FI62369B - METHODS FOR APPARATUS FOR CONTROL OF CENTRIFUGAL EQUIPMENT INVERKAN PAO MAELDEN I MASSAFIBRERINGSAPPARATEN - Google Patents

Description

-------- rftl ANNOUNCEMENT / -07 ^ 0 [B] C ^) UTLAGG NI NGSSKRI FT 623 69 'S (51) Kv.lk.Wci.3 D 21 D 1/38 FINLAND —FINLAND (21 ) Pwunttlhtlwwi · - P * t «rtanaMcn <n (790 ^ 00 (22) Hakamitpilvi - AnaSkntngadi · 15-02.79 (23) Okupflvi — GlfclghMadtf 15-02.79 (41) Tullut | ulklMkal - Blhrtt offuntllg 18.08.79

National Board of Patents and Registration · / 44) NUrttvik * lp «non |« Monthly date— 31.08.82

Patent- OCh regi * ter * tyrelκη Anadfcan utlafd och ittl. »Krlft * n publlctrud (32) (33) (31) PjT ^ utty utuolkMis— Bugird priorltet 17.02.78 USA (US) 878557 (71) (72) Rolf Bertil Reinhall, ·. 83U, 171 Place NE, Bellevue, Washington 98008, USA (7 * 0 Oy Kolster Ab (5 * 0 Method and apparatus for adjusting the effect of centrifugal force on a pulp in a pulp defibrator - Method and apparatus for controlling the centrifugal force of inverted head i massafibreringsapparaten

In the grinding process, for which the grinding discs according to the invention are particularly well suited, the pulp is ground in a grinding space formed between two circular discs which rotate relative to each other in a fluid medium. Each plate comprises plate segments which are annular around the plates and have burrs and grooves which are approximately radial and which cut the pulp fibers in a manner similar to grinding. A screw feeder or the like feeds a pulp, which may consist of wood chips, bagasse, pulp or the like, through an opening in the center of the fixed grinding disc into the "eye" of the grinding chamber, where it is driven by the centrifugal force of the discs to their perimeter. to the surrounding housing.

2

In order to develop the required centrifugal force to accelerate the stock radially outwards from the inner center of the grinding chamber and to achieve the desired degree of defibering and operating power in the grinding chamber, the plates must be given a high rotational speed, e.g. in the order of 1500-3600 rpm. However, the relatively large centrifugal force provided, which is necessary to accelerate the fusion from the inner plate part and which determines the power of the device, at the same time applies a gradually increasing centrifugal force to the pulp as it travels radially outwards towards the outer part of the plate. This increased centrifugal force accelerates the speed of the pulp as it travels radially outward to such an extent that, unless special measures are taken to hold the pulp in the outer part of the plate, the pulp is unloaded prematurely from the grinding space only in a partially treated state. This problem is further exacerbated when steam or other gas is evolved during grinding work as a result of high input power or dryness of the stock. In this case, steam or other gas flows outwards with the stock through the grinding space between the plates and further accelerates the radial flow of the stock. Since the centrifugal acceleration on the pulp is proportional to the diameter of the plate and the square of the plate speed according to Newton's law of force and motion, the larger the diameter of the plate in the device, the greater the problem of controlling the flow of the pulp through the outer grinding chamber. Depending on the application and the power required, the normal diameter of the plate in the grinders currently used is in the range of 508-1625.6 mm. Even if the larger diameter plates were rotated at relatively low speeds in the range of 900-1800 rpm, they still produce an accelerating centrifugal force on the stock in the order of 700-2800 g. Assuming, for example, that the plate rotates at 900 rpm and develops a centrifugal force of 700 g, then if the speed were increased to 1800 rpm, the centrifugal force would increase by a factor of 4, giving an evolving, increased centrifugal force of 2800 g.

Although large diameter sheets are desirable in terms of power, they require a lot of energy, which is partly wasted due to their high circumferential speed and thus increased centrifugal force, making the peripheral part of the grinding chamber substantially inefficient for fiberization purposes. In addition, the high circumferential speed of these large plates causes a serious noise problem.

Due to the growing need for high throughput fiberization equipment with sufficient grinding power, it has proven problematic in the industry to control the radial movement of the stock between the outer portions of the opposing segments of the grinding sheets to achieve maximum performance. It is to be understood that as the pulp advances through the radial channel, it alternates between the abrasive segments of the opposing plates and the more pulp is processed in one treatment, i. the longer the residence time in the grinding space, the more efficient and economical the grinding process. If the flow of the stock is not slowed down appropriately, the movement of the pulp will proceed rapidly, as explained herein, and the defibering operation will be impaired. In the past, attempts have been made to slow down the movement of the stock through the grinding space by arranging the burrs and grooves in the grinding segments so that they can also act as a flow retarder. Examples of these companies are the applicant's patents No. 3,674,217, Dvm. 4.7. 1972 and 3,974,471, dated. 08/17/1976; and U.S. Patent No. 3,040,997, issued to Donald A. Borden on June 26, 1962, U.S. Patent No. 3,125,306 to E. Collberg et al., and U.S. Patent No. 1,091,654 to Hamache.

Although these burrs and grooves act as a flow retarder, they still do not utilize the entire working area of the grinding chamber because the grooves or channels between the burrs are spread out over a larger area at the circumference of the grinding chamber than at its interior. Besides, they do not solve the problem of the circumferential speed of the large-diameter plates used today.

Another example of an attempt to solve a flow control problem is co-filed in Application No. 713,433, filed August 11, 1976 in the name of Bo A. Ahrel, now Patent No. The main object of the present invention is to solve the problem of high-pressure steam in the circumferential region of the grinding chamber. To prevent very fast steam from blowing the partially defibered pulp out of the circumferential grinding area, Ahrel has used centrifugal force to separate the steam and open the escape route to the steam, while the steam-free pulp is held between opposite grindings.

4,6269

Other examples of prior practice include U.S. Patent Nos. 1,098,325, 1,226,032, 3,684,200, and 3,845,909; and British Patent No. 1,848,569, German Patent No. 1,217,754 and Swedish Patent No. 187,564.

Po. It is a main object of the invention to provide a method and apparatus for controlling the effect of centrifugal force on a pulp as it passes through an abrasive space formed between opposite abrasive segments of abrasive discs, utilizing the entire abrasive space without special additional retention means. during transit through the grinding chamber.

Another object is to develop two grinding wheels with the smallest possible diameter and which form a longer grinding space.

In addition, it is an object to develop two grinding discs which form a grinding space for controlling the flow rate of the stock through the space and for controlling the discharge by further adjusting the effect of the centrifugal force on the outside of the grinding space.

In addition, the aim is to prevent energy losses due to steam and other fluids escaping from the grinding chamber.

The invention relates to two grinding discs forming a grinding space comprising an outer zone extending at an angle to the inner radial zone from a point radially spaced from the center. The degree of angle or inclination can be calculated according to the size of the grinding wheels and the residence time required for the best grinding performance. In the internal radial zone, the centrifugal force is used as much as possible to increase the acceleration force acting on the stock to move the stock continuously away from the inlet or "eye" of the grinding chamber. In the outer zone, on the other hand, the centrifugal force is divided into a radial vector force and an axial force kt, which reduces the acceleration force in the outflow direction and at the same time prolongs the residence time in the grinding space, resulting in each zone being utilized for best grinding power. By making the outer zone e.g. cylindrical, i.e. so that the outer zone zone extends at an angle of 90 ° to the radial zone, the radial and axial vector forces are combined into a single vector parallel to the plane of the radial zone, which substantially neutralizes the effect of the centrifugal force on the outflowing stock. If, on the other hand, the angle is more than 90 °, i.e. blunt, is the direction of the central exhaust vector forces opposite to that of the outflow. Although the magnitude of the angle is not critical to the invention, the 45-90 ° range can be considered suitable for most practical applications, depending on the size and power of the defibering device. However, as shown herein, the angle of the sloping portion and its junction at a radial distance from the center relative to the equipment used and the material to be treated must be calculated so as to maintain the stock in an environment of steam or other fluid throughout the grinding space.

If necessary, according to the invention, the effect of the centrifugal force on the pulp in the outer, inclined grinding zone can also be adjusted by changing the angle between the myriads and grooves of the opposite plate segments relative to the base line of the grinding space.

As used herein, the term "inclined" means any angle between a blunt and a sharp angle, including a right angle.

In the drawings: Fig. 1 shows a vertical section of a part of a defibering device according to the invention? Fig. 2 shows a schematic view of the grinding space formed between the fixed plate and the rotating plate; Fig. 3 shows a fragmentary bottom view of the grinding segment in the outer grinding zone, showing a part of the grinding surface with burrs and grooves; Figures 4 and 5 schematically show two alternative arrangements of the grinding chamber; Fig. 6A shows a schematic view showing the outer, frustoconical grinding space in a non-accelerating flow mode and at the same time a perspective view of the outer, fixed grinding wheel; and Fig. 6B shows a vector diagram thereof showing the effect of burrs and grooves on the stock? Fig. 7A is a view similar to Fig. 6A showing the outer grinding space in the flow accelerating state; and Fig. 7B shows a vector diagram thereof; Fig. 8A shows a conical grinding state in a flow retarding state; and Fig. 8B shows a vector diagram thereof; and 6 62369 Fig. 9 shows a fragmentary sectional view of a rotary grinding wheel according to the invention.

In Fig. 1, reference numeral 10 denotes a housing having a rotating plate and a fixed plate, indicated by the corresponding general reference numerals 12 and 14. The rotating plate is mounted on a shaft 16 mounted on a frame 18 of the device in the usual manner shown in e.g. No. 3 212 271. The opposite surfaces of the discs are provided with standard abrasive segments 20, 22, 24 and resp. 26, 28 and 30, as shown, e.g., in U.S. Patent No. 3,974,491, form a grinding space 32 therebetween. The grinding space comprises an inner zone or a primary grinding zone extending radially outward substantially perpendicular to the plane of the axis of rotation. The raw material, e.g., wood chips, which have been treated with steam in the usual manner and preheated in a steam vessel (as shown, e.g., in U.S. Patent No. 4,030,969), is fed into the central opening of the solid plate 14, which forms an outlet zone or " an eye "37 in a tube portion 36 connected to the frame 10. From the" eye "37, the centrifugal force generated by the rotational movement of the plate 12 accelerates the steam-treated chips or the like radially outward.

The abrasive segments 20, 22 and 24 on the rotating plate 12 are removably mounted in the usual manner, as shown in Figure 9, on a bracket 38 attached to a shaft 16 as shown, e.g., in U.S. Patent No. 3,827,644. , which translates the substance in the "eye" 37 into a radial portion of the grinding chamber 32. The clearance of the fixed plate 14 and the rotating plate 12 can be adjusted in the usual manner by an adjusting mechanism 44, as also shown in said U.S. Patent No. 3,827,644.

The device part 18 includes conventional bearing neck and bearing parts and a servomotor mechanism, indicated by reference numeral 19, as described in U.S. Patent No. 3,212,721, referred to above, and need not be described further herein because they do not form part invention.

According to the invention, the radial grinding zone 32 coincides with an inclined, outer grinding zone 46 which, in the embodiment of Figures 1-3, extends at an obtuse angle to the radial or primary grinding zone, thus forming a combined abrasive space having a frustoconical shape in the example shown. An outer or secondary grinding zone is formed between an annular portion 48 removably mounted on the rotating plate segment support 38 as shown in Fig. 9 and an annular portion 50, the latter being mounted on the bottom of the fixed plate 14. The ring portion 50 has an inner surface 52 separated from the outer surface 54 of the rotating ring portion 48 around it. The annular portion 50 of the fixed plate is axially adjustable so that the width of the grinding space 46 between the grinding surfaces 52 and 54 can be adjusted. For this purpose, the annular portion 50 is slidably disposed in a cylindrical annular cavity 56 in a fixed base and is driven by pistons 58 mounted to reciprocate in the cylinder 60 and spaced apart along the circumference of the cavity 56. The pistons are connected to the ring portion 50 by piston rods 62.

The ring portion 50 can be moved toward the rotating ring portion 48 by supplying hydraulic fluid to the outer portion of the chamber 64 to narrow the space 46. In contrast, the supply of fluid to the opposite end of the pistons in the chamber 66 expands the space. The hydraulic fluid moving the pistons 58 is pumped from the reservoir 68 through lines 74, 76 by means of a pump 70 and a reversing valve 72. The hydraulic fluid is returned to the reservoir 68 via line 78.

The cams 80 are positioned on the outer wall of the piston cylinders so as to extend into the chamber 64 and contact the piston 58. These cams carry a drive wheel 82 which is driven by a motor 84 via a transmission belt 86. With this drive mechanism, the cam can be adjusted axially to form a stop for the pistons and thus to ensure the width of the grinding space 46.

Between the two abrasive zones 32 and 46 there is an expanded annular space 88 into which a cooling and / or chemically reactive liquid, e.g. water with or without selected chemicals, can be fed through a channel 90 and a pressure pipe 92 in the fixed ring portion 50. The space 94 at the rear of the ring portion 50 communicates with the tube 96 to allow pressure medium, e.g., water, to pass through and thus maintain a higher pressure in the space 94 than the grinding space 46, forcing a weak flow of pressure medium into the ring cavity 56 to prevent powdered pulp from penetrating the ring portion 59 and the cavity. 56 between sliding surfaces.

According to the invention, the grinding chamber 46 extends at an angle to the vertical plane 98 of the inner grinding chamber 32. This angle may vary depending on the equipment and material to be ground and must be calculated so that the centrifugal force acting on the pulp is sufficiently slowed inside throughout the time it passes through the combined grinding zones. Thus, the angle can also be kept equal to the adjustable outlet valve, which controls the speed at which the defibered pulp exits the grinding housing. However, experiments have shown that the best results are obtained if the angle is more than 45 °, and preferably more than 60 °. However, particularly good results have been obtained with angles in the range of 75-82 °.

In the inner radial grinding zone 32, the centrifugal force accelerates the stock from the "eye" 37 radially outward at a substantially constant flow rate due to the deceleration effect produced by the sharp "bend" of the channel at the point where the secondary grinding zone coincides with the primary radial zone. Thus, the rotational speed of the plates can be increased, which improves the fiberization efficiency, despite the increasing centrifugal force. As explained above, this centrifugal force is important to accelerate the stock through the interior of the radial channel, but unless properly decelerated or controlled, it causes the partially treated stock to be blown out at the periphery of conventional sheets used heretofore. Therefore, this partial elimination or complete deceleration of the effect of the centrifugal force on the stock in the peripheral zone of the grinding space where this force is not required is po. a major achievement of the invention.

To shed light on the above problem, it should be explained that although a high rotational speed of the plates is desirable not only to accelerate the stock but also to develop high frictional stresses in the grinding space to achieve sufficient fiberization and fiber separation, high rotational speeds, e.g. 900-1800 rpm, require or even e.g. 3600 rpm, 9 62369 a large amount of energy which is converted into high heat in the grinding mode. Therefore, water or other flowable coolants must be added to the grinding process to prevent charring or heat degrading of the stock. These coolants evaporate, at least in part, in the grinding space, causing them to expand and develop a high pressure, which increases the centrifugal acceleration of the stock when steam or other gas is blown out through the grinding space at the circumference of conventional grinding wheels. Because defibering or grinding is usually performed in an environment of steam or other fluid, wasting a lot of steam or other liquid medium, resulting in high energy losses. Po. the invention largely avoids these energy losses.

When the pulp is subjected to initial fiberization in the primary or radiation zone under the back pressure of the centrifugal force braked, it enters the outer, i.e. secondary grinding zone 46, whereby the Sulo wood is subjected to a substantially lower acceleration force. In this way, the centrifugal force, which increases in relation to the radial length of the grinding space, is compensated, resulting in a slowed flow rate and a longer residence time of the pulp in the grinding space. The centrifugal force on the stock has a tractor perpendicular to the baseline of the space 46, which force is applied against the fixed grinding wheel 14 or its adjustable ring part 50, and the force vector in the flow direction forms only a relatively small part of the centrifugal force.

Due to its inclination with respect to the plane 98 of the radial grinding space, very small adjustments can be made in the width of the grinding space 46 with respect to the relatively large displacements of the ring part 50.

Figure 3 shows a portion of the grinding surface 54 of a plate segment in an outer grinding zone with burrs or dams 100 and intermediate grooves or channels 102 which may be interrupted by transverse bursts 104 forming mechanical stops for pulp flow. The grinding surface 52 of the fixed segment is provided with similar burrs and grooves. Thus, the movement of the pulp, while the pulp is forced outward in the inclined grinding space, is alternately stopped by the transverse bursts 104 of the second grinding segment and rolled into the grooves of the opposite segment, so that the pulp alternately moves between two to the interior 106, which minimizes the separation of steam or other fluid from the stock.

The segments in the grinding space 32 can be provided with similar burrs and grooves.

The raw material fed to the "eye" of the grinding chamber of the screw feeder 34 is usually preheated or pretreated with steam and has a dry matter content of at least about 15-20%. As described above, water or other coolant is fed through lines 92, through which chemicals, such as oxidizing or reducing agents, can also be added, as well as adjusting the pH of the stock and adding lignin degrading compounds. Due to the high circumferential velocity prevailing in this range, the space can also be used to mix gas mixtures with the treated mass, e.g. SC, sn, oxygen, ozone and the like gases which can be used in grinding.

The fully fiberized stock is discharged into the interior 106 of the housing, to which it is subjected to a vortex motion and from which it is removed via a line 108. The discharge rate is controlled by the discharge valve 110 so that a predetermined pressure is maintained in the grinding wheel housing. In so-called thermo-mechanical pulping, the temperature in the grinding chamber must be in the range of 100-160 ° C, depending on the residence time in the grinding chamber, and the water addition must be calculated to obtain a corresponding vapor pressure in the grinding chamber, which may not be the same as the surrounding plate.

Due to their weight, the high speed of the abrasive segments 20, 22 and 24 also develops a considerable centrifugal torque in the direction of the outwardly rotating plate and applies torque to the support plate 38, which tends to rotate or bend this circumferentially to the right in Figure 1. the width varies along a sloping path. By providing the support portion 38 with an annular portion 48 extending axially away from the support plate away from the abrasive segments, the torque can be balanced to maintain a uniform clearance between the segments. To this end, the center of gravity of the rotating plate segments 46 11 62369 of the inclined grinding zone is in a central plane extending through the support plate 38 as shown in Fig. 9.

According to Fig. 4, the outer grinding belt is divided into two parts: an inner part 111 which is inclined with respect to the plane 98 at an acute angle ^1; and an outer part 112 which is cylindrical and therefore forms an angle of 90 ° with respect to the plane 98. The angle of the inner part 111 should preferably be more than 45 °. In the outer part 112, the centrifugal force is neutralized by the fixed plate, and the inner part 111 completely adjusts the flow rate.

In the embodiment shown in Fig. 5, the outer grinding zone 46 comprises a portion 111 and a portion 114 having inclination angles <* - 1 and 1, respectively. Qe.3 are sharp and blunt, respectively. Thus, the acute angle ^3 is preferably less than 90 ° and greater than 45 °, and the obtuse angle *3 is preferably greater than 90 °, so that the pressure is forced out by the pressure generated in the inner zones against the tangential vector of centrifugal force.

Figures 6A, 6B, 7A, 7B, 8A and 8B show how the effect of the centrifugal force can be further adjusted in the outer, inclined part of the grinding chamber. In Figs. 6B, 7B and 8B, the center line of the grooves of the fixed plate is drawn in solid lines, while the center line of the grooves of the rotating plate is drawn in broken lines. The arrows on the left in the drawing indicate the direction of rotation.

In Figs. 6A and 6B, the center line of the grooves of the two opposite segments is aligned with the base line of the grinding surface, so that it does not accelerate or decelerate the flow.

Figures 7A and 7B show how the angle of the burrs and grooves of the opposite abrasive segments can be changed relative to the baseline of the abrasive space to accelerate the flow of pulp in the frustoconical abrasive space toward the discharge opening and thus increase the centrifugal force effect. Figures 8A and 8B show the angle between the burrs and grooves of the opposite abrasive segments with respect to the baseline of the frustoconical abrasive space in the flow retarding state.

The plate segments selected to obtain the desired flow rate can be replaced in the defibrillator fairly quickly in the same conventional manner as worn or damaged segments are replaced.

12 62369

The purpose of grinding is to defiber the raw material with as little damage as possible and to achieve this. the quality required for end use. In this context, it is very important that power is as high as possible and energy consumption is kept to a minimum in order to keep production costs low. There are many variables in the pulp that require fairly rapid adjustment as the pulp passes through the grinding space. These variables include: various raw materials; The moisture content; the length of the grinding zone; grinding wheel rotation speed; and energy transmission efficiency. Most of these variables can be effectively addressed by adjusting the load or grinding pressure in the grinding space.

The system according to the invention forms a very efficient and flexible means of influencing the result of grinding work. By dividing the grinding space into two zones, namely a radial zone, in which the grinding pressure can be increased under the influence of the centrifugal force generated by the rotational movement of the plates; and as a sloping zone coinciding with the radial zone at a calculated radial distance from its central interior, the grinding pressure can be reduced, if desired, and the flow rate of the stock can be adjusted by changing the effect of centrifugal force in the sloping zone. The angle of inclination can be easily calculated so that the grinding space becomes fully utilized for its entire length, while the stock is kept in a fluid medium throughout the transit.

The invention increases the flexibility of the control method by changing the angle between the burrs and grooves of the opposite grinding segments in the outer zone relative to the base line of the grinding space.

If, during pulping, the angle of the sloping outer grinding space does not respond properly to the raw material being processed, the plate size used, the feed force, or other variables, corrections can be made by changing the plate segments in the outer grinding zone without replacing the entire rotating plate. In addition, the invention allows small adjustments in the width of the inclined grinding chamber during pulping without stopping the operation.

The defibering devices to which the invention can be applied usually include devices which provide complete information on the state of pulping, such as load and grinding pressure, pulp consumption rate, cooling water demand and other variables, 13 62369 which affect the grinding process so that fairly quick adjustments can be made according to the invention. using. These devices are conventional in the art and do not form any part of the invention, so they do not require a description.

It is, of course, clear that although the inner plate is described as a rotating plate and the outer plate as a fixed plate, the outer plate may rotate and the inner plate may be fixed, or both may rotate relative to each other within the scope of the invention. It is obvious to a person skilled in the art to make such modifications.

Claims (9)

14 62369 A grinding device for a fibrous, preferably lignocellulosic, material provided with rotating grinding members having opposite surfaces delimiting a slot having grooves and grooves in the walls for processing the material and projecting in the radial inner zone (32) substantially in a plane perpendicular to the plane , characterized in that the refining means also have a radially outer refiner zone (46) extending in the axial direction, the base lines forming an angle towards the inner zone so large that the centrifugal force is conveyed out of the inner zone at substantially full power. the material is braked and thus the residence time in the outer zone increases due to the fact that the component acting perpendicular to the base line of the centrifugal force is larger than the component acting in the direction of the base line, whereby the radially outer component of the outer refining zone is already the grinding surface is formed on the fixed grinding member (50) and the opposing radially inner grinding surface on the rotating grinding member (48), wherein the grinding members (12, 46; 14, 48) which delimit both refining zones are adapted to be individually mounted for separate adjustment of the slit width in the inner and outer zones. Grinding device according to Claim 1, characterized in that the outer grinding slot forms an angle with the base lines in a plane perpendicular to the axis of rotation which is greater than 60 ° and preferably up to 75 ° -82 °. A refining device according to claim 1 or 2, characterized in that the outer refining slot has an outer part which is substantially cylindrical (112, Fig. 4) or tilts inwards towards the axis of rotation (114, Fig. 5). Grinding device according to Claim 1 or 2, characterized in that the fixed, annular grinding element (50) can be moved relative to the other grinding elements with grinding surfaces by means of a pressure element (58) for individually adjusting the size of the outer grinding gap (46). Grinding device according to one of the preceding claims, characterized in that ridges is provided with ridges is 62369 and grooves on the grinding surfaces of the inclined outer grinding zone (46), which are further adapted to control the effect of centrifugal force on the pulp and thus its flow rate through the grinding slot. Grinding device according to claim 5, characterized in that the ridges and grooves in the opposite grinding surfaces of the outer grinding zone (46) are arranged at an angle to the base line in order to accelerate or slow down the flow of pulp through the inclined grinding slot. A refining device according to claim 1, characterized in that the fixed refining member (50) has an annular channel (90) communicating with the refining slot for receiving a medium for pulp treatment depending on the variable factors occurring during the refining process. A refining device according to claim 4, characterized in that the fixed refining member (50) can be moved axially in the member (14) supporting the refining member by means of pressure members (58). A refining device according to claim 8, characterized in that said member is formed by a fixed refining member (14) which forms the second refining surface of the inner refining zone (32). 16 62369