EP4212606A1 - Biomass gasification process - Google Patents

Abstract

Gasification process comprising the following steps: a) bringing into contact in a main reactor (100) balls (200) made of steel, alloy, glass or ceramic, at a temperature between 600°C and 1000°C, with a mixture to be treated comprising water and a biomass, the biomass comprising an organic part and salts, the main reactor (100) pressurized at more than 224 bars and at a temperature above 200°Cb) gasifying the organic part in the presence beads, whereby a gas phase, an aqueous phase and a solid residue are formed, and whereby the salts precipitate on the beads (200), forming a shell (210) of salts covering the beads (200),c) separating the balls (200) of the organic part,d) regenerating the balls (200).

Description

TECHNICAL AREA

The present invention relates to the general field of energy recovery from biomass.

The invention relates to a method for the gasification of biomass.

The invention also relates to a gasification device.

The invention is particularly advantageous since it makes it possible to easily separate the salts of the carbonaceous material from the biomass, which increases the gasification yield.

The invention finds applications in numerous industrial fields, and in particular for the recovery of waste from the paper industry such as black liquor, but also for the recovery of sludge from purification stations.

PRIOR ART

Currently, in a context of scarcity of fossil resources and an increase in global warming, it is necessary to find alternative solutions to oil. In particular, research has focused on the energy recovery of bio-resources and in particular on the recovery of household or industrial waste such as black liquor from the preparation of paper pulp.

Most processes for the thermochemical transformation of biomass include a step of gasification of the biomass into supercritical water. This process is a recovery route well suited to wet resources.

This process consists in gasifying the biomass in the presence of water in the supercritical state (typically, at temperatures of 500°C to 600°C) to obtain a synthesis gas composed essentially of carbon monoxide (CO), dihydrogen (H ₂ ) and carbon dioxide (CO ₂ ). From CO and H ₂ , it is then possible to obtain chains of CH ₂ hydrocarbons similar to those coming from hydrocarbons of fossil origin and thus produce a synthetic fuel. Carbon is thus recovered in the form of methane or Syngas to produce fuels.

The gasification step can be preceded by a pyrolysis step.

However, this process in supercritical water is confronted with problems of fouling by the (inorganic) salts and the minerals contained in the resource which directly impact the efficiency of the process.

The hydrothermal gasification process of biomass can be carried out at lower temperature (between 374°C and 500°C) in the presence of a catalyst such as ruthenium as catalyst [1]. However, such catalysts are sensitive to pollutants, and in particular to sulphur, and are easily deactivated under supercritical conditions. Sulfur compounds can also produce hydrogen sulphide H ₂ S. They are therefore separated before the gasification step, using an absorbent bed (metal or metal oxide) to form insoluble sulphides. The biomass is also pre-treated with a heat treatment of at least 300°C. During the process, the salts precipitate and can be recovered. Thanks to the use of ruthenium, methane is mainly produced.

The separation of sulphate ions can also be achieved by the addition of cations, for example calcium cations or barium cations [2].

It is also possible to separate salts by precipitation under supercritical conditions [3]. The separator contains a fluidized bed which may include grains of sand, glass, ceramic or metal balls. The size of these elements is chosen so that they do not pass through the grids. Heat exchangers integrated in the salt separator are also used. The salts are separated from the supercritical fluid, for example, with a hydrocyclone type device. Even if the heat exchange system by tubes is effective, such a system is bulky.

Another document describes a system for recovering salts in a fluidized bed with particles [4]. Hydrothermal gasification takes place in a tube. This bed is composed of one or more components like sand, original aggregates mineral (pebbles), particles of stainless steel, glass or ceramic for example. The particles have dimensions of 20µm to 1mm. These components are introduced either at the same time as the biomass or prior to the introduction of the biomass. The salts present in the biomass can solidify and then form part of the bed of particles.

However, such a solution cannot be used with a viscous material like concentrated black liquor because the system could quickly clog. Moreover, such a system cannot operate continuously because it must be stopped to recover the particles containing the salt.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a gasification process remedying the drawbacks of the prior art, and in particular a process making it possible to easily recover the inorganic salts initially present in the biomass.

1. a) mettre en contact dans un réacteur principal des billes chauffées à une température entre 600°C et 1000°C, et de préférence entre 900°C et 1000°C, avec un mélange à traiter comprenant de l'eau et une biomasse, la biomasse comprenant une partie organique et des sels,
   • les billes étant en un matériau choisi parmi un acier, un alliage métallique, du verre ou une céramique, et ayant de préférence un diamètre compris entre 500µm et 2mm, de préférence entre 700 µm et 1 mm,
   • le réacteur principal est pressurisé à plus de 222 bars, par exemple à plus de 250 bars et, de préférence chauffé à une température supérieure à 200°C et inférieure à 374°C, par exemple comprise entre 200°C et 300°C,
2. b) gazéifier au moins partiellement la matière organique, en présence des billes à une température supérieure à 374°C et à une pression supérieure à 222 bars, de préférence à une température comprise entre 400°C et 500°C et à une pression supérieure à 250 bars (par exemple à une température de 450°C et à une pression de 300 bars), moyennant quoi on forme une phase gazeuse, une phase aqueuse et un résidu solide, et moyennant quoi les sels précipitent sur les billes, formant une coquille de sels recouvrant les billes,
   Le procédé comprend en outre les étapes suivantes :
3. c) séparer les billes recouvertes par la coquille de sels de la partie organique,
4. d) régénérer les billes par exemple selon les sous-étapes suivantes :
   • d1) dissoudre la coquille de sels des billes, par exemple en lavant les billes avec une solution aqueuse à une température inférieure à 374°C, moyennant quoi les sels sont dissous,
   • d2) chauffer les billes à une température comprise entre 600°C et 1000°C et de préférence entre 900°C et 1000°C, ce qui permet également de retirer d'éventuelles traces de carbone, l'étape d2) étant de préférence réalisée par combustion présence de dioxygène.

For this, the present invention proposes a biomass gasification process comprising the following steps:

1. a) bringing beads heated to a temperature between 600°C and 1000°C, and preferably between 900°C and 1000°C, into contact in a main reactor with a mixture to be treated comprising water and a biomass, the biomass comprising an organic part and salts,
   • the balls being made of a material chosen from a steel, a metal alloy, glass or a ceramic, and preferably having a diameter of between 500 μm and 2 mm, preferably between 700 μm and 1 mm,
   • the main reactor is pressurized to more than 222 bars, for example to more than 250 bars and, preferably heated to a temperature above 200°C and below 374°C, for example between 200°C and 300°C,
2. b) at least partially gasifying the organic matter, in the presence of the beads at a temperature above 374°C and at a pressure above 222 bars, preferably at a temperature between 400°C and 500°C and at a pressure greater than 250 bars (for example at a temperature of 450° C. and at a pressure of 300 bars), whereby a gaseous phase, an aqueous phase and a solid residue are formed, and whereby the salts precipitate on the beads, forming a shell of salts covering the balls,
   The method further comprises the following steps:
3. c) separating the balls covered by the shell of salts from the organic part,
4. d) regenerating the balls for example according to the following sub-steps:
   • d1) dissolving the salt shell of the beads, for example by washing the beads with an aqueous solution at a temperature below 374°C, whereby the salts are dissolved,
   • d2) heating the beads to a temperature of between 600°C and 1000°C and preferably between 900°C and 1000°C, which also makes it possible to remove any traces of carbon, step d2) preferably being produced by combustion in the presence of oxygen.

The invention differs fundamentally from the prior art by bringing a stream to be treated containing the biomass and water into contact with balls heated to very high temperatures (between 600° C. and 1000° C., or even between 900°C and 1000°C) in a pressurized reactor at more than 222 bars. When the mixture to be treated comes into contact with the hot balls, a significant heat exchange takes place: the balls provide enough energy to increase the temperature of the reaction mixture in situ and for the conditions in the main reactor to become supercritical (ie temperature above 374°C and pressure above 222 bar). The water contained in the flow of matter is then under supercritical conditions. The salts contained in the biomass precipitate on the beads, forming a shell around them. The salts are thus trapped on the beads and separated from the carbonaceous material of the biomass.

Advantageously, the mixture to be treated is preheated to a temperature of 150° C. to 300° C., before step a).

Advantageously, the method comprises a step during which ethanol is injected into the main reactor to dissolve the oils contained in biomass or resulting from step a). Ethanol can be injected into the main reactor simultaneously with the flow of material or after step a).

Advantageously, the balls fall into the main reactor by gravity.

During step b), the recoverable organic part is gasified. During step b), the organic part can be gasified in the main reactor or preferably in a gasification reactor (also called supercritical water reactor (SCW)).

The gasification takes place at a temperature preferably below 600°C and preferably below 500°C.

Step b) leads to partial gasification of the biomass. At the end of the process, it is possible to terminate the biomass gasification process.

Advantageously, the process also comprises a subsequent step e) during which another gasification step is carried out at a pressure greater than 222 bars and preferably greater than 250 bars to completely gasify the organic matter (i.e. to gasify the organic matter not carbonated during step b). According to a first variant, the temperature during step e) is between 600 and 700°C. This embodiment is advantageous in the case where the biomass contains sulphur. According to another variant, step e) is carried out in the presence of a catalyst at low temperature (i.e. at a temperature below 500° C.): this is a catalytic gasification reaction.

According to an advantageous embodiment variant, the sub-steps d1) and d2) are carried out in the main reactor. The balls are for example washed in the main reactor, whereby they can be directly reused for a new cycle.

According to a very advantageous variant, the main reactor or the gasification reactor is in fluid communication with a recovery chamber and the balls are recovered in the recovery chamber, for example by gravity, during step c).

Advantageously, sub-step d1) is carried out in the recovery chamber.

Advantageously, sub-step d2) is carried out by means of a heating reactor or by means of several heating reactors positioned in series, the reactor or reactors being positioned between the recovery chamber and the main reactor. For example, a preheating reactor and a heating reactor placed in series will be used.

Advantageously, during sub-step d1), the beads are washed, preferably with the aqueous phase resulting from step b), optionally diluted. This dissolves the salts present on the balls and thus cleans the balls. The liquid thus obtained is evacuated with the salts. These salts could ideally be reused by the paper industry or other industries, for example. Optionally water can be added for this regeneration step to be able to completely recover the salts.

Advantageously, the energy can be supplied by the solid residue or char produced during the hydrothermal gasification and/or by other carbonaceous bioresources. For this, a stage of combustion of the tank deposited on balls can take place by injecting oxygen, advantageously into the preheating reactor.

Advantageously, the solid residue from step b) is used to contribute to the heating of the balls to a temperature between 600° C. and 1000° C. and preferably between 900° C. and 1000° C. during sub-step d2) .

• fonctionnement en cycle fermé limitant les problèmes d'étanchéité à haute pression et haute température,
• mise en oeuvre de solutions technologiques éprouvées,
• pouvoir piéger et récupérer en continu des sels par nettoyage en continu des billes,
• améliorer des échanges de chaleur par contact direct entre les billes et l'eau supercritique,
• pouvoir recycler les billes utilisées,
• valoriser le carbone piégé par combustion,
• recycler la phase aqueuse pour le lavage des billes,
• convertir en énergie le char produit et piégé lors de la réaction par combustion (comme apport calorifique au procédé),
• recycler la phase aqueuse pour le lavage des billes,
• certains gaz non valorisables peuvent être utilisés pour faire fonctionner une turbine par exemple,
• éviter de boucher le dispositif et pouvoir traiter des matières visqueuses,
• il n'y a pas besoin de réaliser préalablement de pyrolyse : toutes étapes de conversion se déroulent dans des conditions hydrothermales,
• l'étape de gazéification se déroule à haute température (autour de 600 °C) sans catalyseur ou avec un catalyseur,

The process has many advantages:

• closed cycle operation limiting sealing problems at high pressure and high temperature,
• implementation of proven technological solutions,
• be able to continuously trap and recover salts by continuously cleaning the balls,
• improve heat exchange by direct contact between the balls and the supercritical water,
• be able to recycle the balls used,
• recover the carbon captured by combustion,
• recycle the aqueous phase for washing the beads,
• convert the char produced and trapped during the combustion reaction into energy (as a heat input to the process),
• recycle the aqueous phase for washing the beads,
• certain non-recoverable gases can be used to operate a turbine, for example,
• avoid clogging the device and be able to process viscous materials,
• there is no need to perform pyrolysis beforehand: all conversion steps take place under hydrothermal conditions,
• the gasification step takes place at high temperature (around 600°C) without a catalyst or with a catalyst,

The invention also relates to a gasification device.

• un réacteur principal, de préférence configuré pour être pressurisé à plus de 222 bars, par exemple à plus de 250 bars et, de préférence chauffé à une température supérieure à 200°C, par exemple comprise entre 200°C et 300°C, le réacteur principal comprenant une entrée de mélange à traiter, une entrée de billes et une sortie pour évacuer une solution comprenant les billes et le mélange à traiter,
• un réacteur de gazéification apte à être chauffé à une température supérieure à 374°C, de préférence entre 400°C et 600°C, encore plus préférentiellement entre 400°C et 500°C, et soumis à une pression supérieure à 222 bars, de préférence supérieure à 250 bars, le réacteur de gazéification étant relié à la sortie du réacteur principal, le réacteur de gazéification étant muni d'une sortie,
• des billes en un matériau choisi parmi l'acier, un alliage métallique, du verre ou une céramique, les billes ayant de préférence un diamètre compris dans la gamme allant de 500 µm à 2 mm, de préférence de 700 µm à 1 mm,
• une chambre de récupération des billes, reliée à la sortie du réacteur de gazéification et munie d'une sortie pour évacuer un mélange comprenant une phase gazeuse et une phase aqueuse et une sortie pour évacuer les billes,
• un système de circulation permettant de faire circuler les billes dans le réacteur principal, dans le réacteur de gazéification puis la chambre de récupération.

The gasification device comprising:

• a main reactor, preferably configured to be pressurized to more than 222 bars, for example to more than 250 bars and, preferably heated to a temperature greater than 200°C, for example between 200°C and 300°C, the main reactor comprising an inlet for the mixture to be treated, an inlet for beads and an outlet for evacuating a solution comprising the beads and the mixture to be treated,
• a gasification reactor capable of being heated to a temperature greater than 374°C, preferably between 400°C and 600°C, even more preferably between 400°C and 500°C, and subjected to a pressure greater than 222 bars, preferably greater than 250 bars, the gasification reactor being connected to the outlet of the main reactor, the gasification reactor being provided with an outlet,
• balls made of a material chosen from steel, a metal alloy, glass or a ceramic, the balls preferably having a diameter comprised in the range going from 500 μm to 2 mm, preferably from 700 μm to 1 mm,
• a bead recovery chamber, connected to the outlet of the gasification reactor and provided with an outlet to evacuate a mixture comprising a gaseous phase and an aqueous phase and an outlet to evacuate the beads,
• a circulation system allowing the balls to circulate in the main reactor, in the gasification reactor and then in the recovery chamber.

Advantageously, the device further comprises a heating reactor or several heating reactors (for example a preheating reactor and a heating reactor) placed in series, the heating reactor(s) being positioned between the recovery chamber and the main reactor , the heating reactor being configured to heat the beads before injecting them into the main reactor via the bead inlet. The heating reactor makes it possible to regenerate the beads before a new use. The balls can thus circulate continuously and cyclically in the aforementioned elements (main reactor, gasification reactor, recovery chamber, heating reactor).

This device is particularly interesting since it makes it possible to trap the salts and to recover them easily.

The device does not include a fluidized bed.

The heat exchange system is very efficient. The supply of energy is more effective by the direct in situ supply of heat inside the reactor.

Other characteristics and advantages of the invention will emerge from the additional description which follows.

It goes without saying that this additional description is only given by way of illustration of the subject of the invention and should in no way be interpreted as a limitation of this subject.

BRIEF DESCRIPTION OF DRAWINGS

• La figure 1 représente de manière schématique et en coupe un dispositif de gazéification d'une biomasse permettant de séparer les sels de la partie organique de la biomasse selon un mode de réalisation particulier de l'invention.
• La figure 2 représente de manière schématique un dispositif de gazéification d'une biomasse permettant de séparer les sels de la partie organique de la biomasse selon un autre mode de réalisation particulier de l'invention.
• La figure 3 est un graphique représentant des profils de température et de pression en fonction du temps d'un réacteur contenant des billes en verre et de la liqueur noire, selon un mode de réalisation particulier de l'invention.
• La figure 4 est un cliché photographique de billes de verre après mise en contact avec de la liqueur noire, chauffage 420°C et refroidissement, selon un mode de réalisation particulier de l'invention.

The present invention will be better understood on reading the description of exemplary embodiments given purely for information and in no way limiting with reference to the appended drawings in which:

• There figure 1 shows schematically and in section a device for gasifying a biomass making it possible to separate the salts from the organic part of the biomass according to a particular embodiment of the invention.
• There figure 2 schematically represents a device for gasification of a biomass making it possible to separate the salts from the organic part of the biomass according to another particular embodiment of the invention.
• There picture 3 is a graph representing temperature and pressure profiles as a function of time of a reactor containing glass beads and black liquor, according to a particular embodiment of the invention.
• There figure 4 is a photographic negative of glass beads after contact with black liquor, heating to 420° C. and cooling, according to a particular embodiment of the invention.

The different parts shown in the figures are not necessarily shown on a uniform scale, to make the figures more readable.

The different possibilities (variants and embodiments) must be understood as not mutually exclusive and can be combined with each other.

Also, in the description below, terms that depend on the orientation, such as "top", "bottom", etc. of a structure apply assuming that the structure is oriented as shown in the figures.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

• réaliser une ou plusieurs fois un cycle comprenant les étapes suivantes :
  1. a) pressuriser et chauffer le réacteur principal 100 à plus de 222 bars, notamment à plus de 250 bars et à une température supérieure à 200°C, par exemple à une température comprise entre 200°C et 300°C,
     • puis mettre en contact, dans le réacteur principal 100, les billes 200 chauffées à une température entre 600°C et 1000°C, et de préférence entre 900°C et 1000°C, avec un mélange à traiter comprenant de l'eau et une biomasse, la biomasse comprenant une partie organique et des sels,
     • les billes étant en un matériau choisi parmi un acier, un alliage métallique, du verre ou une céramique, et ayant de préférence un diamètre compris entre 500 µm et 2 mm,
  2. b) réaliser une première gazéification (gazéification partielle) de la matière organique à une température supérieure à 374°C et à une pression supérieure à 222 bars, de préférence à une température entre 400°C et 500°C et à une pression supérieure à 250 bars (par exemple à une température de 450°C et à une pression de 300 bars), moyennant quoi on forme une phase gazeuse, une phase aqueuse et un résidu solide,
     • lors de l'étape b), la matière organique étant gazéifiée en présence des billes 200,
     • moyennant quoi les sels précipitent sur les billes 200, formant une coquille 210 de sels recouvrant les billes 200,
     • le procédé comprenant en outre les étapes suivantes :
  3. c) collecter les billes 200 recouvertes par la coquille de sels 210 de la partie organique valorisable (gaz de synthèse),
  4. d) régénérer les billes 200 selon les sous-étapes suivantes :
     • d1) retirer la coquille de sels 210 des billes 200, par exemple en lavant les billes 200 avec une solution aqueuse, la solution aqueuse étant à une température inférieure à 374°C, moyennant quoi les sels sont dissous,
     • d2) chauffer les billes à une température comprise entre 600°C et 1000°C et de préférence entre 900°C et 1000°C.
  5. e) de préférence, réaliser une deuxième étape de gazéification (gazéification totale) pour gazéifier la matière organique non gazéifiée lors de l'étape b).

We will now describe the biomass gasification process in more detail. In particular, we will describe in greater detail a gasification process operating in a closed loop. The method comprises the following cycle of steps ( Fig. 1 and 2 ):

• carry out one or more times a cycle comprising the following steps:
  1. a) pressurizing and heating the main reactor 100 to more than 222 bars, in particular to more than 250 bars and to a temperature greater than 200° C., for example to a temperature between 200° C. and 300° C.,
     • then bringing into contact, in the main reactor 100, the balls 200 heated to a temperature between 600° C. and 1000° C., and preferably between 900° C. and 1000° C., with a mixture to be treated comprising water and a biomass, the biomass comprising an organic part and salts,
     • the balls being made of a material chosen from a steel, a metal alloy, glass or a ceramic, and preferably having a diameter of between 500 μm and 2 mm,
  2. b) carrying out a first gasification (partial gasification) of the organic matter at a temperature above 374°C and at a pressure above 222 bars, preferably at a temperature between 400°C and 500°C and at a pressure above 250 bars (for example at a temperature of 450° C. and at a pressure of 300 bars), whereby a gas phase, an aqueous phase and a solid residue are formed,
     • during step b), the organic matter being gasified in the presence of the balls 200,
     • whereby the salts precipitate on the balls 200, forming a shell 210 of salts covering the balls 200,
     • the method further comprising the following steps:
  3. c) collecting the balls 200 covered by the shell of salts 210 from the recoverable organic part (syngas),
  4. d) regenerating the balls 200 according to the following sub-steps:
     • d1) removing the shell of salts 210 from the beads 200, for example by washing the beads 200 with an aqueous solution, the aqueous solution being at a temperature below 374° C., whereby the salts are dissolved,
     • d2) heating the beads to a temperature between 600°C and 1000°C and preferably between 900°C and 1000°C.
  5. e) preferably, carrying out a second gasification stage (total gasification) to gasify the organic material not gasified during stage b).

By biomass, we mean any inhomogeneous material of biological origin, which can be almost dry, such as sawmill residues or straw, or soaked in water, such as household waste.

Advantageously, the biomass has a moisture content greater than 50%.

It may be algae (microalgae or macroalgae for example), agricultural waste (cake, crown wood waste, etc.) or industrial waste (from the paper industry in particular), household waste, sludge from treatment plants, or waste water.

Subsequently, biomass refers to any type of natural, industrial or household waste containing a recoverable organic part and an inorganic part. In particular, it may be black liquor.

Biomass contains a non-negligible amount of inorganic matter, typically between 1 and 10% by mass. By between X and Y, it is meant here and hereafter that the terminals are included.

The inorganic part of the biomass can be formed from sodium carbonate salts and/or calcium carbonate salts and/or potassium carbonate salts.

The biomass can also have a low sulfur or nitrogen content, for example from 1 to 5% by mass.

We will now describe in more detail the different steps of these different embodiments.

Prior to step a), certain materials can be pretreated and/or finely ground in order to avoid clogging upstream of the reactor.

Preferably, the biomass is ground before step a).

The mixture to be treated can be preheated to a temperature of 150° C. to 300° C., before step a).

During step a), the balls 200 are brought into contact with a flow of material containing water and the biomass.

The material flow includes biomass and water. For example, the material flow comprises 10 to 20% biomass.

The material flow can be injected under pressure. It is advantageously injected under pressure and at a temperature between 150 and 300°C, preferably between 200°C and 300°C.

The flow of material is injected, for example, by piston injection.

The beads 200 are at a temperature between 600°C and 1000°C, preferably between 700°C and 1000°C and even more preferably between 900°C and 1000°C.

The biomass introduced into the reactor 100 is at a temperature between for example between 10°C and 300°C, preferably between 20°C and 250°C. The biomass can for example be preheated to a temperature between 150°C and 300°C, for example between 150°C and 250°C. The biomass is at a temperature below the critical temperature (i.e. below 374°C).

Advantageously, the main reactor 100 where the bringing into contact between the balls 200 and the biomass takes place is pressurized. It is in particular at a pressure greater than 222 bars and preferably greater than 250 bars. Thus, when the biomass comes into contact with the hot balls 200, the balls 200 supply the energy necessary for the biomass so that the conditions become supercritical. The salts in contact with the hot surface of the balls precipitate and coat these balls, thus forming a shell around the balls. The shell of salts can be continuous or discontinuous.

The salts can begin to deposit on the balls 200 during step a).

The salts are, for example, sodium carbonate and/or calcium carbonate and/or potassium carbonate salts.

Carbon and/or carbonaceous material can also be trapped along with the salts on the beads. Step d2) enables them to be valued.

The balls 200 can be made of steel, metal alloy, ceramic (alumina or SiC for example) or glass.

In particular, an alloy resistant to corrosion and to high temperatures will be chosen.

Balls 200 may include a coating, for example ceramic or a catalytic material such as ruthenium. The coating can be continuous or discontinuous. When the biomass comprises a low level of sulfur or nitrogen, balls without catalytic coating will advantageously be chosen to avoid poisoning.

Preferably, for continuous operation, metal balls (in particular steel or metal alloy) will be chosen.

The diameter of the balls 200 is for example between 500 μm and 2 mm, and preferably between 700 μm and 1 mm. The dimensions of the balls 200 depend in particular on the device used and in particular on the size of the pipes and the valves as well as the filters for example used during step d). Advantageously, balls having a satisfactory specific surface will be chosen.

During step a) or after step a), ethanol can be injected to ensure the dissolution of the oils present in the reactor. The ethanol will be able to dissolve the carbonaceous material and in particular the oil (tar) which could be deposited on the surface of the balls and prevent the deposit of salts. Advantageously, the use of ethanol also prevents the beads from sticking together. A fraction of the ethanol can also decompose into hydrogen and methane improving the conversion of matter.

Ethanol can be introduced into the reactor with the material flow. Ethanol can be added at low concentration, for example 5 to 10% of the initial material flow. According to another embodiment variant, the ethanol is added directly to the salt separator.

During step b), the material is subjected to a first step of gasification in a supercritical medium. It is a partial gasification.

The gasification reaction can take place with or without a catalyst.

• une phase gazeuse comprenant des gaz incondensables comprenant, entre autres du monoxyde de carbone (CO), du dioxyde de carbone (CO₂), du dihydrogène (H₂), du méthane (CH₄),
• une phase solide : des résidus solides carbonés que l'on regroupe sous les noms de « char », « charbon végétal », et
• une phase aqueuse.

Once the gasification reaction is complete, we obtain:

• a gaseous phase comprising incondensable gases comprising, inter alia, carbon monoxide (CO), carbon dioxide (CO ₂ ), dihydrogen (H ₂ ), methane (CH ₄ ),
• a solid phase: solid carbonaceous residues that are grouped together under the names of "char", "vegetable charcoal", and
• an aqueous phase.

Traces of bio-oils can also be obtained under supercritical conditions up to 400°C.

During step c), the carbonaceous material is collected (i.e. the carbonaceous material is separated from the salts). This step is carried out at a temperature above 374° C. so as not to dissolve the salts. Preferably it is carried out at a temperature between 374°C and 400°C.

• la biomasse peut être gazéifiée dans le réacteur principal 100 utilisé lors de l'étape a) et les billes 200 recouvertes de sels 210 sont sorties du réacteur 100 et/ou la matière carbonée est évacuée du réacteur principal 100 ; par exemple, les billes 200 sont extraites du réacteur 100 grâce à un sas positionné dans la partie basse du réacteur, ou
• la biomasse est gazéifiée dans un réacteur de gazéification 300 en présence des billes 200, puis les billes 200 recouvertes de sels 210 sont sorties du réacteur de gazéification 300 et/ou la matière carbonée est évacuée du réacteur de gazéification 300; par exemple, les billes 200 sont extraites du réacteur 300 grâce à un sas positionné dans la partie basse du réacteur 300.

Several embodiments can be implemented:

• the biomass can be gasified in the main reactor 100 used during step a) and the balls 200 covered with salts 210 are taken out of the reactor 100 and/or the carbonaceous material is evacuated from the main reactor 100; for example, the beads 200 are extracted from the reactor 100 thanks to an airlock positioned in the lower part of the reactor, or
• the biomass is gasified in a gasification reactor 300 in the presence of the balls 200, then the balls 200 covered with salts 210 are taken out of the gasification reactor 300 and/or the carbonaceous material is evacuated from the gasification reactor 300; for example, the balls 200 are extracted from the reactor 300 thanks to an airlock positioned in the lower part of the reactor 300.

The balls 200 act as a support for the salts. Their removal from the reactor is thus facilitated.

Then, during step d), the balls are regenerated. The beads are washed with an aqueous solution. Advantageously, they are washed with the aqueous phase from step b). The aqueous phase can be used as it is or diluted. Stage d) makes it possible to recover the salts by dissolution in the liquid phase.

Washing is advantageously carried out with mechanical agitation and/or a vibrating device and/or in the presence of ultrasound.

The temperature during step d) is for example between 300 and 320° C., which makes it possible to optimize the efficiency of the process.

This cleaning phase lasts for example approximately 15 to 20 minutes in batch configuration. For continuous operation, residence times of a few seconds to a few minutes, for example from 10 seconds to 5 minutes, preferably from 30 seconds to 2 minutes, can be chosen.

The aqueous phase containing the salts is evacuated and filtered. The pores of the filter are preferably small enough to avoid losing the chars containing the valuable carbon.

It is possible to carry out step d) at each cycle or after several cycles. The frequency of step d) depends on the quantity of salts recovered at the surface of the balls.

The aqueous, gaseous and solid phases are separated. The separation preferably takes place at a lower temperature. The aqueous phase and the solid residues are for example used to regenerate the beads 200 (step d)). The aqueous phase can be diluted with mains water if the volume of the aqueous phase is not sufficient to clean the beads.

Advantageously, the method comprises a step during which the balls are subjected to a combustion step. This step makes it possible to remove the residual carbon ('char') deposited on their surface during step a) and/or b).

The step of combustion of the residual char deposited on the balls 200 can take place in the main reactor 100 used during step a). If the balls have been extracted from this reactor 100, for example during step c), they can be reintroduced into the reactor 100 by means of a conveying device (for example a piston).

Preferably, the combustion takes place in a heating reactor 800 positioned upstream of the main reactor 100 and making it possible to heat the balls 200 before introducing them into the main reactor 100 ( figure 4 ). Burning is advantageously carried out at a temperature between 700°C and 1000°C and preferably between 900°C and 1000°C. It is advantageously carried out at atmospheric pressure (1 bar).

Other carbonaceous materials from the same process may be added. For example, it may be carbonaceous materials from the paper industry: tree bark and other compounds from wood.

It has been measured by calorimetry that the residual solid with the salt has a calorific value of 15 MJ/kg for the gasification of black liquor at 600°C. If the salt is extracted, the solid contains an energy greater than 30 MJ/kg (Dulong). This may be enough to provide the energy for combustion.

This step advantageously allows the balls to be preheated in order to carry out a new cycle.

This cycle of steps is advantageously repeated several times until the desired quantity of gas is obtained.

• soit à basse température (typiquement à une température inférieure à 500°C) en présence d'un catalyseur : il s'agit d'une réaction de gazéification catalytique,
• soit à haute température (typiquement à une température comprise entre 600 et 700°C) ; ce mode de réalisation est avantageux dans le cas où la biomasse contient du soufre.

At the end of the salt separation process, it is possible to complete the biomass gasification process (step e):

• either at low temperature (typically at a temperature below 500°C) in the presence of a catalyst: this is a catalytic gasification reaction,
• either at high temperature (typically at a temperature of between 600 and 700° C.); this embodiment is advantageous in the case where the biomass contains sulphur.

Although this is in no way limiting, the invention particularly finds applications in the field of the paper industry and in particular for the upgrading of black liquor.

We will now describe in greater detail the device for implementing the closed-loop method.

• un réacteur de principal 100 (aussi appelé réacteur de prégazéification),
• un réacteur de gazéification 300,
• une chambre 500 de récupération des billes (aussi appelée chambre de séparation).
• un réacteur de chauffage 800 relié au réacteur principal 100.

The device comprises the following elements positioned successively in series ( figures 1 and 2 ):

• a principal 100 reactor (also called a pregasification reactor),
• a gasification reactor 300,
• a ball recovery chamber 500 (also called a separation chamber).
• a heating reactor 800 connected to the main reactor 100.

• une entrée de matière à traiter 101 disposée au niveau du réacteur principal 100,
• une sortie de saumure 603 disposée entre la chambre de récupération 500 et le réacteur de chauffage 800, pour évacuer la saumure,
• une sortie 502 de mélange eau/gaz disposée au niveau de la chambre de récupération 500 pour évacuer un mélange d'eau supercritique et de gaz de synthèse, la sortie de mélange 502 eau/gaz étant avantageusement reliée à un autre réacteur de gazéification (non représenté) pour terminer le processus de gazéification de la biomasse.

The device comprises at least two inputs and at least one output:

• an inlet of material to be treated 101 arranged at the level of the main reactor 100,
• a brine outlet 603 arranged between the recovery chamber 500 and the heating reactor 800, to evacuate the brine,
• a water/gas mixture outlet 502 arranged at the level of the recovery chamber 500 to evacuate a mixture of supercritical water and synthesis gas, the water/gas mixture outlet 502 being advantageously connected to another gasification reactor (not shown) to complete the biomass gasification process.

For a device operating continuously, the balls 200 circulate continuously in the various components of the device. For example, part of the 200 balls are in the main reactor 100 while another part is in the gasification reactor 300 and another part of the 200 balls is in the recovery chamber 500.

This variant allows continuous operation of the device. It makes it possible to have a unit dedicated to heating the balls with or without combustion, a unit dedicated to gasification and a unit dedicated to washing the balls. Thus, subjecting the combustion reactor to numerous pressure and temperature variations (heating, then washing) is avoided. Such extreme variations in temperature and pressure can quickly stress the reactor material. A wider range of material can be used. In addition, heat exchange after combustion is simplified.

• mettre en oeuvre l'étape a) dans le réacteur principal 100, l'étape a) pouvant conduire au début de la gazéification de la matière organique, les billes pouvant commencer à se couvrir de sels lors de cette étape,
• mettre en oeuvre l'étape b) dans le réacteur de gazéification 300 (de préférence il s'agit d'un tube), en présence des billes 200 pour avoir le temps de séjour optimal,
• mettre en oeuvre l'étape c) en acheminant les billes 200 dans la chambre de récupération 500,
  puis après la réalisation d'un ou plusieurs cycles, on met en oeuvre les étapes suivantes :
• mettre en oeuvre l'étape d1) dans la chambre de récupération 500 et, de préférence, dans une chambre de dissolution des sels 600 (de préférence il s'agit d'un tube), pour avoir le temps de séjour optimal,
• mettre en oeuvre l'étape d2) dans le réacteur de chauffage 800 positionné en amont du réacteur principal 100,
• de préférence mettre en oeuvre l'étape e) dans un autre réacteur de gazéification reliée à la sortie 502 de la chambre de récupération 500.

This continuous mode of operation may include the following cycle of steps:

• implementing step a) in the main reactor 100, step a) possibly leading to the start of the gasification of the organic matter, the balls possibly beginning to become covered with salts during this step,
• implement step b) in the gasification reactor 300 (preferably it is a tube), in the presence of the beads 200 to have the optimal residence time,
• implement step c) by conveying the balls 200 into the recovery chamber 500,
  then after the completion of one or more cycles, the following steps are implemented:
• implement step d1) in the recovery chamber 500 and, preferably, in a salt dissolution chamber 600 (preferably it is a tube), to have the optimal residence time,
• implement step d2) in the heating reactor 800 positioned upstream of the main reactor 100,
• preferably implement step e) in another gasification reactor connected to the outlet 502 of the recovery chamber 500.

We will now describe in more detail the arrangement of the various components of the device.

The main reactor or pregasification reactor 100 comprises the inlet of material to be treated 101, an inlet for beads 102 and an outlet 103 for evacuating a reaction medium comprising beads, water and biomass.

Biomass can be stored in a storage reactor. A transfer system comprising a transfer lock can be arranged between the storage reactor and the main reactor or pregasification reactor 100 to transfer the biomass from the storage reactor to the main reactor 100.

Bead inlet 102 is also connected to heating reactor 800.

• à haute pression (typiquement supérieure à 250 bar) et à température ambiante (entre 20 et 25°C), ou
• à haute pression (typiquement supérieure à 222 bars et de préférence supérieure à 250 bars) et à une température supérieure à 200°C et de préférence inférieure à 374°C (par exemple 300°C).

The heated balls 200 are brought into contact with the mixture to be treated in the main reactor or pregasification reactor 100. The reactor can be:

• at high pressure (typically above 250 bar) and at ambient temperature (between 20 and 25°C), or
• at high pressure (typically greater than 222 bars and preferably greater than 250 bars) and at a temperature greater than 200° C. and preferably less than 374° C. (for example 300° C.).

The balls 200 transfer their heat to the mixture to be treated: the temperature of the mixture increases and goes into supercritical conditions (temperature above 374° C.). A reaction mixture is formed in the main reactor or pregasification reactor 100.

The reaction mixture is then conveyed into the gasification reactor 300 connected to the outlet 103. This reactor is for example a tube. It has a suitable length so that the energy stored in the balls is transferred to the supercritical water and that the salts are deposited on the balls 200 when the water passes into the gas phase.

At the outlet 302 of the gasification reactor 300, the reaction mixture is discharged into a recovery chamber 500. In this chamber 500, a mixture of gas and supercritical water is separated on the one hand and the balls 200 on the other hand. covered by the shell of salts 210. The lower part of the chamber 500 is regulated at a temperature below the critical temperature of 374° C. (for example at a temperature of 360° C.) so that the supercritical gas becomes liquid again and so redissolve the salts in the water. An outlet 502 makes it possible to evacuate the supercritical water and the synthesis gas. An exit 503 makes it possible to evacuate the balls.

To promote the dissolution of the salts, the balls 200 can pass through a dissolution chamber 600, advantageously in the form of a tube, filled with water, for example by gravity, over a suitable length. The tube comprises a first end connected to the outlet 503 of the separation chamber 500. At the other end of the tube 600, the brine outlet 603 makes it possible to evacuate the salt-laden liquid. The extracted bit rate is advantageously equivalent to the input bit rate.

The tube 600 is at a temperature below 374° C. in order to be able to dissolve the salts. Preferably, it is at a temperature above 300°C to avoid to cool the solution too much and then minimize the energy input during the heating of beads 200.

The tube 600 supplies a pre-heating reactor 700 with balls 200 via the outlet 602. This reactor 700 is advantageously provided with an Archimedean screw to convey the balls 200 from the bottom to the top of the reactor 700. During the phase of conveying of the balls, the reactor is heated (either electrically or by a hot gas produced by a burner) to allow the residual water to pass under supercritical conditions and the storage of energy in the balls, the latter being stripped of salts .

The reactor 700 can be provided with a dioxygen inlet 701. Advantageously, the use of dioxygen makes it possible to burn the residual carbon deposited on the balls 200.

A heating reactor 800, for example a spiral heat exchanger, is placed between the pre-heating reactor 700 and the main reactor 100. 200 at a temperature adapted to the desired test conditions (typically between 700° C. and 1000° C., preferably between 900° C. and 1000° C.) for example thanks to the hot fumes generated by a burner.

The balls thus overheated feed the main reactor 100 via the inlet 102 by gravity for a new cycle.

Illustrative and non-limiting example of an embodiment with a batch type reactor

In this example, a 500 ml batch reactor (TOP industrie) was used. In the batch reactor, 90 g of glass beads were added with 27 g of water and 3 g of ethanol. The beads are preheated to a temperature of at least 700°C. The reactor was heated to a temperature of 400-420°C. About 27 g of black liquor was injected. The pressure is around 250 bar. After the temperature reached 420°C for 5 minutes, the reactor was cooled according to the heat treatment shown in the graph of the Figure 3 . Then the gases formed were analyzed. At this temperature, mainly nitrogen, carbon dioxide and hydrogen in small quantities are formed.

Once cooled the reactor was opened. The beads are separated from the aqueous phase. It was observed that the balls were coated with a rather hard layer of salts and welded together ( Figure 4 ). The salt layer can be recovered, for example, by vigorously mixing the beads, which breaks up the salt layer and/or by washing with an aqueous solution.

Illustrative and non-limiting example of an embodiment with a reactor operating continuously

By way of illustration and not limitation, we will now give in more detail the dimensioning of a gasification unit capable of treating 100 kg/h of biomass in continuous mode. Such a unit is for example represented on the picture 2 .

The boundary conditions are as follows: Tcold in element 500 = 360°C, Tgas outlet (S1)=500°C, Tbrine (S2)=360°C.

The resource E is injected at the input 101. It is a biomass at 20% DM. The flow rate is 100 kg/h. The biomass is at ambient temperature Tamb=20°C.

The balls are made of 304L stainless steel with a diameter of 2 mm, Cp=500 J/kg°K, Ro=7000 kg/m ³ . There are approximately 34,000 marbles.

When the beads are introduced into reactor 100 via bead inlet 102, they are at a temperature of 790°C. The flow rate is 1000 kg/h. The power to be supplied and exchanged is 60 kW.

The reactor 100 makes it possible to bring the hot balls into contact and to mix them with the biomass. The reactor 100 is made of Inconel 600. The biomass inlet 101 can be perpendicular to the flow of beads or countercurrent to the flow of beads. The biomass inlet 101 has a diameter of 15 mm. It may be a vertical tapping positioned at the top of the reactor 100. Preferably, it is a side tapping.

The ball inlet 102 has a diameter of 17.1 mm and a thickness of 3.2 mm (tangential side stitching).

Advantageously, the reactor 100 comprises a cylindrical part at the inlets 101 and 102 and a cone-shaped part at the outlet 103 to facilitate the evacuation of the mixture. The outlet cone has for example a height H=200 mm. The cylindrical part has for example a diameter D=100 mm and a height H=400 mm.

The reactor outlet 103 has, for example, a diameter of 20 mm. It is connected to the inlet of gasification reactor 300.

The gasification reactor 300 is made of Inconel 600. The reactor 300 is preferably a 20×2.7 mm tube with a length L=2000 mm. For example, it has an adjustable tilt (20 to 60°). The electrical power is Pelec=5 kW (compensation for thermal losses).

The outlet 302 of the gasification reactor 300 has, for example, a diameter of 20mm.

The recovery chamber 500 is a solid/gas separator made of Inconel 600. The gas outlet 502 for evacuating the gases (S1) has, for example, a diameter of 15 mm.

The recovery chamber 500 has, for example, the following dimensions: D=100 mm and H=400 mm. The lower part of the chamber 500 preferably has a cone shape to facilitate the evacuation of the balls. The diameter of the outlet 503 is, for example, 20 mm. The outlet cone has for example a height H=200 mm. The bottom of the chamber is at a temperature below 374° C. (for example 360° C.) so that the supercritical gas becomes liquid again and to resolubilize the salts.

The redissolution of the salts can be improved by using an additional component 600. For example, it can be a 304L stainless steel tube, having for example a length L=2000 mm. The inclination is adjustable (10 to 45°).

The diameter of the outlet 602 allowing the balls to be transferred to the preheating reactor 700 is, for example, 20 mm. The diameter of the brine outlet 603 (S2) is, for example, 20 mm.

The Archimedes screw of element 700 can be made of 304L stainless steel. This is, for example, a 20x2mm tube with spirally crimped fins, thickness=5 mm, pitch=20 mm, Dext screw= 100 mm, Length=1000 m. The Archimedes screw motor has, for example, a power of P=1kw with reduction gear, and a variable speed of 0 to 10 rpm.

The heating reactor 700 is made of 304L stainless steel. Preferably, it is a tube of dimensions: 100x5mm and L=1100mm. The inlet 801 of the heating reactor 800 is a side tapping, for example, with a diameter of 20 mm. The output of the reactor 800 is a side tapping, for example, with a diameter of 17.1 mm. The Pelec power is 20 kW. For example, heating cords wound around the reactor 800 are used. The reactor is preferably tubular. The heating coil is in Inconel 625 with the following characteristics: Tube 17.1x3.2 mm, L=5000 mm wound in a helix (D=320 mm). For example, we choose 5 turns on H=800 mm and Pelec=40 kW (Kanthal type radiant heating zone).

REFERENCES

1. [1] US 2010/0154305 A1
2. [2] US 2014/0054507 A1
3. [3] WO 2016/113685 A1
4. [4] US 2017/0218286 A1

Claims (11)

Biomass gasification process comprising the following steps: a) bringing beads (200) heated to a temperature between 600°C and 1000°C, and preferably between 900°C and 1000°C, into contact in a main reactor (100), with a mixture to be treated comprising water and a biomass, the biomass comprising an organic part and salts, the balls being made of a material chosen from a steel, a metal alloy, glass or a ceramic, and preferably having a diameter of between 500 μm and 2 mm, during step a), the main reactor (100) being pressurized to more than more than 222 bars, for example to more than 250 bars and, preferably heated to a temperature above 200° C. and below 374° C. , for example at a temperature between 200° C. and 300° C., b) at least partially gasifying the organic material, in the presence of the balls (200), at a temperature above 374°C and at a pressure above 222 bars, preferably at a temperature between 400°C and 500°C and at a pressure greater than 250 bar, whereby a gaseous phase, an aqueous phase and a solid residue are formed, and whereby the salts precipitate on the balls (200), forming a shell (210) of salts covering the balls (200 ),
the method further comprising the following steps: c) separating the balls (200) covered by the shell (210) of salts from the organic part, d) regenerating the balls (200) for example according to the following sub-steps: d1) removing the shell of salts (210) from the balls (200), for example by washing the balls (200) with an aqueous solution at a temperature below 374°C, whereby the salts are dissolved, d2) heating the beads (200) to a temperature between 600°C and 1000°C and preferably between 900°C and 1000°C, step d2) preferably being carried out by combustion in the presence of oxygen. Process according to Claim 1, characterized in that the process comprises a step during which ethanol is injected into the main reactor (100) to dissolve the oils contained in the biomass. Process according to one of the preceding claims, characterized in that the process also comprises a subsequent step e) during which another gasification step is carried out at a pressure greater than 222 bars and preferably greater than 250 bars in order to gasify the organic matter not gasified during stage b), the temperature during stage e) being between 600 and 700° C. or stage e) being carried out in the presence of a catalyst at a temperature below 500 °C. Process according to any one of the preceding claims, characterized in that , during stage b), the organic part is gasified in a gasification reactor (300). Process according to Claim 4, characterized in that the gasification reactor (300) is in fluid communication with a recovery chamber (500) and in that , during step c), the balls (200) are recovered in the recovery chamber (500). Process according to Claim 5, characterized in that the sub-step d2) is carried out in a heating reactor (800) positioned between the recovery chamber (500) and the main reactor (100). Process according to any one of the preceding claims, characterized in that the mixture to be treated is preheated to a temperature of 150°C to 250°C, before step a). Process according to any one of the preceding claims, characterized in that during sub-step d1) the beads (200) are washed with the aqueous phase resulting from step b), optionally diluted. Process according to any one of the preceding claims, characterized in that the solid residue resulting from stage b) is used to heat the balls (200) to a temperature between 600°C and 1000°C and preferably between 900° C and 1000°C during sub-step d2). Process according to any one of the preceding claims, characterized in that the biomass has a moisture content greater than 50%, the biomass preferably comprising microalgae, macroalgae, agricultural waste such as cake, wood waste , household waste, sludge from treatment plants or waste water, the biomass possibly being ground before step a). Gasification device comprising: - a main reactor (100), preferably configured to be pressurized to more than 222 bars, for example to more than 250 bars and, preferably heated to a temperature greater than 200°C, for example between 200°C and 300 °C, comprising an inlet of the mixture to be treated (101), an inlet (102) of beads and an outlet (103) for evacuating a solution comprising the beads (200) and the mixture to be treated, - a gasification reactor (300) capable of being heated to a temperature between 400°C and 600°C, preferably between 400°C and 500°C, and pressurized to a pressure greater than 222 bars, preferably greater than 250 bars, the reactor of gasification reactor (300) being connected to the outlet (103) of the main reactor (100), the gasification reactor (300) being provided with an outlet (302), - balls (200) made of a material chosen from steel, a metal alloy, glass or a ceramic, the balls preferably having a diameter in the range from 500 μm to 2 mm, - a ball recovery chamber (500), connected to the outlet (302) of the gasification reactor (300) and provided with an outlet (502) for evacuating a mixture comprising a gaseous phase and an aqueous phase and a outlet (503) to evacuate the balls, - a circulation system allowing the balls to circulate successively in the main reactor (100), in the gasification reactor (300) then the recovery chamber (500), the device further comprising a heating reactor (800), positioned between the recovery chamber (500) and the main reactor (100), the heating reactor (800) being configured to heat the beads before injecting them into the reactor main (100) via the entry (102) of balls.

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