Method for treating complex waste

Abstract

The invention relates to a method for treating a mixture M1 comprising at least organic matter, said method comprising: a. a step of hydrothermal treatment of a mixture M1 making it possible to obtain, on the one hand, liquid carbon dioxide CO2liq1 and, on the other hand, a mixture M2 comprising more than 50% by dry weight of mineral matter and organic matter in a proportion of less than 50% by dry weight, relative to the total dry weight of the mixture M2, b. a separation step carried out on at least one fraction of the mixture M2 making it possible to obtain, on the one hand, a stream M3 enriched with mineral material and, on the other hand, a stream M4 comprising organic matter and carbon dioxide, said separation step being carried out in the presence of supercritical carbon dioxide.

Description

TITLE OF THE INVENTION: METHOD FOR TREATING COMPLEX WASTE TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to the field of treatment of complex waste, comprising organic and inorganic matter, such as aqueous waste, sludge, and sewage. PRIOR ART

[0002] Against the backdrop of climate change and increasing scarcity of resources, the search for treatment methods that make the best possible use of energy from the various wastes produced by human activity is in full swing.

[0003] Biomass and waste containing organic matter can be converted into energy by decomposing the organic fraction to produce biogas, a high-energy fuel composed mainly of methane (50-60%) and CO2 (40-50%).

[0004] This energy conversion of the organic fraction of waste is carried out by biochemical technologies, notably anaerobic digestion, or by thermochemical technologies such as thermal methods (combustion, pyrolysis, etc.) or hydrothermal methods (hydrothermal liquefaction / gasification, etc.).

[0005] These methods are not always optimally efficient.

[0006] Pretreatments have been proposed to improve the methods.

[0007] The most widely applied pretreatments can be classified into three general categories:

[0008] - thermal methods (e.g. thermal hydrolysis),

[0009] - physical or mechanical methods (e.g. ultra-sonication, high-pressure homogenization, etc.),

[0010] - and chemical techniques (alkaline or acid pre-treatment, oxidation by ozonation, etc.).

[0011] The object of the present invention is to facilitate the conversion and improve the efficiency of biogas production, by virtue of a method for treating biomass and complex waste that optimizes both the treatment itself and the energy expenditure. SUMMARY OF THE INVENTION

[0012] The invention relates to a method for treating a mixture M1 comprising at least organic matter, said method comprising:

[0013] a. a step of hydrothermal treatment of a mixture M1 making it possible to obtain, on the one hand, liquid carbon dioxide CO2liq1 and, on the other hand, a mixture M2 comprising more than 50% by dry weight of mineral matter and organic matter in a proportion of less than 50% by dry weight, relative to the total dry weight of the mixture M2,

[0014] b. a separation step carried out on at least one fraction of the mixture M2 making it possible to obtain, on the one hand, a stream M3 enriched with mineral matter and, on the other hand, a stream M4 comprising organic matter and carbon dioxide, said separation step being carried out in the presence of supercritical carbon dioxide.

[0015] According to one embodiment, the treatment method according to the invention comprises one or more of the following features: - the method further comprises a step of pressurizing and / or heating liquid carbon dioxide in order to obtain supercritical carbon dioxide prior to its introduction in the separation step b); and / or - the method further comprises a separation step c) carried out on at least one fraction of the stream M4 in order to obtain, on the one hand, carbon dioxide and, on the other hand, a stream M5 of organic matter, said method optionally further comprising a digestion step carried out on at least one fraction of the stream M5 after optional cooling; and / or - the method further comprises a step of storing liquid carbon dioxide in a storage device, said storage device being supplied by at least one fraction of the liquid carbon dioxide from the hydrotreatment step a) CO2liq1 and where appropriate with at least one fraction of the carbon dioxide from the separation step c) of the stream M4; and / or - the treatment step a) comprises:

[0016] • a step of hydrothermal treatment of the mixture M1 making it possible to obtain a gas stream FG, an aqueous stream FL and the mixture M2,

[0017] • a liquefaction step carried out on all or part of the gas stream FG, preferably on the entire gas stream FG, making it possible to obtain a stream of liquid carbon dioxide CO2liq1, at least one fraction of which will be used in step b).

[0018] According to one embodiment, the step of hydrothermal treatment a) comprises hydrothermal gasification, said hydrothermal gasification preferably being carried out at a temperature ranging from 350°C to 700°C, preferably from 400°C to 600°C, even more preferably from 450°C to 550°C, and / or at a pressure ranging from 200 to 450 bar, preferably from 250 to 300 bar.

[0019] According to one embodiment, the step of hydrothermal treatment a) comprises: - hydrothermal gasification of at least one fraction of the mixture stream M1, making it possible to obtain a stream M6 comprising a mixture of gas and liquid and the stream M2, - a step of cooling and expanding at least one fraction of the stream M6 to a temperature ranging from 30 to 150°C, preferably from 50 to 100°C, and to a pressure ranging from 1 bar to 100 bar, making it possible to obtain, on the one hand, a gas stream M8 and, on the other hand, a liquid stream M7, - a separation step of at least one fraction of the gas stream M8 making it possible to obtain, on the one hand, a stream enriched with carbon dioxide M9 and, on the other hand, a stream depleted of carbon dioxide 71, - a liquefaction step of at least one fraction of the stream M9 making it possible to obtain a liquid carbon dioxide stream on the one hand and a gas stream 81 on the other hand, at least one fraction of said liquid carbon dioxide stream preferably being introduced into a storage device 3.

[0020] According to one embodiment, the step of hydrothermal treatment a) comprises: - a hydrothermal gasification of at least one fraction of the mixture stream M1, making it possible to obtain a stream M6 comprising a mixture of gas and liquid and the stream M2, - a step of cooling at least one fraction of the stream M6 to a temperature ranging from 0 to 90°C, preferably from 10 to 70°C, more preferably from 25 to 50°C, making it possible to obtain, on the one hand, a gas stream M10 and, on the other hand, a liquid stream M11, the liquid stream M11 being at a pressure ranging from 150 to 350 bar, - a step in which at least one fraction of the liquid stream M11 is expanded to a pressure ranging from 35 to 100 bar, making it possible to obtain, on the one hand, a stream enriched with liquid carbon dioxide CO2liq1 and, on the other hand, a liquid stream M12 depleted of carbon dioxide, at least one fraction of said stream of liquid carbon dioxide CO2liq1 preferably being introduced into a storage device 3, preferably said method further comprises: - a separation step carried out on at least one fraction of the gas stream M10, making it possible to obtain, on the one hand, a stream enriched with carbon dioxide M13 and, on the other hand, a stream depleted of carbon dioxide M14, - an expansion step carried out on at least one fraction of the stream M13 to a pressure ranging from 35 to 100 bar, making it possible to obtain, on the one hand, a stream enriched with liquid carbon dioxide CO2liq1’ and, on the other hand, a liquid stream M15 depleted of liquid carbon dioxide, at least one fraction of said liquid carbon dioxide stream CO2liq1’ preferably being introduced into a storage device.

[0021] According to one embodiment, the step of hydrothermal treatment a) comprises wet oxidation, preferably carried out at a temperature ranging from 250°C to 400°C, preferably from 300°C to 350°C, and / or at a pressure ranging from 40 to 200 bar, preferably from 60 to 100 bar, preferably the wet oxidation comprises: - a wet oxidation step of the mixture M1 making it possible to obtain a liquid stream M21 and a gas stream M22, - a liquefaction step for at least one fraction of the gas stream M22, preferably all of the gas stream M22, making it possible to obtain a liquid carbon dioxide stream CO2liq1, - a step of cooling at least one fraction of the liquid stream M21, preferably all of the liquid stream M21, - a filtration step for the stream M21 making it possible to obtain an aqueous stream and the stream M2.

[0022] The present invention also relates to an installation for implementing a treatment method according to the invention, said installation comprising: - at least one hydrothermal treatment device 1 supplied by at least one fraction of the mixture M1 and including at least two outlets, a liquid carbon dioxide CO2liq1 outlet line and a stream M2 outlet line, - a separating device 2 downstream of the stream M2 outlet line including at least one carbon dioxide inlet and including at least two outlets, a stream M3 outlet line and a stream M4 outlet line.

[0023] The installation according to the invention may further comprise one or more of the following features: - at least one liquid carbon dioxide storage device 3 including at least one inlet supplied by the liquid carbon dioxide CO2liq outlet line downstream of the hydrotreatment device 1 and including at least one liquid carbon dioxide CO2liq outlet, and / or - at least one pressurizing and / or heating device 4 supplied by a liquid carbon dioxide CO2liq outlet line downstream of the storage device 3 and including at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2sc outlet line supplying the separating device 2, - and optionally at least one recirculation loop for recirculating a fraction of the carbon dioxide recovered downstream of the separating device 2 in the stream M4 line to the separating device 2 and where appropriate to the storage device 3 or pressurization and / or heating device 4; and / or at least one heat exchanger selected from: • a heat exchanger 202, 31 for recovering heat from the matter stream treated in the treatment device 201, 30’ and transferring it to the mixture M1 stream upstream of the treatment device 201, 30’, • a heat exchanger 4, 4’ for recovering heat from the matter stream treated in the treatment device 20, 201, 30, 30’ and transferring it to the liquid carbon dioxide stream upstream of the separating device 2, preferably the installation comprises said two heat exchangers.

[0024] According to one embodiment of the installation according to the invention, the hydrothermal treatment device 1 includes: - a hydrothermal gasification reactor 20 including at least one stream M6 outlet line and one stream M2 outlet line, a cooling and expansion device 5 supplied by at least one fraction of the stream M6, and where appropriate of the stream M6’, and including a gas stream M8 outlet and a liquid stream M7 outlet, - a separating device 6 supplied by at least one fraction of the stream M8 and including an outlet line for stream M9 enriched with carbon dioxide and an outlet line for stream 71 depleted of carbon dioxide, said separating device 6 preferably being a membrane separating device or a solvent extraction device, - a liquefaction device 7 supplied by at least one fraction of the stream M9 enriched with carbon dioxide and including a gas stream 81 outlet line and a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line preferably supplying a storage device 3.

[0025] According to one embodiment of the installation according to the invention, the hydrothermal treatment device 1 includes: - a hydrothermal gasification reactor 20 including at least one stream M6 outlet line and one stream M2 outlet line, - a cooling device 8 supplied with at least one fraction of the stream M6, and where appropriate of the stream M6’, and including a gas stream M10 outlet and a liquid stream M11 outlet, - an expansion device 9 supplied by at least one fraction of the stream M11 and including a liquid stream M12 outlet line and a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line preferably supplying a storage device 4, said hydrothermal treatment device 1 preferably further including: - a separating device 10 supplied by at least one fraction of the stream M10 and including an outlet line for stream M13 enriched with carbon dioxide and an outlet line for stream M14 depleted of carbon dioxide, - an expansion device 11 supplied by at least one fraction of the stream M13 and including a liquid carbon dioxide stream outlet line and a liquid stream M15 outlet line, said liquid carbon dioxide stream outlet line preferably supplying a storage device 3.

[0026] According to one embodiment of the installation according to the invention, the hydrothermal treatment device 1 includes: - a wet oxidation device 30 supplied by the stream of the mixture M1 line, and including at least one liquid stream F21 outlet and one gas stream M22 outlet, - a liquefaction device LQ supplied by at least one fraction of the gas stream M22 and including at least one carbon dioxide CO2liq1 outlet line, - a cooling and separating device RF supplied by at least one liquid stream fraction M21 and including at least one stream M2 outlet line and one stream outlet FL, - a separating device 2 downstream of the stream M2 outlet line including at least one supercritical carbon dioxide inlet CO2sc and including at least two outlets, a stream M3 outlet line and a stream M4 outlet line, said carbon dioxide CO2liq1 outlet line optionally being connected with the supercritical carbon dioxide CO2sc inlet line, said carbon dioxide outlet line possibly comprising a storage device 3 and / or a heating and / or pressurizing device 4.

[0027] The invention facilitates the recovery of mineral matter and the recovery of organic matter.

[0028] The invention thus proposes a method for treating biomass and complex waste that optimizes both the recovery of mineral matter and organic matter and energy expenditure, while making use of the co-product of these energy conversions, namely CO2. BRIEF DESCRIPTION OF THE FIGURES

[0029] [Fig.1] is an installation for carrying out a treatment method according to one embodiment of the invention.

[0030] [Fig.2] is an installation for carrying out a treatment method according to one embodiment of the invention.

[0031] [Fig.3] is an installation for carrying out a treatment method according to one embodiment of the invention.

[0032] [Fig.4] is an installation for carrying out a treatment method according to one embodiment of the invention.

[0033] [Fig.5] is an installation for carrying out a treatment method according to one embodiment of the invention.

[0034] [Fig.6] is an installation for carrying out a treatment method according to one embodiment of the invention.

[0035] [Fig.7] is an installation for carrying out a treatment method according to one embodiment of the invention.

[0036] [Fig.8] is an installation for carrying out a treatment method according to one embodiment of the invention.

[0037] [Fig.9] is an installation for carrying out a treatment method according to one embodiment of the invention.

[0038] [Fig.10] is an installation for carrying out a treatment method according to one embodiment of the invention.

[0039] [Fig.11] is an installation for carrying out a treatment method according to one embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] The invention relates to a method for treating a mixture M1 comprising at least organic matter, said method comprising: a. a step of hydrothermal treatment of a mixture M1 making it possible to obtain, on the one hand, liquid carbon dioxide and, on the other hand, a mixture M2 comprising more than 50% by dry weight of mineral matter and organic matter in a proportion of less than 50% by dry weight, relative to the total dry weight of the mixture M2, b. a separation step carried out on at least one fraction of the mixture M2 making it possible to obtain, on the one hand, a stream M3 enriched with mineral matter and, on the other hand, a stream M4 comprising organic matter and carbon dioxide, said separation step being carried out in the presence of supercritical carbon dioxide.

[0041] For the purposes of the present invention, the expression “#at least one fraction#of a mixture or stream#” has the same meaning as the expression “#all or part of said mixture#or stream”. In the case of a part of said mixture or of said stream, this expression refers to a certain proportion of said mixture or said stream. For example, for the purposes of this expression, “#each fraction of the mixture#” or “#each fraction of the stream#” will have the same composition.

[0042] In the context of the present invention, the expression “where appropriate” means “if applicable”.

[0043] • Mixture M1

[0044] Mixture M1 is typically a biomass. The biomass can be a paste or liquid; it may particularly be sewage sludge, food and agri-food waste. Preferably, it is sewage sludge.

[0045] According to one embodiment, the mixture M1 comprises from 5 to 50% by weight of solids, preferably from 15 to 35% by weight of solids, with respect to the total weight of the mixture M1.

[0046] According to one embodiment, the method of the invention comprises a grinding step and / or a hydrolysis step of the mixture M1, said hydrolysis step then preferably being carried out at a pressure ranging from 1 to 8 bars and at a temperature ranging from 70 to 165°C, in order to obtain a hydrolyzed mixture M1’, at least one fraction of said hydrolyzed mixture M1’ being then implemented in step a) of the method of the invention.

[0047] • step of hydrothermal treatment a)

[0048] The step of hydrothermal treatment a) yields at least: - a stream of carbon dioxide in liquid form and - a stream of mixture M2.

[0049] The mixture M2 comprises:

[0050] - more than 50% by dry weight of mineral matter, preferably more than 70% by dry weight of mineral matter, or even more than 80% by dry weight of mineral matter, and

[0051] - less than 50% by dry weight of organic matter, preferably less than 30% by dry weight of organic matter, or even less than 20% by dry weight of organic matter,

[0052] based on the total dry weight of the mixture M2.

[0053] Typically, the stream of mixture M2 will be an aqueous stream comprising at least 30% by weight of water, preferably at least 40% by weight of water, or even at least 50% by weight of water, based on the total weight of the mixture M2.

[0054] The step of hydrothermal treatment may comprise one or more heat exchanges and / or one or more separation steps to recover at least one stream of carbon dioxide in liquid form and at least one stream of treated matter M2.

[0055] According to one embodiment of the invention, the method comprises two heat exchanges: - a heat exchange X2 for transferring heat from the stream of matter treated in treatment step a) to the stream of matter M1 upstream of the treatment step a), - a heat exchanger X1, X1’ for transferring heat from the stream of matter treated in the treatment step a) to the liquid carbon dioxide stream upstream of the separation step b) and, where appropriate (i.e., if the method comprises a storage step), downstream of the storage step.

[0056] According to one embodiment of the invention, the treatment step comprises: - a treatment step making it possible to obtain a gas stream FG, an aqueous stream and a stream M2, the stream M2 typically being a brine-type stream, the aqueous stream typically including a proportion of water greater than the proportion of water in the stream M2, - a liquefaction step carried out on all or part of the gas stream FG, preferably on the entire gas stream FG, making it possible to obtain a stream of liquid carbon dioxide, at least a fraction of which will be used in step b).

[0057] The hydrothermal treatment can be selected from hydrothermal gasification (HG) and wet oxidation (WO).

[0058] • Separation step b)

[0059] The method of the invention comprises a separation step carried out on at least one fraction of the mixture M2 making it possible to obtain: - on the one hand, a stream M3 enriched with mineral matter, and - on the other hand, a mineral-depleted stream M4, the stream M4 comprising organic matter and carbon dioxide.

[0060] This separation step b) is carried out in the presence of supercritical carbon dioxide.

[0061] In fact, the inventors discovered that supercritical carbon dioxide, due to its particular properties, could be used to separate the mineral matter from the organic matter present in the stream M2 resulting from the hydrothermal treatment.

[0062] Supercritical carbon dioxide is carbon dioxide at a temperature of at least 31.25°C and a pressure of at least 74 bar.

[0063] Supercritical carbon dioxide is a fluid state of carbon dioxide (CO2) obtained when it is kept above its critical temperature and pressure of 31.25°C and 74 bar, respectively. At these pressures and temperatures, the state of the CO2 means that it still has a high density: 0.47 g / cm3.

[0064] Supercritical CO2 has properties that lie somewhere between those of a fluid in its gaseous state and those of a fluid in its liquid state. Its properties can be adjusted by changing the external parameters (temperature and / or pressure).

[0065] By virtue of its viscosity, density and high level of diffusion, supercritical CO2 will be able to enter and dissolve in biological matrices, acting on the bonds between the organic matter and the water present in the matrix during the separation step of the organic matter (and mineral matter recovery).

[0066] In particular, the supercritical CO2 exhibits a significant quadrupole moment and, linked to its microscopic solvent behavior, this molecule can participate in hydrogen bond interactions and act as both a weak Lewis acid and base during the separation step of the organic matter.

[0067] Step b) is preferably carried out in a separating device.

[0068] Preferably, the supercritical carbon dioxide is introduced into a separating device via a separate inlet from the mixture M2, preferably via continuous injection.

[0069] At the end of the separation step, a stream M3 enriched with mineral matter is obtained and a stream M4 comprising organic matter and carbon dioxide is obtained. The stream M4 will also be referred to as “stream depleted of mineral matter”.

[0070] For the purposes of the present invention, when separating a given stream X, “a stream enriched with mineral matter” means a stream comprising a mass ratio of mineral matter greater than the mass ratio of mineral matter in the given stream X, these mass ratios being defined as a proportion of dry matter.

[0071] For the purposes of the present invention, when separating a given stream X, the term “stream depleted of mineral matter” means a stream comprising a mass ratio of mineral matter lower than the mass ratio of mineral matter in the given stream X, these mass ratios being defined as a proportion of dry matter.

[0072] According to one embodiment, the method further comprises a step of pressurizing and / or heating liquid carbon dioxide in order to obtain supercritical carbon dioxide prior to its introduction in the separation step b).

[0073] According to one embodiment, the method further comprises a separation step c) carried out on at least one fraction of the stream M4 in order to obtain, on the one hand, carbon dioxide gas and, on the other hand, a stream M5 of organic matter, said method optionally further comprising a digestion step carried out on at least one fraction of the stream M5 comprising organic matter. Typically, the stream of organic matter M5 will be cooled before being implemented in the digestion step.

[0074] All or part of said gaseous carbon dioxide from step c), preferably part of the gaseous carbon dioxide from step c), can be liquefied, and optionally converted to supercritical form for use in step b) of the invention.

[0075] According to one embodiment, the method further comprises a step of storing liquid carbon dioxide in at least one storage device, said storage device being supplied by at least one fraction of the liquid carbon dioxide from the hydrotreatment step a) and optionally where appropriate by a fraction of the carbon dioxide from the separation step c) of the stream M5. Said gaseous carbon dioxide fraction from the separation c) can be cooled upstream of the storage device or inside the storage device so as to liquefy the carbon dioxide.

[0076] Preferably, the carbon dioxide is stored in the storage device in liquid form, typically at a temperature ranging from 56°C to 31°C and a pressure ranging from 5 bar to 73 bar. For example, the carbon dioxide can be stored at -20°C and 20 bar.

[0077] Preferably, when such a storage device is present, at least one fraction, preferably all, of the supercritical carbon dioxide used in step b) comes from the storage device.

[0078] Thus, when the method of the invention comprises a step of pressurizing and / or heating liquid carbon dioxide in order to obtain supercritical carbon dioxide prior to its introduction in the separation step b), said step is preferably carried out on the liquid carbon dioxide downstream of the storage device.

[0079] Based on the temperature and pressure of the carbon dioxide from the treatment step a) or, where applicable, from the storage device, the carbon dioxide may optionally be heated and / or pressurized so as to bring the carbon dioxide to supercritical conditions, prior to use in the separation step b).

[0080] Based on the temperature of the fluid M2, the carbon dioxide can be brought into contact with the fluid M2 in liquid form and brought under supercritical conditions in contact with the fluid M2 for the separation step of step b).

[0081] • Treatment step a): hydrothermal gasification (HG)

[0082] According to one embodiment, the treatment step a) is a hydrothermal gasification step, preferably carried out at a temperature ranging from 350°C to 700°C, preferably from 400°C to 600°C, even more preferably from 450°C to 550°C, and / or at a pressure ranging from 200 to 450 bar, preferably from 250 to 300 bar.

[0083] Hydrothermal gasification (HG) is a thermal depolymerization process used to convert organic matter present in a humid environment into a mixture comprising only small molecules under high to moderate temperature and pressure.

[0084] During the HG process, the carbon and hydrogen in an organic matter are converted thermochemically under near-critical or supercritical conditions. Part is converted into water-soluble compounds with low molar masses.

[0085] Another part is converted into gaseous products such as carbon dioxide (CO2), methane (CH4), dihydrogen (H2), carbon monoxide (CO), light hydrocarbons such as ethane (C2H6) and propane (C3H8).

[0086] During residence in the hydrothermal gasification reactor at temperatures less than 400°C, the organic matter undergoes, among other reactions, very rapid (several seconds) homogeneous hydrolysis-based decomposition. In fact, implementation under near-critical or supercritical conditions makes it possible to use the unique properties of supercritical water as a solvent, allowing homogeneous solvation and reaction conditions, leading to very high reaction kinetic speeds. As a result, a much shorter residence time and a much higher heating rate than in conventional hydrolysis are used, limiting or even avoiding the secondary condensation and polymerization reactions responsible for bio-oil and bio-char formation.

[0087] When the HG operates at temperatures above 400°C, radical decomposition of polymers (involving in particular decarboxylation, deamination reactions by breaking C-N bonds, and C-C or C-O cleavage) predominates, while endothermic steam reforming is the main reaction pathway for converting small molecules with 1 to 3 carbon atoms into carbon oxides and dihydrogen, and nitrogen into ammonia.

[0088] Methane is also produced by the methanation of CO and CO2, using dihydrogen.

[0089] As a result, HG can be seen as a decomposition process transforming the organic residues present in the stream M1h into a more readily biodegradable matter and into ammonia dissolved in the liquid phase.

[0090] The treatment conditions (in particular temperature, pressure, and to a lesser extent residence time) of the HG can be adjusted to not only produce a gaseous fraction containing CH4, CO, CO2 and H2 (syngas), but also to produce an aqueous effluent, containing mainly easily digestible compounds, notably carboxylic acids, on the one hand, and ammonia in the form of the ammonium salt of the carbonic acids produced, on the other.

[0091] Typically, in the context of the present invention, this HG step makes it possible to obtain a stream of mineral matter M2 and a stream M6 comprising a mixture containing gas and liquid.

[0092] In the context of the present invention, the stream M2 will be referred to indifferently as a stream of inorganic matter or a stream of mineral matter.

[0093] The stream of mineral matter M2 will typically comprise a higher proportion of mineral matter than the proportion of mineral matter in the stream M1.

[0094] The stream of matter M6 will typically comprise a higher mass ratio of organic matter than the mass ratio of organic matter in the stream M1.

[0095] Also typically, the stream of mineral matter M2 will comprise a higher proportion of mineral matter than the proportion of mineral matter in the stream M6.

[0096] Also typically, the stream of matter M6 will comprise a higher proportion of organic matter than the proportion of organic matter in the stream M2.

[0097] Hydrothermal gasification is the term used to describe the entire treatment chain leading, on the one hand, to the production of a gas through the transformation of organic matter and, on the other, to a plurality of liquid fractions containing more or less mineral matter.

[0098] Typically, hydrothermal gasification involves at least pressurizing and tempering the biomass, in particular at temperatures above 350°C and at pressures preventing vaporization of the medium.

[0099] According to one embodiment, hydrothermal gasification is carried out in a gasification reactor#: - at a temperature ranging from 400°C to 600°C, preferably 450°C to 550°C, and / or - at a pressure ranging from 200 to 450 bar, preferably 250 to 300 bar.

[0100] The hydrothermal gasification may also comprise a separation of the mineral fraction (salts) M2 and may involve the use of catalysts.

[0101] Mineral matter includes salts comprising anions such as phosphates, sulfates, chlorides, carbonates and hydrocarbonates with counterions such as sodium, magnesium, calcium, ammonium and metals.

[0102] Preferably, the (overall) residence time of the stream M1 in the HG step a) typically ranges from 1 min to 20 min, preferably from 2 min to 10 min, more preferably from 3 to 5 min.

[0103] In one embodiment, the hydrothermal gasification step is carried out in a gasification reactor in the presence of at least one catalyst. Preferably, the catalyst is selected from metals on activated carbon, such as ruthenium, nickel, palladium or platinum.

[0104] The catalyst can be in the form of a bed of solid particles within the gasification reactor.

[0105] The hydrothermal gasification step will thus generally lead to a mixture comprising inorganic matter (salts) and organic matter.

[0106] In the context of the invention, the HG step typically includes a separation step making it possible to obtain a stream M2 enriched in inorganic matter and a stream MO depleted of inorganic matter. The stream M6 will then generally be a stream of gas dissolved in a liquid effluent.

[0107] For the purposes of the present invention, when separating a given stream X, "a stream enriched with inorganic matter#" means a stream comprising a mass ratio of inorganic matter greater than the mass ratio of inorganic matter in the given stream X, these mass ratios being defined as a proportion of dry matter.

[0108] For the purposes of the present invention, when separating a given stream X, the term “stream depleted of inorganic matter#” means a stream comprising a mass ratio of inorganic matter lower than the mass ratio of inorganic matter in the given stream X, these mass ratios being defined as a proportion of dry matter.

[0109] According to one embodiment, at the outlet of the hydrothermal gasification, a carbon dioxide stream is obtained by a so-called “high-pressure” separation or by a “low-pressure” site separation from at least one fraction of the stream M6 from the hydrothermal gasification reactor, optionally from the stream M6’ or M6’’.

[0110] • So-called “low-pressure” separation

[0111] According to one embodiment of the method of the invention, the treatment step a) is a hydrothermal gasification step comprising: - hydrothermal gasification of at least one fraction of the stream of mixture M1, making it possible to obtain a treated stream M6 comprising a mixture of gas and liquid and the stream M2, - a step of cooling and expanding at least one fraction of the stream M6 to a temperature ranging from 30 to 150°C, preferably from 50 to 100°C, and to a pressure ranging from 1 bar to 100 bar, making it possible to obtain a gas stream M8 and a liquid stream M7, - a separation step of at least one fraction of the gas stream M8 making it possible to obtain, on the one hand, a stream M9 enriched with carbon dioxide and, on the other hand, a stream 71 depleted of carbon dioxide, - a liquefaction step for at least one fraction of the stream M9, typically at a temperature ranging from -56°C to 31°C and at a pressure ranging from 5 to 73 bar, making it possible to obtain a liquid carbon dioxide stream CO2liq1 on the one hand (CO2-enriched stream) and a gas stream 81 (CO2-depleted stream) on the other hand.

[0112] According to one embodiment using a storage device, at least one fraction of said liquid carbon dioxide stream CO2liq1 is preferably introduced into the storage device.

[0113] Preferably, the liquefaction step comprises a cooling step and / or a compression step. It is used to liquify the carbon dioxide.

[0114] • So-called “high-pressure” separation

[0115] According to one embodiment of the method of the invention, the treatment step a) is a hydrothermal gasification step comprising: - hydrothermal gasification used on at least one fraction of the stream of mixture M1, making it possible to obtain a treated stream M6 comprising a mixture of gas and liquid and the stream M2 - a step of cooling at least one fraction of the stream M6 to a temperature ranging from 0 to 90°C, preferably from 10 to 70°C, more preferably from 25 to 50°C, making it possible to obtain on the one hand a gas stream M10 and on the other hand a liquid stream M11 (stream comprising dissolved CO2), the liquid stream M11 being at a pressure ranging from 150 to 350 bar, - an expansion step in which at least one fraction of the liquid stream M11 is expanded to a pressure ranging from 35 bar to 100 bar, making it possible to obtain on the one hand a liquid carbon dioxide stream CO2liq1 (CO2-enriched stream) and on the other hand a liquid stream M12 (CO2-depleted stream).

[0116] According to one embodiment using a storage device, at least one fraction of said liquid carbon dioxide stream is preferably introduced into the storage device.

[0117] According to this so-called “high pressure” embodiment, preferably, carbon dioxide can also be recovered from all or part of the gas stream M10.

[0118] Thus, according to one embodiment, the method further comprises: - a separation step carried out on at least one fraction of the gas stream M10, making it possible to obtain, on the one hand, a stream M13 enriched with carbon dioxide and, on the other hand, a stream M14 depleted of carbon dioxide, - an expansion step carried out on at least one fraction of the stream M13 at a pressure ranging from 35 to 100 bar, making it possible to obtain both a liquid carbon dioxide stream CO2liq1’ and a liquid stream M15.

[0119] According to one embodiment using a storage device, at least one fraction of said liquid carbon dioxide stream CO2liq1’ is preferably introduced into the storage device.

[0120] • Heat exchanges

[0121] According to one embodiment, the treatment step a) is a hydrothermal gasification step which produces at least one treated stream M6 comprising gas and liquid, and the method of the invention comprises a heat exchange X1 between at least one fraction of the treated stream M6 from the hydrothermal gasification step and the liquid carbon dioxide stream upstream of step b) and, where applicable, downstream of the storage device and upstream of the separation step b), said heat exchange thus allowing the liquid carbon dioxide to be at least partially heated prior to its use in step b) and allowing the stream M6 to be at least partially cooled. The cooled stream is referred to as stream M6’.

[0122] According to this embodiment, at least one fraction of the stream M6’ can be separated using a so-called “low-pressure” separation or a so-called “high-pressure” separation as defined in the present invention in order to obtain a stream of liquid carbon dioxide CO2liq (CO2liq1).

[0123] According to one embodiment, the treatment step a) is a hydrothermal gasification step comprising a preliminary heating step of the stream of mixture M1, said preliminary heating step comprising at least one heat exchange substep X2 between the treated stream M6 from the hydrothermal gasification step and the stream M1, said heat exchange X2 thus allowing at least partial heating of the mixture M1 and allowing at least partial cooling of the treated stream M6, in order to obtain a stream M6’.

[0124] According to this embodiment, the method preferably further comprises a heat exchange X1’ between the treated stream M6’ and the liquid carbon dioxide stream upstream of step b) and, where applicable, downstream of the storage device and upstream of the separation step b), said heat exchange X1’ thus allowing the liquid carbon dioxide to be at least partially heated prior to its use in step b) and allowing the stream M6’ to be at least partially cooled so as to obtain a stream M6’’.

[0125] According to this embodiment, at least one fraction of the stream M6” can be separated using a so-called “low-pressure” separation or a so-called “high-pressure” separation as defined in the present invention in order to obtain a stream of liquid carbon dioxide CO2liq (CO2liq1 or CO2liq1’).

[0126] • Treatment step a): wet oxidation (WO)

[0127] According to one embodiment, the step of hydrothermal treatment a) is a wet oxidation step, preferably carried out at a temperature ranging from 250°C to 400°C, preferably from 300°C to 350°C, and / or at a pressure ranging from 40 to 200 bar, preferably from 60 to 100 bar.

[0128] This wet oxidation step may optionally comprise preheating of the matter (mixture M1) (i) by heat exchange with the output matter (treated matter comprising liquid and gas), (ii) by additional heating of the matter, or (iii) by oxygen injection (via air, pure oxygen or any other oxygenated derivative).

[0129] The wet oxidation treatment step may thus comprise: - a wet oxidation step of the mixture M1 making it possible to obtain a liquid stream M21 and a gas stream M22, - a liquefaction step for at least a fraction of the gas stream M22, preferably all of the gas stream M22, making it possible to obtain a liquid carbon dioxide stream, - a step of cooling at least one fraction of the liquid stream M21, preferably all of the liquid stream M21, making it possible to obtain the stream M2, - a separation step, for example by filtration, of the liquid stream M21 in order to separate the liquid from the mineral matter, thus obtaining an aqueous stream FL and the stream of matter M2, this separation step in particular allowing the stream of matter M2 to be concentrated into mineral matter before being used in step b).

[0130] The gas stream M22 contains mainly CO2 and optionally oxygen.

[0131] The gas stream M22 can be cooled by one or more heat exchanges.

[0132] The wet oxidation step may optionally comprise one or two heat exchanges prior to a separation making it possible to obtain the streams M21 and M22.

[0133] The separation of the mixture M20 resulting from the wet oxidation treatment can be carried out under pressure or after expansion of the mixture M20.

[0134] In this way, a heat exchange X1 can be provided between the stream of matter M20 treated by WO and the stream of liquid carbon dioxide upstream of step b) and, where appropriate, downstream of the storage device and upstream of the separation step b), this heat exchange X1 allowing (i) the treated matter M20 to be cooled and (ii) the liquid CO2 to be heated upstream of step b) and, where appropriate, downstream of the storage device and upstream of the separation step b).

[0135] It is also possible to provide a heat exchange X2 between the WO-treated matter stream M20 and the stream M1 upstream of the WO, this heat exchange X2 allowing i) the WO-treated matter stream M20 to be cooled and (ii) the mixture M1 upstream of the WO to be heated or preheated.

[0136] According to an embodiment implementing WO treatment, the method of the invention comprises: - a first heat exchange X2 for recovering heat from the stream of treated matter M20 (M20 comprising a mixture of gas and liquid) and transferring it to the stream of matter M1 upstream of the WO; a cooled stream of matter M20' is then obtained, and - a second heat exchanger X1’ for recovering heat from the stream of cooled matter M20’ (M20’ comprising a mixture of gas and liquid) and transferring it to the liquid carbon dioxide stream upstream of step b) and where appropriate downstream of the storage device and upstream of step b); a stream of cooled matter M20’’ is then obtained.

[0137] According to this embodiment, typically, the stream of matter M20’’ will then be separated into a liquid stream M21 and a gas stream M22.

[0138] The present invention further relates to an installation as such and an installation for implementing the method of the invention.

[0139] The installation according to the invention comprises: - at least one hydrothermal treatment device 1 supplied by at least one fraction of the mixture M1 and including at least two outlets, a liquid carbon dioxide CO2liq outlet line and a stream M2 outlet line, - a separating device 2 including at least one inlet supplied by the stream M2 outlet line and at least one supercritical carbon dioxide inlet and including at least two outlets, a stream M3 outlet line and a stream M4 outlet line.

[0140] According to one embodiment, the installation according to the invention comprises at least one storage device 3 including at least one inlet supplied by the liquid carbon dioxide CO2liq outlet line downstream of the treatment device 1 and including at least one liquid carbon dioxide CO2liq2 outlet for supplying the separating device 2 or a pressurizing and / or heating device 4 located upstream of the separating device 2.

[0141] According to one embodiment, the installation according to the invention further includes at least one separating device SP having at least one inlet supplied by the stream M4 outlet line and including at least one gaseous carbon dioxide outlet and one organic matter M5 outlet.

[0142] According to one embodiment not shown in the figures, the installation according to the invention does not comprise a storage device.

[0143] According to one embodiment not shown in the figures, the installation according to the invention does not comprise a separating device SP.

[0144] [Fig.1] is one embodiment of the invention, where the installation comprises: - a feed line of mixture M1, - a hydrothermal treatment device 1 supplied by at least one fraction of the mixture M1 and including three outlets, a liquid carbon dioxide CO2liq1 outlet line, a stream M2 outlet line and an aqueous stream FL outlet line, - a separating device 2 downstream of the stream M2 outlet line including at least one supercritical carbon dioxide CO2sc inlet and including at least two outlets, a stream M3 outlet line and a stream M4 outlet line, - a liquid carbon dioxide storage device 3 including at least one inlet supplied by the liquid carbon dioxide CO2liq1 outlet line downstream of the hydrotreatment device 1 and including at least one liquid carbon dioxide CO2liq2 outlet,

[0145] - a pressurizing and / or heating device 4 supplied by a liquid carbon dioxide CO2liq2 outlet line downstream of the storage device 3 and including at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2sc outlet line supplying the separating device 2, - a separating device SP downstream of the separating device 2 including at least one inlet supplied by the stream M4 outlet line and including at least one gaseous carbon dioxide outlet and one organic matter M5 outlet, and - a recirculation loop for recirculating a fraction of the carbon dioxide CO2 recovered downstream of the separating device SP to the storage device 3.

[0146] Said recirculation loop may optionally comprise a cooling and expansion device and / or the storage device 3 may optionally comprise a cooling and expansion device not shown in the figures. This allows carbon dioxide gas to be liquefied for storage.

[0147] Preferably, said recirculation loop includes a bypass, as shown in the figures. Indeed, in the context of the method of the invention, it is preferable to recycle and reuse, upstream of the separation step b), only a fraction of the carbon dioxide recovered downstream of the separation step.

[0148] According to one embodiment, the installation according to the invention comprises: - at least one liquid carbon dioxide storage device 3 including at least one inlet supplied by the liquid carbon dioxide CO2liq1 outlet line downstream of the hydrotreatment device 1 and including at least one liquid carbon dioxide CO2liq2 outlet, and - at least one pressurizing and / or heating device 4 supplied by a liquid carbon dioxide CO2liq2 outlet line downstream of the storage device 3 and including at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2sc outlet line supplying the separating device 2, and - optionally at least one recirculation loop for recirculating a fraction of the carbon dioxide recovered downstream of the separating device 2 in the stream M4 line to the pressurizing and / or heating device 4 or, where appropriate, to the storage device 3.

[0149] According to one embodiment, the hydrothermal treatment device 1 includes a hydrothermal gasification reactor 20 or a wet oxidation device 30.

[0150] The installation according to the invention, including a hydrothermal gasification reactor 20, can be adapted to implement a so-called low-pressure separation.

[0151] According to this embodiment, preferably, the hydrothermal treatment device 1 includes: - a hydrothermal gasification reactor 20 including at least one stream M6 outlet line and one stream M2 outlet line, - a cooling and expansion device 5 supplied by at least one fraction of the stream M6, and optionally the stream M6’, and including a gas stream M8 outlet and a liquid stream M7 outlet, - a separating device 6 supplied by at least one fraction of the stream M8 and including an outlet line for stream M9 enriched with carbon dioxide and an outlet line for stream 71 depleted of carbon dioxide, said separating device 6 preferably being a membrane separating device or a solvent extraction device, - a liquefaction device 7 supplied by at least one fraction of the stream M9 enriched with carbon dioxide and including an aqueous stream 81 outlet line and a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line preferably supplying a storage device 3.

[0152] The liquefaction device 7 can be a cooling device and / or a compression device.

[0153] [Fig.2] is an embodiment in which the treatment step a) is a hydrothermal gasification step in which the carbon dioxide is recovered by “low pressure” separation. As shown in [Fig.2], the treatment device 1 includes: - a hydrothermal gasification reactor 20 including a stream M6 outlet line and a stream M2 outlet line, - a cooling and expansion device 5 supplied by the stream M6 line, and including a gas stream M8 outlet and a liquid stream M7 outlet, - a separating device 6 supplied by the stream M8 line and including an outlet line for stream M9 enriched with carbon dioxide and an outlet line for stream 71 depleted of carbon dioxide, said separating device 6 preferably being a membrane separating device or a solvent extraction device, - a liquefaction device 7 supplied by the line for stream M9 enriched with carbon dioxide and including a gas stream 81 outlet line and a liquid carbon dioxide CO2liq1 stream outlet line, said liquid stream CO2liq1 outlet line preferably supplying the storage device 3.

[0154] [Fig.3] is an embodiment where the method includes a heat exchange between the stream M6 leaving the hydrothermal gasification reactor and the pressurizing and / or heating device 4, which on the one hand cools the stream M6 (to obtain a stream M6’) and on the other hand heats the liquid carbon dioxide CO2liq2 (to obtain supercritical carbon dioxide CO2sc).

[0155] Thus, according to one embodiment, the hydrothermal treatment device 1 includes a hydrothermal gasification reactor 20 including at least one stream M6 outlet line, in which installation the pressurizing and / or heating device 4 includes at least one heat exchanger for recovering heat from the stream M6 for transfer to the liquid carbon dioxide upstream of the separating device 2, said heat exchanger including at least one stream M6’ outlet line and one supercritical carbon dioxide outlet line.

[0156] The installation according to the invention, including a hydrothermal gasification reactor 20, can be adapted to implement a so-called high-pressure separation.

[0157] According to one embodiment, the hydrothermal treatment device 1 includes: - a hydrothermal gasification reactor 20 including at least one stream M6 outlet line and one stream M2 outlet line, - a cooling device 8 supplied by at least one fraction of the stream M6, and where appropriate of the stream M6’, and including a gas stream M10 outlet and a liquid stream M11 outlet, - an expansion device 9 supplied by at least one fraction of the stream M11 and including a liquid stream M12 outlet line and a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line preferably supplying a storage device 3.

[0158] Preferably, according to this embodiment, the treatment device 1 further includes: - a separating device 10 supplied by at least one fraction of the stream M10 and including an outlet line for stream M13 enriched with carbon dioxide and an outlet line for stream M14 depleted of carbon dioxide, - an expansion device 11 supplied by at least one fraction of the stream M13 and including a liquid carbon dioxide stream outlet line and a liquid stream M15 outlet line, said liquid carbon dioxide stream outlet line preferably supplying a storage device 3.

[0159] [Fig.4] is an embodiment in which treatment step a) is a hydrothermal gasification step in which carbon dioxide is recovered by “high pressure” separation. As shown in [Fig.4], the treatment device 1 includes: - a hydrothermal gasification reactor 20 including at least one stream M6 outlet line and one stream M2 outlet line, - a cooling device 8 supplied by the stream M6 line, and including a gas stream M10 outlet and a liquid stream M11 outlet, - an expansion device 9 supplied by the stream M11 line and including a liquid stream M12 outlet line and a liquid carbon dioxide stream CO2liq1 outlet line, said liquid carbon dioxide stream CO2liq1 outlet line preferably supplying a storage device 3.

[0160] [Fig.5] differs from [Fig.4] in that the method includes a heat exchange between the stream M6 leaving the hydrothermal gasification reactor and the liquid carbon dioxide CO2liq2 for example in the pressurizing and / or heating device 4, which on the one hand cools the stream M6 (to obtain a stream M6’) and on the other hand heats the liquid carbon dioxide CO2liq2 (to obtain supercritical carbon dioxide CO2sc), upstream of the separating device 2.

[0161] [Fig.6] differs from [Fig.4] in that the treatment device 1 further comprises: - a separating device 10 supplied by the stream M10 line and including an outlet line for stream M13 enriched with carbon dioxide and an outlet line for stream M14 depleted of carbon dioxide, - an expansion device 11 supplied by the stream M13 line and including a liquid carbon dioxide stream CO2liq1’ outlet line and a liquid stream M15 outlet line, said liquid carbon dioxide stream CO2liq1’ outlet line preferably supplying a storage device 3.

[0162] [Fig.6] is an embodiment where the storage device 3 includes an inlet for the stream CO2liq1 and an inlet for the stream CO2liq1’. According to an embodiment not shown, the stream CO2liq1 and CO2liq1’ lines can be combined upstream of the storage device 3.

[0163] [Fig.7] is a low-pressure separation method in which the method includes exchanging heat in a heat exchanger 202 supplied with at least one fraction of the stream M6 leaving a gasification reactor 201, to cool the stream M6 (to obtain a stream M6’) and at least partially heat the mixture M11 upstream of the gasification reactor 201 (to obtain a stream M1’).

[0164] [Fig.8] is a high-pressure separation method in which the method includes exchanging heat in a heat exchanger 202 supplied with at least one fraction of the stream M6 leaving a gasification reactor 201, to cool the stream M6 (to obtain a stream M6’) and at least partially heat the mixture M1 upstream of the gasification reactor 201 (to obtain a stream M1’).

[0165] [Fig.9] is an embodiment of the method using an HG step with low-pressure separation, and [Fig.10] is an embodiment of the method using an HG step with high-pressure separation.

[0166] According to an embodiment shown in [Fig.9] and [Fig.10], the method includes two heat exchanges: - a first heat exchange in a heat exchanger 202 supplied by at least a fraction of the stream M6 leaving a gasification reactor 201, on one hand to cool the stream M6 (to obtain a stream M6’) and at least partially heat the mixture M1 upstream of the gasification reactor 201 (to obtain a stream M1’), - a second heat exchange between the stream M6’ downstream of the heat exchanger 202 and the liquid carbon dioxide CO2liq2 for example in the pressurizing and / or heating device 4, which on the one hand cools the stream M6’ (to obtain a stream M6”) and on the other hand heats the liquid carbon dioxide CO2liq2 (to obtain supercritical carbon dioxide CO2sc).

[0167] According to one embodiment, the hydrothermal treatment device 1 includes a wet oxidation device 30, 30’. According to this embodiment, the installation according to the invention may comprise: - a wet oxidation device 30 supplied by the stream of the mixture M1 line, and including at least one liquid stream M21 outlet and one gas stream M22 outlet, - a liquefaction device LQ supplied by at least one fraction of the gas stream M22 and including at least one carbon dioxide CO2liq1 outlet line, - a cooling and separating device RF supplied with at least one fraction of liquid stream M21 and including at least one stream M2 outlet line and an aqueous stream FL outlet, said separating device may comprise a filtration device, said separation allowing the stream M2 to be concentrated in mineral matter prior to its use in step b) of the method of the invention, - a separating device 2 downstream of the stream M2 outlet line including at least one supercritical carbon dioxide CO2sc inlet and including at least two outlets, a stream M3 outlet line and a stream M4 outlet line, said carbon dioxide CO2liq1 outlet line optionally being connected with the supercritical carbon dioxide CO2sc inlet line, said carbon dioxide outlet line possibly comprising a storage device 3 and / or a heating and / or pressurizing device 4.

[0168] Thus, according to one embodiment shown in [Fig.10], the installation according to the invention comprises: - a wet oxidation device 30 supplied by a mixture M1, and including a liquid stream F21 outlet and a gas stream M22 outlet,

[0169] - a liquefaction device LQ supplied by at least one fraction of the gas stream M22 and including at least one carbon dioxide CO2liq1 outlet line (and a gas stream outlet line),

[0170] - a cooling and separating device RF supplied with at least one fraction of liquid stream M21 and including at least one liquid stream FL outlet line and a stream M2 outlet line, the separating device may for example be a filtration device, this separation allowing the stream of matter M2 to be concentrated in mineral matter prior to its use in step b),

[0171] - a separating device 2 downstream of the stream M2 outlet line including at least one supercritical carbon dioxide CO2sc inlet and including at least two outlets, a stream M3 outlet line and a stream M4 outlet line,

[0172] - a liquid carbon dioxide storage device 3 including at least one inlet supplied by the liquid carbon dioxide CO2liq1 outlet line downstream of the hydrotreatment device 1 and including at least one liquid carbon dioxide CO2liq2 outlet,

[0173] - a pressurizing and / or heating device 4 supplied by a liquid carbon dioxide CO2liq2 outlet line downstream of the storage device 3 and including at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2sc outlet line supplying the separating device 2, - a separating device SP downstream of the separating device 2 including at least one inlet supplied by the stream M4 outlet line and including at least one gaseous carbon dioxide outlet and one organic matter M5 outlet, and - a recirculation loop for recirculating a fraction of the carbon dioxide CO2 recovered downstream of the separating device SP to the storage device 3.

[0174] Said recirculation loop may optionally comprise a cooling and expansion device and / or the storage device 3 may optionally comprise a cooling and expansion device not shown in the figures. This allows carbon dioxide gas to be liquefied for storage.

[0175] According to one embodiment shown in [Fig.11], the method of the invention comprises two heat exchanges. Thus, [Fig.11] differs from [Fig.10] by the presence of these two heat exchanges: - a first heat exchange carried out in a first heat exchanger 31 to recover heat from the stream M20 from the wet oxidation device 30’ and transfer it to mixture M1 upstream of the hydrothermal treatment; a cooled stream M20’ is obtained,

[0176] - a second heat exchange carried out in a second heat exchanger 4’ for recovering heat from the stream M20’ and transferring it to the carbon dioxide upstream of the separating device 2; the heat exchanger 4’ may correspond to the pressurizing and / or heating device 4 or be part of the pressurizing and / or heating device 4, and by the presence of a separating device SP2 supplied by the stream M20’’ and including a liquid stream F21 outlet and a gas stream M22 outlet.

Claims

1. A method for treating a mixture M1 comprising at least organic matter, said method comprising:a. a step of hydrothermal treatment of a mixture M1 making it possible to obtain, on the one hand, liquid carbon dioxide CO2liq1 and, on the other hand, a mixture M2 comprising more than 50% by dry weight of mineral matter and organic matter in a proportion of less than 50% by dry weight, relative to the total dry weight of the mixture M2,b. a separation step carried out on at least one fraction of the mixture M2 making it possible to obtain, on the one hand, a stream M3 enriched with mineral matter and, on the other hand, a stream M4 comprising organic matter and carbon dioxide, said separation step being carried out in the presence of supercritical carbon dioxide.

2. The treatment method according to claim 1, further comprising a step of pressurizing and / or heating liquid carbon dioxide in order to obtain supercritical carbon dioxide prior to its introduction in the separation step b).

3. The treatment method according to claim 1 or 2, further comprising a separation step c) carried out on at least one fraction of the stream M4 in order to obtain on the one hand carbon dioxide and on the other hand a stream M5 of organic matter, said method optionally further comprising a digestion step carried out on at least one fraction of the stream M5 after optional cooling.

4. The treatment method according to any one of claims 1 to 3, further comprising a step of storing liquid carbon dioxide in a storage device, said storage device being supplied by at least one fraction of the liquid carbon dioxide from the hydrotreatment step a) CO2liq1 and optionally by at least one fraction of the carbon dioxide from the separation step c) of the stream M4.

5. The treatment method according to any one of claims 1 to 4, wherein the treatment step a) comprises:- a step of hydrothermal treatment of the mixture M1 making it possible to obtain a gas stream FG, an aqueous stream FL and the mixture M2,- a liquefaction step carried out on all or part of the gas stream FG, preferably on the entire gas stream FG, making it possible to obtain a stream of liquid carbon dioxide CO2liq1, at least a fraction of which will be used in step b).

6. The treatment method according to any one of claims 1 to 5, wherein the step of hydrothermal treatment a) comprises hydrothermal gasification, said hydrothermal gasification preferably being carried out at a temperature ranging from 350°C to 700°C, preferably from 400°C to 600°C, even more preferably from 450°C to 550°C, and / or at a pressure ranging from 200 to 450 bar, preferably from 250 to 300 bar.

7. The treatment method according to claim 6, wherein said hydrothermal gasification step comprises:- a hydrothermal gasification of at least one fraction of the stream of mixture M1, making it possible to obtain a stream M6 comprising a mixture of gas and liquid and the stream M2,- a step of cooling and expanding at least one fraction of the stream M6 to a temperature ranging from 30 to 150°C, preferably from 50 to 100°C, and to a pressure ranging from 1 bar to 100 bar, making it possible to obtain, on the one hand, a gas stream M8 and, on the other hand, a liquid stream M7,- a separation step of at least one fraction of the gas stream M8 making it possible to obtain, on the one hand, a stream M9 enriched with carbon dioxide and, on the other hand, a stream 71 depleted of carbon dioxide,- a step of liquefaction of at least one fraction of the stream M9 making it possible to obtain a liquid carbon dioxide stream on the one hand and a gas stream 81 on the other hand, at least one fraction of said liquid carbon dioxide stream preferably being introduced into a storage device 3.

8. The treatment method according to claim 6, wherein said hydrothermal gasification step comprises:- a hydrothermal gasification of at least one fraction of the stream of mixture M1, making it possible to obtain a stream M6 comprising a mixture of gas and liquid and the stream M2,- a step of cooling at least one fraction of the stream M6 to a temperature ranging from 0 to 90°C, preferably from 10 to 70°C, more preferably from 25 to 50°C, making it possible to obtain, on the one hand, a gas stream M10 and, on the other hand, a liquid stream M11, the liquid stream M11 being at a pressure ranging from 150 to 350 bar,- a step in which at least one fraction of the liquid stream M11 is expanded to a pressure ranging from 35 to 100 bar, making it possible to obtain, on the one hand, a stream enriched with liquid carbon dioxide CO2liq1 and, on the other hand, a liquid stream M12 depleted of carbon dioxide, at least one fraction of said liquid carbon dioxide stream CO2liq1 preferably being introduced into a storage device 3,preferably said method further comprises:- a separation step carried out on at least one fraction of the gas stream M10, making it possible to obtain, on the one hand, a stream M13 enriched with carbon dioxide and, on the other hand, a stream M14 depleted of carbon dioxide,- an expansion step carried out on at least one fraction of the liquid stream M13 to a pressure ranging from 35 to 100 bar, making it possible to obtain, on the one hand, a stream enriched with liquid carbon dioxide CO2liq1’ and, on the other hand, a liquid stream M15 depleted of liquid carbon dioxide, at least one fraction of said liquid carbon dioxide stream CO2liq1 preferably being introduced into a storage device.

9. The treatment method according to any one of claims 1 to 5, wherein the step of hydrothermal treatment a) comprises wet oxidation, preferably carried out at a temperature ranging from 250°C to 400°C,preferably from 300°C to 350°C, and / or at a pressure ranging from 40 to 200 bar, preferably from 60 to 100 bar,preferably the wet oxidation comprises:- a wet oxidation step of the mixture M1 making it possible to obtain a liquid stream M21 and a gas stream M22,- a liquefaction step for at least one fraction of the gas stream M22, preferably all of the gas stream M22, making it possible to obtain a liquid carbon dioxide stream CO2liq1,- a step of cooling at least one fraction of the liquid stream M21, preferably all of the liquid stream M21,- a filtration step for the stream M21 in order to obtain an aqueous stream and the stream M2.

10. An installation for implementing a treatment method according to any one of claims 1 to 9, said installation comprising:- at least one hydrothermal treatment device (1) supplied by at least one fraction of the mixture M1 and including at least two outlets, a liquid carbon dioxide CO2liq1 outlet line and a stream M2 outlet line,- a separating device (2) downstream of the stream M2 outlet line including at least one carbon dioxide inlet and including at least two outlets, a stream M3 outlet line and a stream M4 outlet line.

11. The installation according to claim 10, further including:- at least one liquid carbon dioxide storage device (3) including at least one inlet supplied by the liquid carbon dioxide CO2liq outlet line downstream of the hydrotreatment device (1) and including at least one liquid carbon dioxide CO2liq outlet, and / or- at least one pressurizing and / or heating device (4) supplied by a liquid carbon dioxide CO2liq outlet line downstream of the storage device (3) and including at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2sc outlet line supplying the separating device (2),- and optionally at least one recirculation loop for recirculating a fraction of the carbon dioxide recovered downstream of the separating device (2) in the stream M4 line to the separating device (2) and optionally to the storage device (3) or pressurization and / or heating device (4).

12. The installation according to claim 10 or 11, comprising at least one heat exchanger selected from:- a heat exchanger (202, 31) for recovering heat from the stream of matter treated in the treatment device (201, 30’) and transferring it to the stream of mixture M1 upstream of the treatment device (201, 30’),- a heat exchanger (4, 4’) for recovering heat from the stream of matter treated in the treatment device (20, 201, 30, 30’) and transferring it to the liquid carbon dioxide stream upstream of the separating device (2),preferably the installation comprises said two heat exchangers.

13. The installation according to any one of claims 10 to 12, wherein the hydrothermal treatment device (1) includes:- a hydrothermal gasification reactor (20) including at least one stream M6 outlet line and one stream M2 outlet line,- a cooling and expansion device (5) supplied with at least one fraction of the stream M6, and optionally stream M6’, and including a gas stream M8 outlet and a liquid stream M7 outlet,- a separating device (6) supplied by at least one fraction of the stream M8 and including an outlet line for stream M9 enriched with carbon dioxide and an outlet line for stream 71 depleted of carbon dioxide, said separating device (6) preferably being a membrane separating device or a solvent extraction device,- a liquefaction device (7) supplied by at least one fraction of the stream M9 enriched with carbon dioxide and including a gas stream 81 outlet line and a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line preferably supplying a storage device (3).

14. The installation according to any one of claims 10 to 12, wherein the hydrotreatment device (1) includes:- a hydrothermal gasification reactor (20) including at least one stream M6 outlet line and one stream M2 outlet line,- a cooling device (8) supplied with at least one fraction of the stream M6, and optionally of the stream M6’, and including a gas stream M10 outlet and a liquid stream M11 outlet,- an expansion device (9) supplied by at least one fraction of the stream M11 and including a liquid stream M12 outlet line and a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line preferably supplying a storage device (4),said hydrothermal treatment device (1) preferably further including:- a separating device (10) supplied by at least one fraction of the stream M10 and including an outlet line for stream M13 enriched with carbon dioxide and an outlet line for stream M14 depleted of carbon dioxide,- an expansion device (11) supplied by at least one fraction of the stream M13 and including a liquid carbon dioxide stream outlet line and a liquid stream M15 outlet line, said liquid carbon dioxide stream outlet line preferably supplying a storage device (3).

15. The installation according to any one of claims 10 to 12, wherein the hydrotreatment device (1) includes:- a wet oxidation device (30) supplied by the stream of mixture M1 line, and including at least one liquid stream F21 outlet and one gas stream M22 outlet,- a liquefaction device LQ supplied by at least one fraction of the gas stream M22 and including at least one carbon dioxide CO2liq1 outlet line,- a cooling and separating device RF supplied by at least one fraction of liquid stream M21 and including at least one stream M2 outlet line and a stream FL outlet,- a separating device (2) downstream of the stream M2 outlet line including at least one supercritical carbon dioxide CO2sc inlet and including at least two outlets, a stream M3 outlet line and a stream M4 outlet line,said carbon dioxide CO2liq1 outlet line optionally being connected with the supercritical carbon dioxide CO2sc inlet line, said carbon dioxide outlet line possibly comprising a storage device (3) and / or a heating and / or pressurizing device (4).

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