Method for treating complex waste

Abstract

The invention relates to a method for treating a mixture M1 comprising at least organic matter, the method comprising: a. a step of pressurising the mixture M1 to a pressure ranging from 1 to 100 bar, in order to obtain a mixture stream M1p; b. a step of hydrolysing at least one fraction of the mixture M1p in the presence of supercritical carbon dioxide, in order to obtain a hydrolysed mixture stream M1h; c. a step of treating at least one fraction of the hydrolysed mixture stream M1h, the treatment step allowing a stream of liquid carbon dioxide CO2liq1 to be obtained; d. a step of pressurising and / or heating at least one fraction of the liquid carbon dioxide CO2liq1 downstream of the treatment step c), in order to obtain all or part of the supercritical carbon dioxide used in step b).

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: - thermal methods (e.g. thermal hydrolysis), - physical or mechanical methods (e.g. ultra-sonication, high-pressure homogenization, etc.), - and chemical techniques (alkaline or acid pre-treatment, oxidation by ozonation, etc.).

[0008] The object of the present invention is to facilitate the conversion and improve the efficiency of biogas production, by virtue of a method for pretreating biomass and complex waste that optimizes both the treatment itself and the energy expenditure, while making use of the co-product of these energy conversions, namely CO2. SUMMARY OF THE INVENTION

[0009] The invention relates to a method for treating a mixture M1 comprising at least organic matter, said method comprising: a. a step of pressurizing the mixture M1 to a pressure ranging from 1 to 100 bar, in order to obtain a mixture stream M1p, b. a step of hydrolyzing at least one fraction of the mixture M1p in the presence of supercritical carbon dioxide, in order to obtain a hydrolyzed mixture stream M1h, c. a treatment step for producing biogas carried out on at least one fraction of the hydrolyzed mixture stream M1h, said treatment step allowing a stream of liquid carbon dioxide CO2liq1 to be obtained, d. a step of pressurizing and / or heating at least one fraction of the liquid carbon dioxide CO2liq1 downstream of treatment step c), in order to obtain all or part of the supercritical carbon dioxide used in step b).

[0010] According to one embodiment, the method comprises one or more of the following features: - at least a fraction of the liquid carbon dioxide from step c) is introduced into one or more storage devices, with pressurization and / or heating step d) then being carried out downstream of the storage device(s); and / or - at least a fraction of the carbon dioxide used during hydrolysis is recovered downstream of hydrolysis for reuse in pressurization and / or heating step d), where appropriate after storage in one or more storage devices; and / or - at least a fraction of the carbon dioxide used during hydrolysis is recovered downstream of hydrolysis to be reintroduced directly at the hydrolysis inlet; and / or - 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.

[0011] According to one embodiment, the treatment step c) is a hydrothermal gasification, 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.

[0012] According to a first embodiment, hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising: - a hydrothermal gasification of at least one fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter, - a step of cooling and expanding at least one fraction of the stream M4 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 M5 and a liquid stream M7, - a step of separating at least one fraction of the gas stream M5 making it possible to obtain, on the one hand, a stream M6 enriched with carbon dioxide and, on the other hand, a stream 71 depleted of carbon dioxide, - a step of liquefying at least one fraction of the stream M6 making it possible to obtain the liquid carbon dioxide stream CO2liq1 on the one hand and a gas stream 81 on the other hand, at least one fraction of said liquid carbon dioxide CO2liq1 stream is used in pressurization and / or heating step d), where appropriate after storage in one or more storage devices.

[0013] According to a second embodiment, hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising: - a hydrothermal gasification of at least one fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter, - a step of cooling at least one fraction of the stream M4 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 M8 and, on the other hand, a liquid stream M9, the liquid stream M9 being at a pressure ranging from 150 to 350 bar, - a step in which at least one fraction of the liquid stream M9 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 M10 depleted of carbon dioxide, at least one fraction of said liquid carbon dioxide CO2liq1 stream is used in pressurization and / or heating step d), where appropriate after storage in one or more storage devices, preferably, according to this second embodiment, said method further comprises: - a separation step carried out on at least one fraction of the gas stream M8, making it possible to obtain, on the one hand, a stream M12 enriched with carbon dioxide and, on the other hand, a stream M11 depleted of carbon dioxide, - an expansion step carried out on at least one fraction of the liquid stream M12 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 M13 depleted of liquid carbon dioxide, at least one fraction of said liquid carbon dioxide CO2liq1’ stream is implemented during pressurization and / or heating step d), where appropriate after storage in one or more storage devices.

[0014] According to one embodiment, step d) comprises at least one step of heat exchange between at least one fraction of the stream M4 from the hydrothermal gasification step and the liquid carbon dioxide stream upstream of hydrolysis and, where appropriate, downstream of the storage device, said heat exchange thus allowing the liquid carbon dioxide to be at least partially heated and allowing the stream M4 to be at least partially cooled.

[0015] According to one embodiment, the hydrothermal gasification step comprises a preliminary heating step of the mixture stream M1h, said preliminary heating step comprising at least one heat exchange sub-step between at least one fraction of the stream M4 from the hydrothermal gasification step and the stream M1h, said heat exchange thus allowing at least partial heating of the mixture M1h and allowing at least partial cooling of the stream M4, in order to obtain a stream M4’.

[0016] According to this embodiment, the method preferably further comprises a heat exchange between the stream M4’ and the liquid carbon dioxide stream upstream of hydrolysis and, where appropriate, downstream of the storage device, said heat exchange thus allowing the liquid carbon dioxide to be at least partially heated and allowing the stream M4’ to be at least partially cooled so as to obtain a stream M4’’.

[0017] According to one embodiment, the treatment in step c) is a digestion, said treatment comprising: - a digestion carried out on at least one fraction of the mixture stream M1h, making it possible to obtain a gas stream M14, - a separation step carried out on at least one fraction of the gas stream M14, making it possible to obtain a stream M16 enriched with carbon dioxide and a stream M15 depleted of carbon dioxide, - a liquefaction step carried out on at least one fraction of the stream M16 enriched with carbon dioxide, making it possible to obtain a liquid carbon dioxide stream.

[0018] The invention also relates to an installation for implementing a treatment method according to the invention, said installation comprising: - at least one pressurization pump 1, including an outlet line for stream M1p, - at least one hydrolysis reactor 2 configured to be supplied by at least one fraction of stream M1p and including at least one outlet line for stream M1h, - a treatment device 3 configured for biogas production, configured to be supplied by at least one fraction of stream M1h and including at least two outlets, an outlet line for liquid carbon dioxide CO2liq, a pressurization and / or heating device 5 supplied by a liquid carbon dioxide CO2liq outlet line downstream of the treatment device 3 and including at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2s outlet line being configured to supply the hydrolysis reactor 2.

[0019] According to one embodiment, the installation further comprises at least one storage device 4 including at least one inlet supplied by the outlet line for liquid carbon dioxide CO2liq downstream of the treatment device 3 and including at least one outlet for liquid carbon dioxide CO2liq2 supplying the pressurization and / or heating device 5, preferably said installation further comprises at least one recirculation loop for recirculating at least a fraction of the carbon dioxide recovered downstream of the hydrolysis reactor 2 to the storage device 4.

[0020] According to one embodiment of the installation, the treatment device 3 includes a hydrothermal gasification reactor 31 including at least one stream M4 outlet line, in which installation the pressurization and / or heating device 5 includes at least one heat exchanger for recovering heat from the stream M4 for transfer to the liquid carbon dioxide upstream of the hydrolysis reactor 2, said heat exchanger including at least one stream M4’’ outlet line and one supercritical carbon dioxide outlet line.

[0021] According to a first embodiment of the installation, the hydrothermal treatment device 3 includes: - a hydrothermal gasification reactor (31) including at least one outlet line for stream M4, - a cooling and expansion device 6 supplied by at least one fraction of the stream M4, and where appropriate the stream M4’’, and including a gas stream M5 outlet and a liquid stream M7 outlet, - a separating device 7 supplied by at least one fraction of the stream M5 and including an outlet line for stream M6 enriched with carbon dioxide and an outlet line for stream 71 depleted of carbon dioxide, said separating device 7 preferably being a membrane separating device or a solvent extraction device, - a liquefaction device 8 supplied by at least one fraction of the stream M6 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 supplying the pressurization and / or heating device 5 or, where applicable, supplying the storage device 4.

[0022] According to a second embodiment of the installation, the treatment device 3 includes: - a hydrothermal gasification reactor 31 including at least one outlet line for the stream M4, - a cooling device 9 supplied by at least one fraction of the stream M4, and where appropriate of the stream M4’’, and including a gas stream M8 outlet and a liquid stream M9 outlet, - an expansion device 10 supplied by at least one fraction of the stream M9 and including a liquid stream M10 outlet line and a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line supplying the storage device 4, said hydrothermal treatment device 3 preferably further including: - a separating device 11 supplied by at least one fraction of the stream M8 and including an outlet line for stream M12 enriched with carbon dioxide and an outlet line for stream M11 depleted of carbon dioxide, - an expansion device 12 supplied by at least one fraction of the stream M12 and including a liquid carbon dioxide stream outlet line and a liquid stream M13 outlet line, said liquid carbon dioxide stream outlet line supplying the storage device 4.

[0023] According to another embodiment of the installation, the treatment device 3 includes: - a digester 32 supplied by the stream M1h line and including an outlet for gas stream M14, - a separating device 13 supplied by at least one fraction of the stream M14 and including an outlet line for stream M16 enriched with carbon dioxide and an outlet line for stream M15 depleted of carbon dioxide, - a liquefaction device 14 supplied by at least one fraction of stream M16 and including a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line supplying the pressurization and / or heating device 5 or, where applicable, supplying the storage device 4.

[0024] The invention facilitates the conversion and improves the yield of biogas production and digestion of organic matter.

[0025] The invention thus proposes a method for pretreating biomass and complex waste that optimizes both the treatment per se and the energy expenditure, while making use of the co-product of these energy conversions, namely CO2. BRIEF DESCRIPTION OF THE FIGURES

[0026] [Fig.1] is an installation for carrying out the method according to one embodiment of the invention.

[0027] [Fig.2] is an installation for carrying out the method according to one embodiment of the invention.

[0028] [Fig.3] is an installation for carrying out the method according to one embodiment of the invention.

[0029] [Fig.4] is an installation for carrying out the method according to one embodiment of the invention.

[0030] [Fig.5] is an installation for carrying out the method according to one embodiment of the invention.

[0031] [Fig.6] is an installation for carrying out the method according to one embodiment of the invention.

[0032] [Fig.7] is an installation for carrying out the method according to one embodiment of the invention.

[0033] [Fig.8] is an installation for carrying out the method according to one embodiment of the invention.

[0034] [Fig.9] is an installation for carrying out the method according to one embodiment of the invention.

[0035] [Fig.10] is an installation for carrying out the method according to embodiment of the invention.

[0036] [Fig.11] is an installation for carrying out the method according to one one embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] The invention relates to a method for treating a mixture M1 comprising at least organic matter, said method comprising: a. a step of pressurizing the mixture M1 at a pressure ranging from 1 to 300 bar, preferably 20 to 100 bar, in order to obtain a mixture stream M1p, b. a step of hydrolyzing at least one fraction of the mixture M1p in the presence of supercritical carbon dioxide, in order to obtain a hydrolyzed mixture stream M1h, c. a treatment step for producing biogas carried out on at least one fraction of the hydrolyzed mixture stream M1h, said treatment step allowing a stream of liquid carbon dioxide CO2liq to be obtained, d. a pressurization and / or heating step carried out on at least one fraction of the liquid carbon dioxide CO2liq downstream of treatment step c) in order to obtain all or part of the supercritical carbon dioxide carried out in step b).

[0038] 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.

[0039] In the context of the present invention, the expression “where appropriate” means “if applicable”.

[0040] • Mixture M1

[0041] 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.

[0042] 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.

[0043] According to one embodiment, the method of the invention comprises a grinding step and / or a thermal or biological 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 pressurized in step a) making it possible to obtain the mixture stream M1p that will then be implemented in step b) of the method of the invention.

[0044] Grinding will then improve the specific surface area, allowing better hydrolysis.

[0045] • Pressurization step a)

[0046] The method according to the invention comprises a step of pressurizing the mixture M1 preferably to a pressure ranging from 1 to 300 bar, preferably from 20 to 100 bar, said mixture M1 optionally already being pressurized before step a).

[0047] A mixture stream M1p is then obtained.

[0048] • Step b) hydrolysis

[0049] The method according to the invention comprises a step of hydrolysis of at least one fraction of the mixture M1p in the presence of supercritical carbon dioxide.

[0050] Supercritical carbon dioxide is carbon dioxide at a temperature of at least 31.25°C and a pressure of at least 74 bar.

[0051] 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.

[0052] 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).

[0053] 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 hydrolysis step of the organic matter.

[0054] 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 hydrolysis step of the organic matter.

[0055] Typically, the hydrolysis step is carried out in one or more hydrolysis reactors.

[0056] During the hydrolysis step, the supercritical carbon dioxide is preferably introduced continuously into the hydrolysis device(s), preferably via an inlet separate from the inlet for mixture M1p.

[0057] At the end of hydrolysis, a hydrolyzed mixture stream M1h is obtained. The mixture M1h will typically be at a temperature above the supercritical temperature of the CO2 and at a pressure above the supercritical pressure of the CO2.

[0058] Hydrolysis can be carried out with residence times ranging from 5 minutes to 90 minutes.

[0059] The hydrolysis is preferably carried out at a temperature ranging from 40°C to 300°C and / or at a pressure ranging from 80 bar to 250 bar.

[0060] The ratio between the viscosity of the mixture M1 and the viscosity of the mixture M1h is preferably at least 5, preferably at least 10, even more preferably at least 100.

[0061] The viscosity defined in the context of the present invention is a kinematic viscosity measured at the same temperature (e.g. 20°C) using rheometers adapted to the viscosity to be measured (cylinder-cylinder, planeplane) and by measuring the two viscosities at the same shear rate (in s-1), typically taking care to eliminate turbulence problems and to comply with rheological rules (e.g. spacing between cylinders depending on particle size).

[0062] According to one embodiment, at least a fraction of the carbon dioxide used during hydrolysis is recovered downstream of hydrolysis to be reintroduced directly at the hydrolysis inlet.

[0063] • Treatment step c)

[0064] The method of the invention comprises a treatment step allowing biogas production and implementation on at least one fraction of the hydrolyzed mixture stream M1h.

[0065] This treatment step produces at least one stream of liquid carbon dioxide CO2liq. This carbon dioxide stream can be obtained by liquefying at least one fraction of a stream obtained during the treatment method according to the invention. Examples of liquefaction are given below. • Storage

[0066] According to one embodiment, the method of the invention further comprises a storage step. According to this embodiment, at least one fraction of the liquid carbon dioxide CO2liq from treatment step c) is introduced into one or more storage devices, where the carbon dioxide is stored. The storage device(s) may optionally comprise one or more cooling devices. These cooling devices can thus be used to liquefy the carbon dioxide.

[0067] Preferably, according to this embodiment, the carbon dioxide is stored in the storage device in a 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.

[0068] The storage device(s) can also be supplied with at least one fraction of the carbon dioxide, preferably in liquid form, recovered downstream of hydrolysis.

[0069] One or more storage devices can be provided as part of the present invention.

[0070] • Pressurization and / or heating step d)

[0071] The method of the invention comprises a pressurization and / or heating step carried out on at least one fraction of liquid carbon dioxide downstream of treatment step c) in order to obtain all or part of the supercritical carbon dioxide carried out in step b).

[0072] Thus, this step d) brings the carbon dioxide to supercritical conditions.

[0073] According to one embodiment, at least a fraction of the liquid carbon dioxide from step c) is introduced into one or more storage devices, with pressurization and / or heating step d) then being carried out downstream of the storage device(s).

[0074] Depending on the storage temperature and pressure, the carbon dioxide will then typically be heated and / or pressurized downstream of said storage device, in order to bring the carbon dioxide to supercritical conditions, prior to its implementation in hydrolysis step b).

[0075] Step d) is typically carried out in a pressurization and / or heating device 5.

[0076] Step d) may comprise one or more sub-steps. Thus, according to one embodiment, step d) comprises at least one heat exchange sub-step wherein heat from the mixture stream treated in step c) is recovered and transferred to the liquid carbon dioxide upstream of the hydrolysis step and where appropriate (that is, when the method comprises a storage step in a storage device) downstream of the storage device. This heat exchange sub-step thus allows the carbon dioxide from step d) to be at least partially heated to supercritical conditions.

[0077] According to one embodiment of the invention, the method comprises at least one heat exchange for transferring heat from the stream of matter treated in treatment step c) to the liquid carbon dioxide stream upstream of hydrolysis step b) and, where appropriate, downstream of the storage step.

[0078] According to one embodiment of the invention, the method comprises two heat exchanges: - a heat exchange for transferring heat from the stream of matter treated in treatment step c) to the stream of matter M1h upstream of treatment step c), - a heat exchange for transferring heat from the stream of matter treated in treatment step c) to the liquid carbon dioxide stream upstream of hydrolysis step b) and, where appropriate, downstream of the storage step.

[0079] • Treatment step c): hydrothermal gasification (HG)

[0080] According to one embodiment, treatment step c) 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.

[0081] 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.

[0082] 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.

[0083] 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).

[0084] 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.

[0085] 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.

[0086] Methane is also produced by the methanation of CO and CO2, using dihydrogen.

[0087] 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.

[0088] 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.

[0089] Typically, in the context of the present invention, this HG step makes it possible to obtain a stream of mineral matter M3 and a stream M4 comprising a mixture containing gas and liquid.

[0090] In the context of the present invention, the stream M3 will be referred to indifferently as a stream of inorganic matter or a stream of mineral matter.

[0091] The stream of mineral matter M3 will typically comprise a higher proportion of mineral matter than the proportion of mineral matter in the stream M1h.

[0092] The stream of matter M4 will typically comprise a higher mass ratio of organic matter than the mass ratio of organic matter in the stream M1h.

[0093] Also typically, the mineral matter stream M3 will comprise a higher proportion of mineral matter than the proportion of mineral matter in the stream M4.

[0094] Also typically, the stream of matter M4 will comprise a higher proportion of organic matter than the proportion of organic matter in the stream M3.

[0095] The stream M4 will comprise a mixture of gas and liquid; this gas more particularly comprises CO2.

[0096] Hydrothermal gasification is the term used to describe the entire processing 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 inorganic matter.

[0097] 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.

[0098] 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.

[0099] The hydrothermal gasification may also comprise a separation of the mineral fraction (salts) M3 and may involve the use of catalysts.

[0100] Mineral matter includes salts comprising anions such as phosphates, sulfates, chlorides, carbonates and hydrocarbonates with counterions such as sodium, magnesium, calcium, ammonium and metals.

[0101] Preferably, the (overall) residence time of the stream M1h in HG step c) typically ranges from 1 min to 20 min, preferably from 2 min to 10 min, more preferably from 3 to 5 min.

[0102] 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.

[0103] The catalyst can be in the form of a bed of solid particles within the gasification reactor.

[0104] The hydrothermal gasification step will thus generally lead to a mixture comprising inorganic matter (salts) and organic matter.

[0105] In the context of the invention, the HG step typically includes a separation step making it possible to obtain a stream M3 enriched in inorganic matter and a stream M4 depleted of inorganic matter. The stream M4 will then generally be a stream of gas dissolved in a liquid effluent.

[0106] 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.

[0107] 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.

[0108] 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” separation from at least one fraction of the stream M4 from the hydrothermal gasification reactor, where appropriate from the stream M4’ or M4’’ obtained after one or more heat exchanges of the stream M4.

[0109] • So-called “low-pressure” separation

[0110] According to one embodiment of the method of the invention, hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising: - a hydrothermal gasification of at least one fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter, - a step of cooling and expanding at least one fraction of the stream M4 to a temperature ranging from 20 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 M5 and a liquid stream M7, - a step of separating at least one fraction of the gas stream M5 making it possible to obtain, on the one hand, a stream M6 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 M6, 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 on the one hand (stream referred to as “CO2-enriched stream”) and a gas stream 81 (stream referred to as “CO2-depleted stream”) on the other hand.

[0111] According to the embodiment using one or more storage devices, at least one fraction of said liquid carbon dioxide stream is introduced into at least one storage device.

[0112] Preferably, the liquefaction step comprises a cooling step and / or a compression step. It is used to liquify the carbon dioxide.

[0113] • So-called “high-pressure” separation

[0114] According to one embodiment of the method of the invention, hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising: - a hydrothermal gasification of at least one fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter, - a step of cooling at least one fraction of the stream M4 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 M8 and, on the other hand, a liquid stream M9 (stream comprising dissolved CO2), the liquid stream M9 being at a pressure ranging from 150 to 350 bar; - an expansion step in which at least one fraction of the liquid stream M9 is expanded, typically to a pressure ranging from 35 bar to 100 bar, making it possible to obtain on the one hand a liquid carbon dioxide stream (“CO2-enriched stream”) and on the other hand a liquid stream M10 (“CO2-depleted stream”).

[0115] According to the embodiment using one or more storage devices, at least one fraction of said CO2-enriched stream is introduced into at least one storage device.

[0116] According to this so-called “high pressure” embodiment, preferably, carbon dioxide can also be recovered from all or part of the stream M8.

[0117] Thus, according to one embodiment, the method further comprises: - a separation step carried out on at least one fraction of the gas stream M8, making it possible to obtain, on the one hand, a stream M12 enriched with carbon dioxide and, on the other hand, a stream M11 depleted of carbon dioxide, - an expansion step carried out on at least one fraction of the stream M12 at a pressure ranging from 35 to 100 bar, making it possible to obtain both a liquid carbon dioxide stream (“CO2-enriched stream”) on the one hand and a liquid stream M13 (“CO2-depleted stream”) on the other hand.

[0118] According to the embodiment using one or more storage devices, at least one fraction of said CO2-enriched stream is introduced into at least one storage device.

[0119] • Heat exchanges

[0120] According to one embodiment, treatment step c) is a hydrothermal gasification step which produces at least one stream M4 comprising gas and liquid, and the method of the invention comprises a heat exchange X1 between at least one fraction of the stream M4 from the hydrothermal gasification step and the liquid carbon dioxide stream upstream of the hydrolysis and, where appropriate, downstream of the storage device, said heat exchange thus allowing the liquid carbon dioxide to be at least partially heated and allowing the stream M4 to be at least partially cooled. The cooled stream is referred to as stream M4’’. This heat exchange X1 may correspond to step d) of the invention or to a sub-step of step d) of the invention.

[0121] According to this embodiment, at least one fraction of the stream M4’’ 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.

[0122] According to one embodiment, treatment step c) is a hydrothermal gasification step comprising a preliminary heating step of the mixture stream M1h, said preliminary heating step comprising at least one heat exchange substep X2 between the stream M4 from the hydrothermal gasification step and the stream M1h, said heat exchange X2 thus allowing at least partial heating of the mixture M1h and allowing at least partial cooling of the stream M4, in order to obtain a stream M4’.

[0123] According to this embodiment, at least one fraction of the stream M4’ 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.

[0124] According to this embodiment, the method preferably further comprises a heat exchange between the stream M4’ and the liquid carbon dioxide stream upstream of hydrolysis and, where appropriate, downstream of the storage device, said heat exchange X1’ thus allowing the liquid carbon dioxide to be at least partially heated and allowing the stream M4’ to be at least partially cooled so as to obtain a stream M4’’. This heat exchange X1’ may correspond to step d) of the invention or to a sub-step of step d) of the invention.

[0125] According to this embodiment, at least one fraction of the stream M4’’ 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.

[0126] 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 c) to the stream of matter M1h upstream of treatment step c), - a heat exchange X1, X1’ for transferring heat from the stream of matter treated in treatment step c) to the liquid carbon dioxide stream upstream of hydrolysis step b) and, where appropriate, downstream of the storage step.

[0127] • Treatment step c): digestion

[0128] According to one embodiment, treatment step c) is a digestion. Preferably, according to this embodiment, treatment step c) comprises: - a digestion carried out on at least one fraction of the mixture stream M1h, making it possible to obtain a gas stream M14, - a separation step carried out on at least one fraction of the gas stream M14, making it possible to obtain a stream M16 enriched with carbon dioxide and a stream M15 depleted of carbon dioxide, - a liquefaction step carried out on at least one fraction of the stream M16 enriched with carbon dioxide, typically to a temperature ranging from -56°C to +31°C, making it possible to obtain a liquid carbon dioxide stream, said liquefaction step preferably being carried out by cooling and / or compression.

[0129] A stream of digested matter M17 is obtained downstream of the digestion.

[0130] According to the embodiment using one or more storage devices, at least one fraction of said liquid carbon dioxide stream is introduced into at least one storage device.

[0131] The present invention further relates to an installation as such and an installation for implementing the method of the invention.

[0132] The installation according to the invention comprises: - at least one pressurization pump 1, including an outlet line for stream M1p, - at least one hydrolysis reactor 2 supplied by at least one fraction of stream M1p and including a feed line for supercritical carbon dioxide CO2sc, and including at least one outlet line for stream M1h, - a treatment device 3 supplied by at least one fraction of stream M1h and including at least one liquid carbon dioxide CO2liq1 outlet line, - a pressurization and / or heating device 5 supplied by a liquid carbon dioxide CO2liq outlet line downstream of the treatment device 3 and including at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2sc supplying the hydrolysis reactor 2.

[0133] According to one embodiment, the installation according to the invention comprises at least one storage device 4 including at least one inlet supplied by the liquid carbon dioxide CO2liq outlet line downstream of the treatment device 3 and including at least one liquid carbon dioxide CO2liq outlet for supplying the pressurization and / or heating device 5.

[0134] According to one embodiment not shown in the figures, the installation according to the invention does not comprise a storage device.

[0135] According to an embodiment not shown in the figures, the installation further comprises at least one recirculation loop for recirculating at least one fraction of the carbon dioxide recovered downstream of the hydrolysis reactor 2 to the storage device 4 or to the pressurization and / or heating device 5 when the installation does not comprise a storage device.

[0136] Said recirculation loop may optionally comprise a cooling and expansion device and / or the storage device 4 may optionally comprise a cooling and expansion device not shown in the figures. This liquefies the carbon dioxide, which is optionally in gaseous form, for storage or use during hydrolysis.

[0137] According to one embodiment, the pressurization and / or heating device 5 comprises at least one heat exchanger, said heat exchanger allowing heat to be recovered from the stream of treated matter in the treatment device and transferred to the carbon dioxide upstream of the hydrolysis step. This embodiment of the installation allows the heat exchange X1 (or heat exchange X1’ when the installation comprises a heat exchanger for carrying out the heat exchange X2) to be carried out.

[0138] According to one embodiment, the treatment device 3 further comprises a heat exchanger for transferring heat from the stream of matter treated in treatment step c) to the stream of matter M1h upstream of treatment step c). This embodiment of the installation allows the heat exchange X2 to be carried out.

[0139] [Fig.1] is one embodiment of the invention, where the installation comprises: - a feed line of mixture M1, - a pressurization pump 1 supplied by the feed line of mixture M1 and including an outlet line for stream M1p, - a hydrolysis reactor 2 supplied by at least one fraction of stream M1p and with a feed line for supercritical carbon dioxide CO2sc, and including at least one outlet line for stream M1h and an outlet line for carbon dioxide CO2, - a treatment device 3 supplied by at least one fraction of stream M1h and including at least one liquid carbon dioxide CO2liq1 outlet line, a storage device 4 supplied with at least one fraction from the liquid carbon dioxide CO2liq1 outlet line downstream of the treatment device 3 and including at least one liquid carbon dioxide CO2liq2 outlet, - a pressurization and / or heating device 5 supplied by the liquid carbon dioxide CO2liq2 outlet line downstream of the storage device 4 and including at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2sc supplying the hydrolysis reactor 2, - a carbon dioxide recirculation loop between the carbon dioxide CO2 outlet line downstream of the hydrolysis reactor and the storage device 4.

[0140] According to one embodiment, the treatment device 3 comprises a hydrothermal gasification reactor 31.

[0141] The installation according to the invention, including a hydrothermal gasification reactor 31, can be adapted to implement a so-called low-pressure separation.

[0142] According to this embodiment, preferably, the treatment device 3 includes: - a hydrothermal gasification reactor 31 including at least one outlet line for stream M4 and at least one outlet line M3, - a cooling and expansion device 6 supplied by at least one fraction of the stream M4, and where appropriate the stream M4’, and including a gas stream M5 outlet and a liquid stream M7 outlet, - a separating device 7 supplied by at least one fraction of the stream M5 and including an outlet line for stream M6 enriched with carbon dioxide and an outlet line for stream 71 depleted of carbon dioxide, said separating device 7 preferably being a membrane separating device or a solvent extraction device, - a liquefaction device 8 supplied by at least one fraction of the stream M6 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 supplying the storage device 4.

[0143] The liquefaction device 8 can be a cooling device and / or a compression device.

[0144] [Fig.2] is an embodiment in which treatment step c) is a hydrothermal gasification step in which the carbon dioxide is recovered by “low pressure” separation. As shown in [Fig.2], the treatment device 3 includes: - a hydrothermal gasification reactor 31 including at least one outlet line for the stream M4, - a cooling and expansion device 6 supplied by at least one fraction of the stream M4, and including a gas stream M5 outlet and a liquid stream M7 outlet, - a separating device 7 supplied by at least one fraction of the stream M5 and including an outlet line for stream M6 enriched with carbon dioxide and an outlet line for stream 71 depleted of carbon dioxide, said separating device 7 preferably being a membrane separating device or a solvent extraction device, - a liquefaction device 8 supplied by at least one fraction of the stream M6 enriched with carbon dioxide and including an aqueous stream 81 outlet line and a liquid carbon dioxide CO2liq1 stream outlet line, said liquid carbon dioxide stream outlet line supplying the storage device 4.

[0145] [Fig.3] is an embodiment where the method includes a heat exchange between the stream M4 leaving the hydrothermal gasification reactor and the pressurization and / or heating device 5, which on the one hand cools the stream M4 (to obtain a stream M4’’) and on the other hand heats the liquid carbon dioxide CO2liq2 (to obtain supercritical carbon dioxide CO2sc). This [Fig.3] shows an embodiment of the installation for carrying out the heat exchange X1 as defined in the invention.

[0146] The installation according to the invention, including a hydrothermal gasification reactor 31, can be adapted to carry out a so-called high-pressure separation.

[0147] According to this embodiment, preferably, the treatment device 3 includes: - a hydrothermal gasification reactor 31 including at least one outlet line for the stream M4, - a cooling device 9 supplied by at least one fraction of the stream M4, and where appropriate of the stream M4’’, and including a gas stream M8 outlet and a liquid stream M9 outlet, - an expansion device 10 supplied by at least one fraction of the stream M9 and including a gas stream M10 outlet line and a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line supplying the storage device 4.

[0148] Said expansion device 10 may optionally further comprise a cooling device so as to obtain carbon dioxide in liquid form.

[0149] Preferably, according to this embodiment, the treatment device 3 further comprises: - a separating device 11 supplied by at least one fraction of the stream M8 and including an outlet line for stream M12 enriched with carbon dioxide and an outlet line for stream M11 depleted of carbon dioxide, - an expansion device 12 supplied by at least one fraction of the stream M12 and including a liquid carbon dioxide stream outlet line and an aqueous stream M13 outlet line, said liquid carbon dioxide CO2liq1’ stream outlet line supplying the storage device 4.

[0150] Said expansion device 12 may optionally further comprise a cooling device so as to obtain carbon dioxide in liquid form.

[0151] [Fig.4] is an embodiment in which treatment step c) is a hydrothermal gasification step in which carbon dioxide is recovered by “high pressure” separation. As shown in [Fig.4], the treatment device 3 includes: - a hydrothermal gasification reactor 31 including at least one outlet line for the stream M4, - a cooling device 9 supplied by at least one fraction of the stream M4, and including a gas stream M8 outlet and a liquid stream M9 outlet, - an expansion device 10 supplied by at least one fraction of the stream M9 and including a gas stream M10 outlet line and a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line supplying the storage device 4.

[0152] [Fig.5] differs from [Fig.4] in that the method includes a heat exchange between the stream M4 leaving the hydrothermal gasification reactor and the liquid carbon dioxide CO2liq2 for example in the pressurization and / or heating device 5, which on the one hand cools the stream M4 (so as to obtain a stream called M4’’) and on the other hand heats the liquid carbon dioxide CO2liq2 (to obtain supercritical carbon dioxide CO2sc). This [Fig.5] is an embodiment of the installation for carrying out the heat exchange X1 as defined in the invention.

[0153] [Fig.6] differs from [Fig.4] in that the treatment device 3 further comprises: - a separating device 11 supplied by at least one fraction of the stream M8 and including an outlet line for stream M12 enriched with carbon dioxide and an outlet line for stream M11 depleted of carbon dioxide, - an expansion device 12 supplied by at least one fraction of the stream M12 and including a liquid carbon dioxide stream outlet line and an aqueous stream M13 outlet line, said liquid carbon dioxide CO2liq1’ stream outlet line supplying the storage device 4.

[0154] [Fig.6] is an embodiment where the storage device 4 includes an inlet for the CO2liq1 stream and an inlet for the CO2liq1’ stream. According to an embodiment not shown, the CO2liq1 and CO2liq1’ stream lines can be combined upstream of the storage device 4.

[0155] [Fig.7] is an embodiment of the method with low-pressure separation in which the method includes exchanging heat in a heat exchanger 312 supplied by at least one fraction of the stream M4 leaving a gasification reactor 311, on the one hand, to cool the stream M4 (to obtain a stream M4’) and, on the other hand, to at least partially heat the mixture M1h upstream of the gasification reactor 311 (to obtain a stream M2). This [Fig.7] is an embodiment of the installation for carrying out the heat exchange X2 as defined in the invention.

[0156] [Fig.8] is a high-pressure separation method in which the method includes exchanging heat in a heat exchanger 312 supplied by at least one fraction of the stream M4 leaving a gasification reactor 311, to cool the stream M4 (so as to obtain a stream M4’) and at least partially heat the mixture M1h upstream of the gasification reactor 311 (so as to obtain a stream M2). This [Fig.8] is an embodiment of the installation for carrying out the heat exchange X1 as defined in the invention.

[0157] [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.

[0158] According to an embodiment shown in [Fig.9] and [Fig.10], the method includes two heat exchanges: - a first heat exchange X2 in a heat exchanger 312 supplied by at least a fraction of the stream M4 leaving a gasification reactor 311, on one hand to cool the stream M4 (to obtain a stream M4’) and on the other hand to at least partially heat the mixture M1h upstream of the gasification reactor 311 (to obtain a stream M2), - a second heat exchange X1’ between the stream M4’ downstream of the heat exchanger 312 and the liquid carbon dioxide CO2liq2 for example in the pressurization and / or heating device 5, which on the one hand cools the stream M4’ (so as to obtain a stream M4”) and on the other hand heats the liquid carbon dioxide CO2liq2 (to obtain supercritical carbon dioxide CO2sc).

[0159] According to one embodiment, the treatment device 3 includes a digester 32. According to this embodiment, preferably, the treatment device 3 includes: - a digester 32 supplied by the stream M1h line and including an outlet for gas stream M14, - a separating device 13 supplied by at least one fraction of the stream M14 and including an outlet line for stream M16 enriched with carbon dioxide and an outlet line for stream M15 depleted of carbon dioxide, - a liquefaction device 14 supplied by at least one fraction of the stream M16 and including a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line supplying a storage device 4 when such a storage device is present or supplying the pressurization and / or heating device 5 when the installation does not include a storage device.

[0160] The liquefaction device 14 can be a cooling device and / or a compression device.

[0161] [Fig.11] is an embodiment where treatment step c) is a digestion step. According to an embodiment shown in [Fig.11], the treatment device 3 includes: - a digester 32 supplied by the stream M1h line and including an outlet for gas stream M14, - a separating device 13 supplied by at least one fraction of the stream M14 and including an outlet line for stream M16 enriched with carbon dioxide and an outlet line for stream M15 depleted of carbon dioxide, - a liquefaction device 14 supplied by at least one fraction of the stream M16 and including a liquid carbon dioxide CO2liq1 stream outlet line, said carbon dioxide stream outlet line supplying a storage device 4 when such a storage device is present or supplying the pressurization and / or heating device 5 when the installation has no storage device.

[0162] The stream of digested matter is shown by the stream M17 in [Fig.11], at the outlet of the digester 32.

Claims

1. A method for treating a mixture M1 comprising at least organic matter, said method comprising:a. a step of pressurizing the mixture M1 to a pressure ranging from 1 to 100 bar, in order to obtain a mixture stream M1p,b. a step of hydrolyzing at least one fraction of the mixture M1p in the presence of supercritical carbon dioxide in order to obtain a hydrolyzed mixture stream M1h,c. a treatment step for producing biogas carried out on at least one fraction of the hydrolyzed mixture stream M1h, said treatment step allowing a stream of liquid carbon dioxide CO2liq1 to be obtained,d. a step of pressurizing and / or heating at least one fraction of the liquid carbon dioxide CO2liq1 downstream of treatment step c), in order to obtain all or part of the supercritical carbon dioxide used in step b).

2. The treatment method according to claim 1, wherein at least a fraction of the liquid carbon dioxide from step c) is introduced into one or more storage devices, with pressurization and / or heating step d) then being carried out downstream of the storage device(s).

3. The treatment method according to claim 1 or 2, wherein at least a fraction of the carbon dioxide used during hydrolysis:is recovered downstream of hydrolysis for reuse in pressurization and / or heating step d) (i), where appropriate after storage in one or more storage devices; and / or(ii) is recovered downstream of hydrolysis to be reintroduced directly at the hydrolysis inlet.

4. The treatment method according to any one of claims 1 to 3, wherein the treatment step c) is a hydrothermal gasification, preferably carried out at a temperature ranging from 350°C to 700°C, preferably from 400°C to600°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.

5. The treatment method according to claim 4, wherein hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising:- a hydrothermal gasification of at least one fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter,- a step of cooling and expanding at least one fraction of the stream M4 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 M5 and a liquid stream M7,- a step of separating at least one fraction of the gas stream M5 making it possible to obtain, on the one hand, a stream M6 enriched with carbon dioxide and, on the other hand, a stream (71) depleted of carbon dioxide,- a step of liquefying at least one fraction of the stream M6 making it possible to obtain the liquid carbon dioxide stream CO2liq1 on the one hand and a gas stream (81) on the other hand, at least one fraction of said liquid carbon dioxide CO2liq1 stream is used in pressurization and / or heating step d), where appropriate after storage in one or more storage devices.

6. The treatment method according to claim 4, wherein hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising:- a hydrothermal gasification of at least one fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter,- a step of cooling at least one fraction of the stream M4 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 M8 and,on the other hand, a liquid stream M9, the liquid stream M9 being at a pressure ranging from 150 to 350 bar,- a step in which at least one fraction of the liquid stream M9 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 M10 depleted of carbon dioxide, at least one fraction of said liquid carbon dioxide CO2liq1 stream is used in pressurization and / or heating step d), where appropriate after storage in one or more storage devices,preferably said method further comprising:- a separation step carried out on at least one fraction of the gas stream M8, making it possible to obtain, on the one hand, a stream M12 enriched with carbon dioxide and, on the other hand, a stream M11 depleted of carbon dioxide,- an expansion step carried out on at least one fraction of the liquid stream M12 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 M13 depleted of liquid carbon dioxide, at least one fraction of said liquid carbon dioxide CO2liq1’ stream is implemented during pressurization and / or heating step d), where appropriate after storage in one or more storage devices.

7. The treatment method according to any one of claims 4 to 6, wherein step d) comprises at least a step of heat exchange between at least one fraction of the stream M4 from the hydrothermal gasification step and the liquid carbon dioxide stream upstream of hydrolysis and, where appropriate, downstream of the storage device, said heat exchange thus allowing the liquid carbon dioxide to be at least partially heated and allowing the stream M4 to be at least partially cooled.

8. The treatment method according to any one of claims 4 to 6, wherein the hydrothermal gasification step comprises a preliminary heatingstep of the mixture stream M1h, said preliminary heating step comprising at least one heat exchange sub-step between at least one fraction of the stream M4 from the hydrothermal gasification step and the stream M1h, said heat exchange thus allowing at least partial heating of the mixture M1h and allowing at least partial cooling of the stream M4, in order to obtain a stream M4’,the method preferably further comprising a heat exchange between the stream M4’ and the liquid carbon dioxide stream upstream of hydrolysis and, where appropriate, downstream of the storage device, said heat exchange thus allowing the liquid carbon dioxide to be at least partially heated and allowing the stream M4’ to be at least partially cooled so as to obtain a stream M4’’.

9. The treatment method according to any one of claims 1 to 3, wherein treatment step c) is a digestion, the treatment comprising:- a digestion carried out on at least one fraction of the mixture stream M1h, making it possible to obtain a gas stream M14,- a separation step carried out on at least one fraction of the gas stream M14, making it possible to obtain a stream M16 enriched with carbon dioxide and a stream M15 depleted of carbon dioxide,- a liquefaction step carried out on at least one fraction of the stream M16 enriched with carbon dioxide, making it possible to obtain a liquid carbon dioxide stream.

10. An installation for implementing a treatment method according to any one of claims 1 to 9, said installation comprising:- at least one pressurization pump (1), including an outlet line for stream M1p,- at least one hydrolysis reactor (2) configured to be supplied by at least one fraction of stream M1p and including at least one outlet line for stream M1h,- a treatment device (3) configured for biogas production, configured to be supplied by at least one fraction of stream M1h and including at least two outlets, an outlet line for liquid carbon dioxide CO2liq,- a pressurization and / or heating device (5) supplied by a liquid carbon dioxide CO2liq outlet line downstream of the treatment device (3) and including at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2s outlet line being configured to supply the hydrolysis reactor (2).

11. The installation according to the preceding claim, further comprising at least one storage device (4) including at least one inlet supplied by the outlet line for liquid carbon dioxide CO2liq downstream of the treatment device (3) and including at least one outlet for liquid carbon dioxide CO2liq2 supplying the pressurization and / or heating device (5), preferably said installation further comprises at least one recirculation loop for recirculating at least a fraction of the carbon dioxide recovered downstream of the hydrolysis reactor (2) to the storage device (4).

12. The installation according to claim 10 or 11, wherein the treatment device (3) includes a hydrothermal gasification reactor (31) including at least one stream M4 outlet line, in which installation the pressurization and / or heating device (5) includes at least one heat exchanger for recovering heat from the stream M4 for transfer to the liquid carbon dioxide upstream of the hydrolysis reactor (2), said heat exchanger including at least one stream M4’’ outlet line and one supercritical carbon dioxide outlet line.

13. The installation according to any one of claims 10 to 12, wherein the treatment device (3) includes:- a hydrothermal gasification reactor (31) including at least one outlet line for stream M4,- a cooling and expansion device (6) supplied by at least one fraction of the stream M4, and where appropriate the stream M4’’, and including a gas stream M5 outlet and a liquid stream M7 outlet,- a separating device (7) supplied by at least one fraction of the stream M5 and including an outlet line for stream M6 enriched with carbon dioxide and an outlet line for stream (71) depleted of carbon dioxide, said separating device (7) preferably being a membrane separating device or a solvent extraction device,- a liquefaction device (8) supplied by at least one fraction of the stream M6 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 the pressurization and / or heating device (5) or, where appropriate, supplying the storage device (4).

14. The installation according to any one of claims 10 to 12, wherein the treatment device (3) includes:- a hydrothermal gasification reactor (31) including at least one outlet line for stream M4,- a cooling device (9) supplied by at least one fraction of the stream M4, and where appropriate of the stream M4’’, and including a gas stream M8 outlet and a liquid stream M9 outlet,- an expansion device (10) supplied by at least one fraction of the stream M9 and including a liquid stream M10 outlet line and a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line supplying the storage device (4),said hydrothermal treatment device (3) preferably further including:- a separating device (11) supplied by at least one fraction of the stream M8 and including an outlet line for stream M12 enriched with carbon dioxide and an outlet line for stream M11 depleted of carbon dioxide,- an expansion device (12) supplied by at least one fraction of the stream M12 and including a liquid carbon dioxide stream outlet line and a liquidstream M13 outlet line, said liquid carbon dioxide stream outlet line supplying the storage device (4).

15. The installation according to claim 10 or 11, wherein the treatment 5 device (3) includes:- a digester (32) supplied by the stream M1h line and including an outlet for the gas stream M14,- a separating device (13) supplied by at least one fraction of the stream M14 and including an outlet line for stream M16 enriched with carbon dioxide 10 and an outlet line for stream M15 depleted of carbon dioxide,- a liquefaction device (14) supplied by at least one fraction of stream M16 and including a liquid carbon dioxide stream outlet line, said liquid carbon dioxide stream outlet line supplying the pressurization and / or heating device (5) or, where applicable, supplying the storage device (4).15

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