GB2087758A - A device for separating solid/ liquid mixtures - Google Patents

Abstract

In a solid sleeve screw centrifuge 1 for dewatering slurry and having a screen element 3, flow through the centrifuge is uni-directional. The screen element 3 may be cylindrical or conical. <IMAGE>

Description

SPECIFICATION A device for separating solid/liquid mixtures The invention relates to a device for separating solid/liquid mixtures, more particularly for dewatering slurry containing fine materials.

Solid sleeve screen centrifuges are used, as shown by German Auslegeschrift No. 1 532 683 for example, to separate solid/liquid mixtures, the material extracted at the centre of the centrifuge being passed in these solid sleeve screen centrifuges in contraflowto the solids and extracted. In these known solid sleeve screen centrifuges however it is not possible to prevent a significant proportion of fine materials present in the solid/liquid mixture from getting into the material extracted from the centre of the centrifuge and being extracted therewith.

An object ofthe present invention lies in providing a device which avoids the above disadvantages and makes use of the advantages of the screen portion, i.e. good secondary dewatering and the possibility of washing the product. It is also an object of the present invention to make it possible to separate off fine materials present in the solid/liquid mixture in a simple and economic manner. According to the present invention there is provided a device for separating solid/liquid mixtures comprising a unidirectional flow solid sleeve screw centrifuge with a screen element attached thereto.In practice it has been proved that even fine materials are separated from the liquid by the uni-directional flow in a solid sleeve screw centrifuge with a screen element and can be extracted together with the remaining solid materials so that the material extracted at the centre of the centrifuge is effectively free of any concentrations of fine material.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings.

As the drawing shows, the uni-directional solid sleeve screw centrifuge in accordance with the invention comprises a cylindrical solid sleeve member 1, a conical member 2 and a preferably cylindric-e al screen member or element 3. The solid/liquid mixture which is to be separated is supplied to the centrifuge at the left-hand end in the direction of arrow 4.

This solid/liquid mixture passes through the cylindrical solid sleeve member 1 of the centrifuge during operation in uni-directional flow from left to right and the solids, more particularly the fine materials present in the solid/liquid mixture are separated by the action of centrifugal force. A screw conveyor not shown in greater detail in the drawing is provided for transporting the solids and is driven at a slightly higher or lower speed than the centrifuge drum. The solids separated from the liquid in the centrifuge drum are taken by the coils of the screw conveyor, transported through the cylindrical screen element 3 where they are subjected to subsequent dewatering.

The material extracted at the centre of the centrifuge and which is free of solids is received by elements not shown in greater detail in the drawing but which are tubular or channel-like elements known per se, approximately in the transition region between the solid sleeve member 1 and the conical member 2 and is removed from the centrifuge drum in the direction of arrow 7 or arrow 8. Besides being cylindrical the screen member 3 can, if desired, be slightly conical (3') towards the extraction end as indicated by dashes in the drawing. This has the advantage that less transport power is needed to extract the solids in this region since, by virtue of the centrifugal forces the solids support the sliding movement on the screen surface to the outside.

Moreover, there is the possibility of so forming the screen member that like the conical member 2 it tapers slightly outwards. This may also be advisable in some cases.

The above-described uni-directional flow solid sleeve screw centrifuge with attached screen member makes it possible not only to improve the separation quite considerably in comparison to known solid sleeve screen centrifuges, particularly with respect to separating fine materials from the liquid or the material extracted at the centre, but is also characterised by particularly good clarification and secondary dewatering of the solid in the screen member. A virtually solid-free substance is obtained at the centre of the centrifuge in a simple and economic manner; a high solid yield is also obtained.

1. A device for separating solid/liquid mixtures, comprising a uni-directional flow solid sleeve screw centrifuge with a screen element attached thereto.

2. A device according to claim 1, wherein the screen element is cylindrical.

3. A device according to claim 1, wherein the screen element is conical.

4. A device for separating solid/liquid mixtures substantially as herein described with reference to the accompanying drawing.

5. A method of dewatering slurry containing fine materials employing a device as claimed in any preceding claim.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A device for separating solid/liquid mixtures The invention relates to a device for separating solid/liquid mixtures, more particularly for dewatering slurry containing fine materials. Solid sleeve screen centrifuges are used, as shown by German Auslegeschrift No. 1 532 683 for example, to separate solid/liquid mixtures, the material extracted at the centre of the centrifuge being passed in these solid sleeve screen centrifuges in contraflowto the solids and extracted. In these known solid sleeve screen centrifuges however it is not possible to prevent a significant proportion of fine materials present in the solid/liquid mixture from getting into the material extracted from the centre of the centrifuge and being extracted therewith. An object ofthe present invention lies in providing a device which avoids the above disadvantages and makes use of the advantages of the screen portion, i.e. good secondary dewatering and the possibility of washing the product. It is also an object of the present invention to make it possible to separate off fine materials present in the solid/liquid mixture in a simple and economic manner. According to the present invention there is provided a device for separating solid/liquid mixtures comprising a unidirectional flow solid sleeve screw centrifuge with a screen element attached thereto.In practice it has been proved that even fine materials are separated from the liquid by the uni-directional flow in a solid sleeve screw centrifuge with a screen element and can be extracted together with the remaining solid materials so that the material extracted at the centre of the centrifuge is effectively free of any concentrations of fine material. A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings. As the drawing shows, the uni-directional solid sleeve screw centrifuge in accordance with the invention comprises a cylindrical solid sleeve member 1, a conical member 2 and a preferably cylindric-e al screen member or element 3. The solid/liquid mixture which is to be separated is supplied to the centrifuge at the left-hand end in the direction of arrow 4. This solid/liquid mixture passes through the cylindrical solid sleeve member 1 of the centrifuge during operation in uni-directional flow from left to right and the solids, more particularly the fine materials present in the solid/liquid mixture are separated by the action of centrifugal force. A screw conveyor not shown in greater detail in the drawing is provided for transporting the solids and is driven at a slightly higher or lower speed than the centrifuge drum. The solids separated from the liquid in the centrifuge drum are taken by the coils of the screw conveyor, transported through the cylindrical screen element 3 where they are subjected to subsequent dewatering. The material extracted at the centre of the centrifuge and which is free of solids is received by elements not shown in greater detail in the drawing but which are tubular or channel-like elements known per se, approximately in the transition region between the solid sleeve member 1 and the conical member 2 and is removed from the centrifuge drum in the direction of arrow 7 or arrow 8. Besides being cylindrical the screen member 3 can, if desired, be slightly conical (3') towards the extraction end as indicated by dashes in the drawing. This has the advantage that less transport power is needed to extract the solids in this region since, by virtue of the centrifugal forces the solids support the sliding movement on the screen surface to the outside. Moreover, there is the possibility of so forming the screen member that like the conical member 2 it tapers slightly outwards. This may also be advisable in some cases. The above-described uni-directional flow solid sleeve screw centrifuge with attached screen member makes it possible not only to improve the separation quite considerably in comparison to known solid sleeve screen centrifuges, particularly with respect to separating fine materials from the liquid or the material extracted at the centre, but is also characterised by particularly good clarification and secondary dewatering of the solid in the screen member. A virtually solid-free substance is obtained at the centre of the centrifuge in a simple and economic manner; a high solid yield is also obtained. CLAIMS

1. A device for separating solid/liquid mixtures, comprising a uni-directional flow solid sleeve screw centrifuge with a screen element attached thereto.

2. A device according to claim 1, wherein the screen element is cylindrical.

3. A device according to claim 1, wherein the screen element is conical.

4. A device for separating solid/liquid mixtures substantially as herein described with reference to the accompanying drawing.

5. A method of dewatering slurry containing fine materials employing a device as claimed in any preceding claim.