Method for treating organic waste

Abstract

The invention relates to a treatment method comprising:-a step of providing a fermentable first stream M2 and a fermentable second stream M3,-a step of hydrothermal gasification of at least a portion of the fermentable second stream M3 to obtain a mineral stream M4, an organic substance stream M5 and a gas,-digestion DG1 of at least a portion of the fermentable first stream M2, the digestion DG1 is capable of obtaining a stream M61 and a gas,-a digestion DG2 of at least a portion of the stream M5 of organic matter produced by hydrothermal gasification, the digestion being capable of obtaining a stream M62 and a gas.

Description

Technical Field

[0001] The present invention relates to the field of complex waste treatment and recycling. Background Art

[0002] Against the backdrop of climate change and resource scarcity, research is underway into methods for recycling as much energy as possible from all types of waste generated by human activities.

[0003] These technologies vary and can be divided into so-called "low-tech" products and so-called "high-tech" products.

[0004] "Low-tech" products allow energy to be produced and resources to be reused at low cost but usually with low yield.

[0005] "High-tech" products allow the production of energy at high yields and the reuse of resources, but usually also have very high costs.

[0006] The methods of the prior art generally do not allow all these products to be recycled in an industrially reliable manner, in particular by controlling production costs and energy consumption.

[0007] The present invention proposes the common use of these "low-tech" products and these "high-tech" products to achieve a synergy that will find the technical-economic optimum for optimal reuse of biomass while controlling production costs.

[0008] A "low-tech" product is, for example, anaerobic digestion of biomass. This digestion is a robust product, but for some products (such as lignin), the yield is so low that building a plant to produce very low gas yields would not result in any return on investment and would therefore not be of industrial interest.

[0009] On the other hand, a "high-tech" product implemented on a product that could have been processed with a "low-tech" product with good yields has little economic value compared to the "low-tech" product. In this case, the difference in yield between the two technologies does not justify the difference in investment. In other words, the marginal difference in output is too small relative to the marginal difference in investment. Hydrothermal gasification is an example of a "high-tech" product that produces a lot of gas compared to the input product, but at a high cost.

[0010] By combining digestion and hydrothermal gasification in an intelligent (optimized) way, optimal gas production efficiency is achieved while minimizing investment costs. Summary of the invention

[0011] The present invention relates to a processing method, comprising:

[0012] - a step of providing a first stream M2 which is easy to ferment and a second stream M3 which is difficult to ferment,

[0013] - a step of hydrothermal gasification of at least part of the second difficult to ferment stream M3 in order to obtain a mineral stream M4, a stream of organic matter M5 and a gas,

[0014] - a digestion DG1 of at least a portion of the first stream M2 susceptible to fermentation, which digestion DG1 makes it possible to obtain a stream M61 and a gas, and

[0015] - digestion DG2 of at least part of the stream M5 of organic matter resulting from hydrothermal gasification, which digestion makes it possible to obtain a stream M62 and a gas,

[0016] Wherein, the digestion steps DG 1 and DG 2 can be carried out in two different digesters or in the same digester,

[0017] wherein the readily fermentable first stream M2 is characterized in that a 20-day mesophilic digestion at 35-40° C. is capable of reducing the organic matter present in the first stream by more than 40% by weight, and

[0018] The difficult to ferment second stream M3 is characterized in that 20 days of mesophilic digestion at 35-40° C. is not able to convert more than 40% by weight of the organic matter present in the second stream into biogas.

[0019] According to one embodiment of the method of the present invention:

[0020] - digestion DG1 and DG2 are carried out in two different digesters, digestion DG1 can obtain digestion product M61 and gas, digestion DG2 can obtain digestion product M62 and gas, the method also includes a step of mixing at least part of stream M62 and at least part of stream M61 to obtain stream M63, or

[0021] - Digestion of DG1 and DG2 is carried out in the same digester, and digestion product M6 and gas can be obtained.

[0022] According to one embodiment, the method of the invention further comprises, upstream of the hydrothermal gasification step, a separation step of the mixture M1 comprising at least organic matter to obtain, on the one hand, a first stream M2 which is easily fermentable, and, on the other hand, a second stream M3 which is difficult to ferment.

[0023] According to one embodiment, the method of the invention further comprises, downstream of the digestion, a dehydration step carried out on at least a portion of the digestate M6 or on at least a portion of the stream M63 in order to obtain a dehydrated organic matter stream M7.

[0024] Preferably, the entirety of the digestate M6 or the entirety of the stream M63 is introduced into a dewatering device for a dewatering step.

[0025] Preferably, at least a portion of the dehydrated organic matter stream M7 is recycled upstream of the hydrothermal gasification step.

[0026] According to one embodiment of the process according to the invention, the entirety of the first stream M2 susceptible to fermentation is used for the digestion of DG1.

[0027] According to one embodiment of the process according to the invention, the entire difficult-to-ferment second stream M3 is used in the hydrothermal gasification step.

[0028] According to one embodiment of the process of the invention, the hydrothermal gasification step is carried out at a pressure of 200 to 450 bar, more preferably 250 to 300 bar and / or at a temperature of 350 to 600 °C, preferably 400 to 550 °C.

[0029] According to one embodiment of the method of the present invention, the hydrothermal gasification step includes a separation step, a cooling step and an expansion step, wherein the separation step can obtain a stream M4 rich in inorganic substances and a stream M3' poor in inorganic substances, the cooling step can cool the stream M3', and the expansion step can expand the cooled stream M3' to obtain gas and stream M5, and the cooling step is preferably carried out by heat exchange with the portion of the second stream M3 that is difficult to ferment.

[0030] According to one embodiment of the process of the invention, digestions DG1 and DG2 are carried out in the same digester and said portion of organic matter flow M5 is introduced into a recirculation loop of the digester in which flow M6' circulates from the outlet to the inlet of the digester.

[0031] According to one embodiment, the method of the invention further comprises a cooling step downstream of the hydrothermal gasification step and upstream of the digestion: before introducing said portion of the organic matter flow M5 into the digester for the digestion step, it is cooled to a temperature less than or equal to 60°C, preferably less than or equal to 40°C.

[0032] According to one embodiment of the process according to the invention, at least part of the organic substance stream M5 resulting from the hydrothermal gasification step is introduced into a digester for digestion without prior cooling.

[0033] According to one embodiment of the method of the invention, the digestion is anaerobic digestion.

[0034] According to one embodiment of the method of the invention, said portion of the first stream M2 susceptible to fermentation and said portion of the stream M5 of organic matter are mixed upstream of the digestion step to obtain a mixture M8, which is introduced into a digester and then digested in the same digester DG1 and DG2.

[0035] The inventors have discovered that hydrothermal gasification does not always have 100% organic conversion, and that it is advantageous not to push the thermal reaction conditions of hydrothermal gasification to reduce costs, but to use anaerobic digestion to complete the conversion of organics to gas.

[0036] BRIEF DESCRIPTION OF THE DRAWINGS

[0037] [ Figure 1 ] shows an implementation method of an apparatus for implementing the processing method according to the present invention.

[0038] [ Figure 2 ] shows an implementation method of an apparatus for implementing the processing method according to the present invention.

[0039] [ Figure 3 ] shows an embodiment of an apparatus for implementing the processing method according to the present invention.

[0040] [ Figure 4 ] shows an embodiment of an apparatus for implementing the processing method according to the present invention.

[0041] [ Figure 5 ] shows an embodiment of an apparatus for implementing the processing method according to the present invention.

[0042] [ Figure 6 ] shows an embodiment of an apparatus for implementing the processing method according to the present invention. DETAILED DESCRIPTION

[0043] The present invention relates to a processing method, comprising:

[0044] - a step of providing a first stream M2 which is easy to ferment and a second stream M3 which is difficult to ferment,

[0045] - a step of hydrothermal gasification of at least part of said second difficult to ferment stream M3 in order to obtain a mineral stream M4, a stream of organic matter M5 and a gas,

[0046] = digestion DG1 of at least a portion of said first stream M2 susceptible to fermentation to obtain a stream M61 and a gas, and

[0047] - digesting DG2 at least part of the stream M5 of organic matter coming from the hydrothermal gasification, making it possible to obtain a stream M62 and a gas,

[0048] It is to be understood that digestion steps DG1 and DG2 may be performed in two different digesters or in the same digester.

[0049] According to one embodiment of the processing method:

[0050] - the digestions DG1 and DG2 are carried out in two different digesters, said digestion DG1 making it possible to obtain a digestion product M61 and gases, said digestion DG2 making it possible to obtain a digestion product M62 and gases, said method also comprising a step of mixing at least a portion of the stream M62 with at least a portion of the stream M61 in order to obtain a stream M63, or

[0051] - The digestion of DG1 and DG2 is carried out in the same digester, making it possible to obtain digestion products M6 and gases.

[0052] Thus, the present invention relates to the treatment of a group of biomasses, one part of which is susceptible to fermentation and another part of which is difficult to ferment.

[0053] Within the meaning of the present invention, the expression "at least a part of a mixture or a 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, the expression refers to a certain proportion of said mixture or said stream. For example, "every part of a mixture" or "every part of a stream" will have the same composition in the sense of this expression.

[0054] Therefore, within the meaning of the present invention, the expression "step X carried out on the entire stream M coming from step y" means that steps X and y are continuous and that there is no intermediate separation step between steps X and y, it being understood that there may be a cooling / heating of the stream M between steps X and y, in particular by heat exchange, which heat exchange may optionally involve a stream exchange.

[0055] Stream M2 and Stream M3

[0056] Within the meaning of the present invention, the readily fermentable first stream M2 is characterized in that a mesophilic digestion at 35-40° C. for 20 days makes it possible to reduce the organic matter present in said first stream by more than 40% by weight.

[0057] Within the meaning of the present invention, the difficult to ferment second stream M3 is characterized in that 20 days of mesophilic digestion at 35-40° C. are not able to convert more than 40% by weight of the organic matter present in said second stream into biogas.

[0058] These characteristics are to be understood in the context of the good practice methods known to those skilled in the art for measuring the methanogenic potential of a substrate ("Biochemical Methane Potential"), which can measure the gas production of a substrate under mesophilic conditions. These good practice methods are mentioned, for example, in standard NF ISO 19388:2023.

[0059] The first stream M2 susceptible to fermentation can be selected, for example, from biomass from food waste collection, food fats and oils, fractions recovered by primary decantation of a water treatment station. This can especially be the organic matter fraction from the primary decantation at the inlet of a purification station.

[0060] The difficult to ferment second stream M3 can be selected, for example, from lignocellulosic waste (eg manure, straw, cellulosic agricultural waste), biological sludge from a purification station. It can especially be biomass from a purification station after biological treatment.

[0061] For example, in the case of treatment at a purification station, a so-called "primary treatment" step consisting of simple decantation of the input organic matter generally produces a readily fermentable residue in a digester, and this has a yield of organic matter conversion that can generally exceed 50%.

[0062] On the other hand, "biological treatment" following "primary treatment" generally results in a residue whose digestibility may be less than 30%.

[0063] According to one embodiment, the treatment method according to the invention comprises the step of separating a mixture M1 comprising at least organic matter in order to obtain, on the one hand, a first stream M2 easily fermentable and, on the other hand, a second stream M3 difficult to ferment.

[0064] The separation step can be carried out, for example, by washing and decanting the mixture M1 , thus allowing the production of two separate streams: an easily fermentable stream M2 and a difficult to ferment stream M3 .

[0065] The mixture M1 can be selected from manure, food waste.

[0066] For example, manure containing both straw and animal manure usually consists of a difficult-to-ferment fraction (the straw) and easily fermentable material (the manure).

[0067] Separation of these two streams, for example by washing and decanting (unlike feces, straw is not soluble in water), can produce two separate streams: one easily fermentable stream and another difficult to fermentable stream.

[0068] According to one embodiment, the stream M2 susceptible to fermentation 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 M2.

[0069] Hydrothermal gasification

[0070] The treatment method according to the invention comprises at least one hydrothermal gasification (GH) step carried out on at least a portion of the second difficult-to-ferment stream M3.

[0071] Hydrothermal gasification (GH) is a thermal depolymerization process for converting organic matter present in a moist medium into a mixture containing only small molecules at high to moderate temperatures and pressures.

[0072] In the GH process, carbon and hydrogen of organic substances are converted thermochemically under quasi-critical or supercritical conditions. Part of the conversion is into water-soluble low-molar-mass compounds.

[0073] The other part is converted into gaseous products such as carbon dioxide (CO2), methane (CH4), hydrogen (H2), carbon monoxide (CO), light hydrocarbons such as ethane (C2H6) and propane (C3H8).

[0074] During residence 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 during liquefaction, but at a much faster rate. In fact, implementation under quasi-critical or supercritical conditions makes it possible to use the unique properties of supercritical water as a solvent, which allows to achieve homogeneous reaction and solvation conditions, leading to very high reaction kinetic rates. Thus, shorter residence times and higher heating rates are used compared to conventional hydrolysis, limiting or even avoiding secondary reactions of condensation and polymerization leading to the formation of bio-oil and biochar.

[0075] When GH is carried out at temperatures above 400°C, free radical decomposition of the polymer (particularly involving decarboxylation, deamination via C-N bond cleavage, and CC or CO cracking reactions) dominates, while endothermic steam reforming is the main reaction pathway for converting small molecules containing 1 to 3 carbon atoms into carbon oxides and hydrogen, and nitrogen into ammonia.

[0076] Methane is also produced by methanation of CO and CO2 using hydrogen.

[0077] Therefore, GH can be considered as a decomposition process that transforms the organic residues in stream M3 into more easily biodegradable substances and ammonia dissolved in the liquid phase.

[0078] The treatment conditions of GH (in particular temperature, pressure and, to a lesser extent, residence time) can be adjusted so as to produce not only a gaseous fraction (synthesis gas) containing CH4, CO, CO2 and H2, but also an aqueous effluent which contains, on the one hand, predominantly easily digestible compounds, in particular carboxylic acids, and, on the other hand, predominantly ammonia in the form of ammonium salts of the produced carbonic acid.

[0079] It should be noted that GH is different from hydrothermal liquefaction (HTL), in particular because the conversion and decomposition levels of organic matter in HTL are not as high as in GH, even when GH is used under moderate temperature conditions.

[0080] Under HTL conditions, water still contains HO- and H3O+ ions that initiate the hydrolysis of organic matter.

[0081] The hydrolysis takes place only on the surface of the cellulose compound contained in the organic fraction which dissolves very little in the subcritical medium, giving a rather low decomposition conversion.

[0082] The condensation reaction of the intermediates (mainly including aldol condensation, Friedel-Craft alkylation or acylation) is an important reaction pathway leading to the formation of biocrude oil, which is an oil that can be used as a fuel (also called bio-oil), i.e., the biocrude oil contains organic molecules containing 5 or more carbon atoms (usually 8 to 16 carbon atoms). On the other hand, the liquid products of GH mainly contain compounds that are easily biodegradable.

[0083] GH differs from pyrolysis in that it is carried out in an aqueous medium, with the water being in a supercritical or quasi-critical state.

[0084] GH differs from "conventional" gasification of organic matter in that "conventional" gasification reduces the carbon / hydrogen mass ratio (C / H), which results in products with increased calorific value, including gases consisting primarily of syngas (a mixture of H2 / CO), bio-oils and / or carbonaceous solids (char).

[0085] This GH step makes it possible to obtain a mineral stream M4, a stream of organic matter M5 and gases.

[0086] The mineral stream M4 generally contains a greater mineral proportion than in the stream M3 .

[0087] The organic substance flow M5 generally comprises a greater mass proportion of organic substance than the mass proportion of organic substance in the flow M3 .

[0088] Also typically, the mineral stream M4 contains a greater mineral proportion than the mineral proportion in the stream M5 .

[0089] Also typically, the organic substance flow M5 comprises a greater proportion of organic substance than the proportion of organic substance in the flow M4 .

[0090] The term "hydrothermal gasification" refers to a whole process chain which produces gases by conversion of organic substances on the one hand and several liquid fractions containing more or less inorganic substances on the other hand.

[0091] Typically, such hydrothermal gasification involves at least subjecting the biomass to pressure and temperature, in particular at a temperature above 350° C. and at a pressure such that evaporation of the medium is avoided.

[0092] According to one embodiment, the hydrothermal gasification is carried out in a gasification reactor:

[0093] - at a temperature of 350°C to 600°C, preferably 350°C to 550°C, and / or

[0094] - at a pressure of 200 to 450 bar, preferably 250 to 300 bar.

[0095] Hydrothermal gasification may also include separation of the inorganic fraction (salts) and may use a catalyst.

[0096] Among the inorganic substances, there may be mentioned salts containing anions such as phosphate, sulfate, chloride, carbonate and bicarbonate with, for example, sodium, magnesium, calcium, ammonium and metals as counterions.

[0097] Preferably, the (total) residence time of the stream M4 lean in inorganic substances in step d) of GH is generally between 1 minute and 20 minutes, preferably between 2 minutes and 10 minutes, more preferably between 3 and 5 minutes.

[0098] According to 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 chosen from metals on activated carbon, such as metals of the ruthenium, nickel, palladium or platinum type.

[0099] The catalyst may be in the form of a bed of solid particles within the gasification reactor.

[0100] Thus, the hydrothermal gasification step will generally produce a mixture comprising inorganic substances (salts) and organic substances. In the context of the present invention, generally, the GH step comprises a separation step capable of obtaining, on the one hand, a stream M4 enriched in inorganic substances and, on the other hand, a stream M3' depleted in inorganic substances. The stream M3' is then generally a gaseous stream dissolved in a liquid effluent.

[0101] Within the meaning of the present invention, in the context of the separation of a given stream X, the term "stream enriched in inorganic matter" refers to a stream comprising a weight proportion of inorganic matter greater than the weight proportion of inorganic matter in the given stream X, these weight proportions being defined as proportions of dry matter.

[0102] Within the meaning of the present invention, in the context of the separation of a given stream X, the term "stream depleted in inorganic matter" refers to a stream comprising a weight proportion of inorganic matter which is less than the weight proportion of inorganic matter in the given stream X, these weight proportions being defined as proportions of dry matter.

[0103] The separation of the streams M3 ′ and M4 can be carried out by separation occurring by gravity settling during the hydrothermal gasification of the mixture in the GH reactor.

[0104] Typically, step GH comprises a step of cooling stream M3' prior to the expansion step which makes it possible to obtain, on the one hand, a gas and, on the other hand, a liquid stream M5. According to one embodiment, said cooling step is carried out by heat exchange with the difficult-to-ferment fraction M3 of the second stream (upstream of GH). Thus, the difficult-to-ferment stream M3 upstream of the GH step recovers the heat present in stream M3', making it possible to cool stream M3' and to heat stream M3.

[0105] During the hydrothermal gasification step, in particular a stream M4 rich in inorganic substances is recovered. Preferably, the ratio of the concentration of inorganic substances in M4 to the concentration of inorganic substances in M3 is at least 2, more preferably at least 5.

[0106] At the end of the hydrothermal gasification, after possible internal heat recovery, the output stream may have a possibly high temperature (above 150° C.), and separation between gas and liquid generally occurs, producing a gas stream and an organic substance stream M5. This separation can be carried out at atmospheric pressure or under pressure.

[0107] The hot liquid portion M5 contains organic matter (organic matter flow) and can therefore advantageously heat the digester by returning it to the digester. In fact, the bacteria present in the digester may require heat (37-55° C.) for their metabolic activity.

[0108] This potentially high heat return must advantageously be performed under conditions where thermal shock cannot occur.

[0109] This mixing can be done, for example, in the sludge recirculation loop of the digester with a high flow rate to which a low flow rate of the hot liquid fraction is added.

[0110] According to one embodiment, the method further comprises, downstream of the hydrothermal gasification step and upstream of the digestion step, the step of cooling the portion of the organic matter stream M5 to a temperature less than or equal to 60°C, preferably less than or equal to 40°C, before introducing it into the digester for the digestion step.

[0111] Digestion

[0112] The processing method according to the present invention comprises:

[0113] - digestion DG1 of at least a portion of the first stream M2 susceptible to fermentation, making it possible to obtain a stream M61 and a gas, and

[0114] - digestion DG2 of at least part of the stream M5 of organic matter resulting from the hydrothermal gasification, making it possible to obtain a stream M62 and a gas,

[0115] It is to be understood that digestion steps DG1 and DG2 may be performed in two different digesters or in the same digester.

[0116] In the context of the treatment method of the invention, digestion of DG1 and DG2 may be performed in the same digester or in two different digesters.

[0117] Therefore, the method of the present invention comprises a digestion step selected from:-

[0118] i. a digestion step DG1 carried out in a first digester on at least part of a first stream M2 susceptible to fermentation, making it possible to obtain a stream M61 and gases, and a digestion step DG2 carried out in a second digester on at least part of a stream M5 of organic matter resulting from hydrothermal gasification, making it possible to obtain a stream M62 and gases, or

[0119] ii. a digestion step DG carried out in a digester on at least part of the first stream M2 susceptible to fermentation and on at least part of the stream M5 of organic matter resulting from hydrothermal gasification, making it possible to obtain a stream M6 and a gas.

[0120] According to a preferred embodiment, the digestion step is chosen from a digestion step DG carried out in a digester on at least part of the first stream M2 susceptible to fermentation and at least part of the stream M5 of organic matter produced by hydrothermal gasification, making it possible to obtain digestion products M6 and gases.

[0121] Typically, digestion takes place in digesters (also called tanks).

[0122] Advantageously, the digestion carried out in the method according to the invention is anaerobic digestion.

[0123] Preferably, the digestion is carried out in the absence of oxygen at a temperature of 20 to 60°C.

[0124] When mesophilic digestion is carried out, the temperature in the digester is 33°C to 37°C and the residence time is 14 to 22 days. When the digestion is only treating pure liquid effluent, the residence time can be significantly reduced. It should be noted that the stream M5 produced by GH will be a liquid stream.

[0125] When thermophilic digestion is carried out, the temperature in the digester is 55°C to 60°C and the residence time is 8 to 12 days. When the digestion is only treating pure liquid effluent, the residence time can be significantly reduced.

[0126] Residence time and temperature are two factors that influence the optimization of good degradation of sludge and thus energy production.

[0127] At the end of the digestion step, biogas is obtained.

[0128] As used herein, "anaerobic treatment" refers to anaerobic digestion that produces biogas. Anaerobic treatment is typically performed in anaerobic tanks.

[0129] Anaerobic digestion can be either mesophilic or thermophilic.

[0130] Such biogas usually comprises a mixture consisting essentially of methane, carbon dioxide and water. The biogas may optionally contain other gases, such as hydrogen, oxygen, nitrogen or hydrogen sulfide, but these other gases together account for less than 10% by weight of the total weight of the biogas.

[0131] Anaerobic digestion is a process involving microorganisms that break down biodegradable materials in the absence of oxygen.

[0132] The process produces a digestate and a gaseous fraction comprising methane and typically consisting essentially of methane and CO2, also known as biogas.

[0133] Advantageously, anaerobic digestion is the digestion of an effluent containing only soluble components, in particular soluble carbon, ie no longer containing suspended solids.

[0134] Advantageously, the suspended solids are already dissolved during the hydrothermal gasification step.

[0135] In the case where the method carries out two digestions DG1 and DG2 in two different digesters, the digestion carried out on stream M2 can then be carried out under different conditions than the digestion carried out on stream M5. For example, the digestion carried out on stream M5 can be a UASB (upflow anaerobic sludge blanket digestion) type digestion, i.e. a digestion treating soluble carbon.

[0136] For example, in the case where the stream M2 contains a significant portion of solid matter (typically greater than 3% by weight of solid matter), the digestion carried out on the stream M2 will advantageously be of the infinite mixing type with a stirring system of the digester to ensure homogeneity in the system.

[0137] The anaerobic treatment is usually carried out at a pH of 7.0-7.5, preferably 7.0-7.2.

[0138] According to an advantageous embodiment, digestions DG1 and DG2 are carried out in the same digester and the organic matter stream M5 resulting from the gasification is introduced into a recirculation loop in which the stream M6' circulates from the outlet of the digester to the inlet of the digester. This embodiment is particularly advantageous when there is no cooling device between the hydrothermal gasification reactor and the digester.

[0139] Preferably, the input flow rate D1 of the organic matter flow M5 in the recirculation loop M6' of the digester is smaller than the circulation flow rate D2 of the sludge in the circulation loop of the digester.

[0140] Normally, the flow rate of the stream M5 at the end of the hydrothermal gasification is not controlled.

[0141] The flow rate of flow M6' can be controlled and adjusted according to the flow rate of flow M5.

[0142] According to one embodiment, the method further comprises a cooling step downstream of the hydrothermal gasification step and upstream of the digestion, i.e. before introducing a portion of the organic stream M5 into the digester for digestion, it is cooled to a temperature less than or equal to 60° C., preferably less than or equal to 40° C. This additional cooling step can be carried out using, for example, industrial water.

[0143] This additional cooling step of stream M5 is preferably carried out in the case where the heat flow provided by M5 would lead to a temperature that is too high throughout the digester (in the total mass of the digester). In fact, in this case, it is advantageous to remove heat from stream M5 before introducing it into the digester.

[0144] According to one embodiment of the method, part of the first stream M2 susceptible to fermentation and part of the stream M5 of GH-producing organic matter are mixed upstream of the digestion step in order to be introduced into the digester in the form of a mixture M8.

[0145] An additional cooling step of the stream M5 is preferably carried out when it is mixed with the stream M2 upstream of the digester, in particular when this mixture M8 would (in the absence of such cooling) result in excessively high temperatures (generally temperatures above 45° C.).

[0146] At the end of digestion, this treatment method makes it possible to obtain:

[0147] - in the case where the digestions DG1 and DG2 are carried out in two different digesters, a first digestion product M61 (and gases) and a second digestion product M62 (and gases), or

[0148] - In case digestion of DG1 and DG2 is carried out in the same digester (this may be referred to as digestion DG), the digestion product M6 (and gas).

[0149] Preferably, in the case where the digestion of DG1 and DG2 is carried out in two different digesters, the method further comprises a step of mixing at least part of the stream M62 with at least part of the stream M61 so as to obtain the stream M63.

[0150] According to one embodiment, in case the digestion DG1 and DG2 is carried out in two different digesters, the method further comprises a step of mixing the gas streams coming from each digester before the optional gas treatment step. Indeed, if the method comprises a subsequent step of treating the downstream gases, it is advantageously appropriate to centralize the treatment.

[0151] According to one embodiment, in case the digestion of DG1 and DG2 is carried out in the same digester, the method may optionally comprise a step of treating the gas coming from said digester.

[0152] According to one embodiment, the treatment method further comprises a dehydration step downstream of the digestion of:

[0153] - at least a portion of the digestion product M6 produced by digestion of DG, preferably all of the digestion product M6 produced by digestion of DG, or

[0154] - At least a part of the stream M63, preferably the whole of the stream M63.

[0155] Preferably, the dehydrated material produced by the dehydration is introduced into the gasification reactor or into the stream M3 upstream of the gasification reactor.

[0156] According to one embodiment, the treatment method according to the invention comprises a step of recycling the sludge (stream M6') from the outlet of the digester to the inlet of the digester, said step preferably being implemented in a recycling loop. According to this embodiment, stream M5 is then preferably introduced into the recycling loop of the sludge coming from the digester.

[0157] Preferably, according to this embodiment, the treatment method comprises a step of controlling the flow rate of the sludge thus recycled and regulating said flow rate as a function of the flow rate of the stream M5 , the flow rate of the stream M5 then being generally not controlled.

[0158] In practice, a recirculation loop may be provided from the outlet of the digester to its inlet, allowing the recirculation of the sludge from the outlet of the digester to its inlet to be achieved. According to this embodiment, it is possible to consider introducing the stream M5 into the recirculation loop so that it is then introduced into the digester through this loop mixed with the sludge of the recirculation loop. According to this embodiment, a control unit may therefore be provided to control the sludge flow in the recirculation loop and to regulate it according to the flow of the stream M5, the flow of the stream M5 itself not being controlled.

[0159] Injecting the stream M5 into the recirculating sludge, instead of directly into the digester, makes it possible to avoid thermal shock and excessive temperature rise in the digester. This control and this regulation of the flow rate also further allows to control and limit the temperature rise in the digester.

[0160] Preferably, the flow rate of the recycled sludge is adjusted so as not to produce a temperature increase of more than 5° C. in the mixed flow after the introduction of flow M5 .

[0161] The treatment method according to the invention can be implemented in an apparatus.

[0162] The invention also relates to the device itself for implementing the treatment method. Figures 1 to 4An embodiment of an apparatus for carrying out the treatment method according to the invention is shown without limiting the scope thereof.

[0163] According to one embodiment, the device comprises:

[0164] - Hydrothermal gasification reactor GH,

[0165] a digester DG comprising at least one outlet for digestate M6 and a gas outlet,

[0166] - Stream supply line connecting the outlet (stream M5) and the inlet of the hydrothermal gasification reactor:

[0167] i. Either a mixing device upstream of the digester,

[0168] ii. Either digester DG,

[0169] - Stream supply lines that feed:

[0170] i. Either a mixing device, if any,

[0171] ii. Either digester DG,

[0172] a dehydration unit DH optionally fed by the digestate line M6, comprising an outlet for water and an outlet for the dehydrated stream M7,

[0173] - Optionally a recirculation loop allowing at least part of the dehydrated stream M7 to be recycled to the inlet of the reactor GH.

[0174] According to another embodiment, the device comprises:

[0175] - Hydrothermal gasification reactor GH,

[0176] a digester DG1 comprising at least one outlet for digestate M61 and one outlet for gases,

[0177] - a flow supply line M2 feeding DG1,

[0178] a digester DG2 comprising at least one outlet for digestate M62 and one outlet for gases,

[0179] - a stream supply line M5 connecting the outlet of the hydrothermal gasification reactor GH and the inlet of the digester DG2,

[0180] - optionally fed by the digestate M61 line and the digestate M62 line stream M63 line

[0181] a dehydration unit DH optionally fed by the line of stream M63, comprising an outlet for water and an outlet for the dehydrated stream M7,

[0182] - Optionally a recirculation loop allowing to recirculate at least part of the dehydrated stream M7 to the inlet of the reactor GH.

[0183] according to Figure 1 Equipment shown:

[0184] - a supply line for a stream M2 susceptible to fermentation to feed the digester DG,

[0185] a supply line of a difficult-to-ferment stream M3 feeding a hydrothermal gasification reactor GH comprising an outlet for a stream M4 for minerals, an outlet for a stream M5 for organic matter and an outlet for gases,

[0186] - The stream M5 output line feeds the digester DG comprising an outlet for gases and an outlet M6 for organic matter called digestate.

[0187] according to Figure 2 In one embodiment shown, the digester DG comprises a sludge recycling circuit, in which said sludge M6' preferably has a sufficiently high flow rate to avoid a significant increase in the temperature of said circuit after the introduction of the stream M5. For example, the temperature increase will preferably be less than or equal to 5°C. Therefore, the flow rate of the stream M6' of the circuit will therefore be adapted to the temperature and flow rate of the stream M5 to avoid such a temperature increase in the stream M5' (the stream in the circuit after the introduction of the stream M5).

[0188] According to this embodiment, the recirculation circuit then advantageously comprises a variable speed pump which allows the return temperature of the circuit to be controlled.

[0189] according to Figure 2 In the embodiment shown comprising a recirculation loop, the stream M2 can be introduced directly into the digester DG and / or into the recirculation loop, preferably upstream of the injection M5.

[0190] Figure 3 The embodiment shown in Figure 1 The embodiment shown in differs in that the method comprises a preliminary step of separating the mixture M1. Thus, the apparatus according to this embodiment comprises a separation device SP fed by a supply line of stream M1 and comprising two outlets, an outlet for stream M2 and an outlet for stream M3.

[0191] This embodiment including the separation preparatory step can also be Figure 2 The illustrated embodiment is implemented within the context of a sludge recirculation loop using a digester.

[0192] Figure 4 The embodiment shown is similar to Figure 1The embodiment shown differs in that the method also comprises a dehydration step downstream of the digestion step for dehydrating the digestate before recycling it into the gasification reactor. Thus, according to this embodiment, the plant comprises a dehydration device DH fed by a flow M6 pipeline, comprising an outlet for water and an outlet for dehydrated organic matter M7 connected to the inlet of the gasification reactor.

[0193] This embodiment including the dehydration step can also be Figure 2 The embodiment shown is implemented using a sludge recirculation loop of the digester, and / or Figure 3 The embodiment shown is carried out within the scope of a separate preliminary step.

[0194] according to Figure 5 In one embodiment shown, the plant comprises mixing means MG which allow the flow M2 to be mixed with the flow M5 generated by the GH. The mixed flow M8 coming from the mixing means is then introduced into the digester DG.

[0195] According to one embodiment not shown, the plant comprises a cooling device downstream of the hydrothermal gasification reactor, which is supplied with the flow M5 containing organic matter and is capable of cooling the organic matter flow M5 to a temperature less than or equal to 60°C, preferably less than or equal to 40°C, before introducing it into the digester for digestion.

[0196] According to one embodiment not shown in the figures, the gasification reactor GH will comprise:

[0197] - separation means for obtaining a stream M3' of gas dissolved in the liquid effluent and a stream M4, and

[0198] - cooling means, preferably heat recovery means, for cooling the stream M3' and preferably at least partially heating the stream M3 upstream of the reactor GH, and

[0199] An expansion device supplied with at least part of the flow M3 ′ making it possible to obtain, on the one hand, a gas flow and, on the other hand, a flow M5 (of the liquid effluent type).

[0200] according to Figure 6 One embodiment shown is a plant according to the invention comprising, downstream of the reactor GH, a digester DG2 supplied with at least a portion of the stream M5 and a digester DG1 supplied with the stream M2 .

[0201] According to this embodiment, the plant advantageously comprises mixing means capable of mixing the digestate M61 produced by DG1 and the digestate M62 produced by DG2 so as to be directed to the supply line of the stream M63 .

[0202] According to this embodiment, the plant may also comprise, downstream of said mixing means, a dehydration device DH fed by the line stream M63 and comprising an outlet for water and an outlet for dehydrated organic matter M7 connected to the inlet of the reactor GH.

[0203] According to an embodiment not shown, the gas flows produced by DG1 and DG2 can be combined before being optionally introduced into a gas treatment unit.

[0204] The device according to the invention may of course comprise one or more of the features described in the context of the method according to the invention.

Claims

1. A processing method comprising: - a step of providing a first stream M2 which is easy to ferment and a second stream M3 which is difficult to ferment, - a step of hydrothermal gasification of at least part of the second difficult to ferment stream M3 in order to obtain a mineral stream M4, a stream of organic matter M5 and a gas, - a digestion DG1 of at least a portion of the first stream M2 susceptible to fermentation, which digestion DG1 makes it possible to obtain a stream M61 and a gas, and - digestion DG2 of at least part of the stream M5 of organic matter resulting from hydrothermal gasification, which digestion makes it possible to obtain a stream M62 and a gas, Wherein, the digestion steps DG 1 and DG 2 can be carried out in two different digesters or in the same digester, wherein the readily fermentable first stream M2 is characterized in that 20 days of mesophilic digestion at 35-40°C is able to reduce the organic matter present in the first stream by more than 40% by weight, and The difficult to ferment second stream M3 is characterized in that 20 days of mesophilic digestion at 35-40° C. is not able to convert more than 40% by weight of the organic matter present in the second stream into biogas.

2. The processing method according to claim 1, wherein: - digestion DG1 and DG2 are carried out in two different digesters, digestion DG1 can obtain digestion product M61 and gas, digestion DG2 can obtain digestion product M62 and gas, the method also includes a step of mixing at least part of stream M62 and at least part of stream M61 to obtain stream M63, or - Digestion of DG1 and DG2 is carried out in the same digester, and digestion product M6 and gas can be obtained.

3. The treatment method according to claim 1 or 2, further comprising a separation step upstream of the hydrothermal gasification step: separating the mixture M1 containing at least organic matter to obtain a first flow M2 that is easy to ferment on the one hand, and a second flow M3 that is difficult to ferment on the other hand.

4. The treatment method according to any one of claims 2 to 3, further comprising a dehydration step performed on at least a portion of the digestion product M6 or at least a portion of the convection flow M63 downstream of the digestion to obtain a dehydrated organic matter flow M7.

5. The processing method according to claim 4, wherein: The entirety of the digestate M6 or the entirety of the stream M63 is introduced into a dewatering device for a dewatering step.

6. The processing method according to claim 4 or 5, wherein: At least part of the dehydrated organic mass stream M7 is recycled upstream of the hydrothermal gasification step.

7. The processing method according to any one of claims 1 to 6, wherein: The entirety of the readily fermentable first stream M2 was used to digest DG1.

8. The processing method according to any one of claims 1 to 7, wherein: The entirety of the difficult to ferment second stream M3 is used in the hydrothermal gasification step.

9. The processing method according to any one of claims 1 to 8, wherein: The hydrothermal gasification step is carried out at a pressure of 200 to 450 bar, more preferably 250 to 300 bar and / or at a temperature of 350 to 600 °C, preferably 400 to 550 °C.

10. The process according to any one of claims 1 to 9, wherein: The digestions DG1 and DG2 are carried out in the same digester and said portion of the organic matter flow M5 is introduced into a recirculation loop of the digester in which a flow M6 ′ circulates from the outlet to the inlet of the digester.

11. The treatment method according to any one of claims 1 to 10 further comprises a cooling step downstream of the hydrothermal gasification step and upstream of the digestion: before introducing the portion of the organic matter flow M5 into the digester for the digestion step, it is cooled to a temperature less than or equal to 60°C, preferably less than or equal to 40°C.

12. The processing method according to any one of claims 1 to 11, wherein: The hydrothermal gasification step comprises a separation step, a cooling step and an expansion step, wherein the separation step is capable of obtaining a stream M4 rich in inorganic substances and a stream M3' poor in inorganic substances, the cooling step is capable of cooling the stream M3', the expansion step is capable of expanding the cooled stream M3' to obtain gas and stream M5, and the cooling step is preferably performed by heat exchange with the portion of the second stream M3 that is difficult to ferment.

13. The processing method according to any one of claims 1 to 10, wherein: At least part of the organic mass stream M5 resulting from the hydrothermal gasification step is introduced into a digester for digestion without prior cooling.

14. The processing method according to any one of claims 1 to 13, wherein: Digestion is anaerobic.

15. The processing method according to any one of claims 1 to 14, wherein: Said portion of the first stream M2 susceptible to fermentation is mixed with said portion of the stream M5 of organic matter upstream of the digestion step to obtain a mixture M8 which will be introduced into a digester in which the digestion of DG1 and DG2 is then carried out.

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