System and method for treating effluent from an oil platform

Abstract

The invention relates to a system (100) for treating an effluent (1, 3) from an oil platform and comprising a polluting material, said system (100) being configured to receive said effluent (1, 3) from an oil platform, to generate a direct current whose current density is between 1.4 A / m² and 7.5 A / m², in particular between 1.7 A / m² and 5.5 A / m², most particularly between 1.75 A / m² and 1.8 A / m², to carry out the electrozonation of the effluent (1, 3) received by ozone partially decomposed with the direct current generated and thus obtain an electrozoned effluent (9), and to carry out a catalytic ozonation of the electrozoned effluent (9) in order to obtain a treated effluent. Figure for the abstract: Figure 1

Description

Title of the invention: System and method for treating an effluent from an oil platform Technical field

[0001] The present invention relates to the field of treatment of an effluent comprising polluting material and more particularly concerns a system and a method for treating an effluent from an oil platform. Prior art

[0002] It is known to remove polluting matter from an effluent by membrane separation, evapo-concentration or physico-chemical treatment processes. These processes are separation processes and not treatment processes. Their operating costs are very high. They also generate a large quantity of sludge, which is very bulky to store and harmful to the environment because it must be treated.

[0003] Conventional treatment methods also exist. These conventional methods are, for example, flotation, dissolved air or ozone flotation, electrolysis, electrocoagulation, electrozonation or ozoflotation. However, these conventional methods have disadvantages.

[0004] Flotation, dissolved air flotation and dissolved ozone flotation require the addition of chemicals (coagulants and flocculants) to increase their efficiency. Dissolved ozone flotation also requires special equipment and the contact time of the dissolved ozone with the material must be perfectly controlled for this process to be efficient.

[0005] Electrolysis has the disadvantages of electrical consumption, fragility of the electrodes, the problem of electrode clogging due to the formation of scale (limescale and metal oxides) and their frequent replacement. The generation of by-products such as hydrogen and chlorine and the low efficiency also pose problems.

[0006] Electrocoagulation uses the same principle as electrolysis with the addition of coagulant. In addition to the problems of electrolysis, the addition of coagulant increases the volume of sludge generated and involves additional costs.

[0007] The treatment efficiency of electrozonation is satisfactory. However, it has the same drawbacks as electrolysis.

[0008] Ozoflotation is a less efficient process than the conventional treatment processes mentioned above.

[0009] These conventional methods also require a pretreatment step which is difficult to optimize and control, especially in the case of effluent to be treated having variable quality and containing hydrocarbons and / or detergents.

[0010] Another effluent treatment method is described in CN 108 423 893. In this method, the effluent to be treated and the ozone are brought into contact between electrodes, which promotes the oxidation of the effluent to be treated by the ozone and the coagulation of the ozone to eliminate the polluting material from the effluent. Unlike electrolysis, the method described in CN 108 423 893 uses low currents because the current density is 19 mA / cm2, or 190 A / m2. However, the method described in CN 108 423 893 has the disadvantages linked to the electrodes of electrolysis, i.e. fragility of the electrodes, clogging of the electrodes due to the formation of scale and frequent replacement. In addition, the method described in CN 108 423 893 is not very efficient. In fact, the chemical oxygen demand (COD) is only reduced by 48%.Document US5972196A describes a method for sterilizing tools and medical waste by high current density catalysis between 0.1 A / cm2 and 2.5 A / cm2, or between 1000 A / m2 and 25000 A / m2, which requires a large expenditure of electrical energy and is therefore not satisfactory in its application to the treatment of effluents, particularly from an oil platform.

[0011] There is therefore a need for a simple and effective solution to at least partially remedy these drawbacks. Statement of the invention

[0012] For this purpose, the invention firstly relates to a system for treating an effluent from an oil platform and comprising a polluting material, said system being configured to receive said effluent (1, 3) from an oil platform, to generate a direct current whose current density is between 1.4 A / m2 and 7.5 A / m2, in particular between 1.7 A / m2 and 5.5 A / m2, most particularly between 1.75 A / m2 and 1.8 A / m2, to carry out the electrozonation of the effluent (1, 3) received by ozone partially decomposed with the direct current generated and thus obtain an electrozoned effluent (9), and to carry out a catalytic ozonation of the electrozoned effluent (9) in order to obtain a treated effluent. This is then referred to as hybrid ozonation.

[0013] The selected limited value range [1.4 A / m2; 7.5 A / m2] is narrow compared to the known value range and is sufficiently far from any specific example disclosed in the prior art.

[0014] Advantageously, the treatment system of the invention is very efficient. Indeed, the electrozonation step makes it possible to reduce the chemical oxygen demand (COD) by more than 90%. The catalytic ozonation step then makes it possible to reduce the chemical oxygen demand to almost 0 ppm.

[0015] Without wishing to be bound by any theory, the inventor is of the opinion that the high efficiency of the electrozonation step is due to the combination:

[0016] - the oxidizing power of ozone which makes it possible to eliminate part of the matter polluting the effluent by oxidation, and

[0017] - of the coagulating criterion of ozone which allows ozone to fragment another part of the polluting material from the effluent while electrically charging it in order to promote the coagulation, then the flocculation, of the fragmented particles of the polluting material. Advantageously, the coagulating criterion of ozone is promoted and increased by the direct current density included in the ranges indicated above and by the partially decomposed ozone used in the electrozonation step.

[0018] By promoting and increasing the coagulating criterion of ozone, the system of the invention also generates less sludge than conventional systems.

[0019] The use of the selected limited value range [1.4 A / m2; 7.5 A / m2] therefore gives rise to singular technical effects. Furthermore, the person skilled in the art would not have seriously considered working in the selected limited value range [1.4 A / m2; 7.5 A / m2] given that it is unusual and the usual ranges are very different.

[0020] The system of the invention is also economical in electricity because the direct current density implemented during the electrozonation step is low, in particular lower than for electrolysis.

[0021] For the purposes of the present invention, the term "effluent" means a flow, preferably liquid, comprising polluting material. Typically, the effluent may have a chemical oxygen demand (COD) of between 200 mg / L and 13,500 mg / L.

[0022] The effluent used in the system according to the invention is an effluent from an oil platform. The composition of the effluent from an oil platform varies considerably depending on the region, the geology of the formation, the types of fluids, the recovery process, the operating conditions and the management of the oil wells.

[0023] Typically, the polluting material of the effluent from an oil platform may contain suspended particles, dissolved organic products, additives used for oil well management (drilling, completion, fracturing and well treatment), additives used for the conditioning of injection water, additives used for the separation of the fluid leaving an oil well, additives for enhanced oil recovery, dissolved salts, heavy metals, radioactive materials, residues of bacterial activity (biofilm, FeS, etc.) and dissolved gases (CO2, O2, H2S, etc.) and mixtures thereof.

[0024] The suspended particles can be: minerals such as clays, silica, calcium minerals, sulfur minerals, iron minerals, and / or residues of bacterial corrosion, and / or organic such as residual emulsions, bacteria and / or asphaltenes.

[0025] The dissolved organic products may be phenols, naphthalenes, and / or hydrocarbons such as a mixture of benzene, toluene, ethylbenzene and xylene (BTEX) or polycyclic aromatic hydrocarbons (PAH). Additives used for enhanced oil recovery may be alkaline additives, surfactants, polymers and / or bacteria.

[0026] In one embodiment, the system comprises a reactor comprising a side wall having a cylindrical shape along a vertical axis of revolution and a bottom delimiting a reaction space.

[0027] Advantageously, the reactor comprises a porous membrane positioned in the reaction space.

[0028] Advantageously, the reactor comprises at least two electrodes, including at least one anode and at least one cathode, for example exactly two electrodes: one anode and one cathode.

[0029] Preferably, the electrodes have a tubular circular cylindrical shape.

[0030] More preferably, the electrodes are made of aluminum.

[0031] Advantageously, the electrodes are positioned in the reaction space, upstream of the porous membrane in the direction of an ozone flow and concentrically with respect to each other and, possibly with respect to the side wall.

[0032] Advantageously, the reactor comprises a port for injecting a mixture of ozone and effluent located at the bottom of the reactor, preferably positioned upstream of the porous membrane positioned in the reaction space.

[0033] Advantageously, the system comprises a porous membrane, preferably placed in the reactor, configured to provide the partially decomposed ozone by filtering a received ozone stream, said membrane comprising a support and a metal oxide on the surface of the support, the support being selected from an oxidized ceramic, a metal alloy, a chromium compound and mixtures thereof, and the metal oxide being selected from titanium dioxide, manganese oxide, cerium oxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof, the partially decomposed ozone being obtained by passing a stream of ozone through said porous membrane.

[0034] Preferably, the partially decomposed ozone comprises between 1% by mass and 99.9% by mass of ozone.

[0035] Advantageously, the system comprises a catalyst for implementing catalytic ozonation, said catalyst comprising a support chosen from an activated alumina, a clay, an activated carbon, an oxidized ceramic and their mixtures, and an active phase on the surface of the support and chosen from palladium, a metal alloy, manganese oxide, cerium oxide, titanium dioxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof.

[0036] Advantageously, the system is configured to pretreat the effluent received by dissolved air flotation in order to obtain a pretreated effluent, this pretreated effluent then being used in electrozonation to obtain a flotelectrozoned effluent. This is then referred to as flotelectrozonation.

[0037] Advantageously, the system is configured to carry out an evapo-concentration of the effluent making it possible to obtain a concentrated effluent, this concentrated effluent then being used in electrozonation or in pretreatment by dissolved air flotation.

[0038] In addition to the electrozoned effluent, a residue can be obtained as a result of electrozoning the received effluent with partially decomposed ozone with the generated direct current.

[0039] Advantageously, the system is configured to recycle the residue obtained during electrozonation in the unit / step for pre-treatment of the effluent by dissolved air flotation.

[0040] Advantageously, the system is configured to treat the electrozoned effluent by low-pressure dissolved air flotation in order to obtain a treated flotelectrozoned effluent, this treated flotelectrozoned effluent then undergoing the catalytic ozonation step.

[0041] The invention also relates to a method for treating an effluent from an oil platform and comprising a polluting material, said method comprising a step of electrozonation of the effluent from an oil platform by partially decomposed ozone to obtain an electrozoned effluent, the electrozonation being carried out with a direct current density of between 1.4 A / m2 and 7.5 A / m2, in particular between 1.7 A / m2 and 5.5 A / m2, most particularly between 1.75 A / m2 and 1.8 A / m2, and a step of catalytic ozonation of said electrozoned effluent in order to obtain a treated effluent.

[0042] Advantageously, the partially decomposed ozone comprises between 1% by mass and 99.9% by mass of ozone.

[0043] Advantageously, the step of electrozoning the effluent is carried out in a reactor, said reactor comprising a side wall having a cylindrical shape along a vertical axis of revolution and a bottom delimiting a reaction space, an ozone injection port and an effluent injection port or a port for injecting a mixture of ozone and effluent, and at least two electrodes, an anode and a cathode, in the reaction space.

[0044] Advantageously, the partially decomposed ozone is obtained by passing a flow of ozone through a porous membrane comprising a support and a metal oxide. metal on the surface of the support, the support being selected from an oxidized ceramic, a metal alloy, a chrome compound and mixtures thereof, and the metal oxide being selected from titanium dioxide, manganese oxide, cerium oxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof.

[0045] In a preferred embodiment, ozone and effluent are injected into the reaction space and pass through the porous membrane to produce partially decomposed ozone, to destabilize foams and to settle large particles from the effluent. Then, between the two electrodes, the pollutant material in the effluent is treated with the partially decomposed ozone. The residue can then be easily separated from the electrozoned effluent on top of the reactor.

[0046] Advantageously, the method further comprises, before the electrozonation step, a pretreatment step by dissolved air flotation making it possible to obtain a pretreated effluent, this pretreated effluent then being used in the electrozonation step to obtain a flotelectrozoned effluent. This is then referred to as flotelectrozonation.

[0047] Advantageously, the method further comprises, before the electrozonation step or before the dissolved air flotation pretreatment step, a step of evaporation-concentration of the effluent making it possible to obtain a concentrated effluent, this concentrated effluent then being used in the electrozonation step or in the dissolved air flotation pretreatment step.

[0048] Advantageously, the residue obtained during the electrozonation step is recycled in the unit / step for pretreatment of the effluent by dissolved air flotation.

[0049] Advantageously, the method further comprises, between the electrozonation step and the catalytic ozonation step, a step of treatment by low-pressure dissolved air flotation of the electrozoned effluent obtained during the electrozonation step to obtain a treated electrozoned effluent, this treated electrozoned effluent then undergoing the catalytic ozonation step.

[0050] Advantageously, the catalytic ozonation step of the effluent is carried out by a catalyst comprising a support chosen from an activated alumina, a clay, an activated carbon, an oxidized ceramic and their mixtures, in particular from activated alumina, clay, activated carbon and their mixtures, most particularly being activated alumina or activated carbon,

[0051] Advantageously, the catalytic ozonation step of the effluent is carried out by a catalyst comprising an active phase chosen from palladium, a metal alloy, manganese oxide, cerium oxide, titanium dioxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof, in particular palladium, the metal alloy, manganese oxide, cerium oxide and mixtures thereof, most particularly being a mixture of palladium and the metal alloy, a mixture of palladium and manganese oxide or a mixture of palladium, oxide manganese and cerium oxide.

[0052] Advantageously, the method further comprises, after the catalytic ozonation step, a step of disinfecting a mixture comprising the treated effluent and ozone by passing this mixture through a porous membrane to obtain a disinfected effluent. Brief description of the drawings

[0053] Other characteristics and advantages of the invention will become apparent upon reading the description which follows. This description is purely illustrative and should be read in conjunction with the appended drawings in which:

[0054] [Fig-1] [Fig.l] schematically illustrates an embodiment of the system according to the invention.

[0055] [Fig.2] [Fig.2] schematically illustrates an embodiment of the method according to the invention. Description of the embodiments

[0056] [Fig.l] illustrates an example of a system 100 according to the invention for treating an effluent 1 from an oil platform.

[0057] System 100

[0058] With reference to [Fig.l], the system 100 comprises a pretreatment unit 2, an anti-scale treatment unit 4, a reactor 6 and a catalytic ozonation unit 10

[0059] Pretreatment unit 2

[0060] The pretreatment unit 2 is configured to carry out a pretreatment by dissolved air flotation of the effluent 1 in order to obtain a pretreated effluent 3. The effluent 1 can undergo pre-ozonation before its admission into the pretreatment unit 2, in a manner known per se.

[0061] Anti-scale treatment unit 4

[0062] The anti-scale treatment unit 4 is configured to carry out an anti-scale treatment of the pre-treated effluent 3 before being mixed with ozone 5.

[0063] Reactor 6

[0064] The reactor 6 comprises a porous membrane 7 and electrodes 8 and defines a reaction space.

[0065] According to a particular embodiment, the reactor 6 comprises: a side wall having a cylindrical shape along a vertical axis of revolution and a bottom delimiting a reaction space, an ozone injection port and an effluent injection port or a port for injecting a mixture of ozone and effluent (not shown for the sake of clarity), and at least two electrodes 8, an anode and a cathode, in the reaction space.

[0066] For the purposes of the present invention, the term "wall having a cy shape" is understood to mean: lindrique" a wall in the general shape of a cylinder, a cylinder being a surface generated by a straight line which moves parallel to the vertical axis of revolution, resting on two fixed planes. Typically, the cylinder may be a prism with a polygonal base such as a prism with a triangular base, a square base or a rectangular base. The cylinder may also be a circular cylinder, in particular a right circular cylinder characterized by a radius r and a height h. According to a specific embodiment the cylinder is a circular cylinder so that the side wall has a right circular cylindrical shape.

[0067] For the purposes of the present invention, the term "reaction space" means the internal part of the reactor, i.e. the volume between the side wall and the bottom, the reactor being open at the top and possibly having no cover to facilitate the recovery of the residue and the preozonated effluent obtained during electrozonation.

[0068] For the purposes of the present invention, the term "ozone injection port" means any element adapted to introduce a flow of ozone or partially decomposed ozone into the reaction space of the reactor. Typically, the ozone injection port is adapted to be connected to a gas line. For example, the ozone injection port may be a gas connection.

[0069] For the purposes of the present invention, the term "effluent injection port" means any element adapted to introduce a flow of the effluent intended to undergo electrozonation into the reaction space of the reactor. Typically, the effluent injection port is adapted to be connected to a liquid line. For example, the effluent injection port may be a liquid connection.

[0070] For the purposes of the present invention, the term "port for injecting a mixture of ozone and effluent" means any element adapted to introduce a flow of mixture of ozone and effluent intended to undergo electrozonation in the reaction space of the reactor. Typically, this effluent injection port is adapted to be connected to a pipe containing a gas / liquid mixture.

[0071] The ozone injection port, the effluent injection port, the port for injecting a mixture of ozone and effluent may be located at a lower part of the reactor, preferably at the bottom of the reactor. This configuration is suitable for operation of the reactor in co-current mode.

[0072] For the purposes of the present invention, the terms "bottom", "low", "high", "above" and "vertical" are used to designate elements of the reactor 6 implementing the electrozonation of the process of the invention and must therefore be considered when the reactor 6 is in its normal position of use.

[0073] Membrane 7

[0074] The porous membrane 7 is configured to partially decompose the ozone 5, to destabilize the foams and to settle the bulky particles from the effluent. pretreated 3. The porous membrane 7 is also configured to destabilize the calcium ions of the pretreated effluent 3, thus protecting the electrodes 8 from possible limescale deposits and consequently promoting the coagulating criterion of ozone which allows the ozone to fragment part of the polluting material of the pretreated effluent 3 while electrically charging it in order to promote the coagulation, then the flocculation, of the fragmented particles of the polluting material.

[0075] For the purposes of the present invention, the term "partially decomposed ozone" means a mixture of ozone and compounds resulting from the decomposition of ozone such as hydroxyl radicals "OH" and singlet oxygens.

[0076] Typically, the partially decomposed ozone may comprise between 1% by mass and 99.9% by mass, in particular between 5% by mass and 90% by mass, most particularly between 10% by mass and 50% by mass of ozone. In the present application, these mass percentages are defined relative to the total mass of the partially decomposed ozone.

[0077] According to one embodiment, the partially decomposed ozone is obtained by passing, preferably at a constant flow rate, a flow of ozone through the porous membrane 7. For this purpose, the porous membrane 7 comprises a support and a metal oxide on the surface of the support. The passage of the flow of ozone through the porous membrane 7 can be done at the temperature of the effluent.

[0078] Typically, the porous membrane 7 may have a porosity of between 5 and 80, in particular between 15 and 50, most particularly between 21 and 27. The porosity may be determined according to standard NF ISO 5017 (May 2013).

[0079] The porous membrane 7 can be obtained by one of the methods of synthesis of porous membranes known to those skilled in the art.

[0080] The support of the porous membrane 7 can be chosen from an oxidized ceramic, a metal alloy, a chrome compound and their mixtures, in particular from the oxidized ceramic and a mixture of the metal alloy and the chrome compound.

[0081] For the purposes of the present invention, the term "oxide ceramic" means a ceramic consisting mainly of one or more metal oxides such as aluminum oxide, zirconium dioxide, titanium dioxide and mixtures thereof, in particular a mixture of aluminum oxide, zirconium dioxide and titanium dioxide.

[0082] Typically the oxidized ceramic may comprise: between 80% by mass and 99% by mass, in particular between 90% by mass and 95% by mass, very particularly between 92% by mass and 94% by mass of aluminum oxide, 10% by mass or less, in particular between 2% by mass and 9% by mass, very particularly between 4.5% by mass and 5.5% by mass of titanium dioxide, and 10% by mass or less, in particular between 1% by mass and 3% by mass, very particularly between 1.5% by mass and 2.5% by mass of zirconium dioxide. In the present application, these mass percentages are defined relative to the total mass of the oxidized ceramic.

[0083] Typically, the metal alloy may comprise iron, chromium, nickel, carbon, molybdenum or mixtures thereof.

[0084] According to one embodiment, the metal alloy may comprise: at least 10% by mass, in particular between 15% by mass and 25% by mass, very particularly between 16% by mass and 19% by mass of chromium, at least 5% by mass, in particular between 7% by mass and 15% by mass, very particularly between 8% by mass and 13% by mass of nickel, 2% by mass or less, in particular 1% by mass or less, very particularly between 0.01% by mass and 0.1% by mass of carbon, optionally 10% by mass or less, in particular between 0.5% by mass and 5% by mass, very particularly between 1% by mass and 3% by mass of molybdenum, the remainder being iron. In the present application, these mass percentages are defined relative to the total mass of the metal alloy. For the purposes of the present invention, "the remainder being iron" means iron and unavoidable impurities.

[0085] According to a particular embodiment, the metal alloy may comprise: between 16% by mass and 19% by mass of chromium, between 8% by mass and 13% by mass of nickel, between 0.01% by mass and 0.1% by mass of carbon, the remainder being iron.

[0086] According to another particular embodiment, the metal alloy may comprise: between 16% by mass and 19% by mass of chromium, between 8% by mass and 13% by mass of nickel, between 0.01% by mass and 0.1% by mass of carbon, between 1% by mass and 3% by mass of molybdenum, the remainder being iron.

[0087] The chrome compound is a metal alloy which may comprise: between 0.1% by mass and 20% by mass, in particular between 16.5% by mass and 18% by mass of chromium, between 4% by mass and 25% by mass, in particular between 10% by mass and 13% by mass of nickel, 0.06% by mass or less, in particular 0.03% by mass or less of carbon, between 1% by mass and 3% by mass, in particular between 2% by mass and 2.5% by mass of molybdenum, the remainder being iron. In the present application, these mass percentages are defined relative to the total mass of chrome compound.

[0088] According to a particular embodiment, the mixture of the metal alloy and the chrome compound may comprise more than 50% by mass of iron, between 0.07% by mass and 0.3% by mass of carbon, between 10.5% by mass and 26% by mass of chromium and between 9% by mass and 21% by mass of nickel. In the present application, these mass percentages are defined relative to the total mass of the mixture of the metal alloy and the chrome compound.

[0089] According to another particular embodiment, the mixture of the metal alloy and the chrome compound may comprise more than 50% by mass of iron, between 0.07% mass and 0.3% mass of carbon, between 16% mass and 26% mass of chromium, between 1.5% mass and 21% mass of nickel and between 1% mass and 3% mass of molybdenum.

[0090] The metal oxide of the porous membrane may, for example, be chosen from titanium dioxide, manganese oxide, cerium oxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof, in particular from titanium dioxide, iron oxide, aluminum oxide and mixtures thereof, more particularly being titanium dioxide.

[0091] The support and the metal oxide of the porous membrane 7 are chosen independently of each other by a person skilled in the art. However, a person skilled in the art will avoid choosing the same metal oxide as a support (if the support is an oxidized ceramic) and as a metal oxide. For example, a person skilled in the art will avoid choosing aluminum oxide, or titanium dioxide, as a support and as a metal oxide. A person skilled in the art may nevertheless choose an oxidized ceramic comprising a mixture of metal oxides as a support and a metal oxide from this mixture as a metal oxide. For example, a person skilled in the art may choose an oxidized ceramic comprising a mixture of aluminum oxide, titanium dioxide and zirconium dioxide as a support and titanium dioxide as a metal oxide.

[0092] The porous membrane 7 may comprise less than 50% by mass, in particular between 0.1% by mass and 30% by mass, most particularly between 1% by mass and 5% by mass of metal oxide. In the present application, these mass percentages are defined relative to the total mass of the porous membrane 7.

[0093] The porous membrane 7 may comprise 50% by mass or more, in particular between 70% by mass and 99.9% by mass, most particularly between 95% by mass and 99% by mass of support. In the present application, these mass percentages are defined relative to the total mass of the porous membrane 7.

[0094] Typically, in the porous membrane 7, the mass content of metal oxide represents between 1% and 99%, in particular between 1% and 30%, very particularly between 1% and 5.5% of the mass content of support.

[0095] According to a particular embodiment, the porous membrane 7 may have a porosity of between 21 and 27, and comprise: between 1% by mass and 5% by mass of titanium dioxide as metal oxide, and between 95% by mass and 99% by mass of the mixture of the metal alloy and the chrome compound as support, said mixture of the metal alloy and the chrome compound comprising between 0.07% by mass and 0.3% by mass of carbon, between 16% by mass and 26% by mass of chromium and between 1.5% by mass and 21% by mass of nickel.

[0096] According to a particular embodiment, the porous membrane 7 may have a porosity between 21 and 27, and comprising: between 3% by mass and 7% by mass of titanium dioxide as a metal oxide, and between 93% by mass and 97% by mass of an oxidized ceramic as a support, said oxidized ceramic comprising between 92% by mass and 94% by mass of aluminum oxide, between 4.5% by mass and 5.5% by mass of titanium dioxide, and between 1.5% by mass and 2.5% by mass of zirconium dioxide.

[0097] According to one embodiment, the effluent can also pass through the porous membrane 7. Advantageously, this can make it possible to destabilize the foams and to settle the large particles of the effluent and therefore to increase the efficiency of the electrozonation. This also makes it possible to destabilize the calcium ions possibly present in the effluent, thus protecting the electrodes used during the electrozonation from a possible deposit of limestone and therefore from clogging. This embodiment advantageously makes it possible to space out the duration between two replacements of the electrodes used in the electrozonation.

[0098] The reactor 6 preferably comprises the porous membrane 7 in the reaction space at the outlet of the ozone injection port and possibly the effluent injection port, or the port for injecting a mixture of ozone and effluent. This configuration allows the ozone injected into the reaction space to pass through the porous membrane 7 to be partially decomposed and that, possibly, the effluent injected into the reaction space also passes through the porous membrane 7.

[0099] Electrodes 8

[0100] The reactor 6 comprises at least two electrodes 8, an anode and a cathode, for carrying out the electrozonation. Typically, the anode may be made of titanium, iron, aluminum or their mixtures, in particular iron, aluminum or their mixtures, especially aluminum. The cathode may, for example, be made of titanium, iron, aluminum or their mixtures, in particular iron, aluminum or their mixtures, especially aluminum.

[0101] Each of the electrodes 8 implemented in the electrozonation may have a plate shape, a solid cylindrical shape or a tubular cylindrical shape. When the electrode 8 has a solid cylindrical shape then it may have a solid circular cylindrical shape. When the electrode 8 has a tubular cylindrical shape then it may have a tubular circular cylindrical shape.

[0102] Preferably, the electrodes are positioned concentrically with respect to each other, and optionally with respect to the side wall of the reactor.

[0103] The reactor 6 may also comprise a system for cleaning the electrodes 8. This system may, for example, be a scraper, a rotating brush or both.

[0104] Catalytic ozonation unit 10

[0105] With reference to [Fig.l], the catalytic ozonation unit 10 is configured to receive the electrozoned effluent 9 comprising residual polluting material and concentrated ozone and to remove said residual polluting material. The residue 11 from the reactor 6 is preferably recycled into the pretreatment unit 2.

[0106] In order to carry out the catalytic ozonation of the electrozoned effluent, the catalytic ozonation unit 10 comprises a catalyst. Said catalyst typically comprises a support and an active phase on the surface of the support.

[0107] The catalyst support may be chosen from an activated alumina, a clay, an activated carbon, an oxidized ceramic and their mixtures, in particular from activated alumina, clay, activated carbon and their mixtures, in particular being activated alumina or activated carbon.

[0108] Advantageously, these supports can absorb part of the residual polluting material and therefore increase the efficiency of catalytic ozonation.

[0109] For the purposes of the present invention, the term "activated alumina" means a porous aluminum oxide with a high specific surface area, i.e. a specific surface area of, for example, between 200 m2 / g and 350 m2 / g. Typically, the high specific surface area can be determined by the method based on the Brunauer, Emmett and Teller theory (BET method) according to standard ISO 9277:2010.

[0110] For example, the clay may be kaolinite, particularly Kaolinite KGa-2. The oxidized ceramic of the catalyst support is the same as that of the porous membrane support described above.

[0111] The active phase of the catalyst may be chosen from palladium, a metal alloy, manganese oxide, cerium oxide, titanium dioxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof, in particular palladium, the metal alloy, manganese oxide, cerium oxide and mixtures thereof, in particular being a mixture of palladium and the metal alloy, a mixture of palladium and manganese oxide or a mixture of palladium, manganese oxide and cerium oxide.

[0112] Advantageously, catalytic ozonation is very efficient with such an active phase.

[0113] The metal alloy of the active phase of the catalyst is the same as that of the support of the porous membrane described above.

[0114] The support and the active phase of the catalyst are chosen independently of each other by a person skilled in the art. However, a person skilled in the art will avoid choosing the same metal oxide as a support (if the support is an oxidized ceramic or an activated alumina) and as an active phase. For example, a person skilled in the art will avoid choosing aluminum oxide, or titanium dioxide, as a support and as an active phase. A person skilled in the art may nevertheless choose an oxidized ceramic comprising a mixture of metal oxides as a support and a metal oxide of this mixture as the active phase. For example, a person skilled in the art may choose an oxidized ceramic comprising a mixture of aluminum oxide, titanium dioxide and zirconium dioxide as the support and titanium dioxide as the active phase.

[0115] The catalyst may comprise less than 50% by mass, in particular between 0.1% by mass and 30% by mass, most particularly between 1% by mass and 5% by mass of active phase. In the present application, these mass percentages are defined relative to the total mass of the catalyst.

[0116] The catalyst may comprise 50% by mass or more, in particular between 70% by mass and 99.9% by mass, most particularly between 95% by mass and 99% by mass of support. In the present application, these mass percentages are defined relative to the total mass of the catalyst.

[0117] Typically, in the catalyst, the mass content of active phase represents between 1% and 99%, in particular between 1% and 30%, very particularly between 1% and 5.5% of the mass content of support.

[0118] According to one embodiment, the catalyst may comprise: a support chosen from an activated alumina, a clay, an activated carbon, an oxidized ceramic and their mixtures, in particular from activated alumina, clay, activated carbon and their mixtures, very particularly being activated alumina or activated carbon, and an active phase chosen from palladium, the metal alloy, manganese oxide, cerium oxide, titanium dioxide, iron oxide, copper oxide, aluminum oxide and their mixtures, in particular palladium, the metal alloy, manganese oxide, cerium oxide and their mixtures, very particularly being a mixture of palladium and the metal alloy, a mixture of palladium and manganese oxide or a mixture of palladium, manganese oxide and cerium oxide.

[0119] According to a first preferred embodiment: the catalyst support is activated carbon, the support content being between 90% by mass and 99% by mass, in particular between 93% by mass and 95% by mass, most particularly being 94% by mass, and the active phase is a mixture comprising palladium and the metal alloy, the palladium content being between 0.5% by mass and 1.5% by mass relative to the total mass of the catalyst, the metal alloy content being between 4.5% by mass and 5.5% by mass relative to the total mass of the catalyst, and the metal alloy comprising: between 16% by mass and 19% by mass of chromium, between 8% by mass and 13% by mass of nickel, between 0.01% by mass and 0.1% by mass of carbon, the remainder being iron, or between 16% by mass and 19% by mass of chromium, between 8% by mass and 13% by mass of nickel, between 0.01% by mass and 0.1% by mass of carbon, between 1% by mass and 3% by mass of molybdenum,the rest being iron.

[0120] According to a second preferred embodiment: the catalyst support is activated alumina, the content of the support being between 90% by mass and 99% by mass, in particular between 93% by mass and 95% by mass, most particularly being 94% by mass, and the active phase is a mixture comprising palladium and manganese oxide, the palladium content being between 0.5% by mass and 1.5% by mass relative to the total mass of the catalyst and the manganese oxide content being between 4% by mass and 6% by mass relative to the total mass of the catalyst.

[0121] According to a third preferred embodiment: the catalyst support is clay, the content of the support being between 90% by mass and 99% by mass, in particular between 92% by mass and 95% by mass, most particularly being 93% by mass, and the active phase is a mixture comprising palladium, metal alloy and cerium oxide, the palladium content being between 0.5% by mass and 1.5% by mass relative to the total mass of the catalyst, the manganese oxide content being between 4% by mass and 6% by mass relative to the total mass of the catalyst and the cerium oxide content being between 0.5% by mass and 1.5% by mass relative to the total mass of the catalyst.

[0122] Advantageously, the catalysts of these preferred embodiments make it possible to obtain an ozonation rate of between 0.2 and 0.4 g of ozone / g of COD. This ozonation rate is much lower than the theoretical rate of 1 g of ozone / g of COD. The catalytic ozonation step of the process of the invention using these catalysts therefore requires little ozone to be effective.

[0123] The catalyst can be obtained by one of the catalyst synthesis methods known to those skilled in the art.

[0124] Example of implementation

[0125] The process comprises several steps E1...E8 including an electrozonation step E6 and a catalytic ozonation step E7.

[0126] In a step E1, the effluent 1 undergoes preozonation (optional) before its admission into unit 2.

[0127] Since oils and materials that can trap ozone can reduce the effectiveness of the electrozonation step E6, the effluent 1 undergoes a pretreatment step by dissolved air flotation in the pretreatment unit 2 in a step E2, in order to obtain a pretreated effluent 3. The contents of oils and materials that can trap ozone in the pretreated effluent are lower than the contents of oils and materials that can trap ozone in the effluent, in particular these contents can advantageously be zero. The pretreatment step E2 by dissolved air flotation is a conventional step for those skilled in the art who will know how to implement it.

[0128] Then, preferably, in a step E3, the pretreated effluent 3 undergoes a treatment anti-limescale passing through the anti-limescale treatment unit 4 before being mixed with ozone 5 in a step E4.

[0129] This mixture is then injected into the bottom of the reactor 6 and passes through the porous membrane 7 in a step E5 before undergoing electrozonation by the electrodes 8 in a step E6.

[0130] The porous membrane 7 allows the partial decomposition of the ozone 5, the destabilization of the foams and the decantation of large particles from the pretreated effluent 3. The porous membrane 7 also allows the destabilization of the calcium ions of the pretreated effluent 3, thus protecting the electrodes 8 from a possible limescale deposit and consequently promoting the coagulating criterion of the ozone which allows the ozone to fragment a part of the polluting material of the pretreated effluent 3 while electrically charging it in order to promote the coagulation, then the flocculation, of the fragmented particles of the polluting material.

[0131] Electrozonation E6 of the effluent 1 by partially decomposed ozone is carried out with a direct current density of between 1.4 A / m2 and 7.5 A / m2, in particular between 1.7 A / m2 and 5.5 A / m2, very particularly between 1.75 A / m2 and 1.8 A / m2.

[0132] During the electrozonation step E6, the effluent 1 undergoes the combined treatment of oxidation by ozone and coagulation of the partially decomposed ozone to obtain on the one hand a residue and on the other hand an electrozoned effluent. Indeed, part of the polluting material of the effluent is eliminated by oxidation with ozone.

[0133] In parallel, under the effect of the electric field generated by the electrodes implemented in the electrozonation step E6, fine ozone bubbles obtained by deformation of ozone bubbles fragment another part of the polluting material of the effluent to obtain fragmented particles of polluting material. The coagulating criterion of ozone charges these fragmented particles of polluting material which facilitates their coagulation and the formation of flocs. The flocs formed are stabilized thanks to the ions generated by the electrodes under the effect of the direct current density. The residue obtained during the electrozonation step E6 can comprise the stabilized flocs and the fragmented particles of coagulated but not flocculated polluting material.

[0134] Typically, the ozone concentration during the electrozonation step E6 may be between 0.1 ppm and 12 ppm, in particular between 0.5 ppm and 5 ppm, more particularly between 1 ppm and 2 ppm.

[0135] Typically, the contact time between the effluent and the partially decomposed ozone may be less than 2 hours, in particular between 15 minutes and 1.5 hours, more particularly between 30 minutes and 1 hour.

[0136] The electrozonation step E6 may not remove all of the polluting material from the effluent. Thus, the electrozoned effluent may comprise polluting material re- side.

[0137] The electrozoned effluent is also concentrated in ozone because it comprises the ozone which has not reacted during the electrozonation step E6. To eliminate the residual polluting material, the electrozoned effluent undergoes the catalytic ozonation step E7. More precisely, the electrozoned effluent 9 comprising residual polluting material and concentrated ozone is sent to the catalytic ozonation unit 10 in order to eliminate the residual polluting material.

[0138] The catalytic ozonation step E7 uses the catalyst described above. The catalytic ozonation step E7 can be carried out with the ozone included in the electrozoned effluent. Thus, advantageously, the treatment method of the invention is economical in ozone because the catalytic ozonation step E7 can be carried out without additional ozone addition.

[0139] The method may further comprise, between step E6 and step E7, a step E6-7 of treatment by low-pressure dissolved air flotation of the electrozoned effluent obtained during step E6 to obtain a treated electrozoned effluent, this treated electrozoned effluent then undergoing the catalytic ozonation step E7. Advantageously, this treatment step E6-7 makes it possible to increase the efficiency of the method of the invention by treating part of the residual polluting material of the electrozoned effluent.

[0140] The method may also comprise, at the end of the electrozonation step E6, in a step E65, the recycling of the residue 11 from the reactor 6 in the pretreatment unit 2 by dissolved air flotation in a step E8.

[0141] In other words, recycling the residue 11 in the pretreatment unit 2 makes it possible to increase the efficiency of pretreatment without adding an external chemical coagulant, in particular to achieve almost zero contents of oils and substances that can trap ozone. In fact, the inventor has found that the residue 11, which may include stabilized flocs and coagulated but non-flocculated pollutant matter particles, can replace an external chemical coagulant conventionally used to increase the efficiency of dissolved air flotation. Examples

[0142] Example 1: Electro-ozonation step E6

[0143] The process of the invention is tested with an effluent from an oil platform, the characteristics of which are shown in Table 1 below. This effluent undergoes successively an electro-ozonation step, a catalytic ozonation step and a reverse osmosis filtration step.

[0144] The electrozonation step E6 of the process of the invention is tested on a pilot scale with the following parameters:

[0145] - the porous membrane is composed of:

[0146] - 94% by mass of an oxidized ceramic as support, the oxidized ceramic comprising 93% by mass of aluminum oxide, 5% by mass of titanium dioxide and 2% by mass of zirconium dioxide, and

[0147] - 6% by mass of titanium dioxide as metal oxide,

[0148] - porosity of the porous membrane: 22,

[0149] - ozone flow rate: 20 L / min,

[0150] - direct current density of 1.78 A / m2,

[0151] - ozone concentration of 1 to 2 ppm,

[0152] - aluminum anode and aluminum cathode,

[0153] - maximum effluent flow rate of 5000 liters per hour,

[0154] - contact time of 1 hour.

[0155] The catalytic ozonation step is implemented with the following parameters:

[0156] - the catalyst is composed of 93% by mass of clay (Kaolinite KGa-2) as support, and 1% by mass of palladium, 5% by mass of manganese oxide and 1% by mass of cerium oxide as active phase, these mass percentages being defined in relation to the total mass of the catalyst,

[0157] - Flow rate of the effluent to be treated: 2 L / h,

[0158] - Ozone flow rate: 5 g / h,

[0159] - Contact time: 30 min.

[0160] The reverse osmosis filtration step is implemented with a reverse osmosis membrane having an active surface area of ​​148.6 m2, a maximum flow rate of 55 m3 / day, and an average NaCl rejection rate of 96%.

[0161] The chemical oxygen demand (COD) and salinity of the effluent are measured before and after the electrozonation step, after the catalytic ozonation step and after the reverse osmosis filtration step. The COD and salinity removal rates (reduction expressed in (%)) are shown in Table 1 below.

[0162] [Tables 1] Parameters Effluent before electrozonation step Effluent after electrozonation step Effluent after catalytic ozonation step Effluent after Flow rate 2 L / h 2 L / h 2 L / h 2 L / h Temperature 16.3°C 16.3°C 16.3°C 16.3°C PH 8.12 7.7 8.45 8.45 COD 2850 mg / L 1162 mg / L 165 mg / L 165 mg / L

[0163] These results demonstrate that the process of the invention makes it possible to reduce COD by more than 90% and salinity by more than 95%.

Claims

Claims

1. System (100) for treating an effluent (1, 3) from an oil platform and comprising a polluting material, said system (100) being configured to: - receive said effluent (1, 3) from an oil platform, - generate a direct current whose current density is between 1.4 A / m2 and 7.5 A / m2, in particular between 1.7 A / m2 and 5.5 A / m2, very particularly between 1.75 A / m2 and 1.8 A / m2, - carry out the electrozonation of the effluent (1, 3) received by ozone partially decomposed with the direct current generated and thus obtain an electrozoned effluent (9), - carry out a catalytic ozonation of the electrozoned effluent (9) in order to obtain a treated effluent.

2. System (100) according to claim 1, said system (100) comprising a reactor (6) for carrying out the electrozonation of the effluent (1, 3) received, said reactor (6) comprising a side wall having a cylindrical shape along a vertical axis of revolution and a bottom delimiting a reaction space, an ozone injection port and an effluent injection port or a port for injecting a mixture of ozone and effluent, and at least two electrodes, an anode and a cathode, in the reaction space.

3. A system (100) according to any preceding claim, said system (100) comprising a porous membrane (7) configured to provide partially decomposed ozone by filtering a received ozone stream, said membrane (7) comprising a support and a metal oxide on the surface of the support, the support being selected from an oxidized ceramic, a metal alloy, a chromium compound and mixtures thereof, and the metal oxide being selected from titanium dioxide, manganese oxide, cerium oxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof, the partially decomposed ozone being obtained by passing a stream of ozone through said porous membrane.

4. System (100) according to any one of the preceding claims, said system (100) comprising a catalyst for carrying out catalytic ozonation, said catalyst comprising a support selected from activated alumina, clay, activated carbon, oxidized ceramic and mixtures thereof, and an active phase at the surface of the support and selected from palladium, a metal alloy, manganese oxide, cerium oxide, titanium dioxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof.

5. Method for treating an effluent from an oil platform and comprising a polluting material, said method comprising a step of electrozonation (E6) of the effluent (1, 3) from an oil platform by partially decomposed ozone to obtain an electrozoned effluent (9), the electrozonation (E6) being carried out with a direct current density of between 1.4 A / m2 and 7.5 A / m2, in particular between 1.7 A / m2 and 5.5 A / m2, very particularly between 1.75 A / m2 and 1.8 A / m2, and a step of catalytic ozonation (E7) of said electrozoned effluent (9) in order to obtain a treated effluent.

6. Method according to the preceding claim, said method further comprising, before the electrozonation step (E6), a pretreatment step by dissolved air flotation (E2) making it possible to obtain a pretreated effluent (3), this pretreated effluent (3) then being implemented in the electrozonation step (E6).

7. Method according to any one of claims 5 or 6, said method further comprising, before the electrozonation step (E6) or before the dissolved air flotation pretreatment step (E2), a step of evaporation-concentration of the effluent making it possible to obtain a concentrated effluent, this concentrated effluent then being used in the electrozonation step (E6) or in the dissolved air flotation pretreatment step.

8. Method according to any one of claims 5 to 7, said method further comprising, between the electrozonation step (E6) and the catalytic ozonation step (E7), a step (E6-7) of treatment by low pressure dissolved air flotation of the electrozoned effluent obtained during the electrozonation step (E6) to obtain a treated electrozoned effluent, this treated electrozoned effluent then undergoing the catalytic ozonation step.

9. Method according to any one of claims 5 to 8, said method further comprising, after the catalytic ozonation step (E7), a step of disinfecting a mixture comprising the treated effluent and ozone by passing this mixture through a porous membrane to obtain a disinfected effluent.

10. Method according to any one of claims 5 to 9, in which the residue (11) obtained during the electrozonation step (E6) is recycled in the pretreatment unit (2) of the effluent by dissolved air flotation.

Images