Method for processing biomass by co-grinding with fossil-based feedstocks

Abstract

The present invention relates to a novel method for processing a feedstock comprising biomass, said method comprising at least the following steps: a) drying said feedstock at a temperature of 20-180°C for a period of 5-180 minutes, b) torrefaction of the feedstock from step a) to produce at least one torrefaction biomass solids effluent, c) co-grinding the torrefaction biomass solids effluent from step b) in the presence of at least one solid fossil feedstock to obtain a powder. [Selection diagram] None

Description

[Technical Field]

[0001] The present invention relates to the treatment of biomass for its upgrading, in particular for carbonization, production of liquid hydrocarbons and optionally for petrochemical and / or chemical base stocks and / or production of hydrogen.

[0002] More particularly, the present invention relates to a method for processing a biomass-containing feedstock intended for injection into a gasification reactor for the production of hydrocarbons, particularly gasoline, diesel and kerosene. [Background technology]

[0003] In the field of the present invention, those skilled in the art are constantly striving to improve the conditioning of biomass, in particular to improve its heating value.

[0004] More specifically, improving the particle size distribution of the powder obtained by biomass-based treatment processes and the energy costs associated with this treatment are essential parameters in the preparation of biomass, especially in the most widespread gasification processes.

[0005] The processing of biomass is well known to those skilled in the art for the purpose of upgrading its quality through the production of hydrocarbons. The main steps in this processing are drying, thermal treatment such as torrefaction, and comminution. These steps are described in particular in WO 2014 / 068253. The main parameters of this processing are the properties of the powder obtained, in particular its size, the energy cost of comminution, and more generally the energy cost of the process.

[0006] Patent document 2 (WO 2013 / 114328) describes a process for grinding a carbon-containing feedstock derived from biomass in the presence of additives in the form of micron-sized powders, the additives being derived from mineral materials such as magnesium stearate or silica in the form of microbeads and / or plant materials such as woody or fossil carbon. This document aims to improve the properties of the powder obtained by grinding the biomass, such as flowability and suitability for fluidization, which makes it possible to obtain an intimate mixture of powders with small particle sizes. This document does not describe the use of additives other than in powder form, but only in micron-sized dimensions, during the grinding of the biomass. Optimizing the treatment and conditioning of biomass, in particular by simplifying the processes carried out and reducing the energy costs of said steps, especially the grinding step, remains an important challenge in the field of the present invention. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] WO2014 / 068253 [Patent Document 2] WO2013 / 114328 Summary of the Invention [Means for solving the problem]

[0008] Surprisingly, the inventors have discovered that at least one solid fossil feedstock have A method for processing biomass feedstocks by co-grinding at least one of the feedstocks in a mixture has been discovered.

[0009] Advantageously, said co-grinding allows for the grinding of the feedstock and the drying and grinding of the fossil feedstock. Indeed, grinding of the biomass feedstock is an exothermic process, and the heat generated advantageously allows for the simultaneous drying of the fossil feedstock. A further advantage of the process according to the invention is the reduction of the energy costs of the process due to the energy integration of the gases formed during the different steps.

[0010] The subject of the present invention is to provide a new process for the treatment of a feedstock comprising biomass, said process comprising at least the following steps: a) drying said feedstock at a temperature comprised between 20 and 180°C for a time comprised between 5 and 180 minutes. b) torrefying the feedstock from step a) to produce at least one torrefaction biomass solids effluent; and c) co-grinding the torrefaction biomass solids effluent from step b) in the presence of at least one solid fossil feedstock to obtain a powder.

[0011] The amount of residual water at the end of drying step a) is comprised between 0 and 5% by weight relative to the total weight of the feedstock. The dimensions of the solid fossil feedstock introduced in co-grinding step c) are comprised between 1 and 100 mm, preferably between 2 and 80 mm. The solid fossil feedstock introduced into co-grinding step c) has a moisture content comprised between 3.1 and 30% by weight, preferably between 4 and 25% by weight.

[0012] An advantage of the method according to the invention is that it makes it possible to obtain an intimate mixture of powders of small particle size distribution derived from biomass and fossil feedstocks.

[0013] The advantage of the co-grinding according to the invention is that the transfer of the thermal energy released by the grinding of the biomass to the fossil feedstock allows drying of the fossil feedstock simultaneously with the co-grinding step. A further advantage of the invention is that by combining a series of steps operating under specific conditions, it is possible to process biomass at limited energy costs and to enable their energy integration.

[0014] Preferably, the method comprises a step d) of final drying of the powder obtained at the end of step c) at a temperature comprised between 100 and 300°C.

[0015] Preferably, the final drying step d) is carried out simultaneously with the co-grinding step c).

[0016] Preferably, the biomass is selected from any type of biomass, preferably solid type biomass, in particular lignocellulosic type biomass.

[0017] Non-limiting examples of types of biomass are, for example, residues from agricultural operations (especially straw, corn cobs), residues from forestry operations, products from forestry operations, residues from sawmills, and dedicated crops, such as short rotation coppice.

[0018] Preferably, the method comprises a step i) of pre-treatment of the biomass, preferably a primary comminution.

[0019] Preferably, the torrefaction step b) is carried out at a temperature comprised between 200 and 350°C, preferably between 220 and 340°C, preferably between 250 and 320°C, more preferably between 270 and 300°C, for a time comprised between 5 and 180 minutes, preferably between 15 and 60 minutes, at an absolute operating pressure preferentially comprised between 0.1 and 15 bar, preferably between 0.1 and 10 bar, more preferably between 0.5 and 1.5 bar.

[0020] Preferably, the method comprises a step ii) of combustion of the torrefaction gas (11) derived from step b).

[0021] Preferably, energy derived from step ii) of the combustion of the torrefaction gas (11) is used to provide the heat energy required in the steps of this method, preferably steps a), b) and / or d).

[0022] Preferably, the solid fossil feedstock (9) introduced in co-grinding step c) is selected from solid fossil hydrocarbons such as coal, petcoke, oil tanker residues, bituminous sands or derivatives thereof, and oil shale or derivatives thereof.

[0023] Preferably, the solid fossil feedstock (9) is subjected to a pre-drying step iii).

[0024] Preferably, the torrefaction biomass solids effluent from step b) is introduced into co-grinding step c) in a weight percentage of torrefaction biomass solids effluent in the total solids feedstock, said weight percentage being comprised between 1 and 99 wt%, preferably between 50 and 98 wt%, more preferably between 40 and 95 wt%, said total solids feedstock being the sum of the torrefaction biomass solids effluent and the fossil feedstock.

[0025] Preferably, the solid fossil feedstock introduced into the co-grinding step c) has a moisture content comprised between 5 and 20% by weight.

[0026] Preferably, the method comprises one or more steps e) of storage of the effluent from one or any step of the method, preferably steps a), b), c) or d).

[0027] Preferably, the method comprises a step f) of transporting, preferably pneumatic transporting.

[0028] Preferably, the process comprises a gasification step g) at a temperature comprised between 800 and 1800°C, preferably between 1000 and 1600°C, more preferably between 1200 and 1500°C, advantageously at a pressure comprised between 20 and 120 bar, preferably between 25 and 60 bar, more preferably between 30 and 50 bar absolute. DETAILED DESCRIPTION OF THE INVENTION

[0029] (Definitions and Abbreviations) Throughout, the following terms or abbreviations have the following meanings:

[0030] Biomass refers, without limitation, to materials from solid types of biomass, especially lignocellulosic types of biomass. Non-limiting examples of types of biomass are, for example, residues from agricultural operations (especially straw, corn cobs), residues from forestry operations, forestry products, residues from sawmills, and those related to dedicated crops, such as short-rotation forests.

[0031] Solid fossil material means, without limitation, materials that, alone or in admixture, are solid under the conditions of the comminution process and are selected from solid fossil hydrocarbons such as coal, petcoke, oil tanker residue, bituminous sands or derivatives thereof, and oil shale or derivatives thereof. Anhydrous weight loss means the percentage of material lost in the torrefaction process (excluding water) compared to the total weight (excluding water) injected in the torrefaction process.

[0032] Torrefaction refers to a heat treatment method at a temperature of 200 to 350°C, and is generally carried out in an oxygen-deficient atmosphere.

[0033] Gasification refers to a process that performs a partial oxidation reaction to convert a feedstock into synthesis gas, which consists mostly of carbon monoxide and hydrogen.

[0034] Co-grinding refers to grinding a biomass feedstock in the presence of a solid fossil feedstock.

[0035] Relationship or weight ratio means the ratio of the weight of the component to the total weight of the feedstock.

[0036] Characteristic dimension refers to the measurement of the length of a particle along its largest dimension.

[0037] Anisotropic refers to the variable strength properties of a material depending on the direction of the force to which it is subjected.

[0038] Moisture content means the ratio of the weight of water contained in the feedstock to the total weight of the feedstock.

[0039] The various embodiments presented within the meaning of the present invention can be used alone or in combination with each other, without any restrictions on this combination.

[0040] (Feed material) According to the present invention, the feedstock for this process comprises biomass, either alone or in mixtures. The amount of water contained in the crude feedstock is 0.0 to 70.0 wt.%, preferably 5.0 to 70.0 wt.%, more preferably 10.0 to 70.0 wt.%.

[0041] The biomass is selected from any type of biomass, preferably solid type biomass, in particular lignocellulosic type biomass.

[0042] Non-limiting examples of types of biomass are, for example, residues from agricultural operations (especially straw, corn cobs), residues from forestry operations, products from forestry operations, residues from sawmills, and dedicated crops for example short rotation coppice.

[0043] Preferably, the biomass is of the lignocellulosic type, which essentially contains three natural components: cellulose, hemicellulose and lignin, present in variable amounts depending on its origin.

[0044] The lignocellulosic type biomass feedstock is preferably used in its raw form, i.e. in the whole form of its three components, cellulose, hemicellulose, and lignin.

[0045] In a preferred embodiment of the invention, the lignocellulosic biomass is selected from grass biomass, residues from agricultural operations (in particular straw, corn cobs, crushed sugarcane stalks), residues from forestry operations, or residues from sawmills, such as wood chips or other types of woody material.

[0046] In a preferred embodiment of the invention, said feedstock (1) can optionally be subjected to a pretreatment step i) before being introduced into step a) of the process according to the invention, the purpose of which is to enable the pretreated feedstock (2) to be injected into the drying step a).

[0047] The pretreatment step i) is a function of the type of feedstock in question. Preferably, it is a primary comminution step of said feedstock, making it possible to reduce its particle size distribution to a characteristic size between 10 and 50 mm. Said primary comminution step i) is advantageously carried out according to techniques known to those skilled in the art. Pretreatment step i) can also advantageously comprise shaping the feedstock, for example by pelletizing, compressing or other techniques known to those skilled in the art, with the aim of facilitating its transport, storage and subsequent processing in drying step a) of the method according to the invention.

[0048] (drying process a)) According to the present invention, the process comprises a step of drying the feedstock (1), which may be pretreated (2). The drying step a) is carried out by contacting the feedstock with a hot gas stream, which is then cooled. The hot gas stream enters the process at a temperature of 50 to 500°C, preferably 100 to 450°C, more preferably 150 to 350°C, for 5 to 180 minutes, preferably 10 to 100 minutes, more preferably 15 to 60 minutes, to produce the dried, optionally pretreated feedstock (3). The dried solid leaves the process at a temperature of 40 to 120°C, preferably 50 to 90°C, even more preferably 60 to 80°C. The purpose of drying is to remove the water contained in the feedstock. According to the present invention, the amount of residual water at the end of the drying step a) is between 0 and 5% by weight, based on the total weight of the feedstock.

[0049] The energy required for drying is generally provided by contacting the feedstock with a hot gas stream.

[0050] The hot gas stream used in the drying step may advantageously originate from the combustion of the input to the process, and preferably from the combustion of natural gas, and / or from the combustion of a gas stream originating from another step of the process.

[0051] For example, combustion of gases resulting from torrefaction step b) produces a hot gas stream that can be used to dry the feedstock by any method known to those skilled in the art. The gaseous effluent from step a) containing water can be used to preheat air to enable the combustion of natural gas and / or the combustion of the gas stream resulting during torrefaction.

[0052] In a particular embodiment, said feedstock (1) introduced in step a) consists of biomass as defined above.

[0053] (Torrefaction process b) According to the invention, the dry feedstock (3) from step a) is sent to a torrefaction step b) to produce at least one torrefaction biomass solids effluent (4).

[0054] Torrefaction is a process of mild pyrolysis in the temperature range of 200-350°C. The process is generally characterized by low temperature gradients (<50°C / min) and long residence times (20-60 min).

[0055] According to the present invention, the torrefaction step b) is carried out at a temperature of 200 to 350°C, preferably 220 to 340°C, more preferably 250 to 320°C, and even more preferably 270 to 300°C, for 5 to 180 minutes, preferably 15 to 60 minutes, at an absolute pressure of 0.1 to 15 bar, preferably 0.1 to 10 bar, and more preferably 0.5 to 1.5 bar (1 bar = 0.1 MPa). The torrefaction operation is carried out in an environment with an oxygen content of less than 10% by volume, preferably 0 to 10% by volume, more preferably 0 to 8% by volume, and even more preferably 0 to 3% by volume.

[0056] At around 200 °C, hemicellulose, the most reactive compound of lignocellulosic biomass, begins to undergo devolatilization and carbonization reactions. At this temperature level, cellulose and lignin are not significantly converted to their moieties.

[0057] The decomposition products of lignocellulosic biomass are produced in the form of condensable gases (mainly water, formic acid, acetic acid and other organic compounds) and non-condensable gases (mainly CO and CO2).

[0058] Torrefaction modifies the structure of lignocellulosic biomass and therefore its properties. In particular, the torrefaction operation makes the biomass more brittle and weakens its highly anisotropic properties. For example, it is well known to those skilled in the art that wood, due to its fibrous nature, has a much greater elastic resistance when stretched in the direction of the fibers than when applied transversely.

[0059] Thus, compared to a coarse biomass powder of a certain average particle size measurement, a much lower grinding energy (an effect related to the brittleness of the material) is required to obtain an equivalent powder based on the same biomass subjected to a torrefaction step, and the final shape of the obtained solid particles is closer to spherical particles (an effect related to less anisotropic properties), which facilitates the subsequent grinding.

[0060] The torrefaction step b) can advantageously be carried out in equipment of the rotary kiln, rotary torrefaction furnace, screw conveyor furnace, moving bed furnace and fluidized bed furnace type.

[0061] According to the present invention, the torrefaction step b) produces a solid effluent called torrefaction biomass (4).

[0062] Torrefaction step b) also allows the production of a combustible gaseous effluent (11), called torrefaction gas, whose amount, depending on the operating conditions, is preferably 5-40%, more preferably 10-35%, of the weight of the dried biomass derived from initial step a). One of the important parameters of the torrefaction step is the weight loss (expressed as a weight percentage), defined as the ratio of weight loss between the initial dried biomass and the dried torrefied biomass. The greater this loss, the lower the solid mass yield by weight and the greater the amount of torrefaction gas produced. The lower calorific value (LCV) of this gas is also known to be a function of the percentage of anhydrous weight loss (AWL), which is an increasing function of this ratio for a particular feedstock.

[0063] According to the invention, the selection of a sufficiently high rate of anhydrous weight loss during the torrefaction step makes it possible to limit the consumption of input fuel in this process, especially during the drying step, thus limiting the use of fuels of fossil origin by reusing the torrefaction gas produced in the torrefaction step.

[0064] In a preferred embodiment, the percentage of anhydrous weight loss is selected so that the heat released by combustion (internal or external post-combustion) of the torrefaction gases provides the energy required for at least one drying step. Preferably, the anhydrous weight loss is comprised between 1.0 and 40.0% by weight, preferably between 5.0 and 35.0% by weight, more preferably between 15.0 and 30.0% by weight, relative to the total weight of the feedstock (3) introduced into the torrefaction step b).

[0065] In one embodiment of this method, the torrefaction gas (11) is sent to a combustion step ii) where it is combusted in the presence of air and optionally natural gas to generate a hot gas stream (12) to a combustion chamber, which can be sent to drying steps a) and / or d) or the hot gas stream (13) can be sent to torrefaction step b). Combustion step ii) may or may not be advantageously integrated with torrefaction step b).

[0066] In one embodiment of this method, the energy generated during step ii) of combustion of torrefaction gas (11) from step b) is used to provide the energy required for at least one step of this method, preferably drying step a), and preferably using gas stream (12) for final drying step d) or gas stream (13) for torrefaction step b). The thermal energy from combustion step ii) is transferred to steps a), b) and / or d) by means known to those skilled in the art.

[0067] A portion of the hot gas stream (12) coming from the combustion step ii) can advantageously be sent to a heat exchange step making it possible to preheat the air used in the drying step a) and in the final drying step d).

[0068] In one embodiment of this process, a portion of the hot gas stream (13) originating from the combustion step ii) is injected directly into the torrefaction step b) so as to provide the energy required for the conversion of the biomass feedstock by gas / solid heat exchange.

[0069] If the flow rate of the combustible torrefaction gases resulting from step b) is insufficient, additional fuel, preferably natural gas, can be introduced in combustion step ii) to obtain the energy required for the various processes consuming thermal energy.

[0070] At the end of the torrefaction step b), the resulting torrefaction biomass solids effluent (4) has a moisture content of 0.0 to 5.0% by weight, preferably 0.0 to 3.0% by weight. Torrefaction biomass solids means the solids obtained by torrefaction of biomass.

[0071] The torrefaction biomass solids (4) obtained at the end of step b) may optionally be stored in an optional storage step before being introduced into the co-grinding step c) of the method according to the invention. This storage step can be advantageously realized according to methods known to those skilled in the art. Preferably, the torrefaction biomass solids can be stored in tanks equipped with screw conveyors, in silos or in suitable open-cell hangars.

[0072] In the advantageous case where the co-grinding step c) is carried out continuously, the storage step allows the torrefaction step b) and the optional combustion step ii) to continue operating in order to continue to generate the hot gas stream (12) required for the drying step a) and the final drying step d).

[0073] (Co-grinding process c) According to the invention, the method comprises step c) of co-grinding the torrefaction biomass solids effluent (4) in the presence of at least one solid fossil feedstock (9) to obtain a ground feedstock (5), also referred to as ground powder (5). The solid effluent (4) results from step b) and has been optionally stored in an optional storage step. The co-grinding step c) is carried out at a temperature between 0°C and 150°C, preferably between 20°C and 100°C, more preferably between 50°C and 90°C. The solid fossil feedstock (9) and the torrefaction biomass solids (4) are ground simultaneously in one and the same mill.

[0074] The purpose of the co-grinding step c) is to reduce the particle size distribution of the two feedstocks (4) and (9) introduced in said step c) while providing a particle shape suitable for subsequent transport and use and preferably for injection into their gasification process. The particles of the effluent (5) at the end of the co-grinding step c) have a characteristic size comprised between 50 and 200 microns, preferably between 70 and 200 microns, more preferably between 80 and 150 microns.

[0075] The solid fossil feedstock (9) introduced in the co-grinding step c) is preferably selected from solid fossil hydrocarbons such as coal, petcoke, oil tanker residues, bituminous sands or derivatives thereof, and oil shale or derivatives thereof.

[0076] Preferably, the dimensions of the solid fossil feedstock introduced in co-grinding step c) are comprised between 1 and 100 mm, preferably between 2.0 and 80 mm, more preferably between 3.0 and 70 mm, even more preferably between 4.0 and 60 mm, and most preferably between 5 and 50 mm.

[0077] In certain embodiments, the fossil feedstock may have dimensions of 30 to 100 millimeters, preferably 35 to 90 millimeters, more preferably 40 to 80 millimeters, and even more preferably 45 to 70 millimeters.

[0078] In another particular embodiment, the fossil feedstock may have a size of 1.0 to 60 millimeters, preferably 2.0 to 50 millimeters, more preferably 3.0 to 40 millimeters, and even more preferably 4.0 to 30 millimeters.

[0079] Preferably, the solid fossil feedstock (9) may be subjected to an optional grinding step to reduce the size of said feedstock and allow its introduction into the co-grinding step c).

[0080] The solid fossil feedstock (9) can advantageously be subjected to a pre-drying step iii) depending on its initial moisture content before being introduced into said co-grinding step c), which makes it possible to obtain a pre-dried fossil feedstock (10) suitable for injection into the co-grinding step c).

[0081] Preferably, the moisture content of the fossil feedstock (9) or (10) introduced into the co-grinding step c) is comprised between 3.1 and 30.0% by weight, preferably between 4.0 and 25.0% by weight, very preferably between 5.0 and 20.0% by weight.

[0082] Preferably, the torrefaction biomass solids effluent (4) and the solid fossil feedstock (9) or (10) are introduced into the co-grinding step c) so that the weight percentage of the torrefaction biomass solids effluent relative to the total solid feedstock introduced into the co-grinding step c) is comprised between 1 and 99 wt%, preferably between 50 and 98 wt%, more preferably between 40 and 95 wt%, where the solid feedstock refers to the sum of the torrefaction biomass solids (4) and the fossil feedstock (9) or (10).

[0083] Preferably, the co-grinding step can be carried out in the presence of additional compounds useful in the subsequent gasification step, said compounds being selected from vitrified ash, sand, limestone, lime or other compounds known to those skilled in the art, used alone or in mixtures.

[0084] Preferably, the mill is selected to optimize the pneumatic conveying of the powder (5) obtained from step c) and to minimize the minimum fluidization velocity (MFV) and its own energy consumption.

[0085] Preferably, said co-grinding step c) is carried out in a "roller mill", a "universal" or "attrition" type mill, or any other type of mill known to those skilled in the art.

[0086] Surprisingly, the applicant has noticed that co-grinding the torrefaction biomass solids (4) with the solid fossil feedstock (9) or (10) results in, in addition to the comminution of the solid fossil feedstock (9) or (10), particularly efficient drying of said feedstock (9) or (10). Indeed, comminution is a highly exothermic process. Additionally, the implementation described in accordance with the present invention allows for intimate mixing of the two feedstocks. Thus, by co-grinding a less moist feedstock, such as the torrefaction biomass solids effluent, with a moist feedstock, such as the solid fossil feedstock, the heat generated by the comminution of the biomass can be transferred to the moisture contained in the moist solid fossil feedstock, thus optimizing its drying. This co-drying advantageously simplifies the number of steps in the process and limits energy consumption.

[0087] (Optional final drying step d)) Preferably, the process according to the invention can comprise a final drying step d) of the powder (5) obtained at the end of step c), which is carried out by contacting the feedstock with a gas stream which enters the process at a temperature between 50 and 150°C, preferably between 70 and 120°C, to produce a dry powder (6).

[0088] The purpose of the optional final drying step d) is to reduce the moisture content of the powder (5) resulting from step c) to an acceptable level for injection into the subsequent processing step, preferably the gasification step. Preferably, the optional final drying step d) makes it possible to reduce the moisture content of the powder obtained at the end of step c) to less than 3.0% by weight, preferably between 1.0 and 3.0% by weight.

[0089] Preferably, the final drying step d) is carried out simultaneously with the co-grinding step c).

[0090] The thermal energy required for this drying is provided by combustion of an input stream to the process (such as natural gas) or, preferentially, by energy integration by means of a heat exchanger in which the hot gas stream from the combustion step ii) is used to preheat the drying air.

[0091] According to the invention, the selection of a sufficiently high rate of anhydrous weight loss in torrefaction step b) makes it possible to limit the use of input fuel in the process in step d), in particular to limit the use of fuels of fossil origin.

[0092] (Optional storage step e)) The method according to the invention can advantageously comprise one or more steps e) of storage of the effluents from one or more steps of the method, preferably from steps a), b), c) or d). Preferably, the effluents from steps c) or d) are stored to produce a stored effluent (7), also called stored powder (7).

[0093] The storage allows the retention of a buffer volume of feedstock. This volume is necessary to maintain the ability to operate the downstream section in the event of a shutdown of the upstream section. The storage step e) preferably consists of silos with a sufficient effective volume to ensure the supply of the downstream section. For example, the volume of these silos should provide a 24-48 hour supply to the downstream section.

[0094] The storage step e) may also include a pressurization system with various successive tanks operating successively to increase the storage pressure of the feedstock until it reaches a pressure compatible with injection into the next step, preferably the gasification step.

[0095] (Optional transport process f)) The effluent (5) from step c) or the effluent (6) from step d) or the effluent (7) from storage step e) can advantageously be subjected to a transport step f). The effluents thus transported are also called transport effluents (8) or transport powders (8). Transport step f) makes it possible to transport the effluents (5), (6) or (7), preferably blended to have the desired composition, to a subsequent step, preferably a gasification step g).

[0096] Preferably, the transport step f) is carried out according to the pneumatic transport technique.

[0097] The carrier gas used in step f) of the pneumatic transfer is preferably nitrogen, carbon dioxide or another inert gas that avoids the formation of zones containing explosive atmospheres (ATEX powder) and is compatible with the subsequent downstream steps, preferably the gasification step g).

[0098] The carrier gas is calculated according to methods known to those skilled in the art to obtain both the desired flow rate and transport density.

[0099] The parameters of the torrefaction step b) and the co-grinding step c) are selected to optimize the quality of this transport (the minimum fluidization velocity (MFV) is optimized according to the energy consumption of these sections).

[0100] (Optional gasification step g) The powder coming from steps c), d) or storage step e) can be transported to step f), preferably blended to have the desired composition and advantageously sent to a subsequent gasification step g).

[0101] The gasification step g) carries out a partial oxidation reaction which converts the feedstock into a synthesis gas consisting mostly of carbon monoxide and hydrogen. The gasification step g) is advantageously operated in the presence of a controlled amount of oxygen in the form of a flow rate which is controlled and which comprises at least 90% by volume of oxygen, preferably at least 96% by volume of oxygen.

[0102] The gasification step g) of the effluent (8) is advantageously carried out according to methods known to those skilled in the art.

[0103] It is preferably carried out in a gasifier of the fixed or fluidized bed type, or preferably in an entrained flow gasifier equipped with cooled walls, at high temperatures, i.e., between 800 and 1800°C, preferably between 1000 and 1600°C, more preferably between 1200 and 1500°C, and at absolute pressures advantageously comprised between 2 and 12 MPa, preferably between 2.5 and 6 MPa, more preferably between 3 and 5 MPa. Such high temperatures make it possible to obtain a high carbon conversion, thus reducing the amount of unconverted carbon in the ash produced and therefore the amount of ash recycled to the gasifier.

[0104] In certain embodiments of the invention, the method comprises steps a), b), and c), or steps a), b), c), and d), or steps a), b), c), d), and e), or steps a), b), c), d), e) and f), or steps a), b), c), d), e), f) and g).

[0105] In certain embodiments of the invention, the method consists of steps a), b), and c), or steps a), b), c), and d), or steps a), b), c), d), and e), or steps a), b), c), d), e) and f), or steps a), b), c), d), e), f) and g).

[0106] DESCRIPTION OF THE DRAWINGS FIG. 1 shows the general layout of the prior art process implemented in Example 1. The processing of biomass and solid fossil feedstock is carried out independently until injection into the optional gasification step g). The biomass feedstock (I) may undergo a pretreatment step i) before being introduced into step a). The pretreated biomass feedstock (II) or the unpretreated biomass feedstock (I) is dried in step a) to produce a dried biomass feedstock (III), also referred to as effluent (III). The effluent (III) from step a) is then torrefied in step b). The torrefaction step b) produces a solid effluent, referred to as torrefaction biomass (IV). The torrefaction biomass solid effluent (IV) resulting from step b) is then ground in step c). Optionally, the powder (V) from grinding step c) may be dried in a final drying step d). The powder (V) from step c) or the powder (VI) from step d) may be subjected to a storage step e). The stored powder (VII) or the crushed powder (V) or the dry powder (VI) may be subjected to a transport step f). The thus transported powder (VIII) may be subjected to a gasification step g). The solid fossil feedstock (IX) is crushed in a step c'). The powder (X) resulting from the crushing step c') is dried in a final drying step d') to produce a dry powder (XI). The powder (XI) resulting from step d') undergoes a storage step e'). The stored powder (XII) or the dry powder (XI) or the crushed powder (X) is subjected to a transport step f'). The thus transported powder (XIII) may be subjected to a gasification step g).

[0107] FIG. 2 shows the general layout of the process according to the present invention as implemented in Example 2. The biomass feedstock (1) may undergo a pretreatment step i) before introduction into step a). The pretreated biomass feedstock (2) or biomass feedstock (1) is dried in step a) to produce a dried biomass feedstock (3), also referred to as effluent (3). The effluent (3) from step a) is then torrefied in step b). The torrefaction step b) produces a solid effluent (4), referred to as torrefaction biomass. The torrefaction biomass solid effluent (4) from step b) is then co-ground in step c) in the presence of at least one solid fossil feedstock (9) to obtain a powder. The solid fossil feedstock (9) may undergo a pre-drying step iii) before introduction into the co-grinding step c), thereby obtaining a pre-dried fossil feedstock (10). The powder (5) from the co-grinding step c) can optionally be dried during a final drying step d). The co-ground powder (5) from step c) or the dry powder (6) from step d) may be subjected to a storage step e). The stored powder (7) or the ground powder (5) or the dry powder (6) may be subjected to a transport step f). The transported powder (8) may be subjected to a gasification step g). The torrefaction gas (11) from the torrefaction step b) is sent to a combustion step ii) where it is combusted to generate a hot gas stream (12) that enables heating of the drying step a) directly or indirectly via a heat exchanger. The gas from the combustion step ii) is combusted to generate a hot gas stream (13) that is sent to the torrefaction step b).

[0108] Figure 3 shows the general layout of the process according to the invention as implemented in Example 3. This method is a variant of the process as implemented in Example 2 and further includes energy integration in the final drying step d). In this variant, the final drying step d) can be heated by the torrefaction gas (12) either directly or indirectly via a heat exchanger.

[0109] The following examples illustrate the present invention without, however, limiting its scope. [Example]

[0110] Example 1: Process without co-milling (prior art) FIG. 1 shows the general layout of a prior art process according to Example 1.

[0111] According to this embodiment, the process can process two feedstocks. Feedstock A is a lignocellulosic biomass type in the form of oak wood chips with a characteristic size of 20-30 mm. The moisture content of this feedstock is 30% by weight. Fossil (coal) type feedstock B, in the form of particles with characteristic sizes ranging from 5 to 50 mm.

[0112] In this process there is no co-grinding step, nor is there a step of energy integration between the preparation lines of feedstock A and feedstock B.

[0113] The treatment process of feedstock A comprises an energy integration step from the torrefaction step b) to the drying step a) of the feedstock.

[0114] The objective of this method is to prepare one tonne of feedstock per hour for downstream processes (here, the gasification process). The feedstock produced must consist of 75% dry ash-free (DAF) biomass and 25% dry ash-free (DAF) fossil feedstock.

[0115] (Description of the preparation line for feedstock A) Feedstock A is sent to a drying step to reduce the moisture content of the feedstock to 3% by weight. The temperature of the solids at the end of the drying step is 70°C. The dried chips are conveyed to a torrefaction step operating at an average temperature of 300°C. The anhydrous weight loss during the torrefaction step is 27%. The residual moisture of the chips at the end of this step is considered to be zero.

[0116] The dried and torrefied chips are sent to a milling process, the technology of which is known to those skilled in the art, for example a milling process of the roller mill type. This process allows the particle size distribution of the majority (90% of the particles) to be reduced to less than 90 microns. The technique used to characterize the particle size distribution uses sieves according to standard NFEN 933.

[0117] According to this embodiment, there is no step called a final drying step: the feedstock A in the form of a dried and torrefied powder is sent by pneumatic conveying in a dilution stage to a storage step and then to a pneumatic conveying step that allows it to be injected into the downstream gasification process. Here, pneumatic conveying is carried out in a dense phase. This dense phase pneumatic conveying step is carried out here using an inert carrier gas. In this embodiment, the gas is nitrogen.

[0118] (Description of the preparation line for feedstock B) Feedstock B is sent directly to a grinding process whose technology is known to those skilled in the art, for example a roller mill type grinding process (for crushing). This process allows the particle size distribution of the majority (90% of the particles) to be reduced to less than 90 microns. The technique used to characterize the particle size distribution uses sieves according to standard NFEN 933. Simultaneously with the grinding process, the feedstock undergoes a final drying process which allows the moisture content to be 3% by weight. This final drying process is carried out using a natural gas burner which heats a gas stream which is brought into direct contact with the feedstock as it is ground, drying it.

[0119] The feedstock B in the form of a dry powder is sent by pneumatic transport in a dilution stage to a storage step, and then sent to a pneumatic transport step that allows it to be injected into the downstream gasification process. Here, pneumatic transport is carried out in a dense phase. The dense phase pneumatic transport step is carried out using nitrogen as an inert carrier gas.

[0120] The following table shows the utility consumption for this layout:

[0121] [Table 1]

[0122] The power consumed includes the power required for grinding in the centrifugal mill.

[0123] The consumed natural gas corresponds to the primary and final drying steps.

[0124] The nitrogen meets the requirements for pneumatic transport and aeration within the silo.

[0125] Example 2: Process with co-grinding and no energy integration into the process (according to the invention) FIG. 2 shows the layout of the process according to the invention as carried out in Example 2.

[0126] According to this embodiment, the process can process two feedstocks. Feedstock A of lignocellulosic biomass type in the form of oak wood chips with a characteristic size of 20-30 mm. The moisture content of this feedstock is 30% by weight. Fossil (coal) type feedstock B, in the form of particles with a characteristic size between 10 and 30 mm. Biomass type

[0127] In this process, there is a co-grinding step between the preparation line of feedstock A and the preparation line of feedstock B, and there is no energy integration into the drying step d). The co-grinding and final drying steps are carried out simultaneously.

[0128] The heat from the combustion of the torrefaction gas is used in the torrefaction step b) and the drying step a).

[0129] The objective of this process is to prepare one tonne of feedstock per hour for the downstream gasification process. The feedstock produced must consist of 75% dry ash-free (DAF) biomass and 25% dry ash-free (DAF) fossil feedstock.

[0130] (Mixed Feedstock Preparation Line Description) Feedstock A is sent to a drying step, which reduces the moisture content of the feedstock to 3% by weight. At the end of the drying step, the temperature of the solids is 70°C. The dried chips are conveyed to a torrefaction step operating at an average temperature of 300°C.

[0131] The anhydrous weight loss during the torrefaction process is 27%. The residual moisture of the chips at the end of this process is negligible and is considered to be zero.

[0132] The dried torrefaction chips are sent to a co-grinding process, for example of the centrifugal roller mill type, whose techniques are known to those skilled in the art. Feedstock B is conveyed directly to this same mill.

[0133] This process reduces the particle size distribution to a majority (90% of the particles) below 90 microns. The technique used to characterize the particle size distribution uses sieves according to standard NFEN933.

[0134] According to this embodiment, the feedstock mixture undergoes a drying step d) simultaneously with the grinding step. An unexpected effect of this grinding and drying of the mixture is the reduction of the energy required to dry feedstock B. In fact, the grinding of feedstock A is exothermic and generates heat that is used to dry feedstock B. The heat generated by the grinding of feedstock A allows for a significant reduction in the energy consumed for drying. This effect is reflected in the natural gas consumption of the burner and allows for an increase in the temperature of the burner atmosphere. The mixture of feedstocks A and B in the form of a dry powder resulting from grinding is sent by pneumatic transport in a dilution stage to a storage step and then to a pneumatic transport step, where it can be injected into the downstream gasification process. Here, pneumatic transport is carried out in a dense phase. The dense-phase pneumatic transport step is carried out here using an inert carrier gas, which in this example is nitrogen.

[0135] The following table shows the utility consumption for this layout:

[0136] [Table 2]

[0137] The power consumed includes the power required for grinding in the centrifugal mill.

[0138] The consumed natural gas corresponds to the final drying step d).

[0139] The nitrogen meets the requirements for pneumatic transport and aeration within the silo.

[0140] Example 3: Process involving co-grinding with energy integration into the final drying step d) (according to the invention) FIG. 3 shows the layout of the process according to the invention as carried out in Example 3.

[0141] This process includes a co-grinding step between the preparation lines for feedstock A and feedstock B, thus allowing the two feedstocks to be processed in one and the same preparation line. Furthermore, this method includes energy integration into the final drying step d).

[0142] The co-grinding and final drying steps are carried out simultaneously.

[0143] The characteristics of the feedstocks A and B used in this method are identical to those of the feedstocks A and B used in Example 2.

[0144] The heat generated from the combustion of the torrefaction gas is used in the torrefaction step b) and the drying step a).

[0145] The advantage of the process carried out in this example is the energy integration from the powder torrefaction step of the feed mixture to the final drying step, in this case the anhydrous weight loss is about 28%, which advantageously makes it possible to generate the heat required for said final drying.

[0146] Energy integration, also called heat integration, is performed here indirectly using heat exchangers.

[0147] The following table shows the utility consumption for this layout:

[0148] [Table 3]

[0149] The power consumed includes the power required for grinding in the centrifugal mill.

[0150] The consumed natural gas corresponds to the final drying step d).

[0151] The nitrogen meets the requirements for pneumatic transport and aeration within the silo.

[0152] These examples clearly show that the co-grinding of feedstocks A and B (Example 2) allows a significant reduction in natural gas consumption from 130 (Example 1) to 109 MJ / h. Furthermore, the energy integration into the final drying step d) (Example 3) is self-heating, i.e., no external energy supply is required. The input feedstock flow rate to the process is 1.04 t / h for an output of 1.0 t / h. The corresponding anhydrous weight loss therefore makes it possible to generate the heat required for the heat integration of torrefaction and final drying of the feedstock. [Brief explanation of the drawings]

[0153] [Figure 1] 1 shows the general layout of the prior art process implemented in Example 1. [Figure 2] 1 shows a general layout of the process according to the invention as carried out in Example 2. [Figure 3] 1 shows a general layout of the process according to the invention as carried out in Example 3.

Claims

1. 1. A method for processing a feedstock comprising biomass, comprising at least the following steps: a) drying said feedstock at a temperature comprised between 20 and 180°C for a time comprised between 5 and 180 minutes, b) torrefying the dry feedstock from step a) to produce at least one torrefaction biomass solids effluent; and c) co-grinding the torrefaction biomass solid effluent from step b) in the presence of at least one solid fossil feedstock to obtain a powder; a method comprising: the amount of residual water at the end of drying step a) is comprised between 0.0% and 5.0% by weight relative to the total weight of the feedstock, the size of the solid fossil feedstock introduced in co-grinding step c) is comprised between 1 and 100 millimeters, preferably between 2.0 and 80 millimeters; the solid fossil feedstock introduced into co-grinding step c) has a moisture content comprised between 3.1 and 30.0% by weight, preferably between 4.0 and 25.0% by weight, A process wherein the amount of residual water at the end of torrefaction step b) is comprised between 0.0% and 3.0% by weight relative to the total weight of the feedstock.

2. 2. The method according to claim 1, comprising a step d) of final drying of the powder obtained at the end of step c) at a temperature comprised between 100 and 300°C.

3. 3. The method according to claim 1 or 2, wherein the final drying step d) is carried out simultaneously with the co-grinding step c).

4. The method according to any one of claims 1 to 3, wherein the biomass is selected from solid lignocellulosic type biomass.

5. The method according to any one of claims 1 to 4, comprising a step i) of pre-treating the biomass, preferably a primary comminution.

6. 6. The process according to any one of the preceding claims, wherein the torrefaction step b) is carried out at a temperature comprised between 200 and 350°C, preferably between 220 and 340°C, preferably between 250 and 320°C, more preferably between 270 and 300°C, for a time comprised between 5 and 180 minutes, preferably between 15 and 60 minutes, at an absolute operating pressure comprised between 0.1 and 15 bar, preferably between 0.1 and 10 bar, more preferably between 0.5 and 1.5 bar.

7. The method according to any one of claims 1 to 6, comprising a step ii) of combustion of the torrefaction gas (11) resulting from step b).

8. 8. The method according to any one of claims 1 to 7, wherein energy from step ii) of the combustion of the torrefaction gas (11) is used to provide the thermal energy required in the steps of the method, preferably steps a), b) and / or d).

9. 9. The method according to any one of claims 1 to 8, wherein the solid fossil feedstock (9) introduced in co-grinding step c) is selected from solid fossil hydrocarbons such as coal, pet coke, oil tanker residue, bituminous sand or derivatives thereof, and oil shale or derivatives thereof.

10. The method according to any one of claims 1 to 9, wherein the solid fossil feedstock (9) is subjected to a step iii) of pre-drying.

11. 11. The method according to any one of claims 1 to 10, wherein the torrefaction biomass solids effluent from step b) is introduced into co-grinding step c) in a proportion comprising 1 to 99 wt. %, preferably 50 to 98 wt. %, more preferably 40 to 95 wt. % of the torrefaction biomass solids effluent in the total solids feedstock, the total solids feedstock being the sum of the torrefaction biomass solids effluent and the fossil feedstock.

12. 12. The method according to any one of claims 1 to 11, wherein the solid fossil feedstock introduced into co-grinding step c) has a moisture content comprised between 5.0 and 20.0 wt.%.

13. 13. The method according to any one of claims 1 to 12, comprising one or more steps e) for storage of the effluent from one or any step of the method, preferably steps a), b), c) or d).

14. The method according to any one of claims 1 to 13, comprising a step f) of transporting, preferably pneumatically transporting.

15. g) a gasification step g) at a temperature comprised between 800 and 1800°C, preferably between 1000 and 1600°C, more preferably between 1200 and 1500°C, and at an absolute pressure advantageously comprised between 2 and 12 MPa, preferably between 2.5 and 6 MPa, more preferably between 3 and 5 MPa.

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