This is Part 2 of our interview with Arthur Pacunana, Mine Planning Superintendent at Phu Bia Mining Limited in Laos. In Part 1, we talked about what makes an optimal mine schedule and a successful planning process.
LAST WEEK, WE TALKED ABOUT HOW MINING OPERATIONS ARE FORCED TO BECOME MORE FLEXIBLE AND EFFICIENT IN LIGHT OF VOLATILE COMMODITY PRICES AND CHANGING MINE SITE CONDITIONS. HOW HAS YOUR MINE PLANNING STRATEGY CHANGED TO COMBAT THIS?
Changing conditions such as harder ore types and higher arsenic grades, together with the mining downturn, has enabled our Phu Kham and Ban Houayxai sites to develop an optimal mine planning strategy and maximize value generated throughout the mine life – from the short term through to the long term.
Since 2013, with the support of our production management system, the use of GEOVIA MineSchedTM as a mine planning tool at Phu Kham and Ban Houayxai has included short-term and medium-term planning horizons (full-year forecasts and 5 year budget schedule), as well as providing significant input into long term strategy.
In addition to a general life-of-mine development strategy, we defined a high-grade strategy that brought high-grade material to the processing facility earlier in the mine life while balancing the total material mined, and therefore the mining cost.
The high-grade strategy was achieved by changing the medium-term planning from a bench-by-bench scheduling method to a polygon scheduling method. This enabled the opening up of higher grade areas to ensure metal targets were achieved. This method required more schedule processing, but gave more detailed and strict direction to the short-term plans and operations.
An example of the polygon mining scheduling method is illustrated below:
The higher-grade strategy using the polygon scheduling method has been successful in producing the highest metal tonnes, highest ore mined, and highest total material movement achieved in a quarter (Q4 2015) at Phu Kham.
During late 2014 and early 2015, ore mining at Phu Kham was concentrated on the lower benches of the pit, resulting in harder ore being fed to the mill. This subsequently resulted in a drop in mill throughput by up to 25% at various times. Medium-term planners were able to resolve this issue by using the ore hardness attribute to determine mill hours per tonne, and then use mill hours as the process target input in MineSched, rather than the usual tonnes per day target or copper grade target. This ensured the harder ore was properly blended to the mill and that metal targets were achieved during this period.
Another common process target input used at Phu Kham is the contained copper metal tonnes per hour (Cutph) process control limit. The Phu Kham concentrator has an installed online stream analyzer (OSA) providing near real time head grade information as used in the process control algorithm. The Phu Kham plant has a limit of 15 Cutph. Above this, the process plant circuit concentrate may exceed the capacity of the circuit and overflow into storage bunds. Above the setpoint point value where high grade exceed the capacity of the circuit the throughput rate is correspondingly reduced. Using a Cutph process target, rather than the usual copper grade target, helps to manage high-grade spikes in the pit and to ensure that copper metal is not lost.
Optimizing project value becomes increasingly difficult for mining engineers when they are faced with having to satisfy multiple targets or constraints. At Phu Kham, it is common for us to deal with maintaining copper-grade specifications, whilst maintaining control of arsenic contaminant levels. Minimum and maximum grade constraints can be input into MineSched to ensure that these constraints are respected over the mine plan whilst achieving planned production.
WHAT DOES THE REPORTING PROCESS NOW LOOK LIKE AT PHU BIA?
Reporting deliverables are now populated through MineSched’s raw data using excel lookups and PMS custom formats. This has aided in the standardization of reporting of the long-term and short-term schedules at Phu Kham and Ban Houayxai.
Improved reporting and communication of short-term plans have also improved compliance of daily production plans. The below image shows how daily production plans are tracked and measured for compliance to the weekly plan.
The procedure involves daily monitoring, interaction, analyzing and reviewing of the weekly plan with key stakeholders (mine operations, mine technical services, mill processing, and mobile maintenance) for reliability and confidence.
Improved compliance to weekly plans has increased our key stakeholders’ understanding of and confidence in the plan, improved accountability for the plan, and improved the execution and attainment of the development and production targets.
Check out Part 1 of Arthur’s interview: Adapting Mine Planning to Changing Conditions. Or, read more about the latest updates in MineSched.
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