Method for treating lignocellulosic biomass

Abstract

The present invention relates to a method for treating lignocellulosic biomass, the method using at least one reactor (9; 14) for treating the biomass, the reactor (9; 14) being provided with a supply device (6; 11) having a biomass inlet and a biomass outlet, the biomass outlet being in fluid communication with the inlet of the reactor, whereby, when the biomass passes through the supply device (6; 11) and is sent to the reactor (9; 14), a residue (8; 13), which is a mixture of solids and liquids, is extracted from the biomass via an extraction outlet provided in the device, the residue being separated into a solid residue (32; 42) and a liquid residue (31; 41), and at least a part of the solid residue (32; 42) being returned to the supply device or one of the supply devices.

Description

Technical Field

[0001] The present invention relates to a method for treating lignocellulosic biomass to produce a "second generation" (2G) sugar liquor. These sugar liquors may 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. This method generally includes three steps, namely, preparation of the liquor, impregnation of the biomass with this liquor, and pretreatment of the impregnated biomass, which is carried out, for example, by cooking and optionally in combination with steam explosion.

Background Art

[0002] Lignocellulosic biomass represents one of the most abundant renewable resources on earth. The substrates under consideration are very diverse and relate to both lignaceous substrates such as various woods (hardwoods and softwoods), by-products derived from agriculture (wheat straw, corn cobs, etc.) or other agricultural foods, and by-products derived from industries such as paper.

[0003] Methods for the biochemical conversion of lignocellulosic biomass to 2G sugar liquor include, inter alia, a pretreatment step and a step of enzymatic hydrolysis with an enzyme cocktail. These methods usually also include an impregnation step before pretreatment. The sugar liquor obtained from hydrolysis is then treated, for example, by fermentation, and this method also includes a separation step and / or a step of purifying the final product.

[0004] Lignocellulosic biomass is composed of three main polymers: cellulose (35% - 50% by weight) is a polysaccharide consisting essentially of hexose; hemicellulose (20% - 30% by weight) is usually a polysaccharide consisting essentially of pentose; lignin (15% - 25% by weight) is a high molecular weight polymer with a complex structure and is composed of aromatic alcohols linked via ether bonds. These various molecules are involved in the unique properties of the plant wall and are organized in a complex entanglement.

[0005] Among the three base polymers that make up lignocellulosic biomass, cellulose and hemicellulose enable the production of 2G sugar liquor.

[0006] Normally, hemicellulose is mainly decomposed into sugars during pretreatment, and cellulose is converted to glucose by enzymatic hydrolysis. However, crude cellulose is still difficult for enzymes to access, and therefore the need for pretreatment remains. This pretreatment makes it possible to modify the physicochemical properties of lignocellulosic biomass and improve the accessibility of cellulose to enzymes and its reactivity to enzymatic hydrolysis.

[0007] There are many advantageous techniques for performing this pretreatment, which will be collectively referred to hereinafter as "cooking": acid cooking, alkaline cooking, cooking by autohydrolysis, steam explosion, and the "organosolv pulping" method. The latter method is related to pretreatment in the presence of one or more organic solvents and generally water. The solvent may be an alcohol (ethanol), an acid such as acetic acid or formic acid, or alternatively acetone. The "organosolv pulping" method leads to the dissolution of at least a part of the lignin and a part of the hemicellulose. Therefore, there are two outlet streams: the pretreated substrate having residual cellulose, hemicellulose, and lignin, and the solvent phase containing the dissolved lignin and a part of the hemicellulose. Generally, there is a step of solvent regeneration, which enables the extraction of the lignin stream. Certain "organosolv pulping" treatments (especially treatment with ethanol) are combined with the addition of strong acids (e.g., H2SO4). It may be envisaged to place the biomass in contact with the solvent via an impregnation reactor before the cooking phase or to place the biomass in contact with an acid catalyst before performing the "organosolv pulping" cooking.

[0008] Various configurations have been 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 (Non - Patent Document 1) or the publication "Bioethanol production from agricultural wastes: An overview", N. Sarkar, S. Kumar Ghosh, S. Bannerjee, K. Aikat, Renewable Energy 37 (2012) 19 - 27 (Non - Patent Document 2).

[0009] One of the most effective pretreatments is steam explosion, especially steam explosion under acidic conditions, which allows for almost complete hydrolysis of hemicellulose and a significant improvement in the accessibility and reactivity of cellulose to enzymes. Other treatment(s) may be carried out before this pretreatment.

[0010] All these pretreatments are applied first to biomass in solid form: the aim of the pretreatment is to break them down.

[0011] Patent Documents 1 and 2 propose a method that includes a first step of hydrolysis of hemicellulose to C5 sugars under mild conditions that protect against degradation. This step is carried out in a first reactor at a pressure of 1.5 bar (0.15 MPa) or more and a temperature of 110 °C or more by injection of steam, optionally in the presence of a weak acid. After this step, washing is carried out to extract and recover the sugar liquor obtained from hemicellulose (generally a liquor of C5 and C6 sugars, the relative proportions of which depend in particular on the nature of the biomass), and then the remaining biomass rich in cellulose and lignin is sent to a second step (second reactor), where steam explosion is carried out. This second reactor is operated at a higher pressure than the first reactor by injection of high-pressure steam, which causes a sudden expansion of the biomass (steam explosion).

[0012] When the treatment requires pressure steps (such as impregnation, cooking-type pretreatment, etc.), it is necessary to use solid biomass introduction means that can be adapted to these pressure steps. This is the case, for example, of a compression screw, one embodiment of which is described in Patent Document 3.

[0013] Patent Document 4 describes a method that includes impregnating biomass with an acidic liquor, followed by steaming and steam explosion of the impregnated biomass, and adjusting the acidity of the acidic liquor and recycling it. Patent Document 5 also describes a method for pretreating biomass by performing steam explosion following acid impregnation, and further includes cleaning the reactor feed means and recycling the cleaning water to this method.

[0014] An object of the present invention is to improve the treatment of lignocellulosic biomass. An object of the present invention is, in particular, to improve the introduction of biomass into a reactor that performs one or more of the biomass treatment steps.

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

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Documents

[0017]

Non-Patent Document 1

[0018] [Summary of the Invention] The present invention first relates to a method for treating lignocellulosic biomass containing solids at a content of up to 90% by weight. The method includes the use of at least one reactor for treating the biomass. The reactor is equipped with a biomass feeding device having a biomass inlet and a biomass outlet, and the biomass outlet is in fluid connection with the inlet of the reactor. This method is characterized by the following facts: - Residue is extracted from the biomass, while it is passed through the extraction outlet provided in the device towards the reactor in the feeding device. The residue is referred to as solid - liquid residue, which is a mixture of the solid and the liquid, and - The solid - liquid residue is separated into a solid residue and a liquid residue, and - At least a part of the solid residue is re - introduced into the same feeding device or, in the case of multiple reactors, into one of the feeding devices.

[0019] In the context of the present invention, the expression "lignocellulosic biomass containing X% of solids" means biomass that naturally contains X% of solids ("natural" biomass) or biomass having this content after one or more operations prior to the method according to the present invention. The solid content indicated by this solid content (abbreviation "SC") is measured according to the standard ASTM E1756 - 08(2015) "Standard Test Method for Determination of Total Solids in Biomass".

[0020] In the context of the present invention, "solid - liquid residue" is understood to mean a liquid containing suspended solids (solid particles). "Solid residue" is understood to mean a residue containing at least 20% by weight of solids (in particular at least 30% by weight or at least 40% by weight, or even at least 50% by weight of solids depending on the separation method considered) and having the solid consistency of sludge - type or acid - impregnated biomass fragments. This residue generally contains 20% to 50% by weight of solids.

[0021] "Liquid residue" is understood to mean a residue having the consistency of a liquid containing at least 50% by weight of liquid, in particular at least 80% by weight of liquid, and containing no or substantially no suspended solid particles.

[0022] The present invention, which will be described in detail below, is advantageously applicable to any type of reactor used in a biomass conversion process, and more particularly to a biomass impregnation reactor (when impregnation is envisaged, whether this is by a liquor containing a chemical compound, for example an acid, a base or an oxidizing agent, or by an aqueous - based liquor, and whether or not it naturally releases an acid, in particular acetic acid, by autolysis of the biomass) and / or to a heat - treatment reactor for steaming or steam explosion.

[0023] Before the treatment of lignocellulosic biomass, one or more pretreatment steps are carried out, in particular at least one screening / cleaning operation ( "removal of metals") for removing foreign substances of the metal type from the biomass, at least one optional mechanical grinding for reducing the biomass to particles having a size suitable for treatment in each of the treatment reactors / treatment reactors, at least one washing of the biomass, in particular with water, etc. The order and number of steps are variable.

[0024] The present invention consists in proposing to extract from the biomass a residue that is partially solid and partially liquid before it enters the reactor, and to make optimal use of it.

[0025] Specifically, it has already been known to extract / collect the liquid (aqueous) residue / liquid washing water from the feeding means of the reactor in question to adjust the solid content of the biomass and to wash the equipment for feeding the biomass into the reactor, etc. Therefore, the problem is to recover this residue and reuse it "as it is" as an aqueous liquid supplement in this method, which is considered to be a mere liquid and should be recovered to reduce the consumption of water and / or chemicals (e.g., the acid of the impregnating liquor) in the method.

[0026] However, although this extracted residue may actually contain a high proportion of liquid (water), it also contains solid material (even if it is only in the case of washing the feeding equipment with water to prevent its fouling): it is a liquid filled with solid particles.

[0027] And it has been pointed out by the present inventors that, when separated from the rest of the extracted residue, this solid residue (these particles) has a very interesting and upgradable composition.

[0028] Therefore, the solid residue obtained from the solid-liquid residue extracted from the feed device of the impregnation reactor contains sugar polymers and lignin and has a composition very similar to the composition of the biomass introduced into the feed device, which may be either natural biomass or biomass that has already undergone one or more treatments (mechanical treatments of the grinding or metal removal type, or chemical treatments of the type where water is added to adjust the solid content of the biomass before impregnation or other treatments).

[0029] The composition of the solid residue obtained from the solid-liquid residue extracted from the feed device of the digestion reactor may differ from that of natural biomass, especially if it has been pre-impregnated with an acidic, basic or oxidizing liquor and / or has undergone other pretreatment steps: in the case where the impregnation is with a liquor, such as an acid, the residue can contain traces of this liquor (for example, it may contain acid in the form of the liquor formulation), it may contain less hemicellulose, some of which can be converted to sugars under the action of the impregnating liquor, and it may contain less cellulose and lignin. This residue may also contain fewer extractable species (monomeric sugars, ash, etc.) than the biomass. This is because the impregnation acts on these soluble species.

[0030] The present invention makes good use of these observations to upgrade this solid residue separately and improve the performance of the process as a whole to the best possible extent, having a series of extremely significant advantages as follows: - By separating the solid-liquid residue, it is possible to recover a liquid residue that does not contain or substantially does not contain solid particles, thereby enabling this liquid to be recycled more completely (for example, there is no risk of the equipment for recirculating washing water being disrupted or contaminated by particles). - By recycling the separated solid residue, the efficiency of the method for the conversion of biomass to sugars is increased (by pretreatment to produce sugars, especially C5 sugars, and then enzymatic hydrolysis to produce C6 sugar type sugars), and the efficiency of biomass to ethanol is increased (by pretreatment, enzymatic hydrolysis and fermentation). This is because biomass derivatives containing sugars / components that would otherwise be lost and can still be converted to sugars are reincorporated into the biomass conversion method; - The liquid residue stripped from the solid particles can be used to reduce the water consumption of the method: The solid-liquid residue obtained from the feed device of the digestion reactor may therefore contain up to 80% by weight of water, and recovering this water is very advantageous because the method is water-intensive. Furthermore, the solid-liquid residue extracted from the feed device of the impregnation reactor may contain water at a significant content, which is at least the water content of natural biomass and may increase up to a minimum of 30% by weight, depending on the nature of the biomass. - The liquid residue obtained from the solid-liquid residue extracted in the feed device of the digestion reactor and originating from acid-impregnated biomass will contain acid at a certain content and can therefore be used as a supplement for producing the impregnation liquor, thus reducing the acid consumption of the method (obviously, the same advantage of reducing chemical consumption applies when impregnation is carried out with a basic or oxidizing liquor); this liquid residue is contained, for example, in the impregnation liquor, exists in the biomass in a residual manner in various steps of the conversion method, and may be used to modify the pH / amount of the oxidizing agent outside the preparation of the impregnation liquor itself.

[0031] According to the present invention, at least one of the feed devices or the feed devices can be cleaned by the flow of the cleaning fluid between the cleaning inlet and the cleaning outlet of the feed device, and the cleaning outlet is preferably also the extraction outlet for the solid-liquid residue.

[0032] In this case, the solid-liquid residue contains a high content of liquid (water) because it includes the water contained in the biomass and the washing water.

[0033] According to the present invention, at least a part of the liquid residue can be reintroduced into the same feeding device or, in the case of multiple reactors, into one of the feeding devices.

[0034] According to the present invention, in one variant, the method includes the use of several reactors for treating the biomass, at least a part of the solid residue is reintroduced into one of the feeding devices of the reactors, and at least a part of the liquid residue is reintroduced into another of the feeding devices.

[0035] In one variant, the solid residue obtained from the feeding device of the impregnation reactor can be reintroduced at the inlet of the feeding device, for example, together with the biomass feedstock entering this device.

[0036] In another variant, the solid residue obtained from the feeding device of the digestion reactor can be reintroduced at the inlet of the feeding device, for example, together with the biomass feedstock entering this device, and this biomass feedstock may, in some cases, be pre-impregnated.

[0037] The solid residue obtained from the feeding device of the impregnation reactor can also be sent to the feeding device of the digestion reactor (or vice versa), however, the favorable effect on the biomass conversion efficiency is smaller than that of the above two variants.

[0038] Advantageously, at least one of the feeding devices creates a pressure increase between the biomass inlet and the biomass outlet of the device, and this pressure increase causes compression of the biomass leading to extraction of the solid-liquid residue.

[0039] One of the feeding devices may be, among other things, at least a feeding screw, which is at least partially conical and includes a casing with a cage, and this cage has openings that allow the extraction of solid-liquid residues from the biomass and the flow of washing fluid. This compression screw (also called a "plug screw") creates a sealed plug of biomass at the downstream part of the screw, which creates compression on the biomass, and this compression is reflected by the pressure difference between the biomass inlet and the biomass outlet of the screw, and this pressure difference is, for example, at least 0.05 MPa, for example, about 0.5 MPa. The compression applied to the biomass may therefore lead to the discharge of some of the liquid contained in the biomass, especially when the SC of the biomass is less than 80% before it enters the pressurized feeding means.

[0040] According to the present invention, the solid-liquid residue can be separated into solid residue and liquid residue by at least one separation device or screening unit selected from a centrifugal separation device, a drainage device or a pressurization device.

[0041] The method according to the present invention may include a step of impregnating the biomass with an impregnating liquor containing a chemical catalyst, and the step is performed by introducing the biomass into a reactor or one of the reactors through its / their feeding device.

[0042] The method according to the present invention may include a step of treating the biomass by cooking or steam explosion, and the step is performed by introducing the biomass into a reactor or one of the reactors through its / their feeding device.

[0043] The method according to the invention may include a step of treating biomass by enzymatic hydrolysis, said step being carried out in an enzymatic hydrolysis reactor equipped with its feeding device after its steaming or steam explosion. The feeding device of this reactor is of the conventional type, which may be, for example, an endless screw device (compression of the biomass at this stage is not common).

[0044] The method according to the invention may include at least one step of treating biomass by fermentation, said step being carried out in a fermentation reactor equipped with its feeding device after or concomitant with the enzymatic hydrolysis step. The feeding device of this fermentation reactor is of the conventional type, which may be, for example, an endless screw device (compression of the biomass at this stage is not common). It should be noted that enzymatic hydrolysis and fermentation may be carried out in the same reactor.

[0045] The method according to the invention may include at least one step of treating biomass aimed at separating a solvent or alcohol, said step being carried out in a separation reactor equipped with its feeding device after the fermentation step. As described in detail below, this reactor may be any part of the equipment, and in particular includes at least one distillation column, and its feeding device is any conventional device for this type of equipment.

[0046] According to one embodiment of the invention, at least a part of the solid residue is reintroduced into the feeding device of the impregnation reactor or the feeding device of the steaming reactor, and the liquid residue is preferably reused for the preparation of the impregnation liquor.

[0047] According to one embodiment of the invention, at least a part of the solid residue is reintroduced into the feeding device of the enzymatic hydrolysis reactor, and the liquid residue is preferably reused for the preparation of the impregnation liquor.

[0048] According to one embodiment of the present invention, while the residue can be extracted from the biomass, it passes through the feeding device towards the impregnation reactor and / or towards the digestion reactor via an extraction outlet provided in the device, and the residue is called a solid-liquid residue and is a mixture of solid and liquid. - Then, the solid-liquid residue is separated into a solid residue and a liquid residue, and - At least a part of the solid residue is reintroduced into the same feeding device (thus of the impregnation or digestion reactor) or into at least one of the feeding devices of an enzymatic hydrolysis reactor, a fermentation reactor or a separation reactor.

[0049] In this configuration, the solid residue obtained from the pretreatment of the biomass (digestion with optional prior impregnation) is thus reused and introduced into a reactor downstream of one or more pretreatment reactors, the purpose of which is to convert the pretreated biomass (which is at the outlet of the digestion reactor) into sugars (called hydrolysates), and then, optionally, into a solvent or an alcohol of the ethanol type (called a fermentation mash, from which the desired alcohol or solvent is separated by known methods).

[0050] According to one embodiment, the method according to the present invention may include the following steps: - a) Preparing, in a preparation zone, an impregnation liquor containing a chemical catalyst for impregnating the biomass; the catalyst is selected from acid catalysts, base catalysts and oxide catalysts, and preferably is an acid catalyst. - b) Introducing the biomass into an impregnation reactor by means of a first feeding device; the first feeding device is cleaned by the flow of a first cleaning fluid between the cleaning inlet and the cleaning outlet of the device (6). - c) Introducing the liquor into the impregnation reactor via the inlet of the first liquor (4) of the reactor. - d) transferring the impregnated and then drained biomass from the impregnation reactor outlet to the inlet of the delignification pretreatment reactor via at least one second feeding device; the second feeding device is cleaned by the flow of a second cleaning fluid between the cleaning inlet and the cleaning outlet of the feeding device, - e) pretreating the biomass in the reactor by delignification or steam explosion, - f) extracting solid-liquid residues from the biomass; the solid-liquid residues pass through at least one of the two feeding devices and then each of the solid-liquid residues / solid-liquid residues is separated into a solid residue and a liquid residue, and at least a part of the solid residue is reintroduced as a biomass supplement into at least one of the feeding devices, and at least a part of the liquid residue is reintroduced as a cleaning fluid supplement into at least one of the feeding devices or into the recaustic liquid preparation zone or the impregnation reactor as a supplement for the impregnation recaustic liquid.

[0051] The present invention also relates to any plant implementing the above method.

[0052] The plant according to the present invention may thus comprise at least one biomass treatment reactor, said reactor comprising a biomass feeding device having a biomass inlet and a biomass outlet, said biomass outlet being in fluid connection with the inlet of the reactor, and during the passage of the biomass through the feeding device towards the reactor, the extraction of residues from the biomass is effected via an extraction outlet provided within said device, said residues being called solid-liquid residues and being a mixture of solids and liquids, and the plant also comprises: - at least one device, or screening unit, for separating the solid-liquid residues into a solid residue and a liquid residue; said device being selected, inter alia, from a centrifugal separation device, a draining or pressurizing device, or a screening unit, - means for reintroducing at least a part of the solid residue into the same feeding device or, in the case of a plurality of reactors, into one of said feeding devices, - Means for optionally reintroducing at least a portion of the liquid residue into the plant, in particular into one of the feed devices / feed devices.

[0053] The means for reintroducing the liquid and / or solid residue are of the prior art and may include any suitable hydraulic connection means (equipment of the type of pipes, pumps or filters, valves).

[0054] Another subject of the invention lies in the use of the above method or plant for treating wood, straw, agricultural residues, and all energy dedicated crops, in particular annual or perennial plants, such as lignocellulosic biomass of the miscanthus type, to produce sugars, biofuels or bio-based molecules.

DETAILED DESCRIPTION OF THE INVENTION

[0055] (List of Drawings) Figure 1 is a schematic view of a plant for converting lignocellulosic biomass to which the method according to the invention may be applied.

[0056] Figure 2 is a block diagram of a method according to the prior art using the plant of Figure 1.

[0057] Figure 3 is a block diagram of a part of the method according to the invention, which modifies the method according to Figure 2.

[0058] Figure 4 is a block diagram illustrating a first variant of the method according to the invention.

[0059] Figure 5 is a block diagram illustrating a second variant of the method according to the invention.

[0060] Figure 6 is a block diagram illustrating a third variant of the method according to the invention.

[0061] Figure 7 is a block diagram illustrating a fourth variant of the method according to the invention.

[0062] Figure 8 is a block diagram illustrating a fifth variation of the method according to the present invention.

[0063] Figure 9 is a schematic diagram of a variation according to the present invention of a plant for converting lignocellulosic biomass as described in FIG. 1.

[0064] It should be noted that the same reference numerals relate to the same flow or the same device between the figures.

[0065] (Description of Embodiment) FIG. 1 very schematically shows a non-limiting example of a plant for converting lignocellulosic biomass to which the present invention can be applied, the plant being provided for pretreatment of the biomass including impregnation with an acidic liquor, then cooking / steam explosion, then enzymatic hydrolysis, and subsequently alcohol fermentation, to convert the biomass to ethanol.

[0066] The present invention is applied to different plants in a similar manner, and in particular, there are the following: - Plants that target only the production of sugars and thus are not provided for alcohol fermentation. - Plants that are provided for cooking pretreatment without prior impregnation with a liquor (e.g., self-hydrolysis). - Plants that are provided for cooking pretreatment with prior impregnation with a non-acidic liquor, e.g., a basic liquor or an oxidative liquor.

[0067] Specifically, the present invention is intended to be applied to any reactor used in a biomass conversion method, including but not limited to reactors for impregnation and cooking.

[0068] Figure 1 thus represents biomass conversion carried out in the following manner: The crushed biomass (5) (optionally impregnated with a catalyst liquor) is introduced into an impregnation reactor (9) by means of a pressure-fed means (6), which is a screw and is also known as a plug screw feeder, the end of which is conical and which has a casing with a drainage screen, a wash water inlet (7) and a wash water outlet (8). A sealed plug of biomass is created in the downstream part of the screw, which creates compression on the biomass and is reflected by a pressure difference between the biomass inlet and the biomass outlet of the screw: at least 0.05 MPa. The compression applied to the biomass may lead to the discharge of the liquid portion contained in the biomass, especially when the SC of the biomass is less than 80% before entering the pressure-fed means (6). The liquid thus extracted is mixed with the wash water and withdrawn by the used wash water (8).

[0069] The impregnation reactor is also supplied with an acidic liquor (4) (sulfuric acid supplemented with water) originating from a liquor preparation tank (3), and the tank itself is supplied with an acid (2) and water (1). The reactor includes a biomass impregnation zone (9a) surrounded by a biomass drainage zone (9b).

[0070] The impregnated and drained biomass (10) leaves the reactor (9) and is fed to a steam explosion hydrolysis reactor (14) via another feed screw (11) similar in operation to the feed screw (6). In this screw, due to the compression exerted on the biomass, the liquid (13) obtained from this pressurization, also called the condensate, is recovered and consists of water and acid. The screw is washed with a wash liquid (12) (water and / or recycled liquid as seen below) using a dedicated inlet, which is then discharged via an outlet through which the condensate (13) is also discharged.

[0071] The reactor (14) is also supplied with steam (15). When leaving the reactor (14), the biomass-steam mixture moves to a tool (17) for separating the biomass (19) and the steam (18). The biomass (19) is then processed in an enzymatic hydrolysis reactor (20) and then hydrolyzed into sugars. When the hydrolyzed biomass (21) (also called hydrolyzed mash) is fermented into alcohol (23) called fermentation mash, it is then transported to one or more distillation columns to obtain concentrated alcohol (25) and crude distillation residue (26).

[0072] This is only one example of a plant and may have numerous variations. Therefore, enzymatic hydrolysis and fermentation may be carried out together in the same reactor, which is called SSCF (simultaneous saccharification and co-fermentation). (1): Entry to the water liquor preparation tank (2): Entry to the acid liquor preparation tank (3): Liquor preparation tool (tank) (4): Acidic liquor to the impregnation tool (reactor) (5) Ground biomass (6): Screw of the impregnation tool (plug screw feeder) (7): Water for cleaning the plug screw feeder of the impregnation tool (8): Cleaning liquid outlet of the plug screw feeder (6) of the impregnation tool (9): Impregnation tool (reactor) (9a): Impregnation zone of the impregnation tank (9) (9b): Drainage zone of the impregnation tank (9) (10): Impregnated and drained biomass (11): Screw of the pretreatment tool (plug screw feeder) (12): Water for cleaning the plug screw feeder of the pretreatment tool (13): Compressed material from the plug screw feeder of the pretreatment tool (14): Pretreatment pulping tool (crushing reactor) (15): Injection of steam for pretreatment (16): Pretreated biomass and steam (17): Tool (cyclone) for separating steam and pretreated biomass (18): Steam to condensation (19): Pretreated biomass (20): Enzymatic hydrolysis reactor (21): Hydrolysate containing sugars (22): Alcoholic (ethanol) fermentation reactor (23): Fermented wine containing ethanol (alcohol) (24): Ethanol recovery device, for example, one or more distillation columns (25): Concentrated alcohol (26): Residue (as a mixture or separated solids and liquids depending on the arrangement of (24)) (Method) The following is a more detailed description of various steps of a biomass conversion method in which the present invention may be advantageously applied using such a plant: (This is an example and the present invention is not limited thereto).

[0073] (Step a) of conditioning lignocellulosic biomass) This treatment method includes, in its first step, a step of conditioning lignocellulosic biomass, and at least one grinding is performed to obtain biomass particles with a size of up to 300 mm. It is of course possible to perform several consecutive grinding steps to achieve the target particle size. Generally, the particle size (maximum size) of the ground biomass is up to 300 mm, usually at least 1 mm, and often 2 - 200 mm. Any method known to those skilled in the art can be used to perform this step. Usually, straw is ground by a screen from 5 mm to 100 mm. For wood, it is generally chipped into parallelepiped chips with a length of 20 - 160 mm, a width of 10 - 100 mm, and a thickness of 2 - 20 mm. The ground lignocellulosic biomass is transported to the next step by any means known to those skilled in the art, in particular by a screw conveyor.

[0074] (Step b) of impregnation with acid liquor) The treatment method according to the present invention includes step b) of impregnating a lignocellulosic substrate with an acid liquor to obtain an impregnated lignocellulosic substrate, and its pH is 0.1 - 3. This step aims to prepare a lignocellulosic substrate for the pretreatment step.

[0075] The impregnation is carried out in an impregnation reactor at a temperature of 10°C - 90°C, and preferably at atmospheric pressure. The residence time of the lignocellulosic substrate in the impregnation reactor is usually from 10 seconds to 180 minutes, preferably 30 seconds - 60 minutes, and even more preferably 30 seconds - 15 minutes. Preferably, the impregnation step is carried out in a single step.

[0076] The impregnation reactor or impregnator is equipped with one or more screws, which transfer the lignocellulosic substrate from its inlet to the outlet opening. The impregnator further comprises one or more lines for carrying the acid liquor and, if necessary, one or more lines for withdrawing the acid liquor. The inlet and outlet lines of the acid liquor are generally installed to function by co-current or counter-current recycling.

[0077] The acid liquor is an aqueous solution of a strong acid, which is selected from, for example, sulfuric acid, hydrochloric acid, and nitric acid. For example, the acid content is in the range of 0.5% to 4% by weight.

[0078] (Step c) of solid / liquid separation on the lignocellulosic substrate impregnated with the acid liquor) According to step c) of the treatment method of the present invention, the lignocellulosic substrate impregnated with the acid liquor is subjected to a solid / liquid separation step to obtain a lignocellulosic substrate having a solid content of 15% to 70% by weight and the used acid liquor. Preferably, the lignocellulosic substrate impregnated with the acid liquor is first drained to extract at least a part of the acid-free liquor, and then treated by solid / liquid separation.

[0079] The solid / liquid separation step may be carried out by any technique known to those skilled in the art, which may be, for example, decantation, centrifugation, or pressurization.

[0080] Preferably, upon transfer to the pretreatment step d), the lignocellulosic substrate is pressurized, which is done when the pretreatment step d) performs the steam explosion method described below. This method of performing step c) is carried out, for example, by a screw called a "plug screw feeder", and its operation has already been described above. The formation of the plug of the pressurized lignocellulosic substrate ensures the pressure resistance of the steam explosion reactor and, therefore, prevents dangerous steam leakage. The screw conveyor is also provided with one or more lines for extracting the used liquor (called condensate) separated during pressurization. The condensate can be recycled to the impregnation step b) and / or the washing step with the washing liquid (12) passing through the feed screw (11).

[0081] The wet biomass obtained at the end of the solid / liquid separation step c) can be denoted by the term "washed and acidified lignocellulosic substrate", and its solid content is preferably 15% to 70% by weight, more preferably 40% to 65% by weight.

[0082] (Step d) of pretreating the washed and acidified lignocellulosic substrate) According to step c) of the present method, the washed and acidified lignocellulosic substrate undergoes a pretreatment step d).

[0083] Cellulose (and in some cases hemicellulose), which is the target of enzymatic hydrolysis, is not directly accessible to the enzyme. This is the reason for the pretreatment of the biomass before the enzymatic hydrolysis step.

[0084] The pretreatment is directed, inter alia, towards modifying the physical and physicochemical properties of the cellulose fraction, such as its degree of polymerization and its crystalline state.

[0085] Various types of pretreatment are known to those skilled in the art, and those skilled in the art combine chemical treatment and heat treatment. Mention may be made in particular of acid or alkaline steaming, the organosolv process, treatment with ionic liquids and the steam explosion process.

[0086] A preferred pretreatment method is steam explosion (or "SteamEx") carried out in an acidic medium. This is a method in which the lignocellulosic substrate is rapidly heated to a high temperature by injecting pressurized steam. The treatment is stopped by rapid decompression.

[0087] The operating conditions of the steam explosion method are as follows: - The steam is injected directly into the reactor; - The temperature of the reactor is generally 150 °C to 220 °C, preferably 170 °C to 210 °C; - The pressure is 5 to 25 bar (absolute) (0.5 to 2.5 MPa), more preferably 8 to 19 bar (absolute) (0.8 to 1.9 MPa). - The residence time before the expansion phase ranges from 10 seconds to 50 minutes, preferably from 3 minutes to 30 or 40 minutes.

[0088] Steam explosion may be carried out in batch or continuous mode, and the decompression step allowing the destruction of the biomass structure may proceed in one or more steps.

[0089] At the end of the steam explosion pretreatment step, a pretreated lignocellulosic substrate having a high solids content, generally 20 wt% to 70 wt%, and a vapor phase are obtained, and the vapor phase is then condensed.

[0090] In the context of the present invention, the pretreated lignocellulosic substrate obtained at the end of step d) of the treatment method according to the present invention is advantageously used as a feedstock in a "second generation" method for generating solvents and / or alcohols from lignocellulosic biomass.

[0091] The present invention also relates to a method for generating solvents and / or alcohols from lignocellulosic biomass, comprising at least the following steps: i) treating the lignocellulosic biomass by the treatment method according to the present invention; obtaining a treated lignocellulosic substrate; ii) performing enzymatic hydrolysis of the treated lignocellulosic substrate; obtaining a hydrolyzate containing fermentable sugars; iii) fermenting the hydrolyzate obtained from step ii); obtaining a fermentation mash containing solvents and / or alcohols; iv) separating solvents and / or alcohols from the fermentation mash.

[0092] After steam explosion under acidic conditions, the pH of the pretreated lignocellulosic substrate is generally lower than the pH suitable for the medium for enzymatic hydrolysis. Therefore, the lignocellulosic substrate treated by step I) of the method for producing a solvent and / or alcohol is subjected to a neutralization step to bring its pH to a value of 4 to 6.

[0093] For the neutralization step, an aqueous solution containing a neutralizing agent that can be selected from all weak bases or strong bases known to those skilled in the art is used. The term "base" refers to any chemical species that gives an aqueous solution with a pH above 7 when added to water. Preferably, the neutralizing agent is selected from potassium hydroxide, sodium hydroxide, aqueous ammonia, and lime. Even more preferably, the neutralizing agent is selected from potassium hydroxide and aqueous ammonia, either alone or in combination with each other. Preferably, the neutralizing agent is used in an aqueous solution, and the weight concentration is 2% to 75%, even more preferably 20% to 70%.

[0094] The temperature at which the neutralization is carried out is 15°C to 95°C, preferably 20°C to 70°C. Generally, the temperature of the neutralization step is not precisely controlled and is simply governed by the heat released by the acid-base neutralization reaction.

[0095] The neutralization step can be carried out continuously, in batch mode, or in fed-batch mode.

[0096] It should be noted that an optional washing step can be carried out on all or part of the pretreated lignocellulosic substrate before or after the neutralization step.

[0097] If washing is applied, the liquid stream is brought into contact with the pretreated lignocellulosic substrate, and then the liquid is separated from the solid. The washing step can be carried out by percolation, by continuous mixing and liquid / solid separation operations, by washing on a belt filter or by any other technique known to those skilled in the art. The washing liquid used can be water or a process stream. The weight ratio between the washing liquid added and the liquid contained in the substrate to be washed is generally from 0.5 to 4. The washing step results in a sugary wash liquor containing a part of the hemicellulose solubilized during pretreatment. This wash liquor can be used, for example, as a carbon source for the production of biocatalysts (enzymes and / or microorganisms). The temperature at which the washing step is generally carried out is from 10 °C to 95 °C.

[0098] (Step ii) of enzymatic hydrolysis) The pretreated lignocellulosic substrate is optionally neutralized and washed and sent to step ii) of the enzymatic hydrolysis of the process.

[0099] The solid content of the pretreated lignocellulosic substrate sent to the enzymatic hydrolysis step is generally from 15% to 70% by weight.

[0100] The purpose of the enzymatic hydrolysis is to hydrolyze (depolymerize) hemicellulose and cellulose into fermentable sugars, preferably glucose, by means of a biocatalyst.

[0101] The enzymatic hydrolysis process is carried out under mild conditions. The temperature at that time is about 40°C to 55°C, preferably about 45°C to 50°C, and the pH at that time is from 4.0 to 5.5, more preferably 4.8 to 5.2. The solid content of the enzymatic hydrolysis medium is 5% by weight to 45% by weight, preferably 10% by weight to 30% by weight. The enzymatic hydrolysis is carried out by enzymes produced by microorganisms. Natural or genetically modified microorganisms, such as fungi of the genus Trichoderma, Aspergillus, Penicillium or Schizophyllum, or anaerobic bacteria, such as those of the genus Clostridium, produce a cocktail of enzymes that particularly contain cellulases and hemicellulases suitable for the extensive enzymatic hydrolysis of cellulose and hemicellulose.

[0102] The enzymatic hydrolysis can be carried out continuously or in batch mode or in fed-batch mode in one or more reactors. The residence time is 12 hours to 200 hours, preferably 24 hours to 120 hours, more preferably 48 hours to 120 hours.

[0103] At the end of step ii), the hydrolyzate containing fermentable sugars is recovered from the bioreactor, and the hydrolyzate is then processed in the fermentation step iii).

[0104] It should be noted that the obtained hydrolyzate can optionally undergo one or more treatment steps before the fermentation step. For example, these can be pH adjustment, partial purification aimed at limiting the content of inhibitory compounds to the fermenting microorganisms, or at least partial separation of the solid residues contained in the hydrolyzate.

[0105] (Step iii) of fermentation of the hydrolyzate) According to step iii) of the method for producing a solvent and / or alcohol, the optionally treated hydrolyzate is sent to a fermentation step. This fermentation step enables the conversion of fermentable sugars into the desired solvent and / or alcohol by one or more microorganisms of different genera. Fermentation methods are known to those skilled in the art.

[0106] The term "solvent" is intended to denote an organic compound other than an alcohol, for example, an organic compound having a ketone group, for example, acetone.

[0107] The term "alcohol" particularly denotes ethanol, propanol, isopropanol and butanol.

[0108] The natural or genetically modified microorganisms can be selected, for example, from Saccharomyces cerevisiae, Schizosaccharomyces pombe, Saccharomyces uvarum, Saccharomyces diastaticus, Kluyveromyces fragilis, Candida shehate, Pichia stipitis, Pachysolen tannophilus or the bacteria Zymomonas mobilis, Clostridium acetobutylicum, Escherichia coli.

[0109] In the context of the present invention, the fermentation step makes it possible to produce, for example, ethanol alone or as a mixture with butanol, propanol, isopropanol and / or acetone. For example, the fermenting microorganisms may be able to produce an "ABE (acetone - butanol - ethanol)" mixture or alternatively an "IBE (isopropanol - butanol - ethanol)" mixture.

[0110] Preferably, the selected microorganism is a natural or genetically modified yeast of the genus Saccharomyces that can produce ethanol.

[0111] At the end of step iii), the fermentation broth is diluted in the target product and then recovered.

[0112] According to one embodiment of the method, steps ii) and iii) are carried out simultaneously in at least one identical bioreactor, and enzymatic hydrolysis and fermentation are carried out simultaneously according to a method represented by the term "Simultaneous Saccharification and Fermentation (SSF)". When the hydrolysis step is mixed with the fermentation step, the operating conditions, in particular the temperature conditions, can be adapted to be compatible with the tolerance range of the fermenting microorganism. For example, the temperature can be lowered to 28°C to 45°C, preferably 30°C to 35°C when fermentation is carried out by yeast of the genus Saccharomyces. The pH is preferably adjusted to 5 to 5.5 to promote the performance of the yeast.

[0113] The production unit for carrying out the method according to the present invention may include, in addition to the plants already described, a unit for in situ production of enzymes and / or yeast.

[0114] (Step iv) of separating the solvent and / or alcohol from the fermentation broth) The method according to the present invention may finally include a step of separating one or more target products from the fermentation broth, and in some cases, it may be preceded by a solid / liquid separation step to remove at least a part of the solids contained in the fermentation broth.

[0115] Preferably, the step of separating one or more target products, such as ethanol, uses one or more distillations, which is a technique well known to those skilled in the art.

[0116] (Feedstock: Lignocellulosic biomass) According to the present invention, the feedstock of the method may be biomass alone or as a mixture. The amount of water contained in the crude feedstock is generally at least 10% by weight, especially 10% to 70% by weight.

[0117] The crude biomass is selected from any type of biomass, preferably solid type biomass, in particular lignocellulosic type biomass. Non-limiting examples of biomass types are related to, for example, agricultural residues (especially straw, corn cobs), forestry management residues, forestry management products, wood mill residues and dedicated crops, such as short rotation coppice.

[0118] Preferably, the crude biomass is also called natural type biomass and is lignocellulosic biomass. It essentially contains three natural components present in variable amounts depending on its origin: cellulose, hemicellulose and lignin.

[0119] The lignocellulosic biomass feedstock is preferably used in its crude form, i.e., containing all of these three components of cellulose, hemicellulose and lignin.

[0120] In one preferred embodiment of the present invention, the lignocellulosic biomass is selected from grass biomass, agricultural residues, such as straw waste, corn cobs, sugarcane bagasse, forestry management residues or wood mill residues, such as wood chips or any other type of woody residue.

[0121] (Impregnating fluid) The optional fluid injected for impregnation is an aqueous liquid solution, optionally containing an acid, at a temperature of 10 °C to 95 °C and atmospheric pressure. The pH of this chemical solution is 0.1 to 12.0, preferably 0.1 to 7, preferably 0.3 to 2. According to a preferred embodiment, the liquor used is an acid-catalyzed liquor, and the pH of the liquor is adjusted to 0.1 to 4, especially 0.3 to 2. Examples of acids that may be used include at least one acid selected from sulfuric acid, hydrochloric acid, nitric acid and oxalic acid. Their content is preferably 0.2 wt% to 8 wt% in the aqueous phase.

[0122] Return to each of FIGS. 2 - 8 one by one: All of these figures are variations of biomass pretreatment. For the sake of simplicity in explaining the present invention, they are described as being provided by impregnation with an acid fluid followed by steam explosion digestion. It should be noted, however, that the present invention is equally applicable to pretreatment without impregnation, or pretreatment with non - acidic impregnation, or digestion without steam explosion otherwise.

[0123] FIG. 2 shows a diagram of the pretreatment section of a biomass conversion method that can be applied, for example, to the plant from FIG. 1, representing that the present invention will modify the following, along with (optional) impregnation with an impregnation fluid and the subsequent known sequence of biomass digestion / steam explosion: (ground) biomass (5) enters a transfer zone containing a compression screw feeding device (6) and may optionally be washed by the flow of a water - type washing fluid (7) (discharged in the form of used wash liquor (8)), and the biomass is carried to an impregnation reactor (9), which is also fed with an impregnation fluid (4) via a preparation tank (3), and the preparation tank (3) is fed with water (1) and an impregnation compound (2) (of the acid or base type). As indicated above, impregnation may be omitted. Impregnation may be carried out in batch mode (immersion of biomass in a tank containing the impregnation fluid) or in continuous mode, for example, by spray - spraying or by passage of the biomass through a stirred reactor.

[0124] It is therefore possible to have different feeding modes and impregnation modes, for example, having a conveyor belt that carries the biomass under a device for spray - spraying the impregnation fluid.

[0125] The impregnated biomass (10) then passes through a transfer zone containing a compression feeding screw (11) and is washed with a washing fluid (12) (washing water), and the used washing water (13) is discharged. Next, the biomass is fed to a digestion reactor (14) in the presence of steam (15) and is then extracted from the reactor in the form of pretreated biomass (16) to continue the method of its conversion to sugars or alcohols.

[0126] Figure 3 illustrates the first modification step according to the invention of the method according to Figure 2: The fluid (8) extracted from the feed device (6) of the impregnation reactor (9) may be water originating from 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 a solid / liquid separation device (30), at the outlet of which the liquid phase / residue (31) and the solid residue (32) are recovered. This device may be, for example, a screening unit. These two residues can thus be individually upgraded / reused in a very advantageous manner as described below.

[0127] 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, it is conveyed to a solid / liquid separation device (40), at the outlet of which the liquid phase / residue (41) and the solid residue (42) are recovered. This device may also be, for example, a screening unit. These two residues can thus be individually upgraded / reused in a very advantageous manner as described below.

[0128] This separation of the solid residue and the liquid residue and their upgrading / reuse may, of course, be carried out only on the feed device of the impregnation device / reactor (9) or only on the feed device of the digestion device / reactor (14), or on both devices.

[0129] Figure 4 illustrates the upgrading (impregnation step) of the solid residue (32), which is carried out by re-injecting the residue (32) together with the biomass feedstock (5) at the inlet of the feeding device (6). In this scenario, the composition of the solid residue (32) is similar / very similar to or even identical to the composition of the biomass (5), although it may be in the form of smaller-sized particles (if the feeding device is of the compression screw type, it has a mechanical action on the biomass).

[0130] By recycling the solid residue (32) together with the ground biomass (5) to the inlet of the impregnation reactor (9), it is possible not to lose this solid stream and to obtain a "clear" liquid residue (31) (free from visible suspended particles), which can also be reused. This recycling of the solid makes it possible to increase the yield of this process because the residue (32) contains sugar polymers, to increase the lignin yield because the residue (32) contains lignin, and to reduce the water consumption of this process because the residue also contains water. The solid / liquid separation may be carried out on all or part of the stream (8) leaving the feeding device (6), and this recycling of the solid residue (32) may be carried out on all or part of the said solid residue.

[0131] Figure 5 illustrates the upgrading (cooking step) of the solid residue (42), which is carried out by re-injecting the residue (42) at the inlet of the feeding device (12) of the cooking device / reactor (14). In this scenario, the solid residue (42) has a different composition from the residue (32), provided that it is obtained from biomass impregnated with an impregnating liquid, in particular a highly acidic impregnating liquid, and / or from the washing water of the feeding device which may contain this fluid / acid at a certain content rate.

[0132] By recycling the solid residue (42) together with the impregnated biomass (10), this solid stream is not lost and a clear liquid residue (41) (also called the condensate) can be obtained. This solid recycling makes it possible to increase the yield of the process because stream (42) contains sugar polymers, to increase the lignin yield because stream (42) contains lignin, and to reduce the consumption of the impregnating liquid (2) because the residue (42) contains the impregnating liquid. The solid / liquid separation may be performed on all or part of the stream (13) leaving the feeding device (11), and this recycling of the solid residue (42) may be performed on all or part of the said solid residue.

[0133] It is also possible to recycle all or part of the solid residue (42) at the impregnation inlet together with the ground biomass (5), but this recycling does not seem very advantageous since a second impregnation of the already acidic biomass by the residue (42) then takes place.

[0134] Figure 6 shows both the reinjection of the solid residue (32) according to Figure 4 and the reinjection of the solid residue (42) according to Figure 5, and thus illustrates an embodiment in which the invention is applied twice in the biomass conversion process and has the same advantages as described with respect to Figures 4 and 5. Each of the two solid residue reuses may be performed on the whole of each residue or only on a part thereof. It is also possible to envisage combining all or part of the two solid residues and reusing them together in the process.

[0135] Figure 7 shows the reinjection of the two solid residues (32) and (42) according to Figure 6, but also shows the reuse of the corresponding two liquid residues (31) and (41): - The liquid residue (31) is reinjected into the cleaning inlet of the feeding device (6) of the impregnation device, which is essentially water - The liquid residue (41) is reinjected into the impregnating liquor preparation tank; specifically, this residue (41) contains acid at a certain content rate (if the example of acid impregnating liquor is continued to be adopted), and by reinjecting it into the tank (3), an advantageous replenishment of water and acid is provided.

[0136] Recycling of the liquid residues (31) and (41) makes it possible to reduce the consumption of water and impregnating liquid. This recycling can be carried out for all or part of the liquid residue. Similar to the case of solid residue, in this method, it is also possible to assume that they are combined at least in part and recycled together.

[0137] Figure 8, in relation to Figure 7, proposes a modification for reusing the liquid residues (31) and (41): the dotted arrows indicate various alternative or cumulative possibilities for reinjecting them completely or partially into the biomass pretreatment method. Therefore, the liquid residue (31) (the one upstream of the impregnating device) can also be reinjected completely or partially as makeup water into the impregnating liquor preparation tank (3). It can be reinjected completely or partially as washing water (12) for the feeding device (11) of the digester device (14), or as washing water (7) for the feeding device (6) of the impregnating device (9) if washing is also provided for this device (9). It can also be added completely or partially to the liquid residue (41) and flow into its reinjection circuit. Conversely, the liquid residue (41) can itself also be added completely or partially to the liquid residue (31) and then reused together in the tank (3) for example to prepare the impregnating liquor (4) (these two modifications are not shown in the figure).

[0138] It should also be noted that these liquid residues (31), (41), especially at least the residue (41) containing acid, may be directly reused / reinjected in the impregnating device (9) if its acid content rate is preferably not controlled upstream.

[0139] Finally, it should be noted that at least one of these liquid residues (31), (41) may be reused in a step following their digestion that requires a supply of water and / or a supply of water having an acidic pH downstream of the pretreatment in the biomass conversion process.

[0140] Figure 9 proposes a modification according to the invention of the plant described in Figure 1: here, the feed devices of the impregnation reactor (9) and the digestion reactor (14), or the two solid residues obtained from at least one of them, are at least partially reintroduced downstream of the biomass pretreatment. The dotted lines indicate various alternative or cumulative options for completely or partially reintroducing these solid residues: they can thus be reintroduced, inter alia, at the inlet of the hydrolysis reactor (20) or of the fermentation reactor (22) or even at the inlet of the separation facility (24) via their own feed devices, which are conventional (for example, openings of one or more pipes or endless screw systems into inlets made in the reactor). The solid residues thus mix with the pretreated biomass stream (19) and / or the hydrolysis stream (21) and / or the fermentation mash (23).

[0141] The last option represented in Figure 9 consists of directly introducing all or part of the solid residues (32) and / or (42) into the final residue (26) obtained from the separation of the fermentation mash that can be upgraded as fuel. In this case, the amount of the final residue (26) in or outside the plant itself, and thus the amount of fuel that can be reused, is directly increased. This is a different type of upgrading and does not seek to increase the efficiency of the biomass conversion of the process, but rather to make the best use of the residues of the process.

[0142] (Example) They relate to a method for the pretreatment of lignocellulosic biomass by impregnation with an acid liquor as described in FIG. 1 and then steam explosion.

[0143] The term "potential sugars (xylose, glucose)" used hereinafter defines various editions of sugars regardless of their form: monomeric or polymeric sugars. Specifically, after pretreatment by steaming, some of the sugars remain in the form of sugar polymers (e.g., cellulose or hemicellulose), and some of the sugars are in the form of sugar monomers (e.g., glucose or xylose). This measurement may 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 this sugar in polymeric form (e.g., cellulose), it is necessary to subtract the water of hydrolysis from this amount.

[0144] (Example 1: Comparison) The biomass (5) is wheat straw lignocellulosic biomass. Its composition is indicated in Table 1 below.

[0145]

Table 1

[0146] After hydrolysis, cellulose is converted to glucose or glucose oligomers, and hemicellulose is converted to xylose or xylose oligomers.

[0147] This 50 mm ground biomass (5) at 642 kg / h is introduced into the process with a throughput of wash water (7) of 200 kg / h. A first solid / liquid stream (8) of 203.8 kg / h leaves the process, and in this stream, 1.3 kg / h is potential glucose and 1.1 kg / h is potential xylose. In the impregnation step (reactor (9)), 1622.6 kg / h of water and 84.2 kg / h of sulfuric acid are added to the reactor from the preparation tank (3) to form the impregnation liquid (4).

[0148] At the inlet of the digestion 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 a second solid / liquid stream (13) of 5099.9 kg / h leaves the zone (11). In this stream (13), 2.7 kg / h is potential glucose, 2.2 kg / h is potential xylose, and 45.6 kg / h is acid. The digestion reactor (14) is heated by a steam stream (15) of 3471.1 kg / h. At the outlet of this reactor (14), a stream (16) of 4803.8 kg / h of pretreated biomass containing 237.8 kg / h of potential glucose and 155.2 kg / h of xylose leaves.

[0149] At the limit of the pretreatment, that is, between the entry of the biomass (5) into the feed device (6) and the exit of the biomass (5) from the digestion reactor (14), 98.1 wt% of potential glucose and 78.8 wt% of potential xylose are thus retained.

[0150] (Example 2: Conforming to the present invention) It is carried out according to a variant of the invention represented in Figure 4: the recovered solid residue is recycled to the inlet of the impregnation reactor.

[0151] The biomass feedstock is the same as that in Example 1. The throughput is the same as in the case of Example 1: This 50 mm ground biomass (5) at 642 kg / h is introduced into the process at a throughput of 200 kg / h of wash water (7). The first solid / liquid stream (8) at 203.8 kg / h leaves the transfer zone (6) and enters the impregnator (9). This stream is separated in a separation tool (30) into a liquid stream / residue (31) at 192 kg / h and a solid stream / residue (32) at 11.8 kg / h. The separation tool (30) is a screening unit.

[0152] This solid residue (32) obtained from the solid / liquid separation is relatively wet (25% SC) and consists of 1.3 kg / h of potential glucose and 1.1 kg / h of potential xylose. It is recycled to the inlet of the feeding device (6) together with the ground biomass (5). Surprisingly, the recycling of this solid residue (32) at the impregnation inlet does not cause accumulation in the feeding device (6) despite its small particle size and the fact that the solid residue is first passed through the holes of the cage of the feeding screw: It is entrained by the ground biomass (5) and enters the impregnation reactor (9). In the impregnation step, the same amounts of water and sulfuric acid are added to the tank (3) to prepare the impregnation liquid (4) as in the case of Example 1.

[0153] The remainder of the process is the same as in Example 1. At the outlet of the digestion reactor (14), a stream of pretreated biomass (16) at 4815.5 kg / h containing 239.2 kg / h of potential glucose and 156.1 kg / h of potential xylose leaves.

[0154] At the limit of the pretreatment (the meaning of this term is the same as in Example 1), 98.6 wt% of the potential glucose and 79.2 wt% of the potential xylose are thus retained, i.e., the increase in yield is 1.0 point. Furthermore, according to the present invention, it has become possible to recycle the solid (32) which had no use until then.

[0155] (Example 3: Conforming to the present invention) This is done according to a variation of the present invention represented in FIG. 5: The recovered solid residue is recycled to the inlet of the digester reactor. The same feedstock as in the two preceding examples is processed here.

[0156] This 50 mm ground biomass (5) at 642 kg / h is introduced into the process with a throughput of wash water (7) of 200 kg / h. A first solid / liquid stream (13) of 203.8 kg / h leaves the process by compression of the impregnated biomass in the feed screw (11). In this stream, 1.3 kg / h is potential glucose and 1.1 kg / h is potential xylose. In the impregnation step, 1622.6 kg / h of water and 84.2 kg / h of sulfuric acid are added from tank (3) to prepare the impregnation liquid (4).

[0157] The throughput is the same as in Examples 1 and 2: This 50 mm ground biomass at 642 kg / h is introduced into the process (introduced into the impregnation reactor (9)) with a throughput of wash water (7) of 200 kg / h. A first solid-liquid stream (8) of 203.8 kg / h leaves the process. In this stream, 1.3 kg / h is potential glucose and 1.1 kg / h is potential xylose. In the impregnation step (reactor (9)), the same amount of water as in Examples 1 and 2 is used, but only 84 kg / h of sulfuric acid (a saving of 0.2 wt% compared to the previous example) is added to tank (3) to prepare the impregnation liquid (4).

[0158] At the inlet of the digestion reactor (14), the impregnated biomass (10) is fed into 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 exits the transfer zone (11) and enters the digestion reactor (14). This stream (13) is separated in a separation tool (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. This solid stream (42) obtained from the solid / liquid separation is relatively wet (26.1% SC) and consists of 2.7 kg / h of potential glucose, 2.2 kg / h of potential xylose and 0.2 kg / h of sulfuric acid. It is recycled together with the impregnated biomass (10). Surprisingly, the recycling of this residue (42) at the digestion inlet does not cause accumulation in the circuit in the compression screw feeding device (11) despite its small particle size and the fact that the solid residue is first passed through the holes in the cage of the feed screw. It is entrained by the biomass (10) and enters the digestion reactor (14).

[0159] The digestion reactor (14) is heated by a steam stream (15) of 3471.1 kg / h. At the outlet of this reactor, a stream of 4829.6 kg / h of pretreated biomass (16) containing 240.5 kg / h of potential glucose and 157.4 kg / h of xylose exits.

[0160] (At the limit of the pretreatment from the inlet of the feeding device (6) to the outlet of the reactor (14)), 99.2 wt% of the potential glucose and 79.9 wt% of the potential xylose are thus retained, i.e., the increase in the yield is 2.2 points. Furthermore, the solid (42) that had no use until then was recycled, reducing the acid consumption by 0.2 wt%.

[0161] Table 2 below indicates the composition of the ground biomass (5) and the solid residue (32) recovered from the feeding device of the impregnation reactor (9).

[0162] [Table 2]

[0163] The composition of the residue (32) is very similar to that of the starting biomass, and it can be seen that the water content is significantly higher.

[0164] Table 3 below again indicates the composition of the ground biomass (5) and the composition of the solid residue (42) recovered from the feed device of the digester reactor (14).

[0165] [Table 3]

[0166] The composition of the residue (42) is similar to that of the starting biomass, and it can be seen that the water content and even the sulfuric acid content are significantly higher, which justifies the advantage of recycling it.

[0167] (Example: Consistent with the present invention) Perform it according to the modification of the present invention shown in FIG. 6: Here, 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 digester reactor (14). The same feedstock as in the previous example is processed here.

[0168] Apply the throughput, which is the result of the recycling described in Examples 2 and 3, to Example 4: The yield is high at the limit of the pretreatment by recycling these two solid residues, and the acid consumption is reduced.

[0169] With the limits of the pretreatment, 99.7 wt% of the potential glucose and 80.3 wt% of the potential xylose were retained, i.e., the improvement in yield was 3.2 points. Furthermore, two solids (32), (42) that had no use until then were recycled. The combined crude throughput of these two residues is important. This is because it represents 6% of the crude throughput of the lignocellulosic biomass. Finally, the acid consumption decreased by 0.2 wt%.

Brief Description of the Drawings

[0170]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Claims

1. A method for processing lignocellulosic biomass containing up to 90% by weight of solids, comprising the use of at least one reactor ((9), (14)) for processing the biomass, wherein the reactor ((9), (14)) comprises a biomass feeding device ((6), (11)) having a biomass inlet and a biomass outlet, the biomass outlet being fluidly connected to the reactor inlet, and the method is characterized by the following: - While extracting the residue ((8); (13)) from the biomass, it is passed through the feeding device ((6); (11)) toward the reactor ((9); (14)) via an extraction outlet provided within the device, and the residue, called solid-liquid residue, is a mixture of solids and liquids. - Separating the solid-liquid residue into solid residue ((32); (42)) and liquid residue ((31); (41)), - At least a portion of the solid residue ((32); (42)) is reintroduced into the same feeding device, or into one of the feeding devices in the case of multiple reactors.

2. The method according to item 1, characterized in that a feeding device ((6); (11)) or at least one thereof is cleaned by the flow of a cleaning fluid ((7); (12)) between a cleaning inlet and a cleaning outlet of the feeding device, the cleaning outlet preferably also being an extraction outlet for solid-liquid residue.

3. The method according to (2), characterized in that at least a portion of the liquid residue ((31); (41)) is reintroduced into the same feeding device, or into one of the feeding devices in the case of multiple reactors.

4. The method according to 1, comprising the use of several reactors ((9); (14)) to process the biomass, wherein at least a portion of the solid residue ((32); (42)) is reintroduced into one of the feed devices of the reactor, and at least a portion of the liquid residue ((31); (41)) is reintroduced into another of the feed devices.

5. The method according to 1, characterized in that a feeding device ((6); (11)) or at least one thereof creates a pressure increase between the biomass inlets of the device, and this pressure increase causes compression of the biomass leading to the extraction of solid-liquid residues ((8); (13)).

6. The method according to 1, wherein the feeding device ((6); (11)) or at least one thereof is a feeding screw, which is, in particular, at least partially conical and includes a cowling with a cage, the cage having an opening that allows for the extraction of solid-liquid residue ((8); (13)) from biomass and optionally the flow of a washing fluid ((7); (12)).

7. The method according to claim 1, characterized in that the solid-liquid residue ((8); (13)) is separated into solid residue ((32); (42)) and liquid residue ((31); (41)) by at least one separation device ((30); (40)) selected from a centrifugal separator, a drainage device, or a pressurizing device, or by a screening unit.

8. The method according to claim 1, comprising the step of impregnating biomass with an impregnation liquor liquid (4) containing a chemical catalyst, wherein the step is carried out by introducing the biomass into an impregnation reactor (9) or one of them through its / their feeding device (6).

9. The method according to claim 1, comprising the step of treating biomass by pulverization or steam explosion, wherein the step is carried out by introducing the biomass into a pulverizer (14) or one thereof through its / their feeding device (11).

10. The method according to 9, comprising at least one step of treating biomass by enzymatic hydrolysis, wherein the step is carried out in an enzymatic hydrolysis reactor (20) equipped with a feeding device, following the pulping or steam explosion thereof.

11. The method according to claim 1, comprising at least one step of treating biomass by fermentation, wherein the step is carried out in a fermentation reactor (22) equipped with a feeding device, either after or in conjunction with an enzymatic hydrolysis step.

12. The method of claim 8, characterized in that a residue ((8); (13)) is extracted from biomass, while being passed through an extraction outlet provided in a feeding device ((6); (11)) toward an impregnation reactor (9) and / or a pulping reactor (14), wherein the residue, called a solid-liquid residue, is a mixture of solids and liquids: - Separating the solid-liquid residue into solid residue ((32); (42)) and liquid residue ((31); (41)), - At least a portion of the solid residue ((32); (42)) is reintroduced into the same feeding device ((6); (11)) or into at least one of the feeding 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 12, dependent on claim 9, characterized in that at least a portion of the solid residue ((32); (42)) is reintroduced to the feeding device of the impregnation reactor (9) or the feeding device of the pulping reactor (14), and the liquid residue ((31); (41)) is reused for the preparation of the impregnation liquor.

14. The method according to claim 12, dependent on 10, characterized in that at least a portion of the solid residue ((32); (42)) is reintroduced into the feeding device of the enzymatic hydrolysis reactor (20), and the liquid residue ((31); (41)) is reused for the preparation of the impregnation liquor.

15. The method according to claim 1, comprising the following steps: - a) A step of preparing an impregnation liquor liquid (4) containing a chemical catalyst (2) for impregnation of biomass (5) in a preparation zone (3); the catalyst is selected from an acidic catalyst, a basic catalyst and an oxidizing catalyst, preferably an acidic catalyst. - b) A step of introducing biomass (5) into the impregnation reactor (9) by a first feeding device (6); cleaning the first feeding device by the flow of a first cleaning fluid (7) between the cleaning inlet and the cleaning outlet of the device (6). - c) A step of introducing the liquor liquid into the impregnation reactor (9) through the inlet of the first liquor liquid (4) of the reactor, - d) A step of transferring the impregnated and then drained biomass (10) from the outlet of the impregnation reactor to the inlet of the pre-digestion reactor (14) via at least one second feeding device (11); cleaning the second feeding device by the flow of a second cleaning fluid (12) between the cleaning inlet and cleaning outlet of the feeding device. - e) A step of pre-treating the biomass (10) in the reactor (14) by pulverization or steam explosion, - f) Extracting solid-liquid residue ((8); (13)) from biomass through at least one of two feeding devices ((6); (11)), then separating the solid-liquid residue / solid-liquid residue into solid residue ((32); (42)) and liquid residue ((31); (41)), reintroducing at least a portion of the solid residue as biomass supplement into at least one of the feeding devices ((6); (11)), and reintroducing at least a portion of the liquid residue ((31); (41)) as washing fluid supplement into at least one of the feeding devices ((6); (11)) or as supplement for impregnation liquor into the liquor preparation zone (3) or impregnation reactor (9).

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