JP2012532999A - Equipment for screening fiber suspensions - Google Patents

Abstract

  The present invention relates to a screen for fiber suspension, in particular a screen for removing coarse particles. The screen comprises a casing, a conduit connected to the casing, supplying a fiber suspension to the apparatus, discharging rejects and accepts, and a drum disposed inside the housing and rotating about a vertical axis; The screening surface of the drum is provided with an opening through which the accepting portion flows. The supply conduit and the outlet conduit are arranged so that the fiber suspension is supplied to the space between the casing and the screen drum and the accept is discharged from the interior of the screen drum. The opening in the screening surface is a slot, the longitudinal orientation of the slot with respect to the direction of drum rotation is -40 degrees to +40 degrees, and the length to width ratio is 1.05 to 10. The slots form slot rows and the outer surface of the screening surface is formed such that ridges are provided between the slot rows.

Description

  The present invention relates to an apparatus for screening fibers and the like in the chemical pulp and paper industry, in particular for a coarse screening that separates coarse particles such as knots, stones and other solid particles from fiber suspensions. It is about. The present invention relates to an apparatus having a rotating screen drum.

  In wood pulp sorter processing, screens are used to separate the acceptable fibers in the suspension from undesirable materials. A typical screen structure has a supply conduit for the fiber suspension. The fiber suspension may be produced by cooking wood chips or with a defibrator that obtains secondary pulp fibers. The suspension may include knots, sliver, bark particles, earth and sand, metal particles, and other undesirable materials.

  Inside the screen of the casing, the fiber suspension flows around a cylindrical screen, often referred to as a plate or basket, and acceptable fiber pieces, or accepts, pass through the screen plate, while rejecting. Remains on the first side of the screen plate and is discharged from the reject opening in the casing. As the cylindrical screen plate, or screen drum, rotates, the fiber suspension passes through the impact or turbulence elements to enhance the flow of the fiber suspension through the surface of the screen plate, and thus screening. Is also promoted. The screen plate has a hole or slot opening with dimensions suitable for the screening process. The size of the screen plate opening must be suitable so that the accepted fibers pass through the screening surface and prevent the passage of unwanted material.

  EP-A-275967 (FI 76139) shows a method and apparatus for separating knots. Here, a generally low level of MC concentration (6-8%) is realized. Expansion of the usable concentration range is achieved by appropriately sizing and designing the contour of the screening surface and optimizing the screen drum rotation speed and pulp feed rate. In the device described in this publication, the rotation direction of the drum is the same as the pulp supply direction, and the reject discharge direction is the same as the rotation direction of the drum. Further, the screen drum is contoured so that ridges are provided between the screen openings on the drum outer surface, the ridges having a front surface rising from the drum outer surface to an inclined position, and a rear surface substantially perpendicular to the outer surface. Is provided. The inclination angle of the bulge with respect to the drum axis is −45 to +45 degrees. The opening in the drum may be a hole or a slot, but usually the screening surface of this type of screen is provided with a round hole whose diameter can vary between 5 and 15 mm depending on the purpose of the application.

  EP 1357222 (U.S. Published Application 2004004032) describes a screening screen for fiber suspensions having a fixed screen drum, inside which a blade member is rotated to move the screening surface. It is clean. The screening surface is provided with elongated openings having a width of 1-8 mm and a length to width ratio of 2-20. The object of this invention is to increase the proportion of long fibers in the accept. U.S. Pat. No. 4,904,417 also shows a screen with a fixed screen drum. The slots in the screening surface are parallel to each other but can be tilted with respect to the drum axis.

European Patent Application No. 275967 European Patent No. 1357222 US Patent No. 490417

  The object of the present invention is to provide a rotating screen drum for a coarse screen which can reach high concentrations (up to more than 6%) in a more energy efficient manner than before.

The present invention relates to an apparatus for screening a fiber suspension, and more particularly to an apparatus for coarse screening that removes coarse particles such as knots. The device is arranged to rotate around a vertical shaft (7) in the casing, a supply conduit for the fiber suspension and an outlet conduit for rejecting and accepting, and a vertical shaft (7) in the casing, the accepting part flowing. A screen drum (5) having a screening surface (20) provided with an opening (21). The supply and outlet conduits of this device are arranged so that the fiber suspension is fed into the space between the casing and the screen drum and the accepting portion is discharged from the inside of the screen drum. According to the present invention, the openings in the screening surface are slots, in which the longitudinal orientation with respect to the direction of drum rotation is -40 degrees to +40 degrees, and the ratio of slot length to width is 1. .05 to 10 and this slot forms a slot row, and the outer surface of the screening surface is shaped so that a ridge is provided between the slot rows.

  According to a preferred embodiment, the longitudinal direction / longitudinal axis of the opening is −30 to +30 degrees, preferably −15 to +15 degrees with respect to the direction of rotation of the drum. According to a preferred embodiment, the direction in which the longitudinal direction of the opening extends is substantially the same as the direction of rotation of the drum, i.e. perpendicular to the longitudinal axis of the screen drum.

  The slot is rectangular or elliptical. The edge of the slot end is square or round. Usually, the slot is elongated. The width is usually 4 to 12 mm. The ratio of slot length to width is 1.05 to 10, preferably 2 to 8.

  The slots are arranged side by side in the axial direction of the drum, thereby forming a slot row / slot region, and these slot rows / slot regions are spaced apart from each other in the circumferential direction of the drum. Normally, the vertical slot rows are inclined.

  According to a preferred embodiment, the outer surface of the drum screening surface is formed such that ridges are arranged between the slot rows / slot regions. The outer surface refers to the side of the drum where the fiber suspension is supplied, the accepting portion flows through the opening to the other surface and the rejecting portion remains there. Preferably, the ridges are arranged at an angle of -5 to +20 degrees, usually 15 degrees with respect to the vertical axis of the drum. The line in the vertical slot row relative to the drum vertical axis is such that the end of the slot forms a line that is substantially parallel to the ridge, i.e., typically inclined relative to the drum vertical axis. Can be changed.

  This profile is formed by ridges having front and rear surfaces that are at an angle to the plane of the screen surface and possibly surfaces that are substantially parallel to the plate plane between the front and rear surfaces. Optimize pulp circulation time and turbulence according to the final separation (accept / reject) by the angle of inclination of the ridge, the direction of the inclination with respect to the direction of rotation, the rotation speed of the drum, and the rising angle of the front surface of the ridge Is possible. If the front surface of the ridge receiving the flow is inclined backwards, i.e. the front surface rises from the plane of the screening surface and the rear surface is vertical, a flow is obtained that flows evenly through the openings in the screening surface. This flow prevents the suspension flow that may occur under certain circumstances from being disturbed in the opposite direction. According to one embodiment, the front surface of the ridge may be perpendicular to the plane of the screen surface and thus the rear surface may be lowered. In that case, the front face opposes the flow and mixes the flow, thereby increasing the flow through the screening surface and thus increasing the production capacity of the device, while at the same time reducing the separation capacity. The front and back surfaces of the ridge can also be inclined symmetrically.

  According to a preferred embodiment of the invention, the ridges are also arranged in the slot area so that ridges are also provided between the slots arranged side by side. Therefore, in that case, the outer shape is a shape in which the ridges are interrupted by the slots. The slot region may be provided with one or more structures formed as described above, and these structures are arranged in a slot row / slot region and a slot row / slot region with respect to the vertical axis of the drum. It has the same tilt angle as the structure in between. That is, the ridges are parallel to the slot rows.

  According to a specific example, the slots of the vertical row of slots are arranged horizontally such that each slot of the row of slots is located in the same horizontal line, ie the first horizontal line group, every other row. And, each slot of the slot row is arranged so that every other row is positioned in the second horizontal line group.

  According to a preferred embodiment of the invention, the longitudinal position / angle of each slot arranged in one slot row with respect to the direction of drum rotation varies from top to bottom along the drum axis. The longitudinal direction of the uppermost slot is parallel to the rotation direction of the drum. On the other hand, the longitudinal orientation of the underlying slot is inclined downward from the slot front end in the drum rotation direction, so the slot front end (in the drum rotation direction) is located above the rear end. Usually, the lower slot is inclined downwardly from the upper slot. The inclination angle of the underlying slot is 1-5 degrees, usually 2-4 degrees larger. According to another embodiment, the longitudinal orientation of the uppermost slot is still parallel to the direction of rotation of the drum, but the subsequent underlying slot is inclined upwards with respect to the direction of rotation, and thus the rotation of the drum The front end of the slot in the direction is located below the rear end. Therefore, the rear end of the next lower slot is inclined upwardly more than the upper slot. The inclination angle of the underlying slot is 1-5 degrees, usually 2-4 degrees larger. In these embodiments, the two slots arranged side by side may be substantially parallel, but it is appropriate to arrange most of the slots in one slot row at different inclination angles. .

  According to a preferred embodiment of the invention, the longitudinal position / angle of each slot in a row of slots relative to the direction of rotation varies from bottom to top along the drum axis and the longitudinal direction of the bottom slot The direction of is parallel to the direction of rotation of the drum, but the slot located thereon is inclined with respect to the direction of rotation. Therefore, the next upper slot can be tilted upward, so that the slot front end in the direction of drum rotation is located below the slot rear end. Usually, the upper slot is inclined more than the lower slot. The inclination angle of the upper slot is 1-5 degrees, usually 2-4 degrees larger. According to a preferred embodiment of the present invention, the slot above may be similarly inclined so that the front end of the slot in the direction of drum rotation is located above the rear end of the slot. In that case, the slot is inclined downward with respect to the rotation direction. In these embodiments, the two slots arranged side by side, such as the two slots at the bottom, may be substantially parallel, but most of the slots in one slot row are inclined at different angles. It is appropriate to arrange with.

  In the above example where the slope is directed downward, the production capacity of the device increases and the concentration also increases. If the slope is upward, the separation capability of the device is increased, i.e. a cleaner accept is obtained.

  According to the apparatus according to the embodiment of the present invention, it is possible to separate coarse particles such as knots and the like from the fiber suspension more efficiently than before and at a higher concentration (up to 6%). It becomes. Since the slot is elongated, the “projection” of the slot remains reasonably large so that the speed of the screen drum can be increased. Higher speeds enable higher concentrations. If round holes are provided on the screening surface, the upper limit speed will be reached earlier, and if the speed increases, the hole output will decrease, and the holes will be clogged earlier. In an apparatus according to embodiments of the present invention, screening is usually more energy efficient to reduce rotational speed or increase production capacity.

  An example of the invention will now be described in more detail with reference to the accompanying drawings.

1 is a schematic side view of an apparatus according to the present invention. The top view of the screening surface by an Example. FIG. 6 is a top view of a screening surface according to another example. FIG. 6 is a top view of a screening surface according to another example. The top view of the screening surface by an Example. Sectional drawing which made the screening surface by an Example straight. The top view of the screening surface by an Example. The top view of the screening surface by an Example. The top view of the screening surface by an Example. The top view of the screening surface by an Example.

  FIG. 1 shows a screen according to a preferred embodiment of the present invention. The screen comprises a substantially cylindrical outer casing 1 to which a fiber suspension inlet conduit 2, an accept outlet conduit 3 and a reject outlet conduit 4 are connected, a screen drum 5, and an interior of the screen drum 5. And one or more stationary blades 6 extending near the surface of the screen drum. The rotating screen drum 5 is attached to a shaft 7 which functions by, for example, a belt driving body (not shown) in a substantially known manner. A space 8 between the screen drum 5 and the outer casing 1 has an annular shape. The aforementioned conduits 2 and 4 are connected to the outer casing 1 in the annular space. The fiber suspension is supplied to the space 8 and the accept that flows through the screening surface is discharged from the interior of the screen drum. The blade 6 is attached to a fixed frame 10 by an arm 9, and the fixed frame 10 supports the shaft 7 via a bearing. The blade 6 is disposed inside the drum 5. Here, the blade applies an appropriate positive or negative impact to the drum 5, thereby cleaning the screening surface of the drum.

  FIG. 2 shows a straightened view of the screening surface shape according to the preferred embodiment. The profile plate 20 is formed with an opening 21 and a profile 22 between the openings 21. As can be seen, the opening 21 according to the invention is a slot. The slot shape is rectangular and the edge of the slot end can be square or round. The ratio of slot length L to width W is 1.05 to 10, preferably 2 to 8, depending on the purpose of the application. The width W is usually 4 to 12 mm. In this embodiment, the longitudinal direction 23 of the slot 21 is parallel to the rotational direction 24 of the drum 5.

  The slots are arranged vertically in the drum axis direction, and the slot row / slot region 11 is formed at intervals in the circumferential direction of the drum. The ridges 22 and the vertical slot rows are not aligned with respect to the drum's vertical axis, but are inclined rows. The ridges and slot rows form an angle of -5 to +20 degrees, usually 15 degrees, i.e. an angle [beta], relative to the drum vertical shaft 7.

  Each slot of the vertical slot row 11 can be arranged in the horizontal direction so as to form a row parallel to the horizontal direction. FIG. 2 shows an alternative embodiment in which the slots 21 of the vertical row of slots 11 are arranged horizontally such that every slot of the row of slots is located at the same horizontal position every other row. Therefore, each slot of the vertical slot row is arranged so that each slot of the vertical slot row 11 is located at the same horizontal position every other row, that is, in the first horizontal line group 12a. Are arranged in the horizontal direction so that every other row is positioned in the second horizontal line group 12b.

  In FIG. 3, the longitudinal / longitudinal axis 23 of the slot 21 forms an angle α with respect to the drum rotation direction 24, which is −40 to +40 degrees. The angle α is approximately +25 degrees in FIG. 3a and approximately −24 degrees in FIG. 3b.

  FIG. 4 shows the outer shape of the plate 20. This screening surface can be considered to be formed of a plate having ridges 22 and a planar portion 26 between the ridges 22, which is provided with a machined opening 21. . In the embodiment of FIG. 4, ridges are further provided in the slot region, and the ridges 25 are arranged between the slots arranged side by side. Thus, in that case, the shape is such that the ridge rows are interrupted by the slots. The slot region can be formed with one or more shapes formed as described above, and these shapes are preferably in the slot row / slot region 11 and the slot row / slot with respect to the drum vertical axis. The inclination angle is the same as that of the shape body 22 between the regions 11.

  Figures 5a and 5b show cross-sectional views with straightened screening surface shapes. The inner surface 27 of the plate 20 is flat except for the openings. In FIG. 5 b, the ridges 22 on the outer surface of the plate 20 are substantially in the front surface 29 rising at an angle from the plane 28 of the plate 20, a surface 30 substantially parallel to the plane 28 of the plate 20, and the plane 28 of the plate 20. It is formed from a rear surface 31 that is vertically vertical and a portion 26 between the openings 21 of the flat surface 28. On the other hand, the screen plate is formed by a plate with a ridge 22 formed from said portions 29, 30 and 31 and a planar portion 28 between the ridges 22 with machined openings 21. Can be considered. In the embodiment of FIG. 5a, the front surface 29 is perpendicular to the plane 28 of the plate and the rear surface is inclined.

  If the front surface of the outer ridge that receives the flow is inclined backwards, i.e. the front surface rises from the plane of the screening surface and the rear surface is vertical (Fig. 5b), this inclined front surface allows the pulp entering the drum, e.g. In any case, a flow that flows uniformly through the screening surface opening on the screening surface can be obtained. This flow prevents the suspension flow that may occur under certain circumstances from being disturbed in the opposite direction. If the front surface of the ridge is perpendicular to the plane of the screening surface and the back surface of the ridge is lowered (Fig. 5a), the front surface is against the flow and mixes the flow, thereby increasing the flow through the screening surface and thus Equipment production capacity increases.

  It can be seen from FIGS. 2 to 4 that the ridge 22 is somewhat inclined with respect to the drum axis and the direction of drum rotation. The angle of inclination of the ridge, the direction of the inclination with respect to the direction of rotation, the rotational speed of the drum, and the rising angle of the ridge 29 can optimize the pulp circulation time in the screen according to the final separation obtained. It becomes. The orientation of the ridge 22 is such that when the ridge 22 is tilted backward on the screen drum 5, the ridge 22 tends to lift the fiber suspension above the screen drum. Thereby, the time during which the fiber suspension circulates in the screen is increased, the separation becomes more accurate, the amount of rejection is reduced, and the amount of acceptance is increased. On the other hand, if the ridge is tilted forward, the circulation time is reduced and the production capacity is increased. In addition to the above factors, the height of the screen drum also affects the operating speed, the tilt angle, etc.

  According to the embodiment of FIG. 6, the position of each slot 21 in one slot row in the longitudinal direction 23 relative to the drum rotation direction 24 varies from top to bottom as viewed along the drum shaft 7. Go (Fig. 6a). The longitudinal direction of the uppermost slot 21 'is parallel to the drum rotation direction (ie, perpendicular to the drum axis). The longitudinal orientation of the next slot 21 ″ is then inclined (relative to the drum axis) from the slot front end 32 in the drum rotation direction, so that the slot front end 32 (in the drum rotation direction) is the rear end 33. Therefore, the next lower slot is inclined below the upper slot, and the inclination angle of the lower slot is usually 1-5 degrees, usually In this type of embodiment, the change in slot orientation can be thought of as going down from top to bottom, according to another embodiment (FIG. 6b), the length of the top slot. The orientation of the direction is parallel to the direction of rotation of the drum, but the subsequent underlying slot is inclined upward with respect to the direction of rotation, so the slot front end 32 'in the direction of rotation of the drum is 33 ', so that the rear end of the next lower slot is inclined upwards more than the slot above it. 5 degrees, typically 2 to 4 degrees larger, in this type of embodiment, the change in slot orientation can be considered to rise from top to bottom, in these examples it was placed up and down The two slots may be substantially parallel, but it is appropriate to arrange the majority of the slots in one slot row at different tilt angles.

  According to a preferred embodiment of the present invention (FIGS. 6c, d), the position / angle of each slot in a row of slots in the longitudinal direction relative to the direction of rotation of the drum is from below as viewed along the drum axis. Turning upward, the longitudinal orientation of the bottom slot is parallel to the direction of rotation of the drum, but the slot located next up is inclined with respect to the direction of rotation. The next upper slot is therefore inclined upwards (FIG. 6c), so that the slot front end 32 "in the direction of drum rotation is located below the slot rear end 33". Normally, the upper slot is more inclined than the lower slot. The inclination angle of the upper slot is 1-5 degrees, usually 2-4 degrees larger. In this type of embodiment, the change in slot orientation can be thought of as increasing from bottom to top. According to a preferred embodiment of the present invention (FIG. 6d), the upper slot is positioned so that the slot front end 32 ′ ″ in the direction of drum rotation is above the slot rear end 33 ′ ″. Similarly, it may be inclined. In that case, the slot is inclined downward with respect to the rotation direction. In this type of embodiment, the change in slot orientation can be thought of as going down from bottom to top.

  In the embodiment in which the slots are inclined downwards (FIGS. 6a and 6d), a higher production capacity is obtained. In the embodiment in which the slots are inclined upwards (FIGS. 6b and 6c), higher cleanliness is obtained because the contaminating particles flow from top to bottom.

  As will be apparent from the above, the method and apparatus according to the present invention have eliminated the disadvantages of the prior art apparatus and method, and thus have made it possible to increase the production capacity of the screening apparatus. However, the foregoing has only described some of the most important embodiments of the present invention in more detail, and these embodiments are not limited to the claims that define the protection scope of the present invention alone. It should be noted that the present invention is not limited.

Claims (15)

An apparatus for screening a fiber suspension, especially an apparatus for removing coarse particles such as knots, the apparatus comprising:
A casing (1);
A supply conduit (2) for the fiber suspension and an outlet conduit (4, 3) for rejection and acceptance;
A screen drum (5) having a screening surface (20) arranged in the casing for rotation around a vertical shaft (7) and provided with an opening (21) through which the accepting portion flows, The supply conduit and outlet conduit are such that the fiber suspension is supplied to a space (8) between the casing and the screen drum, and the accepting portion is discharged from the inside of the screen drum. In the arranged device,
The opening in the screening surface is a slot (21) having a longitudinal orientation with respect to the direction of rotation of the drum of -40 to +40 degrees and a length to width ratio of 1.05 to 10, A fiber suspension characterized in that the slots form a row of slots (11) and the outer surface of the screening surface is formed such that ridges (22) are arranged between the rows of slots. Screening device.   2. Fiber according to claim 1, characterized in that the longitudinal direction (23) of the slot is -30 to +30 degrees, preferably -15 to +15 degrees with respect to the direction of rotation of the drum. A device for screening suspensions.   3. The apparatus for screening fiber suspensions according to claim 1 or 2, characterized in that the longitudinal direction of the slot (21) is parallel to the direction of rotation of the drum.   The device for screening fiber suspensions according to any one of claims 1 to 3, characterized in that the slots (21) are arranged in a vertical direction.   Device for screening fiber suspensions according to any one of claims 1 to 4, characterized in that the ratio of length to width of the slot (21) is 2-8. .   The ridge (22) is preferably arranged at an angle of -5 to +20 degrees, preferably +15 degrees with respect to the vertical axis (7) of the screen drum. The apparatus which screens the fiber suspension as described in any one of Claim 1-5.   The slots (21) arranged side by side form a vertical row of slots and the ends of the slots form a line parallel to the ridges (22). 6. An apparatus for screening the fiber suspension described in 6.   In the slots (21) of the vertical slot row (11), the slots in the vertical slot row are positioned on the same horizontal line, that is, the first horizontal line group (12a) every other row. 2 to 3, wherein the slots are arranged so that each slot in the row of slots is located in the second horizontal line group (12b) every other row. An apparatus for screening a fiber suspension according to any one of Items 7 to 7.   The outer surface of the screening surface (20) is formed such that one or more ridges (25) are also provided between the slots arranged side by side above and below a slot region. An apparatus for screening a fiber suspension according to claim 6 or 7.   The outer shape is substantially parallel to the plane of the plate between the front surface (29) and the rear surface (31), and optionally between the front surface and the rear surface, with an angle to the plane of the screening surface. 10. A device for screening fiber suspensions according to any one of claims 1 to 9, characterized in that it is formed by ridges (22, 25) having a smooth surface (30).   11. The front surface (29) of the ridge receiving flow is inclined backwards, i.e. the front surface rises from the plane of the screening surface and the rear surface (31) is vertical. Device for screening fiber suspensions.   11. A device for screening fiber suspensions according to claim 10, characterized in that the front surface (29) of the ridge is perpendicular to the plane of the screening surface and the rear surface (31) is lowered.   The apparatus for screening fiber suspension according to claim 10, wherein the front surface and the rear surface of the ridge are inclined.   The position / angle of the longitudinal direction (23) of the slot (21 ′, 21 ″) arranged side by side in one slot row (11) with respect to the rotation direction (24) of the drum is the drum 14. The apparatus for screening fiber suspensions according to any one of claims 1 to 13, characterized in that it varies along an axis.   The longitudinal position of the slot (21 ″) in the slot row is inclined with respect to the longitudinal position of the slot (21 ′) positioned above or below. An apparatus for screening a fiber suspension according to claim 14.

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