US3921512A

US3921512A - Apparatus for treating slurries

Info

Publication number: US3921512A
Application number: US343236A
Authority: US
Inventors: Michael P H Burns
Original assignee: Watford Engineering Ltd
Current assignee: Watford Engineering Ltd
Priority date: 1972-03-29
Filing date: 1973-03-21
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25
Also published as: JPS497862A; GB1430592A

Abstract

De-watering apparatus comprises an inclined hollow perforated tubular member having a slurry inlet at its bottom end. Inside the tubular member, an Archimedian screw is arranged around an upwardly inclined rotatable shaft, and this lifts the slurry which becomes de-watered by the effect of gravity exerted on the raised mass of the slurry. At its upper end the shaft is outwardly tapered to reduce the surface area of the Archimedian platform and thus the slurry volume per pitch which can be carried. A piston is slidably mounted on the upper end of the shaft and exerts a controllable back pressure against the raised slurry, to increase the de-watering effect.

Description

United States Patent 1191 1111 3,921,512 Burns 1 1 Nov. 25, 1975 [54] APPARATUS FOR TREATING SLURRIES 3,092,338 6/1963 Reinhalll 100/117 X 3,426,677 2/1969 Combs et al. 100/117 [75] Invent Bums Hurley 3,688,687 9/1972 Craig et al. 100/117 England [73] Assignee: Watiord Engineering Limited, Primary ExaminerPeter Feldman Watford, England Attorney, Agent, or Firm-Mason, Mason & Albright [22] Filed: Mar. 21, 1973 Appl. No.: 343,236

[57] ABSTRACT De-watering apparatus comprises an inclined hollow perforated tubular member having a slurry inlet at its bottom end. Inside the tubular member, an Archimedian screw is arranged around an upwardly inclined rotatable shaft, and this lifts the slurry which becomes de-watered by the effect of gravity exerted on the raised mass of the slurry, At its upper end the shaft is outwardly tapered to reduce the surface area of the Archimedian platform and thus the slurry volume per pitch which can be carried. A piston is slidably mounted on the upper end of the shaft and exerts a controllable back pressure against the raised slurry, to increase the de-watering effect.

1 Claim, 3 Drawing Figures a 68 60 r 70 5a g1; /l52 98- 78 L92 7 \84 54 i US. Patent Nov. 25, 1975 Sheet2 of3 3,921,512

i 12/ I GGDQ Nov. 25, 1975 Sheet 3 of 3 3,921,512

US. Patent APPARATUS FOR TREATING SLURRIES The invention relates to apparatus for extracting liquid from slurries, mixtures, suspensions, and the like, all hereinafter referred to generically as slurries, and more particularly though not exclusively to de-watering apparatus.

According to the invention, there is provided apparatus for extracting liquid from a slurry, comprising means for moving the slurry along a confined space so as to extract at least some of the liquid from the slurry by the effect of pressure generated within the confined space by the mass of the slurry, and means for mechanically applying a controllable back pressure to the slurry at its distal end so as to increase the effectiveness of liquid extraction.

According to the invention, there is also provided dewatering apparatus, comprising a base supporting an upwardly inclined perforated hollow tubular member, a continuous platform arranged helically about the axis of the tubular member and rotatable within the member about that axis so as to raise a slurry to be dewatered, the volume per pitch of the platform progressively decreasing towards the upper end of the tubular member, and piston means movable along the said axis at the upper end of the tubular member to apply a variable back pressure to the slurry raised through the tubular member, whereby water is extracted from the slurry by the effect of gravity on the mass of the slurry and the squeezing action exerted on the slurry by the said back pressure.

De-watering apparatus embodying the invention will now be described by way of example and with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic side view of the apparatus;

FIG. 2A is a cross section through the apparatus of FIG. 1; and

FIG. 2B is an enlarged cross section of the upper portion of FIG. 2A.

The apparatus comprises an inclined hollow rectangular housing 5 mounted on a base 6. Inside the housing are arranged two perforated hollow cylinders 7 (FIG. 2A) each containing a shaft 8 which is rotatably mounted in upper and lower bearings 10 and 12 (the latter may be of the water lubricated type). At its upper end, each shaft 8 is drivingly connected to a respective electric motor 14 through a respective gearbox 16 via

pulleys

18 and 20 and a belt 22. Only one cylinder and shaft assembly is visible in FIG. 2 and this will be described in detail below with its ancillary equipment. The other cylinder and shaft assembly is identical.

As shown in FIG. 2A, the shaft 8 carries an Archimedian screw or flight 24 which thus rotates with the shaft.

The slurry from which the water is to be extracted enters the apparatus through a pipe 30 (FIG. 1) and a manually controllable valve 32. This leads to an inlet 34 (FIG. 2A) to the interior of the perforated cylinder 7. At its upper end, the cylinder 7 discharges into a chamber 36 through the gap between the top of the cylinder 7 and the underside of a piston 38. The chamber 36 has a single stock outlet 40.

It will be appreciated that the two perforated cylinder and shaft assemblies have a common pipe 30, valve 32 and inlet 34. In addition, a common water outlet 42, in communication with a pipe 44 and a valve 46, is provided and is in communication with the space within 2 the housing 5 but outside the two perforated cylinders 7.

In operation, in each perforated cylinder 7 the shaft 8 and the Archimedian screw 24 are rotated together by the motor 14 at, for example, revolutions per minute. The slurry entering via. the inlet 34 is carried upwards by the rotating screw 24. As the slurry travels up the axis of the shaft8 on the Archimedian screw, water drains through the perforated cylinder 7 and the slurry thickens. This continuous action creates a plug of drying slurry within the cylinder and hence increases the pressure. This increase of pressure causes further de-watering, and the thickened slurry then exits from the cylinder 7 into the chamber 36 and thence through theoutlet 40. The extracted water drops to the bottom of the apparatus and exits via the water outlet 42.

As shown in FIG. 2A, the upper end of the shaft 8 has an enlarged, tapered, cross section given by a built-up portion 50. The effect of the tapered portion 50 is to reduce progressively the surface area on the Archimedian screw 24 towards the upper end of the shaft, thus reducing the slurry volume per pitch which can be lifted.

The piston 38 (FIG. 2B) is sli dable on the upper end of the shaft 8 but rotates with the shaft, being driven by a key 52 which is screwed to the shaft and engages in a slot 54 in the inner periphery of the piston. An O-ring 56 makes a seal between the piston 38 and the shaft 8.

The piston 38 presents generally the shape of an inverted cone, and a series of vanes 58 are bolted to the inverted base of the cone so as to rotate, in the chamber 36, as the piston rotates with the shaft 8.

Movement of the piston 38 is controlled by a control piston 60. The piston 60 is also of annular form and slides within an annular cylinder 62 which is mounted on the underside of the top wall 64 of the chamber 36. O-

rings

66 and 68 provide seals.

The piston 60 is locked against rotation with the shaft by means of a key 70 which is screwed to the outer wall of the cylinder 62 and engages in a keyway 72 on the control piston 60. Two

rings

74 and 76 which are respectively fixed (by dowel pins 78) to the control piston 60 and the main piston 38, carry rubbing bearing

rings

80 and 82 which thus allow relative rotation between the two pistons. A bearing ring 84 fixed to the main piston 38 engages in a circular recess in the control piston 60 and locates the two pistons for sliding movement together. The control piston 60 is shaped to provide an annular chamber 86 which is in communication with a lubricating oil inlet 88 through a gap 90 between the inner wall of the cylinder 62 and the shaft 80. By this means, the chamber 86 can be filled with oil, and this oil lubricates the keyway 54 and also, via a passageway 92, the

bearing rings

80 and 82. In addition, the oil damps the movement of the piston 60. A seal ring 94 seals off the

bearing rings

80 and 82 from the chamber 36. A drain plug 95 may be removed to drain out the oil.

A tubular shaped bellows 96 is fixed at one end to the outside of the cylinder 62 and at the other end to a ring 98 on the piston 60 and shuts off the sliding surfaces of the piston 60 from the chamber 36.

The cylinder 62 is pressurized with compressed air through an air inlet 100. The compressed air is taken from a suitable compressed air supply via a manually controllable valve 102 which feeds to an automatic pressure regulator 104. The outlet pressure of the pressure regulator 104 is controlled by a knob 106, indi- 3 cated on a dial 108, and applied to the cylinder 62 through the inlet 100. A manually operable valve 110 allows the cylinder 62 to be vented to atmosphere. The

pressure regulator 104 and its associated components are not shown in FIG. 2.

In operation, the pressure applied to the control piston 60 and the cylinder 62 is transmitted to the main piston 38 and causes the undersurface of this piston to generate a controlled back pressure against the plug of slurry being raised upwardly by the Archimedian screw 24. This back pressure very considerably increases the effectiveness of water extraction in the apparatus, and improves the consistency of the final output stock. If the slurry plug is lumpy, then the automatic pressure regulator 104 allows the pistons 38 and 60 to rise, in order to let the lump pass, and the piston 60 then moves downwardly again, lowering the piston 38.

The vanes 58 which rotate with the piston 38 are advantageous in that they help to eject continuously the thickened stock through the outlet 40.

It will be appreciated that each of the two cylinders 7 has its own pair of pistons 38 and 60 which are separately controlled.

The housing 5 is provided with an inspection cover 114 which is held in place by wing screws 116 and can be lifted off after removal of the screws.

The interior of each perforated cylinder 7 may be inwardly and upwardly tapered instead of or in addition to the taper on the shaft 8. In this case, the outer diameter of the screws 24 would be progressively reduced to match.

Although the perforated cylinders have been shown as inclined to the horizontal, which is the preferred position for low consistency slurries, the cylinders may instead be arranged at other positions including horizontally. A

What is claimed is:

1. Apparatus for thickening a semi-liquid slurry comprising tubular perforated housing means defining a confined space inclined to both the horizontal and the vertical and having an inlet at its lower end for receiving the slurry,

helical screw means for lifting the slurry within the confined space away from the slurry inlet so as to extract at least some of the liquid from the slurry by the effect of gravitational pressure generated within the confined space on and by the mass of the moving slurry, said helical screw means comprising,

rotatable shaft means mounted within the perforated housing means co-axially therewith, said shaft means having an upper end portion extending beyond the upper end of the perforated housing means, and

a helical thread form fast for rotation with the shaft means, said helical thread form defining with the housing means, a helical passage, the cross-section of said passage progressively reducing towards its upper end,

casing means surrounding the housing means, said casing means havingan outlet at its lower end for the extracted liquid,

means separating the inlet from the outlet,

means defining a chamber enclosing the upper end portion of the perforated housing means, the upper end of the perforated housing means communicating with the chamber for discharging thickened slurry into the chamber,

means defining an outlet from said chamber,

means located in said chamber for applying a controllable back pressure to the moving slurry so as to increase the effectiveness of liquid extraction, said means comprising,-

first piston means mounted on the shaft means adjacent the upper end ofthe housing means, said piston means having a conical surface co-axial, with the shaft means, said surface diverging towards the upper end of the shaft means, said surface facing the upper end of the housing means and defining therewith anrannular gap leading from the interior of said housing means into the chamber,

means connecting the piston means to the shaft means to permit axial sliding movement of the piston means relative to the shaft means while rendering the piston means fast for rotation with the shaft means,

second piston means surrounding the shaft means above the first piston means, said second piston means including an annular chamber surrounding the shaft means,

means defining a cylinder surrounding the upper end portion of the shaft means, said cylinder comprising an inner annular wall co-axial with the shaft means, and an outer annular wall surrounding the inner wall and spaced therefrom, the upper end portion of the second piston means being located within the cylinder means between the walls,

means securing the second piston means against rotation with the shaft means while'permitting axial movement of the second piston means,

downwardly facing annular bearing means carried by said second piston means co-axially with said shaft means, and V I upwardly facing annular bearing means carried by said first piston means co-axially with said shaft means, said downwardly facing annular bearing means engaging said upwardly facing bearing means,

means feeding pressurised fluid to said cylinder whereby said fluid applies a downwards force to said second piston means, and said downwards force is transmitted to said first piston means through said bearing means to provide said back pressure,

means for adjusting the pressure of fluid fed to said cylinder whereby to control said back pressure,

and

means for feeding lubricating fluid into said annular chamber defined by the second piston means, said fluid lubricating the bearing means and acting to damp movement of the second pistonmeans.

Claims

1. Apparatus for thickening a semi-liquid slurry comprising tubular perforated housing means defining a confined space inclined to both the horizontal and the vertical and having an inlet at its lower end for receiving the slurry, helical screw means for lifting the slurry within the confined space away from the slurry inlet so as to extract at least some of the liquid from the slurry by the effect of gravitational pressure generated within the confined space on and by the mass of the moving slurry, said helical screw means comprising, rotatable shaft means mounted within the perforated housing means co-axially therewith, said shaft means having an upper end portion extending beyond the upper end of the perforated housing means, and a helical thread form fast for rotation with the shaft means, said helical thread form defining with the housing means, a helical passage, the cross-section of said passage progressively reducing towards its upper end, casing means surrounding the housing means, said casing means having an outlet at its lower end for the extracted liquid, means separating the inlet from the outlet, means defining a chamber enclosing the upper end portion of the perforated housing means, the upper end of the perforated housing means communicating with the chamber for discharging thickened slurry into the chamber, means defining an outlet from said chamber, means located in said chamber for applying a controllable back pressure to the moving slurry so as to increase the effectiveness of liquid extraction, said means comprising, first piston means mounted on the shaft means adjacent the upper end of the housing means, said piston means having a conical surface co-axial with the shaft means, said surface diverging towards the upper end of the shaft means, said surface facing the upper end of the housing means and defining therewith an annular gap leading from the interior of said housing means into the chamber, means connecting the piston means to the shaft means to permit axial sliding movement of the pIston means relative to the shaft means while rendering the piston means fast for rotation with the shaft means, second piston means surrounding the shaft means above the first piston means, said second piston means including an annular chamber surrounding the shaft means, means defining a cylinder surrounding the upper end portion of the shaft means, said cylinder comprising an inner annular wall co-axial with the shaft means, and an outer annular wall surrounding the inner wall and spaced therefrom, the upper end portion of the second piston means being located within the cylinder means between the walls, means securing the second piston means against rotation with the shaft means while permitting axial movement of the second piston means, downwardly facing annular bearing means carried by said second piston means co-axially with said shaft means, and upwardly facing annular bearing means carried by said first piston means co-axially with said shaft means, said downwardly facing annular bearing means engaging said upwardly facing bearing means, means feeding pressurised fluid to said cylinder whereby said fluid applies a downwards force to said second piston means, and said downwards force is transmitted to said first piston means through said bearing means to provide said back pressure, means for adjusting the pressure of fluid fed to said cylinder whereby to control said back pressure, and means for feeding lubricating fluid into said annular chamber defined by the second piston means, said fluid lubricating the bearing means and acting to damp movement of the second piston means.