EP2827996A2

EP2827996A2 - Solid bowl screw-type centrifuge

Info

Publication number: EP2827996A2
Application number: EP13717724.2A
Authority: EP
Inventors: Heinz Solscheid; Robert Wagenbauer
Original assignee: Hiller GmbH
Current assignee: Hiller GmbH
Priority date: 2012-03-22
Filing date: 2013-03-21
Publication date: 2015-01-28
Also published as: WO2013139920A3; JP2015510840A; US20150018190A1; CN104302405A; DE102012102478A1; WO2013139920A2; CA2868195A1

Abstract

The solid bowl screw-type centrifuge is used to continually separate a composition of free-flowing substances with different densities. The solid bowl screw-type centrifuge has a rotor drum (12), rotatable about a horizontal axis (16), with a cylindrical drum section (18) and a conical drum section (20), and a conveying screw (22) mounted therein, rotating about the same axis (16), with a helical vane (26) attached to a hollow shaft (24) for transporting the heavy phase to discharge openings (28) in the conical drum section (20). On a front wall (40) closing the cylindrical drum section (18), at least one outflow opening (62) for the light phase is provided with a device for setting the fluid level. According to the invention, the device for setting the fluid level consists of a control element (42) with means for braking or accelerating the fluid particles of the light phase, said control element being rotatively driven at a speed different to the drum speed and releasing a flow through an annular clearance (60) to the inner wall (58) of the drum.

Description

Full-jacketed slug centrifuge

description

The invention relates to a solid bowl screw centrifuge according to the preamble of patent claim 1.

In screw centrifuges of the prior art, for. B. according to DE 39 21 327, the device for adjusting the fluid level consists of a weir, which can be mechanically adjusted during operation. The mixture to be separated is fed via a static feed pipe into a feed chamber integrated in the screw body and from there into the working space of the centrifuge and subjected to a corresponding centrifugal acceleration on the basis of the drum speed. In the working space of the centrifuge, the usually specific heavier solid settles on the drum inner wall and is conveyed by the screw conveyor to openings at the end of the conical drum and thrown off. The clarified centrate, the light phase, flows in the worm gear opposite to the solid transport direction and leaves the centrifuge via the weir opening.

The known from DE 39 21 327 weir is adjusted for adjusting the liquid level via an axially displaceable ring and a deflecting member in the radial direction.

Another adjustment option is described and illustrated in EP 702 599 Bl, where the weir damper is adjusted axially to change the passage relative to a stationary throttle damper.

In DE 103 36 350 AI a Vollmantelschneckenzentrifuge is described and shown, in which a paring disc is arranged non-rotatably on the stationary during operation feed pipe, which is connected upstream of a throttle disk. Both discs can by means of a Electric drive can be adjusted axially. Alternatively, the throttle disk may be formed as a member rotating with the drum.

The invention has for its object to simplify constructively in a worm centrifuge of the type specified in claim 1 type device for adjusting the liquid level while maintaining the possibility of level adjustment during operation.

This object is achieved in that the means for adjusting the liquid level consists of a control means for braking or accelerating the liquid particles of the light phase, which is driven in rotation at a different speed of the drum rotation and leaves a through-flow annular gap to the drum inner wall.

This solution has the considerable advantage over the prior art that no weir with a mechanical adjusting mechanism is required for the adjustment of the liquid level, because instead a control is provided whose speed is variable.

In a development of the invention, the control element is designed as an immersion disk whose surface discontinuities can slow down or accelerate the liquid particles. As Oberflächendiskontinuitäten axially projecting ribs are possible from the immersion disk, but also slots or holes in the immersion disk, protrusions or surface roughening. These may be provided on one side or on both sides of the immersion disk.

Alternatively, it is possible to form the control as a vane rotor.

The control can be attached to the hollow shaft of the screw conveyor, so that at the same time the speed of the control is connected with a change in the screw speed.

In a variant of the invention, the control can be rotatably mounted on a hollow shaft stub of the rotor drum and with its own rotary drive in the form of a motor be connected. When the control element decelerates, the rotary drive acts as an output for a generator.

Further features and advantages of the invention will become apparent from the claims and from the following description of exemplary embodiments, which are illustrated in the drawing. In this show:

1 shows the schematic, partially sectioned view of a screw centrifuge in a first embodiment of the invention,

FIG. 2 shows two communicating tubes with a liquid filling,

FIG. 3 shows the U-tube of FIG. 2 with two liquids of different density,

4 shows the centrifuge shown in FIG. 1 with a drive motor for the control element, FIG.

FIG. 5 shows a variant of FIG. 4,

FIG. 6 shows a further variant of FIG. 4,

FIG. 7 shows a variant of FIG. 6 as a three-phase centrifuge;

FIG. 8 shows a further modified embodiment for the principle of FIG. 6,

FIG. 9 shows an enlarged detail view from FIG. 8,

10 shows a variant of Figure 8 and

FIG. 11 shows a detailed illustration from FIG. 10.

Figure 1 shows schematically a first embodiment of a solid bowl screw centrifuge 10 according to the invention. This consists in known manner of a rotor drum 12 which is supported at both ends in radial bearings 14 and rotatable about a horizontal axis 16 by a drive, not shown. The rotor drum has a cylindrical drum portion 18 and a conical drum portion 20.

In the rotor drum 12, a screw conveyor 22 is rotatably mounted about the axis 16 at a speed deviating from the drum speed. The rotary drive required for this purpose is also not shown. The screw conveyor 22 consists of a hollow shaft 24, are mounted on the screw helix 26 for the transport of the heavy phase to discharge openings 28 in the conical drum section 20.

A left-hand hollow tube stub 30 of the rotor drum 12 leads through a supply pipe 32, not shown in Figure 1 (see Figure 6), for the mixture to be separated (Feed suspension) axially into a formed in the hollow shaft 24 feed chamber 34, lead from the feed openings 36 in the working space 38 of the screw helix 26.

During operation of the centrifuge, the screw helix 26 conveys the specifically heavy phase (thick material), which assumes the height ho to the drum inner wall, into the conical drum section 20, from which it is discharged via the discharge opening 28. The liquid, light phase (centrate) with the height hp flows in the opposite direction to the end of the cylindrical drum portion 18 end wall 40, before which the control element 42 according to the invention is arranged. In the example of Figure 1, this consists of a radially oriented plunger 44, projecting from the axial ribs 46 in the direction of the end wall 40. The plunger 44 is attached here to a cylindrical ring 48 which is rotatably supported by two ball bearings 50 on the hollow shaft stub 30. At its end projecting from the drum 12, the ring 48 has a pulley 52 for the belt connection 54 with an electric motor 56 (see Figure 4).

In the region of the control element 42, the pressure behaves as in a U-tube in which the Zentratteilchen initially flow radially to the drum inner wall 58 to then flow through the annular gap 60 and the overflow 62 in the end wall 40 to the outside.

Figure 2 shows a U-tube, the two tubes are filled with a liquid of height h. At the vertex of the U-tube there is a pressure p = h · p · g with p = density of the liquid and g = gravitational acceleration.

FIG. 3 shows a corresponding model of a rotating U-tube in the region of the control element 42 of FIG. At the apex applies to the pressures Pz of the centrate F (liquid phase) and P _{D of} the thick material D (heavy phase):

PF = PD where z = centrifugal acceleration:

PD = h _D -pD-z FIG. 1 shows the different angular velocities of the rotor drum and the control element cos. The angular velocity of the rotor drum determines the angular velocity of the liquid phase:

The angular velocity cos of the control element 42 designed as a dip disk 44 with or without ribs 46 is approximately equal to the angular velocity of the thick material (heavy phase), but different from the centrate:

COs Φ

Three different cases are considered below. In the first case, the dip disk 44 of the control element 42 is designed without ribs 46, as shown in FIG. 11. In this case, a Zentratteilchen maintains the recorded on the inner wall of the drum 58 peripheral speed. This means that as the diameter decreases, the angular velocity of the centrate particle must increase. The centrate rushes ahead of the surrounding drum wall. By increasing the angular velocity, the centrifugal acceleration z and thus the fluid pressure in the gap 60 between the immersion disk 44 and the drum inner wall 58 increases. In this gap, the pressure behaves as in the U-tube of Figure 2, d. H. from the liquid columns on both sides of the dip disk 44, the same pressure is generated. Since the liquids in front of and behind the dip disk 44 have the same density p but are subject to different centrifugal accelerations, the pressure balance can only be achieved by increasing the height of the liquid column in the working space 38 of the centrifuge. In extreme cases, this can lead to an undesirable overflow of liquid through the solids discharge 28.

Case 2 corresponds to the sketches shown in FIGS. 6, 7, 8, 9, according to which the dipping disc 44 is fastened on the hollow shaft 24 of the screw conveyor 22 and provided with ribs 46 on its side facing the end wall 40. A Zentratteilchen has first recorded on the drum inner wall 58 peripheral speed. As the diameter decreases, the centrate particle becomes the radius and the screw speed imposed corresponding peripheral speed. (The screw speed differs only insignificantly from the drum speed). This means that as the diameter decreases, the angular velocity of the centrate particle remains unchanged. The centrate has about the same angular velocity as the surrounding drum wall. As a result, there is no undesired leveling of the centrifuge working space 38 by the U-tube effect (the density of the liquid and the centrifugal acceleration are the same).

The third case corresponds to the representation in FIG. 4, according to which the control element 42 with the immersion disk 44 provided with ribs 46 can be driven by a motor 56 (or braked by a generator) relative to the drum speed. Alternatively, the control 42 as outlined in Figure 5 as a rotor 64 with i. w. radially aligned wings 66 may be formed. The brake case will be explained below; the drive case is correspondingly reversed.

The Zentratteilchen enters with the recorded on the drum inner wall 58 peripheral speed in the gap 60 between plunger 44 and end wall 40 a. In the region of the ribs 46 and the wing 66, the centrate particles are approximately forced to the speed of the immersion disk 44 or wing 66. The peripheral speed of the Zentratteilchens is decelerated according to the speed of the plunger or vanes and the diameter considered. The braking energy is converted into electrical energy in the generator. According to the lower peripheral speed, the centrifugal acceleration acting on the centrate particle is reduced. The equilibrium condition in the gap 60 between plunger 44 and drum inner wall 58 adjusts itself by a reduction of the liquid level in the working space 38 of the centrifuge. When using wings 66, a partition wall 68 to the working space 38 of the centrifuge is required.

In the example of Figure 6, as already mentioned, the plunger 44 of the control element 42 is mounted directly on the hollow shaft 24 of the screw conveyor 22, the rotary drive is known and not shown. Between the ribs 46, the plunger 44 has discharge openings 70 for the discharge of the liquid phase. FIG. 7 shows a three-phase version of the centrifuge with circumferentially distributed, radially adjustable overflow tubes 72 for discharging a light liquid. The discharge openings 70 for the discharge of a heavy liquid can be closed by screws 74. In the conical drum section 20, the solids are discharged via the discharge opening 28.

The embodiment illustrated in FIGS. 8 and 9 is comparable to the version of FIG. 7, in which the immersion disk 44 is fastened to the hollow shaft 24 of the screw conveyor 22 and provided with ribs 46. In FIG. 9, one of the screws 74 for closing the discharge opening 70 in the immersion disk 44 can be clearly seen.

Finally, FIGS. 10 and 11 once again show a version with immersion disk 44 without ribs. The means for decelerating or accelerating the liquid particles may consist of other surface discontinuities, e.g. As roughening or protrusions.

By influencing the liquid level during operation of the centrifuge, the following possibilities arise:

1. Adjustment of the centrifuge with modified feed quantities or fluctuating solids concentration.

2. Influence the dryness of the solid and the clarity of the centrate.

3. Adaptation of the transport behavior of the solid to specific product properties.

Claims

claims

A solid bowl screw centrifuge for continuously separating a mixture of flowable materials of different densities, comprising a rotor drum (12) rotatable about a horizontal axis (16) and having a cylindrical barrel portion (18) and a conical barrel portion (20) and a bearing therein the same axis (16) rotating screw conveyor (22) mounted on a hollow shaft (24) helix (26) for transporting the heavy phase to discharge openings (28) in the conical drum section (20), while at one of the cylindrical drum section (18) final End wall (40) is provided at least one outlet opening (62) for the light phase with a device for adjusting the liquid level, characterized in that the means for adjusting the liquid level of a control element (42) with means for decelerating or accelerating the liquid particles of the light Phase, with one of the drumming eldrehzahl different rotational speed is driven in rotation and to the drum inner wall (58) leaves a flow-through annular gap (60).

2. solid bowl centrifuge according to claim 1, characterized in that the control element (42) in the flow direction of the light phase in front of the cylindrical drum section (18) final end wall (40) is arranged.

3. solid bowl centrifuge according to claim 1 or 2, characterized in that the control element (42) is designed as a dipping disc (44).

4. solid bowl centrifuge according to claim 1 or 2, characterized in that the control element (42) as a rotor (64) with wings (66) is formed.

5. Solid bowl screw centrifuge according to claim 3 or 4, characterized in that the means for braking or accelerating the liquid particles formed on the control (42) formed surface discontinuities.

6. Solid bowl screw centrifuge according to claim 5, characterized in that the means as by the control (42) axially projecting ribs (46) are formed.

7. A solid bowl centrifuge according to one of the preceding claims, characterized in that the control element (42) on the hollow shaft (24) of the screw conveyor (22) is fixed.

8. A solid bowl centrifuge according to one of claims 1 to 6, characterized in that the control element (42) is rotatably mounted on a hollow shaft stub (30) of the rotor drum (12) and connected to its own rotary drive (56) or rotary drive.

9. A solid bowl screw centrifuge according to any one of claims 5 to 8, characterized in that the surface discordmuity consists of at least one outflow opening (70).

10. A solid bowl centrifuge according to claim 9, characterized in that the drain opening (70) is closable.

11. A solid bowl centrifuge according to one of the preceding claims, characterized in that on the rotor drum (12) in the flow direction of the light phase before the control (42) at least one radially inwardly projecting overflow pipe (72) is arranged for a three-phase separation.