Field of the invention

The present invention relates to an apparatus configured to recycle lignocellulosic fibres from a fibreboard, e.g. LDF, HDF or MDF, comprising compressed lignocellulosic fibres and a binding agent.

Background

Fibreboard is an engineered wood product that is made out of lignocellulosic fibres, most typically wood fibres. The lignocellulosic fibres in fibreboards are oblong (the ratio length: width typically exceeds 10) fibres, which are fairly short, e.g. less than 5 mm. In order to provide fibreboard, wood fibres are pressed, typically with a binder (e.g. a urea-formaldehyde resin). Fibreboard is a fairly dense product typically having a density of at least 0.5 kg/dm ³ .

Another engineered wood product is particleboard. Particleboard is less dense and comprise larger, more irregular wood particles. Particleboard is a cheap product, typically used when cost is a more decisive factor than strength. Particleboard may be mechanically re-recycled as the board is not too dense to allow for simple mechanical disintegration. Further, the wood particles in particleboard are large and thus tolerant to mechanical disintegration. Even if their sizes are reduced, the wood particles still be sufficiently large to provide the desired mechanical properties to particleboard comprising re-cycled wood particles.

Fibreboards, especially medium-density fibreboards (MDF), are used a lot in the furniture industry. They have a smoother and more homogenous interior than particleboard. In addition, they are stronger and have a smoother surface. Types of fibreboard in the art include medium-density fibreboard (MDF), and high-density fibreboard (HDF). For pieces of furniture that will be visible, a veneer of wood or a foil is often glued onto fibreboard to give it the appearance of conventional wood. Alternatively, a layer of lacquer is applied to the fibreboard to obtain the desired appearance. Fibreboards are produced from fresh wood. Recycling of fibreboards and especially HDF to produce new fibreboards is not known in the industry for commercial boards, and recently discovered methods in this field are known to be difficult and costly. For instance, these processes have the disadvantage that the initial fibre geometry is disturbed during recycling, which results in expensive methods. There is however a growing interest in sustainability throughout the world. In the furniture industry there is thus a need for improved devices for recycling of fibreboards to reduce the use of fresh wood. Especially, it would be of interest to be able to recycle fibreboards in furniture in a more cost efficient way.

Summary

Accordingly, there is according to a first aspect of the invention provided an apparatus configured to recycle lignocellulosic fibres from a fibreboard comprising compressed lignocellulosic fibres bonded together by a binding agent. The apparatus comprises a transport screw arranged within a closed metallic housing. The housing is configured to steam pieces of the fibreboard at super-atmospheric pressure to decompress and release the lignocellulosic fibres by hydrating them, as well as hydrolysing the binding agent. The transport screw is arranged for transporting the fibreboard pieces, upon being steamed, from an inlet of the housing, at which the fibreboard pieces are fed to the housing, to an outlet of the housing, at which steamed portions comprising released lignocellulosic fibres exit the housing. The apparatus further comprises a steam generator in communication with the housing, whereby the fibreboard pieces may be steamed at super-atmospheric pressure in the housing to provide the steamed portions comprising released lignocellulosic fibres, wherein the pressure in the housing is between 1.1 and 7 bar absolute pressure, and the temperature is between 103 °C and 165 °C, during use of the apparatus. In addition, the apparatus comprises an inlet pressure lock configured to receive the fibreboard pieces at atmospheric pressure and to deliver them to the housing, via the inlet, at super- atmospheric pressure; and an outlet pressure lock configured to receive the steamed portions comprising released lignocellulosic fibres via the outlet and ejecting recycled lignocellulosic fibres during a sudden expansion of super-atmospheric pressure.

This apparatus is advantageous in that it provides an efficient means for recycling of fibreboard particles. Hence, such fibreboard particles may be reused for other purposes. The apparatus is easy to operate and is not cumbersome to manoeuvre. Hence, the apparatus disclosed herein may recycle fibreboard particles from furniture parts. It is especially suitable for the process disclosed in WO 2021/112749. Further, the apparatus allows for recycling of lignocellulosic fibres from a fibreboard at a relatively low temperature and pressure, as opposed to processes and apparatuses known in the art. That the apparatus is configured to operate at low temperature and low pressure (.1 and 7 bar absolute pressure, and the temperature is between 103 °C and 165 °C) is advantageous since it contributes to an efficient hydrolysis of the fibreboard particles inside the housing.

In one embodiment the closed metallic housing, enclosing the transport screw, has a circular cross-section, the diameter of the cross-section increasing from the inlet of the housing to the outlet of the housing; and/or wherein the pitch of the transport screw increases from an end of the transport screw at the inlet of the housing to an end of the transport screw at the outlet of the housing, whereby the steamed portions comprising released lignocellulosic fibres may expand upon being steamed. This is advantageous in that the cavity inside the housing which can enclose pieces of the fibreboard will increase from the inlet end towards the outlet end of the housing, which allows for expansion of the fibres inside the housing. Expansion of the fibres inside the housing facilitate the processing within the housing. Further, when the diameter of the crosssection of the housing increases from the inlet of the housing to the outlet of the housing, the space inside the housing increases, which facilitate the opening of the fibres present inside the housing, and thus cause an efficient opening of the fibres. An efficient opening of the fibres has a positive effect of the quality of the recycled released lignocellulosic fibres.

In another embodiment, an end of the transport screw at the outlet of the housing is threaded in opposite direction to the threading over the rest of the transport screw, whereby the steamed portions comprising released lignocellulosic fibres may be compressed before being ejected via the outlet pressure lock. Such an opposite threading will force steamed portions comprising released lignocellulosic fibres to be pushed backwards towards the inlet of the housing once being steamed, thus compressing the fibres further. It is envisaged that compressed fibres will then expand more suddenly during the steam explosion, i.e. during the sudden expansion of super- atmospheric pressure at the outlet pressure lock, causing an efficient opening of the fibres. An efficient opening of the fibres has a positive effect of the quality of the recycled released lignocellulosic fibres.

In yet a further embodiment, the apparatus comprises at least a first pinn mill arranged downstream of the outlet pressure lock configured to open the recycled lignocellulosic fibres after having been ejected. Preferably a second pinn mill is arranged downstream of the first pinn mill, and more preferably a third pinn mill is arranged downstream of the second pinn mill. The pinn mill(s) is/are advantageous in that it/they can mechanically disintegrate the ejected recycled lignocellulosic fibres into smaller fractions. Hence, the lumps or agglomerates of fibres can be separated efficiently and the pinn mill(s) can further open the fibres in the recycled lignocellulosic fibres.

In another embodiment the apparatus further comprises a fibre sifter arranged downstream of the outlet pressure lock. Preferably, the fibre sifter is arranged upstream or downstream of a dryer. A fibre sifter may further facilitate the separation of agglomerated fibres. Hence, lumps or agglomerates of fibres can be separated efficiently with the aid from a fibre sifter, which also can further open the fibres in the recycled lignocellulosic fibres.

In yet a further embodiment, the transport screw is separated from the closed housing by a distance element, whereby any condense water may be separated from the steamed portions comprising released lignocellulosic fibres. Hence, the recycled released lignocellulosic fibres will have an even lower moisture level after the sudden expansion of super-atmospheric pressure at the outlet pressure lock. This decrease the need for further time consuming drying of the recycled lignocellulosic fibres. A distance element may be advantageous even if the apparatus typically is operated to minimize any condensation. In the case where the transport screw is separated from the closed housing by a distance element, the transport screw may be enclosed by a perforated tube. In such case, the perforated tube is arranged within the closed housing at a distance from the closed housing, whereby any condense water may be separated from the steamed portions comprising released lignocellulosic fibres.

In a further embodiment, the closed housing is provided with heating means to heat at least an inner surface of the closed housing, whereby condensation of water an inner surface of the closed housing may be minimized and/or condensed water may be evaporated. Also, this has the advantage that the recycled released lignocellulosic fibres will have an even lower moisture level after the sudden expansion of super-atmospheric pressure at the outlet pressure lock. This decrease the need for further time consuming drying of the recycled lignocellulosic fibres.

In one embodiment, the outlet pressure lock comprises a pipe, configured as a blow line, whereby the recycled lignocellulosic fibres are accelerated and opened after having been ejected. Optionally the blow line has an inlet for adding glue to the released lignocellulosic fibres, whereby the glue may be distributed among the fibres upon being transported within the blow line. In this way, glue is incorporated into the recycled lignocellulosic fibres in an efficient manner.

In another embodiment, the apparatus further comprises a separation unit configured to separate recycled lignocellulosic fibres of a first size from recycled lignocellulosic fibres of a second size, wherein the first size exceeds a set threshold, whereas the second size is equal or less than the threshold. Preferably, the separation unit is a sieve. This facilitates the sorting of the recycled lignocellulosic fibres and separates the fibres in an efficient manner.

In a further embodiment, the apparatus further comprises an ultrasonic transmitter, such as an ultrasonic transducer, configured to open the recycled lignocellulosic fibres after having been ejected by subjecting them to ultra sound, the ultrasonic transmitter being arranged downstream of the outlet pressure lock. The use of ultra sound is an efficient and environmentally friendly way of opening the recycled lignocellulosic fibres. Further, the mechanical impact on the fibres is low, leaving the opened fibres essentially intact.

The apparatus may further comprise a low pressure chamber in direct communication with the outlet pressure lock. In such case, the low pressure chamber is provided with a pump configured to evacuate the chamber to provide sub-atmospheric pressure, whereby the pressure drop in ejecting the recycled lignocellulosic fibres may be increased. This results in that the pressure drop when ejecting the recycled lignocellulosic fibres may be increased, causing a stronger steam explosion reaction, which in turn causes a more efficient disintegration of the fibres as well as more finely disintegrated fibres.

In one embodiment, the inlet pressure lock is a plug screw feeder, whereby pieces of the fibreboard may be fed continuously to the closed housing. Optionally the plug screw feeder is in communication with a steam generator.

The housing and the transport screw therein may be longitudinal and extend along a centre axis, and the inlet may be facing upwards from the housing and the outlet may be facing downwards from the housing. This is advantageous since the apparatus may take advantage of gravity when both fibreboard particles are introduced into the housing and when recycled fibreboard portions exists the apparatus through the outlet pressure lock.

In one embodiment, the steam generator is in communication with the housing through pipe connections at more than one position of the perimeter of the housing. Preferably at between 2 and 10 positions of said perimeter, more preferably between 4 and 8 positions of said perimeter, and most preferred between 5 to 7 of said perimeter. This allows for an even and efficient distribution of steam into the housing. Further, this facilitates the supply and regulation of the pressure inside the housing. In such case, each pipe connection may be in communication with the housing through a plurality of pipe inlet valves. This is advantageous since it facilitates the supply and regulation of the pressure within the housing even further.

The apparatus may further comprise a driving unit configured to operate the transport screw. Preferably the driving unit is an engine.

The pressure in the housing may be between 1.2 and 6 bar absolute pressure, and the temperature may be between 105°C and 159°C during use of the apparatus, such as a pressure of 1.5 to 3 bar absolute pressure and a temperature of 111°C to 134°C, during use of the apparatus. These parameters are advantageous since they contribute to an efficient hydrolysis of the fibreboard particles inside the housing. As can be seen, the apparatus is typically designed to operate at moderate over pressure.

In one embodiment, the inlet pressure lock comprises a first valve gate, a second valve gate being the inlet, an intermediate chamber there between, and a pressure regulating means, and the outlet pressure lock comprises a first valve gate being the outlet, a second valve gate, and an intermediate chamber there between. The pressure regulating means is arranged configured to adjust pressure within the intermediate chamber of the inlet pressure lock. In such case, the pressure regulating means in communication with the intermediate chamber may regulate the pressure therein with steam or compressed air. This is advantageous since the arrangement of the inlet pressure lock provides fibreboard particles to the housing at an elevated over pressure equal or higher than the pressure inside the housing. Further, the arrangement of the outlet pressure lock facilitates the steam explosion, i.e. the sudden expansion of super-atmospheric pressure.

Further, the pressure regulating means may be arranged configured to increase the pressure within the intermediate chamber of the outlet pressure lock to a pressure higher than the pressure at the outlet of the housing, whereby the pressure drop in ejecting the recycled lignocellulosic fibres may be increased. This results in a stronger and more efficient steam explosion.

In one embodiment, the valve gates are selected from the group consisting of a knife gate valve (sliding gate), a butterfly gates valve, preferably having a deflector cone, or a calotte valve. Alternatively, the valve gates may be rotary valves or a ball valves. Given the moderate pressure, there is no need for more complex cascades of valves, such as combinations of rotary valves.

The outlet pressure lock may comprise a first valve gate being the outlet, a second valve gate, and an intermediate chamber there between, the first valve being a sliding gate and the second valve gate being a butterfly gate. Preferably, a cross-section of the outlet pressure lock increases from the first valve gate to the second valve gate, and more preferably the intermediate chamber being conical. This is advantageous in that it reduces the risk of fibres getting stacked in the outlet pressure lock. Further, its envisaged that butterfly gate provides for rapid and efficient steam explosion.

The housing and the transport screw may be arranged pivotally, the inlet end being arranged lower than the outlet end. Hence, the housing is inclined, with the inlet end being arranged lower than the outlet end. This is advantageous in that the steam explosion taking place at the outlet pressure gate may take advantage of the gravity since the outlet end is elevated from the ground surface GS. Moreover, the pivotal arrangement facilitates the disintegration of the fibres due to shear forces exerted on the fibres by the transport device. When the housing is inclined, the fibres inside the housing will due to gravity fall backwards, towards the inlet of the housing, when being processed inside the housing. Hence, the steamed portions comprising released lignocellulosic fibres may be compressed before being ejected via the outlet pressure lock. The inclination of the housing will force the fibres therein to be pushed backwards towards the inlet of the housing, thus compressing the fibres further. This may cause the compressed fibres to expand more suddenly during the steam explosion, i.e. during the sudden expansion of super-atmospheric pressure at the outlet pressure lock, causing an efficient opening of the fibres.

Alternatively, the housing and the transport screw are horizontally arranged.

In another embodiment, the apparatus further comprises a dryer arranged in communication with the outlet pressure lock, the dryer having a drying part for drying recycled lignocellulosic fibres received via an inlet end. The dryer facilitates the process of adjusting required material and moisture conditions of the recycled fibres and may eliminate and separate contaminations from the recycled fibres.

The dryer may have an inlet chamber, the inlet chamber having an inlet for receiving recycled lignocellulosic fibres from the outlet pressure lock, a steam outlet for withdrawing steam, and separate fibre outlet. The fibre outlet is in direct communication with the inlet end of the drying part of the dryer.

In a further embodiment, a steam separation chamber is arranged downstream the outlet pressure lock and upstream the dryer. Such steam separation chamber has an inlet for receiving recycled lignocellulosic fibres from the outlet pressure lock, a steam outlet for withdrawing steam, and separate fibre outlet for withdrawing fibres.

In yet another embodiment, the dryer has a cylindrical shape and comprises an inlet end in communication with the outlet pressure lock, an outlet end, an inner perforated drum optionally arranged inside an outer isolating housing, the inner perforated drum being arranged in between the inlet end and the outlet end, a transport tool arranged within the perforated drum for transporting recycled lignocellulosic fibres received at the inlet end from the outlet pressure lock through the inner perforated drum to the outlet end, and optionally at least one air nozzle configured to introduce air into the perforated drum, thereby creating a flow of air within the dryer. Preferably the transport tool is a rotatable transport screw.

The fibreboard may be a Low Density Fibreboard (LDF), a Medium Density Fibreboard (MDF) or a High Density Fibreboard (HDF).

In one embodiment, the moisture content of the fibreboard pieces does not exceed 25% based on the dry weight of the fibreboard pieces. Preferably, the moisture content of the fibreboard pieces to be steamed does not exceed 20%, such as 15%, based on the dry weight 20 of the fibreboard pieces. This is beneficial since the drying efforts after completion of the steam explosion and recycling of the fibreboard materials are reduced. Another advantage of a low moisture content of 25% or lower is that waste water emanating from the apparatus is avoided.

In a further embodiment, the moisture content of the steamed portions comprising released lignocellulosic fibres is 15 to 30% based on the dry weight of the portions.

These moisture parameters also facilitate the hydrolysation of the binder present in the fibreboard particles, and the decompression of the fibres, such that recycled lignocellulosic fibres having intact fibre lengths are obtained using the apparatus. Further, a low moisture content implies that a dryer arranged in communication with the outlet pressure lock efficiently may dry ejected recycled lignocellulosic fibres, as the moisture content in the ejected recycled lignocellulosic fibres also is low.

In yet another embodiment, the apparatus further comprises a compressed air generator in communication with the housing configured to introduce compression air into the housing. This is advantageous since the apparatus may then combine the use of compressed air and stem to regulate the pressure inside the housing.

Brief description of the drawings

These and other aspects, features and advantages of which the invention is capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which:

Fig. 1A shows an apparatus for recycling of lignocellulosic fibres from a fibreboard comprising a transport screw and pressure locks.

Fig. IB shows an apparatus for recycling of lignocellulosic fibres from a fibreboard comprising a transport screw and pressure locks according to another embodiment;

Fig- 2 shows an inlet pressure lock comprised in the apparatus disclosed herein;

Fig- 3 shows an outlet pressure lock comprised in the apparatus disclosed herein;

Fig- 4 shows a dryer optionally comprised in the apparatus disclosed herein,

Fig. 5 shows a housing of the apparatus disclosed herein; and

Fig. 6 shows further optional features, which may be comprised in the apparatus disclosed herein.

Detailed description

The following description focuses on an embodiment of the present invention applicable to an apparatus for recycling of lignocellulosic fibres from a fibreboard 10 comprising compressed lignocellulosic fibres bonded together by a binding agent. However, it will be appreciated that the invention is not limited to the specific exemplary embodiment described.

Fig. 1A shows an apparatus 100 for recycling of lignocellulosic fibres from a fibreboard 10 comprising compressed lignocellulosic fibres bonded together by a binding agent. For instance, the fibreboard 10 may be a low density fibreboard (LDF), a high density fibreboard (HDF) or a medium density fibreboard (MDF). As indicated by the dashed line in Fig. 1 A, the apparatus 100 extends along a longitudinal centre axis A. Further, the apparatus 100 has an inlet end 112 and an outlet end 114.

The apparatus 100 is provided with a transport screw 110 arranged within a closed housing 111, in which fibreboard pieces 11 of the fibreboard 10 will be steamed at super-atmospheric pressure. The housing I l l is preferably made of a metal, such as a ferrous metal, for instance steel or stainless steel. The fibreboard pieces 11 are formed from crushing the fibreboard 10 into smaller pieces 11. As shown in Fig. 1A, the metallic closed housing 111 is oblong and typically has a length in the range of 4 to 10 m.

Commonly, the fibreboard pieces 11 have a mix of different dimensions, the largest dimension being in the range of 5 to 50 cm. The thickness of fibreboard pieces 11 (i.e. the thickness of the fibreboard 10 crushed) is typically in the range 10 to 50 mm. For instance, the fibreboard pieces 11 may be fairly quadratic and have dimensions of between 5x5 mm and 50x50 mm, preferably the fibreboard pieces 11 have a dimension of about 30x30 mm.

The transport screw 110 will convey, preferably continuously, the fibreboard pieces 11 during the recycling process from an inlet 116 of the housing 111 to an outlet 118 of the housing 111. Hence, the fibreboard pieces 11 are fed to the housing 111 through the inlet 116 and exit the housing 111 through the outlet 118 as steamed portions 12 comprising released lignocellulosic fibres.

The closed metallic housing 111 enclosing the transport screw 110 preferably has a circular cross-section. Optionally, the diameter of the cross-section increases from the inlet 116 of the housing 111 towards the outlet 118 of the housing 111 and/or the pitch of the transport screw 110 increases from an end of the transport screw 110 at the inlet 116 of the housing 111 to an end of the transport screw 110 at the outlet 118 of the housing 111, i.e. having a so called progressive thread design (not shown herein in the Figures). Both these optional designs gives increasingly more space within the closed housing 111 towards the outlet 118, thus providing more room for the steamed portions 12, which in turn facilitates the expansion of the steamed portions 12 comprising released lignocellulosic fibres while being steamed. Further, it allows for processing more material than in a housing with a cross-section with constant diameter as the filling rate can be increased if the diameter of the cross-section increases from the inlet 116 of the housing 111 towards the outlet 118 of the housing. Moreover, having a tapered diameter, a progressive thread design or adopting a faster rotation of a second half of the transport screw 110 can also facilitate the maintenance of a constant filling rate.

If the circular cross-section has a continuous diameter, approximately 30% of the space inside the housing 111 holding the transport screw 110 is filled with fibreboard pieces 11 while typically 50% of the space inside the housing 11 is filled with steamed portion 12 comprising released lignocellulosic fibres. The increased volume is caused by the expansion of the fibres occurring during the transportation and steaming of the fibreboard pieces 11. Furthermore, the housing 111 is arranged at a distance DI, D2 from a ground surface GS. Three supports 150 are used to hold the housing 111 at a preferred distance DI, D2 from the ground surface GS. In Fig. 1 A, the housing 111 is pivotally arranged, which facilitates the disintegration of the fibres due to shear forces exerted on the fibres by the transport screw 110. In Fig. 1 A, the housing 111 is inclined, having the inlet 116 arranged closer to the ground surface GS than the outlet 118. Moreover, the pivotal, inclined, arrangement where the inlet end 112 is arranged lower than the outlet end 114 contributes to that gravity can be used to facilitate the filling and release of the fibres to and from the housing 111.

When arranged inclined as shown in Fig. 1 A, an angle between the housing 111 and the ground surface GS is preferably in the range of 15 to 30 degrees, preferably about 20 degrees. A possible distance DI is between 20 and 50 cm, preferably about 30 to 40 cm and a possible distance D2 may be between 1.5 and 2.5 meters, preferably about 2 m. However, the housing 111 may also be arranged horizontally.

In Fig. 1 A, the transport screw 110 has a centre shaft 105 and a blade 108 extending therefrom. In Fig. 1 A the blade 108 is a continuous screw, also denoted worm, extending from the shaft 105 in a helical manner.

The inlet 116 is part of an inlet pressure lock 120 which will receive fibreboard pieces 11 at atmospheric pressure through a first valve gate 121 and deliver the pieces 11 to the housing 111 via the inlet 116 at a super-atmospheric pressure. Hence, the inlet 116 is also a second valve gate 116 of the inlet pressure lock 120. Between the first 121 and second valve gate 116, there is an intermediate chamber 122 which is connected to and in fluid communication with the steam generator 160. Optionally, the intermediate chamber 122 is coupled to a pressure regulating means 127, operating separately from the steam generator 160. The steam generator 160 is in communication with the housing 111, whereby the apparatus 100 is configured to steam the fibreboard pieces 11 at super-atmospheric pressure in the housing 111 to provide the steamed portions 12 comprising released lignocellulosic fibres. The pressure in the housing I l l is preferably between 1.1 and 7 bar absolute pressure, and the temperature is preferably between 103 °C and 165 °C, during use of the apparatus 100.

Further, the outlet 118 is part of an outlet pressure lock 130 configured to receive the steamed portions 12 comprising released lignocellulosic fibres from the housing 111 through the outlet 118, which is also a first valve gate 118 of the outlet pressure lock 130. The outlet pressure lock 130 further comprises a second valve gate 131 and an intermediate chamber 132 there between. The outlet pressure lock 130 will eject recycled lignocellulosic fibres 13 from the apparatus 100.

The inlet pressure lock 120 and the outlet pressure lock 130 will be explained more in the following with reference to Figs 2 and 3.

As an option not shown in Fig. 1 A, instead shown in Fig. 5, an end of the transport screw 110 located at the outlet 118 of the housing 111 may be threaded in an opposite direction to the threading over the rest of the transport screw 110. Hence, the blades 108 extending from the centre shaft 105 at the outlet 118 are angled towards the blades 108 of the remaining part of the transport screw 110, as shown in Fig. 5. This transport screw 110 design will have an end section which feeds the pieces 11 backwards towards the inlet 116 of the closed housing 111. Thus, the steamed portions 12 comprising released lignocellulosic fibres may be compressed before being ejected via the outlet pressure lock 130. Alternatively, the oppositely threaded end portion of the transport screw 110 may extend beyond the outlet pressure lock 130 thus feeding the steamed portions 12 backwards towards the outlet pressure lock 130.

In an alternative embodiment, the transport screw 110 may be separated from the closed housing 111 by a distance element, such that any condense water is separated from the steamed portions 12 comprising released lignocellulosic fibres.

Further optionally, as shown in Fig. 5, the transport screw 110 can be enclosed by perforated tube 180 arranged within the closed housing 111 at a distance D3 from the closed housing 111, such that any condense water may be separated from the steamed portions 12 comprising released lignocellulosic fibres.

Furthermore, as also shown in Fig. 5, the closed housing 111 may be provided with heating means 190 configured to heat at least an inner surface of the closed housing 111 in order to decrease and/or evaporate condensation of water an inner surface of the closed housing 111. These designs further decreases the moisture content of the steamed portions 12.

A steam generator 160 is coupled to and is in communication with the housing 111. In Fig. 1A, the steam generator 160 is connected to the housing through one pipe connection 161 at one position. However, the steam generator 160 may be connected to the housing 111 through several pipe connections 161 along the extension and perimeter of the housing 111. Also, each pipe connection 161 along the housing 111 may comprise a plurality of inlet valves 162, as shown in Fig. IB. In Fig. IB, there are seven pipe connections 161, each in turn comprising three inlet valves 162. However, there may be for instance five inlet valves 162 per pipe connection 161. In addition to the pipe connections 161 and inlet valves 162 of the apparatus 100 shown in Fig. IB, the apparatus 100 comprises the same components as the apparatus shown in Fig. 1 A.

The steam generator 160 controls the pressure inside the housing 111 and elevates the pressure therein to a super-atmospheric pressure. Hence, the steam generator 160 operates using steam to regulate the pressure inside the housing 111.

Figs 2 and 3 show schematic drawings of the inlet and outlet pressure locks 120, 130, respectively, each comprising the intermediate chamber 122, 132, which separates a first valve gate 116, 118 from a second valve gate 121, 131. The intermediate chamber 122, 132 is arranged vertically between the first valve gate 116, 121 and the second valve gate 118, 131.

The valve gates 121, 116, 118, 131 are selected from the group consisting of a knife gate valve (sliding gate), a butterfly gates valve, preferably having a deflector cone, or a calotte valve. Such gates, especially knife gate valves (sliding gate) and butterfly gates valves, are suitable for gating pieces of lignocellulosic fibres 11 and/or steamed portions 12 comprising released lignocellulosic fibres with low moisture content.

Optionally, the outlet pressure lock 130 has a first valve gate being the outlet 118, a second valve gate 131, and an intermediate chamber 132 there between, where the first valve is a sliding gate and the second valve gate 131 is a butterfly gate. Preferably its cross-section increases from the first valve gate to the second valve gate 131, and more preferably the intermediate chamber 132 is conical.

Moreover, the apparatus 100 may further comprise a low pressure chamber in direct communication with the outlet pressure lock 130. The low pressure chamber is provided with a pump for evacuating the low pressure chamber to provide sub- atmospheric pressure. This results in that the pressure drop when ejecting the recycled lignocellulosic fibres 13 may be increased, causing a stronger steam explosion reaction.

Further optionally, the inlet pressure lock 120 can be a plug screw feeder, such that pieces 11 of the fibreboard 10 may be fed continuously to the closed housing 111. Such a plug screw feeder may further be in communication with a steam generator.

In Fig. 2, a pressure regulating means 127, 160 is coupled to the intermediate chamber 122. The steam generator 160 may act as the pressure regulating means, or a separate pressure regulating means 127 is used. If the intermediate chamber 122 is coupled to the steam generator 160, as indicated by the dashed lines in Figs 1 A and IB connecting the intermediate chamber 122 to said steam generator 160, the steam generator 160 supplies the intermediate chamber 122 with steam, thereby elevating the pressure therein to a pressure corresponding to the overpressure in the housing 111 or to an overpressure exceeding the pressure within said housing 111. Optionally, the pressure regulating means 127 is a separate pressure regulator, either being a steam generator or a compressed air generator.

Each valve gate 116, 118, 121, 131 has a valve switch 116a, 118a, 121a, 131a connected thereto, which controls the opening and closure of the valve gate 116, 118, 121, 131.

Optionally, the outlet pressure lock 130 comprises a pipe 200, configured as a blow line 200. This is schematically shown in Fig. 6. The use of a blow line 200 accelerates and opens the recycled lignocellulosic fibres 13 after they have been ejected from the outlet pressure lock 130. Such a blow line 200 can further be provided with an inlet for adding a glue to the released lignocellulosic fibres 13, such that the glue is distributed among the fibres 13 when transported within the blow line 200. In this way, glue is incorporated into the fibres 13 in an efficient manner.

Alternatively, the inlet pressure lock 120 has a first valve gate 121, a second valve gate being the inlet 116, an intermediate chamber 122 there between, and a pressure regulating means 127, and the outlet pressure lock 130 comprises a first valve gate being the outlet 118, a second valve gate 131, and an intermediate chamber 132 there between, and the pressure regulating means 127 is arranged for increasing the pressure within the intermediate chamber 132 of the outlet pressure lock 130 to a pressure higher than the pressure at the outlet 118 of the housing 111, such that the pressure drop when ejecting the recycled lignocellulosic fibres 13 is increased. An increased pressure drop causes a more sudden and stronger steam explosion reaction when ejecting the recycled lignocellulosic fibres 13, resulting in a more efficient disintegration of the fibres as well as more finely disintegrated fibres. The pressure and duration of the increased pressure in the intermediate chamber 132 can be adapted to obtain a desired steam explosion reaction.

Fig. 6 further shows that the apparatus 100 may comprise a separation unit 210 for separating assemblies of recycled lignocellulosic fibres 13 of a first size from assemblies of recycled lignocellulosic fibres 13 of a second size. In such case, the first size exceeds a set threshold, whereas the second size is equal or less than the threshold. This is advantageous since the ejected recycled lignocellulosic fibres 13 after the steam explosion sometimes form aggregates or assemblies of fibres rather than comminuted fibres. A separation unit 210 can disintegrate such assemblies of recycled lignocellulosic fibres 13 efficiently. The separation unit 210 can for instance be a sieve, such as a rotating sieve. As shown in Fig. 6, the separation unit 210 can be arranged downstream of the outlet pressure lock 130 of the apparatus 100 such that recycled lignocellulosic fibres 13 being larger than the set threshold is separated from the remaining recycled lignocellulosic fibres 13 before drying takes place. Hence, said separation unit 210 may be arranged downstream of the outlet 130 but upstream of a potential dryer 170, as indicated by the dashed lines in Fig. 6.

Alternatively, as further shown in Fig. 6, the apparatus 100 may comprise an ultrasonic transmitter 220, such as an ultrasonic transducer, configured to open the recycled lignocellulosic fibres 13 after they have been ejected by subjecting them to ultra sound. Such an ultrasonic transmitter 220 is arranged downstream of the outlet pressure lock 130 as indicated by the dashed lines in Fig. 6. The ultra sound may also be combined with pressure shock waves to efficiently open the recycled lignocellulosic fibres 13. The ultrasonic transmitter 220 may be arranged also downstream from the optional dryer 170 as shown in Fig. 6.

Fig. 6 further comprises three optional pinn mills 230A, 230B, 230C. In order to further facilitate the opening of the ejected recycled lignocellulosic fibres 13, the apparatus 100 may further comprise at least a first pinn mill 230A arranged downstream of the outlet pressure lock 130, and downstream of the optional dryer 170 is used. Preferably a second pinn mill 230B can also arranged downstream of the first pinn mill 230 A, or even more preferably a third pinn mill 230C is further arranged downstream of the second pinn mill 230B. The pinn mill(s) 230 A, 230B, 230C mechanically disintegrates the ejected recycled lignocellulosic fibres 13 into smaller fractions. Hence, the pinn mill(s) 230A, 230B, 230C can separate lumps or agglomerates of fibres 13 as well as further open the fibres in the recycled lignocellulosic fibres 13.

Further, the apparatus 100 may comprise a fibre sifter 240 arranged downstream of the outlet pressure lock 130 as shown in Fig. 6. The fibre sifter 240 may be arranged either upstream or downstream of a potential dryer 170 as indicated by the dashed lines and boxes in Fig. 6.

The fibre sifter 240 preferably works together with an adjustable upwardly directed air flow. The recycled lignocellulosic fibres 13 are fed from above into the upwardly directed air flow provided from the fibre sifter. The speed of the air flow can be adjusted in such a way that recycled lignocellulosic fibres 13 below a certain pre-set threshold surface:weight ratio become airborne by the pressure from the air flow. These fibres 13 are then transported upwards by the air flow towards and into a cyclone and further to the targeted fraction. Recycled lignocellulosic fibres 13 which are too heavy or agglomerated (as well as other parts, such as contaminations) with a not acceptable surface:weight ratio falling outside the pre-set threshold, are too large to become airborne and will instead, with the aid from gravity, flow downwards into a fraction of not acceptable parts. The fibre sifter 240 may further be designed in such a way that critical parts (recycled lignocellulosic fibres 13 which are not directly airborne by the air flow or flowing downwards) like fibre agglomerations, are forced into a turbulence zone by the air flow and circulated a plurality of times until they are separated and able to become airborne or become separated by gravitational forces.

The operation of the apparatus 100 will now be explained in more detail with reference to the Figs 1-3.

The pressure locks 120, 130 used in the apparatus 100 each operate sequentially, independently from each other. For instance, during operation of the apparatus 100 the inlet pressure lock 120 may be opened and closed a plurality of times while a batch of previously inserted fibreboard particles 11 are transported towards the outlet pressure lock 130. The apparatus 100 operates in a sequential continuous process with the aid from the pressure locks 120, 130, which are regulated independently from each other.

Hence, during operation of the apparatus 100, the inlet pressure lock 120 shown in Fig. 2 will let fibreboard particles 11 in from above through the first valve gate 121 and subsequently close the first valve gate 121 with the valve gate switch 121a. Then, the pressure regulating means 127, 160 introduces steam or compressed air into the intermediate chamber 122 to achieve the same or higher pressure than the super-atmospheric pressure inside the housing 111 in the intermediate chamber 122.

When the intermediate chamber 122 and the fibreboard particles 11 have been pressurised, the second valve gate 116 (i.e. the inlet 116 to the housing 111) is opened by the valve switch 116a such that the fibreboard particles 11 fall into the housing 111.

Once in the housing 111, the transport screw 110 will convey the fibreboard particles 11 through the housing 111 along the axis A. The driving unit 115 connected to the centre axis 105 cause the transport screw 110 to rotate inside the housing 111, such that material is conveyed from the inlet end 112 towards the outlet end 114. During such transportation, the steam generator 160 ensures that the pressure inside the housing 111 is a super-atmospheric pressure by introducing steam and/or compression air into the housing 111 through the pipe connect! on(s) 161. When the fibreboard pieces 11 are subjected to the overpressure, the fibreboard pieces 11 are exposed to heat and moisture, which dissolves the adhesive binder and the pieces 11 release the lignocellulosic fibres due to the hydration. Moreover, the binding agent comprised in the pieces 11 are hydrolyzed. This process transforms the fibreboard pieces 11 into portions 12 comprising released lignocellulosic fibres during the transportation within the housing 111 of the apparatus 100. Thus, when the pieces 11 have reached the outlet pressure lock 130, they have been transformed into portions 12 comprising released lignocellulosic fibres.

In addition, the transport screw 110 mechanically shears the fibreboard particles 11, disintegrating the fibres therein. As described above, the diameter of the cross-section of the housing 111 can be tapered and/or the transport screw 110 can have a successively increased pitch in order to provide an increasingly spacious cavity inside the housing 111 to facilitate the expansion of the fibreboard particles 11.

Optionally, during operation, the housing 111 may be fed with steam in a first half of its length and compressed air in the second half of its length. In such case, the fibres 11 will not absorb the same amount of moisture as if only steam is used, but the moisture available will have a longer period of time to conduct the hydrolysation. A compressed air generator 164 is in such embodiment arranged in fluid communication with the housing 111 in addition to the steam generator 160, as indicated by the dashed lines of the compressed air generator 164 shown in Fig. 1 A.

The outlet pressure lock 130 is also operated repeatedly and sequentially, but in a reverse order and in a slightly different way compared to the inlet pressure lock 120. The outlet pressure lock 130 is configured to receive the steamed portions 12 comprising released lignocellulosic fibres via the outlet 118.

Firstly, the outlet 118, i.e. the first valve gate 118, is opened such that conveyed portions 12 comprising released lignocellulosic fibres fall into the intermediate chamber 132 of the outlet pressure lock 130. Hence, the intermediate chamber 132 is pressurized by the overpressure present in the housing 111 when the first valve gate 118 is opened, i.e. the intermediate chamber 132 is pressurized by the steam injected into the housing 111.

Since the pressure inside the intermediate chamber 132 is an ambient pressure before the opening of the first valve gate 118, the pressure in the intermediate chamber 132 is elevated upon opening of the first valve gate 118. In this way, an overpressure is achieved in the intermediate chamber 132 holding the portions 12 comprising released lignocellulosic fibres. The first valve gate 118 is closed by the valve switch 118a and then, rapidly thereafter, the second valve gate 131 is opened, causing a sudden expansion of the overpressure in the intermediate chamber 132 of the outlet pressure lock 130. Thus, pressure loss in the intermediate chamber 132 is achieved by opening the second valve gate 131. This releases the portions 12 from the outlet pressure lock 130. Preferably, the second valve gate 131 is a butterfly valve. Further, the separate intermediate chamber 132, implies that more material may be a released in each cycle.

This sudden expansion of the overpressure is referred to as a so called steam explosion herein. The steam explosion in turn results in that the steam, which had penetrated the fibres in the portions 12, expands considerably and forcefully, whereby single fibres are torn apart and thus separated from each other. In order to provide an efficient steam explosion, the second valve gate 131 is preferably a valve allowing for rapid opening and release of the fibres, such as a knife gate valve (sliding gate) or a butterfly gates valve.

The weakest point in the fibre portions 12 are the hydrolysed binding joints. Therefore, the separation during the steam explosion separates the binder joints while the lignocellulosic fibres of the portions 12 remain intact such that recycled lignocellulosic fibres 13 are obtained. The preservation of the fibres in the recycled fibres 13 is an advantage since reuse of these fibres is facilitated when the recycled fibres 13 are intact and not shortened.

A pressure inside the housing I l l is preferably between 1.1 and 10 bar absolute pressure, and the temperature is between 103 °C and 180°C during use of the apparatus 100, such as a pressure of 1.1 to 7 bar absolute pressure and at a temperature of 103 °C to 165 °C, or a pressure of 1.2 to 6 bar absolute pressure and a temperature of 105°C to 159°C, or a pressure of 1.5 to 3 bar absolute pressure and at a temperature of 111°C to 134°C, during use of the apparatus 100.

Due to that the operating pressure in the housing 111 can be maintained at a relatively low level, such as between 1.1 and 10 bar absolute pressure (preferably 1.5 to 3 bar absolute pressure), there is no need to pressurize the intermediate chamber 132 with a separate pressurizing source. Hence, the outlet pressure lock 130 has clear advantages compared to other pressure outlets in similar apparatuses and processes.

For instance, the patent application WO 2020/188606A1 discloses a process and reactor for pretreatment of organic waste, which may include garden waste and waste wood. However, the reactor and process of this patent application relies on a pressure-relief section as a pressure lock outlet to achieve a steam explosion. As opposed to the outlet pressure lock of the present invention, the pressure-relief section in WO 2020/188606A1 is pressurized by a separate steam and/or gas injection to avoid a pressure drop in a high-pressure retention section where the organic material is subjected to overpressure. The high-pressure retention section operates at a much higher overpressure (i.e. 10 to 30 bar) than the housing 111 of the present invention, and thus require that the pressure-relief section is pressurized before it is opened towards the high-pressure retention section to avoid a pressure drop therein. Further, the pressurerelief section is adapted to gate liquid material.

Valve gates selected from the group consisting of a knife gate valve (sliding gate), a butterfly gates valve, preferably having a deflector cone, or a calotte valve, are suitable for operating at moderate pressure. While they efficiently gate large portions of released fibres in each cycle, they are however not suitable for high pressure applications. Further, they are less suitable for gating liquid fibre mass. Combinations of cascades of rotary valves, as disclosed in WO 2020/188606A1, are suitable for gating a liquid fibre mass at high temperature and pressure.

Preferably, the moisture content of the fibreboard pieces 11 does not exceed 25% based on the dry weight of the fibreboard pieces 11, more preferably the moisture content of the fibreboard pieces 11 to be steamed does not exceed 20%, such as 15%, based on the dry weight of the fibreboard pieces 11. The purpose of keeping the moisture content at this level is to reduce the drying efforts after completion of the steam explosion and recycling of the fibreboard materials. Further, also the moisture content of the steamed portions 12 comprising released lignocellulosic fibres is typically low, preferably 15 to 30% based on the dry weight of the portions. Another advantage of a low moisture content of 25% or lower is that waste water emanating from the apparatus 100 is avoided.

These parameters also facilitate the hydrolysation of the binder present in the fibreboard particles 11, and the decompression of the fibres 11, such that recycled fibres 13 having intact fibre lengths are obtained using the apparatus 100.

The moisture content of the fibreboard pieces 11 also differs from the organic waste subjected to overpressure in the reactor disclosed in WO 2020/188606A1, which require a wetting and mixing section to wet and process the waste material to be treated in the reactor. Since the apparatus 100 of the present invention is configured to treat fibreboard pieces 11 for recycling, rather than organic waste material comprising solid waste wood, such a wetting and mixing section is can be dispensed with. In addition, as described above, the process for treating organic waste material disclosed in WO 2020/188606A1 requires a very high operating pressure and that the pressure-relief section (being the outlet section) is pressurized by a separate pressurizing source during each pressure relief cycle.

With reference to Fig. 4, the apparatus 100 (not shown) optionally further comprises a dryer 170 arranged in communication with the outlet pressure lock 130 at an inlet end 171. The dryer 170 facilitates the process of adjusting required material and moisture conditions of the recycled fibres 13 and may eliminate and separate contaminations from the recycled fibres 13. Hence, the dryer 170 receives the recycled fibres 13, which have been subjected to the steam explosion in the outlet pressure lock 130.

The arrangement of the dryer 170 together with the outlet pressure lock 130 is mainly associated with processing a quite dry material, as the steamed portions 12 comprising released lignocellulosic fibres (their moisture content preferably being 15 to 30% based on the dry weight of the portions). As described above, the moisture content of the fibreboard pieces 11 does not exceed 25% based on the dry weight of the fibreboard pieces 11 and the moisture content of the steamed portions 12 comprising released lignocellulosic fibres is typically 15 to 30% based on the dry weight of the portions. Several other reactors and processes treating organic material, such as the reactor disclosed in WO 2020/188606A1, relies on wetting of the material to be processed, rather than processing substantially dry material as conducted by the apparatus 100 herein.

The dryer 170 has a drying part for drying recycled lignocellulosic fibres 13 received via the inlet end 171. The dryer 170 preferably has a cylindrical shape arranged in a substantially horizontal direction and comprises the inlet end 171, an outlet end 172, and an inner perforated drum 174 arranged inside an outer isolating housing 175. It is arranged for drying a material already being quite dry, as the steamed portions 12 comprising released lignocellulosic fibres.

The inlet end 171 to which the outlet pressure lock 130 is connected forms an expansion zone 170A of the dryer 170. The expansion zone 170A is equipped with two sets of rotating baffles 176C inside an expansion zone housing 175A for feeding recycled fibres 13, received in the expansion zone 170A, into the inner perforated drum 174.

After the expansion zone 170A there is a drying zone 170B, in which further moisture may evaporate from the hot recycled fibres 13 through the perforations of the perforated drum 174. By providing the perforated drum 174 inside the outer isolating housing 175, dust and recycled fibres 13 which have been shredded or fined into a particle size sufficiently small to penetrate through the perforations of the drum 174 will exit the drum 174 and enter the space between 170D the housing 175 and the drum 174. By having an outer isolating housing 175, the residual heat of the hot recycled fibres 13 may serve to evaporate water, lowering the already low moisture content of the recycled fibres 13 and not be lost to the surrounding.

Preferably, a separation zone 170C is arranged at the outlet end 172 of the dryer 170 in which dried recycled fibres 13 which have remained in the drum 174 until they reach the outlet end 172 exit the dryer 170 through an outlet 173. The dryer 170 is designed to remove steam from the recycled lignocellulosic fibres 13. Hence, it can also be referred to as a conditioner. The aim is to give each recycled lignocellulosic fibre 13 the chance to evaporate and quickly release moisture to the surrounding atmosphere. A preferred outlet moisture of the dried recycled fibres 13 at the outlet end 172 after the fibres 13 have exited the outlet 173 is below 30%, more preferred below 25%, and most preferred below 20%.

Further, a first transport tool 176A, such as a first rotating feed screw, is arranged within the perforated drum 174. The first feed screw 176A has an angled orientation, e.g. a right-angled orientation. A second transport tool 176B, being a second rotating feed screw, is arranged between the outside of the drum 174 and the inner side of the housing 175. The second feed screw 176B has an angled orientation opposite to the one of the first feed screw 176A, e.g. a left-angled orientation.

The dryer 170 further comprises a centre rotational axis 177. The first feed screw 176A, the second feed screw 176B, and the rotating baffles 176C are attached to the centre rotational axis 177. Rotation of the centre rotational axis 177 causes the first feed screw 176A, the second feed screw 176B, and the rotating baffles 176C to rotate. Since the first and second feed screws 176A, 176B have oppositely arranged angled orientation, the rotation of the centre axis 177 will cause the first feed screw 176A to transport the recycled fibres 13 from the inlet end 171 towards the outlet end 172, whereas the second feed screw 176B will in turn transport recycled fibres 13, which have exited the drum 174 to enter the space between 170D, in opposite direction back towards the inlet end 171. In addition, the baffles 176C will rotate and thereby push recycled fibre material 13 entering the dryer 170 from the outlet gate 130 into the drum 174.

Apart from transporting the recycled fibres 13 from the inlet end 171 to the outlet end 172, the first transport tool 176A may also serve to further separate the recycled fibres 13 from each other. Still the transport is gentle to avoid reducing the fibre length. Optionally, an angle of the centre rotation axis 177 may be adjusted. Further optionally, the first transport tool 176A may be a pneumatic transport tool or a linear mechanical transport tool.

During operation, the first feed screw 176A feeds the recycled fibres 13 from the inlet end 171 and the expansion zone 170A through the drying zone 170B of the perforated drum 174 towards the outlet end 172. A plurality of air nozzles (not shown) introduce hot or cold air into the perforated drum 174 such that the recycled fibres 13 are further dried in the drying zone 170B. The drying process create conditions which ease and support water evaporation and which decrease the risk of formation of lumps and/or fibre balls. The pressure inside the dryer 170 is preferably an ambient pressure, to provide a gentle transportation of the recycled fibres 13.

Once the dried recycled fibres 13 reach the separation zone 170C at the outlet end 172, the recycled fibres 13 will pass through the outlet 173 or, if lumps or fibre balls have been formed which have a larger particle size than the target fraction, these will may exit the dryer through an oversize outlet (not shown). The separation zone 170C further comprises an active or passive steam/hot moisturised air outlet 178. Also the inlet end may comprise a passive/active steam outlet. Further, a disintegrator, such as a fine opener (not shown in Fig. 4), may be arranged at the outlet end 172 of the dryer 170, upstream, or downstream, of the outlet 173, to further separate the recycled fibres 13 from each other. Before being used in producing fibreboards, the recycled fibres 13 may be subject to size fractioning, e.g. in a classifier.

Preferably, the dryer 170 has an inlet chamber having an inlet for receiving the recycled lignocellulosic fibres 13 from the outlet pressure lock 130, a steam outlet for withdrawing steam, and a separate fibre outlet in direct communication with the inlet end of the drying part of the dryer 170.

Further optionally, a steam separation chamber can be arranged downstream the outlet pressure lock 130 and upstream the dryer 170. The steam separation chamber has an inlet for receiving recycled lignocellulosic fibres 13 from the outlet pressure lock 130, a steam outlet for withdrawing steam, and separate fibre outlet for withdrawing fibres.

Without further elaboration, it is believed that one skilled in the art may, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative and not limitative of the disclosure in any way whatsoever. Although the present invention has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and other embodiments than the specific embodiments described above are equally possible within the scope of these appended claims.

In the claims, the term "comprises/comprising" does not exclude the presence of other elements or steps. Additionally, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous.

In addition, singular references do not exclude a plurality. The terms "a", "an", “first”, “second” etc. do not preclude a plurality.