Not all mining is equal and neither are the costs associated with each mining method and metal…
The world is facing a deficit of new high grade copper deposits, which is forcing miners to mine lower grade deposits. In order to process the ore economically, the hydrometallurgical process of heap leaching is being employed to extract metals from lower grade deposits.
Costmine Intelligence’s Mining Cost Service recently published a report titled, Estimating Costs of Copper Heap Leach Irrigation as part of its ongoing service to its clients to keep them informed on the latest cost developments in the mining industry.
In this report, analyst Aaron Seleya dives into the costs associated with the specific aspect of copper heap leach irrigation, from pumps at the barren pond to flush manifolds on the pad..
What is Heap Leaching?
Heap leaching is a hydrometallurgical process used for the extraction of metals from low-grade copper, gold, or uranium ores. This process involves piling the mined ore in heaps, by either truck or conveyor, on a lined leach pad. A barren acid or cyanide leach solution is then applied to the pile via an irrigation system installed on top of the stacked ore.
As the solution seeps through the ore heap, it strips the desired commodity from the ore and suspends it within the solution. After this reaction occurs, the captured fluid is now “pregnant” with the metal. After exiting the ore heap, the pregnant solution is funnelled to a pond and pumped to the next phase of the extraction process.
There is more on this irrigation system below.
Heap leaching has a couple advantages over other processing methods for low grade ores.
It can be developed in the shortest amount of time, and it has a low capital cost relative to other methods. This can be particularly advantageous for oxide and mixed copper ore deposits
Costmine Insights: Not all Mines are the Same
A “one-size-fits-all” approach to heap leach design will not produce the best results.
The characteristics of a leach pad, such as heap height, ore size, and leach duration, are driven by the unique properties of the ore at a given site. In addition to this, topography and climate can determine decisions such as leach pad shape and irrigation type. These conditions vary greatly from one site to the next, and as one would expect, costs for irrigation do as well.
For the pad and irrigation design assumptions used in their article, Costmine Intelligence determined that HDPE (High Density Poly Ethylene) supply items constitute the largest portion of the overall supply cost for all size operations studied, between 63 to 73%. Pumps comprise the largest of the capital costs, with their portion of the overall cost diminishing with larger designs.
Given the large role of HDPE materials in heap leach operations, the distance between the barren pond and the base of the heap was a standout factor in the report’s analysis.
Each of the cost models assumes a value of 1,000 feet. This value can greatly affect total costs since large diameter HDPE main feed pipes are used to carry leach solution over this distance.
On the large end of the leach pad size spectrum, a significant price increase of HDPE products could be a contributing factor as to whether or not a heap leach project is economically feasible.
Because of this, the report recommends for supply purchases and mine construction to begin soon after project feasibility is determined.
This report and its insights are part of a larger service at Costmine Intelligence to keep engineers and cost estimators up to date on the latest trends.
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