PROCESS 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 hydrolysis of the mixture M1 making it possible to obtain a hydrolyzed mixture M1h, b) pressurizing the mixture M1h in order to obtain a stream M1p, c) a step of heating the mixture M1p resulting from step b) in order to obtain a mixture M2, d) a solubilization step carried out on at least a fraction of the mixture M2 resulting from step c), optionally a heating step, and a separation step in order to obtain a stream M4 enriched in soluble matter and a stream M3 depleted in soluble matter, e) a step of cooling and expanding at least a fraction of the stream M4 enriched in soluble matter resulting from step d), in order to obtain a stream M5, f) a digestion step carried out on at least a fraction of the stream M5 resulting from step e). Figure for abstract: Fig. 1

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 matter and inorganic matter, such as aqueous waste, sludge and sewage sludge. STATE OF THE ART

[0002] Sludge digestion, carried out in a digester, is a partial degradation of organic matter by biological means, resulting from a series of reactions, leading to the formation of a gaseous mixture called biogas. This biogas is a source of energy, whether it is recovered in the form of electricity, heat, or used as fuel, in particular as fuel or by injection as town gas.

[0003] The digestion process involves microorganisms, mainly bacteria, which decompose or convert raw materials to produce biogas and effluent. The process involves a series of reactions involving bacteria, mainly hydrolysis, acidogenesis, acetogenesis and methanogenesis.

[0004] Hereinafter, the term "biogas" will refer to the gas resulting from the digestion process. This biogas comprises a mixture essentially consisting of methane, carbon dioxide and water. The biogas may optionally include other gases, such as hydrogen, oxygen, nitrogen, hydrogen sulfide, but collectively they represent less than 10% of the biogas. The biogas can be burned directly with oxygen and used as fuel. The methane contained in the biogas (known as biomethane) can also be concentrated to replace natural gas.

[0005] State-of-the-art processes are typically not sufficiently selective. Yields are insufficient for a large proportion of organic matter since they are often limited to 30-35% yield on organic matter.

[0006] The concept of thermal hydrolysis has been implemented and allows for an increase in digestion yields of 5 to 15%. These batch or continuous concepts are based on a temperature of 140-170°C and a residence time of 30 minutes. These yields are certainly interesting but a large part of the increase in yield goes into the heating of this equipment because thermal recoveries always lead to heating of the initial product to around 100°C.

[0007] Furthermore, these treatments concentrate on the organic part of the material and neglect the interest in recovering the mineral fraction rich in phosphorus, for example.

[0008] There is therefore a need to propose a treatment process with high efficiency, good thermal management and improvement of the quality of the treated material for the recovery of waste containing organic matter and inorganic matter. Summary of the invention

[0009] The invention relates to a method for treating a mixture Ml comprising at least organic matter, said method comprising:

[0010] a) a step of hydrolysis of the mixture Ml at a temperature ranging from 70 to 165°C and at a pressure ranging from 1 to 8 bars making it possible to obtain a hydrolyzed mixture Mlh, the ratio between the viscosity of the mixture Ml and the viscosity of the mixture Mlh being at least 2,

[0011] b) pressurizing the mixture Mlh to a pressure ranging from 20 to 350 bars, in order to obtain a flow Mlp,

[0012] c) a step of heating the mixture Mlp from step b) to a temperature ranging from 250 to 450°C, in order to obtain a mixture M2,

[0013] d) a solubilization step carried out on at least a fraction of the mixture M2 resulting from step c), optionally a heating step at a temperature ranging from 250 to 450°C, and a separation step in order to obtain a flow M4 enriched in soluble materials and a flow M3 depleted in soluble materials,

[0014] said step d) being carried out in one or more reactors with an overall hydraulic residence time of less than or equal to 20 minutes,

[0015] e) a step of cooling and expanding at least a fraction of the flow M4 enriched in soluble matter from step d), in order to obtain a flow M5,

[0016] f) a digestion step carried out on at least a fraction of the M5 stream from step e).

[0017] According to one embodiment, the method of the invention further comprises an additional separation step e') implemented on at least one fraction of the flow M5 from step e) making it possible to obtain a gaseous fraction FG and a liquid flow M5', the digestion step f) then being implemented in a digester on at least one fraction, preferably the entirety, of the liquid flow M5', said gaseous fraction FG preferably also being introduced into the digester during said digestion step f).

[0018] Preferably, the separation step comprises an extraction of the M4 stream enriched in soluble materials and an extraction of the M3 stream depleted in soluble materials, preferably via two separately controlled outlets.

[0019] According to one embodiment, the heating step c) comprises at least two sub-steps, at least one of said sub-steps making it possible to heat the mixture Mlp at a rate greater than or equal to 100°C / minute, preferably greater than or equal to 200°C / minute, preferably greater than or equal to 400°C / minute.

[0020] Preferably, the heat present in the flow M4 enriched with soluble materials from step d) is recovered. Preferably, the heat is recovered by heat exchange between the flow M4 enriched with soluble materials from step d) and the mixture Mlp, preferably said heat exchange makes it possible to at least partially heat the mixture Mlp during the heating step c).

[0021] According to one embodiment, during step e) the flow M4 enriched with soluble materials is cooled to a temperature less than or equal to 60°C, preferably less than or equal to 40°C.

[0022] According to one embodiment, said cooling step comprises at least two sub-steps, preferably said first sub-step is implemented by heat exchange between the heat of the flow M4 and the mixture Mlp and makes it possible to obtain a cooled flow M4' and said second sub-step is a step of expansion of the cooled flow M4' to a pressure ranging from 2 to 10 bars making it possible to produce expansion steam, said expansion steam possibly being injected into the mixture Ml upstream of step a) or during step a).

[0023] According to one embodiment, the mixture M1 comprises from 5 to 50% by weight of solid materials, preferably from 15 to 25% by weight of solid materials, relative to the total weight of the mixture M1.

[0024] According to one embodiment, at least one additive is added to at least one stream chosen from: - The flow of mixture Ml upstream of step a), - The mixture Ml during step a), - the flow of mixture Mlh upstream of step b), - the flow of mixture Mlp upstream of step c), - the mixture Mlp during step c), - the mixture flow during step d), - the flow M3 depleted in soluble matter from step d).

[0025] According to one embodiment, the method of the invention further comprises at least one step of upgrading at least one fraction of the M3 stream, said at least one upgrading step preferably being chosen from a hydrothermal gasification step, a wet oxidation step.

[0026] The invention also relates to an installation for implementing a treatment method according to the invention, said installation comprising: - At least one hydrolysis reactor 1 possibly comprising a stirring device, supplied at the inlet by a supply line for the mixture M1 to be treated and comprising an outlet line for the hydrolyzed mixture, said at least one hydrolysis reactor being possibly preceded by a device for grinding or equipped with a recirculation loop equipped with a grinding device or followed by a grinding device, upstream of the pump 3, - a pressurizing pump 3 supplied at the inlet with the hydrolyzed mixture, possibly ground, and comprising an outlet line for the mixture Mlp, - a heating device 4 comprising an inlet allowing at least a fraction of the mixture Mlp to be introduced downstream of the pump 3, and comprising at least one outlet for the mixture M2, - a reactor 5 comprising an inlet allowing the introduction of at least part of the mixture M2 from the heating device 4 and comprising at least two outlets, one outlet for the flow M3 and one outlet for the flow M4, • said reactor 5 possibly comprising heating means, and • said reactor 5 comprising separation means making it possible to extract a flow M3 depleted in soluble materials and a flow M4 enriched in soluble materials, - possibly a heat exchanger 9 making it possible to recover the heat present in the flow M4 enriched with soluble materials at the outlet of the reactor 5, - an expansion device 10 supplied with at least a fraction of the flow M4 enriched with soluble materials previously cooled, and comprising an outlet for the flow M5, - possibly a separation device 12 supplied by at least a fraction of the flow M5 and comprising an outlet for a gaseous fraction and an outlet for the liquid flow M5', - a digestion device 11 supplied with at least a fraction of the flow M5 or where appropriate with at least a fraction of the liquid flow M5' and at least a part of the gaseous fraction.

[0027] According to one embodiment, the reactor 5 comprises: - a solubilization reactor 52 comprising an inlet allowing the introduction of at least part of the mixture M2 from the heating device 4 and comprising an outlet line for a mixture M6, - possibly a heating device 53 comprising an inlet allowing the introduction of at least a portion of the mixture M6 from the solubilization reactor 52 and comprising an outlet line for a mixture M6', - a separation device 51 supplied with at least a fraction of the mixture M6 or with at least a fraction of the mixture M6' when a heating device 53 is present, and comprising at least two outlets, one outlet for the flow M3 and one outlet for the flow M4.

[0028] According to one embodiment, the heating device 4 comprises a heat exchanger making it possible to exchange heat between the flow M4 enriched in soluble matter from the reactor 5 and the flow Mlp downstream of the pressurization pump 3, a cooled flow M4' is thus obtained.

[0029] According to one embodiment, the installation further comprises a heat exchanger 9 downstream of the heating device 4 making it possible to recover the heat present in the flow M4' and to transfer it to the mixture M1 for thermal hydrolysis, preferably via steam production.

[0030] The invention makes it possible to improve the treatment of an organic material in a complex matrix. The improvement in the treatment allows for better recovery of inorganic materials, such as salts, on the one hand, and organic material on the other.

[0031] The treatment method according to the invention allows limited energy expenditure, without this being to the detriment of the quality of the recovery.

[0032] The inventors have observed that increasing the temperature beyond the hydrolysis temperatures can lead to the production of compounds that are potentially refractory to digestion, in particular because of long residence times which lead to molecular reorganizations of the short chains produced by hydrolysis or by radical destruction at these high temperatures. Thus, the invention makes it possible to control the residence times at these high temperatures and in particular the speed of the temperature increase in order to improve digestibility.

[0033] The invention also proposes a solubilization step allowing the water to act as a catalyst for chemical reactions, making it possible to obtain a more homogeneous mixture where all of the material is in intimate contact with the water. This solubilization step, carried out under controlled temperature and residence time conditions, makes it possible to improve the quality of the treated material for better digestion of said treated material. BRIEF DESCRIPTION OF THE FIGURES

[0034] [Fig.l] is a schematic representation of a treatment method according to the invention.

[0035] [Fig.2] is a schematic representation of a treatment method according to the invention.

[0036] [Fig.3] is a schematic representation of a treatment method according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] The invention relates to a method for treating a mixture Ml comprising at least organic matter, said method comprising:

[0038] a. a step of hydrolysis of the mixture Ml at a temperature ranging from 70 to 165°C and at a pressure ranging from 1 to 8 bars making it possible to obtain a hydrolyzed mixture Mlh, the ratio between the viscosity of the mixture Ml and the viscosity of the mixture Mlh being at least 2, preferably at least 4, more preferably at least 10,

[0039] b. pressurizing the mixture Mlh to a pressure ranging from 20 to 350 bars, preferably from 170 to 210 bars, in order to obtain a flow Mlp,

[0040] c. a step of heating the mixture Mlp from step b) to a temperature ranging from 250 to 450°C, preferably from 250 to 400°C, more preferably from 250 to 350°C, in order to obtain a flow of mixture M2,

[0041] d. a solubilization step carried out on at least a fraction - preferably the whole - of the mixture M2 from step c), optionally a heating step at a temperature ranging from 250 to 450°C, preferably from 250 to 400°C, more preferably from 300 to 350°C, and a separation step in order to obtain a stream M4 enriched in soluble materials and a stream M3 depleted in soluble materials, said step d) being carried out in one or more reactors with an overall hydraulic residence time of less than or equal to 20 minutes, preferably less than or equal to 10 minutes, more preferably less than or equal to 5 minutes,

[0042] e. a step of cooling and expanding at least a fraction, preferably all of the flow M4 enriched in soluble matter from step d), in order to obtain a mixture flow M5,

[0043] e'. optionally a separation step implemented on at least one fraction - preferably the entirety of the flow M5 from step e) making it possible to obtain a gaseous fraction FG and a liquid flow M5',

[0044] f. a digestion step carried out on at least one fraction, preferably the entirety, of the mixture flow M5 from step e) or where appropriate (i.e. when step e') is present) on at least one fraction, preferably the entirety, of the liquid flow M5' and preferably on at least part of the gaseous fraction FG.

[0045] For the purposes of the present invention, the expression "at least a fraction of a mixture or stream" has the same meaning as the expression "all or part of said mixture or stream". When it is a part of said mixture or 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.

[0046] Thus, within the meaning of the present invention, the expression “step X implemented on the entire flow M from step Y” means that steps X and Y are successive and that there is neither an intermediate step nor a separation between steps X and Y.

[0047] For the purposes of the present invention, the expression “where appropriate of step X” introduces a characteristic present when step X is present.

[0048] For the purposes of the present invention, the expression “where appropriate of the flow X” introduces a characteristic present when the flow X is present.

[0049] Mixture Ml comprising at least organic matter

[0050] The mixture M1 comprises at least organic matter. Typically, the mixture M1 further comprises inorganic matter. Among the inorganic matter, mention may be made of salts comprising anions such as phosphates, sulfates, chlorides, carbonates and hydrocarbonates with, as counterions, for example, sodium, magnesium, calcium, ammonium and metals.

[0051] The mixture Ml can for example be chosen from primary, mixed or biological sludge from municipal and industrial treatment plants.

[0052] According to one embodiment, the mixture M1 comprises from 5 to 50% by weight of solid matter, preferably from 15 to 25% by weight of solid matter, relative to the total weight of the mixture ML Hydrolysis step a)

[0053] The process according to the invention comprises a step of hydrolysis of the mixture ML

[0054] The hydrolysis step is carried out at a temperature ranging from 70 to 165°C and at a pressure ranging from 1 to 8 bars. These conditions make it possible to avoid vaporization of the medium.

[0055] According to one embodiment, the temperature during the hydrolysis step a) ranges from 100 to 165°C, or even from 140 to 165°C.

[0056] The hydrolysis step makes it possible to reduce the viscosity of the mixture. Thus, step a) makes it possible to obtain a hydrolyzed mixture Mlh also called hydrolyzate.

[0057] The hydrolysis step makes it possible to degrade the organic matter, in particular it makes it possible to break the chemical bonds and to depolymerize the organic matter by the effect of water.

[0058] The mixture Mlh will typically have a viscosity at least 2 times lower, preferably at least 4 times lower, more preferably at least 10 times lower than the viscosity of the mixture ML

[0059] Thus, the ratio between the viscosity of the mixture Ml and the viscosity of the mixture Mlh is at least 2, preferably at least 4, more preferably at least 10.

[0060] The viscosity defined in the context of the present invention is a kinematic viscosity measured at the same temperature (20°C for example) using rheometers adapted to the viscosity to be measured (cylinder - cylinder, plane - plane) and measuring at the same shear (in s1) the two viscosities, typically taking care to eliminate turbulence problems and to respect the rheological rules (for example spacing between cylinders as a function of the granulometry).

[0061] The step of hydrolysis of the mixture M1 can be carried out in one or more hydrolysis reactors in parallel or in series.

[0062] Said hydrolysis step makes it possible to hydrolyze the mixture M1 thanks in particular to maintaining an average hydraulic residence time at the desired temperatures and pressures (preferably, temperatures ranging from 70 to 165°C and pressures ranging from 1 to 8 bars), it being understood that if the hydrolysis step is carried out in several hydrolysis reactors, the temperature may be identical or different in the different reactors, likewise, the pressure may be identical or different in the different reactors.

[0063] Advantageously, the hydrolysis step will implement an internal energy recovery step, thus minimizing the thermal consumption of the hydrolysis. For example, there could be an energy recirculation loop from the hot hydrolyzate to the cold product to be hydrolyzed via, for example, the production of expansion steam from the hot hydrolyzate and injection into the cold product to be hydrolyzed or heat exchange.

[0064] At the outlet of the hydrolysis step, a hydrolyzate Mlh is obtained, said hydrolyzate Mlh is not necessarily at the temperatures and pressures desired for hydrolysis. Indeed, before leaving the hydrolysis step, the hydrolyzate could possibly undergo a cooling and / or expansion step.

[0065] In particular, for example if the hydrolysis is carried out at a high temperature, for example ranging from 100 to 165°C, then it might be desirable to cool the hydrolysate for example to a temperature below 90°C, so that the Mlh stream has a lower temperature for pressurization in step b) of the process of the invention.

[0066] The extraction of the Mlh hydrolysate can be controlled by measuring the viscosity.

[0067] In the context of the treatment method of the invention, the hydrolysis step allows to achieve a double objective: - On the one hand, by reducing the viscosity, hydrolysis will allow better heat exchange and therefore a faster temperature rise of the Mlp mixture. In addition, the reduction in viscosity will allow uniformity of the temperature of the Mlp mixture becoming M2 during the heating stage and will reduce or even prevent harmful carbonization reactions. - On the other hand, by hydrolysis a greater part of the solid matter of the mixture Ml will be in contact with water which will allow the matter Mlh to be of a better quality (more uniform) to prepare a flow of soluble matters via more homogeneous solubilization reactions (by maximizing the quantity of soluble matters and minimizing the quantity of matters that are difficult to digest), which will improve the quality of digestion. In other words, hydrolysis will accelerate solubilization during step d) and will make solubilization more homogeneous, and these advantages are even more important when the hydrolysis is accompanied by a grinding step.

[0068] According to one embodiment, an additive is added to the mixture Ml to be treated upstream of the hydrolysis device or to the mixture during the hydrolysis or to the mixture Mlh downstream of the hydrolysis device.

[0069] According to one embodiment, a controlled quantity of steam can be injected into the hydrolysis reactor and diffused through the mixture M1. This control can be carried out by measuring the temperature in the hydrolysis reactor. Thus, when the set temperature is reached, the injection of steam can be stopped.

[0070] Steam can be injected: - upstream of the hydrolysis in the inlet with a dynamic mixer type mixer, and / or - directly into the hydrolysis reactor, preferably in the lower part tangentially to avoid sludge blockages, and / or - in a hydrolyzed sludge recirculation loop.

[0071] According to one embodiment, during the hydrolysis, the mixture M1 is mixed, for example it is stirred.

[0072] The hydrolysis reactor may be a batch reactor, possibly stirred.

[0073] Before pressurization b), the treatment method may optionally comprise a grinding step, preferably mechanical grinding.

[0074] When present, the step of grinding the mixture Ml can be carried out before, during or after the hydrolysis. In the latter case, the grinding is then carried out on the mixture Mlh.

[0075] When the process of the invention implements a hydrolysis step combined with a grinding step, then the process of the invention may optionally comprise a step of recirculation of at least a fraction of the ground hydrolysate at the inlet of the hydrolysis step.

[0076] According to one embodiment, the hydrolysis reactor(s) comprise a recirculation loop provided with a grinding device, making it possible to introduce at least a fraction of the hydrolyzate into said grinding device and to return at least a fraction, preferably all of the hydrolyzate thus ground, to the inlet of the hydrolysis step.

[0077] The objective of this grinding step is to reduce the particle size of the mixture M1, typically so that the particle size of the solid fraction is less than 1000 μm, preferably less than 500 μm, preferably less than 100 μm.

[0078] A particle size “less than X pm” is understood to mean that 95% of the solid particles are retained in the X pm square mesh sieve and that the remaining 5% do not have a size greater than 3 times X pm.

[0079] In addition to the reduction in particle size which makes it possible to minimize downstream blockages, the grinding step allows homogenization of the mixture Ml and a reduction in viscosity which will allow much better control of heating and solubilization.

[0080] In the same way as the hydrolysis step, grinding and reduction of particle size also contributes to the homogenization of the biomass and its solubilization.

[0081] In reactors using high pressures, it is difficult to have mechanical agitation, the reduction in viscosity implemented thanks to the hydrolysis step and / or the grinding step also makes it possible to improve the internal turbulence and therefore to improve homogenization in the pressurized reactors. Pressurization step b)

[0082] The method according to the invention comprises a step of pressurizing the mixture Mlh to a pressure ranging from 20 to 350 bars, preferably from 50 to 300 bars, preferably from 150 to 270 bars, preferably from 170 to 220 bars, preferably from 170 to 210 bars. A flow of mixture Mlp is obtained.

[0083] In particular, the pressurization makes it possible to bring the mixture Mlh to a pressure sufficient for the mixture to be in a mainly liquid phase. More specifically, the pressure in the mixture M4 will typically be higher than the saturated vapor pressure of said mixture M4 to maintain the water in the liquid phase.

[0084] For the pressurization step, a pump can be provided on the line at the outlet of the hydrolysis reactor.

[0085] In another embodiment, a pump provided for this purpose supplies the pressurization pump. Heating step c)

[0086] The process according to the invention comprises a step of heating the mixture Mlh resulting from step b) to a temperature ranging from 250 to 450°C, preferably ranging from 250 to 400°C, more preferably from 300 to 400°C.

[0087] A flow M2 is obtained at the end of heating step c).

[0088] The heating step can be implemented in a heat exchanger, for example by heat exchange using as heating fluid the flow M4 enriched with soluble materials from step d) of the process.

[0089] The heating step c) may optionally comprise several heating sub-steps via one or more heat exchangers.

[0090] Preferably, at least one heating sub-step is implemented by heat exchange using as heating fluid the flow M4 enriched with soluble materials from step d) of the process.

[0091] Advantageously, when the heating step comprises at least two heating sub-steps, at least one of these sub-steps is implemented at a high speed.

[0092] Thus, according to a preferred embodiment, at least one heating sub-step is implemented at a speed greater than or equal to 100°C / minute, preferably greater than or equal to 200°C / minute, more preferably greater than or equal to 400°C / minute.

[0093] Thus, in at least one heating sub-step, to achieve a high heating rate when a heat exchanger is implemented, it is appropriate to have the highest possible average delta T, typically greater than 50°C, preferably greater than 100°C, preferably greater than 200°C.

[0094] The average delta T is the average of the delta T at all points of the exchanger. The average delta T can be calculated as the logarithmic delta T taken from the inlet temperatures and the outlet temperatures of each fluid.

[0095] The heating step c) may thus be a combination between, on the one hand, the heat exchange with the flow M4 whose absolute temperature is limited by the needs of the process and, on the other hand, the heat exchange with another fluid which itself may be heated by electricity, hot gases or directly available heat from an external source or finally the exchanger may be directly heated by electricity by induction, or thermal resistance, or microwaves.

[0096] Thus, a heat exchanger may be present downstream of the pressurization pump, said heat exchanger being configured to recover the heat from the flow M4 enriched with soluble materials from step d) and to heat the mixture Mlp before the solubilization step d).

[0097] According to one embodiment, an additive is added upstream of the solubilization step, in the mixture flow Mlp during the heating step of step c) and / or downstream of step c) in the flow M2.

[0098] According to one embodiment, the additive is chosen from oxidizing reagents such as liquefied oxygen, hydrogen peroxide, air or permanganate salts such as potassium permanganate, or from alkaline reagents such as for example KOH, NaOH, KHCO3, K2CO3, CaO, Ca(OH)2, CaCO3, Ca(HCO3)2, Mg(OH)2, MgO.

[0099] If the method comprises a step of adding an additive of the oxidizing reagent type, then preferably, said addition step is carried out in the mixture flow M2 downstream of the heating step c).

[0100] According to an advantageous embodiment, the installation for implementing the method comprises at least one heat exchanger sized to allow rapid heating of the mixture Mlp, for example at a speed greater than or equal to 100°C / minute, preferably greater than or equal to 200°C / minute, more preferably greater than or equal to 400°C / minute.

[0101] Viscosity is the key element to improve heating rates.

[0102] Thus, the hydrolysis step a) is advantageously carried out so that the viscosity of the hydrolyzed waste (Mlp) is compatible with the desired heating rate in step c).

[0103] Failure to reach the design temperatures (setpoint) at the outlet of heating step c) is an indicator that the viscosity in the Mlh mixture is still too high. A measurement of the viscosity at the outlet of the hydrolysis will also make it possible to verify the decrease in viscosity.

[0104] According to one embodiment, the method comprises a continuous measurement of the viscosity in the mixture Mlh.

[0105] Too slow a heating rate during step c) can lead to uncontrolled parasitic reactions (char-tar) due to excessively long residence times. Step d)

[0106] Step d) of the method of the invention comprises: - a solubilization step (step dl) implemented on at least a fraction of the mixture M2 from step c), - possibly a heating step (step d2) at a temperature ranging from 250 to 450°C, and - a separation step (step d3) in order to obtain a flow M4 enriched in soluble materials and a flow M3 depleted in soluble materials.

[0107] Step d) of the process is carried out in one or more reactors with an overall hydraulic residence time of less than or equal to 20 minutes, preferably less than or equal to 10 minutes, preferably less than or equal to 5 min.

[0108] The overall hydraulic residence time is the average residence time of a drop of M2 from the inlet of the material M2 (start of step d)) and the outlet of the flow M4 enriched in soluble materials (end of step d).

[0109] The reactor(s) for implementing step d) may be tubular reactors and / or continuously stirred tank reactors and / or baffled tank reactors or other types of reactors allowing uniformity of residence times in the reactor, said reactor(s) possibly comprising one or more filters. Solubilization step dl)

[0110] The method according to the invention comprises a step dl) of solubilization of at least a fraction of the mixture M2 resulting from step c). Preferably, the solubilization step is carried out on the entire mixture M2 resulting from step c).

[0111] The solubilization step makes it possible to make the organic matter of the mixture M2 homogeneous in a hydrothermal environment and makes it possible to make at least part of the organic matter of the M2 mixture soluble.

[0112] Thus, typically, this solubilization step is distinguished from a liquefaction step where the organic matter becomes insoluble in water (oil formation) and can therefore separate from the water.

[0113] Advantageously, the solubilization step does not include the formation of oil.

[0114] The solubilization step makes it possible to prepare an M6 mixture also called M6 liquid liquor.

[0115] Thus, the liquid liquor M6 will typically comprise at least organic matter and at least inorganic matter.

[0116] According to one embodiment, the solubilization step is carried out in a tubular reactor or in a continuously stirred tank reactor.

[0117] Preferably, the residence time in the solubilization step dl) is less than or equal to 20 minutes, preferably less than or equal to 10 minutes, preferably less than or equal to 5 minutes. Possible heating step d2)

[0118] The process according to the invention may optionally comprise, during step d), a heating step (step d2) of all or part of the mixture present during solubilization, before separation step d3).

[0119] Preferably, when implemented, the heating step d2) is implemented on the entire mixture present during solubilization, before the separation step d3).

[0120] When implemented, heating step d2) makes it possible to heat the mixture to a temperature ranging from 250 to 450°C, preferably from 250 to 400°C, more preferably from 300 to 400°C.

[0121] This step d2) makes it possible to reach a thermal range which promotes the separation of the soluble fraction and the insoluble fraction by gravity thanks to the modification of the precipitation constants and the density of the medium.

[0122] The heating step can be implemented by direct heating or by indirect heating, for example by heat exchange.

[0123] The heating step may be carried out in the solubilization reactor(s) or in one or more reactors downstream of the solubilization reactor(s).

[0124] At the exit of the optional heating step d2), the heated mixture will be called mixture M6'. Separation step d3)

[0125] The method according to the invention comprises a step d3) of separation of at least a fraction of the mixture obtained after solubilization dl) and where appropriate after heating d2), in order to obtain an M4 flow enriched in soluble matter and an M3 flow depleted in soluble matter.

[0126] For the purposes of the present invention, the term “flow enriched in soluble materials” means a flow comprising a mass proportion of soluble materials greater than the mass proportion of soluble materials in the mixture M2.

[0127] For the purposes of the present invention, the term “flow depleted in soluble materials” means a flow comprising a mass proportion of soluble materials lower than the mass proportion of soluble materials in the mixture M2.

[0128] A soluble material will be the material obtained after filtration in a 40 pm filter (material not retained by said 40 pm filter) then drying of an initial material.

[0129] According to one embodiment, the ratio between the concentration of soluble materials in the flow M4 enriched with soluble materials and the concentration of soluble materials in the mixture M2 is greater than or equal to 2, preferably greater than or equal to 5.

[0130] The separation step d3) can be carried out in the reactor(s) of step d).

[0131] Thus, according to one embodiment, this separation step d3) can be carried out in the same reactor(s) as the solubilization step dl).

[0132] Alternatively, the separation step d3) can be implemented in a separate separation device comprising a line for supplying the mixture M6 from step d1) or, where appropriate, the mixture M6' from step d2) and two outlet lines: (i) a line for extracting the flow M3 depleted in soluble matter and (ii) a line for extracting the flow M4 enriched in soluble matter.

[0133] The separation device may be a separation device by gravity or by hydraulic effect, such as a cyclone, typically equipped in the lower part with a drainage system operating continuously or intermittently or by filtration.

[0134] According to an advantageous embodiment, step d) is implemented in a reactor allowing a differentiation of the residence times between the so-called solid fraction (enriched in insoluble materials) and the so-called liquid fraction (enriched in soluble materials).

[0135] This differentiation of residence times can for example be implemented via a filter placed in the reactor of step d) which allows the liquid to pass without passing the solid.

[0136] This differentiation of residence times makes it possible both to minimize the liquid residence times to avoid the formation of recombinant products but also to allow time to solubilize the non-solubilized material which will remain longer in the reactor of step d).

[0137] According to one embodiment, the reactor of step d) comprises an outlet for a flow M3 depleted in soluble matter.

[0138] The process is thus carried out so as to separate the solubilized material from the non-solubilized material. solubilized, at the end of step d).

[0139] Typically, the separation step is implemented by controlling the mass residence time, preferably by controlling the residence time of the soluble materials.

[0140] Thus, according to an advantageous embodiment, the separation step comprises an extraction of the M4 stream enriched in soluble materials followed by an extraction of the M3 stream depleted in soluble materials, preferably via two different outlets. In particular, the residence time of the insoluble material will be controlled.

[0141] The extraction of the M3 flow can be done by a continuous or non-continuous outlet (for example sequenced), which will allow a residence time of this insoluble material greater than that of the soluble material.

[0142] The extraction of the M4 flow can be controlled according to the input of the M2 flow.

[0143] For example, if the reactor has two outlets, preferably, the flow M4 enriched in soluble materials will be extracted through an outlet in the upper part of the reactor and the M3 flow depleted in soluble materials will be extracted through an outlet in the lower part of the reactor.

[0144] Preferably, the outlet in the upper part of the reactor is located at an altitude higher than the inlet and the outlet in the lower part of the reactor is located at an altitude lower than the inlet.

[0145] According to one embodiment, the heat present in the flow M4 enriched with soluble materials from step d) is recovered, said recovered heat preferably making it possible to at least partially heat the mixture Mlp during step c) and / or the mixture Ml during step a).

[0146] Preferably, this heat recovery is implemented by heat exchange between the flow M4 enriched in soluble materials from step d) and the mixture Mlp and / or ML

[0147] According to one embodiment, at least one additive is added to the M3 stream depleted in soluble matter from step d). According to one embodiment, said additive is added to the M3 stream in a recovery reactor located downstream of the M3 stream outlet.

[0148] Preferably, said additive is chosen from oxidizing reagents such as liquefied oxygen, hydrogen peroxide, air or permanganate salts such as potassium permanganate, or from magnesium salts such as for example magnesium hydroxide (Mg(OH)2), magnesium oxide (MgO) or magnesium chloride (MgC12) or from alkaline reagents such as for example KOH, NaOH, KHCO3, K2CO3, CaO, Ca(OH)2, CaCO3, Ca(HCO3)2, Mg(OH)2, MgO, or from ammoniacal solutions such as ammonium hydroxide or ammonium chloride or from a mixture of these reagents.

[0149] When a recovery device is implemented, then it is possible to provide a residence time which then makes it possible to precipitate the salts targeted by the addition of said additive.

[0150] According to one embodiment, the mixture M1 comprises phosphorus and the flow M3 depleted in soluble matter resulting from step d) comprises at least 70% by weight of the total weight of phosphorus present in the mixture M1. In other words, at least 70% by weight of the phosphorus present in the mixture M1 is recovered in the flow M3 depleted in soluble matter resulting from step d).

[0151] According to one embodiment, the mixture M1 comprises phosphorus and the flow M3 depleted in soluble matter resulting from step d) comprises phosphorus, preferably in a proportion ranging from 1 to 20% by dry weight, relative to the total dry weight of the flow M3 depleted in soluble matter resulting from step d).

[0152] According to one embodiment of the method, at least one first additive is added to the mixture M upstream of step d) and at least one second additive is added to the stream M3 depleted in soluble matter from step d), the first additive preferably being different from the second additive.

[0153] The mixture M upstream of step d) can thus be: - the mixture Ml upstream of step a), - the mixture Ml during step a), - the Mlh mixture upstream of step b), - the Mlp mixture upstream of step c), - the Mlp mixture during step c), or - the mixture M2 downstream of step c) and upstream of step d).

[0154] Preferably, said additives are chosen from oxidizing reagents such as liquefied oxygen, hydrogen peroxide, air or permanganate salts such as potassium permanganate, or from magnesium salts such as for example magnesium hydroxide (Mg(OH)2), magnesium oxide (MgO) or magnesium chloride (MgC12) or from alkaline reagents such as for example KOH, NaOH, KHCO3, K2CO3, CaO, Ca(OH)2, CaCO3, Ca(HCO3)2, Mg(OH)2, MgO, or from ammoniacal solutions such as ammonium hydroxide or ammonium chloride or from a mixture of these reagents. Cooling and relaxation stage e)

[0155] The method according to the invention comprises a cooling step and an expansion step implemented on at least a fraction, preferably all of the M4 stream enriched in soluble matter from step d), in order to obtain a cooled and expanded M5 stream.

[0156] The M5 stream is a liquid stream which may optionally include an insoluble gaseous fraction.

[0157] According to one embodiment, the M4 flow enriched in soluble materials is cooled to a temperature less than or equal to 60°C, preferably less than or equal to 40°C, before being relaxed.

[0158] Cooling can be implemented using a cooling device chosen from a heat exchanger integrated or not into a rankine, flash, scrubber cycle.

[0159] According to one embodiment, the cooled M4 stream is expanded in an expansion device to a pressure ranging from 1 to 10 bar. A cooled and expanded M5 stream is obtained. This expansion step makes it possible to reduce the pressure before injection into the digester, a device generally under low overpressure (less than 1 bar relative).

[0160] According to this embodiment, the cooled and expanded M5 flow feeds the digestion device.

[0161] Following the expansion and before the digestion, it is possible to separate the gaseous fraction possibly present in the M5 flow and made insoluble by the expansion and to specifically recover this gaseous fraction in order to specifically send at least part of the gaseous fraction into the digester, for example via an inlet different from that of the M5 flow, or into another device.

[0162] As described during the heating phase, the flow M4 can partially or completely heat the flow Mlp during the heating step c) and / or the flow Ml during the step a).

[0163] When, in order to achieve sufficiently high heating rates, the flow M4 only partially heats the flow Mlp, the other part of the flow Mlp can be heated by another fluid during step c), and in this case, the flow M4 is generally not sufficiently cooled, this cooled flow being called flow M4'.

[0164] In this case, the residual heat of the flow M4' can be used to heat the fluid M1 during the hydrolysis step, for example by expansion of the flow M4' to a pressure of 2-10 bars, the expansion steam can thus be used in this case to heat the mixture ML by direct injection.

[0165] According to this embodiment, the heating step c) is implemented partly in a heat exchanger, said heat exchanger making it possible to partly heat the flow Mlp and partly cool the flow M4 from step d).

[0166] According to this embodiment, the partially cooled stream M4' undergoes additional cooling by expansion in a cooling device, which will produce steam which can then be injected into the hydrolysis reactor of step a).

[0167] If this proves necessary, the cooled M4' flow could undergo a second cooling, downstream of the first cooling, for example by dilution with water or by heat exchange with a cold source to reach a temperature less than or equal to 60°C, preferably less than or equal to 40°C.

[0168] Thus, the cooling step can be implemented in one or more dis- positive cooling in series.

[0169] According to one embodiment, the method of the invention further comprises a separation step e') carried out on at least one fraction of the flow M5 from step e) making it possible to obtain a gaseous fraction FG and a liquid flow M5'. According to this embodiment, the digestion step f) will then preferably be carried out on at least one fraction, preferably the entirety of the liquid flow M5'. Digestion stage f)

[0170] The method according to the invention comprises at least one digestion step, preferably an anaerobic digestion step. Anaerobic digestion after a hydrolysis treatment and separation of inorganic matter makes it possible, for example, to increase the production of biogas compared to standard digestion because the organic polymers such as lignin or cell wall have been solubilized and broken into shorter, more easily digestible chains and there is less competition between the methanogenic and inorgano-reducing bacteria.

[0171] The digestion step f) is carried out in a digestion device.

[0172] The digestion device during step f) is supplied with at least a fraction of the flow M5 from step e), preferably by the entire flow M5, and / or, when step e') is present by at least a fraction of the liquid flow M5' from step e'), preferably by the entire flow M5'.

[0173] According to the embodiment implementing a separation step e'), then preferably, the digestion device will be supplied by at least two inlets, a first inlet for introducing the liquid flow M5' and a second inlet for introducing the gaseous fraction FG.

[0174] Anaerobic digestion can be mesophilic or thermophilic.

[0175] When mesophilic digestion is carried out, then the temperature in the digester ranges from 33°C to 37°C and the residence time is 16 to 22 days.

[0176] When thermophilic digestion is carried out, then the temperature in the digester ranges from 55° to 60°C and the residence time is 10 to 12 days.

[0177] Residence time and temperature are two factors influencing the proper degradation of sludge and therefore the optimization of energy production.

[0178] In the context of the present invention, the flow to be digested being sufficiently liquid, the digestion can be of the UASB type and the residence times reduced.

[0179] At the end of the digestion step f), a biogas is obtained.

[0180] This biogas typically comprises a mixture essentially consisting of methane, carbon dioxide and water. The biogas may optionally comprise other gases, such as hydrogen, oxygen, nitrogen, hydrogen sulfide but these other gases collectively represent less than 10% by total weight of the biogas. Possible step(s) for valorizing the M3 flow

[0181] The M3 stream depleted in soluble matter from step d) will typically comprise organic matter and inorganic matter.

[0182] According to one embodiment, the method further comprises at least one step of upgrading at least one fraction of the M3 stream, said at least one upgrading step preferably being chosen from a hydrothermal gasification step, a wet oxidation step (OVH).

[0183] This additional step will make it possible to recover the organic matter still present in this M3 stream while simultaneously recovering the insoluble inorganic matter present in this M3 stream. Thus, this M3 stream, which could be considered as non-recoverable waste in the processes of the state of the art, will generate recoverable by-products.

[0184] Thus, the process of the invention will allow on the one hand excellent solubilization to enable good quality digestion and on the other hand to convert the M3 flow into a recovered material.

[0185] Hydrothermal gasification (GH) 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.

[0186] During GH, carbon and hydrogen in an organic material are converted thermochemically under near-critical or supercritical conditions. A portion is converted into low molar mass compounds soluble in water.

[0187] Another part is converted into gas products such as carbon dioxide (CO2), methane (CH4), dihydrogen (H2), carbon monoxide (CO), light hydrocarbons such as ethane (C2H6) and propane (C3H8).

[0188] During the stay in the hydrothermal gasification reactor at temperatures below 400°C, the organic matter undergoes, among other reactions, a decomposition based on hydrolysis, similar to the reactions occurring in the liquefaction process, but much faster. Indeed, an implementation in quasi-critical or supercritical conditions allows the use of the unique properties of supercritical water as a solvent, which allow homogeneous solvation and reaction conditions, leading to very high reaction kinetic rates. As a result, a much shorter residence time and a much higher heating rate than those of conventional hydrolysis are used, limiting or even avoiding the secondary condensation and polymerization reactions responsible for the formation of bio-oil and biochar.

[0189] When the GH operates at a temperature above 400°C, the radical decomposition of the polymers (involving in particular decarboxylation reactions, deamination by breaking CN bonds, and CC or CO cleavage) is predominant, while endothermic steam reforming is the main reaction pathway to convert small molecules with 1 to 3 carbon atoms into carbon oxides and dihydrogen and nitrogen into ammonia.

[0190] Methane is also produced by methanation of CO and CO2, using dihydrogen.

[0191] Consequently, GH can be considered as a decomposition process transforming the organic residues present in the M3 stream into a more easily biodegradable material and into ammonia dissolved in the liquid phase.

[0192] The treatment conditions (in particular the temperature, the pressure, and to a lesser extent the residence time) of the GH can be adjusted to not only produce a gaseous fraction containing CH4, CO, CO2 and H2 (synthesis gas), but also to produce an aqueous effluent, containing mainly on one side easily digestible compounds, in particular carboxylic acids and on the other side ammonia in the form of ammonium salt of the carbonic acids produced.

[0193] It should be noted that GH is different from hydrothermal liquefaction (HTL), particularly in that the conversion rate and the level of decomposition of organic matter in HTL are not as high as in GH, even when GH is operated under moderate temperature conditions.

[0194] Under HTL conditions, water still contains HO- and H3O+ ions which initiate the hydrolysis of organic matter.

[0195] Hydrolysis only takes place on the surface of the cellulose compounds contained in the organic fraction which dissolves very little in the subcritical medium giving fairly low conversions in decomposition.

[0196] Condensation reactions (mainly including Aldol condensation, Friedel-Craft alkylation or acylation) of the intermediates are an important reaction pathway, leading to the formation of a biocrude which is an oil (also called bio-oil) that can be used as a fuel, i.e. the biocrude contains organic molecules containing 5 or more carbon atoms, usually 8 to 16 carbon atoms. In contrast, the liquid product of GH mainly contains readily biodegradable compounds.

[0197] GH differs from pyrolysis in that it is carried out in a medium containing water, the water being in a supercritical or quasi-critical state.

[0198] GH differs from “conventional” gasification of organic materials in that “conventional” gasification reduces the carbon / hydrogen (C / H) mass ratio, which leads to products with increased calorific value, including a gas mainly composed of synthesis gas (mixture of H2 / CO), bio-oil and / or carbonaceous solid (char).

[0199] In the treatment method according to the invention, the hydrothermal gasification step is typically implemented in a hydrothermal gasification reactor, supplied at the inlet with at least one fraction of flow M3, said fraction of flow M3 can come directly from step d) or said fraction of flow M3 can be pressurized and / or preheated and / or additivated with an additive upstream of the gasification reactor.

[0200] According to one embodiment, the gasification reactor is a tubular reactor.

[0201] Preferably, the hydrothermal gasification step is carried out at a temperature temperature below 600°C, preferably at a temperature ranging from 350°C to less than 600°C, more preferably ranging from 450 to less than 600°C.

[0202] Preferably, the hydrothermal gasification step is carried out at a pressure greater than or equal to 220 bars, preferably greater than or equal to 250 bars.

[0203] Preferably, the (overall) residence time of the M3 stream in the GH step typically ranges from 1 min to 20 min, preferably from 2 min to 10 min, more preferably from 3 to 5 min.

[0204] According to a preferred embodiment, the hydrothermal gasification step is carried out in the presence of a catalyst. Preferably, the catalyst is chosen from metals on activated carbon, for example of the ruthenium, nickel, palladium or platinum type. The catalyst may be in the form of a bed of solid particles within the gasification reactor.

[0205] Wet oxidation makes it possible to destroy organic matter while producing heat for the heating step c) as well as acetic acid which can be sent to the digestion step f).

[0206] The invention also relates to an installation for implementing the treatment method according to the invention.

[0207] [Fig.l] to [Fig.3] illustrate an installation according to the invention, without limiting its scope.

[0208] The installation according to the invention comprises: - one or more hydrolysis reactors 1 possibly comprising a stirring device, supplied at the inlet by a supply line for the mixture Ml to be treated and comprising an outlet line for the hydrolyzed mixture Mlh, said hydrolysis reactor(s) 1 possibly being preceded by a grinding device or provided with a recirculation loop provided with a grinding device or followed by a grinding device, upstream of the pump 3, - a pressurizing pump 3 supplied at the inlet with the hydrolyzed mixture Mlh possibly ground, - a heating device 4 comprising an inlet for introducing at least a fraction of the mixture Mlp, and comprising at least one outlet for the mixture M2, - a reactor 5 comprising an inlet allowing the introduction of at least a fraction of the mixture M2 from the heating device 4 and comprising at least two outlets, one outlet for the flow M3 and one outlet for the flow M4, • said reactor 5 possibly comprising heating means, and • said reactor 5 comprising separation means making it possible to extract a flow M3 depleted in soluble materials and a flow M4 enriched in soluble materials, - possibly a heat exchanger 9 making it possible to recover the heat present in the flow M4 enriched with soluble materials at the outlet of the reactor 5, - an expansion device 10 supplied with at least a fraction of the flow M4 enriched with soluble materials previously cooled, and comprising an outlet for the flow M5, - possibly a separation device 12 supplied by at least a fraction of the flow M5 and comprising an outlet for a gaseous fraction and an outlet for the liquid flow M5', - a digestion device 11 supplied with at least a fraction of the flow M5 or where appropriate with at least a fraction of the liquid flow M5' and at least a part of the gaseous fraction.

[0209] Preferably, the reactor 5 comprises one or more filters.

[0210] According to an embodiment illustrated in [Fig.2], the reactor 5 comprises: - a solubilization reactor 52 comprising an inlet allowing the introduction of at least part of the mixture M2 from the heating device 4 and comprising an outlet line for a mixture M6, - possibly a heating device 53 comprising an inlet allowing the introduction of at least a portion of the mixture M6 from the solubilization reactor 52 and comprising an outlet line for a mixture M6', - a separation device 51 supplied with at least a fraction of the mixture M6 or with at least a fraction of the mixture M6' when a heating device 53 is present, and comprising at least two outlets, one outlet for the flow M3 and one outlet for the flow M4.

[0211] According to one embodiment, the separation device 51 consists of one or more filters.

[0212] According to one embodiment, the heating device 4 is a heat exchanger making it possible to exchange heat between the heat of the flow M4 coming from the reactor 5 and the Mlp flow downstream of the pressurization pump 3 (and upstream of reactor 5).

[0213] According to one embodiment, the heat exchanger 9 makes it possible to recover the heat present in the flow M4 and to transfer it to the mixture M1 in the hydrolysis device 1 or upstream of the hydrolysis device.

[0214] Preferably, the heat exchanger 9 is downstream of the heating device 4 and makes it possible to recover the heat present in the flow M4'.

[0215] Thus, according to a preferred embodiment of the installation, the flow line M4 downstream of the reactor 5 successively comprises a heat exchanger (corresponding to the heating device 4) and a heat exchanger 9 and an expansion device 10.

[0216] According to one embodiment of the invention, the expansion device 10 comprises two outputs: - a first outlet for the mixture flow which will feed the digester 11, and - a second outlet, separate from the first outlet, for the steam.

[0217] According to this embodiment, the installation further comprises a steam supply line from the second outlet of the expansion device 10 to the mixture supply line M1 and / or to the hydrolysis reactor 1.

[0218] According to one embodiment, the installation further comprises at least one injection device making it possible to inject an additive into at least one element chosen from:

[0219] - The supply line for the mixture Ml upstream of the hydrolysis reactor 1,

[0220] - The hydrolysis reactor 1,

[0221] - The mixing line Mlh downstream of the hydrolysis reactor 1 and the possible grinding device,

[0222] - The mixing line M2 downstream of the heating device 4 and upstream of the reactor 5,

[0223] - The line of the M3 flow at the outlet of the reactor 5 (if applicable of the safety device preparation 51).

[0224] [Fig. 3] illustrates an embodiment of the invention in which the installation comprises a separation device 12 supplied by the flow line M5 from the device 10, and comprising an outlet for the gaseous fraction FG and an outlet for the liquid flow M5'. According to the embodiment illustrated in [Fig. 3], the gaseous fraction FG from the separation device 12 is injected into the digester 11 via an inlet different from the flow inlet M5'.

[0225] Thus, according to one embodiment of the installation according to the invention, the digester 11 has two inlets: - a first inlet allowing the introduction of at least a fraction of the flow M5' from the separation device 12 and a second inlet, separate from the first inlet, allowing the introduction of at least a fraction of the gaseous fraction FG from the separation device 12.

[0226] According to one embodiment of the invention, the installation further comprises, on a flow outlet line M3 downstream of the reactor 5, at least one recovery device, preferably chosen from a hydrothermal gasification device or a wet oxidation device, said recovery device preferably being present downstream of the additive injection line when it is present.

[0227] The installation according to the invention may of course comprise one or more of the characteristics described within the framework of the method according to the invention.

Claims

Claims

1. Method for treating a mixture Ml comprising at least organic matter, said method comprising: a. a step of hydrolysis of the mixture Ml at a temperature ranging from 70 to 165°C and at a pressure ranging from 1 to 8 bars making it possible to obtain a hydrolyzed mixture Mlh, the ratio between the viscosity of the mixture Ml and the viscosity of the mixture Mlh being at least 2, b. pressurizing the Mlh mixture to a pressure ranging from 20 to 350 bars, in order to obtain a Mlp flow, c. a step of heating the mixture Mlp from step b) to a temperature ranging from 250 to 450°C, in order to obtain a mixture M2, d. a solubilization step carried out on at least a fraction of the mixture M2 from step c), optionally a heating step at a temperature ranging from 250 to 450°C, and a separation step in order to obtain a flow M4 enriched in soluble materials and a flow M3 depleted in soluble materials, said step d) being carried out in one or more reactors with an overall hydraulic residence time of less than or equal to 20 minutes, e. a step of cooling and expanding at least a fraction of the M4 stream enriched in soluble matter from step d), in order to obtain a M5 stream, f. a digestion step implemented on at least a fraction of the M5 stream from step e).

2. Method according to claim 1, further comprising an additional separation step e') carried out on at least a fraction of the flow M5 from step e) making it possible to obtain a gaseous fraction FG and a liquid flow M5', the digestion step f) then being carried out in a digester on at least a fraction, preferably the whole, of the liquid flow M5', said gaseous fraction FG preferably also being introduced into the digester during said digestion step

3. JJ- A method according to claim 1 or 2, wherein the separation step comprises an extraction of the M4 stream enriched in soluble matter and an extraction of the M3 stream depleted in soluble matter, preferably via two separately controlled outlets.

4. Treatment method according to any one of claims 1 to 3, in which the heating step c) comprises at least two sub-steps, at least one of said sub-steps making it possible to heat the mixture Mlp at a rate greater than or equal to 100°C / minute, preferably greater than or equal to 200°C / minute, more preferably greater than or equal to 400°C / minute.

5. Treatment method according to one of claims 1 to 4, in which the heat present in the M4 stream enriched with soluble materials from step d) is recovered.

6. Treatment method according to claim 5, in which the heat is recovered by heat exchange between the flow M4 enriched in soluble materials from step d) and the mixture Mlp, preferably said heat exchange makes it possible to at least partially heat the mixture Mlp during the heating step c).

7. Treatment method according to any one of claims 1 to 6, wherein during step e) the M4 stream enriched in soluble materials is cooled to a temperature less than or equal to 60°C, preferably less than or equal to 40°C.

8. Treatment method according to any one of claims 1 to 7, wherein said cooling step comprises at least two sub-steps, preferably said first sub-step is implemented by heat exchange between the heat of the flow M4 and the mixture Mlp and makes it possible to obtain a cooled flow M4' and said second sub-step is a step of expansion of the cooled flow M4' to a pressure ranging from 2 to 10 bars making it possible to produce expansion steam, said expansion steam possibly being injected into the mixture Ml upstream of step a) or during step a).

9. A treatment method according to any one of claims 1 to 8, wherein the mixture Ml comprises from 5 to 50% by weight of solids, preferably from 15 to 25% by weight of solids, relative to the total weight of the mixture Ml.

10. Treatment method according to any one of claims 1 to 9, in which at least one additive is added to at least one stream chosen from: - The mixture flow Ml upstream of step a), - The mixture Ml during step a), - the mixture flow Mlh upstream of step b), - the mixture flow Mlp upstream of step c), - the mixture Mlp during step c), - the mixture flow during step d), - the flow M3 depleted in soluble matter from step d).

11. Process for treating any one of claims 1 to 10, further comprising at least one step of upgrading at least a fraction of the M3 stream, said at least one upgrading step preferably being chosen from a hydrothermal gasification step, a wet oxidation step.

12. Installation for implementing a treatment method according to any one of claims 1 to 11, comprising: - At least one hydrolysis reactor (1) possibly comprising a stirring device, supplied at the inlet by a supply line for the mixture Ml to be treated and comprising an outlet line for the hydrolyzed mixture, said at least one hydrolysis reactor being possibly preceded by a grinding device or provided with a recirculation loop provided with a grinding device or followed by a grinding device, upstream of the pump (3), - a pressurizing pump (3) supplied at the inlet by the optionally ground hydrolyzed mixture, and comprising an outlet line for the mixture Mlp, - a heating device (4) comprising an inlet for introducing at least a fraction of the mixture Mlp downstream of the pump (3), and comprising at least one outlet for the mixture M2,- a reactor (5) comprising an inlet for introducing at least part of the mixture M2 from the heating device (4) and comprising at least two outlets, one outlet for the flow M3 and one outlet for the flow M4, • said reactor (5) possibly comprising heating means, and • said reactor (5) comprising se- means, preparation allowing the extraction of an M3 flow depleted in soluble materials and an M4 flow enriched in soluble materials, - possibly a heat exchanger (9) allowing the recovery of the heat present in the M4 flow enriched with soluble materials at the outlet of the reactor (5), - an expansion device (10) supplied with at least a fraction of the flow M4 enriched with soluble materials previously cooled, and comprising an outlet for the flow M5, - possibly a separation device (12) supplied by at least a fraction of the flow M5 and comprising an outlet for a gaseous fraction and an outlet for the liquid flow M5', - a digestion device (11) supplied with at least a fraction of the flow M5 or where appropriate with at least a fraction of the liquid flow M5' and at least a part of the gaseous fraction.

13. Installation according to claim 12, in which the reactor (5) comprises: - a solubilization reactor (52) comprising an inlet allowing the introduction of at least part of the mixture M2 from the heating device (4) and comprising an outlet line for a mixture M6, - possibly a heating device (53) comprising an inlet allowing the introduction of at least part of the mixture M6 from the solubilization reactor (52) and comprising an outlet line for a mixture M6', - a separation device (51) supplied with at least a fraction of the mixture M6 or with at least a fraction of the mixture M6' when a heating device (53) is present, and comprising at least two outlets, one outlet for the flow M3 and one outlet for the flow M4.

14. Installation according to claim 12 or 13, in which the heating device (4) comprises a heat exchanger for exchanging heat between the flow M4 enriched in soluble materials from the reactor (5) and the Mlp flow downstream of the pressurization pump (3), a cooled M4' flow is thus obtained.

15. Installation according to claim 14, further comprising a heat exchanger (9) downstream of the heating device (4) making it possible to recover the heat present in the flow M4' and to transfer it to the mixture M1 for thermal hydrolysis, preferably via steam production.

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