Mines and plants have to find ways to process large tonnages of low-grade ore at low costs and in an energy efficient manner to overcome the many hurdles triggered by a sluggish global economy and low commodity prices, as well as the challenge of depleting higher grade orebodies.
In addition to the rising labour costs, fuel and consumables as well as the trend to more stringent governmental regulations and taxation schemes related to greenhouse gases (CO2 emissions), mining houses around the globe are now forced to rethink their conventional truck shovel mining methods, and the OEMs to strongly focus on service and process optimisation for their customers.
Transporting ore and waste in the most economic, efficient and environmentally friendly way is important to the operation of any open-pit mine. In-pit solutions such as the in-pit crushing and conveying systems (IPCC) are now capable of saving more than just fuel.
In-pit crushing and conveying (IPCC) is generally applied in three configurations: fully mobile, semi-mobile and stationary.
In fully mobile systems, shovels/excavators feed the fully mobile crushing plant directly and trucks are confined to a clean-up fleet. Crushers are mounted on tracks and move with shovels. Connecting crushers to a main conveyor requires mobile belt wagons, mobile bridges or link conveyors.
For semi-mobile IPCC systems, the crusher stations are located near the working face, requiring small (in number) truck fleets shuttling between shovel/excavator and crusher. Crushers can be relocated regularly to keep pace with an advancing face (vertically or horizontally) or relocated strategically (e.g. once every 3–10 years).
In fixed IPCC systems, the crusher stations are away from the actual mining face, often placed on or near the pit rim, leaving the trucks complete flexibility inside the pit. Semi-mobile and stationary IPCC systems could be easily retro-fitted into existing open pit operations without major redesign or rescheduling of the pit.
In-pit crushing and conveying (IPCC) could gradually substitute most pit haul trucking operations, but many mines delay conveyor installation beyond the ideal date for change. In >85% of studies, comparing IPCC with truck-optimised pit designs, conveying still generates large operating savings. Conveyors are much more capital and energy efficient on large operations, cheaper to operate per tonne moved, and require low technical maintenance. In-pit crushing also reduces haulage road development and maintenance needs.
Despite IPCC having numerous advantages such as high system availability, less operational expenditures, being electrically driven for low CO2 footprint, as well as boasting of tailor-made solutions according to open pit design and material characteristics, not all companies have adopted the solution.
The hindrance to IPCC adoption by most companies has to do with high capital cost, ore characteristics, mine planning and operational reliability, however this can be circumvented by proper mine planning, as this will assist in selecting the appropriate equipment, e.g. Semi-Mobile Plants.
Case study on thyssenkrupp’ semi-mobile crushing plants (SMCP)
Semi-mobile crushing plants (SMCP) vary in design and capacity to offer different equipment solutions for diverse commodity applications, with output delivery ranging between 200 t/h to 12 000 t/h, depending on the requirement.
“We can supply a SMCP for most in-pit mineral mining applications, depending on the pit planning design,” states thyssenkrupp Minerals Processing Product Manager, Demitri Kokoroyanis.
thyssenkrupp’s cost-effective in-pit semi-mobile crushing solutions are well suited for all minerals and ores and can lead to significantly reduced operating and capital expenditure (opex and capex). “In terms of opex savings, our in-pit crushing and conveying (IPCC) systems reduce the requirement for intermittent materials transport; fewer trucks lower diesel consumption, greenhouse gases (CO2 emissions), fleet maintenance costs and labour,” affirms Kokoroyanis.
The semi-mobile plant’s support on pontoons is designed to accommodate all static and dynamic loads and just require a base allowing for certain ground pressure. In most cases, a bed of compacted gravel is all that is required to ensure a suitable foundation and since the gravel bed is acting like a buffer the plants are particular suitable also for mine sites affected by frequent seismic activity. As a result costly civil work can be eliminated or substantial savings can be realised compared with common stationary crushing plants.
Another benefit is the ability of the SMCP’s to be moved by transport crawlers or self- propelled modular transporters. Usually; after being stationed in one place for a number of years, it can be moved in the mine closer to the actual excavation spot to minimise truck haulage distances. Kokoroyanis adds that thyssenkrupp’s specialist mine planning service offers advice to customers on how best to incorporate an IPCC system.
The fact that machinery is not overly complex and the main system can be connected to and be controlled from the operation room, facilitates equipment monitoring by semi-skilled operators. The IPCC system has a feature that enables it to connect to the global 24/7 service centre in Germany which allows for constant system monitoring.
The slowdown in large new projects has paved the way for an increase in upgrades and optimisation of existing plants.
Kokoroyanis adds that despite the current state of the mining industry, neither sales nor interest in SMCPs and IPCCs has waned and that they have seen a significant increase in interest in some mining areas on the African continent.
Sources: ThyssenKrupp Industrial Solutions South Africa, 2016 (www.thysenkrupp-industrial-solutions.com