Improved process for converting feedstock containing biomass fraction for production of hydrocarbons by means of Fischer-Tropsch synthesis

Abstract

The invention relates to a process for converting a feedstock comprising at least one biomass fraction into hydrocarbons, comprising: a step a) of pretreating the feedstock; a water electrolysis step b) for obtaining a hydrogen stream and an oxygen stream, wherein water is at least partially produced by the Fischer-Tropsch synthesis carried out in step e); a step c) of gasifying the feedstock pretreated in step a), in the presence of all or part of the oxygen stream obtained from the water electrolysis step b), to obtain a gaseous effluent comprising synthesis gas; an optional step d) of conditioning the gas effluent comprising the synthesis gas obtained from step c); and a step e) of synthesis, subjecting the gas effluent obtained from step c) or optionally obtained from step d) to Fischer-Tropsch synthesis in the presence of all or part of the hydrogen obtained from the water electrolysis step b) to produce a stream comprising synthetic liquid hydrocarbons and at least one gas effluent.

Description

Field of the Invention

[0001] The present invention relates to the upgrading of the value of biomass, typically for the production of liquid hydrocarbons, biofuels and optionally for the production of petrochemical bases and / or chemical bases and / or hydrogen.

[0002] More particularly, the present invention relates to an integrated process for converting a feedstock containing at least one biomass fraction, comprising a gasification step, a water electrolysis step and a synthesis step by the Fischer-Tropsch reaction, with the aim of producing hydrocarbons, in particular high-quality LPG (liquefied petroleum gas), naphtha, gasoline, kerosene and gas oil fractions or lubricant bases. Prior Art

[0003] A large number of patents describe pipelines for producing synthetic hydrocarbons via the Fischer-Tropsch synthesis, in which generally steps of hydrotreatment and isomerization of the hydrocarbon-based fraction obtained in the synthesis are combined.

[0004] Patent application WO 2014 / 068253 A1 relates to a pipeline for producing biofuels from lignocellulosic biomass. Said patent application describes the possibility of injecting hydrogen into any point of the process pipeline. The injected hydrogen is produced by any means known to those skilled in the art, and there is no particular distinction or integration between the hydrogen production process and the biofuel production pipeline process.

[0005] Patent US 9562196 describes a process for producing synthetic hydrocarbons in which the hydrogen content at the inlet of the Fischer-Tropsch unit is adjusted by reforming the naphtha produced by the Fischer-Tropsch synthesis. The disadvantage of this step is that the amount of finished product produced is reduced by consuming the naphtha produced, thereby reducing the productivity of the Fischer-Tropsch synthesis step.

[0006] Patent application WO 2015 / 101717 describes the supply of external hydrogen to regulate the H of the synthesis gas produced by the gasification of carbon-based feedstocks (and in particular biomass). 2 / CO ratio. In particular, the document describes a method comprising the steps of: a step of reforming carbon monoxide with steam to enrich the synthesis gas produced by gasification with hydrogen; and a step of regulating the production of synthesis gas according to the amount of hydrogen by means of an external hydrogen supply to maintain a constant production of synthetic fuel. The reaction of reforming carbon monoxide with steam is also called the "water gas shift" reaction.

[0007] One of the problems encountered by those skilled in the art in the field of the present invention relates to improving the production yield on an industrial scale as well as the economic and energetic performance of production lines while complying with increasingly stringent environmental constraints.

[0008] In the context of the present invention, the Applicant has proposed a novel process which presents an optimal integration of the gasification, Fischer-Tropsch synthesis and water electrolysis steps, making it possible to achieve improved production yields and better economic and energetic performances (energy efficiency, production costs, etc.), while at the same time complying with environmental constraints, such as setting the emissions of greenhouse gases at lower and lower thresholds. SUMMARY OF THE INVENTION

[0010] In particular, the present invention relates to a method for converting a feedstock comprising at least one biomass fraction into hydrocarbons, the method comprising

[0011] - Step a), pre-treating the raw material,

[0012] - step b), electrolysis of water into oxygen and hydrogen for producing a hydrogen stream and an oxygen stream, wherein the water is at least partly obtained from the Fischer-Tropsch synthesis step e),

[0013] - a step c) of gasifying the feedstock pretreated in step a) in the presence of all or part of the oxygen stream obtained in step b) of the water electrolysis, so as to obtain a gaseous effluent comprising synthesis gas,

[0014] - an optional step d) of conditioning the gaseous effluent comprising synthesis gas obtained from step c) so as to obtain a gaseous effluent comprising purified synthesis gas,

[0015] - step e) of subjecting the gaseous effluent obtained from step c) or optionally from step d) to Fischer-Tropsch synthesis in the presence of all or part of the hydrogen obtained in water electrolysis step b) to produce a stream comprising synthetic liquid hydrocarbons and at least one gaseous effluent.

[0016] One advantage of the present invention is that it provides a process presenting an optimal integration of the gasification, Fischer-Tropsch synthesis and water electrolysis steps, making it possible to achieve improved production yields and better economic and energetic performance (energy efficiency, production costs, etc.), while at the same time complying with environmental constraints, such as setting the emission of greenhouse gases at lower and lower thresholds.

[0017] Another advantage of the process according to the invention is that the implementation of a steam reforming step for generating hydrogen is limited or even omitted, which makes it possible to reduce CO in the biofuel production process. 2 emissions, and may also maximize the amount of CO obtained from the gasification step, thereby increasing the material yield of the process and / or reducing the amount of input feedstock. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention relates to a process for converting a feedstock comprising at least one biomass fraction into renewable hydrocarbons.

[0020] Raw material type

[0021] The biomass fraction may comprise any type of biomass, preferably solid type biomass, and in particular lignocellulose type biomass. Non-limiting examples of biomass types relate to, for example, agricultural residues (especially straw, corn husks), forestry management residues, forestry management products, sawmill residues and specialized crops, such as short rotation coppice.

[0022] The feedstock converted in the process according to the invention may also contain a fraction of at least one further feedstock, preferably a fraction of at least one gaseous, solid and / or liquid hydrocarbon-based feedstock ("co-process"). In the context of the present invention, the hydrocarbon-based feedstock fraction is understood to be a feedstock fraction that may advantageously contain at least coal, petroleum coke, natural gas, oil residues, crude oil, topped crude oil, deasphalted oil, deasphalted asphalts, oil conversion process derivatives (e.g. HCO / FCC slurries, coking heavy GO / VGO, visbreaking or similar thermal process residues, etc.), tar sands or their derivatives, shale gas and bituminous shale or their derivatives, liquid biomass (e.g. rapeseed oil, palm oil, pyrolysis oil, etc.) or biomass slurry (corresponding to a mixture of liquid biomass and solid hydrocarbon-based feedstock). According to the process according to the invention, the hydrocarbon-based feedstock fraction may be a gaseous, solid or liquid hydrocarbon-based feedstock fraction or a mixture thereof.

[0023] Thus, the feedstock for the process according to the invention may be a feedstock comprising at least one solid biomass fraction and optionally at least one fraction of another gaseous, solid or liquid feedstock, alone or as a mixture.

[0024] Typically, the feedstock used in the process of the invention comprises a biomass fraction of at least 20%, preferably at least 50%, preferably at least 70%, and more preferably at least 90%.

[0025] The individual steps of the method according to the invention are described below.

[0026] a) Raw material pretreatment step

[0027] According to the present invention, the method comprises a step of pretreating the raw material a). Preferably, the pretreating step comprises at least one of the operations of drying a1), roasting a2) or grinding a3) described below. Preferably, the pretreating step comprises a drying operation a1), a roasting operation a2) and a grinding operation a3).

[0028] In the embodiment in which the raw materials used are already dried, the pretreatment step comprises a roasting operation a2) and a grinding operation a3).

[0029] When the hydrocarbyl feed fraction is a gaseous or liquid hydrocarbyl feed fraction, it is advantageously introduced directly into the gasification step c) without being subjected to a pretreatment step a).

[0030] a1) Drying operation

[0031] The raw material pretreatment step a) may advantageously include a raw material drying operation a1), which is advantageously carried out at a temperature of 20 to 180° C., preferably 60 to 160° C., and preferably 100 to 140° C. for 5 to 180 minutes and preferably 15 to 60 minutes. At the inlet of the drying operation a1), the raw material generally contains a water content of 15% to 80% by mass. The residual water content in the raw material at the end of the drying operation is advantageously less than 25% by mass, preferably less than 15% by mass, and more preferably less than 10% by mass. The drying operation can be carried out in any manner known to those skilled in the art.

[0032] The energy required for drying is generally provided by contacting the feedstock with a hot gas stream.

[0033] The hot gas stream used in the drying step can advantageously originate from the combustion of a process input, and preferably from the combustion of natural gas and / or from the combustion of a gas stream obtained from another step of the process. For example, the combustion of the gases obtained from the roasting step a2) produces a hot gas stream which can be used to dry the feedstock by any method known to a person skilled in the art.

[0034] The aqueous gas effluent obtained from step a1) can be used to preheat air to enable the combustion of natural gas and / or the gas stream produced during the torrefaction process.

[0035] a2) Baking operation

[0036] The raw material pretreatment step a) may comprise a roasting operation a2), preferably roasting the dried raw material obtained from the drying operation a1).

[0037] The roasting operation a2) can be carried out in a roasting furnace, which produces a more friable raw material effluent, and therefore requires less energy to finely grind to obtain a roasted effluent. The roasting operation is advantageously carried out at a temperature of 220 to 350° C., preferably 250 to 320° C. and more preferably 270 to 300° C. for a time of 5 to 180 minutes and preferably 15 to 60 minutes, and the absolute operating pressure is preferably 0.01 to 1.5 MPa, preferably 0.01 to 1.0 MPa and more preferably 0.05 to 0.15 MPa. The roasting operation is carried out in an environment in which the oxygen content is advantageously less than 10% by volume, preferably less than 8% by volume and preferably less than 3% by volume.

[0038] The torrefaction operation has the advantage of reducing the energy costs of the grinding operation a3) and is accompanied by a solid loss of 5% to 40% by mass, preferably 10% to 35% by mass. However, this solid loss is accompanied by a much more limited loss of calorific value, of the order of 5% to 20%. In this respect, the torrefaction operation makes it possible to increase the energy content per unit volume of the biomass.

[0039] a3) Grinding operation

[0040] The raw material pretreatment step a) may comprise a grinding operation a3), preferably of the roasting effluent obtained from operation a2).

[0041] The grinding operation a3) can be carried out under conditions that allow the raw material particles to be reduced to a size suitable for processing in the gasification unit as an entrained stream (step c). At the end of the grinding operation a3), 90% of the raw material particles preferably have an equivalent diameter of less than 300 microns and 90% of the raw material particles preferably have an equivalent diameter greater than 1 micron; preferably, 90% of the raw material particles have an equivalent diameter of less than 200 microns and 90% of the raw material particles have an equivalent diameter greater than 5 microns; and more preferably, 90% of the raw material particles have an equivalent diameter of less than 100 microns and 90% of the raw material particles have an equivalent diameter greater than 10 microns. The equivalent diameter (expressed as d e ) For example, according to the following relationship definition:

[0042] Where V is the volume of the particle,

[0043] S is the surface area of ​​a sphere with the same volume as the particle.

[0044] In a particular embodiment, the grinding step a3) can be carried out in the presence of a second biomass or fossil raw material, so that the grinding is carried out simultaneously in the same mill. When the second raw material is a fossil-based raw material, it can be selected from solid fossil hydrocarbons such as coal and petroleum coke. When the second raw material is biomass, it can be selected from biomass raw materials as defined above. An advantage of grinding in the presence of a second raw material is that it allows efficient grinding and drying of the second raw material.

[0045] Preferably, the grinding step a3) can be carried out in the presence of additional compounds useful for the subsequent gasification step; said compounds are chosen from vitrified ash, sand, limestone, lime or other compounds known to those skilled in the art, alone or as a mixture.

[0046] Preferably, the mill is chosen so as to optimize the pneumatic conveying of the powder obtained at the end of step a3) by minimizing the minimum fluidization velocity (MFS) and its inherent energy consumption.

[0047] Preferably, the co-grinding step a3) is carried out in a mill such as a roller mill, a universal mill, an attritor or any other type of mill known to a person skilled in the art.

[0048] Electrolysis step b)

[0049] The process according to the invention comprises a step of electrolysing water into oxygen and hydrogen for producing a hydrogen stream and an oxygen stream, wherein the water is at least partly, and preferably entirely, obtained from the Fischer-Tropsch synthesis step e).

[0050] The oxygen obtained at the end of step b) is fed partly or completely to the gasification step c). Advantageously, the oxygen produced by electrolysis has a purity of at least 98.5% by weight (on a dry basis). Impurities that may be present in the oxygen produced are water and / or hydrogen.

[0051] According to the invention, all or part of the hydrogen obtained at the end of electrolysis step b) is fed to the Fischer-Tropsch synthesis step e).

[0052] Advantageously, the hydrogen obtained at the end of the electrolysis step b) is fed to the Fischer-Tropsch synthesis step e) with a purity of at least 99.8% by weight (on a dry basis). Preferably, the hydrogen fed to step e) contains less than 100 ppm of oxygen and / or water, preferably less than 60 ppm, preferably less than 40 ppm, preferably less than 30 ppm and preferably less than 15 ppm.

[0053] Preferably, all of the hydrogen produced in electrolysis step b) is introduced into the Fischer-Tropsch synthesis step e).

[0054] Advantageously, the molar ratio between hydrogen and carbon monoxide (expressed as H 2 / CO) is from 0.5 to 4, preferably from 1 to 3, more preferably from 1.5 to 2.5 and very preferably equal to 2, wherein the hydrogen originates from step d) of conditioning the synthesis gas and step b) of water electrolysis.

[0055] The electrolysis step b) can be carried out by any means known to the person skilled in the art, for example by alkaline electrolysis, by proton exchange membranes, by anion exchange membranes or by solid oxide electrolysis.

[0056] One advantage of the water electrolysis step b) is the production of dehydrogenation, making it possible to obtain fuels with reduced greenhouse gas emissions in compliance with the European Red II Directive.

[0057] Another advantage associated with recycling the water obtained from the Fischer-Tropsch synthesis step e) to the electrolysis step b) is the reduction of the water consumption of the process and, therefore, the operating costs.

[0058] Another advantage associated with the electrolysis step b) is that the oxygen produced is used in the process in the gasification step c), which makes it possible to limit and even dispense with the use of an air separation unit, thus limiting the investment and operating costs of the process. In addition, the excess oxygen can be advantageously used for SRU / TGTU (sulfur recovery unit / tail gas treatment unit) tail gas treatment and / or for the oxygen-enriched combustion of the combustible gases and residual gases of the unit and / or for the combustion of torrefaction gases.

[0059] Gasification step c)

[0060] The process according to the invention comprises a gasification step c) of the feedstock pretreated in step a), said step c) being carried out in the presence of all or part of the oxygen obtained from the water electrolysis step b), and preferably in the presence of all the oxygen obtained from the water electrolysis step b). Thus, the gasification step c) allows the production of a gaseous effluent comprising synthesis gas.

[0061] The gasification step involves a partial oxidation reaction which converts the feedstock into a synthesis gas comprising mainly carbon monoxide and hydrogen. The gasification step is advantageously carried out in the presence of a controlled amount of oxygen in the form of an oxygen stream obtained from the electrolysis step b), said oxygen stream having a purity of at least 98.5% by weight (on a dry basis). The use of said oxygen makes it possible to limit the amount of inert compounds, such as the amount of nitrogen in the case of using air as the oxygen source, which makes it possible to limit the accumulation of inert substances and therefore the problems associated with velocity or pressure losses and therefore to reduce the size of the equipment used, making it possible to further limit the investment and operating costs of the process.

[0062] Advantageously, the gaseous effluent corresponding to the synthesis gas obtained from the gasification step c) consists mainly of water (H 2 O), carbon monoxide (CO), hydrogen (H 2 ) and carbon dioxide (CO 2 ) and may contain impurities originally derived from a biomass fraction and / or from a fraction derived from another feedstock, in particular a hydrocarbon feedstock.

[0063] According to the invention, the oxygen used in the gasification step is obtained wholly or partly from the water electrolysis step b).

[0064] Advantageously, in addition to the oxygen stream derived from the water electrolysis step b), an oxygen stream originating from the air separation step can also be used in the gasification step c).

[0065] In a particular embodiment, all oxygen introduced into the gasification step c) is obtained from the water electrolysis step b).

[0066] Step c) of gasification of the raw material is carried out in a gasifier of fixed bed or fluidized bed type, or preferably in a cooled-wall entrained flow gasifier, at high temperature, i.e. at a temperature of 800 to 1800° C., preferably 1000 to 1600° C., and more preferably 1200 to 1500° C., and at an absolute pressure advantageously of 2 to 12 MPa, preferably 2.5 to 6.0 MPa, and more preferably 3.0 to 5.0 MPa. The high temperature makes it possible to obtain a high degree of carbon conversion and thus reduce the amount of unconverted carbon in the ash produced and therefore reduce the amount of ash recycled to the gasifier.

[0067] The entrained-flow gasifier is preferably a gasifier known to those skilled in the art as a cooled-wall entrained-flow gasifier. The cooled wall defines a gasification chamber which is itself located in the gasifier. The water used to cool the walls of the gasification chamber circulates in coils placed outside the walls of the gasification chamber. The water is partially evaporated, thereby generating a medium-pressure stream of steam. This cooling of the wall allows a protective ash layer to be formed on the inner wall of the gasification chamber. In particular, the raw materials introduced into the gasifier contain inorganic compounds that form ash after gasification. At the gasification temperature, this liquid ash in the form of droplets solidifies when it encounters the cooled wall and forms a solid layer that acts as an insulator. Therefore, the thermal protection of the gasification chamber wall is first provided by the solidified ash layer, and secondly by the layer of molten ash (flowing to the bottom of the gasifier) ​​in contact with the gas phase. Therefore, the combustion chamber wall is very resistant to high temperatures and resistant to high temperature changes. In addition, due to its composition, especially its high content of alkaline compounds, the ash derived from biomass is corrosive to the refractory lining. Therefore, gasification technologies that use internal refractory materials to protect the walls are difficult to operate because they deteriorate rapidly, requiring frequent renewal. In addition, refractory materials are highly sensitive to thermal shocks, which destroy the protective layer by cracking.

[0068] In a cooled wall entrained flow gasifier, at least two burners, and preferably four or more burners, are placed in the gasification chamber, the walls of which are cooled and which function at a temperature sufficient to allow the ash contained in the feedstock to melt. In addition, the feedstock introduced into the gasifier may have very different properties. For example, the lower heating value (LCP) of biomass is lower than that of petroleum coke, the ash content of biomass may be much lower than that of coal, and the melting point of ash may vary greatly from one biomass to another. Therefore, the melting point of ash may vary depending on the composition of the feedstock introduced into the gasification chamber. Similarly, the minimum gasification temperature may be adjusted to be above the melting point of ash by changing the characteristics of the feedstock with different properties and the proportions of the various components (other biomass, other hydrocarbon feedstocks, etc.) and / or by injecting a flux (e.g. lime) together with the feedstock.

[0069] In a preferred variant of the invention, the synthesis gas produced in the gasification chamber comes out of the gasification chamber in a co-currentwise manner with the liquid ash flowing to the bottom of the gasifier. This co-current configuration has the advantage of avoiding the risk of liquid ash clogging the discharge pipe relative to a configuration in which the synthesis gas is discharged from the gasification chamber to the top while the liquid ash flows to the bottom. In particular, depending on its viscosity, the liquid ash flowing only in the pipe may flow with difficulty and / or become partially solidified, partially or completely block the discharge pipe and cause the facility to be interrupted for maintenance. These phenomena may occur in particular during transient phases of temperature increase or decrease or during adjustment processes associated with changing the properties of the raw materials. The configuration according to the invention has the advantage that the flow of gas from the gasification chamber in the discharge pipe in a co-current manner with the liquid ash promotes the flow of this ash to the bottom of the gasifier and prevents the risk of clogging (even in transient phases).

[0070] In a preferred variant of the invention, the synthesis gas and liquid ash enter an intense liquid quenching zone in contact with at least one water film, as described in patent application DE 102007044726. The quenching zone is located below the gasification chamber and is divided into a hot drying zone at the top and a cooler more humid zone at the bottom. The hot drying zone located below the gasification chamber is characterized by the presence of synthesis gas and liquid ash flowing to the bottom of the gasifier. The cooler and more humid part is located below the hot drying zone and is characterized by the presence of water-saturated synthesis gas, solidified ash and liquid water. The temperature of the synthesis gas at the outlet of the cool and humid zone corresponds to the thermodynamic equilibrium temperature between the gas phase and the liquid phase at the operating pressure of the gasifier.

[0071] This configuration with quenching allows the removal of fine, sticky ash particles carried over during the scrubbing of the syngas, thereby reducing the risk of blockages in downstream pipes and units. In addition, the high temperature in the gasification chamber allows the molten ash to flow easily to the bottom on the walls of the gasification chamber before falling into the quenching zone. After entering the cold and wet unit, the cooled ash stops at the bottom of the water-filled gasifier. After contact with water, the molten ash is immediately cooled and vitrified into dense particles. These particles are then extracted from the gasifier in the form of a mixture (or slurry) of water and solid ash by decompression. Most of the mineral compounds contained in the raw materials form molten ash. This configuration advantageously makes it possible to encapsulate dangerous products such as heavy metals in the vitrified ash. The vitrification process makes this ash very stable and it is non-leachy.

[0072] In an alternative variant of the invention, the prepared synthesis gas leaves the gasification chamber via the top, while the molten ash flows countercurrently along the wall relative to the synthesis gas to the bottom of the gasifier filled with water. After contact with water, the molten ash immediately solidifies to form small-sized particles. These particles are then extracted from the gasifier in the form of a slurry (a mixture of water and solid ash) by decompression. Since most of the mineral compounds contained in the raw materials form molten ash, this configuration advantageously makes it possible to encapsulate hazardous products such as heavy metals in vitrified ash. The vitrification process makes this ash very stable and it is not leached. The synthesis gas leaving the gasification chamber via the top and the finest molten ash particles it carries are cooled by a stream of cooled synthesis gas without solid particles. This cooling makes it possible to solidify the molten ash into non-sticky solid particles. After this first step of preliminary cooling, the synthesis gas is sent to a heat exchanger to produce steam. In order to remove fine solid particles, the synthesis gas is then passed through a section for separating the gas phase and the solid phase, and the separation uses any technology known to those skilled in the art, such as a cartridge filter. A portion of this cooled particulate-free syngas is recycled to the gasifier outlet to cool the syngas exiting the top of the gasifier.

[0073] Optional step d) of conditioning the synthesis gas

[0074] The method according to the invention may comprise a step d) of conditioning the synthesis gas obtained from the gasification step c). The synthesis gas obtained from the gasification step c) consists mainly of carbon monoxide (CO), hydrogen (H 2 ), carbon dioxide (CO 2 ) and water (H 2 O) composition, and may contain impurities originally derived from the biomass fraction and / or from a fraction of another raw material, especially a hydrocarbon feedstock. These impurities are essentially metals, in particular alkali metals (Na, K), sulfur compounds, and chlorine-containing compounds and nitrogen-containing compounds. In particular, the content of halogenated compounds originally present in the feedstock according to the invention in the crude hydrocarbon feedstock fraction (before drying) can reach at least 250 ppm by mass, and in the case of the crude biomass fraction (before drying) is at least 10000 ppm by mass.

[0075] Preferably, step d) includes steps d1) and / or d2) and / or d3) and / or d4) and / or d5) and / or d6) and / or d7) and / or d8), and preferably consists of steps d1) and / or d2) and / or d3) and / or d4) and / or d5) and / or d6) and / or d7) and / or d8).

[0076] Step d1) of washing with water and fractionation of the synthesis gas

[0077] Preferably, step d) comprises steps d1) of washing with water and fractionation of the synthesis gas.

[0078] Thus, the synthesis gas obtained from the gasification step c) is advantageously subjected to a step d1) of scrubbing with water to remove traces of solids and a portion of the water-soluble gaseous compounds present in the synthesis gas. This operation can be carried out via any type of technology known to a person skilled in the art, including Venturi effect water scrubbers or Venturi scrubbers, scrubbing towers with all types of inserts, etc.

[0079] Preferably, at the outlet of the water washing step, the synthesis gas is subjected to a step of fractionation into at least two effluents, the at least two effluents being a first part and an additional part, which are subjected to the following steps:

[0080] -) a step d2 of removing halogenated compounds by passing said first portion through at least one suitable guard bed;

[0081] - an optional step d3) of subjecting the effluent obtained from step d2) to steam reforming of carbon monoxide;

[0082] - catalytic hydrolysis of the compounds COS and HCN contained in the additional part of the effluent obtained from step d1) into H 2 S and NH 3 Step d4).

[0083] In another embodiment, the effluent obtained from step d3) is advantageously recombined with an additional portion of the effluent obtained from step d1) before being treated in step d4) of the catalytic hydrolysis of compounds COS and HCN.

[0084] Thus, the "first part" and the "additional part" of the effluent obtained from step d1) of washing with water and fractionation of the synthesis gas are subjected to separate treatment steps. The first part is subjected to step d2) of removing halogenated compounds; while the additional part is subjected to catalytic hydrolysis of the compounds COS and HCN to H 2 S and NH 3 Step d4). The fractionation of the synthesis gas and the separate and different treatment of the effluents make it possible to reduce the size of the units and the amount of catalyst used in said units.

[0085] Preferably, the respective proportions of said first part and said additional part of the effluent obtained from step d1) are advantageously determined so as to obtain at the outlet of step d7) an effluent which is fed to a Fischer-Tropsch step e), wherein H 2 The CO / CO molar ratio is advantageously between 0.5 and 4, preferably between 1 and 3, more preferably between 1.5 and 2.5, and is preferably equal to 2.

[0086] Step d2) of removing halogenated compounds

[0087] Preferably, step d) comprises a step d2) of removing halogenated compounds.

[0088] Step d2 of removing halogenated compounds on at least one suitable guard bed is advantageously carried out on the first part of the effluent obtained from step d1). Step d2) allows the halogenated compounds (advantageously chlorine) contained in the first part of the effluent to be substantially removed before the first part of the effluent is sent to the carbon monoxide steam reforming unit (step d3). Fixed bed reactor technology will advantageously facilitate the absorption of halogenated compounds (especially chlorine) contained in the first part of the synthesis gas with the help of absorption substances known to those skilled in the art. Advantageously, step d2 is carried out on at least one guard bed in the presence of an absorption substance containing a zeolite-type active phase and / or a zinc oxide active phase and / or an alkaline oxide (such as aluminum oxide) active phase). The active phase can be doped or promoted with one or more compounds of alkali metals and / or alkaline earth metals and / or rare earth metal elements. The active phase can be, for example, doped with a sodium compound (for example, with Na 2 O) promoted alumina.

[0089] In the context of the present invention, a first portion of the effluent obtained from step d1) is passed through at least one guard bed, making it possible to achieve the specifications required for the carbon monoxide steam reforming unit d3). At the outlet of step d2) for removing halogenated compounds, the effluent generally contains less than 10 ppm by volume of chlorine, advantageously less than 5 ppm by volume of chlorine, preferably from 0.1 ppm to 5 ppm by volume of chlorine, more preferably from 1 ppm to 3 ppm by volume of chlorine, and even more preferably from 1 ppm to 2 ppm by volume of chlorine.

[0090] Step d3) of steam reforming of carbon monoxide

[0091] Step d) of conditioning of the synthesis gas optionally comprises a step of steam reforming of the carbon monoxide.

[0092] Step c) of gasifying the feedstock according to the invention (as carried out in the present invention) may result in the production of hydrogen and carbon monoxide in a H2O2 atmosphere which is not optimal for the Fischer-Tropsch reaction. 2 The optimum H / CO molar ratio, particularly when the catalyst used is a cobalt-based catalyst, is advantageously about 2. 2 / CO molar ratio in order to orient the reaction towards the production of middle distillates.

[0093] In order to achieve the H required for Fischer-Tropsch synthesis 2 / CO molar ratio, according to the invention, the effluent obtained from step d2) of removal of halogenated compounds is optionally directed to a carbon monoxide steam reforming section d3) in order to prepare a gas stream rich in hydrogen and depleted in carbon monoxide.

[0094] When the hydrogen produced in the water electrolysis step b) does not allow the required H to be obtained at the inlet of the Fischer-Tropsch synthesis step e) 2 / CO ratio, proceed to step d3).

[0095] All or part of the hydrogen produced in the carbon monoxide steam reforming step d3) can also advantageously be fed to the Fischer-Tropsch synthesis step e).

[0096] The carbon monoxide steam reforming reaction step d3) is advantageously carried out at an inlet temperature close to the temperature of the synthesis gas obtained from the water washing and fractionation step d1), so that the energy consumption on the entire pipeline can be reduced, thereby increasing the value of the biomass. Preferably, step d3) is carried out at an inlet temperature of 150 to 280°C, preferably 200 to 280°C.

[0097] Advantageously, the carbon monoxide steam reforming reaction step d3) is carried out at an absolute pressure of 2.0 to 12 MPa, preferably 2.5 to 6.0 MPa, and more preferably 3.0 to 5.0 MPa; at an hourly space velocity HSV (volume of feedstock / volume of catalyst / hour) of 1000 to 10000 h -1 , preferably 1000 to 9000h -1 , and more preferably 1500 to 8500h -1 at a temperature of 150 to 550 ℃, preferably 200 to 500 ℃.

[0098] The catalyst used in this step d3) is a catalyst comprising at least one element from group VIII of the Mendeleev periodic table and at least one element from group VIB (group VIII corresponds to groups 8, 9 and 10 and group VIB corresponds to group 6 according to the new notation of the periodic table: Handbook of Chemistry and Physics, 81st edition, 2000-2001). Preferably, the catalyst is a catalyst comprising sulfided cobalt and / or sulfided molybdenum. The catalyst support is generally a porous solid selected from alumina, silica and silica-alumina. Preferably, the catalyst support is alumina. The catalyst used can be promoted with an alkali metal or alkaline earth metal promoter. The carbon monoxide conversion reaction makes it possible to significantly increase the hydrogen content in the effluent fed to the Fischer-Tropsch synthesis step e).

[0099] If necessary, water in liquid form, preferably in the form of steam and preferably in the form of superheated steam, can be supplied upstream of the carbon monoxide steam reforming step in order to adjust the H at the inlet of the unit for step d3). 2 O / CO ratio. Advantageously, step d3) is carried out at a H ratio of 0.5 to 100, preferably 0.5 to 25, and more preferably 1.5 to 10. 2O / CO ratio. Due to the exothermic nature of the carbon monoxide steam reforming reaction, the temperature of the gas effluent obtained from this step is between 250 and 550 ° C. The gas effluent is advantageously cooled to the operating temperature of the hydrolysis unit, which is between 100 and 400 ° C, preferably between 200 and 350 ° C. The cooling is advantageously carried out by producing steam that can be used in the process line according to the invention or for power generation.

[0100] In one variant of the process according to the invention, the H content of the gas stream entering step e) of the Fischer-Tropsch synthesis may be increased by adding an external gas stream enriched in hydrogen produced by any means known to the person skilled in the art, including water electrolysis, natural gas steam reforming followed by a pressure swing adsorption (PSA) step, or by a temperature swing adsorption (TSA) step or by membrane separation. 2 The / CO molar ratio is adjusted to its optimal level of about 2, in order to orient the reaction towards the production of middle distillates. This hydrogen-rich gas stream can be injected into any point of the pipeline downstream of the gasification step c) and makes it possible to reduce the size of the carbon monoxide steam reforming step d3).

[0101] In one variant of the process according to the invention, part of the gas obtained from the carbon monoxide steam reforming step d3) and optionally upstream or downstream of said step d3) can advantageously be sent to a unit for preparing hydrogen by any means known to a person skilled in the art, preferably by pressure swing adsorption (PSA) or by temperature swing adsorption (TSA) or by membrane separation. The prepared hydrogen is advantageously used in the hydrotreatment and / or isomerization step f).

[0102] Step d4) of catalytic hydrolysis of compounds COS and HCN

[0103] Preferably, step d) comprises a step d4) of catalytic hydrolysis of the additional portion of compounds COS and HCN obtained from step d1).

[0104] The additional portion obtained from step d1) is subjected to catalytic hydrolysis of COS and HCN to H 2 S and NH 3 The step d4) of catalytic hydrolysis of carbon oxysulfide (COS) and hydrogen cyanide (HCN) is advantageously carried out in the presence of a catalyst containing a platinum-based compound or an oxide of an element selected from titanium, zirconium, aluminum, chromium and zinc or a mixture thereof.

[0105] Preferably, the hydrolysis catalyst is a catalyst based on titanium oxide. The catalyst used may also contain at least alkali metals, alkaline earth metals and / or rare earth metals, for example obtained from precursors such as potassium hydroxide, zirconium oxide, sodium carbonate or barium carbonate, sodium or barium bicarbonate, calcium sulfate, sodium acetate or barium acetate, or sodium or barium oxalate. The hydrolysis step is advantageously carried out at a temperature of 100 to 400° C., preferably 200 to 350° C.

[0106] Advantageously, the effluent at the outlet of the hydrolysis unit of step d4) contains less than 25 ppm by volume of COS and less than 5 ppm by volume of HCN, preferably less than 10 ppm by volume of COS and less than 1 ppm by volume of HCN, and more preferably less than 5 ppm by volume of COS and less than 0.1 ppm by volume of HCN.

[0107] In one variant of the process according to the invention, the effluent obtained from the carbon monoxide steam reforming step d3) is at least partly fed as a mixture with the additional portion to a reactor for the catalytic hydrolysis of COS and HCN to H 2 S and NH 3 Advantageously, the effluent obtained from the carbon monoxide steam reforming step d3) is sent to the catalytic hydrolysis step (step d4) as a mixture with the additional part after cooling to a temperature preferably between 100 and 400° C., preferably between 200 and 350° C.

[0108] Combined with step d5)

[0109] Preferably, at least a portion, preferably all, of the effluent obtained from step d2) of removal of halogenated compounds and optionally the effluent obtained from step d3) of steam reforming of carbon monoxide is recombined in step d5) with at least a portion of the effluent obtained from step d4) of catalytic hydrolysis before being sent to the water washing step d6).

[0110] Step d6) of washing and recombining the effluent with water

[0111] Preferably, step d) comprises a step d6) of washing the mixed effluent obtained at the end of steps d2) and d4) with water. Step d6) makes it possible to remove water-soluble impurities such as NH 3 and HCl, these impurities are particularly harmful to the operation of removing acid gases in step d7).

[0112] In one variant of the process according to the invention, the mixed effluent obtained at the end of steps d2) and d4) may be subjected to a step of removing heavy metals in advance on at least one suitable guard bed. The removal step makes it possible to substantially remove heavy metals, such as lead, arsenic and mercury, before treating the effluent in a step d6) of washing with water, and more particularly before a step d7) of removing acidic gases. With the aid of absorbents known to those skilled in the art, fixed bed reactor technology will advantageously facilitate the absorption of heavy metals contained in the synthesis gas. Advantageously, the removal step is carried out on at least one or more guard beds in the presence of one or more absorbents containing one or more active phases. Advantageously, the active phase contains at least one sulfur compound, such as elemental sulfur loaded, and / or metal sulfides such as copper sulfide and / or zinc sulfide, and at least one noble metal such as silver, gold or palladium, and / or a silver-exchanged zeolite, and / or a transition metal oxide such as copper oxide or nickel oxide. Advantageously, the (one or more) active phases are supported on, for example, alumina, silica, silica-alumina or activated carbon.

[0113] Advantageously, passing the effluent through at least one guard bed of the removal step makes it possible to reach the specifications required at the inlet of step d7) for the removal of acid gases (step d7) and of the Fischer-Tropsch synthesis unit of step e).

[0114] In a second variant according to the invention, the step of removing heavy metals is carried out between step d6) of washing with water and step d7) of removing acid gases.

[0115] In a third variant according to the invention, the step of removing heavy metals is carried out after step d7) of removing acidic gases, when the solvent used in step d6) is a chemical solvent derived from alkanolamines, which, as known to those skilled in the art, is less sensitive to the presence of heavy metals than physical solvents.

[0116] At the outlet of the heavy metal removal step, the content of lead, arsenic and mercury in the effluent is generally less than 1 ppb by volume, preferably less than 0.5 ppb by volume, more preferably less than 0.1 ppb by volume, and even more preferably less than 0.01 ppb by volume.

[0117] Acid gas removal step d7)

[0118] Preferably, step d) may also advantageously include a step d7) of removing acid gases. Step d7) is dedicated to removing residual acid gases, such as sulfur compounds (H 2 S) or CO 2 .

[0119] The step d7) advantageously comprises the CO in the synthesis gas obtained in step d6) 2 The content is greater than 5% by weight, preferably greater than 10% by weight and preferably greater than 20% by weight relative to the weight of the effluent.

[0120] Step d7) is carried out by using a chemical or physical solvent or a mixture of a chemical and physical solvent or any other method known to those skilled in the art. The chemical solvent can be, for example, a primary amine, a secondary amine or a tertiary amine derived from an alkanolamine such as monoethanolamine (MEA), diethanolamine (DEA) or methyldiethanolamine (MDEA). The physical solvent can be, for example, a mixture based on polyethylene glycol (PEG) dialkyl ethers, such as PEG diethyl ether or dibutyl ether, or methanol.

[0121] The step of removing the acid gases is carried out, for example, using a tower for absorbing the acid gases, with the aid of a chemical or physical solvent used, followed by a solvent regeneration step to reduce the solvent consumption in the unit. This regeneration step can advantageously be carried out in two steps, so as to first remove the CO-rich 2 The gas stream, and secondly the removal of H-rich 2 In one variant of the process according to the invention, the CO-rich 2 The gas stream H 2 S and is advantageously recycled into the gasification step c).

[0122] Final purification step d8)

[0123] Preferably, step d) comprises a final purification step d8). In particular, the cobalt-based catalyst used in the Fischer-Tropsch synthesis step e) is highly sensitive to the presence of impurities in the synthesis gas (which in this respect only tolerates impurities in amounts of the order of ppb (parts per billion)). At the outlet of step d7), the synthesis gas may still contain about 100 ppb by volume of H 2 S and COS.

[0124] Advantageously, the final purification step d8) is carried out on at least one guard bed and can be carried out in order to completely adsorb the last traces of impurities remaining in the synthesis gas, such as halogenated compounds, H 2 S, COS, HCN and NH 3 The final purification step d8) is carried out by any means known to the person skilled in the art, for example over at least one guard bed based on zinc oxide ZnO, Cu / ZnO or activated carbon, and makes it possible to achieve the required specifications in terms of impurities in the synthesis gas used in the Fischer-Tropsch synthesis step e).

[0125] Advantageously, at the outlet of step d8), the synthesis gas has a sulfur content of less than 100 ppb by volume, preferably less than 50 ppb by volume, more preferably less than 10 ppb by volume; an HCN content of less than 100 ppb by volume, preferably less than 50 ppb by volume, more preferably less than 10 ppb by volume, and an NH 3 The content is less than 100 ppm by volume, preferably less than 10 ppm by volume, and more preferably less than 1 ppm by volume.

[0126] Preferably, step d) includes steps d1) and / or d2) and / or d3) and / or d4) and / or d5) and / or d6) and / or d7) and / or d8), and preferably consists of steps d1) and / or d2) and / or d3) and / or d4) and / or d5) and / or d6) and / or d7) and / or d8).

[0127] Fischer-Tropsch synthesis catalytic reaction step e)

[0128] The process according to the invention comprises a step e) of subjecting the effluent from the gasification step c) and optionally from the step d) of conditioning the gaseous effluent comprising synthesis gas, and preferably from the final purification step d8), to a Fischer-Tropsch synthesis, said effluent comprising carbon monoxide (CO) and hydrogen, in the presence of all or part of the hydrogen obtained from the water electrolysis step b) at an H concentration optimal for the Fischer-Tropsch reaction. 2 The Fischer-Tropsch synthesis step e) is introduced in a molar ratio of 1:1 to 1:1 in order to produce a stream comprising synthetic liquid hydrocarbons and at least one gaseous effluent.

[0129] Advantageously, the molar ratio of carbon monoxide to hydrogen (expressed as H 2 / CO) is from 0.5 to 4, preferably from 1 to 3, more preferably from 1.5 to 2.5 and very preferably equal to 2, wherein the hydrogen originates from step d) of conditioning the synthesis gas and step b) of water electrolysis.

[0130] Step c) of gasifying the feedstock according to the invention (as carried out in the present invention) may result in the production of hydrogen and carbon monoxide in a H2O2 atmosphere which is not optimal for the Fischer-Tropsch reaction. 2 The optimum H / CO molar ratio, particularly when the catalyst used is a cobalt-based catalyst, is advantageously about 2. 2 / CO molar ratio in order to orient the reaction towards the production of middle distillates.

[0131] Advantageously, all the hydrogen obtained from the electrolysis step b) is used in the Fischer-Tropsch synthesis step e). Optionally, the supply of hydrogen may be necessary to obtain an optimal H for the Fischer-Tropsch reaction. 2 / CO molar ratio. In this case, the supply can be obtained from the optional carbon monoxide steam reforming step d3).

[0132] Advantageously, the optional carbon monoxide steam reforming step d3) may be carried out at an absolute pressure of 2 to 12 MPa, preferably 2.5 to 6.0 MPa, and more preferably 3.0 to 5.0 MPa; at an hourly space velocity HSV (volume of feedstock / volume of catalyst / hour) of 1000 to 10000 h -1 , preferably 1000 to 9000h -1 , and more preferably 1500 to 8500h -1 ; At a temperature of 150 to 550°C, preferably 200 to 550°C, and more preferably 250 to 500°C.

[0133] The catalyst used in the carbon monoxide steam reforming step is a catalyst comprising at least one element from Group VIII of the Mendeleev Periodic Table and / or at least one element from Group VIB (according to the Periodic Table: Handbook of Chemistry and Physics, 81st edition, Group VIII corresponds to Groups 8, 9 and 10 and Group VIB corresponds to Group 6 in the new notation of 2000-2001). Preferably, the catalyst is a catalyst comprising sulfided cobalt and / or sulfided molybdenum. The catalyst carrier is typically a porous solid selected from alumina, silica and silica-alumina. Preferably, the catalyst carrier is alumina. The catalyst used can be promoted with an alkali metal or alkaline earth metal promoter. The carbon monoxide conversion reaction makes it possible to significantly increase the hydrogen content in the effluent fed to the Fischer-Tropsch synthesis step e).

[0134] Advantageously, part or all of the water formed during the Fischer-Tropsch synthesis step e) is fed to the electrolysis step b). Recycling the water formed in step e) to step b) makes it possible to reduce the operating costs of the process according to the invention.

[0135] In one embodiment, the water formed during the Fischer-Tropsch synthesis step e) is advantageously subjected to a treatment step before being recycled to the water electrolysis step b) in order to obtain the specifications required for step b). The treatment step may advantageously comprise removing oxygenates from the water formed during step e).

[0136] The Fischer-Tropsch synthesis step e) is carried out in a reaction unit comprising one or more suitable reactors, the technology of which is known to those skilled in the art. They can be, for example, multi-tubular fixed bed reactors, or bubble column reactors (also known as slurry bubble columns), or microchannel reactors.

[0137] According to a preferred embodiment of the invention, step e) involves one or more bubble column reactors. Since the synthesis is highly exothermic, this embodiment makes it possible, inter alia, to improve the thermal control of the reactors with only minor pressure losses.

[0138] The catalyst used in this Fischer-Tropsch synthesis step e) is generally any catalytic solid known to the person skilled in the art for carrying out the Fischer-Tropsch synthesis. Preferably, the catalyst used in said step comprises cobalt or iron, more preferably cobalt. The catalyst used in step e) is generally a supported catalyst. The support may for example be based on alumina, silica or titania.

[0139] Temperature and pressure conditions are variable and are adjusted according to the catalyst used in step e). The absolute pressure is generally 1.0 to 6.0 MPa, preferably 1.5 to 3.5 MPa, and preferably 2.0 to 3.0 MPa. The temperature may generally be 170 to 280° C., preferably 190 to 260° C., and preferably 210 to 240° C.

[0140] According to one variant of the process according to the invention, at least one gas fraction obtained from the Fischer-Tropsch synthesis (step e) is advantageously recycled to the gasification step c) in order to be converted into synthesis gas and thus to improve the mass yield of the process line.

[0141] In another configuration of the process according to the invention, at least part of the gaseous fraction obtained from the Fischer-Tropsch synthesis e) is advantageously sent to a separate unit for preparing synthesis gas (for example POx: partial oxidation, SMR: steam methane reforming, ATR: autothermal reforming, EHTR: enhanced heat transfer reformer, etc.); this synthesis gas can be recycled to any point in the pipeline upstream of the gasification step c) and the hydrotreatment and / or isomerization step f).

[0142] In another configuration of the process according to the invention, at least part of the gas fraction obtained from the Fischer-Tropsch synthesis step e) can at least partially supply energy for the drying operation a1) and / or the torrefaction operation a2) in order to maximize the energy efficiency of the process line.

[0143] In another configuration of the process according to the invention, the gas fraction obtained from step e) of the Fischer-Tropsch synthesis makes it possible to generate electricity in a combined cycle, which electricity can be supplied partly together with the steam produced in steps c), d3) and e) in order to improve the energetic efficiency of the process line.

[0144] These different configurations may be advantageously combined in order to optimize the economic benefits of the integrated process line according to the invention.

[0145] Hydrotreatment and / or isomerization step f)

[0146] The process of the invention advantageously comprises a step f) of hydrotreating and / or isomerizing at least part of, and preferably all of, the stream comprising liquid hydrocarbons obtained from step e) of the Fischer-Tropsch synthesis.

[0147] Step f) is carried out in the presence of hydrogen under customary operating conditions known to those skilled in the art and is intended to increase the value of the hydrocarbon fraction obtained from step e) by producing liquid hydrocarbons, in particular very high quality liquid biofuels, namely bio-naphtha, bio-gasoline, bio-kerosene, bio-gas oil and bio-lubricant bases.

[0148] The hydrogen required to carry out step f) can advantageously be obtained in whole or in part from the water electrolysis step b).

[0149] One possible option is to prepare paraffin fractions, ie base products for petrochemical processes, for example to prepare C10-C13 fractions aimed at producing (bio)LAB (linear alkylbenzenes), or (bio)waxes for various industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS BRIEF DESCRIPTION OF THE DRAWINGS

[0151] Figure 1 The process according to the invention is shown according to claim 1 and comprises a step of isomerizing the effluent obtained from the process according to the invention.

[0152] The biomass is introduced via line 1 into a pretreatment unit (A) where it undergoes a drying step a1), a torrefaction step a2) and / or a grinding step a3).

[0153] The pretreated biomass is fed via line 2 to the gasification step in unit (C) as a mixture with the oxygen 11 produced during the water 10 electrolysis step taking place in the water electrolysis unit (B).

[0154] The water used in electrolysis unit (B) comes at least partly from the Fischer-Tropsch synthesis step carried out in unit (E).

[0155] During the water electrolysis step, a hydrogen stream is produced and sent via line 8 to the Fischer-Tropsch synthesis step upstream of unit (E).

[0156] The gasification step of the pretreated biomass taking place in unit (C) in the presence of oxygen 11 obtained from the water electrolysis step makes it possible to produce a gaseous effluent containing synthesis gas, which leaves the gasification unit (C) via conduit 3 and is sent to an optional step d) for conditioning the effluent containing synthesis gas, which step may include a step d1) of washing and fractionating the synthesis gas with water and / or a step d2) of removing halogenated compounds and / or a step d3) of steam reforming of carbon monoxide and / or a step d4) of catalytic hydrolysis of compounds COS and HCN and / or a step d5) of recombination of the effluent and / or a step d6) of washing the recombined effluent with water and / or a step d7) of removing acid gases and / or a step d8) of final purification of the effluent containing synthesis gas.

[0157] The effluent comprising the optionally purified synthesis gas is then sent via conduit 5 to a Fischer-Tropsch synthesis step, which is carried out in the presence of at least part of the hydrogen stream 8 produced during the water electrolysis step in unit (E). During the Fischer-Tropsch synthesis step a stream 6 comprising synthetic liquid hydrocarbons is produced and can be sent to a hydrotreatment and / or isomerization step f) not shown in the figure.

[0158] Figure 2 The method according to Comparative Example 1 is shown. A description of the method is given in Example 1. Example

[0159] Example 1 (Comparative)

[0160] Example 1 reproduces the method described in patent application WO 2014 / 058253, which comprises the following steps:

[0161] A step of pre-treating by baking;

[0162] an air separation step to produce an oxygen stream;

[0163] The step of entrained-bed gasification;

[0164] a step of steam reforming of carbon monoxide;

[0165] Acid gas removal and final purification steps;

[0166] Steps of the Fischer-Tropsch synthesis.

[0167] The process according to Example 1 is comparable since it does not involve a water electrolysis step. Figure 2 The method carried out in Comparative Example 1 is shown.

[0168] Example 1 Processing of 100 t / h of dry biomass introduced into the pretreatment step via line 1. The torrefied lignocellulosic biomass at the outlet of the pretreatment unit A via line 2 contained 50% by weight of carbon and 40% of oxygen.

[0169] The torrefied biomass 2 is then introduced into a gasification unit C in the presence of an oxygen stream 7 produced in the air separation unit (B).

[0170] The CO produced by the gasification unit (on a molar basis) is CO 2 3 times, that is, 67.4t / h. The H at the outlet of the gasification unit 2 The / CO ratio is 0.5.

[0171] At the outlet of the gasification unit C, an effluent comprising synthesis gas 3 is produced and is sent to the carbon monoxide steam reforming unit D. The carbon monoxide steam reforming unit makes it possible to increase this ratio from 0.5 to 2.

[0172] The effluent 4 leaving the carbon monoxide steam reforming unit is subsequently sent to a unit (D′) comprising a step of removing acid gases from the effluent comprising synthesis gas and a step of final purification of said effluent.

[0173] The effluent comprising the purified synthesis gas 5 is then fed to a Fischer-Tropsch synthesis unit E to produce a stream comprising liquid hydrocarbons 6 .

[0174] Below are the steps of the method leading to a reduction in carbon yield:

[0175] 23% carbon loss during the roasting step;

[0176] A further 19% carbon loss occurs during the gasification step;

[0177] A further 29% of carbon is lost in the carbon monoxide steam reforming step.

[0178] Carbon loss is calculated according to the following formula: (C inlet - C outlet) / C inlet*100

[0179] The total carbon yield of the pipeline is therefore 29% by weight, ie the total material yield is 17% by weight.

[0180] The total carbon yield was calculated according to the following formula: (C biomass - C effluent FT) / C biomass * 100.

[0181] The material yield was calculated according to the following formula: (Qbiomass-QeffluentFT) / Qbiomass*100, where Q is the flow rate.

[0182] CO 2 It is mainly produced through the following two steps:

[0183] The gasification step is expressed as 35.3t / h,

[0184] The flow rate of the carbon monoxide steam reforming step is 88.2 t / h.

[0185] These emissions do not take into account CO2 emissions from utility production processes. 2 .

[0186] The amount of oxygen required to provide energy to the gasification step is 46 t / h.

[0187] The Fischer-Tropsch synthesis step makes it possible to produce a synthetic liquid hydrocarbon effluent represented by 17 t / h.

[0188] Example 2 (according to the present invention)

[0189] Example 2 reproduces Figure 1 The method according to the present invention is shown in and comprises the following steps:

[0190] Step a) of pre-treatment by baking;

[0191] Step b) of electrolysis of alkaline water;

[0192] Step c) of entrained-bed gasification;

[0193] step d) of conditioning the synthesis gas;

[0194] Step e) of the Fischer-Tropsch synthesis.

[0195] The method of Example 2 according to the present invention differs from the method of Example 1 in that it involves a water electrolysis step instead of a carbon monoxide steam reforming step.

[0196] 100 t / h of dry biomass are processed in a torrefaction unit (A) via line 1. The torrefied lignocellulosic biomass 2 contains 50% by weight of carbon and 40% of oxygen.

[0197] The torrefied biomass is then fed to a gasification unit C in the presence of an oxygen stream 11 produced in a water 10 electrolysis unit (B).

[0198] As in Example 1, the amount of CO produced by the gasification unit (on a molar basis) is CO 2 3 times of that, i.e., the amount of CO is 67.4t / h. 2 The ratio of H / CO was 0.5. In this embodiment, H 2 / CO ratio increased from 0.5 to 2.

[0199] The amount of hydrogen required is 7.2 t / h. In order to produce such a large amount of hydrogen, the electrolysis byproduct oxygen is produced in an amount of 58 t / h. This flow rate is higher than the flow rate required for the gasification step (46 t / h, see the previous example).

[0200] At the outlet of the gasification unit C an effluent comprising synthesis gas 3 is produced and sent to a synthesis gas conditioning unit D to produce a purified effluent 5 which is then sent to a Fischer-Tropsch synthesis unit E in the presence of a hydrogen stream 6 produced in the water electrolysis unit B.

[0201] The individual steps of the method leading to a reduction in carbon yield are as follows:

[0202] 23% carbon loss during the roasting step;

[0203] A further 19% of carbon is lost during the gasification step.

[0204] The total carbon yield of the pipeline is therefore 58% by weight, ie the total material yield is 34% by weight.

[0205] The Fischer-Tropsch synthesis step produces about 43 t / h of water, ie 66% of the water required for the electrolysis step, and a synthetic liquid hydrocarbon effluent representing 34 t / h.

[0206] CO released into the atmosphere 2 The amount (i.e. 35.3 t / h) is mainly derived from the gasification step. The CO emitted by this process 2 Emissions are reduced by 70% relative to the reference scenario and water consumption is reduced by 2 / 3 relative to that required by the electrolyser, significantly improving the environmental balance of the channel.

[0207] With respect to Example 1, the method according to the present invention makes it possible to:

[0208] increasing by 100% the amount of synthesized hydrocarbons obtained at the end of the Fischer-Tropsch synthesis step,

[0209] The CO 2 85% reduction in emissions,

[0210] Reduce water consumption by 2 / 3 compared to that required by the electrolyzer.

[0211] The method according to the invention thus makes it possible to significantly improve the environmental balance of the channel and to limit the operating costs of the method.

Claims

1. A method for converting a feedstock comprising at least one biomass fraction into hydrocarbons, the method comprising - step a), pre-treating the raw material, - step b) of electrolyzing water into oxygen and hydrogen for producing a hydrogen stream and an oxygen stream, wherein the water is at least partly obtained from the Fischer-Tropsch synthesis step e), - a step c) of gasifying the feedstock pretreated in step a) in the presence of all or part of the oxygen stream obtained from the water electrolysis step b) so as to obtain a gaseous effluent comprising synthesis gas, - an optional step d) of conditioning the gaseous effluent comprising synthesis gas obtained from step c) so as to obtain a gaseous effluent comprising purified synthesis gas, - step e) of subjecting the gaseous effluent obtained from step c) or optionally from step d) to Fischer-Tropsch synthesis in the presence of all or part of the hydrogen obtained from the water electrolysis step b) to produce a stream comprising synthetic liquid hydrocarbons and at least one gaseous effluent.

2. A method as claimed in claim 1, wherein the pretreatment step a) comprises at least one operation from drying a1), baking a2) or grinding a3).

3. A process as claimed in claim 1 , in which the molar ratio between hydrogen and carbon monoxide, expressed as H2 / CO, introduced into the effluent of the Fischer-Tropsch synthesis step e), is between 0.5 and 4, preferably between 1 and 3, more preferably between 1.5 and 2.5, and very preferably equal to 2, the hydrogen originating from the step d) of conditioning the synthesis gas and the step b) of water electrolysis.

4. A process as claimed in any one of the preceding claims, wherein the electrolysis step b) is carried out by alkaline electrolysis, by proton exchange membranes, by anion exchange membranes or by solid oxide electrolysis.

5. A process as claimed in any one of the preceding claims, wherein in addition to the oxygen stream derived from the water electrolysis step b), an oxygen stream originating from the air separation step can also be used in the gasification step c).

6. A process as claimed in any one of claims 1 to 5, wherein all of the oxygen introduced into the gasification step c) is obtained from the water electrolysis step b).

7. A method as claimed in any one of the preceding claims, wherein step d) comprises and preferably consists of the following steps: d1) washing and fractionation of the synthesis gas with water, and / or d2) removal of halogenated compounds, and / or d3) steam reforming of carbon monoxide, and / or d4) catalytic hydrolysis of compounds COS and HCN, and / or d5) recombination, and / or d6) washing the recombination effluent with water, and / or d7) removal of acid gases, and / or d8) final purification.

8. A process as claimed in any one of the preceding claims, wherein water formed during the Fischer-Tropsch synthesis step e) is fed partly or completely to the electrolysis step b).

9. A process as claimed in any one of the preceding claims, wherein at least part of the gas fraction obtained from the Fischer-Tropsch synthesis step e) is recycled to the gasification step c) for conversion into synthesis gas.

10. A process as claimed in any one of claims 1 to 8, wherein at least part of the gas fraction obtained from the Fischer-Tropsch synthesis step e) can at least partly supply energy for the drying operation a1) and / or the torrefaction operation a2).

11. A process as claimed in any one of the preceding claims, wherein the Fischer-Tropsch synthesis step e) is followed by a step f) of hydrotreating and / or isomerising the hydrocarbon fraction obtained from step e).

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