WO2025083367A1 - Method for treating by-products resulting from the production of synthetic fuels and production unit for implementing same - Google Patents

Abstract

The invention relates to a method for treating by-products resulting from the production of synthetic fuels, which comprises the combination of at least three treatments, including an anaerobic biological treatment, an aerobic biological treatment for producing an aerobic mixed liquor, and a treatment of the aerobic mixed liquor by ozonation. This method allows for the production of biogas that can be transformed into dihydrogen to supply a biofuel refinery. The invention also provides a production unit that allows this method to be implemented.

Description

Process for treating co-products from the production of synthetic fuels and production unit for its implementation

Technical Field

[0001] The present invention relates to the field of the treatment of co-products generated by the production of synthetic fuels, whether upstream - at the stage of pre-treatment of raw materials - or during the synthesis itself. The invention relates in particular to the treatment of co-products resulting from the pre-treatment of raw materials intended for the biofuel industry,

[0002] The invention proposes a method for treating co-products as well as an installation for implementing this method, which make it possible to optimize the recovery of the co-products and reduce the carbon footprint, Prior art

[0003] The production of synthetic fuels is based on chemical reactions generating multiple co-products, essentially organic, throughout the production line.

[0004]These co-products include in particular waste water - from the washing of intermediate products and the washing of installations - which includes a high concentration of solid matter and hydrophobic matter, but also solid residues from the purification of reagents (Le. raw materials) and reaction by-products. The purification of reagents and the pretreatment of raw materials are essential for this industry which uses numerous reaction catalysts, sensitive to impurities,

[0005] In the second and third generation biofuel industry, the raw materials used are solid, liquid or semi-solid fatty substances at room temperature (called FOG in English for Fat, Oil and Grease) which include undesirable compounds which must be removed by pretreatment processes. These pretreatments of lipid raw materials consist of treating unrefined vegetable or animal oils (natural or recycled) in order to isolate a fraction containing lipid materials of interest. refined for processing into biofuel, for example fatty acid triglycerides and fatty acids in the case of renewable diesel. Crude vegetable and animal oils and fats are generally subjected to several chemical pretreatment stages to remove undesirable compounds that may reduce the biofuel production yield. The choice of pretreatment reagents, the number of stages and the order of the treatment stages varies depending on the nature of the raw material. Also, co-products are in some cases generated in large quantities and are extremely varied in nature - mineral, organic, solid, liquid or pasty. In addition, the organic matter content of co-products can be very high - which makes their management complex and costly to consider transformation into valuable products.

[0006]This is the reason why, for example, only wastewater from the pretreatment of raw materials is currently treated in biorefineries. The wastewater is simply subjected to physical separation treatments such as flotation or fixation on activated carbon, which lead to a transfer of pollution. The solid co-products are generally treated by incineration, which is very energy-intensive and increases the carbon footprint of the biofuel. [0007] There is therefore a need to treat the co-products generated by the synthetic fuel industry, in particular the co-products from the refining of organic raw materials, using a process with a limited or even zero carbon footprint. Independently of this aspect, it would be desirable to optimize the energy efficiency of a unit for treating these co-products.

[0008] Such a treatment process would make it possible to reduce the overall carbon footprint of producing a synthetic fuel.

[0009] It would be particularly advantageous to process concentrated, or even highly concentrated, co-products without consuming too much energy. Optimizing the recovery of co-products by increasing the proportion of biogas produced, accompanied by a reduction in the quantities of biological sludge is also sought.

[0010] There also remains a need to improve the management of co-products generated by the pre-treatment of raw materials, particularly lipid raw materials used for the production of biodiesel and renewable diesel.

[0011] The invention aims in particular to remedy one or more of the drawbacks linked to the refining of raw materials from the biofuel industry of the state of the art mentioned above. Description of the invention

[0012]This objective is achieved by proposing a method for treating co-products from the production of synthetic fuels, comprising the combination of at least three treatments, including an anaerobic biological treatment, an aerobic biological treatment to produce an aerobic mixed liquor, and an ozonation treatment of the aerobic mixed liquor.

[0013] The invention also proposes an installation allowing the implementation of this process, for example a co-product treatment unit and a biorefinery.

[0014] In a first embodiment, the concentrated residues and the waste water feed an anaerobic digester which produces, in addition to biogas, an effluent whose liquid part feeds an aerobic digester and undergoes ozonation.

[0015] In a second embodiment, a fatty fraction is extracted from the wastewater, so that the anaerobic treatment is carried out on the fatty fraction of the wastewater and not on the wastewater itself. In this version, the concentrated residues undergo, independently of the wastewater, aerobic treatment and ozonation.

[0016] The method and installation of the invention proposed for the treatment of co-products advantageously makes it possible to reduce the carbon footprint of a synthetic fuel production unit, in particular by one of the following five means or by the combination of several of them. [0017] First, the reduction of the carbon footprint can be achieved through an energy-autonomous process.

[0018] The invention also has the advantage of producing exclusively biogenic carbon dioxide.

[0019] In a particular embodiment, the method comprises a treatment for transforming biogenic methane into dihydrogen, preferably accompanied by a treatment for converting biomethane into green dihydrogen to supply a renewable diesel production unit. This valorization of biogas thus makes it possible to reduce the share of blue dihydrogen used for the hydrotreatment of the treated raw materials. The method of the invention makes it possible to provide green energy up to a value of 4.3 MWh per tonne of chemical oxygen demand (COD). A co-product treatment facility according to the invention supplied with 10 t/d of lipid raw materials (quantified by their COD) can produce 16 GWh/year of green energy, while a co-product treatment facility according to the invention supplied with 50 t/d of lipid raw materials (quantified by their COD) can produce 80 GWh/year of green energy.

[0020] The invention also makes it possible to reduce the quantity of biological sludge resulting from the treatment of co-products, which is of particular interest for co-products with a high carbon content.

[0021] Finally, the invention limits, or even eliminates, the transfers of pollution associated with the use of activated carbon or an ion exchanger practiced in the prior art. Brief description of the drawings

[0022] Figure 1 is a diagram representing a first embodiment of the invention. The anaerobic digestion of all the liquid and solid co-products is followed by an aerobic treatment of the digested effluent.

[0023] Figure 2 shows a second embodiment of the invention, in which the solid co-products and the waste water are treated separately. The anaerobic treatment is carried out on the fatty fraction of the waste water while the concentrated residues undergo, independently of the waste water, an aerobic treatment and ozonation. [0024] Figure 3 is a diagram of a unit for producing a synthetic fuel according to the invention comprising a sub-unit for treating co-products, a sub-unit for producing dihydrogen from biogas and a hydrotreatment section.

Description of the embodiments

[0025] A first subject of the invention relates to a method for treating co-products resulting from the production of a synthetic fuel, the co-products comprising concentrated residues and/or waste water, said method comprising:

- biological treatment in an anaerobic reactor to produce biogas,

- biological treatment in an aerobic reactor of a treated liquid to produce a mixed liquor and treated water,

- ozonation treatment of the mixed liquor.

[0026] The method may further comprise treating the biogas to extract the biogenic methane it contains, and the biogenic methane may then be converted into green dihydrogen.

[0027] A synthetic fuel, within the meaning of the invention, is a paraffinic fuel whose production process comprises at least one step of chemical transformation of the raw material used, as opposed to fossil fuels which are extracted from oil by refining.

[0028] The invention particularly relates to a synthetic fuel chosen from biofuels and synthetic fuels.

[0029] The term "biofuel" means a fuel produced from biomass, a source of carbon: this is the case for biodiesel and renewable diesel produced from natural organic oils and fats. "Synthetic fuels", such as synthetic naphtha or synthetic diesel, include the category of electro-fuels produced from renewable or decarbonized electricity.

[0030] The synthetic fuel targeted by the present invention is for example chosen from hydrotreated vegetable oils such as biodiesel, biopropane, bionaphtha, biokerosene, renewable diesel including fatty acid methyl esters, synthetic diesel and synthetic naphtha.

[0031] The invention relates to the management of co-products formed in the synthetic fuel industry and, within the meaning of the invention, the term "co-product" means a chemical compound or a mixture of chemical compounds resulting from one of the stages of production of a synthetic fuel, which can be recovered. These stages include the purification (also called pre-treatment) of raw materials, and the transformation of raw materials into biofuel (including the synthesis and purification of the finished product).

[0032] The physical state of the co-product may be liquid, pasty or solid, regardless of the stage at which it is formed in the fuel synthesis chain. In a particular embodiment, the co-product comprises a mineral or organic fatty body.

[0033] For example, the method of the invention relates to a co-product resulting from the pre-treatment of raw materials, these raw materials being essentially of a lipid nature in the case of biofuels produced from vegetable oils or animal fats. The present invention therefore relates in particular to the co-products formed during the implementation of a method for pre-treatment of the raw material(s) necessary for the production of a biofuel.

[0034] In a particular embodiment of the invention, the co-products are derived from the pretreatment of raw materials intended for the production of a synthetic fuel chosen from biofuels.

[0035] The co-products may comprise wastewater, concentrated residues or a mixture thereof. According to one embodiment, the co-products comprise concentrated residues and wastewater, which feed the anaerobic reactor as an inlet.

[0036] The term “waste water” means used water discharged during a process for producing a synthetic fuel, in particular water discharged during pretreatment of a raw material comprising lipid compounds. (including oils, greases and/or waxes) or during a process of synthesizing synthetic fuel from a raw material.

[0037] “Concentrated residues” means solid or pasty, organic or inorganic co-products.

[0038] The method of the invention provides improved management of concentrated inorganic solid residues (such as mineral waxes or coloring earths) and organic solid residues such as gums.

[0039] In a particular embodiment, the method applies to the treatment of co-products formed during the pretreatment of raw materials used for the production of a biofuel.

[0040] Both biodiesel and renewable diesel synthesis processes use catalysts that have the disadvantage of being deactivated upon contact with secondary compounds present in the lipid raw material. On the other hand, the raw materials contain compounds that are not converted into biofuel. It is therefore necessary to carry out pretreatment of the fats to limit the impurity content and ensure a good biofuel production yield.

[0041] Pretreatment depends on the nature of the raw material used and uses various physical and chemical techniques including neutralization with soda, degumming under acidic conditions to remove phospholipids, bleaching on coloring earths to remove phospholipids and oxidized compounds, absorption, neutralizing distillation by steam injection (also called deacidification) to remove free fatty acids and volatile compounds, drying, washing and filtration to remove solids including waxes. Some pretreatment steps aim to limit the levels of undesirable products present in the raw material or to eliminate them. Some pretreatment steps themselves generate contaminants which are added to the impurities in the raw material and which need to be removed in additional steps. [0042] For example, the raw materials intended for a renewable diesel manufacturing unit can successively undergo degumming (by the action of citric acid or phosphoric acid), neutralization (with a base), washing with water, then decolorization by acid treatment and adsorption on bleaching earths and activated carbon.

[0043] The co-products generated during the production of synthetic fuels, such as the co-products generated during the pre-treatment of raw materials intended for the manufacture of biofuels, have very varied chemical compositions and physical states, which makes their management all the more difficult to implement. In the case of a renewable diesel feedstock, the waste produced by the pre-treatment of the raw materials consists of wash water (liquid), acid gums (organic and pasty) or spent bleaching earth (SBE), which are solid.

[0044]Thus, the co-products targeted by the present invention may come from the chemical refining of crude oils, and be chosen from washing waters, neutralization pastes, acid gums, waxes, used bleaching earths, used winterization earths, deodorization condensates, fatty acid distillates, esterification waters, aeroflotation greases and their mixtures.

[0045] The method of the invention can also be applied to the treatment of co-products formed during the synthesis of a biofuel or a synthetic fuel.

[0046] According to a first embodiment of the method of the invention, co-products comprising concentrated residues (pasty or solid) and wastewater undergo anaerobic treatment and aerobic treatment in sequence. The concentrated residues and the wastewater are initially placed in the same anaerobic reactor to produce a first effluent which is subjected to anaerobic biological treatment. This treatment generates, in addition to a biogas, a second effluent. The treatment of the second effluent by separation produces an anaerobic treatment sludge and a liquid treated, the latter being intended to undergo aerobic treatment and ozonation treatment. The anaerobic treatment sludge is then eliminated.

[0047]Alnso, the first embodiment of the invention provides a biological treatment in the anaerobic reactor which produces, in addition to the biogas, a first effluent, and the method comprises a treatment by separation of the first effluent, producing biological sludge and the treated liquid.

[0048] In a second embodiment, the co-products comprise wastewater and solid residues which are treated separately. The wastewater is degreased and deoiled, for example in a separation tank, to separate the water from the oils and produce a fat fraction and a treated liquid. The anaerobic treatment is applied only to the fat fraction of the wastewater. The anaerobic treatment and the ozonation treatment are carried out on concentrated residues. This embodiment allows external treatment of the solid co-products in an anaerobic digestion plant combined with an aerobic digestion plant, such as an MBBR reactor.

[0049]According to a particularly advantageous embodiment of the invention, the co-products are characterized by a high, or even very high, total chemical oxygen demand (COD). Thus, the total COD of the co-products of the invention preferably comprises a high biodegradable COD (correlated to a high BOD), possibly accompanied by a hard (or refractory) COD.

[0050] The process of the invention makes it possible in particular to treat co-products whose chemical oxygen demand is between 10 g/L and 600 g/L, but also to treat both solid residues and waste water. The chemical oxygen demand will be measured according to the ISO 6060:1989 standard, in accordance with the practice of a person skilled in the art.

[0051] Waste water has, for example, a chemical oxygen demand of between 10 g/L and 50 g/l and concentrated pasty residues can have a chemical oxygen demand of between 100 g/L and 200 g/L: this is the case in particular for acid gums resulting from the pretreatment of materials raw materials used for the production of HVO (Hydrotreated Vegetable Oil) biofuels. The chemical oxygen demand of the solid concentrated residues that can be efficiently managed by the process of the invention can reach a value between 300 and 500 g/L. Such solid residues are, for example, spent bleaching earths from the purification of raw materials for HVO biofuels.

[0052] Measurements of the chemical oxygen demand may be carried out using sensors at any point in the installation, essentially at the inlet on the co-products, or in the material flows within the installation, in order to optimize the efficiency of the process and adapt the parameters of the different devices, in particular the load of the digesters and the intensity of the ozonation.

[0053] The method of the invention makes it possible to generate treated water whose chemical oxygen demand is less than 0.1 g/L. The quantity of biological sludge is advantageously minimized compared to the methods of the prior art.

[0054] The ozonation treatment of the mixed liquor can be carried out using devices known to those skilled in the art, the term "mixed liquor" designating, in the present description, the mixture of an aqueous liquid to be purified and aerobic microorganisms which are suspended in the liquid and ensure its purification. Ozonation, combined with aerobic biological treatment, is particularly useful for treating concentrated, or even very concentrated, co-products, the biodegradation of refractory materials being increased.

[0055] The method of the invention is therefore advantageous for the management of co-products whose chemical oxygen demand is greater than 10 g/L, preferably greater than 20 g/L. In a particular embodiment, the method of the invention is particularly suitable for the management of co-products whose chemical oxygen demand is greater than 150 g/L, or even greater than 170 g/L. The chemical oxygen demand of the co-products which are treated by the method of the invention may be greater than a value chosen from the group consisting of 10 g/L, 20 g/L, 50 g/L, 80 g/, 100 g/L, 120 g/L, 140 g/L, 160 g/L, 180 g/L, 200 g/L, 250 g/L and 300 g/L. The chemical oxygen demand of co-products is generally less than 500 g/L. The chemical oxygen demand The oxygen content of co-products depends on their composition: they can consist solely of concentrated residues, or consist of a mixture of wastewater and concentrated residues.

[0056]According to a particular embodiment, the ozone is injected into a circuit conveying the mixed liquor. The ozone can be injected using an injector or a static mixer. For example, ozonation is carried out on the mixed liquor extracted from the bioreactor, in particular in a recirculation loop. The device used for ozonation comprises an ozonation tower in which the mixed liquor circulates. Alternatively, the ozone produced by an ozonator is injected directly into a circuit conveying the mixed liquor.

[0057] A person skilled in the art will be able to adapt the quantity of ozone required to the composition of the mixed liquor. The recycling of the mixed liquor is preferably configured so as to optimize the consumption of co-products by the biomass.

[0058] Aerobic treatment can be carried out in an activated sludge reactor, a fixed bed reactor or a moving bed reactor. It is preferred to use a moving bed biofilm reactor (MBBR) having a smaller relative volume or a higher relative treatment capacity, due to the suspension of the microorganisms and their higher biomass concentration.

[0059] The anaerobic treatment can be carried out in an anaerobic reactor comprising a three-phase separator. The three-phase separator incorporates a degassing tank to release the gas, a separation chamber for separating the liquid from the sludge and a solids recovery tank. This separator advantageously makes it possible to optimize the operation of the fixed-bed digester, in particular for the treatment of flows whose chemical oxygen demand is greater than 300 g/L.

[0060] The method of the invention may comprise a treatment for separating the mixed liquor and the biogas generated by the anaerobic treatment. The temperature value will be chosen by a person skilled in the art so as to optimize the production of biogas. For example, the treatment may comprise a step mesophilic digestion, around 35°C, a thermophilic digestion step between 50°C and 60°C, or a combination of the two steps.

[0061] The biogas resulting from the anaerobic treatment comprises biomethane and carbon dioxide, so that the process can also comprise a treatment of the biogas to separate the biogenic methane and the biogenic carbon dioxide. The biomethane obtained can be recovered in several ways, for example by compression (to supply the city gas network), by transformation into dihydrogen, or by combustion (to heat the aerobic and anaerobic reactors or to heat a thermal dryer for drying the biological sludge if necessary). The biomethane can also be used to drive alternators generating electricity, which powers various treatment equipment. In a particular embodiment of the invention, the process comprises a treatment for transforming the biomethane (also called biogenic methane) into dihydrogen. [0062]As stated above, the co-products treated according to the invention are generated during the production of a synthetic fuel. According to a particular embodiment, the synthetic fuel is a biofuel, the term "biofuel" referring to a fuel produced from biomass. [0063] Three generations of biofuels are distinguished depending on the origin of the biomass used and the associated transformation processes. A first-generation biofuel is an agrofuel produced from crops traditionally intended for food. These biofuels are derived from plant materials, such as sugar beet or cereals for the production of bioethanol, or rapeseed and sunflower for the production of biodiesel. In second-generation biofuels, the plant biomass is non-food, which makes it possible to offer a renewable diesel. This involves wood, straw, agricultural and forestry residues, or dedicated crops (lignocellulosic biomass), making it possible in particular to offer renewable diesel. Finally, the third-generation biomass is of marine origin, and uses algae that produce lipid materials, [0064] Diesel biofuels include different products, manufactured from oils from oleaginous plants, animal fats or used oils.

[0065] Fatty acid methyl esters (FAME) are obtained by a transesterification reaction of triglyceride molecules, which mainly constitute vegetable oils extracted from plant seeds, with methanol. One of these fatty acid methyl esters, biodiesel (mixed with fossil diesel and supplied to stations in the form of B7 or B10 diesel), is produced from vegetable oils extracted from oilseed plants such as rapeseed, corn, sunflower, palm and soybean.

[0066] Another diesel biofuel, renewable diesel (supplied at the pump as XTL diesel) is produced by hydrotreating and hydrocracking vegetable oils or animal fats, generally from animal fat residues such as tallow, used cooking vegetable oils, industrial waste such as effluent discharged from mills where palm fruits are crushed to obtain oil (Palm Oil Mill Effluent or POME in English), and black liquor from the manufacture of kraft paper (PPO paper in English).

[0067] Other biofuels such as biopropane, bionaphtha and sustainable aviation fuels (SAF) such as biokerosene are produced using the same process.

[0068] Biofuels obtained by hydrotreatment of used oils of vegetable origin are referred to as hydrotreated vegetable oils or HVO biofuels (Hydrotreated Vegetable Oil in English). Hydrotreatment consists of removing the oxygen atoms contained in the starting biomass to obtain alkanes (also called parrafins). This treatment, carried out at very high temperature in the presence of a catalyst, consumes gaseous dihydrogen, and releases carbon dioxide and water. Hydrotreatment is followed by hydrocracking by which the alkanes undergo a change in the configuration of their carbon and hydrogen atoms (isomerization). [0069] The method of the invention also aims at the treatment of co-products generated during the production of synthetic fuels by Fisher-Tropsch reaction (Fisher-Tropsch synthesis in English or FTS). These fuels are obtained by conversion of a mixture of carbon monoxide and dihydrogen (called syngas or synthetic gas) in the presence of a catalyst, to obtain a product of interest (liquid hydrocarbons with a short chain length corresponding to diesel and gasoline cuts) and co-products (solid hydrocarbons). This category of synthetic fuels includes electro-fuels (e-fuels or e-fuels in English) produced from renewable electricity (from solar or wind for example) or from decarbonized electricity. E-diesel, e-gasoline and e-kerosene are examples.

[0070]In Figure 1, wastewater co-products and solid residues - including co-products from the pretreatment of raw materials during the production of HVO biofuels or fatty acid methyl esters (FAME) - undergo biological treatment in an anaerobic reactor (1). At least 90% of the organic matter (corresponding to 90% of the chemical oxygen demand) entering the anaerobic digester is converted into biogas, a mixture of biogenic CH ₄ and CO2. The treated effluent leaving the anaerobic digester undergoes a separation treatment (3) to separate the biological sludge and separated water. The separation can be carried out in a decanter, in a flotation tank or through membranes.

[0071] Separated biological sludge, which is still too loaded with biomass to be discharged directly into the environment, may undergo additional treatment steps. The separated biological sludge is then removed from the site for disposal.

[0072] The biogas produced by the digester comprises approximately between 50% and 80% by volume of biomethane, the remainder being predominantly carbon dioxide. The biogas preferably undergoes a separation treatment (2) to separate the biomethane and carbon dioxide.

[0073] The separated water from the anaerobic digester is subjected to biological treatment in an aerobic reactor (4) to degrade the organic matter residual (biodegradable COD) and refractory organic matter (refractory COD or Hard COD in English). The biodegradability of refractory organic matter is increased by carrying out ozonation treatment (5) of the mixed liquor extracted from the aerobic bioreactor, ozonation being carried out for example in a mixed liquor recirculation loop. The solids contained in the treated water leaving the aerobic bioreactor are separated from the main flow by flotation, clarification, filtration or membranes. The sludge produced during the separation step can be recycled with the sludge from the anaerobic digester to be simultaneously dewatered, then disposed of off-site. The treated water from the biological treatment in the aerobic reactor can be discharged either to existing facilities or directly into the environment, depending on the discharge permit.

[0074] In this embodiment, the method makes it possible to transform co-products having a COD equal to 200 g/L to obtain an effluent outlet whose COD is less than 0.1 g/L.

[0075] In the scheme of Figure 2, the concentrated residues are treated separately from the wastewater. The concentrated residues may be transported to an off-site anaerobic digestion facility to undergo biological treatment in an anaerobic reactor (1) for degradation and conversion to biogas. The biogas undergoes separation treatment (2) of biogenic methane and carbon dioxide.

[0076] Untreated wastewater may contain up to 10% fats, oils and fats (FOG). The FOG is degraded by biological treatment in an on-site aerobic reactor (4). However, since the wastewater is incompatible with the downstream biological treatment step, the stream is passed through a flotation unit to undergo degreasing treatment (6) and remove the FOG from the main stream. The separated concentrated FOG may then be sent to an off-site digestion facility to undergo biological treatment in an anaerobic reactor (1), resulting in the production of biogenic CO2 and _CH4 . [0077] The biodegradability of refractory organic materials can be increased by ozonation treatment (5) of the mixed liquor extracted from the aerobic bioreactor. The solids contained in the water treated by the aerobic reactor are separated from the main flow by flotation, by clarification, by filtration or on membranes. The sludge produced by a separation treatment (3) is dehydrated and evacuated off-site. The treated water from the aerobic treatment can be discharged either to existing installations or directly into the environment, depending on the discharge standards or regulations. [0078] The invention provides a particularly advantageous solution for reducing the carbon footprint of biofuel production units, including HVO and FAME biofuels, which generate co-products that are both liquid and solid, more or less concentrated. The invention makes it possible to manage all of the co-products simultaneously or separately, and makes it possible to limit the quantity of sludge and to produce biomethane, which can be directly used in several industries, including that of HVO biofuels. The method of the invention essentially makes it possible to propose two modes of implementation. A first solution is based on anaerobic digestion of all of the co-products generated by the refining of lipid raw materials, followed by aerobic treatment of the digested effluents. When the solid residues cannot be treated on the site of the pre-treatment unit, the invention proposes an alternative solution consisting of an outsourced treatment of these residues by anaerobic treatment, the aqueous co-products being subject to a separate aerobic treatment, [0079] The method of the invention can be implemented in a co-product treatment facility, said facility being able to be located on the biofuel production site or on another site. The facility includes an anaerobic reactor, an aerobic reactor, and an ozonation means for bringing ozone into contact with the mixed liquor produced by the aerobic treatment. [0080] A second subject of the invention relates to a unit for producing a synthetic fuel provided with a co-product treatment sub-unit comprising an aerobic reactor, an ozone production means, an anaerobic reactor producing a biogas, and optionally a biogas treatment means to extract the biogenic methane.

[0081] The unit advantageously comprises a means for recirculating the mixed liquor from the aerobic reactor to the inlet of the latter. In this embodiment, the ozone production means is configured to ozonate the mixed liquor.

[0082] The production unit may comprise a sub-unit for transforming biogenic methane into green dihydrogen, intended to supply a section for hydrotreatment and hydroisomerization of raw materials.

[0083] In a particular embodiment, the production unit is a biorefinery in which the biomethane produced by the anaerobic treatment is converted into dihydrogen in a steam reforming unit, which dihydrogen is used to transform the raw materials into alkanes (hydrotreatment), and to transform these alkanes into biofuels (hydroisomerization).

[0084] An example of a biorefinery producing a synthetic fuel comprises a hydrotreatment and hydroisomerization section supplied as input by raw materials which are treated in a raw material treatment subunit. This subunit generates co-products in the form of wastewater and/or concentrated residues which are treated in a co-product treatment subunit, which can operate according to the method described above. In this embodiment, the co-product treatment subunit advantageously comprises a means for recovering and treating a biogas which it produces. The biogas treatment means comprises a means for separating the methane and the carbon dioxide which it contains. The biorefinery can then comprise a subunit for converting the biogenic methane from the biogas into dihydrogen, as well as a means feeding the hydrotreatment and hydroisomerization section into dihydrogen as an energy source.

[0085] The production unit of the invention is configured to implement the method described previously in the context of the first project of the invention. Consequently, the characteristics which have been described above in relation to the first subject of the invention, as well as one of the combinations of these characteristics can be repeated to describe the production unit which is the subject of the second subject of the invention, so that they are not repeated in this part,

[0086] The production unit illustrated in Figure 3 comprises a co-product treatment sub-unit (8) provided with an aerobic reactor, an ozone production means, an anaerobic reactor producing biogas, and a biogas treatment means for extracting biogenic methane.

[0087]This subunit may advantageously be installed on the site of a biorefinery producing HVO biofuels from lipid raw materials such as FOG. The site comprises a raw material hydrotreatment and hydroisomerization section (9) for transforming the FOG, and a transformation subunit (10) producing dihydrogen from methane, also called a reforming section. In this installation, the biogenic methane produced by the co-product processing subunit (8) may advantageously totally or partially replace the fossil methane to feed the reforming section, and thus produce green dihydrogen, the dihydrogen being essential to the operation of the biorefinery to carry out the hydrotreatment and hydroisomerization of the FOG. In a particular embodiment, the biorefinery may also comprise a raw material pretreatment unit for generating refined raw materials and raw material co-products, on site. The co-products are advantageously treated in the co-product treatment sub-unit (8) while the refined raw materials are used to feed the raw material hydrotreatment and hydroisomerization section (9). [0088] The term "comprises/comprising" does not exclude the presence of other elements or steps. Furthermore, although listed individually, a plurality of means, elements or method steps may be implemented in a single unit or in a single device. [0089] The reference signs in the claims are provided merely by way of example and should in no way be interpreted as limiting the scope of the claims,

[0090] Although the present invention has been described above with reference to specific embodiments, it is not intended to be limited to the specific form shown herein. Furthermore, although features are shown individually, they may be advantageously combined.

Claims

Claims [Claim 1] Process for treating co-products from the production of a synthetic fuel, the co-products being chosen from concentrated residues, waste water and their mixtures, said process comprising: - biological treatment in an anaerobic reactor (1) to produce biogas, - biological treatment in an aerobic reactor (4) of a treated liquid to produce a mixed liquor and treated water, and - ozonation treatment (5) of the mixed liquor. [Claim 2] Method according to claim 1, characterized in that the co-products comprise concentrated residues and waste water, which feed the anaerobic reactor as input. [Claim 3] Method according to claim 2, characterized in that the biological treatment in the anaerobic reactor (1) produces, in addition to the biogas, a first effluent, and in that the method comprises a separation treatment (3) of the first effluent, producing biological sludge and the treated liquid. [Claim 4] A method according to claim 1, characterized in that the co-products comprise waste water, which undergoes a degreasing treatment (6) to produce a fatty fraction and the treated liquid. [Claim 5] Method according to claim 4, characterized in that the fatty fraction of the waste water undergoes biological treatment in the anaerobic reactor (1). [Claim 6] Method according to claim 4 or 5, characterized in that the co-products comprise, in addition to waste water, concentrated residues which undergo biological treatment in the anaerobic reactor (1). [Claim 7] Method according to one of the preceding claims, characterized in that it comprises a treatment of the biogas (2) to separate the biogenic methane and the biogenic carbon dioxide. [Claim 8] Method according to one of the preceding claims, characterized in that the co-products resulting from the production of a synthetic fuel are co-products from the pre-treatment of raw materials used for the production of synthetic fuel. [Claim 9] Method according to one of the preceding claims, characterized in that the anaerobic reactor comprises a three-phase separator. [Claim 10] Method according to claim 7, characterized in that the method comprises a treatment for transforming biogenic methane into dihydrogen. [Claim 11] Method according to one of the preceding claims, characterized in that the synthetic fuel is chosen from hydrotreated vegetable oils such as biodiesel, biopropane, bionaphtha, biokerosene, renewable diesel, synthetic diesel and synthetic naphtha. [Claim 12] A synthetic fuel production unit (7) having a co-product processing sub-unit (8) comprising an aerobic reactor, an ozone production means, an anaerobic reactor producing a biogas, and a biogas processing means for extracting biogenic methane. [Claim 13] Production unit according to claim 12, characterized in that it comprises a sub-unit for transforming biogenic methane into green dihydrogen (10), which feeds the raw material hydrotreatment and hydroisomerization section (9).