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Reviewofthein-pitcrushingandconveying(IPCC)systemanditscasestudyincopperindustryCONFERENCEPAPEROCTOBER2011

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Review of the in-pit crushing and conveying (IPCC) system and its case study in copper industry

Mohammad Reza Tavakoli Mohammadi1, Seyed Ahmad Hashemi2, Seyed Farhad Moosakazemi3

Abstract The material transport system in an open pit mine significantly affects the capital and operating costs. All truck haulage is the most common and is a reliable and flexible transport system. On the other hand, this system is very expensive and can cost up to 50% of total mining costs. Its costs are continuously increasing due to the inflation of the fuel, tire and labour expenditures. In-pit crushing and conveying (IPCC) is an alternative transport system which requires a higher initial investment but gives substantial saving in operating cost. IPCC is the superior technology for large open pit mines with high outputs. The main purpose of this review is to describe and compare IPCC system types. Afterward, their advantage, disadvantage and reasons for applying have been demonstrated. Finally, their case studies in copper industry have been accomplished.

Key words: Crushing; Conveying; IPCC; Copper.

1 PhD student of mineral processing, Tarbiat Modares University

2 MSc of mineral processing, process manager of Kani Faravar (Middle East Mineral Processing Eng. Co.)

3 BSc student of mining engineering, Sharood University of Technology

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1. Introduction Currently the mining industry is increasing its focus on operational excellence and safety performance toward zero-harm levels. Factors driving this increased focus include the need to obtain greater efficiencies not only to address the rising capital costs for mining assets such as equipment, fuel, tyres, and manpower, but their overall operation as well, and in-pit crushing and conveying is an important part of this [1].

In 1956, the first mobile crusher was installed in a limestone quarry in Hover, West Germany. The crusher enabled the quarry operator to take advantage of continuous belt conveyor haulage and eliminated a problem of high-cost road construction and maintenance in wet soft ground, with resultant cost savings. Since that time, the number of mobile in-pit crushing and conveying operations has increased to over 1000 [2].

2. Definition of in-pit crushing and conveying (IPCC) system A continuous processing system that includes the shovel, crusher, spreader and all appropriate conveyors that reduces rock of mine (ROM) to a conveyable size. In fact, IPCC is the use of fully mobile, semi-mobile or fixed in-pit crushers coupled with conveyors and spreaders (for waste) or stackers (for ore) to remove material from an open-pit mine. Following figures make a good view of In-Pit crushing system [3,4].

Fig 1: Different parts of IPCC system [3].

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Fig 2: Crushing arrngement of IPCC system [5].

3. In-pit crushing system In-pit crushing and conveying is an alternative system for transport in open pit mines. Depending on individual parameters, it can achieve full or partial replacement of trucks for material transport within and out of a mine. If a mine provides two conveyors, both ore and waste are conveyed out of the pit. By this way, the truk transport on long uphill distance is eliminated. When the mine supplies only one conveyor, it conveys ore and waste on different shifts, or all the waste is transported by trucks to the surface.

The in-pit crusher is moved down every one or two years, to keep the truck haulage to a minimum. The relocation takes 2-3 days. For short moving times the processing plant can be fed from a stockpile. In longer stoppages, usually in European operations, the move coincides with a general mine holiday period.

The crusher is located next to an embankment, so that truks are able to dump the material directly from the embankment into the hopper/feeder above the crusher. Under an alternative arrangment, the crusher is located closer to the centre and has a separate feeder with the feeder tail-end located in the recess in the pit floor. The trucks dump the material from the pit floor into the hopper on the feeder. Belt conveyors can be one of the most efficient means of transporting material out of the pit [4].

3-1. Types of in-pit crushing systems Fixed or semi-fixed systems Fixed systems are typically ex-pit and are designed to reduce haulage distance to the waste dump.

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Semi-fixed systems may be in-pit but fixed within a pit stage [6]. These are mounted on a steel platform, which reduces the need for a concrete foundation. Any planned relocation would not be for less than 10 years [2].

Fig 3: Fixed In-Pit system [3].

Semi-mobile systems This unit works close to the mine face but is moved less frequently than a mobile crusher. The transport mechanism may be a permanent part of the crusher frame [2]. Semi-mobille systems are suited to harder rocks and higher capacities (up to 10000tph) [6]. In this method, trucks are used to transport material from the mine face to the in-pit crusher, often moving between levels. As mining advances, the hauling distance to the crusher increase, eventually requiring the crusher and conveyors to be relocated [7].

Fig 4: Semi-mobile system [6].

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Fully mobile systems Fully mobile systems are based on sizers and limited to softer rocks and the shovel capacity ( 5000 tph) [6]. These type of crushers work at the mine face, are directly fed by an excavator, and move in unison with the excavator on them own transport mechanism as mining progresses [2]. High-angle conveyors can be used to avoid overly long mine conveyors to transport material from the pit [7].

Fig 5: Fully mobile system [5].

Fig 6: High-angle conveyors [7].

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Fig 7: Comparsion slope of ramps in conventional & in-pit system [3].

Relocatable systems This term is used in Europe for crushers with temporary support foundations. The crusher plant is moved in sections. In the United States, this term refers to units that can be moved on an highway with a minimum amount of dismantling [2].

Movable systems A movable crusher is centrally located in a mine near the same level as the mines working face. It is relocated every 1 to 2 years, as required, to maintain the relationship between distance and elevation from the face [2].

3-2. Comparison of in-pit crushing system types Conveyor transport requires a smaller size distribution than truck haulage. While some marginal ores may be processed by dump leaching without crushing, the majority of ore mined for conventional processing generally requires crushing. On the basis, it is logical to consider that the primary crusher may be located in the pit in order to condition ore for conveyor transport.

Waste, on the other hand, does not require crushing for truck transport, but does require a size reduction for conveyor transport, and this is an additional cost burden of waste conveying [8]. Comparison of different in-pit crushing system are as following tables:

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Table.1.A: Comparison of different in-pit crushing system [8] IPCC Crushing Options Fully Mobile Semi Mobile Fixed

Throughput

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4-1. Comparison of conveyor system types The conveying system has most impact within the open pit environment due t the space required for installation, its permance, low mobility and its impact on other unit operations. While fixed conveying systems are frequently with fixed crusher installations, more mobile systems have found limited application in large hard rock open pits, and a greater emphasis is put on this type of system in this analysis [8]. Comparison of different conveying system are as following tables:

Table 2. A. Comparison of conveying system [8]

IPCC Conveying System Dedicated Ramp Conveyor Tunnel Conveyor on Haul Road

Conveyor Angle

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5. IPCC system advantages Energy efficiency - conveying is more efficient than other forms of material transport. Mine life, up to 50-60 years of operation - need at least four years to pay back capital and

+10 is ideal. Material movements - need at least 10 Mt/y (prefer 25 Mt) per stage. Electricity cost versus diesel cost electricity costs ($/kWh) less than 25% of diesel price

($/litre). Number of material types - co-disposal makes dump development difficult but not

impossible. Rock strengths - if < 70 MPa then use of sizers or double rolls crushers (DRC) makes

IPCC cheaper in both capital and operating costs but new hybrid DRC can process up to 150 MPa.

Space for operation - at least 100 m needed for IPCC. Dumping restrictions - any height restrictions? (IPCC dumps can otherwise be formed

much higher in a single pass, with less ancillary equipment needs). IPCC lends itself to easy automation. Timing - IPCC is ideally suited to new operations or an expansion, rather than steady state

operation. It is also, generally, capex neutral compared to trucks when taking into account replacement schedule and operating expenditure is less.

Vertical advance rates - moving crushers more than say twice a year creates a lot of system downtime at seven days per move.

Gravity - conveyors can generate power on downhill runs. Truck cycle times - in a mining operation IPCC may not work well below 25 min cycle

times. In a quarry where IPCC is processing ore this can be much lower [9]. Minimal dependency on weather. Ability to adjust to economic changes quickly. Lower maintenance cost. Highly reduced road preparation. Major environmental advantages due to:

- Electrically driven motrs versus burned fuel. - Prevention of dust on the haulage route. - In total less consumption of energy and consumables [10].

Substantial saving in civil works. Lower installation cost than stationary crushing plants. Flexibility to alter the primary crusher location and conveying scheme as the mine

develops. Safe mine operation due to less moving equipment [5].

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6. IPCC system disadvantages The initial cost of system is normally higher than that of the truck haulage system,

because the complete conveyor and crusher are bought to start production whereas the truck fleet can be bought in stages to set up production.

The mining operation is completely dependent on availability of the conveyors. This availability is over 95% but a shutdown of one belt can stop the entire production [3].

Relocation of the crusher and extension of the conveyor is expensive and requires a shutdown of the mining operation for a period from 2-3 days.

Material must be crushed to a size of minus 250 mm before loading onto the conveyor [4]. IPCC and shovel do not operate together [3]. In-pit crushing required for conveying (hard rock) even if not needed (overburden). Less flexible in mining layout. Less flexible in capacity [11].

7. Reasons for applying Size of mines getting larger. Labour shortages and need to keep manning levels low. Strip ration increasing. Fluctuating fuel cost. New environmental regulations. Greater Pressure to reduce operating cost. Need to quickly respond to changing market demand [3]. Maintain flexibility. Ore may go to number of destinations. Ore blending and priorities may change. Higher mineral prices support and justify the development of larger, deeper pits with

higher waste and/or material movements. Soaring oil prices drive shift to less expensive electric power. The supply of large truck tires remains difficult. Carbon emissions will result in increased mining costs and create an environmental

impact. There is an opportunity to improve safety with fewer moving vehicles. Mining costs are currently escalating rapidly. Mine production per man hour can increase dramatically. IPCC realizes fully integrated automation processes. Less logistics and handling of fuel, oil and parts result in lower costs [2,4].

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8. Is IPCC righ for a special case? IPCC could work at such operation if at least some of the following apply:

You have a long mine life (more than 10 years). You have laden uphill hauls or long distances. Large and steady tonnages of material are

being moved. Electricity price ($/KWh) is less than 40% of diesel net price ($/liter). No more than three material types. Your cutbacks can be reasonably wide (>150m/164 yards). Manpower issues prevail. Reducing carbon and dust emissions is important. You want lower operating costs! [2,3,4].

9. Case studies in copper industry This technology has been developed from starting capacities achieved 25 years ago of 300 to 700 t/h, and is operating successfully, with major benefits for the user [10].

9-1. Twin Buttes This open pit operation in Pima County, Arizona uses an overburden handling system, consisting of three 1.5 m wide belt conveyors, with a capacity of 7200 tonnes/h each. The mine also employs a few kilometers of conveyors to move crushed ore from two in-pit crushers to stockpiles on the surface [12].

9-2. Duval Corporaation Sierrita Copper Mine This large open pit in Sahuarita, Arizona, 150000 tonnes of waste. During 1982-83, the mine developed an existing haulage system based on stationary in-pit ore crushing and conveying into movable in-pit crushing with extendable conveying for ore and waste. The new system consisits of three movable 1.5 * 2.2 m (60-89 in) gyratory crushers, transporter unit, movable stacker, and 7.3 km of conveyors with installed power of 14000 kw. The total capital investment was estimated at 32 million U.S. dollars. Average cost savings are $0.32/tonne at a nominal mining cost of $1.10 tonne. This new system allowed the mine to reduce the truck fleet by 25%. Moreover, average truck requirements were reduced by 37%, which eliminates all truck capital expenditures over the next ten year period. It is estimated that a reduction in a vertical truck lift of only 30 meters can save one million dollars of operating costs per crusher annually [13].

9-3. Bingham Canyon Copper Mine

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This open pit in Utah, U.S.A is currently under modernization to achieve a production of 70000 tonnes of ore per day using in-pit crushing and conveyor transport. The system consisits of a semi-mobile 1.5 * 2.7 m (60-109 in) gyratory crusher and six belt conveyors.

The crusher weighs 1200 tonnes and is installed on concrete foundatios in a recess on a bench at the conveyor tunnel portal elevation. It is fed by 154 tonne trucks from two sides. Total height of the installation is approximately 30 m. Ore is crushed to a size of 250 mm at a throughput rate of 9000 tonnes per hour. The feed hopper has a capacity if 600 m3. The discharge belt is 3 m wide and 26 m long, with infinitely adjustable speed between zero and 0.5 m/s. the plant is equipped with a hydraulic crane of 110 tonne lifting capacity and a hydraulic rock breaker.

The mine uses six conveyors of a total length of about 8.5 km. The longest conveyor, which is 6 km long, runs through a tunnel excavated in the pit wall to the surface. All conveyor belts are 1.8 m wide. Total Installed drive power is 12900 kw [14].

9-4. Gibraltar Mines This open pit mine in McLeese Lake, B.C. produces 37000 tonnes of copper-molybdenum ore daily from four pits. In 1980, an in-pit crushing and conveying system was installed in the East Pit. The system comprises a 1.4 * 1.9 m (54-74 in) gyratory crusher and three flights of conveyors of a total length of about 10 km and lift of 145m. crushed ore is loaded onto a slow speed 2.13 m wide discharge conveyor, then transferred onto a 1.5 m wide two-flight overland conveyor transporting ore to the processing plant. Average capacity of the system is 1800 tonnes per hour, and during the last five years the system handled 45 million tonnes of ore [15].

9-5. Island Copper Mines This open pit at Port Hardy, B.C. Canada produces 43000 tonnes of copper ore daily at a stripping ratio of 2:1. It is a mine which converted its all-truck system into in-pit crushing and conveying. The new system, installed in 1985, employs a portable crusher station, and out of pit conveyor which transports ore through an inclined tunnel to the surface facilitates. Waste is still handled by trucks. Total investment in the entire system was 24.3 million CDN dollars, with expected saving of $0.19/tonnes. The payback period is 4 years and the truck fleet was reduced from 25 to 14 units [16].

9.6. Highland Valley Copper This open pit mine, located in the Highland Valley, B.C., produces 120000 tonnes of copper/molybdenum ore per day from two pits. Recently, the company has installed two in-pit 1.5 * 2.2 m (60-89 in) gyratory crushers for ore crushing, at a cost of $20 million. Each crusher has a capacity of 6000 tonnes/h and has its own conveypr system transporting ore to the Lornex mill over a distance of 2.5 km [17].

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9-7. Mao Moh Mine The large in-iit crushing, continuous haulage and spreading system with high capacity for overburden was commissioned in 1984 in the open-pit mine Mae Moh of the Thai Electricity Commission EGAT in Northern Thailand [10].

9-8. Syncrude Mine The largest double roll crusher currently in operation is in an oilsand open-pit mine at Fort McMurray at Syncrude Canada Ltd. This was supplied by ThyssenKrupp Fordertechnik and has a capacity of 5,500 t/h. In 1997, two more double roll in-pit crushers from ThyssenKrupp Fordertechnik, each with a capacity of 7,500 t/h for oilsand, were installed at the Syncrude open-pit mine [10].

9-9. Chuquicamata and Escondida Mines Figures 8 and 9 show the large open pit mines of Chuquicamata and Escondida in Chile [10].

Fig 8: Chuquicamata mine chile [10].

Fig. 9: In-pit crushing continuous haulage and spreading system at Escondida mine/chile [10].

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These are circular copper ore mines where the copper is covered by a very hard material. Before installation of the conveyor the waste material was transported along the circular ramps: a very expensive operation. ThyssenKrupp Fordertechnik has supplied in the last decades In-Pit crushing continuous haulage and spreading systems for both of these mines, which have drastically reduced the costs of operation.

ThyssenKrupp Frdertechniks In-Pit crushing continuous haulage and spreading systems in Indonesia, China, Chile, Brazil, USA, Canada, South Africa, Zaire, Thailand, Australia, Europe etc. prove that this technology is suitable for large open-pit mines and operates at high performance levels with a very long service life under any climatic conditions [10].

10. Conclusion While each mining situation needs to be independently evaluated, in-pit crushing and conveying systems are increasingly cost effective in the following circumstances:

High capacity Long mine life Deeper pits Longer haulage distance High fuel cost High labour cost Remote controlled operation.

11. Refrence [1] In-pit crushing and conveying-gathering momentum, 2011, International Mining. [2] Frizzell, E.M. & Martin,T.W. 1990, In-pit crushing and conveying, Chapter 13.5. [3] Scot Szalanski, P.E., 2009, Optimizing in-pit crusher conveyor performance, P&H Mining Equipment. [4] Radlowski, J.K., 1988, In-pit crushing and conveying as an alternative to an all truck system in open pit mines, The University of British Columbia. [5] Koehler, F., 2010, In-pit crushing looms the way into Australia, Mining Magazine Congress. [6] In-pit crushing and conveying (IPCC), 2010, Alan Cooper-Principal Consultant, Snowden Group. [7] Bulk materials handling in mining, 2007, Sandvik Mining and Construction. [18] Tutton D. & Streck, W., 2009, The application of mobile in-pit crushing and conveying in large, hard rock open pit mines, Mining Magazine Congress. [9] IPCC innovations, 2009, International Mining. [10] Schroder, D.L., 2003, The use of in-pit crushing and conveying methods to significantly reduce transportation costs by truck, Coaltrans Asia, Bali International Convention Centre. [11] Oberrisser, H., 2009. Fully mobile crushers as part of total IPCC solutions, Sandvik Mining & Construction, Mining Magazine Congress. [12] Argall, J.G.O., 1976. Twin Buttes pit gets bigger, 550000 tones moved out of pit each day. World Mining, PP. 72-75. [13] Anon., 1979. Pit crushers and conveyors move Sierrita ore and waste, PP. 279-28. [14] Kaerst, D., 1987. Modern equipment for Kennecotts Bingham Canyon copper mine, Bulk Solid Handling, Vol. 7, No. 2. [15] Engineered Solutions for Material Handling, 2010, Synergy Engineering Ltd.

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[16] Anon., 1984. Island copper: in-pit crusher and conveyor system under construction. Island Miner, Vol. 11, No. 1, pp. 1-2. [17] Valley copper mines ltd., Vancouver, B.C., 1980. Valley copper project, Stage II Study, Vol. 1, Mining Plan.