part of the charges coming from the current source 130 risks being accumulated in the accumulator 140. The resistance 136 is configured to prevent this phenomenon, at least in part.

In some embodiments, the device 200 comprises a variable resistor 185 positioned on the electrical connection between the electrocatalytic cell and the capacitor 125. The resistance value expressed in ohms of the variable resistor 125 is controlled by a control means 162 depending on of an intensity value measured by a sensor 180 of current intensity. The variation of the value of variable resistor 185 makes it possible to promote the capture of the excess charges generated at the level of the anode surface 120 either towards the accumulator 140 or towards the capacitor 125. Preferably, the capture of the excess charges by the accumulator 140 is favored as long as the accumulator 140 is able to accept the excess charges generated. Excess charges not accumulated by accumulator 140 are picked up by capacitor 125.

In some embodiments, the device 200 comprises, in branch across the terminals of the electrical capacitor 125, a switch 190 and a secondary electrical consumer 195. In some embodiments, the secondary electrical consumer 195 is an electrical resistor. In embodiments, the secondary electrical consumer 195 is a rechargeable battery. In embodiments, secondary electrical consumer 195 is a lithium-ion battery.

In some embodiments, the secure electrocatalytic water treatment device 200 comprises a plurality of capacitors connected in parallel.

The opening and closing of the switch 190 are controlled by an actuator 160. The closing of the switch 190 makes it possible to connect the shunt circuit comprising the secondary electrical consumer 195 to the terminals of the electrical capacitor 125.

In embodiments, the actuator 160 is connected to a clock 165 and actuates the opening and closing of the switch 190 at regular time intervals.

In embodiments, the actuator 160 is connected to an ammeter 181 and actuates the opening and closing of the switch 190 according to the current intensity value measured by the ammeter 181.

In some embodiments, the device 200 comprises a sensor for measuring a physical value representative of the electric current flowing in the electrocatalytic device or in one of its components. In embodiments, this measured physical value is either an electrical voltage value, or an electrical current value, or a charge rate of the capacitor 125.

In embodiments, the actuator 160 is connected to a sensor 150 and the actuator 160 controls the opening or closing of the switch 190 according to the value measured by the sensor 150.

In some embodiments, the value measured by the sensor 150 is an electrical intensity value and the actuator 160 actuates the closing of the switch 190 when the measured intensity value is greater than or equal to a predetermined threshold. Conversely, actuator 160 actuates the opening of switch 190 when the measured intensity value is below a predetermined threshold.

In some embodiments, the actuator 160 actuates the closing of the switch 190 according to the charge rate of the capacitor 125. The charge rate of the capacitor 125 is expressed as a percentage of the maximum possible voltage across the terminals of the capacitor 125. The actuator 160 actuates the closing of the switch 190 when the measured load rate is greater than or equal to a predetermined threshold. In some embodiments, the actuator 160 activates the closing of the switch 190 when the measured load rate is greater than or equal to a predetermined value between 40 and 80%. In embodiments, the actuator 160 actuates the closing of the switch 190 when the measured load rate is greater than or equal to 63%.

In embodiments, the device 200 comprises a switch 145 positioned between the capacitor 125 and the accumulator 140 and a switch 170 positioned between the capacitor 125 and the source of electrical voltage 130. The actuator 160 actuates the opening of the switches 145 and 170 when switch 190 is closed. Conversely, actuator 160 activates the closing of switches 145 and 170 when switch 190 is open. These provisions allow the capacitor 125 to be switched off to allow its discharge by means of the secondary electrical consumer 195.

In embodiments, device 200 includes means 155 configured to prevent electrical accumulator 140 from discharging to capacitor 125. In embodiments, means 155 is a diode.

Figure 3 shows a sequence of specific steps in a process 300 for secure water treatment.

During a step 305 of applying an electric voltage, an electric voltage is supplied between an anode and a cathode immersed in an electrolytic liquid.

During a step 310 of electrocatalytic generation, hydroxyl radicals are generated on the anode surface. This reaction also reveals available charges.

During a step 315 of storing electric charges, at least part of the electric charges generated during step 310 is stored by an electric capacitor and/or by an electric accumulator electrically connected to the anode.

These provisions make it possible to prevent the appearance of explosive gases at the cathode and in particular to prevent the appearance of dihydrogen.

During a step 325 of dissipation or recovery of electric charges, electric charges stored by the electric capacitor are dissipated or recovered by means of a secondary electric consumer.

In some embodiments, during a measurement step 320, a physical value representative of the current flowing in the capacitor or in the electric circuit electrically connected to the electric capacitor is measured. In some embodiments, step 325 is initiated based on the value measured in step 320.

In embodiments, the value measured in step 320 is the capacitor charge rate.

In some embodiments, the method 300 comprises a step of storing electrical charges resulting from the electrocatalytic formation of hydroxyl radicals or from the direct oxidation of soluble organic compounds, by means of an electric battery.

Claims (10)

Safe electrocatalytic water treatment device (100, 200), characterized in that it comprises:
- at least one electrocatalytic cell comprising at least one anode (120) and one cathode (115) immersed in a tank (110) containing electrolytic liquid,
- at least one electric voltage source (130) configured to supply an electric voltage between the cathode and the anode and to generate hydroxyl radicals on the anode surface by electrocatalytic oxidation of water and
- at least one electric accumulator (140) and/or an electric capacitor (125) electrically connected to the anode, in order to prevent the appearance of explosive gases at the cathode, in particular in order to prevent the generation of dihydrogen. Electrocatalytic device according to Claim 1, which comprises an electric accumulator (140) which acts as the main consumer of the additional charges generated at the anode resulting from the electrocatalytic formation of hydroxyl radicals or from the direct oxidation of soluble organic compounds and a capacitor electric (125) configured to recover the charges not accumulated by the electric accumulator. Electrocatalytic device according to one of Claims 1 or 2, in which the electric accumulator and/or the electric capacitor is electrically connected directly to the anode. Electrocatalytic device according to one of Claims 1 to 3, which comprises a secondary electrical consumer (195) positioned on an electrical circuit in shunt across the terminals of the electrical capacitor to recover or dissipate the charges picked up by the latter. Electrocatalytic device according to claim 4, in which the secondary electric consumer is a rechargeable electric battery configured to store the electric charges accumulated at the terminals of the capacitor or a resistor dissipating the electric charges accumulated at the terminals of the capacitor by Joule effect. Electrocatalytic device according to one of Claims 4 to 5, which comprises a measurement sensor (180, 150, 181) of a physical value representative of the electric current flowing in the electrocatalytic device or in one of its components and which comprises an actuator (160) controlling the opening or closing of a switch (190), positioned on the electric circuit in bypass across the terminals of the electric capacitor, according to the physical value measured. An electrocatalytic device according to claim 6, wherein the physical value representative of the electrical current flowing in the measured electrocatalytic device is a charge rate of the capacitor. Electrocatalytic device according to one of Claims 1 to 7, in which the anode and the cathode are inert with respect to the electrolytic liquid. Electrocatalytic device according to one of Claims 1 to 8, in which the anode is a conductive oxide anode and the cathode is a metallic cathode or a conductive oxide cathode resistant to the conditions of the medium. Secure process (300) for the electrocatalytic treatment of water, by means of a secure electrocatalytic water treatment device, characterized in that it comprises the following steps:
- application (305) of an electric voltage between an anode and a cathode immersed in an electrolytic liquid,
- electrocatalytic (310) generation of hydroxyl radicals and electric charges on the anode surface,
- storage (315) of electric charges by an electric accumulator and/or an electric capacitor electrically connected to the anode, in order to prevent the appearance of explosive gases at the cathode, in particular in order to prevent the appearance of dihydrogen.