FR3029531A1 - PROCESS FOR THE PRETREATMENT OF LIGNOCELLULOSIC BIOMASS IN HYDRATES INORGANIC SALTS - Google Patents

Abstract

The invention relates to a method for treating lignocellulosic biomass comprising at least: a) a step of suspending the lignocellulosic biomass in a liquid medium comprising at least one hydrated inorganic salt, b) a solid-liquid separation step applied to the suspension obtained in step a) making it possible to obtain, on the one hand, a solid fraction and, on the other hand, a liquid fraction, c) at least one step of cooking the solid fraction obtained in step b) in a liquid medium comprising at least one hydrated inorganic salt, d) a solid-liquid separation step applied to the mixture resulting from the c) step of obtaining a solid fraction on the one hand and a liquid fraction on the other hand ; the method being characterized in that the liquid phase of the mixture obtained in step c) has an inorganic salt concentration higher than that of the liquid phase of the suspension obtained in step a); said inorganic salt concentration of the mixture obtained in step c) being at least 45% by weight.

Description

FIELD OF THE INVENTION The invention relates to the field of the production of biofuels and bio-sourced chemicals. More particularly, the invention relates to the field of pretreatment and conversion of lignocellulosic biomass for the production of biofuels and bio-sourced chemicals. Background Art In the face of increasing pollution and global warming, numerous studies are currently being conducted to utilize and optimize renewable bio-resources, such as lignocellulosic biomass. Lignocellulosic biomass is composed of three main polymers: cellulose (35 to 50%), hemicellulose (23 to 32%) which is a polysaccharide essentially consisting of pentoses and hexoses and lignin (15 to 25%) which is a polymer of complex structure and high molecular weight, from the copolymerization of phenylpropenoic alcohols. These different molecules are responsible for the intrinsic properties of the plant wall and are organized in a complex entanglement.

Cellulose, the majority of this biomass, is thus the most abundant polymer on Earth and the one with the greatest potential for forming materials and biofuels. However, the potential of cellulose and its derivatives has not, for the moment, been fully exploited, mainly because of the difficulty of extracting cellulose. Indeed, this step is made difficult by the very structure of the plants. The technological barriers identified in the extraction and transformation of cellulose include its accessibility, its crystallinity, its degree of polymerization, the presence of hemicellulose and lignin. It is therefore essential to develop new pretreatment methods for lignocellulosic biomass for easier access to cellulose and to allow its transformation.

In particular, the production of biofuels is an application requiring pretreatment of the biomass. Indeed, the second generation of biofuel uses as load vegetable or agricultural waste, such as wood, straw, or plantations with high growth potential such as miscanthus. This raw material is perceived as an alternative, sustainable solution having little or no impact on the environment and its low cost and high availability make it a solid candidate for biofuel production. The production of chemical intermediates by biotechnological processes, which use in particular one or more fermentation steps, also requires pretreatment of the biomass to use a lignocellulosic raw material whose use does not compete with the feed. The principle of the process for conversion of lignocellulosic biomass by biotechnological processes uses a step of enzymatic hydrolysis of the cellulose contained in the plant material to produce glucose. The glucose obtained can then be fermented into different products such as alcohols (ethanol, 1,3-propanediol, 1-butanol, 1,4-butanediol, etc.) or acids (acetic acid, lactic acid, 3- hydroxypropionic acid, fumaric acid, succinic acid, etc.).

However, the cellulose contained in the lignocellulosic biomass is particularly refractory to enzymatic hydrolysis, especially since the cellulose is not directly accessible to the enzymes. To overcome this refractory nature, a pretreatment step upstream of the enzymatic hydrolysis is necessary. There are many methods of chemical, enzymatic, microbiological treatment of cellulose-rich materials to improve the subsequent stage of enzymatic hydrolysis. These methods are for example: steam explosion, organosolv process, dilute or concentrated acid hydrolysis or AFEX ("Ammonia Fiber Explosion") process. These techniques are still perfectible and suffer in particular still too high costs, problems of corrosion, low yields and difficulties of extrapolation at the industrial level (F. Talebnia, D. Karakashev, I. Angelidaki Biores, Technol 2010, 101, 4744-4753).

3029531 3 Natural lignocellulosic biomass also contains water in a greater or lesser quantity depending on the type of biomass, the growing area and the harvest period. For example, the dryness of eucalyptus varies between 43 and 48% and that of poplar between 45 and 50%.

FR2963008, FR2963009 or FR2979913 have shown that a pretreatment of the lignocellulosic biomass could be obtained by cooking the biomass in a hydrated inorganic salt. However, a low dryness of the biomass can then cause a dilution of the hydrated inorganic salt used in the cooking step and thus limit the effectiveness of this pretreatment. There is still a need to improve pretreatment processes for lignocellulosic biomass.

DETAILED DESCRIPTION OF THE INVENTION The method for treating lignocellulosic biomass according to the present invention comprises at least: a) a step of suspending the lignocellulosic biomass in a liquid medium comprising at least one hydrated inorganic salt of formula (1) ): MX, .yH20 wherein M is a metal selected from Groups 1 to 13 of the Periodic Table, X is an anion and n is an integer from 1 to 6 and y is from 0.5 to 12, B) a solid-liquid separation step applied to the suspension obtained in step a) making it possible to obtain, on the one hand, a solid fraction and, on the other hand, a liquid fraction, c) at least one cooking step of the solid fraction obtained in step b) in a liquid medium comprising at least one hydrated inorganic salt of formula (2): M'X'n, · zH 2 O wherein M 'is a metal selected from groups 1 to 13 of the periodic table, X 'is an anion and is not an integer between 1 and 6 and z being between 0.5 and 12, d) at least one solid-liquid separation step applied to the mixture resulting from the cooking step c) making it possible to obtain a solid fraction and a liquid fraction; The process being characterized in that the liquid phase of the mixture obtained in step c) has an inorganic salt concentration higher than that of the liquid phase of the suspension obtained in step a); said inorganic salt concentration of the mixture obtained in step c) being at least 45% by weight.

The "liquid phase of the suspension obtained in step a)" is understood according to the invention as being the liquid phase resulting from the addition of the liquid medium of step a) and of the liquid phase resulting from biomass. . The "liquid phase of the mixture obtained in step c)" is understood according to the invention as being the liquid phase resulting from the addition of the liquid medium of step c) and of the liquid phase resulting from the solid fraction. from step b). Preferably, in the process according to the present invention M = M 'and X = X'. Direct cooking of lignocellulosic biomass in a liquid medium consisting of a hydrated inorganic salt, relates four quantities related to each other namely: the dryness of the biomass; the biomass content in the cooking stage (content expressed as dry basis); the concentration of the inorganic salt at the input of the cooking step; and the concentration of the inorganic salt in the liquid phase of the cooking medium. In this relation, the choice of the value of three quantities imposes the value of the fourth magnitude.

Thus, in one case, with respect to a direct cooking of the lignocellulosic biomass in an inorganic salt hydrated according to the prior art, the method according to the present invention has the advantage for a dryness of the fixed biomass, a concentration of the inorganic salt at the inlet of the fixed cooking step and a concentration of the inorganic salt in the liquid phase of the fixed cooking medium, to allow the content (expressed in dry basis) of the biomass in the cooking. In another case, the method according to the present invention has the advantage over a direct cooking of the lignocellulosic biomass in the inorganic salt hydrated according to the prior art, for a dryness of the fixed biomass, a content (expressed in dry basis) of the biomass in the fixed cooking step and a concentration of the inorganic salt at the input of the fixed cooking step, of allowing to increase the concentration of the inorganic salt in the liquid phase of the cooking medium .

According to yet another scenario, the process according to the present invention has the advantage over a direct cooking of the lignocellulosic biomass in the inorganic salt hydrated according to the prior art, for a dryness of the fixed biomass, a content of (expressed as dry basis) of the biomass in the fixed cooking step and a concentration of the inorganic salt in the liquid phase of the fixed cooking medium, to allow to reduce the concentration of the inorganic salt at the input of the cooking step . Charge The process according to the invention makes it possible to effectively transform various types of native lignocellulosic biomass or residual cellulosic substrates in spite of initial levels of high water. The lignocellulosic biomass, or lignocellulosic materials used in the process according to the invention is obtained from wood (hardwood and resinous), raw or treated, by-products of agriculture such as straw, plant fibers, forest crops, residues of alcoholic, sugar and cereal plants, residues of the paper industry, marine biomass (eg, cellulosic macroalgae) or transformation products of cellulosic or lignocellulosic materials. The lignocellulosic materials can also be biopolymers and are preferably rich in cellulose. Lignocellulosic biomass can also be a residual solid fraction at the end of enzymatic hydrolysis of a lignocellulosic substrate. The lignocellulosic biomass may also be the residual solid fraction after enzymatic hydrolysis of a lignocellulosic substrate, fermentation and separation of the fermentation product. Preferably, the lignocellulosic biomass used is wood, wheat straw, wood pulp, miscanthus, rice straw or maize stalks, a residual solid fraction at the end of enzymatic hydrolysis of a lignocellulosic substrate or a residual solid fraction after enzymatic hydrolysis of a lignocellulosic substrate, fermentation and separation of the fermentation product.

According to the method of the present invention, the different types of lignocellulosic biomass can be used alone or in mixture. The water content of the lignocellulosic biomass according to the present invention is advantageously between 5% and 95% by weight relative to the total mass of the lignocellulosic biomass, preferably between 15% and 90% by weight, even more preferably between 40% and 85% weight. Step a) Suspending The lignocellulosic biomass suspension step is carried out in the presence of a hydrated inorganic salt of formula (1): MX, yH 2 O wherein M is a metal selected from groups 1 at 13 of the Periodic Table, X is an anion and n is an integer in the range of 1 to 6 and is in the range of 0.5 to 12. In the suspending step a) the lignocellulosic biomass is present. in an amount preferably between 2% and 25% by weight of the total mass of the suspension, preferably in an amount of between 5% and 20% by weight. Anion X can be a monovalent, divalent or trivalent anion. Preferably, the anion X is a halide anion chosen from Cl-, F-, Br and I-, a perchlorate anion (010, a, a thiocyanate anion (SCNI a nitrate anion (NO3), a para- methylbenzene sulfonate (CH3-C6H4-5031 an acetate anion (CH3000-), a sulfate anion (5042-), an oxalate anion (02042-) or a phosphate anion (P043-), and even more preferably an anion X is a chloride, Preferably the metal M in formula (1) is selected from lithium, iron, zinc or aluminum.

More particularly, the hydrated inorganic salt of formula (1) is selected from: LiCl.sub.2H.sub.2 O, LiCl.sub.2H.sub.2 O, ZnCl.sub.2.2H.sub.2 O, ZnCl.sub.2.4H.sub.2 O, ZnCl.sub.12.8H.sub.2 O and FeCl.sub.3.6H.sub.2 O. In a particularly preferred manner, the salt is chosen from ZnCl 2 .2.5H 2 O, ZnCl 2 .4H 2 O and ZnCl 2 .8H 2 O.

The step a) of suspending the biomass may be carried out in a medium that may comprise a mixture of different hydrated inorganic salts corresponding to the formula (1). Advantageously, the operating temperature of step a) is between 0 ° C. and 120 ° C., even more preferably between 35 ° C. and 60 ° C. The duration of step a) is between 10 seconds and 12 hours, preferably between 5 minutes and 6 hours and even more preferably less than 30 minutes.

The step a) of suspending the lignocellulosic biomass can be carried out in the presence of one or more organic solvents, chosen from alcohols such as methanol, ethanol, n-propanol, isopropanol, propylene glycol, and the like. n-butanol, isobutanol or tert-butanol, diols and polyols such as ethanediol, propanediol or glycerol, amino alcohols such as ethanolamine, diethanolamine or triethanolamine, ketones such as acetone or methyl ethyl ketone, carboxylic acids such as formic acid or acetic acid, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile, aromatic solvents such as benzene, toluene, xylenes, alkanes . According to another embodiment, the suspension of the cellulosic substrate can be carried out in the absence of an organic solvent. The suspension can be carried out according to any suspension techniques known to those skilled in the art.

Preferably, the liquid medium of step a) consists of one or more hydrated inorganic salts. Step b) of separation of the suspension resulting from step a) According to the invention, the suspension obtained in step a) is subjected to a separation step 30 making it possible to obtain on the one hand a solid fraction and on the other hand a liquid fraction. The separation of a solid fraction and a liquid fraction containing the hydrated inorganic salt and water can be carried out by the usual solid-liquid separation techniques. For example, the separation of the solid fraction after step a) can be carried out by decantation, filtration or centrifugation. Advantageously, the temperature of implementation of step b) is between 0 ° C. and 120 ° C., even more preferably between 30 ° C. and 70 ° C. The solid fraction resulting from the separation step b) is composed of solid matter in a content of between 5% and 60% by weight, and preferably between 10% and 45% by weight, and of a liquid phase. The presence of liquid in this fraction is related to the limitations of liquid / solid separation devices. The solid material contains most of the cellulose of the initial substrate, between 60% and 100% by weight, and preferably between 75% and 99% by weight of the cellulose initially introduced into the process. Step c) of cooking the solid fraction resulting from the separation step b) The step of cooking the solid fraction separated in step b) is carried out in the presence of a hydrated inorganic salt of formula (2) Where M 'is a metal selected from Groups 1 to 13 of the Periodic Table, X' is an anion and n 'is an integer from 1 to 6 and z being understood between 0.5 and 12. A mixture of hydrated inorganic salts may be used for cooking the solid fraction from step b).

According to the process of the present invention, the liquid phase of the mixture obtained in step c) has an inorganic salt concentration higher than that of the liquid phase of the suspension obtained in step a); said inorganic salt concentration of the liquid phase of the mixture obtained in step c) being at least 45% by weight, preferably at least 50% by weight. The X 'anion, which is identical or different from the X anion, may be a monovalent, divalent or trivalent anion. Preferably, the anion X 'identical to or different from the anion X, preferably identical to the anion X, is a halide anion chosen from Cl-, F-, Br and I-, a perchlorate anion (0104 ), a thiocyanate anion (SON-), a nitrate anion (NO3-), a paramethylbenzene sulfonate anion (CH3-061-14-503), an acetate anion (CH3000-), a sulfate anion (5042-), an anion oxalate (02042-) or a phosphate anion (P043_). Even more preferably, the anion X 'is a chloride. Preferably, the metal M 'in the formula (2) identical or different from the metal M in the formula (1), preferably identical to the metal M in the formula (1), is chosen from lithium, iron, zinc or aluminum. More particularly, the hydrated inorganic salt of formula (2) is chosen from: LiCl.sub.2H.sub.2 O, LiCl.sub.2.2H.sub.2 O, ZnCl.sub.12.1.5H.sub.2 O, ZnCl.sub.2.2H.sub.2 O, ZnCl.sub.2.2H.sub.2 O and FeCl.sub.3.6H.sub.2 O. In a particularly preferred manner, the salt is chosen from ZnCl 2 .1.5H 2 O, ZnCl 2 .2H 2 O and ZnCl 2 .5H 2 O. Preferably, the firing temperature of step c) is between -20 ° C. and 250 ° C, preferably between 20 and 160 ° C. When the metal M 'of the hydrated inorganic salt is selected from groups 1 and 2 of the periodic table, the firing temperature is preferably between 100 ° C and 160 ° C. When the metal M 'of the hydrated inorganic salt is chosen from groups 3 to 13 of the periodic table, the firing temperature is preferably between 20 ° C. and 120 ° C. The duration of the cooking of step c) is between 0.5 minutes and 168 hours, preferably between 5 minutes and 24 hours, and even more preferably between 20 minutes and 12 hours. According to the method of the present invention, several successive firing steps can be performed.

The firing step can be carried out in the presence of one or more organic solvents, chosen from alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol or tertanol. butanol, diols and polyols such as ethanediol, propanediol or glycerol, amino alcohols such as ethanolamine, diethanolamine or triethanolamine, ketones such as acetone or methyl ethyl ketone, carboxylic acids such as formic acid or acetic acid, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile, aromatic solvents such as benzene, toluene, xylenes, alkanes.

According to another embodiment, the firing step can be carried out in the absence of an organic solvent. In the cooking step c), the solid fraction is present in an amount of between 4% and 40% by weight of the total mass of the mixture, preferably in an amount of between 5% and 30% by weight. Preferably, the liquid cooking medium of step c) consists of one or more hydrated inorganic salts. Step d) solid-liquid separation of the mixture resulting from step c) The separation step d) can be carried out directly on the mixture resulting from step c) of cooking or after addition of at least one anti- solvent. The addition of the anti-solvent promotes the precipitation of the solid fraction. Preferably, this separation is carried out after addition of at least one anti-solvent. The separation of a solid fraction and a liquid fraction containing the hydrated inorganic salt and optionally the anti-solvent may be carried out by the usual solid-liquid separation techniques, for example by decantation, by filtration or by centrifugation.

The anti-solvent used is a solvent or a mixture of solvents chosen from water, alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol or tert-butanol, diols and polyols such as ethanediol, propanediol or glycerol, amino alcohols such as ethanolamine, diethanolamine or triethanolamine, ketones such as acetone or methyl ethyl ketone, carboxylic acids such as formic acid or acetic acid, esters such as ethyl acetate or isopropyl acetate dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile. Preferably, the anti-solvent is selected from water, methanol or ethanol.

Most preferably, the anti-solvent is water alone or in admixture, and preferably alone. At the end of the separation step d), a solid fraction and a liquid fraction are obtained.

The solid fraction resulting from the separation step d) is composed of solid matter in a content of between 5% and 60% by weight, and preferably between 10% and 45% by weight, and of a liquid phase. The presence of liquid in this fraction is related to the limitations of liquid / solid separation devices. The solid material contains most of the cellulose of the initial substrate, between 60% and 100% by weight, and preferably between 75% and 99% by weight of the cellulose initially introduced into the process. The liquid fraction contains the hydrated inorganic salt or salts used during the baking step, and optionally the anti-solvent.

Step e) treatment of the solid fraction resulting from the separation step d) The solid fraction obtained at the end of the separation step d) can be subjected to a treatment step e) carried out by means of one or more washes, neutralization, pressing, and / or drying.

These additional treatments may in particular have the purpose of eliminating traces of hydrated inorganic salts in this solid fraction.

The washes can be carried out with an anti-solvent or with water. The washes may also be made with a stream from a processing unit of products from the pretreatment process of the present invention.

The neutralization can be carried out by suspending the solid fraction obtained in step d) in water and adding a base. By the term base, we refer to any chemical species which, when added to water, gives an aqueous solution of pH greater than 7. The neutralization can be carried out by an organic or inorganic base. Among the bases which can be used for the neutralization, mention may be made of soda, potassium hydroxide, sodium and potassium carbonate, sodium and potassium bicarbonate and ammonia. The solid fraction obtained at the end of the separation step d) may optionally be pressed or dried to increase the percentage of dry matter contained in the solid.

Optionally, the solid fraction can be washed. Stage f) Purification of the liquid fraction resulting from stage d) According to one particular embodiment of the invention, the liquid fraction resulting from stage d) can be subjected to a purification stage f) to concentrate the inorganic salt contained in the liquid fraction. The purification step f) can in particular be a step of separation of the inorganic salt hydrate and the anti-solvent. This separation can be carried out by any method known to those skilled in the art, such as, for example, evaporation, precipitation, extraction, passage over ion exchange resin, electrodialysis, chromatographic methods, solidification. hydrated inorganic salt by lowering the temperature or adding a third body, reverse osmosis. Advantageously, the inorganic salt from step f) can be recycled in the cooking step c) and / or in the suspension step a).

According to one embodiment of the invention, the liquid fraction resulting from step b) can be sent to a purification step f '). Steps f) and f ') can be conjoined or separated.

Preferably, the purification step f) has at least one step of evaporation of the anti-solvent. Evaporation is a separation technique known to those skilled in the art. This involves bringing the liquid to be concentrated at the bubble point temperature (for liquid pressure) and separating the formed vapors from the liquid. During the evaporation, as during a distillation, the compositions of the vapor and liquid phases are governed by the thermodynamic equilibria and can be different depending on the species in the presence. For example, in the case of evaporation of an inorganic salt solution and water, the vapor will be composed solely of water and the inorganic salt will concentrate in the liquid phase.

In the case of highly non-ideal solutions, such as inorganic salt and water solutions for example, the boiling temperature of the liquid is higher than that of water. The difference between the two is ebullioscopic elevation (EER). The ebullioscopic elevation of water solutions containing hydrated inorganic salt increases with salt concentration.

Several evaporation technologies exist depending on the constraints of the process. Examples include falling film evaporators, forced circulation evaporators, sloped tube evaporators, plate evaporators, short vertical tube evaporators, stirred film evaporators, etc. Evaporation can be carried out in a controlled manner. 25 pressure or under vacuum. Techniques are known to decrease the energy consumption of the evaporation step. For example, multi-effect evaporation is a well-known technique for limiting the energy consumption of the evaporation step. It consists in condensing the vapors of an effect to heat a following effect. To ensure heat transfer, the operating temperature of the heat receiving effect must be lower than the condensation temperature of the vapors used for heating. The mechanical recompression of the vapors 3029531 14 can also be applied, it consists in mechanically recompressing the vapors resulting from an effect to increase their pressure, and therefore their condensation temperature, and use the energy of their condensation to heat the effect considered. . Thermocompression or ejectocompression can also be used. All of these techniques have in common that they are more difficult to apply and less effective on solutions with high ebullioscopic elevation. The use of hydrated inorganic salts with a higher water content is therefore preferred to limit the energy consumption of the evaporation step.

DESCRIPTION OF THE FIGURES The process will be described with reference to FIG. 1 and FIG. 2. The lignocellulosic biomass is introduced via line 1 into the reactor 2 in which the lignocellulosic biomass is suspended in a reactor. medium comprising at least one hydrated inorganic salt. The medium comprising one or more hydrated inorganic salts of formula (1) and optionally an organic solvent is introduced via line 3. At the outlet of reactor 2, the suspension is extracted via line 4. This suspension is sent to equipment in which the solid-liquid separation takes place. The separation of a solid fraction and a liquid fraction containing the hydrated inorganic salt and water can be carried out by the usual solid-liquid separation techniques. For example, the separation of the solid fraction can be carried out by decantation, filtration or centrifugation.

After solid-liquid separation, the liquid fraction containing the hydrated inorganic salt (s) and water and the solid fraction (7) are withdrawn via line (6). This solid fraction is composed of the majority of the initial lignocellulosic biomass 1 solids and a liquid phase.

The solid fraction is sent via line 7 to the cooking reactor 8. The medium comprising at least one hydrated inorganic salt of formula (2) is introduced via line 9.

The mixture resulting from the baking step is sent through the pipe 10 into the separation equipment 11 in which the solid-liquid separation takes place. The separation of a solid fraction and a liquid fraction containing the hydrated inorganic salt and water can be carried out by the usual solid-liquid separation techniques. After solid-liquid separation, the liquid fraction containing the hydrated inorganic salt (s) and water is withdrawn via line 14, and the solid fraction is discharged via line 13. The solid fraction contains most of the cellulose present in the cellulosic substrate introduced in line 1. This cellulose has the property of being particularly reactive in enzymatic hydrolysis. According to the embodiment of FIG. 2, the firing step c) is followed by a solid-liquid separation step carried out in the equipment 11. An anti-solvent is optionally added via line 12. A solid fraction (also called cake) containing the majority of the solid is withdrawn through line 13. The liquid containing the inorganic salt (s) hydrated (s) and optionally the anti-solvent is removed by driving 14 and sent to the reactor 15 for a purification step f). A solution of concentrated hydrated inorganic salt (s) is withdrawn through line 17, and the residue of the purification is withdrawn via line 16. All or part of the liquid flowing in line 6 may be sent to a reactor 18 for a purification step f '). A solution of concentrated hydrated inorganic salt (s) is withdrawn through line (20), and the residue of the purification is removed via line (19).

Steps f) and f ') may be a single step or separate steps. Optionally, steps f) and f ') can be successively carried out, one of the outgoing flows (16 or 17) of the reactor 15 being fed to the reactor 18, or vice versa. The solutions of inorganic salt (s) hydrated (s) circulating in the lines 17 and / or 20 may be recycled all or in part in the lines 3 and / or 9 introduction of inorganic salt (s) (s) ) hydrated (s) reactors 2 and 8. They can be recycled separately or 3029531 16 mixed. Optionally, a portion 6a of the liquid flowing in the pipe 6 and / or a portion 14a of the liquid flowing in the pipe 14 can be recycled (s) alone or in mixture in the pipes 3 and / or 9.

When the solid / liquid separations are performed in batch mode, the solid-liquid separation equipment 5 and 11 may be one and the same apparatus operated under similar and / or different conditions.

EXAMPLES EXAMPLE 1 Non-Conforming to the Invention 200 tons of miscanthus containing 40% of water are cooked in a hydrated inorganic salt of formula: LiCl 2 .H 2 O The baking has a duration of 3 hours at a temperature of 30.degree. 140 ° C and is performed in batch with a loading / unloading time of 1h. The desired concentration of LiCl in the liquid phase of the cooking medium is 50% by weight (mass of LiCl / mass of the liquid phase). Consequently, according to the material balance established in the table below, the dry mass (DM) used in the baking step is 10.17% by weight (dry mass of biomass / total mass of the reaction medium). Miscanthus LiCI.2H20 Cooking medium Total ton 200 980 1180 MS of biomass tonne 120 120 Water tonne 80 450.0 530.0 LiCI tonne 0 530.0 530.0 Example 2 according to the invention As in Example 1, 200 tonnes of miscanthus containing 40% water. The suspension is prepared prior to cooking with a hydrated inorganic salt of formula: LiCl 3 .H 2 O. This step has a duration of 30 minutes and is carried out at a dry weight (DM) content of 8% by weight. and at a temperature of 100 ° C. The LiCl concentration of the liquid medium during this step is 41.4% by weight (mass of LiCl / mass of the liquid phase). A solid-liquid separation is produced at the outlet, which makes it possible to obtain a solid fraction (called a cake) and a liquid fraction. The solid content of the solid fraction is 30% by weight. The cake is then engaged in the firing step with a hydrated inorganic salt of formula: LiCl 2 .H 2 O The baking has a duration of 3 hours at a temperature of 140 ° C. and is carried out batchwise with a loading time. unloading of 1h. The desired concentration of LiCl in the liquid phase of the cooking medium is 50% by weight (mass of LiCl / mass of the liquid phase). Consequently, according to the material balance established in the table below, the dry mass (DM) used in the baking step is 12.15% by weight. Miscanthus LiCI. Medium of Cake LiCI liquid outlet.

2H20 Medium of 3H20 suspension (1) cooking (2) Total ton 200 1300 1500 400 1100 587.7 987.7 MS of ton 120 120 120 0 120.0 biomass Water ton 80 728.2 808.2 164.0 644.2 269.8 433.8 LiCI ton 0 571.8 571.8 116.0 455.8 317.8 433.8 The process according to the present invention has therefore increased the dry mass ratio (MS) of the biomass used in the cooking step of 19.5%. Example 3 Non-Conforming to the Invention The baking of 50 tons / hour of enzymatic hydrolysis residue (HE residue) containing 55% of water in a hydrated inorganic salt of formula: Fe (NO 3) 3.7H 2 O 20 cooking has a duration of 5 hours and is carried out continuously. The dry mass (DM) used in the baking step is 16.20% by weight (dry mass of biomass / total mass of the cooking medium). The flow rates expressed in tons per hour (ton / h) are presented in the table below. The concentration of Fe (NO 3) 3 in the liquid phase of the cooking medium is thus 50.2% by weight (mass of Fe (NO 3) 3 / mass of the liquid phase).

Residue HE Fe (NO3) 3.7H20 Cooking medium Total ton / h 50 88.9 138.9 MS biomass ton / h 22.5 22.5 Water ton / h 27.5 30.5 58.0 Fe (NO3) 3 ton / h 58.4 58.4 Example 4 no In accordance with the invention, 50 t / h of enzymatic hydrolysis residue (HE residue) containing 55% of water is prepared in a hydrated inorganic salt of formula: Fe (NO 3) 3 .12H 2 O duration of 5 hours and is carried out continuously. The dry mass (DM) used in the baking step is 16.20% (dry mass of biomass / total mass of the cooking medium). The flow rates expressed in tons per hour (ton / h) are presented in the table below. The concentration of Fe (NO 3) 3 in the liquid phase of the cooking medium is thus 40.3% by weight.

15 Residue HE Fe (NO3) 3.12H20 Cooking medium Total ton / h 50 88.9 138.9 MS of biomass ton / h 22.5 22.5 Water ton / h 27.5 41.9 69.4 Fe (NO3) 3 ton / h 46.9 46.9 Example 5 according to the As in Examples 3 and 4, 50 tons / hour of enzymatic hydrolysis residue containing 55% water is treated. The suspension is carried out beforehand with a hydrated inorganic salt of formula: Fe (NO 3) 3 .12H 2 O This stage has a duration of 20 minutes and is carried out at a dry weight (DM) content of 10% by weight. (dry mass of biomass / total mass of the suspension), continuously. The concentration of Fe (NO 3) 3 in the liquid phase during this step is 45.6% by weight. A solid-liquid separation is produced as output, which makes it possible to obtain a solid fraction (called cake) whose solids content is 35% and a liquid fraction. The cake is then engaged in the firing step with a hydrated inorganic salt of the same formula as in the first step, of formula: Fe (NO 3) 3 .12H 2 O The firing has a duration of 5 hours and is carried out continuously. The dry mass (MS) of biomass used in the cooking step is 16.20% by weight. The flow rates expressed in tonnes per hour (ton / h) are shown in the table below. The concentration of Fe (NO 3) 3 in the liquid phase of the cooking medium is thus 50.2% by weight. Residue HE Fe (NO3) 3. Medium Cake Outlet Fe (NO3) 3. Medium of 12H20 of liquid 12H20 cooking baking Total ton 50.0 175.0 225.0 64.3 160.7 74.6 138.9 / h MS of ton 22.5 22.5 22.5 0.0 22.5 biomass / h Water ton 27.5 82.6 110.1 22.7 87.4 25.6 48.3 / h Fe (NO3) 3 ton 0.0 92.4 92.4 The method according to the present invention has thus made it possible to increase the hydration of the hydrated inorganic salt used, while maintaining the same dry mass (DM) biomass concentrations in the baking stage and at the same time. inorganic salt in the liquid phase of the cooking medium compared with Example 3. Compared to Example 4, the process according to the present invention allowed using the same inorganic salt hydrated Fe (NO3) 3.12H20 20 have a higher Fe (NO3) 3 salt concentration in the liquid phase of the baking step.

EXAMPLE 6 Non-Conforming to the Invention The firing of 40 tonnes / hour of beech wood residue containing 45% of water is carried out in a hydrated inorganic salt of formula: ZnCl2.2H2O Cooking has a duration of 2h at a temperature of 80 ° C and is performed in batch, with a loading / unloading time of 1h. The dry mass (DM) used in the cooking step is 6.0% by weight. The flow rates expressed in tons per hour (ton / h) are shown in the table below. The concentration of ZnCl 2 in the liquid phase of the cooking medium is thus 75.0% by weight. At the end of cooking, water is added to the medium in the proportions 4 tons of water per ton of cooking medium, then the medium is sent to a solid-liquid separation stage where it is treated in 3 hours. . At the end of this separation, a cake comprising 25% by weight of dry mass is obtained and 1378 tonnes / hour of liquid comprising ZnCl 2 and water are produced. Evaluation of 1 batch of cooking Beech ZnC12.2H20 Cooking medium Total ton / h 120 980 1100 MS of biomass ton / h 66 66 Water ton / h 54 204.6 258.6 ZnCl2 tonne / h 0 775.4 775.4 Example 7 according to the invention 20 As in Example 6, 40 tons / hour of beech wood containing 45% water is treated. The suspension is carried out beforehand with a hydrated inorganic salt of formula: ZnCl 2 · 6H 2 O This step has a duration of 15 minutes and is carried out at a dry weight (DM) content of 7.5% by weight, continuously. The concentration of ZnCl 2 of the liquid medium during this step is 52.1% by weight (mass of ZnCl 2 / mass of the liquid phase). A solid-liquid separation is obtained at the outlet, which makes it possible to obtain a solid fraction (called a cake) whose solid content (MS) is 35% by weight and a liquid fraction with a flow rate of 230.5 tonnes / 3029531 22 hours. The cake is then engaged in the firing step with a hydrated inorganic salt of formula: ZnCl 2 · 2H 2 O The firing has a duration of 2 h at a temperature of 80 ° C. and is carried out batchwise with a loading / unloading time. 1h. The dry mass (DM) used in the cooking step is 7.60% by weight. Flow rates are shown in the table below. The concentration of ZnCl 2 in the liquid phase of the cooking medium is thus 75.0% by weight (mass of ZnCl 2 / mass of the liquid phase). At the end of cooking, water is added to the medium in the proportions 4 tons of water / ton of cooking medium, then the medium is sent to a solid-liquid separation stage where it is treated in 3 hours. At the end of this separation, a cake comprising 25% of dry mass is obtained and 1070 tonnes / hour of liquid comprising ZnCl 2 and water are produced.

15 Beech ZnC12.6H20 Cake Release liquid suspension Total ton / h 40 253.3 293 62.9 230.5 MS of ton / h 22 22 22 0 biomass Water ton / h 18 111.9 129.9 19.6 110.4 ZnCl2 ton / h 0 141.4 141.4 21.3 120.1 Assessment on 1 baking batch Cake ZnC12.2H20 Baking medium Total ton / h 125.7 453 579 MS of biomass ton / h 44.0 44.0 Water ton / h 39.1 94.6 133.8 ZnCl2 ton / h 42.6 358.6 401.2 The process according to the present invention thus allowed to increase the biomass dry mass (MS) rate used in iso-concentration cooking of the inorganic salt in the liquid phase of the cooking medium compared with Example 6. The higher biomass dry mass 3029531 23 allows a reduction in the production of liquid effluent to be treated, which went from 1378 to 1300 tonnes / hour on the two liquid outlets, a reduction of nearly 6%.

Claims (13)

1. A method for treating lignocellulosic biomass comprising at least: a) a step of suspending the lignocellulosic biomass in a liquid medium comprising at least one hydrated inorganic salt of formula (1): MX, yH20 in which M is a metal selected from Groups 1 to 13 of the Periodic Table, X is an anion and n is an integer from 1 to 6 and y is from 0.5 to 12, b) a solid-liquid separation step applied to the suspension obtained in step a) making it possible to obtain, on the one hand, a solid fraction and, on the other hand, a liquid fraction, c) at least one step of cooking the solid fraction obtained in step b) in a liquid medium comprising at least one hydrated inorganic salt of formula (2): M'X'n, .zH 2 O wherein M 'is a metal selected from groups 1 to 13 of the periodic table, X' is an anion and n ' is an integer between 1 and 6 and z being between 0.5 and 12, d) a solid-liquid separation step applied to the mixture from step c) of firing to obtain on the one hand a solid fraction and on the other hand a liquid fraction; the method being characterized in that the liquid phase of the mixture obtained in step c) has an inorganic salt concentration higher than that of the liquid phase of the suspension obtained in step a); said inorganic salt concentration of the mixture obtained in step c) being at least 45% by weight. 2) Process according to claim 1 wherein the temperature of implementation of step a) is between 0 ° C and 120 ° C. 3) Method according to one of the preceding claims wherein the metal M in the formula (1) is selected from lithium, iron, zinc or aluminum. 3029531 25 4) Method according to one of the preceding claims wherein the anion X is a halide anion selected from Cl-, F-, Br and I-, a perchlorate anion (010, a, a thiocyanate anion (SCNI a nitrate anion) (NO3), a para-methylbenzene sulfonate anion (CH3-C6H4-503), an acetate anion (CH3000-), a sulfate anion (50421 an oxalate anion (02042-) or a phosphate anion (P043-). 5) Method according to one of the preceding claims wherein the metal M 'in the formula (2) identical or different from the metal M in the formula (1) is selected from lithium, iron, zinc or aluminum . 10 6) Method according to one of the preceding claims wherein the anion X 'identical or different from the anion X is a halide anion selected from Cl-, F-, Br and I-, a perchlorate anion (0104), a thiocyanate anion (SCNI a nitrate anion (NO3), a paramethylbenzene sulfonate anion (CH3-C61-14-503), an acetate anion (CH3000-), a sulfate anion (50421 an oxalate anion (02042-) or an anion phosphate (P043-). 7) Method according to one of the preceding claims wherein the solid fraction from the separation step d) is composed of solid material in a content between 5% and 60% by weight and a liquid phase. 20 8) Method according to one of the preceding claims wherein the firing temperature of step c) is between -20 ° C and 250 ° C. 9) Method according to one of the preceding claims wherein, in the step a) of suspension, the lignocellulosic biomass is present in an amount of between 2% and 25% by weight basis dry mass of the total mass of the suspension. 3029531 26 10) Method according to one of the preceding claims wherein the solid fraction obtained at the end of the separation step d) is subjected to a step e) of treatment carried out by means of one or more washes, of neutralization, pressing, and / or drying. 5 11) Method according to one of the preceding claims wherein the liquid fraction from step d) is subjected to a purification step f) for concentrating the inorganic salt contained in the liquid fraction. 10 12) Method according to one of the preceding claims wherein the lignocellulosic biomass, or lignocellulosic materials used is obtained from wood, raw or treated, by-products of agriculture such as straw, plant fiber, forest crops, residues of alcoholic, sugar and cereal plants, residues of the paper industry, marine biomass or transformation products of cellulosic or lignocellulosic materials. 13) Method according to one of the preceding claims wherein the water content of the lignocellulosic biomass is between 5% and 95% by weight.