FR3120873A1 - BIOMATERIAL FROM VAPOCRACKED LIGNOCELLULOSIC BIOMASS - Google Patents

Abstract

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.

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 preparation process 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, etc.

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).

Existing steam cracking processes make 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.

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

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 powder form, consisting of:

• have 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 : biomaterials using all or part of steam-cracked powders, with or without natural fibers, do not require synthetic chemicals, both a source of atmospheric pollution by their production or their end of life, but also in terms 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.

In addition, the absence of water or its drastic reduction for pressing during manufacturing (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) while 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) bringing natural cohesion capacities 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", granules of medium compression density), and to use it as a raw material (more or less fibrous powders made by steam cracking, used alone) or as 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 is flexible. In fact, the steam-cracked powder can be used alone, in which case panels are obtained with low breaking strength (slightly 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 go in the direction of a light finished 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 of:

• have a lignocellulosic biomass
• treating said biomass by steam cracking until a powder is obtained
• pressing said powder, alone or in combination with a fibrous material or a binder, for densification.

By “lignocellulosic biomass”, we mean 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”, we mean a material integrating at least in part a raw material of natural or biosourced origin.

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 with a humidity level 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 conduit;

- 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.

The Treatment Severity Factor is defined by the formula:

FS=Log10(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 compressed powder 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 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% 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 suitable for being densified on its own. The resulting biomaterial will tend to have medium strength and will preferably be used as packing material, especially as insulation.

In a particular embodiment, the method for producing a biomaterial is implemented by steam cracking a fibrous biomass. 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 a binder can represent up to 50% of the constituents of the biomaterial. This allows the production of a biomaterial with good cohesion and good mechanical resistance; 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 non-fibrous biomass. The powder obtained is non-fibrous in nature and is used as a binder in combination with a fibrous material.

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 itself can 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 a 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.

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 coming 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 biomass, particularly in the case of biomass from materials to be recycled. It is also possible to mix powders from different batches of steam cracked powders. The invention offers a great flexibility of implementation in the treatment of the biomass as well as 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 Log ₁₀ FS = 4.05 for oak (C4) and Log ₁₀ FS 4.15 for spruce (E6).

The powders were then shaped according to the following protocol:

• sampling of the mass of fibers to be sampled according to the size of the test panel,
• moistening the fibers to be above the fiber saturation point (30% humidity),
• dispersion of the fibers in the mold (200 x 200 mm) trying to obtain a homogeneous distribution,
• manual pressing using a plate 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 stages of time and pressure, at different temperatures (Cf. table of Tests in the column “pressing time”).

The results are shown in Table 1:

Test No. material type Mass
Sample (g) Amount of water or glue Temperature (°C) Pressing time Comments on the obtained biomaterial 1 C4 120 Embedded Particles 200 2.5 minutes at 80kN and
2.5 mins at 40kN Particles too wet
-->
water migration during
pressing 2 C4 125 Partially Drowned 200 1 min at 8 kN, 1.5 min at 20 kN,
1 min at 40 kN, 1 min at 12 kN Particles too wet
-->
water migration during
pressing 3 C4 120 40g 200 30 sec at 8 kN, 1.5 min at 20 kN,
1 min at 80 kN, 1 min at 20 kN First complete structure,
panel crumbling phenomenon 4 E6 120 60g 200 30 sec at 8 kN, 1.5 min at 20 kN,
1 min at 80 kN, 1 min at 20 kN Good structure, presence
of water improves the rigidity and the surface finish (to be compared with panel N°7) 5 Native spruce 120 60g 200 30 sec at 8 kN, 1.5 min at 20 kN,
1 min at 80 kN, 1 min at 20 kN Native Spruce: the structure is existing
but nevertheless very crumbly and not water resistant 6 native oak 120 40g 200 30 sec at 8 kN, 1.5 min at 20 kN,
1 min at 80 kN, 1 min at 20 kN Native Oak: the structure is
existing but extremely friable. Impossibility of cutting a 5 cm square to carry out the standardized tests for swelling 7 E6 120 0 200 30 sec at 8 kN, 1.5 min at 20 kN,
1 min at 80 kN, 1 min at 20 kN E6 without Water, the mechanical resistance
seems less important compared to panel N°4 (E6 with Water) 8 C4 120 0 200 30 sec at 8 kN, 1.5 min at 20 kN,
1 min at 80 kN, 1 min at 20 kN C4 without Water, the mechanical resistance
once again seems less important compared to panel N°3 (C4 with Water) 9 E6 110 Phenolic Glue 12.1 g
BAKELITE PF 1866 HW Kundenmuster UN 3267 (52% Dry extract)
200 30 sec at 8 kN, 1.5 min at 20 kN,
1 min at 80 kN, 1 min at 20 kN The panel is not convincing,
very powdery and crumbly but it seems to be light. This is from the blender breaking the fibers 10 E6 110 Phenolic Glue 12.1g
BAKELITE PF 1866 HW Kundenmuster UN 3267 (52% Dry extract)
200 2.5 mins at 150 kN
2.5 mins at 80 kN, 1 min at 20 kN The panel is not convincing,
very powdery and crumbly but it seems to be light. This is from the mixer breaking the fibers. The increase in pressure does not have a big impact on these 2 panels 11 E6 and C4 120 (60 and 60) 50g 200 2.5 mins at 150 kN
2.5 mins at 80 kN, 1 min at 20 kN The mixture increases the cohesion
general of the panel. The cohesive oak powder is added to the spruce fibers giving good mechanical resistance (we also remove the crumbling effect) 12 E6 and C4 160 (80 and 80 with spruce
- oak - spruce) 65g 200 2.5 mins at 300 kN
2.5 mins at 150 kN, 1 min at 50 kN Increase in density (transition
from 600 to 800 kg/m ³ ) and pressure to obtain a more compact panel (increased rigidity) 13 E6 and C4 160 (80 and 80 with spruce
- oak - spruce) 40g (10 - 20 -10) 200 2.5 mins at 250 kN
2.5 mins at 150 kN, 1 min at 50 kN Tests on mixtures of layers
successive to increase the cohesion with the adhesive powder in the center (C4) and the fibrous E6 on the outsides
Good rigidity 14 E6 and C4 160 (80 and 80 with oak - spruce - oak) 35g (7.5 - 20 - 7.5) 200 2.5 mins at 250 kN
2.5 mins at 150 kN, 1 min at 50 kN Same test but with cohesive powder
of C4 on the outsides and fibers of E6 in the center. Rigidity seems equivalent to panel n°13 but the layers of oak are crumbling
Good rigidity 15 E6 and C4 160 (80 and 80 with oak - spruce - oak) 0 200 2.5 mins at 300 kN
2.5 mins at 150 kN, 1 min at 50 kN Same panel as n°14 but
without water by increasing the pressure for the first 2.5 minutes.
Less adhesion (compared to n°14) but good rigidity 16 E6 and C4 160 (80 and 80 mix) 0 200 2.5 mins at 500 kN
2.5 mins at 300 kN, 1 min at 150 kN Mixture with increased pressure but without water.
Very good rigidity and good cohesion 17 E6 and C4 160 (80 and 80 mix) 35 200 2.5 mins at 500 kN
2.5 mins at 300 kN, 1 min at 150 kN Panel similar to No. 16 with the addition of water which
increases the cohesion of the mixture, very good rigidity. Lamination for 3-point bending test

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:

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

Essay
Actual density (kg/m ³ ) Swelling (%) 3 613.2 13.1% 4 606.0 9.4% 5 556.8 217.4% 7 565.6 25.4% 8 548.1 10.0% 9 484.5 28.1% 10 461.6 16.0% 11 632.7 11.4% 13 833.4 17.2% 14 796.9 12.7% 15 729.0 16.1%

Table 2 : Bending strength tests according to EN 310: Shaping of the specimens (width = 5 cm and length = 20 x thickness + 50 mm or 150 mm (5 mm thick specimen). The machine gives directly the maximum force at break is F _max and one 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
• l 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 specimen no. 17 are presented in Table 3 below:

Resistance to
breaking (N) Specimen thickness (mm) Specimen width (mm) Constraint
Bending (Mpa) -0.128 4.24 48.3 0.0012

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 swelling shows that the sandwich panels absorb less water (lower weight gain and lower water evacuation on the paper).

The pressure does not affect the water resistance but rather the rigidity of the panel as well as the quantity of material to be pressed. Whether or not there is 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 bring cohesion and resistance to water 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 mix (or softwood-hardwood, or fibrous product-powdery product) gives the most satisfactory results for the 3 criteria assessed: 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 character of steam-cracked powders has many advantages, they could for example be used to replace glue or else as an addition to reduce the quantity of glue 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 (11)

Process for producing a biomaterial from steam-cracked lignocellulosic biomass in powder form, consisting of:

• have a lignocellulosic biomass
• treating said biomass by steam cracking until a powder is obtained
• pressing said powder, alone or in combination with a fibrous material, for densification.

A method according to claim 1 wherein said densified powder alone is fibrous in nature. A method according to claim 1 wherein said powder is non-fibrous in nature and is densified in association with a fibrous material. Process according to Claim 1, in which the said densified powder alone is a mixture of steam-cracked powders of fibrous and non-fibrous nature. Use of a powder obtained by steam cracking of a lignocellulosic biomass as raw material for the preparation of a biomaterial. Use according to claim 5 wherein said powder is the sole component of the biomaterial. Use of a non-fibrous powder obtained by steam cracking of a lignocellulosic biomass as a binder for the preparation of a biomaterial. Use according to claim 5 wherein said powder is mixed with a fibrous material and/or a binder. Biomaterial obtained from steam-cracked lignocellulosic biomass in the form of fibrous or non-fibrous powder. Biomaterial according to claim 9 comprising a mixture of wood powders of fibrous nature and of non-fibrous nature prepared by steam cracking. Use of a biomaterial as defined in one of claims 9 or 10 as a packing product, insulating product and/or composite panels.