An advanced coursework and a project submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements of MSc. Engineering
(Mining), November 2015 / General
For mining operations, both underground and open cast, there are generally
accepted criteria used to arrive at the optimum mining method with which to exploit
the ore body economically. Having selected the optimum mining method, mining
companies should then make the decision to also select the optimum technology to
apply given the various options that are now available.
In the case of a shallow massive ore body where open-pit mining has been selected
as the optimum mining method, the use of conventional trucks and shovels has been
the popular choice but over the years, as pit become deeper, and stripping ratios
increase, growing interest and adoption of in-pit crushing and conveying for both ore
and waste has been gaining ground with several mining sites currently now
operating, testing the systems or conducting studies at various stages for In-pit
Crushing and Conveying (IPCC) in its different configurations (Chadwick, 2010).
Open pit mining general involves the movement of pre-blasted or loose waste ahead
of underlying ore out of the pit or to a previously mined part of the pit. This is then
followed by the drilling and blasting or loosening of the ore and transportation to the
processing plant or stockpiles.
The conventional Truck and Shovel open pit operation involves the use of shovels –
electric rope shovels, diesel or electric hydraulic shovels or excavators or front-end
loaders to load the blasted, or loose waste and ore material in the pit onto mining
trucks which haul the material to crushers or stockpiles if it is ore or to waste dumps
in the case of waste.
In a Fully Mobile IPCC (FMIPCC) system, the broken or loose material in the pit is
loaded into a crusher or sizer by a shovel, continuous miner or dozer, crushed to a
manageable size and transported by conveyor belts to the waste dump where it is
deposited in place using spreaders if it is waste or onto stockpiles if it is ore.
A combination of the two systems is where trucks dump material loaded at the face
into a semi mobile crusher or sizer located in the pit close to the loading points
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before conveying to destination thereby reducing truck haulage distance. In the
semi-mobile configuration, the crusher is relocated closer to the loading points to
minimise the hauling distance. Other various configurations are also employed
depending on the various considerations. Although the Truck and Shovel system is
considered as the convention in open pit mining, the IPCC system is not a new
concept and has been operational on a number of mines worldwide for quite a
number of years (Szalanski, 2010). Loading and hauling receive great attention
especially in a high volume open pit mines due to the high cost contribution to the
overall operation and therefore, if optimised, good cost savings can be realised
(Lamb, 2010).
Figure 1: Sishen Mining Cost Breakdown
In the case of Sishen Loading and Hauling costs constituted 67% of the mining costs
including labour mining support services in 2013 (Kumba Iron Ore, 2013). This
picture remains unchanged to a large extent. In some cases the hauling cost alone
can make up as much as 60% of the mining operating cost (Meredith May, 2012)
Selection of a materials handling system between Truck and Shovel (T/S) and In-pit
Crushing and Conveying (IPCC) has proven to be difficult due to limited
understanding of the IPCC system especially its advantages and disadvantages
relative to the Truck and Shovel system. The aim of this research was to unpack
these two systems in terms of their applicability using studies conducted at Sishen
6,5%
8,8%
29,1%
22,7%
9,7%
0,6%
1,3%
0,4% 7,0%
4,2%
3,7% 5,9%
Sishen Mining Cost 2013
Blasting Drilling Hauling
L&H Contractors Loading Maintenance Other
Mining Manangement Mining Engineering Mining Other
Resource Management SHEQ Mining Support
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Mine as well as develop some scorecard that could be used to select one over the
other one.
Sishen Case Study
Sishen Mine is an iron ore open pit mine located in the Northern Cape province of
South Africa and is part of Kumba Iron Ore Company which is
Anglo American PLC. The mine has been in operation since 1953 with the current
life of mine going up to 2030. It produces 44Mt tonnes of product from a 56Mt
mine ore at a life of mine strip ratio of 4. One of the planned expansion
the north part of the mine known as the GR80 and GR50 areas. Mining in these
areas will require pre-stripping of
290Mt of clay material over the life of mine to expose the ore in pre
volume phases.
Figure2: Sishen Pit –Sishen Mine 2014.
Sishen mine is constantly evaluating various technologies in its mining operations
aimed at improving its bottom line by way of increasing productivity and efficiency,
reducing costs and improving safety, however, the last time that the mine considered
evaluating a technology that significantly could have resulted in a totally different
operational philosophy was i
contracted to institute a study to evaluate technology options for mining and moving
majority owned by
a minimum of 437Mt of calcrete and the underlying
pre-
g in 2007 when Snowden Mining Consultants
run-ofmine
areas is in
-planned time and
were
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55 Mt of the calcrete/clay material per year from the waste pushback area in the
GR80/GR50 area of the mine from 2009 till 2030. Snowden completed the
Prefeasibility study in early 2008 in which they evaluated a conventional Truck and
Shovel operation as well as IPCC. Economic viability of both systems in various
configurations was demonstrated with the use of larger trucks and shovels ranked as
the most economic option in terms of Net Present Cost (NPC), unit owning and
operating cost per mined tonne and, to a less extent, in terms of risk and other
considerations. In this case, the Truck and Shovel option was more economic than
both IPCC configurations. However the small difference in the cost figures gave rise
to interest in further evaluations.
Following the Snowden study, Sishen engaged Sandvik Mining and Construction in
2008, to review the work done by Snowden and provide more detail and practical
input to the IPCC system at scoping level. In the review, the IPCC system was
shown to be the economic approach for the waste removal from the target area in
terms of owning and operating cost. Practicality was also demonstrated and the case
for the consideration of the IPCC system was put forward to Sishen.
A further consultant, Sinclair Knight Merz (SKM) of Australia, was engaged, in the
later part of 2008, to further evaluate and optimise the IPCC option to further
demonstrate practically in detail at a feasible study level and strengthen its case by
mitigating perceived risk. This included equipment specifications, mine and
equipment layout per period per bench and risk assessment on the IPCC options.
The mine, however, implemented the conventional truck and shovel option using
larger equipment. The final decision was to stick with the current set up of Truck and
Shovel system and gradually replace the current fleet of 730E Komatsu (190 tonne
payload) trucks with the 930E or equivalent ( 320 tonne payload) and the current
XPB 2300 P& H electric rope shovels and CAT 994/Komatsu WA1200 front end
loaders with XPC 4100 P&H electric rope shovels, Komatsu PC8000/Liebherr 996
diesel hydraulic shovels and LeTournea L-2350 front end loaders to reduce the
number of equipment and manage the operational cost.
This decision was based on issues around initial capital investment, flexibility of the
system to suit changing mining plans, ability of current personnel to run the system
and general low risk appetite for change. The adopted option has its own challenges
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such as supporting infrastructure requirements, labour intensity and associated low
productivity and high cost, fleet management challenges to achieve required
productivity constantly, supplies such as fuel and tyres and safety issues due to
traffic density.
A high level recalculation of the costs using current information was done as part of
this research. For simplicity, no escalations or discounting were applied on future
expenditure. The estimated unit owning and operating costs in 2014 terms for the
study area were as follows:-
Fully Mobile IPCC (FMIPCC) option ZAR 10.38/t,
Semi Mobile IPCC (SMIPCC) option ZAR 13.12/t,
Truck and Shovel option ZAR 15.80/t.
The objective of this research is to use lessons from the Sishen case as well as
other operations and gather expert views with the aim of establishing criteria that
could be applied in a preliminary evaluation that would determine the suitability of
either of the materials handling options.
General Approach
The costs were recalculated using as much current information as possible. Other
considerations including advantages and disadvantages of either of the systems
were examined in more detail, with real life examples examined where possible. This
resulted in the establishment of generalized criteria for the selection of mining and
transport technology for a large open pit mine with focus on conventional Truck and
Shovel systems on one hand and IPCC systems, in their various formats, on the
other. These criteria which identify conditions necessary for the successful adoption
and implementation of either of the systems could then be used as input into the
decision to carry out any further detailed studies of the options. The previous study
reports on the Sishen mine case were examined, input parameters to the
calculations checked and the general approached analyzed for practicality. The
relative costs were also viewed for comparative purposes.
Literature on these two main systems was reviewed including that from conferences.
Other large operations running either one or both systems were looked at to gain
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further insight. Original Equipment suppliers’ views on these systems were also
looked at through many articles in the public domain. Sishen mine has previously
had the IPCC system running in the same part of the mine in a semi mobile
configuration, crushing and conveying waste. It was then changed to become a
supplementary system for the ore handling system and the in pit crusher has never
been relocated. The Truck and Shovel system took over the movement of all the
waste and most of the ore at the mine. Lessons from these experiences were
incorporated in this study.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/20589 |
| Date | January 2016 |
| Creators | Banda, Nelson |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (84 leaves), application/pdf, application/pdf |
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