AN ACCEPT TANK MIXING ARRANGEMENT

Abstract

An accept tank arrangement for mixing of pulped fiber suspension including sidewalls (3,4) including opposite arched ends (2) and an elongated section (1) between the arched ends (2). The accept tank has mixers (10) each located within one of the arched ends (2). The mixers (10) have axles (11) on which are mounted propellers (12). The mixers (10) are aligned horizontally and each axle points to a respective point on the elongated section (1) of the sidewall (3) which away from an end of the elongate section by at least 25% of the length of the elongated section (1). The propellers (12) are symmetrically positioned with respect to a center-point of the accept tank. Within the center of the elongated section is an elongated centerpiece (6) having rounded ends. The accept tank has a substantially flat bottom at least at the elongated section (1) of the accept tank.

Claims

1. An accept tank arrangement for mixing of pulped fiber suspension, the accept tank arrangement comprising: an accept tank comprising sidewalls including a first elongated sidewall and a second elongated sidewall on opposite side of the accept tank from the first elongated sidewall, and a first arched sidewall end and a second arched sidewall end at an end of the accept tank opposite to the first arched sidewall; an accept outlet in one of the first and second elongated sidewalls, a first mixer having a first axel driving a first propeller a region within the tank boarded by the first arched sidewall end, wherein a first axis of the first axel projects through a first point on the first elongated sidewall no less than twenty-five percent (25%) of a length of the first elongated sidewall away from the first arched sidewall end, a second mixer having a second axel driving a second propeller in a region within the tank boarded by the second arched sidewall end, wherein a second axis of the second axel projects through a second point on the second elongated sidewall no less than twenty-five percent (25%) of a length of the second elongated sidewall away from the second arched sidewall end, and an accept outlet.

2. The accept tank arrangement of claim 1, wherein the said first axle on a side of accept tank opposite a longitudinal center line of the accept tank than the accept outlet.

3. The accept tank arrangement of claim 1, wherein the first mixer and the second mixer are the only mixers in the accept tank.

4. The accept tank arrangement of claim 1, wherein the first and second propellers are arranged symmetrically about a center point of the accept tank.

5. The accept tank arrangement of claim 1, further comprising an elongated centerpiece aligned with a longitudinal centerline of the accept tank and extending upward from a bottom of the accept tank, wherein the elongated section has a length no less than 50% of the length of the first elongated sidewall.

6. The accept tank arrangement of claim 5, wherein the elongated centerpiece has rounded ends and a width no greater than 30% of a width of the accept tank.

7. The accept tank arrangement of claim 1, wherein the accept tank has a bottom which includes a flat bottom region adjacent each of the first and second elongated sidewalls, variation of a depth at flat bottom region is less than 5% of the length of the first elongated sidewall.

8. The accept tank arrangement of claim 1, further comprising a reject outlet located at least partially at a bottom of the accept tank and at least partially within one of the first and second arched sidewalls.

9. The accept tank arrangement of claim 1, wherein at least a part of the accept outlet is between the first elongated sidewall and second elongated sidewall, the accept outlet is proximate ends for the first and second elongated sidewalls, and the accept outlet on a side of an elongated centerline of the accept tank opposite to the first or second propeller nearest the accept outlet.

10. The accept tank arrangement of claim 1, further comprising a reject outlet downstream of the accept outlet along a flow direction within the accept tank and adjacent the elongated sidewall nearest the accept outlet.

11. The accept tank arrangement of claim 1, wherein the first axle and the second axle are each oriented in a horizontal plane at an angle in a range of 15 to 35 degrees from a longitudinal center line of the accept tank.

12. The accept tank arrangement of claim 11, wherein the range is 20 to 30 degrees.

13. The accept tank arrangement of any of claim 1, wherein a length of the accept tank is in a range of 1.5 to 2 times a width of the accept tank.

14. The accept tank arrangement of claim 1, wherein the first and second propellers each have a diameter in a range of 10% to 20% of a width of the accept tank.

15. An accept tank assembly for mixing of pulped fiber suspension, the accept tank comprising: an accept tank with a bottom, sidewalls of the accept tank extending around a periphery of the bottom, the sidewalls including a first elongated sidewall, a second elongated sidewall opposite to the first elongated sidewall, a first arched sidewall at first ends of the first and second elongated sidewalls and a second arched sidewall at second ends of the first and second elongated sidewall, an accept outlet for the accept tank, a first mixer having a first axel driving a first propeller boarded by the first arched sidewall, wherein a first axis of the first axel projects through a first point on the first elongated sidewall at least twenty-five percent (25%) of a total length of the first elongated sidewall away from the first arched sidewall, and a second mixer having a second axel driving a second propeller in a region within the tank boarded by the second arched sidewall, wherein a second axis of the second axel projects through a second point on the second elongated sidewall at least twenty-five percent (25%) of a total length of the elongated sidewall away from the second arched sidewall.

16. The accept tank assembly of claim 15, further comprising an elongated centerpiece aligned with a longitudinal centerline of the accept tank and extending upward from the bottom, wherein the elongated section has a length no less than 50% of the length of the first elongated sidewall.

17. The accept tank assembly of claim 15, further comprising a reject outlet in the bottom and at least partially bordered by one of the first and second arched sidewalls.

18. The accept tank assembly of claim 15, wherein the accept outlet is proximate ends for the first and second elongated sidewalls and on a side of an elongated centerline of the accept tank opposite to the first or second propeller nearest the accept outlet.

19. The accept tank assembly of claim 15, wherein the first axle and the second axle are each oriented in a horizontal plane at an angle in a range of 15 to 35 degrees from a longitudinal center line of the accept tank.

20. The accept tank assembly of claim 15, wherein the first and second propellers each have a diameter in a range of 10% to 20% of a width of the accept tank.

Description

LIST OF DRAWINGS

[0010] The invention will be described in more detail with reference to the appended drawings in which:

[0011] FIG. 1 illustrates a top view of an embodiment of an accept tank arrangement and

[0012] FIG. 2 illustrates a side view of the accept tank arrangement.

DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 illustrates a top view of an embodiment of an accept tank arrangement and FIG. 2 illustrates a side view of the accept tank arrangement. An accept tank is usually placed under a screened end part of a drum pulper, which processes wastepaper or other fibrous material. Suspension of pulped fibers and small particles drop through the screen to the accept tank directly or flow down along a funnel part 5 surrounding the tank. The accept tank preferably has a substantially flat bottom at least at central elongated section 1 The elongated section 1 has sidewalls 3 which are normally vertical and straight. The sidewall 3 may also be longitudinally curved, preferably outwards in order to create an oval form of the tank. At both ends of the tank are arched ends 2 which have vertical arched sidewalls 4. A straight section may exist between two arched sidewall 4 sections. The arched corner sections ensure that the flow will smoothly circulate in and out of the arched ends 2. The bottom of the accept tank has preferably bevels 7 at all edges for avoiding steady water and precipitation of heaviest particles at the edges. The direction of the circular flow is marked with an arrow in. FIG. 1.

[0014] Preferably an elongated centerpiece 6 is positioned within the middle of the elongated section 1 for preventing interaction between right and left direction flows. For best flow properties, both ends of the elongated centerpiece 6 are rounded. The elongated centerpiece should have enough width in order to minimize turbulence at the ends of it, where the circular flow will turn to another side of the tank. Preferred width of the elongated centerpiece 6 is between 10% to 30% of the width of the tank.

[0015] A mixer 10 normally comprises an electric motor, a gearbox, and an axle 11 with a propeller 12 at the end of the axle 11. The propeller 12 typically creates propulsion flow away to the direction of the center line of the axle 11. Any other combinations that is illustrated may be used for the implementing the invention as the main effect is based on the initial position and direction of the propulsion flow. For example, a short propellor axle 11 and a 90 degrees gearbox like in outboard engines can be used instead. The propeller 12 may have a fan tube around it for best propulsion performance, but any stable crossflow obstacles should be avoided for avoiding accumulation of fibers around them.

[0016] Horizontal alignment a of at least one axle 11 of the mixer 10 is such that the centerline of the axle i.e. the thrust vector of the mixer is aimed at a point P, which is at the sidewall of the elongated section 1 at least 25% of the length of the elongated section 1 away from the beginning of the elongated section 1. More advantageously, the point P lies within 30 to 60% of the length of the elongated section 1 from the beginning of the elongated section 1. For best flowing properties, the propeller 12 at the end of the at least one axle 11 is located within the arched end 2. In principle, best flow properties are achieved, if the positions and alignments are symmetric with respect to the centerpoint of the tank. The horizontal alignment a of the at least one axle of the mixers is from 15 to 35 degrees and more preferably from 20 to 30 degrees from the longitudinal center line of the accept tank. Because the accept outlet 10 affects a bit to the flow, the propeller 12 at that side of the tank may be positioned and/or aligned differently depending of the position, dimensions and form of the accept outlet 10.

[0017] An accept outlet 8 is preferably positioned far away in flow direction from a propeller 12. The accept outlet 8 may be for example a downward curved tube. The accept outlet 8 tube may be profiled to have an optimized streamlined shape for least drag effect to the circular flow. If the tank has a reject outlet 9, it should be placed after the accept outlet 8, where the flow is slowest and most turbulent. Preferably the reject outlet 9 is located at least partially within the curved end 2. Any known design of a reject outlet 9 with conveying means can be used. Some suitable examples of reject outlets are disclosed in publication CN108330719.