AU698183B2 - Laterally stepped centrifuge basket for the dewatering of particulate material - Google Patents

Description

LATERALLY STEPPED CENTRIFUGE BASKET FOR THE DEWATERING OF PARTICULATE MATERIAL

BACKGROUND OF THE INVENTION

The present invention relates to a centrifuge basket for the dewatering of particulate material, such as washed small coal or refuse.

In particular, the present invention relates to a centrifuge basket of the kind which comprises a revolvable screen of substantially truncated conical shape, widening towards a discharge end, and which is provided with at least one lateral step.

DESCRIPTION OF THE PRIOR ART

Discharge action of such a centrifuge basket, due to centrifugal force, is assisted by the oscillation and/or vibration of the revolving screen, such that the vibrational oscillation component, directed parallel to the revolving screen, is superimposed to the forward feeding component of a centrifugal force. As a result, the discharge of viscous centrifugal material with angles of repose on the screen larger than the angle of slope of the latter is ensured.

In the dewatering of washed small coal or refuse, the deposit settling on the screen offers considerable resistance to the passage of water to the revolving screen, so that the dewatering process becomes increasingly slower and difficult with increasingly finer grain size of processed material.

In order to reduce this problem, it has been previously proposed, for instance, in Australian Patent 520314 (39982/78), assigned to Siebtechnik GmbH, of whom the Applicant is a wholly owned subsidiary, to "step" the revolving screen in one of more radial planes. Such an arrangement is illustrated in Fig. 1.

As shown in Fig. 1 , this prior art vibratory centrifuge is comprised of a centrifuge casing 2 having a revolving screen 1 therein, which is rotatably driven in the direction of arrow fl and vibrates axially in the direction of arrow f2. The screen is of coned form widening towards the discharge end. The material is supplied through the charging pipe 4 with a distributing funnel 5. The revolving screen 1 substantially comprises three truncated shaped separate sections a, b and c which are joined to one another by radially directed steps 3, so as to collectively provide a stepped revolving screen. The stepping arrangement causes a loosening or rearrangement of the layers being moved to the discharge end such that the final dewatered product has greatly enhanced characteristics.

SUMMARY OF THE INVENTION

The present invention seeks to provide a centrifuge basket, which provides a more enhanced dewatering operation than the prior art devices.

The present invention seeks to provide a uniquely different and improved arrangement of "stepping" such that a more enhanced dewatering operation is achieved by the centrifuge.

The present invention seeks to provide a centrifuge basket which has a unique stepped arrangement such that the product to be dewatered travels over more steps than if those steps are provided in a radial plane.

In one broad form, the present invention provides a centrifuge basket for the dewatering of particulate material, comprising a revolvable screen of substantially truncated conical shape and having at least one step in a lateral direction.

Preferably, said screen is comprised of a plurality of substantially quadrilaterally shaped sections, said steps being provided between edges of adjoining quadrilaterals.

Perhaps most preferably, said screen is comprised of a plurality of substantially trapezoidally shaped sections, said steps being provided between edges of adjoining trapezia.

In a preferred form of the invention, said stepped revolvable screen covers substantially the entire inner surface of said centrifuge basket. Alteraatively, said stepped revolvable screen covers only a portion of the inner dewatering surface of said centrifuge basket.

In a further broad form, the present invention provides a centrifuge basket wherein said revolvable screen is embodied as an insertable component of smaller overall diameter than said basket, also of conical shape, and provided internally of said centrifuge surface to form a dewatering cone.

A most preferred form of the invention is wherein in use, said centrifuge is vibrated in an axial direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the following detailed description of preferred but non-limiting embodiments thereof, described in connection with the accompanying drawings, wherein:

Fig. 1 illustrates a prior art centrifuge basket, shown in cross-section, having a plurality of steps in various radial planes;

Fig. 2 illustrates a revolvable screen centrifuge basket device which may be utilised in a centrifuge, Fig. 2(a) illustrating an end elevational view thereof, Fig. 2(b) illustrating a sectional view through line A of Fig. 2(a), and Fig. 2(c) detailing a portion of the diagram shown in Fig. 2(a);

Fig. 3 illustrates a centrifuge basket similar to that of Fig. 2, but with a pre-dewatering cone supplied therein, Fig. 3(a) illustrating an elevational view thereof, Fig. 3(b) illustrating a sectional view thereof, Fig. 3(c) detailing part of that sectional view of Fig. 3(b), and, Fig. 3(d) detailing a part of Fig. 3(a); and,

Fig. 4 shows an arrangement of fins on the outside of the centrifuge basket to assist in the centrifuge process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

A centrifuge basket in accordance with the first aspect of the present invention is provided with a revolvable screen of substantially truncated conical shape and having at least one step in a lateral direction.

Throughout the specification, the 'step(s)' is/are defined as being disposed in a 'lateral direction'. The term 'lateral direction' is intended to include any direction transverse to a 'radial plane' direction (as described in Australian Patent No. 520314 (39982/78) by Siebtechnik GmbH). That is, it should be understood to include a step between the edges of adjoining polygonal sections which are joined to make up the substantially truncated conically shaped screen - whether the polygonal sections are of substantially similar shape or not, and/or, to include steps provided in a spiral or helical shaped configuration on the screen, etc.

A centrifuge basket in accordance with the present invention may be embodied as either a stepped revolvable screen "basket" such as shown in Fig. 2(a), and/or a stepped pre-dewatering "cone" such as illustrated in Fig. 3. That is, a laterally stepped basket may be utilised on it's own, or a laterally stepped pre-dewatering cone may be utilised with remaining standard type components of a centrifuge basket, or, a laterally stepped centrifuge basket may be utilised in conjunction with a laterally stepped pre-dewatering cone. The important aspect is that, either, the centrifuge basket or the pre-dewatering cone should be provided with at least one step in the lateral direction.

The configuration of the lateral steps will be hereinafter described with reference to Figs. 2 and 3. As shown in Fig. 2, a screen basket 10, is comprised of a plurality of quadrilateral, or more preferably, trapezoidal, sections 11. The most preferred implementation is where each of the sections 11 are of similar shape to the remaining sections 11, for ease of manufacture. It is however to be appreciated that irregular shaped sections 11 may be utilised.

At the edges 12, joining each section 11, a step is provided in the lateral direction, perhaps best illustrated in Fig. 2(c). These sections 11 may be either cover the entire inner surface of the centrifuge, or just a portion thereof.

In operation, most preferably, the centrifuge basket is vibrated in the direction of arrow f3, in addition to being rotated in the direction of arrow f4.

Consequently, in use, whereas the prior art devices as shown in Fig. 1, enable the material to be "stepped", for example, twice prior to discharge, in the device in accordance with the present invention, such as illustrated in Fig. 2(a), the material would be stepped many more times prior to discharge, with the advantageous result that a higher amount of dewatering occurs. The number of steps undergone by particulate material would of course depend upon the number of sections 11 provided to make up the basket 10, vibrational frequency in the direction of arrow D, and also on the angular velocity in the direction of arrow f4. Such speeds of vibration and rotation could of course be easily varied by an operator, depending upon the moisture characteristics of the initial product and of the desired dewatered product.

As shown in Fig. 3, in addition, or in alternative, to providing a laterally stepped 'basket' 10, a laterally stepped 'pre-dewatering cone' 6 may be inserted within the centrifuge. The pre-dewatering cone 6 is of course, of smaller overall dimension than the basket 10, also of truncated conical shape. A different grading of screen or sieve may, in a preferred embodiment, be utilised in the cone 6 to that of the basket 10, to facilitate an initial larger amount of moisture removal from the product. Once again, the characteristics of the particular screen utilised for the cone 6 and also for the basket 10, would depend on the initial moisture characteristics of the input material and of the desired product. The laterally stepped pre-dewatering cone 6 may of course also be utilised in combination with a standard or laterally unstepped basket 10.

Perhaps however, most preferably, the pre-dewatering cone 6 with lateral steps is utilised in combination with a laterally stepped basket 10. This would have the effect that the particulate material would not only undergo moisture reduction as it is stepped in a later direction, but also, undergo moisture reduction as it steps from the cone 6 to the basket 10, which is essentially a step provided in a radial plane. It will be appreciated that the characteristics of the particular screen such as overall dimension, step height, etc., will be able to be selected by an operator, dependent upon the input and output characteristics of the particulate material. Reference is however made to Australian Patent No. 520314 (39982/78) for particular details as to desirable step heights, etc. (which specification should be considered to be incorporated entirely herein by reference thereto).

In the construction of the laterally stepped centrifuge, the 'steps' 12 may be configured in such a manner that extensions or fins 13 (see Figs. 2(c) and 3(c)) extend radially outwardly of the exterior surface of the basket 10. In operation as the basket 10 rotates, an airflow is created by the fins 13, which acts to assist the transportation of the particulate material and/or the water in and/or out of the tangential outlet of the centrifuge. An illustration of this is shown in Fig. 4, wherein the basket 10 provided with fins 13, and rotated in the direction of arrow f5, creates a windstream in the direction of arrows 15 which assists the transportation of water and other filtered particulate or fluid matter through the tangential output 14, and assists the inhaling of the particulate material through the input 16.

Whilst various preferred embodiments of the present invention have been hereinbefore described, it should be understood that numerous variations and modifications will become apparent to persons skilled in the art. All such variations and modifications should be considered to fall within the scope of the invention as broadly hereinbefore described.

Claims (10)

THE CLAIMS

1. A centrifuge basket for the dewatering of particulate material, comprising a revolvable screen of substantially truncated conical shape and having at least one step in a lateral direction.

2. A centrifuge basket as claimed in claim 1, wherein said screen is comprised of a plurality of substantially quadrilaterally shaped sections, said step(s) being provided between edges of adjoining quadrilaterals.

3. A centrifuge basket as claimed in claims 1 or 2, wherein said screen is comprised of a plurality of substantially trapezoidally sections, said step(s) being provided between edges of adjoining trapezia.

4. A centrifuge basket as claimed in any one of claims 1 to 3, wherein said revolvable screen covers substantially the entire inner surface of said centrifuge.

5. A centrifuge basket as claimed in any one of claims 1 to 3, wherein said revolvable screen covers only a portion of the entire inner surface of said centrifuge.

6. A centrifuge basket as claimed in claim 5, wherein said revolvable screen is embodied as an insertable component of smaller overall diameter than said centrifuge surface, also of conical shape, and provided internally of said centrifuge basket surface, to form a de-watering cone.

7. A centrifuge basket as claimed in any one of claims 1 to 6, wherein in use, cone is vibrated in an axial direction.

8. A centrifuge basket as claimed in any one of claims 1 to 7, wherein fins are provided on the outside surface of said screen.

9. A centrifuge basket, substantially as herein described with reference to the accompanying drawings.

10. A method of dewatering of particulate material, using a centrifuge basket substantially as herein described with reference to the accompanying drawings.