AU2010333700B2

AU2010333700B2 - Method and apparatus for delivering a grinding media to a grinding mill

Info

Publication number: AU2010333700B2
Application number: AU2010333700A
Authority: AU
Inventors: Katie Elizabeth Barns; Voltaire Villadolid; Peter Charles Woodall
Original assignee: Glencore Technology Pty Ltd
Current assignee: Glencore Technology Pty Ltd
Priority date: 2009-12-14
Filing date: 2010-12-10
Publication date: 2014-07-17
Anticipated expiration: 2030-12-10
Also published as: CA2783495A1; CA2783495C; PE20130332A1; CL2012001591A1; ZA201203817B; WO2011072324A1; AU2010333700A1

Abstract

An apparatus (10) for delivering a grinding media from a holding vessel or storage vessel to a grinding mill, the vessel holding a quantity of the grinding media, the grinding media being in the form of a particulate material, the vessel having an outlet at lower end. The apparatus (10) comprises a housing (12) positioned below the outlet of the vessel, the housing (12) receiving grinding media from the vessel, a nozzle (80) delivering a liquid to the housing, and a mixing chamber (110) having an inlet for receiving liquid and grinding media. The inlet of the mixing chamber (110) is spaced from an outlet of the nozzle (80) whereby liquid exiting the nozzle (80) entrains grinding media in the housing (12) and a mixture of liquid and grinding media enters the inlet of the mixing chamber (110) and is further mixed in the mixing chamber. The mixing chamber has an outlet through which the mixture passes into a diffuser (130) and then on to a pump box of a grinding mill. The mixture may be dewatered prior to passing to the pump box.

Description

WO 2011/072324 PCT/AU2010/001675 1 METHOD AND APPARATUS FOR DELIVERING A GRINDING MEDIA TO A GRINDING MILL. FIELD OF THE INVENTION 5 The present invention relates to a method and apparatus for delivering a grinding media to a grinding mill. BACKGROUND TO THE INVENTION 10 Grinding mills are widely used in the grinding of ores and concentrates. Grinding mills take the form of ball mills, tower mills, vertical attrition mills, horizontal attrition mills, stirred mills as well as other types used to grind materials. An example of a grinding mill is the mill sold by Xstrata -Technology under the trademark 15 IsaMillTM. Grinding mills are often operated to grind a slurry containing a liquid (normally water), the ore or concentrate and a grinding media. The grinding media may comprise particulate material, such as sand, ceramic, metal or other material. In many 20 grinding mills, a slurry of the ore or concentrate is mixed with the grinding media. This mixing may take place either just before entrance to the grinding mill or within the grinding mill itself. A number of different arrangements have been utilised to feed the grinding media to 25 the grinding mill. The terms "feeding to a grinding mill" or "delivery to a grinding mill" are general terms, and in reality, grinding media is fed into a pumpbox along with the material to be ground, and this is then pumped into the mill. Throughout this specification, the expressions "feeding to a grinding mill", "delivering to a grinding mill" or similar expressions are to be taken to include directly feeding to the mill or 30 feeding to a pumpbox or an intermediate vessel and thereafter to the mill. The material to be ground, or other material, may also be fed to the pumpbox or other intermediate vessel.

WO 2011/072324 PCT/AU2010/001675 2 In some arrangements, augers or screw conveyors are used to transfer the grinding media from a hopper to the grinding mill. In other arrangements, pneumatic conveying may be used to transfer the grinding media from a hopper to the grinding mill. Some attempts have also been made to use hydraulic conveying to transfer 5 grinding media to the grinding mill. However, none of these arrangements are entirely satisfactory for use with many grinding media presently in use. For example, ceramic grinding media are relatively coarse, dense particulates that are also highly abrasive. Existing screw conveyors have difficulty in transferring ceramic grinding media. Existing pneumatic and hydraulic conveying apparatus have trouble coping with the 10 highly abrasive nature of ceramic grinding media, which causes a short operational life for the pneumatic or hydraulic conveying apparatus and necessitates periods of downtime to replace that apparatus. While this invention is suited to ceramic grinding media, it also has applications with 15 steel based media. BRIEF DESCRIPTION OF THE INVENTION In one aspect, the present invention provides an apparatus for delivering a grinding 20 media from a holding vessel or storage vessel to a grinding mill, the vessel holding a quantity of the grinding media, the grinding media being in the form of a particulate material, the vessel having an outlet at lower end thereof, the apparatus comprising: - a housing positioned below the outlet of the vessel, the housing receiving grinding media from the vessel, 25 - a nozzle delivering a liquid to the housing, - a mixing chamber having an inlet for receiving liquid and grinding media, the inlet of the mixing chamber being spaced from an outlet of the nozzle whereby liquid exiting the nozzle entrains grinding media in the housing and a mixture of liquid and grinding media enters the inlet of the mixing chamber and is further mixed in the 30 mixing chamber, - a diffuser having an inlet for receiving the mixture of liquid and grinding media from the mixing chamber, the diffuser including a portion defining a generally divergent flow path therein, WO 2011/072324 PCT/AU2010/001675 3 - the diffuser having an outlet through which the mixture passes for supply to the grinding mill. In one embodiment, the present invention provides an apparatus for delivering a 5 grinding media from a holding vessel or storage vessel to a grinding mill, the vessel holding a quantity of the grinding media, the grinding media being in the form of a particulate material, the vessel having an outlet at lower end thereof, the apparatus comprising: - a housing positioned below the outlet of the vessel, the housing receiving grinding 10 media from the vessel, - the housing having a first side opening and a second side opening, - a nozzle connected to the first side opening, the nozzle delivering a liquid to the housing, - a mixing chamber connected to the second side opening, the mixing chamber having 15 an inlet for receiving liquid and grinding media, the inlet of the mixing chamber being spaced from an outlet of the nozzle whereby liquid exiting the nozzle entrains grinding media in the housing and a mixture of liquid and grinding media enters the inlet of the mixing chamber and is further mixed in the mixing chamber, - a diffuser having an inlet for receiving the mixture of liquid and grinding media 20 from the mixing chamber, the diffuser including a portion defining a generally divergent flow path therein, - the diffuser having an outlet through which the mixture passes for supply to the grinding mill. 25 In one embodiment a small amount of water is added to the media in the holding vessel or storage vessel above the apparatus to assist in the movement of the media into the housing In one embodiment no water is added to. the media in the holding vessel or storage 30 vessel above the apparatus. In this embodiment, the media leaving the holding vessel or storage vessel is either essentially dry or it may have essentially the same water content as the media entering the hopper or vessel or it may have a lower water content than the media entering the hopper or vessel (for example, the holding vessel or storage vessel may be provided with dewatering apparatus or drying apparatus).

WO 2011/072324 PCT/AU2010/001675 4 In one embodiment, the nozzle is a replaceable nozzle. In one embodiment, the mixing chamber is a replaceable mixing chamber. 5 In one embodiment, the diffuser is a replaceable diffuser. In one embodiment, a liquid supply system (such as a water supply system) that includes a liquid supply pump is provided for delivering liquid to the nozzle. The 10 liquid supply system may include a non-return facility to prevent the media flowing back into the liquid supply system when a liquid delivery pump stops. In one embodiment a screen or other dewatering technique or apparatus, such as a dewatering cyclone, can be used to separate the grinding media from the delivery 15 liquid being added to the mill tominimise delivery fluid from being added to the grinding mill. This is- preferably positioned on the inlet of the slurry holding tank or pumpbox where the media is delivered from the apparatus, the water being returned directly to the process or water system. Other dewatering techniques such as poly deck screens, pre-densifiers, or settling devices such as tanks allowing the water to 20 bypass the tank, while the media settles in the tank, and exits via an automated valve or a pressure sensitive device acting due to the media load such as a "duck bill" can also be used. In one embodiment, the housing includes a water inlet positioned below the outlet of 25 the vessel, enabling the grinding media to be wetted. The water inlet is suitably positioned so that it wets the media prior to the media contacting the liquid flow from the nozzle. It has been found that wetting the media prior to contacting the media with the liquid from the nozzle surprisingly increases the media transfer rates. 30 In one embodiment, the holding vessel or storage vessel has one or more sides consisting of a portion of screen used to dewater the media that is being stored in the housing vessel.

WO 2011/072324 PCT/AU2010/001675 5 In some embodiments of the present invention, the housing may include an opening having a closure, the closure being removable to gain access to an interior volume of the housing. This is advantageous in that any blockages in the housing caused by the grinding media can be easily cleared by opening the housing to gain access to the 5 interior volume of the housing and hence to the site of the blockage. Clearing of the blockage may be as simple as poking into the blockage with a rod, or by removing the blockage from the housing. In some embodiments of the present invention, a valve is positioned to control flow of 10 grinding material from the outlet of the holding vessel or storage vessel into the housing. The valve may be operated so that it is normally partly opened to allow a trickle of grinding media to pass therethrough. The valve may be moved to a fully opened position in the event that a blockage or bridging occurs in the grinding media in the vicinity of the valve. The valve may also be closed fully during shutdowns for 15 maintenance of the installation. The valve is suitably a knife gate valve having a large opening so that it can be opened wide if bridging of the grinding media in the vessel outlet occurs. The housing may be provided with a viewing port in order to allow an operator in to 20 view the interior volume of the housing. The viewing port may be provided by a transparent portion in a wall of the housing. The viewing port may be provided in the form of a window in a wall of the housing. The nozzle may be connected to the housing via any appropriate connection. For 25 example, the nozzle may be connected to the housing via a flange connection. For example, the housing may have a conduit or projection extending from aside wall, the conduit or projection having a flange at an outer end thereof, and the nozzle may also be provided with a complementary shaped flange for joining to the flange of the conduit or projection. Appropriate nuts and bolts may be used to connect the nozzle to 30 the flange connection. The nozzle may be fitted by inserting the nozzle through the opening in the side wall of the housing such that the nozzle extends into the interior volume of the housing and connecting the nozzle to the housing.

WO 2011/072324 PCT/AU2010/001675 6 In some embodiments, the nozzle may include a nozzle insert. The nozzle insert may extend through a nozzle housing that is connected to the housing. The mixing chamber may be connected to the housing via any appropriate connection. 5 For example, the mixing housing may be. connected to the housing via a flange connection. In one embodiment, the housing may have a conduit or projection extending from the sidewall, the conduit or projection having a flange at an outer end thereof, and the mixing chamber may also be provided with a complementary shaped flange for joining to the flange of the conduit or projection. Appropriate nuts and bolts 10 may be used to connect the mixing chamber to the flange connection. The mixing chamber may be fitted by inserting the mixing chamber through the opening in the side wall of the housing such that the mixing chamber extends at. least partly into the interior volume of the housing and connecting the mixing chamber to the housing. 15 The mixing chamber may include a mixing chamber insert. The mixing chamber insert may extend through a mixing chamber housing that is connected to the housing. The diffuser may be connected to the mixing chamber or to the housing. For example, the diffuser may be connected to the mixing chamber or to the housing via a flange 20 connection. It will be understood that the diffuser is positioned such that the mixture of grinding media and liquid leaving the mixing chamber passes into the diffuser. In some embodiments, the diffuser is connected to an upwardly extending pipe will conduit that forms part of the delivery piping or conduits for delivering the mixture of 25 liquid and grinding media to the grinding mill. It has been found that having the pipe or conduit extending from the diffuser in an upwardly direction minimises or avoids settling of the grinding media in that pipe or conduit. The supply of liquid to the nozzle should be sufficiently high to ensure an adequate 30 transfer of grinding media. The actual flow rate of water may depend upon nozzle size and the amount or rate of grinding media to be transferred. A pump may be used to supply delivery liquid to the nozzle. Use of a pump ensures that a stable flow and pressure of delivery liquid can be provided. Although addition of process water through a pipe may be adequate to provide delivery liquid, the flow of process water WO 2011/072324 PCT/AU2010/001675 7 might vary due to variations in pressure in other parts of the overall process water circuit. The nozzle used in the present invention may have a ratio of outlet diameter to inlet 5 diameter of from 10% to 50%, more preferably from 15% to 35%, even more preferably from 20% to 30%. In some embodiments of the present invention, the mixing chamber may have a ratio of diameter to length of from 5% to 30%, more preferably from 10% to 20%, even 10 more preferably from 10% to 15%. These ratios have been found to provide sufficient length in the mixing chamber to produce good mixing between the liquid and the grinding media. The diffusor may have a ratio of inlet diameter to outlet diameter that falls within the 15 range of up to 75%, preferably from 30% to 75%, more preferably from 40% to 60%. Use of a divergent diffuser is likely to minimise the likelihood of blockages in the grinding media delivery system 20 In some embodiments, it may be possible to omit the diffuser. Accordingly, in another aspect, the present invention provides an apparatus for delivering a grinding media from a holding vessel or storage vessel to a grinding mill, the vessel holding a quantity of the grinding media, the grinding media being in the form of a particulate material, the vessel having an outlet at lower end thereof, the apparatus comprising: 25 a housing positioned below the outlet of the vessel, the housing receiving grinding media from the vessel, a nozzle delivering a liquid to the housing, and a mixing chamber having an inlet for receiving liquid and grinding media, the inlet of the mixing chamber being spaced from an outlet of the nozzle whereby liquid exiting 30 the nozzle entrains grinding media in the housing and a mixture of liquid and grinding media enters the inlet of the mixing chamber and is further mixed in the mixing chamber, the mixing chamber having an outlet through which the mixture passes for supply to the grinding mill.

WO 2011/072324 PCT/AU2010/001675 8 In one embodiment of this aspect of the present invention, the apparatus comprises: - a housing positioned below the outlet of the vessel, the housing receiving grinding media from the'vessel, - the housing having a first side opening and a second side opening, 5 - a nozzle connected to the first side opening, the nozzle delivering a liquid to the housing, - a mixing chamber connected to the second side opening, the mixing chamber having an inlet for receiving liquid and grinding media, the inlet of the mixing chamber being spaced from an outlet of the nozzle whereby liquid exiting the nozzle entrains 10 grinding media in the housing and a mixture of liquid and grinding media enters the inlet of the mixing chamber and is further mixed in the mixing chamber, the mixing chamber having an outlet through which the mixture passes for supply to the grinding mill. A 5 In a third aspect, the present invention provides a method for delivering grinding media to a grinding mill, the method comprising the steps of supplying grinding media from a vessel into a housing, the housing being provided with a nozzle for providing a transverse flow of liquid through the housing such that the transverse flow of liquid entrains grinding media in the housing and forms a mixture of liquid and 20- grinding media, the mixture of liquid and grinding media entering a mixing chamber and passing through the mixing chamber into a diffuser, causing the mixture of liquid and grinding media to pass through a flow path having a divergent portion in the diffuser and subsequently delivering the mixture of liquid and grinding media to a grinding mill. 25 In a fourth aspect, the present invention provides a method for delivering grinding media to a grinding mill, the method comprising the steps of supplying grinding media from a vessel into a housing, the housing being provided with a nozzle for providing a transverse flow of liquid through the housing such that the transverse flow 30 of liquid entrains grinding media in the housing and forms a mixture of liquid and grinding media, the mixture of liquid and grinding media entering a mixing chamber. and passing through the mixing and subsequently delivering the mixture of liquid and grinding media to a grinding mill, WO 2011/072324 PCT/AU2010/001675 9 In one embodiment of the method of the present invention, the .step of delivering the mixture of liquid and grinding media to a grinding mill comprises passing the mixture of liquid and. grinding media along an upwardly extending conduit or pipe. The upwardly extending conduit or pipe may be connected to the diffuser. It has been 5 found that settling of the grinding media is minimised or avoided into the upwardly extending conduit or pipe. The upwardly extending conduit or pipe may extend upwardly at an angle to the vertical. 10 In some embodiments, the method comprises wetting the media prior to mixing with the liquid from the nozzle. For example, a water inlet may be provided in or just below the outlet to the vessel so that a small amount of water is added to the media flowing through the outlet or exiting the outlet to thereby wet the media. The wetted 15 media then comes into contact with the delivery liquid. It has been surprisingly found that this can increase the rate of delivery of the media. The water inlet may alternatively be provided in an upper part of the housing. In some embodiments of the method of the present invention, the method further 20 comprises providing a valve to control the flow of grinding media from the vessel to the housing, the valve being normally operated in a partly open condition to allow a trickle of grinding media to flow therethrough, the valve being opened more fully in the event that bridging of the grinding media or a blockage in the grinding media in the vicinity of the valve occurs. 25 In the method of the present invention; a liquid (which will typically be water) is provided under pressure to the nozzle. This establishes a transverse flow of liquid in the housing. The housing is suitably arranged such that it is positioned below the vessel such that the grinding media drops through an outlet of the vessel into the 30 housing. The grinding media that is in the housing becomes entrained by the flow of liquid leaving the nozzle. The liquid leaving the nozzle suitably flows in a transverse direction through the housing. The nozzle has an outlet that is suitably positioned near but spaced from an inlet of the mixing chamber. The outlet of the nozzle and the inlet of the mixing chamber are both suitably within an interior volume of the housing. The WO 2011/072324 PCT/AU2010/001675 10 mixture of liquid and grinding media that enters the housing flows along and through the housing. This assists in forming a more homogenous mixture of liquid and grinding media. The mixture then passes into the diffuser where it moves along a divergent flow path. The mixture leaving the diffuser is then passed into the grinding 5 mill. Advantageously, in embodiments of the present invention, one or more of the nozzle, mixing chamber and diffuser are replaceable components. In this manner, if those components wear, for example due to the abrasive nature of the grinding media being 10 transported, it is a simple matter to shutdown the apparatus for a short period of time, remove the replaceable component that needs replacing and replace that component with a new or reconditioned component. Replacement of both the nozzle and the mixing chamber may be further simplified in embodiments where the nozzle or the mixing chamber comprise a nozzle insert or a mixing chamber insert. 15 In some embodiments of the present invention, the nozzle insert is made from a wear resistant material. Similarly, in some embodiments of the present invention, the mixing chamber insert is made from a wear resistant material. Examples of suitable material from which the nozzle insert and the mixing chamber insert may be made 20 include polyurethane, ceramic material, hardened steel or other wear resistant materials. This list should not be considered to be limiting and the person skilled in the art would be able to readily identify other wear resistant materials suitable for use. BRIEF DESCRIPTION OF THE DRAWINGS 25 Figure 1 shows a side elevation of an apparatus for delivering a grinding media to a grinding mill in accordance with an embodiment of the present invention; Figure 2 shows a similar view of the apparatus shown in figure 1, but with intemal 30 details of the apparatus shown in dashed outline; Figure 3 is an isometric view of the apparatus shown in figure 1; WO 2011/072324 PCT/AU2010/001675 11 Figure 4 is an isometric view of a nozzle suitable for use in the apparatus shown in figure 1; Figure 5 is a side elevation view of the nozzle shown in figure 4, with internal details 5 shown in dashed outline; Figure 6 is an isometric view of a mixing chamber suitable for use in the apparatus shown in figure 1; 10 Figure 7 is a side elevation view of the mixing chamber shown in figure 6, with internal details shown in dashed outline; Figure 8 is an isometric view of a diffuser suitable for use in the apparatus shown in figure 1; and 15 Figure 9 is a side elevation cross sectional view of the diffuser shown in figure 8. DETAILED DESCRIPTION OF THE DRAWINGS 20 The person skilled in the art will appreciate that the drawings have been provided for the purposes of illustrating preferred embodiments of the present invention. Therefore, it will be understood that the present invention should not be considered to be limited solely to the features as described and shown with reference to the accompanying drawings. 25 Figures 1 to 3 show various views of an apparatus in accordance with an embodiment of the present invention. The apparatus 10 includes a housing 12. Housing 12 includes an inlet 14. Inlet 14 is placed into alignment with an outlet of a vessel that holds or stores the grinding media. In order to secure the housing 12 to the outlet of the vessel, 30 a flange 16 having a plurality of openings, some of which are numbered at 18 in figure 3, is bolted'to a similar flange on the outlet of the vessel. The housing 12 includes a lower outlet 20 that is closed by a movable closure 22. Movable closure 22 may be hinged at hinge 24 to the housing 12. This enables the WO 2011/072324 PCT/AU2010/001675 12 closure 22 to be selectively opened and closed. The closure 22 may need to be opened for maintenance of the housing or for emptying a buildup of grinding media in the lower part of the housing 12. A flange 26 may be provided around the outlet 20 of the housing 12 in order to enable a closure base plate 28 to be mounted to the outlet 20. 5 The base plate 28 carries the hinge 24. It may also carry a U-shaped member 30 that can receive a projecting member 32 in order to retain the closure 22 in the closed position. A chain 34 may be used to avoid the possibility of loss of the projecting member 32. 10 The housing 12 also includes an inspection plate 36 that is bolted to a flange 38 (see figure 3) on the front of the housing 12. The inspection plate 36 can be removed for maintenance. The housing 12 also includes a first side opening 40 and a second side opening 42. 15 First side opening 40 has a flange 44. Second side opening 42 has a flange 46. Side opening 40 is positioned at the end of a lateral extension 48 of housing 12. Similarly, opening 42 is positioned at the end of a lateral extension 50 of housing 12. Lateral extensions 48, 50 may be formed by welding or otherwise joining pipes to the 20 main body of housing 12. The apparatus 10 shown in figures 1 to 3 includes a delivery water supply, a nozzle, a mixing chamber and a diffuser. Each of these features will now be described. 25 The delivery water supply 52 is positioned to the left of flange 44 in the views shown in figures 1 and 2. The delivery water supply 52 includes a water inlet 54. Water inlet 54 is joined to a water supply. system (not shown). The water supply system will typically include a pump for providing a controllable delivery flow rate and pressure. A hon-return valve or non-return system may be provided between the pump and the 30 housing 12 to prevent the back flow of grinding media into the water supply system or the pump when the pump is turned off. The water inlet 54 forms an inlet to supply water spool 56. A flange 60 extends around inlet 54 and the spool 56 includes a first end that is closed by plug 62. Plug 62 is joined via plug flange 64 to spool flange 66.

WO 2011/072324 PCT/AU2010/001675 13 The supply water spool 56 includes an outlet having a flange 68 extending therearound. Flange 68 is joined to flange 70 of rodding spool 72. Rodding spool 72 effectively provides a communication conduit between the supply water spool 56 and the housing 12. Appropriate flanges that are shown in figures 1 to 3 but not numbered 5 enable the rodding spool to be connected to the housing 12. The apparatus 10 also includes a nozzle 80. Nozzle 80 shown in figures 4 and 5: Nozzle 80 is designed to be inserted through the first side opening 40 of the housing 12. Nozzle 80 includes nozzle housing 82, Which will typically be made from steel. A 10 nozzle insert 84, which is made from a wear resistant material, such as polyurethane, hardened steel or a ceramic material, is fitted inside nozzle housing 82. Nozzle insert 84 is removable from the nozzle housing 82. This is advantageous in that the internal parts of the nozzle 80 are subject to wear and if the nozzle insert 84 becomes worn, it is a relatively simple matter to remove the nozzle 80 from the apparatus 10, replace 15 the worn nozzle insert 84 with a new or reconditioned nozzle insert and then replace the repaired nozzle back into the apparatus 10. The nozzle housing 82 includes a generally cylindrical portion 86 that has a flange 88 extending at one end. A jacking ring 90 is provided adjacent to flange 88. The flange 20 88 and jacking ring 90 are used to connect the nozzle 82 to the flange 44 of the first side opening 40 of the housing 12. The nozzle 80 includes an inlet opening 92. Inlet opening 92 receives delivery water from the delivery water system. The nozzle 80 also includes a nozzle outlet 94. The 25 nozzle also includes a nozzle chamber 96 that has a converging portion 98 (see figure 5). As a result of the converging portion 98, the nozzle outlet 94 has a smaller diameter than the nozzle in 92. In some embodiments of the present invention, the ratio of the nozzle outlet to the nozzle inlet diameters may be up to about 50%. In some embodiments, the ratio of nozzle outlet to the nozzle inlet diameters falls within 30 the range of 20 to 30%. In some embodiments, the diameter of the feed inlet of nozzle may be about 66mm, and the outlet of the nozzle may have a diameter of between 15and 20mm, giving a ratio of outlet to inlet of 22% to 30% in that specific embodiment. It will be appreciated that the nozzle dimensions should not be considered to be limited to these particular dimensions.

WO 2011/072324 PCT/AU2010/001675 14 The use of the nozzle 80 causes the delivery water that is supplied to the housing to increase in velocity as it flows through the nozzle and into the housing. This assists in the delivery water entraining the grinding media in the housing. 5 As best shown in figure 2, the nozzle 80 is positionea sucn mat mne outlet 94 is positioned quite close to the centre line 100 of housing 12. The apparatus 10 also includes a mixing chamber 110. The mixing chamber 110 is 10 best shown in figures 6 and 7. The mixing chamber 110 includes a mixing chamber housing 112 and a mixing chamber insert 114. Mixing chamber insert 114 is a removable insert made from a hard wearing material, such as polyurethane, ceramic or hardened steel. It will be appreciated that a mixture of grinding media and water flows through mixing chamber 110. This mixture can be quite abrasive and as a result 15 the mixing chamber 110 can be subject to high wear conditions. Using a mixing chamber insert 114 of a hard wearing material means that the life of the mixing chamber insert 114 is maximised. Further, when the mixing chamber insert 114 has reached the end of its usable life, it can be removed and replaced with a new or reconditioned mixing chamber insert. 20 The mixing chamber housing 112 includes a flange 116 that may also be-fitted with a. jacking ring 118. Flange 116 and jacking ring 118 may be used to connect the mixing chamber 110 to the second side opening 42 of housing 12. 25 The mixing chamber 110 includes a mixing chamber outlet 120 and a mixing chamber inlet 122. As can be seen from figure 7, the mixing chamber inlet 122 is defined by radiussed, outwardly divergent walls 124. As can best be seen from figure 2, the mixing chamber inlet 122 is positioned close to 30 the centre line 100 of housing 12. Therefore, as can also be seen from figure 2, the outlet 94 of the nozzle 80 is spaced only a relatively short distance away from the inlet 122 of the mixing chamber 110.

WO 2011/072324 PCT/AU2010/001675 15 In one specific embodiment, the mixing chamber had a length of 300mm and a diameter of 40mm for the majority of the length of the chamber ( the feed end of the mixing chamber is curved to the outer edge). The ratio of diameter to length for the mixing chamber of this specific embodiment is about 13%. It will be appreciated that 5 the dimensions of the mixing chamber should not be considered to be limited to these specific dimensions. In operation of the apparatus 10, grinding media drops down through inlet 14 of housing 12. A fast flowing flow of water passes through the outlet 94 of the nozzle 80 10 and into the inlet 122 of the mixing chamber 110. This fast flowing flow of water entrains grinding media and carries grinding media with the flow of water into the mixing chamber 110. As the flow of water and entrained grinding media flow through the mixing chamber 110, they become relatively homogenously mixed. .15 The apparatus 10 shown in figure 1 also includes a diffuser 130. The diffuser 130 is best shown in figures 8 and 9. The diffuser 130 includes a diffuser housing 132 having a flange 134. A jacking ring 136 may be fitted next to flange 134. The diffuser housing 132 will typically be made from steel. 20 The diffuser 130 is also fitted with a diffuser insert 138. Diffuser insert 138 may be made from a hard wearing material, such as polyurethanes, a ceramic or hardened steel. It will be appreciated that a mixture of water and grinding media flows through the diffuser 130. This mixture is very abrasive. Therefore, manufacturing the diffuser insert 138 from a hard wearing material maximises the effective working life of the 25 insert. When the diffuser insert 138 becomes worn, it can be removed from the diffuser housing 132 and replaced with a new or reconditioned diffuser insert. This allows for simple maintenance and reconditioning of the diffuser 130. As can be seen from figure 9, the diffuser includes a diffuser inlet 140, a diverging 30 portion 142 and a diffuser outlet 144. As the diameter of the diffuser outlet 144 is larger than the diameter of the diffuser inlet 140, the velocity of the flow of water and grinding media passing out through the diffuser outlet 144 is lower than the velocity of the mixture of flowing into the diffuser inlet 140. It will be understood that the high flow conditions at the inlet occurred because the high water'flow rate leaving the WO 2011/072324 PCT/AU2010/001675 16 nozzle 80 is required in order to pick up and entrain grinding media within the housing 12. However, once the grinding media has been properly taken up into and entrained by the delivery water, the very high rates of flow may not be required to convey the entrained grinding media to the mill or to the pump box. Therefore, it is 5 desirable to slow down that flow in order to minimise wear and abrasion in piping located downstream of the apparatus 10. The diffuser 130 allows this to occur. The diffuser 130 is connected via the flange 134 to the flange 46 of the second side opening 42. 10 Figure 10 shows a schematic flow diagram of the apparatus 10 shown in figures 1 to 3 being located in a feed flow sheet for feeding grinding media to a pumpbox and then to a grinding mill. The apparatus 10 is mounted to a hopper or storage vessel 200 that holds or stores the grinding media. A water pump 202 provides water to water inlet 15 54. A mixture of water and grinding media exit the apparatus 10 through outlet 144. The mixture of grinding media and conveying water passes along pipe, which shown schematically at 204 and into the slurry pumpbox 208. A slurry stream 210, which may comprise a slurry containing ore or concentrate, is mixed with the grinding media in the slurry pumpbox 208. The mixture of grinding media and slurry exit slurry 20 pumpbox 208 through outlet 212 and is transferred via slurry pump 214 into grinding mill 216. In some embodiments, the pipe 204 may include a portion that is angled upwardly from the outlet 144 of apparatus 10. It is believed that having an upwardly angled part 25 in this pipe that extends from the outlet 144 assists in avoiding settling of the grinding media in the pipe 204. Also shown in figure 10 is water stream 220 that can be added to the hopper or storage vessel 200. It has been found that adding water to the grinding media into the 30 hopper or storage vessel can assist in transferring grinding media via the apparatus 10 into the slurry pump box 208. The water stream 220 may be added at any part of the storage hopper. For example, the water stream 220 may add water to the grinding media at a point just above the outlet of the hopper or storage vessel 200 into the apparatus 10. Alternatively, the water stream 220 may be added to any other part of WO 2011/072324 PCT/AU2010/001675 17 the storage vessel. As a further alternative, the additional water may be added to the grinding media at a point just above the mixing chamber of apparatus 10. Alternatively no water at all is added at all to any part of the hopper or storage vessel, or just above the mixing chamber so that. the media leaving the holding vessel or 5 storage vessel is either essentially dry or has essentially the same water content as media entering the hopper or storage vessel or has a water content lower than the media entering the hopper or vessel. The hopper or vessel may be provided with dewatering apparatus, such as- a screen or screens in a side or a wall or floor, to lower the water content of the media entering the hopper or vessel prior to discharge of the 10 -media from the hopper or vessel. Figure 11 shows a flow sheet of a slightly modified version of the flow sheet shown in figure 10. For convenience, features in figure 11 that are common with the features shown in figure 10 are denoted by the same reference numerals. The apparatus shown 15 in figure 11 also includes a dewatering device 222. Dewatering device 222 may comprise, for example, a screen. Other dewatering devices may also be used, such as poly-deck screens, pre-densifiers, or settling devices such as tanks allowing the water to pass through the tank, while the media settles in the tank, and exits via a automated valve or a pressure sensitive device acting due to the media load such as a "duck bill". 20 The dewatering device' transfers dewatered media 224 to the slurry pump box 208. Water 230 that is removed from the mixture of water and grinding media leaving pipe 204 by the dewatering device may be returned as a water feed to pump 202. Alternatively, the water stream 230 may be reused in other parts of the plant or as process water. 25 The embodiment of Figure 11 does not add water to the media leaving the holding vessel or storage vessel 200. Indeed, holding vessel or storage vessel 200 may have a screen 201 in a wall or floor portion to allow for dewatering of the media in the holding vessel or storage vessel 200 so that the media leaving the holding vessel or 30 storage vessel 200 has a lower water content than the media entering the hopper or storage vessel 200. Other dewatering devices or drying apparatus may be used. It will also be appreciated that, in an alternative embodiment, the media being returned to the holding vessel or storage vessel 200 may be dewatered to a desired water content prior to being returned to the holding vessel or storage vessel 200.

WO 2011/072324 PCT/AU2010/001675 18 Example. A test rig instructed similar to the apparatus shown in figures 1 to 3 was used to 5 conduct some experimental runs to measure the transfer of grinding media from a hopper. The results are shown in Table 1 below. The results show that satisfactory transfer of grinding media can be achieved when the grinding media exiting the holding vessel is dry. However, the results also show that by adding water (and not a lot) to the system just above the nozzle/mixing chamber, the transfer of media 10 increased 3 fold. This is assuming that the media in the holding vessel is de-watered but still damp (in table 1, the notation "dry" refers to grinding media -that has been dewatered but is still damp). Table 1 15 Flowrate 15mm Nozzle 20mm Nozzle Tonnes per Hour Wet Dry Wet Dry Run 1 19.49 8.50 22.52 7.09 Run 2 18.93 7.93 22.08 8.06 AVERAGE 19.21 8.22 22.30 8.03 The testwork has indicated the flowrate when using dry media with different nozzles has negligiable effect on the flowrate. However when the media is wetted the flowrate did increase from a 19.21tph average to a 22.30 tph average using a larger nozzle 20 diameter. Wetting of the media was achieved in having a water addition inlet on the mixing chamber. For the current set up this was a 2" (50 mm) water inlet. 25 Without wishing to be bound by theory, the improvement in the flowrate with a wet system compared to a dry system, is thought to be due to the water allowing the media to "slip" easier down into the mixing chamber, while when the system is dry, the WO 2011/072324 PCT/AU2010/001675 19 increased friction between the particles prevents free movement of the media downwards into the mixing chamber. This allows the invention to be used in two modes. The first in a wetted mode, which 5 allows higher flowrates of media to be delivered to an empty mill after a shutdown, which minimises the time required to get up to working power. The second mode is when the media is dry, and can be used for media addition while the mill is operating, when small addition rates are. required for mill power control rather than large addition rates which can cause unsteady mill operation. 10 Alternatively the media is added dry to allow media to be delivered to an empty mill after a shutdown as well as while the mill is operating. Those skilled in the art will appreciate that the present invention may be susceptible to 15 variations and modifications other than those specifically described. It will be appreciated that the present invention encompasses all such variations and modifications that fall within its spirit and scope.

Claims

1. An apparatus for delivering a grinding media from a holding vessel or storage vessel to a grinding mill, the vessel holding a quantity of the grinding media, the grinding media being in the form of a particulate material, the vessel having an outlet at lower end thereof, the apparatus comprising: - a housing positioned below the outlet of the vessel, the housing receiving grinding media from the vessel, - a nozzle delivering a liquid to the housing, - a mixing chamber having an inlet for receiving liquid and grinding media, the inlet of the mixing chamber being spaced from an outlet of the nozzle whereby liquid exiting the nozzle entrains grinding media in the housing and a mixture of liquid and grinding media enters the inlet of the mixing chamber and is further mixed in the mixing chamber, - a diffuser having an inlet for receiving the mixture of liquid and grinding media from the mixing chamber, the diffuser including a portion defining a generally divergent flow path therein, - the diffuser having an outlet through which the mixture passes for supply to the grinding mill.

2. An apparatus as claimed in claim 1 wherein the housing has a first side opening and a second side opening, the nozzle being connected to the first side opening, the nozzle delivering a liquid to the housing, and the mixing chamber being connected to the second side opening.

3. An apparatus as claimed in claim 1 or claim 2 further comprising a liquid supply system that includes a liquid supply pump for delivering liquid to the nozzle.

4. An apparatus as claimed in claim 3 wherein the liquid supply system includes a non return facility to prevent the media flowing back into the liquid supply system when the liquid delivery pump stops.

5. An apparatus as claimed in any one of the preceding claims wherein the housing includes a water inlet positioned below the outlet of the vessel, enabling the grinding media to be wetted. 21

6. An apparatus as claimed in any one of the preceding claims wherein the housing includes an opening having a closure, the closure being removable to gain access to an interior volume of the housing.

7. An apparatus as claimed in any one of the preceding claims wherein a valve is positioned to control flow of grinding material from the outlet of the holding vessel or storage vessel into the housing.

8. An apparatus as claimed in claim 7 wherein the valve comprises a knife gate valve having a large opening so that it can be opened wide if bridging of the grinding media in the holding vessel or storage vessel outlet occurs.

9. An apparatus as claimed in any one of the preceding claims wherein the housing is provided with a viewing port in order to allow an operator to view the interior volume of the housing

10. An apparatus as claimed in any one of the preceding claims wherein the nozzle includes a nozzle insert.

11. An apparatus as claimed in claim 10 wherein the nozzle insert extends through a nozzle housing that is connected to the housing.

12. An apparatus as claimed in any one of the preceding claims wherein the housing has a conduit or projection extending from a sidewall, the conduit or projection having a flange at an outer end thereof, and the mixing chamber is be provided with a complementary shaped flange forjoining to the flange of the conduit or projection.

13. An apparatus as claimed in any one of the preceding claims wherein the mixing chamber includes a mixing chamber insert.

14. An apparatus as claimed in claim 13 wherein the mixing chamber insert extends through a mixing chamber housing that is connected to the housing. 22

15. An apparatus as claimed in any one of the preceding claims wherein the diffuser is connected to an upwardly extending pipe or conduit that forms part of the delivery piping or conduits for delivering the mixture of liquid and grinding media to the grinding mill.

16. An apparatus for delivering a grinding media from a holding vessel or storage vessel to a grinding mill, the vessel holding a quantity of the grinding media, the grinding media being in the form of a particulate material, the vessel having an outlet at lower end thereof, the apparatus comprising: - a housing positioned below the outlet of the vessel, the housing receiving grinding media from the vessel, - a nozzle delivering a liquid to the housing, and - a mixing chamber having an inlet for receiving liquid and grinding media, the inlet of the mixing chamber being spaced from an outlet of the nozzle whereby liquid exiting the nozzle entrains grinding media in the housing and a mixture of liquid and grinding media enters the inlet of the mixing chamber and is further mixed in the mixing chamber, the mixing chamber having an outlet through which the mixture passes for supply to the grinding mill.

17. A method for delivering grinding media to a grinding mill, the method comprising the steps of supplying grinding media from a holding vessel or storage vessel into a housing, the housing being provided with a nozzle for providing a transverse flow of liquid through the housing such that the transverse flow of liquid entrains grinding media in the housing and forms a mixture of liquid and grinding media, the mixture of liquid and grinding media entering a mixing chamber and passing through the mixing chamber into a diffuser, causing the mixture of liquid and grinding media to pass through a flow path having a divergent portion in the diffuser and subsequently delivering the mixture of liquid and grinding media to a grinding mill.

18. A method for delivering grinding media to a grinding mill, the method comprising the steps of supplying grinding media from a holding vessel or storage vessel into a housing, the housing being provided with a nozzle for providing a transverse flow of liquid through the housing such that the transverse flow of liquid entrains grinding media in the housing and forms a mixture of liquid and grinding media, the mixture of liquid and 23 grinding media entering a mixing chamber and passing through the mixing and subsequently delivering the mixture of liquid and grinding media to a grinding mill.

19. A method as claimed in claim 17 or claim 18 wherein the step of delivering the mixture of liquid and grinding media to a grinding mill comprises passing the mixture of liquid and grinding media along an upwardly extending conduit or pipe.

20. A method as claimed in any one of claims 17 to 19 further comprising wetting the media prior to mixing with the liquid from the nozzle.

21. A method as claimed in claim 20 wherein a water inlet is provided in or just below the outlet to the vessel so that a small amount of water is added to the media flowing through the outlet or exiting the outlet to thereby wet the media.

22. A method as claimed in any one of claims 17 to 21 further comprising providing a valve to control the flow of grinding media from the vessel to the housing, the valve being normally operated in a partly open condition to allow a trickle of grinding media to flow therethrough, the valve being opened more fully in the event that bridging of the grinding media or a blockage in the grinding media in the vicinity of the valve occurs.