CA1329333C - Method and apparatus for separating knots - Google Patents
Method and apparatus for separating knotsInfo
- Publication number
- CA1329333C CA1329333C CA000556763A CA556763A CA1329333C CA 1329333 C CA1329333 C CA 1329333C CA 000556763 A CA000556763 A CA 000556763A CA 556763 A CA556763 A CA 556763A CA 1329333 C CA1329333 C CA 1329333C
- Authority
- CA
- Canada
- Prior art keywords
- screen cylinder
- cylinder
- screen
- reject
- suspension
- 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.)
- Expired - Fee Related
Links
- 238000000034 method Methods 0.000 title claims abstract description 19
- 239000000725 suspension Substances 0.000 claims abstract description 19
- 239000000835 fiber Substances 0.000 claims abstract description 15
- 238000000926 separation method Methods 0.000 claims description 6
- 238000012216 screening Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 238000005243 fluidization Methods 0.000 claims description 2
- 238000007599 discharging Methods 0.000 claims 4
- 239000007787 solid Substances 0.000 claims 4
- 238000011144 upstream manufacturing Methods 0.000 claims 3
- 238000005507 spraying Methods 0.000 claims 2
- 238000007865 diluting Methods 0.000 claims 1
- 239000007788 liquid Substances 0.000 claims 1
- 238000012545 processing Methods 0.000 abstract description 4
- 238000012360 testing method Methods 0.000 abstract description 3
- 239000002023 wood Substances 0.000 abstract description 2
- 238000010790 dilution Methods 0.000 description 4
- 239000012895 dilution Substances 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 208000028659 discharge Diseases 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 241001052209 Cylinder Species 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 230000003292 diminished effect Effects 0.000 description 1
- 230000003467 diminishing effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 229940090441 infed Drugs 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000010349 pulsation Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
- D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
- D21D5/02—Straining or screening the pulp
- D21D5/06—Rotary screen-drums
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Paper (AREA)
- Filtration Of Liquid (AREA)
- Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
- Ultra Sonic Daignosis Equipment (AREA)
- Medicines Containing Material From Animals Or Micro-Organisms (AREA)
- Separation Of Solids By Using Liquids Or Pneumatic Power (AREA)
- Control And Other Processes For Unpacking Of Materials (AREA)
Abstract
(57) Abstract The invention relates to a method and apparatus for separating knots. Especially the method and the apparatus are meant to be adjusted in separating knots from the fibre suspensions of wood processing industry. According to the prior art a problem acknowledged has been the quick wear of the screen surface of the knotter when the screen surface has been profiled. On the other hand the ability to separate with the unprofiled screen has been unsatisfactory. When using a profiled screen cylinder (5) it has been noticed in the performed tests to be most prefarable to feed the pulp from the connections (2) in the direction of rotation of the screen cylinder and also to discharge the reject from the connections (4) and the accept from the connections (3) of the cylinder (5) in the direction of rotation. A result from this is not only lesser wear of the screen surface, but also a significantly smaller consumption of power per pulp ton than in the apparatuses in accordance with the prior art.
Fig. 2
Fig. 2
Description
Method and app~ratus or separating knots The present invention relates to a method and apparatus for separating knots. The method and apparatus are in particular suitable in separating knots from high consistency pulp.
There are several different kinds of knot separators already known. An apparatus is introduced in US Pat. No. 3,947,314 which includes an outer casing, an inner screen casing, of cylindrical configuration, a rotating screw conveyor inside the screen casing and an inlet adjacent the lower end of the screen casing, accept outlet adjacent the lower end of the outer casing and a reject outlet adjacent the upper end of the screen casing.The whole apparatus is preferably slightly inclined in relation to the vertical. The apparatus functions in the way that the pulp including knots or other fairly large piece,s of wood is fed to the lower end of the screen casing to be lifted by the screw conveyor. When the screw conveyor lifts the pulp the fine fibers pass through the holes or slots of the perforated casing and are discharged through the accept outlet in the lower end of the outer casing. The coarser material which is not filtered through the holes of the screen casing is carried to the upper end of the screen casing and falls from there to the reject chute.
Another apparatus according to prior art is introduced in SE
patent publication 316363 in which there is substantially a slightly conic downwards broadening rotating screen cylinder inside the cylindrical casing. Inside the screen cylinder there are stationary pulsation means arranged to ensure that the openings of the æcreen cylinder remain open. The pulp is tangentially fed to a annular channel situated at the upper end of the outer casing, of which channel the pulp flows along the horizontal plate arranged on the outer casing spirally towards the shaft of the screen cylinder. In the middle part of the above mentioned plate there is a hole through which t 329333 the pulp falls down on the end cover of the rotating screen cylinder, which has radial ribs giving the pulp its initial rotational motion. From the cover the pulp is dashed due to the centrifugal force to the downwards narrowing space between the screen cylinder and the outer casing. The fines pass through the screen cylinder to the accept ~ide. The material left over between the outer casing and the screen cylinder, the reject, is discharged finally to an annular channel in the lower end of the outer casing, from where the reject is discharged to the tangential outlet.
As a third arrangement is introduced an apparatus according to the US patent publication 4,441,999 which consists of a cylindrical outer casing and a rotating screen cylinder.
Inside the screen cylinder there are one or more stationary unrotating blades. The pulp is tangentially fed between the screen cylinder and the outer casing, but opposite to the direction of rotation of the cylinder. The accept is dis-charged from the inside of the screen cylinder at the end of the cylinder and the reject tangentially, but opposite to the Airection of rotation of the cylinder. In accordance with the present arrangement, the screen cylinder consists of openings that open to the inside of the cylinder and of connecting pieces which in principle consist of radial arms and parts bent forward to the direction of the pulp flow coming to the cylinder which produce pressure pulses to the pulp to keep the holes of the screen cylinder open. The apparatus in accordance with this publication was found to operate especially well in paper machine short circulation and equivalent where it enabled the dampening of the fluctuation of the pressure inconvenient to further processing.
The latter two devices are characterized in that they reach the consistency range of ~ - 6 ~, whereas the device according to the first e~ample functions only in the consistency of up to 1,5 - 2 ~. Plugging of the holes cn the screen surface limits the operation in all devices. Yet, in stock processing the aim is consistently towards higher consistencies, because it is it is in every respect more preferable to tend to treat the pulp in different process stages in the same consistency without thickening and dilution. If it is possible to raise the processing consistencv, savings can be gained in both device and transportation charges and also considerably in the consumption of energy.
An improved method and apparatus for separating knots has been developed on the basis of the description above, which reaches the so called low range of the MC-consistency (6 - 8 ~ ) and diminishes significantly the consumption of energy.
The rise of the applicable range of consistency is achieved by the correct measuring and formulation of the screen profile, and optimizing the rotational speed of the cylinder with respect to the feeding speed of the pulp. In addition to that it has been possible to diminish the comsumption of energy of the knotter itself essentially compared to the apparatus of the US publication 4,441,999. This is mainly due to changing the direction of rotation of the screen cylinder to parallel to the direction of the pulp feed. According to the performed tests the consumption of energy of the knotter of the present invention has been measured to have been at most 0,6 kWh/ mass ton. Furthermore the change of the direction of rotation has diminished the wear of the screen cylinder.
Additionally one advantage of an apparatus in accordance with the present invention is facilitation of reject outlet com-pared to the approach in accordance with the US patent 4,441,999, because in the apparatus according to the present invention the reject is discharged in the direction of the rotation of the screen cylinder. This pumping effect together with dilution water led to the reject in the discharge stage significantly facilitates the adjustment of the amount of re~ect. Thus even with higher consistencies the reject rate can be maintained between 2 to 10 % by using the screen in accordance with the present invention.
......
1 3~9333 The method according to the present invention is among other things characterized in that the fibre suspension is tangen-tially introduced in the direction of rotation of the screen cylinder and the reject is discharged tangentially in the direction of rotation of the screen cylinder.
The apparatus according to the present invention is characte-rized in that the direction of rotation of the cylinder is parallel to direction of pulp feed from the inlet connection, the direction of the outlet of the reject from the outlet connection is the same as the direction of rotation of the cylinder and that the cylinder is contoured in the way that on the outer surface of the cylinder there are ridges between the openings.
The method and the apparatus according to the present inven-tion are further described with reference to the accompanying drawings, in which ig. 1 is a partly sectional side view of the apparatus according to the invention, ig. 2 ifi a partly sectional top view of an apparatus according to Fig. 1, ig. 3 is a straightened sectional side view of the screen profile according to a preferred embodiment, and ig. 4 i8 an over view of the screen according to Fig. 3.
The knotter in Fig. 1 and 2 of the drawings describes a preferred embodiment of the invention substantially consisting of a cylindrical outer housing 1, in which there is the inlet connection 2 for the pulp, outlet connection 3 for the accept and outlet connection 4 for the reject, screen cylinder 5, and 1 32q333 of one or more stationary unrotating blades 6 inside the screen cylinder 5 extending near the surface of the screen cylinder. The screen cylinder 5 is attached by members 12 on the shaft 7 which functions e.g. by belt drive (not intro-duced). The space 8 between the screen cylinder 5 and the outer housing 1 is annular and sealed at the ends with radial plates 9 and 10 projecting from the outer housing 1 towards the shaft. The above mentioned connections 2 and 4 are tangen-tially attached to the outer housing 1 of the annular space 8.
- In addition to that a feed pipe 11 of the dilution water is arranged to the reject connection 4, with which, if necessary, the consistency of the reject is lowered in order to facili-tate further screening.
The blades 6 are attached with arms 13 and 14 to a stationary frame 15 which also forms a strut for the shaft 7 through the bearing 16. The biades 6 are positioned in the cylinder 5 so that the blade situated near the reject connection 4 is +
10 - 45 aside from it. Correspondingly, the other blade is 10 - 45 aside from the input connection 2. Thus the above men-tioned blades generate the applicable pulse, positive and/or negative, to the c~linder 5.
In Figs. 3 and 4 there is described an opened screen in accordance with one preferred embodiment. The contoured plate 20 consists of openings 21 and of lands 22 between them. Plate 20 is plain on the inner surface 23 excluding the openings.
The outer surface of the plate 20 consists of front surfaces 25 ricing in a certain angle from the plane 24 of the plate 20, substantially of the surfaces 26 parallel to the plane 24 of the plate 20, substantially of the end surfaces 27 upright to the plane 24 of the plate 20 and of parts 28 of the plane 24 between the openings 21. On the other hand ~he screen plate h can be considered to consist of a plate which has ridges 29 which consist of the above mentioned parts 25, 26 and 27, and of the plane like parts -8 between them, in which the openings 21 are machined.
, . . .
As it appears in Fig. 4 the openings 21 are preferably holes (or slots) the diameter of which can range depending on the application at least between 5 - l5 mm. It also appears in Fig. 4 that the ridges 29 can be slightly declined from the axial direction of the plate. By the declination angle of the ridges, the direction of the declination in respect to the direction of rotation, the speed of rotation and the ascending angle of the part 25 of the ridges the circulation time of the pulp in the knotter can be optimized in relation with the result of the separation. The circumferential speed of the cylinder used in the performed tests has been 4 - lO m/s and for the feed of the pulp 2 m/s in the performed experiments.
In that case the speed difference between the cylinder and the pulp is 2 - 8 m/s. The gradient plane 25 of the ridges 29 of the screen plate 20 receives the pulp coming into the cylin-der, tending to accelerate its speed. The direction of the ridges 29 has the effect that if the ridges 29 on the screen cylinder 5 are backwards inclined, they tend to raise the pulp upwards in the cylinder, thereby the circulation time of the pulp in the knotter becomes longer, the separation takes place more accurately and the amount of reject diminishes while the amount of accept grows.
If the ridges are forwards inclined the circulation time becomes shorter and the separation is not anymore so accurate.
In addition to the above mentioned factors also the height of the screen cylinder effects on the speed, inclination angles, etc. used.
The method and apparatus in accordance with the present invention function in the following way. The pu1p i3 tangen-tially fed by pressure into the space between the rotating screen cylinder and the outer housing of the knotter and in the same direction as the rotating motion of the screen. The riclges of the screen cylinder subject the infed pulp to circumgerential forces for increasing its speed of motion and, due to the shape of the ridges, also shear forces for opening 1 32~333 the bonds between the pulp particles, i.e. the fibres. The ridges cause at the outlet end in front of the surface 27 a low pressure zone that attracts the loose fibres through openings 21 with the help of the pressure difference between the inlet connections 2 and the accept connections 3. The heavier particles carried by the pulp sling towards the surface of the housing 1 when hitting the ridges, whereby they are also subjected to the centrifugal force. In that case the liahter particles of the pulp are enriched near the surface of the screen cylinder and are separated from the pulp in the abo~e mentioned way. Due to the contours of the surface of the cylinder a slight fluidization takes place near the surface of the screen cylinder, helping the separation and on the other hand also diminishing the consumption of enerqy of the sepa-ration and the wear of the screen cylinder. The heavy par-ticles separated onto the surface of the outer housing of the knotter circulate down the housing surface along the spiral path and are tangentially discharged from the knotter through the connection 4. The discharge is activated more by feeding, if necessary, dilution water to the reject from the pipe 11.
As already mentioned above, the apparatus in accordance with the invention described above has made it possible to diminish the consumption of energy in respect to the prior art more than 30 % and at the same time it has been possible to in-crease the consistency of the pulp up to the lower range of the MC-consistency. As a byproduct a less wearing screen cylinder and an apparatus better adjustable in its function and in its end products has also been brought about. For example, merely changing the rotational speed of the cylinder it is possible to ad~ust the apparatus applicable to most dif-ferent consistencies and different kinds of pulps. When this method is added by a possibility to produce screen cylinders having varying inclination angles of ridges or openings of variable sizes, one is able to talk about an ultimately optimized knotter.
1 3293:3~
It has to be noticed that above has only been shown one preferred embodiment of the apparatus in accordance with the present invention which may in reality differ a lot from the form shown above and yet not differ from the inventive idea which is more closely described in the accompanying claims.
It is namely quite possible that in some case it is necessary to use an inclination angle of two or more ridges or that the speeds of the pulp suspension and the cylinder differ a lot from the example shown above, substantial is, however, only the difference of the speeds which according to the claims is 2 - 8 m/s.
There are several different kinds of knot separators already known. An apparatus is introduced in US Pat. No. 3,947,314 which includes an outer casing, an inner screen casing, of cylindrical configuration, a rotating screw conveyor inside the screen casing and an inlet adjacent the lower end of the screen casing, accept outlet adjacent the lower end of the outer casing and a reject outlet adjacent the upper end of the screen casing.The whole apparatus is preferably slightly inclined in relation to the vertical. The apparatus functions in the way that the pulp including knots or other fairly large piece,s of wood is fed to the lower end of the screen casing to be lifted by the screw conveyor. When the screw conveyor lifts the pulp the fine fibers pass through the holes or slots of the perforated casing and are discharged through the accept outlet in the lower end of the outer casing. The coarser material which is not filtered through the holes of the screen casing is carried to the upper end of the screen casing and falls from there to the reject chute.
Another apparatus according to prior art is introduced in SE
patent publication 316363 in which there is substantially a slightly conic downwards broadening rotating screen cylinder inside the cylindrical casing. Inside the screen cylinder there are stationary pulsation means arranged to ensure that the openings of the æcreen cylinder remain open. The pulp is tangentially fed to a annular channel situated at the upper end of the outer casing, of which channel the pulp flows along the horizontal plate arranged on the outer casing spirally towards the shaft of the screen cylinder. In the middle part of the above mentioned plate there is a hole through which t 329333 the pulp falls down on the end cover of the rotating screen cylinder, which has radial ribs giving the pulp its initial rotational motion. From the cover the pulp is dashed due to the centrifugal force to the downwards narrowing space between the screen cylinder and the outer casing. The fines pass through the screen cylinder to the accept ~ide. The material left over between the outer casing and the screen cylinder, the reject, is discharged finally to an annular channel in the lower end of the outer casing, from where the reject is discharged to the tangential outlet.
As a third arrangement is introduced an apparatus according to the US patent publication 4,441,999 which consists of a cylindrical outer casing and a rotating screen cylinder.
Inside the screen cylinder there are one or more stationary unrotating blades. The pulp is tangentially fed between the screen cylinder and the outer casing, but opposite to the direction of rotation of the cylinder. The accept is dis-charged from the inside of the screen cylinder at the end of the cylinder and the reject tangentially, but opposite to the Airection of rotation of the cylinder. In accordance with the present arrangement, the screen cylinder consists of openings that open to the inside of the cylinder and of connecting pieces which in principle consist of radial arms and parts bent forward to the direction of the pulp flow coming to the cylinder which produce pressure pulses to the pulp to keep the holes of the screen cylinder open. The apparatus in accordance with this publication was found to operate especially well in paper machine short circulation and equivalent where it enabled the dampening of the fluctuation of the pressure inconvenient to further processing.
The latter two devices are characterized in that they reach the consistency range of ~ - 6 ~, whereas the device according to the first e~ample functions only in the consistency of up to 1,5 - 2 ~. Plugging of the holes cn the screen surface limits the operation in all devices. Yet, in stock processing the aim is consistently towards higher consistencies, because it is it is in every respect more preferable to tend to treat the pulp in different process stages in the same consistency without thickening and dilution. If it is possible to raise the processing consistencv, savings can be gained in both device and transportation charges and also considerably in the consumption of energy.
An improved method and apparatus for separating knots has been developed on the basis of the description above, which reaches the so called low range of the MC-consistency (6 - 8 ~ ) and diminishes significantly the consumption of energy.
The rise of the applicable range of consistency is achieved by the correct measuring and formulation of the screen profile, and optimizing the rotational speed of the cylinder with respect to the feeding speed of the pulp. In addition to that it has been possible to diminish the comsumption of energy of the knotter itself essentially compared to the apparatus of the US publication 4,441,999. This is mainly due to changing the direction of rotation of the screen cylinder to parallel to the direction of the pulp feed. According to the performed tests the consumption of energy of the knotter of the present invention has been measured to have been at most 0,6 kWh/ mass ton. Furthermore the change of the direction of rotation has diminished the wear of the screen cylinder.
Additionally one advantage of an apparatus in accordance with the present invention is facilitation of reject outlet com-pared to the approach in accordance with the US patent 4,441,999, because in the apparatus according to the present invention the reject is discharged in the direction of the rotation of the screen cylinder. This pumping effect together with dilution water led to the reject in the discharge stage significantly facilitates the adjustment of the amount of re~ect. Thus even with higher consistencies the reject rate can be maintained between 2 to 10 % by using the screen in accordance with the present invention.
......
1 3~9333 The method according to the present invention is among other things characterized in that the fibre suspension is tangen-tially introduced in the direction of rotation of the screen cylinder and the reject is discharged tangentially in the direction of rotation of the screen cylinder.
The apparatus according to the present invention is characte-rized in that the direction of rotation of the cylinder is parallel to direction of pulp feed from the inlet connection, the direction of the outlet of the reject from the outlet connection is the same as the direction of rotation of the cylinder and that the cylinder is contoured in the way that on the outer surface of the cylinder there are ridges between the openings.
The method and the apparatus according to the present inven-tion are further described with reference to the accompanying drawings, in which ig. 1 is a partly sectional side view of the apparatus according to the invention, ig. 2 ifi a partly sectional top view of an apparatus according to Fig. 1, ig. 3 is a straightened sectional side view of the screen profile according to a preferred embodiment, and ig. 4 i8 an over view of the screen according to Fig. 3.
The knotter in Fig. 1 and 2 of the drawings describes a preferred embodiment of the invention substantially consisting of a cylindrical outer housing 1, in which there is the inlet connection 2 for the pulp, outlet connection 3 for the accept and outlet connection 4 for the reject, screen cylinder 5, and 1 32q333 of one or more stationary unrotating blades 6 inside the screen cylinder 5 extending near the surface of the screen cylinder. The screen cylinder 5 is attached by members 12 on the shaft 7 which functions e.g. by belt drive (not intro-duced). The space 8 between the screen cylinder 5 and the outer housing 1 is annular and sealed at the ends with radial plates 9 and 10 projecting from the outer housing 1 towards the shaft. The above mentioned connections 2 and 4 are tangen-tially attached to the outer housing 1 of the annular space 8.
- In addition to that a feed pipe 11 of the dilution water is arranged to the reject connection 4, with which, if necessary, the consistency of the reject is lowered in order to facili-tate further screening.
The blades 6 are attached with arms 13 and 14 to a stationary frame 15 which also forms a strut for the shaft 7 through the bearing 16. The biades 6 are positioned in the cylinder 5 so that the blade situated near the reject connection 4 is +
10 - 45 aside from it. Correspondingly, the other blade is 10 - 45 aside from the input connection 2. Thus the above men-tioned blades generate the applicable pulse, positive and/or negative, to the c~linder 5.
In Figs. 3 and 4 there is described an opened screen in accordance with one preferred embodiment. The contoured plate 20 consists of openings 21 and of lands 22 between them. Plate 20 is plain on the inner surface 23 excluding the openings.
The outer surface of the plate 20 consists of front surfaces 25 ricing in a certain angle from the plane 24 of the plate 20, substantially of the surfaces 26 parallel to the plane 24 of the plate 20, substantially of the end surfaces 27 upright to the plane 24 of the plate 20 and of parts 28 of the plane 24 between the openings 21. On the other hand ~he screen plate h can be considered to consist of a plate which has ridges 29 which consist of the above mentioned parts 25, 26 and 27, and of the plane like parts -8 between them, in which the openings 21 are machined.
, . . .
As it appears in Fig. 4 the openings 21 are preferably holes (or slots) the diameter of which can range depending on the application at least between 5 - l5 mm. It also appears in Fig. 4 that the ridges 29 can be slightly declined from the axial direction of the plate. By the declination angle of the ridges, the direction of the declination in respect to the direction of rotation, the speed of rotation and the ascending angle of the part 25 of the ridges the circulation time of the pulp in the knotter can be optimized in relation with the result of the separation. The circumferential speed of the cylinder used in the performed tests has been 4 - lO m/s and for the feed of the pulp 2 m/s in the performed experiments.
In that case the speed difference between the cylinder and the pulp is 2 - 8 m/s. The gradient plane 25 of the ridges 29 of the screen plate 20 receives the pulp coming into the cylin-der, tending to accelerate its speed. The direction of the ridges 29 has the effect that if the ridges 29 on the screen cylinder 5 are backwards inclined, they tend to raise the pulp upwards in the cylinder, thereby the circulation time of the pulp in the knotter becomes longer, the separation takes place more accurately and the amount of reject diminishes while the amount of accept grows.
If the ridges are forwards inclined the circulation time becomes shorter and the separation is not anymore so accurate.
In addition to the above mentioned factors also the height of the screen cylinder effects on the speed, inclination angles, etc. used.
The method and apparatus in accordance with the present invention function in the following way. The pu1p i3 tangen-tially fed by pressure into the space between the rotating screen cylinder and the outer housing of the knotter and in the same direction as the rotating motion of the screen. The riclges of the screen cylinder subject the infed pulp to circumgerential forces for increasing its speed of motion and, due to the shape of the ridges, also shear forces for opening 1 32~333 the bonds between the pulp particles, i.e. the fibres. The ridges cause at the outlet end in front of the surface 27 a low pressure zone that attracts the loose fibres through openings 21 with the help of the pressure difference between the inlet connections 2 and the accept connections 3. The heavier particles carried by the pulp sling towards the surface of the housing 1 when hitting the ridges, whereby they are also subjected to the centrifugal force. In that case the liahter particles of the pulp are enriched near the surface of the screen cylinder and are separated from the pulp in the abo~e mentioned way. Due to the contours of the surface of the cylinder a slight fluidization takes place near the surface of the screen cylinder, helping the separation and on the other hand also diminishing the consumption of enerqy of the sepa-ration and the wear of the screen cylinder. The heavy par-ticles separated onto the surface of the outer housing of the knotter circulate down the housing surface along the spiral path and are tangentially discharged from the knotter through the connection 4. The discharge is activated more by feeding, if necessary, dilution water to the reject from the pipe 11.
As already mentioned above, the apparatus in accordance with the invention described above has made it possible to diminish the consumption of energy in respect to the prior art more than 30 % and at the same time it has been possible to in-crease the consistency of the pulp up to the lower range of the MC-consistency. As a byproduct a less wearing screen cylinder and an apparatus better adjustable in its function and in its end products has also been brought about. For example, merely changing the rotational speed of the cylinder it is possible to ad~ust the apparatus applicable to most dif-ferent consistencies and different kinds of pulps. When this method is added by a possibility to produce screen cylinders having varying inclination angles of ridges or openings of variable sizes, one is able to talk about an ultimately optimized knotter.
1 3293:3~
It has to be noticed that above has only been shown one preferred embodiment of the apparatus in accordance with the present invention which may in reality differ a lot from the form shown above and yet not differ from the inventive idea which is more closely described in the accompanying claims.
It is namely quite possible that in some case it is necessary to use an inclination angle of two or more ridges or that the speeds of the pulp suspension and the cylinder differ a lot from the example shown above, substantial is, however, only the difference of the speeds which according to the claims is 2 - 8 m/s.
Claims (20)
1. A method for separating knots and other solids from a fibre suspension by using a screening device with a screen cylinder, said cylinder having an outer surface and an inner surface, said method comprising the steps of:
(a) rotating said screen cylinder in a predetermined direction;
(b) introducing the suspension directly to the outer surface of said screen cylinder by causing same to flow tangentially with respect to the outer surface and in said predetermined direction;
(c) discharging rejected stock from an annular chamber defined by said outer surface and by a generally cylindric outer housing of said screening device in a direction which is tangential with respect to said outer surface and is coincident with said predetermined direction; and (d) flowing an accept through the screen cylinder, while subjecting the cylinder to pressure pulses generated near said inner surface thereof.
(a) rotating said screen cylinder in a predetermined direction;
(b) introducing the suspension directly to the outer surface of said screen cylinder by causing same to flow tangentially with respect to the outer surface and in said predetermined direction;
(c) discharging rejected stock from an annular chamber defined by said outer surface and by a generally cylindric outer housing of said screening device in a direction which is tangential with respect to said outer surface and is coincident with said predetermined direction; and (d) flowing an accept through the screen cylinder, while subjecting the cylinder to pressure pulses generated near said inner surface thereof.
2. The method of claim 1, further including the step of spraying the rejected stock with water in the vicinity of a reject outlet of said device, to thus reduce the consistency of the rejected stock in order to facilitate discharge thereof from said device.
3. An apparatus for separating knots and other solids from a fibre suspension, comprising, in combination:
(a) a perforated cylinder having an outer surface, an inner surface, and screening openings extending between the two surfaces, said cylinder being rotatably disposed inside a generally cylindric outer housing;
(b) rotating means for imparting to the cylinder a rotary motion in a predetermined direction relative to said housing;
(c) at least one blade for generating negative or positive pulses and disposed inside said cylinder at a close spacing from said inner surface of the cylinder;
(d) tangential inlet means adapted to direct a flow of the fibre suspensioninto the housing and directly to said outer surface, in said predetermined direction;
(e) reject outlet means adapted to direct a flow of rejected stock from a chamber between the housing and said outer surface in a direction tangential of and coincident with the sense of rotation of said cylinder;
(f) accept outlet means adapted to direct a flow of accepted stock from inside the cylinder away from the housing;
(g) a plurality of elongated, equidistantly spaced - apart ridges protruding from said outer surface of the cylinder.
(a) a perforated cylinder having an outer surface, an inner surface, and screening openings extending between the two surfaces, said cylinder being rotatably disposed inside a generally cylindric outer housing;
(b) rotating means for imparting to the cylinder a rotary motion in a predetermined direction relative to said housing;
(c) at least one blade for generating negative or positive pulses and disposed inside said cylinder at a close spacing from said inner surface of the cylinder;
(d) tangential inlet means adapted to direct a flow of the fibre suspensioninto the housing and directly to said outer surface, in said predetermined direction;
(e) reject outlet means adapted to direct a flow of rejected stock from a chamber between the housing and said outer surface in a direction tangential of and coincident with the sense of rotation of said cylinder;
(f) accept outlet means adapted to direct a flow of accepted stock from inside the cylinder away from the housing;
(g) a plurality of elongated, equidistantly spaced - apart ridges protruding from said outer surface of the cylinder.
4. The apparatus according to claim 3, wherein each of the ridges includes:
(a) a leading surface sloping toward the outer surface of said cylinder, and forwardly in the direction of rotation of the cylinder; and (b) a trailing surface generally at right angles to said outer surface.
(a) a leading surface sloping toward the outer surface of said cylinder, and forwardly in the direction of rotation of the cylinder; and (b) a trailing surface generally at right angles to said outer surface.
5. The apparatus according to claim 3 or 4, wherein the ridges are disposed each on a helical line.
6. The apparatus according to claim 5, the helix angle of the ridges is between -45° and + 45°.
7. The apparatus according to claim 3, wherein the openings in the cylinder are either holes or slots.
8. The apparatus of claim 3, comprising flow ration control means adapted to maintain the difference between the circumferential speed of the cylinder and the feeding speed of the fibre suspension at about 2 - 8 m/s.
9. The apparatus according to claim 3, wherein said blade is spaced from said reject outlet by an angle of between about 10° upstream or downstream of the reject outlet and about 45° downstream or upstream, respectively, of the reject outlet.
10. The apparatus according to claim 3 or claim 9, wherein said blade is spaced from said inlet means by an angle of between about 10° upstreamor downstream of said inlet means, and about 45° downstream or upstream, respectively, of the inlet means.
11. A method of separating knots and other solids from a pulp fibre suspension in an apparatus having an upwardly extending outer housing, an upwardly extending screen cylinder having an interior and mounted for rotation within and spaced inwardly from said outer housing and forming an annular space therebetween, said screen cylinder having a contoured outer surface facing the annular space with openings therethrough between the annular space and the interior of the screen cylinder, and at least one blade arranged within the interior of and adjacent said screen cylinder for subjecting said screen cylinder to pressure pulses, comprising the steps of rotating said screen cylinder at a rotational speed;
flowing the fibre suspension to be treated into the apparatus directly into the annular space tangentially to the outer surface of said screen cylinder in the direction of rotation of said screen cylinder at a feed speed less than the rotational speed of the screen cylinder for utilizing the feed speed in carryingout the method;
increasing the feed speed of the fibre suspension by the rotational speed of the screen cylinder and thereby effecting a slight fluidization at the contoured outer surface of the screen cylinder and facilitating the centrifugal separation of knots;
positioning the at least one blade in the range of ? 10° to 45° relative to one of an input connection and a reject connection;
flowing an accept of the suspension directly through the screen cylinder into the interior of the screen cylinder flowing in the direction of rotation of the screen cylinder and discharging the accept tangentially from the interior of thescreen cylinder in the direction of the rotation of the screen cylinder;
discharging a reject of said suspension from the annular space tangentially of the outer surface of said screen cylinder and in the rotational direction of the screen cylinder and facilitating the discharge of the reject bythe rotational speed of the screen cylinder; and subjecting pressure pulses to the screen cylinder from within the screen cylinder for loosening and displacing fibre stuck in the openings of said screencylinder.
flowing the fibre suspension to be treated into the apparatus directly into the annular space tangentially to the outer surface of said screen cylinder in the direction of rotation of said screen cylinder at a feed speed less than the rotational speed of the screen cylinder for utilizing the feed speed in carryingout the method;
increasing the feed speed of the fibre suspension by the rotational speed of the screen cylinder and thereby effecting a slight fluidization at the contoured outer surface of the screen cylinder and facilitating the centrifugal separation of knots;
positioning the at least one blade in the range of ? 10° to 45° relative to one of an input connection and a reject connection;
flowing an accept of the suspension directly through the screen cylinder into the interior of the screen cylinder flowing in the direction of rotation of the screen cylinder and discharging the accept tangentially from the interior of thescreen cylinder in the direction of the rotation of the screen cylinder;
discharging a reject of said suspension from the annular space tangentially of the outer surface of said screen cylinder and in the rotational direction of the screen cylinder and facilitating the discharge of the reject bythe rotational speed of the screen cylinder; and subjecting pressure pulses to the screen cylinder from within the screen cylinder for loosening and displacing fibre stuck in the openings of said screencylinder.
12. A method according to claim 11, including the step of spraying liquid into the reject while discharging the reject for facilitating discharge flow of the reject and diluting the consistency of the reject.
13. Method, as set forth in claim 11, wherein arranging the difference in the rotational speed of the screen cylinder and the feed speed of the fibre suspension in the range of 2 to 8 m/s.
14. An apparatus for separating knots and other solids from a pulp fibre suspension comprising an upwardly extending outer housing having an inlet connection for the fibre suspension flowing therein at a feed speed, an outlet connection for a reject of the suspension and an outlet connection for an accept of the suspension, an upwardly extending single screen cylinder located within and spaced inwardly from said housing and forming therebetween an annular space, said screen cylinder having an upwardly extending axis and being rotatable about said axis, said screen cylinder having openings therethrough from the annular space to the interior space of said screen cylinder and having a contoured outer surface, said screen cylinder being rotatably mounted within said outer housing, means for rotatably mounting said screen cylinder for moving at a rotational speed in excess of the suspension inlet feed speed and including a shaft located within and spaced inwardly from said screen cylinder and at least one blade located in a stationary position within and adjacent to an inside surface of said screen cylinder, said Inlet connection and said outlet connections mounted on and opening from said outer housing tangentially with respect to the rotation of said screen cylinder and the rotation of said screen cylinder being the same as the direction of flowof fibre suspension into the annular space between said outer housing and said cylinder, said inlet connection opening directly into said annular space.
15. An apparatus according to claim 14, wherein said screen cylinder has a vertical axis, the contoured outer surface of said screen cylinder includes ridges sloping downwardly relative to the vertical axis.
16. An apparatus as set forth in claim 15, wherein said screen cylinder has an outer surface and an inner surface the openings through said screen cylinder terminate in the outer surface in a cylindrical surface said ridges extend outwardly from the cylindrical surface and each said ridge comprises a first surface inclined outwardly from said cylindrical surface and at an end thereof spaced outwardly from said cylindrical surface is connected to said cylindrical surface by an end surface extending substantially perpendicular to the cylindrical surface.
17. An apparatus as set forth in claim 14, wherein said openings through said screen cylinder are in the form of slots.
18. An apparatus as set forth in claim 14, wherein said openings through said screen cylinder are in the form of circular holes.
19. An apparatus as set forth in claim 14, wherein at least two said blades are located within said screen cylinder in angularly spaced relation and one of said blades is located in the range of ? 10° to 45° from the reject outlet connection for selectively affording one of a positive or negative pulse.
20. An apparatus as set forth in claim 14, wherein two said blades are located in angularly spaced relation within said screen cylinder and one of saidblades is spaced in the range of ? 10° to 45° from said pulp inlet connection for selectively affording one of a positive or negative pressure pulse.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI870190 | 1987-01-19 | ||
| FI870190A FI76139C (en) | 1987-01-19 | 1987-01-19 | Twigs separation method and apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1329333C true CA1329333C (en) | 1994-05-10 |
Family
ID=8523793
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000556763A Expired - Fee Related CA1329333C (en) | 1987-01-19 | 1988-01-18 | Method and apparatus for separating knots |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0275967B1 (en) |
| JP (2) | JPH0696834B2 (en) |
| AT (1) | ATE69472T1 (en) |
| CA (1) | CA1329333C (en) |
| DE (2) | DE275967T1 (en) |
| FI (1) | FI76139C (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4308225C1 (en) * | 1993-03-16 | 1994-11-24 | Escher Wyss Gmbh | Process for sorting fiber suspension and screening device for carrying it out |
| SE515589C2 (en) * | 1999-03-10 | 2001-09-03 | Valmet Fibertech Ab | Screening device for separating fiber suspensions, and stator for use in the screening device |
| US6254729B1 (en) | 1999-03-22 | 2001-07-03 | Voith Sulzer Paper Technology North America, Inc. | Pulper with extraction plate assembly having removable inserts and method of manufacturing same |
| JP4909693B2 (en) * | 2006-07-24 | 2012-04-04 | 相川鉄工株式会社 | Screen device |
| FI20095769A7 (en) * | 2009-07-07 | 2011-01-08 | Andritz Oy | Apparatus for processing fiber suspension |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH182068A (en) * | 1935-03-21 | 1936-01-31 | Miag Muehlenbau & Ind Ag | Classifier for fiber-containing goods, in particular for paper making materials. |
| SE315479B (en) * | 1963-10-21 | 1969-09-29 | Knutsilplatar Malm N Ab | |
| US3363759A (en) * | 1964-04-29 | 1968-01-16 | Bird Machine Co | Screening apparatus with rotary pulsing member |
| DE1905832U (en) * | 1964-09-16 | 1964-12-03 | Hermann Finckh G M B H | SECURE FOR PAPER FABRIC SUSPENSIONS. |
| SE316363B (en) | 1966-12-01 | 1969-10-20 | Karlstad Mekaniska Ab | |
| SE374148B (en) * | 1972-08-31 | 1975-02-24 | S E E Ahlfors | |
| US3947314A (en) | 1974-04-29 | 1976-03-30 | The Black Clawson Company | Method of treating paper fibers in a stationary screen |
| US4017387A (en) * | 1975-08-11 | 1977-04-12 | The Black Clawson Company | Screening apparatus |
| SE427124B (en) * | 1980-01-28 | 1983-03-07 | Celleco Ab | DEVICE FOR FILING OF FIBER PASS PENSIONS |
| SE426958B (en) * | 1980-02-25 | 1983-02-21 | Celleco Ab | SEPARATOR FOR DIVISION OF AN INCOMING MIXTURE OF CELLULOSA SUSPENSION OR SIMILAR AND GROUND HEAVY PARTICLES |
| WO1986003688A1 (en) * | 1984-12-25 | 1986-07-03 | Mitsubishi Jukogyo Kabushiki Kaisha | Pressure slit screen |
| JPS61207689A (en) * | 1985-03-12 | 1986-09-16 | 三菱重工業株式会社 | Screening apparatus |
| JPS61207690A (en) * | 1985-03-12 | 1986-09-16 | 三菱重工業株式会社 | Screening apparatus |
| JPS61207069A (en) * | 1985-03-12 | 1986-09-13 | Nec Corp | semiconductor equipment |
-
1987
- 1987-01-19 FI FI870190A patent/FI76139C/en not_active IP Right Cessation
-
1988
- 1988-01-18 CA CA000556763A patent/CA1329333C/en not_active Expired - Fee Related
- 1988-01-19 DE DE198888100678T patent/DE275967T1/en active Pending
- 1988-01-19 JP JP63007648A patent/JPH0696834B2/en not_active Expired - Fee Related
- 1988-01-19 DE DE8888100678T patent/DE3866116D1/en not_active Revoked
- 1988-01-19 EP EP88100678A patent/EP0275967B1/en not_active Expired - Lifetime
- 1988-01-19 AT AT88100678T patent/ATE69472T1/en not_active IP Right Cessation
-
1991
- 1991-07-31 JP JP3191588A patent/JPH0533280A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0275967B1 (en) | 1991-11-13 |
| EP0275967A2 (en) | 1988-07-27 |
| EP0275967A3 (en) | 1989-02-08 |
| JPH0696834B2 (en) | 1994-11-30 |
| JPS63249792A (en) | 1988-10-17 |
| JPH0533280A (en) | 1993-02-09 |
| FI76139B (en) | 1988-05-31 |
| FI870190A0 (en) | 1987-01-19 |
| DE3866116D1 (en) | 1991-12-19 |
| ATE69472T1 (en) | 1991-11-15 |
| FI76139C (en) | 1988-09-09 |
| DE275967T1 (en) | 1989-06-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |