Method and system for upgrading wood quality

Abstract

Provided is a method of manufacturing a densified, dimensioned wood product, the method comprising: selecting a wood feedstock, which is one of dimensioned lumber, unmilled lumber, timber or stranded timber; exposing the wood feedstock to ammonia under a cyclic positive and negative pressure in a vessel; the ammonia infiltrating and impregnating the wood feedstock to provide impregnated wood feedstock; removing the impregnated wood feedstock from the vessel; exposing the impregnated wood feedstock to a high pressure and a temperature in a two-axis radio-frequency (RF) press, such that the impregnated wood feedstock reaches a uniform temperature of not more than 150ºC; and thermally modifying the densified dimensioned wood product. No adhesives or resins are used.

Description

[0001] METHOD AND SYSTEM FOR UPGRADING WOOD QUALITY

[0002] FIELD

[0003] The present technology is directed to the production of densified, dimensionally stable lumber from waste wood, underutilized wood and milled lumber. More specifically, it is a vapour-phase chemical and thermal system and method of use thereof that can be used to produce highly stable structural lumber that is of superior quality than the wood feedstock from which it was derived.

[0004] BACKGROUND

[0005] United States Patent No. 8,468,715 discloses a method for forming an engineered wood product from pulpwood, comprising providing a quantity of pulpwood; crushing and scrimming the pulpwood to form a mat; drying in a first drying step the mat in a first pass dryer; applying a resin to the mat; and, drying in a second drying step the mat in a second pass dryer. The drying process controls moisture content using the rate of change between the entering and exiting airflow temperature. The resulting product has a high modulus of elasticity and modulus of rupture. As there are not wood fibers the resultant wood product it cannot be used as structural lumber. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0006] United States Patent No. 8,268,430 discloses a method for producing a manufactured wood product using less desirable or discarded natural wood and a manufactured wood product produced by the described method. This inventive method comprises utilizing less desirable or discarded natural wood pieces by slicing the wood pieces into elongated strips that are then partially separated into elongate sections that maintain fibrous connectivity between the elongate sections. The elongate sections are dried and covered or impregnated with an adhesive. A second drying follows the adhesive application and the elongated strips are then arranged lengthwise in a mold for cold or hot pressing. This method would not be suitable for dry wood. Cutting does not allow the fibers to retain their natural length, thus reducing the strength of the wood product. There is no disclosure to producing densified, dimensionally stable, structural lumber. United States Patent No. 7,537,669 and 7,537,031 disclose methods and apparatus for use in the manufacture of reconstituted or reconsolidated steamed-pressed long fiber wood products. More particularly, the invention relates to methods and apparatus for use in the manufacture of reconstituted or reconsolidated wood products using crushing and steam pressing methods and apparatuses. The logs first have to be conditioned with steam and then are cracked into mats using crushers. As the wood fibers are not orientated along a single axis, the resultant wood product is not suitable for use as structural lumber. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0007] United States Patent No. 5,279,691 discloses a process and apparatus for forming a reconsolidated wood product, and a partially rended natural wood bundle therefor, comprises partially rending natural wood to form a plurality of flexible open lattice work webs each of naturally interconnected wood strands which are generally aligned along a common grain direction with a substantial proportion of the strands in each web being substantially discrete but incompletely separated from each other. Each web is of increased width laterally and correspondingly decreased thickness compared to the natural wood but they may vary in dry wood densities. To avoid this the webs are compacted widthwise to substantially uniform dry wood densities and this may involve weighing the webs and measuring their moisture content. The compacted webs are then abutted width-to-width and partially rended natural wood bundles of preselected widths and dry wood densities are cut from the mat. The bundles may then be at least partly superposed, compressed and bonded together to form the desired product. The product produced by the rending is a lattice or web. As the wood fibers are not orientated along a single axis, the resultant wood product cannot be used as structural lumber. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0008] United States Patent No. 4,695,345 discloses a method and apparatus for forming a reconsolidated wood product from natural wood which has been rended to form flexible open lattice work webs of naturally interconnected wood strands. The webs are laid one over the other in overlapping fashion, treated with a bonding agent, and compressed in a compression apparatus having two members which are cyclically moved towards each other, to effect compression of the webs, and then moved away from each other to permit further webs to be positioned for compression in the compression device. Movement of the webs through the apparatus is effected by engaging the bonded webs, after compression and when the members are moved away from each other, so as to draw following laid in webs into the space between the members. As the wood fibers are not orientated along a single axis, the resultant wood product does not have the strength of an orientated strand board. The product produced by the rending is a lattice or web. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0009] Unites States Patent No. 4,711 ,689 describes a process for forming a reconsolidated wood product, wherein a bonding agent is applied to a lattice work web of interconnected wood strands that are subsequently subjected to compression in order to consolidate the interconnected wood strands into the reconsolidated wood product. A wax is applied to the wood strands before the application of the bonding agent in order to limit the pick-up of the bonding agent by the wood strands. As the wood fibers are not orientated along a single axis, the resultant wood product does not have the strength of an orientated strand board. The product produced by the rending is a lattice or web. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0010] United States Patent No. 4,711 ,684 discloses a process for the production of reconsolidated wood products. The patent describes a process for the partial rending of wood to form a flexible open lattice work web of naturally interconnected wood strands that are generally aligned along a common grain direction. The rending describe within the patent is achieved by rolling the natural wood between a pair of rollers, arranged with generally parallel axes, so as to engage the natural wood from either side with repetitive back and forth movements of one roller relative to the other roller. As the wood fibers are not orientated along a single axis, the resultant wood product does not have the strength of an orientated strand board. The product produced by the rending is a lattice or web. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0011] United States Patent No. 4,704,316 discloses a reconsolidated wood product formed by compressing and bonding natural wood which has been rended to form open lattice work webs of naturally interconnected wood strands. The webs are laid over each other in overlapping fashion so as to extend at an angle to the direction of extent of the product, with opposite ends of the webs being closest to respective opposed surfaces of the product. The product produced by the rending is a lattice or web. As the wood fibers are not orientated along a single axis, the resultant wood product does not have the strength for use as structural lumber. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0012] United States Patent Application Publication No. 20240001585 discloses a method for densifying a hygroscopic material. The method is for hygroscopic material which may be a natural hygroscopic material or wood. The method comprises the steps of providing the hygroscopic material to be densified; pre-conditioning of the hygroscopic material by adjusting the moisture content of the hygroscopic material to a value within a predefined moisture range, if required; simultaneously heating and pressing the gas-tight packed hygroscopic material under predefined temperature and pressure conditions, whereby the moisture content of the hygroscopic material is kept constant; and obtaining a densified material. The densification process involves sequentially increasing temperature and then pressure at a controlled moisture content, with a dwell time between. As the hygroscopic material is preferably dried to 10 to 15% before the heating and pressure treatment, the hygroscopic material is preferable packed in a gas-tight covering. This method would not be scalable and requires very precise conditions.

[0013] United States Patent Application No. 20120076975 and 20080110565 disclose a composite wood product and its method of manufacture. The wood product comprises aligned, substantially straight wood strands cut from veneer, disposed side by side lengthwise in substantially parallel relationship with adhesive bonding together the strands. The product is produced in a billet having a width in the range of about 3 ft. to 12 ft. and with a thickness in the range of about 1.1 inches to 2 inches. The strand ends are distributed in a specific pattern that approximates maximizing the minimum distance between strand ends. The wide sides of the billet are coated with a dark colored resin. The billet may be sawn lengthwise into sizes used for joists and rafters. Such a sawn product (e.g. 1.5" by 9.25") has the wide sides a dark resin color and the narrow sawn sides mostly wood colored. The strands are parallel to its length. The process involves cutting the wood to produce strands. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0014] United States Patent Application No. 20080000548 discloses a method of making engineered strand wood products in relation to a number of different possible criteria is provided. Such a method may involve any combination of different screening procedures to determine the best wood sources from which individual strands may be prepared. Such screening procedures may include initial determinations of certain physical characteristics of individual logs, further or initial determinations of certain physical characteristics of portions of sawn logs, further or initial determinations of certain physical characteristics of individual strands, and any combinations thereof. Additionally, after the initial physical characteristic sorting is completed, optionally the wood may be cut into uniformly sized and shaped strands for incorporation within a target strand product. Still further, such strands, in substantially uniform size and shape, as well as substantially uniform physical characteristics, may then be incorporated into a target strand product in specific predetermined configurations. Such various possible combinations of screening procedures and / or selective stranding processes results in strand products (boards, lumber, and the like) of improved properties over previously made strand products. Thus, encompassed within this invention are processes involving each of these procedures either individually or in combination with other sequential processes for the production of desired strand products. The process involves cutting the wood to produce strands. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0015] United States Patent Application No. 20070144663 discloses a process for the production of engineered wood products, or oriented strand wood products, having certain desired or predetermined properties by selection of the strands used in the products. The present teachings provide a process which has enhanced utilization of wood resources, reduced product variability, and can produce engineered wood product of various grades and properties on the same production line. The process involves cutting the wood to produce strands. There is no disclosure to producing densified, dimensionally stable, structural lumber. United States Patent Application No. 20050000185 discloses a method of forming a composite beam includes cutting an elongated piece of wood to produce strands having cross sections with a substantially symmetrical equilateral polygonal shape. Resin is then applied to the strands, and the strands are formed into a composite beam. The process involves cutting the wood to produce strands. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0016] Australian Patent Application No. 2010342749 discloses methods of preparing wood for use in a manufactured wood product. The methods advantageously include providing a wood piece and breaking at least a portion of the naturally occurring, generally elongate internal structure. Methods of making manufactured wood products are also described herein. These methods advantageously include additionally heat-treating the wood pieces, applying an adhesive to the wood pieces, drying the wood pieces, and pressing the wood pieces in a mold. The process involves cutting the wood to produce strips and then breaking the strips laterally. This reduces the strength of the product. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0017] Australian Patent Application No. 2010342713 discloses a manufactured eucalyptus wood product comprises a plurality of adhesively bonded and pressed eucalyptus wood strips, each of the eucalyptus wood strips is of generally the same length and comprises a naturally-occurring, generally elongate internal structure extending generally along one axis of the strip that has been at least partially laterally broken and at least permeated by an adhesive. The eucalyptus wood strips are oriented roughly parallel to one another along their length. The manufactured eucalyptus wood product comprises an amount of adhesive in the range of about 0.1 % by weight to about 15% by weight. The manufactured eucalyptus wood product has a wood grain appearance or look. The manufactured eucalyptus wood products may have aesthetic and structural qualities that are suitable for high traffic, high visibility applications such as wood flooring. The process involves breaking the wood strips laterally. This reduces the strength of the product. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0018] WO201 1085555 discloses a system for producing manufactured wood products includes a spindleless lathe, a rolling machine or crushing machine, a cutting machine, a heat- treating unit, a first dryer, an adhesive application unit, a second dryer, a pressing unit, and a third dryer. The system can be centrally and / or remotely operated. In some embodiments, the system is fully automated. This reduces the strength of the product. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0019] United States Patent Application No. 20100119857 discloses a method for producing a manufactured wood product using less desirable or discarded natural wood and a manufactured wood product produced by the described method. This inventive method comprises utilizing less desirable or discarded natural wood pieces by slicing the wood pieces into elongated strips that are then partially separated into elongate sections with alternating step sections that maintain fibrous connectivity between the elongate sections. The elongate sections are impregnated with an adhesive and pressed in a mold. The process involves cutting the wood to produce strips. There is no disclosure to producing densified, dimensionally stable, structural lumber.

[0020] US Patent No. 4548675 discloses a non-sulfur chemical and mechanical pulping process for producing pulp from woody materials. The process is particularly suited for producing corrugating medium pulp from hardwood chips although the process can be adapted to production of other types of pulp and can use other types of woody materials. The process comprises impregnation and dilution of the chips in a dilute aqueous pulping solution of a lower alkanolamine catalyzed with ammonium hydroxide. The preferred alkanolamine is monoethanolamine present in a weight ratio to ammonium hydroxide of about 1 part to 1 part or less to 1 part to 3 parts or more. The pulping solution may be repeatedly reused and the process of this invention does not produce environmentally objectionable byproducts. This method is specific to pulping.

[0021] US Patent Application Publication No. 20210053248 discloses a method of manufacturing engineered wood, the method comprising: feeding wood through a processor while exposing the wood to compressive and tensile forces to produce naturally oriented strands of fibers; adding an adhesive to naturally oriented strands of fibers to provide adhesive covered strands; feeding the adhesive covered strands into a press; applying a first pressure to the adhesive covered strands to provide a pressed wood with a selected first dimension and a selected second dimension; and applying a second pressure normal to the first pressure to the pressed wood to provide an engineered wood having the selected first dimension, the selected second dimension and a selected third dimension and a selected density. An installation for manufacturing the engineered wood is also provided. This system and method require that an adhesive be added, thereby increasing the cost of production.

[0022] United States Patent No. 5021531 discloses lignin, or a lignin derived material, which has been significantly demethylated (e.g., the demethylated lignin found in the raffinate produced as a by-product of dimethyl sulfide production which can be carried out using the spent liquor from wood pulping operations) can be isolated by a process wherein an organic solvent is added to a lignin-containing aqueous solution. The organic solvent is typically a polar, and at least a partially water-immiscible substance such as, for example, ethyl acetate. The resulting lignin-containing aqueous solution / organic solvent mixture is acidified to produce a water layer which is discarded and an organic solvent layer which contains the demethylated lignin. Upon its recovery, the demethylated lignin is preferably dried and stored until it is used (along with an alkali, an aldehyde and an adhesive filler) in compounding an adhesive of the type generally used in the manufacture of plywood. This is a multi-step and complicated method of producing non-native depolymerized lignin. Further, it undoubtedly contains some sulphur compounds.

[0023] United States Patent No. 9617452 discloses powdered adhesives for making lignocellulosic composite products and methods for making same. The powdered adhesive can include a powdered phenol-aldehyde resin and a powdered kraft lignin. The powdered kraft lignin can contain less than 3 wt % of ash, as measured according to ASTM D2584-11 . The powdered adhesive can contain less than 10 wt % of water. This product will contain sulphur compounds and is not a method of producing native depolymerized lignin which can be used for the in situ impregnation of the wood product from which it was derived.

[0024] What is needed is a simple process and system to manufacture engineered wood products from timber or dimensioned lumber. It would be preferable if the system impregnated wood products such as milled lumber, timber and stranded timber with ammonia. It would be preferable if the impregnated wood product could be subjected to high pressure to produce dense, dimensionally stable, structural lumber. It would be preferable if there was no need for an adhesive. It would be preferable if the system could be used on underutilized wood such as damaged trees, for example, but not limited to those with rot, fire damaged, insect damaged and the like and wood from trees such as soft hardwoods that would benefit from improved mechanical properties. It would be still more preferable if the density and dimensional stability could be improved in milled lumber, thereby upgrading the quality of the resultant wood product. It would be more preferable if this treated milled lumber was structurally superior to the non-densified milled lumber and could be graded higher. It would be preferable if the process was scalable.

[0025] SUMMARY

[0026] The present technology is a simple process and system to manufacture engineered wood products from timber or lumber. The system impregnates milled lumber, timber and stranded timber with ammonia and then, using heat and pressure produces dense, dimensionally stable, structural lumber. No adhesive needs to be added. The system can be used on underutilized wood such as damaged trees, for example, but not limited to those with decay, those that are fire damaged, those that are insect damaged and the like and wood from trees such as soft hardwoods that would benefit from improved mechanical properties. Stabilization of the wood fibres occurs during the thermal curing stage. The density and dimensional stability can be improved in milled lumber, thereby upgrading the quality of the wood product. This treated milled lumber is structurally superior to the non-densified milled lumber. The process is scalable.

[0027] In one embodiment, a method of manufacturing a densified, dimensioned wood product is provided, the method comprising: selecting a wood feedstock, which is one of dimensioned lumber, unmilled lumber, timber or stranded timber; exposing the wood feedstock to ammonia under a cyclic positive and negative pressure in a vessel; the ammonia infiltrating and impregnating the wood feedstock to provide impregnated wood feedstock; removing the impregnated wood feedstock from the vessel; and exposing the impregnated wood feedstock to a high pressure and a temperature in a two-axis radiofrequency (RF) press, such that the impregnated wood feedstock reaches a uniform temperature of between about 110°C to 150°C, thereby manufacturing the densified, dimensioned wood product from the wood feedstock.

[0028] In the method, the ammonia may be anhydrous ammonia.

[0029] The method may further comprise heating the wood feedstock in the vessel.

[0030] In the method, the ammonia may be ammonium hydroxide.

[0031] In the method, the heating may be between 100°C to 190°C.

[0032] In the method, the cyclic positive and negative pressures may be 200 to 1655 kilo Pascals (kPa), positive pressure and about 100 kPa negative pressure to absolute pressure.

[0033] In the method, the high pressure in the two-axis RF press may be 5 mega Pascals (MPa) to 50 MPa.

[0034] The method may further comprise kiln drying the densified, dimensioned wood product.

[0035] The method may further comprise further dimensioning the densified, dimensioned wood product to provide dimensionally stable construction lumber.

[0036] In the method, the further dimensioning may be one or more of ripping, planing and end cutting.

[0037] In the method, the wood feedstock may be timber and the method may further comprise debarking the timber.

[0038] The method may be done without adding an adhesive or resin.

[0039] In the method, the infiltrating and impregnating may be done at a temperature below the depolymerization temperature of lignin.

[0040] In another embodiment, a system for the manufacture of densified, dimensionally stable construction lumber is provided, the system comprising a high-pressure vessel configured for retaining a wood feedstock and impregnating the wood feedstock at high pressure to provide an impregnated wood feedstock; and a two-axis radio-frequency press configured to densify and mold the impregnated wood feedstock into the densified, dimensionally stable construction lumber. The system may further comprise a ripping saw, a planar and an end cutter, all downstream from the two-axis radio-frequency press and a debarker, the debarker located between the high-pressure vessel and the two-axis radio-frequency press.

[0041] In another embodiment, a densified, dimensionally stable wood product is provided, the densified dimensionally stable wood product manufactured by the method of any one of claims 1 to 13 and consisting of: the wood feedstock, which is one of dimensioned lumber, unmilled lumber, timber or stranded timber.

[0042] In another embodiment, a densified, dimensionally stable wood product is provided, the densified dimensionally stable wood product manufactured by the method of claim 13 and comprising: the wood feedstock, which is one of dimensioned lumber, unmilled lumber, timber or stranded timber.

[0043] In the densified, dimensionally stable wood product, the timber may be a soft hardwood.

[0044] In the densified dimensionally stable wood product, the wood feedstock may be stranded timber.

[0045] FIGURES

[0046] Figure 1 is a schematic of the lumber upgrading system of the present technology.

[0047] Figure 2 is a schematic of the installation of the present technology.

[0048] Figure 3 is a block diagram of the method of lumber upgrading with the system of Figure 1.

[0049] Figure 4 is a flow diagram of the processing steps in the installation.

[0050] DESCRIPTION

[0051] Except as otherwise expressly provided, the following rules of interpretation apply to this specification (written description and claims): (a) all words used herein shall be construed to be of such gender or number (singular or plural) as the circumstances require; (b) the singular terms "a", "an", and "the", as used in the specification and the appended claims include plural references unless the context clearly dictates otherwise; (c) the antecedent term "about" applied to a recited range or value denotes an approximation within the deviation in the range or value known or expected in the art from the measurements method; (d) the words "herein", "hereby", "hereof", "hereto", "hereinbefore", and "hereinafter", and words of similar import, refer to this specification in its entirety and not to any particular paragraph, claim or other subdivision, unless otherwise specified; (e) descriptive headings are for convenience only and shall not control or affect the meaning or construction of any part of the specification; and (f) "or" and "any" are not exclusive and "include" and "including" are not limiting. Further, the terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted.

[0052] Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Where a specific range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is included therein. All smaller sub ranges are also included. The upper and lower limits of these smaller ranges are also included therein, subject to any specifically excluded limit in the stated range.

[0053] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the relevant art. Although any methods and materials similar or equivalent to those described herein can also be used, the acceptable methods and materials are now described.

[0054] Definitions:

[0055] Dimensioned lumber - in the context of the present technology, dimensioned lumber is lumber that has been milled to current specifications. This includes but is not limited to 2x4s, 2x6s, 2x8s, 2x1 Os, 2x12s, 4x4s, 6x6s and 8x8s. Dimensioned lumber includes finger-jointed lumber. It is also known as milled lumber. Dimensionally stable lumber - in the context of the present technology dimensionally stable lumber is lumber that does not shrink, warp, cup, twist, crack, bow and the like and has high durability.

[0056] Densified wood - in the context of the present technology, densified wood is wood that has been treated to increase the density and has superior mechanical properties to the wood from which it was derived.

[0057] Upgraded lumber - in the context of the present technology, upgraded lumber is lumber that is milled from densified wood and is graded higher than that from non-densified wood.

[0058] Unmilled lumber - in the context of the present technology, unmilled lumber is any lumber that has been rough cut to a dimension and requires milling to become dimensioned lumber. It includes non-atmospherically seasoned, non-kiln dried, and seasoned / kilned lumber.

[0059] Timber - in the context of the present technology, timber is unmilled wood, which has been harvested.

[0060] Structural lumber - in the context of the present technology, structural lumber is lumber that is used as studs, joists, risers, beams, rafters, trusses, headers and the like and includes Select Structural, Construction Standard Utility and Stud. It is a subset of dimensioned lumber.

[0061] Construction lumber - in the context of the present technology, construction lumber includes structural lumber, decorative lumber and unmilled lumber.

[0062] DETAILED DESCRIPTION

[0063] As shown in Figure 1 , a lumber upgrading system, generally referred to as 2, includes a rotary debarker 4, a log trolley 6, which is on rails 8, a first step feeder 10, a pressure vessel 12, which includes racks 14 with weigh scales 16, a front-end loader with grapple 18, a chain conveyor 20, a second step feeder 22, a radio frequency (RF) press 24, a third step feeder 26, a ripsaw 28, a fourth step feeder 30, a planar 32, an end trimmer 34, a kiln 36, a chain conveyor 38 and an automatic stacker and bander 40. A forklift 42 may also be included. As shown in Figure 2, an installation, generally referred to as 50, includes the lumber upgrading system 2, noting that some of the feeder mechanisms of the upgrading system 2 are not shown in Figure 2. The installation also includes a fifth step feeder 52, a computed tomography (CT) scanner 54, a cut-off saw 56, a vertical grinder 58, a conduit 60 and an overhead chip bin 62.

[0064] As would be known to one skilled in the art, the trolley and rail system, conveyors and step feeders can be replaced with any suitable wood feedstock delivery mechanism.

[0065] As shown in Figure 3, when logs are used, the front-end loader 18 transfers 140 the bundle from a truck to the debarker 4. The wood is debarked 142 as needed to provide debarked wood feedstock. The debarked wood feedstock is transferred 144 to the log trolley 6, which delivers 146 it to the first step feeder 10, which in turn delivers 148 it to the pressure vessel 12, which functions as the infiltration and impregnation vessel 12. Lumber products are offloaded 150 with the forklift 42 to the log trolley 6, which delivers 146 it to the first step feeder 10, which in turn delivers 148 it to the pressure vessel 12. The debarked wood feedstock or the lumber feedstock (collectively referred to as the wood feedstock) are loaded 152 onto the racks 14. The weight of the wood feedstock is measured 154 with the weigh scales 16. Aqueous ammonia (ammonium hydroxide) is added 156 to the wood feedstock in the pressure vessel 12. Alternatively, the aqueous ammonia is added 158 to the pressure vessel 12 and the wood feedstock is then added 160. Infiltrating and impregnation 162 follows. These are essentially concurrent. Alternatively, the wood feedstock may be infiltrated by the ammonia as a separate step, followed by impregnation. The weight of the wood feedstock is measured 168 with the weigh scales 16 during the ammonia treatment. When the treatment ends 170, the weight of the resultant feedstock is again measured 172. The wood feedstock in this embodiment is raw timber, unmilled lumber or lumber. There is no pulp produced. The infiltrating and impregnating are done under cyclic positive and negative pressures of about 200 to about 1655 kilo Pascals (kPa), positive pressure, preferably about 1400 kPa and about 100 kPa negative pressure to absolute pressure (total vacuum), preferably about 50 kPa and a temperature of about 100°C to about 190°C, preferably 140°C for about half an hour to about two hours and any times therebetween. The temperature range is below the depolymerization temperature for lignin but is high enough to vapourize the aqueous ammonia. For larger debarked wood feedstocks the exposure time may be longer. As would be known to one skilled in the art, the lower pressures are employed with the lower temperatures and the higher pressures are employed with the higher temperatures. The target ammonia uptake range is 1 to 2% by mass. This is determined by measuring the weight of the wood feedstock as outlined above. In an alternative embodiment, anhydrous ammonia (gaseous) is used and the infiltrating and impregnating are done at ambient temperatures. Without being bound to theory, ammonia softens the cellulose, so that the press doesn’t damage the fibres, allowing the densification to be rapidly effected. The method using gaseous ammonia is more efficient than the method using aqueous ammonia.

[0066] Once the wood feedstock has been impregnated, to provide impregnated wood feedstock, it is transferred 174 onto the chain conveyor 20 and the second step feeder 22 to the RF press 24. The RF press 24 is a two-axis press and both densifies 176 and molds 178 the treated feedstock to provide a two-dimensionally sized, densified wood product. Without being bound to theory, the RF press 24 causes the water and the ammonia to vapourize. The impregnated wood feedstock is loaded into the two-axis RF press 24 at ambient temperature and then heats the wood fibres to between about 110°C and 150°C, preferably 140°C and applies 0.1 mega Pascals (MPa) to 50 MPa on the wood fibers. Heating occurs in a matter of minutes as the rise in temperature is very rapid. Advantageously, it is also a uniform rise in temperature. Without being bound to theory, this is caused by the electromagnetic waves being absorbed by the water in the fibres. As the temperature is not high, the fibres are not damaged (the temperature is below the temperature at which hemicellulose degrades and well below the temperature at which lignin depolymerizes), noting that other densification methods damage the fibres because of the high heat used. This is a batch process which takes a few minutes (3 to 5 minutes using the present batch size of four boards) per batch. As the RF press 24 is a two- axis press, lateral and vertical pressure are exerted equally and concomitantly. This ensures uniformity in the wood product. The molded, densified product is then ripped 180 and planed 182. End cutting 184 may be before ripping 180, after ripping 180 and before planing 182 or after both ripping 180 and planing 182. At this time, targeted dimensionally stable wood products (upgraded wood products) are provided 196. These are moved 186 to the kiln 34 where they are thermally modified 188 by blocking hydroxyl sites at temperatures below the lignin depolymerization temperature. The upgraded wood product is then moved 190 by the chain conveyor 36 to the automatic stacker and bander 38 where they are stacked 192 and banded 194.

[0067] The pilot production can achieve 192 boards / day(24hr). This is 4 boards / 30mins or 8 boards / hr. The first scale up is for 5 boards / min or 300 boards / hr or 30,000 cubic meters a year.

[0068] The resultant engineered wood product has been shown to be dimensionally stable, have an increased density, and be suitable for structural applications. In general, when dimensioned lumber is the starting product, the finished, densified product is graded with a higher grading than the starting material. Results show about a four-fold increase in strength. Uses of the engineered wood product include upgraded deciduous and coniferous lumber and timbers for building components such as nail- or dowel-laminated timber panels, decorative facades, high-end furniture, rail ties, and certified structural components, such as glue-laminated beams.

[0069] In another embodiment, the wood feedstock is stranded timber. Stranding is as disclosed in US Patent Application Publication No. 20210053248, the contents of which are incorporated by reference in their entirety herein. The steps are as described above.

[0070] In an alternative embodiment, the starting material is longitudinal or chopped fiber strands or mechanically ground fibers. The steps are as described above.

[0071] The steps taken in the installation 50 are shown in Figure 4. Logs delivered from harvesting are fed 300 onto the fifth step feeder 52, which loads 302 them onto the CT scanner 54. Oversize logs are moved 304 to a log pile, while those that are correctly sized are moved 306 to the cut-off saw 56. The logs are sorted 308 into sawmill quality logs and upgrading quality logs based on their CT scanner images. Those that are sawmill quality are sent 310 to an end user. Those that are upgrading quality logs are taken 312 to the debarker 4 and then follow the path as outlined in Figure 3. Trim end from the cut-off saw 56, bark from the debarker 4 and shaving from the planer 32 enter 314 the vertical grinder 58, pass through the conduit 60 and are stored in the overhead chip bin 62 before being sent to a power plant. The same installation can be used for lumber that is to be upgraded rather than raw logs.

[0072] Regardless of the wood feedstock and the processing method used, the densified, dimensioned structural lumber does not contain any adhesives, whether chemical adhesives that are added during processing in other prior art processes, or depolymerized and repolymerized lignin-based adhesives produced in situ.

[0073] The degree of densification is dependent upon the wood feedstock and the desired outcome. For straightening structural lumber, densification can be as low as a 0.1 % increase in density, as the objective is to straighten and not to densify. For a soft hardwood such as Aspen or Alder, a cant can be densified 1.33-fold so that it matches the density and strength of Douglas fir. Densification of Alder or Aspen by 1 .78-fold can produce a wood product with the density of a hardwood such as Maple. The maximum densification is 4-fold, which represents a 75% reduction in volume. From Table 1 , one can easily select a species of wood to be densified, look up the density of the species that they want the wood product to emulate and adjust the pressure of the two-axis RF press to produce that desired density. Regardless of the wood feedstock, for example, but not limited to wood with rot, insect damaged wood, charred wood, stranded wood and the like, one can select the desired density and produce a wood product with that density.

[0074] The densities that can be obtained using the two-axis RF press are shown in Table 1 .

[0075] Table 1 . Densities of a range of woods.

[0076] Species Density

[0077] ((kg / m3)

[0078] Alder 400 - 700

[0079] Afrorm os ia 710 Agba 510

[0080] Apple 650 - 850

[0081] Ash, white 650 - 850

[0082] Ash, black 540

[0083] Ash, European 710

[0084] Aspen 420

[0085] Balsa 160

[0086] Bamboo 300 - 400

[0087] Basswood 300 - 600

[0088] Beech 700 - 900

[0089] Birch, British 670

[0090] Birch, European 670

[0091] Box 950 - 1200

[0092] Butternut 380

[0093] Cedar of Lebanon 580

[0094] Cedar, western red 380

[0095] Cherry, European 630 Chestnut, sweet 560

[0096] Cottonwood 410

[0097] Cypress 510

[0098] Dogwood 750

[0099] Douglas Fir 530

[0100] Ebony 1100 - 1300

[0101] Elm, American 570

[0102] Elm, English 550 - 600

[0103] Elm, Dutch 560

[0104] Elm, Wych 690

[0105] Elm, Rock 820

[0106] Gaboon 430

[0107] Greenheart 1040

[0108] Gum, Black 590

[0109] Gum, Blue 820

[0110] Gum, Red 540

[0111] Hackberry 620 Hemlock, western 500

[0112] Hickory 830

[0113] Holly 750

[0114] Iroko 660

[0115] Juniper 550

[0116] Keruing 740

[0117] Larch 500 - 550

[0118] Lignum Vitae 1170 - 1330

[0119] Lime, European 560

[0120] Locust 650 - 700

[0121] Logwood 900

[0122] Madrone 740

[0123] Magnolia 570

[0124] Mahogany, African 500 - 850

[0125] Mahogany, Cuban 660

[0126] Mahogany, Honduras 650

[0127] Mahogany, Spanish 850 Maple 600 - 750

[0128] Meranti, dark red 710

[0129] Myrtle 660

[0130] Oak 600 - 900

[0131] Oak, American Red 740

[0132] Oak, American White 770

[0133] Oak, English Brown 740

[0134] Obeche 390

[0135] Oregon Pine 530

[0136] Parana Pine 560

[0137] Pear 600 - 700

[0138] Pecan 770

[0139] Persimmon 900

[0140] Philippine Red Loan 590

[0141] Pine, pitch 670

[0142] Pine, Corsican 510

[0143] Pine, radiata 480 Pine, Scots 510

[0144] Pine, white 350 - 500

[0145] Pine, yellow 420

[0146] Plane, European 640

[0147] Plum 650 - 800

[0148] Poplar 350 - 500

[0149] Ramin 670

[0150] Redwood, American 450

[0151] Redwood, European 510

[0152] Rosewood, Bolivian 820

[0153] Rosewood, East Indian 900

[0154] Sapele 640

[0155] Satinwood 950

[0156] Spruce 400 - 700

[0157] Spruce, Canadian 450

[0158] Spruce, Norway 430

[0159] Spruce, Sitka 450 Spruce, western white 450

[0160] Sycamore 400 - 600

[0161] Tanguile 640

[0162] Teak, Indian 650 - 900

[0163] Teak, African 980

[0164] Teak, Burma 740

[0165] Utile 660

[0166] Walnut 650 - 700

[0167] Walnut, Amer Black 630

[0168] Walnut, Claro 490

[0169] Walnut, European 570

[0170] Water gum 1000

[0171] Whitewood, European 470

[0172] Willow 400 - 600

[0173] Yew 670

[0174] Zebrawood 790

[0175] Example 1 A densified wood product manufactured by the method of the present technology was compared to a densified wood product manufactured using monoethanolamine:ammonium hydroxide as an exemplary primary, secondary, or tertiary alkanolamines, mixed with ammonium hydroxide. The densified wood product of the present technology was manufactured using ammonium hydroxide in the pressure vessel and applying both heat and pressure. It was also manufactured using anhydrous ammonia in the pressure vessel, using only heat. These two methods were followed with the RF two-axis press densification. The monoethanolamine:ammonium hydroxide mixture was subjected to heat and pressure in the pressure vessel. This chemistry and method is known to depolymerize lignin and at least partially delignify the wood feedstock. This method was followed with the RF two-axis press densification. Raman spectroscopy was used to examine the resultant wood products. The results confirmed that the monoethanolamine:ammonium hydroxide mixture at least partially delignified and therefore at least partially depolymerized the lignin in the fibres. Neither the ammonium hydroxide nor the anhydrous ammonia delignified the fibres. Significantly, scanning electron microscopy showed that the combination of monoethanolamine:ammonium hydroxide treatment and densification led to damage to the fibres. In contrast, the combination of ammonium hydroxide treatment or anhydrous ammonia treatment fibres and densification led to little or no damage to the fibres. Thus, the methods of the present technology maintain the chemical integrity of the fibres of the wood products in addition to densifying. Without being bound to theory, this is probably why the methods lead to structural lumber that is graded higher than lumber from the non-treated counterpart.

[0176] While example embodiments have been described in connection with what is presently considered to be an example of a possible most practical and / or suitable embodiment, it is to be understood that the descriptions are not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the example embodiment. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, many equivalents to the specific example embodiments specifically described herein.

Claims

CLAIMS1 . A method of manufacturing a densified, dimensioned wood product, the method comprising: selecting a wood feedstock, which is one of dimensioned lumber, unmilled lumber, timber or stranded timber; exposing the wood feedstock to ammonia under a cyclic positive and negative pressure in a vessel; the ammonia infiltrating and impregnating the wood feedstock to provide impregnated wood feedstock; removing the impregnated wood feedstock from the vessel; and exposing the impregnated wood feedstock to a high pressure and a temperature in a two-axis radio-frequency (RF) press, such that the impregnated wood feedstock reaches a uniform temperature of between 110°C and 150°C, thereby manufacturing the densified, dimensioned wood product from the wood feedstock.

2. The method of claim 1 , wherein the ammonia is anhydrous ammonia.

3. The method of claim 1 , further comprising heating the wood feedstock in the vessel.

4. The method of claim 3, wherein the ammonia is ammonium hydroxide.

5. The method of claim 3 or 4, wherein the heating is between 100°C to 190°C.

6. The method of any one of claims 1 to 5, wherein the cyclic positive and negative pressures are 200 to 1655 kilo Pascals (kPa), positive pressure and about 100 kPa negative pressure to absolute pressure.

7. The method of any one of claims 1 to 6, wherein the high pressure in the two-axis RF press is 5 mega Pascals (MPa) to 50 MPa.

8. The method of any one of claims 1 to 7, further comprising kiln drying the densified, dimensioned wood product.

9. The method of any one of claim 1 to 8, further comprising further dimensioning the densified, dimensioned wood product to provide dimensionally stable construction lumber.

10. The method of claim 9, wherein the further dimensioning is one or more of ripping, planing and end cutting.

11. The method of any one of claims 1 to 10, wherein the wood feedstock is timber and the method further comprises debarking the timber.

12. The method of any one of claims 1 to 11 , wherein the method is done without adding an adhesive or resin.

13. The method of claim 12, wherein the infiltrating and impregnating is done at a temperature below the depolymerization temperature of lignin.

14. A system for the manufacture of densified, dimensionally stable construction lumber, the system comprising a high-pressure vessel configured for retaining a wood feedstock and impregnating the wood feedstock at high pressure to provide an impregnated wood feedstock; and a two-axis radio-frequency press configured to densify and mold the impregnated wood feedstock into the densified, dimensionally stable construction lumber.

15. The system of claim 14, further comprising a ripping saw, a planar and an end cutter, all downstream from the two-axis radio-frequency press and a debarker, the debarker located between the high-pressure vessel and the two-axis radiofrequency press.

16. A densified, dimensionally stable wood product, the densified dimensionally stable wood product manufactured by the method of any one of claims 1 to 13 and consisting of: the wood feedstock, which is one of dimensioned lumber, unmilled lumber, timber or stranded timber.

17. A densified, dimensionally stable wood product, the densified dimensionally stable wood product manufactured by the method of claim 13 and comprising: the wood feedstock, which is one of dimensioned lumber, unmilled lumber, timber or stranded timber.

18. The densified, dimensionally stable wood product of claim 16 or 17, wherein the timber is a soft hardwood.

19. The densified dimensionally stable wood product of claim 16 or 17, wherein the wood feedstock is stranded timber.