Process for treating lignocellulosic biomass

Abstract

The invention relates to a method for treating lignocellulosic biomass, in which said biomass is treated using at least one reactor (9, 14) equipped with a feed device (6, 11) equipped with a biomass inlet and a biomass outlet, said biomass outlet being fluidly connected to the inlet of the reactor, when the biomass passes through the feeding device (6; 11) to the reactor (9; 14) from the biomass via an extraction outlet provided in the device, a residue (8; 13) which is a mixture of solid and liquid,-separating the residue into a solid residue (32; 42) and the liquid residue (31; 41),-separating the solid residue (32; 42) is reintroduced into the feed device, or into one of the feed devices.

Description

Technical Field

[0001] The present invention relates to a method for treating lignocellulosic biomass to produce "second generation" (2G) sugar liquors. These sugar liquors can be used to produce other products (e.g. alcohols, such as ethanol, butanol or other molecules, such as solvents, such as acetone, etc.) via biochemical pathways. The method generally comprises three steps, namely liquid preparation, impregnation of biomass with the liquid, and pretreatment of the impregnated biomass, such as by cooking, optionally combined with steam explosion. Prior art

[0002] Lignocellulosic biomass represents one of the most abundant renewable resources on Earth. The substrates considered are very diverse and they involve wood substrates such as various woods (hardwood and softwood), by-products derived from agriculture (wheat straw, corn cobs, etc.) or other agricultural products, paper industry, etc.

[0003] The method for biochemically converting lignocellulosic biomass into 2G sugar liquor particularly comprises a pretreatment step and a step of enzymatic hydrolysis with an enzyme mixture. These methods also generally comprise a soaking step before the pretreatment. The sugar liquor produced by the hydrolysis is then processed, for example by fermentation, and the method also comprises a separation step and / or a purification step of the final product.

[0004] Lignocellulosic biomass consists of three major polymers: cellulose (35% to 50% by weight), a polysaccharide consisting essentially of hexoses; hemicellulose (20% to 30% by weight), a polysaccharide usually consisting essentially of pentoses; and lignin (15% to 25% by weight), a structurally complex and high molecular weight polymer consisting of aromatic alcohols linked via ether bonds. These different molecules are responsible for the intrinsic properties of plant walls and are organized into complex entanglements.

[0005] Of the three basic polymers that make up lignocellulosic biomass, cellulose and hemicellulose are those that are capable of producing 2G sugar liquor.

[0006] Usually, hemicellulose is mainly decomposed into sugar during pretreatment, and cellulose is converted into glucose by enzymatic hydrolysis. However, enzyme is still difficult to contact crude cellulose, so pretreatment is needed. This pretreatment makes it possible to change the physicochemical properties of lignocellulosic biomass, thereby improving the accessibility of cellulose to enzyme and its reactivity to enzymatic hydrolysis.

[0007] There are many advantageous techniques for carrying out this pretreatment, which will be summarized below under the general term "cooking": acid cooking, alkaline cooking, cooking by autohydrolysis, steam explosion and "organosolv pulping" processes. The latter process involves pretreatment in the presence of one or more organic solvents and usually water. The solvent can be an alcohol (ethanol), an acid (such as acetic acid or formic acid) or acetone. The "organosolv pulping" process results in at least partial dissolution of the lignin and partial dissolution of the hemicellulose. Thus, there are two outlet streams: a pretreated matrix with residual cellulose, hemicellulose and lignin, and a solvent phase containing dissolved lignin and part of the hemicellulose. There is usually a step of solvent regeneration, which makes it possible to extract the lignin stream. Certain "organosolv pulping" treatments (especially with ethanol) are combined with the addition of strong acids (such as H2SO4). It is also conceivable to contact the biomass with a solvent via an impregnation reactor before the cooking stage, or to contact the biomass with an acid catalyst before carrying out the "organosolv pulping" cooking.

[0008] Various configurations are reported, for example, in the publication “Production of bioethanol from lignocellulosic materials via the biochemical pathway: A review”, M. Balat, Energy Conversion and Management 52 (2011) 858–875 or in the publication “Bioethanol production from agricultural wastes: An overview”, N. Sarkar, S. Kumar Ghosh, S. Bannerjee, K. Aikat, Renewable Energy 37 (2012) 19-27.

[0009] One of the most effective pretreatments is steam explosion, especially under acidic conditions, which enables almost complete hydrolysis of hemicellulose and significantly improves the accessibility and reactivity of cellulose to enzymes. This pretreatment may be preceded by other treatments.

[0010] All these pretreatments are applied to biomasses that are initially in solid form: the purpose of the pretreatments is to decompose them.

[0011] Patents US-8057639 and US-8512512 propose a method comprising a first step of hydrolyzing hemicellulose to C5 sugars under mild conditions to protect them from degradation. This step is carried out in a first reactor at a pressure of 1.5 bar (0.15 MPa) or higher by injecting steam, at a temperature of 110°C or higher and optionally in the presence of a weak acid. After this step, washing is performed to extract and recover the sugar solution obtained from the hemicellulose (usually a sugar solution of C5 sugars and C6 sugars, the relative proportion of which depends in particular on the nature of the biomass), and then the residual biomass rich in cellulose and lignin is sent to a second step (a second reactor), where steam explosion occurs. The second reactor is operated at a higher pressure than the first reactor, wherein high-pressure steam is injected, which causes the biomass to expand suddenly (steam explosion).

[0012] When the treatment requires a pressure step (impregnation, cooking type pretreatment, etc.), a solid biomass introduction device compatible with these pressure steps must be used. For example, this is the case with compression screws, one embodiment of which is described in patent US 4,599,138.

[0013] Patent FR 3075203 describes a process involving impregnation of biomass with an acidic liquid, followed by cooking and steam explosion of the impregnated biomass, wherein the acidity of the acidic liquid is adjusted and it is recycled. Patent FR 3075201 also describes a process for pre-treating biomass by acid impregnation followed by steam explosion, as well as washing the reactor feed and recycling the washing water to the process.

[0014] The object of the present invention is thus to improve the processing of lignocellulosic biomass.The object of the present invention is in particular to improve the introduction of biomass into a reactor where one or more biomass processing steps are carried out.

[0015] The object of the present invention is more particularly to improve the steps of impregnation and / or steam explosion cooking of biomass as described in the above-mentioned prior art documents. The object of the present invention is also to make the treatment method, and in particular these two steps, more efficient in terms of energy and / or treatment fluid consumption and / or biomass conversion efficiency. Summary of the invention

[0016] The present invention firstly relates to a method for treating lignocellulosic biomass comprising a solid content of up to 90% by weight, said method comprising treating said biomass using at least one reactor, said reactor being equipped with a biomass feed device, said biomass feed device being equipped with a biomass inlet and a biomass outlet, said biomass outlet being fluidically connected to the inlet of the reactor. Said method is characterized by the fact that

[0017] - when the biomass flows towards the reactor through the feeding device, a residue is extracted from the biomass via an extraction outlet provided in said device, said residue being a mixture of solid and liquid, called solid-liquid residue,

[0018] - and separating the solid-liquid residue into a solid residue and a liquid residue,

[0019] - and reintroducing at least a portion of the solid residue into the same feed device or, in the case of a plurality of reactors, into one of said feed devices.

[0020] In the context of the present invention, the expression "lignocellulosic biomass comprising a solid content of X%" refers to a biomass naturally comprising a solid content of X% ("natural" biomass) or a biomass having this content after one or more operations preceding the method according to the invention. And the solid content (abbreviation "SC") represents the solid content measured according to the standard ASTM E1756-08 (2015) "Standard Test Method for Determination of Total Solids in Biomass".

[0021] In the context of the present invention, a "solid-liquid residue" is understood to mean a liquid containing suspended solids (solid particles). A "solid residue" is understood to mean a residue comprising at least 20% by weight of solids (in particular at least 30% or 40% by weight, or even at least 50% by weight of solids, depending on the separation process considered) and having a solid consistency of the sludge type or acid-impregnated biomass chips. The residue generally comprises from 20% to 50% by weight of solids.

[0022] “Liquid residue” is understood to mean a residue which comprises at least 50% by weight of liquid, in particular at least 80% by weight of liquid, and has a liquid consistency which is free or essentially free of suspended solid particles.

[0023] The present invention, as will be described in detail below, can be advantageously applied to any type of reactor used in a biomass conversion process, and more particularly to biomass impregnation reactors (when impregnation is envisaged, whether by a liquid containing compounds such as acids, bases or oxidants or by a water-based liquid, wherein the biomass autolyzes naturally releasing acids, in particular acetic acid) and / or cooking or steam explosion thermal treatment reactors.

[0024] Prior to the treatment of the lignocellulosic biomass, one or more pretreatment steps are required, for example, notably, at least one screening / cleaning operation in order to remove foreign elements of the metal type from the biomass ("demetallization"), at least one optional mechanical grinding in order to reduce the biomass to particles of a size suitable for treatment in the / each treatment reactor, at least one washing of the biomass, in particular with water, etc., wherein the order and number of steps are variable.

[0025] The invention consists in proposing to extract a partially solid and partially liquid residue from the biomass before it enters the reactor and to make optimal use of it.

[0026] In particular, it is known to extract / recover a liquid (aqueous) residue / liquid washing water from the feed device of the reactor in question in order to adjust the solids content of the biomass, to wash the equipment feeding the reactor with biomass, etc. The problem then is to recover this residue in order to reuse it "as is" as aqueous liquid make-up in the process, considering that it is simply a liquid to be recovered in order to reduce the consumption of water and / or chemicals (e.g. acid in the impregnation liquid) in the process.

[0027] However, the residue of this extraction, although it may in fact contain a high proportion of liquid (water), also contains solid material (even if the feed equipment is only washed with water to prevent it from fouling): it is a liquid loaded with solid particles.

[0028] And the inventors have shown that, once separated from the rest of the extraction residue, this solid residue (these particles) has a very interesting and modifiable composition.

[0029] The solid residue obtained from the solid-liquid residue extracted from the feed device of the impregnation reactor thus contains sugar polymers, lignin and has a formulation very similar to that of the biomass introduced into the feed device, which can be natural biomass or biomass that has undergone one or more treatments (mechanical treatment of the grinding or metal removal type, or chemical treatment with the addition of water to adjust the solid content of the biomass before impregnation or other treatment).

[0030] The solid residue obtained from the solid-liquid residue extracted from the feed device of the digestion reactor has a different formulation than the native biomass, in particular if the native biomass has previously been impregnated with an acidic, alkaline or oxidizing liquid and / or has been otherwise pretreated: in the case of impregnation with a liquid (e.g. an acid), the residue may contain traces of this liquid (e.g. it may contain the acid in the liquid formulation), it may also contain less hemicellulose, part of which has been able to be converted into sugars under the action of the impregnation liquid, it may also contain less cellulose and lignin. This residue may also contain less extractable species (monomeric sugars, ash, etc.) than the biomass, since the impregnation acts on these soluble species.

[0031] The present invention has then made full use of these observations to upgrade the solid residue alone in order to improve as much as possible the performance of the entire process, which has a considerable series of advantages:

[0032] - by separating the solid-liquid residue, a liquid residue free or substantially free of solid particles can be recovered, which makes it possible to recycle the liquid more efficiently (e.g. the particles do not interfere / risk contaminating the equipment for recycling the wash water),

[0033] - by recycling the separated solid residue, the efficiency of the conversion of biomass to sugars (by pretreatment to produce sugars, in particular C5 sugars, followed by enzymatic hydrolysis to produce sugars of the C6 sugar type) or the conversion of biomass to ethanol (by pretreatment, enzymatic hydrolysis and fermentation) is increased, since biomass derivatives that would otherwise be lost and that contain sugars / components that can still be converted to sugars are reintroduced into the biomass conversion process,

[0034] - the liquid residue freed of its solid particles can be used to reduce the water consumption of the process: the solid-liquid residue obtained from the feed of the digestion reactor can contain up to 80% by weight of water, so the recovery of this water is very advantageous, since the process is water-intensive, and even the solid-liquid residue extracted from the feed of the impregnation reactor can contain a large amount of water, which is at least the water content of the native biomass, which varies according to the nature of the biomass, but can rise to at least 30% by weight,

[0035] The liquid residue obtained from the solid-liquid residue extracted from the feed device of the digestion reactor and originating from the acid-impregnated biomass will contain a certain content of acid and can therefore be used as a supplement for the production of the impregnation liquor, which will reduce the acid consumption of the process (obviously, the same advantage of reducing the consumption of chemical substances if the impregnation is carried out with an alkaline or oxidizing liquid is present). This liquid residue can also be used to correct, for example, the pH / amount of oxidizing agents contained in the impregnation liquor and present in a residual manner in the biomass during the various steps of the biomass conversion process (except the preparation of the impregnation liquor itself).

[0036] According to the invention, the feed device or at least one of the feed devices can be washed by circulating a washing fluid between a washing inlet and a washing outlet of said feed device, which washing outlet is preferably also an extraction outlet for the solid-liquid residue.

[0037] In this case, the solid-liquid residue contains a high content of liquid (water) since it includes water contained in the biomass and in the washing water.

[0038] According to the invention, at least a portion of the liquid residue can be reintroduced into the same feed device or, in the case of a plurality of reactors, into one of said feed devices.

[0039] According to the invention, in a variant, the method comprises using a plurality of reactors to treat said biomass, reintroducing at least part of the solid residue into one of the feed means of said reactors and reintroducing at least part of the liquid residue into another of said feed means.

[0040] In a variant, the solid residue obtained from the feed device of the impregnation reactor can be reintroduced at the inlet of the feed device, for example together with the biomass feedstock entering the device.

[0041] In another variant, the solid residue obtained from the feed device of the digestion reactor can be reintroduced at the inlet of the feed device, for example together with the biomass feedstock entering the device, which biomass feedstock has optionally been pre-impregnated.

[0042] It is also possible to send the solid residue obtained from the feed of the impregnation reactor to the feed of the cooking reactor (or vice versa), but this has a less favorable effect on the biomass conversion efficiency than in the first two variants.

[0043] Advantageously, at least one of the feeding devices generates a pressure increase between the biomass inlet and the biomass outlet of said device, which pressure increase generates a compression of the biomass, thereby causing the extraction of a solid-liquid residue.

[0044] Thus, at least one of the feed devices may be a feed screw, which is in particular at least partially conical, comprising a housing provided with a cage provided with openings allowing the extraction of solid-liquid residues from the biomass and the circulation of washing fluids. As is known, such compression screws (also called "plug screws") form a sealing plug of the biomass in the downstream part of the screw, which produces a compression of the biomass, which is reflected in a pressure difference between the biomass inlet and the biomass outlet of the screw, for example of at least 0.05 MPa, for example of about 0.5 MPa. Thus, the compression applied to the biomass may lead to the discharge of a portion of the liquid contained in the biomass, in particular when the SC of the biomass before entering the pressurized feed device is less than 80%.

[0045] According to the present invention, the solid-liquid residue can be separated into a solid residue and a liquid residue by at least one separation device selected from a centrifugal device, a draining or pressing device, or a screening unit.

[0046] The method according to the invention may comprise a step of impregnating the biomass with an impregnation liquid containing a chemical catalyst, said step being carried out by introducing the biomass into the reactor or one of the reactors through its / their feeding means.

[0047] The method according to the invention may comprise a step of treating the biomass by cooking or steam explosion, said step being carried out by introducing the biomass into the reactor or one of the reactors through its / their feeding means.

[0048] The method according to the invention may comprise a step of treating the biomass by enzymatic hydrolysis, said step being carried out after cooking or steam explosion of the biomass in an enzymatic hydrolysis reactor equipped with its feeding device. The feeding device of the reactor is conventional, it may be, for example, a headless screw device (the biomass is usually not compressed at this stage).

[0049] The method according to the present invention may include at least one step of treating biomass by fermentation, which is carried out in a fermentation reactor equipped with its feed device after or simultaneously with the enzymatic hydrolysis step. The feed device of the fermentation reactor is conventional, and it can be, for example, a headless screw device (biomass is usually not compressed at this stage). It should be noted that enzymatic hydrolysis and fermentation can also be carried out in the same reactor.

[0050] The method according to the invention may comprise at least one step of treating the biomass, which step is aimed at separating the solvent or the alcohol, said step being carried out after the fermentation step and in a separate reactor equipped with a feeding device thereof. As described in detail below, the reactor may be any piece of equipment, which in particular comprises at least one distillation column, the feeding device of which is any conventional device of this type of equipment.

[0051] According to one embodiment of the invention, at least part of the solid residue is reintroduced into the feed device of the impregnation reactor or into the feed device of the digestion reactor, and the liquid residue is preferably reused for preparing the impregnation liquor.

[0052] According to one embodiment of the invention, at least a portion of the solid residue is reintroduced into the feed device of the enzymatic hydrolysis reactor and the liquid residue is preferably reused for preparing the impregnation liquor.

[0053] According to one embodiment of the present invention, when the biomass flows to the impregnation reactor and / or the cooking reactor through the feeding device, a residue can be extracted from the biomass via an extraction outlet provided in the device, and the residue is called a solid-liquid residue, which is a mixture of solid and liquid.

[0054] - then separating the solid-liquid residue into a solid residue and a liquid residue,

[0055] - and reintroducing at least part of the solid residue into the same feed device (thus the feed device of the impregnation or cooking reactor) or into at least one of the feed devices of the enzymatic hydrolysis reactor or the fermentation reactor or the separation reactor.

[0056] In this configuration, the solid residue obtained from the pretreatment of the biomass (cooking, optional pre-impregnation) is thus reused in order to introduce it into a reactor downstream of the pretreatment reactor intended to convert the pretreated biomass (at the outlet of the cooking reactor) into sugars, (then called hydrolysate) and then optionally into a solvent or alcohol of the ethanol type (then called fermentation broth, from which the alcohol or solvent of interest is separated in a known manner).

[0057] According to one embodiment, the method according to the present invention may comprise the following steps:

[0058] -a) preparing an impregnation liquid in a preparation zone, said impregnation liquid containing a chemical catalyst for impregnation of the biomass, the catalyst being selected from the group consisting of an acid catalyst, a basic catalyst and an oxidation catalyst, and preferably an acid catalyst,

[0059] -b) introducing the biomass into the impregnation reactor through a first feeding device which performs washing by circulating a first washing fluid between a washing inlet and a washing outlet of said device (6),

[0060] -c) introducing a liquid into the impregnation reactor via a first liquid (4) inlet of the reactor,

[0061] -d) transferring the impregnated and drained biomass from the outlet of the impregnation reactor to the inlet of the digestion pretreatment reactor via at least one second feeding device, said second feeding device being washed by circulating a second washing fluid between a washing inlet and a washing outlet of said feeding device,

[0062] -e) pre-treating the biomass in the reactor by cooking or steam explosion,

[0063] -f) extracting from the biomass a solid-liquid residue passing through at least one of the two feeding devices and then separating the / each solid-liquid residue into a solid residue and a liquid residue, wherein at least a portion of the solid residue is reintroduced into at least one of the feeding devices as biomass supplement and at least a portion of the liquid residue is reintroduced into at least one of the feeding devices as washing fluid supplement or as supplement to the impregnation liquid in the liquid preparation zone or the impregnation reactor.

[0064] The invention also relates to any device for implementing the above method.

[0065] The device according to the invention may thus comprise at least one biomass processing reactor, said reactor being equipped with a biomass feeding device, said biomass feeding device being equipped with a biomass inlet and a biomass outlet, said biomass outlet being fluidically connected to the inlet of the reactor, wherein when the biomass flows to the reactor through the feeding device, a residue is extracted from the biomass via an extraction outlet provided in said device, said residue being a mixture of solid and liquid, said device also comprising

[0066] at least one device for separating the solid-liquid residue into a solid residue and a liquid residue, in particular chosen from a centrifugal device, a draining or pressing device, or a screening unit,

[0067] - means for reintroducing at least part of the solid residue into the same feed means or, in the case of a plurality of reactors, into one of said feed means,

[0068] - Optionally, means for reintroducing at least a portion of the liquid residue into the apparatus, in particular into the feed device / one of the feed devices.

[0069] The means for reintroducing the liquid and / or solid residues are conventional and may comprise any suitable hydraulic connection means (pipes, pump or filter type devices, valves).

[0070] Another subject of the invention is the use of a method or an apparatus as described above for processing the following types of lignocellulosic biomass: wood, straw, agricultural residues and all dedicated energy crops, in particular annual or perennial plants, such as Miscanthus, in order to produce sugars, biofuels or bio-based molecules.

[0071] List of Figures

[0072] Figure 1 is a schematic diagram of an apparatus for converting lignocellulosic biomass to which the method according to the invention can be applied.

[0073] Figure 2 is used Figure 1 Block diagram of a prior art method for a device.

[0074] Figure 3 is a block diagram of a part of the method according to the invention, modified according to Figure 2 method.

[0075] Figure 4 is a block diagram illustrating a first variant of the method according to the invention.

[0076] Figure 5 is a block diagram illustrating a second variant of the method according to the invention.

[0077] Figure 6 is a block diagram illustrating a third variant of the method according to the invention.

[0078] Figure 7 is a block diagram illustrating a fourth variant of the method according to the invention.

[0079] Figure 8 is a block diagram illustrating a fifth variant of the method according to the invention.

[0080] Fig. 9 yes Figure 1 Schematic diagram of a variant according to the invention of the device for converting lignocellulosic biomass described in .

[0081] It should be noted that from one figure to another, the same reference numerals relate to the same streams or the same equipment.

[0082] Description of the implementation plan

[0083] Figure 1 A non-limiting example of an apparatus for converting lignocellulosic biomass in which the invention can be applied is very schematically represented, which provides for pretreatment of the biomass comprising impregnation with an acidic liquid, followed by cooking / steam explosion, then enzymatic hydrolysis, followed by alcohol fermentation, in order to convert the biomass into ethanol.

[0084] The invention is applicable in a similar manner to different devices, in particular:

[0085] - plants that aim only at producing sugars and therefore do not carry out alcohol fermentation,

[0086] - equipment that provides cooking pretreatment without prior impregnation with a liquid (e.g. autolysis),

[0087] - Equipment that provides cooking pretreatment without prior impregnation with a non-acidic liquid (such as an alkaline or oxidizing liquid).

[0088] In particular, the present invention is intended to be applied to any reactor used in a biomass conversion process, including but not limited to impregnation reactors and digestion reactors.

[0089] Figure 1 Thus, a biomass conversion is represented in the following manner: ground biomass 5, optionally impregnated with a catalytic liquid, is introduced into an impregnation reactor 9 by means of a pressurized feeder 6, which is a screw, also called a plug screw feeder, the end of which is conical, which has a hood with a draining screen, a wash water inlet 7 and a wash water outlet 8. In the downstream part of the screw, a hermetic plug of biomass is produced, which produces a compression of the biomass, which is reflected in a pressure difference of at least 0.05 MPa between the biomass inlet and the biomass outlet of the screw. The compression applied to the biomass can lead to the discharge of part of the liquid contained in the biomass, in particular when the SC of the biomass before the biomass enters the pressurized feeder 6 is less than 80%. The liquid thus extracted is mixed with the wash water and is pumped out together with the used wash water 8.

[0090] The impregnation reactor is also supplied with acidic liquid 4 (water supplemented with sulphuric acid) originating from a liquid preparation tank 3 which is itself supplied with acid 2 and water 1. The reactor comprises a biomass impregnation zone 9a, above which is a biomass draining zone 9b.

[0091] The impregnated and drained biomass 10 leaves the reactor 9 in order to feed a steam explosion cooking reactor 14 via another feed screw 11 similar in its operation to the feed screw 6. In this screw, due to the compression exerted by the biomass, the liquid 13 produced by this pressing, also called pressate, is recovered, which contains water and acid. The screw is washed with a washing fluid 12 (water and / or recycled liquid, as seen below) using a dedicated inlet, which is then discharged via an outlet, through which the pressate 13 is also discharged.

[0092] Steam 15 is also supplied to the reactor 14. After leaving the reactor 14, the biomass-steam mixture enters a means 17 for separating the biomass 19 and the steam 18. The biomass 19 is then processed in an enzymatic hydrolysis reactor 20 and then once hydrolyzed to sugars, the hydrolyzed biomass 21 (also called hydrolysis must) enters an alcohol fermentation reactor 22. The biomass fermented to alcohol 23 (called fermentation must) is then sent to one or more distillation columns to obtain concentrated alcohol 25 and raw vinasses 26.

[0093] This is only one example of an apparatus, many variations of which are possible. Thus, enzymatic hydrolysis and fermentation can be carried out together in the same reactor, which is then referred to as SSCF (simultaneous saccharification and co-fermentation).

[0094] 1: Water enters the liquid preparation tank

[0095] 2: Acid enters the liquid preparation tank

[0096] 3: Liquid preparation tools (tanks)

[0097] 4: Acidic solution to the impregnation tool (reactor)

[0098] 5: Ground biomass

[0099] 6: Screw of the impregnation tool (plug screw feeder)

[0100] 7: Water for washing the plug screw feeder of the dipping tool

[0101] 8: Washing fluid outlet of the plug screw feeder 6 of the dipping tool

[0102] 9: Impregnation tool (reactor)

[0103] 9a: Dipping area of ​​dipping tank 9

[0104] 9b: Drainage area of ​​immersion tank 9

[0105] 10: Soaked and drained biomass

[0106] 11: Screw of pre-treatment tool (plug screw feeder)

[0107] 12: Water for washing the screw feeder of the pretreatment tool

[0108] 13: Pressed liquid from the plug screw feeder of the pre-treatment tool

[0109] 14: Pretreatment cooking tool (explosion reactor)

[0110] 15: Inject steam for pretreatment

[0111] 16: Pretreated biomass and steam

[0112] 17: Means for separating steam and pre-treated biomass (cyclone separator)

[0113] 18: Steam to condensation

[0114] 19: Pretreated biomass

[0115] 20: Enzyme hydrolysis reactor

[0116] 21: Sugary hydrolysate

[0117] 22: Alcohol (ethanol) fermentation reactor

[0118] 23: Fermented wine containing ethanol (alcohol)

[0119] 24: Ethanol recovery unit, such as a distillation tower

[0120] 25: Concentrated alcohol

[0121] 26: Residue (solids and liquids, as a mixture or separated according to the arrangement of 24)

[0122] method

[0123] The various steps of a biomass conversion method using such an apparatus are described in more detail below, and the present invention can be advantageously applied thereto: (This is an example, and the present invention is not limited thereto).

[0124] Step a) Conditioning of lignocellulosic biomass

[0125] The treatment method comprises in its first step the conditioned lignocellulosic biomass with at least one grinding, to obtain the biomass particles with a size of at most 300mm. Of course, several continuous grinding steps can be carried out to reach the target particle size. Generally speaking, the ground biomass has at most 300mm, usually at least 1mm, and often a particle size (maximum size) between 2 to 200mm. Any method known to those skilled in the art can be used to carry out this step. Usually, the stalk is ground with a screen of 5 to 100mm. For wood, it is usually cut into parallelepiped fragments, with a length between 20 to 160mm, a width between 10 to 100mm, and a thickness between 2 to 20mm. The ground lignocellulosic biomass is sent to the next step by any means (particularly screw conveyor) known to those skilled in the art.

[0126] Step b) impregnation with acid solution

[0127] The treatment method according to the invention comprises a step b) of impregnating the lignocellulosic substrate with an acid solution to obtain an impregnated lignocellulosic substrate, the pH of which is between 0.1 and 3. This step aims at preparing the lignocellulosic substrate for a pretreatment step.

[0128] The impregnation is carried out in an impregnation reactor at a temperature between 10° C. and 90° C. and preferably at atmospheric pressure. The residence time of the lignocellulosic substrate in the impregnation reactor is generally between 10 seconds and 180 minutes, preferably between 30 seconds and 60 minutes and still more preferably between 30 seconds and 15 minutes. Preferably, the impregnation step is carried out in a single step.

[0129] The impregnation reactor or impregnator is equipped with one or more screws for conveying the lignocellulosic substrate from its inlet to its outlet. The impregnator is also equipped with one or more pipelines for conveying acid solution and, if necessary, one or more pipelines for withdrawing acid solution. The acid solution inlet and outlet pipelines are usually installed to function by co-current or counter-current recirculation.

[0130] The acid solution is an aqueous solution of a strong acid, for example, the strong acid is selected from sulfuric acid, hydrochloric acid and nitric acid, for example, the acid content is between 0.5 wt % and 4 wt %.

[0131] Step c) Solid / liquid separation on a lignocellulosic substrate impregnated with an acid solution

[0132] According to step c) of the treatment method of the present invention, the lignocellulosic substrate impregnated with the acid solution is subjected to a solid / liquid separation step so as to obtain a lignocellulosic substrate having a solid content between 15% and 70% by weight and spent acid solution. Preferably, before the solid / liquid separation treatment, the lignocellulosic substrate impregnated with the acid solution is first drained to extract at least a portion of the free acid solution.

[0133] The solid / liquid separation step may be performed by any technique known to the person skilled in the art, for example it may be decantation, centrifugation or pressing.

[0134] Preferably, the pressing of the lignocellulosic substrate is carried out simultaneously with its transfer to the pretreatment step d), which is then subjected to the steam explosion method described below. This method of carrying out step c) is carried out, for example, by means of a screw called a "plug screw feeder", the operation of which has been described above. The formation of a plug of pressed lignocellulosic substrate ensures the pressure tightness of the steam explosion reactor, thereby preventing a dangerous escape of steam. The screw conveyor is also provided with one or more lines for withdrawing the waste liquid separated during the pressing process, called pressate. The pressate can be recycled to the impregnation step b) and / or to the step of washing with a washing fluid 12 passed through the feed screw 11.

[0135] The wet biomass obtained at the end of the solid / liquid separation step c), which may be indicated by the term "washed and acidified lignocellulosic substrate", preferably has a solids content between 15 and 70% by weight and more preferably between 40 and 65% by weight.

[0136] Step d) Pretreatment of the washed and acidified lignocellulosic substrate

[0137] According to step c) of the method, the washed and acidified lignocellulosic substrate is subjected to a pretreatment step d).

[0138] The cellulose (and optionally hemicellulose) that is the target of the enzymatic hydrolysis cannot be directly exposed to the enzymes. This is why the biomass is subjected to a pretreatment prior to the enzymatic hydrolysis step. The pretreatment is mainly intended to change the physical and physicochemical properties of the cellulose fraction, such as its degree of polymerization and crystalline state.

[0139] Various types of pretreatment are known to the person skilled in the art, which combine chemical and thermal treatments. Particular mention may be made of acidic or alkaline cooking, organosolv methods, ionic liquid treatments and steam explosion methods.

[0140] The preferred pretreatment method is steam explosion (or "SteamEx") in an acidic medium. This method rapidly raises the lignocellulosic substrate to a high temperature by injecting pressurized steam. The treatment can be stopped by suddenly reducing the pressure.

[0141] The operating conditions of the steam explosion method are as follows:

[0142] - direct steam injection into the reactor;

[0143] - the temperature of the reactor is generally between 150°C and 220°C, preferably between 170°C and 210°C,

[0144] - the pressure is between 5 and 25 bar absolute (0.5 and 2.5 MPa), more preferably between 8 and 19 bar absolute (0.8 and 1.9 MPa),

[0145] The residence time before the expansion phase is between 10 seconds and 50 minutes and preferably between 3 minutes and 30 or 40 minutes.

[0146] Steam explosion can be performed in batch or continuous mode, and the depressurization step to decompose the biomass can be performed in one or more steps.

[0147] At the end of the steam explosion pretreatment step, a pretreated lignocellulosic substrate with a high solids content (generally between 20 and 70% by weight) and a subsequent condensed vapour phase is obtained.

[0148] In the context of the present invention, the pretreated lignocellulosic substrate obtained at the end of step d) of the treatment process according to the invention is advantageously used as feedstock in a "second generation" process for producing solvents and / or alcohols from lignocellulosic biomass.

[0149] The present invention also relates to a method for producing solvents and / or alcohols from lignocellulosic biomass, comprising at least the following steps:

[0150] i) treating the lignocellulosic biomass by the treatment method according to the invention to obtain a treated lignocellulosic substrate;

[0151] ii) enzymatically hydrolyzing the treated lignocellulosic substrate to obtain a hydrolysate containing fermentable sugars;

[0152] iii) fermenting the hydrolyzate obtained in step ii) to obtain a fermentation broth containing a solvent and / or alcohol;

[0153] iv) separating the solvent and / or alcohol from the fermentation broth.

[0154] After steam explosion under acidic conditions, the pH of the pretreated lignocellulosic substrate is generally below the pH compatible with the enzymatic hydrolysis medium. Therefore, the lignocellulosic substrate treated according to step I) of the process for producing solvents and / or alcohols is subjected to a neutralization step to bring its pH to a value between 4 and 6.

[0155] For the neutralization step, an aqueous solution containing a neutralizing agent is used, which can be chosen from all weak or strong bases known to the person skilled in the art. The term "base" means any chemical species which, when added to water, produces an aqueous solution with a pH greater than 7. Preferably, the neutralizing agent is chosen from potassium hydroxide, sodium hydroxide, ammonia and lime. More preferably, the neutralizing agent is chosen from potassium hydroxide and ammonia, alone or in combination with each other. Preferably, the neutralizing agent is used in the form of an aqueous solution, wherein the weight concentration is between 2% and 75%, and still more preferably between 20% and 70%.

[0156] Neutralization is carried out at a temperature between 15° C. and 95° C., preferably between 20° C. and 70° C. In general, the temperature of the neutralization step is not precisely controlled, but is simply controlled by the heat released by the acid-base neutralization reaction.

[0157] The neutralization step can be performed in continuous, batch or fed-batch mode.

[0158] It is worth noting that all or part of the pretreated lignocellulosic substrate may be subjected to an optional washing step before or after the neutralization step.

[0159] If washing is applied, the liquid stream is contacted with the pretreated lignocellulosic substrate, and then the liquid is separated from the solid. The washing step can be carried out by diafiltration, continuous mixing and liquid / solid separation operation, washing on a belt filter or any other technology known to those skilled in the art. The washing fluid used can be water or a process stream. The weight ratio of the added washing fluid to the liquid contained in the substrate to be washed is generally 0.5 to 4. The washing step produces a sugar-containing washing liquid, which contains a part of hemicellulose that is solubilized during the pretreatment process. This washing liquid can, for example, be used as a carbon source for producing a biocatalyst (enzyme and / or microorganism). The washing step is generally carried out at a temperature of 10 ℃ to 95 ℃.

[0160] Step ii) Enzymatic hydrolysis

[0161] The pretreated lignocellulosic substrate (optionally neutralized and washed) is sent to the enzymatic hydrolysis step ii) of the process.

[0162] The solids content of the pretreated lignocellulosic substrate fed to the enzymatic hydrolysis step is typically between 15% and 70% by weight.

[0163] The purpose of enzymatic hydrolysis is to hydrolyze (depolymerize) hemicellulose and cellulose into fermentable sugars, preferably glucose, by means of biocatalysts.

[0164] The enzymatic hydrolysis step is carried out under mild conditions at a temperature of the order of 40° C. and 55° C., preferably between 45° C. and 50° C. and a pH of 4.0 to 5.5, and still more preferably between 4.8 and 5.2. The solids content of the enzymatic hydrolysis medium is from 5% to 45% by weight, preferably from 10% to 30% by weight. The enzymatic hydrolysis is carried out by means of enzymes produced by microorganisms. Natural or genetically modified microorganisms, such as fungi of the genera Trichoderma, Aspergillus, Penicillium or Schizophyllum, or anaerobic bacteria such as Clostridium, produce enzyme mixtures containing in particular cellulases and hemicellulases, suitable for extensive hydrolysis of cellulose and hemicellulose.

[0165] The enzymatic hydrolysis can be carried out continuously or in batch or fed-batch mode in one or more reactors. The residence time is between 12 hours and 200 hours, and preferably between 24 hours and 120 hours, and still more preferably between 48 hours and 120 hours.

[0166] At the end of step ii), a hydrolysate containing fermentable sugars is recovered from the bioreactor and this hydrolysate is then processed in a fermentation step iii).

[0167] It is worth noting that, before the fermentation step, the hydrolyzate obtained may optionally undergo one or more treatment steps. For example, these treatment steps may be to restore the pH, partially purify to limit the inhibitor compound content of the fermenting microorganism, or at least partially separate the solid residues contained in the hydrolyzate.

[0168] Step iii) Fermentation of the hydrolysate

[0169] According to step iii) of the process for producing solvents and / or alcohols, the optionally treated hydrolysate is sent to a fermentation step which enables the conversion of the fermentable sugars into the solvents and / or alcohols of interest by one or more microorganisms of different genera. Fermentation methods are well known to those skilled in the art.

[0170] The term "solvent" is intended to mean organic compounds other than alcohols, for example organic compounds having a ketone functionality, such as acetone.

[0171] The term "alcohol" denotes in particular ethanol, propanol, isopropanol and butanol.

[0172] The natural or genetically modified microorganism can be selected from, for example, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Saccharomyces vitis, Saccharomyces diastaticus, Kluyveromyces fragilis, Candida shehatae, Pichia stipitis, Pachysolen tanninophilus or the bacterium Zymomonas mobilis, Clostridium acetobutylicum, Escherichia coli.

[0173] In the context of the present invention, the fermentation step makes it possible, for example, to produce ethanol alone or in mixture with butanol, propanol, isopropanol and / or acetone. For example, the fermenting microorganism may be able to produce an "ABE (acetone-butanol-ethanol)" mixture or an "IBE (isopropanol-butanol-ethanol)" mixture.

[0174] Preferably, the microorganism selected is a native or genetically modified Saccharomyces yeast capable of producing ethanol.

[0175] At the end of step iii), the fermentation broth diluted in the product of interest is recovered.

[0176] According to one embodiment of the method, steps ii) and iii) are carried out simultaneously in at least one and the same bioreactor, so that enzymatic hydrolysis and fermentation are carried out simultaneously according to the method represented by the term "simultaneous saccharification and fermentation (SSF)". When the hydrolysis step is combined with the fermentation step, the operating conditions, in particular the temperature conditions, can be adjusted to be compatible with the tolerance of the fermenting microorganisms. For example, when fermentation is carried out using yeast of the genus Saccharomyces, the temperature can be reduced to between 28°C and 45°C, and preferably between 30°C and 35°C. The pH is preferably adjusted to between 5 and 5.5 in order to promote the performance of the yeast.

[0177] In addition to the equipment already described, the production unit for carrying out the method according to the invention may also comprise a unit for the in situ production of enzymes and / or yeasts.

[0178] Step iv) Separating the solvent and / or alcohol from the fermentation broth

[0179] The method according to the invention may finally comprise a step of separating the target product from the fermentation broth, optionally preceded by a solid / liquid separation step to remove at least part of the solid matter contained in the fermentation broth.

[0180] Preferably, the step of isolating the product of interest (eg, ethanol) employs one or more distillations, which are techniques well known to those skilled in the art.

[0181] Raw material: Lignocellulosic biomass

[0182] According to the invention, the raw materials for the process can be individual biomasses or as a mixture. The amount of water contained in the raw raw materials is generally at least 10% by weight, in particular 10% to 70% by weight.

[0183] The raw biomass is selected from any type of biomass, preferably solid type biomass, and in particular lignocellulosic type biomass. Non-limiting examples of biomass types relate to, for example, agricultural residues (in particular straw, corn cobs), forestry management residues, forestry management products, lumber mill residues and special crops, such as short-rotation coppice.

[0184] Preferably, the crude biomass, also called natural biomass, is lignocellulosic biomass. It basically comprises three natural components, which are present in variable amounts depending on their origin: cellulose, hemicellulose and lignin.

[0185] The lignocellulosic biomass feedstock is preferably used in its crude form, ie containing all three components of cellulose, hemicellulose and lignin.

[0186] In a preferred embodiment of the invention the lignocellulosic biomass is selected from grass biomass, agricultural residues (eg straw waste, corn cobs, bagasse), forestry management residues or lumber mill residues (eg wood chips) or any other type of woody residue.

[0187] Immersing fluid:

[0188] The optional fluid injected for impregnation is an aqueous liquid solution optionally containing an acid at a temperature between 10° C. and 95° C. and a pressure at atmospheric pressure. The pH of the chemical solution is between 0.1 and 12.0, preferably between 0.1 and 7, preferably between 0.3 and 2. According to a preferred embodiment, the liquid used is an acid-catalyzed liquid, and the pH of the liquid is adjusted to between 0.1 and 4, in particular between 0.3 and 2. Examples of acids that can be used include at least one acid selected from sulfuric acid, hydrochloric acid, nitric acid and oxalic acid. Their content in the aqueous phase is preferably between 0.2% by weight and 8% by weight.

[0189] Review each one Figures 2 to 8 : All these figures are variations of biomass pretreatment. It should be noted that, for simplicity of the invention, they are described by impregnation with an acidic fluid followed by steam explosion cooking, but the invention is equally applicable to pretreatment without impregnation, or with non-acidic impregnation, or cooking without steam explosion.

[0190] Figure 2 Schematic diagram showing the pretreatment part of a biomass conversion process, which can be applied, for example, Figure 1 The apparatus of , in which the known sequence is (optionally) impregnation with an impregnation fluid followed by cooking / steam explosion of the biomass, is modified by the present invention: the (ground) biomass 5 enters a conveying zone comprising a compression screw feed device 6 which can optionally be washed by circulation of an aqueous washing fluid 7 (discharged in the form of used washing fluid 8) and conveys the biomass to an impregnation reactor 9 which is also supplied with an impregnation fluid 4 via a preparation tank 3 supplied with water 1 and an impregnation compound 2 (acidic or alkaline). As mentioned above, impregnation may not be performed. Impregnation may also be performed in different ways, in batch mode (immersing the biomass in a tank containing the impregnation fluid), or in continuous mode, for example by spraying, or by passing the biomass through a stirred reactor.

[0191] Therefore, different feeding modes and impregnation modes can be used, such as a conveyor belt conveying the biomass below a device spraying the impregnation fluid.

[0192] The impregnated biomass 10 then enters a conveying zone comprising a compressed feed screw 11, is washed by a washing fluid 12 (wash water), and the spent wash water 13 is discharged. The biomass then enters a cooking reactor 14 in the presence of steam 15, and is then extracted from the reactor in the form of pretreated biomass 16 to continue its process of conversion into sugars or alcohols.

[0193] Figure 3 The present invention shows Figure 2 The first improvement step of the method: the fluid 8 extracted from the feed device 6 of the impregnation reactor 9 can be water originating from the natural biomass (or water added to the biomass before entering the feed device) and / or used washing water obtained from the washing water 7. This fluid 8 actually consists of a liquid phase (water) and suspended solid particles (of the biomass). According to the invention, it is conveyed to the outlet of the solid / liquid separation device 30, where the liquid phase / residue 31 and the solid residue 32 are recovered. This device can be, for example, a screening unit. Therefore, these two residues will be able to be separately upgraded / reused in a very advantageous way, as described below.

[0194] In a similar manner, the fluid 13 extracted from the feed device 11 of the digestion reactor 14 also consists of a liquid phase (water) and suspended solid particles (of the biomass). According to the invention, the fluid 13 is conveyed to the outlet of the solid / liquid separation device 40, where the liquid phase / residue 41 and the solid residue 42 are recovered. This device can also be a screening unit, for example. Thus, as described below, the two residues will be able to be separately upgraded / reused in a very advantageous manner.

[0195] This separation and upgrading / recycling of solid and liquid residues can be carried out only on the feed equipment of the impregnation unit / reactor 9, or only on the feed equipment of the cooking unit / reactor 14, or naturally on both units.

[0196] Figure 4 The upgrading (impregnation step) of the solid residue 32 is shown by reinjecting the residue 32 together with the biomass raw material 5 at the inlet of the feeding device 6. In this case, the solid residue 32 has a similar / very similar or even the same composition as the biomass 5, but it can be in the form of particles of smaller size (when the feeding device is of the compression screw type, it has a mechanical effect on the biomass).

[0197] Recycling the solid residue 32 to the inlet of the impregnation reactor 9 together with the ground biomass 5 makes it possible to not lose this solid stream and to obtain a "clear" liquid residue 31 (free from visible suspended particles) which can also be reused. This solid recycling makes it possible to increase the yield of the process, since the residue 32 contains sugar polymers, to increase the yield of lignin, since the residue 32 contains lignin, and to reduce the water consumption of the process, since the residue also contains water. The solid / liquid separation can be carried out on all or part of the stream 8 leaving the feeding device 6, and this recycling of the solid residue 32 can be carried out on all or part of said solid residue.

[0198] Figure 5 The upgrading of the solid residue 42 (cooking step) is shown, which is carried out by reinjecting the residue 42 at the inlet of the feed device 12 of the cooking device / reactor 14. In this case, the solid residue 42 has a different composition than the residue 32, since it is obtained from the biomass impregnated with a steeping liquid, in particular this steeping liquid is highly acidic, and / or from the washing water of the feed device, which washing water may also contain a certain content of this fluid / acid.

[0199] Recycling the solid residue 42 together with the impregnated biomass 10 makes it possible to not lose this solid stream and to obtain a clear liquid residue 41 (also called pressate). This solid recycling makes it possible to increase the yield of the process, since the stream 42 contains sugar polymers, to increase the yield of lignin, since the stream 42 contains lignin, and to reduce the consumption of the impregnation liquid 2, since the residue 42 contains the impregnation liquid. The solid / liquid separation can be carried out on all or part of the stream 13 leaving the feeding device 11, and this recycling of the solid residue 42 can be carried out on all or part of said solid residue.

[0200] It is also possible to recirculate all or part of the solid residue 42 together with the ground biomass 5 at the impregnation inlet, but this recirculation seems less advantageous since the already acidic biomass is then impregnated a second time with the residue 42 .

[0201] Figure 6 Indicates based on Figure 4 Re-injection of solid residue 32 and according to Figure 5 The solid residue 42 is re-injected, and thus an embodiment of the invention is shown to be applied twice in a biomass conversion process, which has the same advantages as for Figure 4 and Figure 5 The same as those described above. Each reuse of the two solid residues can be carried out on all or part of each residue. It is also conceivable to combine all or some of the two solid residues in order to reuse them together in the process.

[0202] Figure 7 Indicates based on Figure 6 The two solid residues 32 and 42 are reinjected, while the corresponding two liquid residues 31 and 41 are also reused:

[0203] - Reinjection of the liquid residue 31 , which is essentially water, into the wash inlet of the feed device 6 of the impregnation device.

[0204] - Re-injecting the liquid residue 41 into the impregnation liquid preparation tank. Specifically, this residue 41 contains a certain amount of acid (if we continue to use acid liquid as an example), and re-injecting it into the tank 3 can achieve a beneficial replenishment of water and acid.

[0205] The recycling of the liquid residues 31 and 41 makes it possible to reduce the water consumption and the impregnation fluid consumption. This recycling can be carried out on all or part of the liquid residues. As with the solid residues, it is also conceivable to combine them at least partially so as to recycle them together in the method.

[0206] Figure 8 Proposed relative to Figure 7 Variants for reusing the liquid residues 31 and 41: The dashed arrows indicate various alternative or cumulative options for reinjecting them in whole or in part into the biomass pretreatment method. Thus, the liquid residue 31 (the one upstream of the impregnation device) can also be reinjected in whole or in part into the impregnation liquid preparation tank 3 as make-up water. It can also be discharged in whole or in part as washing water 12 for the feed device 11 of the cooking device 14, or as washing water 7 for the feed device 6 of the impregnation device 9 (if this device also provides washing). It can also be added in whole or in part to the liquid residue 41 and follow its reinjection circuit. Conversely, the liquid residue 41 itself can also be added in whole or in part to the liquid residue 31 and then reused together in the tank 3, for example to prepare the liquid 4 (these two variants are not shown in the figure).

[0207] It should also be noted that these liquid residues 31 , 41 , and in particular the residue 41 containing at least acid, can also be directly reused / reinjected in the impregnation device 9 , if its acid content is preferably controlled upstream.

[0208] Finally, it should be noted that at least one of these liquid residues 31 , 41 may also be reused in a step of the biomass conversion process downstream of its pretreatment, after its cooking, requiring the supply of water and / or water with an acidic pH.

[0209] Fig. 9 According to the present invention, Figure 1Improvements of the device described in : here, the two solid residues obtained from the feed devices of the impregnation reactor 9 and the cooking reactor 14 or at least one of them are at least partially reintroduced downstream of the biomass pretreatment. The dashed lines represent various alternative or cumulative options for the complete or partial reintroduction of these solid residues: thus, they can be reintroduced at the inlet of the hydrolysis reactor 20 or the fermentation reactor 22 or even at the inlet of the separation device 24, in particular through their own feed devices, which are conventional (for example, pipes or endless screw systems leading to inlets made in the reactors). Thus, the solid residues are mixed with the pretreated biomass flow 19 and / or the hydrolysis product flow 21 and / or the fermentation liquid 23.

[0210] Fig. 9 The last option shown consists in introducing all or some of the solid residues 32 and / or 42 directly into the final residue 26 obtained from the separation of the fermentation broth, which final residue 26 can be reformed into fuel. In this case, the amount of final residue 26 and therefore the amount of fuel that can be reused in the plant itself or outside the plant is directly increased. This is another type of reforming, the purpose of which is not to increase the biomass conversion efficiency of the process, but to maximize the use of the residues of the process. Example

[0211] They involve pretreatment of lignocellulosic biomass by acid impregnation followed by steam explosion, e.g. Figure 1 shown.

[0212] The term "potential sugar (xylose, glucose)" used below defines versions of various sugars, regardless of their form: monomeric sugars or polymeric sugars. Specifically, after pretreatment by cooking, a portion of the sugars still exist in the form of sugar polymers (such as cellulose or hemicellulose), while a portion of the sugars exist in the form of sugar monomers (such as glucose or xylose). This measurement can be performed using the standard ASTM E1758-01 (2020) "Standard Test Method for Determination of Carbohydrates in Biomass by High Performance Liquid Chromatography". As defined in the standard, in order to express the amount of sugar in polymer form (such as cellulose), hydrolysis water must be subtracted from that amount.

[0213] Example 1 (comparative)

[0214] Biomass 5 is wheat straw lignocellulosic biomass. Its composition is shown in Table 1 below:

[0215] Table 1

[0216] Cellulose 34％ weight Hemicellulose 27％ weight Lignin 15％ weight water 10％ weight other 14％ weight

[0217] After hydrolysis, cellulose is converted to glucose or glucose oligomers, and hemicellulose is converted to xylose or xylose oligomers.

[0218] 642 kg / h of this 50 mm ground biomass 5 enters the process with a production of 200 kg / h of wash water 7. 203.8 kg / h of a first solid / liquid stream 8 leaves the process, in which there are 1.3 kg / h of potential glucose and 1.1 kg / h of potential xylose. In the impregnation step (reactor 9), 1622.6 kg / h of water and 84.2 kg / h of sulfuric acid are added from the preparation tank 3 to the reactor and constitute the impregnation liquor 4.

[0219] At the inlet of the cooking reactor 14, the impregnated biomass 10 is fed to the transfer zone 11. The transfer zone 11 (compression screw) is washed with 4087.0 kg / h of water 12, and 5099.9 kg / h of a second solid / liquid stream 13 leaves the zone 11. In this stream 13, there are 2.7 kg / h of potential glucose, 2.2 kg / h of potential xylose and 45.6 kg / h of acid. The cooking reactor 14 is heated by a steam stream 15 of 3471.1 kg / h. At the outlet of this reactor 14, 4803.8 kg / h of a pretreated biomass stream 16 leaves, which contains 237.8 kg / h of potential glucose and 155.2 kg / h of xylose.

[0220] At the limit of the pretreatment, ie between the inlet of the biomass 5 feeding device 6 and its outlet from the cooking reactor 14 , 98.1% by weight of the potential glucose and 78.8% by weight of the potential xylose have therefore been retained.

[0221] Example 2 (according to the present invention)

[0222] It is in accordance with Figure 4 The variant of the invention shown is carried out in which the recovered solid residue is recycled to the inlet of the impregnation reactor.

[0223] The biomass feedstock was the same as in Example 1. The throughput was the same as in Example 1: 642 kg / h of this 50 mm ground biomass 5 entered the process with a throughput of 200 kg / h of wash water 7. A first solid / liquid stream 8 of 203.8 kg / h left the transfer zone 6 and entered the impregnator 9. This stream was separated in the separation means 30 into a liquid stream / residue 31 of 192 kg / h and a solid stream / residue 32 of 11.8 kg / h. The separation means 30 was a screening unit.

[0224] The solid residue 32 resulting from the solid / liquid separation is relatively moist (25% SC) and contains 1.3 kg / h of potential glucose and 1.1 kg / h of potential xylose. It is recycled at the inlet of the feed device 6 together with the ground biomass 5. Surprisingly, despite the small particle size of the solid residue 32 and the fact that the solid residue first passes through the holes of the feed screw cage, the circulation of the solid residue 32 at the impregnation inlet does not lead to accumulation in the feed device 6: it is entrained with the ground biomass 5 into the impregnation reactor 9. In the impregnation step, the same amounts of water and sulfuric acid as in Example 1 are added to the tank 3 for preparing the impregnation liquor 4.

[0225] The rest of the process is the same as in Example 1. At the outlet of the cooking reactor 14 4815.5 kg / h of pretreated biomass stream 16 leave, which contains 239.2 kg / h of potential glucose and 156.1 kg / h of potential xylose.

[0226] Thus, at the limit of pretreatment (this term has the same meaning as in Example 1), 98.6% by weight of the potential glucose and 79.2% by weight of the potential xylose have been retained, i.e., the yield has been increased by 1.0 percentage point. In addition, the present invention has made it possible to recycle the solids 32, which previously had no purpose.

[0227] Example 3 (according to the present invention)

[0228] It is in accordance with Figure 5 The variant of the invention shown is carried out in which the recovered solid residue is recycled to the inlet of the digestion reactor. The feedstock treated here is the same as in the two previous examples.

[0229] 642 kg / h of this 50 mm ground biomass 5 enters the process with a production of 200 kg / h of wash water 7. By compressing the impregnated biomass in the feed screw 11, 203.8 kg / h of the first solid / liquid stream 13 leaves the process. In this stream, there are 1.3 kg / h of potential glucose and 1.1 kg / h of potential xylose. In the impregnation step, 1622.6 kg / h of water and 84.2 kg / h of sulfuric acid are added to the tank 3 for the preparation of the impregnation liquid 4.

[0230] The throughput is the same as in Examples 1 and 2: 642 kg / h of this 50 mm ground biomass enters the process with a throughput of 200 kg / h of wash water 7 (which enters the impregnation reactor 9). 203.8 kg / h of a first solid / liquid stream 8 leaves the process. In this stream, there are 1.3 kg / h of potential glucose and 1.1 kg / h of potential xylose. In the impregnation step (reactor 9), the amount of water used is the same as in Examples 1 and 2, but only 84 kg / h of sulfuric acid (a saving of 0.2 wt% compared to the previous examples) is added to tank 3 to prepare the impregnation liquor 4.

[0231] At the inlet of the digestion reactor 14, the impregnated biomass 10 is fed to the transfer zone 11. The transfer zone 11 is washed with 4087 kg / h of water 12, and a second solid / liquid stream 13 of 5097.9 kg / h leaves the transfer zone 11 and enters the digestion reactor 14. This stream 13 is separated in the separation means 40 (here a screening unit) into a liquid stream / residue 41 of 5074.1 kg / h and a solid stream / residue 42 of 23.8 kg / h. The solid stream 42 resulting from the solid / liquid separation is relatively moist (26.1% SC) and contains 2.7 kg / h of potential glucose, 2.2 kg / h of potential xylose and 0.2 kg / h of sulfuric acid. It is circulated with the impregnated biomass 10. Surprisingly, despite the small particle size of this residue 42 and the fact that the solid residue first passes through the holes of the feed screw cage, recycling this residue 42 at the digester inlet does not lead to accumulation in the circuit of the compression screw feed device 11. It is entrained by the biomass 10 into the digester reactor 14.

[0232] The cooking reactor 14 is heated by a 3471.1 kg / h steam flow 15. At the outlet of the reactor, a stream of 4829.6 kg / h of pretreated biomass 16 leaves, which contains 240.5 kg / h of latent glucose and 157.4 kg / h of xylose.

[0233] Thus, at the end of the pretreatment (from the inlet of the feed device 6 to the outlet of the reactor 14), 99.2% by weight of the potential glucose and 79.9% by weight of the potential xylose remain, i.e. the yield has been increased by 2.2 percentage points. In addition, the solids 42 have been recycled, which previously had no purpose, and the acid consumption has been reduced by 0.2% by weight.

[0234] Table 2 below shows the composition of the ground biomass 5 and of the solid residue 32 recovered from the feed device of the impregnation reactor 9 .

[0235] Table 2

[0236]

[0237] It can be seen that the composition of the residue 32 is very similar to the starting biomass, with a significantly higher water content.

[0238] Table 3 below again shows the composition of the ground biomass 5 and of the solid residue 42 recovered from the feed device of the digestion reactor 14:

[0239] Table 3

[0240]

[0241] It can be seen that the residue 42 has a similar composition to the starting biomass, with a significantly higher water content, and additional sulfuric acid content, which demonstrates the advantage of recycling it.

[0242] Example 4 (according to the present invention)

[0243] It is in accordance with Figure 6 The variant of the invention shown is carried out in which the recovered solid residue 32 is recycled to the inlet of the impregnation reactor 9 and the recovered solid residue 42 is recycled to the inlet of the digestion reactor 14. The raw materials treated here are the same as in the previous embodiment.

[0244] The throughput of the recycling results described in Examples 2 and 3 applies to Example 4: by recycling both solid residues, the yield is increased at the limit of the pretreatment and the acid consumption is reduced.

[0245] At the limit of pretreatment, 99.7% by weight of potential glucose and 80.3% by weight of potential wood sugars have been retained, i.e., output has increased by 3.2 percentage points. In addition, two solids 32, 42 are recycled, before which they had no purpose. The combined crude production of these two residues is significant because it accounts for 6% of the crude production of lignocellulosic biomass. Finally, acid consumption has reduced by 0.2% by weight.

Claims

1. A method for treating lignocellulosic biomass containing a solid content of up to 90% by weight, the method comprising treating the biomass using at least one reactor (9, 14), the reactor (9, 14) being equipped with a biomass feed device (6, 11), the biomass feed device being equipped with a biomass inlet and a biomass outlet, the biomass outlet being fluidically connected to the inlet of the reactor, characterized in that - When the biomass passes through the feeding device (6; 11) when flowing to the reactor (9; 14), a residue (8; 13) is extracted from the biomass via an extraction outlet provided in the device, the residue being called solid-liquid residue, being a mixture of solid and liquid, - the solid-liquid residue is separated into a solid residue (32; 42) and a liquid residue (31; 41), - and reintroducing at least a portion of the solid residue (32; 42) into the same feed device or, in the case of a plurality of reactors, into one of said feed devices.

2. The method according to the preceding claim, characterized in that The feed device or at least one of the feed devices (6; 11) is washed by circulating a washing fluid (7; 12) between a washing inlet and a washing outlet of said feed device, the washing outlet preferably also being an extraction outlet for the solid-liquid residue.

3. A method according to any of the preceding claims, characterised in that At least part of the liquid residue (31; 41) is reintroduced into the same feed device or, in the case of a plurality of reactors, into one of the feed devices.

4. A method according to any one of the preceding claims, characterised in that The method comprises using a plurality of reactors (9; 14) to process the biomass, consisting in reintroducing at least a portion of the solid residue (32; 42) into one of the feed devices of the reactors, and in reintroducing at least a portion of the liquid residue (31; 41) into another of the feed devices.

5. The method according to any one of the preceding claims, characterized in that The feed device or at least one of the feed devices (6; 11) generates a pressure increase between the biomass inlet of the device, which pressure increase generates a compression of the biomass, thereby causing the extraction of a solid-liquid residue (8; 13).

6. A method according to any one of the preceding claims, characterised in that The feed device or at least one of the feed devices (6; 11) is a feed screw, in particular at least partially conical, comprising a housing equipped with a cage equipped with openings allowing the extraction of solid-liquid residues (8; 13) from the biomass and optionally the circulation of a washing fluid (7; 12).

7. A method according to any one of the preceding claims, characterised in that The solid-liquid residue (8; 13) is separated into a solid residue (32; 42) and a liquid residue (31; 41) by at least one separation device (30; 40) selected from a centrifugal device, a draining or pressing device or a screening unit.

8. A method according to any one of the preceding claims, characterised in that It comprises the step of impregnating the biomass with an impregnation liquid (4) containing a chemical catalyst by introducing the biomass into the impregnation reactor (9) or one of the impregnation reactors through its / their feeding device (6).

9. A method according to any one of the preceding claims, characterised in that It comprises a step of treating the biomass by cooking or steam explosion, said step being carried out by introducing the biomass into a cooking reactor (14) or one of the cooking reactors through its / their feeding means (11).

10. The method according to the preceding claim, characterized in that It comprises at least one step of treating the biomass by enzymatic hydrolysis, said step being carried out after cooking or steam explosion of the biomass in an enzymatic hydrolysis reactor (20) equipped with a feeding device thereof.

11. The method according to the preceding claim, characterized in that It comprises at least one step of treating the biomass by fermentation, said step being carried out after or simultaneously with the enzymatic hydrolysis step in a fermentation reactor (22) equipped with a feeding device therefor.

12. The method according to any one of claims 8 to 11, characterized in that When the biomass flows through the feeding device (6; 11) to the impregnation reactor (9) and / or to the cooking reactor (14), a residue (8; 13) is extracted from the biomass via an extraction outlet provided in the device, the residue being a mixture of solid and liquid, - the solid-liquid residue is separated into a solid residue (32; 42) and a liquid residue (31; 41), - and reintroducing at least a portion of the solid residue (32; 42) into the same feed device (6; 11) or into at least one of the feed devices of the enzymatic hydrolysis reactor (20) and / or the fermentation reactor (22) and / or the separation reactor (24).

13. The method according to claim 9 and the preceding claims, characterized in that At least part of the solid residue (32; 42) is reintroduced into the feed device of the impregnation reactor (9) or the feed device of the cooking reactor (14), and the liquid residue (31; 41) is reused for preparing the impregnation liquid.

14. The method according to claims 10 and 12, characterized in that At least part of the solid residue (32; 42) is reintroduced into the feed device of the enzymatic hydrolysis reactor (20), and the liquid residue (31; 41) is reused for preparing an impregnation liquor.

15. A method as claimed in any one of the preceding claims, comprising the steps of: a) preparing an impregnation liquid (4) in a preparation zone (3), said impregnation liquid containing a chemical catalyst (2) for impregnating the biomass (5), the catalyst being selected from the group consisting of an acid catalyst, a basic catalyst and an oxidation catalyst, and preferably an acid catalyst, - b) introducing the biomass (5) into the impregnation reactor (9) through a first feeding device (6) which performs washing by circulating a first washing fluid (7) between a washing inlet and a washing outlet of said device (6), -c) introducing liquid into the impregnation reactor (9) via the first liquid inlet (4) of the reactor, -d) transferring the impregnated and drained biomass (10) from the outlet of the impregnation reactor to the inlet of a cooking pretreatment reactor (14) via at least one second feeding device (11), which is washed by circulating a second washing fluid (12) between the washing inlet and the washing outlet of the feeding device, -e) pre-treating the biomass (10) in the reactor (14) by cooking or steam explosion, -f) extracting from the biomass a solid-liquid residue (8; 13) passing through at least one of the two feeding devices (6; 11), and then separating the / each solid-liquid residue into a solid residue (32; 42) and a liquid residue (31; 41), wherein at least a portion of the solid residue is reintroduced into at least one of the feeding devices (6; 11) as a biomass supplement, and at least a portion of the liquid residue (31; 41) is reintroduced into at least one of the feeding devices (6; 11) as a washing fluid supplement or as a supplement to the impregnation liquid in the liquid preparation zone (3) or the impregnation reactor (9).

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