Exploiting the metallurgical throughput–recovery relationship to optimise resource value as part of the production scheduling process

• Metallurgical throughput–recovery should be integrated into resource planning.
• A fluctuating mill throughput rate may create additional economic value.
• Minor additional costs associated with implementing fluctuating mill throughputs.
• Higher opportunity costs tend to favour a higher initial mill throughput.
• Mathematical programming provides powerful means for solving complex problems.

A single process plant throughput rate to achieve a certain recovery at a certain cost is often assumed over the life of a resource project for strategic planning purposes. The process plant throughput–recovery relationship that exists for each ore type can and should be exploited for the purpose of creating additional economic value within the resource plan. This paper investigates the impact on Net Present Value (NPV) of strategic resource plans when allowing a fluctuating process plant throughput rate over the life of a base metals operation in comparison to only considering a single fixed throughput rate for a given plant size configuration. The metallurgical throughput–recovery relationship is confirmed as being an important factor in planning the extraction of the resource to feed a given process plant of fixed size since this impacts heavily upon the production schedule and therefore the NPV of the project. Mathematical programming to better aid the decision making process is investigated in comparison to traditional manual approaches to thus help determine the best throughput rate to use in each period. Results suggest that it would seem reasonable to expect an increase of around 4.0% in NPV when allowing a fluctuating process plant throughput rate over a single fixed throughput rate over the life of a midsize underground operation when using a mathematical programming approach.