MINING SYSTEM

Abstract

A method of mining ore in a mine pit (3) and a mine are disclosed. The method comprises mining ore from a floor (5) of a mine pit and/or collecting ore on the floor using at least one mobile excavation machine (11) and transporting ore within the mine pit on at least one mobile flexible conveyor (13). The method also comprises transporting ore that has been transported along the flexible conveyor from within the pit to outside the pit on at least one ladder conveyor (23) that extends up the wall of the pit.

Description

The present invention relates to open pit mining of ore that contains valuable metals.

The present invention relates particularly, although by no means exclusively to mining of iron ore.

Conventional open pit mining of iron ore comprises progressively drilling and blasting sections of an ore body so that the ore can be picked up by shovels or other suitable excavators and transported from a pit on haulage trucks. It is known to mine iron ore in large blocks using a series of benches so that various mining activities can be carried out concurrently in a pit. A bench, which may be for example 40-200 m long by 20-100 m deep by 10-15 m high and containing many thousands of tonnes of ore and/or other material, is first drilled to form a pattern of “blast” holes. The material removed during the course of drilling the blast holes is analysed, for example by chemical analysis, to determine whether, on average, the ore is (a) high grade, (b) low grade or (c) waste material. The cut-off between high and low grades is dependent on a range of factors and may vary from mine to mine and in different sections of mines. The bench of ore is blasted using explosives, typically ANFO (ammonium nitrate/fuel oil) based, that are dispensed in specially designed bulk dispensing trucks which can regulate the explosive density prior to loading down the blast holes. The blasted material is picked up by earth moving vehicles in the form of excavators such as electric rope shovels, diesel hydraulic excavators, or front end loaders and placed into haulage vehicles such as trucks and transported from the mine pit. The ore is processed outside the mine pit depending on the grade determination. For example, waste ore is used as mine fill, low grade ore is stockpiled or used to blend with high grade ore, and high grade ore is processed further as required to form a marketable product.

Because conventional open pit mining uses blasting, care must be taken in drilling and blasting in the vicinity of proposed walls of the mine to minimise blast-induced damage. The slopes of the walls must take account of such damage and cable bolting is often employed to provide additional slope stability. The slope of the wall of a mine may be staggered in a series of steps known as “berm”. Some of these berms are wide enough to provide for a haulage road to be established passing up the wall of the mine. Typically, such haulage roads progressive wind their way up the wall in a series of switch backs. The time taken for haulage of blasted ore increases with the depth of the pit.

The present invention is an alternative mining method to the above-described method.

The mining method of the present invention may be used as the only method of mining in a mine pit or as one of several mining methods in a mine pit.

According to the present invention there is provided a method of mining ore in a mine pit that comprises the steps of:

• • (a) mining ore from a floor of a mine pit and/or collecting ore on the pit floor using at least one mobile excavation machine;
  • (b) transporting mined and/or collected ore within the mine pit on at least one mobile flexible conveyor; and
  • (c) transporting ore that has been transported along the flexible conveyor from within the pit to outside the pit on at least one ladder conveyor that extends up the wall of the pit.

The method may comprise transferring ore that has been transported up the wall of the pit along the ladder conveyor onto at least one main conveyor and transporting the ore along the main conveyor to a processing plant and/or a load-out station.

The term “mobile excavation machine” is understood herein to mean any machine that is capable of moving over a pit floor and mining ore that forms the pit floor and/or collecting ore on the pit floor. It is noted that the pit floor is unlikely to be a flat surface and typically will be an uneven surface with loose rocks on the floor.

The mobile excavation machine may be a continuous surface miner.

The continuous surface miner may comprise, by way of example, a drum that carries a plurality of cutting elements, such as cutter picks, and is rotatable about a horizontal axis and cuts into and thereby mines material that forms a pit floor as the surface miner advances across the pit floor. The mobile excavation machine may be any other type of continuous surface miner.

The continuous surface miner may excavate ore to a depth in a range of 300-600 mm and at a rate of at least 900 tph (more typically at least 1200 tph) and travel at a speed of at least 5 m/min (more typically at least 10 m/min).

The term “mobile flexible conveyor” is understood herein to mean a conveyor that is both mobile and flexible and can move across the floor of the mine pit in a linear and a non-linear manner and can continue to operate while moving across the pit floor.

The term “mobile flexible conveyor” does not include conveyors that persons in the mining industry refer to as “shiftable” or “movable” conveyors. A “shiftable” or “movable” conveyor is a conveyor that can be repositioned in a mine after a period of mining has been completed. In other words, the conveyor is not mobile in the sense that it can move continuously, for example, to keep pace with a mobile excavation machine or other mobile machine while continuing to operate to transport mined and/or collected ore along the conveyor.

Typically, the mobile flexible conveyor has to meet any one or more of three basic requirements, namely (a) be sufficiently mobile to keep pace with an associated mobile excavation machine or other mobile machine while operating and transporting ore on the conveyor, (b) allow lateral, flexible movement while operating and transporting ore on the conveyor and, by way of example be capable of moving up or down steps of up to 400 mm in a pit floor, and (c) allow lengthwise extension and contraction while operating and transporting ore on the conveyor.

The mobile flexible conveyor may be of a type described in Australian patent 767395 in the name of Michael Pietsch. The disclosure in the Australian patent is incorporated herein by cross-reference.

The method may comprise transferring mined and/or collected ore directly from the mobile excavation machine to the mobile flexible conveyor.

The method may comprise transferring mined and/or collected ore from the mobile excavation machine to a mobile feed system, such as a mobile hopper or a mobile crusher, and then transferring ore from the mobile feed system to the mobile flexible conveyor.

The method may comprise continuously mining and/or collecting ore from the pit floor with the mobile excavation machine, and moving (a) the mobile flexible conveyor or (b) the mobile feed system/mobile flexible conveyor assembly to track the movement of the mobile excavation machine, and continuously transferring mined and/or collected ore from the mobile excavation machine to the mobile flexible conveyor or the mobile feed system/mobile flexible conveyor assembly.

The method may comprise transferring mined and/or collected ore from the mobile excavation machine to form a pile of ore on the pit floor.

The method may comprise transferring ore away from the ore pile on the mobile flexible conveyor.

The method may comprise transferring ore from the mobile flexible conveyor to at least one mobile trunk conveyor that extends along a section of the pit floor to the ladder conveyor.

The term “mobile trunk conveyor” is understood herein to mean a “shiftable” or “movable” conveyor as described above.

The mobile trunk conveyor may be located on the pit floor in a lower region of the pit.

The mobile trunk conveyor may follow a linear or a non-linear path.

The mobile trunk conveyor may receive ore from a plurality of mobile flexible conveyors covering more than one part of the pit.

The method may comprise periodically adjusting the position of the mobile trunk conveyor in response to a lowering of the pit floor.

The term “ladder conveyor” as used herein is understood to mean a conveyor that is able to transport ore from a mine pit directly up a wall of the mine pit from the pit floor, with the wall being a steep wall at an angle of at least 20° to the horizontal.

The wall of the mine pit may be at least 30°, in many instances at least 65° to the horizontal.

The pit wall may be at least 20 m and typically at least 40 m high.

The ladder conveyor may be a single conveyor from the pit floor to the rim of the mine pit and extends up the pit wall without transfer points along the length of the conveyor, i.e. without the ore being off-loaded at an upper end of one section of the conveyor and loaded onto a lower end of a successive section of the conveyor.

The ladder conveyor may extend up the pit wall without a switchback.

The ladder conveyor may comprise a belt that at least substantially encloses ore being conveyed on the conveyor.

The method may comprise extending the ladder conveyor in response to a general lowering of the pit floor.

The main conveyor may be located on a rim of the pit or at a base of a local topography surrounding the pit and follow the topography thereof.

The main conveyor may receive ore from more than one part of the pit or from a series of pits.

According to the present invention there is also provided a mine that comprises at least one pit having a pit floor and a pit wall that defines at least a part of the pit, at least one mobile excavation machine for mining ore from the pit floor and/or collecting or on the pit floor, at least one mobile flexible conveyor for transporting mined and/or collected ore within the mine pit, and at least one ladder conveyor for transporting mined and/or collected ore from the pit.

The mine may comprise a main conveyor outside the pit for transporting mined and/or collected ore from the pit to a processing plant or a load-out station.

The mine may comprise a plurality of pits and at least one main conveyor outside the pits for transporting mined and/or collected ore from the pits to a processing plant or a load-out station.

The pit wall may be at least 30°, in many instances at least 65° to the horizontal.

The pit wall may be at least 20 m and typically at least 40 m high.

The ladder conveyor may be a single conveyor from the pit floor to the rim of the mine pit and extends up the pit wall without transfer points along the length of the conveyor, i.e. without the ore being off-loaded at an upper end of one section of the conveyor and loaded onto a lower end of a successive section of the conveyor.

The ladder conveyor may extend up the pit wall without a switchback.

The pit floor may be at a plurality of different levels.

By way of example, the mine may be an iron ore mine.

The present invention is now described by way of example only with reference to the accompanying FIGURE which is a schematic diagram of a layout of a mine pit that illustrates one embodiment of a method of mining iron ore in accordance with the present invention.

The following description is in the context of mining iron ore. It is understood that the present invention is not limited to mining iron ore and extends to mining other ores.

It is also understood that the mine layout shown in the FIGURE is schematic and is intended to represent a mine layout in a very general sense.

With reference to the FIGURE, a mine pit generally identified by the numeral 3 and having a pit floor 5 is defined at least in part by mine walls 7. The mine walls 7 are shown as opposed straight walls for convenience only and the present invention is not limited to this arrangement. The pit floor 5 may be at one level. Alternatively, the pit floor 5 may be on multiple levels, i.e. multiple benches, which may be isolated from each other or interconnected by ramps (not shown).

The method of the present invention makes it possible for the angle of inclination of each mine wall 7 from the pit floor to be relatively steep, thereby minimising the loss of mined area. The angle of inclination is at least 20°. In many situations, the angle may be at least 45°.

Each mine wall 7 may comprise a series of steps or be one continuous wall. The method of the present invention makes it possible to form the mine walls 7 as steeper walls than is currently the case and, where steps are required, the steps need not be as wide as is currently the case. More particularly, the method of the present invention makes it possible to form steeper mine walls 7 without the increased use of cable bolting or other mechanical means to provide additional slope stability.

A plurality of mobile excavation machines in the form of surface miners 11 excavates ore from the pit floor 5. It is noted that the pit floor 5 is unlikely to be a flat surface and typically it will be uneven with loose rocks on the floor. By way of example, the surface miners 11 may comprise a drum that carries a plurality of cutter picks and is rotatable about a horizontal axis and cuts into and thereby mines material that forms the pit floor as the surface miner advances across the pit floor. Typically, the surface miner can mine ore to a depth in a range of 300-600 mm at a rate of at least 900 tph and can travel at a speed of at least 5 m/min.

The surface miners 11 make it possible to mine ore directly from the pit floor 5 and avoid the need to drill and blast a mine at least in certain sections of the mine pit 3.

The surface miners 11 (and other equipment) may be controlled remotely or by operators on the miners. In either case, typically the paths of movement of the surface miners 11 (and other equipment) within the mine pit 3 are in accordance with a mining plan. The paths of movement include, by way of example, a surface miner 11 advancing in one direction for a predetermined distance and mining ore from the pit floor, turning around and advancing in the opposite direction for the predetermined distance and mining ore from the pit floor, and repeating this pattern of movement to mine ore from a section of the pit floor.

One group of the surface miners 11 shown in the FIGURE transfers mined ore to mobile flexible conveyors 13 directly onto the conveyors 13 or via mobile feed systems 15 located at forward ends of the conveyors 13.

The mobile flexible conveyors 13 may be of any suitable type. By way of example, the mobile flexible conveyors 13 may be as manufactured by International Conveying Systems International and described by way of example in Australian patent 767395.

The mobile feed systems 15 may be hoppers.

Alternatively, or in addition, the mobile feed systems 15 may be in the form of crushers that produce at least some size reduction of the ore.

This group of the surface miners 11 moves continuously in defined paths of movement in accordance with the mining plan and the associated mobile flexible conveyors 13 and mobile feed systems 15 track the movement of the surface miners 11 to receive mined ore from the surface miners 11.

Another group of the surface miners 11 shown in the FIGURE transfers mined ore outwardly from the surface miners 11 as the miners 11 advance and forms a pile in the form of a windrow 21 (or a series of windrows—not shown) within the mine pit 3. The ore in the windrow is transferred via mobile feed systems 43 onto mobile flexible conveyors 13. The mobile feed systems 43 may be hoppers. Alternatively, or in addition, the mobile feed systems 43 may be in the form of crushers that produce at least some size reduction of the ore.

Whilst the windrow 21 is shown as a straight windrow, the present invention is not confined to this arrangement and the form of the windrow or pile may be determined as required given the topography of the mine.

The mobile flexible conveyors 13 make it possible to operate a mine without trucks as a main option for transporting mined ore from a mine pit 3. This is a benefit in terms of operating costs, particularly in large, deep mine pits where travel distances and time from mining areas to processing plant, such as crushers or a load-out station can be significant.

Moreover, the use of a combination of surface miners 11 and mobile flexible conveyors 13 and mobile feed systems 15 makes it possible to form a pit floor 5 that can accommodate movement of mobile flexible conveyors 13 and mobile feed systems 15 across the pit floor 5.

The ore is transported via the mobile flexible conveyors 13 across the pit floor 5 either (a) directly to a ladder conveyor 23 that is arranged to transport the ore from the mine 3 directly up the mine wall 7 or (b) to an internal trunk conveyor 27, i.e. a “shiftable” or “movable” conveyor that extends along the pit floor 5 adjacent the wall 7 and transports the ore to the ladder conveyor 23.

The trunk conveyor 27 may have a series of transfer stations 37 for receiving ore from the trucks and feeding ore onto the trunk conveyor 27.

The ladder conveyor 23 may be in a fixed location against the wall 7 or may be mounted for movement along the length of the wall 7. In the latter case, the trunk conveyor 27 is arranged to be shiftable or movable or otherwise able to be extended to accommodate the change in location of the ladder conveyor 23. In both cases, the ladder conveyor 23 may be extendable in length as the pit depth increases.

The ladder conveyor 23 transfers the ore via a transfer point 61 onto a conveyor assembly 29 that extends along the rim of the mine pit 3 and interconnects a series of pits and/or different sections of the same pit and transports the ore to a processing plant, such as a crusher, or to a load-out station.

The conveyor assembly 29 may be of a type that facilitates separation of ore into two process streams, with one stream, such as a high grade ore, being transported for processing in a crusher, and the other stream, such as waste ore, being transported to a stockpile for subsequent use as a fill material.

It is relevant to note that the arrangement shown in the FIGURE represents a section of a pit only and the mining method illustrated with reference to the FIGURE is repeated in other sections of the pit 3. It may also be the case that other mining methods are used in different sections of the pit 3. In any event, the mined ore is transported from the mine via ladder conveyors 23 and is delivered to the conveyor assembly 29.

The ladder conveyor 23 may be any suitable conveyor. By way of example, the ladder conveyor 23 may be of the type manufactured by International Conveying Systems International and described in Australian patent 767395 in the name of Michael Pietsch.

The mobile trunk conveyor 27 may be of any suitable type. By way of example, the mobile trunk conveyor may be the same design as the mobile flexible conveyors 13 such as manufactured by International Conveying Systems International and described in Australian patent 767395, but operated in a more static mode.

Many modifications may be made to the method of the present invention summarised in the FIGUREs and described above without departing from the spirit and scope of the present invention.

By way of example, whilst the FIGURE shows surface miners 11 transferring mined ore outwardly from the surface miners 11 as the miners 11 advance and forming a windrow 21 within the mine pit 3, the present invention is not so limited and the mined ore could be feed downwardly from the miners 11 and form windrows behind the miners 11.

By way of example, whilst the FIGURE shows one ladder conveyor 23, the present invention is not so limited and extends to arrangements in which there is a plurality of ladder conveyors in a pit.

By way of example, whilst the FIGURE shows a pit floor that has one level only, the present invention is not so limited and extends to mines in which the pit floor has a plurality of levels.

By way or example, whilst the FIGURE discloses the use of mobile excavation machines in the form of surface miners 11 that mine ore from the pit floor, the present invention is not so limited and extends to the use of mobile excavation machines that collect, i.e. excavate, broken or previously mined ore on the pit floor.

Claims

1-19. (canceled)

20. A method of mining ore in a mine pit that comprises the steps of:

(a) mining ore from a floor of a mine pit and/or collecting ore on the pit floor using at least one mobile excavation machine;

(b) transporting mined and/or collected ore within the mine pit on at least one mobile flexible conveyor; and

(c) transporting ore that has been transported along the flexible conveyor from within the pit to outside the pit on at least one ladder conveyor that extends up the wall of the pit.

21. The method defined in claim 20, comprising transferring ore that has been transported along the ladder conveyor onto at least one main conveyor and transporting the ore to a processing plant and/or a load-out station.

22. The method defined in claim 20 or claim 21, wherein the mobile excavation machine is a continuous surface miner.

23. The method defined in claim 22, wherein the continuous surface miner excavates ore to a depth in a range of 300-600 mm and at a rate of at least 900 tph and travel at a speed of at least 5 m/min (more typically at least 10 m/min).

24. The method defined in claim 20, wherein the mobile flexible conveyor (a) is sufficiently mobile to keep pace with an associated mobile excavation machine or other mobile machine while operating and transporting ore on the conveyor, (b) allows lateral, flexible movement while operating and transporting ore on the conveyor and, by way of example is capable of moving up or down steps of up to 400 mm in a pit floor, and (c) allows lengthwise extension and contraction while operating and transporting ore on the conveyor.

25. The method defined in claim 20, comprising transferring mined and/or collected ore directly from the mobile excavation machine to the mobile flexible conveyor.

26. The method defined in claim 20, comprising transferring mined and/or collected ore from the mobile excavation machine to a mobile feed system, such as a mobile hopper or a mobile crusher, and then transferring ore from the mobile feed system to the mobile flexible conveyor.

27. The method defined in claim 25 or claim 26, comprising continuously mining and/or collecting ore from the pit floor with the mobile excavation machine and moving (a) the mobile flexible conveyor or (b) the mobile feed system/mobile flexible conveyor assembly to track the movement of the mobile excavation machine, and continuously transferring mined and/or collected ore from the mobile excavation machine to the mobile flexible conveyor or the mobile feed system/mobile flexible conveyor assembly.

28. The method defined in claim 20, comprising transferring mined and/or collected ore from the mobile excavation machine to form a pile of ore on the pit floor.

29. The method defined in claim 28, comprising transferring ore away from the ore pile on the mobile flexible conveyor.

30. The method defined in claim 20, comprising transferring ore from the mobile flexible conveyor to at least one mobile trunk conveyor that extends along a section of the pit floor to the ladder conveyor.

31. The method defined in claim 30, comprising transferring ore from a plurality of mobile flexible conveyors to the at least one mobile trunk conveyor.

32. The method defined in claim 20, wherein the ladder conveyor is a single conveyor from the pit floor to the rim of the mine pit and extends up the pit wall without transfer points along the length of the conveyor, i.e. without the ore being off-loaded at an upper end of one section of the conveyor and loaded onto a lower end of a successive section of the conveyor.

33. A mine that comprises at least one pit having a pit floor and a pit wall that defines at least a part of the pit, at least one mobile excavation machine for mining ore from the pit floor and/or collecting ore on the pit floor, at least one mobile flexible conveyor for transporting mined and/or collected ore within the mine pit, and at least one ladder conveyor for transporting mined and/or collected ore from the pit.

34. The mine defined in claim 33, comprising a main conveyor outside the pit for transporting mined and/or collected ore from the pit to a processing plant or a load-out station.

35. The mine defined in claim 33 or claim 34, wherein the pit wall is at least 30°, in many instances at least 65° to the horizontal.

36. The mine defined in claim 35, wherein the pit wall is at least 20 m and typically at least 40 m high.

37. The method defined in claim 33, wherein the ladder conveyor is a single conveyor from the pit floor to the rim of the mine pit and extends up the pit wall without transfer points along the length of the conveyor, i.e. without the ore being off-loaded at an upper end of one section of the conveyor and loaded onto a lower end of a successive section of the conveyor.

38. The method defined in claim 33, comprising a plurality of pits and at least one main conveyor outside the pits for transporting mined and/or collected ore from the pits to a processing plant or a load-out station.