EP0294832A2 - Pulp screening apparatus - Google Patents
Pulp screening apparatus Download PDFInfo
- Publication number
- EP0294832A2 EP0294832A2 EP88109280A EP88109280A EP0294832A2 EP 0294832 A2 EP0294832 A2 EP 0294832A2 EP 88109280 A EP88109280 A EP 88109280A EP 88109280 A EP88109280 A EP 88109280A EP 0294832 A2 EP0294832 A2 EP 0294832A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- grooves
- screen
- rotor
- plane
- perforations
- 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.)
- Granted
Links
Images
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
- D21D5/023—Stationary screen-drums
- D21D5/026—Stationary screen-drums with rotating cleaning foils
-
- 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
- D21D5/16—Cylinders and plates for screens
Definitions
- U.S. Serial No. 738,743 is the Continuation-in-Part of U.S. Serial No. 472,742, which was issued as U.S.P. 4,529,520.
- the subject matter of U.S. Serial Nos. 472,742 and 738,743 is incorporated herein by reference.
- the present application relates generally to apparatuses for screening fiber suspensions of consistency between 0.3% up to 6%, and in particular, to a screening apparatus for screening papermaking pulp containing wood portions and other undesirable particles of various sizes and types.
- a pulp screening apparatus which comprises a vessel, a cylindrical screen within the vessel, a rotating element moving in the vicinity of the screen at a predetermined speed, an inlet for the unscreened pulp, an outlet for the accept screened pulp in the vessel, another outlet for the reject, in operative communication with the screen.
- the rotating element has a contour surface with grooves formed of a first bottom plane parallel to the envelope surface of the screen, an inclined plane and a side plane.
- the side plane is essentially perpendicular to the first bottom plane.
- the inclined plane forms an angle between 30° - 60° with the first plane.
- the upper plane is parallel to the first plane.
- the screen is also provided with grooves.
- pulp is produced by cooking wood which separates the wood into fibers. Due to the different properties of the wood even from the same tree, some of the fibers do not separate and are dispersed as fiber bundles usually called debris, shives or slivers which form the reject. There are also other impurities, such as bark, which must be removed.
- the screen must separate the undesirable impurities and debris called the rejects from the accept portion. In order to avoid substantial losses of fibers which could be carried over together with the debris in the reject portion, it is necessary to remove the impurities efficiently and selectively.
- the stock enters at the inlet end of the screening zone and travels in an angle along the screening surface with the acceptable portions of the stock passing through the screening surface and with the rejectable portions of the pulp traveling along the screening surface essentially in a spiral path and passing out of the screening zone at the reject end.
- the liquid that accompanies the fibrous stock passes through the screening surface more easily than the fibers. Therefore, as the stock travels along the screening zone, it tends to crease in consistency which means that the fiber-to-water ratio is increased. If this ratio increases too much, the screening process will be slowed down or will be even interrupted. In order to prevent this slow-down or interruption, it has been common practice to add more water to the stock to replace some of the water which has passed through the screening surface so as to maintain a satisfactory screening consistency on the inlet side.
- Another method used to maintain the screening consistency on the inlet side is to intentionally feed the apparatus with over-diluted stock so that the excess water at the inlet will be sufficient to allow for continuity of screening throughout the screening zone.
- both methods of adding more water during the screening or initially over-diluting the stock have undesirable effects such as diminishing the capacity of the screen by the amount of water added.
- Pulps of different consistencies require screens with different contours. Different contours are also required with pulp suspensions having different physical properties and for different applications.
- An object of the present invention is to separate the long fibers from slives and debris efficiently and selectively.
- Another object is to provide a screening apparatus which may be operated under smooth flow as well as under more turbulent flow conditions.
- Still another object is to maintain the desired screening efficiency without adding water during the screening operation and without using initially an overly diluted stock.
- a further object is to provide a screening apparatus which can operate at pulp feed consistencies between 0.3% up to 6%.
- Still another object is to provide a rotor which may be used with a variety of contoured screens, for a variety of pulp suspensions, which may provide the pumping effect required with the low consistency suspensions and which may provide the turbulence required for higher consistency stocks.
- the screening apparatus comprises a housing having an inlet for allowing fibrous stock to be introduced into the interior of the housing, an outlet for allowing the accepted screened stock to be removed from the housing, an outlet for the reject, a contoured screen within the housing, a rotor moving in the vicinity of the screen at a predetermined speed and forming together with the screen an annular screening chamber, the rotor having at least one partially contoured surface on the side facing screen and provided with a plurality of perforations along at least a portion of the length of the screening chamber to allow fibrous stock to be introduced into the screening chamber and to prevent the undesired debris of the stock from entering the chamber.
- the pulp flows from the outside to the inside of the screen and the contoured surface of the screen is on the outside of the screen.
- the screening apparatus includes a pressurized housing 1, a cylindrical screen 3 positioned within the housing, a rotor 4 mounted within the screen on the upper part of a rotatable, veritcal shaft 5.
- the housing has an inlet 6 for allowing unscreened pulp suspension to be introduced into a chamber 7 in the upper part of the housing, an outlet 8 for accepted (screened) stock, a reject chamber 19 and an outlet 9 for rejected stock in the lower end.
- a screening chamber 12 is formed between the cylindrical screen and the rotor.
- Numeral 15 designates the accept chamber.
- Numeral 2 designates a removable cover for the housing and numeral 11 designates a plate closing the upper end of the screening chamber.
- the housing includes an additional structure 17 which, together with a flange 18, forms a partition between the second chamber and a third chamber 19 which is the reject chamber in the bottom part of the housing.
- the stock inlet 6 communicates directly with the first chamber
- the accept outlet 8 communicates directly with the second chamber
- the reject outlet 9 communicates directly with the third chamber.
- axial bars or foils 20 which extend along at least a portion of the length of the rotor are mounted on a support adjacent the inner surface of the rotor.
- a plate 21 closes the lower end of the rotor. Openings 22 in the lower end of the rotor drum 23 provide communication between the space inside the rotor and the reject chamber.
- the screen plate 3 has a contoured surface. According to one embodiment, shown in Fig. 2, the cylindrical screen plate has grooves 24 in the inlet surface. Also the outside and the inside surfaces of the rotor are contoured with grooves 25 and 26, but the rotor could have only one contour surface facing the screen. The contour surface is not necessarily continuous.
- the grooves 25 on the screen side of the rotor are formed of a bottom plane 27 and two side planes 28 and 29.
- the grooves 26 on the inlet side of the rotor are likewise formed by a bottom plane 30 and two side planes 31 and 32.
- the bottom planes 27 and 30 are generally perpendicular to the side planes 32 and 29.
- the side planes 28 and 31 are generally inclined with respect to the cylindrical outer and inner surfaces.
- the angle ⁇ is formed between upper plane 33 and the inclined plane 28 and is in this embodiment between 5° and 60°.
- the angle ⁇ is formed between the envelope surface 34 and side plane 31 and is between 10° and 60°.
- the symbol H1 designates the distance between the bottom plane 27 and the upper plane 33 in the outer surface of the rotor and may be between 1/16 inch and 2 inches.
- the symbol H2 designates the distance between the bottom plane 30 and the envelope surface 34 in the inlet side of the rotor and may be between 1/16 inch and 2 inches.
- the symbols B1 and B2 designate the width of the bottom planes 27 and 30 in the outer and inner surface respectively of the rotor and may be as low as 1/8 inch and as long as 2 inches.
- the rotor 23 has a plurality of perforations 35 extending along a portion (L in Fig. 1) of its axial length beginning from its upper end and a size allowing fibrous stock to pass through the rotor but preventing foreign objects of larger size than the inlet openings 36 of the perforations from entering the screening zone 12.
- the inlet openings of the perforations are positioned in the bottom plane of the grooves 26 on the inlet side of the rotor and the discharge openings 37 are positioned either on the upper plane 33 of the outlet surface of the rotor or on the inclined plane 28 or on the bottom plane 27.
- the perforations in the rotor are either cylindrical or preferably slotted in section.
- the discharge opening of the perforations is preferably larger than the inlet opening.
- the grooves as well as the perforations of the rotor are larger than the grooves and the perforations of the screen in the embodiment of Fig. 2 but this in not essential.
- the rotor may also be constructed of profiled bars which, when assembled, form longitudinal openings therebetween which then constitute the perforations of the rotor.
- the profiled bars may be represented by the dotted lines drawn through the openings of the rotor as shown in Fig. 2.
- the inclined side plane on each surface of the rotor can be the leading side plane or the trailing plane of the groove in relation to the direction of the rotation of the rotor in the embodiment of Fig. 2.
- the rotor may rotate in different directions, that is, clockwise as shown in Fig. 2, for high efficiency, or counterclockwise to achieve high capacity.
- the grooves 25 and 26 may be located in relation to each other as shown in Fig. 2, that is the inclined planes being the downflow sides of the grooves. However, either or both of the grooves 25 and 26 may be formed so that the perpendicular planes 29, 32 are the downflow sides of the grooves. It is also possible that the grooves are so formed that every second groove has as its downflow side the inclined plane and the others have the perpendicular plane. Also it is possible to arrange the grooves in groups so that a certain group of grooves has as its downflow side the inclined planes and the next group of grooves the perpendicular planes.
- pulp suspension is supplied to the first chamber 7 in the upper end of the apparatus through inlet 6 and flows into the rotor 4.
- the fibrous stock flows through the perforations in the rotor to the screening chamber and particles larger than the perforations will not pass through the perforations of the rotor.
- the large cross-sectional area of the rotor allows heavy foreign material to settle for rejection through the openings 22 at the lower end of the rotor and allows the pulp suspension to flow in an almost radial direction towards the inner surface of the rotor.
- the stock which enters the screening chamber is set into circumferential motion by the rotor and subjected to high-intensity pulses and turbulence when flowing over essentially in a direction perpendicular to the grooves on the screen surface.
- the angle between the direction of the grooves and the axial direction of the cylinder of the screen plate may be from 0° to 45°.
- the acceptable fibers pass through the perforations in the screen to be collected in the chamber 15 surrounding the screen and are removed through the outlet 8 as accepted stock. Any stock not passing through the perforations of the rotor or the screen is collected in the chamber 19 in the lower end of the housing and is discharged through the outlet 9 as rejects.
- the screening chamber 12 between the rotor and the screen can be as narrow as 1 mm and as large as 50 mm.
- the screening chamber When the screening chamber is narrow, between 1 and 3 mm, an effective hydrodynamic interaction between the grooved surfaces of the rotor and the screen facing each other is achieved, and advantageous conditions for the screening are provided. This also permits the screen to efficiently handle stock of high consistency, up to 6%.
- the groove in the screen is formed of a bottom plane 40 which is substantially parallel with the envelope surface 42 of the screen surface, an upstream side plane 44 as seen standing from the bottom of the groove and a downstream side plane 45.
- the angle ⁇ between the envelope surface of the screen surface and the upstream side plane 44, or in other words between the plane tangenting the envelope surface of the screen surface close to this side plane and this side plane is approximately 90° and the angle ⁇ between the envelope surface of the screen surface and the downstream side plane 45 is 5° - 60°.
- the angle is ⁇ 5° - 60° and the angle ⁇ is 90°.
- the perforations of the screen plate are disposed on the bottom planes 40 of the grooves.
- the grooves 52 are U-shaped, and both side planes 44 and 45 are substantially perpendicular to the envelope surface 42 of the screen surface.
- the screen surface is undulant and both sides 44 and 45 of the grooves 52 are inclined with regard to the envelope surface 42 of the screen surface.
- the surface of the rotor which does not face the screen is not necessarily grooved and it is not necessary that the entire surface of the rotor be grooved.
- the inlet side of the rotor also may have a contour surface, for instance, the contour of the screen as shown in Figs. 3-8.
- This example describes a typical screening apparatus with a cylindrical rotor having an outer diameter of 20 inches and a thickness of 3/8 inch.
- Depth (H1 and H2) of grooves of the rotor 1/8 inch Width (B1 and B2) of bottom plane: 3/16 inch Angle ( ⁇ and ⁇ ) 50° Width of axial slots (36): 1/16 inch Circumferential spacing of grooves, that is the distance between consecutive grooves 26: 0.5 inch Width (W) of the screening chamber: 3/16 inch
- the grooves have two side planes, a bottom plane and an upper plane, one side plane is perpendicular to the envelope surface of the screen and the other side plane is curved, convex or concave with respect to the envelope surface.
- Fig. 8 the sides of the grooves have an inverted V-shape configuration.
- Figs. 1 and 2 show an apparatus intended for outflow operation
- the apparatus according to Fig. 9 may be readily adapted for inflow configuration according to which the pulp is fed into the outer surface of the rotor, goes through the perforations inwardly, flows into the screening chamber. Thereafter the accept portion passes through the finer perforations of the screen into the accept chamber and the remaining reject portion in the screening chamber moves towards the reject chamber. This operation is particularly advantageous when large dirt type particles are to be removed.
- Another advantage of the apparatus according to the present invention is that it may be retrofitted and used with conventional screen housings, resulting in major capital savings.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Paper (AREA)
Abstract
Description
- The present application is a Continuation-in-Part of U.S. Serial No. 738,743 filed on May 29, 1985 in the name of Harry Lampenius and Frey Frejborg. U.S. Serial No. 738,743 is the Continuation-in-Part of U.S. Serial No. 472,742, which was issued as U.S.P. 4,529,520. The subject matter of U.S. Serial Nos. 472,742 and 738,743 is incorporated herein by reference.
- The present application relates generally to apparatuses for screening fiber suspensions of consistency between 0.3% up to 6%, and in particular, to a screening apparatus for screening papermaking pulp containing wood portions and other undesirable particles of various sizes and types.
- In U.S. Serial No. 738,743, a pulp screening apparatus is described which comprises a vessel, a cylindrical screen within the vessel, a rotating element moving in the vicinity of the screen at a predetermined speed, an inlet for the unscreened pulp, an outlet for the accept screened pulp in the vessel, another outlet for the reject, in operative communication with the screen. The rotating element has a contour surface with grooves formed of a first bottom plane parallel to the envelope surface of the screen, an inclined plane and a side plane. The side plane is essentially perpendicular to the first bottom plane. The inclined plane forms an angle between 30° - 60° with the first plane. The upper plane is parallel to the first plane. The screen is also provided with grooves.
- In the paper making process, pulp is produced by cooking wood which separates the wood into fibers. Due to the different properties of the wood even from the same tree, some of the fibers do not separate and are dispersed as fiber bundles usually called debris, shives or slivers which form the reject. There are also other impurities, such as bark, which must be removed. The screen must separate the undesirable impurities and debris called the rejects from the accept portion. In order to avoid substantial losses of fibers which could be carried over together with the debris in the reject portion, it is necessary to remove the impurities efficiently and selectively.
- It should be stressed that different applications have different requirements. In some applications, it is necessary to achieve a high content of long fibers, especially secondary fibers, in the accepts because the long fibers give strength to the final product, for instance paper. In other applications, on the other hand, the contrary is true. For instance, in virgin or pulp mill fibers, it is desirable to concentrate the long fibers in the reject for reject refining.
- In some applications, it is preferable to operate the screen under smoother flow conditions while in other applications, it is advantageous to operate the screen under more turbulent conditions.
- In pulp screening apparatus having a screen member and a rotor which form an annular screening zone, the stock enters at the inlet end of the screening zone and travels in an angle along the screening surface with the acceptable portions of the stock passing through the screening surface and with the rejectable portions of the pulp traveling along the screening surface essentially in a spiral path and passing out of the screening zone at the reject end. During the screening process, the liquid that accompanies the fibrous stock passes through the screening surface more easily than the fibers. Therefore, as the stock travels along the screening zone, it tends to crease in consistency which means that the fiber-to-water ratio is increased. If this ratio increases too much, the screening process will be slowed down or will be even interrupted. In order to prevent this slow-down or interruption, it has been common practice to add more water to the stock to replace some of the water which has passed through the screening surface so as to maintain a satisfactory screening consistency on the inlet side.
- Another method used to maintain the screening consistency on the inlet side is to intentionally feed the apparatus with over-diluted stock so that the excess water at the inlet will be sufficient to allow for continuity of screening throughout the screening zone. However, both methods of adding more water during the screening or initially over-diluting the stock have undesirable effects such as diminishing the capacity of the screen by the amount of water added.
- Many proposals have been made to solve the problems discussed hereinabove. In
Swedish Patent 37 4148 to S.E.E. Ahlfors published in 1975 the apparatus comprises a pressure screen having a coarse screening drum and a fine screening drum, the former surrounding the latter and provided with pulse generating means and perforations on the back side of or immediately behind the pulse generating means. This apparatus has the drawback that it cannot be readily used in an existing housing as a retrofit and would be very expensive since two motors are required to rotate the two drums, one independently from the other. - In Finnish Patent 66218 to Sunds Defibrator Aktiebolag, published in 1979, a screen apparatus is described in which a rotating coarse screening drum and a fine screening drum, are provided. The former is provided with pumping means to remove by suction, impurities which have plugged the openings of the fine screening drum. This proposal which involves coarse screening and fine screening has met only with parial success because of high manufacturing cost and low general performance. Further, due to the size and operational conditions of the pumping pipes, this apparatus cannot be readily used in a conventional housing as a retrofit.
- The apparatus of Finnish Patent 66218 is also described in Tappi Journal, September, 1986,
page 27, and in Tappi Proceedings, (1986) Engineering Conference, pp. 585-587. - Pulps of different consistencies require screens with different contours. Different contours are also required with pulp suspensions having different physical properties and for different applications.
- An object of the present invention is to separate the long fibers from slives and debris efficiently and selectively.
- Another object is to provide a screening apparatus which may be operated under smooth flow as well as under more turbulent flow conditions.
- Still another object is to maintain the desired screening efficiency without adding water during the screening operation and without using initially an overly diluted stock.
- A further object is to provide a screening apparatus which can operate at pulp feed consistencies between 0.3% up to 6%.
- Still another object is to provide a rotor which may be used with a variety of contoured screens, for a variety of pulp suspensions, which may provide the pumping effect required with the low consistency suspensions and which may provide the turbulence required for higher consistency stocks.
- To achieve the above objects, the screening apparatus according to the invention comprises a housing having an inlet for allowing fibrous stock to be introduced into the interior of the housing, an outlet for allowing the accepted screened stock to be removed from the housing, an outlet for the reject, a contoured screen within the housing, a rotor moving in the vicinity of the screen at a predetermined speed and forming together with the screen an annular screening chamber, the rotor having at least one partially contoured surface on the side facing screen and provided with a plurality of perforations along at least a portion of the length of the screening chamber to allow fibrous stock to be introduced into the screening chamber and to prevent the undesired debris of the stock from entering the chamber.
- Other objects and features of the present invention will be apparent from the following description taken in conjunction with the appended drawings, of which:
- Fig. 1 is a side elevation view, partly broken away, of a screening apparatus according to the invention.
- Fig. 2 illustrates the embodiment of the screening apparatus according to the present invention and specifically with the rotor being located on the inlet side of the screen. The rotor is always disposed on the inlet side of the screen but the apparatus may be operated in an outflow or inflow manner. In the outflow manner of Fig. 2 the pulp flows from the inside to the outside of the screen and the contoured surface of the screen is on the inside of the screen.
- Figs. 3,4,5,6,7 and 8 illustrate screenplates which may be used together with the rotor according to the present invention.
- Fig. 9 illustrates an apparatus intended for inflow configuration.
- In the embodiment of Fig. 9, the pulp flows from the outside to the inside of the screen and the contoured surface of the screen is on the outside of the screen.
- As illustrated in Figs. 1 and 2 the screening apparatus includes a pressurized
housing 1, acylindrical screen 3 positioned within the housing, a rotor 4 mounted within the screen on the upper part of a rotatable,veritcal shaft 5. The housing has an inlet 6 for allowing unscreened pulp suspension to be introduced into achamber 7 in the upper part of the housing, an outlet 8 for accepted (screened) stock, areject chamber 19 and anoutlet 9 for rejected stock in the lower end. Ascreening chamber 12 is formed between the cylindrical screen and the rotor.Numeral 15 designates the accept chamber. - Numeral 2 designates a removable cover for the housing and
numeral 11 designates a plate closing the upper end of the screening chamber. Aflange 14 in the upper end of the cylindrical screen by means of which the screen member is fixed to thestructure 10 and thestructure 10 form a partition between thefirst chamber 7 in the upper part of the housing which is the infeed chamber and asecond chamber 15 which is the accept chamber. The latter is formed between thevertical walls 16 of the housing and the cylindrical screen which second chamber surrounds the cylindrical screen. The housing includes anadditional structure 17 which, together with aflange 18, forms a partition between the second chamber and athird chamber 19 which is the reject chamber in the bottom part of the housing. The stock inlet 6 communicates directly with the first chamber, the accept outlet 8 communicates directly with the second chamber and thereject outlet 9 communicates directly with the third chamber. - Essentially, axial bars or
foils 20 which extend along at least a portion of the length of the rotor are mounted on a support adjacent the inner surface of the rotor. Aplate 21 closes the lower end of the rotor.Openings 22 in the lower end of therotor drum 23 provide communication between the space inside the rotor and the reject chamber. - The
screen plate 3 has a contoured surface. According to one embodiment, shown in Fig. 2, the cylindrical screen plate hasgrooves 24 in the inlet surface. Also the outside and the inside surfaces of the rotor are contoured withgrooves - The
grooves 25 on the screen side of the rotor are formed of abottom plane 27 and twoside planes grooves 26 on the inlet side of the rotor are likewise formed by abottom plane 30 and twoside planes - The bottom planes 27 and 30 are generally perpendicular to the side planes 32 and 29. The side planes 28 and 31 are generally inclined with respect to the cylindrical outer and inner surfaces. The angle α is formed between
upper plane 33 and theinclined plane 28 and is in this embodiment between 5° and 60°. The angle β is formed between theenvelope surface 34 andside plane 31 and is between 10° and 60°. - The symbol H₁ designates the distance between the
bottom plane 27 and theupper plane 33 in the outer surface of the rotor and may be between 1/16 inch and 2 inches. The symbol H₂ designates the distance between thebottom plane 30 and theenvelope surface 34 in the inlet side of the rotor and may be between 1/16 inch and 2 inches. The symbols B₁ and B₂ designate the width of the bottom planes 27 and 30 in the outer and inner surface respectively of the rotor and may be as low as 1/8 inch and as long as 2 inches. - The
rotor 23 has a plurality ofperforations 35 extending along a portion (L in Fig. 1) of its axial length beginning from its upper end and a size allowing fibrous stock to pass through the rotor but preventing foreign objects of larger size than theinlet openings 36 of the perforations from entering thescreening zone 12. The inlet openings of the perforations are positioned in the bottom plane of thegrooves 26 on the inlet side of the rotor and thedischarge openings 37 are positioned either on theupper plane 33 of the outlet surface of the rotor or on theinclined plane 28 or on thebottom plane 27. - The perforations in the rotor are either cylindrical or preferably slotted in section. The discharge opening of the perforations is preferably larger than the inlet opening.
- The grooves as well as the perforations of the rotor are larger than the grooves and the perforations of the screen in the embodiment of Fig. 2 but this in not essential. The rotor may also be constructed of profiled bars which, when assembled, form longitudinal openings therebetween which then constitute the perforations of the rotor. The profiled bars may be represented by the dotted lines drawn through the openings of the rotor as shown in Fig. 2.
- The inclined side plane on each surface of the rotor can be the leading side plane or the trailing plane of the groove in relation to the direction of the rotation of the rotor in the embodiment of Fig. 2.
- The rotor may rotate in different directions, that is, clockwise as shown in Fig. 2, for high efficiency, or counterclockwise to achieve high capacity.
- The
grooves grooves perpendicular planes - In the outflow operation shown in Figs. 1 and 2, pulp suspension is supplied to the
first chamber 7 in the upper end of the apparatus through inlet 6 and flows into the rotor 4. The fibrous stock flows through the perforations in the rotor to the screening chamber and particles larger than the perforations will not pass through the perforations of the rotor. The large cross-sectional area of the rotor allows heavy foreign material to settle for rejection through theopenings 22 at the lower end of the rotor and allows the pulp suspension to flow in an almost radial direction towards the inner surface of the rotor. Due to the interaction between the rotating grooved surface of the rotor and the pulp suspension which is prevented from rotating by the essentiallyaxial flow interruptors 20, high-intensity pulses and turbulence are generated which prevent a mat of fibers from forming at the openings in thegrooves 26. By adjusting the position and the inclination of the flow interruptors in relation to the grooved surface, the intensity of the pulses and the turbulence can be varied. If required, dilution water could be directed through the flow interruptors toward the grooved surface in the lower part of the rotor. - The stock which enters the screening chamber is set into circumferential motion by the rotor and subjected to high-intensity pulses and turbulence when flowing over essentially in a direction perpendicular to the grooves on the screen surface. The angle between the direction of the grooves and the axial direction of the cylinder of the screen plate may be from 0° to 45°. The acceptable fibers pass through the perforations in the screen to be collected in the
chamber 15 surrounding the screen and are removed through the outlet 8 as accepted stock. Any stock not passing through the perforations of the rotor or the screen is collected in thechamber 19 in the lower end of the housing and is discharged through theoutlet 9 as rejects. - The
screening chamber 12 between the rotor and the screen can be as narrow as 1 mm and as large as 50 mm. - When the screening chamber is narrow, between 1 and 3 mm, an effective hydrodynamic interaction between the grooved surfaces of the rotor and the screen facing each other is achieved, and advantageous conditions for the screening are provided. This also permits the screen to efficiently handle stock of high consistency, up to 6%.
- In the embodiments of Figs. 3 and 4, the groove in the screen is formed of a
bottom plane 40 which is substantially parallel with theenvelope surface 42 of the screen surface, anupstream side plane 44 as seen standing from the bottom of the groove and adownstream side plane 45. In Fig. 3, the angle α between the envelope surface of the screen surface and theupstream side plane 44, or in other words between the plane tangenting the envelope surface of the screen surface close to this side plane and this side plane is approximately 90° and the angle β between the envelope surface of the screen surface and thedownstream side plane 45 is 5° - 60°. In Fig. 4 the angle is α 5° - 60° and the angle β is 90°. The perforations of the screen plate are disposed on the bottom planes 40 of the grooves. - In the embodiment illustrated in Fig. 5, the
grooves 52 are U-shaped, and bothside planes envelope surface 42 of the screen surface. - In the embodiment of Fig. 6, the screen surface is undulant and both
sides grooves 52 are inclined with regard to theenvelope surface 42 of the screen surface. - The surface of the rotor which does not face the screen is not necessarily grooved and it is not necessary that the entire surface of the rotor be grooved.
- The inlet side of the rotor also may have a contour surface, for instance, the contour of the screen as shown in Figs. 3-8.
- This example describes a typical screening apparatus with a cylindrical rotor having an outer diameter of 20 inches and a thickness of 3/8 inch.
Depth (H₁ and H₂) of grooves of the rotor: 1/8 inch
Width (B₁ and B₂) of bottom plane: 3/16 inch
Angle (α and β ) 50°
Width of axial slots (36): 1/16 inch
Circumferential spacing of grooves, that is the distance between consecutive grooves 26: 0.5 inch
Width (W) of the screening chamber: 3/16 inch - In the embodiment of Fig. 7, in the screen, the grooves have two side planes, a bottom plane and an upper plane, one side plane is perpendicular to the envelope surface of the screen and the other side plane is curved, convex or concave with respect to the envelope surface.
- In Fig. 8 the sides of the grooves have an inverted V-shape configuration.
- Although Figs. 1 and 2 show an apparatus intended for outflow operation, the apparatus according to Fig. 9 may be readily adapted for inflow configuration according to which the pulp is fed into the outer surface of the rotor, goes through the perforations inwardly, flows into the screening chamber. Thereafter the accept portion passes through the finer perforations of the screen into the accept chamber and the remaining reject portion in the screening chamber moves towards the reject chamber. This operation is particularly advantageous when large dirt type particles are to be removed.
- Another advantage of the apparatus according to the present invention is that it may be retrofitted and used with conventional screen housings, resulting in major capital savings.
Claims (28)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US61594 | 1987-06-11 | ||
US07/061,594 US4880540A (en) | 1983-01-26 | 1987-06-11 | Pulp screening apparatus |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0294832A2 true EP0294832A2 (en) | 1988-12-14 |
EP0294832A3 EP0294832A3 (en) | 1989-03-08 |
EP0294832B1 EP0294832B1 (en) | 1991-04-17 |
Family
ID=22036818
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP88109280A Expired - Lifetime EP0294832B1 (en) | 1987-06-11 | 1988-06-10 | Pulp screening apparatus |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0294832B1 (en) |
BR (1) | BR8807561A (en) |
DE (2) | DE3862433D1 (en) |
FI (1) | FI882569A (en) |
WO (1) | WO1988009843A1 (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH03505759A (en) * | 1989-03-02 | 1991-12-12 | エイ.アフルストロム コーポレーション | Method and apparatus for concentrating fiber suspension |
WO1996023930A1 (en) * | 1995-02-03 | 1996-08-08 | Hermann Finckh Maschinenfabrik Gmbh & Co. | Fibre suspension pressure sorting machine and sieve for such pressure sorting machines |
WO1997002384A1 (en) * | 1995-07-03 | 1997-01-23 | Sunds Defibrator Industries Ab | Sealing device |
ES2155410A1 (en) * | 1999-08-24 | 2001-05-01 | Perez Ernesto Pastor | Apparatus for purifying paper pulp comprises three independent purification phases and contains rotor divided into two different parts rotating within the carcasse provided with double walls |
WO2004046457A1 (en) * | 2002-11-19 | 2004-06-03 | Advanced Fiber Technologies (Aft) Oy | Method and apparatus for treating fiber suspension |
USRE39940E1 (en) | 1990-08-16 | 2007-12-18 | Advanced Fiber Technologies (Aft) Trust | Screen plates and methods of manufacture |
US8297445B2 (en) | 2007-11-14 | 2012-10-30 | Filtration Fibrewall Inc. | Screen basket |
US8469198B2 (en) | 2005-05-09 | 2013-06-25 | Kadant Canada Corp. | Screen basket with replaceable profiled bars |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
AU6713190A (en) * | 1989-10-23 | 1991-05-16 | Beloit Corporation | Basket profile for screens |
FI121794B (en) * | 2009-10-23 | 2011-04-15 | Andritz Oy | Device for treating fiber suspension |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1070451A (en) * | 1964-04-29 | 1967-06-01 | Ingersoll Rand Canada | Screening apparatus |
GB1118646A (en) * | 1965-03-30 | 1968-07-03 | Ingersoll Rand Canada | Screening apparatus |
FR2193638A1 (en) * | 1972-07-24 | 1974-02-22 | Nivoba Bv | |
US3939065A (en) * | 1972-08-31 | 1976-02-17 | Ahlfors S E E | Screening device |
FR2384889A1 (en) * | 1977-03-23 | 1978-10-20 | Finckh Maschf | SCRUBBER-SORTER FOR THE SEPARATION OF FIBER SUSPENSIONS |
EP0079811A1 (en) * | 1981-11-18 | 1983-05-25 | E. + M. Lamort Société Anonyme dite: | Screening devices for paper stock, and their screens |
US4529520A (en) * | 1983-01-26 | 1985-07-16 | A. Ahlstrom Osakeyhtio | Screen plate |
EP0206975A2 (en) * | 1985-06-20 | 1986-12-30 | Beloit Corporation | High consistency pressure screen and method of separating accepts and rejects |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0205623B1 (en) * | 1984-12-25 | 1989-09-13 | Mitsubishi Jukogyo Kabushiki Kaisha | Pressure slit screen |
FI77481C (en) * | 1985-05-29 | 1989-03-10 | Ahlstroem Oy | Strainer. |
-
1988
- 1988-06-01 WO PCT/FI1988/000085 patent/WO1988009843A1/en unknown
- 1988-06-01 BR BR888807561A patent/BR8807561A/en unknown
- 1988-06-01 FI FI882569A patent/FI882569A/en not_active IP Right Cessation
- 1988-06-10 DE DE8888109280T patent/DE3862433D1/en not_active Expired - Fee Related
- 1988-06-10 DE DE1988109280 patent/DE294832T1/en active Pending
- 1988-06-10 EP EP88109280A patent/EP0294832B1/en not_active Expired - Lifetime
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1070451A (en) * | 1964-04-29 | 1967-06-01 | Ingersoll Rand Canada | Screening apparatus |
GB1118646A (en) * | 1965-03-30 | 1968-07-03 | Ingersoll Rand Canada | Screening apparatus |
FR2193638A1 (en) * | 1972-07-24 | 1974-02-22 | Nivoba Bv | |
US3939065A (en) * | 1972-08-31 | 1976-02-17 | Ahlfors S E E | Screening device |
FR2384889A1 (en) * | 1977-03-23 | 1978-10-20 | Finckh Maschf | SCRUBBER-SORTER FOR THE SEPARATION OF FIBER SUSPENSIONS |
EP0079811A1 (en) * | 1981-11-18 | 1983-05-25 | E. + M. Lamort Société Anonyme dite: | Screening devices for paper stock, and their screens |
US4529520A (en) * | 1983-01-26 | 1985-07-16 | A. Ahlstrom Osakeyhtio | Screen plate |
EP0206975A2 (en) * | 1985-06-20 | 1986-12-30 | Beloit Corporation | High consistency pressure screen and method of separating accepts and rejects |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH03505759A (en) * | 1989-03-02 | 1991-12-12 | エイ.アフルストロム コーポレーション | Method and apparatus for concentrating fiber suspension |
USRE39940E1 (en) | 1990-08-16 | 2007-12-18 | Advanced Fiber Technologies (Aft) Trust | Screen plates and methods of manufacture |
WO1996023930A1 (en) * | 1995-02-03 | 1996-08-08 | Hermann Finckh Maschinenfabrik Gmbh & Co. | Fibre suspension pressure sorting machine and sieve for such pressure sorting machines |
US6029825A (en) * | 1995-02-03 | 2000-02-29 | Hermann Finckh Maschinenfabrik Gmbh & Co. | Pressure sorter for sorting fiber suspensions as well as screen for such a pressure sorter |
WO1997002384A1 (en) * | 1995-07-03 | 1997-01-23 | Sunds Defibrator Industries Ab | Sealing device |
AU691120B2 (en) * | 1995-07-03 | 1998-05-07 | Sunds Defibrator Industries Ab | Sealing device |
US6113104A (en) * | 1995-07-03 | 2000-09-05 | Valmet Fibertech Aktiebolag | Sealing device |
ES2155410A1 (en) * | 1999-08-24 | 2001-05-01 | Perez Ernesto Pastor | Apparatus for purifying paper pulp comprises three independent purification phases and contains rotor divided into two different parts rotating within the carcasse provided with double walls |
WO2004046457A1 (en) * | 2002-11-19 | 2004-06-03 | Advanced Fiber Technologies (Aft) Oy | Method and apparatus for treating fiber suspension |
US8469198B2 (en) | 2005-05-09 | 2013-06-25 | Kadant Canada Corp. | Screen basket with replaceable profiled bars |
US8297445B2 (en) | 2007-11-14 | 2012-10-30 | Filtration Fibrewall Inc. | Screen basket |
Also Published As
Publication number | Publication date |
---|---|
EP0294832B1 (en) | 1991-04-17 |
FI882569A0 (en) | 1988-06-01 |
DE3862433D1 (en) | 1991-05-23 |
FI882569A (en) | 1988-12-12 |
DE294832T1 (en) | 1989-07-13 |
WO1988009843A1 (en) | 1988-12-15 |
BR8807561A (en) | 1990-04-17 |
EP0294832A3 (en) | 1989-03-08 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4880540A (en) | Pulp screening apparatus | |
CA2133630C (en) | Method and apparatus for screening waste paper pulp | |
US5000842A (en) | Method and apparatus for treating fiber suspension | |
EP0473354B1 (en) | Apparatus for pressurised screening of a fibrous material liquid suspension | |
US4744894A (en) | Fibrous stock screening apparatus | |
EP0294832B1 (en) | Pulp screening apparatus | |
US5798025A (en) | Apparatus for screening waste paper pulp | |
EP0774022B1 (en) | Method and apparatus for screening a fiber suspension | |
US5172813A (en) | Method and an apparatus for treating fiber suspension | |
US4383918A (en) | High turbulence screen | |
US5224603A (en) | Apparatus for treating fiber suspension | |
US6391153B1 (en) | Process and apparatus for the production of cellulose pulps of improved quality | |
CA1275973C (en) | Rotating element for a screening apparatus with a contour surface | |
EP4144913A1 (en) | Pulp screening machine | |
US6571957B1 (en) | Screening apparatus for fiber suspension | |
US20040004032A1 (en) | Process for wet screening fibrous suspensions | |
EP0398685A1 (en) | A method and an apparatus for treating fiber suspension | |
EP0299258A1 (en) | A high flow capacity barrier type screening apparatus and method therefor | |
EP0067912B1 (en) | Paper making stock screen and a system for treating paper making stock | |
AT408771B (en) | SORTER FOR CLEANING A FIBER SUSPENSION | |
EP0312273B1 (en) | Method and apparatus for treating fiber suspension | |
WO1987004474A1 (en) | Screen cylinder | |
US5034120A (en) | Method for keeping a screen or filter surface clear | |
JPH0423038B2 (en) | ||
EP1159482B1 (en) | Screening apparatus |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 19881017 |
|
AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): DE ES FR GB IT SE |
|
PUAL | Search report despatched |
Free format text: ORIGINAL CODE: 0009013 |
|
AK | Designated contracting states |
Kind code of ref document: A3 Designated state(s): DE ES FR GB IT SE |
|
EL | Fr: translation of claims filed | ||
DET | De: translation of patent claims | ||
RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: A. AHLSTROM CORPORATION |
|
17Q | First examination report despatched |
Effective date: 19891110 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE ES FR GB IT SE |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRE;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.SCRIBED TIME-LIMIT Effective date: 19910417 Ref country code: ES Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY Effective date: 19910417 Ref country code: SE Effective date: 19910417 |
|
REF | Corresponds to: |
Ref document number: 3862433 Country of ref document: DE Date of ref document: 19910523 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 19910530 Year of fee payment: 4 |
|
EN | Fr: translation not filed | ||
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Effective date: 19910906 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed | ||
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Effective date: 19920610 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 19920610 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Effective date: 19930302 |