The Sishen Iron Ore mine, situated in the Northern Cape Province, is the flagship for
Iscor' mining division. Sishen accounts for 78% of SA iron
ore and 4% of the global sea borne iron ore trade. Sishen Iron Ore mine is the 3rd
largest iron ore mine in the world, producing 27 million annual product tons.
Sishen is the only major iron ore mine in the world that beneficiates 100% of
production. Sishen maintains a healthy geographic spread for global sales with
35 customers in 17 countries, and is well known for its high quality iron ore.
Iscor iron ore mine is committed to add value to its shareholders and therefore
continuous improvement is a way of life at Sishen iron ore mine. The iron ore
grade variation associated with this production is required to be within a very
narrow range, and at the same time impurities within the ore need to be
minimized. In order to achieve all of the above-mentioned factors, the
management of Sishen Mine have recognized the need for a specialized mine
planning tool.
The XPAC AutoScheduler is a mine planning and
scheduling software system developed by Runge Mining in Australia, and is used
at most of the Iscor collieries as well as at their Zinc mining operations. The
XPAC system has recently been implemented at the Sishen Iron Ore
mine, and is driven by their medium and long term planning technician Wayne Louw.
Louw comments:"Over the years, we have looked at several mine planning systems with a view to obtaining one system capable of providing us with a total solution as far as grade control, production planning, costs and scheduling goes. So far, XPAC is the only system, which has provided that solution, and we no longer need to transfer data through several software systems. Xpac caters for all these requirements in one software package."
Database Functionality
The database functionality of XPAC provides a user-friendly interface to the mine design system used at the mine. In situ data pertaining to grade and tonnage is imported into XPAC. The data is then analysed to indicate preferred areas within the mine which may be combined to provide an optimal blend when scheduling is performed. A record in the database represents each mining block, and these records contain information relevant to the mining block.
The Scheduling Process
In
order to optimize the scheduling process, mining costs are also included for
mining blocks. These costs relate to drilling and blasting, loading and hauling
as well as secondary equipment costs. A prediction of the associated profit for
each block or a combination of blocks can be made. Using this technique, a cost
ranking exercise has been completed for each pit at the mine to indicate its
profitability. During scheduling, the combination of material from each pit is
controlled in order to achieve the best blending scenario.
The AutoScheduler is capable of generating life-of-mine schedules in a relatively short period of time. Several alternatives are easily achieved in a single day. Dependency rules are defined which ensure mining logic and integrity is maintained. Undermining is therefore eliminated. The export requirements for the ore delivered to Saldanha are very precise. The quality of the blend of material derived from several pits must fall within stringent specifications. These targets apply to Iron content as well as impurities like Phosphorous and Potassium. XPAC produces mining schedules, which satisfy these criteria, while restrictions pertaining to material derived from the various pits are also adhered to. Production targets are stored in a comprehensive calendar database, which allows for day-to-day scheduling as well as annual scheduling scenarios.
The haul road networks within the mine have been imported into XPAC. It is therefore possible to predict hauling distances to major network nodes like primary crushers, stockpiles and waste dumps. Sishen makes use of a Pantograph Trolley Assist system which dramatically reduces hauling costs. The Pantograph system has been successfully modeled within the XPAC system, and detailed haul route profiles can now be simulated to predict the optimal route to use when transporting material out of the pit. In addition, the system is capable of predicting cycle times, truck hours and the number of trucks required on the haul route. With this information available, the engineer is able to make accurate assessments of the associated expenses with mining operations. In particular, diesel costs can be predicted.
Another requirement at the mine is dump creation scheduling. Each dump position is accurately recorded in XPAC. The material placed on the dump is recorded and the monthly requirements in dump capacity can be predicted. Using the haul road network, it is possible to decide the best suited dumping position. The final schedules can be represented graphically. Period progress plots depict the mining operations as they are planned. These plots are three-dimensional, and the mining operations can be animated on the plot to simulate equipment positions and movement. The animation is useful for visualizing and comparing possible mining alternatives.
The Runge software suite is also used extensively in southern Africa by the SASOL group and De Beers use the systems at their underground mining operations. MRM Mining Services (Pty) Ltd represent Runge's interests in South Africa.
MRM engineers recently completed the life of mine schedule for the De Beers Premier C-Cut project using the Xpac AutoScheduler. MRMS commenced with the project in January 2000, and revised the schedule with the new mining layout in November 2000.
The model reported a complete physical mining plan for the two phases of the project:
The C-Cut project was co-ordinated by Premier Mine engineers who worked closely with MRM staff. "The logistics of putting in a block cave in the environment envisaged at Premier, requires detailed planning and XPAC was able to meet the sophisticated inter-dependencies of this planning. This has given us a higher degree of confidence in our design." says the Project Manager Alistair Croll.
The project work was completed by Olaf Wyberneit, Senior Mining Consultant at MRMS. Project requirements included the modelling of the all the ancillary development required to open up the block cave. The development was scheduled using the XPAC AutoScheduler and was based on targets set by the client. The targets are typically estimates of the level of production, which are deemed to be feasible at that particular stage of the development process. Mining activities that were scheduled included development of the extraction level, undercut level, ventilation level and the ground handling level. The scheduling of all the activities required to initiate the block cave including ring drilling and blasting and trough opening, formed part of the exercise.
Criteria for the scheduling process include the requirement of mining activity interaction. For example the extraction level may not be developed inside the stress zone of the caving process. Unique scheduling features of the XPAC AutoScheduler allowed the modeling of dynamic logic to be incorporated. The columns within the caving area go through a maturing process when they are opened up. The logic controlling the maturing process had to reside within the column definition in XPAC, as it is not possible to predict when the maturing process will begin before the scheduling has been run. This process is a function of other activities within the orebody as well, and XPAC successfully modelled the maturing process of the columns, which resulted in a high level of confidence for the predicted tonnage build up.
Working in a graphical environment allows the schedule to be critically analysed to ensure that no mining logic rules are broken. This is difficult to achieve when analyzing simplified period progress plots or bar chart progress plots. The three-dimensional graphical environment in XPAC allows for progress plots of the schedule as well as plots pertaining to grade or rock type. The mining progress can be visualized by animating the blocks being mined. Results of the schedule are analyzed in a simulation environment to indicate where assumptions have resulted in schedules that are not practically achievable. Alternative scenarios have been explored, and where necessary, the schedule has been modified.
Apart from reporting the physical mining plan, bills
of quantities have been placed into the database. Thus, as activities occur,
reports are generated of the bills of quantities required. BoQ's include
explosives, support materials, drill steel etc. In the future the model can be
easily enhanced to report on manning requirements or equipment hours. These may
be used to drive a zero based cost model.
XPAC has been successfully used to schedule opencast and underground mines, and is not mining method specific. Other mining institutions in Southern Africa using the Runge Software include Glencore, Sasol and Iscor. Additional software solutions offered by MRM and Runge include a truck and loader simulation package, Talpac, a financial modeling tool called Xeras and a dragline simulation package called Dragsim.