By Imre Viljoen
Ceenex has completed many cutting-edge simulations of mining logistics from pit to ship via barge transshipment during the projects’ Pre-Feasibility and Feasibility phases. These have been undertaken for leading Engineer, Procure, Construct and Manage contractors working on flagship mining projects on the continent.
Our simulations identify where exactly the bottleneck is in the entire system and whether throughput targets can be met on time and at minimal cost.
They also help to determine the optimal run-of-mine stockpile size to effectively buffer mining plant production. By being able to ascertain the tip bin capacity and conveyor feed rate, it is also possible to buffer the feed conveyor from truck tipping.
Moreover, our modelling can determine the number and capacities of plant modules that are required for the project, as well as product stockpile size to effectively buffer transport to port from plant production.
Our simulations also help to verify the number and capacity of trucks and trains that are required to transport the required tonnes at the lowest cost and least risk. This is in addition to determining the required port stockpile size to effectively buffer barge loading from overland transport.
Moreover, the ability to determine the ideal loading rate enables the optimisation of the number and capacity of tugboats and barges, as well as their loading processes.
Our simulations also facilitate improved vessel loading rates. This is based on a better understanding of the minimum vessel loading rate for a specific barge configuration.
They have also helped to develop operating philosophies for those operations that interact with and have an impact on the entire throughput rate of the system.
All decisions are subjected to the bottlenecks identified in this complex logistical system.
A case in point is deciding whether to increase barge capacity when available loading time is constraining the system.
The decision to increase the number of barges so that there is always one available to load and ensuring that they are all accompanied by a tugboat with each tide needs to be weighed against the increase in draft and corresponding increase in loading time. While optimising between quays, barge capacity, loading time and rate will increase throughput, it will come at a cost.
Therefore, the aim is to find a perfect balance between the number, capacity and loading rate, with additional options to increase the quays-side loading draft.
Deploying too many small barges will impact throughput due to the extensive docking and undocking time involved. At the same time, large barges increase the likelihood of missing a tide or prematurely stopping loading to make a tide.
The challenge is to have a fully loaded barge ready to sail by the time the tide is high enough without over-engineering barge size or loading rate. Generally, empty barges are unconstrained by tides.
Our simulations also simplify the process of establishing different and seemingly impossible scenarios to ascertain the true limitations of the operation.
For example, they have demonstrated how increasing the number of loading and hauling equipment may not necessarily impact the overall system throughput when the mine is not the bottleneck.
We have also shown that shift changes, when forced to take place at the same point in the cycle for all trucks and at the same time in a truck logistical system, can seriously impede productivity.
Moreover, Ceenex’s models have demonstrated that shift changes and multiple shiftchange locations are sometimes a preferred alternative to increasing the number of trucks in the system. This is considering that the additional trucks usually just end up in queues at the start of each cycle.
Furthermore, we have demonstrated how demand-based refuelling of trucks using well-located refuel stations and queue management systems are significantly more effective than schedule-based refuelling at an off-site depot.
We look forward to assisting you to optimise your pit-to-ship mining projects.
Imre Viljoen is an Executive Director of Ceenex. He is also Head of the firm’s Business Engineering Division.