OA17761A - Method to explore open pit iron ore mines. - Google Patents

Abstract

A truckless mining method for open pit iron ore mines is described, which uses an organized production line, which does not use trucks for the transportation of the ore from the mining front. This method presents a lower operating cost when compared to the traditional mining methods that use trucks.

Description

METHOD TO EXPLORE OPEN PIT IRON ORE MINES

Field ofthe Invention [001] A truckless open pit iron ore mining method is described. This method is different from the traditional mining methods because it employs conveyor belts, instead of trucks, to transport the iron ore from the mining fronts.

Background ofthe Invention [002] The method traditionally used to exploit the ore in open pit iron ore mines is as follows: initially, planning ofthe mining program is performed, during which the areas to be explored and the best configuration of excavation are defined according to the topography of the area to be explored. During this step the locations where the ramps, roads and accesses are to be built are also defined. These ramps, roads and accesses, in the future, will enable the access ofthe equipment to the interior ofthe mine.

[003] The first stage of operation ofthe mine is the drilling and dismantling process which consists in the blasting of a rock mass with the use of explosives.

[004] After dismantling ofthe mass, the ore is carried by means of bulldozers to large sized dump trucks. The ore is then transported by these trucks to the ore processing plant.

[005] Each one of these trucks is capable of transporting a limited amount of material (according to its own capacity). Furthermore, the environmental impact caused by these trucks, resulting from the high consumption of diesel and tires, also constitutes a big problem of the state of the art.

[006] To eliminate the use of trucks in open pit iron ore mines, certain pioneer techniques were implemented, consisting in the substitution of these trucks for mobile crushing Systems, using relocatable and other peripheral equipment.

[007] One of the referred techniques is revealed in document US20110175429, which présents a method for the exploration of open pit mines , which includes the following sequential exploration stages:

Stage 1 - blasting of a rock bank;

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Stage 2 - collection of the dismantled material;

Stage 3 - transportation ofthe collected material to a rock crusher;

Stage 4 - transportation of the fine particulate out of the mine by means of a conveyor belt.

[008] Despite innovating in the techniques used up to now to transport iron ore, the previous technique revealed in US20110175429 is incomplète and incipient since, when we substitute the machinery currently used in iron ore mines for mobile conveyor belts and rock crushers as established in the document US20110175429, we continue to face a sériés of bottlenecks in the production line that impair the processing of large volumes of iron ore, resulting in production interruptions.

[009] Therefore, it is necessary to develop a new method to explore open pit mines: one that employs conveyor belts in place of dump trucks for the removal of the material from the mine and is efficient and free from bottlenecks in the production process.

Objectives ofthe Invention [010] This invention has as its objective a method of mining iron ore in open pit mines that uses conveyor belts instead of trucks to transport the ore.

[011] This invention also has as its objective a method of mining iron ore in open pit mines that considerably increases the productivity of iron ore and présents a lower operational cost compared to the existing methods.

Brief Description ofthe Figures

This invention is described in greater detail based on the respective figures:

Figure 1 - reveals a view in an upper perspective of the map of an iron ore mine, explored using the technologies presented in this invention.

Figure 2 - consists of an operational flowchart of one of the preferred configurations of this invention.

Figure 3 - reveals a schematic drawing ofthe collection of soft material using an electric cable bulldozer and a mobile primary rock crusher.

Figure 4- reveals a schematic drawing ofthe collection of soft material using an electric cable bulldozer, a mobile primary rock crusher and a Mobile Belt Wagon.

Figure 5 - reveals a schematic drawing of the collection of hard material, using portable modular conveyors, hydraulic bulldozers and mobile primary rock crushers equipped with jaws.

Figure 6 - reveals a schematic drawing ofthe collection of hard material, using portable modular conveyors, hydraulic bulldozers and mobile primary rock crushers equipped with jaws and Mobile Belt Wagons.

Detailed Description ofthe Invention [012] The invention consists in the application of a truckless mining method in open pit iron ore mines. This method présents as its main innovation the substitution of transportation traditionally performed by trucks, for transportation performed by conveyor belts 3, 4, 5, 13, 13', 15, 16, 22, 23. Furthermore, the configuration of the operation at the mining fronts 30 is inedited in open pit iron ore mines.

[013] In summary, the truckless mining method is characterized by the use of an organized production line, which includes the following pièces of equipment arranged in sequence, the first of them being placed in contact with the benches 20 of a mine and the last being placed in direct contact with an ore processing plant: mining front equipment 30, bench conveyors 3, bench connection conveyors 4, connection conveyors 5, transfer station 6, buffer pile 12, and TCLD (Long Distance Conveyor Belt) 14; the bench conveyors 3 and the bench connection conveyors 4 are relocatable; the connection conveyors 5 are fixed; conveyors 3,4, 5 can be extended; the transfer station 6 is designed to separate the stérile material from the iron ore collected from the mining front 30 and to act as interface between the connection conveyors and the TCLD 14; and the TCLD 14 is designed to transport the separated iron ore from the transfer station 6 to an iron ore processing plant.

[014] The main advantage resulting from the use of this invention is a réduction in operating costs (dollar per ton of ore) when compared to the other operations that use trucks to transport the iron ore. It should be pointed out that the réduction in operating costs is not due exclusively to the substitution of trucks for integrated conveyor belts, but also a sériés offactors related to the arrangement ofthe conveyors S and other equipment of the mining front.

[015] In the preferred configuration of the invention, the basic mining sequence starts off with the drilling and dismantling of 100% of the material to be excavated. In this preferred configuration, the benches 20 reveal the following dimensions: 15 m high and 70 m wide. The excavation is performed by a bulldozer 1 that directly feeds a 10 mobile rock crusher 2, which in turn reduces the size ofthe excavated material so as to enable its transportation. The rock crusher 2 is designed so as to accompany the bulldozer 1 as it progresses along the mining front. This piece of equipment unloads the material coming from the primary crushing onto a belt wagon 17, 18, when necessary, which is used to transport ore or stérile material from the rock crusher 2 to 15 the bench conveyor 3. We point out that the stérile material is the part of the ore that cannot be used in the production process.

[016] The bench conveyors 3 transport the material from the mining fronts 30 to the bench connection conveyors 4, which, in turn, direct this material to the connection conveyors 5, which take it to the Transfer Station 6. This station is responsible for 20 directing the ore and stérile material to their respective destinations (see Figures 1 and

2).

[017] The ore is deposited in the buffer pile 12, by means of an ore transfer conveyor

13. After passing through the buffer pile 12, the ore is transported by a second ore transfer conveyor 13', which directs this material to the Long Distance Conveyor Belt 25 (TCLD) 14, which subsequently transports it to the Processing Plant.

[018] The stérile material is deposited in two distinct piles, one for structural ferricrete 9 and the other for frank stérile material 10, each being fed by an Overland conveyor 15, 16, leaving from the Transfer Station. The déposition ofthe material in the piles is performed using a Mobile Tripper Spreader (MTS) 19. With this equipment it is possible to create radial piles of ferricrete 9 and stérile material 10 and thus optimize the space occupied by the déposition of this material.

[019] Going back to the définition of the equipment that constitutes the mining front 30, these equipment components are divided into a system for working with soft material and a system for working with hard material. The term soft material refers to the following lithologies: friable hématite, manganèse ferrous hématite, structural ferricrete, chemical ferricrete, decomposed mafic rock, among other rocks that reveal a similar degree of hardness. The term hard material, on the other hand, refers to the following lithologies: compact hématite, jaspillite and mafic rock, among other rocks that reveal a similar degree of hardness.

[020] The system used to mine the soft material is used for the primary production of high grade ore and soft residual material.

[021] In the preferred configuration ofthe invention, the soft material mining system (as revealed in Figures 3 and 4) is made up ofthe following components: electric cable Bulldozer 1, Mobile Sizing Rig (MSR) 2, Mobile Belt Wagon (MBW) 17.

[022] In this system, the electric cable Bulldozer 1 unloads the material directly into the MSR 2, characterized by being a double roller rock crusher, and this material is then crushed until it reaches a granulometry that is adéquate for transportation. After being crushed, the ore is transferred to the MBW 17 or directly to the bench conveyors 3. The MBW 17 can be used when mining is performed on the same level ofthe bench conveyor3 and mainly when mining is performed on a bench 20 located above or below the bench conveyor3. The MBW 17 can be used in the operation of the soft material system as well as in the operation ofthe hard material system.

[023] The electric cable Bulldozer 1 was selected for work in soft material system due to the fact that this equipment présents greater productivity among ail the bulldozers currently available in the market. At the moment, there are no hydraulic bulldozers in the market capable of reaching the same productivity. If conventional hydraulic

I bulldozers were used, instead of 1 electric cable Bulldozer, it would be necessary to use a larger number of de bulldozers and to increase the number of work fronts.

[024] The hard material mining Systems are used in the mine in place of the soft material System when hard or high density material is encountered. The hard material S mining Systems can be easily moved to the locations where they are required and présent a lower production capacity than the soft material mining system [025] The hard material system (such as shown in Figures 5 and 6) consists of the following equipment components: hydraulic Bulldozer 1', jaw-type Mobile Rock Crusher (MCR) 2', regular Portable Modular Conveyor (PMC-A) 18, spécial Portable

Modular Conveyor (PMC-AA) 21 and Mobile Belt Wagon (MBW) 17.

[026] The mining operation is planned using hydraulic Bulldozers Γ, similar to a Komatsu PC 5500, to feed the mobile jaw-type rock crushers (MCR) 2'. The MCR 2' is connected to the bench conveyor 3 using, at least, one PMC-A 18 and can be extended with the insertion of an additional PMC-A 18. The connection ofthe PMC-A 18 with the bench conveyor 3 is performed by means of a PMC-AA 21 that has two entrances. The MBW 17 and PMC-A 18 connection system allows for flexibility in mining in different locations and configurations, as well as for mining fronts located above or below the level ofthe conveyor.

[027] This system, on the other hand, opérâtes using two units at each mining front

30. Each hydraulic Bulldozer 1' feeds one MCR 2'. The MCR 2' reduces the size of the excavated material and unloads it onto portable modular conveyors 18 and/or subsequently onto a MBW 17 (in certain cases the MBW 17 is not required, in other words, the PMC-As 18 unload directly onto the bench conveyors 3, see Figure 5). This system also includes a hydraulic breakerto break large boulders (large agglomérations of material) installed on top ofthe MCR 2'.

[028] Observe that, in order to balance the production flow of the hard and soft material mining fronts 30, the mining front 30 that opérâtes with the hard material system is equipped with two parallel operating Unes instead of just one line. This is because the equipment designed to operate with hard material is naturally less productive than the machinery builtto operate with soft material.

[029] In relation to conveyor belts 3, 4, 5 located both inside the mine and also close to it, three types of equipment can be seen: bench conveyor3, bench connection 5 conveyor 4 and connection conveyor 5.

[030] The bench conveyors 3 and the bench connection conveyors 4 are of the relocatable type. The connection conveyors 5, on the other hand, are fixed.

[031] When it is necessary to relocate the bench conveyors 3 and the bench connection conveyors 4, devices called Crawlers and tracked tractors are used.

Crawlers are motorized machines, mounted on tracks, designed to transport large and heavy structures ( document EP0252465 reveals an example of a Crawler compatible with the method of this invention). The tracked tractors used to move the conveyors are equipped with spécial heads designed to provide an interface between the conveyor rail structure and the tractor.

[032] There are basically three types of possible displacements of the bench conveyors 3 and bench connection conveyors 4: trackshifting, horizontal repositioning and conveyor extension

Trackshifting [033] The bench conveyor 3 must be repositioned as the mining front advances. This type of displacement generally occurs on the horizontal level, but it is also possible on inclinations of up to 10%. As these displacements occur regularly, it would not be practical to disassemble the conveyor 3 prior to its displacement. This technique is therefore used to laterally displace the bench conveyor 3.

[034] Tracked tractors equipped with a spécial device connected to the rail travel alongside the bench conveyor 3 resulting in a slight parallel movement. This technique displaces the rail (and the bench conveyor 3), laterally towards the tractor, approximately 500 a 600 mm. The tractors repeat this procedure until the bench

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conveyor 3 is displaced to the desired location.

[035] A trackshift can occur in parallel or in a pivoting operation. In the pivoting operation, one end of the conveyor remains fixed and the more distant end is displaced the greater distance. This operation occurs with the conveyors ofthe stérile material/ferricrete pile 22, 23. The trackshift in parallel operation involves the uniform latéral displacement of the entire conveyor 22, 23. The conveyor head units are displaced using the crawler. The end modules ofthe conveyors 22, 23 are repositioned using tracked tractors.

Horizontal repositioning [036] Horizontal repositioning operations involve the complété disassembly and transport ofthe bench conveyor 3 to a different horizontal level ofthe mine.

[037] This operation involves the disassembly, transportation to a new location and subséquent re-assembly of ail the conveyor components. This task requires a large number of support vehicles including closed trucks and the crawler.

Conveyor extensions [038] Ali the conveyors that exist in the system can be extended. The extension of the conveyors inside the mine 3, 4 is periodically required, as the mining operations advance. The extension of the conveyors involves the installation of intermediate conveyor modules and additional belts to extend the conveyor. The additional modules are placed before interrupting the operation ofthe conveyor, thus optimizing downtime. The extension includes cutting of the belt, repositioning of the tail end, installation of additional modules in the opening left by the tail end and, lastly, installation and splicing ofthe new belt.

[039] The connection conveyors 5 feed the transfer station 6, which remains fixed during the entire useful life of the mine. The ore recently separated from the stérile material follows from the transfer station to the buffer pile 12, whose function is to store iron ore in a quantity that is sufficient to guarantee a continuous flow of material to the Long Distance Conveyor Belt (TCLD) 14 for a spécifiée! period of time. This way, even if the transfer station 6 is shut down for a few moments - for maintenance or emergency reasons, for example - the buffer pile 12 guarantees at least one hour of supply of material to the TCLD 14.

[040] The work régime adopted by the mine allows the TCLD 14 to operate 24 hours a Day, 365b days a year, without any interruptions. Furthermore, even if there is the need to reposition conveyors 3, 4, 5,13,13', 15,16, 22, 23 or in the case of emergency situations or maintenance services, the method described in this report is designed so as to overcome ali these problems, allowing for the continuous distribution of material 10 to the ore Processing Plant.

[041] Having described a few main examples of embodiment of the invention, it should be pointed out that the scope of protection conferred by this document includes ail other reasonable alternative forms of embodiment of the invention, which is hereby defined and limited only by the attached list of claims.

Claims (6)

1. Method for the exploration of open pit iron ore mines , characterized by the use of an organized production line, which includes the following pièces of equipment arranged in sequence, the first of them being placed in contact with the benches 20 of

5 a mine and the last being placed in direct contact with an ore processing plant: mining front equipment (30), bench conveyors (3), bench connection conveyors (4), connection conveyors(5), transfer station (6), buffer pile (12), and TCLD (14); the bench conveyors and bench connection conveyors (3,4) are relocatable; the connection conveyors (5) are fixed; the three conveyors (3, 4, 5) can be extended; the transfer station (6) is designed to 10 separate the stérile material from the iron ore collected from the mining front (30) and to act as interface between the connection conveyors and the TCLD (14); and the TCLD (14) is designed to transport the separated iron ore from the transfer station 6 to an iron ore processing plant.

2. Method for the exploration of open pit iron ore mines, according to claim 1, 15 characterized by the fact that the buffer pile (12) has the capacity to feed the TCLD (14) for, at least, one continuous hour, even if the buffer pile does not receive any new material from the transfer station (6).

3. Method for the exploration of open pit iron ore mines , according to claim 1, characterized by the fact that it consists of two types of mining fronts (30), the first type of

20 mining front (30) adapted for operation with soft material and the second mining front (30) adapted for operation with hard material.

4. Method for the exploration of open pit iron ore mines , according to claim 3, characterized by the fact that the first type of mining front (30), adapted for operation with soft material, includes: an electric cable bulldozer (1), that unloads the material

25 directly into a double roller rock crusher denominated Mobile Sizing Rig (2), and subsequently the material is transferred directly to the bench conveyors (3) or to the Mobile Belt Wagon (17), designed to enable communication between the bench conveyor(3) and the bulldozer (1) positioned at a higher or lower level.

5. Method for the exploration of open pit iron ore mines , according to claim 3, characterized by the fact that the second type mining front (30), adapted for operation with hard material, includes: two hydraulic bulldozers (1'), two jaw type mobile rock crushers (2'), at least, two regular portable modular conveyors (18), one spécial modular

5 conveyor (21) and one Mobile Belt Wagon (17); each bulldozer (1') communicates with a single jaw type mobile rock crusher (2'), which, in turn, communicates with a single regular portable modular conveyor (18) which can be extended with the insertion of an additional regular portable modular conveyor (18); each regular portable modular conveyor (18) communicates with a spécial modular conveyor (21), which consists of two entrances and 10 which, on the side opposite to the two entrances, communicates directly with the bench conveyor (3) or with a Mobile Belt Wagon (17) which also communicates with the bench conveyor(3).

6. Method for the exploration of open pit iron ore mines , according to claim 1, characterized by the fact that the stérile material separated at the transfer station (6) is

15 deposited in two distinct piles, one pile for structural ferricrete (9) and one pile for stérile material (10), each being fed by a Mobile Tripper Spreader (19) which créâtes radial piles; each Mobile Tripper Spreader (19) being fed by an Overland conveyor (15) and (16), coming from the Transfer Station (6).