METHOD FOR TREATMENT OF BIOMASS FOR INJECTION INTO A GASIFICATION REACTOR

Abstract

A biomass processing method comprising the following steps: a) supplying a biomass powder, for example, wood bark powder, the particle size of the biomass powder preferably being less than 200 µm; b) supplying an alginate solution comprising water and alginate, for example, potassium alginate or sodium alginate; c) adding the biomass powder to the alginate solution and mixing, thereby forming a colloidal suspension; d) adding the colloidal suspension dropwise to an ionotropic coagulation bath comprising multivalent ions, thereby forming biomass beads. Figure for abstract: 11

Description

Title of the invention: METHOD FOR PROCESSING BIOMASS FOR INJECTION INTO A GASIFICATION REACTOR Technical field

[0001] The present invention relates to the general field of shaping powders from biomass (raw or treated by thermochemical conversion).

[0002] The invention relates to a process for treating biomass and waste to agglomerate them in the form of "balls".

[0003] The invention also relates to biomass pellets thus obtained.

[0004] The invention also relates to a biomass gasification process using such pellets.

[0005] The invention also relates to the use of such beads as adsorbent products implemented in water treatment.

[0006] The invention is particularly interesting because it allows the formation of biomass pellets of calibrated diameter and aspect ratio close to 1 (almost perfectly spherical shape). These pellets exhibit good flowability properties and can be stored without risk of explosion or compaction.

[0007] The invention has applications in many industrial fields, in particular for the gasification of biomass (for example dust and other fine-sized carbonaceous waste in industry, for example in the paper industry) or for the depollution / decontamination of water, air and more generally of gases such as H2S, a pollutant of methanization gases. STATE OF THE PRIOR ART

[0008] In order to deal with energy dependence on fossil hydrocarbons, one of the most promising solutions is the production of synthesis gas (Syngas) and molecules of interest from biomass and / or carbonaceous waste (resource).

[0009] The valorization of carbonaceous products (biomass and waste) can be carried out by a gasification process (thermo-conversion) in an entrained flow reactor (EFR). This process consists of gasifying the resource, typically at temperatures ranging from 900 °C to 1400 °C and pressures ranging from 1 to 30 bar, to obtain a synthesis gas composed essentially of carbon monoxide (CO), dihydrogen (H2), and carbon dioxide (CO2). From CO and H2, it is then possible to obtain CH2 hydrocarbon chains similar to those derived from fossil hydrocarbons and thus produce a synthetic fuel. The carbon is thus valorized in the form of methane or syngas to produce fuels.

[0010] The gasification process also allows for the co-generation of heat and electricity.

[0011] Conventionally, before implementing the gasification step, the resource is mechanically pretreated through a grinding step to adapt the particle size to the conveying and injection system of the gasification reactors (typically less than 2 mm). This step is carried out using various grinding technologies, for example knife mills, hammer mills, chain mills, etc.

[0012] The grinding step also leads to the formation of fine particles (<200 µm). Fine powders containing lignocellulosic components are cohesive and elongated, which leads to flow difficulties due to electrostatic attraction (Van der Waals forces) between the reactor walls and the powder. These fine particles, which are generally difficult to convey, also increase ATEX risks (explosive atmosphere) and cause blockages throughout the system, leading to process shutdowns.

[0013] To avoid these drawbacks, fine particles (<200 pm) are separated from other particles by industrial screening equipment and are generally little or not at all recovered.

[0014] However, the fines fraction can thus represent 20 to 50% by mass of the ground material (depending on the severity of the grinding and the friability of the resource).

[0015] It is therefore essential to be able to make use of this fine powder, for example by transforming it into granules.

[0016] In order to be used in a gasification reactor, the granules must have a diameter between 200 µm and 3 mm. Fine powders with particle sizes smaller than 200 µm present blockage problems. Powders larger than 3 mm have low thermo-conversion efficiencies because the residence time of the feedstock in the reactor is short (a few seconds).

[0017] Various techniques exist for forming granules from fine particles, including wet granulation.

[0018] For example, in document FR 3 059 008 A1, pellets are obtained from a wet pelletizing process of biomass. The process comprises the following steps:

[0019] - biomass drying,

[0020] - biomass grinding,

[0021] - wet granulation of biomass in the presence of a binder, in particular starch, thereby moist granules are formed,

[0022] - drying to obtain dry granules and, optionally, sieving.

[0023] The granules are then injected into a gasification reactor. Satisfactory results regarding the flowability of the granules were obtained. However, this The process has some drawbacks: the particle size of the granules is not uniform, hence the need for a sieving step (sieve size: 900 µm), and a drying step is required (spreading the granules in thin layers and then drying them at room temperature for 8 hours), which complicates the process. Furthermore, the granules disintegrate easily, which poses a problem for their transport and conveying to the gasification plants.

[0024] In other technical fields, particularly the food and pharmaceutical industries, encapsulation processes exist for forming beads with a liquid core / gelling agent shell structure. For example, in document FR 2964017 A1, the process comprises the following steps:

[0025] - separate conveying in a double jacket of a first liquid solution containing the first product (active ingredient) and a second liquid solution containing a liquid polyelectrolyte to be gelled, for example alginate,

[0026] - formation of a series of drops each comprising a central nucleus containing the active ingredient, and a peripheral film completely covering the central core,

[0027] - contacting the droplet, formed in a gaseous volume at the outlet of the double envelope, with a gelling solution.

[0028] - immersion of each drop in a gelling solution containing a reagent suitable for react with the film's electrolyte.

[0029] The capsules obtained contain a liquid core and a gelled outer surface. However, such capsules are fragile (low mechanical strength over time). Furthermore, they have a high moisture content (typically greater than 80% wt%) and therefore cannot achieve good energy efficiency in a gasification reactor of the entrained flow reactor (EFR) type.

[0030] Furthermore, the beads produced by this process are submillimeter in size (particle size less than 500 pm). A drying step of these beads involves a reduction in particle size (syneresis effect of gels), which can become less than 200 pm; this is not suitable for a gasification plant, such as an RFE.

[0031] Finally, such a process is a batch manufacturing process, and the gelling bath is not recyclable, which complicates industrial-scale production. Description of the invention

[0032] An object of the present invention is to provide a biomass treatment process leading to the formation of biomass pellets having dimensions suitable for use in a gasification process and resulting in good gasification yield, the process being simple to implement, requiring little costly and with a low, or even zero, impact on the environment, including when implemented on an industrial scale.

[0033] To this end, the present invention proposes a biomass treatment process comprising the following steps:

[0034] a) supply a biomass powder, for example a wood bark powder, the particle size of the biomass powder preferably being less than 200 µm,

[0035] b) provide an alginate solution comprising water and alginate, for example potassium alginate or sodium alginate,

[0036] c) add the biomass powder to the alginate solution and mix, thereby forming a colloidal suspension,

[0037] d) add dropwise the colloidal suspension to an ionotropic coagulation bath comprising multivalent ions, thereby forming biomass beads.

[0038] The invention differs from the prior art in particular by the use of alginate to form biomass pellets by wet granulation. The alginate is mixed with the biomass before being injected dropwise into an ionotropic coagulation bath. This wet granulation process leads to the formation of pellets with a homogeneous size distribution and calibrated diameter. The pellets are formed from a homogeneous mixture of alginate and biomass (both in surface area and volume).

[0039] Such beads are easy to convey and inject into gasification reactors (e.g., entrained flow reactor, EFR). The fine particles are thus recovered.

[0040] Alginate is a natural polysaccharide obtained from algae. Alginate has the unique property of instantly forming a hydrogel in the presence of multivalent ions, particularly divalent ions. The carboxyl groups of alginate have the property of chelating divalent ions of opposite charge (e.g., Ca2+), leading to the formation of rigid three-dimensional networks. This is referred to as an "ionotropic" hydrogel.

[0041] By hydrogel, we mean a hydrophilic polymeric network capable of absorbing up to several thousand times its dry mass in water.

[0042] Advantageously, the ionotropic coagulation bath is an aqueous solution of calcium nitrate.

[0043] According to a highly advantageous embodiment, the ionotropic coagulation bath is an aqueous solution of calcium nitrate and potassium nitrate. The addition of potassium nitrate to the coagulation bath improves the catalytic effects during the RFE gasification process, and the thermo-conversion is enhanced.

[0044] Advantageously, the ionotropic coagulation bath has a pH between 3 and 7.

[0045] Advantageously, the alginate / biomass mass ratio of the colloidal suspension is between 0.01%m and 50%m, preferably between 1%m and 10%m, for example 1%m.

[0046] Advantageously, step d) is carried out using an injection nozzle, preferably having an outlet orifice of 1 mm to 20 mm in diameter. The use of a nozzle reduces the width of the particle size distribution: there are fewer possible rearrangements between the grains, an increase in porosity, and a decrease in compaction. This is beneficial for flowability, by reducing the risk of bridging / blocking.

[0047] Advantageously, the process includes a subsequent step e) in which the biomass particles are dried, for example with forced air, preferably at a temperature between 20°C and 30°C. This step is particularly advantageous when the pellets are used in a dry gasification process.

[0048] Advantageously, the process is carried out continuously:

[0049] - step a) is carried out in a first reactor,

[0050] - step b) is carried out in a second reactor, the first reactor and the second The reactor is in fluidic communication with a mixing tank.

[0051] - step c) is carried out in the mixing tank, in fluidic communication with an injection nozzle positioned opposite a tank containing the ionotropic bath, the tank advantageously being equipped with a pH probe, the tank being equipped with an outlet positioned opposite an element equipped with a multitude of openings, configured to evacuate the beads to a drying device and allowing a liquid phase to be recovered through the openings, the liquid phase being advantageously reinjected into the tank.

[0052] This continuous process is simple to implement and the various elements of the installation are easy to use. The entire process can be carried out at ambient temperature (typically between 20 and 25°C) and at ambient pressure (typically at a pressure of Ibar).

[0053] The process has many advantages, including one or more of the following:

[0054] - the fine biomass powder is distributed homogeneously within the beads,

[0055] - obtain micrometer-sized beads (typically larger than 50 µm and preferably larger than 200 µm) and preferably of millimeter size, which limits problems related to the handling and conveying of fine powders: blockages, health risks (including cancers associated with wood powders or the risk of Alzheimer's and / or pulmonary diseases) and ATEX (risk of explosion related to powders...),

[0056] - modify the surface condition of the balls: the balls are smoother, which reduces the powder-to-powder and powder-to-wall friction, thus avoiding blockages / vaults / consolidations

[0057] - modify the mechanisms of particle interactions (electrostatic forces, Van der Waals forces...) dependent on particle size; a decrease in these interactions leads to reduced agglomeration between particles and blockages, improving particle flowability.

[0058] - the agglomeration of the beads does not require any external intervention (the (this phenomenon occurs on its own) and the energy expenditure related to this agglomeration is zero.

[0059] - not having strong consolidation within the beads, which facilitates disintegration in reactor): the ball can easily break down in RFE where residence times are short because the particles are not highly compacted.

[0060] - the properties of the particles are not modified by the mechanism agglomeration and once released they have the same behavior in gasification as if they had not been agglomerated into beads.

[0061] The invention also relates to biomass pellets obtained from the process described above. The pellets obtained are rigid.

[0062] Advantageously, the biomass pellet comprises a homogeneous mixture of alginate and biomass. Preferably, the biomass is wood bark.

[0063] The composition of the bead is homogeneous over its surface and volume. The resulting beads do not have a core / shell structure. The alginate is found throughout the entire volume of the bead.

[0064] Advantageously, the aspect ratio of the ball is close to 1 (almost perfectly spherical shape). This considerably reduces conveying problems due to interaction between the balls because of their morphology (asperities promoting snagging but also possibilities of grain rearrangement in the interstices).

[0065] Advantageously, the ball has a diameter between 1mm and 20mm.

[0066] The beads may also contain inorganic species (calcium and, preferably, potassium) which promote the gasification kinetics by catalytic effect.

[0067] The biomass pellets thus obtained have many properties: ease of storage and handling, better flowability.

[0068] The invention also relates to a gasification process comprising a step in which biomass pellets as defined above are gasified in a gasification reactor, in particular an entrained flow gasification reactor.

[0069] The biomass pellets can be raw or torrefied.

[0070] The use of such beads facilitates the implementation of the gasification process (and in particular the conveying and injection steps) compared to processes using fine biomass powders or biomass pastes and thus increases the profitability of the gasification process.

[0071] It allows the gasification of fine biomass powders (particle size <200 pm) transformed into biomass pellets (size between, for example, 200 pm and 3 mm) and thus increases profitability since all powders can be gasified.

[0072] The natural binder derived from biomass itself volatilizes easily in the reactor: the ball can disintegrate in a few seconds in RFE and the fine particles are released and gasified; the binder can itself participate in the gasification yield.

[0073] Alginate can have an impact on the morphology and wall structure of the beads formed, which may promote the penetration of reactive gases during gasification.

[0074] The beads contain less sulfur in proportion compared to beads made solely of biomass, which reduces the phenomena of catalyst poisoning during gasification.

[0075] The invention also relates to the use of biomass beads, as defined above, for example, wood bark beads, as adsorbent products used in water treatment. The beads form a filter medium for the adsorption of pollutants in liquid effluents. They can also form a filter medium for the adsorption of pollutants in gaseous effluents.

[0076] An increase in bed porosity can promote interaction between the fluid being treated and the filter medium. If the particles are too tightly interlocked, there is a risk that the fluid will not flow properly through the filter medium.

[0077] Other features and advantages of the invention will become apparent from the following supplementary description.

[0078] It goes without saying that this additional description is given only as an illustration of the object of the invention and should in no case be interpreted as a limitation of this object. Brief description of the drawings

[0079] The present invention will be better understood upon reading the description of exemplary embodiments given by way of illustration only and in no way limiting, with reference to the accompanying drawings in which: [Fig.1] represents a manufacturing protocol for biomass pellets according to a particular embodiment of the invention.

[0080] [Fig.2] Schematic representation of a pilot production line of continuous ball feed (capacity: 100 kg / h), according to another particular embodiment of the invention.

[0081] [Fig.3A]

[0082] [Fig.3B] are photographic images representing wet biomass pellets produced from wood bark powder, according to another particular embodiment of the invention.

[0083] [Fig.4A]

[0084] [Fig.4B] are photographic images representing ionotropic coagulation baths containing wet biomass beads produced from wood bark powder, according to another particular embodiment of the invention.

[0085] [Fig.5A] is a graph representing the particle size distribution of fine wood bark powder.

[0086] [Fig.5B] is a graph representing the size distribution of bark balls, obtained from a fine powder of wood bark, according to another particular embodiment of the invention.

[0087] [Fig.6A] is a photographic image representing particles of a fine biomass powder.

[0088] [Fig.6B] is a photographic image representing wet balls produced from wood bark powder, shown in [Fig.6A], according to another particular embodiment of the invention.

[0089] [Fig.6C] is a photographic image representing dry balls produced from wood bark powder, shown in [Fig.6A], according to another particular embodiment of the invention.

[0090] [Fig.7] schematically represents an avalanche angle.

[0091] [Fig.8A]

[0092] [Fig.8B]

[0093] [Fig.8C] represent avalanche angles of a biomass powder.

[0094] [Fig.8D]

[0095] [Fig.8E]

[0096] [Fig.8F] represent avalanche angles of glass beads.

[0097] [Fig.8G]

[0098] [Fig.8H]

[0099] [Fig.81] represent avalanche angles of biomass logs, according to a mode of a particular implementation of the invention.

[0100] [Fig.9] is a scanning electron microscope image of a bead of biomass, according to a particular embodiment of the invention.

[0101] [Fig.1OA]

[0102] [Fig.1OB] are images obtained by scanning electron microscopy of the inside of a biomass bead, according to a particular embodiment of the invention.

[0103] [Fig. 11] is a graph representing the percentage by mass and the temperature as a function of time for gasification tests on a wood bark powder and on wood bark biomass logs obtained according to a particular embodiment of the invention.

[0104] The different parts represented in the figures are not necessarily shown on a uniform scale, in order to make the figures more legible.

[0105] The different possibilities (variants and embodiments) should be understood as not being mutually exclusive and can be combined with each other.

[0106] Furthermore, in the description below, orientation-dependent terms such as "above", "below", etc. of a device apply assuming that the structure is oriented in the manner illustrated in the figures.

[0107] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0108] Subsequently, even though the description refers to biomass from the forestry and agricultural industries, the invention is applicable to other types of biomass, for example, food waste, household waste, agricultural waste, microplastics, nanoparticles, fine particles from industrial processes, carbon black, sewage sludge, etc. It can also relate to raw materials or materials resulting from the thermochemical conversion of biomass, such as fine particles from a carbonization process. The invention is useful for recovering dust and other small-sized waste (typically less than 200 µm), facilitating its storage and disposal (e.g., quenching baths or cyclones in gasification reactors, sawmills, etc.).

[0109] Although this is not limiting in any way, the invention finds particular applications for valorizing fine wood bark powders.

[0110] The biomass processing method comprises the following steps ([Fig. 1]):

[0111] a) supplying a biomass powder,

[0112] b) provide an alginate solution comprising water and alginate, for example potassium alginate or sodium alginate,

[0113] c) add the biomass powder to the alginate solution and mix, thereby forming a colloidal suspension,

[0114] d) add dropwise the colloidal suspension to an ionotropic coagulation bath comprising multivalent ions, thereby forming biomass beads.

[0115] e) optionally dry the biomass particles, for example with forced air, preferably at a temperature between 20°C and 30°C.

[0116] The biomass powder supplied in step a) comprises biomass particles. The particle size is preferably less than 200 µm. The particle size is, for example, between 1 µm and 1000 µm, preferably between 1 µm and 200 µm.

[0117] In the context of this invention, the term biomass implies any material (homogeneous and inhomogeneous) of plant and / or animal origin containing carbon, such as biomass from forest residues, agricultural residues, household waste, tire waste, carbon black, sewage sludge, animal bone waste, etc. All these resources can be dry or wet.

[0118] Biomass can also refer to biomass treated by various thermo-conversion processes, such as, for example, torrefaction, pyrolysis, hydrothermal carbonization, hydrothermal liquefaction, and / or carbon residues. For example, the term biomass also refers to biochars (pyrolysis), biocoals (torrefaction), hydrochars (hydrothermal carbonization), and chars (gasification).

[0119] The biomass powder is preferably a wood bark powder.

[0120] The alginate solution provided in step b) is, for example, a solution containing an alginate mass content ranging from 0.01 wt% to 50 wt%, preferably from 1 wt% to 10 wt%. Preferably, the alginate is sodium alginate: it is an inexpensive and widely commercially available reagent.

[0121] Step c) is, for example, carried out under magnetic stirring. The speed of rotation of the mixture and the duration of the mixing will be chosen by a person skilled in the art. Step c) is carried out until a homogeneous mixture is obtained.

[0122] The ionotropic coagulation bath (also called a spherification bath) is an aqueous solution. The solution contains multivalent ions (for example, divalent or trivalent ions, preferably divalent ions) that can react with the alginate to form a polymer. For example, these could be copper, cadmium, barium, calcium, cobalt, nickel, iron, zinc, or manganese ions.

[0123] Calcium ions are preferred. These ions are not toxic and their use does not require an additional purification step compared to other ions.

[0124] The ionotropic coagulation bath is, for example, a calcium chloride solution.

[0125] Preferably, the ionotropic coagulation bath is an aqueous solution of calcium nitrate, which may further comprise potassium nitrate.

[0126] Preferably, the ionotropic coagulation bath has a pH between 3 and 7. A pH of 4 will be chosen for example.

[0127] The ionotropic bath may also include substances to give particular properties to the beads, for example dyes, flame inhibitors and / or accelerators, etc.

[0128] The ionotropic bath may contain species that chelate multivalent ions, in particular calcium ions.

[0129] The alginate / biomass mass ratio of the colloidal suspension is between 0.01%m and 50%m, preferably between 1%m and 10%m, for example 1%m.

[0130] Step d) is carried out using an injection nozzle, preferably having an outlet orifice of 1 mm to 20 mm in diameter. A diameter of 3 mm will be chosen for example.

[0131] Step e) of drying is advantageously carried out in air at ambient temperature (typically 20 to 25°C). No energy input is required. Forced air can be used. For example, wet beads with a diameter of 3 mm have a diameter of 1.45 mm after drying.

[0132] Advantageously, the entire process is carried out at room temperature.

[0133] According to a particularly advantageous embodiment, the process is carried out continuously. For example, the continuous process is carried out using the biomass pellet production line shown in [Fig. 2]. Such an installation makes it possible to obtain up to 100 kg / h of pellets.

[0134] Step a) is carried out in a first reactor 100.

[0135] Step b) is carried out in a second reactor 200.

[0136] The first reactor and the second reactor are in fluidic communication with a mixing tank 300, equipped with a mixer 310.

[0137] Step c) is carried out in the mixing tank 300.

[0138] The mixing reservoir 300 is in fluidic communication with one or more injection nozzles 320 arranged opposite a tank 400 containing the ionotropic coagulation bath.

[0139] A flow meter 330 can be used to control the flow at the level of the nozzle(s) 320.

[0140] The tank 400 is advantageously equipped with a mixing device 410 and / or a pH 420 probe. The pH 420 probe allows, in particular, to determine if the quantity of divalent ions is still sufficient.

[0141] The balls 10 fall by gravity to the bottom of the tank 400.

[0142] Advantageously, the tank 400 is equipped with an outlet 430 arranged opposite a recovery element 500.

[0143] For example, a double guillotine system 440 arranged at the bottom of the tank allows a fraction of the volume of the tank 400 formed of a liquid phase 20 and a solid phase (beads 10) to be evacuated.

[0144] The recovery element 500 is provided with a multitude of openings. The dimensions of the openings are smaller than the dimensions of the beads 10. The liquid phase passes through the openings. The solid elements (beads 10) are conveyed, for example, to a drying device 600.

[0145] The recovery element 500 can be an inclined tray or a conveyor belt.

[0146] The drying device 600 operates, for example, with forced air.

[0147] The liquid phase 20 is advantageously reinjected into the tank 400.

[0148] The beads obtained with the process described above comprise a homogeneous mixture of alginate and biomass. The beads have a diameter of between 1 mm and 20 mm, for example 3 mm.

[0149] The aspect ratio of the ball is advantageously close to 1.

[0150] The beads obtained are rigid materials, stable over time (several years, for example between 1 and 5 years).

[0151] The beads can then be used in a gasification process. The beads can be used raw or roasted.

[0152] The gasification process is implemented in a gasification reactor, in particular an entrained flow gasification reactor.

[0153] The gasification process can be carried out continuously in an installation comprising a gasification reactor, for example with entrained flow, and upstream of this a biomass pellet production line intended to implement the biomass treatment process.

[0154] Alternatively, the beads can be used as adsorbents in various liquid or gaseous effluent treatments (such as, for example, the removal of H2S from the biomethane production process by anaerobic digestion). In particular, this can involve the treatment of aqueous effluents, for example, industrial wastewater. For instance, the beads can adsorb all or part of certain elements present in aqueous effluents. Examples include lead, zinc, and nickel. Water purification processes designed to remove mineral particles from polluted water can also be used. After an initial particle removal step by filtration or centrifugation, the fine particles can advantageously be collected and then removed by the process of the invention.

[0155] The waters are thus decontaminated / depolluted.

[0156] Illustrative and non-limiting examples of an embodiment:

[0157] Production of beads in the laboratory:

[0158] In this example, 40g of biomass powder (particle size less than 100pm) were added to a solution comprising 10g of alginate and 990mL of water.

[0159] The colloidal suspension thus obtained was mixed for 30 min at 300 rpm.

[0160] The colloidal suspension was then added dropwise into a bath of ionotropic coagulation (10g of Ca(NO3)2 and 990mL of water).

[0161] This yields biomass pellets. The pellets are dried at room temperature (20-25°C). The pellets can then be injected into an entrained flow gasification reactor.

[0162] Industrial-scale production of marbles:

[0163] According to another example, biomass “beads” (<200 pm) were prepared in three stages on a pilot line (Figures 1 and 2):

[0164] - step 1: One liter of sodium alginate solution (1% w) is prepared by the 10 kg of sodium alginate is dissolved in 990 kg of water in a reactor 200. The mixture is mechanically stirred at 300 rpm for 1 h (to obtain complete homogenization of the solution). Then, a mass of biomass powder ranging from 1-100 kg (particle size < 200 µm) is mixed with the alginate solution under agitation (at 300 rpm) for 1 h in a mixing tank 300.

[0165] - step 2: The flow rate of the injection of the alginate and biomass powder mixture The ionotropic coagulation bath (containing 10 kg of calcium nitrate and 10 kg of potassium nitrate dissolved in 980 kg of water) is controlled by a peristaltic pump (flow rate 1 m³ / h) in tank 400. At the outlet of pump 330, a system of nozzles (320) with a diameter of 0.3 mm is installed, allowing for the metering of uniformly sized droplets into the ionotropic coagulation bath. The desired droplet diameter can be adjusted and controlled according to the nozzle diameter (typically from 1 mm to 20 mm, preferably 3 mm).

[0166] - step 3: The beads formed in the ionotropic bath have a residence time The water is left in the ionotropic bath for more than 30 minutes, then collected and air-dried (at 22°C) for 5 to 10 hours. The water from the ionotropic bath is recycled within the system, and the pH is monitored. The initial pH of the bath is above 3 and below 7.

[0167] A sample of the beads 10 is carried out by an airlock 440 positioned at the foot of the coagulation bath with gravity dewatering on a perforated tray 500 with recovery and reinjection of the collected water 20 into the bath and collection and drying by air circulation of the beads 10.

[0168] The ionotropic bath in the tank 400 and the colloidal alginate / biomass powder suspension in the mixing tank 300 are homogenized using an agitator 410, 310 equipped with blades.

[0169] Monitoring the water level in the mixing tank 300 to continuously adjust the dosage of biomass powder and alginate.

[0170] During the bead formation process, the pH of the bath gradually increases. The evolution of the pH of the ionotropic coagulation bath is monitored using a pH 420 probe (to determine when to replace it when the coagulation efficiency drops and impacts the quality of the beads). The initial pH of the bath is greater than pH 3.0 and less than pH 7.0. During the bead formation process, The pH of the bath increases gradually; if the pH > 7.0, the addition of 10 kg of calcium nitrate and 10 kg of potassium nitrate is necessary.

[0171] Characterization of the dimensions of the balls:

[0172] The average diameter of the beads at the end of the laboratory process was 0.3 mm (figures 3A and 3B). However, this diameter can be adjusted and controlled according to the diameter of the nozzles used in the manufacturing process (typically from 1 mm to 20 mm, preferably 3 mm).

[0173] The pilot-scale example confirmed the repeatability of the results obtained (Figures 4A and 4B). The beads are uniform and homogeneous (0.3 mm). The wet beads were air-dried (without any energy input to the system). The size of the dry beads is 1.45 mm, half that of the wet beads.

[0174] The size of the dry beads corresponds to the optimum particle size for injection into an RFE reactor, however this size can be adjusted according to the diameter of the nozzles used during manufacturing (typically from 1 mm to 20 mm, preferably 3 mm).

[0175] The particle size distribution of the fine wood bark powder and air-dried logs was checked using a CAMSIZER XT particle analyzer (manufacturer: Retsch Technology).

[0176] Figures 5A and 5B show that the mean diameter (d50) of the powder samples is 48.9 pm and for the dried beads is 1445 pm, a factor of 30 compared to the fine powder. The particle size distribution of the beads is less spread out than that of the fine wood bark powder, indicating a monodisperse (less spread out) distribution for the beads.

[0177] It has also been verified that the drying step reduces the particle size by a factor of 2 compared to freshly produced wet beads (Figures 6A, 6B and 6C).

[0178] Composition of the beads:

[0179] The characterization results of the biomass pellets and powder (particularly wood bark) are presented in Table 1 below. The pellet formation process does not alter the carbon content or the higher heating value (HHV) of the final product compared to the powder (17 MJ / kg). However, the manufacturing process may slightly increase the ash content by approximately 2% wt% due to the presence of divalent ions in the ionotropic bath.

[0180] It should be noted that the percentage of sulfur present in the pellets is lower than that of biomass powder, which is particularly interesting when the gasification process is carried out in the presence of a catalyst.

[0181] Table 1. Elemental analyses.

[0182] [Tables 1] Elemental Analysis Ash Content Gross Heating Value Biomass c H (%) DM (%) O (%) (%) (MJ kg1) Bark Powder 42.2 5.42 0.72 0.29 40.9 9.84 17.0 Bark Powder Pellets 42.7 5.71 0.72 0.18 39.5 11.87 16.9

[0183] Cohesiveness tests (avalanche angle):

[0184] The cohesiveness tests were carried out using a rotating drum (REVOLUTION, manufacturer: Mercury Scientific Inc., USA) equipped with a suitable camera that allows the determination of the average avalanche angle of samples. The avalanche angle represents the ability of a free powder (in the absence of mechanical constraints other than its own weight) to consolidate. The closer the angle is to zero, the more the powder "collapses" and spreads out. The closer this angle is to 90°, the more the powder tends to form arches and vaults that impede its flow (highly cohesive powder).

[0185] The avalanche angle is determined by the angle formed by the upper half of the powder surface in the drum with the horizontal, before an avalanche ([Fig.7]).

[0186] Avalanche angle measurements were taken for:

[0187] - a biomass powder (particle size <200 pm) ([Fig.8A], 8B and 8C),

[0188] - glass beads with a diameter of 0.3 mm (figures 8D, 8E and 8F),

[0189] - a biomass powder produced according to the invention (0 3 mm) (figures 8G, 8H and 81).

[0190] The average angle results on 1000 avalanches are listed in the following table 2.

[0191] Biomass powder (particle size <200 µm) exhibits high cohesiveness, resulting in a high avalanche angle (87.7°). This value is also an indicator of potential blockage / conveying problems frequently encountered in gasification processes. Indeed, high cohesiveness leads to low powder flowability, meaning a poor ability to flow under pressure, for example, through an injector.

[0192] The "spherification" procedure improves the flowability of the powder for injection into an entrained flow reactor. The bark beads have an avalanche angle half that of the powder, resulting in improved flowability. The avalanche angle of the biomass beads (40.3°) is close to the values ​​obtained with the glass beads (39.2°) and demonstrates the process's effectiveness in improving injection into an entrained flow reactor.

[0193] Table 2. Avalanche angle (average over 1000 avalanches).

[0194] [Tables2] Avalanche angle (Bark powder F 200 pm) Glass beads (0.3 mm) Bark powder beads (0.3 mm) 87.7° 39.2° 40.3°

[0195] Humidity level:

[0196] Measurements of the moisture content of the air-dried beads at room temperature (22°C, for 10 h) were carried out in a laboratory oven at 105 °C (for 24 h) following the EN18134 standard. The results confirm a residual moisture content of 1.2%m.

[0197] It should be noted that the initial moisture content of freshly prepared beads (which have not undergone a drying step) is 90%. The air-drying step is effective in volatilizing almost all of the water present in the beads, which saves energy costs in the preparation process and allows for better management of the resource for its injection into gasification reactors.

[0198] Morphology of the surface of the beads:

[0199] Scanning electron microscopy (SEM) images were obtained to verify the surface structure of the biomass beads. The analyses confirm a rigid and compact structure ([Fig. 9]). The biomass powder is distributed over the entire surface of the bead, and the alginate-based biopolymer acts as a binder that facilitates the spherical agglomeration of the biomass powder.

[0200] The morphology within the beads was also observed under a microscope (by cutting a bead in two halves with a scalpel). The images in Figures 10A and 10B show a homogeneous surface inside the bead, which confirms a total distribution of the biomass powder throughout the volume of the spheres.

[0201] Gasification tests:

[0202] Steam gasification tests were carried out in an ATG thermo-conversion device (SETSYS, manufacturer SETARAM, France), using biomass powder (in particular wood bark powder: particle size < 200 µm) and biomass pellets (in particular wood bark pellets: particle size 0.3 mm). For these tests, the ATG device was heated at a rate of 10 °C / min, up to 900 °C. Once this temperature was reached, thermochemical gasification was carried out by injecting steam for a 70-minute holding period.

[0203] Figure 11 shows the results of mass loss as a function of temperature during the gasification process. The gasification results of the beads (containing calcium and potassium ions from the production process) show a steeper ramp and faster conversion kinetics than those of the powder. raw biomass. This is due to the catalytic effect of calcium and potassium ions on the process.

[0204] The pellet production process improves the flowability of the biomass powder as well as its thermo-conversion kinetics in a gasification reactor (e.g., driven flow reactor).

Claims

Claims

1. A method of treating biomass to produce biomass beads suitable for use in a gasification process, the method comprising the following steps: a) providing a biomass powder, for example a wood bark powder, the particle size of the biomass powder preferably being less than 200 pm, b) providing an alginate solution comprising water and alginate, for example potassium alginate or sodium alginate, c) adding the biomass powder to the alginate solution and mixing, whereby a colloidal suspension is formed, d) adding the colloidal suspension dropwise to an ionotropic coagulation bath comprising multivalent ions, said ionotropic coagulation bath being an aqueous solution of calcium nitrate, whereby biomass beads suitable for use in a gasification process are formed.

2. A method of treating biomass to manufacture biomass beads suitable for use in a gasification process, the method comprising the following steps: a) providing a biomass powder, for example a wood bark powder, the particle size of the biomass powder preferably being less than 200 pm, b) providing an alginate solution comprising water and alginate, for example potassium alginate or sodium alginate, c) adding the biomass powder to the alginate solution and mixing, whereby a colloidal suspension is formed, d) adding the colloidal suspension dropwise to an ionotropic coagulation bath comprising multivalent ions, said ionotropic coagulation bath being an aqueous solution of calcium nitrate and potassium nitrate, whereby biomass beads suitable for use in a gasification process are formed.

3. Method according to claim 1 or 2, characterized in that the method comprises a subsequent step e) during which dries the biomass particles, for example with forced air, preferably at a temperature between 20°C and 30°C.

4. Method according to any one of the preceding claims, characterized in that the ionotropic coagulation bath has a pH between 3 and 7.

5. Method according to any one of the preceding claims, characterized in that the alginate / biomass mass ratio of the colloidal suspension is between 0.01% m and 50% m, preferably between 1% m and 10% m, for example 1% m.

6. Method according to any one of the preceding claims, characterized in that step d) is carried out by means of an injection nozzle, preferably having an outlet orifice of 1 mm to 20 mm in diameter.

7. Method according to any one of the preceding claims, characterized in that the method is carried out continuously, Step a) being carried out in a first reactor (100), Step b) being carried out in a second reactor (200), The first reactor (100) and the second reactor (200) being in fluid communication with a mixing tank (300), step c) being carried out in the mixing tank (300), in fluid communication with an injection nozzle (320) arranged opposite a tank (400) containing the ionotropic bath, the tank (400) being advantageously provided with a pH probe (420), the tank (400) being provided with an outlet (430) arranged opposite an element (500) provided with a multitude of openings, configured to evacuate the beads towards a drying device (600) and making it possible to recover a liquid phase through the openings, the liquid phase being advantageously reinjected into the tank (400).

8. Biomass ball suitable for use in a gasification process and obtained according to the process according to any one of claims 2 to 7, comprising a homogeneous mixture of alginate and biomass, preferably wood bark.

9. Ball according to claim 8, characterized in that it has a diameter of between 1mm and 20mm.

10. Ball according to one of claims 8 and 9, characterized in that the aspect ratio of the ball is close to 1.

11. A gasification process comprising a step during which biomass balls as defined in

12. any one of claims 8 to 10, in a gasification reactor, in particular an entrained flow gasification reactor. Use of biomass balls, as defined in any one of claims 8 to 10, for example wood bark balls, as adsorbent products used in water treatment.

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