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

Abstract

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

Description

Technical Field

[0001] The present invention relates to the improvement of the value of biomass, typically for the production of liquid hydrocarbons, biofuels, and in some cases, petrochemical-based and / or chemical-based and / or hydrogen production.

[0002] More particularly, the present invention relates to an integrated method for converting a feedstock containing at least one biomass fraction, for the purpose of producing fractions of hydrocarbons, especially high-quality LPG (liquefied petroleum gas), naphtha, gasoline, kerosene, and gas oil, or a lubricating oil base, including a gasification step, a water electrolysis step, and a synthesis step by Fischer-Tropsch reaction.

Background Art

[0003] Most patents describe a line for the production of synthetic hydrocarbons via Fischer-Tropsch synthesis, in which the steps of hydrotreating and isomerization of hydrocarbon-based fractions obtained from this synthesis are often combined.

[0004] The patent application (Patent Document 1) includes a line for the production of biofuels from lignocellulosic biomass. The patent application describes the possible injection of hydrogen at any point in the process line. The hydrogen to be injected is generated by any means known to those skilled in the art, without particular distinction or integration between the hydrogen production process and the process of the biofuel production line.

[0005] Patent Document 2 describes a method for producing synthetic hydrocarbons, in which the adjustment of the hydrogen content is made by reforming the naphtha produced by Fischer-Tropsch synthesis at the inlet of the Fischer-Tropsch unit. The drawback of this step is that it reduces the amount of the final product produced by consuming the naphtha produced, and thus reduces the productivity of the Fischer-Tropsch synthesis step.

[0006] The patent application (Patent Document 3) describes supplying external hydrogen to adjust the H2 / CO ratio of a carbon-based feedstock, more particularly synthesis gas produced by gasification of biomass. In particular, the document describes a process that includes converting carbon monoxide with steam to make the synthesis gas produced by gasification rich in hydrogen, and adjusting the production of synthesis gas according to the amount of hydrogen by external supply of hydrogen to maintain a constant production of synthetic fuel. The reaction of converting carbon monoxide with steam is also known as the "water gas shift" reaction.

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

[0008] In the case of the present invention, the applicant proposes a novel method. This presents an optimal integration of a gasification process, a Fischer-Tropsch synthesis process and a water electrolysis process, achieving improved production yield and better economics and energy performance (energy efficiency, production cost, etc.), while at the same time enabling compliance with environmental constraints, such as the emission of greenhouse gases set at ever lower thresholds.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Means for Solving the Problems

[0010] (Brief Description of the Invention) In particular, the present invention relates to a method for converting a feedstock containing at least one biomass fraction into hydrocarbons, said method comprising the following steps: - Step a); pretreating the feedstock, - Step b); electrolyzing water into oxygen and hydrogen to produce a hydrogen stream and an oxygen stream; the water is at least partially obtained from the Fischer-Tropsch synthesis step e), - Step c); 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); obtaining a gaseous effluent containing synthesis gas, - Optional step d); conditioning the gaseous effluent containing the synthesis gas obtained from step c); obtaining a gaseous effluent containing purified synthesis gas, - Step e); performing Fischer-Tropsch synthesis on the gaseous effluent obtained from step c) or from the optional step d) in the presence of all or part of the hydrogen obtained from the water electrolysis step b); generating a stream containing synthetic liquid hydrocarbons and at least one gaseous effluent.

[0011] One advantage of the present invention is to provide a method that presents an optimal integration of the steps of gasification, Fischer-Tropsch synthesis and water electrolysis, thereby achieving improved production yields as well as better economics and energy performance (energy efficiency, production costs, etc.), while at the same time being able to comply with environmental constraints, such as the emission of greenhouse gases set at ever lower thresholds.

[0012] Another advantage of the method according to the present invention is to limit and even omit the implementation of a steam reforming step for generating hydrogen, thereby reducing the CO2 emissions of the biofuel production method, and also maximizing the amount of CO obtained from the gasification step, and thus making it possible to increase the material yield of the method and / or reduce the amount of the input feedstock.

Embodiments for Carrying Out the Invention

[0013] (Detailed Description of the Invention) The present invention relates to a method for converting a feedstock containing at least one biomass fraction into renewable hydrocarbons.

[0014] (Type of Feedstock) The biomass fraction may include any type of biomass, preferably solid-type biomass, particularly lignocellulosic-type biomass. Non-limiting examples of the type of biomass relate to, for example, agricultural residues (especially straw, corn husks), forestry management residues, forestry management products, wood mill residues and dedicated crops, for example, short-rotation coppice.

[0015] The feedstock to be converted in the method according to the present invention may also include at least a part of another feedstock, preferably at least a part of a gaseous, solid and / or liquid hydrocarbon-based feedstock ("co-processing"). The hydrocarbon-based feedstock fraction is, in the context of the present invention, at least coal, petroleum coke, natural gas, petroleum residues, crude oil, atmospheric residue, deasphalted oil, deasphalted asphalt, derivatives of oil conversion processes (for example, HCO / FCC slurry, coking heavy GO / VGO, bis-breaking or residues of similar thermal processes, etc.), bituminous sands or their derivatives, shale gas and oil shale or their derivatives, liquid biomass (for example, rapeseed oil, palm oil, pyrolysis oil, etc.), or a biomass slurry (corresponding to a mixture of a solid hydrocarbon-based feedstock and a liquid biomass) which may advantageously contain a feedstock fraction. According to the method of the present invention, the hydrocarbon-based feedstock fraction may be a gaseous, solid or liquid hydrocarbon-based feedstock fraction or a mixture thereof.

[0016] The feedstock for the method according to the present invention may therefore be a feedstock containing at least one solid biomass fraction and, optionally, at least a part of another gaseous, solid or liquid feedstock, either alone or as a mixture.

[0017] Generally, the feedstock used in the method of the present invention contains at least 20%, preferably at least 50%, preferably at least 70%, more preferably at least 90% of the biomass fraction.

[0018] The various steps of the method according to the present invention are described below.

[0019] (a) Feedstock pretreatment step) According to the present invention, the method includes a step a) of pretreating the feedstock. Preferably, the pretreatment step includes at least one of the operations of drying a1), roasting a2), or milling a3) described below. Preferably, the pretreatment step includes a drying operation a1), a roasting operation a2), and a milling operation a3).

[0020] In embodiments where the feedstock used is already dry, the pretreatment step includes a roasting operation a2) and a milling operation a3).

[0021] If the hydrocarbon-based feedstock fraction is a gaseous or liquid hydrocarbon-based feedstock fraction, it is advantageously introduced directly into the gasification step c) without being subjected to the pretreatment step a).

[0022] (a1) Drying operation) The feedstock pretreatment step a) may include a feedstock drying operation a1), and advantageously is carried out at a temperature of 20 to 180 °C, preferably 60 to 160 °C, preferentially 100 to 140 °C, for a time of 5 to 180 minutes, preferentially 15 to 60 minutes. At the inlet of the drying operation a1), the feedstock generally contains water at a content of 15% to 80% by mass. The content of residual water in the feedstock at the end of the drying operation is advantageously less than 25% by mass, preferably less than 15% by mass, more preferably less than 10% by mass. The drying operation may be carried out by any means known to those skilled in the art.

[0023] The energy required for drying is generally supplied by placing the feedstock in contact with a high-temperature gas stream.

[0024] The high-temperature gas stream used in the drying process may advantageously originate from the combustion of the process feedstock, preferably the combustion of natural gas and / or the combustion of a gas stream obtained from another step of the process. For example, the combustion of the gas obtained from the roasting step a2) generates a high-temperature gas stream, which can be used to dry the feedstock by any method known to those skilled in the art.

[0025] The gaseous effluent obtained from step a1) containing water may be used to preheat the natural gas and / or air enabling combustion of the gas stream generated during roasting.

[0026] (a2) Roasting operation) The feedstock pretreatment step a) may include a roasting operation a2), preferably carried out on the dried feedstock obtained from the drying operation a1).

[0027] The roasting operation a2) may be carried out in a roasting furnace, which produces a more brittle feedstock effluent, resulting in less energy required to finely mill to obtain the roasted effluent. The roasting operation is preferably carried out at a temperature of 220 - 350 °C, preferably 250 - 320 °C, more preferably 270 - 300 °C, for a time of 5 - 180 minutes, preferably 15 - 60 minutes, preferably at an absolute operating pressure of 0.01 - 1.5 MPa, preferably 0.01 - 1.0 MPa, more preferably 0.05 - 0.15 MPa. The roasting operation is carried out in an environment where the oxygen content is preferably less than 10% by volume, preferably less than 8% by volume, more preferably less than 3% by volume.

[0028] The roasting operation has the advantage of reducing the energy cost of the milling operation a3) and involves a solid loss of 5% - 40% by mass, preferably 10% - 35% by mass. However, this solid loss is accompanied by a much more limited loss of calorific value of about 5% - 20%. In this regard, the roasting operation makes it possible to increase the energy content per unit volume of the biomass.

[0029] (a3) Milling operation) The feedstock pretreatment step a) may include the milling operation a3), and is preferably carried out on the roasted effluent obtained from the operation a2).

[0030] The milling operation a3) may be carried out under conditions that allow the reduction of the feedstock particles to a size suitable for entrained flow in the gasification unit (step c). At the end of the milling operation a3), 90% of the feedstock particles preferably have an equivalent diameter of less than 300 microns, and 90% of the feedstock particles preferably have an equivalent diameter of more than 1 micron; preferably, 90% of the feedstock particles have an equivalent diameter of less than 200 microns, and 90% of the feedstock particles have an equivalent diameter of more than 5 microns; more preferably, 90% of the feedstock particles have an equivalent diameter of less than 100 microns, and 90% of the feedstock particles have an equivalent diameter of more than 10 microns. The equivalent diameter is shown as d e and is defined, for example, according to the following relational expression:

[0031]

Number

[0032] wherein V is the volume of the particle, S is the surface area of a sphere having the same volume as the particle.

[0033] In a particular embodiment, the milling step a3) may be carried out in the presence of a second biomass or fossil feedstock and is milled simultaneously in one and the same mill. If the second feedstock is of fossil origin, it may be selected from solid fossil hydrocarbons, such as coal and petroleum coke. If the second feedstock is biomass, it may be selected from the biomass feedstocks defined above. One advantage of milling in the presence of a second feedstock is that it enables the efficient milling and drying of the second feedstock.

[0034] Preferably, the milling step a3) may be carried out in the presence of additional compounds useful for the subsequent gasification step; said compounds are selected from glassy ash, sand, limestone, lime or other compounds known to those skilled in the art, either alone or as a mixture.

[0035] Preferably, the mill is selected to optimize the pneumatic transport of the powder obtained at the end of step a3) by minimizing the minimum fluidization velocity (MFS) and its inherent energy consumption.

[0036] Preferably, said co - milling step a3) is carried out in a mill, for example, a roller mill, a universal mill, an attrition mill or any other type of mill known to those skilled in the art.

[0037] (Electrolysis step b)) The method according to the invention includes the step of electrolysis of water into oxygen and hydrogen for the production of a hydrogen stream and an oxygen stream, in which step the water is obtained, at least in part, preferably completely, from the Fischer - Tropsch synthesis step e).

[0038] The oxygen obtained at the end of step b) is sent, in part or in whole, to the gasification step c). Advantageously, the purity of the oxygen produced by electrolysis is at least 98.5% by weight (on a dry basis). The impurities that may be present in the produced oxygen are water and / or hydrogen.

[0039] According to the invention, all or part of the hydrogen obtained at the end of the electrolysis step b) is sent to the Fischer - Tropsch synthesis step e).

[0040] Advantageously, the hydrogen obtained at the end of the electrolysis step b) is sent to the Fischer - Tropsch synthesis step e), and its purity is at least 99.8% by weight (on a dry basis). Preferably, the hydrogen sent 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, preferably less than 15 ppm.

[0041] Preferably, all of the hydrogen generated in the electrolysis step b) is introduced into the Fischer-Tropsch synthesis step e).

[0042] Advantageously, the molar ratio between hydrogen and carbon monoxide of the effluent introduced into the Fischer-Tropsch synthesis step e) (shown as H2 / CO) is from 0.5 to 4, preferably from 1 to 3, more preferably from 1.5 to 2.5, and most preferably equal to 2, and the hydrogen originates from the syngas conditioning step d) and the water electrolysis step b).

[0043] The electrolysis step b) may be carried out by any means known to those skilled in the art, such as alkaline electrolysis, proton exchange membranes, anion exchange membranes or solid oxide electrolysis.

[0044] One advantage of the water electrolysis step b) is that it produces decarbonized hydrogen, making it possible to obtain fuels whose greenhouse gas emissions are eligible under the European Red II directive.

[0045] Another advantage associated with the recycling of the water obtained from the Fischer-Tropsch synthesis step e) to the electrolysis step b) is that it reduces the water consumption of the process and thus the operating costs.

[0046] 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 omit the use of an air separation unit, limiting the investment and operating costs of the process. Furthermore, the excess oxygen may advantageously be used for SRU / TGTU (sulfur recovery unit / tail gas treatment unit) tail gas treatment and / or for oxygen combustion of the combustible and residual gases of the unit and / or for combustion of the roasting gas.

[0047] (Gasification step c)) The method according to the invention comprises a step c) of gasifying a 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), preferably all of the oxygen obtained from the water electrolysis step b). The gasification step c) thus enables the production of a gaseous effluent containing synthesis gas.

[0048] The gasification step includes a partial oxidation reaction, which converts the feedstock into synthesis gas mainly containing carbon monoxide and hydrogen. The gasification step is preferably carried out in the presence of a controlled amount of oxygen obtained from the electrolysis step b) in the form of an 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 nitrogen in the case of using air as the oxygen source, thereby limiting the accumulation of inert substances and hence the problems related to rate or pressure loss, and thus making it possible to reduce the size of the equipment used and further limit the investment and operating costs of the process.

[0049] Advantageously, the gaseous effluent corresponding to the synthesis gas obtained from the gasification step c) is mainly composed of water (H2O), carbon monoxide (CO), hydrogen (H2) and carbon dioxide (CO2), and may contain impurities originating from the initial biomass fraction and / or another feedstock, especially a hydrocarbon feedstock fraction.

[0050] According to the invention, the oxygen used in the gasification step is obtained wholly or partly from the water electrolysis step b).

[0051] Advantageously, in addition to the oxygen stream derived from the water electrolysis step b), an oxygen stream originating from an air separation step may be used in the gasification step c).

[0052] In a particular embodiment, all of the oxygen introduced into the gasification step c) is obtained from the water electrolysis step b).

[0053] The gasification step c) of the feedstock is carried out in a fixed bed or fluidized bed type gasifier, or preferably in a cooled wall entrained flow gasifier, at a high temperature, i.e., 800 to 1800 °C, preferably 1000 to 1600 °C, more preferably 1200 to 1500 °C, and advantageously at an absolute pressure of 2 to 12 MPa, preferably 2.5 to 6.0 MPa, more preferably 3.0 to 5.0 MPa. The high temperature makes it possible to obtain a high degree of carbon conversion, and thus to reduce the amount of unreacted carbon in the resulting ash, and thus to reduce the amount of ash recycled to the gasifier.

[0054] The entrained flow gasifier is preferably a gasifier known to those skilled in the art as a cooled wall type entrained flow gasifier. The cooling wall defines the gasification chamber and is itself located within the gasifier. The water used to cool the walls of the gasification chamber flows through coils arranged outside the walls of the gasification chamber. The water is partially vaporized, thus generating a flow of medium pressure steam. This cooling of the walls enables the formation of a protective ash layer on the inner wall of the gasification chamber. Specifically, the feedstock introduced into the gasifier contains inorganic compounds, which form ash after gasification. At the gasification temperature, this liquid ash is in the form of droplets and solidifies when it comes into contact with the cooled wall, forming a solid layer that acts as an insulator. Therefore, the thermal protection of the gasification chamber walls is provided firstly by the layer of solidified ash and secondly by the layer of molten ash, which flows towards the bottom of the gasifier in contact with the gas phase. The combustion chamber walls are therefore very resistant to high temperatures and high temperature fluctuations. Furthermore, as a result of their composition, especially their high content of alkaline compounds, the ash derived from biomass is corrosive to refractory type linings. As a result, gasification technologies using internal refractory materials as wall protection are difficult to operate due to their rapid deterioration and require frequent replacement. Furthermore, refractory materials are very sensitive to thermal shock, which destroys this protective layer by fragmentation.

[0055] In a cooled-wall co-current gasifier, at least two burners, preferably four or more burners, are arranged in the gasification chamber according to the capacity of the gasifier, the walls of which are cooled and function at a temperature sufficient to enable the melting of the ash contained in the feedstock. Furthermore, the feedstock introduced into the gasifier may have very different properties. By way of example, the lower calorific value (LCP) of biomass is lower than that of petroleum coke, the ash content of biomass is much lower than that of coal, and the melting point of the ash may vary greatly from one biomass to another. Therefore, the melting point of the ash may vary depending on the composition of the feedstock introduced into the gasification chamber. Similarly, the minimum gasification temperature exceeding the melting point of the ash may be adjusted by modifying the properties of the feedstock with different characteristics and the proportions of various constituents (other biomass, other hydrocarbon feedstocks, etc.), and / or by injecting a solvent (e.g., limestone) together with the feedstock.

[0056] In a preferred version of the present invention, the synthesis gas generated in the gasification chamber appears therefrom in co-current with the liquid ash flowing towards the bottom of the gasifier. This co-current configuration has the advantage of avoiding the risk of clogging of the liquid ash discharge pipe as opposed to a configuration in which the synthesis gas is exhausted from the gasification chamber towards the top while the liquid ash flows towards the bottom. Specifically, since the liquid ash flows only inside the pipe, depending on its viscosity, it may become difficult to flow and / or partially solidify, obstructing the discharge pipe partially or completely, which may lead to the shutdown of the facility for maintenance. These phenomena may occur particularly during transient phases of temperature increase or decrease, or during regulation related to changes in the properties of the feedstock. The configuration according to the present invention has the advantage that the gas flowing in co-current with the liquid ash in the discharge pipe of the gasification chamber promotes the flow of this ash towards the bottom of the gasifier and prevents the risk of clogging even during transient phases.

[0057] In a preferred version of the invention, the synthesis gas and the liquid ash are transferred to a quench zone as described in patent application DE 102007044726 and come into contact with at least the water film. This quench zone is arranged below the gasification chamber and separates the high-temperature dry zone at the top from the lower, cooler and more humid zone. The high-temperature dry zone located below the gasification chamber is characterized by the presence of the synthesis gas and the liquid ash flowing towards the bottom of the gasifier. The cooler and more humid part is located below the high-temperature dry 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 cold and humid zone corresponds to the temperature of the thermodynamic equilibrium between the gas phase and the liquid phase at the operating pressure of the gasifier.

[0058] This configuration by quenching enables the removal of fine adhesive ash particles entrained during the scrubbing of the synthesis gas, and thus reduces the risk of fouling in downstream piping and units. Furthermore, due to the high temperature in the gasification chamber, the molten ash can easily flow towards the bottom on its walls before falling into the quench zone. After moving to the cold and humid unit, the cooled ash ends at the bottom of the gasifier filled with water. When in contact with water, this molten ash is immediately cooled and vitrified as high-density particles. These particles are then extracted from the gasifier in the form of a mixture (or slurry) of water and solid ash by reducing the pressure. Most of the mineral compounds contained in the feedstock form the molten ash. This configuration advantageously enables the encapsulation of harmful products, such as heavy metals, in the vitrified ash. By the glass-solidification method, this ash becomes very stable and is not leachable.

[0059] In an alternative version of the invention, the resulting synthesis gas exits the gasification chamber through the top, while the molten ash flows countercurrently relative to the synthesis gas along the walls and reaches the bottom of the gasifier filled with water. When contacting water, the molten ash rapidly solidifies and forms 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 reduced pressure. Since most of the mineral compounds contained in the feedstock form the molten ash, this configuration advantageously enables encapsulating harmful products, such as heavy metals, in the vitrified ash. By the glass solidification method, this ash becomes very stable and is not leachable. The synthesis gas exiting the gasification chamber through the top and the finest molten ash particles entrained therewith are cooled by a stream of cooled synthesis gas free of solid particles. This cooling enables solidifying the molten ash as non-adhesive solid particles. After this first step of pre-cooling, the synthesis gas is sent to a heat exchanger to generate steam. To remove the fine solid particles, the synthesis gas then passes through a section for separating the gas phase and the solid phase using any technique known to those skilled in the art, such as a cartridge filter. A part of this cooled synthesis gas free of particles is recycled to the outlet of the gasifier to cool the synthesis gas exiting at the top of the gasifier.

[0060] (Optional step d) of conditioning the synthesis gas) The method according to the invention may include a step d) of conditioning the synthesis gas obtained from the gasification step c). The synthesis gas obtained from the gasification step c) mainly consists of carbon monoxide (CO), hydrogen (H₂), carbon dioxide (CO₂) and water (H₂O), and may initially contain impurities originating from the biomass fraction and / or another feedstock, especially fractions of hydrocarbon feedstocks. These impurities are essentially metals, especially alkali metals (Na, K), sulfur compounds as well as chlorinated and nitrogenous compounds. In particular, the halogenated compounds initially present in the feedstock according to the invention may reach a content of at least 250 ppm by mass in the crude hydrocarbon feedstock fraction (before drying) and at least 10,000 ppm by mass in the case of the crude biomass fraction (before drying).

[0061] Preferably, step d) includes, preferably consists of, step d1) and / or d2) and / or d3) and / or d4) and / or d5) and / or d6) and / or d7) and / or d8).

[0062] (Step d1) of scrubbing with water and fractionating the synthesis gas) Preferably, step d) includes step d1) of scrubbing with water and fractionating the synthesis gas.

[0063] Therefore, the synthesis gas obtained from the gasification step c) is preferably subjected to step d1) of scrubbing with water to remove traces of solids in the synthesis gas and also some of the water-soluble gaseous compounds. This operation may be carried out via any type of technique known to those skilled in the art, including venturi effect water scrubbers, or venturi scrubbers, scrubbing columns with all types of inserts, etc.

[0064] Preferably, at the outlet of the water scrubbing step, the synthesis gas is subjected to a step of fractionation into at least two effluents, a first part and an additional part, which are subjected to the following steps: - Step d2); removing the halogenated compound by passing said first portion over at least one suitable guard bed; - Optional step d3); steam reforming of carbon monoxide carried out on the effluent obtained from step d2); - Step d4); catalytic hydrolysis of the compounds COS and HCN contained in said additional portion of the effluent obtained from step d1) to H2S and NH3.

[0065] In another embodiment, the effluent obtained from step d3) is preferably recombined with the additional portion of the effluent obtained from step d1) before being treated in step d4) of catalytic hydrolysis of the compounds COS and HCN.

[0066] Therefore, the "first portion" and "additional portion" effluents obtained from the scrubbing wash with water and fractionation of the synthesis gas in step d1) are subjected to separate treatment steps. The first portion is subjected to step d2) for removal of the halogenated compound; while the additional portion is subjected to step d4) for catalytic hydrolysis of the compounds COS and HCN to H2S and NH3. The fractionation of the synthesis gas and the separate and different treatment of the effluents make it possible to reduce the size of the unit and the amount of catalyst used in said unit.

[0067] Preferably, the respective proportions of said first portion and said additional portion of the effluent obtained from step d1) are advantageously determined so as to obtain an effluent at the outlet of step d7) with an H2 / CO molar ratio preferably equal to 0.5 to 4, preferably 1 to 3, more preferably 1.5 to 2.5, preferably 2, which is fed to the Fischer-Tropsch step e).

[0068] (Step d2) for removal of the halogenated compound) Preferably, step d) includes step d2) for removal of the halogenated compound.

[0069] Step d2) of removing the halogenated compound on at least one suitable guard bed is preferably carried out on the first portion of the effluent obtained from step d1). By step d2), before the first portion of the effluent is sent to the carbon monoxide steam reforming unit (step d3), substantial removal of the halogenated compound, preferably chlorine, contained in said portion becomes possible. Fixed bed reactor technology is advantageous for taking up the halogenated compounds, especially chlorine, contained in the syngas of the first portion by uptake masses known to those skilled in the art. Advantageously, step d2) is carried out on at least one guard bed in the presence of an active phase of zeolite type, and / or zinc oxide, and / or basic oxides such as alumina. The active phase may be doped or promoted by one or more compounds of elements of alkali metals and / or alkaline earth metals and / or rare earth metals. The active phase may be, for example, alumina promoted by a sodium compound such as Na2O.

[0070] In the context of the present invention, passing the first portion of the effluent obtained from step d1) through at least one guard bed makes it possible to achieve the specifications required for the carbon monoxide steam reforming unit d3). At the outlet of step d2) for removing the halogenated compound, the effluent generally contains less than 10 volume ppm of chlorine, preferably less than 5 volume ppm of chlorine, preferably 0.1 volume ppm to 5 volume ppm of chlorine, more preferably 1 volume ppm to 3 volume ppm of chlorine, even more preferably 1 volume ppm to 2 volume ppm of chlorine.

[0071] (Step d3) of steam reforming of carbon monoxide) Step d) of conditioning the syngas may optionally include a step of steam reforming of carbon monoxide.

[0072] Step c) of the gasification of the feedstock according to the invention, for example, the step as carried out in the present invention, may result in the production of hydrogen and carbon monoxide at an H2 / CO molar ratio that is not optimal for the Fischer-Tropsch reaction, especially when the catalyst used is a cobalt-based catalyst that advantageously requires an optimal H2 / CO molar ratio of about 2 for the production of middle distillates.

[0073] In order to achieve the H2 / CO molar ratio required by Fischer-Tropsch synthesis, the effluent obtained from step d2) for the removal of halogenated compounds, according to the present invention, is in some cases directed to a carbon monoxide steam reforming section d3), resulting in a gas stream rich in hydrogen but depleted in carbon monoxide.

[0074] Step d3) is carried out in cases where it is not possible to obtain the desired H2 / CO ratio at the inlet of the Fischer-Tropsch synthesis step e) with the hydrogen generated in the water electrolysis step b).

[0075] All or part of the hydrogen generated in the carbon monoxide steam reforming step d3) may advantageously be sent to the Fischer-Tropsch synthesis step e).

[0076] The carbon monoxide steam reforming reaction step d3) is preferably carried out at an inlet temperature close to the temperature of the synthesis gas obtained from the water scrubbing and fractionation step d1), making it possible to reduce the energy consumption throughout the line for the valorization of biomass. Preferably, the inlet temperature when step d3) is carried out is 150 - 280°C, preferably 200 - 280°C.

[0077] Preferably, the absolute pressure when the carbon monoxide steam reforming reaction step d3) is carried out is 2.0 - 12 MPa, preferably 2.5 - 6.0 MPa, more preferably 3.0 - 5.0 MPa; the space-time velocity HSV (volume of feedstock / volume of catalyst / time) at that time is 1000 - 10,000 h -1 preferably 1000 - 9000 h -1, more preferably 1500 to 8500 h -1 ; the temperature at that time is 150 to 550 °C, preferably 200 to 500 °C.

[0078] The catalyst used in this step d3) is a catalyst containing at least one element from Group VIII and at least one element from Group VIB of the Mendeleev periodic table (Group VIII corresponds to Groups 8, 9, and 10 according to the new notation of the periodic table: Handbook of Chemistry and Physics, 81st edition, 2000 - 2001, and Group VIB corresponds to Group 6). Preferably, the catalyst is a catalyst containing cobalt sulfide and / or molybdenum sulfide. The carrier for the catalyst is usually a porous solid selected from the group consisting of alumina, silica, and silica - alumina. Preferentially, the carrier for the catalyst is alumina. The catalyst used may be promoted by a promoter of an alkali metal or an alkaline earth metal. The carbon monoxide conversion reaction can significantly increase the hydrogen content in the effluent sent to the Fischer - Tropsch synthesis step e).

[0079] Optionally, a feed of water in liquid form, preferably in the form of steam, more preferably in the form of superheated steam, may be provided upstream of the carbon monoxide steam reforming step to adjust the H2O / CO ratio at the inlet of the unit for step d3). Advantageously, step d3) is carried out at an H2O / CO ratio of 0.5 to 100, preferably 0.5 to 25, more preferably 1.5 to 10. Due to the exothermic nature of the carbon monoxide steam reforming reaction, the temperature of the gaseous effluent obtained from this step is 250 to 550 °C. This gaseous effluent is advantageously cooled to the operating temperature of the hydrolysis unit, which is 100 to 400 °C, preferably 200 to 350 °C. This cooling is advantageously carried out by generating steam that may be used for the process line or power generation according to the present invention.

[0080] In one variant of the method according to the invention, the H2 / CO molar ratio of the gas stream entering the Fischer-Tropsch synthesis step e) may be adjusted to its optimal level of about 2, by adding a hydrogen-rich external gas stream generated by any means known to those skilled in the art, including: water electrolysis, steam reforming of natural gas followed by a pressure swing adsorption (PSA) step, or a temperature swing adsorption (TSA) step, or membrane separation. This hydrogen-enriched gas stream may be injected at any point in the line located downstream of the gasification step c), making it possible to reduce the size of the carbon monoxide steam conversion step d3).

[0081] In one variant of the method according to the invention, not only a part of the gas obtained from the carbon monoxide steam conversion step d3), but also optionally a part of the gas upstream or downstream of said step d3) may advantageously be sent to a unit for hydrogen production carried out by any means known to those skilled in the art, preferably by pressure swing adsorption (PSA) or temperature swing adsorption (TSA) or membrane separation. The hydrogen produced is advantageously used in the hydrogenation treatment and / or isomerization step f).

[0082] (Step d4) of the catalytic hydrolysis of compounds COS and HCN) Preferably, step d) includes step d4) of the catalytic hydrolysis of the additional amounts of compounds COS and HCN obtained from step d1).

[0083] The additional amounts obtained from step d1) are subjected to step d4) of the catalytic hydrolysis of COS and HCN to H2S and NH3, thereby making it possible to obtain a purified effluent. This step makes it possible to remove COS and HCN, which are poisons for the Fischer-Tropsch synthesis catalyst. According to the invention, the step d4) of the catalytic hydrolysis of carbonyl sulfide (COS) and hydrogen cyanide (HCN) is advantageously carried out in the presence of a catalyst containing an oxide of an element selected from the group comprising platinum-based compounds, or titanium, zirconium, aluminum, chromium and zinc, or mixtures thereof.

[0084] Preferably, the hydrolysis catalyst is a titanium oxide-based catalyst. The catalyst used may contain at least an alkali metal, an alkaline earth metal and / or a rare earth metal. For example, it can be obtained from precursors such as potassium hydroxide, zirconium dioxide, sodium carbonate or barium carbonate, sodium bicarbonate or barium bicarbonate, calcium sulfate, sodium acetate or barium acetate, or sodium oxalate or barium oxalate. The hydrolysis step is preferably carried out at a temperature of 100 to 400 °C, more preferably 200 to 350 °C.

[0085] Advantageously, the effluent at the outlet of the hydrolysis unit in step d4) contains less than 25 volume ppm of COS and less than 5 volume ppm of HCN, preferably less than 10 volume ppm of COS and less than 1 volume ppm of HCN, more preferably less than 5 volume ppm of COS and less than 0.1 volume ppm of HCN.

[0086] In one variant of the method according to the invention, the effluent obtained from the carbon monoxide steam reforming step d3) is at least partially sent, as a mixture with said additional part, to a step (step d4)) for the catalytic hydrolysis of COS and HCN to H2S and NH3. Advantageously, the effluent obtained from the carbon monoxide steam reforming step d3) is preferably cooled to a temperature of 100 to 400 °C, more preferably 200 to 350 °C, as a mixture with said additional part, and then sent to the catalytic hydrolysis step (step d4)).

[0087] (Recombination step d5)) Preferably, at least a part, preferably all, of the effluent obtained from the step d2) for the removal of halogenated compounds and optionally from the carbon monoxide steam reforming step d3) is recombined with at least a part of the effluent obtained from the catalytic hydrolysis step d4) in step d5) and then sent to the water scrubbing step d6).

[0088] (Scrubbing of the recombined effluent with water step d6)) Preferably, step d) includes a step d6) of scrubbing the mixed effluent obtained at the end of steps d2) and d4) with water. Step d6) makes it possible to remove water-soluble impurities that are particularly harmful to the operation of step d7) for removing acid gases, such as NH3 and HCl.

[0089] In one variant of the method according to the invention, the mixed effluent obtained at the end of steps d2) and d4) may be pre-treated in a step of removing heavy metals on at least one suitable guard bed. By said removal step, it becomes substantially possible to remove heavy metals, such as lead, arsenic and mercury, before the effluent is treated in the water scrubbing step d6), and more particularly before the acid gas removal step d7). Fixed bed reactor technology would be advantageous for taking up heavy metals contained in the synthesis gas by uptake masses known to those skilled in the art. Advantageously, the removal step is carried out on at least one or more guard beds in the presence of one or more uptake masses containing one or more active phases. Advantageously, said active phase contains at least one sulfur compound, such as supported elemental sulfur, and / or a metal sulfide, such as sulfides of copper and / or zinc, 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 an oxide of copper or nickel. Advantageously, said one or more active phases are supported, for example, on alumina, silica, silica-alumina or activated carbon.

[0090] Advantageously, the passage of the effluent through at least one guard bed of the removal step makes it possible to achieve the required specifications at the inlet of the acid gas removal step d7) (step d7), and also the specifications required for the Fischer-Tropsch synthesis unit of step e).

[0091] In a second variant according to the invention, the step of removing heavy metals is carried out between the water scrubbing step d6) and the acid gas removal step d7).

[0092] In a third modification according to the present invention, the step of removing heavy metals is carried out after the step d7) of removing acid gas when the solvent used in step d6) is a chemical solvent derived from an alkanolamine, which is known to those skilled in the art to be less sensitive to the presence of heavy metals than a physical solvent.

[0093] At the outlet of the step for removing heavy metals, the effluent generally has lead, arsenic and mercury at a content of less than 1 volume ppb, preferably less than 0.5 volume ppb, more preferably less than 0.1 volume ppb, and even more preferably less than 0.01 volume ppb.

[0094] (Step d7) of removing acid gas) Preferably, step d) may advantageously include step d7) of removing acid gas. Step d7) is intended to remove acid gas remaining in the synthesis gas obtained from step d5), for example, sulfur compounds (H2S) or CO2.

[0095] Said step d7) is advantageously carried out in the case where the CO2 content in the synthesis gas obtained from step d6) is more than 5% by weight, preferably more than 10% by weight, preferably more than 20% by weight relative to the weight of said effluent.

[0096] Step d7) is carried out by using a chemical or physical solvent, or a mixture of chemical and physical solvents, or any other means known to those skilled in the art. The chemical solvent may be, for example, a primary, secondary or tertiary amine derived from an alkanolamine, for example, monoethanolamine (MEA), diethanolamine (DEA) or methyldiethanolamine (MDEA). The physical solvent may be based on, for example, polyethylene glycol (PEG) dialkyl ether, for example, PEG diethyl ether or dibutyl ether, or a mixture of methanol.

[0097] The process for removing acid gas is carried out, for example, using a column for the absorption of acid gas by a chemical or physical solvent used, followed by a solvent regeneration process that reduces the consumption of the solvent within the unit. This regeneration process may advantageously be carried out in two steps, first removing a gas stream rich in CO2 and second removing a gas stream rich in H2S. In one variant of the method according to the invention, the CO2-rich gas stream is purified from H2S and advantageously recycled to the gasification step c).

[0098] (Final purification step d8)) Preferably, step d) includes the final purification step d8). Specifically, the cobalt-based catalyst used in the Fischer-Tropsch synthesis step e) is very sensitive to impurities present in the synthesis gas, and in this regard, only amounts on the order of ppb (parts per billion) are tolerated. At the outlet of step d7), the synthesis gas may still contain impurities at a content of about 100 ppb by volume of H2S and COS.

[0099] Advantageously, the final purification step d8) is carried out on at least one guard bed and may be carried out to completely adsorb the last traces of impurities remaining in the synthesis gas, such as halogenated compounds, H2S, COS, HCN, and NH3. The final purification step d8) is carried out by any means known to those skilled in the art, for example, at least one guard bed based on zinc oxide ZnO, Cu / ZnO, or activated carbon, making it possible to achieve the specifications required for the impurities in the synthesis gas used in the Fischer-Tropsch synthesis step e).

[0100] Advantageously, at the outlet of step d8), the sulfur content of the synthesis gas is less than 100 volume ppb, preferably less than 50 volume ppb, more preferably less than 10 volume ppb; the HCN content is less than 100 volume ppb, preferably less than 50 volume ppb, more preferably less than 10 volume ppb, and the NH3 content is less than 100 volume ppm, preferably less than 10 volume ppm, more preferably less than 1 volume ppm.

[0101] Preferably, step d) includes, preferably consists of, step d1) and / or d2) and / or d3) and / or d4) and / or d5) and / or d6) and / or d7) and / or d8).

[0102] (Step e) of Fischer - Tropsch synthesis catalyst reaction) The method according to the invention comprises, from the gasification step c), optionally from an optional step d) of conditioning the gaseous effluent containing synthesis gas, and preferably from the final purification step d8), the Fischer - Tropsch synthesis step e) of the effluent obtained. The said effluent containing carbon monoxide (CO) and hydrogen is introduced into the Fischer - Tropsch synthesis step e) at an optimal H2 / CO molar ratio for the Fischer - Tropsch reaction in the presence of all or part of the hydrogen obtained from the water electrolysis step b), resulting in a stream containing synthetic liquid hydrocarbons and at least one gaseous effluent.

[0103] Advantageously, the molar ratio between carbon monoxide and hydrogen (expressed as H2 / CO) when the Fischer - Tropsch synthesis step e) is carried out is from 0.5 to 4, preferably from 1 to 3, more preferably from 1.5 to 2.5, and most preferably equal to 2. The hydrogen originates from the step d) of conditioning the synthesis gas and the water electrolysis step b).

[0104] The gasification step c) of the feedstock according to the invention, for example, the process carried out in the present invention may lead to the production of hydrogen and carbon monoxide at an H2 / CO molar ratio that is not optimal for the Fischer - Tropsch reaction, especially when the catalyst used is a cobalt - based catalyst, which advantageously requires an optimal H2 / CO molar ratio of about 2 for the production of middle distillates.

[0105] Advantageously, all of the hydrogen obtained from the electrolysis step b) is used in the Fischer-Tropsch synthesis step e). In some cases, a hydrogen supply may be required to have an H2 / CO molar ratio optimal for the Fischer-Tropsch reaction. In this case, the supply may be obtained from an optional carbon monoxide steam reforming step d3).

[0106] Advantageously, the optional carbon monoxide steam reforming reaction step d3) may be carried out at an absolute pressure of 2 to 12 MPa, preferably 2.5 to 6.0 MPa, more preferably 3.0 to 5.0 MPa; the space velocity HSV (volume of feedstock / volume of catalyst / time) at that time is 1000 to 10,000 h -1 , preferably 1000 to 9000 h -1 , more preferably 1500 to 8500 h -1 ; the temperature at that time is 150 to 550 °C, preferably 200 to 550 °C, more preferably 250 to 500 °C.

[0107] The catalyst used in this carbon monoxide steam reforming step is a catalyst containing at least one element from Group VIII of the Mendeleev periodic table and / or at least one element from Group VIB (Group VIII corresponds to Groups 8, 9 and 10 according to the new notation in the periodic table: Handbook of Chemistry and Physics, 81st edition, 2000 - 2001, and Group VIB corresponds to Group 6). Preferably, the catalyst is a catalyst containing cobalt sulfide and / or molybdenum sulfide. The carrier for the catalyst is usually a porous solid selected from the group consisting of alumina, silica and silica-alumina. More preferably, the carrier for the catalyst is alumina. The catalyst used may be promoted by a promoter of an alkali metal or alkaline earth metal. The carbon monoxide reforming reaction can significantly increase the hydrogen content in the effluent sent to the Fischer-Tropsch synthesis step e).

[0108] Advantageously, the water formed during the Fischer-Tropsch synthesis step e) is partially or completely sent 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.

[0109] In one embodiment, the water formed during the Fischer-Tropsch synthesis step e) advantageously undergoes a treatment step before being recycled to the water electrolysis step b) to meet the requirements of step b). The treatment step may advantageously consist of removing oxygenated compounds from the water formed during step e).

[0110] 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 may be, for example, multitubular fixed-bed reactors, or bubble column reactors, also known as slurry bubble columns, or microchannel reactors.

[0111] According to a preferred embodiment of the invention, step e) includes one or more bubble column reactors. Since the synthesis is highly exothermic, this embodiment makes it possible, inter alia, to improve the heat control of the reactor and create only a small pressure loss.

[0112] The catalyst used in this Fischer-Tropsch synthesis step e) is generally any catalyst solid known to those skilled in the art for carrying out Fischer-Tropsch synthesis. Preferably, the catalyst used in said step contains cobalt or iron, more preferably cobalt. The catalyst used in step e) is generally a supported catalyst. The support may be based on, for example, alumina, silica or titanium.

[0113] The temperature and pressure conditions are variable and are adapted to the catalyst used in this step e). The absolute pressure is generally 1.0 to 6.0 MPa, preferably 1.5 to 3.5 MPa, and preferentially 2.0 to 3.0 MPa. The temperature may generally be 170 to 280 °C, preferably 190 to 260 °C, and preferentially 210 to 240 °C.

[0114] According to one variant of the method of the present invention, at least one gaseous fraction obtained from the Fischer-Tropsch synthesis (step e) is advantageously recycled to the gasification step c) and converted into synthesis gas, and thus improves the mass yield of the process line.

[0115] In another configuration of the method according to the present invention, the gaseous fraction obtained from the Fischer-Tropsch synthesis e) is advantageously sent, at least in part, to an independent synthesis gas production unit (for example, POx: partial oxidation, SMR: steam methane reforming, ATR: autothermal reforming, EHTR: enhanced heat transfer reformer, etc.); this synthesis gas may be recycled to any point in the line upstream of the gasification step c) and the hydrogenation and / or isomerization step f).

[0116] In another configuration of the method according to the present invention, at least a part of the gaseous fraction obtained from the Fischer-Tropsch synthesis step e) can supply energy to the drying operation a1) and / or the calcination operation a2), maximizing the energy efficiency of the process line.

[0117] In another configuration of the method according to the present invention, it becomes possible to generate electricity in a combined cycle in which the gaseous fraction obtained from the Fischer-Tropsch synthesis step e) partially feeds the steam generated in steps c), d3) and e), increasing the energy efficiency of the process line.

[0118] These various configurations may advantageously be combined to optimize the economy of the integrated method line according to the present invention.

[0119] (Step f) of hydrogenation treatment and / or isomerization) The method of the present invention advantageously includes at least a part, preferably all, of the hydrogenation treatment and / or isomerization step f) of the stream containing the liquid hydrocarbons obtained from the Fischer-Tropsch synthesis step e).

[0120] Step f) is carried out under general operating conditions known to those skilled in the art in the presence of hydrogen, and is directed towards increasing the value of the hydrocarbon fraction obtained from step e) by the production of liquid hydrocarbons, in particular very high-quality liquid biofuels, namely bio-naphtha, bio-gasoline, bio-kerosene, bio-gas oil and bio-lubricant base.

[0121] The hydrogen required to carry out step f) may advantageously be obtained wholly or partly from the water electrolysis step b).

[0122] One possible option is the production of a paraffinic fraction, the production of a base product for petrochemical processes, for example the production of a C10 - C13 fraction intended for the production of (bio)LAB (linear alkylbenzene), or the production of (bio)wax for various industrial applications.

[0123] (Brief Description of the Drawings) (Description of the Drawings) Figure 1 illustrates the method of the invention according to claim 1 and includes the step of isomerizing the effluent obtained from the method according to the invention.

[0124] The biomass is introduced via pipe (1) into the pretreatment unit (A), where it undergoes a drying step a1), a roasting step a2) and / or a milling step a3).

[0125] The pretreated biomass is then sent via pipe (2) as a mixture with the oxygen (11) generated during the electrolysis of water (10) carried out in the water electrolysis unit (B) to the gasification step in unit (C).

[0126] The water used in the electrolysis unit (B) is obtained at least in part from the Fischer-Tropsch synthesis process carried out in unit (E).

[0127] During the water electrolysis process, a hydrogen stream is generated and sent via pipe (8) upstream of unit (E) to the Fischer-Tropsch synthesis process.

[0128] The step of gasifying the pretreated biomass is carried out in unit (C) in the presence of oxygen (11) obtained from the water electrolysis process, which makes it possible to produce a gaseous effluent containing synthesis gas, which exits the gasification unit (C) via pipe (3) and is sent to an optional step d) for conditioning the effluent containing synthesis gas, which may include step d1) of scrubbing with water and fractionating the synthesis gas and / or step d2) of removing halogenated compounds and / or step d3) of steam reforming of carbon monoxide and / or step d4) of catalytic hydrolysis of compounds COS and HCN and / or step d5) of recombination of the effluent and / or step d6) of scrubbing the recombined effluent with water and / or step d7) of removing acid gases and / or step d8) of final purification of the effluent containing synthesis gas.

[0129] The effluent containing optionally purified synthesis gas is then sent via pipe (5) to the Fischer-Tropsch synthesis process, which is carried out in unit (E) in the presence of at least a portion of the hydrogen stream (8) generated during the water electrolysis process. A stream (6) containing synthetic liquid hydrocarbons is generated during the Fischer-Tropsch synthesis process and may be sent to a hydrogenation treatment and / or isomerization step f) not shown.

[0130] Figure 2 illustrates the method according to Comparative Example 1. The description of this method is given in Example 1.

[0131] (Example) (Example 1 (Comparative)) Example 1 reproduces the method described in patent application WO 2014 / 058253 and includes the following steps: A step of pretreatment by roasting; A step of performing air separation to generate an oxygen stream; A step of gasifying the entrained stream; A step of steam reforming of carbon monoxide; A step of removing acid gas and final purification; A step of Fischer-Tropsch synthesis.

[0132] The method according to Example 1 is a comparative example in that it does not include a water electrolysis step. The method performed in Comparative Example 1 is shown in Figure 2.

[0133] Example 1 processes 100 t / h of dry biomass introduced into the pretreatment step via pipe (1). The roasted lignocellulosic biomass at the outlet of the pretreatment unit A via pipe (2) contains 50 wt% carbon and 40% oxygen.

[0134] The roasted biomass (2) is then introduced into the gasification unit C in the presence of the oxygen stream (7) generated in the air separation unit (B).

[0135] The gasification unit produces, on a molar basis, 3 times as much CO as CO2, i.e., an amount of 67.4 t / h. The H2 / CO ratio at the outlet of the gasification unit is 0.5.

[0136] At the outlet of the gasification unit C, an effluent (3) containing synthesis gas is produced and sent to the carbon monoxide steam reforming unit D. The carbon monoxide steam reforming unit makes it possible to increase the ratio from 0.5 to 2.

[0137] The effluent (4) exiting the carbon monoxide steam reforming unit is then sent to unit (D’). Unit (D’) includes a step of removing acid gas from the effluent containing synthesis gas and a step of final purification of the effluent.

[0138] The effluent containing the purified synthesis gas (5) is then sent to a Fischer-Tropsch synthesis unit E to produce a stream containing liquid hydrocarbons (6).

[0139] The various steps of the following methods that result in a decrease in carbon yield are as follows: Roasting step; carbon loss 23%; Gasification step; further carbon loss of 19%; Carbon monoxide steam reforming step; further carbon loss of 29%.

[0140] The carbon loss is calculated according to the following formula: (C_inlet - C_outlet) / C_inlet × 100 The total carbon yield of the line is therefore 29% by weight, i.e., the total material yield is 17% by weight.

[0141] The total carbon yield is calculated according to the following formula: (C_biomass - C_outlet_FT) / C_biomass × 100.

[0142] The material yield is calculated according to the following formula: (Q_biomass - Q_outlet_FT) / Q_biomass × 100; Q is the flow rate.

[0143] CO2 is mainly generated in the following two steps: Gasification step; the flow rate is shown as 35.3 t / h; Carbon monoxide steam reforming step; the flow rate is shown as 88.2 t / h.

[0144] These emissions do not take into account the CO2 emitted for the production of utilities.

[0145] The amount of oxygen required to supply energy to the gasification step is 46 t / h.

[0146] The Fischer-Tropsch synthesis process enables the production of a synthetic liquid hydrocarbon effluent corresponding to 17 t / h.

[0147] (Example 2 (Conforming to the present invention)) Example 2 reproduces the method according to the present invention shown in FIG. 1 and includes the following steps: Step a) of pretreatment by roasting; Step b) of alkaline water electrolysis; Step c) of gasification of the entrained stream; Step d) of conditioning the synthesis gas; Step e) of Fischer-Tropsch synthesis.

[0148] The method of Example 2 according to the present invention differs from the method of Example 1 in that it includes a step of water electrolysis instead of a step of carbon monoxide steam reforming.

[0149] Example 2 processes 100 t / h of dry biomass via pipe (1) in the roasting unit (A). The roasted lignocellulosic biomass (2) contains 50 wt% carbon and 40% oxygen.

[0150] The roasted biomass is then sent to the gasification unit C in the presence of the oxygen stream (11) generated in the electrolysis unit (B) of water (10).

[0151] Similar to Example 1, the gasification unit produces CO in an amount three times that of CO2, i.e., 67.4 t / h of CO, on a molar basis. The H2 / CO ratio at the outlet of the unit is 0.5. In this example, the H2 / CO ratio increases from 0.5 to 2 by the supply of external hydrogen generated by alkaline electrolysis.

[0152] The required amount of hydrogen is 7.2 t / h. To produce such an amount of hydrogen, oxygen, which is an electrolysis by-product, 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).

[0153] The effluent containing syngas (3) is generated at the outlet of the gasification unit C, sent to the syngas conditioning unit D to produce a purified effluent (5), and then sent to the Fischer-Tropsch synthesis unit E in the presence of a hydrogen stream (6) generated in the water electrolysis unit B.

[0154] The various steps of the method that result in a decrease in carbon yield are as follows: Roasting step; carbon loss 23%; Gasification step; further carbon loss of 19%.

[0155] The total carbon yield of the line is, therefore, 58% by weight, i.e., the total material yield is 34% by weight.

[0156] The Fischer-Tropsch synthesis step produces about 43 t / h of water, i.e., 66% of the water required for the electrolysis step, and the synthetic liquid hydrocarbon effluent corresponds to 34 t / h.

[0157] The amount of CO2 released into the atmosphere mainly originates from the gasification step, i.e., 35.3 t / h. The CO2 emissions released by this method are reduced by 70% relative to the reference scheme, the water consumption is reduced by 2 / 3 relative to the consumption required for the electrolysis cell, and the environmental balance of the process is significantly improved.

[0158] Relative to Example 1, the method according to the present invention enables the following: Increasing the amount of synthetic hydrocarbons obtained at the end of the Fischer-Tropsch synthesis step by 100%, Reducing the CO2 emissions of the method by 85%, Reducing the water consumption by 2 / 3 relative to the consumption required for the electrolysis cell.

[0159] Therefore, the method according to the present invention makes it possible to significantly improve the environmental balance of the process and to limit the operating costs of the method.

Claims

1. A method for converting a feedstock containing at least one biomass fraction into hydrocarbons, the method comprising the following steps: - Step a); pretreating the feedstock, - Step b); electrolyzing water into oxygen and hydrogen to produce a hydrogen stream and an oxygen stream; the water is obtained at least partially from the Fischer-Tropsch synthesis step e), - Step c); 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); obtaining a gaseous effluent containing synthesis gas, - Optional step d); conditioning the gaseous effluent containing the synthesis gas obtained from step c); obtaining a gaseous effluent containing purified synthesis gas, - Step e); performing Fischer-Tropsch synthesis on the gaseous effluent obtained from step c) or from the optional step d) in the presence of all or part of the hydrogen obtained from the water electrolysis step b); producing a stream containing synthetic liquid hydrocarbons and at least one gaseous effluent.

2. The method according to claim 1, wherein the pretreatment step a) comprises at least one of the operations of drying a1), roasting a2) or milling a3).

3. The molar ratio between hydrogen and carbon monoxide of the effluent introduced into the Fischer-Tropsch synthesis step e) (shown as H ２ / CO) is from 0.5 to 4, preferably from 1 to 3, more preferably from 1.5 to 2.5, most preferably equal to 2, and the hydrogen is from the conditioning step d) of the synthesis gas and the water electrolysis step b) according to the method of claim 1.

4. The method according to any one of claims 1 to 3, wherein the electrolysis step b) is carried out by alkaline electrolysis, proton exchange membrane, anion exchange membrane or solid oxide electrolysis.

5. The method according to any one of claims 1 to 4, wherein in addition to the oxygen stream originating from the water electrolysis step b), an oxygen stream originating from an air separation step may be used in the gasification step.

6. The method according to 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. Step d) comprises the steps of scrubbing with water and fractionating the synthesis gas d1) and / or removing halogenated compounds d2) and / or steam reforming of carbon monoxide d3) and / or catalytic hydrolysis of compounds COS and HCN d4) and / or recombination d5) and / or scrubbing the recombined effluent with water d6) and / or removing acid gas d7) and / or final purification d8), preferably consisting of them, the method according to any one of claims 1 to 6.

8. The method according to any one of claims 1 to 7, wherein water formed during the Fischer-Tropsch synthesis step e) is partially or wholly sent to the electrolysis step b). **Claim 9** The method according to any one of claims 1 to 8, wherein at least a part of the gaseous fraction obtained from the Fischer-Tropsch synthesis step e) is recycled to the gasification step c) and converted into synthesis gas. **Claim 10** The method according to any one of claims 1 to 8, wherein at least a part of the gaseous fraction obtained from the Fischer-Tropsch synthesis step e) can be fed, at least partially with energy, to the drying operation a1) and / or the roasting operation a2). **Claim 11** The method according to any one of claims 1 to 10, wherein after the Fischer-Tropsch synthesis step e), a step f) of hydrotreating and / or isomerizing the hydrocarbon fraction obtained from step e) is carried out.

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