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WO2016038250A1 - Procédé et appareil de production de matière lignocellulosique fine - Google Patents

Procédé et appareil de production de matière lignocellulosique fine Download PDF

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Publication number
WO2016038250A1
WO2016038250A1 PCT/FI2015/050591 FI2015050591W WO2016038250A1 WO 2016038250 A1 WO2016038250 A1 WO 2016038250A1 FI 2015050591 W FI2015050591 W FI 2015050591W WO 2016038250 A1 WO2016038250 A1 WO 2016038250A1
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WIPO (PCT)
Prior art keywords
grinding
grinding wheel
wheel
rotation axis
serrated
Prior art date
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.)
Ceased
Application number
PCT/FI2015/050591
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English (en)
Inventor
Erkki Saharinen
Ilkka NURMINEN
Lauri Salminen
Jari Leino
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VTT Technical Research Centre of Finland Ltd
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VTT Technical Research Centre of Finland Ltd
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Publication of WO2016038250A1 publication Critical patent/WO2016038250A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B19/00—Single-purpose machines or devices for particular grinding operations not covered by any other main group
    • B24B19/22—Single-purpose machines or devices for particular grinding operations not covered by any other main group characterised by a special design with respect to properties of the material of non-metallic articles to be ground
    • B24B19/24—Single-purpose machines or devices for particular grinding operations not covered by any other main group characterised by a special design with respect to properties of the material of non-metallic articles to be ground of wood, e.g. furniture
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B53/00—Devices or means for dressing or conditioning abrasive surfaces
    • B24B53/06—Devices or means for dressing or conditioning abrasive surfaces of profiled abrasive wheels
    • B24B53/07—Devices or means for dressing or conditioning abrasive surfaces of profiled abrasive wheels by means of forming tools having a shape complementary to that to be produced, e.g. blocks, profile rolls
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D5/00—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting only by their periphery; Bushings or mountings therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D5/00—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting only by their periphery; Bushings or mountings therefor
    • B24D5/02—Wheels in one piece
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
    • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
    • D21B1/14—Disintegrating in mills
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D2203/00—Tool surfaces formed with a pattern

Definitions

  • the invention relates to production of lignocellulosic material from raw wood by mechanical grinding.
  • the invention relates to an apparatus comprising a grinding wheel and means for feeding raw wood material against the grinding wheel to produce fine material.
  • the invention relates to a corresponding grinding method.
  • Cellulosic nano- or microfibrillated materials are today among the most interesting renewable raw materials.
  • the interest for fibrillar material is due to its extraordinarily high specific strength, thermal stability, hydrophilicity, and broad capacity for chemical modification.
  • cellulosic small fibrillar materials have potential in novel products with a range of enhanced properties.
  • One substantial production expense of nano- or microcellulose comes from the energy required for defibrillation of the starting materials.
  • Mechanical pulping is a common method for producing fibrillar material. Mechanical pulps are produced by specified attrition processes. Groundwood (GW), pressure groundwood (PGW), and thermomechanical pulp (TMP) all apply similar shear and compression forces to fresh wood and fibres. In grinding, a high strain rate of cyclic compressive loads heat, loosen and fatigues the wood, whereas shear loads free the hot fatigued fibres from the solid wood. As a result, a competent pulp is obtained. As a result of the process, mechanical pulps comprise a continuum of different kinds of particles, conventionally from long fibres of up to 3 mm to shorter fibres, and debris or fine materials of very small dimensions.
  • the fines can be flaky or fibrillar. Fibrillar fines are like yarns in that they have a larger specific surface area and are, therefore, favoured over flake and chunky fines as regards strength development.
  • US 4,560,439 discloses a grinding system where a feeder pushes wood chips into a chamber wherein a piston compresses the chips into a grinder zone between grinding members.
  • the compression direction of the piston is parallel to an axis of a rotatable grinding member which has grinding protrusions in saw teeth configuration or otherwise overlapping each other in the direction of movement.
  • DE 3210321 discloses a system which utilizes relative oscillation of two working means, between which there is a narrow column and through which column the feedstock is moved, which causes defibering of the material.
  • transversal wood grinding logs are pressed against a rotating stone, and the log axis as well as the longitudinal axis of the fibres is aimed parallel to the rotation axis of the grinding stone.
  • the stone surface velocity is perpendicular to the fibres axis.
  • the grinding is called longitudinal.
  • the aspects of wood alignment have been studied earlier in for example Brauns, O., and Gavelin, G. (1959).
  • An addition aim of the invention is to provide an apparatus and method whose
  • the invention is based on the idea of providing a grinding apparatus with a grinding wheel with a surface profile serrated in the axial direction of the wheel.
  • the serration comprises surface features which are at an oblique angle with respect to the rotation axis of the wheel. This is in contrast with prior art surface profiling schemes, in which there may be variation only in the circumferential direction of the wheel (although such profiling additionally is not excluded).
  • raw wood material comprising fibers at least mainly oriented along the longitudinal direction of the raw wood material are fed to the presently profiled wheel in transverse or tangentially rotated oblique angles, the fibers of the raw wood material meet the grinding surface at an oblique angle at the regions of the oblique surface features.
  • the serrated surface profile covers the entire cylindrical surface of the wheel (or at least the portion where the raw material is fed), whereby a vast majority of the fibers meet the surface at oblique angle.
  • the apparatus according to the invention comprises a rotatable grinding wheel having a rotation axis and around the rotation axis a grinding surface capable of separating fine material from wood by grinding effect and a feeder for feeding raw wood material against the grinding surface during rotation of the grinding wheel.
  • the grinding surface comprises a serrated surface profile in the axial direction of the wheel.
  • the edge of the wheel when viewed in the radial cross-sectional plane of the wheel, the edge of the wheel has a serrated shape.
  • the serration comprises a pattern of surface features having oblique angle with respect to the rotation axis. In this way, even fibers fed to the grinder in purely transversal grinding orientation, meet the grinding surface in oblique angle and are ground to finer particles.
  • the present method for producing fine lignocellulosic material comprises rotating a generally cylindrical grinding wheel having a grinding surface, and feeding raw wood material against the grinding surface for producing said fine material by grinding.
  • the grinding wheel comprises a serrated grinding surface profile having a pattern of surface features at oblique angle with respect to the rotation axis. Feeding is preferably carried out such that so that average fiber orientation of the raw wood material is in a tangential plane of the grinding surface.
  • the grinding wheel according to the invention results in considerably higher amount of fine material in the produced pulp as compared with other fiber fractions.
  • the invention thus allows for separation of the fine material production from long fiber production. As the fine fraction is larger or even close to 100%, less or no post-processing at all is needed in order to obtain an essentially pure fines-containing mass. This provides significant cost- savings.
  • the invention has very low investment and operating costs, as it can exploit existing grinding apparatuses, with only a straight-forward modification to or replacement of a conventional grinding wheel as a minimum.
  • Optional modifications include replacement or provision of a serrated finger bar and a wheel profile-maintaining
  • flaky fines are interest as far as properties of light scattering and bulk are concerned. Flaky fines are also organic filler and therefore environmentally beneficial. By adjusting grinding parameters the process can produce fibrillar or flaky fines.
  • Fig. 1 shows a grinding apparatus set-up according to one embodiment of the invention.
  • Figs. 2A-C shows a detailed illustration of grinding wheel surface profiles according to alternative embodiments of the invention.
  • Fig. 3 illustrates a profiled finger bar arrangement according to one embodiment of the invention.
  • FIGs. 4A and 4B depict grinding wheel sharpening arrangements according to alternative embodiments.
  • FIGs. 5A-C shows schematically how material, in this specific case fibrillar material, is separated from wood fibers with different surface angles of the grinding wheel.
  • Figs. 6A and 6B illustrate alignment of wood with respect to a grinding wheel used in grinding trials.
  • Figs. 7A and 7B illustrate as a graph the percentage of Bauer McNett Fractions shown as a function of radial and tangential alignment between fibre and stone, respectively.
  • Figs. 7C and 7D show graphs of length- weighted average fibre length of pulp and specific sedimentation volume of fines, respectively, versus the radial and tangential grinding angle.
  • Fig. 7E shows a graph of specific energy consumption, fines amount, and fines quality in grinding versus radial alignment between wood and a grinding stone.
  • Figs. 9A to 9C illustrate the effect of environmental parameters on the energy consumption of the grinding process and properties of the resulting fibrillar product.
  • Grinding wheel refers to a rotatable member having a cylindrical outer surface having an abrasive surface suitable for grinding.
  • the term “cylindrical” refers to the general form of the wheel (excluding the serrated profile).
  • Axial directions refer to the direction of the rotational axis, which is typically also the longitudinal axis of symmetry of the grinding wheel. This direction is occasionally also called “transverse”, as it is transverse to the direction of movement of the wheel surface.
  • “Radial” refers to the direction along a radius of the grinding wheel.
  • “Circumferential” direction means along the circumference of the grinding wheel.
  • “Tangential” direction refers to a direction parallel to a tangent of the cylindrical grinding wheel.
  • “Tangential plane” is a plane defined by a tangent of the cylinder and axial direction intersecting the tangent.
  • Wood angle is the angle between reference and the longitudinal axis of wood fiber.
  • Random (grinding) angle refers to deviation of wood fiber orientation from the axial direction in the radial direction.
  • Tiential (grinding) angle refers deviation of wood fiber orientation from the axial direction in the tangential direction.
  • Raw wood material refers to wood material in which the original natural fiber orientation and structure are preserved. In particular, the term refers to logs and other forms of wood material also conventionally used for industrial scale grinding processes.
  • “Serrated surface profile” of the grinding wheel refers to a surface shape having radial height variations on the surface along the axial direction (in the radial plane) of the grinding wheel.
  • the serrated surface profile comprises repeating pattern of oblique-angle features such that the whole grinding surface is covered and causing transversely fed fiber to meet the stone surface at a radial angle.
  • the wheel radius is essentially constant along the circumference of the wheel at each particular axial location. In other words, the grinding wheel is rotationally symmetric along its full length.
  • the grinding wheel is only partially rotationally symmetric.
  • the grinding wheel is partially and preferably mainly (at least 50 % of the axial length) rotationally symmetric and the wheel radius is essentially constant along the circumference of the wheel at most axial locations.
  • "Oblique angle" between fiber orientation and grinding surface means any angle between but not including zero angle and normal angle. Particularly preferred angle ranges are disclosed elsewhere in this document.
  • major of fibers meeting the grinding surface at oblique angle is used to take into account the fact that in practice, all serrated surfaces comprise also non-oblique surface portions for example at the tops of ridges or bottoms of grooves of the serration.
  • all serrated surfaces comprise also non-oblique surface portions for example at the tops of ridges or bottoms of grooves of the serration.
  • “Flaky” stands for plate-like particles having generally a smaller height that width and length. Typically, the flakes have an average height of 0.01 to 3 mm, in particular 0.05 to 1.5 mm. The average width of the flakes is on the order of 0.1 to 30 mm, in particular 0.15 to 10 mm. The average length of the flakes is 0.1 to 75 mm, typically 0.5 to 50 mm.
  • Fibres generally have an aspect ratio (length to average diameter) of more than 6, in particular more than 10. Typically, the fibres have an average length of 0.1 to 150 mm, for example about 0.2 to 100 mm. As shown in Figure 7C, the length- weighted fibre length can be roughly in the range of 100 to 900 ⁇ .
  • the present apparatus for producing lignocellulosic fibrillar material from wood comprises a rotatable grinding wheel which has a rotation axis and exhibiting about the rotation axis a grinding surface which is capable of separating fibrillar material from wood by grinding effect.
  • the apparatus has a feeder for feeding raw wood material and for forcing it against the grinding surface during rotation of the grinding wheel.
  • the grinding surface of the grinding wheel has a surface profile which is serrated in the direction of the rotation axis.
  • the serration preferably comprises a pattern of surface features having oblique angle with respect to the rotation axis.
  • the feeder is typically arranged to apply a force to the raw material, the force being directed towards the rotation axis of the grinding wheel, i.e. at a normal angle with respect to the generally cylindrical shape of grinding wheel. If the raw material includes logs, the longitudinal axes of the logs are typically parallel to the axis of the grinding wheel according to the transversal grinding principle, whereby the serration alone produces the desired oblique grinding angle.
  • the serrated surface profile comprises one or more zones of similar surface features repeating on the grinding surface in the axial direction of the grinding wheel. Similarity of the features and periodicity of the profile is beneficial as concerns the initial forming and maintenance of the profile ("sharpening" of the wheel), and ensures production of even-quality fibrillar material.
  • the surface features have a cross-sectional form of isosceles triangles in a plane defined by the rotation axis and a radial direction of the grinding wheel. That is, the features rise as symmetric triangles with sides in the above-mentioned oblique angle with respect to the axial direction of the wheel. Put periodically, the whole surface therefore has "zigzag" profile.
  • the surface features comprise an equal amount of oblique surfaces towards both ends of the grinding wheel in order to cancel out reaction forces parallel to the rotation axis due to feeding of the raw material.
  • This embodiment minimized potentially harmful axial forces experienced by the grinding wheel, its shaft, bearings and rotation motor.
  • the abovementioned embodiment comprising periodic isosceles triangles can be made to satisfy this requirement but there are also other possibilities, as will be described later.
  • the feeder is adapted to feed the raw wood material against the grinding surface such that fiber orientation of the raw wood material is in the plane tangential to the grinding wheel, i.e., an imaginary cylinder placed around the grinding surface.
  • the oblique-angled surface features ensure that there is a radial angle between the wood fibers and the grinding surface.
  • there may be tangential angle which is defined by the relative orientation of the feeder and the wheel.
  • the tangential angle is preferably 0-45°.
  • the apparatus comprises a finger bar placed at a distance from the grinding wheel and having an edge towards the grinding wheel shaped to match the serrated surface profile of the grinding wheel.
  • the apparatus comprises a burr comprising a surface profile matching at least a portion of the serrated surface profile of the grinding wheel and means for pressing the burr against the grinding wheel for maintaining the serrated surface profile of the grinding wheel.
  • the raw wood material fed to the apparatus preferably comprises logs, in particular debarked logs.
  • the fine lignocellulosic fibrillar material produced using the principle of the invention has a percentage of Bauer McNett fraction F ⁇ 200 of at least 50 %. This kind of end material has been shown to be completely achievable using the present invention, contrary to any previous mechanical grinding method.
  • the serrated surface profile covers essentially the whole grinding surface, that is, at least the portion of the grinding wheel that the feeder is capable of feeding wood material to. In one embodiment, the profile covers the entire axial width of the grinding wheel. In one embodiment, the serrated surface profile covers at least a part of the grinding surface, preferably at least 50 % of the grinding surface, in particular essentially all the grinding surface, such as at least 90 % of the grinding surface.
  • the oblique angle is in the range of 5-75°, in particular 10- 45°.
  • the angle is preferably constant (but may incline in either axial direction, depending on the axial location), but may also vary so that the angle of at least portion, preferably all, of the profile is within one of the abovementioned ranges.
  • the grinding surface is made of ceramic material, in which case the oblique angle is preferably 5-60°, in particular 5-45°.
  • the grinding surface is made of metal, in which case the oblique angle is preferably steeper, that is, 60- 75°.
  • the feeder comprises means for adjusting the speed of feeding the raw wood material against the grinding surface and or means for adjusting the rotation speed of the grinding wheel.
  • the temperature prevailing at the grinding zone where the raw wood material meets the grinding surface means for adjusting grinding consistency and/or means for dosing chemical to the grinding zone and/or to the separated fibrillar material.
  • Figure 1 shows main parts of the present apparatus according to one embodiment.
  • the apparatus comprises a grinding wheel 10 and a feeder piston 18 for pressing logs 16 or other raw wood material against the grinding wheel 10 so that the fiber orientation of each log 16 is the same.
  • the feeder typically comprises walls (not shown) keeping the logs 16 in the desired position between the feeder piston 18 and the grinding wheel 10.
  • the grinding wheel is supported by a shaft 11 so that it is rotatable about its longitudinal axis 11.
  • the shaft 11 is connected to drive means (not shown) for rotating the grinding wheel 11.
  • the cylinder surface of the grinding wheel 10 is provided with serrated surface profile 12, in this case covering the whole cylinder surface.
  • the wheel 10 in the illustrated case has also rotational symmetry, i.e. the surface profile is independent of the radial angle of the wheel.
  • Fig. 2A shows the surface profile 22A of Fig. 1 in more detail on a grinding wheel 20A.
  • the profile 22A comprises a repeating pattern of surface features having a cross-sectional shape of isosceles triangles with constant ascent and descent angles a.
  • the features repeat one another so as to form an alternating pattern of ridges and grooves of similar geometry.
  • the period of the profile is denoted with L and height with H. This way, the whole surface is serrated and oblique in one or the other direction (excluding the optimally infinitesimally short ridge tops an groove bottoms).
  • transverse reaction forces during grinding cancel each other, as there is obliqueness equally much in both axial directions.
  • the angle a is preferably 5-75°, in particular 10-75°, typically 10-45°.
  • the period L may be for example 2-200 mm, in particular 5- 20 mm, and the height H for example 0.5-100 mm, in particular 1-20 mm.
  • Fig. 2B shows an alternative embodiment comprising on a grinding wheel 20B profile 22B with features having a cross-sectional shape of essentially right-angled triangles one after another so as to form slanted serration taking reminding sawtooth profile.
  • the profile preferably comprises triangles in both orientations so that axial reaction forces cancel out during grinding.
  • Fig. 2A preferably essentially the whole surface is profiled so that the whole surface is at an oblique angle with respect to the axial direction.
  • Fig. 2C shows still another variation of the surface profile on a grinding wheel 20C.
  • the profile 22C is otherwise similar to that of Fig. 2A, but comprises a variable angle in the oblique portions. It is, however, preferable that the angle does not fall below a certain minimum angle a is 5° so that there will not be surface portions which are nearly parallel with the wood fibers.
  • the half-period or period L of the profile may be for example 2-100 mm, in particular 5-30 mm, and the height H for example 1-100 mm, in particular 2-10 mm.
  • the diameter of the grinding wheel can be for example 20-300 cm and length 10-300 cm. It should be noted that the dimensions of the surface features are exaggerated in Figures 1 and 2A-C.
  • the surface profile may take also other forms than those discussed above and illustrated in the drawings within the scope of the invention.
  • the profile may also be a combination of two or more of the above examples.
  • the surface profile is independent on the radial angle. That is, there are no surface height variations in the circumferential direction of the grinding wheel.
  • the surface height is different depending on the radial angle of the grinding wheel. That is, there is a surface profile in the circumferential direction of the grinding wheel in addition to the axial profile discussed above.
  • a circumferential profile may bring additional advantages in terms of grinding speed or energy consumption, for example.
  • the serrated grinding wheels of the present kind suit for normal atmospheric or pressurized grinders, normal feeding method and normal raw material.
  • the wheels can be made from normal grinding stone materials (typically ceramics) and using normal stone conditioning. Change is needed only in a stone preparation ("sharpening") phase and optionally in the finger bar of the grinder.
  • Fig. 3 shows a potential finger bar arrangement with a serrated finger bar 39 having an edge profile matching with the serrated surface profile of the grinding wheel 32.
  • Figs. 4A and 4B illustrate alternative configurations for maintaining the surface profile of in particular ceramic grinding wheels 40, using one or more conical burrs 47A, 47B.
  • a flat burr travels continuously by the stone as in normal lathe.
  • the present concept according to Fig. 4A trues and sharpens the stone in stepwise and burring tool wide steps.
  • a burring tool 47 A having a surface profile matching with the desired surface feature geometry of the grinding wheel 40.
  • the burring tool 47 A is moved one period length at a time and engaged with the wheel 40 as it rotates about is axis 41 in order to true and sharpen one axial section of the wheel at a time.
  • the wheel gets the desired serrated profile.
  • This sharpening can be performed to a normal grinding stone and it can be conditioned with water jet as usual. Serrated sharpening has low costs and enable a wide range of angles.
  • a wide burring tool 47B which is capable of treating a larger surface or in this case the whole surface of the wheel 40 at one time.
  • a combination of the embodiments of The burring tool 47A, 47B can be for example a shaped (conical) roll or a blade. In case of a blade, the burring is carried out according to the lathe principle.
  • a serrated metallic wheel in particular steel wheel
  • grit impregnated steel can be used.
  • the serration is such wheel may be axially symmetric with respect to axial centre point of the wheel to cancel out transverse reaction forces due to the helical, screw-like, shape.
  • a correspondingly modified finger bar can also be provided.
  • a ceramic grinding wheel is preferred if the grinding angle a is 1-60°, in particular 5° - 45°, whereas a metallic, optionally serrated, grinding wheel is most suitable for high grinding angles a of 60° and more.
  • a quality optimum for strengthening purposes is around 15°.
  • a sharp stone is expected to provide good balance between energy consumption and amount of small particles.
  • the production of small particles is flexible regarding the log moisture and quality.
  • the feeding means may be arranged to produce pressure pulses on the raw material so as to improve bonding ability of the fibrillar fines produced.
  • the grinding process is carried out in the presence of water.
  • the water is provided to the grinding zone where the grinding wheel and the wood to be ground meet.
  • the water can be brought in the form of a shower directed to the wheel, to the raw wood material, or both (directly to the grinding zone).
  • the apparatus may additionally comprise means for adjusting environmental parameters of the grinding process.
  • the quality of the fibrillar material and/or the energy consumption of the process can be varied over a wide range with a given surface profile of the grinding wheel.
  • the mechanical properties e.g. strength, bulk
  • chemical properties e.g. binding capability
  • optical properties e.g. scattering properties
  • trade-off between binding capacity and light scattering properties can be controlled.
  • the ability to produce different grades of fibrillar material without having to change the massive grinding wheel has huge economic advantages.
  • the environmental parameters may comprise one or more of the following: feeding speed of the wood, tangential speed of the surface of the grinding wheel (i.e. peripheral speed), grinding temperature, grinding consistency, and chemical dosing to water shower directed to the grinding area (during treatment) and/or to the ground fibril mass (post treatment).
  • feeding speed of the wood tangential speed of the surface of the grinding wheel (i.e. peripheral speed)
  • grinding temperature i.e. grinding temperature
  • grinding consistency i.e. peripheral speed
  • the feeding speed may be variable e.g. between 0.1 and 10 mm/s, in particular 0.2 - 2 mm/s, or any subrange thereof.
  • means for adjusting the rotation speed of the grinding wheel for setting its peripheral speed to a desired value. Again, this adjustment can be achieved by directly controllable drive for rotating the wheel or by adjustable gearing between wheel and its drive. Higher rotational speed typically consumes slightly more energy but may again have positive impact on the chemical, mechanical and/or optical properties of the resulting fibrous mass.
  • the temperature of the wood material arriving at the grinding zone can be carried out by various techniques.
  • the raw wood material may be heated before it enters the grinding zone, a heated water shower may be directed to grinding zone, the grinding wheel can be heated, or pressure between the wood and the wheel can be adjusted to increase of decrease heat-producing friction.
  • Adjustment of the temperature of a water shower has proven to be a particularly effective and easily controllable way of reaching desired grinding temperatures in the range of 20 - 170 degrees Celsius.
  • the casing can be pressurized and this makes it possible to use higher shower water temperatures than in atmospheric grinding, as a means to prevent
  • means for adjusting the grinding consistency can comprise e.g. a changeable surface mesh of the grinding wheel.
  • means for adding chemical to the grinding zone or to the ground mass immediately after grinding For example, there may be provided an aqueous jet or shower directed at the grinding zone and adjustable dosing equipment for adding one or more chemicals to the aqueous jet or shower.
  • the one or more chemicals comprise alkaline peroxide, which is suitable both for application during grinding (to the grinding zone) and as a post treatment chemical (e.g. to a collector of the fibrillated material). In particular in the case of post treatment also other oxidizing chemicals and e.g. ozone treatment are effective.
  • Adjusting one or more of the abovementioned environmental parameters provides considerable advantages as concerns the variety of products the fibrillated mass, obtained from a single grinding apparatus, can be used in. For example, one can produce strong and well light scattering material for papers based on mechanical mass, decrease the amount of refining needed for TMP fibers, achieve chemimechanical grinding of hardwood for fine paper products and the like or an additive for improving the retention and strength of papers and cardboards. Additionally, the chemical compatibility of lignin-containing fibrous mass can be improved for composite materials.
  • Example 1 Effect of grinding angle
  • the following experimental data illustrate the effect on oblique-angled grinding on the resulting mass.
  • the data are obtained using a laboratory-size ceramic-wheel grinder, but similar results can be expected in industrial size grinders, if the angles grinder material and roughness are used. Measurement setup
  • Three spruce logs were cut to 34x34 mm blocks with various angles in relation to the axis of the logs.
  • Diameter of the grinding stone of the custom-built laboratory grinder used was 300 mm, with a grinding area of 35 mm both in length and in width.
  • the peripheral speed of the stone was 15 m/s, and the stone type was Norton A601-N5VG.
  • a water shower with water temperature between 60 °C and 68 °C was used, and the wood feeding rate was kept constant at 0.5 mm/s.
  • the fractional composition was determined with a Bauer-McNett apparatus (SCAN-CM 6) using the Tyler series: 28-mesh, 48-mesh, 100-mesh, and 200-mesh wires.
  • the pulp fibre lengths were measured by the Valmet FS300 fibre analyser and given as length- weighted averages.
  • the fines character was determined by measuring the specific sedimentation volume (Marton, R., and Robie, J.D. (1969). "Characterization of mechanical pulps by a settling technique". Tappi J. 52(12), 2400-2406; Heikkurinen, A., and Hattula, T. (1993). "Mechanical pulp fines - Characterization and implications for defibration mechanisms". 1993 Mechanical pulping Conference, Technical Association of the Norwegian Pulp and Paper Industry, Oslo, Norway, 294-308).
  • Macroscopic wood surfaces after grinding were captured by a photo camera using the macro tool with the closest possible distance to the samples.
  • grinding was found to be surprisingly sensitive to the wood and stone radial angle. If this angle differs from zero, the process starts to require more energy, produces shorter fibres and more fines. With radial angles higher than 30°, almost pure fines are produced. The radial angle largely determines the fibre length and the quality of fines. Thus, pulp composition and fines quality in grinding can be controlled by the wood alignment angle against the stone surface. Radial grinding with small angles (5-15°) leads to fatigue-based refining, in which the fibre structure is loosened by fatigue before the fibres are bent onto the surface. Pressure pulses produce fibrillar fines and fibres of good bonding ability. When the angle becomes bigger, the fibres are worn and crushed immediately on the surface into small particles with low bonding ability.
  • Figs. 8A-B and 9A-C and Table 2 illustrate results of experiments carried out to test the influence of adjustment of environmental parameters, in this case particularly the wood feed speed, temperature, peripheral speed of the stone and stone surface mesh on the energy consumption of grinding and resulting fines quality.
  • the experiments comprised grinding different woods (spruce, aspen and birch) using two different serrated wheel ("V-stone” with angle of 15 degrees) surface meshes ("Stone 1": 60 and "Stone 2": 70-open (70-open was sharper than 60 in this case), two different peripheral speeds (10 and 20 m/s) and two different temperatures (17 and 65 C) and different wood feed speeds (0.3-0.9 mm/s) in selected combinations and measuring the energy consumption (see Figs. 8A-B) and properties of products manufactured from the resulting fibrillar material (see Table 2 and Figs. 9A-C).
  • Fig. 8A illustrates the influence of stone sharpness and the feed speed on the energy consumption.
  • the feed speed is kept at a constant level of 0.5 mm/s (apart from two reference measurements with a V-stone and a flat stone).
  • Fig. 8B a strong dependence on the stone surface sharpness and wood feed speed of two different stones on energy consumption, also peripheral speed and temperature have noticeable effects on the energy consumption.
  • Table 2 shows that the properties, in particular tensile strength, light scattering properties, binding strength and air permeance can be varied over a wide range by changing the environmental parameters. Table 2. Properties of Spruce products obtained
  • V-fines 1 corresponds to “triangles” product (combined sample of all “triangles") of Fig. 8A, where dynamic drainage jar (DDJ)-fines content was 95%
  • V-fines 2 corresponds to "Spruce 70-20 m/s-65C" product of Fig. 8B, where Bauer McNett (BMcN)-fmes content was 87%.
  • Figs. 9A to 9C illustrate the effect of 15-angle serration and surface mesh on the fines content, light scattering coefficient and tensile index of the ground products, respectively, compared with that achievable with a flat stone (60 mesh).
  • Fig. 9A shows that with the serrated stones the fines content was considerably higher than that obtained with a flat stone with the same wood feed angle.
  • Fig. 9B shows that the light scattering coefficient was significantly lower, depending on the mesh.
  • Fig. 9C shows that the tensile index was higher with lower mesh value and vice versa.
  • the quality of the product can be changed with surface sharpness and production. Higher sharpness and higher production rate reduced energy consumption and strength properties but improved light scattering.
  • novel apparatus and method are suitable for use on an industrial scale for defibered pulp, in particular mechanical or semimechanical pulp.
  • the present technology is suitable for production of fine lignocellulosic particles.
  • This material may be utilized as large range in strength, bulk, and optical improvement agent. This will improve the economics.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Debarking, Splitting, And Disintegration Of Timber (AREA)

Abstract

L'invention concerne un appareil et un procédé de production de matière fibrillaire lignocellulosique à partir du bois. L'appareil comprend une meule rotative (10) ayant un axe de rotation et autour de l'axe de rotation une surface de meulage apte à séparer la matière fibrillaire du bois par effet de meulage, et un dispositif d'alimentation (18) permettant d'amener la matière de bois brut contre la surface de meulage pendant la rotation de la meule (10). Selon l'invention, la surface de meulage de la meule (10) comprend un profil de surface dentelé dans la direction de l'axe de rotation, la dentelure comprenant un motif de caractéristiques de surface présentant un angle oblique par rapport à l'axe de rotation. L'invention concerne un appareil efficace à l'échelle industrielle et un procédé de production de matière fibrillaire lignocellulosique présentant une forte proportion de particules fines.
PCT/FI2015/050591 2014-09-09 2015-09-09 Procédé et appareil de production de matière lignocellulosique fine Ceased WO2016038250A1 (fr)

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FI20145787A FI20145787A7 (fi) 2014-09-09 2014-09-09 Menetelmä ja laitteisto hienojakoisen lignoselluloosamateriaalin valmistamiseksi
FI20145787 2014-09-09

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1795064A (en) * 1929-04-12 1931-03-03 Oswego Board Corp Machine for producing wood pulp
GB422680A (en) * 1933-06-09 1935-01-16 Neyret Beylier Atel Improvements in apparatus for grinding, refining and hydrating fibrous substances
US3132815A (en) * 1961-07-24 1964-05-12 Karlstad Mekaniska Ab Grindstone for manufacture of wood pulp
US4560439A (en) * 1980-12-23 1985-12-24 Ranhagen Ernst G Method and grinder for the manufacture of pulp
US20020151263A1 (en) * 2001-03-30 2002-10-17 Fw Roberts Manufacturing Company, Inc. Burr for preparing a homogeneous pulpstone surface
DE102007018573A1 (de) * 2007-04-18 2008-10-23 Weima Maschinenbau Gmbh Messerrotor für eine Zerkleinerungsvorrichtung

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1795064A (en) * 1929-04-12 1931-03-03 Oswego Board Corp Machine for producing wood pulp
GB422680A (en) * 1933-06-09 1935-01-16 Neyret Beylier Atel Improvements in apparatus for grinding, refining and hydrating fibrous substances
US3132815A (en) * 1961-07-24 1964-05-12 Karlstad Mekaniska Ab Grindstone for manufacture of wood pulp
US4560439A (en) * 1980-12-23 1985-12-24 Ranhagen Ernst G Method and grinder for the manufacture of pulp
US20020151263A1 (en) * 2001-03-30 2002-10-17 Fw Roberts Manufacturing Company, Inc. Burr for preparing a homogeneous pulpstone surface
DE102007018573A1 (de) * 2007-04-18 2008-10-23 Weima Maschinenbau Gmbh Messerrotor für eine Zerkleinerungsvorrichtung

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