FI108052B - refiner - Google Patents

Description

108052

The present invention relates to a refiner segment for the production of mechanical pulp for the production of paper or board according to the preamble of claim 1.

The production of mechanical pulp by grinding requires large amounts of energy. Energy is consumed by the mechanical power of the refiner and by the steam used in the process. Electricity is used to rotate the refiner, and often the required steam is also produced with electrical energy, which results in high electrical energy consumption. During shaking, most of the energy is converted to steam. There are three main reasons for high energy consumption: 1) the whole process runs at a poor efficiency, so energy is converted into heat, 2) the heat generated due to the poor efficiency has to be removed. Cooling uses steam supplied to the refiner, which is generated by electrical energy and requires 20 naturally occurring energy to produce the steam, 3) steam is also used to transport the pulp of fiber in the refiner. Also the pressure and temperature in the refiner blades rise high, up to 7 bar (0.7 MPa), which forces the refiner and process to be sized to high forces. Pressure and temperature also affect fiber quality and physiology, and as the pressure increases, the brightness of the fiber decreases and the soluble (COD) content increases. The fiber distribution is also · »· V * difficult to control. The fibers have a long residence time in the refiner, which also indicates poor efficiency.

30 * *: * · *: The pulp used to make mechanical pulp consists of '. two refining discs disposed opposite each other.

»» «

The grinding surfaces of the discs are formed of interchangeable segments with grooves forming grinding teeth and: brushes. The second refiner disc has an opening in the center axis: ··· from which the material to be refined (wood chips) is fed to the refiner. The distance between the discs of the refiner is at its maximum in the center of the disks 2 108052 and decreases as it moves towards the periphery to gradually grind the material to be ground. The grooves and brushes of the refiner can be positioned parallel to the radius of the disc or at an oblique angle to the radius. The downward grooves with respect to the direction of rotation 5 reduce the need for energy and the upstream grooves respectively slow down the movement of the refiner discs.

The shape of the surfaces of the grinding discs has been considered to have an effect on the quality of the pulp being produced. The radial straight grooves increase the yield of the long fibers, since the fibers then separate from one another mainly by abrasion and rotation in the grooves. The straight groove refiner discs thus provide 15 long-fiber pulps for demanding paper grades. Correspondingly, the refiner discs with oblique grooves provide shorter fiber and finer pulp for high quality papers with good printing surface. In practice, the direction of the grooves does not necessarily have a substantial effect on the structure of the pulp fibers, but other factors determine the type of pulp obtained.

: 'Energy consumption of the radiator with radial grooves is very high. With a diagonal downward slope «·« · 25-mill refiner has lower energy consumption and • ·. ···. in it, the grooves produce a pumping effect that moves the fibers between the refiner discs towards the outer periphery. In this case, the amount of steam used to transport the fibers can be reduced and the energy consumption is reduced.

30 Thanks to the pumping effect, the pulp has a shorter residence time • · · * .V pi and a shorter residence time, lower pressure and heat • · · V: the lighter the pulp obtained.

«M ··. ···. U.S. Patent No. 5,362,003 discloses a milling segment in which the segment is radially * ··· * diverged by at least two rings, and within each circumference the angle of the milling fins '· *' · with respect to the radius is different. In the inner ring 3 108052 the angle of the refiner grooves relative to the beam is quite large and in the outer ring the angle is close to the beam direction. In this way, the pumping effect is achieved on the inner periphery and the energy consumption is reduced.

It is an object of the present invention to provide a refiner segment by which the amount of energy required to produce mechanical pulp can be substantially reduced.

The invention is based on the fact that the grooves and brushes of at least the outermost refiner segment are formed by continuous arcs in the direction of rotation of the refiner ring.

According to a preferred embodiment of the invention, the segment is divided into two or more parts. Specifically, the refining segment according to the invention is characterized by what is stated in the characterizing part of claim 1 of claim 20.

The invention provides considerable advantages.

I <I

The main advantage of the invention is the significant reduction in the energy consumption 4 I 4 i 25. Up to 15% have been achieved in tests performed. ** ·. lower specific energy consumption in the first-stage refiner, so if the invention is applied to all refining stages, the savings achieved will increase accordingly. If the refiner continues to use the two-stage 30 turbine-like refiner segments, the radial of the pulp • 1 ·. · · · · · · · · · · · · · · · · · · · · Acceleration can be further increased, thus further reducing energy consumption. The retention time of the pulp in the refiner ··· decreases as the radial acceleration increases, thus reducing the amount of conveying transport vapor and, at the same time, decreasing the brightness decrease as the amount of solutes. The pressure and * 1 1 · temperature in the refiner also decrease. has a direct effect on pulp brightness and energy consumption, the required shaft power and refiner strength calculations, so that the refiner segment of the present invention can be designed with less load. The continuous arc-shaped teeth provide substantially greater pumping effect than Further, according to the invention, the pumping effect is sought to be transmitted to the outer or outer grinding rings of the refiner which have a higher speed of movement than the center of the refiner ring and thus the pumping action of the teeth 10 is greater.

The invention will now be explained in more detail with reference to the accompanying drawings.

Figure 1 shows one embodiment of the invention from above.

Figure 2 shows the embodiment of Figure 1 in cross-section.

Figures 1 and 2 illustrate a refiner segment corresponding to a portion of the refiner ring circle. The milling ring is assembled from such segments by forming a complete circle. The segment is bounded by V .: thus the outer periphery of the circle 11, the inner ·: · the periphery 12 of the smaller circle and these edges connect the straight edges 13 of the radius of the circle.

• I

. ** ·. The segments are fixed in place by screws screwed into the • · · screw holes in the refiner.

The segment shown in Figures 1 and 2 consists of two wedges 1, 2, the inside of which is a large-toothed grinding ring • t · * · '· * 1 and an outer smaller-toothed actual grinding ring 1.

• · · * The grinding ring 1 is narrower than the grinding ring 2, so ··· the residence time of the wood and pulp to be milled is smaller. he 1 in area is shorter than in area 2 of refiner.

\ 35 The teeth of the chopping ring 3 are quite large and shaped from single teeth to saw-like for efficient chopping of wood chips. Each tooth 3 is formed in the shape of an arc of a frustum 108052 image so that the inside of the arc points in the direction of rotation of the refiner. The position of the arc relative to the radius 4 of the refining ring changes outwardly in the radial direction so that the arc turns in the direction of the radius 7. In other words, the angle of the tangent to the radius decreases. With this design, the pulp to be comminuted is provided with an initial radial velocity which effectively transfers the pulp to the grinding ring 2 while the teeth work like the pump blades. On the other hand, the shape of the arc of the teeth is 10 in the opposite direction of rotation, i.e., the shape of the tooth resists rotational motion. However, since the inner periphery 1 has a minimum peripheral velocity and a torque arm relative to the refiner axis, the energy consumption caused by such tooth design is not high. However, a higher pulverized pulp peripheral speed results in greater energy savings.

Following the inner ring 1 is followed by a spacer 6 which serves to guide the material to be milled to the outer ring 2.

20

In the outer circumference, i.e., the grinding ring 2, the direction of the arc of the teeth is rotated in a forward direction with respect to the direction of rotation, and the direction of the arc relative to the radius 7 becomes steeper when moving towards the outer circumference. Thus, the tangent angle of the teeth 25 of the grinding ring 2 with respect to the radius 7 increases as ♦ ·. ···. moving farther from the center of the milling ring. At the periphery of the segment · · ·, the arc of the tooth 4 is already almost perpendicular to the radius. In this way, a high radial velocity can be given to the mass coming from the grinding ring. . 30 because the curved teeth 4 throw and push the pulp between the grinding fins due to their shape in the direction of the radius ··· * .1 1 outwards. This design of the tooth reduces ··· energy consumption because the teeth 4 are oriented * «· ·. '· 1. in the direction of rotation of the device and • · · ·. 35 the velocity of the pulp to be treated increases radially,

• I I

The · · 1 delay time is reduced and less steam is required to transport the pulp in the refiner. For these reasons, too, the amount of energy required to process a certain amount of pulp 6 108052 is reduced. In this example, the outer periphery is formed of two rows of tooths of different curvature, but it can equally well be formed of a single toothed row of which the curvature 5 and the change in curvature are suitably selected.

The thickness and height of both first and second peripheral teeth are reduced when moving in the peripheral direction. At the same time, the clearance between the refiner rings is also reduced. The clearance between the teeth of the opposing rings of the refiner 10 may be, for example, 5 mm at the inner edge of the refiner segment and 1-2 mm at the outer periphery.

Thus, the segment and its surface to which the teeth are attached become wedge-shaped as seen in Figure 2. The purpose of the tapered taper clearance and the decreasing height of the teeth 3, 15 4 is to provide a gradual comminution of the material to be treated as it moves towards the periphery. The groove 5 between the teeth 4 of the grinding ring 2 narrows and lowers as it moves towards the outer ring, while the width 20 of the groove 8 between the teeth of the grinding ring 1 remains the same as the depth of the groove decreases. The inner surface 9 of the teeth 3 of the grinding ring 1, i.e. the surface pointing in the direction of rotation, may be outwardly inclined, and the teeth 3 may be provided with notches which divide the tooth into sections. The oblique surface and the knife feed V between the teeth: 25 substances out of the gap 8 between the teeth 3, whereupon the · ·· material is again subjected to grinding.

In a tooth arrangement according to the invention, the flow in the radial direction functions like a flow in a multi-stage turbine.

3 0 The flow from the first ring 1 (phase) hits • · «I.I, guided by the teeth 3 through the spacer 6, to the second ring 2 • · · *. to the reaction flange formed by the teeth 4, whereby the kinetic energy of the flow pushes the teeth of the second ring 2 · · ·: << t! the effect of the refining ring in the direction of rotation and the refiner. 35 the energy required to operate. A similar effect can be achieved if several internal refiner • • segments are used in which flow is controlled in a similar manner. However, in this case, there must be a fixed guide vane or dentition between the rotating segments so that the direction of the reaction flow is the same as the direction of rotation of the flour.

5

In addition to the above, the present invention has other embodiments.

The defining arc of the teeth of the dentition and the grooves between them may vary. However, it is essential that the teeth of the outermost periphery are directed in a forward direction so as to provide a high radial velocity, while also braking as little rotation as possible. It is also advantageous to form the outermost teeth based on a continuous arc, since the breaks sometimes arc to cut off the flow and cause unnecessary turbulence. However, the shape of the arc may change, for example, so that the teeth of the same circumference are formed by successive arcs of different shapes which are seamlessly connected in succession.

*

(I

<<

I I I

I {> <(• • • • • • • • • • • • • • •

• M

* · ·•••••••••••• <<*

MM

«* ·

• I

• · • • t * * • * * I * <»4 · • •»

Claims (7)

8 108052 A refiner segment for forming a refining ring for treating and refining a raw material containing fibrous material for the production of paper and board comprising: a refining surface forming a circular portion defined by an outer circumferential edge formed by an arc 10 (11) and an inner smaller circumferential portion; this edge (12) and these edges connecting the straight edges (13) in the radial direction of the circle, - the teeth (3, 4) formed on the grinding surface and the grooves (5, 8) between the teeth, - at least one circumference of the teeth (3, 4) (2) for grinding the material, and 20. means for attaching the refiner segment to the periphery of the refiner, characterized in that the teeth (4) of the at least one periphery (2) are formed at least. a single continuous arc, directed · · · c in the direction of rotation of the milling rim and having a tangent and a segment of the arcs the angle between the beam (7) increases as the outer edge 30 moves. 4 4 *, • 4 <f'f> j Segment according to Claim 1, characterized in that the teeth of the at least one circumference are formed by arcs whose angle between the tangent and the radius of the refiner segment (7) decreases towards the outer edge. so that the arc turns towards the beam direction. A segment according to claim 1, characterized in that the segment comprises two nested rings (1, 2). Segment according to Claim 3, characterized in that the outer peripheral teeth (4) are formed by at least one continuous arc 10 which is directed downwardly with respect to the rotation of the refining periphery so as to provide a radial velocity towards the outer edge (11) of the segment. The segment according to claim 4, characterized in that the teeth (3, 4) of the inner periphery (1) and the outer periphery (2) are arranged such that the teeth (3) of the inner periphery direct the flow of the teeth (4) of the outer periphery. ) inside the arc to form a reaction flow similar to that of a multi-stage turbine. 20V Segment according to claim 1, characterized in that the teeth of at least one circumference are formed by a continuous continuous arc. • I 4 I · «(« «« • « A segment according to claim 1, characterized in that the teeth of at least one circumference are formed by at least two successive interconnected ... shapes of different shapes. «Φ · • · · · · · · * * · · t t t t t t t t t t t. * m • · IM 10 1 08052