EP4308352A1

EP4308352A1 - Biomaterial from steam-cracked lignocellulosic biomass

Info

Publication number: EP4308352A1
Application number: EP22714493.8A
Authority: EP
Inventors: Frédéric MARTEL; Adriana QUINTERO-MARQUEZ
Original assignee: Europeenne de Biomasse SAS
Current assignee: Europeenne de Biomasse SAS
Priority date: 2021-03-17
Filing date: 2022-03-17
Publication date: 2024-01-24
Also published as: WO2022195232A1; FR3120873B1; FR3120873A1; AU2022237941A1

Abstract

The invention relates to the field of biomaterials. More particularly, the invention relates to a biobased biomaterial obtained from a steam-cracked lignocellulosic biomass in powder form, and also to the method for preparing same and the uses thereof. The invention also relates to the use of a powder obtained by steam cracking for preparing biomaterials.

Description

BIOMATERIAL FROM VAPOCRACKED LIGNOCELLULOSIC BIOMASS

The invention relates to the field of biomaterials. More particularly, the invention relates to a biosourced biomaterial obtained from a steam-cracked lignocellulosic biomass in powder form, as well as its method of preparation and its uses. The invention also relates to the use of a powder obtained by steam cracking for the preparation of biomaterials.

Field of invention

Materials such as particle board, fibreboard, plywood, OSB, insulation, designed from wood use different processes (grinding, mixing, pressing, heat treatment) and different formulations (fibers + glues) to obtain products with specific characteristics. water resistance (measured by swelling), flexural strength (breaking stress), elasticity, cohesion, tearing, ...

In the case of fiberboard, for example, the fibers are moistened to be above the saturation point of the fibers, they are mixed with the chosen glue (phenolic glue, with urea, and/or formaldehyde), the fibers are dispersed in a mould, trying to obtain a homogeneous distribution, pressing according to a program of progressive pressure increase (which can go up to 5 to 10 N/mm2) in steps of a few minutes, with temperatures up to 200°C. The problems observed are the breakage of the fibers during mixing with the adhesives, the consumption of water which is then lost during pressing in the form of steam, which contributes to excessive energy consumption, and finally the presence of toxic volatile organic compounds during the use of the material in indoor atmosphere.

The manufacture of materials by heating and chemical decomposition of wood (retification process) makes it possible to avoid added chemical compounds. But this is not suitable for all applications, and the retification of wood is a batch process (drying oven), therefore more expensive, and without energy recovery.

Dry and continuous biomass treatment systems are used by panel makers (medium-density fiber-based panel) but with the addition of impregnating glue. Batch (steam explosion) and continuous (steam cracking) dry biomass processing systems are mainly used by black pellet manufacturers and for biotechnology (but with chemical auxiliaries). Hydrothermal treatment, also called aqueous fractionation, solvolysis, hydrothermolysis, differs from steam cracking, or, in that it consists of using water at high temperature and high pressure in order to promote the disintegration and separation of the lignocellulosic matrix . This technique is not suitable for the production of black granules since the products obtained are mainly liquid.

Pyrolysis is the chemical decomposition of an organic compound by intense heating in the absence of oxygen. The compounds obtained after pyrolysis differ in their characteristics from those obtained by steam cracking. Steam cracking cannot be likened to a pyrolysis technique in that it uses a steam explosion and is done in the presence of oxygen.

It is also necessary to differentiate the roasting processes which are characterized by a thermochemical treatment between 100 and 300°C making it possible to modify part of the organic matter to break the fibers while eliminating the water.

The prior art describes processes for obtaining biomaterials from steam-cracked biomass, however these processes are not satisfactory with regard to ecological aspects because they use a large quantity of water and chemical products.

In this regard, we can cite patent CN110253708, which describes a process for producing a sheet of rubber in which plant fibers are cooked and then mixed with an alkaline solution. The mixture undergoes a first steam explosion treatment, the temperature of which is maintained at 115-125 degrees, and the gas pressure is maintained at 1.2-1.7 MPa. The powder resulting from this first treatment is mixed with an alkaline solution. The product obtained at the end of the last stage is mixed and pressed into a sheet.

Patent CN105856379 describes a method for preparing a high-strength lignocellulosic panel comprising in particular a step of “flash-explosion” of a material rich in lignocellulosic fiber. Said flash explosion step is carried out at a temperature of between 120 and 150° C. and a pressure of between 1 and 1.5 MPA. The next step, the "flash-explosion" consists of "uniformly mixing, then adjusting the water content to 1 to 25%, and adhesive (PVA and/or gelatin) (see claim 1). Then, the mixture obtained undergoes a step of paving, hot pressing and then a cooling molding step. Methods for adjusting the steam cracking parameter are also known from the prior art. Patent WO2020/260801 describes a method for producing a biofuel by continuous or discontinuous steam cracking of ligno-cellulosic biomass characterized in that: A numerical model of the optimal steam cracking parameters is recorded according to the type of plant constituents of the biomass ; The steam cracking reactor is fed with heterogeneous biomass; The type of plant constituents of the biomass is measured at least once during the treatment; The adjustment of the steam cracking parameters is controlled as a function of the type of plant constituents of the biomass measured and of said numerical model.

It is possible to carry out a steam cracking process making it possible to produce a lignocellulosic biomass powder, dry, pretreated, without chemical additives, stable and economically viable for commodities such as energy or biotechnologies, therefore a fortiori viable for products with high added value.

The methods of the prior art involving a treatment of the biomass by steam cracking are not envisaged for the production of biomaterial.

Faced with environmental challenges, it is desirable to have new biomaterials that are more ecological and whose production costs are viable.

Disclosure of Invention

The inventors propose to produce new biomaterials from steam-cracked lignocellulosic biomass.

Thus, the invention relates to a method for producing a biomaterial from steam-cracked lignocellulosic biomass in the form of a powder, consisting in: providing a lignocellulosic biomass; treating said biomass by steam cracking until a powder is obtained; pressing said powder alone or in association with a fibrous material for densification.

The invention also relates to the use of a powder obtained by steam cracking of a lignocellulosic biomass as a raw material for the preparation of a biomaterial.

Finally, the invention relates to a biomaterial obtained from steam-cracked powder and its uses. Advantages of the invention

The ecological aspect of the invention is essential: the methods for preparing biomaterials using all or part of steam-cracked powders, with or without natural fibers, do not require synthetic chemicals. However, these chemicals used conventionally for this purpose (for example urea-formaldehyde glues) are both a source of atmospheric pollution through their production or their end of life, but also of toxicity during the manufacture of biomaterials. In addition, the absence of synthetic chemicals in the finished product avoids the release of toxic products during use: no contamination of closed spaces.

Furthermore, the absence of water or its drastic reduction for steam cracking and pressing during manufacture (densification stage) reduces energy costs (less heating) and gaseous or liquid effluents.

This process allows the recycling of waste wood and furnishing or deconstruction elements (so-called “B” wood), whereas these woods are unsuitable for combustion as natural biomass so far only have to become incinerators. Reused in this way after steam cracking (which gives them a homogeneous neutral form), they return to their original use.

The use of steam-cracked biomass (wood in particular), which brings natural capacities of cohesion, makes it possible to reduce environmental impacts (few or no chemicals, pressing processes without water and with less energy).

Biomass steam cracking is mainly used for the production of biofuels in the form of dense granules (black pellets). The production costs for the use of steam-cracked material as a biomaterial can be reduced by taking, in parallel with a main use (black pellet), an intermediate production product (powder or "granules", c granules of medium compression density), and to use it as a raw material (the more or less fibrous powders produced by steam cracking, used alone) or an auxiliary for the manufacture of fiber material (the finest powders, used as glue or natural binder). Production costs can also be reduced by optimizing the process by recovering the energy produced during steam cracking (volatile organic compounds (VOC), steam, heat, etc.).

The process is very interesting because it can be modulated. Indeed, the steam cracked powder can be used alone, we then obtain panels with a low breaking strength. (a little low bending stress), but good resistance to swelling. This type of biomaterial is suitable for use as a packing material (insulation for example), which does not undergo bending or high stress (vapocracked powders of one or more species representing 100% of the biomaterial). Alternatively, the steam-cracked powder can be used as a binder / natural glue mixed with biomass fibers, we then obtain fiberboards with the reinforcement of more or less prepared natural fibers, and a cohesion obtained with the powder after a pressing without water and without chemical glues. The biomaterial then has good mechanical strength and can be used in the manufacture of composite panels.

In addition, one can play on the raw material and on the treatment for different applications: a softwood will give a fibrous product; a hardwood, non-fibrous product. Very high steam cracking treatment severity will support product density and swelling resistance. A low severity will mean a light end product.

Finally, the steam cracking of the biomass reinforces the hydrophobic character of the biomaterial, by limiting the swelling of the finished product, which is important for uses in humid atmospheres, in particular during the construction phases of wooden dwellings, while the braces are exposed, as long as the building is neither out of water nor out of air.

DETAILED DESCRIPTION OF THE INVENTION

A first object of the invention relates to a method for producing a biomaterial from steam-cracked lignocellulosic biomass in powder form, consisting in: having a lignocellulosic biomass having a humidity level of between 5 and 27% treating said biomass by steam cracking until a powder is obtained at a pressure of between 10 and 25 bars and a temperature is between 180 and 220°C until a powder is obtained pressing said powder, alone or in combination with a fibrous material or a binder, for densification.

The process according to the invention has the particularity of being implemented without adding any chemical product. In addition, no water is added for steam cracking. By “chemical product” within the meaning of the invention, is meant any substance formed by chemical treatment or by the assembly of several different chemical elements in defined proportions which can be used as an auxiliary in processes for the preparation of composite materials, like adhesives or support materials, in particular glues such as vinyl glues, acrylic glues, cyanoacrylate adhesives, neoprene adhesives, epoxy adhesives, MS polymer adhesives, polyurethane adhesives (PU), two-component adhesives (epoxies, polyurethanes), thermosetting adhesives (urea-formaldehyde), aqueous adhesives and solvent-based adhesives and cyanoacrylate adhesives.

By "lignocellulosic biomass" is meant a plant material whose major constituents are cellulose, hemicellulose and lignin. The proportions of these components vary according to the plant species. In the context of the invention, the lignocellulosic biomass of interest is mainly wood, in particular softwood or hardwood, but can also incorporate agricultural residues, co-products of agriculture and agro-industry, or wood from furnishing or deconstruction waste.

By "biomaterial" is meant a material integrating at least in part a raw material of natural or biosourced origin.

It is known from the state of the art that glues have a certain degree of toxicity. It is known in particular that:

For all cyanoacrylate glues, contact with the skin and especially the eyes must be avoided and the vapors must not be breathed.

Neoprene glues all give off highly flammable vapours, so smoking should be avoided during use and it is advisable to ventilate the room well. They are irritating to the eyes and the skin and their inhalation may cause drowsiness or dizziness. Finally, they are toxic to aquatic environments.

Epoxy glues contain bisphenol-A-epichlorohydrin which makes them irritating. Some are corrosive and can cause skin burns and serious eye damage. These glues are also toxic to aquatic environments.

Polymer and acrylic MS adhesives have the advantage of being very weakly toxic and therefore bear no special mention. However, some indicate that they can cause an allergic reaction.

The steam cracking step is carried out under so-called "dry" conditions, that is to say that the lignocellulosic biomass to be steam cracked has a low humidity rate of between 5 and 27% and that no water or no chemicals are added. In a preferred embodiment, the steam cracking is carried out by applying a severity factor of between 3 and 5.

In a particular embodiment, the steam-cracked powder is obtained as follows:

- Obtaining, from wood chips, wood fragments whose size is between 0.5 and 14 mm and having a moisture content between 5 and 27%;

- continuous introduction of a predetermined volume per minute of said wood fragments into a pressurized reactor, said reactor being supplied with substantially saturated steam, the pressure of which is between 10 and 25 bars and the temperature is between 180 and 220°C;

- exposure of the fragments of wood introduced into said reactor to said steam for a time sufficient to obtain steam cracking of between 5 and 30 minutes, the value of said exposure time and the value of the temperature of said substantially saturated steam being selected so that the severity factor is between 3 and 5, preferably between 3.5 and 4.5;

- continuous extraction from said reactor of the same predetermined volume of wood fragments per minute, through a plurality of orifices opening into a conduit substantially at atmospheric pressure, so as to cause explosive decompression of said extracted wood fragments of said reactor in said pipe;

- separation of said decompressed fragments of wood and of the residual steam extracted from said reactor, said fragments of wood obtained after separation forming said combustible material in powder form. In a preferred embodiment, said lignocellulosic biomass has a moisture content of between 5 and 12%.

In a preferred embodiment, the pressure in the steam cracking step is between 16 and 21 bar.

In a preferred embodiment, the temperature in the steam cracking step is between 200 and 214°C.

These three preferred embodiments can be combined two by two or all three together.

The Treatment Severity Factor is defined by the formula:

FS=Logl0(time(min)*exp((T°C-100)/14.75)).

The higher the temperature and the longer the treatment time, the more the severity increases, the more transformation is observed in the product, the more carbonaceous matter is lost in the evaporates. The product of the steam cracking process is recovered in the form of powder or in the form of weakly compressed granules also called “granules”. These granules correspond to a form of powder compressed so as to give it the form of a granule but which is easily transformed into powder by a simple mechanical action (mixing). This form of granule can be adopted when packaging the product in order to facilitate its handling (transport, storage) but its characteristics are those of a powder (friability, dispersion).

In addition, the steam cracked powder is dry, so it can be stored and transported, it is stable.

In a first particular embodiment of the invention, the biomass consists of more than 50% of resinous and the powder obtained can be densified alone to give a biomaterial. Indeed, the steam cracking of a resinous wood will give a fibrous powder capable of being densified alone. The biomaterial obtained will tend to have medium strength and will preferably be used as packing material, in particular as insulation.

In a particular embodiment, the method for producing a biomaterial is implemented by steam cracking a biomass of fibrous nature. The powder obtained is fibrous in nature and can be densified alone.

In a second embodiment of the invention, the biomass consists of more than 50% hardwood and the powder obtained (fine and non-fibrous) will preferably be used as a binder with a fibrous material to produce a biomaterial. In a preferred embodiment, the steam-cracked powder used as binder can represent up to 50% of the constituents of the biomaterial. This allows the production of a biomaterial having good cohesion and good mechanical strength; it can be used for making composite panels. This powder allows the cohesion of fibrous materials by pressing without the use of water or chemicals, thus producing an ecological final product.

In a particular embodiment, the method for producing a biomaterial is implemented by steam cracking a biomass of non-fibrous nature. The powder obtained is non-fibrous in nature and is used as a binder in combination with a fibrous material.

In another embodiment, the powder obtained at the steam cracking step is densified alone and is a mixture of steam cracked powders of fibrous and non-fibrous nature.

In a third embodiment, the biomaterial is prepared from a mixture of steam-cracked wood powders of fibrous and non-fibrous nature. Such a mixture gives the biomaterial interesting properties combining water resistance, cohesion and rigidity. In particular, a resinous wood like spruce will give a fibrous product and a hardwood like oak will give a non-fibrous product. Other types of wood within the families of softwoods or hardwoods can also give fibrous and non-fibrous products independently of the softwood or hardwood species, the objective being to have a final product of mixture (before or after steam cracking) having these two characteristics.

By “fibrous steam-cracked powder” within the meaning of the invention, is meant a powder containing at least 80% of particles whose diameter is greater than 500 μm.

By “non-fibrous steam-cracked powder” within the meaning of the invention, is meant a powder containing at least 80% of particles whose diameter is less than 500 μm.

The biomass can itself be a mixture of different species and, in general, the use of the powder obtained will be adapted according to its fiber content.

A second object of the invention relates to the use of a powder obtained by steam cracking of a lignocellulosic biomass as raw material for the preparation of a biomaterial. As mentioned earlier, the use of the powder will depend on whether it is fibrous or non-fibrous in nature.

Thus, a fibrous powder can be used as the only component of the biomaterial. A non-fibrous powder can be used as a binder for the preparation of a biomaterial mixed with a fibrous material.

In another embodiment, the powder is non-fibrous in nature and is densified in association with a fibrous material.

The steam-cracked powder can therefore be used as a mixture with a fibrous material and/or a binder. In a preferred embodiment of the invention, said fibrous material and/or said binder are steam cracked powders. Quite preferably, the different components of the biomaterial all come from the steam cracking of lignocellulosic biomasses, these biomasses come from different species.

Thus, different species can be mixed before steam cracking, making it possible to adapt to the flow of available and often heterogeneous biomasses, in particular in the case of biomass coming from materials to be recycled. It is also possible to mix powders from different batches of steam cracked powders. The invention offers great flexibility of implementation in the treatment of the biomass as well as of the preparation of the biomaterial according to the steam-cracked powders chosen or available.

A third object of the invention relates to a biosourced biomaterial obtained from steam-cracked lignocellulosic biomass in powder form. It can in particular be obtained by the process described above.

Preferably, this biomaterial is 100% biobased and even more preferably, it is composed of 100% steam-cracked biomass. This biomaterial is biodegradable.

Finally, a fourth object of the invention relates to the use of a biomaterial as defined above as a filling product, an insulating product, a construction material.

Biomaterials based on steam-cracked biomass alone, without a binder (steam-cracked powder from resinous trees for example) are generally intended for use as a packing product or an insulating product.

The biomaterials obtained by mixing a steam-cracked biomass (steam-cracked powder from hardwoods for example, as a binder) with a fibrous material (from a steam-cracked biomass or other) constitute dense and more resistant materials, suitable for a use as a construction material (composite panels).

In an advantageous embodiment of the invention, the biomaterial comprises a mixture of wood powders of fibrous nature and of powdery nature prepared by steam cracking. In a particular embodiment, the powder of a fibrous nature is prepared from softwoods such as spruce and the powder of a powdery nature is prepared from hardwoods such as oak.

The present invention will be better understood on reading the examples which follow, provided by way of illustration and should in no way be considered as limiting the scope of the present invention.

EXPERIMENTAL PART

EXAMPLE 1: Preparation of fiberboard from steam-cracked powder without additive Wood powders from spruce and oak were prepared by steam cracking. The severity conditions applied during steam cracking were a decimal logarithm of severity factor Logio FS = 4.05 for oak (C4) and Logio FS 4.15 for spruce (E6).

The powders were then shaped by following the following protocol: sampling of the mass of fibers to be sampled according to the size of the test panel, humidification of the fibers to be above the saturation point of the fibers (30% humidity), dispersion of the fibers in the mold (200 x 200 mm) trying to obtain a homogeneous distribution, pressing manually using a plate which makes it possible to form a moist cake, unmolding of the cake and introduction under the press between 2 sheets of water-repellent paper (to avoid adhesion phenomena), pressing according to the program including different successive levels of time and pressure, at different temperatures (Cf. table of Tests in the column “pressing time”).

The results are shown in Table 1:

Table 1: Summary of tests for the preparation of biomaterials from steam cracking products.

EXAMPLE 2: Characterization of the biomaterials obtained 1. Water swell measurement:

The humidity resistance capacity was evaluated by measuring the thickness of each square specimen (5 x 5 cm) before and after immersion in water at 20°C for 24 hours.

The calculation of the swelling is carried out as follows:

[Math 1]

( ^e after ^e before)

G = in % eavant in which:

G is the swelling e is the thickness

2. Actual density measurement:

The actual density or density is the product of the lengths, widths and thicknesses of the specimens used for the swelling tests

The results are presented in Table 2

Table 2: Bending resistance tests according to IΈN 310: Shaping of the specimens (width = 5 cm and length = 20 x thickness + 50 mm or 150 mm (5 mm thick specimen). The machine directly gives the maximum breaking force is F _max and we can recalculate the resistance to bending f _m .

3. Resistance to bending

The flexural strength f _m (in newtons per square millimeter) of each specimen is calculated from the following formula: in which :

F _max is the breaking load, in newtons t is the thickness of the specimen expressed in millimeters / is the length of the specimen, expressed in millimeters b is the width, expressed in millimeters

The flexural strength of each specimen being expressed with three significant figures.

The results for test piece No. 17 are presented in Table 3 below:

Table 3: Parameters relating to the flexural strength of specimen no. 17

4. Analysis of results The swelling test shows the resistance of the material to water. We notice a clear improvement between the natives and the simple exploded (217.4% against 10%). Also, the C4 oak panels seem to be very water resistant (#3 and #8 with 13 and 10% respectively) which may be related to the powdery look.

The sandwich panels or mixtures oscillate between 11 and 17% which is below the maximum normative values for panels subject to use classes 2 (very impressive for panels without glue and without water for some). Observation after inflation shows that the sandwich panels absorb less water (lower weight gain and lower water evacuation on the paper).

The pressure does not influence the water resistance but rather the rigidity of the panel as well as the quantity of material to be pressed. The presence or absence of water as a binder plays a role in the resistance to swelling: indeed, a panel pressed with water is, according to the results, more resistant to swelling because its cohesion is certainly better.

Panels with phenolic glue do not give good results.

In conclusion, oak seems to provide cohesion and water resistance but makes panels easily crumbled (fine powder) while spruce makes it possible to stiffen the whole (long fibres) but is less cohesive. However, the results are better than with phenolic glue. The oak-spruce mixture (or softwood-hardwood, or fibrous product-powdery product) gives the most satisfactory results as regards the 3 criteria evaluated: water resistance, cohesion and rigidity.

With an average swelling of around 15% on steam-cracked panels 5 mm thick, we note that this value is lower (for panels without glue and even sometimes without water) compared to the swelling over 24 hours for all other types of panels (fibre, MDF, particles, OSB, insulation) which vary between 15% and 25-30%. As regards the mechanical resistance to bending, the experimental results are much lower than the resistances for the other types of panels (0.9 MPa being the lowest value for panels in dry use).

The highly hydrophobic and cohesive nature of steam-cracked powders has many advantages. They could, for example, be used as a replacement for glue or as an addition to reduce the quantity of adhesive in order to obtain the same mechanical characteristics. This powder could also be used as a hydrophobic layer for panels used in humid conditions. Or create water-resistant insulating panels with this steam-cracked powder.

Claims

1. Process for the production of a biomaterial from steam-cracked lignocellulosic biomass in powder form comprising the steps of: having a lignocellulosic biomass having a moisture content of between 5 and 27% treating said biomass by steam-cracking at a pressure between 10 and 25 bars and a temperature is between 180 and 220° C. until a powder is obtained, pressing said powder, alone or in combination with a fibrous material, for densification.

2. Process according to claim 1, in which said densified powder alone is fibrous in nature.

3. Method according to claim 1 wherein said powder is non-fibrous in nature and is densified in association with a fibrous material.

4. Process according to claim 1, in which said densified powder alone is a mixture of steam cracked powders of fibrous and non-fibrous nature.

5. Use of a powder obtained by the process as described in claim 1, as raw material for the preparation of a biomaterial.

6. Use according to claim 5 wherein said powder is the only component of the biomaterial.

7. Use of a non-fibrous powder obtained by the method as described in claim 1 as a binder for the preparation of a biomaterial.

8. Use according to claim 5 wherein said powder is mixed with a fibrous material and / or a binder.

9. Biomaterial obtained from steam-cracked lignocellulosic biomass as described in the process according to claim 1, in which said biomass is in the form of fibrous or non-fibrous powder.

10. Biomaterial according to claim 9 comprising a mixture of wood powders of fibrous nature and of non-fibrous nature prepared by steam cracking.

11. Use of a biomaterial as defined in one of claims 9 or 10 as a packing product, insulating product and/or composite panels.