System for the reduction in applied energy, improved efficiencies and reduced costs in open pit mining

Abstract

The present invention relates to an open pit mining system. The system includes a material lifting machine configured to both: (1) excavate and remove overburden from an open pit of a mine; and (2) excavate and remove valuable material from the open pit. Advantageously, the machine removes the overburden waste material as well as the mined valuable material which would otherwise be conventionally removed by trucks in the pit, out of the pit up the ramps and then onto the processing plant. Accordingly, the use of trucks for transporting valuable material both along and up out of the pit is at least to some extent reduced thereby resulting in improved cost and energy efficiency.

Claims

1. An open pit mining system, the system including: a pre-stripped bench formed by pre-stripping waste adjacent a highwall; a material lifting machine configured to excavate and remove overburden from an open pit of a mine, the material lifting machine further configured to excavate and remove coal from the open pit; and one or more haulage bridges that bridge the open pit, the haulage bridges configured to support a truck loaded with the pre-stripped waste.

2. A mining system as claimed in claim 1, wherein the open pit has no coal haulage ramps.

3. A mining system as claimed in claim 1, wherein the material lifting machine includes a dragline, crawler, or walking crane configured to lift the overburden separately from the coal.

4. A mining system as claimed in claim 1, wherein the open pit is a strip mine pit with an overburden spoil pile formed adjacent the strip mine pit, the spoil pile formed by the material lifting machine and defining a plateau.

5. A mining system as claimed in claim 1, further including excavation and haulage equipment for pre-stripping the waste from the overburden.

6. A mining system as claimed in claim 1, further including a deposited stockpile of removed coal at about the elevation of the material lifting machine.

7. The mining system as claimed in claim 6, further including a haulage truck for hauling removed and deposited coal.

8. A mining system as claimed in claim 1, further including overburden drilling equipment to drill when preparing for blasting the overburden and/or pre-stripped waste.

9. A mining system as claimed in claim 1, further including a spoil reconditioning excavator or dozer for reconditioning land on a low wall side of the open pit.

10. An open pit mining method using one or more material lifting machines, the method including the steps of: pre-stripping waste adjacent a high wall to reveal overburden; the one or more lifting machines: excavating and removing the overburden from an open pit of a mine; and excavating and removing coal from the open pit; and hauling the waste with trucks over one or more overburden bridges crossing the open pit.

11. An open pit mining method as claimed in claim 10, wherein the one or more material lifting machines include a single lifting machine which removes the overburden and also removes the coal.

12. An open pit mining method as claimed in claim 10, wherein the one or more material lifting machines include a first lifting machine removes the overburden whereas a second lifting machine removes the coal.

13. An open pit mining method as claimed in claim 10, not involving forming haulage access ramps to the open pit.

14. An open pit mining method as claimed in claim 10, wherein the open pit is a strip mine pit and the method involves forming an overburden spoil pile adjacent the strip mine pit, the spoil pile formed by the material lifting machine and defining a plateau.

15. An open pit mining method as claimed in claim 10, involving depositing the removed coal at the elevation of the one or more material lifting machines.

16. An open pit mining method as claimed in claim 10, involving hauling away deposited coal in hauling trucks.

17. An open pit mining method as claimed in claim 10, further involving creating a series of the bridges over the open pit.

18. An open pit mining method as claimed in claim 10, wherein the method further involves blasting the overburden adjacent the open pit either during or prior to completion of steps of removing the overburden from the open pit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

(2) FIG. 1 is a schematic perspective diagram showing a known open pit coal mining system;

(3) FIG. 1A is a schematic perspective diagram of the mining system of FIG. 1, showing the low wall spoil;

(4) FIG. 1B is an end sectional view of the mining system of FIG. 1A;

(5) FIG. 1C is a front sectional view of the mining system of FIG. 1A;

(6) FIG. 2 is a schematic perspective diagram showing an open pit coal mining system in accordance with an embodiment of the present invention;

(7) FIG. 2A is a schematic perspective diagram of the mining system of FIG. 2, showing the low wall spoil;

(8) FIG. 2B is an end sectional view of the mining system of FIG. 2A;

(9) FIG. 2C is a front sectional view of the mining system of FIG. 2A;

(10) FIGS. 3A, 3B, and 3C show the sequence of a single dragline working a 30 meter wide strip mine pit of the system of FIG. 2; and

(11) FIGS. 4A and 4B show a dual dragline system for working a 30 meter wide strip mine pit of the system of FIG. 2, and bucket line arrangements to avoid interference with the edge of the high wall.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(12) According to an embodiment of the present invention, there is provided an open pit strip mining system 200 as shown in FIG. 2. The system 200 includes a dragline 202 (i.e. material removing machine) which is otherwise both an excavating tool and a primary lifting tool, configured to remove overburden 102 from an open pit 108 of a mine. The dragline 202 may also remove coal 110 (i.e. valuable material) from the open pit 108.

(13) Advantageously, the dragline 202 removes not only the waste overburden 102, but also mined coal 110 which would otherwise be conventionally removed by excavator and trucks 118 located in the open pit 108. Accordingly, the use of trucks 118 for transporting coal 110 both along and up out of the pit 108 is avoided thereby resulting in improved mining efficiency.

(14) Additionally (or as an alternative to the dragline 202), the mined coal 110 may also be removed from the pit 108 by a primary lifting machine unrelated to the dragline 202, such as a crawling or walking crane, which may be modified in order to operate in the mode required to perform this function. Alternatively, there may also be a 2.sup.nd dragline employed to remove the coal from the open pit, which may or may not also be specially configured to perform this function. Accordingly, the use of trucks 118 for transporting coal 110 both along and up out of the pit 108 is avoided thereby resulting in improved mining efficiency.

(15) The pit 108 has no haulage access ramps 120. Advantageously, the need to create and later fill access ramps 120 is avoided thereby further increasing mining efficiency. Also, there is no need to provide an excavator 114 in the pit, and there is no need for associated equipment which would otherwise be required to build and maintain haul roads in pit for the trucks and service equipment to use, which further increases mining efficiency.

(16) The system 200 further includes a surface excavator 204 and surface waste haulage trucks 206 for pre-stripping high wall surface waste 208 to uncover the overburden 102. Haulage bridges 209 are provided at intervals to optimize the mass haul distance of the pre-stripped waste material along the whole length of the strip mine to enable the off-highway waste haulage trucks 206 to cross the pit 108 when hauling pre-stripped waste 208.

(17) The system 200 further includes a coal stockpile 210, deposited by and adjacent to the dragline 202 on a substantially level overburden platform 212 supporting the dragline 202. Another coal stockpile 211 may alternatively or also be deposited on the pre-stripped bench area adjacent to the dragline 202, or another coal stockpile 213 deposited on the highwall area 222 adjacent to the dragline 202 in the case where no pre-stripping operations are in existence. A loader 214 loads the stockpiles 210, 211, 213 onto comparatively highly efficient coal haulage trucks 216 from the platform/s. The coal haulage trucks 216 may be of a multi-trailer configuration with high capacity and capable of comparatively high speeds, thereby more rapidly hauling the deposited coal stockpiles 210, 211, 213 away to the processing plant some distance away from the open pit, thereby increasing the mining efficiency.

(18) The system may further include an alternative method of transporting the coal stockpiles 210, 211, 213 to the processing plant some distance away. This may be by means of loading the coal onto a conveying system or into wagons of a local mine rail system, which transports the coal at a much higher level of efficiency to the processing plant some distance away from the open pit, thereby increasing the mining efficiency.

(19) The system 200 further includes an overburden drill 218 for drilling when setting explosives for blasting the overburden 102. A spoil reconditioning dozer 220 works on the low wall spoil piles of the pit 108 to recondition the mining landform to a suitable landform according to the requirements set for the post mining requirements of the mine. The spoil reconditioning dozer 220 is not required to push as much material around the low wall spoils since there are no ramps required to be filled, thereby increasing the mining efficiency.

(20) An open pit mining method using the system 200 is now briefly described.

(21) The mining method involves pre-stripping the surface waste 208 (which may also have had to be drilled and blasted) with the excavator 204 to uncover the remaining overburden 102. The pre-stripped waste is hauled over the bridges 209 in trucks 206 crossing the pit 108 thus reducing haulage distance when compared with going around the pit 108. A series of the bridges 209 are created at intervals and the locations of the bridges 209 are entirely unaffected by pit ramps 120 which are not provided.

(22) The mining method further involves drilling with the drill 218 when setting explosives for blasting the overburden 102 along a strip. The dragline 202 rests on the level platform 212 of blasted overburden 102. The dragline 202 lifts and removes overburden 102 from the highwall 106 of the open pit 108. The dragline 202 further removes the coal 110 in the pit 108 which is exposed when the overburden 102 is removed. Additionally (or as an alternative to the dragline 202), the mined coal 110 may also be removed from the pit 108 by a primary lifting machine unrelated to the dragline 202, such as a crawling or walking crane or a second dragline, each of which may be modified in order to operate in the mode required to perform this function.

(23) There may be no equipment or personnel in the pit 108 when the dragline 202 removes the overburden 102 and coal 110. This enables, amongst other things, further blasting adjacent the pit 108 on the high wall 222 side either during or prior to completion of overburden 102 and coal 110 removal. Advantageously, this adjacent high wall side blasting can occur whist material is still being removed from the mine which results in significant mining efficiency gains.

(24) Alternatively there may be the requirement for a dozer to operate in the base 116 of the open pit 108 adjacent the dragline 202 whilst it is undertaking coal removal activities, or adjacent to the other primary lifting machine in the case where a machine other than the overburden waste dragline removes the valuable material. Such dozer may be required in order to ensure that there is a clean separation of valuable material 110 from overburden waste material 102, and so that the remnants of valuable material 110 in the open pit 108 are adequately cleaned up for maximum extraction of the valuable material 110 (ie. a function commonly termed minimizing coal loss in conventional coal mining operations). The dozer may also be involved in the ripping and winning of the coal, and stockpiling the coal for loading at the base of the open pit. In such cases the dozer would access the base 116 of the pit 108 using a temporary steep low wall spoil ramp (not shown) that would be developed by the dragline and the dozer in combination. Such a low wall spoil ramp would be very steep when compared with conventional truck ramps 120, sufficient necessarily to only cater for the dozer to enter and exit the base of the pit 108 for the purpose of clean-up operations. In such cases the temporary steep low wall ramp would be filled in and redeveloped as the mining advances in the ordinary sequence of the overburden removal operations, resulting in no loss of efficiencies.

(25) The operations may require that water that may have accumulated in the base 116 of the pit 108 needs to be removed ie. pumped out of the pit 108. Such operations may be facilitated by pumping such water over the highwall 106 & 222 using specialized highwall water pumping devices with associated pipelines to cater for the water removal, which may not involve personnel having to access the base 116 of the open pit 108. Alternatively the water may be removed by locating a water pumping device in the base of the open pit 108, which may involve personnel having to access the base 116 of the open pit 108.

(26) The operations may further require that specialized maintenance or operational personnel may need to access the base 116 of the pit 108, in the event of machine breakdown, inspection of the valuable material and the mine workings, or associated with the water pumping devices or pipelines etc. In such instances, these personnel would be lifted and carried into and out of the pit 108 by the use of a personnel basket (with appropriate safety procedures) operating from a crane positioned on the highwall 106 & 222 side of the pit 108. If consumable materials were required to be delivered into the base 116 of the open pit 108 in order to continue with the operations (ie. such as fuel to operate the water pumping devices) these may be lifted and carried into and out of the pit 108 by a crane positioned on the highwall 222 side of the pit 108.

(27) The method does not involve forming conventional haulage access ramps 120 to the pit 108 and the lower overall mine profile is shown in FIGS. 2A to 2C, when compared with analogous FIGS. 1A to 1C of the prior art. FIGS. 2A and 2C clearly show the absence ramps with a 30 meter wide strip mine pit 108. The overall dimensions of the exampled worked mining system 100 are once again 3,000 meter length and 1,200 meter width for the sake of comparison. As can best be seen in FIG. 2B, the low wall spoil 112 includes a generally flat pre-strip volume 222 piled low upon a dragline volume 224. The spoil pile 112 adjacent the mine pit 108 defines a substantially level plateau which spans most (>half) of the length of the pit 108 (see FIG. 2C) and most of the width of the mine (see FIG. 2B). After mining ceases, the spoil reconditioning dozer 220 is not required to push as much material around the flat wall spoil 112, thereby greatly increasing the mining efficiency.

(28) Advantageously, the need to create and later fill access ramps 120 is avoided thereby further increasing mining efficiency. The method also does not involve providing an excavator 114 located in the pit 108 to further increase efficiency.

(29) FIGS. 3A-3C show the sequence of a single dragline 202 working the 30 meter wide strip mine pit 108 of FIG. 2. The dragline 202 can be the same or smaller than conventional draglines used on 60 meter wide pits. FIG. 3a shows the dragline 202 configured to remove overburden from the base 116 of the open pit 108. FIG. 3b shows the dragline 202 adding the removed overburden to the adjacent low wall spoil 112, and exposes the coal 110 for separate excavation. Advantageously, as shown in FIG. 3c, the dragline 202 then removes the exposed coal seam 110 and efficiently deposits it in a stockpile 211 on the pre-stripped bench area adjacent to the dragline 202, or another coal stockpile 213 deposited on the highwall area 222 adjacent to the dragline 202 in the case where no pre-stripping operations are in existence. The dragline 202 repeats this process and moves rearwards to extend the strip mine pit 108.

(30) The working of a 30 meter strip mine pit 108 is highly efficient, when compared with known 60+ meter strip mine pits 108 requiring larger equipment (draglines, >200 t excavators, >100 tonne rear dump and belly dump trucks). The following benefits apply for strip widths of less than 40 meters (no coal haulage ramps to pit floor) when compared with conventional 50-80 meter strip width (with coal haulage ramps 120 to pit floor 116):

(31) i. Additional cast blast volume as percentage of total overburden waste volume, lowering overall mining cost and resulting in increased total prime waste removal rate, and consequent faster coal uncovery rate.

(32) ii. The opportunity for improved waste fragmentation due to higher intensity blasting (with an increased powder factor in kg/cubic meter), resulting in faster dragline bucket fill times and consequent improved dragline productivity.

(33) iii. Reduced dragline spoil height (compare FIG. 2B with FIG. 1B) due to tighter spoil peaks, resulting in reduced hoist time, improved dragline excavation productivity and/or a higher dragline operating level within the pit 108. This also allows prestrip volumes to be reduced with significant cost savings.
iv. Reduced dragline waste rehandle percentage by carefully matching site geology (depth, seam dip etc) to dragline operating parameters and strip geometry, resulting in increased total prime waste removal rate, and consequent faster coal uncovery rate.
v. Reduced dragline average bucket swing angles and average hoist distances in conjunction with reduced dragline positioning time on bench by carefully matching site geology (depth, seam dip etc) to preferred dragline operating parameters and strip geometry, resulting in increased dragline productivity and increased total prime waste removal rate, and consequent faster coal uncovery rate.
vi. Reduced amounts of inventory of waste removal activities in advance of the current mining area in pit (relating to drilling, blasting, prestripping, and dragline volumes) that are considered as work-in-progress to deliver each tonne of mined coal, resulting in lower cash outlays and improved financial returns.
vii. Shorter cross-pit prestrip bridges 209 which result in reduced volumes to be managed by the dragline 202 in order to develop and manage the cross-pit bridges 209. This also allows for higher elevations of the cross-pit bridges so that prestrip truck haul costs can be improved/optimised.
viii. The reduced dragline spoil height also results in a reduced height for the hauling and dumping of the prestrip waste material to its final position, which results in further significant cost savings.
ix. Improved dragline safety management, as blast profiles can be essentially flat allowing the dragline 202 to work anywhere on that surface level. The operating bench will be buttressed against the highwall 222 and no unsupported elevated low-wall benches are required.

(34) FIGS. 4A-B show a dual dragline system with minimal radial movement and for working a 30 meter wide strip mine pit 108 of the system of FIG. 2. An overburden (i.e. first) dragline 202a, resting on an in pit bench or shelf and at the end of the mine pit 108, removes overburden from the base 116 of the open pit 108 and adds the removed overburden to the adjacent low wall spoil 112 formed on the shelf. Simultaneously, a coal (i.e. second) dragline 202b, operating at the side of the pit 108, removes the exposed coal seam 110, and places it on the pre-stripped bench area or highwall area 222 upon which the dragline 202b itself rests. The coal dragline 202b need not be as large as the overburden dragline 202a and has a reduced working reach area 400.

(35) The coal dragline 202b can include a modified rigging and dumping arrangement, to reduce line interference with the highwall pit edge, when compared with a conventional dragline. Turning to FIG. 4A, the dragline 202b can have a pulley mechanism 401 located some distance along the boom 404 from the base of the fairleads 402 which provides enough clearance so that the bucket control line 408 does not interfere with the edge of the high wall 222. Alternatively, the bucket control line 408 can extend downward from the end of the boom to control the bucket 406 as shown in FIG. 4B, thereby also avoiding the dragging of the line 408 on the high wall 222 when the coal 110 is being mined or hoisted from the pit 108 in the bucket 408.

(36) A person skilled in the art will appreciate that many embodiments and variations can be made without departing from the ambit of the present invention.

(37) In one embodiment, dragline 202 can be replaced with a crawler, walking crane or any other like primary lifting type machine/device. Such machines may also be specially configured in order to perform this function.

(38) In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.

(39) Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.