EP1866587A1 - Holzwärmebehandlungsverfahren, anlage zur durchführung des verfahren und wärmebehandeltes holz - Google Patents

Holzwärmebehandlungsverfahren, anlage zur durchführung des verfahren und wärmebehandeltes holz

Info

Publication number: EP1866587A1
Authority: EP; European Patent Office
Prior art keywords: wood; temperature; treatment; heat; plates
Prior art date: 2005-04-04
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.): Withdrawn

Application number

EP06726171A

Other languages

English (en)

French (fr)

Inventor

Edmond-Pierre Picard

Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Picard Edmond-Pierre

Original Assignee

Picard Edmond-Pierre

Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)

2005-04-04

Filing date

2006-04-03

Publication date

2007-12-19

2006-04-03 Application filed by Picard Edmond-Pierre filed Critical Picard Edmond-Pierre

2007-12-19 Publication of EP1866587A1 publication Critical patent/EP1866587A1/de

Status Withdrawn legal-status Critical Current

Links

Classifications

- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
- B30B15/34—Heating or cooling presses or parts thereof

Definitions

the invention relates to a method of heat treatment of wood, an installation for the implementation of the method, and heat-treated wood.
Both solid wood and reconstituted wood for example in agglomerated or compressed fibers or particles, have disadvantageous characteristics such as, for example, hydrophilicity, dimensional instability and the tendency to putrefy more or less quickly. Because of these characteristics, when wood freshly cut into boards, cleats or any other elongated product is stored in predetermined dimensions, even if the wood is dried, changes are observed during storage mainly in dimensions and shape of these products. Thus, for example, some initially parallelepipedal pieces are warped, or other pieces are narrowed and cracked. And reconstituted wood tends, in addition, to disintegrate.
Heat treatment of wood at high temperature, under an inert atmosphere to prevent combustion is a commonly used method.
wood in an inert atmosphere By heating wood in an inert atmosphere to a temperature of between 150 and 280 ° C, the wood undergoes a transformation of its constituent molecules as a function, on the one hand, of the temperature curves used and, on the other hand, the environment in which the wood is found during the treatment. Some wood macromolecules are broken and recombine with each other by crosslinking. There is thus polymerization and the characteristics of the wood are transformed.
Document FR-A-2 604 942 describes a process for producing a lignocellulosic material by heat treatment and a material obtained by this process.
This process brings improvements in the behavior of wood, when it is subjected to moisture, with a more or less significant and homogeneous improvement in the mass of its rot-resistance (resistance to pathogens and lignivores usually attacking the wood). situation wet), and with a better dimensional stability, with a modification of its wettability, a transformation of its hydrophilic character into a relatively hydrophobic character, with a definitive and homogeneous shade of the wood in the mass and finally with an increase in its surface hardness .
this treatment makes it possible to remove a posteriori staining defects due to attacks of fungi responsible for blueness or redness of some woods.
this treatment induces a mechanical embrittlement, in particular of bending fracture, inducing a more brittle character that can range from a very slight decrease in performance to a decisive embrittlement rendering this treated wood unsuitable for a particular use in a certain number of applications of wood, especially for structural applications.
the temperature increases slightly beyond a certain limit, the lignin degradation is accentuated, the cellulose fibers are broken in turn, and the wood eventually loses all its mechanical performance.
the presence of oxygen is a factor that decreases the possibilities of improving the qualities of the wood and the degradation of its mechanical qualities and the presence of water is another factor of decrease, the hydrolysis partially replacing the thermolysis of wood, so that wood treated with water vapor in a flow of air is in principle less stable, less rot-proof and more brittle than a wood treated with nitrogen.
nitrogen is a poor conductor of heat, the enrichment of nitrogen in the air makes it particularly difficult to transfer heat from the gas stream to the wood to be heated.
Another difficulty in the heat treatment of wood is that of successfully treating the wood entirely. from the outer edge to the heart. Indeed, to treat a piece of wood at heart and in a homogeneous and optimal way, and to prevent the wood from cracking during the treatment, it must succeed in reaching the high temperature at which we obtain the crosslinking of lignin that allows to the wood to acquire its remarkable qualities, without exceeding it so as not to make the wood lose too much of its mechanical qualities.
the document FR-A-2 751 579 describes a method for treating wood with a glass transition stage, which imposes a temperature curve having a temperature step at the glass transition temperature, independently of the supply means. of calories and the medium making the wood inert to prevent its combustion, which is spontaneous in the air at temperatures above 100 ° C.
An advantageous characteristic obtained by this process is the rectification of the cellulosic fibers, that is to say a chemical bridging (covalent bonds) between the macromolecular chains of the constituents of the material.
the atmosphere is rendered inert by nitrogen, replacing oxygen, or by carbon dioxide or by saturating the air with steam. of water or, finally, by "sintering" the wood in hot oil.
the limits of the process of rétification in terms of performance of the obtained material are due to the sensitivity of the performance curves of the different parameters to be considered at the same time, each of these parameters evolving according to accentuated and non-monotonous curves, with discontinuities and extremes which are not in phase from one parameter to another in an area.
wood is a composite material consisting essentially of three types of polymers: hemicellulose, lignin and cellulose, from the most fragile to at least sensitive to the effect of temperature.
Gentle thermolysis cracks hemicelluloses and begins to modify lignin.
By-products of thermolysis essentially free radicals, would condense and then polymerize on lignin chains, and it is known that these reactions create a new lignin, called "pseudo-lignin" which is more hydrophobic and stiffer. than the initial lignin.
the wood becoming hydrophobic leads to the improvement of its dimensional stability which results in a reduction of its retraction (ASE) and a lowering of the saturation point of the fibers (PSF).
the temperature begins to crack the hemicelluloses, which has a positive effect on hygroscopy of the wood, since this removes the sites of reception of the dipolar molecule of water. At the same time, however, it weakens the wood by breaking some hemicellulose fibers and then almost all the hemicellulose; these fibers, however (which do not belong to the crystalline matrix of wood, made of cellulose) are much less mechanically efficient than lignins and do not play a large role in the overall mechanical performance of wood.
the low exothermicity of these reactions shows that they start at about 200 ° C. In fact, the exothermicity of the reactions begins around 200 ° C. for hardwoods and about 220 ° C.
the mechanical loss has a first maximum before 240 0 C, probably between 230 and 240 0 C, and a minimum between 230 and 250 0 C, probably close to 240 0 C, with a very sudden deterioration after the minimum .
ASE does not move much from 240 to 250 0 C, but we also know from scientific studies that the treatment has a negative effect on the dimensional stability of pine at temperatures below 230 0 C while, beyond, the improvement monotone of retractability, visible on the above table is proportional to the evolution of the parameters temperature and duration of the heat treatment up to (250 ° C., 15 minutes). Beyond this pair of parameters (temperature, duration of exposure), the improvement is no longer sensitive and the mechanical properties are degraded.
EBIO for its part, has a very important improvement between 240 and 250 0 C.
thermolysis has a triple mechanical effect on wood: - a beneficial effect on the hardness of hardwoods which increases all the more importantly that hardwoods are dense and the hardness is unchanged or slightly reduced for conifers a neutral effect on the compression behavior provided not to touch the cellulose (around 250 0 C, there may be beginning of degradation and after it is very exothermic and the destruction is very fast) a partially positive effect of an increase in stiffness but negative because this rigidity is accompanied by a change in visco-elastic behavior to a fragile behavior.
This effect of thermolysis is classically summarized on wood by an increase in Young's modulus which mainly affects the breaking strength and the maximum work before bending failure.
the high temperature treatment processes generally used concern both: theoretical temperature curves, which are not known to come out without greatly altering the trade-off between the fundamental improvement in the imputrescibility and the stability of the wood and the low decrease of its mechanical qualities,
the different heat treatments used have in common a number of characteristics, among which are the stacking with cleats, the phases of wood processing during the thermal cycle and cooling by injection and vaporization of water.
the various installations used for the implementation of a thermal treatment of wood have in common to include cleats that stack the parts to be treated leaving enough space for the passage of gas or liquid flow.
the common feature of the two main known processes is to treat wood placed in an enclosure in which a ventilation system passes a strong flow of heated gas that circulates on the surface of the wood and which therefore convectively transports calories to in contact with wood and the transfer of calories is between a moving flow and the surface of the wood.
this piece of wood When a piece of wood is introduced into an oven to be heated, this piece of wood always contains a certain quantity of water; this water is present in a greater or lesser quantity and in a more or less free form, or, on the contrary, bound, from the water flowing freely to the water of constitution.
water can be present in wood in three different situations, namely in open water, bound water and water of constitution.
Open water is the water present in the porosity of wood, which itself consists of a juxtaposition of micro "canals" oriented in the direction of the wood fiber.
the interior of these channels constitutes the porosity of the wood and the water can circulate there relatively freely as between grains of sand.
the percentage of moisture that is to say the ratio of the total weight of water to the weight of totally dry wood can reach 100 to 200% when the porosity of the wood is saturated with water, and About 30% at the saturation point of the fibers (PSF) when this macro-porosity is empty.
PSF saturation point of the fibers
the wood does not swell when this macro-porosity is empty or fills.
the heated water is present in liquid and vapor form.
Bound water is the water inside the walls of the micro-channels, which also have a internal porosity but a much smaller porosity, which makes the forces related to surface tensions predominant.
the walls of the micro-channels behave with respect to the bound water as would behave clay, for the same reasons, related to the size of the porosity. Because the walls are inflated to the maximum as long as there is water or moist air inside the micro-porosity constituted by the interior of the channels, this microporosity is "crushed" by the swelling of the walls; for this reason, the bound water circulates in a reduced microporosity because of this swelling and thus meets a fairly high resistance to flow, as would exert the porosity of a clay.
This bound water is emptied and fills up to be in equilibrium with the vapor pressure of the ambient air and that is why the wood naturally swells and shrinks in the air with a percentage of moisture varying approximately between 5% minimum. and between 14% and 30% in general.
the water of constitution is that water which is part of the cells themselves as in any living tissue and which can not be extracted by reversible drying without breaking the cell.
the first action of the heat is to dry the wood, that is to say to evacuate the water contained in the wood, starting with all the free water and continuing with the whole of the water. water and leaving in the cells the water of constitution. In fact, this action is done in two movements generated by two distinct forces.
the first movement consists of a migration of water from the inside to the outside of the wood as a result of the rise of the temperature inside the wood.
the water in the wood must first migrate from the heart to the wood surface. This migration of the water inside the wood is operated under the effect of the heat which increases the gas pressure present in the porosity. If it is known that the humidity can reach for example 200% and that the humidity is assumed to be 150% at a given moment, this means that a quantity of water representing 50% of the weight of wood is out of the wood and has been replaced by air (or ambient gas).
the second movement is evacuation of the surface to the outside of the wood by evaporation, related to the low pressure, the high temperature and the low saturation of the water of the ambient air:
the water on the surface can evacuate by evaporation.
the kinetics of evaporation is all the more important as the air at the surface is far from the water saturation.
the air or any other gas
the air may contain as much water as it is hot and the air pressure is low and evaporation takes place as long as the amount of water in the gas is less than the amount that it can contain and this evaporation is all the more rapid because it is far from saturation.
This operation is especially delicate in the sense that, if we try to speed up the process, the pressure of the water is likely to burst the wood (phenomenon of collapse of the wood drying) especially with some woods like the oak drying phase supersaturation, ie when the macro-porosity is still relatively filled by the free water.
the collapse is the result of a vapor overpressure and, it seems, a weakening of the walls with the rise in temperature.
2nd phase raising the temperature of the wood
the temperature of the wood increases; it is a simple endothermic operation: the calories are transformed into a rise in temperature according to the heat capacity of the wood. If the operation took place in the air, the wood would fire spontaneously from a certain temperature under the effect of the vibrations of the wood molecules in the presence of oxygen.
the wood reaches a so-called vitreous phase, from a temperature called glass transition temperature Tg, from which the wood loses its rigidity and becomes malleable.
Tg glass transition temperature
the complexity of the molecules makes that, with the molecular agitation of the temperature, the wood reaches an intermediate rheology between solid and liquid. It is a second-order transition, without latent heat of transformation as in the case of a fusion, but with an increase of the heat capacity and especially of the malleability of the wood which becomes plastic and will preserve the shape acquired in vitreous phase when the temperature will fall below.
the wood consists of many fibrous macromolecules which each have a different glass transition temperature, this temperature increasing with the free length of the fibers, so that the wood becomes more malleable beyond 150 0 C until at 200 ° C.
the wood is colored gradually in the mass of a homogeneous shade that becomes darker with the rise in temperature.
the reticulated wood has modified surface tension characteristics.
the third common feature is the cooling mode. Indeed, the wood being thermally modified in the chamber at a temperature of 230 0 C, it must necessarily be cooled before being taken out of the oven because it would ignite at more than 100 0 C.
the method generally used by the different methods are to incorporate water whose vaporization can cool the wood.
the heat treatments of wood generally applied before the present invention are similar in a particular point: to treat it, the wood is placed in an enclosure in which a ventilation system passes a strong flow of heated gas that circulates on the wood surface and therefore convective transport of calories to contact with the wood and the transfer of calories is between a moving flow and the surface of the wood.
the surface of the wood must be "in the open air", that is to say that one can not put the boards on one another (or possibly two two) but they are placed on sticks (wooden or metal cleats), spaced enough apart so as not to disturb the flow of gas and close enough to prevent the wood from flicking between the chopsticks.
the wood can remain a long time at constant temperature in the same way that a person can stay 1 hour with his body at 37 0 C in a sauna where the air is at 120 0 C, because the air evaporates the air. perspiration water, which helps to cool the skin.
experience shows that the retification at 230 ° C. ends up taking place with a thin wood but after having overcome the wood regulating mechanisms, according to the available moisture, and the exchange is at the same time slow, relatively expensive, incredibly complicated theoretically and it is ultimately difficult to model and appreciate the homogeneity.
this mechanism does not allow, in any case cost-effectively, to re-sharpen pieces of wood 15 cm thick, 20 cm or more fortiori.
profitability can not be improved by faster processing; a certain thickness of wood can not be economically exceeded;
the treatment with the glass transition temperature in the state of the art has two objectives in fact: a first objective of the temperature treatment at the glass transition temperature in the state of the art is to avoid that the outer edge of the a piece of wood may have a temperature above the glass transition temperature while the heart has not yet reached it.
the risk is that the wood becomes more and more plastic and malleable above this glass transition temperature at the edge of the room while another part would remain hard in the heart of the room, having not yet reached this temperature; in the absence of a mechanical stress, this is likely to release tensions on the outside of the room while the heart remains rigid, and thus cause checks and cracks in the wood, by difference between wood moving on the edge and immobile wood in the heart.
a second objective of the temperature treatment at the glass transition temperature in the state of the art is to allow a useful catch-up between the temperatures of the edge and the heart of the wood pieces because the temperature of the gas flow is very long to be transmitted to the edge of the board and that the heart is very late on the edge: we have a double thermal inertia; this double inertia is a serious handicap to control the temperature between 230 0 C and 240 0 C if it is already cool the edge that has had its high temperature time while the heart has not yet reached. The worst situation, when all the heat or cold comes from the outside, is to still need to heat the inside when it is necessary to cool the outside.
the temperature step at 170 0 C or 180 0 C corresponding to the glass transition is therefore very useful for uniform temperature of the wood at a temperature not too far from the crosslinking temperature.
the difficulty of the treatment is to control the temperature in an insulating fibrous material with a temperature to be reached everywhere, this temperature generating a weak exothermic reaction and the risk of exceeding the temperature to be reached, this overtaking on the one hand deteriorating wood and on the other hand a strong exothermic reaction. .
the internal heat itself is the sum of the latent heat of melting or evaporation transformation and the exothermic heat of chemical reactions:
the glass transition phase is a 2nd order transformation and the coefficient C is increased when T reaches the glass transition temperature, but there is no latent heat of transformation.
the first equation makes it possible to understand how heat conduction makes it possible to control the temperature inside the wood when there is an exothermic reaction above 200 ° C.
the thermal conductivity k is indeed very low in the crosslinking phase of wood (around 230 0 C) because the dry wood leads very poorly heat; however, the crosslinking takes place with completely dry wood: there is no more water in the poral space and only these temperatures remain water of constitution.
the experiment of the reaction under nitrogen also shows that the difference of temperature between the temperature to reach necessarily and that to be reached is very small: if one takes the example of a hardwood like the beech, the temperature Treticulation to reach is 235 0 C for more than 30 'and it is known that it is necessary to inject water in quantity to block the exotherm if the wood does not remain at the setpoint of 235 0 C but climbs in temperature up to 242 0 C where a new exothermie awaits, knowing that the wood is lost if it reaches the temperature prohibits 250 0 C or 245 0 C, which sometimes occurs.
the diffusion of the heat left to itself, without chemical reaction obeys the equation
this level has three reasons to be: a long time to diffuse the temperature in the wood a long time to pass the heat of the heat transfer gas to the edge of the a risk that the wood will "move", in the absence of any constraint to clamp it, due to internal if one part is rigid (temperature below the vitreous temperature) and the other flexible part
the analysis shows that the destruction of the lignin fibers is responsible for a loss of performance more or less compensated by a creation of pseudo-lignin, according to the pertinence and the precision of the pair of parameters (maximum temperature, duration of exposure) applied to wood.
a theoretical solution consists of reducing the thermal inertia and playing on the other parameters influencing the thermolysis.
the solution is to reduce thermal inertia and bring calorie directly into the mass.
the other reason is to avoid cracking of the wood by release of stresses; a 'solution would be to force the timber to prevent it from releasing stress is above the glass transition temperature.
T is a cumulative value that integrates history (and cumulates all heterogeneities).
T is a cumulative value means that all differences in heat flux are integrated over the duration of the treatment and result in differences that can be significant because of the low conduction that does not allow to compensate by internal distribution.
the theoretical solution is both to avoid the heterogeneity of the thermal flows in the batch to be treated and the increase of the internal conductivity.
the pressure should be slightly higher 'than atmospheric pressure to prevent oxygen intrusion in case of imperfection security systems and no pressure is only possible on the wooden glass phase because of the need baguettage.
the object of the present invention is to overcome the disadvantages described above.
An advantage particularly sought of the present invention is to expand one end of timber Ia heat treatable, this range covering both the variety of species that form and dimensions of the wood pieces and the state of the pieces of wood , namely pieces of wood previously treated or not with various products.
the object of the invention is achieved with a medium or high temperature treatment process of a solid or reconstituted wood, according to which each of the pieces of wood of a batch to be treated is placed in contact with a thermoregulated conductive press, whose temperature can be accurately controlled in time and intensity, and carried or maintained at the desired temperature by any means of control and thermal control appropriate to the treatment and the amount of wood to be treated and allowing, by conduction, to heat the wood, maintain its temperature and cool it.
each of the pieces of wood a batch to be treated is arranged between two plates or thermoregulated forms placed in direct contact with the wood and allowing, by conduction, to heat the wood, maintain its temperature and cool.
the temperature of said plates or shapes themselves is precisely controlled in time and intensity, and carried or maintained at the desired temperature by any means of control and thermal control appropriate to the treatment and the amount of wood to be treated.
the method may furthermore have at least one of the following characteristics, taken alone or in any technically possible combination: electromagnetic radiation, in particular high or ultra-high frequency radiation, is used to raise the temperature very rapidly in the room. wood evenly between the heart and the edge, which is particularly interesting for thick pieces; these radiations can be emitted by any appropriate source, for example by plates or metal forms of the thermoregulated press, these plates or shapes then being used as transmitting antennas placed in parallel;
the temperature of the plates or forms is regulated to reach a maximum treatment temperature which, depending on the treatment, is in a temperature range of from 100 ° C. to 280 ° C. the temperature of the plates or shapes is controlled, during the treatment, with a maximum difference in temperature between any two points of the treatment boards in contact with the wood less than 10 ° C.
the temperature of the plates or shapes is controlled, during the treatment, with a maximum difference in temperature between any two points of the treatment boards in contact with the wood less than 0.5 ° C. the temperature is greater than 100 ° C .;
the temperature of the plates or shapes is lowered so as to cool the wood for a lag time of less than 10 minutes to reduce the temperature of the plates by 20 ° C. from a stabilized temperature of greater than 100 ° C. when the wood does not not subject to exothermic transformations;
'• plates are used or metal forms as transmitting antennas arranged in parallel for emitting electromagnetic radiation, in particular high or ultrahigh frequency to raise rapidly the temperature within the workpiece evenly between the heart and the edge, which is particularly interesting for thick pieces.
a shaped thermal source is used for controlling the temperature of the plates or forms during the treatment, allowing, when the temperature is higher than 150 ° C., to lower the temperature of the plates or forms of 15 ° C. in less than 1 minute by any point where plates are in contact with the wood to be treated, when the wood is not in exothermic phase;
the temperature of the plates or shapes during the treatment of the wood is controlled so as to maintain the temperature of the plates, even when heat is supplied from the treated wood when it undergoes an exothermic transformation, with a precision of less than 0, 5 0 C, at a high temperature set in advance between 150 0 C and 280 0 C, depending on the essence treated and the treatment conditions, and corresponding to an exothermic phase of the treatment;
the plates or shapes and the wood to be treated disposed between the plates are sealed during the heat treatment in an enclosure equipped with a system enabling the control of time and intensity of the vacuum. and pressure, with a recording of the pressure cycle;
the object of the invention is also achieved with an installation for the implementation of the heat treatment process defined above, that is to say with an installation for a treatment of solid wood or reconstituted by application of medium or high temperature, which comprises at least one thermally controlled conductive press arranged in direct contact with the wood to be treated, the temperature of which can be precisely controlled in time and intensity, and carried or maintained at the desired temperature by any appropriate control and thermal control means the treatment and the quantity of wood to be treated, the press allowing, by conduction, to heat the wood, maintain its temperature and cool, and the installation further comprising means for recording the temperature curve of the thermoregulated press.
the installation comprises a press with at least two thermoregulated plates allowing, by conduction, to heat the wood placed between the plates, the temperature of said plates themselves being precisely controlled in time and Intensity, and carried or maintained at the desired temperature by any means of control and thermal control appropriate to the treatment and the amount of wood to be treated and means for recording the temperature curve.
the installation may also have at least one of the following characteristics, considered in isolation or in any technically possible combination: the installation comprises means for recording the temperature curve; the installation comprises means for recording the temperature curve of the presses (Plates or forms) thermoregulated and all the pieces of wood whose temperature is measured by thermo-couples pressed at the end of each piece on the outer edge on the one hand and the heart on the other. Instead of measuring each piece of wood, it is possible to measure and record a sufficient number of pieces of wood distributed in a statistically representative manner in order to have a statistically representative sample of the batch treated.
the installation comprises means for recording the weight of the whole batch treated; it may suffice, for example, to have all of the plates all of which rest on a plate at the lower end of the enclosure, said base plate resting itself on the ground by means of a scale in order to be able to measure the loss of weight of the batch treated by difference with the compressive force applied to the entire batch to be treated, itself known, measured and recorded.
the installation comprises independent exchangers so that several batches of plates or forms located in the same enclosure can undergo, at the same time and in the same enclosure, different temperature cycles;
the installation comprises means allowing the plates to exert, during the heat treatment, a homogeneous pressure on each piece of wood considered taking into account the appropriate arrangement of the plates and the wood to be treated disposed between the plates, for example installed in piles with woods of constant thickness between each pair of successive plates;
the installation comprises means allowing each plate, except the one located at the bottom of a set of several plates or shapes, to add a mechanical stress exerted on the plate or upper form, resulting in the entire stack by an overpressure piloted and controlled adding to the pressure exerted by a plate or form on the pieces of wood on which it rests, because of its own weight and the weight of the plates and wood located higher on the pile;
the installation comprises a device for controlling and controlling the pressure of each plate or shape on the pieces of wood in contact with the plate or shape considered, regardless of the weight of the plates or shapes or other elements;
the plates or forms intended to receive for heat treatment of the pieces of wood are arranged horizontally with at least one jack on the plate located at the top of the set of plates or forms, to exert the same pressure on all the pieces of wood treated;
the plates or forms intended to receive, for heat treatment, pieces of wood are arranged vertically with cylinders on the plates or shapes located at the ends to exert the same pressure on all the pieces of treated wood; the installation comprises means for recovering juice or flavorings extracted from the wood during processing, with one or more tanks for storing in a differentiated manner in a special and approved vat the aromas or juices from the wood.
the juices and gases from the wood have a specific aromatic composition and these different compositions can be enhanced by an ultra-filtration system or reverse osmosis allowing a concentration of compounds that can be used for pharmacy, perfumery, cosmetology or to extract aromas and flavors for the food industry.
the installation comprises a heat exchanger and a heat transfer fluid circulating in the plates at a determined flow rate through a circuit with heat exchangers adapted to the maximum treatment temperatures, which are between 100 ° C. and 280 ° C., depending on whether the treatment is complete or limited to only some of its potentialities, the temperature of the plates or forms that can be controlled during the treatment, taking into account the thermal inertia and in spite of the disturbances linked to the thermal exchanges with the masses of treated wood, with a maximum difference of temperature between two any points of the treatment boards in contact with wood less than 10 0 C; the installation comprises means for cooling the wood in a lag time of less than 10 minutes in order to lower the temperature of the plates or forms by 20 ° C.
the installation includes means for depolluting a wood previously impregnated with chemicals now undesirable; for this purpose, the installation comprises, in addition to means for heating the product to make it liquid and fluid or gaseous and in addition means for evacuating it by creating an overpressure by heat and the crushing of the poral space above the glass temperature, tanks specially adapted for recovering liquid or gaseous products and means for condensing the gaseous products to be condensed and comprising, in addition to the pumps for creating the vacuum in the chamber, a circuit for to convey them to these tanks, the means of circulating the product in the circuit, said circuit being of adequate material and kept hot enough to maintain the fluidity of the products and to ensure their transport without loss to the tanks in question.
the object of the invention is finally achieved with wood, solid or reconstituted, having undergone treatment according to the method described above.
thermoregulated press makes it possible to communicate to the wood a precise temperature for a precise duration. It is possible to lower the temperature in the whole of the room in a brutal way and to maintain constant a very precise temperature, even in a situation of exothermicity and it is possible to reduce considerably the two thermal inertias relating to the rise in temperature, because conduction is more efficient than convection and compression above the glass transition temperature makes it possible to reduce the porosity and to increase the contact surfaces between wood cells, which makes it possible to increase the conductivity.
thermoregulated press in a vacuum chamber makes it possible to precisely control four parameters which also influence the thermolysis instead of just one: the precise control of the temperature, and the control of the precise time exposure of wood at a precise temperature given the control of the compression of the wood (result of a force applied to the press and passed on to the wood in the form of uniform pressure),
control of the vacuum or of the pressurization of the enclosure control of the chemical atmosphere through the confining gases (gases from the wood due to the fact of thermolysis and remain in the enclosure from the moment chosen to stop or decrease the pumping of 1 enclosure).
thermoduralysis ® because of the low thermal inertia, the process allows more precision: it allows the case to possibly rise possibly higher, in temperature, with a temperature determined to the degree for a very precise time, because it goes down without delay temperature.
the whole curve with respect to the time of the triplet (temperature, compression, pressure) characterizes the process and thermoduralysis ® .
thermolysis The kinetics of thermolysis is modified upward by the pressure, which can be higher or lower than the atmospheric pressure and by the concentration of gases from the current thermolysis which serve as catalysts and which participate in thermolysis, especially free radicals from the cracking of hemicellulose and this concentration and the composition of the gases depends on the moment when the pumping of the chamber and the volume of the chamber and the history of the pumping more or less selective of such part of the gases. It is thus the physicochemical environment that can be controlled and controlled by the three curves Thus, by playing on the curves of the three parameters, the heat treatment is more precise and more sensitive.
the compression itself intervenes in that it decreases the thermal inertia in the wood, but it also changes the pressure in the pore volume of the wood and the geometry.
thermoregulated press is perfectly effective not only for heating, but also for maintaining temperature and for cooling, it is possible, according to the invention, to add a radiation source of heat which does not replace the radiation for 'maintain a temperature despite 1 exothermicity or quench timber but which is added to accelerate the rise in temperature.
thermoduralysis ® which aims to obtain, by gentle thermolysis of wood and thanks to the optimal control of the various parameters that the process according to the invention allows to control, a more durable wood, mechanically more resistant and more homogeneous than the woods obtained according to the current state of the art.
thermoduralysation ® of the wood is a homogeneous treatment having the effect of reducing its hygroscopy, to improve its dimensional stability, to increase its resistance to the agents of degradation and to increase the hardness of surface, not to decrease appreciably or even to improve by densification its physico-mechanical properties and to change the color of the wood which takes a light brown color in the mass, depending on the essence and the treatment parameters applied, definitive in the absence of exposure to the Sun.
the species the more hydrophilic (because the richest in hemicelluloses) become the most hydrophobic, because of their thermocondensation on the lignocellulosic cell structure.
the wood retains its structure, cellulose not being altered preserves its crystallinity and the reinforcement of the material remains unchanged.
Thermoduralysation ® changes the behavior of wood that behaves like clay against water and will behave like sand. There is a small increase in porosity, the wood becomes hydrophobic and there is an improvement of the wettability with respect to oils, paints, monomers, glues and different products by modification of the surface tension.
Thermoduralysation ® of wood (either in the form of a piece of solid wood or lignocellulosic material, with or without a binder) can be defined as a controlled thermolysis of wood leading to a crosslinking process (covalent bonds, chemical bridging ) between the macroscopic chains of the constituents of the wood according to the criteria of the present invention, and which makes it possible to optimize the improvements of imputrescibility, dimensional stability and hydrophobicity of the wood, while maximizing the homogeneity of the treatment and minimizing mechanical performance losses and in particular bending behavior.
thermoregulated press that is to say a press having plates or shapes shaped to be able to be heated and cooled according to a predetermined program, but also according to the instantaneous needs of the course of the process.
a thermoregulated press that is to say a press having plates or shapes shaped to be able to be heated and cooled according to a predetermined program, but also according to the instantaneous needs of the course of the process.
thermoduralysation ® proceeds essentially in the following way: the temperature is mounted according to a precise combination of temperature curves, compression of the wood and pressure of the enclosure and is maintained for a certain duration at the maximum temperature of the treatment , between 200 ° C. and 280 ° C., preferably between 230 ° C. and 240 ° C.
the choice of the pair of parameters depends on the essence of the wood, the thickness of the wood to be treated, the compression of the wood by the effect of the thermoregulated press, the confining pressure and finally the temperature rise curve, as well as the intended use. for wood, without it being necessary, according to the invention, to carry out a temperature step at the glass transition temperature. '
thermoduralysation ® is not content to be a new way of controlling the temperature of the wood in a given chemical environment alone, but on the contrary it is a new way of controlling at the same time several parameters among which find the temperature, which can also be managed much more precisely than with known methods. And the search for performance leads to leaving the ranges previously defined by the two versions of the rétification mentioned above.
the method of the invention and its implementation have two essential characteristics that make it possible to overcome the disadvantages of the methods generally used and to obtain the desired result.
the first of these two characteristics is that the wood thermoduralyser is brought into contact, during the treatment, with a press thermo.
This press which can also be called a thermoregulated conductive press, since it comprises at least one heat-conducting plate or any other solid and thermally conductive form and at least one other plate or shape, makes it possible to transmit heat to direct contact with the wood.
the plates or shapes which may also be solid or perforated, are brought to a temperature which can be increased, maintained and lowered according to a temperature curve, preferably predetermined, and which transmits to the wood a flow of heat by conduction and subsidiarily, significantly or not, by radiation, but not by convection, since there is no distance between the wood and the plates or displacement between them.
a temperature curve preferably predetermined
the plates or shapes may be, according to the invention, subjected to a force which is distributed on the timber in contact with one of which they are in the form of a homogeneous pressure.
thermoduralyser The second characteristic of wood thermoduralyser is that this wood is brought to a thermoduralisation temperature ® depending on the species and preferably located between 230 0 C and 240 0 C, and that the wood is maintained at this thermoduralisation temperature ® for a period depending on the species and the thickness of the wood as well as the mechanical pressure applied by the press. However, this duration generally does not exceed 30 minutes per centimeter of thickness.
thermoregulated presses used in the context of the present invention have, according to the chosen embodiment, only thermoregulated plates or forms. or, in addition to thermoregulated plates, non-thermoregulated plates or forms interposed between two levels of wood.
it may be a press comprising two plates or rigid forms held at a distance from each other by any mechanical means supporting the forces such as for example two perpendicular uprights ; or a single perpendicular amount making the set of two plates or shapes and the two perpendicular uprights a hollow tube or a shape of an I-section (and therefore a standardized section IPN) with the only amount perpendicular to the center.
the press can be used itself to emit microwave radiation or coupled to an electromagnetic field generator to heat the wood in the mass:
thermoregulated press in order to accelerate the process of temperature rise despite the thickness of the wood (especially to treat quartelots) It goes without saying that the electromagnetic radiation emitted by a metal body can increase the temperature but not maintain it despite the exotherm and even less to lower it, which is why it is an important but only complementary means of the conduction means of the thermoregulated press;
Electromagnetic waves are already used to heat a material and the process is used for drying wood (which is easier because the wood to be dried is wet and the water is particularly easy to heat by electromagnetic waves. It is already described in document FR-A-2 751 579 that it is possible to take advantage of a temperature greater than that of the glass transition to exert a force on a part of the piece of wood to modify the density or the shape of this part. This is the classic use on all polymers of the glass transition to shape them, this form remains acquired with rigidity when we go down 1: the temperature of the room and this property is used ancestral way in the case of wood by the merandiers who thus bend the planks of the barrels.
the problem to be solved at the time of the invention was not so much to find a way to raise the temperature, because we have known in physics for a long time that these means are convection, conduction and radiation.
the goal was rather to obtain an increased precision in the pair of parameters (temperature, duration of exposure), and for that it is necessary to be able: to reduce the time of uniform temperature of the room to the maximum desired temperature during the temperature rise to maintain the temperature at a precise temperature even in the event of exothermy to be able to quickly descend the temperature without delay in the whole of the room when the duration of exposure is reached. to reduce the factors of temperature heterogeneity.
the temperature is a conservative value that integrates all the differences related to the flows, to the differences in moisture content, heat flow during the whole treatment
the method according to the invention implements a novel combination of conventional physical principles used separately.
the conduction and the increased internal conductivity by compressing at a temperature greater than the glass transition to decrease the poral space allow this and a complementary heating by microwave or any other electromagnetic field to increase the temperature in the mass (and breaking ends of molecules that make free radicals) allow to respond adequately to the goal of a rapid rise in temperature in minimizing the temperature gradient inside the piece of wood.
thermoduralysation ® compressing the wood, confining it, having a depression or overpressure in the containment, has a significant influence on the reaction kinetics of the thermoduralysation ® and the process consists of to play on the four parameters: - plate temperature curve compression curve pressure curve in the radiation field enclosure
the invention resides both in the means used and in the temperature curves different from those known (no temperature plateau of glass transition and maximum temperature below
this implementation allows to use more advantageous wood (polluted wood, small wood ..) what implementations known in the state of the art do not allow to make, this implementation also allowing significant savings (energy + nitrogen) and time savings
Heated presses in a vacuum chamber without means for cooling to temperatures below 100 ° C. have already been used to dry wood.
Such presses are not usable in the state because it requires heat transfer liquids, heat exchangers and plates constructed to withstand temperatures above 200 ° C.
thermoregulated press itself can be thermoregulated by any useful and effective means.
it may be a hollow body, for example two flat plates separated from one another by mechanical means, and quenched in a thermoregulated bath so that the liquid between the plates carries the conductive plates at the bath temperature, or it may be a primary circuit with a coolant circulation that carries the plates to a controlled temperature close to the temperature of the coolant, with a difference controlled by the calculation of thermal inertia and the conductivity of the system.
each of the two constituent plates of the press can be thermoregulated individually.
a liquid or gas convection between the two plates integral with the conductive press is used to heat the conductive plates, these heating plates in turn the wood in contact with which they are located.
a furnace chamber of the old technique could be used with such presses consisting of two conductive plates separated by mechanical means taking the loads from one plate to another and allowing a gas flow between the plates.
the plates play a role of mechanical distribution plate of the applied force and a role of conductor for the heat: the plates are heated by convection and heat the wood by conduction and radiation.
the plates or shapes or molds being perforated they are not completely impermeable. It may be for example grids whose holes are small enough surface to not allow to make significant traces in depth when a force is applied to the wood and to prevent the plate can damage the piece of wood. If the effect of the holes is negligible, it does not change the interest of the system by bringing an additional advantage.
these holes allow to pass a liquid or gaseous flow that can be absorbed by the pieces of wood in the cooling phase, whether it is a phytosanitary treatment, paraffin, binders etc.
These may be perforated shapes or molds to allow the binder to penetrate into an agglomerated product.
the wood treatment method according to the invention comprises a succession of treatment phases each ensuring the control of three parameters that are the temperature brought to the wood, the pressure of the containment and the mechanical pressure exerted on the wood.
the present invention therefore relates to a wood treatment process, constituted, beyond the previous step of drying the wood, by at least one of the stages of the complete treatment comprising the harvesting of the wood flavors, the depollution of the wood.
the low thermal inertia of the thermal conduction one can control the temperature of the edge of the wood with a relatively smaller delay compared to the temperature of the plates and with, on the other hand, a better thermal conductivity K.
the thermal conductivity K is improved because the wood has been crushed on itself by the effect of the homogeneous pressure exerted on the pieces of wood which becomes more and more malleable when it exceeds its glass transition temperature, between 170 and 180 0 C depending on the species.
the temperature difference between the edge of the wood and the heart of the wood is very largely restricted and this temperature follows very quickly upward or downward the "set" temperature given by the plates.
Such a temperature plateau could be preferably between 190 0 C and 200 0 C to minimize the temperature gradient closer to the end of treatment temperature which is between 230 0 C and 240 0 C depending on the species but, preferably, not at a higher temperature so that time Homogenization does not interfere with the final result of the treatment. It is also possible, if desired, to make an intermediate temperature plateau, for example between 150 0 C and 160 0 C to approach the glass transition and, in the process, the high temperature treatment with a wood at standard temperature.
the duration of such temperature stages can be controlled by representative thermocouples as a function of a maximum temperature difference allowed at the end of the plateau between the edge and the core of the wood, this maximum difference possibly being zero or 2 0 C or 5 0 C or any other difference deemed appropriate so as not to waste too much time while ensuring the desired homogeneity for the final phases of the treatment.
the treatment inside the wood is ideally between 130 and 140 0 C at atmospheric pressure and without compression but may possibly be at a higher temperature due to a possible depression the enclosure or the possibility of going down there 1 temperature very quickly after a very short time.
the temperature of the plates can be much greater than that of wood, to allow a large heat flow by conduction between the plate and the wood to shorten the temperature rise time inside the wood, this higher temperature of the plate can be followed by a sudden cooling of the plate to wear and maintain it at the maximum temperature of the treatment during the chosen exposure time.
Such a practice may have the disadvantage of burning the skin of the wood, this burning can disappear on the four-sided planing that usually follows such treatment.
the temperature of the conductive plates can conveniently be raised to much higher temperatures, up to 280 ° C. or even 300 ° C.
the poral space is completely empty of liquid water (and even more so when the temperature increases) and the vitreous phase which makes the wood plastic is reached.
the crushing of the wood is then possible because of the glass transition and the wood insulation is maximum because the porosity is empty of water.
the plates have a known temperature at all points while it is impossible to control without difficulty the speed and temperature of a heat transfer fluid convection.
a fourth reason is the possible use of an electromagnetic field to increase the temperature quickly and without a gradient of temperature inside the wood, even with a thick piece of wood.
the heat is transmitted to the wood by conduction, the wood being in contact with a homogeneous heating plate at controlled temperature with sufficient inertia.
the heat treatment can be further improved, in particular for the treatment of thick wood pieces, by applying a heating plate on both sides of the wood, and by creating a pressure on the wood by means of a force applied to the wood.
An additional improvement can be achieved by the use of a vacuum chamber. The pressure plays a triple role:
the mechanical pressure increases the pressure inside the wood by decreasing the pore volume, which initially results in an increase in pressure for a given amount of gas and until the evacuation of excess gas to the pore volume.
the interior of this porosity does not succeed in rebalancing the pressure between the porosity of the wood and the exterior.
the internal pressure of the porosity of the wood therefore becomes greater than the external pressure, which allows an easier evacuation of effluents, liquid or gaseous, forbids external gas to enter and replace the voids left by the evacuation of effluents, and allows the internal forces of the wood to oppose.
the mechanical pressure avoids the deformations and serves, on the contrary, to take advantage of the vitreous phase to straighten a wood.
a special press can exert non-homogeneous forces on the wood to give it a particular shape; a piece solid wood can be bent or bent and agglomerated wood in one form can be printed form the mold.
the major problem of the treatment was a weakening of the mechanical performance of the wood; this weakening can be minimized and compensated for, and even beyond this, it is possible to improve these characteristics by densifying the wood: it has been seen that the temperature can be best controlled at the time of crosslinking and it is therefore possible to choose to have compromise performance and one can choose for example to stay 5 minutes at 240 0 C; thanks to the vacuum chamber, it is in the absence of oxygen and the only gases present are the free radicals which have been kept by stopping pumping from the beginning of the chemical reactions; densification in the vitreous phase and crosslinking of densified wood are two irreversible phenomena when the temperature is lowered.
Densification largely offsets, if it is desired, losses of mechanical characteristics to allow conversely to the treatment to induce an improvement of these mechanical characteristics (with however a greater material consumption if it is necessary for example a board of 35 mm for make one of 27 mm after densification).
the vacuum chamber has the characteristics of a super autoclave because it is possible to introduce a product into the chamber and take advantage of the cooling vacuum. We do not need to water to cool and we can cool quickly and we can also, if we want to release a little compression for an expansion of the crushed wood
This same operation can be done by deleting dirty railroad ties but there is no drying of the open water because there is none.
Vacuum enclosures with stacking and heat conduction plates are available in vacuum drying with control of temperature, chamber pressure, battery weight and thermocouple recording at the core and at the surface of the wood.
the plates used in the invention differ (new material and new shape) to adapt to the temperatures and the pressure of use, and the exchangers must also be suitable for temperatures up to at least 240 ° C. C, or 280 C or even 300 C, while drying under vacuum is between 30 C and 80 0 C to 95 C maximum.
the mechanical stresses are different to be able to exert a strong pressure on the wood and it may be necessary to create a model with vertical piles if one wants not only a minimum pressure but also a uniform pressure.
the vacuum chamber makes it possible to recover everything that comes out of the wood.
the technique according to the invention makes it possible to crush the wood in the vitreous phase in order to reduce the poral space and to create a very strong overpressure inside the wood which, added to the vacuum in the enclosure, gives the optimum characteristics for evacuate previously injected chemicals.
a depression in the evacuated enclosure makes it possible at the same time to favor the migration of the products out of the wood by increasing the pressure difference between the inside and the outside of the wood and at the same time makes it possible to collect these products out of the treatment chamber and to a special waste collection tank.
a temperature step at 190 ° C. with the vacuum enclosure is desirable to allow all the juices to come out of the wood and to be collected. '' Then we stop evacuating and we raise the temperature and the volatile products coming out
vacuum pumping makes it possible to recover all the products previously introduced into the wood at a temperature much higher than their melting point. This makes it possible to obtain a sufficient fluidity of the liquid juices and a volatilization of a part of the products. Juices and volatilized products can thus be very well conveyed to tanks specially dedicated for this purpose, in a circuit made of suitable material, for example stainless steel. The circuit is kept warm enough to maintain the fluidity of the products and to ensure their flow without loss to the tanks in question.
the tanks are provided with means for condensing the gases and volatilized products in the tank.
the pressure of the enclosure can be varied using the control means.
the example of piloting below is an example of implementation of treatment with a polluted wood: Low pressure from the start with the vacuum treatment chamber during drying and then temperature rise and glass phase to recover the juice (essences , depollution, etc.) up to 190 ° C. A possible temperature treatment can be carried out if necessary at 190 ° C. until all the polluting juices are extracted.
the method and the installation according to the invention also allow a green wood treatment. It is known that the adherent living nodes can remain adherent if they are treated in green wood, the sap probably serving as a binder. It is useful to have the possibility of drying under vacuum to avoid collapse, speed up the process, obtain homogeneity of drying and continue the treatment without discontinuity or loss of energy, nor loss of time.
Green wood is an ideal quality because it is heat-conductive, saves time and homogeneity, and adheres to green wood.
hot plate vacuum drying is the fastest and most accurate way to carry out drying in the first phase.
the installation according to the invention can be carried out so as to recover cooling energy.
the process of the invention therefore has no need for energy apart from losses and latent heat of transformation during drying.
the plates constitute a primary circuit exchanger with the wood and all the calories are recoverable between two lots treated in phase opposition, one being cooled while the other is heated, with a circuit in exchangers exchanging plates with a secondary circuit. It is possible to use the energy of a batch of hot wood that must be cooled before leaving it in the air at 40 0 C to heat another batch of wood located in another cell with an impact very considerable energy since the energy to cool a wood from 250 0 C to 50 0 C is, apart from losses and internal chemical energies or change of state ('' evaporation) equal to the energy required to raise the temperature of an equivalent mass of wood, from 50 to 250 0 C).
a liquid at 50 0 C can preheat wood at 20 0 C and there is an organization of the storage of calories in balloons and exchange with a management of heat exchangers and phases that must be optimized by a person skilled in the art .
Another solution, according to the invention is to have hollow plates such as metal tubes and soak the batch in a thermoregulated bath whose liquid enters the recesses and heats the plates that transmit heat conduction to the wood and which otherwise also transmit the compression of a force applied for example to the plate at the end of a stack.
One of the goals is to be able to treat wood much thicker than the boards of 27 or 35 MM usually treated.
the goal would be to treat wood of all widths to a thickness of 10cm and ideally 15 or 20 cm.
the interest is to be able to delign then planks whose width is taken in the thickness of the quartelot; for boards 8 cm wide, it takes a quartelot 8 cm thick and most conventional boards having a width less than 10 cm, the fact of being able to treat up to 10 cm is already very interesting. If the treatment time for 16 cm is not too high, quartiles of 16 cm can make boards very wide, which is of interest for a stable wood that does not tile and it also allows to make 2 boards of a standard width of 8 cm.
the heat is transmitted to the wood pieces by conduction, the pieces of wood being placed on a homogeneous heating plate at controlled temperature with sufficient inertia.
the warped or slightly twisted woods are worthless and are part of the material losses of the drying operations, whereas the compression of the wood above the glass transition temperature can be used to straighten these woods.
Thermo-stabilization of wood plywood and reconstituted composite materials, composite materials pressure + temperature allows three distinct and complementary steps: either one starts from a board or plate of plywood or reconstituted wood (agglomerated, Oriented Strandboard "OSB" that is to say, fibreboard wood, medium and composites, etc.) and is subjected to a thermoduralysation ® treatment or it starts from fragmented wood (sawdust-like lignocellulosic fibers, platelets, etc.) that is subjected to a thermoduralysation treatment ® to have a raw material for the manufacture of reconstituted wood whose load will be in thermoduralysed wood ® (powder in polymers and composite materials wood-concrete, wood-plaster ... or fiber chips or particles in agglomerates).
OSB Oriented Strandboard
thermoduralysation ® treatment fragmented wood (sawdust-like lignocellulosic fibers, platelets, etc.) that
thermoregulated process press not only to thermoduralyser ® the wood load but also to have a mold and a means of pressure to polymerize the wood and binder and form 1 the object in compression during the treatment and use if necessary of the chamber which can be pressurized and cooling of the wood to absorb a polymer by internal depression of the wood and in the porosity between juxtaposed and pressed wood fragments.
the first objective is to produce an agglomerated or composite lignocellulosic material associated with a binder and having small variations in shrinkage and swelling in the presence of liquid water or moist air. It is already known that this can be achieved with roasted wood as a filler and also with a wood that has better mechanical characteristics.
the use of wood thermoduralysé ® according to the invention has further improved characteristics.
the other advantage, for an implementation of the method according to variants 2 and 3 is to have a wettability of the Wood thermoduralysé ® improves the impregnation power of lignocellulosic feedstock by the binders.
variant 3 can also use the flexibility of working above the wood transition temperature and having a press to mechanically constrain
thermo-stabilization process according to the invention can be applied to existing reconstituted woods (plywood, chipboard, OSB, medium, composite wood, etc.).
Glues and resins used for these reconstituted materials emit gases that can be toxic or pestilential (urea glues) or create overpressure in the oven or be pollutants.
gases can be toxic or pestilential (urea glues) or create overpressure in the oven or be pollutants.
the vacuum chamber with evacuation towards pollutant collection tanks makes it possible to treat these products
thermoduralysed wood or plywood or reconstituted wood molded objects Furthermore, it also avoids the visual disadvantage in the state of the art of a trace at the place of the cleats. Variant of the process for the manufacture of reconstituted thermoduralysed wood or plywood or reconstituted wood molded objects
two plates When making panels, two plates, at least one of which is heated, form a mold.
the plates may be replaced by two half-shells of which at least one is heating, one serving as cover and for pressing the product (can be injected.
there may be used an apertured press.
the shells are filled with wood fibers in the form of particles of different sizes and possible shapes which can come from sawdust, chips or platelets, possibly with binders which may be thermoplastic or thermosetting resins or products derived from wood lignin. it can be used to make reconstituted wood whose components are all or almost all from the wood
Agglomerated panels can in particular be easily made using the process between two flat plates. '
the adhesives or resins which will harden and polymerize when the temperature rises may have been mixed beforehand with the treatment (or mixed during the treatment using an additional device suitable for the mixture).
Products may be introduced in the vapor or liquid phase at different temperatures below 230 ° C. during the cooling phase.
the advantage of introducing at this stage is that the wood is already thermosiloxed and that one can thus take advantage of its wettability to establish more useful bonds between the binder and the wood.
the new advantages available according to the invention are, for example, a vacuum chamber for providing an environment in which the possible solvent side fumes can be treated, the chamber can be pressurized during the incorporation, and may use molds which are, according to the invention, thermoregulated presses and which may be, according to. the invention of openwork thermoregulated presses.
thermoregulation of the press nothing prevents, in addition to heat and thermoregulation of the press, to have a secondary heat source which may be infrared radiation or microwave radiation etc. Indeed, one can accelerate the process by various radiations, microwaves and preferably high frequencies and better still hyper-frequency as additional source of heat, knowing that the thermoregulated press is still necessary to maintain a temperature despite an exotherm and to lower the temperature to the end of the treatment, so that the radiations accelerate the rise in temperature without replacing the conduction to maintain and lower it.
thermoduralyser ® wood Another possibility is to have such an organization of "press molds" that is installed in a thermoregulated bath and that is maintained without exceeding it at a temperature between 130 and 140 0 C for thermoduralyser ® wood.
reconstituted woods can be made with both the filler and the binder of natural origin and result in reconstituted wood from 95% to 100% of the elements. are the result of wood ...
the advantage is that it can already be done without binder by crosslinking and strengthen the bond with elements derived from lignin that will allow to multiply the chemical bridges
the direct contact of the plate on the wood can be in itself a way to deprive the wood of oxygen in the hypothesis of solid and non-porous plates and particularly adjusted to the surface of the wood, and that can then make it possible to make such a treatment in the absence of enclosure of confinement and ipso facto in the absence, in the nonexistent enclosure, nitrogen or water or carbon dioxide to inert the gaseous medium in contact with wood because this gaseous medium is ultimately negligible in quantity.
the phenomenon is accentuated by the fact of the temperature rise of the wood which creates an overpressure of the gases coming from the wood, so that the small gaseous volume existing between the plate and the Due to an imperfect adjustment, the wood is overpressurized with respect to the atmosphere during the warming phase, but it is the opposite during cooling.
the amount of air available for combustion is not zero but it can remain marginal and the combustion at the surface may be marginal enough to be eliminated during the planing 4 sides after treatment.
the treatment is carried out in a vacuum chamber and in this case there is no in the enclosure to be inerted by nitrogen or carbon dioxide or by water but it is the vacuum that ensures that the amount of oxygen remains low enough to prevent significant combustion.
wood can be modified by the effect of a high temperature by various known methods whose result is to durably modify some of the characteristics of the wood.
thermolysis a composite material consisting essentially of three types of polymers: hemicellulose, lignin and cellulose, more fragile at least sensitive to the effect of temperature.
a controlled thermolysis cracks the hemicelluloses mainly and begins to modify the lignin.
By-products of thermolysis essentially free radicals would condense and then polymerize on lignin chains, and it is known that these reactions create a new "pseudo-lignin" which is more hydrophobic and stiffer than the original lignin .
the invention makes it possible to improve the heat treatment of wood and to obtain the following advantages:
thermoduralysation ® we can not only limit the mechanical losses but, starting from a larger volume and by densifying it can also improve the mechanical performances, which allows to go further in the treatment of the stability or the imputrescibility: o drying of quality and optimal speed, followed in stride (without manipulation or cooling intermediate) thermoduralysation ® because the furnace has characteristics of vacuum dryer and it is therefore logical to follow the two programs, the calories of the drying having begun the work of heating the wood o thermoduralysation ® of several species or thicknesses of wood in the same oven because it is possible to regulate independently several areas of heating plates o thermoduralysation ® of thicker wood: Now, the thermoduralysation ® of studs and in particular of the quartelots with a thickness of 20 cm would allow:
thermodurysed wood ® A stock of undifferentiated thermodurysed wood ® to then delaminate according to the demands of planks of a thickness and a width not determined in advance
Nitrogen (8% of the treatment cost) can be eliminated and the treatment energy (8% of the treatment cost) can be saved by recovering the cooling energy.
Quartels can be used for undifferentiated storage and added value.
the range of reconstituted woods can be increased.
the invention after analyzing the potential of wood, implements a combination of actions in temperature ranges determined utilizing the characteristics of this complex composite material.
the wood When the wood is treated at the glass transition temperature and when the wood, according to the invention, is mechanically constrained by a homogeneous pressure exerted on the wood by hot plates, this avoids a relaxation of the outer edge of the wood which goes on the contrary compression and this avoids the inconvenience of splitting the wood as it passes glass transition temperature.
the invention in this respect renders unnecessary a temperature step at the glass transition temperature or at another temperature.
the depollution starts with drying but is complete only in vitreous phase: the vitreous phase makes it possible to crush the wood and to reduce the poral space, creating ipso facto a very strong overpressure in wood and a very high thermal conductivity that will extract all the products.
the force is applied to the entire load, it avoids baguettage phenomena, obtaining a homogeneity both mechanical and thermal. Thanks to the thermal inertia of the hot plates, in the absence of complicated phenomena of heat transfer, it becomes possible, which was not so far, to ensure a perfect homogeneity of the contribution of calories in the wood. It is at the same time absence of baguettage, absence of temperature difference according to the points of the furnace, absence of difference of speed, absence of difference of degree of humidity absence of difference of exchange coefficient with the skin of the wood, no difference d 1 in the limited evaporation layer.
Another advantage is to make the drying of the wood and thermoduralysation ® without having to leave the dried wood outside.
the ideal is to reach, if possible, a temperature of plasticity of the wood before vaporization or in any case to approach as much as possible to avoid that pressures related to a vaporization of water can not escape outward due to inadequate kinetics do not lead to mechanical fatigue and ultimately to collapse phenomena inside the wood.
the collapse takes place when the pressure difference between the outside and the inside of a cell or pocket of porosity related to the heterogeneity of the wood (because of its constitution or its history) is superior to the resistance capacity of the membrane of the cell (microscopic version) or the surface of the pocket (macroscopic version).
the advantage of being able to exert a uniform pressure on all the surface of the wood is to be able to create a pressure of equilibrium with a pressure higher than the atmospheric pressure. The heat being !
the kinetic principle is to have a sufficiently fast evacuation so that the vapor does not accumulate.
a drainage it is necessary to avoid the "traffic jams" and thus to have a speed of evacuation more and more as one goes towards the outlet, namely the external surface of the wood.
the evacuation force that is exerted on the liquids and gases to propel them towards the outlet is proportional to the pressure difference between the inside and the outside of the wood. When one can exert an overpressure through the wood itself on the interstitial water.
Another advantage is to do the drying of the wood and its thermoduralysatibh ® , without having to leave the dried wood outside.
the presence of water in the wood at the start allows a very good thermal conductivity inside the wood at the start of the drying operation which allows to quickly increase the temperature homogeneously to the heart of the wood. a temperature much higher than that traditionally used for drying under vacuum, taking advantage of the mechanical pressure exerted in the wood to shift up the boiling temperature.
Figure 2 shows a variant of the arrangement of Figure 1;
Figure 3 shows the principle of the application of a compressive force on a set of horizontal plates according to the invention
Figure 4 shows the principle of the application of a compressive force on a set of vertical plates according to the invention
Figure 5 shows schematically an installation according to one embodiment of the invention.
an installation for a treatment of solid or reconstituted wood by application of medium or high temperature comprises at least 1 thermoregulated plate 1, allowing, by conduction, to heat wood B placed between the plates 1 and 2, the plate 2 is preferably thermoregulated or can be a simple mechanical support.
the temperature of said plates themselves is precisely controlled in time and intensity by regulating means forming part of a thermo-regulated heat transfer fluid supply device 3.
the device 3 comprises a heating component and a cooling component as well as regulating means, sensors intended to take the temperature at various locations of the installation, in particular on the plates, and also thermal sensors placed at the end of the board in the heart of the wood and valves or other adjustable means making it possible to vary the heat transfer fluid flow according to the instantaneous needs of the current treatment and determined by the control means.
Figure 1 shows the basic layout of an installation according to the invention. It includes, in addition to plates whose number may vary from installation to the other, a cylinder 4 or, where appropriate, several cylinders 4 distributed on the upper surface of the upper plate 1 and exerting, during the treatment of a batch of wood B, a pressure intended to generate a homogeneous compressive stress on the wood placed between the plates 1, 2.
the metal plates can also be used as transmitting antennas placed in parallel to emit electromagnetic radiation, in particular high or microwave frequencies, to very rapidly raise the temperature in the piece of wood in a homogeneous manner between the core and the edge. which is particularly interesting for thick pieces.
electromagnetic radiation in particular high or microwave frequencies
each of the plates 1, 2 is provided with two connectors 5 making it possible to connect the plates to the thermo-regulated heat transfer fluid supply device 3 and thus to install a circuit for the coolant.
each plate can be connected individually to an individually assigned and regulated circuit, just as all of the plates can be connected to a single circuit of the device 3.
FIG. 1 also shows plates having solid surfaces
the installation according to the invention comprises more than two horizontally arranged plates and can therefore treat two or more layers of wood
the term "wood layer” designating any set of pieces of wood placed between two plates, the pressure exerted on the layers of wood grow from the upper layer to the lower layer because the force FO generating the nominal pressure is increased from plate to plate by an additional force ⁇ Fl, ⁇ F2, ⁇ F3 etc. which depends on the weight of the respective layer of wood.
Figure 3 shows this schematically. '
the installation according to the invention can be provided with counter-adjusting means, individual for each plate, for exerting on each plate forces oriented against the force FO.
these counter-adjusting means are actuated by a pressure-adjustable source that also actuates the jack 4.
the adjustment of the jack 4 and counter-setting means can be performed only at the beginning of the treatment, but also at regular intervals. or not, during the treatment to take into account the reductions of weight and volume of the wood occurring by the treatment and thus to maintain a pressure on the layers of wood the most constant, and the most equal of one layer to another, possible.
the force FO is applied on both end plates.
the FO force is then advantageously, but not necessarily, varied during the treatment to take into account the volume reductions occurring by the treatment.
the plates of the installation according to the invention are carried and maintained at the desired temperature and then cooled to a new temperature by any appropriate control and thermal control means. This means can be adapted to the treatment, the amount of wood to be treated and the type of coolant used.
Figure 5 shows the plates of an installation arranged according to one embodiment of the invention.
the plates are arranged in an enclosure 10 inside which the treatment climate can be varied in different ways, particularly with regard to its temperature, independent of that of the plates or those of each of the plates, and its pressure.
the pressure will be that of a technical vacuum or a partial vacuum.
products contained in the wood are released and collected at the bottom of the enclosure 10.
the collected products are conveyed to a tank 11 or, where appropriate, to several tanks 11 each of which is assigned to a particular product.

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Engineering & Computer Science (AREA)
Mechanical Engineering (AREA)
Chemical And Physical Treatments For Wood And The Like (AREA)

EP06726171A 2005-04-04 2006-04-03 Holzwärmebehandlungsverfahren, anlage zur durchführung des verfahren und wärmebehandeltes holz Withdrawn EP1866587A1 (de)

Applications Claiming Priority (2)

Application Number	Priority Date	Filing Date	Title
FR0503300A FR2883788B1 (fr)	2005-04-04	2005-04-04	Procede de traitement thermique de bois, installation pour la mise en oeuvre du procede, et du bois traite thermiquement
PCT/FR2006/000725 WO2006106217A1 (fr)	2005-04-04	2006-04-03	Procede de traitement thermique de bois, installation pour la mise en oeuvre du procede, et du bois traite thermiquement

Publications (1)

Publication Number	Publication Date
EP1866587A1 true EP1866587A1 (de)	2007-12-19

Family

ID=35427673

Family Applications (1)

Application Number	Title	Priority Date	Filing Date
EP06726171A Withdrawn EP1866587A1 (de)	2005-04-04	2006-04-03	Holzwärmebehandlungsverfahren, anlage zur durchführung des verfahren und wärmebehandeltes holz

Country Status (6)

Country	Link
US (1)	US20080263890A1 (de)
EP (1)	EP1866587A1 (de)
CA (1)	CA2603659A1 (de)
FR (1)	FR2883788B1 (de)
RU (1)	RU2007140577A (de)
WO (1)	WO2006106217A1 (de)

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2006
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- 2006-04-03 CA CA002603659A patent/CA2603659A1/fr not_active Abandoned
- 2006-04-03 RU RU2007140577/06A patent/RU2007140577A/ru not_active Application Discontinuation
- 2006-04-03 EP EP06726171A patent/EP1866587A1/de not_active Withdrawn
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Also Published As

Publication number	Publication date
US20080263890A1 (en)	2008-10-30
WO2006106217A1 (fr)	2006-10-12
CA2603659A1 (fr)	2006-10-12
RU2007140577A (ru)	2009-05-20
FR2883788A1 (fr)	2006-10-06
FR2883788B1 (fr)	2011-08-19

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EP1866587A1 (de)	2007-12-19	Holzwärmebehandlungsverfahren, anlage zur durchführung des verfahren und wärmebehandeltes holz
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