WO2013160864A1

WO2013160864A1 - Separation system

Info

Publication number: WO2013160864A1
Application number: PCT/IB2013/053275
Authority: WO
Inventors: David Neil MINSON; Rhett Charles McELVENNY
Original assignee: DELKOR TECHNIK BV; KOTZE GAVIN SALOMON
Current assignee: DELKOR TECHNIK BV; KOTZE GAVIN SALOMON
Priority date: 2012-04-25
Filing date: 2013-04-25
Publication date: 2013-10-31
Anticipated expiration: 2014-10-25
Also published as: AR090850A1; WO2013160864A4; ZA201408584B

Description

TITLE: SEPARATION SYSTEM

FIELD OF INVENTION

THIS INVENTION relates to the separation of first solid particulate components from second solid particulate components having particle sizes which are generally smaller than that of the first solid components, where the first and second solid components are suspended in a liquid. More particularly, it relates to a separation system and method, as well as a method of modifying a separation system.

BACKGROUND OF INVENTION

The Inventors are aware of separation systems which separate first solid particulate components from second solid particulate components having particle sizes which are smaller than that of the first solid components, where the first and second solid components are suspended in a liquid (hereinafter referred to as the mixture). The mixture is usually an aqueous solution and typically includes water-based Cyanide or, less frequently, acidic solution as the so-called water component. One such system typically includes an endless screening belt which defines a plurality of apertures which apertures are of a suitable size to permit the second solid components to pass therethrough and to inhibit or impede the passage therethrough of the first solid components; a set of rollers around which the screening belt travels; and a drive unit which drives the screening belt around the set of rollers. The path of the belt is such that it includes a generally horizontal separating region onto which the mixture or slurry can be introduced for separation.

A chute or "underpan" is usually positioned below the separating region in order to collect the liquid and second solid components which pass through the apertures. An oversize chute is positioned at a discharge end of the separating region in order to collect the material that remains on the screening belt. In use, the mixture is introduced onto the horizontal separating region from the discharge end or from an end of the separating region opposite the discharge end. Since the densities of the first and second solid components are usually greater than that of the liquid in which they are suspended, the components tend to sink down onto an operatively upper surface of the horizontal separating region. Some of the first solid components and larger second solid components may therefore end up clogging one or more of the apertures of the screening belt, thereby inhibiting the smaller second solid components, as well as the liquid, from passing through those apertures which, as a result, inhibits effective separation. The clogging may also result in some of the mixture eventually overflowing the sides of the belt in the horizontal separating region. This issue has been addressed in the past by installing overflow gutters that collect the overflow material and eventually channel it back to the feeding point where it is again discharged onto the separating region. This solution however causes spillage, loss of product or unwanted product recirculation loops, as well as general housekeeping or maintenance problems. Another solution the Inventors are aware of is to curve sides of the belt upwards to prevent the accumulated mixture from overflowing, however this does not resolve the cause of the problem.

During normal operations, the path of the screening belt in its horizontal separating region is generally straight and the belt merely touches the top sides of the rollers (i.e. the contact areas between the belt and the rollers are relatively small). As the belt becomes flooded (i.e. when clogging occurs), the belt sags between the rollers and the contact areas between the belt and rollers increase (i.e. the amount of wrap around the rollers increases). If the rollers are not perfectly parallel to each other, the increased wrap may cause the belt to be steered away from its central displacement path. This may also occur if there is an uneven load distribution on the belt.

It is an object of this invention to provide means which the Inventors believe will at least alleviate at least some of the above identified problems.

SUMMARY OF INVENTION

In accordance with one aspect of the invention there is provided a separation system for separating first solid particulate components from second solid particulate components having particle sizes which are smaller than that of the first solid components, wherein the first and second solid components are suspended in a liquid to form a mixture or slurry, the system including:

an endless screening belt/cloth which is displaceable along a predetermined path and defining a separating region, the screening belt/cloth defining a plurality of apertures which apertures are of a suitable size to permit the second solid components to pass therethrough and to impede the passage therethrough of the first solid components;

a feed arrangement for feeding mixture onto the screening belt/cloth in the separating region; and

a load management arrangement which is configured to sense a change in load on the screening belt/cloth and adjust at least one operating parameter of the system in response to a change in load being sensed. More specifically, the load management arrangement may be configured to adjust the at least one operating parameter of the system when the load sensed by the load management arrangement reaches or exceeds a predetermined level (i.e. when the screening belt/cloth is overloaded with mixture). The load management arrangement may include a load sensing arrangement which is configured to sense a change in load on the screening belt/cloth; and a controller which is in communication with the load sensing arrangement and which is configured to adjust the at least one operating parameter of the system in response to a change in load being sensed by the load sensing arrangement. More specifically, the controller may be configured to adjust the at least one operating parameter of the system when the load sensed by the load sensing arrangement reaches or exceeds a predetermined level.

The system may include a drive unit which is configured to drive the screening belt/cloth along its predetermined path. The controller of the load management arrangement may be in communication with the drive unit and be configured to adjust the speed by which the drive unit drives the screening belt/cloth, in response to a change in load being sensed, the travel speed of the screening belt/cloth therefore being the operating parameter of the system which is adjusted by the controller. When the mixture is introduced onto the screening belt/cloth in the separating region, the first and second solid components tend to settle on an operatively upper surface of the screening belt/cloth due to their density being greater than that of the liquid. The larger first solid components may as a result clog one or more of the apertures, thereby inhibiting the second solid components, as well as the liquid, from passing through those apertures. The feeding of mixture onto the separating region is usually done continuously. Therefore, with some of the apertures of the screening belt/cloth being clogged, the liquid and second solid components may end up not flowing/passing through the apertures fast enough, which can result in an overloading of mixture in the separating region. A chute is usually provided at an end of the separating region into which part of the mixture which was not discharged through the apertures of the screening belt/cloth, is discharged. By increasing the speed by which the screening belt/cloth travels in the event of overloading, the presented length of the screening belt/cloth and hence the number of apertures passing through the separating region per unit time is increased. Thus, the rate at which the liquid and particles of the second solid components can pass though the screening belt/cloth is increased. In addition, excess (oversize) mixture can be discharged more rapidly into the chute in order to try and reduce the amount of mixture on the screening belt/cloth and to unclog at least some of the clogged apertures. The system may also include at least one spray device which is connected/connectable to a fluid source and which is directed towards the screening belt/cloth, the spray device being operable to discharge/spray fluid onto the screening belt/cloth in order to help unclog some of the clogged apertures. The fluid source may be a water source.

The load management arrangement, or more specifically the controller thereof, may therefore be configured to increase the speed by which the drive unit drives the screening belt/cloth, in response to the load sensed on the screening belt/cloth by the load sensing arrangement reaching or exceeding a predetermined level (i.e. in the event of overloading). The load management arrangement, or more specifically the controller thereof, may also be configured to decrease the speed by which the drive unit drives the screening belt/cloth, in response to the load sensed on the screening belt/cloth by the load sensing arrangement dropping below a predetermined level. Alternatively, the load management arrangement, or more specifically the controller thereof, may be configured to adjust the speed by which the drive unit drives the screening belt/cloth continuously as the load sensed on the screening belt/cloth by the load sensing arrangement changes, by increasing the speed when the load increases above a reference load and decreasing the speed when the load decreases below a reference load.

The load management arrangement may include a tension indicator, at least part of which is configured to be displaceable in a first direction in response to an increase in load on the screening belt/cloth. The load sensing arrangement may include a level or distance sensor which is configured to sense displacement of the at least part of the tension indicator. More specifically, the tension indicator may include a target member and the level or distance sensor may be oriented towards the target member in order to sense displacement of the target member, which would be indicative of a change in load on the screening belt/cloth. The at least part of the tension indicator may include the target member and may be configured to move operatively upwardly in response to an increase in load on the screening belt/cloth, and the level or distance sensor may be positioned directly above the target member in order to sense the level of the target member (i.e. the distance between the sensor and the target surface). The tension indicator may include a tensioner, wherein the screening belt/cloth extends around at least a portion of the tensioner, and wherein at least part of the tensioner is configured to be displaceable in the first direction in response to an increase in load on the screening belt/cloth. The target member may be connected to the at least part of the tensioner.

The target member may define a target surface onto which the level or distance sensor is directed.

The tensioner may include a roller around which the screening belt/cloth extends. The level or distance sensor may accordingly be configured to sense displacement of the roller of the tensioner. The target member may therefore be connected to the roller of the tensioner. In accordance with another aspect of the invention there is provided a method of separating first solid particulate components from second solid particulate components having particle sizes which are smaller than that of the first solid components, wherein the first and second solid components are suspended in a liquid to form a mixture or slurry, the method including feeding the mixture onto an endless screening belt/cloth which is displaceable along a predetermined path, the screening belt/cloth defining a plurality of apertures which apertures are of a suitable size to permit the second solid components to pass therethrough and to impede the passage therethrough of the first solid components, the mixture being fed onto the screening belt/cloth in a separating region, the method further including sensing a change in load on the screening belt/cloth; comparing the load sensed to a reference load; and adjusting at least one operating parameter of the system if the load sensed is greater than the reference load.

The reference load may refer to a specific load on the screening belt/cloth above which overloading will occur.

The method may include increasing the speed by which the screening belt/cloth travels when the load sensed is greater than the reference load. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings. In the drawings:

Figure 1 shows a schematic side view of a separation system in accordance with the invention, in both a normal operating condition and an overloaded condition;

Figure 2 shows a schematic side view of a separating region of a screening cloth of the separation system of Figure 1 , when a mixture is fed onto the screening cloth;

Figure 3a shows a schematic side view of a tension indicator of a load management arrangement of the separation system of Figure 1 , when the system is in its normal operating condition;

Figure 3b shows a schematic side view of the tension indicator of Figure 3a, when the separation system is in its overloaded condition; and

Figure 4 shows an enlarged, plan view of the screening cloth. DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

In Figure 1 , reference numeral 10 refers generally to a separation system in accordance with the invention. The separation system 10 is specifically adapted for separating first solid particulate components from second solid particulate components which are mixed in a liquid (hereinafter referred to as the mixture 12), where the particle sizes of the second solid components are smaller than that of the first solid components. The separation system 10 includes an endless screening cloth 14 (a screening belt can also be used) which defines a plurality of apertures 1 6 which apertures are of a suitable size to permit the second solid components and liquid to pass therethrough and to inhibit or impede the passage therethrough of the first solid components. As shown in Figure 4, the screening cloth 14 is made from a plurality of 0.8mm polyester strands 91 which are woven together and which together define the apertures 1 6. However, for the sake of clearly illustrating the working of the invention, the apertures 1 6 illustrated in Figures 1 -3b are spaced relatively far apart. The specific dimensions of the screening cloth 14, more specifically the apertures 16, as well as the thickness of the strands, may vary depending on the particular application. The screening cloth 14 is fitted around a set of rollers 77.1 -77.5 and is driven along a predetermined path in a first travel direction 100 (the screening cloth 14 can also be driven in the opposite direction) by a drive unit of which the roller 77.5 forms part. The screening cloth 14 passes through a horizontal separating region 18 in which the mixture 12 is introduced onto the screening cloth 14 during use. The screening cloth 14 in the separating region 18 is supported by a series of rollers 17 which rollers are positioned below the separating region 18 and spaced along the travel direction 100 of the screening cloth 14.

The separation system 10 also includes a load management arrangement, generally indicated by reference numeral 67, which is configured to sense overloading of mixture 12 on the screening clothl 4 and adjust at least one operating parameter of the system 10 in response to a change in load being sensed. The load management arrangement 67 includes a tension indicator 58; a load sensing arrangement 31 ; and a controller 81 (e.g. a digital control system). The tension indicator 58 has a tensioner 57 which includes the roller 77.3 which is pivotally connected to a pivot point 52 by means of a swinging arm 54. Due to the pivotal connection, the weight of the roller 77.3 will help tension the screening cloth 14 by forcing that particular part of the cloth 14 which is wrapped around the roller 77.3 downwardly (i.e. as a result of gravitational forces acting on the roller 77.3). As the load on the screening cloth 14 increases, it tends to sag between the rollers 17 which causes the roller 77.3 to be forced upwards from the position shown in solid lines in Figure 1 , as well as in Figure 3a, towards the position shown in broken lines in Figure 1 , as well as in Figure 3b (i.e. an overloaded condition). In order to increase the tension in the screening cloth 14, additional weights could be secured to the roller 77.3.

The tension indicator 58 includes a target member 32 which is connected to, and protrudes from, the roller 77.3. Therefore, as the roller 77.3 pivots upwards (e.g. due to an increase in load on the screening cloth 14), the target member 32 moves upwards therewith. The upward movement of the target member 32 is therefore indicative of an increase in load on the screening cloth 14. The target member 32 defines an operatively upper target surface 33. The load sensing arrangement 31 includes a distance/level sensor 35 which is positioned directly above the target surface 33 and is configured to sense the distance to the target surface 33.

The distance/level sensor 35 is connected to the controller 81 . The controller 81 is configured to receive distance/level information from the distance/level sensor 35 and to determine whether or not the target surface 33 is above a certain maximum level, which would be indicative of an overload of mixture 12 on the screening cloth 14. When the controller 81 establishes that the screening cloth 14 is overloaded, it sends an instruction message to a so-called variable speed drive (VSD) unit 79 to increase the speed by which the drive unit drives the screening cloth 14. The VSD unit 79 is accordingly configured to adjust the speed of the drive unit in response to receiving the instruction from the controller 81 . Once the load on the screening cloth 14 drops below a certain predetermined level, the controller 81 sends an instruction message to the VSD unit 79 to decrease the speed by which the drive unit drives the screening cloth 14 to its normal operating speed. Alternatively, the adjustment of the speed can be done continuously by increasing the speed as the load increases and decreasing the speed as the load decreases. An "underpan" 42 is positioned below the separating region 18 in order to collect the liquid and second solid components which pass thought the apertures 16 in the screening cloth 14. The separation system 10 also includes a chute 43 which is positioned at a discharge end 47 of the separating region 18 in order to collect the first solid components. A feeding arrangement 46 is positioned above the separating region 18 in order to feed the mixture 12 onto the screening cloth 14 in the separating region 18. The feeding arrangement 46 includes an opening 99 through which mixture 12 can be received (see arrow 1 19).

As the mixture 12 is introduced onto the screening cloth 14, some of the first solid components in the mixture 12 may sink down onto an operatively upper surface 23 of the screening cloth 14 in the separating region 18 and end up covering some of the apertures 16, thereby inhibiting the flow of liquid and the passage of second solid components through those apertures 1 6 (see Figure 2).

The feeding of mixture 12 onto the screening cloth 14 in the separating region 18 is usually done continuously and at a steady rate. Therefore, with some of the apertures 1 6 of the screening cloth 14 being clogged, the liquid and second solid components may end up not filtering through the apertures 1 6 fast enough, which will ultimately result in an overload of mixture 12 on the screening cloth 14.

By increasing the speed by which the screening cloth 14 moves in the event of overloading, the presented length of the screening cloth 14 and hence the number of apertures 1 6 passing through the separating region 18 per unit time is increased. Thus, the rate at which the liquid and particles of the second solid components can pass though the screen is increased.

The separation system 10 can include a plurality of water spray devices 121 which devices 121 are positioned below, and directed towards, the screening cloth 14 in its separating region 18. These water spray devices 121 can then be used to discharge/spray fluid onto the screening cloth 14 (in the separating region 18) from below in order to help unclog some of the clogged apertures 1 6. The Inventors believe that the separation system 10 in accordance with the invention provides an effective solution for the overloading problems identified in the background of the specification, thereby promoting efficient separation.

Claims

CLAIMS:

1 . A separation system for separating first solid particulate components from second solid particulate components having particle sizes which are smaller than that of the first solid components, wherein the first and second solid components are suspended in a liquid to form a mixture or slurry, the system including:

a load management arrangement which is configured to sense a change in load on the screening belt/cloth and adjust at least one operating parameter of the system in response to a change in load being sensed.

2. The system of claim 1 , wherein the load management arrangement is configured to adjust the at least one operating parameter of the system when the load sensed by the load management arrangement reaches or exceeds a predetermined level.

3. The system of any of the preceding claims, wherein the load management arrangement includes:

a load sensing arrangement which is configured to sense a change in load on the screening belt/cloth; and

a controller which is in communication with the load sensing arrangement and which is configured to adjust the at least one operating parameter of the system in response to a change in load being sensed by the load sensing arrangement.

4. The system of claim 3, wherein the controller is configured to adjust the at least one operating parameter of the system when the load sensed by the load sensing arrangement reaches or exceeds a predetermined level.

5. The system of claim 3 or claim 4, which includes a drive unit which is configured to drive the screening belt/cloth along its predetermined path.

6. The system of claim 5, wherein the controller is in communication with the drive unit and is configured to adjust the speed by which the drive unit drives the screening belt/cloth, in response to a change in load being sensed, the travel speed of the screening belt/cloth therefore being the operating parameter of the system which is adjusted by the controller.

7. The system of claim 6, wherein the controller is configured to increase the speed by which the drive unit drives the screening belt/cloth, in response to the load sensed on the screening belt/cloth by the load sensing arrangement reaching or exceeding a predetermined level.

8. The system of claim 7, wherein the controller is also configured to decrease the speed by which the drive unit drives the screening belt/cloth, in response to the load sensed on the screening belt/cloth by the load sensing arrangement dropping below a predetermined level.

9. The system of claim 6, wherein the load management arrangement is configured to adjust the speed by which the drive unit drives the screening belt/cloth continuously as the load sensed on the screening belt/cloth by the load sensing arrangement changes, by increasing the speed when the load increases above a reference load and decreasing the speed when the load decreases below a reference load.

10. The system of any of claims 3 to 9, wherein the load management arrangement includes a tension indicator, at least part of which is configured to be displaceable in a first direction in response to an increase in load on the screening belt/cloth.

1 1 . The system of claim 10, wherein the load sensing arrangement includes a level or distance sensor which is configured to sense displacement of the at least part of the tension indicator.

12. The system of claim 1 1 , wherein the tension indicator includes a target member and the level or distance sensor is oriented towards the target member in order to sense displacement of the target member, which would be indicative of a change in load on the screening belt/cloth.

13. The system of claim 12 wherein the at least part of the tension indicator includes the target member and is configured to move operatively upwardly in response to an increase in load on the screening belt/cloth, and wherein the level or distance sensor is positioned directly above the target member in order to sense the level of the target member.

14. The system of claim 12 or claim 13, wherein the target member defines a target surface onto which the level or distance sensor is directed.

15. The system of any of claims 12 to 14, wherein the tension indicator includes a tensioner, wherein the screening belt/cloth extends around at least a portion of the tensioner, and wherein at least part of the tensioner is configured to be displaceable in the first direction in response to an increase in load on the screening belt/cloth.

1 6. The system of claim 15, wherein the target member is connected to the at least part of the tensioner.

17. The system of claim 15 or claim 1 6, wherein the tensioner includes a roller around which the screening belt/cloth extends.

18. The system of claim 17, wherein the level or distance sensor is configured to sense displacement of the roller of the tensioner.

19. The system of claim 18, wherein the target member is connected to the roller of the tensioner.

20. A method of separating first solid particulate components from second solid particulate components having particle sizes which are smaller than that of the first solid components, wherein the first and second solid components are suspended in a liquid to form a mixture or slurry, the method including feeding the mixture onto an endless screening belt/cloth which is displaceable along a predetermined path, the screening belt/cloth defining a plurality of apertures which apertures are of a suitable size to permit the second solid components to pass therethrough and to impede the passage therethrough of the first solid components, the mixture being fed onto the screening belt/cloth in a separating region,

the method further including sensing a change in load on the screening belt/cloth; comparing the load sensed to a reference load; and adjusting at least one operating parameter of the system if the load sensed is greater than the reference load.

21 . The method of claim 20, wherein the reference load refers to a specific load on the screening belt/cloth above which overloading will occur.

22. The method of claim 20 or claim 21 , which includes increasing the speed by which the screening belt/cloth travels when the load sensed is greater than the reference load.