Behind this fundamental truism lie onion-like layers of issues and challenges that impact all new mining developments to some extent: rugged terrain; lack of infrastructure; working with and in underdeveloped communities; government approvals; relatively pristine environments.
With the progressive mining of easier deposits, typically closer to export ports or users, the significance of these challenges in gaining approvals and licence to operate and the cost of getting the ore to the customer increases. Among the most critical of these challenges, is that of a pit to port transport chain, both in terms of viability of the project (the project has no value if the ore cannot get to market) and cost (long transport chains cost more to build and operate).
In an article titled ‘The problem with railways in Australia’ (International Longwall News, 3 February, 2012) the view was expressed that coal and iron ore have less to do with mining than with transport, economics and infrastructure. These, being the bulkiest of bulk resource commodities, make the point particularly clear – but it is also true of other minerals. Australian Bureau of Statistics figures indicate that since 1998 the balance with respect to mine development costs has changed from being equipment (mining and process) dominated to being heavily weighted to enabling infrastructure. Ore transportation has always been a challenging issue but these current trends have resulted in a new focus on getting the most efficient transport chains and achieving lowest cost to market.
While undergoing renewed focus, the means of pit to port transport remain unchanged; roads, conveyors; rail; and, where there is navigable water, barging. The renewed focus is on achieving low capital cost transport as far as possible commensurate with a sustainable, effective and cost efficient transport chain for the life of the mine. Critical challenges centre on the economics of the traditional transport options and fundamental assumptions applied to mine developments over generations of project managers. Rather than build the ‘biggest hammer’ – a peak production transport system from the outset - closer examination of the benefits and risks of staging are becoming more important in developing ore transport chains.
Choosing the optimal transportation method, or combination of methods, is therefore a project by project proposition based on a balanced consideration of all the issues above for the specific environment and project needs.
Implications on the main forms of transportation, and their economics, have changed the view on, and utilisation of, these transport methods. Selection of the optimal form of transportation, or mix of forms, is project specific and depends on a holistic view of a range of cost and engineering factors including:
A brief summary of some of the cost drivers and industry trends of the main transport methods follows.
• Moatize-Nacala railway study, Mozambique
Using the Multi-Criteria Assessment (MCA) planning tool, Aurecon was able to demonstrate the relative merits of the different alignment options from an engineering, geotechnical, operating, social, and environmental perspective. This approach gave our client a full understanding of all the pertinent aspects and enabled them to pursue the option that was engineering and operationally sound, and would have the least social and environmental impact. Consequently, project implementation is not likely to hit unexpected hurdles.
• South African iron ore export (Orex) channel
The project presents many challenges – not the least of which is the length of the supply chain. The Orex channel is an 850 kilometre rail line linking Sishen in the Northern Cape region with the Port of Saldanha, to the north of Cape Town. Our team brought together key skills in port, bulk materials handling, and rail (operations planning and economics) to contemplate a true pit to port solution taken from a whole of logistics chain perspective. Whereas one solution may have taken the position of more infrastructure to address the problem, our approach was a whole-of-supply chain perspective, with a view to improving each element of the chain to its optimal efficiency before resorting to the expense of adding or expanding infrastructure. We first clearly identified the intrinsic interdependencies of the various elements - and how each impacted on the other to diminish the overall effectiveness of the chain. Despite the process nature of this, such thinking is far from typical within rail engineering firms. Our approach was to focus on improving operational efficiency through a master plan. The plan approach (as opposed to previous studies that proposed an infrastructure intensive solution as the only one) contemplated up to seven expansion steps/options to deliver the nominated tonnage growth, at much reduced cost to industry.
Low effective distance limits the applicability of overland conveying as a single solution to the ore transport issue for long chains. The longest single flight conventional coal conveyor, at North Curragh Coal Mine in Queensland, Australia, is about 20 kilometres. Longer distances are possible with multiple flights. An 11 flight phosphate conveyor in the Western Sahara extends 100 kilometres, but each transfer contributes to ore degradation into smaller particle sizes.
Consequently, and due to their relative flexibility of vertical alignment and low ground footprint, conveyors are often used at the rugged mine end and/or the softer ground of the port end as a low operating cost link between the fixed infrastructure and main transport chain.
The relative inflexibility of conventional conveyors in horizontal alignment is thus a major challenge in this regard. More flexible alternatives such as cable belt or pipe conveyor can sometimes address this. A recent example at the Hidden Valley gold mine in Papua New Guinea has a 5.3 kilometre pipe conveyor, the Indiana Jones Conveyor, connecting the mine and process plant on ridges by dropping 500 metres to cross the valley and rise again, and in the process going through horizontal turns totalling 719 degrees, or two full revolutions.
In recent history, advances in belt technology, especially belt rubber and idler technology, have led to lower resistance and wider spaced idlers, contributed to higher speed and capacity conveyors with, counterintuitively, reduction in the belt grade required due to reduced friction and hence reduced belt tensions.
These material and component improvements, combined with improved dynamic analysis, have enabled conveyor technology to push previously defined limits. A maximum speed for conveying of 5 metres per second was, in the recent past, considered reasonable. The PT Kaltim Prima Coal (KPC) 13 kilometre overland conveyor connecting the Sangatta mine coal handling and processing plant with the Tanjung Bara coal port is now running at 8.7 m/s, delivering some 30 Million Tons Per Annum (Mtpa) of coal to the port along a single conveyor line. The future continuations of these advances are likely to further extend the carrying capacity and maximum flight length of conveyors.
Conveyors as the main transport solution for long ore chains present some non-technical issues in terms of community and environment. They have the disadvantage of presenting a permanent physical barrier across the landscape dividing environments and communities in a way rail or roads do not. This in turn presents risks around securing such a long narrow piece of mechanical infrastructure, and maintaining operations when repeated pulling of the stop cord by a single disgruntled community could seriously threaten ore delivery to meet contracts.
Conveyors also come with a relatively wide right of way, accounting for the conveyor and a service road. This presents a potential scar on sensitive environments. A recent innovation, the rope conveyor uses a box shaped belt hanging from catenary cables with long distances of up to two kilometres between low footprint support towers.
Barging of bulk ores remains a favoured start-up option where navigable waterways are available within a reasonable distance of the mine site.
Barging of bulk ores remains a favoured start-up option where navigable waterways are available within a reasonable distance of the mine site. The low infrastructure cost of transporting long distances by water, and the low operating cost of the generally large unit of volume transported by barge, typically 5 000 up to 15 000 tonnes, makes this option attractive. Barging has been the default form of transport for Indonesian coal miners for decades. Only now that mines are becoming remote from navigable rivers are more land based options, especially rail, receiving serious consideration. Rio Tinto Coal Mozambique recently proposed barging on the Zambezi River as their start-up transport option for the Benga and Zambezi coal mines in the Tete basin. The Mozambique Government initially rejected the Environmental Impact Study (EIS) over concerns about dredging impacting on flooding, and the fact that the fast flowing Zambezi current, at around four knots, makes for another logistical challenge of a fast trip downstream loaded but a very slow return against the current.
Seasonality in rivers is also a big issue. Dry seasons and floods have the potential to disrupt the ore chain through reduced navigability, debris and shifting riverbed contours. Coal miners in Central Kalimantan, mining high quality coking coals located on the border with East and South Kalimantan, have been designing their barging operations to cope with several months of not being able to barge during the year due to low flows in the Barito River. Good logistics planning and stockpiling has made this successful at smaller tonnages but it is questionable as to how high production can go with such restrictions. Transferring from barge to ship is the bottleneck in a barging chain. Proportionately, the addition of the largest costs per tonne occurs at this point. Methods range from simple floating cranes direct to ships hold (or even ships gear for smaller geared vessels) to loading via floating transhippers and even transhipping through shore based terminals. Adaro coal has been very successful loading large volumes of over 20 Mtpa of coal through floating cranes and transhippers over many years. Shore based terminals tend to be less dependent on weather conditions and load at higher rates and are therefore regarded as more reliable, especially for higher throughputs.
A recurrently increasing risk as the ore chain lengthens and mines become more remote, and serviced by less transport infrastructure, is the issue of redundancy. Over such long distances, community relations and social licence to operate become paramount in keeping the transport chain open and operating. Minor disagreements, if not well handled, can escalate with major consequences if there is disruption to the ore chain and no practical alternative due to the long distances. Safety along the ore chain is a major consideration and generally well understood by the industry. A community member injured or killed on the chain will inevitably have dire consequences for operations. Even issues of less apparent importance can lead to disruptions. The maintenance of community engagement and relations from the early planning, particularly in relation to land acquisition, through construction and operations attains equal importance with safety. The impracticality of ore chain redundancy and alternative routes over such long distances sees more engagement of mining companies with communities near the mine and those between the mine and the sea.
While transport of the ore to market is the paramount transportation task, mines need supplies to operate. Mines and their workforces consume, among others, large quantities of fuel, explosives, food and spare parts. With mines becoming more remote and in less developed, lower infrastructure locations, the inward logistics chain is also a mission critical challenge. Combining the ore export and supply logistics chains seems an obvious solution to optimising cost updated effectiveness. However, the primacy of the ore delivery often means the push of inward supply onto secondary supply routes, increasing the indirect cost of production per tonne of ore.
The ore transportation task is set to remain an ever increasing challenge to mine developments in search of achieving the lowest delivered cost per tonne. As mines become more remote requiring longer transport routes, encountering more rugged terrain, and as a critical but potentially fragile link in the production chain, optimisation of transport chains will receive increased attention. We can most certainly expect further refinement of transport methodologies and innovations as the 21st century progresses.
• More about author, Andrew Keith >
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